diff options
author | Damien Miller <djm@mindrot.org> | 1999-10-29 09:15:49 +1000 |
---|---|---|
committer | Damien Miller <djm@mindrot.org> | 1999-10-29 09:15:49 +1000 |
commit | 32aa144d7034447fee864d050b35b684519c2e45 (patch) | |
tree | 213473231103f90e2a3e77400a0828572b45d344 | |
parent | 34d0b614b3ee27f5b4fbaf7fb733ddccb02f58d6 (diff) |
Re-imported OpenBSD manpages
-rw-r--r-- | scp.1 | 110 | ||||
-rw-r--r-- | ssh-add.1 | 116 | ||||
-rw-r--r-- | ssh-agent.1 | 163 | ||||
-rw-r--r-- | ssh-keygen.1 | 155 | ||||
-rw-r--r-- | ssh.1 | 966 | ||||
-rw-r--r-- | sshd.8 | 781 |
6 files changed, 2291 insertions, 0 deletions
@@ -0,0 +1,110 @@ | |||
1 | .\" -*- nroff -*- | ||
2 | .\" | ||
3 | .\" scp.1 | ||
4 | .\" | ||
5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | ||
6 | .\" | ||
7 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | ||
8 | .\" All rights reserved | ||
9 | .\" | ||
10 | .\" Created: Sun May 7 00:14:37 1995 ylo | ||
11 | .\" | ||
12 | .\" $Id: scp.1,v 1.3 1999/10/28 23:15:49 damien Exp $ | ||
13 | .\" | ||
14 | .Dd September 25, 1999 | ||
15 | .Dt SCP 1 | ||
16 | .Os | ||
17 | .Sh NAME | ||
18 | .Nm scp | ||
19 | .Nd secure copy (remote file copy program) | ||
20 | .Sh SYNOPSIS | ||
21 | .Nm scp | ||
22 | .Op Fl pqrvC | ||
23 | .Op Fl P Ar port | ||
24 | .Op Fl c Ar cipher | ||
25 | .Op Fl i Ar identity_file | ||
26 | .Sm off | ||
27 | .Oo | ||
28 | .Op Ar user@ | ||
29 | .Ar host1 No : | ||
30 | .Oc Ns Ar file1 | ||
31 | .Sm on | ||
32 | .Op Ar ... | ||
33 | .Sm off | ||
34 | .Oo | ||
35 | .Op Ar user@ | ||
36 | .Ar host2 No : | ||
37 | .Oc Ar file2 | ||
38 | .Sm on | ||
39 | .Sh DESCRIPTION | ||
40 | .Nm | ||
41 | copies files between hosts on a network. It uses | ||
42 | .Xr ssh 1 | ||
43 | for data transfer, and uses the same authentication and provides the | ||
44 | same security as | ||
45 | .Xr ssh 1 . | ||
46 | Unlike | ||
47 | .Xr rcp 1 , | ||
48 | .Nm | ||
49 | will ask for passwords or passphrases if they are needed for | ||
50 | authentication. | ||
51 | .Pp | ||
52 | Any file name may contain a host and user specification to indicate | ||
53 | that the file is to be copied to/from that host. Copies between two | ||
54 | remote hosts are permitted. | ||
55 | .Pp | ||
56 | The options are as follows: | ||
57 | .Bl -tag -width Ds | ||
58 | .It Fl c Ar cipher | ||
59 | Selects the cipher to use for encrypting the data transfer. This | ||
60 | option is directly passed to | ||
61 | .Xr ssh 1 . | ||
62 | .It Fl i Ar identity_file | ||
63 | Selects the file from which the identity (private key) for RSA | ||
64 | authentication is read. This option is directly passed to | ||
65 | .Xr ssh 1 . | ||
66 | .It Fl p | ||
67 | Preserves modification times, access times, and modes from the | ||
68 | original file. | ||
69 | .It Fl r | ||
70 | Recursively copy entire directories. | ||
71 | .It Fl v | ||
72 | Verbose mode. Causes | ||
73 | .Nm | ||
74 | and | ||
75 | .Xr ssh 1 | ||
76 | to print debugging messages about their progress. This is helpful in | ||
77 | debugging connection, authentication, and configuration problems. | ||
78 | .It Fl B | ||
79 | Selects batch mode (prevents asking for passwords or passphrases). | ||
80 | .It Fl q | ||
81 | Disables the progress meter. | ||
82 | .It Fl C | ||
83 | Compression enable. Passes the | ||
84 | .Fl C | ||
85 | flag to | ||
86 | .Xr ssh 1 | ||
87 | to enable compression. | ||
88 | .It Fl P Ar port | ||
89 | Specifies the port to connect to on the remote host. Note that this | ||
90 | option is written with a capital | ||
91 | .Sq P , | ||
92 | because | ||
93 | .Fl p | ||
94 | is already reserved for preserving the times and modes of the file in | ||
95 | .Xr rcp 1 . | ||
96 | .Sh AUTHORS | ||
97 | Timo Rinne <tri@iki.fi> and Tatu Ylonen <ylo@cs.hut.fi> | ||
98 | .Sh HISTORY | ||
99 | .Nm | ||
100 | is based on the | ||
101 | .Xr rcp 1 | ||
102 | program in BSD source code from the Regents of the University of | ||
103 | California. | ||
104 | .Sh SEE ALSO | ||
105 | .Xr rcp 1 , | ||
106 | .Xr ssh 1 , | ||
107 | .Xr ssh-add 1 , | ||
108 | .Xr ssh-agent 1 , | ||
109 | .Xr ssh-keygen 1 , | ||
110 | .Xr sshd 8 | ||
diff --git a/ssh-add.1 b/ssh-add.1 new file mode 100644 index 000000000..0ab93dc67 --- /dev/null +++ b/ssh-add.1 | |||
@@ -0,0 +1,116 @@ | |||
1 | .\" -*- nroff -*- | ||
2 | .\" | ||
3 | .\" ssh-add.1 | ||
4 | .\" | ||
5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | ||
6 | .\" | ||
7 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | ||
8 | .\" All rights reserved | ||
9 | .\" | ||
10 | .\" Created: Sat Apr 22 23:55:14 1995 ylo | ||
11 | .\" | ||
12 | .\" $Id: ssh-add.1,v 1.3 1999/10/28 23:15:49 damien Exp $ | ||
13 | .\" | ||
14 | .Dd September 25, 1999 | ||
15 | .Dt SSH-ADD 1 | ||
16 | .Os | ||
17 | .Sh NAME | ||
18 | .Nm ssh-add | ||
19 | .Nd adds identities for the authentication agent | ||
20 | .Sh SYNOPSIS | ||
21 | .Nm ssh-add | ||
22 | .Op Fl ldD | ||
23 | .Op Ar | ||
24 | .Sh DESCRIPTION | ||
25 | .Nm | ||
26 | adds identities to the authentication agent, | ||
27 | .Xr ssh-agent 1 . | ||
28 | When run without arguments, it adds the file | ||
29 | .Pa $HOME/.ssh/identity . | ||
30 | Alternative file names can be given on the | ||
31 | command line. If any file requires a passphrase, | ||
32 | .Nm | ||
33 | asks for the passphrase from the user. | ||
34 | The Passphrase it is read from the user's tty. | ||
35 | .Pp | ||
36 | The authentication agent must be running and must be an ancestor of | ||
37 | the current process for | ||
38 | .Nm | ||
39 | to work. | ||
40 | .Pp | ||
41 | The options are as follows: | ||
42 | .Bl -tag -width Ds | ||
43 | .It Fl l | ||
44 | Lists all identities currently represented by the agent. | ||
45 | .It Fl d | ||
46 | Instead of adding the identity, removes the identity from the agent. | ||
47 | .It Fl D | ||
48 | Deletes all identities from the agent. | ||
49 | .El | ||
50 | .Sh FILES | ||
51 | .Bl -tag -width Ds | ||
52 | .Pa $HOME/.ssh/identity | ||
53 | Contains the RSA authentication identity of the user. This file | ||
54 | should not be readable by anyone but the user. | ||
55 | Note that | ||
56 | .Nm | ||
57 | ignores this file if it is accessible by others. | ||
58 | It is possible to | ||
59 | specify a passphrase when generating the key; that passphrase will be | ||
60 | used to encrypt the private part of this file. This is the | ||
61 | default file added by | ||
62 | .Nm | ||
63 | when no other files have been specified. | ||
64 | .Pp | ||
65 | If | ||
66 | .Nm | ||
67 | needs a passphrase, it will read the passphrase from the current | ||
68 | terminal if it was run from a terminal. If | ||
69 | .Nm | ||
70 | does not have a terminal associated with it but | ||
71 | .Ev DISPLAY | ||
72 | is set, it | ||
73 | will open an X11 window to read the passphrase. This is particularly | ||
74 | useful when calling | ||
75 | .Nm | ||
76 | from a | ||
77 | .Pa .Xsession | ||
78 | or related script. (Note that on some machines it | ||
79 | may be necessary to redirect the input from | ||
80 | .Pa /dev/null | ||
81 | to make this work.) | ||
82 | .Sh AUTHOR | ||
83 | Tatu Ylonen <ylo@cs.hut.fi> | ||
84 | .Pp | ||
85 | OpenSSH | ||
86 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | ||
87 | removed and newer features re-added. Rapidly after the 1.2.12 release, | ||
88 | newer versions bore successively more restrictive licenses. This version | ||
89 | of OpenSSH | ||
90 | .Bl -bullet | ||
91 | .It | ||
92 | has all components of a restrictive nature (ie. patents, see | ||
93 | .Xr ssl 8 ) | ||
94 | directly removed from the source code; any licensed or patented components | ||
95 | are chosen from | ||
96 | external libraries. | ||
97 | .It | ||
98 | has been updated to support ssh protocol 1.5. | ||
99 | .It | ||
100 | contains added support for | ||
101 | .Xr kerberos 8 | ||
102 | authentication and ticket passing. | ||
103 | .It | ||
104 | supports one-time password authentication with | ||
105 | .Xr skey 1 . | ||
106 | .El | ||
107 | .Pp | ||
108 | The libraries described in | ||
109 | .Xr ssl 8 | ||
110 | are required for proper operation. | ||
111 | .Sh SEE ALSO | ||
112 | .Xr ssh 1 , | ||
113 | .Xr ssh-agent 1 , | ||
114 | .Xr ssh-keygen 1 , | ||
115 | .Xr sshd 8 , | ||
116 | .Xr ssl 8 | ||
diff --git a/ssh-agent.1 b/ssh-agent.1 new file mode 100644 index 000000000..8b9504fa5 --- /dev/null +++ b/ssh-agent.1 | |||
@@ -0,0 +1,163 @@ | |||
1 | .\" $OpenBSD: ssh-agent.1,v 1.7 1999/10/28 08:43:10 markus Exp $ | ||
2 | .\" | ||
3 | .\" -*- nroff -*- | ||
4 | .\" | ||
5 | .\" ssh-agent.1 | ||
6 | .\" | ||
7 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | ||
8 | pp.\" | ||
9 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | ||
10 | .\" All rights reserved | ||
11 | .\" | ||
12 | .\" Created: Sat Apr 23 20:10:43 1995 ylo | ||
13 | .\" | ||
14 | .Dd September 25, 1999 | ||
15 | .Dt SSH-AGENT 1 | ||
16 | .Os | ||
17 | .Sh NAME | ||
18 | .Nm ssh-agent | ||
19 | .Nd authentication agent | ||
20 | .Sh SYNOPSIS | ||
21 | .Nm ssh-agent | ||
22 | .Op Fl c Li | Fl s | ||
23 | .Op Fl k | ||
24 | .Oo | ||
25 | .Ar command | ||
26 | .Op Ar args ... | ||
27 | .Oc | ||
28 | .Sh DESCRIPTION | ||
29 | .Nm | ||
30 | is a program to hold authentication private keys. The | ||
31 | idea is that | ||
32 | .Nm | ||
33 | is started in the beginning of an X-session or a login session, and | ||
34 | all other windows or programs are started as clients to the ssh-agent | ||
35 | program. Through use of environment variables the agent can be located | ||
36 | and automatically used for RSA authentication when logging in to other | ||
37 | machines using | ||
38 | .Xr ssh 1 . | ||
39 | .Pp | ||
40 | The options are as follows: | ||
41 | .Bl -tag -width Ds | ||
42 | .It Fl c | ||
43 | Generate C-shell commands on | ||
44 | .Dv stdout . | ||
45 | This is the default if | ||
46 | .Ev SHELL | ||
47 | looks like it's a csh style of shell. | ||
48 | .It Fl s | ||
49 | Generate Bourne shell commands on | ||
50 | .Dv stdout . | ||
51 | This is the default if | ||
52 | .Ev SHELL | ||
53 | does not look like it's a csh style of shell. | ||
54 | .It Fl k | ||
55 | Kill the current agent (given by the | ||
56 | .Ev SSH_AGENT_PID | ||
57 | environment variable). | ||
58 | .El | ||
59 | .Pp | ||
60 | If a commandline is given, this is executed as a subprocess of the agent. | ||
61 | When the command dies, so does the agent. | ||
62 | .Pp | ||
63 | The agent initially does not have any private keys. Keys are added | ||
64 | using | ||
65 | .Xr ssh-add 1 . | ||
66 | When executed without arguments, | ||
67 | .Xr ssh-add 1 | ||
68 | adds the | ||
69 | .Pa $HOME/.ssh/identity | ||
70 | file. If the identity has a passphrase, | ||
71 | .Xr ssh-add 1 | ||
72 | asks for the passphrase (using a small X11 application if running | ||
73 | under X11, or from the terminal if running without X). It then sends | ||
74 | the identity to the agent. Several identities can be stored in the | ||
75 | agent; the agent can automatically use any of these identities. | ||
76 | .Ic ssh-add -l | ||
77 | displays the identities currently held by the agent. | ||
78 | .Pp | ||
79 | The idea is that the agent is run in the user's local PC, laptop, or | ||
80 | terminal. Authentication data need not be stored on any other | ||
81 | machine, and authentication passphrases never go over the network. | ||
82 | However, the connection to the agent is forwarded over SSH | ||
83 | remote logins, and the user can thus use the privileges given by the | ||
84 | identities anywhere in the network in a secure way. | ||
85 | .Pp | ||
86 | There are two main ways to get an agent setup: Either you let the agent | ||
87 | start a new subcommand into which some environment variables are exported, or | ||
88 | you let the agent print the needed shell commands (either | ||
89 | .Xr sh 1 | ||
90 | or | ||
91 | .Xr csh 1 | ||
92 | syntax can be generated) which can be evalled in the calling shell. | ||
93 | Later | ||
94 | .Xr ssh 1 | ||
95 | look at these variables and use them to establish a connection to the agent. | ||
96 | .Pp | ||
97 | A unix-domain socket is created | ||
98 | .Pq Pa /tmp/ssh-XXXXXXXX/agent.<pid> , | ||
99 | and the name of this socket is stored in the | ||
100 | .Ev SSH_AUTH_SOCK | ||
101 | environment | ||
102 | variable. The socket is made accessible only to the current user. | ||
103 | This method is easily abused by root or another instance of the same | ||
