Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.62
1.62 ! jakob 1: .\" $OpenBSD: ssh-keygen.1,v 1.61 2003/12/22 09:16:58 djm Exp $
1.29 niklas 2: .\"
1.1 deraadt 3: .\" -*- nroff -*-
4: .\"
5: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
6: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7: .\" All rights reserved
8: .\"
1.22 deraadt 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: .\"
1.33 deraadt 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.
1.22 deraadt 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.
1.1 deraadt 28: .\"
1.22 deraadt 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.
1.1 deraadt 39: .\"
1.2 deraadt 40: .Dd September 25, 1999
41: .Dt SSH-KEYGEN 1
42: .Os
43: .Sh NAME
44: .Nm ssh-keygen
1.37 markus 45: .Nd authentication key generation, management and conversion
1.2 deraadt 46: .Sh SYNOPSIS
47: .Nm ssh-keygen
1.56 jmc 48: .Bk -words
1.25 markus 49: .Op Fl q
1.2 deraadt 50: .Op Fl b Ar bits
1.53 stevesk 51: .Fl t Ar type
1.2 deraadt 52: .Op Fl N Ar new_passphrase
53: .Op Fl C Ar comment
1.20 markus 54: .Op Fl f Ar output_keyfile
1.56 jmc 55: .Ek
1.2 deraadt 56: .Nm ssh-keygen
57: .Fl p
58: .Op Fl P Ar old_passphrase
59: .Op Fl N Ar new_passphrase
1.9 markus 60: .Op Fl f Ar keyfile
1.2 deraadt 61: .Nm ssh-keygen
1.37 markus 62: .Fl i
1.20 markus 63: .Op Fl f Ar input_keyfile
1.16 deraadt 64: .Nm ssh-keygen
1.37 markus 65: .Fl e
1.20 markus 66: .Op Fl f Ar input_keyfile
1.16 deraadt 67: .Nm ssh-keygen
1.17 markus 68: .Fl y
1.20 markus 69: .Op Fl f Ar input_keyfile
1.17 markus 70: .Nm ssh-keygen
1.2 deraadt 71: .Fl c
72: .Op Fl P Ar passphrase
73: .Op Fl C Ar comment
1.9 markus 74: .Op Fl f Ar keyfile
75: .Nm ssh-keygen
76: .Fl l
1.35 markus 77: .Op Fl f Ar input_keyfile
78: .Nm ssh-keygen
79: .Fl B
1.20 markus 80: .Op Fl f Ar input_keyfile
1.48 jakob 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
1.57 jakob 86: .Nm ssh-keygen
87: .Fl r Ar hostname
88: .Op Fl f Ar input_keyfile
89: .Op Fl g
1.60 djm 90: .Nm ssh-keygen
91: .Fl G Ar output_file
1.61 djm 92: .Op Fl v
1.60 djm 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
1.61 djm 99: .Op Fl v
1.60 djm 100: .Op Fl a Ar num_trials
101: .Op Fl W Ar generator
1.13 aaron 102: .Sh DESCRIPTION
1.2 deraadt 103: .Nm
1.37 markus 104: generates, manages and converts authentication keys for
1.2 deraadt 105: .Xr ssh 1 .
1.15 deraadt 106: .Nm
1.54 deraadt 107: can create RSA keys for use by SSH protocol version 1 and RSA or DSA
1.58 jmc 108: keys for use by SSH protocol version 2.
109: The type of key to be generated is specified with the
1.25 markus 110: .Fl t
1.52 djm 111: option.
1.15 deraadt 112: .Pp
1.60 djm 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
1.2 deraadt 120: Normally each user wishing to use SSH
1.15 deraadt 121: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 122: key in
1.36 itojun 123: .Pa $HOME/.ssh/identity ,
124: .Pa $HOME/.ssh/id_dsa
1.15 deraadt 125: or
1.36 itojun 126: .Pa $HOME/.ssh/id_rsa .
1.15 deraadt 127: Additionally, the system administrator may use this to generate host keys,
128: as seen in
129: .Pa /etc/rc .
1.2 deraadt 130: .Pp
1.1 deraadt 131: Normally this program generates the key and asks for a file in which
1.12 aaron 132: to store the private key.
133: The public key is stored in a file with the same name but
1.2 deraadt 134: .Dq .pub
1.12 aaron 135: appended.
136: The program also asks for a passphrase.
137: The passphrase may be empty to indicate no passphrase
1.26 markus 138: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 139: arbitrary length.
1.51 stevesk 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
1.1 deraadt 144: not simple sentences or otherwise easily guessable (English
1.42 markus 145: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 146: passphrases), and contain a mix of upper and lowercase letters,
147: numbers, and non-alphanumeric characters.
1.12 aaron 148: The passphrase can be changed later by using the
1.2 deraadt 149: .Fl p
1.1 deraadt 150: option.
1.2 deraadt 151: .Pp
1.12 aaron 152: There is no way to recover a lost passphrase.
153: If the passphrase is
1.49 deraadt 154: lost or forgotten, a new key must be generated and copied to the
1.1 deraadt 155: corresponding public key to other machines.
1.2 deraadt 156: .Pp
1.37 markus 157: For RSA1 keys,
158: there is also a comment field in the key file that is only for
1.12 aaron 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
1.2 deraadt 162: .Dq user@host
163: when the key is created, but can be changed using the
164: .Fl c
1.1 deraadt 165: option.
1.2 deraadt 166: .Pp
1.15 deraadt 167: After a key is generated, instructions below detail where the keys
168: should be placed to be activated.
169: .Pp
1.2 deraadt 170: The options are as follows:
171: .Bl -tag -width Ds
1.60 djm 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.
