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author | Colin Watson <cjwatson@debian.org> | 2010-04-16 09:56:03 +0100 |
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committer | Colin Watson <cjwatson@debian.org> | 2010-04-16 09:56:03 +0100 |
commit | ff0095389ba9a9e4599e6051c8d5bae6777c4d64 (patch) | |
tree | f480bef24195963842fbc6a2f237c4907cfad72e /ssh-keygen.0 | |
parent | 627337d95bee7dd8d4690238a35fffd35072d1fa (diff) | |
parent | 004a7fb9c6a00b13dc98f56599918a54a3506d10 (diff) |
Import 5.5p1 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 pkcs11 | ||
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 -r hostname [-f input_keyfile] [-g] | ||
21 | ssh-keygen -G output_file [-v] [-b bits] [-M memory] [-S start_point] | ||
22 | ssh-keygen -T output_file -f input_file [-v] [-a num_trials] | ||
23 | [-W generator] | ||
24 | ssh-keygen -s ca_key -I certificate_identity [-h] [-n principals] | ||
25 | [-O constraint] [-V validity_interval] file ... | ||
26 | ssh-keygen -L [-f input_keyfile] | ||
27 | |||
28 | DESCRIPTION | ||
29 | ssh-keygen generates, manages and converts authentication keys for | ||
30 | ssh(1). ssh-keygen can create RSA keys for use by SSH protocol version 1 | ||
31 | and RSA or DSA keys for use by SSH protocol version 2. The type of key | ||
32 | to be generated is specified with the -t option. If invoked without any | ||
33 | arguments, ssh-keygen will generate an RSA key for use in SSH protocol 2 | ||
34 | connections. | ||
35 | |||
36 | ssh-keygen is also used to generate groups for use in Diffie-Hellman | ||
37 | group exchange (DH-GEX). See the MODULI GENERATION section for details. | ||
38 | |||
39 | Normally each user wishing to use SSH with RSA or DSA authentication runs | ||
40 | this once to create the authentication key in ~/.ssh/identity, | ||
41 | ~/.ssh/id_dsa or ~/.ssh/id_rsa. Additionally, the system administrator | ||
42 | may use this to generate host keys, as seen in /etc/rc. | ||
43 | |||
44 | Normally this program generates the key and asks for a file in which to | ||
45 | store the private key. The public key is stored in a file with the same | ||
46 | name but ``.pub'' appended. The program also asks for a passphrase. The | ||
47 | passphrase may be empty to indicate no passphrase (host keys must have an | ||
48 | empty passphrase), or it may be a string of arbitrary length. A | ||
49 | passphrase is similar to a password, except it can be a phrase with a se- | ||
50 | ries of words, punctuation, numbers, whitespace, or any string of charac- | ||
51 | ters you want. Good passphrases are 10-30 characters long, are not sim- | ||
52 | ple sentences or otherwise easily guessable (English prose has only 1-2 | ||
53 | bits of entropy per character, and provides very bad passphrases), and | ||
54 | contain a mix of upper and lowercase letters, numbers, and non-alphanu- | ||
55 | meric characters. The passphrase can be changed later by using the -p | ||
56 | option. | ||
57 | |||
58 | There is no way to recover a lost passphrase. If the passphrase is lost | ||
59 | or forgotten, a new key must be generated and copied to the corresponding | ||
60 | public key to other machines. | ||
61 | |||
62 | For RSA1 keys, there is also a comment field in the key file that is only | ||
63 | for 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 initial- | ||
65 | ized to ``user@host'' when the key is created, but can be changed using | ||
66 | the -c option. | ||
67 | |||
68 | After a key is generated, instructions below detail where the keys should | ||
69 | be placed to be activated. | ||
70 | |||
71 | The options are as follows: | ||
72 | |||
73 | -a trials | ||
74 | Specifies the number of primality tests to perform when screening | ||
75 | DH-GEX candidates using the -T command. | ||
76 | |||
77 | -B Show the bubblebabble digest of specified private or public key | ||
78 | file. | ||
79 | |||
80 | -b bits | ||
81 | Specifies the number of bits in the key to create. For RSA keys, | ||
82 | the minimum size is 768 bits and the default is 2048 bits. Gen- | ||
83 | erally, 2048 bits is considered sufficient. DSA keys must be ex- | ||
84 | actly 1024 bits as specified by FIPS 186-2. | ||
85 | |||
86 | -C comment | ||
87 | Provides a new comment. | ||