104 | user. | ||
105 | .Pp | ||
106 | The | ||
107 | .Ev SSH_AGENT_PID | ||
108 | environment variable holds the agent's PID. | ||
109 | .Pp | ||
110 | The agent exits automatically when the command given on the command | ||
111 | line terminates. | ||
112 | .Sh FILES | ||
113 | .Bl -tag -width Ds | ||
114 | .It Pa $HOME/.ssh/identity | ||
115 | Contains the RSA authentication identity of the user. This file | ||
116 | should not be readable by anyone but the user. It is possible to | ||
117 | specify a passphrase when generating the key; that passphrase will be | ||
118 | used to encrypt the private part of this file. This file | ||
119 | is not used by | ||
120 | .Nm | ||
121 | but is normally added to the agent using | ||
122 | .Xr ssh-add 1 | ||
123 | at login time. | ||
124 | .It Pa /tmp/ssh-XXXX/agent.<pid> , | ||
125 | Unix-domain sockets used to contain the connection to the | ||
126 | authentication agent. These sockets should only be readable by the | ||
127 | owner. The sockets should get automatically removed when the agent | ||
128 | exits. | ||
129 | .Sh AUTHOR | ||
130 | Tatu Ylonen <ylo@cs.hut.fi> | ||
131 | .Pp | ||
132 | OpenSSH | ||
133 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | ||
134 | removed and newer features re-added. Rapidly after the 1.2.12 release, | ||
135 | newer versions bore successively more restrictive licenses. This version | ||
136 | of OpenSSH | ||
137 | .Bl -bullet | ||
138 | .It | ||
139 | has all components of a restrictive nature (ie. patents, see | ||
140 | .Xr ssl 8 ) | ||
141 | directly removed from the source code; any licensed or patented components | ||
142 | are chosen from | ||
143 | external libraries. | ||
144 | .It | ||
145 | has been updated to support ssh protocol 1.5. | ||
146 | .It | ||
147 | contains added support for | ||
148 | .Xr kerberos 8 | ||
149 | authentication and ticket passing. | ||
150 | .It | ||
151 | supports one-time password authentication with | ||
152 | .Xr skey 1 . | ||
153 | .El | ||
154 | .Pp | ||
155 | The libraries described in | ||
156 | .Xr ssl 8 | ||
157 | are required for proper operation. | ||
158 | .Sh SEE ALSO | ||
159 | .Xr ssh 1 , | ||
160 | .Xr ssh-add 1 , | ||
161 | .Xr ssh-keygen 1 , | ||
162 | .Xr sshd 8 , | ||
163 | .Xr ssl 8 | ||
diff --git a/ssh-keygen.1 b/ssh-keygen.1 new file mode 100644 index 000000000..2cbcfae10 --- /dev/null +++ b/ssh-keygen.1 | |||
@@ -0,0 +1,155 @@ | |||
1 | .\" -*- nroff -*- | ||
2 | .\" | ||
3 | .\" ssh-keygen.1 | ||
4 | .\" | ||
5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | ||
6 | .\" | ||
7 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | ||
8 | .\" All rights reserved | ||
9 | .\" | ||
10 | .\" Created: Sat Apr 22 23:55:14 1995 ylo | ||
11 | .\" | ||
12 | .\" $Id: ssh-keygen.1,v 1.3 1999/10/28 23:15:49 damien Exp $ | ||
13 | .\" | ||
14 | .Dd September 25, 1999 | ||
15 | .Dt SSH-KEYGEN 1 | ||
16 | .Os | ||
17 | .Sh NAME | ||
18 | .Nm ssh-keygen | ||
19 | .Nd authentication key generation | ||
20 | .Sh SYNOPSIS | ||
21 | .Nm ssh-keygen | ||
22 | .Op Fl q | ||
23 | .Op Fl b Ar bits | ||
24 | .Op Fl N Ar new_passphrase | ||
25 | .Op Fl C Ar comment | ||
26 | .Nm ssh-keygen | ||
27 | .Fl p | ||
28 | .Op Fl P Ar old_passphrase | ||
29 | .Op Fl N Ar new_passphrase | ||
30 | .Nm ssh-keygen | ||
31 | .Fl c | ||
32 | .Op Fl P Ar passphrase | ||
33 | .Op Fl C Ar comment | ||
34 | .Sh DESCRIPTION | ||
35 | .Nm | ||
36 | generates and manages authentication keys for | ||
37 | .Xr ssh 1 . | ||
38 | Normally each user wishing to use SSH | ||
39 | with RSA authentication runs this once to create the authentication | ||
40 | key in | ||
41 | .Pa $HOME/.ssh/identity . | ||
42 | Additionally, the system administrator may use this to generate host keys. | ||
43 | .Pp | ||
44 | Normally this program generates the key and asks for a file in which | ||
45 | to store the private key. The public key is stored in a file with the | ||
46 | same name but | ||
47 | .Dq .pub | ||
48 | appended. The program also asks for a | ||
49 | passphrase. The passphrase may be empty to indicate no passphrase | ||
50 | (host keys must have empty passphrase), or it may be a string of | ||
51 | arbitrary length. Good passphrases are 10-30 characters long and are | ||
52 | not simple sentences or otherwise easily guessable (English | ||
53 | prose has only 1-2 bits of entropy per word, and provides very bad | ||
54 | passphrases). The passphrase can be changed later by using the | ||
55 | .Fl p | ||
56 | option. | ||
57 | .Pp | ||
58 | There is no way to recover a lost passphrase. If the passphrase is | ||
59 | lost or forgotten, you will have to generate a new key and copy the | ||
60 | corresponding public key to other machines. | ||
61 | .Pp | ||
62 | There is also a comment field in the key file that is only for | ||
63 | convenience to the user to help identify the key. The comment can | ||
64 | tell what the key is for, or whatever is useful. The comment is | ||
65 | initialized to | ||
66 | .Dq user@host | ||
67 | when the key is created, but can be changed using the | ||
68 | .Fl c | ||
69 | option. | ||
70 | .Pp | ||
71 | The options are as follows: | ||
72 | .Bl -tag -width Ds | ||
73 | .It Fl b Ar bits | ||
74 | Specifies the number of bits in the key to create. Minimum is 512 | ||
75 | bits. Generally 1024 bits is considered sufficient, and key sizes | ||
76 | above that no longer improve security but make things slower. The | ||
77 | default is 1024 bits. | ||
78 | .It Fl c | ||
79 | Requests changing the comment in the private and public key files. | ||
80 | The program will prompt for the file containing the private keys, for | ||
81 | passphrase if the key has one, and for the new comment. | ||
82 | .It Fl p | ||
83 | Requests changing the passphrase of a private key file instead of | ||
84 | creating a new private key. The program will prompt for the file | ||
85 | containing the private key, for the old passphrase, and twice for the | ||
86 | new passphrase. | ||
87 | .It Fl q | ||
88 | Silence | ||
89 | .Nm ssh-keygen . | ||
90 | Used by | ||
91 | .Pa /etc/rc | ||
92 | when creating a new key. | ||
93 | .It Fl C Ar comment | ||
94 | Provides the new comment. | ||
95 | .It Fl N Ar new_passphrase | ||
96 | Provides the new passphrase. | ||
97 | .It Fl P Ar passphrase | ||
98 | Provides the (old) passphrase. | ||
99 | .El | ||
100 | .Sh FILES | ||
101 | .Bl -tag -width Ds | ||
102 | .It Pa $HOME/.ssh/random_seed | ||
103 | Used for seeding the random number generator. This file should not be | ||
104 | readable by anyone but the user. This file is created the first time | ||
105 | the program is run, and is updated every time. | ||
106 | .It Pa $HOME/.ssh/identity | ||
107 | Contains the RSA authentication identity of the user. This file | ||
108 | should not be readable by anyone but the user. It is possible to | ||
109 | specify a passphrase when generating the key; that passphrase will be | ||
110 | used to encrypt the private part of this file using 3DES. This file | ||
111 | is not automatically accessed by | ||
112 | .Nm | ||
113 | but it is offered as the default file for the private key. | ||
114 | .It Pa $HOME/.ssh/identity.pub | ||
115 | Contains the public key for authentication. The contents of this file | ||
116 | should be added to | ||
117 | .Pa $HOME/.ssh/authorized_keys | ||
118 | on all machines | ||
119 | where you wish to log in using RSA authentication. There is no | ||
120 | need to keep the contents of this file secret. | ||
121 | .Sh AUTHOR | ||
122 | Tatu Ylonen <ylo@cs.hut.fi> | ||
123 | .Pp | ||
124 | OpenSSH | ||
125 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | ||
126 | removed and newer features re-added. Rapidly after the 1.2.12 release, | ||
127 | newer versions bore successively more restrictive licenses. This version | ||
128 | of OpenSSH | ||
129 | .Bl -bullet | ||
130 | .It | ||
131 | has all components of a restrictive nature (ie. patents, see | ||
132 | .Xr ssl 8 ) | ||
133 | directly removed from the source code; any licensed or patented components | ||
134 | are chosen from | ||
135 | external libraries. | ||
136 | .It | ||
137 | has been updated to support ssh protocol 1.5. | ||
138 | .It | ||
139 | contains added support for | ||
140 | .Xr kerberos 8 | ||
141 | authentication and ticket passing. | ||
142 | .It | ||
143 | supports one-time password authentication with | ||
144 | .Xr skey 1 . | ||
145 | .El | ||
146 | .Pp | ||
147 | The libraries described in | ||
148 | .Xr ssl 8 | ||
149 | are required for proper operation. | ||
150 | .Sh SEE ALSO | ||
151 | .Xr ssh 1 , | ||
152 | .Xr ssh-add 1 , | ||
153 | .Xr ssh-agent 1, | ||
154 | .Xr sshd 8 , | ||
155 | .Xr ssl 8 | ||
@@ -0,0 +1,966 @@ | |||
1 | .\" -*- nroff -*- | ||
2 | .\" | ||
3 | .\" ssh.1.in | ||
4 | .\" | ||
5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | ||
6 | .\" | ||
7 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | ||
8 | .\" All rights reserved | ||
9 | .\" | ||
10 | .\" Created: Sat Apr 22 21:55:14 1995 ylo | ||
11 | .\" | ||
12 | .\" $Id: ssh.1,v 1.3 1999/10/28 23:15:50 damien Exp $ | ||
13 | .\" | ||
14 | .Dd September 25, 1999 | ||
15 | .Dt SSH 1 | ||
16 | .Os | ||
17 | .Sh NAME | ||
18 | .Nm ssh | ||
19 | .Nd OpenSSH secure shell client (remote login program) | ||
20 | .Sh SYNOPSIS | ||
21 | .Nm ssh | ||
22 | .Op Fl l Ar login_name | ||
23 | .Op Ar hostname | user@hostname | ||
24 | .Op Ar command | ||
25 | .Pp | ||
26 | .Nm ssh | ||
27 | .Op Fl afgknqtvxCPX | ||
28 | .Op Fl c Ar blowfish | 3des | ||
29 | .Op Fl e Ar escape_char | ||
30 | .Op Fl i Ar identity_file | ||
31 | .Op Fl l Ar login_name | ||
32 | .Op Fl o Ar option | ||
33 | .Op Fl p Ar port | ||
34 | .Oo Fl L Xo | ||
35 | .Sm off | ||
36 | .Ar host : | ||
37 | .Ar port : | ||
38 | .Ar hostport | ||
39 | .Sm on | ||
40 | .Xc | ||
41 | .Oc | ||
42 | .Oo Fl R Xo | ||
43 | .Sm off | ||
44 | .Ar host : | ||
45 | .Ar port : | ||
46 | .Ar hostport | ||
47 | .Sm on | ||
48 | .Xc | ||
49 | .Oc | ||
50 | .Op Ar hostname | user@hostname | ||
51 | .Op Ar command | ||
52 | .Sh DESCRIPTION | ||
53 | .Nm | ||
54 | (Secure Shell) is a program for logging into a remote machine and for | ||
55 | executing commands on a remote machine. It is intended to replace | ||
56 | rlogin and rsh, and provide secure encrypted communications between | ||
57 | two untrusted hosts over an insecure network. X11 connections and | ||
58 | arbitrary TCP/IP ports can also be forwarded over the secure channel. | ||
59 | .Pp | ||
60 | .Nm | ||
61 | connects and logs into the specified | ||
62 | .Ar hostname . | ||
63 | The user must prove | ||
64 | his/her identity to the remote machine using one of several methods. | ||
65 | .Pp | ||
66 | First, if the machine the user logs in from is listed in | ||
67 | .Pa /etc/hosts.equiv | ||
68 | or | ||
69 | .Pa /etc/shosts.equiv | ||
70 | on the remote machine, and the user names are | ||
71 | the same on both sides, the user is immediately permitted to log in. | ||
72 | Second, if | ||
73 | .Pa \&.rhosts | ||
74 | or | ||
75 | .Pa \&.shosts | ||
76 | exists in the user's home directory on the | ||
77 | remote machine and contains a line containing the name of the client | ||
78 | machine and the name of the user on that machine, the user is | ||
79 | permitted to log in. This form of authentication alone is normally not | ||
80 | allowed by the server because it is not secure. | ||
81 | .Pp | ||
82 | The second (and primary) authentication method is the | ||
83 | .Pa rhosts | ||
84 | or | ||
85 | .Pa hosts.equiv | ||
86 | method combined with RSA-based host authentication. It | ||
87 | means that if the login would be permitted by | ||
88 | .Pa \&.rhosts , | ||
89 | .Pa \&.shosts , | ||
90 | .Pa /etc/hosts.equiv , | ||
91 | or | ||
92 | .Pa /etc/shosts.equiv , | ||
93 | and if additionally the server can verify the client's | ||
94 | host key (see | ||
95 | .Pa /etc/ssh_known_hosts | ||
96 | in the | ||
97 | .Sx FILES | ||
98 | section), only then login is | ||
99 | permitted. This authentication method closes security holes due to IP | ||
100 | spoofing, DNS spoofing and routing spoofing. [Note to the | ||
101 | administrator: | ||
102 | .Pa /etc/hosts.equiv , | ||
103 | .Pa \&.rhosts , | ||
104 | and the rlogin/rsh protocol in general, are inherently insecure and should be | ||
105 | disabled if security is desired.] | ||
106 | .Pp | ||
107 | As a third authentication method, | ||
108 | .Nm | ||
