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author | Colin Watson <cjwatson@debian.org> | 2010-01-24 21:19:46 +0000 |
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committer | Colin Watson <cjwatson@debian.org> | 2010-01-24 21:19:46 +0000 |
commit | 1e4cfeee6c17b02af09418c5afe4a4d71aaaf0c8 (patch) | |
tree | 2b17a8cdc39aef9ad5cd73ecc25b3dfaa6d2267a /ssh-keygen.0 | |
parent | 7fe2877662d34ef04c67884cfcffce60a6444f18 (diff) | |
parent | 54af7a4ae8d455791a631bdfaade4b64436ae16a (diff) |
Import 5.3p1 tarball
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1 | SSH-KEYGEN(1) OpenBSD Reference Manual SSH-KEYGEN(1) | ||
2 | |||
3 | NAME | ||
4 | ssh-keygen - authentication key generation, management and conversion | ||
5 | |||
6 | SYNOPSIS | ||
7 | ssh-keygen [-q] [-b bits] -t type [-N new_passphrase] [-C comment] | ||
8 | [-f output_keyfile] | ||
9 | ssh-keygen -p [-P old_passphrase] [-N new_passphrase] [-f keyfile] | ||
10 | ssh-keygen -i [-f input_keyfile] | ||
11 | ssh-keygen -e [-f input_keyfile] | ||
12 | ssh-keygen -y [-f input_keyfile] | ||
13 | ssh-keygen -c [-P passphrase] [-C comment] [-f keyfile] | ||
14 | ssh-keygen -l [-f input_keyfile] | ||
15 | ssh-keygen -B [-f input_keyfile] | ||
16 | ssh-keygen -D reader | ||
17 | ssh-keygen -F hostname [-f known_hosts_file] [-l] | ||
18 | ssh-keygen -H [-f known_hosts_file] | ||
19 | ssh-keygen -R hostname [-f known_hosts_file] | ||
20 | ssh-keygen -U reader [-f input_keyfile] | ||
21 | ssh-keygen -r hostname [-f input_keyfile] [-g] | ||
22 | ssh-keygen -G output_file [-v] [-b bits] [-M memory] [-S start_point] | ||
23 | ssh-keygen -T output_file -f input_file [-v] [-a num_trials] [-W | ||
24 | generator] | ||
25 | |||
26 | DESCRIPTION | ||
27 | ssh-keygen generates, manages and converts authentication keys for | ||
28 | ssh(1). ssh-keygen can create RSA keys for use by SSH protocol version 1 | ||
29 | and RSA or DSA keys for use by SSH protocol version 2. The type of key | ||
30 | to be generated is specified with the -t option. If invoked without any | ||
31 | arguments, ssh-keygen will generate an RSA key for use in SSH protocol 2 | ||
32 | connections. | ||
33 | |||
34 | ssh-keygen is also used to generate groups for use in Diffie-Hellman | ||
35 | group exchange (DH-GEX). See the MODULI GENERATION section for details. | ||
36 | |||
37 | Normally each user wishing to use SSH with RSA or DSA authentication runs | ||
38 | this once to create the authentication key in ~/.ssh/identity, | ||
39 | ~/.ssh/id_dsa or ~/.ssh/id_rsa. Additionally, the system administrator | ||
40 | may use this to generate host keys, as seen in /etc/rc. | ||
41 | |||
42 | Normally this program generates the key and asks for a file in which to | ||
43 | store the private key. The public key is stored in a file with the same | ||
44 | name but ``.pub'' appended. The program also asks for a passphrase. The | ||
45 | passphrase may be empty to indicate no passphrase (host keys must have an | ||
46 | empty passphrase), or it may be a string of arbitrary length. A | ||
47 | passphrase is similar to a password, except it can be a phrase with a se- | ||
48 | ries of words, punctuation, numbers, whitespace, or any string of charac- | ||
49 | ters you want. Good passphrases are 10-30 characters long, are not sim- | ||
50 | ple sentences or otherwise easily guessable (English prose has only 1-2 | ||
51 | bits of entropy per character, and provides very bad passphrases), and | ||
52 | contain a mix of upper and lowercase letters, numbers, and non-alphanu- | ||
53 | meric characters. The passphrase can be changed later by using the -p | ||
54 | option. | ||
55 | |||
56 | There is no way to recover a lost passphrase. If the passphrase is lost | ||
57 | or forgotten, a new key must be generated and copied to the corresponding | ||
