Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.83
1.83 ! markus 1: .\" $OpenBSD: ssh-keygen.1,v 1.82 2010/02/08 22:03:05 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: .\"
1.82 jmc 40: .Dd $Mdocdate: February 8 2010 $
1.2 deraadt 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
1.82 jmc 82: .Fl D Ar pkcs11
1.48 jakob 83: .Nm ssh-keygen
1.64 djm 84: .Fl F Ar hostname
85: .Op Fl f Ar known_hosts_file
1.79 sthen 86: .Op Fl l
1.64 djm 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
1.57 jakob 93: .Nm ssh-keygen
94: .Fl r Ar hostname
95: .Op Fl f Ar input_keyfile
96: .Op Fl g
1.60 djm 97: .Nm ssh-keygen
98: .Fl G Ar output_file
1.61 djm 99: .Op Fl v
1.60 djm 100: .Op Fl b Ar bits
101: .Op Fl M Ar memory
102: .Op Fl S Ar start_point
103: .Nm ssh-keygen
104: .Fl T Ar output_file
105: .Fl f Ar input_file
1.61 djm 106: .Op Fl v
1.60 djm 107: .Op Fl a Ar num_trials
108: .Op Fl W Ar generator
1.13 aaron 109: .Sh DESCRIPTION
1.2 deraadt 110: .Nm
1.37 markus 111: generates, manages and converts authentication keys for
1.2 deraadt 112: .Xr ssh 1 .
1.15 deraadt 113: .Nm
1.54 deraadt 114: can create RSA keys for use by SSH protocol version 1 and RSA or DSA
1.58 jmc 115: keys for use by SSH protocol version 2.
116: The type of key to be generated is specified with the
1.25 markus 117: .Fl t
1.52 djm 118: option.
1.70 djm 119: If invoked without any arguments,
120: .Nm
1.71 jmc 121: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 122: .Pp
1.60 djm 123: .Nm
124: is also used to generate groups for use in Diffie-Hellman group
125: exchange (DH-GEX).
126: See the
127: .Sx MODULI GENERATION
128: section for details.
129: .Pp
1.2 deraadt 130: Normally each user wishing to use SSH
1.15 deraadt 131: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 132: key in
1.68 djm 133: .Pa ~/.ssh/identity ,
134: .Pa ~/.ssh/id_dsa
1.15 deraadt 135: or
1.68 djm 136: .Pa ~/.ssh/id_rsa .
1.15 deraadt 137: Additionally, the system administrator may use this to generate host keys,
138: as seen in
139: .Pa /etc/rc .
1.2 deraadt 140: .Pp
1.1 deraadt 141: Normally this program generates the key and asks for a file in which
1.12 aaron 142: to store the private key.
143: The public key is stored in a file with the same name but
1.2 deraadt 144: .Dq .pub
1.12 aaron 145: appended.
146: The program also asks for a passphrase.
147: The passphrase may be empty to indicate no passphrase
1.26 markus 148: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 149: arbitrary length.
1.51 stevesk 150: A passphrase is similar to a password, except it can be a phrase with a
151: series of words, punctuation, numbers, whitespace, or any string of
152: characters you want.
153: Good passphrases are 10-30 characters long, are
1.1 deraadt 154: not simple sentences or otherwise easily guessable (English
1.42 markus 155: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 156: passphrases), and contain a mix of upper and lowercase letters,
157: numbers, and non-alphanumeric characters.
1.12 aaron 158: The passphrase can be changed later by using the
1.2 deraadt 159: .Fl p
1.1 deraadt 160: option.
1.2 deraadt 161: .Pp
1.12 aaron 162: There is no way to recover a lost passphrase.
163: If the passphrase is
1.49 deraadt 164: lost or forgotten, a new key must be generated and copied to the
1.1 deraadt 165: corresponding public key to other machines.
