Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.112
1.112 ! jmc 1: .\" $OpenBSD: ssh-keygen.1,v 1.111 2013/01/17 23:00:01 djm Exp $
1.1 deraadt 2: .\"
3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
6: .\"
1.22 deraadt 7: .\" As far as I am concerned, the code I have written for this software
8: .\" can be used freely for any purpose. Any derived versions of this
9: .\" software must be clearly marked as such, and if the derived work is
10: .\" incompatible with the protocol description in the RFC file, it must be
11: .\" called by a name other than "ssh" or "Secure Shell".
12: .\"
13: .\"
1.33 deraadt 14: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
15: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
16: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
1.22 deraadt 17: .\"
18: .\" Redistribution and use in source and binary forms, with or without
19: .\" modification, are permitted provided that the following conditions
20: .\" are met:
21: .\" 1. Redistributions of source code must retain the above copyright
22: .\" notice, this list of conditions and the following disclaimer.
23: .\" 2. Redistributions in binary form must reproduce the above copyright
24: .\" notice, this list of conditions and the following disclaimer in the
25: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 26: .\"
1.22 deraadt 27: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 37: .\"
1.112 ! jmc 38: .Dd $Mdocdate: January 17 2013 $
1.2 deraadt 39: .Dt SSH-KEYGEN 1
40: .Os
41: .Sh NAME
42: .Nm ssh-keygen
1.37 markus 43: .Nd authentication key generation, management and conversion
1.2 deraadt 44: .Sh SYNOPSIS
1.97 schwarze 45: .Bk -words
1.2 deraadt 46: .Nm ssh-keygen
1.25 markus 47: .Op Fl q
1.2 deraadt 48: .Op Fl b Ar bits
1.53 stevesk 49: .Fl t Ar type
1.2 deraadt 50: .Op Fl N Ar new_passphrase
51: .Op Fl C Ar comment
1.20 markus 52: .Op Fl f Ar output_keyfile
1.2 deraadt 53: .Nm ssh-keygen
54: .Fl p
55: .Op Fl P Ar old_passphrase
56: .Op Fl N Ar new_passphrase
1.9 markus 57: .Op Fl f Ar keyfile
1.2 deraadt 58: .Nm ssh-keygen
1.37 markus 59: .Fl i
1.95 djm 60: .Op Fl m Ar key_format
1.20 markus 61: .Op Fl f Ar input_keyfile
1.16 deraadt 62: .Nm ssh-keygen
1.37 markus 63: .Fl e
1.95 djm 64: .Op Fl m Ar key_format
1.20 markus 65: .Op Fl f Ar input_keyfile
1.16 deraadt 66: .Nm ssh-keygen
1.17 markus 67: .Fl y
1.20 markus 68: .Op Fl f Ar input_keyfile
1.17 markus 69: .Nm ssh-keygen
1.2 deraadt 70: .Fl c
71: .Op Fl P Ar passphrase
72: .Op Fl C Ar comment
1.9 markus 73: .Op Fl f Ar keyfile
74: .Nm ssh-keygen
75: .Fl l
1.35 markus 76: .Op Fl f Ar input_keyfile
77: .Nm ssh-keygen
78: .Fl B
1.20 markus 79: .Op Fl f Ar input_keyfile
1.48 jakob 80: .Nm ssh-keygen
1.82 jmc 81: .Fl D Ar pkcs11
1.48 jakob 82: .Nm ssh-keygen
1.64 djm 83: .Fl F Ar hostname
84: .Op Fl f Ar known_hosts_file
1.79 sthen 85: .Op Fl l
1.64 djm 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
1.57 jakob 92: .Nm ssh-keygen
93: .Fl r Ar hostname
94: .Op Fl f Ar input_keyfile
95: .Op Fl g
1.60 djm 96: .Nm ssh-keygen
97: .Fl G Ar output_file
1.61 djm 98: .Op Fl v
1.60 djm 99: .Op Fl b Ar bits
100: .Op Fl M Ar memory
101: .Op Fl S Ar start_point
102: .Nm ssh-keygen
103: .Fl T Ar output_file
104: .Fl f Ar input_file