58 | public key to other machines. | ||
59 | |||
60 | For RSA1 keys, there is also a comment field in the key file that is only | ||
61 | for convenience to the user to help identify the key. The comment can | ||
62 | tell what the key is for, or whatever is useful. The comment is initial- | ||
63 | ized to ``user@host'' when the key is created, but can be changed using | ||
64 | the -c option. | ||
65 | |||
66 | After a key is generated, instructions below detail where the keys should | ||
67 | be placed to be activated. | ||
68 | |||
69 | The options are as follows: | ||
70 | |||
71 | -a trials | ||
72 | Specifies the number of primality tests to perform when screening | ||
73 | DH-GEX candidates using the -T command. | ||
74 | |||
75 | -B Show the bubblebabble digest of specified private or public key | ||
76 | file. | ||
77 | |||
78 | -b bits | ||
79 | Specifies the number of bits in the key to create. For RSA keys, | ||
80 | the minimum size is 768 bits and the default is 2048 bits. Gen- | ||
81 | erally, 2048 bits is considered sufficient. DSA keys must be ex- | ||
82 | actly 1024 bits as specified by FIPS 186-2. | ||
83 | |||
84 | -C comment | ||
85 | Provides a new comment. | ||
86 | |||
87 | -c Requests changing the comment in the private and public key | ||
88 | files. This operation is only supported for RSA1 keys. The pro- | ||
89 | gram will prompt for the file containing the private keys, for | ||
90 | the passphrase if the key has one, and for the new comment. | ||
91 | |||
92 | -D reader | ||
93 | Download the RSA public key stored in the smartcard in reader. | ||
94 | |||
95 | -e This option will read a private or public OpenSSH key file and | ||
96 | print the key in RFC 4716 SSH Public Key File Format to stdout. | ||
97 | This option allows exporting keys for use by several commercial | ||
98 | SSH implementations. | ||
99 | |||
100 | -F hostname | ||
101 | Search for the specified hostname in a known_hosts file, listing | ||
102 | any occurrences found. This option is useful to find hashed host | ||
103 | names or addresses and may also be used in conjunction with the | ||
104 | -H option to print found keys in a hashed format. | ||
105 | |||
106 | -f filename | ||
107 | Specifies the filename of the key file. | ||
108 | |||
109 | -G output_file | ||
110 | Generate candidate primes for DH-GEX. These primes must be | ||
111 | screened for safety (using the -T option) before use. | ||
112 | |||
113 | -g Use generic DNS format when printing fingerprint resource records | ||
114 | using the -r command. | ||
115 | |||
116 | -H Hash a known_hosts file. This replaces all hostnames and ad- | ||
117 | dresses with hashed representations within the specified file; | ||
118 | the original content is moved to a file with a .old suffix. | ||
119 | These hashes may be used normally by ssh and sshd, but they do | ||
120 | not reveal identifying information should the file's contents be | ||
121 | disclosed. This option will not modify existing hashed hostnames | ||
122 | and is therefore safe to use on files that mix hashed and non- | ||
123 | hashed names. | ||
124 | |||
125 | -i This option will read an unencrypted private (or public) key file | ||
126 | in SSH2-compatible format and print an OpenSSH compatible private | ||
127 | (or public) key to stdout. ssh-keygen also reads the RFC 4716 | ||
128 | SSH Public Key File Format. This option allows importing keys | ||
129 | from several commercial SSH implementations. | ||
130 | |||
131 | -l Show fingerprint of specified public key file. Private RSA1 keys | ||
132 | are also supported. For RSA and DSA keys ssh-keygen tries to | ||
133 | find the matching public key file and prints its fingerprint. If | ||
