Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.64
1.64 ! djm 1: .\" $OpenBSD: ssh-keygen.1,v 1.63 2004/08/13 00:01:43 jmc 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
1.64 ! djm 84: .Fl F Ar hostname
! 85: .Op Fl f Ar known_hosts_file
! 86: .Nm ssh-keygen
! 87: .Fl H
! 88: .Op Fl f Ar known_hosts_file
! 89: .Nm ssh-keygen
! 90: .Fl R Ar hostname
! 91: .Op Fl f Ar known_hosts_file
! 92: .Nm ssh-keygen
1.48 jakob 93: .Fl U Ar reader
94: .Op Fl f Ar input_keyfile
1.57 jakob 95: .Nm ssh-keygen
96: .Fl r Ar hostname
97: .Op Fl f Ar input_keyfile
98: .Op Fl g
1.60 djm 99: .Nm ssh-keygen
100: .Fl G Ar output_file
1.61 djm 101: .Op Fl v
1.60 djm 102: .Op Fl b Ar bits
103: .Op Fl M Ar memory
104: .Op Fl S Ar start_point
105: .Nm ssh-keygen
106: .Fl T Ar output_file
107: .Fl f Ar input_file
1.61 djm 108: .Op Fl v
1.60 djm 109: .Op Fl a Ar num_trials
110: .Op Fl W Ar generator
1.13 aaron 111: .Sh DESCRIPTION
1.2 deraadt 112: .Nm
1.37 markus 113: generates, manages and converts authentication keys for
1.2 deraadt 114: .Xr ssh 1 .
1.15 deraadt 115: .Nm
1.54 deraadt 116: can create RSA keys for use by SSH protocol version 1 and RSA or DSA
1.58 jmc 117: keys for use by SSH protocol version 2.
118: The type of key to be generated is specified with the
1.25 markus 119: .Fl t
1.52 djm 120: option.
1.15 deraadt 121: .Pp
1.60 djm 122: .Nm
123: is also used to generate groups for use in Diffie-Hellman group
124: exchange (DH-GEX).
125: See the
126: .Sx MODULI GENERATION
127: section for details.
128: .Pp
1.2 deraadt 129: Normally each user wishing to use SSH
1.15 deraadt 130: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 131: key in
1.36 itojun 132: .Pa $HOME/.ssh/identity ,
133: .Pa $HOME/.ssh/id_dsa
1.15 deraadt 134: or
1.36 itojun 135: .Pa $HOME/.ssh/id_rsa .
1.15 deraadt 136: Additionally, the system administrator may use this to generate host keys,
137: as seen in
138: .Pa /etc/rc .
1.2 deraadt 139: .Pp
1.1 deraadt 140: Normally this program generates the key and asks for a file in which
1.12 aaron 141: to store the private key.
142: The public key is stored in a file with the same name but
1.2 deraadt 143: .Dq .pub
1.12 aaron 144: appended.
145: The program also asks for a passphrase.
146: The passphrase may be empty to indicate no passphrase
1.26 markus 147: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 148: arbitrary length.
1.51 stevesk 149: A passphrase is similar to a password, except it can be a phrase with a
150: series of words, punctuation, numbers, whitespace, or any string of
151: characters you want.
152: Good passphrases are 10-30 characters long, are
1.1 deraadt 153: not simple sentences or otherwise easily guessable (English
1.42 markus 154: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 155: passphrases), and contain a mix of upper and lowercase letters,
156: numbers, and non-alphanumeric characters.
1.12 aaron 157: The passphrase can be changed later by using the
1.2 deraadt 158: .Fl p
1.1 deraadt 159: option.
1.2 deraadt 160: .Pp
1.12 aaron 161: There is no way to recover a lost passphrase.
162: If the passphrase is
1.49 deraadt 163: lost or forgotten, a new key must be generated and copied to the
1.1 deraadt 164: corresponding public key to other machines.
1.2 deraadt 165: .Pp
1.37 markus 166: For RSA1 keys,
167: there is also a comment field in the key file that is only for
1.12 aaron 168: convenience to the user to help identify the key.
