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78edb05a | 1 | .\" $OpenBSD: ssh-keygen.1,v 1.80 2009/10/24 00:48:34 dtucker Exp $ |
23c2a7a5 | 2 | .\" |
bf740959 | 3 | .\" -*- nroff -*- |
4 | .\" | |
bf740959 | 5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
bf740959 | 6 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
7 | .\" All rights reserved | |
8 | .\" | |
bcbf86ec | 9 | .\" As far as I am concerned, the code I have written for this software |
10 | .\" can be used freely for any purpose. Any derived versions of this | |
11 | .\" software must be clearly marked as such, and if the derived work is | |
12 | .\" incompatible with the protocol description in the RFC file, it must be | |
13 | .\" called by a name other than "ssh" or "Secure Shell". | |
14 | .\" | |
15 | .\" | |
f3c7c613 | 16 | .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. |
17 | .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. | |
18 | .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. | |
bcbf86ec | 19 | .\" |
20 | .\" Redistribution and use in source and binary forms, with or without | |
21 | .\" modification, are permitted provided that the following conditions | |
22 | .\" are met: | |
23 | .\" 1. Redistributions of source code must retain the above copyright | |
24 | .\" notice, this list of conditions and the following disclaimer. | |
25 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
26 | .\" notice, this list of conditions and the following disclaimer in the | |
27 | .\" documentation and/or other materials provided with the distribution. | |
bf740959 | 28 | .\" |
bcbf86ec | 29 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
30 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
31 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
32 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
33 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
34 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
35 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
36 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
37 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
38 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
bf740959 | 39 | .\" |
e473dcd1 | 40 | .Dd $Mdocdate$ |
bf740959 | 41 | .Dt SSH-KEYGEN 1 |
42 | .Os | |
43 | .Sh NAME | |
44 | .Nm ssh-keygen | |
5deceabb | 45 | .Nd authentication key generation, management and conversion |
bf740959 | 46 | .Sh SYNOPSIS |
47 | .Nm ssh-keygen | |
a4e5acef | 48 | .Bk -words |
fa08c86b | 49 | .Op Fl q |
bf740959 | 50 | .Op Fl b Ar bits |
2a55e100 | 51 | .Fl t Ar type |
bf740959 | 52 | .Op Fl N Ar new_passphrase |
53 | .Op Fl C Ar comment | |
7cd3766c | 54 | .Op Fl f Ar output_keyfile |
a4e5acef | 55 | .Ek |
bf740959 | 56 | .Nm ssh-keygen |
57 | .Fl p | |
58 | .Op Fl P Ar old_passphrase | |
59 | .Op Fl N Ar new_passphrase | |
f095fcc7 | 60 | .Op Fl f Ar keyfile |
bf740959 | 61 | .Nm ssh-keygen |
5deceabb | 62 | .Fl i |
7cd3766c | 63 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 64 | .Nm ssh-keygen |
5deceabb | 65 | .Fl e |
7cd3766c | 66 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 67 | .Nm ssh-keygen |
68 | .Fl y | |
7cd3766c | 69 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 70 | .Nm ssh-keygen |
bf740959 | 71 | .Fl c |
72 | .Op Fl P Ar passphrase | |
73 | .Op Fl C Ar comment | |
f095fcc7 | 74 | .Op Fl f Ar keyfile |
75 | .Nm ssh-keygen | |
76 | .Fl l | |