134 | combined with -v, an ASCII art representation of the key is sup- | ||
135 | plied with the fingerprint. | ||
136 | |||
137 | -M memory | ||
138 | Specify the amount of memory to use (in megabytes) when generat- | ||
139 | ing candidate moduli for DH-GEX. | ||
140 | |||
141 | -N new_passphrase | ||
142 | Provides the new passphrase. | ||
143 | |||
144 | -P passphrase | ||
145 | Provides the (old) passphrase. | ||
146 | |||
147 | -p Requests changing the passphrase of a private key file instead of | ||
148 | creating a new private key. The program will prompt for the file | ||
149 | containing the private key, for the old passphrase, and twice for | ||
150 | the new passphrase. | ||
151 | |||
152 | -q Silence ssh-keygen. Used by /etc/rc when creating a new key. | ||
153 | |||
154 | -R hostname | ||
155 | Removes all keys belonging to hostname from a known_hosts file. | ||
156 | This option is useful to delete hashed hosts (see the -H option | ||
157 | above). | ||
158 | |||
159 | -r hostname | ||
160 | Print the SSHFP fingerprint resource record named hostname for | ||
161 | the specified public key file. | ||
162 | |||
163 | -S start | ||
164 | Specify start point (in hex) when generating candidate moduli for | ||
165 | DH-GEX. | ||
166 | |||
167 | -T output_file | ||
168 | Test DH group exchange candidate primes (generated using the -G | ||
169 | option) for safety. | ||
170 | |||
171 | -t type | ||
172 | Specifies the type of key to create. The possible values are | ||
173 | ``rsa1'' for protocol version 1 and ``rsa'' or ``dsa'' for proto- | ||
174 | col version 2. | ||
175 | |||
176 | -U reader | ||
177 | Upload an existing RSA private key into the smartcard in reader. | ||
178 | |||
179 | -v Verbose mode. Causes ssh-keygen to print debugging messages | ||
180 | about its progress. This is helpful for debugging moduli genera- | ||
181 | tion. Multiple -v options increase the verbosity. The maximum | ||
182 | is 3. | ||
183 | |||
184 | -W generator | ||
185 | Specify desired generator when testing candidate moduli for DH- | ||
186 | GEX. | ||
187 | |||
188 | -y This option will read a private OpenSSH format file and print an | ||
189 | OpenSSH public key to stdout. | ||
190 | |||
191 | MODULI GENERATION | ||
192 | ssh-keygen may be used to generate groups for the Diffie-Hellman Group | ||
193 | Exchange (DH-GEX) protocol. Generating these groups is a two-step pro- | ||
194 | cess: first, candidate primes are generated using a fast, but memory in- | ||
195 | tensive process. These candidate primes are then tested for suitability | ||
196 | (a CPU-intensive process). | ||
197 | |||
198 | Generation of primes is performed using the -G option. The desired | ||
199 | length of the primes may be specified by the -b option. For example: | ||
200 | |||
201 | # ssh-keygen -G moduli-2048.candidates -b 2048 | ||
202 | |||
203 | By default, the search for primes begins at a random point in the desired | ||
204 | length range. This may be overridden using the -S option, which speci- | ||
205 | fies a different start point (in hex). | ||
206 | |||
207 | Once a set of candidates have been generated, they must be tested for | ||
208 | suitability. This may be performed using the -T option. In this mode | ||
209 | ssh-keygen will read candidates from standard input (or a file specified | ||
210 | using the -f option). For example: | ||
211 | |||
212 | # ssh-keygen -T moduli-2048 -f moduli-2048.candidates | ||
213 | |||
214 | By default, each candidate will be subjected to 100 primality tests. | ||
215 | This may be overridden using the -a option. The DH generator value will | ||
216 | be chosen automatically for the prime under consideration. If a specific | ||
217 | generator is desired, it may be requested using the -W option. Valid | ||
218 | generator values are 2, 3, and 5. | ||