109 | supports RSA based authentication. | ||
110 | The scheme is based on public-key cryptography: there are cryptosystems | ||
111 | where encryption and decryption are done using separate keys, and it | ||
112 | is not possible to derive the decryption key from the encryption key. | ||
113 | RSA is one such system. The idea is that each user creates a public/private | ||
114 | key pair for authentication purposes. The | ||
115 | server knows the public key, and only the user knows the private key. | ||
116 | The file | ||
117 | .Pa $HOME/.ssh/authorized_keys | ||
118 | lists the public keys that are permitted for logging | ||
119 | in. When the user logs in, the | ||
120 | .Nm | ||
121 | program tells the server which key pair it would like to use for | ||
122 | authentication. The server checks if this key is permitted, and if | ||
123 | so, sends the user (actually the | ||
124 | .Nm | ||
125 | program running on behalf of the user) a challenge, a random number, | ||
126 | encrypted by the user's public key. The challenge can only be | ||
127 | decrypted using the proper private key. The user's client then decrypts the | ||
128 | challenge using the private key, proving that he/she knows the private | ||
129 | key but without disclosing it to the server. | ||
130 | .Pp | ||
131 | .Nm | ||
132 | implements the RSA authentication protocol automatically. The user | ||
133 | creates his/her RSA key pair by running | ||
134 | .Xr ssh-keygen 1 . | ||
135 | This stores the private key in | ||
136 | .Pa \&.ssh/identity | ||
137 | and the public key in | ||
138 | .Pa \&.ssh/identity.pub | ||
139 | in the user's home directory. The user should then | ||
140 | copy the | ||
141 | .Pa identity.pub | ||
142 | to | ||
143 | .Pa \&.ssh/authorized_keys | ||
144 | in his/her home directory on the remote machine (the | ||
145 | .Pa authorized_keys | ||
146 | file corresponds to the conventional | ||
147 | .Pa \&.rhosts | ||
148 | file, and has one key | ||
149 | per line, though the lines can be very long). After this, the user | ||
150 | can log in without giving the password. RSA authentication is much | ||
151 | more secure than rhosts authentication. | ||
152 | .Pp | ||
153 | The most convenient way to use RSA authentication may be with an | ||
154 | authentication agent. See | ||
155 | .Xr ssh-agent 1 | ||
156 | for more information. | ||
157 | .Pp | ||
158 | If other authentication methods fail, | ||
159 | .Nm | ||
160 | prompts the user for a password. The password is sent to the remote | ||
161 | host for checking; however, since all communications are encrypted, | ||
162 | the password cannot be seen by someone listening on the network. | ||
163 | .Pp | ||
164 | When the user's identity has been accepted by the server, the server | ||
165 | either executes the given command, or logs into the machine and gives | ||
166 | the user a normal shell on the remote machine. All communication with | ||
167 | the remote command or shell will be automatically encrypted. | ||
168 | .Pp | ||
169 | If a pseudo-terminal has been allocated (normal login session), the | ||
170 | user can disconnect with | ||
171 | .Ic ~. , | ||
172 | and suspend | ||
173 | .Nm | ||
174 | with | ||
175 | .Ic ~^Z . | ||
176 | All forwarded connections can be listed with | ||
177 | .Ic ~# | ||
178 | and if | ||
179 | the session blocks waiting for forwarded X11 or TCP/IP | ||
180 | connections to terminate, it can be backgrounded with | ||
181 | .Ic ~& | ||
182 | (this should not be used while the user shell is active, as it can cause the | ||
183 | shell to hang). All available escapes can be listed with | ||
184 | .Ic ~? . | ||
185 | .Pp | ||
186 | A single tilde character can be sent as | ||
187 | .Ic ~~ | ||
188 | (or by following the tilde by a character other than those described above). | ||
189 | The escape character must always follow a newline to be interpreted as | ||
190 | special. The escape character can be changed in configuration files | ||
191 | or on the command line. | ||
192 | .Pp | ||
193 | If no pseudo tty has been allocated, the | ||
194 | session is transparent and can be used to reliably transfer binary | ||
195 | data. On most systems, setting the escape character to | ||
196 | .Dq none | ||
197 | will also make the session transparent even if a tty is used. | ||
198 | .Pp | ||
199 | The session terminates when the command or shell in on the remote | ||
200 | machine exists and all X11 and TCP/IP connections have been closed. | ||
201 | The exit status of the remote program is returned as the exit status | ||
202 | of | ||
203 | .Nm ssh . | ||
204 | .Pp | ||
205 | If the user is using X11 (the | ||
206 | .Ev DISPLAY | ||
207 | environment variable is set), the connection to the X11 display is | ||
208 | automatically forwarded to the remote side in such a way that any X11 | ||
209 | programs started from the shell (or command) will go through the | ||
210 | encrypted channel, and the connection to the real X server will be made | ||
211 | from the local machine. The user should not manually set | ||
212 | .Ev DISPLAY . | ||
213 | Forwarding of X11 connections can be | ||
214 | configured on the command line or in configuration files. | ||
215 | .Pp | ||
216 | The | ||
217 | .Ev DISPLAY | ||
218 | value set by | ||
219 | .Nm | ||
220 | will point to the server machine, but with a display number greater | ||
221 | than zero. This is normal, and happens because | ||
222 | .Nm | ||
223 | creates a | ||
224 | .Dq proxy | ||
225 | X server on the server machine for forwarding the | ||
226 | connections over the encrypted channel. | ||
227 | .Pp | ||
228 | .Nm | ||
229 | will also automatically set up Xauthority data on the server machine. | ||
230 | For this purpose, it will generate a random authorization cookie, | ||
231 | store it in Xauthority on the server, and verify that any forwarded | ||
232 | connections carry this cookie and replace it by the real cookie when | ||
233 | the connection is opened. The real authentication cookie is never | ||
234 | sent to the server machine (and no cookies are sent in the plain). | ||
235 | .Pp | ||
236 | If the user is using an authentication agent, the connection to the agent | ||
237 | is automatically forwarded to the remote side unless disabled on | ||
238 | command line or in a configuration file. | ||
239 | .Pp | ||
240 | Forwarding of arbitrary TCP/IP connections over the secure channel can | ||
241 | be specified either on command line or in a configuration file. One | ||
242 | possible application of TCP/IP forwarding is a secure connection to an | ||
243 | electronic purse; another is going trough firewalls. | ||
244 | .Pp | ||
245 | .Nm | ||
246 | automatically maintains and checks a database containing RSA-based | ||
247 | identifications for all hosts it has ever been used with. The | ||
248 | database is stored in | ||
249 | .Pa \&.ssh/known_hosts | ||
250 | in the user's home directory. Additionally, the file | ||
251 | .Pa /etc/ssh_known_hosts | ||
252 | is automatically checked for known hosts. Any new hosts are | ||
253 | automatically added to the user's file. If a host's identification | ||
254 | ever changes, | ||
255 | .Nm | ||
256 | warns about this and disables password authentication to prevent a | ||
257 | trojan horse from getting the user's password. Another purpose of | ||
258 | this mechanism is to prevent man-in-the-middle attacks which could | ||
259 | otherwise be used to circumvent the encryption. The | ||
260 | .Cm StrictHostKeyChecking | ||
261 | option (see below) can be used to prevent logins to machines whose | ||
262 | host key is not known or has changed. | ||
263 | .Sh OPTIONS | ||
264 | .Bl -tag -width Ds | ||
265 | .It Fl a | ||
266 | Disables forwarding of the authentication agent connection. This may | ||
267 | also be specified on a per-host basis in the configuration file. | ||
268 | .It Fl c Ar blowfish|3des | ||
269 | Selects the cipher to use for encrypting the session. | ||
270 | .Ar 3des | ||
271 | is used by default. It is believed to be secure. | ||
272 | .Ar 3des | ||
273 | (triple-des) is an encrypt-decrypt-encrypt triple with three different keys. | ||
274 | It is presumably more secure than the | ||
275 | .Ar des | ||
276 | cipher which is no longer supported in ssh. | ||
277 | .Ar blowfish | ||
278 | is a fast block cipher, it appears very secure and is much faster than | ||
279 | .Ar 3des . | ||
280 | .It Fl e Ar ch|^ch|none | ||
281 | Sets the escape character for sessions with a pty (default: | ||
282 | .Ql ~ ) . | ||
283 | The escape character is only recognized at the beginning of a line. The | ||
284 | escape character followed by a dot | ||
285 | .Pq Ql \&. | ||
286 | closes the connection, followed | ||
287 | by control-Z suspends the connection, and followed by itself sends the | ||
288 | escape character once. Setting the character to | ||
289 | .Dq none | ||
290 | disables any escapes and makes the session fully transparent. | ||
291 | .It Fl f | ||
292 | Requests | ||
293 | .Nm | ||
294 | to go to background after authentication. This is useful | ||
295 | if | ||
296 | .Nm | ||
297 | is going to ask for passwords or passphrases, but the user | ||
298 | wants it in the background. This implies | ||
299 | .Fl n . | ||
300 | The recommended way to start X11 programs at a remote site is with | ||
301 | something like | ||
302 | .Ic ssh -f host xterm . | ||
303 | .It Fl i Ar identity_file | ||
304 | Selects the file from which the identity (private key) for | ||
305 | RSA authentication is read. Default is | ||
306 | .Pa \&.ssh/identity | ||
307 | in the user's home directory. Identity files may also be specified on | ||
308 | a per-host basis in the configuration file. It is possible to have | ||
309 | multiple | ||
310 | .Fl i | ||
311 | options (and multiple identities specified in | ||
312 | configuration files). | ||
313 | .It Fl g | ||
314 | Allows remote hosts to connect to local forwarded ports. | ||
315 | .It Fl k | ||
316 | Disables forwarding of Kerberos tickets and AFS tokens. This may | ||
317 | also be specified on a per-host basis in the configuration file. | ||
318 | .It Fl l Ar login_name | ||
319 | Specifies the user to log in as on the remote machine. This may also | ||
320 | be specified on a per-host basis in the configuration file. | ||
321 | .It Fl n | ||
322 | Redirects stdin from | ||
323 | .Pa /dev/null | ||
324 | (actually, prevents reading from stdin). | ||
325 | This must be used when | ||
326 | .Nm | ||
327 | is run in the background. A common trick is to use this to run X11 | ||
328 | programs in a remote machine. For example, | ||
329 | .Ic ssh -n shadows.cs.hut.fi emacs & | ||
330 | will start an emacs on shadows.cs.hut.fi, and the X11 | ||
331 | connection will be automatically forwarded over an encrypted channel. | ||
332 | The | ||
333 | .Nm | ||
334 | program will be put in the background. | ||
335 | (This does not work if | ||
336 | .Nm | ||
337 | needs to ask for a password or passphrase; see also the | ||
338 | .Fl f | ||
339 | option.) | ||
340 | .It Fl o Ar option | ||
341 | Can be used to give options in the format used in the config file. | ||
342 | This is useful for specifying options for which there is no separate | ||
343 | command-line flag. The option has the same format as a line in the | ||
344 | configuration file. | ||
345 | .It Fl p Ar port | ||
346 | Port to connect to on the remote host. This can be specified on a | ||
347 | per-host basis in the configuration file. | ||
348 | .It Fl P | ||
349 | Use a non-privileged port for outgoing connections. | ||
350 | This can be used if your firewall does | ||
351 | not permit connections from privileged ports. | ||
352 | Note that this option turns of | ||
353 | .Cm RhostsAuthentication | ||
354 | and | ||
355 | .Cm RhostsRSAAuthentication . | ||
356 | .It Fl q | ||
357 | Quiet mode. Causes all warning and diagnostic messages to be | ||
358 | suppressed. Only fatal errors are displayed. | ||
359 | .It Fl t | ||
360 | Force pseudo-tty allocation. This can be used to execute arbitary | ||
361 | screen-based programs on a remote machine, which can be very useful | ||
362 | e.g. when implementing menu services. | ||
363 | .It Fl v | ||
364 | Verbose mode. Causes | ||
365 | .Nm | ||
366 | to print debugging messages about its progress. This is helpful in | ||
367 | debugging connection, authentication, and configuration problems. | ||
