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3a858356 | 1 | .\" $OpenBSD: ssh-keygen.1,v 1.62 2004/08/12 21:41:13 jakob 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 | .\" |
40 | .Dd September 25, 1999 | |
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 | |
84 | .Fl U Ar reader | |
85 | .Op Fl f Ar input_keyfile | |
21289cd0 | 86 | .Nm ssh-keygen |
87 | .Fl r Ar hostname | |
88 | .Op Fl f Ar input_keyfile | |
89 | .Op Fl g | |
c35a6dc5 | 90 | .Nm ssh-keygen |
91 | .Fl G Ar output_file | |
c6fbc95a | 92 | .Op Fl v |
c35a6dc5 | 93 | .Op Fl b Ar bits |
94 | .Op Fl M Ar memory | |
95 | .Op Fl S Ar start_point | |
96 | .Nm ssh-keygen | |
97 | .Fl T Ar output_file | |
98 | .Fl f Ar input_file | |
c6fbc95a | 99 | .Op Fl v |
c35a6dc5 | 100 | .Op Fl a Ar num_trials |
101 | .Op Fl W Ar generator | |
f54651ce | 102 | .Sh DESCRIPTION |
bf740959 | 103 | .Nm |
5deceabb | 104 | generates, manages and converts authentication keys for |
bf740959 | 105 | .Xr ssh 1 . |
1d1ffb87 | 106 | .Nm |
7203d6bb | 107 | can create RSA keys for use by SSH protocol version 1 and RSA or DSA |
3cbc677d | 108 | keys for use by SSH protocol version 2. |
109 | The type of key to be generated is specified with the | |
fa08c86b | 110 | .Fl t |
3dc93cd8 | 111 | option. |
1d1ffb87 | 112 | .Pp |
c35a6dc5 | 113 | .Nm |
114 | is also used to generate groups for use in Diffie-Hellman group | |
115 | exchange (DH-GEX). | |
116 | See the | |
117 | .Sx MODULI GENERATION | |
118 | section for details. | |
119 | .Pp | |
bf740959 | 120 | Normally each user wishing to use SSH |
1d1ffb87 | 121 | with RSA or DSA authentication runs this once to create the authentication |
bf740959 | 122 | key in |
c0ecc314 | 123 | .Pa $HOME/.ssh/identity , |
124 | .Pa $HOME/.ssh/id_dsa | |
1d1ffb87 | 125 | or |
c0ecc314 | 126 | .Pa $HOME/.ssh/id_rsa . |
1d1ffb87 | 127 | Additionally, the system administrator may use this to generate host keys, |
128 | as seen in | |
129 | .Pa /etc/rc . | |
bf740959 | 130 | .Pp |
131 | Normally this program generates the key and asks for a file in which | |
4fe2af09 | 132 | to store the private key. |
133 | The public key is stored in a file with the same name but | |
bf740959 | 134 | .Dq .pub |
4fe2af09 | 135 | appended. |
136 | The program also asks for a passphrase. | |
137 | The passphrase may be empty to indicate no passphrase | |
b5c334cc | 138 | (host keys must have an empty passphrase), or it may be a string of |
4fe2af09 | 139 | arbitrary length. |
c840d0ad | 140 | A passphrase is similar to a password, except it can be a phrase with a |
141 | series of words, punctuation, numbers, whitespace, or any string of | |
142 | characters you want. | |
143 | Good passphrases are 10-30 characters long, are | |
bf740959 | 144 | not simple sentences or otherwise easily guessable (English |
e5b71e99 | 145 | prose has only 1-2 bits of entropy per character, and provides very bad |
c840d0ad | 146 | passphrases), and contain a mix of upper and lowercase letters, |
147 | numbers, and non-alphanumeric characters. | |
4fe2af09 | 148 | The passphrase can be changed later by using the |
bf740959 | 149 | .Fl p |
150 | option. | |
151 | .Pp | |
4fe2af09 | 152 | There is no way to recover a lost passphrase. |
153 | If the passphrase is | |
91789042 | 154 | lost or forgotten, a new key must be generated and copied to the |
bf740959 | 155 | corresponding public key to other machines. |
156 | .Pp | |
5deceabb | 157 | For RSA1 keys, |
158 | there is also a comment field in the key file that is only for | |
4fe2af09 | 159 | convenience to the user to help identify the key. |
160 | The comment can tell what the key is for, or whatever is useful. | |
161 | The comment is initialized to | |
bf740959 | 162 | .Dq user@host |
163 | when the key is created, but can be changed using the | |