88 | |||
89 | -c Requests changing the comment in the private and public key | ||
90 | files. This operation is only supported for RSA1 keys. The pro- | ||
91 | gram will prompt for the file containing the private keys, for | ||
92 | the passphrase if the key has one, and for the new comment. | ||
93 | |||
94 | -D pkcs11 | ||
95 | Download the RSA public keys provided by the PKCS#11 shared li- | ||
96 | brary pkcs11. | ||
97 | |||
98 | -e This option will read a private or public OpenSSH key file and | ||
99 | print the key in RFC 4716 SSH Public Key File Format to stdout. | ||
100 | This option allows exporting keys for use by several commercial | ||
101 | SSH implementations. | ||
102 | |||
103 | -F hostname | ||
104 | Search for the specified hostname in a known_hosts file, listing | ||
105 | any occurrences found. This option is useful to find hashed host | ||
106 | names or addresses and may also be used in conjunction with the | ||
107 | -H option to print found keys in a hashed format. | ||
108 | |||
109 | -f filename | ||
110 | Specifies the filename of the key file. | ||
111 | |||
112 | -G output_file | ||
113 | Generate candidate primes for DH-GEX. These primes must be | ||
114 | screened for safety (using the -T option) before use. | ||
115 | |||
116 | -g Use generic DNS format when printing fingerprint resource records | ||
117 | using the -r command. | ||
118 | |||
119 | -H Hash a known_hosts file. This replaces all hostnames and ad- | ||
120 | dresses with hashed representations within the specified file; | ||
121 | the original content is moved to a file with a .old suffix. | ||
122 | These hashes may be used normally by ssh and sshd, but they do | ||
123 | not reveal identifying information should the file's contents be | ||
124 | disclosed. This option will not modify existing hashed hostnames | ||
125 | and is therefore safe to use on files that mix hashed and non- | ||
126 | hashed names. | ||
127 | |||
128 | -h When signing a key, create a host certificate instead of a user | ||
129 | certificate. Please see the CERTIFICATES section for details. | ||
130 | |||
131 | -I certificate_identity | ||
132 | Specify the key identity when signing a public key. Please see | ||
133 | the CERTIFICATES section for details. | ||
134 | |||
135 | -i This option will read an unencrypted private (or public) key file | ||
136 | in SSH2-compatible format and print an OpenSSH compatible private | ||
137 | (or public) key to stdout. ssh-keygen also reads the RFC 4716 | ||
138 | SSH Public Key File Format. This option allows importing keys | ||
139 | from several commercial SSH implementations. | ||
140 | |||
141 | -L Prints the contents of a certificate. | ||
142 | |||
143 | -l Show fingerprint of specified public key file. Private RSA1 keys | ||
144 | are also supported. For RSA and DSA keys ssh-keygen tries to | ||
145 | find the matching public key file and prints its fingerprint. If | ||
146 | combined with -v, an ASCII art representation of the key is sup- | ||
147 | plied with the fingerprint. | ||
148 | |||
149 | -M memory | ||
150 | Specify the amount of memory to use (in megabytes) when generat- | ||
151 | ing candidate moduli for DH-GEX. | ||
152 | |||
153 | -N new_passphrase | ||
154 | Provides the new passphrase. | ||
155 | |||
156 | -n principals | ||
157 | Specify one or more principals (user or host names) to be includ- | ||
158 | ed in a certificate when signing a key. Multiple principals may | ||
159 | be specified, separated by commas. Please see the CERTIFICATES | ||
160 | section for details. | ||
161 | |||
162 | -O constraint | ||
163 | Specify a certificate constraint when signing a key. This option | ||
164 | may be specified multiple times. Please see the CERTIFICATES | ||
165 | section for details. The constraints that are valid for user | ||
166 | certificates are: | ||
167 | |||
168 | clear Clear all enabled permissions. This is useful for clear- | ||
169 | ing the default set of permissions so permissions may be | ||
170 | added individually. | ||
171 | |||
172 | force-command=command | ||
173 | Forces the execution of command instead of any shell or | ||
174 | command specified by the user when the certificate is | ||
175 | used for authentication. | ||