1.2 deraadt 177: .It Fl b Ar bits
1.12 aaron 178: Specifies the number of bits in the key to create.
179: Minimum is 512 bits.
1.55 stevesk 180: Generally, 1024 bits is considered sufficient.
1.12 aaron 181: The default is 1024 bits.
1.2 deraadt 182: .It Fl c
1.1 deraadt 183: Requests changing the comment in the private and public key files.
1.50 markus 184: This operation is only supported for RSA1 keys.
1.1 deraadt 185: The program will prompt for the file containing the private keys, for
1.41 stevesk 186: the passphrase if the key has one, and for the new comment.
1.37 markus 187: .It Fl e
1.40 markus 188: This option will read a private or public OpenSSH key file and
189: print the key in a
1.37 markus 190: .Sq SECSH Public Key File Format
191: to stdout.
192: This option allows exporting keys for use by several commercial
193: SSH implementations.
1.57 jakob 194: .It Fl g
1.62 ! jakob 195: Use generic DNS format when printing fingerprint resource records using the
! 196: .Fl r
! 197: command.
1.48 jakob 198: .It Fl f Ar filename
1.9 markus 199: Specifies the filename of the key file.
1.37 markus 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
1.38 markus 205: also reads the
1.37 markus 206: .Sq SECSH Public Key File Format .
207: This option allows importing keys from several commercial
208: SSH implementations.
1.9 markus 209: .It Fl l
1.50 markus 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.
1.2 deraadt 215: .It Fl p
1.1 deraadt 216: Requests changing the passphrase of a private key file instead of
1.12 aaron 217: creating a new private key.
218: The program will prompt for the file
1.1 deraadt 219: containing the private key, for the old passphrase, and twice for the
220: new passphrase.
1.5 aaron 221: .It Fl q
222: Silence
223: .Nm ssh-keygen .
224: Used by
225: .Pa /etc/rc
226: when creating a new key.
1.37 markus 227: .It Fl y
228: This option will read a private
229: OpenSSH format file and print an OpenSSH public key to stdout.
1.25 markus 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.
1.35 markus 239: .It Fl B
240: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 241: .It Fl C Ar comment
1.1 deraadt 242: Provides the new comment.
1.48 jakob 243: .It Fl D Ar reader
244: Download the RSA public key stored in the smartcard in
245: .Ar reader .
1.60 djm 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.
1.2 deraadt 255: .It Fl N Ar new_passphrase
1.1 deraadt 256: Provides the new passphrase.
1.2 deraadt 257: .It Fl P Ar passphrase
1.1 deraadt 258: Provides the (old) passphrase.
1.60 djm 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.
1.48 jakob 267: .It Fl U Ar reader
268: Upload an existing RSA private key into the smartcard in
269: .Ar reader .
1.61 djm 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.
1.57 jakob 280: .It Fl r Ar hostname
1.62 ! jakob 281: Print the SSHFP fingerprint resource record named
! 282: .Ar hostname
! 283: for the specified public key file.
1.2 deraadt 284: .El
1.60 djm 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.
1.2 deraadt 339: .Sh FILES
340: .Bl -tag -width Ds
341: .It Pa $HOME/.ssh/identity
1.36 itojun 342: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 343: This file should not be readable by anyone but the user.
344: It is possible to
1.1 deraadt 345: specify a passphrase when generating the key; that passphrase will be
1.12 aaron 346: used to encrypt the private part of this file using 3DES.
347: This file is not automatically accessed by
1.2 deraadt 348: .Nm
1.1 deraadt 349: but it is offered as the default file for the private key.
1.46 markus 350: .Xr ssh 1
1.15 deraadt 351: will read this file when a login attempt is made.
1.2 deraadt 352: .It Pa $HOME/.ssh/identity.pub
1.36 itojun 353: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 354: The contents of this file should be added to
1.2 deraadt 355: .Pa $HOME/.ssh/authorized_keys
356: on all machines
1.49 deraadt 357: where the user wishes to log in using RSA authentication.
1.15 deraadt 358: There is no need to keep the contents of this file secret.
359: .It Pa $HOME/.ssh/id_dsa
1.36 itojun 360: Contains the protocol version 2 DSA authentication identity of the user.
1.15 deraadt 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.
1.46 markus 368: .Xr ssh 1
1.15 deraadt 369: will read this file when a login attempt is made.
370: .It Pa $HOME/.ssh/id_dsa.pub
1.36 itojun 371: Contains the protocol version 2 DSA public key for authentication.
372: The contents of this file should be added to
1.43 markus 373: .Pa $HOME/.ssh/authorized_keys
1.36 itojun 374: on all machines
1.49 deraadt 375: where the user wishes to log in using public key authentication.
1.36 itojun 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.
1.46 markus 386: .Xr ssh 1
1.36 itojun 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.
1.15 deraadt 390: The contents of this file should be added to
1.43 markus 391: .Pa $HOME/.ssh/authorized_keys
1.15 deraadt 392: on all machines
1.49 deraadt 393: where the user wishes to log in using public key authentication.
1.12 aaron 394: There is no need to keep the contents of this file secret.
1.60 djm 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 .
1.19 aaron 399: .El
1.2 deraadt 400: .Sh SEE ALSO
401: .Xr ssh 1 ,
402: .Xr ssh-add 1 ,
1.8 ericj 403: .Xr ssh-agent 1 ,
1.60 djm 404: .Xr moduli 5 ,
1.30 itojun 405: .Xr sshd 8
1.37 markus 406: .Rs
1.45 deraadt 407: .%A J. Galbraith
408: .%A R. Thayer
1.37 markus 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
1.59 jmc 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.