1.2 deraadt 166: .Pp
1.37 markus 167: For RSA1 keys,
168: there is also a comment field in the key file that is only for
1.12 aaron 169: convenience to the user to help identify the key.
170: The comment can tell what the key is for, or whatever is useful.
171: The comment is initialized to
1.2 deraadt 172: .Dq user@host
173: when the key is created, but can be changed using the
174: .Fl c
1.1 deraadt 175: option.
1.2 deraadt 176: .Pp
1.15 deraadt 177: After a key is generated, instructions below detail where the keys
178: should be placed to be activated.
179: .Pp
1.2 deraadt 180: The options are as follows:
181: .Bl -tag -width Ds
1.60 djm 182: .It Fl a Ar trials
183: Specifies the number of primality tests to perform when screening DH-GEX
184: candidates using the
185: .Fl T
186: command.
1.66 jmc 187: .It Fl B
188: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 189: .It Fl b Ar bits
1.12 aaron 190: Specifies the number of bits in the key to create.
1.72 dtucker 191: For RSA keys, the minimum size is 768 bits and the default is 2048 bits.
1.69 djm 192: Generally, 2048 bits is considered sufficient.
1.72 dtucker 193: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.66 jmc 194: .It Fl C Ar comment
195: Provides a new comment.
1.2 deraadt 196: .It Fl c
1.1 deraadt 197: Requests changing the comment in the private and public key files.
1.50 markus 198: This operation is only supported for RSA1 keys.
1.1 deraadt 199: The program will prompt for the file containing the private keys, for
1.41 stevesk 200: the passphrase if the key has one, and for the new comment.
1.81 markus 201: .It Fl D Ar pkcs11
1.83 ! markus 202: Download the RSA public keys provided by the PKCS#11 shared library
! 203: .Ar pkcs11 .
1.37 markus 204: .It Fl e
1.40 markus 205: This option will read a private or public OpenSSH key file and
1.73 markus 206: print the key in
207: RFC 4716 SSH Public Key File Format
1.37 markus 208: to stdout.
209: This option allows exporting keys for use by several commercial
210: SSH implementations.
1.66 jmc 211: .It Fl F Ar hostname
212: Search for the specified
213: .Ar hostname
214: in a
215: .Pa known_hosts
216: file, listing any occurrences found.
217: This option is useful to find hashed host names or addresses and may also be
218: used in conjunction with the
219: .Fl H
220: option to print found keys in a hashed format.
221: .It Fl f Ar filename
222: Specifies the filename of the key file.
223: .It Fl G Ar output_file
224: Generate candidate primes for DH-GEX.
225: These primes must be screened for
226: safety (using the
227: .Fl T
228: option) before use.
1.57 jakob 229: .It Fl g
1.62 jakob 230: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 231: .Fl r
1.62 jakob 232: command.
1.66 jmc 233: .It Fl H
234: Hash a
235: .Pa known_hosts
1.67 dtucker 236: file.
237: This replaces all hostnames and addresses with hashed representations
238: within the specified file; the original content is moved to a file with
239: a .old suffix.
1.66 jmc 240: These hashes may be used normally by
241: .Nm ssh
242: and
243: .Nm sshd ,
244: but they do not reveal identifying information should the file's contents
245: be disclosed.
246: This option will not modify existing hashed hostnames and is therefore safe
247: to use on files that mix hashed and non-hashed names.
1.37 markus 248: .It Fl i
249: This option will read an unencrypted private (or public) key file
250: in SSH2-compatible format and print an OpenSSH compatible private
251: (or public) key to stdout.
252: .Nm
1.38 markus 253: also reads the
1.74 jmc 254: RFC 4716 SSH Public Key File Format.
1.37 markus 255: This option allows importing keys from several commercial
256: SSH implementations.
1.9 markus 257: .It Fl l
1.77 grunk 258: Show fingerprint of specified public key file.
1.50 markus 259: Private RSA1 keys are also supported.