169: The comment can tell what the key is for, or whatever is useful.
170: The comment is initialized to
1.2 deraadt 171: .Dq user@host
172: when the key is created, but can be changed using the
173: .Fl c
1.1 deraadt 174: option.
1.2 deraadt 175: .Pp
1.15 deraadt 176: After a key is generated, instructions below detail where the keys
177: should be placed to be activated.
178: .Pp
1.2 deraadt 179: The options are as follows:
180: .Bl -tag -width Ds
1.60 djm 181: .It Fl a Ar trials
182: Specifies the number of primality tests to perform when screening DH-GEX
183: candidates using the
184: .Fl T
185: command.
1.2 deraadt 186: .It Fl b Ar bits
1.12 aaron 187: Specifies the number of bits in the key to create.
188: Minimum is 512 bits.
1.55 stevesk 189: Generally, 1024 bits is considered sufficient.
1.12 aaron 190: The default is 1024 bits.
1.2 deraadt 191: .It Fl c
1.1 deraadt 192: Requests changing the comment in the private and public key files.
1.50 markus 193: This operation is only supported for RSA1 keys.
1.1 deraadt 194: The program will prompt for the file containing the private keys, for
1.41 stevesk 195: the passphrase if the key has one, and for the new comment.
1.37 markus 196: .It Fl e
1.40 markus 197: This option will read a private or public OpenSSH key file and
198: print the key in a
1.37 markus 199: .Sq SECSH Public Key File Format
200: to stdout.
201: This option allows exporting keys for use by several commercial
202: SSH implementations.
1.57 jakob 203: .It Fl g
1.62 jakob 204: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 205: .Fl r
1.62 jakob 206: command.
1.48 jakob 207: .It Fl f Ar filename
1.9 markus 208: Specifies the filename of the key file.
1.37 markus 209: .It Fl i
210: This option will read an unencrypted private (or public) key file
211: in SSH2-compatible format and print an OpenSSH compatible private
212: (or public) key to stdout.
213: .Nm
1.38 markus 214: also reads the
1.37 markus 215: .Sq SECSH Public Key File Format .
216: This option allows importing keys from several commercial
217: SSH implementations.
1.9 markus 218: .It Fl l
1.50 markus 219: Show fingerprint of specified public key file.
220: Private RSA1 keys are also supported.
221: For RSA and DSA keys
222: .Nm
223: tries to find the matching public key file and prints its fingerprint.
1.2 deraadt 224: .It Fl p
1.1 deraadt 225: Requests changing the passphrase of a private key file instead of
1.12 aaron 226: creating a new private key.
227: The program will prompt for the file
1.1 deraadt 228: containing the private key, for the old passphrase, and twice for the
229: new passphrase.
1.5 aaron 230: .It Fl q
231: Silence
232: .Nm ssh-keygen .
233: Used by
234: .Pa /etc/rc
235: when creating a new key.
1.37 markus 236: .It Fl y
237: This option will read a private
238: OpenSSH format file and print an OpenSSH public key to stdout.
1.25 markus 239: .It Fl t Ar type
240: Specifies the type of the key to create.
241: The possible values are
242: .Dq rsa1
243: for protocol version 1 and
244: .Dq rsa
245: or
246: .Dq dsa
247: for protocol version 2.
1.35 markus 248: .It Fl B
249: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 250: .It Fl C Ar comment
1.1 deraadt 251: Provides the new comment.
1.48 jakob 252: .It Fl D Ar reader
253: Download the RSA public key stored in the smartcard in
254: .Ar reader .
1.64 ! djm 255: .It Fl F Ar hostname
! 256: Search for the specified
! 257: .Ar hostname
! 258: in a
! 259: .Pa known_hosts
! 260: file, listing any occurances found.
! 261: This option is useful to find hashed host names or addresses and may also be
! 262: used in conjunction with the
! 263: .Fl H
! 264: option to print found keys in a hashed format.
! 265: .It Fl H
! 266: Hash a
! 267: .Pa known_hosts
! 268: file, printing the result to standard output.