368 | The verbose mode is also used to display | ||
369 | .Xr skey 1 | ||
370 | challenges, if the user entered "s/key" as password. | ||
371 | .It Fl x | ||
372 | Disables X11 forwarding. This can also be specified on a per-host | ||
373 | basis in a configuration file. | ||
374 | .It Fl X | ||
375 | Enables X11 forwarding. | ||
376 | .It Fl C | ||
377 | Requests compression of all data (including stdin, stdout, stderr, and | ||
378 | data for forwarded X11 and TCP/IP connections). The compression | ||
379 | algorithm is the same used by gzip, and the | ||
380 | .Dq level | ||
381 | can be controlled by the | ||
382 | .Cm CompressionLevel | ||
383 | option (see below). Compression is desirable on modem lines and other | ||
384 | slow connections, but will only slow down things on fast networks. | ||
385 | The default value can be set on a host-by-host basis in the | ||
386 | configuration files; see the | ||
387 | .Cm Compress | ||
388 | option below. | ||
389 | .It Fl L Ar port:host:hostport | ||
390 | Specifies that the given port on the local (client) host is to be | ||
391 | forwarded to the given host and port on the remote side. This works | ||
392 | by allocating a socket to listen to | ||
393 | .Ar port | ||
394 | on the local side, and whenever a connection is made to this port, the | ||
395 | connection is forwarded over the secure channel, and a connection is | ||
396 | made to | ||
397 | .Ar host:hostport | ||
398 | from the remote machine. Port forwardings can also be specified in the | ||
399 | configuration file. Only root can forward privileged ports. | ||
400 | .It Fl R Ar port:host:hostport | ||
401 | Specifies that the given port on the remote (server) host is to be | ||
402 | forwarded to the given host and port on the local side. This works | ||
403 | by allocating a socket to listen to | ||
404 | .Ar port | ||
405 | on the remote side, and whenever a connection is made to this port, the | ||
406 | connection is forwarded over the secure channel, and a connection is | ||
407 | made to | ||
408 | .Ar host:hostport | ||
409 | from the local machine. Port forwardings can also be specified in the | ||
410 | configuration file. Privileged ports can be forwarded only when | ||
411 | logging in as root on the remote machine. | ||
412 | .El | ||
413 | .Sh CONFIGURATION FILES | ||
414 | .Nm | ||
415 | obtains configuration data from the following sources (in this order): | ||
416 | command line options, user's configuration file | ||
417 | .Pq Pa $HOME/.ssh/config , | ||
418 | and system-wide configuration file | ||
419 | .Pq Pa /etc/ssh_config . | ||
420 | For each parameter, the first obtained value | ||
421 | will be used. The configuration files contain sections bracketed by | ||
422 | "Host" specifications, and that section is only applied for hosts that | ||
423 | match one of the patterns given in the specification. The matched | ||
424 | host name is the one given on the command line. | ||
425 | .Pp | ||
426 | Since the first obtained value for each parameter is used, more | ||
427 | host-specific declarations should be given near the beginning of the | ||
428 | file, and general defaults at the end. | ||
429 | .Pp | ||
430 | The configuration file has the following format: | ||
431 | .Pp | ||
432 | Empty lines and lines starting with | ||
433 | .Ql # | ||
434 | are comments. | ||
435 | .Pp | ||
436 | Otherwise a line is of the format | ||
437 | .Dq keyword arguments . | ||
438 | The possible | ||
439 | keywords and their meanings are as follows (note that the | ||
440 | configuration files are case-sensitive): | ||
441 | .Bl -tag -width Ds | ||
442 | .It Cm Host | ||
443 | Restricts the following declarations (up to the next | ||
444 | .Cm Host | ||
445 | keyword) to be only for those hosts that match one of the patterns | ||
446 | given after the keyword. | ||
447 | .Ql \&* | ||
448 | and | ||
449 | .Ql ? | ||
450 | can be used as wildcards in the | ||
451 | patterns. A single | ||
452 | .Ql \&* | ||
453 | as a pattern can be used to provide global | ||
454 | defaults for all hosts. The host is the | ||
455 | .Ar hostname | ||
456 | argument given on the command line (i.e., the name is not converted to | ||
457 | a canonicalized host name before matching). | ||
458 | .It Cm AFSTokenPassing | ||
459 | Specifies whether to pass AFS tokens to remote host. The argument to | ||
460 | this keyword must be | ||
461 | .Dq yes | ||
462 | or | ||
463 | .Dq no . | ||
464 | .It Cm BatchMode | ||
465 | If set to | ||
466 | .Dq yes , | ||
467 | passphrase/password querying will be disabled. This | ||
468 | option is useful in scripts and other batch jobs where you have no | ||
469 | user to supply the password. The argument must be | ||
470 | .Dq yes | ||
471 | or | ||
472 | .Dq no . | ||
473 | .It Cm Cipher | ||
474 | Specifies the cipher to use for encrypting the session. Currently, | ||
475 | .Dq blowfish , | ||
476 | and | ||
477 | .Dq 3des | ||
478 | are supported. The default is | ||
479 | .Dq 3des . | ||
480 | .It Cm Compression | ||
481 | Specifies whether to use compression. The argument must be | ||
482 | .Dq yes | ||
483 | or | ||
484 | .Dq no . | ||
485 | .It Cm CompressionLevel | ||
486 | Specifies the compression level to use if compression is enable. The | ||
487 | argument must be an integer from 1 (fast) to 9 (slow, best). The | ||
488 | default level is 6, which is good for most applications. The meaning | ||
489 | of the values is the same as in GNU GZIP. | ||
490 | .It Cm ConnectionAttempts | ||
491 | Specifies the number of tries (one per second) to make before falling | ||
492 | back to rsh or exiting. The argument must be an integer. This may be | ||
493 | useful in scripts if the connection sometimes fails. | ||
494 | .It Cm EscapeChar | ||
495 | Sets the escape character (default: | ||
496 | .Ql ~ ) . | ||
497 | The escape character can also | ||
498 | be set on the command line. The argument should be a single | ||
499 | character, | ||
500 | .Ql ^ | ||
501 | followed by a letter, or | ||
502 | .Dq none | ||
503 | to disable the escape | ||
504 | character entirely (making the connection transparent for binary | ||
505 | data). | ||
506 | .It Cm FallBackToRsh | ||
507 | Specifies that if connecting via | ||
508 | .Nm | ||
509 | fails due to a connection refused error (there is no | ||
510 | .Xr sshd 8 | ||
511 | listening on the remote host), | ||
512 | .Xr rsh 1 | ||
513 | should automatically be used instead (after a suitable warning about | ||
514 | the session being unencrypted). The argument must be | ||
515 | .Dq yes | ||
516 | or | ||
517 | .Dq no . | ||
518 | .It Cm ForwardAgent | ||
519 | Specifies whether the connection to the authentication agent (if any) | ||
520 | will be forwarded to the remote machine. The argument must be | ||
521 | .Dq yes | ||
522 | or | ||
523 | .Dq no . | ||
524 | .It Cm ForwardX11 | ||
525 | Specifies whether X11 connections will be automatically redirected | ||
526 | over the secure channel and | ||
527 | .Ev DISPLAY | ||
528 | set. The argument must be | ||
529 | .Dq yes | ||
530 | or | ||
531 | .Dq no . | ||
532 | .It Cm GatewayPorts | ||
533 | Specifies whether remote hosts are allowed to connect to local | ||
534 | forwarded ports. | ||
535 | The argument must be | ||
536 | .Dq yes | ||
537 | or | ||
538 | .Dq no . | ||
539 | The default is | ||
540 | .Dq no . | ||
541 | .It Cm GlobalKnownHostsFile | ||
542 | Specifies a file to use instead of | ||
543 | .Pa /etc/ssh_known_hosts . | ||
544 | .It Cm HostName | ||
545 | Specifies the real host name to log into. This can be used to specify | ||
546 | nicnames or abbreviations for hosts. Default is the name given on the | ||
547 | command line. Numeric IP addresses are also permitted (both on the | ||
548 | command line and in | ||
549 | .Cm HostName | ||
550 | specifications). | ||
551 | .It Cm IdentityFile | ||
552 | Specifies the file from which the user's RSA authentication identity | ||
553 | is read (default | ||
554 | .Pa .ssh/identity | ||
555 | in the user's home directory). | ||
556 | Additionally, any identities represented by the authentication agent | ||
557 | will be used for authentication. The file name may use the tilde | ||
558 | syntax to refer to a user's home directory. It is possible to have | ||
559 | multiple identity files specified in configuration files; all these | ||
560 | identities will be tried in sequence. | ||
561 | .It Cm KeepAlive | ||
562 | Specifies whether the system should send keepalive messages to the | ||
563 | other side. If they are sent, death of the connection or crash of one | ||
564 | of the machines will be properly noticed. However, this means that | ||
565 | connections will die if the route is down temporarily, and some people | ||
566 | find it annoying. | ||
567 | .Pp | ||
568 | The default is | ||
569 | .Dq yes | ||
570 | (to send keepalives), and the client will notice | ||
571 | if the network goes down or the remote host dies. This is important | ||
572 | in scripts, and many users want it too. | ||
573 | .Pp | ||
574 | To disable keepalives, the value should be set to | ||
575 | .Dq no | ||
576 | in both the server and the client configuration files. | ||
577 | .It Cm KerberosAuthentication | ||
578 | Specifies whether Kerberos authentication will be used. The argument to | ||
579 | this keyword must be | ||
580 | .Dq yes | ||
581 | or | ||
582 | .Dq no . | ||
583 | .It Cm KerberosTgtPassing | ||
584 | Specifies whether a Kerberos TGT will be forwarded to the server. This | ||
585 | will only work if the Kerberos server is actually an AFS kaserver. The | ||
586 | argument to this keyword must be | ||
587 | .Dq yes | ||
588 | or | ||
589 | .Dq no . | ||
590 | .It Cm LocalForward | ||
591 | Specifies that a TCP/IP port on the local machine be forwarded over | ||
592 | the secure channel to given host:port from the remote machine. The | ||
593 | first argument must be a port number, and the second must be | ||
594 | host:port. Multiple forwardings may be specified, and additional | ||
595 | forwardings can be given on the command line. Only the root can | ||
596 | forward privileged ports. | ||
597 | .It Cm PasswordAuthentication | ||
598 | Specifies whether to use password authentication. The argument to | ||
599 | this keyword must be | ||
600 | .Dq yes | ||
601 | or | ||
602 | .Dq no . | ||
603 | .It Cm NumberOfPasswordPrompts | ||
604 | Specifies the number of password prompts before giving up. The | ||
605 | argument to this keyword must be an integer. Default is 3. | ||
606 | .It Cm Port | ||
607 | Specifies the port number to connect on the remote host. Default is | ||
608 | 22. | ||
609 | .It Cm ProxyCommand | ||
610 | Specifies the command to use to connect to the server. The command | ||
611 | string extends to the end of the line, and is executed with /bin/sh. | ||
612 | In the command string, %h will be substituted by the host name to | ||
613 | connect and %p by the port. The command can be basically anything, | ||
614 | and should read from its stdin and write to its stdout. It should | ||
615 | eventually connect an | ||
616 | .Xr sshd 8 | ||
617 | server running on some machine, or execute | ||
618 | .Ic sshd -i | ||
619 | somewhere. Host key management will be done using the | ||
620 | HostName of the host being connected (defaulting to the name typed by | ||
621 | the user). | ||
622 | .Pp | ||
623 | .It Cm RemoteForward | ||
624 | Specifies that a TCP/IP port on the remote machine be forwarded over | ||
625 | the secure channel to given host:port from the local machine. The | ||
626 | first argument must be a port number, and the second must be | ||
627 | host:port. Multiple forwardings may be specified, and additional | ||
628 | forwardings can be given on the command line. Only the root can | ||
629 | forward privileged ports. | ||
630 | .It Cm RhostsAuthentication | ||
631 | Specifies whether to try rhosts based authentication. Note that this | ||
632 | declaration only affects the client side and has no effect whatsoever | ||
633 | on security. Disabling rhosts authentication may reduce | ||
634 | authentication time on slow connections when rhosts authentication is | ||
635 | not used. Most servers do not permit RhostsAuthentication because it | ||
636 | is not secure (see RhostsRSAAuthentication). The argument to this | ||
637 | keyword must be | ||
638 | .Dq yes | ||
639 | or | ||
640 | .Dq no . | ||
641 | .It Cm RhostsRSAAuthentication | ||