aaf45d87 | 77 | .Op Fl f Ar input_keyfile |
78 | .Nm ssh-keygen | |
79 | .Fl B | |
7cd3766c | 80 | .Op Fl f Ar input_keyfile |
f0d6bdcf | 81 | .Nm ssh-keygen |
82 | .Fl D Ar reader | |
83 | .Nm ssh-keygen | |
bdffbcdc | 84 | .Fl F Ar hostname |
85 | .Op Fl f Ar known_hosts_file | |
dad77e16 | 86 | .Op Fl l |
bdffbcdc | 87 | .Nm ssh-keygen |
88 | .Fl H | |
89 | .Op Fl f Ar known_hosts_file | |
90 | .Nm ssh-keygen | |
91 | .Fl R Ar hostname | |
92 | .Op Fl f Ar known_hosts_file | |
93 | .Nm ssh-keygen | |
f0d6bdcf | 94 | .Fl U Ar reader |
95 | .Op Fl f Ar input_keyfile | |
21289cd0 | 96 | .Nm ssh-keygen |
97 | .Fl r Ar hostname | |
98 | .Op Fl f Ar input_keyfile | |
99 | .Op Fl g | |
c35a6dc5 | 100 | .Nm ssh-keygen |
101 | .Fl G Ar output_file | |
c6fbc95a | 102 | .Op Fl v |
c35a6dc5 | 103 | .Op Fl b Ar bits |
104 | .Op Fl M Ar memory | |
105 | .Op Fl S Ar start_point | |
106 | .Nm ssh-keygen | |
107 | .Fl T Ar output_file | |
108 | .Fl f Ar input_file | |
c6fbc95a | 109 | .Op Fl v |
c35a6dc5 | 110 | .Op Fl a Ar num_trials |
111 | .Op Fl W Ar generator | |
f54651ce | 112 | .Sh DESCRIPTION |
bf740959 | 113 | .Nm |
5deceabb | 114 | generates, manages and converts authentication keys for |
bf740959 | 115 | .Xr ssh 1 . |
1d1ffb87 | 116 | .Nm |
7203d6bb | 117 | can create RSA keys for use by SSH protocol version 1 and RSA or DSA |
3cbc677d | 118 | keys for use by SSH protocol version 2. |
119 | The type of key to be generated is specified with the | |
fa08c86b | 120 | .Fl t |
3dc93cd8 | 121 | option. |
882c9d5a | 122 | If invoked without any arguments, |
123 | .Nm | |
3543c5e1 | 124 | will generate an RSA key for use in SSH protocol 2 connections. |
1d1ffb87 | 125 | .Pp |
c35a6dc5 | 126 | .Nm |
127 | is also used to generate groups for use in Diffie-Hellman group | |
128 | exchange (DH-GEX). | |
129 | See the | |
130 | .Sx MODULI GENERATION | |
131 | section for details. | |
132 | .Pp | |
bf740959 | 133 | Normally each user wishing to use SSH |
1d1ffb87 | 134 | with RSA or DSA authentication runs this once to create the authentication |
bf740959 | 135 | key in |
140e3e97 | 136 | .Pa ~/.ssh/identity , |
137 | .Pa ~/.ssh/id_dsa | |
1d1ffb87 | 138 | or |
140e3e97 | 139 | .Pa ~/.ssh/id_rsa . |
1d1ffb87 | 140 | Additionally, the system administrator may use this to generate host keys, |
141 | as seen in | |
142 | .Pa /etc/rc . | |
bf740959 | 143 | .Pp |
144 | Normally this program generates the key and asks for a file in which | |
4fe2af09 | 145 | to store the private key. |
146 | The public key is stored in a file with the same name but | |
bf740959 | 147 | .Dq .pub |
4fe2af09 | 148 | appended. |
149 | The program also asks for a passphrase. | |
150 | The passphrase may be empty to indicate no passphrase | |
b5c334cc | 151 | (host keys must have an empty passphrase), or it may be a string of |
4fe2af09 | 152 | arbitrary length. |
c840d0ad | 153 | A passphrase is similar to a password, except it can be a phrase with a |
154 | series of words, punctuation, numbers, whitespace, or any string of | |
155 | characters you want. | |
156 | Good passphrases are 10-30 characters long, are | |
bf740959 | 157 | not simple sentences or otherwise easily guessable (English |
e5b71e99 | 158 | prose has only 1-2 bits of entropy per character, and provides very bad |
c840d0ad | 159 | passphrases), and contain a mix of upper and lowercase letters, |
160 | numbers, and non-alphanumeric characters. | |