1.61 djm 105: .Op Fl v
1.60 djm 106: .Op Fl a Ar num_trials
1.109 dtucker 107: .Op Fl J Ar num_lines
108: .Op Fl j Ar start_line
1.108 dtucker 109: .Op Fl K Ar checkpt
1.60 djm 110: .Op Fl W Ar generator
1.84 djm 111: .Nm ssh-keygen
112: .Fl s Ar ca_key
113: .Fl I Ar certificate_identity
114: .Op Fl h
115: .Op Fl n Ar principals
1.93 djm 116: .Op Fl O Ar option
1.84 djm 117: .Op Fl V Ar validity_interval
1.93 djm 118: .Op Fl z Ar serial_number
1.84 djm 119: .Ar
1.86 djm 120: .Nm ssh-keygen
121: .Fl L
122: .Op Fl f Ar input_keyfile
1.102 stevesk 123: .Nm ssh-keygen
124: .Fl A
1.111 djm 125: .Nm ssh-keygen
126: .Fl k
127: .Fl f Ar krl_file
128: .Op Fl u
1.112 ! jmc 129: .Op Fl s Ar ca_public
! 130: .Op Fl z Ar version_number
1.111 djm 131: .Ar
132: .Nm ssh-keygen
133: .Fl Q
134: .Fl f Ar krl_file
135: .Ar
1.85 jmc 136: .Ek
1.13 aaron 137: .Sh DESCRIPTION
1.2 deraadt 138: .Nm
1.37 markus 139: generates, manages and converts authentication keys for
1.2 deraadt 140: .Xr ssh 1 .
1.15 deraadt 141: .Nm
1.100 naddy 142: can create RSA keys for use by SSH protocol version 1 and DSA, ECDSA or RSA
1.58 jmc 143: keys for use by SSH protocol version 2.
144: The type of key to be generated is specified with the
1.25 markus 145: .Fl t
1.52 djm 146: option.
1.70 djm 147: If invoked without any arguments,
148: .Nm
1.71 jmc 149: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 150: .Pp
1.60 djm 151: .Nm
152: is also used to generate groups for use in Diffie-Hellman group
153: exchange (DH-GEX).
154: See the
155: .Sx MODULI GENERATION
156: section for details.
157: .Pp
1.111 djm 158: Finally,
159: .Nm
160: can be used to generate and update Key Revocation Lists, and to test whether
1.112 ! jmc 161: given keys have been revoked by one.
! 162: See the
1.111 djm 163: .Sx KEY REVOCATION LISTS
164: section for details.
165: .Pp
1.2 deraadt 166: Normally each user wishing to use SSH
1.99 djm 167: with public key authentication runs this once to create the authentication
1.1 deraadt 168: key in
1.68 djm 169: .Pa ~/.ssh/identity ,
1.99 djm 170: .Pa ~/.ssh/id_ecdsa ,
1.68 djm 171: .Pa ~/.ssh/id_dsa
1.15 deraadt 172: or
1.68 djm 173: .Pa ~/.ssh/id_rsa .
1.15 deraadt 174: Additionally, the system administrator may use this to generate host keys,
175: as seen in
176: .Pa /etc/rc .
1.2 deraadt 177: .Pp
1.1 deraadt 178: Normally this program generates the key and asks for a file in which
1.12 aaron 179: to store the private key.
180: The public key is stored in a file with the same name but
1.2 deraadt 181: .Dq .pub
1.12 aaron 182: appended.
183: The program also asks for a passphrase.
184: The passphrase may be empty to indicate no passphrase
1.26 markus 185: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 186: arbitrary length.
1.51 stevesk 187: A passphrase is similar to a password, except it can be a phrase with a
188: series of words, punctuation, numbers, whitespace, or any string of
189: characters you want.
190: Good passphrases are 10-30 characters long, are
1.1 deraadt 191: not simple sentences or otherwise easily guessable (English
1.42 markus 192: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 193: passphrases), and contain a mix of upper and lowercase letters,
194: numbers, and non-alphanumeric characters.