642 | Specifies whether to try rhosts based authentication with RSA host | ||
643 | authentication. This is the primary authentication method for most | ||
644 | sites. The argument must be | ||
645 | .Dq yes | ||
646 | or | ||
647 | .Dq no . | ||
648 | .It Cm RSAAuthentication | ||
649 | Specifies whether to try RSA authentication. The argument to this | ||
650 | keyword must be | ||
651 | .Dq yes | ||
652 | or | ||
653 | .Dq no . | ||
654 | RSA authentication will only be | ||
655 | attempted if the identity file exists, or an authentication agent is | ||
656 | running. | ||
657 | .It Cm CheckHostIP | ||
658 | If this flag is set to | ||
659 | .Dq yes , | ||
660 | ssh will additionally check the host ip address in the | ||
661 | .Pa known_hosts | ||
662 | file. This allows ssh to detect if a host key changed due to DNS spoofing. | ||
663 | If the option is set to | ||
664 | .Dq no , | ||
665 | the check will not be executed. | ||
666 | .It Cm StrictHostKeyChecking | ||
667 | If this flag is set to | ||
668 | .Dq yes , | ||
669 | .Nm | ||
670 | ssh will never automatically add host keys to the | ||
671 | .Pa $HOME/.ssh/known_hosts | ||
672 | file, and refuses to connect hosts whose host key has changed. This | ||
673 | provides maximum protection against trojan horse attacks. However, it | ||
674 | can be somewhat annoying if you don't have good | ||
675 | .Pa /etc/ssh_known_hosts | ||
676 | files installed and frequently | ||
677 | connect new hosts. Basically this option forces the user to manually | ||
678 | add any new hosts. Normally this option is disabled, and new hosts | ||
679 | will automatically be added to the known host files. The host keys of | ||
680 | known hosts will be verified automatically in either case. The | ||
681 | argument must be | ||
682 | .Dq yes | ||
683 | or | ||
684 | .Dq no . | ||
685 | .It Cm User | ||
686 | Specifies the user to log in as. This can be useful if you have a | ||
687 | different user name in different machines. This saves the trouble of | ||
688 | having to remember to give the user name on the command line. | ||
689 | .It Cm UserKnownHostsFile | ||
690 | Specifies a file to use instead of | ||
691 | .Pa $HOME/.ssh/known_hosts . | ||
692 | .It Cm UsePrivilegedPort | ||
693 | Specifies whether to use a privileged port for outgoing connections. | ||
694 | The argument must be | ||
695 | .Dq yes | ||
696 | or | ||
697 | .Dq no . | ||
698 | The default is | ||
699 | .Dq yes . | ||
700 | Note that setting this option to | ||
701 | .Dq no | ||
702 | turns of | ||
703 | .Cm RhostsAuthentication | ||
704 | and | ||
705 | .Cm RhostsRSAAuthentication . | ||
706 | .It Cm UseRsh | ||
707 | Specifies that rlogin/rsh should be used for this host. It is | ||
708 | possible that the host does not at all support the | ||
709 | .Nm | ||
710 | protocol. This causes | ||
711 | .Nm | ||
712 | to immediately exec | ||
713 | .Xr rsh 1 . | ||
714 | All other options (except | ||
715 | .Cm HostName ) | ||
716 | are ignored if this has been specified. The argument must be | ||
717 | .Dq yes | ||
718 | or | ||
719 | .Dq no . | ||
720 | .Sh ENVIRONMENT | ||
721 | .Nm | ||
722 | will normally set the following environment variables: | ||
723 | .Bl -tag -width Ds | ||
724 | .It Ev DISPLAY | ||
725 | The | ||
726 | .Ev DISPLAY | ||
727 | variable indicates the location of the X11 server. It is | ||
728 | automatically set by | ||
729 | .Nm | ||
730 | to point to a value of the form | ||
731 | .Dq hostname:n | ||
732 | where hostname indicates | ||
733 | the host where the shell runs, and n is an integer >= 1. Ssh uses | ||
734 | this special value to forward X11 connections over the secure | ||
735 | channel. The user should normally not set DISPLAY explicitly, as that | ||
736 | will render the X11 connection insecure (and will require the user to | ||
737 | manually copy any required authorization cookies). | ||
738 | .It Ev HOME | ||
739 | Set to the path of the user's home directory. | ||
740 | .It Ev LOGNAME | ||
741 | Synonym for | ||
742 | .Ev USER ; | ||
743 | set for compatibility with systems that use this variable. | ||
744 | .It Ev MAIL | ||
745 | Set to point the user's mailbox. | ||
746 | .It Ev PATH | ||
747 | Set to the default | ||
748 | .Ev PATH , | ||
749 | as specified when compiling | ||
750 | .Nm ssh . | ||
751 | .It Ev SSH_AUTH_SOCK | ||
752 | indicates the path of a unix-domain socket used to communicate with the | ||
753 | agent. | ||
754 | .It Ev SSH_CLIENT | ||
755 | Identifies the client end of the connection. The variable contains | ||
756 | three space-separated values: client ip-address, client port number, | ||
757 | and server port number. | ||
758 | .It Ev SSH_TTY | ||
759 | This is set to the name of the tty (path to the device) associated | ||
760 | with the current shell or command. If the current session has no tty, | ||
761 | this variable is not set. | ||
762 | .It Ev TZ | ||
763 | The timezone variable is set to indicate the present timezone if it | ||
764 | was set when the daemon was started (e.i., the daemon passes the value | ||
765 | on to new connections). | ||
766 | .It Ev USER | ||
767 | Set to the name of the user logging in. | ||
768 | .El | ||
769 | .Pp | ||
770 | Additionally, | ||
771 | .Nm | ||
772 | reads | ||
773 | .Pa $HOME/.ssh/environment , | ||
774 | and adds lines of the format | ||
775 | .Dq VARNAME=value | ||
776 | to the environment. | ||
777 | .Sh FILES | ||
778 | .Bl -tag -width $HOME/.ssh/known_hosts | ||
779 | .It Pa $HOME/.ssh/known_hosts | ||
780 | Records host keys for all hosts the user has logged into (that are not | ||
781 | in | ||
782 | .Pa /etc/ssh_known_hosts ) . | ||
783 | See | ||
784 | .Xr sshd 8 . | ||
785 | .It Pa $HOME/.ssh/random_seed | ||
786 | Used for seeding the random number generator. This file contains | ||
787 | sensitive data and should read/write for the user and not accessible | ||
788 | for others. This file is created the first time the program is run | ||
789 | and updated automatically. The user should never need to read or | ||
790 | modify this file. | ||
791 | .It Pa $HOME/.ssh/identity | ||
792 | Contains the RSA authentication identity of the user. This file | ||
793 | contains sensitive data and should be readable by the user but not | ||
794 | accessible by others (read/write/execute). | ||
795 | Note that | ||
796 | .Nm | ||
797 | ignores this file if it is accessible by others. | ||
798 | It is possible to specify a passphrase when | ||
799 | generating the key; the passphrase will be used to encrypt the | ||
800 | sensitive part of this file using 3DES. | ||
801 | .It Pa $HOME/.ssh/identity.pub | ||
802 | Contains the public key for authentication (public part of the | ||
803 | identity file in human-readable form). The contents of this file | ||
804 | should be added to | ||
805 | .Pa $HOME/.ssh/authorized_keys | ||
806 | on all machines | ||
807 | where you wish to log in using RSA authentication. This file is not | ||
808 | sensitive and can (but need not) be readable by anyone. This file is | ||
809 | never used automatically and is not necessary; it is only provided for | ||
810 | the convenience of the user. | ||
811 | .It Pa $HOME/.ssh/config | ||
812 | This is the per-user configuration file. The format of this file is | ||
813 | described above. This file is used by the | ||
814 | .Nm | ||
815 | client. This file does not usually contain any sensitive information, | ||
816 | but the recommended permissions are read/write for the user, and not | ||
817 | accessible by others. | ||
818 | .It Pa $HOME/.ssh/authorized_keys | ||
819 | Lists the RSA keys that can be used for logging in as this user. The | ||
820 | format of this file is described in the | ||
821 | .Xr sshd 8 | ||
822 | manual page. In the simplest form the format is the same as the .pub | ||
823 | identity files (that is, each line contains the number of bits in | ||
824 | modulus, public exponent, modulus, and comment fields, separated by | ||
825 | spaces). This file is not highly sensitive, but the recommended | ||
826 | permissions are read/write for the user, and not accessible by others. | ||
827 | .It Pa /etc/ssh_known_hosts | ||
828 | Systemwide list of known host keys. This file should be prepared by the | ||
829 | system administrator to contain the public host keys of all machines in the | ||
830 | organization. This file should be world-readable. This file contains | ||
831 | public keys, one per line, in the following format (fields separated | ||
832 | by spaces): system name, number of bits in modulus, public exponent, | ||
833 | modulus, and optional comment field. When different names are used | ||
834 | for the same machine, all such names should be listed, separated by | ||
835 | commas. The format is described on the | ||
836 | .Xr sshd 8 | ||
837 | manual page. | ||
838 | .Pp | ||
839 | The canonical system name (as returned by name servers) is used by | ||
840 | .Xr sshd 8 | ||
841 | to verify the client host when logging in; other names are needed because | ||
842 | .Nm | ||
843 | does not convert the user-supplied name to a canonical name before | ||
844 | checking the key, because someone with access to the name servers | ||
845 | would then be able to fool host authentication. | ||
846 | .It Pa /etc/ssh_config | ||
847 | Systemwide configuration file. This file provides defaults for those | ||
848 | values that are not specified in the user's configuration file, and | ||
849 | for those users who do not have a configuration file. This file must | ||
850 | be world-readable. | ||
851 | .It Pa $HOME/.rhosts | ||
852 | This file is used in | ||
853 | .Pa \&.rhosts | ||
854 | authentication to list the | ||
855 | host/user pairs that are permitted to log in. (Note that this file is | ||
856 | also used by rlogin and rsh, which makes using this file insecure.) | ||
857 | Each line of the file contains a host name (in the canonical form | ||
858 | returned by name servers), and then a user name on that host, | ||
859 | separated by a space. One some machines this file may need to be | ||
860 | world-readable if the user's home directory is on a NFS partition, | ||
861 | because | ||
862 | .Xr sshd 8 | ||
863 | reads it as root. Additionally, this file must be owned by the user, | ||
864 | and must not have write permissions for anyone else. The recommended | ||
865 | permission for most machines is read/write for the user, and not | ||
866 | accessible by others. | ||
867 | .Pp | ||
868 | Note that by default | ||
869 | .Xr sshd 8 | ||
870 | will be installed so that it requires successful RSA host | ||
871 | authentication before permitting \s+2.\s0rhosts authentication. If your | ||
872 | server machine does not have the client's host key in | ||
873 | .Pa /etc/ssh_known_hosts , | ||
874 | you can store it in | ||
875 | .Pa $HOME/.ssh/known_hosts . | ||
876 | The easiest way to do this is to | ||
877 | connect back to the client from the server machine using ssh; this | ||
878 | will automatically add the host key inxi | ||
879 | .Pa $HOME/.ssh/known_hosts . | ||
880 | .It Pa $HOME/.shosts | ||
881 | This file is used exactly the same way as | ||
882 | .Pa \&.rhosts . | ||
883 | The purpose for | ||
884 | having this file is to be able to use rhosts authentication with | ||
885 | .Nm | ||
886 | without permitting login with | ||
887 | .Xr rlogin 1 | ||
888 | or | ||
889 | .Xr rsh 1 . | ||
890 | .It Pa /etc/hosts.equiv | ||
891 | This file is used during | ||
892 | .Pa \&.rhosts authentication. It contains | ||
893 | canonical hosts names, one per line (the full format is described on | ||
894 | the | ||
895 | .Xr sshd 8 | ||
896 | manual page). If the client host is found in this file, login is | ||
897 | automatically permitted provided client and server user names are the | ||
898 | same. Additionally, successful RSA host authentication is normally | ||
899 | required. This file should only be writable by root. | ||
900 | .It Pa /etc/shosts.equiv | ||
901 | This file is processed exactly as | ||
902 | .Pa /etc/hosts.equiv . | ||
903 | This file may be useful to permit logins using | ||
904 | .Nm | ||
905 | but not using rsh/rlogin. | ||
906 | .It Pa /etc/sshrc | ||
907 | Commands in this file are executed by | ||
908 | .Nm | ||
909 | when the user logs in just before the user's shell (or command) is started. | ||
910 | See the | ||
911 | .Xr sshd 8 | ||
912 | manual page for more information. | ||
913 | .It Pa $HOME/.ssh/rc | ||