219 | |||
220 | Screened DH groups may be installed in /etc/moduli. It is important that | ||
221 | this file contains moduli of a range of bit lengths and that both ends of | ||
222 | a connection share common moduli. | ||
223 | |||
224 | FILES | ||
225 | ~/.ssh/identity | ||
226 | Contains the protocol version 1 RSA authentication identity of | ||
227 | the user. This file should not be readable by anyone but the us- | ||
228 | er. It is possible to specify a passphrase when generating the | ||
229 | key; that passphrase will be used to encrypt the private part of | ||
230 | this file using 3DES. This file is not automatically accessed by | ||
231 | ssh-keygen but it is offered as the default file for the private | ||
232 | key. ssh(1) will read this file when a login attempt is made. | ||
233 | |||
234 | ~/.ssh/identity.pub | ||
235 | Contains the protocol version 1 RSA public key for authentica- | ||
236 | tion. The contents of this file should be added to | ||
237 | ~/.ssh/authorized_keys on all machines where the user wishes to | ||
238 | log in using RSA authentication. There is no need to keep the | ||
239 | contents of this file secret. | ||
240 | |||
241 | ~/.ssh/id_dsa | ||
242 | Contains the protocol version 2 DSA authentication identity of | ||
243 | the user. This file should not be readable by anyone but the us- | ||
244 | er. It is possible to specify a passphrase when generating the | ||
245 | key; that passphrase will be used to encrypt the private part of | ||
246 | this file using 3DES. This file is not automatically accessed by | ||
247 | ssh-keygen but it is offered as the default file for the private | ||
248 | key. ssh(1) will read this file when a login attempt is made. | ||
249 | |||
250 | ~/.ssh/id_dsa.pub | ||
251 | Contains the protocol version 2 DSA public key for authentica- | ||
252 | tion. The contents of this file should be added to | ||
253 | ~/.ssh/authorized_keys on all machines where the user wishes to | ||
254 | log in using public key authentication. There is no need to keep | ||
255 | the contents of this file secret. | ||
256 | |||
257 | ~/.ssh/id_rsa | ||
258 | Contains the protocol version 2 RSA authentication identity of | ||
259 | the user. This file should not be readable by anyone but the us- | ||
260 | er. It is possible to specify a passphrase when generating the | ||
261 | key; that passphrase will be used to encrypt the private part of | ||
262 | this file using 3DES. This file is not automatically accessed by | ||
263 | ssh-keygen but it is offered as the default file for the private | ||
264 | key. ssh(1) will read this file when a login attempt is made. | ||
265 | |||
266 | ~/.ssh/id_rsa.pub | ||
267 | Contains the protocol version 2 RSA public key for authentica- | ||
268 | tion. The contents of this file should be added to | ||
269 | ~/.ssh/authorized_keys on all machines where the user wishes to | ||
270 | log in using public key authentication. There is no need to keep | ||
271 | the contents of this file secret. | ||
272 | |||
273 | /etc/moduli | ||
274 | Contains Diffie-Hellman groups used for DH-GEX. The file format | ||
275 | is described in moduli(5). | ||
276 | |||
277 | SEE ALSO | ||
278 | ssh(1), ssh-add(1), ssh-agent(1), moduli(5), sshd(8) | ||
279 | |||
280 | The Secure Shell (SSH) Public Key File Format, RFC 4716, 2006. | ||
281 | |||
282 | AUTHORS | ||
283 | OpenSSH is a derivative of the original and free ssh 1.2.12 release by | ||
284 | Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo | ||
285 | de Raadt and Dug Song removed many bugs, re-added newer features and | ||
286 | created OpenSSH. Markus Friedl contributed the support for SSH protocol | ||
287 | versions 1.5 and 2.0. | ||
288 | |||
289 | OpenBSD 4.6 July 24, 2008 5 | ||