260: For RSA and DSA keys
261: .Nm
1.78 jmc 262: tries to find the matching public key file and prints its fingerprint.
263: If combined with
264: .Fl v ,
265: an ASCII art representation of the key is supplied with the fingerprint.
1.66 jmc 266: .It Fl M Ar memory
267: Specify the amount of memory to use (in megabytes) when generating
268: candidate moduli for DH-GEX.
269: .It Fl N Ar new_passphrase
270: Provides the new passphrase.
271: .It Fl P Ar passphrase
272: Provides the (old) passphrase.
1.2 deraadt 273: .It Fl p
1.1 deraadt 274: Requests changing the passphrase of a private key file instead of
1.12 aaron 275: creating a new private key.
276: The program will prompt for the file
1.1 deraadt 277: containing the private key, for the old passphrase, and twice for the
278: new passphrase.
1.5 aaron 279: .It Fl q
280: Silence
281: .Nm ssh-keygen .
282: Used by
283: .Pa /etc/rc
284: when creating a new key.
1.64 djm 285: .It Fl R Ar hostname
286: Removes all keys belonging to
287: .Ar hostname
1.65 jmc 288: from a
1.64 djm 289: .Pa known_hosts
290: file.
1.65 jmc 291: This option is useful to delete hashed hosts (see the
1.64 djm 292: .Fl H
293: option above).
1.66 jmc 294: .It Fl r Ar hostname
295: Print the SSHFP fingerprint resource record named
296: .Ar hostname
297: for the specified public key file.
1.60 djm 298: .It Fl S Ar start
299: Specify start point (in hex) when generating candidate moduli for DH-GEX.
300: .It Fl T Ar output_file
301: Test DH group exchange candidate primes (generated using the
302: .Fl G
303: option) for safety.
1.66 jmc 304: .It Fl t Ar type
305: Specifies the type of key to create.
306: The possible values are
307: .Dq rsa1
308: for protocol version 1 and
309: .Dq rsa
310: or
311: .Dq dsa
312: for protocol version 2.
1.61 djm 313: .It Fl v
314: Verbose mode.
315: Causes
316: .Nm
317: to print debugging messages about its progress.
318: This is helpful for debugging moduli generation.
319: Multiple
320: .Fl v
321: options increase the verbosity.
322: The maximum is 3.
1.66 jmc 323: .It Fl W Ar generator
324: Specify desired generator when testing candidate moduli for DH-GEX.
325: .It Fl y
326: This option will read a private
327: OpenSSH format file and print an OpenSSH public key to stdout.
1.2 deraadt 328: .El
1.60 djm 329: .Sh MODULI GENERATION
330: .Nm
331: may be used to generate groups for the Diffie-Hellman Group Exchange
332: (DH-GEX) protocol.
333: Generating these groups is a two-step process: first, candidate
334: primes are generated using a fast, but memory intensive process.
335: These candidate primes are then tested for suitability (a CPU-intensive
336: process).
337: .Pp
338: Generation of primes is performed using the
339: .Fl G
340: option.
341: The desired length of the primes may be specified by the
342: .Fl b
343: option.
344: For example:
345: .Pp
1.66 jmc 346: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 347: .Pp
348: By default, the search for primes begins at a random point in the
349: desired length range.
350: This may be overridden using the
351: .Fl S
352: option, which specifies a different start point (in hex).
353: .Pp
354: Once a set of candidates have been generated, they must be tested for
355: suitability.
356: This may be performed using the
357: .Fl T
358: option.
359: In this mode
360: .Nm
361: will read candidates from standard input (or a file specified using the
362: .Fl f
363: option).
364: For example:
365: .Pp
1.66 jmc 366: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 367: .Pp
368: By default, each candidate will be subjected to 100 primality tests.
369: This may be overridden using the
370: .Fl a
371: option.
372: The DH generator value will be chosen automatically for the
373: prime under consideration.
374: If a specific generator is desired, it may be requested using the
375: .Fl W
376: option.