1.12 aaron 195: The passphrase can be changed later by using the
1.2 deraadt 196: .Fl p
1.1 deraadt 197: option.
1.2 deraadt 198: .Pp
1.12 aaron 199: There is no way to recover a lost passphrase.
1.105 djm 200: If the passphrase is lost or forgotten, a new key must be generated
201: and the corresponding public key copied to other machines.
1.2 deraadt 202: .Pp
1.37 markus 203: For RSA1 keys,
204: there is also a comment field in the key file that is only for
1.12 aaron 205: convenience to the user to help identify the key.
206: The comment can tell what the key is for, or whatever is useful.
207: The comment is initialized to
1.2 deraadt 208: .Dq user@host
209: when the key is created, but can be changed using the
210: .Fl c
1.1 deraadt 211: option.
1.2 deraadt 212: .Pp
1.15 deraadt 213: After a key is generated, instructions below detail where the keys
214: should be placed to be activated.
215: .Pp
1.2 deraadt 216: The options are as follows:
217: .Bl -tag -width Ds
1.102 stevesk 218: .It Fl A
219: For each of the key types (rsa1, rsa, dsa and ecdsa) for which host keys
220: do not exist, generate the host keys with the default key file path,
221: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 222: This is used by
1.102 stevesk 223: .Pa /etc/rc
224: to generate new host keys.
1.60 djm 225: .It Fl a Ar trials
226: Specifies the number of primality tests to perform when screening DH-GEX
227: candidates using the
228: .Fl T
229: command.
1.66 jmc 230: .It Fl B
231: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 232: .It Fl b Ar bits
1.12 aaron 233: Specifies the number of bits in the key to create.
1.72 dtucker 234: For RSA keys, the minimum size is 768 bits and the default is 2048 bits.
1.69 djm 235: Generally, 2048 bits is considered sufficient.
1.72 dtucker 236: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 237: For ECDSA keys, the
238: .Fl b
1.107 deraadt 239: flag determines the key length by selecting from one of three elliptic
1.106 djm 240: curve sizes: 256, 384 or 521 bits.
241: Attempting to use bit lengths other than these three values for ECDSA keys
242: will fail.
1.66 jmc 243: .It Fl C Ar comment
244: Provides a new comment.
1.2 deraadt 245: .It Fl c
1.1 deraadt 246: Requests changing the comment in the private and public key files.
1.50 markus 247: This operation is only supported for RSA1 keys.
1.1 deraadt 248: The program will prompt for the file containing the private keys, for
1.41 stevesk 249: the passphrase if the key has one, and for the new comment.
1.81 markus 250: .It Fl D Ar pkcs11
1.83 markus 251: Download the RSA public keys provided by the PKCS#11 shared library
252: .Ar pkcs11 .
1.98 djm 253: When used in combination with
254: .Fl s ,
255: this option indicates that a CA key resides in a PKCS#11 token (see the
256: .Sx CERTIFICATES
257: section for details).
1.37 markus 258: .It Fl e
1.40 markus 259: This option will read a private or public OpenSSH key file and
1.95 djm 260: print to stdout the key in one of the formats specified by the
261: .Fl m
262: option.
263: The default export format is
264: .Dq RFC4716 .
1.96 jmc 265: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 266: several commercial SSH implementations.
1.66 jmc 267: .It Fl F Ar hostname
268: Search for the specified
269: .Ar hostname
270: in a
271: .Pa known_hosts
272: file, listing any occurrences found.
273: This option is useful to find hashed host names or addresses and may also be
274: used in conjunction with the
275: .Fl H
276: option to print found keys in a hashed format.
277: .It Fl f Ar filename
278: Specifies the filename of the key file.
279: .It Fl G Ar output_file
280: Generate candidate primes for DH-GEX.
281: These primes must be screened for
282: safety (using the
283: .Fl T
284: option) before use.
1.57 jakob 285: .It Fl g
1.62 jakob 286: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 287: .Fl r
1.62 jakob 288: command.
1.66 jmc 289: .It Fl H
290: Hash a
291: .Pa known_hosts
1.67 dtucker 292: file.