176 | |||
177 | no-agent-forwarding | ||
178 | Disable ssh-agent(1) forwarding (permitted by default). | ||
179 | |||
180 | no-port-forwarding | ||
181 | Disable port forwarding (permitted by default). | ||
182 | |||
183 | no-pty Disable PTY allocation (permitted by default). | ||
184 | |||
185 | no-user-rc | ||
186 | Disable execution of ~/.ssh/rc by sshd(8) (permitted by | ||
187 | default). | ||
188 | |||
189 | no-x11-forwarding | ||
190 | Disable X11 forwarding (permitted by default). | ||
191 | |||
192 | permit-agent-forwarding | ||
193 | Allows ssh-agent(1) forwarding. | ||
194 | |||
195 | permit-port-forwarding | ||
196 | Allows port forwarding. | ||
197 | |||
198 | permit-pty | ||
199 | Allows PTY allocation. | ||
200 | |||
201 | permit-user-rc | ||
202 | Allows execution of ~/.ssh/rc by sshd(8). | ||
203 | |||
204 | permit-x11-forwarding | ||
205 | Allows X11 forwarding. | ||
206 | |||
207 | source-address=address_list | ||
208 | Restrict the source addresses from which the certificate | ||
209 | is considered valid. The address_list is a comma-sepa- | ||
210 | rated list of one or more address/netmask pairs in CIDR | ||
211 | format. | ||
212 | |||
213 | At present, no constraints are valid for host keys. | ||
214 | |||
215 | -P passphrase | ||
216 | Provides the (old) passphrase. | ||
217 | |||
218 | -p Requests changing the passphrase of a private key file instead of | ||
219 | creating a new private key. The program will prompt for the file | ||
220 | containing the private key, for the old passphrase, and twice for | ||
221 | the new passphrase. | ||
222 | |||
223 | -q Silence ssh-keygen. Used by /etc/rc when creating a new key. | ||
224 | |||
225 | -R hostname | ||
226 | Removes all keys belonging to hostname from a known_hosts file. | ||
227 | This option is useful to delete hashed hosts (see the -H option | ||
228 | above). | ||
229 | |||
230 | -r hostname | ||
231 | Print the SSHFP fingerprint resource record named hostname for | ||
232 | the specified public key file. | ||
233 | |||
234 | -S start | ||
235 | Specify start point (in hex) when generating candidate moduli for | ||
236 | DH-GEX. | ||
237 | |||
238 | -s ca_key | ||
239 | Certify (sign) a public key using the specified CA key. Please | ||
240 | see the CERTIFICATES section for details. | ||
241 | |||
242 | -T output_file | ||
243 | Test DH group exchange candidate primes (generated using the -G | ||
244 | option) for safety. | ||
245 | |||
246 | -t type | ||
247 | Specifies the type of key to create. The possible values are | ||
248 | ``rsa1'' for protocol version 1 and ``rsa'' or ``dsa'' for proto- | ||
249 | col version 2. | ||
250 | |||
251 | -V validity_interval | ||
252 | Specify a validity interval when signing a certificate. A valid- | ||
253 | ity interval may consist of a single time, indicating that the | ||
254 | certificate is valid beginning now and expiring at that time, or | ||
255 | may consist of two times separated by a colon to indicate an ex- | ||
256 | plicit time interval. The start time may be specified as a date | ||
257 | in YYYYMMDD format, a time in YYYYMMDDHHMMSS format or a relative | ||
258 | time (to the current time) consisting of a minus sign followed by | ||
259 | a relative time in the format described in the TIME FORMATS sec- | ||
260 | tion of sshd_config(5). The end time may be specified as a | ||
261 | YYYYMMDD date, a YYYYMMDDHHMMSS time or a relative time starting | ||
262 | with a plus character. | ||
263 | |||
264 | For example: ``+52w1d'' (valid from now to 52 weeks and one day | ||
265 | from now), ``-4w:+4w'' (valid from four weeks ago to four weeks | ||
266 | from now), ``20100101123000:20110101123000'' (valid from 12:30 | ||
267 | PM, January 1st, 2010 to 12:30 PM, January 1st, 2011), | ||
268 | ``-1d:20110101'' (valid from yesterday to midnight, January 1st, | ||
269 | 2011). | ||
270 | |||
271 | -v Verbose mode. Causes ssh-keygen to print debugging messages | ||
272 | about its progress. This is helpful for debugging moduli genera- | ||
273 | tion. Multiple -v options increase the verbosity. The maximum | ||
274 | is 3. | ||
275 | |||
276 | -W generator | ||
277 | Specify desired generator when testing candidate moduli for DH- | ||