! 269: This replaces all hostnames and addresses with hashed representations.
! 270: These hashes may be used normally by
! 271: .Nm ssh
! 272: and
! 273: .Nm sshd ,
! 274: but they do not reveal identifying information should the file's contents
! 275: be disclosed.
! 276: This option will not modify existing hashed hostnames and is therefore safe
! 277: to use on files that mix hashed and non-hashed names.
! 278: .It Fl R Ar hostname
! 279: Removes all keys belonging to
! 280: .Ar hostname
! 281: from a
! 282: .Pa known_hosts
! 283: file.
! 284: This option is useful to delete hashed hosts (see the
! 285: .Fl H
! 286: option above).
1.60 djm 287: .It Fl G Ar output_file
288: Generate candidate primes for DH-GEX.
289: These primes must be screened for
290: safety (using the
291: .Fl T
292: option) before use.
293: .It Fl M Ar memory
294: Specify the amount of memory to use (in megabytes) when generating
295: candidate moduli for DH-GEX.
1.2 deraadt 296: .It Fl N Ar new_passphrase
1.1 deraadt 297: Provides the new passphrase.
1.2 deraadt 298: .It Fl P Ar passphrase
1.1 deraadt 299: Provides the (old) passphrase.
1.60 djm 300: .It Fl S Ar start
301: Specify start point (in hex) when generating candidate moduli for DH-GEX.
302: .It Fl T Ar output_file
303: Test DH group exchange candidate primes (generated using the
304: .Fl G
305: option) for safety.
306: .It Fl W Ar generator
307: Specify desired generator when testing candidate moduli for DH-GEX.
1.48 jakob 308: .It Fl U Ar reader
309: Upload an existing RSA private key into the smartcard in
310: .Ar reader .
1.61 djm 311: .It Fl v
312: Verbose mode.
313: Causes
314: .Nm
315: to print debugging messages about its progress.
316: This is helpful for debugging moduli generation.
317: Multiple
318: .Fl v
319: options increase the verbosity.
320: The maximum is 3.
1.57 jakob 321: .It Fl r Ar hostname
1.62 jakob 322: Print the SSHFP fingerprint resource record named
323: .Ar hostname
324: for the specified public key file.
1.2 deraadt 325: .El
1.60 djm 326: .Sh MODULI GENERATION
327: .Nm
328: may be used to generate groups for the Diffie-Hellman Group Exchange
329: (DH-GEX) protocol.
330: Generating these groups is a two-step process: first, candidate
331: primes are generated using a fast, but memory intensive process.
332: These candidate primes are then tested for suitability (a CPU-intensive
333: process).
334: .Pp
335: Generation of primes is performed using the
336: .Fl G
337: option.
338: The desired length of the primes may be specified by the
339: .Fl b
340: option.
341: For example:
342: .Pp
343: .Dl ssh-keygen -G moduli-2048.candidates -b 2048
344: .Pp
345: By default, the search for primes begins at a random point in the
346: desired length range.
347: This may be overridden using the
348: .Fl S
349: option, which specifies a different start point (in hex).
350: .Pp
351: Once a set of candidates have been generated, they must be tested for
352: suitability.
353: This may be performed using the
354: .Fl T
355: option.
356: In this mode
357: .Nm
358: will read candidates from standard input (or a file specified using the
359: .Fl f
360: option).
361: For example:
362: .Pp
363: .Dl ssh-keygen -T moduli-2048 -f moduli-2048.candidates
364: .Pp
365: By default, each candidate will be subjected to 100 primality tests.
366: This may be overridden using the
367: .Fl a
368: option.
369: The DH generator value will be chosen automatically for the
370: prime under consideration.
371: If a specific generator is desired, it may be requested using the
372: .Fl W
373: option.
374: Valid generator values are 2, 3 and 5.
375: .Pp
376: Screened DH groups may be installed in
377: .Pa /etc/moduli .
378: It is important that this file contains moduli of a range of bit lengths and
379: that both ends of a connection share common moduli.