293: This replaces all hostnames and addresses with hashed representations
294: within the specified file; the original content is moved to a file with
295: a .old suffix.
1.66 jmc 296: These hashes may be used normally by
297: .Nm ssh
298: and
299: .Nm sshd ,
300: but they do not reveal identifying information should the file's contents
301: be disclosed.
302: This option will not modify existing hashed hostnames and is therefore safe
303: to use on files that mix hashed and non-hashed names.
1.84 djm 304: .It Fl h
305: When signing a key, create a host certificate instead of a user
306: certificate.
307: Please see the
308: .Sx CERTIFICATES
309: section for details.
1.85 jmc 310: .It Fl I Ar certificate_identity
1.84 djm 311: Specify the key identity when signing a public key.
312: Please see the
313: .Sx CERTIFICATES
314: section for details.
1.37 markus 315: .It Fl i
316: This option will read an unencrypted private (or public) key file
1.95 djm 317: in the format specified by the
318: .Fl m
319: option and print an OpenSSH compatible private
1.37 markus 320: (or public) key to stdout.
1.109 dtucker 321: .It Fl J Ar num_lines
322: Exit after screening the specified number of lines
323: while performing DH candidate screening using the
324: .Fl T
325: option.
326: .It Fl j Ar start_line
327: Start screening at the specified line number
328: while performing DH candidate screening using the
329: .Fl T
330: option.
1.108 dtucker 331: .It Fl K Ar checkpt
332: Write the last line processed to the file
333: .Ar checkpt
334: while performing DH candidate screening using the
335: .Fl T
336: option.
337: This will be used to skip lines in the input file that have already been
338: processed if the job is restarted.
1.95 djm 339: This option allows importing keys from other software, including several
340: commercial SSH implementations.
341: The default import format is
342: .Dq RFC4716 .
1.111 djm 343: .It Fl k
344: Generate a KRL file.
345: In this mode,
346: .Nm
347: will generate a KRL file at the location specified via the
348: .Fl f
349: flag that revokes every key or certificate presented on the command-line.
350: Keys/certificates to be revoked may be specified by public key file or
351: using the format described in the
352: .Sx KEY REVOCATION LISTS
353: section.
1.86 djm 354: .It Fl L
355: Prints the contents of a certificate.
1.9 markus 356: .It Fl l
1.77 grunk 357: Show fingerprint of specified public key file.
1.50 markus 358: Private RSA1 keys are also supported.
359: For RSA and DSA keys
360: .Nm
1.78 jmc 361: tries to find the matching public key file and prints its fingerprint.
362: If combined with
363: .Fl v ,
364: an ASCII art representation of the key is supplied with the fingerprint.
1.96 jmc 365: .It Fl M Ar memory
366: Specify the amount of memory to use (in megabytes) when generating
367: candidate moduli for DH-GEX.
1.95 djm 368: .It Fl m Ar key_format
369: Specify a key format for the
370: .Fl i
371: (import) or
372: .Fl e
1.96 jmc 373: (export) conversion options.
1.95 djm 374: The supported key formats are:
375: .Dq RFC4716
1.96 jmc 376: (RFC 4716/SSH2 public or private key),
1.95 djm 377: .Dq PKCS8
378: (PEM PKCS8 public key)
379: or
380: .Dq PEM
381: (PEM public key).
382: The default conversion format is
383: .Dq RFC4716 .
1.66 jmc 384: .It Fl N Ar new_passphrase
385: Provides the new passphrase.
1.84 djm 386: .It Fl n Ar principals
387: Specify one or more principals (user or host names) to be included in
388: a certificate when signing a key.
389: Multiple principals may be specified, separated by commas.
390: Please see the
391: .Sx CERTIFICATES
392: section for details.
1.93 djm 393: .It Fl O Ar option
394: Specify a certificate option when signing a key.
1.84 djm 395: This option may be specified multiple times.
396: Please see the
397: .Sx CERTIFICATES
398: section for details.