164 | .Fl c | |
165 | option. | |
166 | .Pp | |
1d1ffb87 | 167 | After a key is generated, instructions below detail where the keys |
168 | should be placed to be activated. | |
169 | .Pp | |
bf740959 | 170 | The options are as follows: |
171 | .Bl -tag -width Ds | |
c35a6dc5 | 172 | .It Fl a Ar trials |
173 | Specifies the number of primality tests to perform when screening DH-GEX | |
174 | candidates using the | |
175 | .Fl T | |
176 | command. | |
bf740959 | 177 | .It Fl b Ar bits |
4fe2af09 | 178 | Specifies the number of bits in the key to create. |
179 | Minimum is 512 bits. | |
63baa058 | 180 | Generally, 1024 bits is considered sufficient. |
4fe2af09 | 181 | The default is 1024 bits. |
bf740959 | 182 | .It Fl c |
183 | Requests changing the comment in the private and public key files. | |
f564d016 | 184 | This operation is only supported for RSA1 keys. |
bf740959 | 185 | The program will prompt for the file containing the private keys, for |
cf7ff074 | 186 | the passphrase if the key has one, and for the new comment. |
5deceabb | 187 | .It Fl e |
b587c165 | 188 | This option will read a private or public OpenSSH key file and |
189 | print the key in a | |
5deceabb | 190 | .Sq SECSH Public Key File Format |
191 | to stdout. | |
192 | This option allows exporting keys for use by several commercial | |
193 | SSH implementations. | |
21289cd0 | 194 | .It Fl g |
3a858356 | 195 | Use generic DNS format when printing fingerprint resource records using the |
196 | .Fl r | |
197 | command. | |
f0d6bdcf | 198 | .It Fl f Ar filename |
f095fcc7 | 199 | Specifies the filename of the key file. |
5deceabb | 200 | .It Fl i |
201 | This option will read an unencrypted private (or public) key file | |
202 | in SSH2-compatible format and print an OpenSSH compatible private | |
203 | (or public) key to stdout. | |
204 | .Nm | |
bcaa828e | 205 | also reads the |
5deceabb | 206 | .Sq SECSH Public Key File Format . |
207 | This option allows importing keys from several commercial | |
208 | SSH implementations. | |
f095fcc7 | 209 | .It Fl l |
f564d016 | 210 | Show fingerprint of specified public key file. |
211 | Private RSA1 keys are also supported. | |
212 | For RSA and DSA keys | |
213 | .Nm | |
214 | tries to find the matching public key file and prints its fingerprint. | |
bf740959 | 215 | .It Fl p |
216 | Requests changing the passphrase of a private key file instead of | |
4fe2af09 | 217 | creating a new private key. |
218 | The program will prompt for the file | |
bf740959 | 219 | containing the private key, for the old passphrase, and twice for the |
220 | new passphrase. | |
221 | .It Fl q | |
222 | Silence | |
223 | .Nm ssh-keygen . | |
224 | Used by | |
225 | .Pa /etc/rc | |
226 | when creating a new key. | |
5deceabb | 227 | .It Fl y |
228 | This option will read a private | |
229 | OpenSSH format file and print an OpenSSH public key to stdout. | |
fa08c86b | 230 | .It Fl t Ar type |
231 | Specifies the type of the key to create. | |
232 | The possible values are | |
233 | .Dq rsa1 | |
234 | for protocol version 1 and | |
235 | .Dq rsa | |
236 | or | |
237 | .Dq dsa | |
238 | for protocol version 2. | |
aaf45d87 | 239 | .It Fl B |
240 | Show the bubblebabble digest of specified private or public key file. | |
bf740959 | 241 | .It Fl C Ar comment |
242 | Provides the new comment. | |
f0d6bdcf | 243 | .It Fl D Ar reader |
244 | Download the RSA public key stored in the smartcard in | |
245 | .Ar reader . | |
c35a6dc5 | 246 | .It Fl G Ar output_file |
247 | Generate candidate primes for DH-GEX. | |
248 | These primes must be screened for | |
249 | safety (using the | |
250 | .Fl T | |
251 | option) before use. | |
252 | .It Fl M Ar memory | |
253 | Specify the amount of memory to use (in megabytes) when generating | |