1.2 deraadt 380: .Sh FILES
381: .Bl -tag -width Ds
382: .It Pa $HOME/.ssh/identity
1.36 itojun 383: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 384: This file should not be readable by anyone but the user.
385: It is possible to
1.1 deraadt 386: specify a passphrase when generating the key; that passphrase will be
1.12 aaron 387: used to encrypt the private part of this file using 3DES.
388: This file is not automatically accessed by
1.2 deraadt 389: .Nm
1.1 deraadt 390: but it is offered as the default file for the private key.
1.46 markus 391: .Xr ssh 1
1.15 deraadt 392: will read this file when a login attempt is made.
1.2 deraadt 393: .It Pa $HOME/.ssh/identity.pub
1.36 itojun 394: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 395: The contents of this file should be added to
1.2 deraadt 396: .Pa $HOME/.ssh/authorized_keys
397: on all machines
1.49 deraadt 398: where the user wishes to log in using RSA authentication.
1.15 deraadt 399: There is no need to keep the contents of this file secret.
400: .It Pa $HOME/.ssh/id_dsa
1.36 itojun 401: Contains the protocol version 2 DSA authentication identity of the user.
1.15 deraadt 402: This file should not be readable by anyone but the user.
403: It is possible to
404: specify a passphrase when generating the key; that passphrase will be
405: used to encrypt the private part of this file using 3DES.
406: This file is not automatically accessed by
407: .Nm
408: but it is offered as the default file for the private key.
1.46 markus 409: .Xr ssh 1
1.15 deraadt 410: will read this file when a login attempt is made.
411: .It Pa $HOME/.ssh/id_dsa.pub
1.36 itojun 412: Contains the protocol version 2 DSA public key for authentication.
413: The contents of this file should be added to
1.43 markus 414: .Pa $HOME/.ssh/authorized_keys
1.36 itojun 415: on all machines
1.49 deraadt 416: where the user wishes to log in using public key authentication.
1.36 itojun 417: There is no need to keep the contents of this file secret.
418: .It Pa $HOME/.ssh/id_rsa
419: Contains the protocol version 2 RSA authentication identity of the user.
420: This file should not be readable by anyone but the user.
421: It is possible to
422: specify a passphrase when generating the key; that passphrase will be
423: used to encrypt the private part of this file using 3DES.
424: This file is not automatically accessed by
425: .Nm
426: but it is offered as the default file for the private key.
1.46 markus 427: .Xr ssh 1
1.36 itojun 428: will read this file when a login attempt is made.
429: .It Pa $HOME/.ssh/id_rsa.pub
430: Contains the protocol version 2 RSA public key for authentication.
1.15 deraadt 431: The contents of this file should be added to
1.43 markus 432: .Pa $HOME/.ssh/authorized_keys
1.15 deraadt 433: on all machines
1.49 deraadt 434: where the user wishes to log in using public key authentication.
1.12 aaron 435: There is no need to keep the contents of this file secret.
1.60 djm 436: .It Pa /etc/moduli
437: Contains Diffie-Hellman groups used for DH-GEX.
438: The file format is described in
439: .Xr moduli 5 .
1.19 aaron 440: .El
1.2 deraadt 441: .Sh SEE ALSO
442: .Xr ssh 1 ,
443: .Xr ssh-add 1 ,
1.8 ericj 444: .Xr ssh-agent 1 ,
1.60 djm 445: .Xr moduli 5 ,
1.30 itojun 446: .Xr sshd 8
1.37 markus 447: .Rs
1.45 deraadt 448: .%A J. Galbraith
449: .%A R. Thayer
1.37 markus 450: .%T "SECSH Public Key File Format"
451: .%N draft-ietf-secsh-publickeyfile-01.txt
452: .%D March 2001
453: .%O work in progress material
454: .Re
1.59 jmc 455: .Sh AUTHORS
456: OpenSSH is a derivative of the original and free
457: ssh 1.2.12 release by Tatu Ylonen.
458: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
459: Theo de Raadt and Dug Song
460: removed many bugs, re-added newer features and
461: created OpenSSH.
462: Markus Friedl contributed the support for SSH
463: protocol versions 1.5 and 2.0.