1.93 djm 399: The options that are valid for user certificates are:
1.84 djm 400: .Bl -tag -width Ds
1.89 jmc 401: .It Ic clear
402: Clear all enabled permissions.
403: This is useful for clearing the default set of permissions so permissions may
404: be added individually.
405: .It Ic force-command Ns = Ns Ar command
406: Forces the execution of
407: .Ar command
408: instead of any shell or command specified by the user when
409: the certificate is used for authentication.
1.84 djm 410: .It Ic no-agent-forwarding
411: Disable
412: .Xr ssh-agent 1
1.85 jmc 413: forwarding (permitted by default).
1.84 djm 414: .It Ic no-port-forwarding
1.85 jmc 415: Disable port forwarding (permitted by default).
1.84 djm 416: .It Ic no-pty
1.85 jmc 417: Disable PTY allocation (permitted by default).
1.84 djm 418: .It Ic no-user-rc
419: Disable execution of
420: .Pa ~/.ssh/rc
421: by
1.85 jmc 422: .Xr sshd 8
423: (permitted by default).
1.89 jmc 424: .It Ic no-x11-forwarding
425: Disable X11 forwarding (permitted by default).
1.88 djm 426: .It Ic permit-agent-forwarding
427: Allows
428: .Xr ssh-agent 1
429: forwarding.
1.84 djm 430: .It Ic permit-port-forwarding
431: Allows port forwarding.
432: .It Ic permit-pty
433: Allows PTY allocation.
434: .It Ic permit-user-rc
435: Allows execution of
436: .Pa ~/.ssh/rc
437: by
438: .Xr sshd 8 .
1.89 jmc 439: .It Ic permit-x11-forwarding
440: Allows X11 forwarding.
441: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 442: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 443: The
444: .Ar address_list
445: is a comma-separated list of one or more address/netmask pairs in CIDR
446: format.
447: .El
448: .Pp
1.93 djm 449: At present, no options are valid for host keys.
1.66 jmc 450: .It Fl P Ar passphrase
451: Provides the (old) passphrase.
1.2 deraadt 452: .It Fl p
1.1 deraadt 453: Requests changing the passphrase of a private key file instead of
1.12 aaron 454: creating a new private key.
455: The program will prompt for the file
1.1 deraadt 456: containing the private key, for the old passphrase, and twice for the
457: new passphrase.
1.5 aaron 458: .It Fl q
459: Silence
460: .Nm ssh-keygen .
1.64 djm 461: .It Fl R Ar hostname
462: Removes all keys belonging to
463: .Ar hostname
1.65 jmc 464: from a
1.64 djm 465: .Pa known_hosts
466: file.
1.65 jmc 467: This option is useful to delete hashed hosts (see the
1.64 djm 468: .Fl H
469: option above).
1.66 jmc 470: .It Fl r Ar hostname
471: Print the SSHFP fingerprint resource record named
472: .Ar hostname
473: for the specified public key file.
1.60 djm 474: .It Fl S Ar start
475: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 476: .It Fl s Ar ca_key
477: Certify (sign) a public key using the specified CA key.
478: Please see the
479: .Sx CERTIFICATES
480: section for details.
1.111 djm 481: .Pp
482: When generating a KRL,
483: .Fl s
1.112 ! jmc 484: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 485: by key ID or serial number.
486: See the
487: .Sx KEY REVOCATION LISTS
488: section for details.
1.60 djm 489: .It Fl T Ar output_file
490: Test DH group exchange candidate primes (generated using the
491: .Fl G
492: option) for safety.
1.66 jmc 493: .It Fl t Ar type
494: Specifies the type of key to create.
495: The possible values are
496: .Dq rsa1
497: for protocol version 1 and
1.100 naddy 498: .Dq dsa ,
499: .Dq ecdsa
500: or
1.66 jmc 501: .Dq rsa
502: for protocol version 2.
1.112 ! jmc 503: .It Fl u
! 504: Update a KRL.
! 505: When specified with
! 506: .Fl k ,
! 507: keys listed via the command-line are added to the existing KRL rather than
! 508: a new KRL being created.