4fe2af09 | 161 | The passphrase can be changed later by using the |
bf740959 | 162 | .Fl p |
163 | option. | |
164 | .Pp | |
4fe2af09 | 165 | There is no way to recover a lost passphrase. |
166 | If the passphrase is | |
91789042 | 167 | lost or forgotten, a new key must be generated and copied to the |
bf740959 | 168 | corresponding public key to other machines. |
169 | .Pp | |
5deceabb | 170 | For RSA1 keys, |
171 | there is also a comment field in the key file that is only for | |
4fe2af09 | 172 | convenience to the user to help identify the key. |
173 | The comment can tell what the key is for, or whatever is useful. | |
174 | The comment is initialized to | |
bf740959 | 175 | .Dq user@host |
176 | when the key is created, but can be changed using the | |
177 | .Fl c | |
178 | option. | |
179 | .Pp | |
1d1ffb87 | 180 | After a key is generated, instructions below detail where the keys |
181 | should be placed to be activated. | |
182 | .Pp | |
bf740959 | 183 | The options are as follows: |
184 | .Bl -tag -width Ds | |
c35a6dc5 | 185 | .It Fl a Ar trials |
186 | Specifies the number of primality tests to perform when screening DH-GEX | |
187 | candidates using the | |
188 | .Fl T | |
189 | command. | |
ce0c0cdc | 190 | .It Fl B |
191 | Show the bubblebabble digest of specified private or public key file. | |
bf740959 | 192 | .It Fl b Ar bits |
4fe2af09 | 193 | Specifies the number of bits in the key to create. |
c6d7b211 | 194 | For RSA keys, the minimum size is 768 bits and the default is 2048 bits. |
60dacb4b | 195 | Generally, 2048 bits is considered sufficient. |
c6d7b211 | 196 | DSA keys must be exactly 1024 bits as specified by FIPS 186-2. |
ce0c0cdc | 197 | .It Fl C Ar comment |
198 | Provides a new comment. | |
bf740959 | 199 | .It Fl c |
200 | Requests changing the comment in the private and public key files. | |
f564d016 | 201 | This operation is only supported for RSA1 keys. |
bf740959 | 202 | The program will prompt for the file containing the private keys, for |
cf7ff074 | 203 | the passphrase if the key has one, and for the new comment. |
ce0c0cdc | 204 | .It Fl D Ar reader |
205 | Download the RSA public key stored in the smartcard in | |
206 | .Ar reader . | |
5deceabb | 207 | .It Fl e |
b587c165 | 208 | This option will read a private or public OpenSSH key file and |
4e3c0053 | 209 | print the key in |
210 | RFC 4716 SSH Public Key File Format | |
5deceabb | 211 | to stdout. |
212 | This option allows exporting keys for use by several commercial | |
213 | SSH implementations. | |
ce0c0cdc | 214 | .It Fl F Ar hostname |
215 | Search for the specified | |
216 | .Ar hostname | |
217 | in a | |
218 | .Pa known_hosts | |
219 | file, listing any occurrences found. | |
220 | This option is useful to find hashed host names or addresses and may also be | |
221 | used in conjunction with the | |
222 | .Fl H | |
223 | option to print found keys in a hashed format. | |
224 | .It Fl f Ar filename | |
225 | Specifies the filename of the key file. | |
226 | .It Fl G Ar output_file | |
227 | Generate candidate primes for DH-GEX. | |
228 | These primes must be screened for | |
229 | safety (using the | |
230 | .Fl T | |
231 | option) before use. | |
21289cd0 | 232 | .It Fl g |
3a858356 | 233 | Use generic DNS format when printing fingerprint resource records using the |
a665982d | 234 | .Fl r |
3a858356 | 235 | command. |
ce0c0cdc | 236 | .It Fl H |
237 | Hash a | |