914 | Commands in this file are executed by | ||
915 | .Nm | ||
916 | when the user logs in just before the user's shell (or command) is | ||
917 | started. | ||
918 | See the | ||
919 | .Xr sshd 8 | ||
920 | manual page for more information. | ||
921 | .It Pa libcrypto.so.X.1 | ||
922 | A version of this library which includes support for the RSA algorithm | ||
923 | is required for proper operation. | ||
924 | .Sh AUTHOR | ||
925 | Tatu Ylonen <ylo@cs.hut.fi> | ||
926 | .Pp | ||
927 | Issues can be found from the SSH WWW home page: | ||
928 | .Pp | ||
929 | .Dl http://www.cs.hut.fi/ssh | ||
930 | .Pp | ||
931 | OpenSSH | ||
932 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | ||
933 | removed and newer features re-added. Rapidly after the 1.2.12 release, | ||
934 | newer versions bore successively more restrictive licenses. This version | ||
935 | of OpenSSH | ||
936 | .Bl -bullet | ||
937 | .It | ||
938 | has all components of a restrictive nature (ie. patents, see | ||
939 | .Xr ssl 8 ) | ||
940 | directly removed from the source code; any licensed or patented components | ||
941 | are chosen from | ||
942 | external libraries. | ||
943 | .It | ||
944 | has been updated to support ssh protocol 1.5. | ||
945 | .It | ||
946 | contains added support for | ||
947 | .Xr kerberos 8 | ||
948 | authentication and ticket passing. | ||
949 | .It | ||
950 | supports one-time password authentication with | ||
951 | .Xr skey 1 . | ||
952 | .El | ||
953 | .Pp | ||
954 | The libraries described in | ||
955 | .Xr ssl 8 | ||
956 | are required for proper operation. | ||
957 | .Sh SEE ALSO | ||
958 | .Xr rlogin 1 , | ||
959 | .Xr rsh 1 , | ||
960 | .Xr scp 1 , | ||
961 | .Xr ssh-add 1 , | ||
962 | .Xr ssh-agent 1 , | ||
963 | .Xr ssh-keygen 1 , | ||
964 | .Xr telnet 1 , | ||
965 | .Xr sshd 8 , | ||
966 | .Xr ssl 8 | ||
@@ -0,0 +1,781 @@ | |||
1 | .\" -*- nroff -*- | ||
2 | .\" | ||
3 | .\" sshd.8.in | ||
4 | .\" | ||
5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | ||
6 | .\" | ||
7 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | ||
8 | .\" All rights reserved | ||
9 | .\" | ||
10 | .\" Created: Sat Apr 22 21:55:14 1995 ylo | ||
11 | .\" | ||
12 | .\" $Id: sshd.8,v 1.3 1999/10/28 23:15:50 damien Exp $ | ||
13 | .\" | ||
14 | .Dd September 25, 1999 | ||
15 | .Dt SSHD 8 | ||
16 | .Os | ||
17 | .Sh NAME | ||
18 | .Nm sshd | ||
19 | .Nd secure shell daemon | ||
20 | .Sh SYNOPSIS | ||
21 | .Nm sshd | ||
22 | .Op Fl diq | ||
23 | .Op Fl b Ar bits | ||
24 | .Op Fl f Ar config_file | ||
25 | .Op Fl g Ar login_grace_time | ||
26 | .Op Fl h Ar host_key_file | ||
27 | .Op Fl k Ar key_gen_time | ||
28 | .Op Fl p Ar port | ||
29 | .Sh DESCRIPTION | ||
30 | .Nm | ||
31 | (Secure Shell Daemon) is the daemon program for | ||
32 | .Xr ssh 1 . | ||
33 | Together these programs replace rlogin and rsh programs, and | ||
34 | provide secure encrypted communications between two untrusted hosts | ||
35 | over an insecure network. The programs are intended to be as easy to | ||
36 | install and use as possible. | ||
37 | .Pp | ||
38 | .Nm | ||
39 | is the daemon that listens for connections from clients. It is | ||
40 | normally started at boot from | ||
41 | .Pa /etc/rc . | ||
42 | It forks a new | ||
43 | daemon for each incoming connection. The forked daemons handle | ||
44 | key exchange, encryption, authentication, command execution, | ||
45 | and data exchange. | ||
46 | .Pp | ||
47 | .Nm | ||
48 | works as follows. Each host has a host-specific RSA key | ||
49 | (normally 1024 bits) used to identify the host. Additionally, when | ||
50 | the daemon starts, it generates a server RSA key (normally 768 bits). | ||
51 | This key is normally regenerated every hour if it has been used, and | ||
52 | is never stored on disk. | ||
53 | .Pp | ||
54 | Whenever a client connects the daemon, the daemon sends its host | ||
55 | and server public keys to the client. The client compares the | ||
56 | host key against its own database to verify that it has not changed. | ||
57 | The client then generates a 256 bit random number. It encrypts this | ||
58 | random number using both the host key and the server key, and sends | ||
59 | the encrypted number to the server. Both sides then start to use this | ||
60 | random number as a session key which is used to encrypt all further | ||
61 | communications in the session. The rest of the session is encrypted | ||
62 | using a conventional cipher, currently Blowfish and 3DES, with 3DES | ||
63 | being is used by default. The client selects the encryption algorithm | ||
64 | to use from those offered by the server. | ||
65 | .Pp | ||
66 | Next, the server and the client enter an authentication dialog. The | ||
67 | client tries to authenticate itself using | ||
68 | .Pa .rhosts | ||
69 | authentication, | ||
70 | .Pa .rhosts | ||
71 | authentication combined with RSA host | ||
72 | authentication, RSA challenge-response authentication, or password | ||
73 | based authentication. | ||
74 | .Pp | ||
75 | Rhosts authentication is normally disabled | ||
76 | because it is fundamentally insecure, but can be enabled in the server | ||
77 | configuration file if desired. System security is not improved unless | ||
78 | .Xr rshd 8 , | ||
79 | .Xr rlogind 8 , | ||
80 | .Xr rexecd 8 , | ||
81 | and | ||
82 | .Xr rexd 8 | ||
83 | are disabled (thus completely disabling | ||
84 | .Xr rlogin 1 | ||
85 | and | ||
86 | .Xr rsh 1 | ||
87 | into that machine). | ||
88 | .Pp | ||
89 | If the client successfully authenticates itself, a dialog for | ||
90 | preparing the session is entered. At this time the client may request | ||
91 | things like allocating a pseudo-tty, forwarding X11 connections, | ||
92 | forwarding TCP/IP connections, or forwarding the authentication agent | ||
93 | connection over the secure channel. | ||
94 | .Pp | ||
95 | Finally, the client either requests a shell or execution of a command. | ||
96 | The sides then enter session mode. In this mode, either side may send | ||
97 | data at any time, and such data is forwarded to/from the shell or | ||
98 | command on the server side, and the user terminal in the client side. | ||
99 | .Pp | ||
100 | When the user program terminates and all forwarded X11 and other | ||
101 | connections have been closed, the server sends command exit status to | ||
102 | the client, and both sides exit. | ||
103 | .Pp | ||
104 | .Nm | ||
105 | can be configured using command-line options or a configuration | ||
106 | file. Command-line options override values specified in the | ||
107 | configuration file. | ||
108 | .Pp | ||
109 | The options are as follows: | ||
110 | .Bl -tag -width Ds | ||
111 | .It Fl b Ar bits | ||
112 | Specifies the number of bits in the server key (default 768). | ||
113 | .Pp | ||
114 | .It Fl d | ||
115 | Debug mode. The server sends verbose debug output to the system | ||
116 | log, and does not put itself in the background. The server also will | ||
117 | not fork and will only process one connection. This option is only | ||
118 | intended for debugging for the server. | ||
119 | .It Fl f Ar configuration_file | ||
120 | Specifies the name of the configuration file. The default is | ||
121 | .Pa /etc/sshd_config . | ||
122 | .Nm | ||
123 | refuses to start if there is no configuration file. | ||
124 | .It Fl g Ar login_grace_time | ||
125 | Gives the grace time for clients to authenticate themselves (default | ||
126 | 300 seconds). If the client fails to authenticate the user within | ||
127 | this many seconds, the server disconnects and exits. A value of zero | ||
128 | indicates no limit. | ||
129 | .It Fl h Ar host_key_file | ||
130 | Specifies the file from which the host key is read (default | ||
131 | .Pa /etc/ssh_host_key ) . | ||
132 | This option must be given if | ||
133 | .Nm | ||
134 | is not run as root (as the normal | ||
135 | host file is normally not readable by anyone but root). | ||
136 | .It Fl i | ||
137 | Specifies that | ||
138 | .Nm | ||
139 | is being run from inetd. | ||
140 | .Nm | ||
141 | is normally not run | ||
142 | from inetd because it needs to generate the server key before it can | ||
143 | respond to the client, and this may take tens of seconds. Clients | ||
144 | would have to wait too long if the key was regenerated every time. | ||
145 | However, with small key sizes (e.g. 512) using | ||
146 | .Nm | ||
147 | from inetd may | ||
148 | be feasible. | ||
149 | .It Fl k Ar key_gen_time | ||
150 | Specifies how often the server key is regenerated (default 3600 | ||
151 | seconds, or one hour). The motivation for regenerating the key fairly | ||
152 | often is that the key is not stored anywhere, and after about an hour, | ||
153 | it becomes impossible to recover the key for decrypting intercepted | ||
154 | communications even if the machine is cracked into or physically | ||
155 | seized. A value of zero indicates that the key will never be regenerated. | ||
156 | .It Fl p Ar port | ||
157 | Specifies the port on which the server listens for connections | ||
158 | (default 22). | ||
159 | .It Fl q | ||
160 | Quiet mode. Nothing is sent to the system log. Normally the beginning, | ||
161 | authentication, and termination of each connection is logged. | ||
162 | .It Fl Q | ||
163 | Do not print an error message if RSA support is missing. | ||
164 | .El | ||
165 | .Sh CONFIGURATION FILE | ||
166 | .Nm | ||
167 | reads configuration data from | ||
168 | .Pa /etc/sshd_config | ||
169 | (or the file specified with | ||
170 | .Fl f | ||
171 | on the command line). The file | ||
172 | contains keyword-value pairs, one per line. Lines starting with | ||
173 | .Ql # | ||
174 | and empty lines are interpreted as comments. | ||
175 | .Pp | ||
176 | The following keywords are possible. | ||
177 | .Bl -tag -width Ds | ||
178 | .It Cm AFSTokenPassing | ||
179 | Specifies whether an AFS token may be forwarded to the server. Default is | ||
180 | .Dq yes . | ||
181 | .It Cm AllowGroups | ||
182 | This keyword can be followed by a number of group names, separated | ||
183 | by spaces. If specified, login is allowed only for users whose primary | ||
184 | group matches one of the patterns. | ||
185 | .Ql \&* | ||
186 | and | ||
187 | .Ql ? | ||
188 | can be used as | ||
189 | wildcards in the patterns. Only group names are valid, a numerical group | ||
190 | id isn't recognized. By default login is allowed regardless of | ||
191 | the primary group. | ||
192 | .Pp | ||
193 | .It Cm AllowUsers | ||
194 | This keyword can be followed by a number of user names, separated | ||
195 | by spaces. If specified, login is allowed only for users names that | ||
196 | match one of the patterns. | ||
197 | .Ql \&* | ||
198 | and | ||
199 | .Ql ? | ||
200 | can be used as | ||
201 | wildcards in the patterns. Only user names are valid, a numerical user | ||
202 | id isn't recognized. By default login is allowed regardless of | ||
203 | the user name. | ||
204 | .Pp | ||
205 | .It Cm CheckMail | ||
206 | Specifies whether | ||
207 | .Nm | ||
208 | should check for new mail for interactive logins. | ||
209 | The default is | ||
210 | .Dq no . | ||
211 | .It Cm DenyGroups | ||
212 | This keyword can be followed by a number of group names, separated | ||
213 | by spaces. Users whose primary group matches one of the patterns | ||
214 | aren't allowed to log in. | ||
215 | .Ql \&* | ||
216 | and | ||
217 | .Ql ? | ||
218 | can be used as | ||
219 | wildcards in the patterns. Only group names are valid, a numerical group | ||
220 | id isn't recognized. By default login is allowed regardless of | ||
221 | the primary group. | ||
222 | .Pp | ||
223 | .It Cm DenyUsers | ||
224 | This keyword can be followed by a number of user names, separated | ||
225 | by spaces. Login is allowed disallowed for user names that match | ||
226 | one of the patterns. | ||
227 | .Ql \&* | ||
228 | and | ||
229 | .Ql ? | ||
230 | can be used as | ||
231 | wildcards in the patterns. Only user names are valid, a numerical user | ||
232 | id isn't recognized. By default login is allowed regardless of | ||
233 | the user name. | ||
234 | .Pp | ||
235 | .It Cm FascistLogging | ||
236 | Specifies whether to use verbose logging. Verbose logging violates | ||
237 | the privacy of users and is not recommended. The argument must be | ||
238 | .Dq yes | ||
239 | or | ||
240 | .Dq no . | ||
241 | The default is | ||
242 | .Dq no . | ||
243 | .It Cm HostKey | ||