1.84 djm 509: .It Fl V Ar validity_interval
510: Specify a validity interval when signing a certificate.
511: A validity interval may consist of a single time, indicating that the
512: certificate is valid beginning now and expiring at that time, or may consist
513: of two times separated by a colon to indicate an explicit time interval.
514: The start time may be specified as a date in YYYYMMDD format, a time
515: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
516: of a minus sign followed by a relative time in the format described in the
517: .Sx TIME FORMATS
518: section of
1.90 jmc 519: .Xr sshd_config 5 .
1.84 djm 520: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
521: a relative time starting with a plus character.
522: .Pp
523: For example:
524: .Dq +52w1d
525: (valid from now to 52 weeks and one day from now),
526: .Dq -4w:+4w
527: (valid from four weeks ago to four weeks from now),
528: .Dq 20100101123000:20110101123000
529: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
530: .Dq -1d:20110101
531: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 532: .It Fl v
533: Verbose mode.
534: Causes
535: .Nm
536: to print debugging messages about its progress.
537: This is helpful for debugging moduli generation.
538: Multiple
539: .Fl v
540: options increase the verbosity.
541: The maximum is 3.
1.66 jmc 542: .It Fl W Ar generator
543: Specify desired generator when testing candidate moduli for DH-GEX.
544: .It Fl y
545: This option will read a private
546: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 547: .It Fl z Ar serial_number
548: Specifies a serial number to be embedded in the certificate to distinguish
549: this certificate from others from the same CA.
550: The default serial number is zero.
1.111 djm 551: .Pp
552: When generating a KRL, the
553: .Fl z
554: flag is used to specify a KRL version number.
1.2 deraadt 555: .El
1.60 djm 556: .Sh MODULI GENERATION
557: .Nm
558: may be used to generate groups for the Diffie-Hellman Group Exchange
559: (DH-GEX) protocol.
560: Generating these groups is a two-step process: first, candidate
561: primes are generated using a fast, but memory intensive process.
562: These candidate primes are then tested for suitability (a CPU-intensive
563: process).
564: .Pp
565: Generation of primes is performed using the
566: .Fl G
567: option.
568: The desired length of the primes may be specified by the
569: .Fl b
570: option.
571: For example:
572: .Pp
1.66 jmc 573: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 574: .Pp
575: By default, the search for primes begins at a random point in the
576: desired length range.
577: This may be overridden using the
578: .Fl S
579: option, which specifies a different start point (in hex).
580: .Pp
1.109 dtucker 581: Once a set of candidates have been generated, they must be screened for
1.60 djm 582: suitability.
583: This may be performed using the
584: .Fl T
585: option.
586: In this mode
587: .Nm
588: will read candidates from standard input (or a file specified using the
589: .Fl f
590: option).
591: For example:
592: .Pp
1.66 jmc 593: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 594: .Pp
595: By default, each candidate will be subjected to 100 primality tests.
596: This may be overridden using the
597: .Fl a
598: option.
599: The DH generator value will be chosen automatically for the
600: prime under consideration.
601: If a specific generator is desired, it may be requested using the
602: .Fl W
603: option.
1.66 jmc 604: Valid generator values are 2, 3, and 5.
1.60 djm 605: .Pp
606: Screened DH groups may be installed in
607: .Pa /etc/moduli .
608: It is important that this file contains moduli of a range of bit lengths and
609: that both ends of a connection share common moduli.
1.84 djm 610: .Sh CERTIFICATES
611: .Nm
612: supports signing of keys to produce certificates that may be used for
613: user or host authentication.
614: Certificates consist of a public key, some identity information, zero or
1.94 jmc 615: more principal (user or host) names and a set of options that
1.84 djm 616: are signed by a Certification Authority (CA) key.
617: Clients or servers may then trust only the CA key and verify its signature
618: on a certificate rather than trusting many user/host keys.
619: Note that OpenSSH certificates are a different, and much simpler, format to
620: the X.509 certificates used in
621: .Xr ssl 8 .
622: .Pp
623: .Nm
624: supports two types of certificates: user and host.
625: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 626: authenticate server hosts to users.