238 | .Pa known_hosts | |
ee8e9906 | 239 | file. |
240 | This replaces all hostnames and addresses with hashed representations | |
241 | within the specified file; the original content is moved to a file with | |
242 | a .old suffix. | |
ce0c0cdc | 243 | These hashes may be used normally by |
244 | .Nm ssh | |
245 | and | |
246 | .Nm sshd , | |
247 | but they do not reveal identifying information should the file's contents | |
248 | be disclosed. | |
249 | This option will not modify existing hashed hostnames and is therefore safe | |
250 | to use on files that mix hashed and non-hashed names. | |
5deceabb | 251 | .It Fl i |
252 | This option will read an unencrypted private (or public) key file | |
253 | in SSH2-compatible format and print an OpenSSH compatible private | |
254 | (or public) key to stdout. | |
255 | .Nm | |
bcaa828e | 256 | also reads the |
e91a8c3f | 257 | RFC 4716 SSH Public Key File Format. |
5deceabb | 258 | This option allows importing keys from several commercial |
259 | SSH implementations. | |
f095fcc7 | 260 | .It Fl l |
639211b7 | 261 | Show fingerprint of specified public key file. |
f564d016 | 262 | Private RSA1 keys are also supported. |
263 | For RSA and DSA keys | |
264 | .Nm | |
a64f8307 | 265 | tries to find the matching public key file and prints its fingerprint. |
266 | If combined with | |
267 | .Fl v , | |
268 | an ASCII art representation of the key is supplied with the fingerprint. | |
ce0c0cdc | 269 | .It Fl M Ar memory |
270 | Specify the amount of memory to use (in megabytes) when generating | |
271 | candidate moduli for DH-GEX. | |
272 | .It Fl N Ar new_passphrase | |
273 | Provides the new passphrase. | |
274 | .It Fl P Ar passphrase | |
275 | Provides the (old) passphrase. | |
bf740959 | 276 | .It Fl p |
277 | Requests changing the passphrase of a private key file instead of | |
4fe2af09 | 278 | creating a new private key. |
279 | The program will prompt for the file | |
bf740959 | 280 | containing the private key, for the old passphrase, and twice for the |
281 | new passphrase. | |
282 | .It Fl q | |
283 | Silence | |
284 | .Nm ssh-keygen . | |
285 | Used by | |
286 | .Pa /etc/rc | |
287 | when creating a new key. | |
bdffbcdc | 288 | .It Fl R Ar hostname |
289 | Removes all keys belonging to | |
290 | .Ar hostname | |
219195e8 | 291 | from a |
bdffbcdc | 292 | .Pa known_hosts |
293 | file. | |
219195e8 | 294 | This option is useful to delete hashed hosts (see the |
bdffbcdc | 295 | .Fl H |
296 | option above). | |
ce0c0cdc | 297 | .It Fl r Ar hostname |
298 | Print the SSHFP fingerprint resource record named | |
299 | .Ar hostname | |
300 | for the specified public key file. | |
c35a6dc5 | 301 | .It Fl S Ar start |
302 | Specify start point (in hex) when generating candidate moduli for DH-GEX. | |
303 | .It Fl T Ar output_file | |
304 | Test DH group exchange candidate primes (generated using the | |
305 | .Fl G | |
306 | option) for safety. | |
ce0c0cdc | 307 | .It Fl t Ar type |
308 | Specifies the type of key to create. | |
309 | The possible values are | |
310 | .Dq rsa1 | |
311 | for protocol version 1 and | |
312 | .Dq rsa | |
313 | or | |
314 | .Dq dsa | |
315 | for protocol version 2. | |
f0d6bdcf | 316 | .It Fl U Ar reader |
317 | Upload an existing RSA private key into the smartcard in | |
318 | .Ar reader . | |
c6fbc95a | 319 | .It Fl v |
320 | Verbose mode. | |
321 | Causes | |
322 | .Nm | |