1.66 jmc 377: Valid generator values are 2, 3, and 5.
1.60 djm 378: .Pp
379: Screened DH groups may be installed in
380: .Pa /etc/moduli .
381: It is important that this file contains moduli of a range of bit lengths and
382: that both ends of a connection share common moduli.
1.2 deraadt 383: .Sh FILES
384: .Bl -tag -width Ds
1.68 djm 385: .It Pa ~/.ssh/identity
1.36 itojun 386: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 387: This file should not be readable by anyone but the user.
388: It is possible to
1.1 deraadt 389: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 390: used to encrypt the private part of this file using 128-bit AES.
1.12 aaron 391: This file is not automatically accessed by
1.2 deraadt 392: .Nm
1.1 deraadt 393: but it is offered as the default file for the private key.
1.46 markus 394: .Xr ssh 1
1.15 deraadt 395: will read this file when a login attempt is made.
1.68 djm 396: .It Pa ~/.ssh/identity.pub
1.36 itojun 397: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 398: The contents of this file should be added to
1.68 djm 399: .Pa ~/.ssh/authorized_keys
1.2 deraadt 400: on all machines
1.49 deraadt 401: where the user wishes to log in using RSA authentication.
1.15 deraadt 402: There is no need to keep the contents of this file secret.
1.68 djm 403: .It Pa ~/.ssh/id_dsa
1.36 itojun 404: Contains the protocol version 2 DSA authentication identity of the user.
1.15 deraadt 405: This file should not be readable by anyone but the user.
406: It is possible to
407: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 408: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 409: This file is not automatically accessed by
410: .Nm
411: but it is offered as the default file for the private key.
1.46 markus 412: .Xr ssh 1
1.15 deraadt 413: will read this file when a login attempt is made.
1.68 djm 414: .It Pa ~/.ssh/id_dsa.pub
1.36 itojun 415: Contains the protocol version 2 DSA public key for authentication.
416: The contents of this file should be added to
1.68 djm 417: .Pa ~/.ssh/authorized_keys
1.36 itojun 418: on all machines
1.49 deraadt 419: where the user wishes to log in using public key authentication.
1.36 itojun 420: There is no need to keep the contents of this file secret.
1.68 djm 421: .It Pa ~/.ssh/id_rsa
1.36 itojun 422: Contains the protocol version 2 RSA authentication identity of the user.
423: This file should not be readable by anyone but the user.
424: It is possible to
425: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 426: used to encrypt the private part of this file using 128-bit AES.
1.36 itojun 427: This file is not automatically accessed by
428: .Nm
429: but it is offered as the default file for the private key.
1.46 markus 430: .Xr ssh 1
1.36 itojun 431: will read this file when a login attempt is made.
1.68 djm 432: .It Pa ~/.ssh/id_rsa.pub
1.36 itojun 433: Contains the protocol version 2 RSA public key for authentication.
1.15 deraadt 434: The contents of this file should be added to
1.68 djm 435: .Pa ~/.ssh/authorized_keys
1.15 deraadt 436: on all machines
1.49 deraadt 437: where the user wishes to log in using public key authentication.
1.12 aaron 438: There is no need to keep the contents of this file secret.
1.60 djm 439: .It Pa /etc/moduli
440: Contains Diffie-Hellman groups used for DH-GEX.
441: The file format is described in
442: .Xr moduli 5 .
1.19 aaron 443: .El
1.2 deraadt 444: .Sh SEE ALSO
445: .Xr ssh 1 ,
446: .Xr ssh-add 1 ,
1.8 ericj 447: .Xr ssh-agent 1 ,
1.60 djm 448: .Xr moduli 5 ,
1.30 itojun 449: .Xr sshd 8
1.37 markus 450: .Rs
1.73 markus 451: .%R RFC 4716
452: .%T "The Secure Shell (SSH) Public Key File Format"
453: .%D 2006
1.37 markus 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.
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