278 | GEX. | ||
279 | |||
280 | -y This option will read a private OpenSSH format file and print an | ||
281 | OpenSSH public key to stdout. | ||
282 | |||
283 | MODULI GENERATION | ||
284 | ssh-keygen may be used to generate groups for the Diffie-Hellman Group | ||
285 | Exchange (DH-GEX) protocol. Generating these groups is a two-step pro- | ||
286 | cess: first, candidate primes are generated using a fast, but memory in- | ||
287 | tensive process. These candidate primes are then tested for suitability | ||
288 | (a CPU-intensive process). | ||
289 | |||
290 | Generation of primes is performed using the -G option. The desired | ||
291 | length of the primes may be specified by the -b option. For example: | ||
292 | |||
293 | # ssh-keygen -G moduli-2048.candidates -b 2048 | ||
294 | |||
295 | By default, the search for primes begins at a random point in the desired | ||
296 | length range. This may be overridden using the -S option, which speci- | ||
297 | fies a different start point (in hex). | ||
298 | |||
299 | Once a set of candidates have been generated, they must be tested for | ||
300 | suitability. This may be performed using the -T option. In this mode | ||
301 | ssh-keygen will read candidates from standard input (or a file specified | ||
302 | using the -f option). For example: | ||
303 | |||
304 | # ssh-keygen -T moduli-2048 -f moduli-2048.candidates | ||
305 | |||
306 | By default, each candidate will be subjected to 100 primality tests. | ||
307 | This may be overridden using the -a option. The DH generator value will | ||
308 | be chosen automatically for the prime under consideration. If a specific | ||
309 | generator is desired, it may be requested using the -W option. Valid | ||
310 | generator values are 2, 3, and 5. | ||
311 | |||
312 | Screened DH groups may be installed in /etc/moduli. It is important that | ||
313 | this file contains moduli of a range of bit lengths and that both ends of | ||
314 | a connection share common moduli. | ||
315 | |||
316 | CERTIFICATES | ||
317 | ssh-keygen supports signing of keys to produce certificates that may be | ||
318 | used for user or host authentication. Certificates consist of a public | ||
319 | key, some identity information, zero or more principal (user or host) | ||
320 | names and an optional set of constraints that are signed by a Certifica- | ||
321 | tion Authority (CA) key. Clients or servers may then trust only the CA | ||
322 | key and verify its signature on a certificate rather than trusting many | ||
323 | user/host keys. Note that OpenSSH certificates are a different, and much | ||
324 | simpler, format to the X.509 certificates used in ssl(8). | ||
325 | |||
326 | ssh-keygen supports two types of certificates: user and host. User cer- | ||
327 | tificates authenticate users to servers, whereas host certificates au- | ||
328 | thenticate server hosts to users. To generate a user certificate: | ||
329 | |||
330 | $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub | ||
331 | |||
332 | The resultant certificate will be placed in /path/to/user_key-cert.pub. | ||
333 | A host certificate requires the -h option: | ||
334 | |||
335 | $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub | ||
336 | |||
337 | The host certificate will be output to /path/to/host_key-cert.pub. In | ||
338 | both cases, key_id is a "key identifier" that is logged by the server | ||
339 | when the certificate is used for authentication. | ||
340 | |||
341 | Certificates may be limited to be valid for a set of principal (us- | ||
342 | er/host) names. By default, generated certificates are valid for all | ||
343 | users or hosts. To generate a certificate for a specified set of princi- | ||
344 | pals: | ||
345 | |||
346 | $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub | ||
347 | $ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub | ||
348 | |||
349 | Additional limitations on the validity and use of user certificates may | ||
350 | be specified through certificate constraints. A constrained certificate | ||
351 | may disable features of the SSH session, may be valid only when presented | ||
352 | from particular source addresses or may force the use of a specific com- | ||