323 | to print debugging messages about its progress. | |
324 | This is helpful for debugging moduli generation. | |
325 | Multiple | |
326 | .Fl v | |
327 | options increase the verbosity. | |
328 | The maximum is 3. | |
ce0c0cdc | 329 | .It Fl W Ar generator |
330 | Specify desired generator when testing candidate moduli for DH-GEX. | |
331 | .It Fl y | |
332 | This option will read a private | |
333 | OpenSSH format file and print an OpenSSH public key to stdout. | |
bf740959 | 334 | .El |
c35a6dc5 | 335 | .Sh MODULI GENERATION |
336 | .Nm | |
337 | may be used to generate groups for the Diffie-Hellman Group Exchange | |
338 | (DH-GEX) protocol. | |
339 | Generating these groups is a two-step process: first, candidate | |
340 | primes are generated using a fast, but memory intensive process. | |
341 | These candidate primes are then tested for suitability (a CPU-intensive | |
342 | process). | |
343 | .Pp | |
344 | Generation of primes is performed using the | |
345 | .Fl G | |
346 | option. | |
347 | The desired length of the primes may be specified by the | |
348 | .Fl b | |
349 | option. | |
350 | For example: | |
351 | .Pp | |
ce0c0cdc | 352 | .Dl # ssh-keygen -G moduli-2048.candidates -b 2048 |
c35a6dc5 | 353 | .Pp |
354 | By default, the search for primes begins at a random point in the | |
355 | desired length range. | |
356 | This may be overridden using the | |
357 | .Fl S | |
358 | option, which specifies a different start point (in hex). | |
359 | .Pp | |
360 | Once a set of candidates have been generated, they must be tested for | |
361 | suitability. | |
362 | This may be performed using the | |
363 | .Fl T | |
364 | option. | |
365 | In this mode | |
366 | .Nm | |
367 | will read candidates from standard input (or a file specified using the | |
368 | .Fl f | |
369 | option). | |
370 | For example: | |
371 | .Pp | |
ce0c0cdc | 372 | .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates |
c35a6dc5 | 373 | .Pp |
374 | By default, each candidate will be subjected to 100 primality tests. | |
375 | This may be overridden using the | |
376 | .Fl a | |
377 | option. | |
378 | The DH generator value will be chosen automatically for the | |
379 | prime under consideration. | |
380 | If a specific generator is desired, it may be requested using the | |
381 | .Fl W | |
382 | option. | |
ce0c0cdc | 383 | Valid generator values are 2, 3, and 5. |
c35a6dc5 | 384 | .Pp |
385 | Screened DH groups may be installed in | |
386 | .Pa /etc/moduli . | |
387 | It is important that this file contains moduli of a range of bit lengths and | |
388 | that both ends of a connection share common moduli. | |
bf740959 | 389 | .Sh FILES |
390 | .Bl -tag -width Ds | |
140e3e97 | 391 | .It Pa ~/.ssh/identity |
c0ecc314 | 392 | Contains the protocol version 1 RSA authentication identity of the user. |
4fe2af09 | 393 | This file should not be readable by anyone but the user. |
394 | It is possible to | |
bf740959 | 395 | specify a passphrase when generating the key; that passphrase will be |
78edb05a | 396 | used to encrypt the private part of this file using 128-bit AES. |
4fe2af09 | 397 | This file is not automatically accessed by |
bf740959 | 398 | .Nm |
399 | but it is offered as the default file for the private key. | |
8a497b11 | 400 | .Xr ssh 1 |
1d1ffb87 | 401 | will read this file when a login attempt is made. |
140e3e97 | 402 | .It Pa ~/.ssh/identity.pub |