254 | candidate moduli for DH-GEX. | |
bf740959 | 255 | .It Fl N Ar new_passphrase |
256 | Provides the new passphrase. | |
257 | .It Fl P Ar passphrase | |
258 | Provides the (old) passphrase. | |
c35a6dc5 | 259 | .It Fl S Ar start |
260 | Specify start point (in hex) when generating candidate moduli for DH-GEX. | |
261 | .It Fl T Ar output_file | |
262 | Test DH group exchange candidate primes (generated using the | |
263 | .Fl G | |
264 | option) for safety. | |
265 | .It Fl W Ar generator | |
266 | Specify desired generator when testing candidate moduli for DH-GEX. | |
f0d6bdcf | 267 | .It Fl U Ar reader |
268 | Upload an existing RSA private key into the smartcard in | |
269 | .Ar reader . | |
c6fbc95a | 270 | .It Fl v |
271 | Verbose mode. | |
272 | Causes | |
273 | .Nm | |
274 | to print debugging messages about its progress. | |
275 | This is helpful for debugging moduli generation. | |
276 | Multiple | |
277 | .Fl v | |
278 | options increase the verbosity. | |
279 | The maximum is 3. | |
21289cd0 | 280 | .It Fl r Ar hostname |
3a858356 | 281 | Print the SSHFP fingerprint resource record named |
282 | .Ar hostname | |
283 | for the specified public key file. | |
bf740959 | 284 | .El |
c35a6dc5 | 285 | .Sh MODULI GENERATION |
286 | .Nm | |
287 | may be used to generate groups for the Diffie-Hellman Group Exchange | |
288 | (DH-GEX) protocol. | |
289 | Generating these groups is a two-step process: first, candidate | |
290 | primes are generated using a fast, but memory intensive process. | |
291 | These candidate primes are then tested for suitability (a CPU-intensive | |
292 | process). | |
293 | .Pp | |
294 | Generation of primes is performed using the | |
295 | .Fl G | |
296 | option. | |
297 | The desired length of the primes may be specified by the | |
298 | .Fl b | |
299 | option. | |
300 | For example: | |
301 | .Pp | |
302 | .Dl ssh-keygen -G moduli-2048.candidates -b 2048 | |
303 | .Pp | |
304 | By default, the search for primes begins at a random point in the | |
305 | desired length range. | |
306 | This may be overridden using the | |
307 | .Fl S | |
308 | option, which specifies a different start point (in hex). | |
309 | .Pp | |
310 | Once a set of candidates have been generated, they must be tested for | |
311 | suitability. | |
312 | This may be performed using the | |
313 | .Fl T | |
314 | option. | |
315 | In this mode | |
316 | .Nm | |
317 | will read candidates from standard input (or a file specified using the | |
318 | .Fl f | |
319 | option). | |
320 | For example: | |
321 | .Pp | |
322 | .Dl ssh-keygen -T moduli-2048 -f moduli-2048.candidates | |
323 | .Pp | |
324 | By default, each candidate will be subjected to 100 primality tests. | |
325 | This may be overridden using the | |
326 | .Fl a | |
327 | option. | |
328 | The DH generator value will be chosen automatically for the | |
329 | prime under consideration. | |
330 | If a specific generator is desired, it may be requested using the | |
331 | .Fl W | |
332 | option. | |
333 | Valid generator values are 2, 3 and 5. | |
334 | .Pp | |
335 | Screened DH groups may be installed in | |
336 | .Pa /etc/moduli . | |
337 | It is important that this file contains moduli of a range of bit lengths and | |
338 | that both ends of a connection share common moduli. | |
bf740959 | 339 | .Sh FILES |
340 | .Bl -tag -width Ds | |
bf740959 | 341 | .It Pa $HOME/.ssh/identity |
c0ecc314 | 342 | Contains the protocol version 1 RSA authentication identity of the user. |
4fe2af09 | 343 | This file should not be readable by anyone but the user. |
344 | It is possible to | |
bf740959 | 345 | specify a passphrase when generating the key; that passphrase will be |
4fe2af09 | 346 | used to encrypt the private part of this file using 3DES. |