244 | Specifies the file containing the private host key (default | ||
245 | .Pa /etc/ssh_host_key ) . | ||
246 | Note that | ||
247 | .Nm | ||
248 | does not start if this file is group/world-accessible. | ||
249 | .It Cm IgnoreRhosts | ||
250 | Specifies that rhosts and shosts files will not be used in | ||
251 | authentication. | ||
252 | .Pa /etc/hosts.equiv | ||
253 | and | ||
254 | .Pa /etc/shosts.equiv | ||
255 | are still used. The default is | ||
256 | .Dq no . | ||
257 | .It Cm KeepAlive | ||
258 | Specifies whether the system should send keepalive messages to the | ||
259 | other side. If they are sent, death of the connection or crash of one | ||
260 | of the machines will be properly noticed. However, this means that | ||
261 | connections will die if the route is down temporarily, and some people | ||
262 | find it annoying. On the other hand, if keepalives are not send, | ||
263 | sessions may hang indefinitely on the server, leaving | ||
264 | .Dq ghost | ||
265 | users and consuming server resources. | ||
266 | .Pp | ||
267 | The default is | ||
268 | .Dq yes | ||
269 | (to send keepalives), and the server will notice | ||
270 | if the network goes down or the client host reboots. This avoids | ||
271 | infinitely hanging sessions. | ||
272 | .Pp | ||
273 | To disable keepalives, the value should be set to | ||
274 | .Dq no | ||
275 | in both the server and the client configuration files. | ||
276 | .It Cm KerberosAuthentication | ||
277 | Specifies whether Kerberos authentication is allowed. This can | ||
278 | be in the form of a Kerberos ticket, or if | ||
279 | .Cm PasswordAuthentication | ||
280 | is yes, the password provided by the user will be validated through | ||
281 | the Kerberos KDC. Default is | ||
282 | .Dq yes . | ||
283 | .It Cm KerberosOrLocalPasswd | ||
284 | If set then if password authentication through Kerberos fails then | ||
285 | the password will be validated via any additional local mechanism | ||
286 | such as | ||
287 | .Pa /etc/passwd | ||
288 | or SecurID. Default is | ||
289 | .Dq yes . | ||
290 | .It Cm KerberosTgtPassing | ||
291 | Specifies whether a Kerberos TGT may be forwarded to the server. | ||
292 | Default is | ||
293 | .Dq no , | ||
294 | as this only works when the Kerberos KDC is actually an AFS kaserver. | ||
295 | .It Cm KerberosTicketCleanup | ||
296 | Specifies whether to automatically destroy the user's ticket cache | ||
297 | file on logout. Default is | ||
298 | .Dq yes . | ||
299 | .It Cm KeyRegenerationInterval | ||
300 | The server key is automatically regenerated after this many seconds | ||
301 | (if it has been used). The purpose of regeneration is to prevent | ||
302 | decrypting captured sessions by later breaking into the machine and | ||
303 | stealing the keys. The key is never stored anywhere. If the value is | ||
304 | 0, the key is never regenerated. The default is 3600 | ||
305 | (seconds). | ||
306 | .It Cm ListenAddress | ||
307 | Specifies what local address | ||
308 | .Nm | ||
309 | should listen on. | ||
310 | The default is to listen to all local addresses. | ||
311 | .It Cm LoginGraceTime | ||
312 | The server disconnects after this time if the user has not | ||
313 | successfully logged in. If the value is 0, there is no time limit. | ||
314 | The default is 600 (seconds). | ||
315 | .It Cm PasswordAuthentication | ||
316 | Specifies whether password authentication is allowed. | ||
317 | The default is | ||
318 | .Dq yes . | ||
319 | .It Cm PermitEmptyPasswords | ||
320 | When password authentication is allowed, it specifies whether the | ||
321 | server allows login to accounts with empty password strings. The default | ||
322 | is | ||
323 | .Dq yes . | ||
324 | .It Cm PermitRootLogin | ||
325 | Specifies whether the root can log in using | ||
326 | .Xr ssh 1 . | ||
327 | The argument must be | ||
328 | .Dq yes , | ||
329 | .Dq without-password | ||
330 | or | ||
331 | .Dq no . | ||
332 | The default is | ||
333 | .Dq yes . | ||
334 | If this options is set to | ||
335 | .Dq without-password | ||
336 | only password authentication is disabled for root. | ||
337 | .Pp | ||
338 | Root login with RSA authentication when the | ||
339 | .Ar command | ||
340 | option has been | ||
341 | specified will be allowed regardless of the value of this setting | ||
342 | (which may be useful for taking remote backups even if root login is | ||
343 | normally not allowed). | ||
344 | .It Cm Port | ||
345 | Specifies the port number that | ||
346 | .Nm | ||
347 | listens on. The default is 22. | ||
348 | .It Cm PrintMotd | ||
349 | Specifies whether | ||
350 | .Nm | ||
351 | should print | ||
352 | .Pa /etc/motd | ||
353 | when a user logs in interactively. (On some systems it is also | ||
354 | printed by the shell, | ||
355 | .Pa /etc/profile , | ||
356 | or equivalent.) The default is | ||
357 | .Dq yes . | ||
358 | .It Cm QuietMode | ||
359 | Specifies whether the system runs in quiet mode. In quiet mode, | ||
360 | nothing is logged in the system log, except fatal errors. The default | ||
361 | is | ||
362 | .Dq no . | ||
363 | .It Cm RandomSeed | ||
364 | Obsolete. Random number generation uses other techniques. | ||
365 | .It Cm RhostsAuthentication | ||
366 | Specifies whether authentication using rhosts or /etc/hosts.equiv | ||
367 | files is sufficient. Normally, this method should not be permitted | ||
368 | because it is insecure. | ||
369 | .Cm RhostsRSAAuthentication | ||
370 | should be used | ||
371 | instead, because it performs RSA-based host authentication in addition | ||
372 | to normal rhosts or /etc/hosts.equiv authentication. | ||
373 | The default is | ||
374 | .Dq no . | ||
375 | .It Cm RhostsRSAAuthentication | ||
376 | Specifies whether rhosts or /etc/hosts.equiv authentication together | ||
377 | with successful RSA host authentication is allowed. The default is | ||
378 | .Dq yes . | ||
379 | .It Cm RSAAuthentication | ||
380 | Specifies whether pure RSA authentication is allowed. The default is | ||
381 | .Dq yes . | ||
382 | .It Cm ServerKeyBits | ||
383 | Defines the number of bits in the server key. The minimum value is | ||
384 | 512, and the default is 768. | ||
385 | .It Cm SkeyAuthentication | ||
386 | Specifies whether | ||
387 | .Xr skey 1 | ||
388 | authentication is allowed. The default is | ||
389 | .Dq yes . | ||
390 | Note that s/key authentication is enabled only if | ||
391 | .Cm PasswordAuthentication | ||
392 | is allowed, too. | ||
393 | .It Cm StrictModes | ||
394 | Specifies whether | ||
395 | .Nm | ||
396 | should check file modes and ownership of the | ||
397 | user's files and home directory before accepting login. This | ||
398 | is normally desirable because novices sometimes accidentally leave their | ||
399 | directory or files world-writable. The default is | ||
400 | .Dq yes . | ||
401 | .It Cm SyslogFacility | ||
402 | Gives the facility code that is used when logging messages from | ||
403 | .Nm sshd . | ||
404 | The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2, | ||
405 | LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7. The default is AUTH. | ||
406 | .It Cm UseLogin | ||
407 | Specifies whether | ||
408 | .Xr login 1 | ||
409 | is used. The default is | ||
410 | .Dq no . | ||
411 | .It Cm X11Forwarding | ||
412 | Specifies whether X11 forwarding is permitted. The default is | ||
413 | .Dq yes . | ||
414 | Note that disabling X11 forwarding does not improve security in any | ||
415 | way, as users can always install their own forwarders. | ||
416 | .It Cm X11DisplayOffset | ||
417 | Specifies the first display number available for | ||
418 | .Nm sshd Ns 's | ||
419 | X11 forwarding. This prevents | ||
420 | .Nm | ||
421 | from interfering with real X11 servers. | ||
422 | .El | ||
423 | .Sh LOGIN PROCESS | ||
424 | When a user successfully logs in, | ||
425 | .Nm | ||
426 | does the following: | ||
427 | .Bl -enum -offset indent | ||
428 | .It | ||
429 | If the login is on a tty, and no command has been specified, | ||
430 | prints last login time and | ||
431 | .Pa /etc/motd | ||
432 | (unless prevented in the configuration file or by | ||
433 | .Pa $HOME/.hushlogin ; | ||
434 | see the | ||
435 | .Sx FILES | ||
436 | section). | ||
437 | .It | ||
438 | If the login is on a tty, records login time. | ||
439 | .It | ||
440 | Checks | ||
441 | .Pa /etc/nologin ; | ||
442 | if it exists, prints contents and quits | ||
443 | (unless root). | ||
444 | .It | ||
445 | Changes to run with normal user privileges. | ||
446 | .It | ||
447 | Sets up basic environment. | ||
448 | .It | ||
449 | Reads | ||
450 | .Pa $HOME/.ssh/environment | ||
451 | if it exists. | ||
452 | .It | ||
453 | Changes to user's home directory. | ||
454 | .It | ||
455 | If | ||
456 | .Pa $HOME/.ssh/rc | ||
457 | exists, runs it; else if | ||
458 | .Pa /etc/sshrc | ||
459 | exists, runs | ||
460 | it; otherwise runs xauth. The | ||
461 | .Dq rc | ||
462 | files are given the X11 | ||
463 | authentication protocol and cookie in standard input. | ||
464 | .It | ||
465 | Runs user's shell or command. | ||
466 | .El | ||
467 | .Sh AUTHORIZED_KEYS FILE FORMAT | ||
468 | The | ||
469 | .Pa $HOME/.ssh/authorized_keys | ||
470 | file lists the RSA keys that are | ||
471 | permitted for RSA authentication. Each line of the file contains one | ||
472 | key (empty lines and lines starting with a | ||
473 | .Ql # | ||
474 | are ignored as | ||
475 | comments). Each line consists of the following fields, separated by | ||
476 | spaces: options, bits, exponent, modulus, comment. The options field | ||
477 | is optional; its presence is determined by whether the line starts | ||
478 | with a number or not (the option field never starts with a number). | ||
479 | The bits, exponent, modulus and comment fields give the RSA key; the | ||
480 | comment field is not used for anything (but may be convenient for the | ||
481 | user to identify the key). | ||
482 | .Pp | ||
483 | Note that lines in this file are usually several hundred bytes long | ||
484 | (because of the size of the RSA key modulus). You don't want to type | ||
485 | them in; instead, copy the | ||
486 | .Pa identity.pub | ||
487 | file and edit it. | ||
488 | .Pp | ||
489 | The options (if present) consists of comma-separated option | ||
490 | specifications. No spaces are permitted, except within double quotes. | ||
491 | The following option specifications are supported: | ||
492 | .Bl -tag -width Ds | ||
493 | .It Cm from="pattern-list" | ||
494 | Specifies that in addition to RSA authentication, the canonical name | ||
495 | of the remote host must be present in the comma-separated list of | ||
496 | patterns ('*' and '?' serve as wildcards). The list may also contain | ||
497 | patterns negated by prefixing them with '!'; if the canonical host | ||
498 | name matches a negated pattern, the key is not accepted. The purpose | ||
499 | of this option is to optionally increase security: RSA authentication | ||
500 | by itself does not trust the network or name servers or anything (but | ||
501 | the key); however, if somebody somehow steals the key, the key | ||
502 | permits an intruder to log in from anywhere in the world. This | ||
503 | additional option makes using a stolen key more difficult (name | ||
504 | servers and/or routers would have to be compromised in addition to | ||
505 | just the key). | ||
506 | .It Cm command="command" | ||
507 | Specifies that the command is executed whenever this key is used for | ||
508 | authentication. The command supplied by the user (if any) is ignored. | ||
509 | The command is run on a pty if the connection requests a pty; | ||
510 | otherwise it is run without a tty. A quote may be included in the | ||
511 | command by quoting it with a backslash. This option might be useful | ||
512 | to restrict certain RSA keys to perform just a specific operation. An | ||
513 | example might be a key that permits remote backups but nothing | ||
514 | else. Notice that the client may specify TCP/IP and/or X11 | ||
515 | forwardings unless they are explicitly prohibited. | ||
516 | .It Cm environment="NAME=value" | ||
517 | Specifies that the string is to be added to the environment when | ||
518 | logging in using this key. Environment variables set this way | ||
519 | override other default environment values. Multiple options of this | ||
520 | type are permitted. | ||
521 | .It Cm no-port-forwarding | ||