353 | mand. For a list of valid certificate constraints, see the documentation | ||
354 | for the -O option above. | ||
355 | |||
356 | Finally, certificates may be defined with a validity lifetime. The -V | ||
357 | option allows specification of certificate start and end times. A cer- | ||
358 | tificate that is presented at a time outside this range will not be con- | ||
359 | sidered valid. By default, certificates have a maximum validity inter- | ||
360 | val. | ||
361 | |||
362 | For certificates to be used for user or host authentication, the CA pub- | ||
363 | lic key must be trusted by sshd(8) or ssh(1). Please refer to those man- | ||
364 | ual pages for details. | ||
365 | |||
366 | FILES | ||
367 | ~/.ssh/identity | ||
368 | Contains the protocol version 1 RSA authentication identity of | ||
369 | the user. This file should not be readable by anyone but the us- | ||
370 | er. It is possible to specify a passphrase when generating the | ||
371 | key; that passphrase will be used to encrypt the private part of | ||
372 | this file using 128-bit AES. This file is not automatically ac- | ||
373 | cessed by ssh-keygen but it is offered as the default file for | ||
374 | the private key. ssh(1) will read this file when a login attempt | ||
375 | is made. | ||
376 | |||
377 | ~/.ssh/identity.pub | ||
378 | Contains the protocol version 1 RSA public key for authentica- | ||
379 | tion. The contents of this file should be added to | ||
380 | ~/.ssh/authorized_keys on all machines where the user wishes to | ||
381 | log in using RSA authentication. There is no need to keep the | ||
382 | contents of this file secret. | ||
383 | |||
384 | ~/.ssh/id_dsa | ||
385 | Contains the protocol version 2 DSA authentication identity of | ||
386 | the user. This file should not be readable by anyone but the us- | ||
387 | er. It is possible to specify a passphrase when generating the | ||
388 | key; that passphrase will be used to encrypt the private part of | ||
389 | this file using 128-bit AES. This file is not automatically ac- | ||
390 | cessed by ssh-keygen but it is offered as the default file for | ||
391 | the private key. ssh(1) will read this file when a login attempt | ||
392 | is made. | ||
393 | |||
394 | ~/.ssh/id_dsa.pub | ||
395 | Contains the protocol version 2 DSA public key for authentica- | ||
396 | tion. The contents of this file should be added to | ||
397 | ~/.ssh/authorized_keys on all machines where the user wishes to | ||
398 | log in using public key authentication. There is no need to keep | ||
399 | the contents of this file secret. | ||
400 | |||
401 | ~/.ssh/id_rsa | ||
402 | Contains the protocol version 2 RSA authentication identity of | ||
403 | the user. This file should not be readable by anyone but the us- | ||
404 | er. It is possible to specify a passphrase when generating the | ||
405 | key; that passphrase will be used to encrypt the private part of | ||
406 | this file using 128-bit AES. This file is not automatically ac- | ||
407 | cessed by ssh-keygen but it is offered as the default file for | ||
408 | the private key. ssh(1) will read this file when a login attempt | ||
409 | is made. | ||
410 | |||
411 | ~/.ssh/id_rsa.pub | ||
412 | Contains the protocol version 2 RSA public key for authentica- | ||
413 | tion. The contents of this file should be added to | ||
414 | ~/.ssh/authorized_keys on all machines where the user wishes to | ||
415 | log in using public key authentication. There is no need to keep | ||
416 | the contents of this file secret. | ||
417 | |||
418 | /etc/moduli | ||
419 | Contains Diffie-Hellman groups used for DH-GEX. The file format | ||
420 | is described in moduli(5). | ||
421 | |||
422 | SEE ALSO | ||
423 | ssh(1), ssh-add(1), ssh-agent(1), moduli(5), sshd(8) | ||
424 | |||
425 | The Secure Shell (SSH) Public Key File Format, RFC 4716, 2006. | ||
426 | |||
427 | AUTHORS | ||
428 | OpenSSH is a derivative of the original and free ssh 1.2.12 release by | ||
429 | Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo | ||
430 | de Raadt and Dug Song removed many bugs, re-added newer features and | ||
431 | created OpenSSH. Markus Friedl contributed the support for SSH protocol | ||
432 | versions 1.5 and 2.0. | ||
433 | |||
434 | OpenBSD 4.7 March 13, 2010 7 | ||