347 | This file is not automatically accessed by | |
bf740959 | 348 | .Nm |
349 | but it is offered as the default file for the private key. | |
8a497b11 | 350 | .Xr ssh 1 |
1d1ffb87 | 351 | will read this file when a login attempt is made. |
bf740959 | 352 | .It Pa $HOME/.ssh/identity.pub |
c0ecc314 | 353 | Contains the protocol version 1 RSA public key for authentication. |
4fe2af09 | 354 | The contents of this file should be added to |
bf740959 | 355 | .Pa $HOME/.ssh/authorized_keys |
356 | on all machines | |
91789042 | 357 | where the user wishes to log in using RSA authentication. |
4fe2af09 | 358 | There is no need to keep the contents of this file secret. |
1d1ffb87 | 359 | .It Pa $HOME/.ssh/id_dsa |
c0ecc314 | 360 | Contains the protocol version 2 DSA authentication identity of the user. |
1d1ffb87 | 361 | This file should not be readable by anyone but the user. |
362 | It is possible to | |
363 | specify a passphrase when generating the key; that passphrase will be | |
364 | used to encrypt the private part of this file using 3DES. | |
365 | This file is not automatically accessed by | |
366 | .Nm | |
367 | but it is offered as the default file for the private key. | |
8a497b11 | 368 | .Xr ssh 1 |
1d1ffb87 | 369 | will read this file when a login attempt is made. |
370 | .It Pa $HOME/.ssh/id_dsa.pub | |
c0ecc314 | 371 | Contains the protocol version 2 DSA public key for authentication. |
372 | The contents of this file should be added to | |
96a7b0cc | 373 | .Pa $HOME/.ssh/authorized_keys |
c0ecc314 | 374 | on all machines |
91789042 | 375 | where the user wishes to log in using public key authentication. |
c0ecc314 | 376 | There is no need to keep the contents of this file secret. |
377 | .It Pa $HOME/.ssh/id_rsa | |
378 | Contains the protocol version 2 RSA authentication identity of the user. | |
379 | This file should not be readable by anyone but the user. | |
380 | It is possible to | |
381 | specify a passphrase when generating the key; that passphrase will be | |
382 | used to encrypt the private part of this file using 3DES. | |
383 | This file is not automatically accessed by | |
384 | .Nm | |
385 | but it is offered as the default file for the private key. | |
8a497b11 | 386 | .Xr ssh 1 |
c0ecc314 | 387 | will read this file when a login attempt is made. |
388 | .It Pa $HOME/.ssh/id_rsa.pub | |
389 | Contains the protocol version 2 RSA public key for authentication. | |
1d1ffb87 | 390 | The contents of this file should be added to |
96a7b0cc | 391 | .Pa $HOME/.ssh/authorized_keys |
1d1ffb87 | 392 | on all machines |
91789042 | 393 | where the user wishes to log in using public key authentication. |
1d1ffb87 | 394 | There is no need to keep the contents of this file secret. |
c35a6dc5 | 395 | .It Pa /etc/moduli |
396 | Contains Diffie-Hellman groups used for DH-GEX. | |
397 | The file format is described in | |
398 | .Xr moduli 5 . | |
089fbbd2 | 399 | .El |
bf740959 | 400 | .Sh SEE ALSO |
401 | .Xr ssh 1 , | |
402 | .Xr ssh-add 1 , | |
0c372277 | 403 | .Xr ssh-agent 1 , |
c35a6dc5 | 404 | .Xr moduli 5 , |
a5ef76f1 | 405 | .Xr sshd 8 |
5deceabb | 406 | .Rs |
7b518233 | 407 | .%A J. Galbraith |
408 | .%A R. Thayer | |
5deceabb | 409 | .%T "SECSH Public Key File Format" |
410 | .%N draft-ietf-secsh-publickeyfile-01.txt | |
411 | .%D March 2001 | |
412 | .%O work in progress material | |
413 | .Re | |
be193d89 | 414 | .Sh AUTHORS |
415 | OpenSSH is a derivative of the original and free | |
416 | ssh 1.2.12 release by Tatu Ylonen. | |
417 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, | |
418 | Theo de Raadt and Dug Song | |
419 | removed many bugs, re-added newer features and | |
420 | created OpenSSH. | |
421 | Markus Friedl contributed the support for SSH | |
422 | protocol versions 1.5 and 2.0. |