522 | Forbids TCP/IP forwarding when this key is used for authentication. | ||
523 | Any port forward requests by the client will return an error. This | ||
524 | might be used, e.g., in connection with the | ||
525 | .Cm command | ||
526 | option. | ||
527 | .It Cm no-X11-forwarding | ||
528 | Forbids X11 forwarding when this key is used for authentication. | ||
529 | Any X11 forward requests by the client will return an error. | ||
530 | .It Cm no-agent-forwarding | ||
531 | Forbids authentication agent forwarding when this key is used for | ||
532 | authentication. | ||
533 | .It Cm no-pty | ||
534 | Prevents tty allocation (a request to allocate a pty will fail). | ||
535 | .El | ||
536 | .Ss Examples | ||
537 | 1024 33 12121.\|.\|.\|312314325 ylo@foo.bar | ||
538 | .Pp | ||
539 | from="*.niksula.hut.fi,!pc.niksula.hut.fi" 1024 35 23.\|.\|.\|2334 ylo@niksula | ||
540 | .Pp | ||
541 | command="dump /home",no-pty,no-port-forwarding 1024 33 23.\|.\|.\|2323 backup.hut.fi | ||
542 | .Sh SSH_KNOWN_HOSTS FILE FORMAT | ||
543 | The | ||
544 | .Pa /etc/ssh_known_hosts | ||
545 | and | ||
546 | .Pa $HOME/.ssh/known_hosts | ||
547 | files contain host public keys for all known hosts. The global file should | ||
548 | be prepared by the admistrator (optional), and the per-user file is | ||
549 | maintained automatically: whenever the user connects an unknown host | ||
550 | its key is added to the per-user file. | ||
551 | .Pp | ||
552 | Each line in these files contains the following fields: hostnames, | ||
553 | bits, exponent, modulus, comment. The fields are separated by spaces. | ||
554 | .Pp | ||
555 | Hostnames is a comma-separated list of patterns ('*' and '?' act as | ||
556 | wildcards); each pattern in turn is matched against the canonical host | ||
557 | name (when authenticating a client) or against the user-supplied | ||
558 | name (when authenticating a server). A pattern may also be preceded | ||
559 | by | ||
560 | .Ql ! | ||
561 | to indicate negation: if the host name matches a negated | ||
562 | pattern, it is not accepted (by that line) even if it matched another | ||
563 | pattern on the line. | ||
564 | .Pp | ||
565 | Bits, exponent, and modulus are taken directly from the host key; they | ||
566 | can be obtained, e.g., from | ||
567 | .Pa /etc/ssh_host_key.pub . | ||
568 | The optional comment field continues to the end of the line, and is not used. | ||
569 | .Pp | ||
570 | Lines starting with | ||
571 | .Ql # | ||
572 | and empty lines are ignored as comments. | ||
573 | .Pp | ||
574 | When performing host authentication, authentication is accepted if any | ||
575 | matching line has the proper key. It is thus permissible (but not | ||
576 | recommended) to have several lines or different host keys for the same | ||
577 | names. This will inevitably happen when short forms of host names | ||
578 | from different domains are put in the file. It is possible | ||
579 | that the files contain conflicting information; authentication is | ||
580 | accepted if valid information can be found from either file. | ||
581 | .Pp | ||
582 | Note that the lines in these files are typically hundreds of characters | ||
583 | long, and you definitely don't want to type in the host keys by hand. | ||
584 | Rather, generate them by a script | ||
585 | or by taking | ||
586 | .Pa /etc/ssh_host_key.pub | ||
587 | and adding the host names at the front. | ||
588 | .Ss Examples | ||
589 | closenet,closenet.hut.fi,.\|.\|.\|,130.233.208.41 1024 37 159.\|.\|.93 closenet.hut.fi | ||
590 | .Sh FILES | ||
591 | .Bl -tag -width Ds | ||
592 | .It Pa /etc/sshd_config | ||
593 | Contains configuration data for | ||
594 | .Nm sshd . | ||
595 | This file should be writable by root only, but it is recommended | ||
596 | (though not necessary) that it be world-readable. | ||
597 | .It Pa /etc/ssh_host_key | ||
598 | Contains the private part of the host key. | ||
599 | This file should only be owned by root, readable only by root, and not | ||
600 | accessible to others. | ||
601 | Note that | ||
602 | .Nm | ||
603 | does not start if this file is group/world-accessible. | ||
604 | .It Pa /etc/ssh_host_key.pub | ||
605 | Contains the public part of the host key. | ||
606 | This file should be world-readable but writable only by | ||
607 | root. Its contents should match the private part. This file is not | ||
608 | really used for anything; it is only provided for the convenience of | ||
609 | the user so its contents can be copied to known hosts files. | ||
610 | These two files are created using | ||
611 | .Xr ssh-keygen 1 . | ||
612 | .It Pa /var/run/sshd.pid | ||
613 | Contains the process ID of the | ||
614 | .Nm | ||
615 | listening for connections (if there are several daemons running | ||
616 | concurrently for different ports, this contains the pid of the one | ||
617 | started last). The contents of this file are not sensitive; it can be | ||
618 | world-readable. | ||
619 | .It Pa $HOME/.ssh/authorized_keys | ||
620 | Lists the RSA keys that can be used to log into the user's account. | ||
621 | This file must be readable by root (which may on some machines imply | ||
622 | it being world-readable if the user's home directory resides on an NFS | ||
623 | volume). It is recommended that it not be accessible by others. The | ||
624 | format of this file is described above. | ||
625 | .It Pa /etc/ssh_known_hosts | ||
626 | This file is consulted when using rhosts with RSA host | ||
627 | authentication to check the public key of the host. The key must be | ||
628 | listed in this file to be accepted. | ||
629 | .It Pa $HOME/.ssh/known_hosts | ||
630 | The client uses this file | ||
631 | and | ||
632 | .Pa /etc/ssh_known_hosts | ||
633 | to verify that the remote host is the one we intended to | ||
634 | connect. These files should be writable only by root/the owner. | ||
635 | .Pa /etc/ssh_known_hosts | ||
636 | should be world-readable, and | ||
637 | .Pa $HOME/.ssh/known_hosts | ||
638 | can but need not be world-readable. | ||
639 | .It Pa /etc/nologin | ||
640 | If this file exists, | ||
641 | .Nm | ||
642 | refuses to let anyone except root log in. The contents of the file | ||
643 | are displayed to anyone trying to log in, and non-root connections are | ||
644 | refused. The file should be world-readable. | ||
645 | .It Pa /etc/hosts.allow, /etc/hosts.deny | ||
646 | If compiled with | ||
647 | .Sy LIBWRAP | ||
648 | support, tcp-wrappers access controls may be defined here as described in | ||
649 | .Xr hosts_access 5 . | ||
650 | .It Pa $HOME/.rhosts | ||
651 | This file contains host-username pairs, separated by a space, one per | ||
652 | line. The given user on the corresponding host is permitted to log in | ||
653 | without password. The same file is used by rlogind and rshd. | ||
654 | The file must | ||
655 | be writable only by the user; it is recommended that it not be | ||
656 | accessible by others. | ||
657 | .Pp | ||
658 | If is also possible to use netgroups in the file. Either host or user | ||
659 | name may be of the form +@groupname to specify all hosts or all users | ||
660 | in the group. | ||
661 | .It Pa $HOME/.shosts | ||
662 | For ssh, | ||
663 | this file is exactly the same as for | ||
664 | .Pa .rhosts . | ||
665 | However, this file is | ||
666 | not used by rlogin and rshd, so using this permits access using SSH only. | ||
667 | .Pa /etc/hosts.equiv | ||
668 | This file is used during | ||
669 | .Pa .rhosts | ||
670 | authentication. In the | ||
671 | simplest form, this file contains host names, one per line. Users on | ||
672 | those hosts are permitted to log in without a password, provided they | ||
673 | have the same user name on both machines. The host name may also be | ||
674 | followed by a user name; such users are permitted to log in as | ||
675 | .Em any | ||
676 | user on this machine (except root). Additionally, the syntax | ||
677 | .Dq +@group | ||
678 | can be used to specify netgroups. Negated entries start with | ||
679 | .Ql \&- . | ||
680 | .Pp | ||
681 | If the client host/user is successfully matched in this file, login is | ||
682 | automatically permitted provided the client and server user names are the | ||
683 | same. Additionally, successful RSA host authentication is normally | ||
684 | required. This file must be writable only by root; it is recommended | ||
685 | that it be world-readable. | ||
686 | .Pp | ||
687 | .Sy "Warning: It is almost never a good idea to use user names in" | ||
688 | .Pa hosts.equiv . | ||
689 | Beware that it really means that the named user(s) can log in as | ||
690 | .Em anybody , | ||
691 | which includes bin, daemon, adm, and other accounts that own critical | ||
692 | binaries and directories. Using a user name practically grants the | ||
693 | user root access. The only valid use for user names that I can think | ||
694 | of is in negative entries. | ||
695 | .Pp | ||
696 | Note that this warning also applies to rsh/rlogin. | ||
697 | .It Pa /etc/shosts.equiv | ||
698 | This is processed exactly as | ||
699 | .Pa /etc/hosts.equiv . | ||
700 | However, this file may be useful in environments that want to run both | ||
701 | rsh/rlogin and ssh. | ||
702 | .It Pa $HOME/.ssh/environment | ||
703 | This file is read into the environment at login (if it exists). It | ||
704 | can only contain empty lines, comment lines (that start with | ||
705 | .Ql # ) , | ||
706 | and assignment lines of the form name=value. The file should be writable | ||
707 | only by the user; it need not be readable by anyone else. | ||
708 | .It Pa $HOME/.ssh/rc | ||
709 | If this file exists, it is run with /bin/sh after reading the | ||
710 | environment files but before starting the user's shell or command. If | ||
711 | X11 spoofing is in use, this will receive the "proto cookie" pair in | ||
712 | standard input (and | ||
713 | .Ev DISPLAY | ||
714 | in environment). This must call | ||
715 | .Xr xauth 1 | ||
716 | in that case. | ||
717 | .Pp | ||
718 | The primary purpose of this file is to run any initialization routines | ||
719 | which may be needed before the user's home directory becomes | ||
720 | accessible; AFS is a particular example of such an environment. | ||
721 | .Pp | ||
722 | This file will probably contain some initialization code followed by | ||
723 | something similar to: "if read proto cookie; then echo add $DISPLAY | ||
724 | $proto $cookie | xauth -q -; fi". | ||
725 | .Pp | ||
726 | If this file does not exist, | ||
727 | .Pa /etc/sshrc | ||
728 | is run, and if that | ||
729 | does not exist either, xauth is used to store the cookie. | ||
730 | .Pp | ||
731 | This file should be writable only by the user, and need not be | ||
732 | readable by anyone else. | ||
733 | .It Pa /etc/sshrc | ||
734 | Like | ||
735 | .Pa $HOME/.ssh/rc . | ||
736 | This can be used to specify | ||
737 | machine-specific login-time initializations globally. This file | ||
738 | should be writable only by root, and should be world-readable. | ||
739 | .Sh AUTHOR | ||
740 | Tatu Ylonen <ylo@cs.hut.fi> | ||
741 | .Pp | ||
742 | Information about new releases, mailing lists, and other related | ||
743 | issues can be found from the SSH WWW home page: | ||
744 | .Pp | ||
745 | .Dl http://www.cs.hut.fi/ssh. | ||
746 | .Pp | ||
747 | OpenSSH | ||
748 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | ||
749 | removed and newer features re-added. Rapidly after the 1.2.12 release, | ||
750 | newer versions bore successively more restrictive licenses. This version | ||
751 | of OpenSSH | ||
752 | .Bl -bullet | ||
753 | .It | ||
754 | has all components of a restrictive nature (ie. patents, see | ||
755 | .Xr ssl 8 ) | ||
756 | directly removed from the source code; any licensed or patented components | ||
757 | are chosen from | ||
758 | external libraries. | ||
759 | .It | ||
760 | has been updated to support ssh protocol 1.5. | ||
761 | .It | ||
762 | contains added support for | ||
763 | .Xr kerberos 8 | ||
764 | authentication and ticket passing. | ||
765 | .It | ||
766 | supports one-time password authentication with | ||
767 | .Xr skey 1 . | ||
768 | .El | ||
769 | .Pp | ||
770 | The libraries described in | ||
771 | .Xr ssl 8 | ||
772 | are required for proper operation. | ||
773 | .Sh SEE ALSO | ||
774 | .Xr rlogin 1 , | ||
775 | .Xr rsh 1 , | ||
776 | .Xr scp 1 , | ||
777 | .Xr ssh 1 , | ||
778 | .Xr ssh-add 1 , | ||
779 | .Xr ssh-agent 1 , | ||
780 | .Xr ssh-keygen 1 , | ||
781 | .Xr ssl 8 | ||