627: To generate a user certificate:
1.84 djm 628: .Pp
629: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
630: .Pp
631: The resultant certificate will be placed in
1.91 djm 632: .Pa /path/to/user_key-cert.pub .
1.84 djm 633: A host certificate requires the
634: .Fl h
635: option:
636: .Pp
637: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
638: .Pp
639: The host certificate will be output to
1.91 djm 640: .Pa /path/to/host_key-cert.pub .
1.98 djm 641: .Pp
642: It is possible to sign using a CA key stored in a PKCS#11 token by
643: providing the token library using
644: .Fl D
645: and identifying the CA key by providing its public half as an argument
646: to
647: .Fl s :
648: .Pp
649: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id host_key.pub
650: .Pp
651: In all cases,
1.84 djm 652: .Ar key_id
653: is a "key identifier" that is logged by the server when the certificate
654: is used for authentication.
655: .Pp
656: Certificates may be limited to be valid for a set of principal (user/host)
657: names.
658: By default, generated certificates are valid for all users or hosts.
659: To generate a certificate for a specified set of principals:
660: .Pp
661: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.92 jmc 662: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub"
1.84 djm 663: .Pp
664: Additional limitations on the validity and use of user certificates may
1.94 jmc 665: be specified through certificate options.
1.93 djm 666: A certificate option may disable features of the SSH session, may be
1.84 djm 667: valid only when presented from particular source addresses or may
668: force the use of a specific command.
1.93 djm 669: For a list of valid certificate options, see the documentation for the
1.84 djm 670: .Fl O
671: option above.
672: .Pp
673: Finally, certificates may be defined with a validity lifetime.
674: The
675: .Fl V
676: option allows specification of certificate start and end times.
677: A certificate that is presented at a time outside this range will not be
678: considered valid.
1.110 jmc 679: By default, certificates are valid from
680: .Ux
681: Epoch to the distant future.
1.84 djm 682: .Pp
683: For certificates to be used for user or host authentication, the CA
684: public key must be trusted by
685: .Xr sshd 8
686: or
687: .Xr ssh 1 .
688: Please refer to those manual pages for details.
1.111 djm 689: .Sh KEY REVOCATION LISTS
690: .Nm
691: is able to manage OpenSSH format Key Revocation Lists (KRLs).
692: These binary files specify keys or certificates to be revoked using a
1.112 ! jmc 693: compact format, taking as little a one bit per certificate if they are being
1.111 djm 694: revoked by serial number.
695: .Pp
696: KRLs may be generated using the
697: .Fl k
698: flag.
699: This option reads one or more files from the command-line and generates a new
700: KRL.
701: The files may either contain a KRL specification (see below) or public keys,
702: listed one per line.
703: Plain public keys are revoked by listing their hash or contents in the KRL and
704: certificates revoked by serial number or key ID (if the serial is zero or
705: not available).
706: .Pp
707: Revoking keys using a KRL specification offers explicit control over the
708: types of record used to revoke keys and may be used to directly revoke
709: certificates by serial number or key ID without having the complete original
710: certificate on hand.
711: A KRL specification consists of lines containing one of the following directives
712: followed by a colon and some directive-specific information.
713: .Bl -tag -width Ds
714: .It Cm serial : Ar serial_number Op -serial_number
715: Revokes a certificate with the specified serial number.
1.112 ! jmc 716: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 717: in decimal, hex or octal.
718: If two serial numbers are specified separated by a hyphen, then the range
719: of serial numbers including and between each is revoked.
720: The CA key must have been specified on the
721: .Nm
722: command-line using the
723: .Fl s
724: option.
725: .It Cm id : Ar key_id
726: Revokes a certificate with the specified key ID string.
727: The CA key must have been specified on the
728: .Nm
729: command-line using the
730: .Fl s
731: option.
732: .It Cm key : Ar public_key
733: Revokes the specified key.
1.112 ! jmc 734: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 735: .It Cm sha1 : Ar public_key
736: Revokes the specified key by its SHA1 hash.