c0ecc314 | 403 | Contains the protocol version 1 RSA public key for authentication. |
4fe2af09 | 404 | The contents of this file should be added to |
140e3e97 | 405 | .Pa ~/.ssh/authorized_keys |
bf740959 | 406 | on all machines |
91789042 | 407 | where the user wishes to log in using RSA authentication. |
4fe2af09 | 408 | There is no need to keep the contents of this file secret. |
140e3e97 | 409 | .It Pa ~/.ssh/id_dsa |
c0ecc314 | 410 | Contains the protocol version 2 DSA authentication identity of the user. |
1d1ffb87 | 411 | This file should not be readable by anyone but the user. |
412 | It is possible to | |
413 | specify a passphrase when generating the key; that passphrase will be | |
78edb05a | 414 | used to encrypt the private part of this file using 128-bit AES. |
1d1ffb87 | 415 | This file is not automatically accessed by |
416 | .Nm | |
417 | but it is offered as the default file for the private key. | |
8a497b11 | 418 | .Xr ssh 1 |
1d1ffb87 | 419 | will read this file when a login attempt is made. |
140e3e97 | 420 | .It Pa ~/.ssh/id_dsa.pub |
c0ecc314 | 421 | Contains the protocol version 2 DSA public key for authentication. |
422 | The contents of this file should be added to | |
140e3e97 | 423 | .Pa ~/.ssh/authorized_keys |
c0ecc314 | 424 | on all machines |
91789042 | 425 | where the user wishes to log in using public key authentication. |
c0ecc314 | 426 | There is no need to keep the contents of this file secret. |
140e3e97 | 427 | .It Pa ~/.ssh/id_rsa |
c0ecc314 | 428 | Contains the protocol version 2 RSA authentication identity of the user. |
429 | This file should not be readable by anyone but the user. | |
430 | It is possible to | |
431 | specify a passphrase when generating the key; that passphrase will be | |
78edb05a | 432 | used to encrypt the private part of this file using 128-bit AES. |
c0ecc314 | 433 | This file is not automatically accessed by |
434 | .Nm | |
435 | but it is offered as the default file for the private key. | |
8a497b11 | 436 | .Xr ssh 1 |
c0ecc314 | 437 | will read this file when a login attempt is made. |
140e3e97 | 438 | .It Pa ~/.ssh/id_rsa.pub |
c0ecc314 | 439 | Contains the protocol version 2 RSA public key for authentication. |
1d1ffb87 | 440 | The contents of this file should be added to |
140e3e97 | 441 | .Pa ~/.ssh/authorized_keys |
1d1ffb87 | 442 | on all machines |
91789042 | 443 | where the user wishes to log in using public key authentication. |
1d1ffb87 | 444 | There is no need to keep the contents of this file secret. |
c35a6dc5 | 445 | .It Pa /etc/moduli |
446 | Contains Diffie-Hellman groups used for DH-GEX. | |
447 | The file format is described in | |
448 | .Xr moduli 5 . | |
089fbbd2 | 449 | .El |
bf740959 | 450 | .Sh SEE ALSO |
451 | .Xr ssh 1 , | |
452 | .Xr ssh-add 1 , | |
0c372277 | 453 | .Xr ssh-agent 1 , |
c35a6dc5 | 454 | .Xr moduli 5 , |
a5ef76f1 | 455 | .Xr sshd 8 |
5deceabb | 456 | .Rs |
4e3c0053 | 457 | .%R RFC 4716 |
458 | .%T "The Secure Shell (SSH) Public Key File Format" | |
459 | .%D 2006 | |
5deceabb | 460 | .Re |
be193d89 | 461 | .Sh AUTHORS |
462 | OpenSSH is a derivative of the original and free | |
463 | ssh 1.2.12 release by Tatu Ylonen. | |
464 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, | |
465 | Theo de Raadt and Dug Song | |
466 | removed many bugs, re-added newer features and | |
467 | created OpenSSH. | |
468 | Markus Friedl contributed the support for SSH | |
469 | protocol versions 1.5 and 2.0. |