737: .El
738: .Pp
739: KRLs may be updated using the
740: .Fl u
741: flag in addition to
742: .Fl k .
743: When this option is specified, keys listed via the command-line are merged into
744: the KRL, adding to those already there.
745: .Pp
746: It is also possible, given a KRL, to test whether it revokes a particular key
747: (or keys).
748: The
749: .Fl Q
750: flag will query an existing KRL, testing each key specified on the commandline.
751: If any key listed on the command-line has been revoked (or an error encountered)
752: then
753: .Nm
754: will exit with a non-zero exit status.
755: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 756: .Sh FILES
1.100 naddy 757: .Bl -tag -width Ds -compact
1.68 djm 758: .It Pa ~/.ssh/identity
1.36 itojun 759: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 760: This file should not be readable by anyone but the user.
761: It is possible to
1.1 deraadt 762: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 763: used to encrypt the private part of this file using 3DES.
1.12 aaron 764: This file is not automatically accessed by
1.2 deraadt 765: .Nm
1.1 deraadt 766: but it is offered as the default file for the private key.
1.46 markus 767: .Xr ssh 1
1.15 deraadt 768: will read this file when a login attempt is made.
1.100 naddy 769: .Pp
1.68 djm 770: .It Pa ~/.ssh/identity.pub
1.36 itojun 771: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 772: The contents of this file should be added to
1.68 djm 773: .Pa ~/.ssh/authorized_keys
1.2 deraadt 774: on all machines
1.49 deraadt 775: where the user wishes to log in using RSA authentication.
1.15 deraadt 776: There is no need to keep the contents of this file secret.
1.100 naddy 777: .Pp
1.68 djm 778: .It Pa ~/.ssh/id_dsa
1.100 naddy 779: .It Pa ~/.ssh/id_ecdsa
780: .It Pa ~/.ssh/id_rsa
781: Contains the protocol version 2 DSA, ECDSA or RSA authentication identity of the user.
1.15 deraadt 782: This file should not be readable by anyone but the user.
783: It is possible to
784: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 785: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 786: This file is not automatically accessed by
787: .Nm
788: but it is offered as the default file for the private key.
1.46 markus 789: .Xr ssh 1
1.15 deraadt 790: will read this file when a login attempt is made.
1.100 naddy 791: .Pp
1.68 djm 792: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 793: .It Pa ~/.ssh/id_ecdsa.pub
1.68 djm 794: .It Pa ~/.ssh/id_rsa.pub
1.100 naddy 795: Contains the protocol version 2 DSA, ECDSA or RSA public key for authentication.
1.15 deraadt 796: The contents of this file should be added to
1.68 djm 797: .Pa ~/.ssh/authorized_keys
1.15 deraadt 798: on all machines
1.49 deraadt 799: where the user wishes to log in using public key authentication.
1.12 aaron 800: There is no need to keep the contents of this file secret.
1.100 naddy 801: .Pp
1.60 djm 802: .It Pa /etc/moduli
803: Contains Diffie-Hellman groups used for DH-GEX.
804: The file format is described in
805: .Xr moduli 5 .
1.19 aaron 806: .El
1.2 deraadt 807: .Sh SEE ALSO
808: .Xr ssh 1 ,
809: .Xr ssh-add 1 ,
1.8 ericj 810: .Xr ssh-agent 1 ,
1.60 djm 811: .Xr moduli 5 ,
1.30 itojun 812: .Xr sshd 8
1.37 markus 813: .Rs
1.73 markus 814: .%R RFC 4716
815: .%T "The Secure Shell (SSH) Public Key File Format"
816: .%D 2006
1.37 markus 817: .Re
1.59 jmc 818: .Sh AUTHORS
819: OpenSSH is a derivative of the original and free
820: ssh 1.2.12 release by Tatu Ylonen.
821: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
822: Theo de Raadt and Dug Song
823: removed many bugs, re-added newer features and
824: created OpenSSH.
825: Markus Friedl contributed the support for SSH
826: protocol versions 1.5 and 2.0.
![[BACK]](/icons/back.gif){kind=icon}
Return to ssh-keygen.1 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh