Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.111
1.111 ! djm 1: .\" $OpenBSD: ssh-keygen.1,v 1.110 2012/08/15 18:25:50 jmc 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: .\"
1.111 ! djm 38: .Dd $Mdocdate: August 15 2012 $
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
! 129: .Op Fl s ca_public
! 130: .Op Fl z version_number
! 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
! 161: given keys have been revoked by one. See the
! 162: .Sx KEY REVOCATION LISTS
! 163: section for details.
! 164: .Pp
1.2 deraadt 165: Normally each user wishing to use SSH
1.99 djm 166: with public key authentication runs this once to create the authentication
1.1 deraadt 167: key in
1.68 djm 168: .Pa ~/.ssh/identity ,
1.99 djm 169: .Pa ~/.ssh/id_ecdsa ,
1.68 djm 170: .Pa ~/.ssh/id_dsa
1.15 deraadt 171: or
1.68 djm 172: .Pa ~/.ssh/id_rsa .
1.15 deraadt 173: Additionally, the system administrator may use this to generate host keys,
174: as seen in
175: .Pa /etc/rc .
1.2 deraadt 176: .Pp
1.1 deraadt 177: Normally this program generates the key and asks for a file in which
1.12 aaron 178: to store the private key.
179: The public key is stored in a file with the same name but
1.2 deraadt 180: .Dq .pub
1.12 aaron 181: appended.
182: The program also asks for a passphrase.
183: The passphrase may be empty to indicate no passphrase
1.26 markus 184: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 185: arbitrary length.
1.51 stevesk 186: A passphrase is similar to a password, except it can be a phrase with a
187: series of words, punctuation, numbers, whitespace, or any string of
188: characters you want.
189: Good passphrases are 10-30 characters long, are
1.1 deraadt 190: not simple sentences or otherwise easily guessable (English
1.42 markus 191: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 192: passphrases), and contain a mix of upper and lowercase letters,
193: numbers, and non-alphanumeric characters.
1.12 aaron 194: The passphrase can be changed later by using the
1.2 deraadt 195: .Fl p
1.1 deraadt 196: option.
1.2 deraadt 197: .Pp
1.12 aaron 198: There is no way to recover a lost passphrase.
1.105 djm 199: If the passphrase is lost or forgotten, a new key must be generated
200: and the corresponding public key copied to other machines.
1.2 deraadt 201: .Pp
1.37 markus 202: For RSA1 keys,
203: there is also a comment field in the key file that is only for
1.12 aaron 204: convenience to the user to help identify the key.
205: The comment can tell what the key is for, or whatever is useful.
206: The comment is initialized to
1.2 deraadt 207: .Dq user@host
208: when the key is created, but can be changed using the
209: .Fl c
1.1 deraadt 210: option.
1.2 deraadt 211: .Pp
1.15 deraadt 212: After a key is generated, instructions below detail where the keys
213: should be placed to be activated.
214: .Pp
1.2 deraadt 215: The options are as follows:
216: .Bl -tag -width Ds
1.102 stevesk 217: .It Fl A
218: For each of the key types (rsa1, rsa, dsa and ecdsa) for which host keys
219: do not exist, generate the host keys with the default key file path,
220: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 221: This is used by
1.102 stevesk 222: .Pa /etc/rc
223: to generate new host keys.
1.60 djm 224: .It Fl a Ar trials
225: Specifies the number of primality tests to perform when screening DH-GEX
226: candidates using the
227: .Fl T
228: command.
1.66 jmc 229: .It Fl B
230: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 231: .It Fl b Ar bits
1.12 aaron 232: Specifies the number of bits in the key to create.
1.72 dtucker 233: For RSA keys, the minimum size is 768 bits and the default is 2048 bits.
1.69 djm 234: Generally, 2048 bits is considered sufficient.
1.72 dtucker 235: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 236: For ECDSA keys, the
237: .Fl b
1.107 deraadt 238: flag determines the key length by selecting from one of three elliptic
1.106 djm 239: curve sizes: 256, 384 or 521 bits.
240: Attempting to use bit lengths other than these three values for ECDSA keys
241: will fail.
1.66 jmc 242: .It Fl C Ar comment
243: Provides a new comment.
1.2 deraadt 244: .It Fl c
1.1 deraadt 245: Requests changing the comment in the private and public key files.
1.50 markus 246: This operation is only supported for RSA1 keys.
1.1 deraadt 247: The program will prompt for the file containing the private keys, for
1.41 stevesk 248: the passphrase if the key has one, and for the new comment.
1.81 markus 249: .It Fl D Ar pkcs11
1.83 markus 250: Download the RSA public keys provided by the PKCS#11 shared library
251: .Ar pkcs11 .
1.98 djm 252: When used in combination with
253: .Fl s ,
254: this option indicates that a CA key resides in a PKCS#11 token (see the
255: .Sx CERTIFICATES
256: section for details).
1.37 markus 257: .It Fl e
1.40 markus 258: This option will read a private or public OpenSSH key file and
1.95 djm 259: print to stdout the key in one of the formats specified by the
260: .Fl m
261: option.
262: The default export format is
263: .Dq RFC4716 .
1.96 jmc 264: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 265: several commercial SSH implementations.
1.66 jmc 266: .It Fl F Ar hostname
267: Search for the specified
268: .Ar hostname
269: in a
270: .Pa known_hosts
271: file, listing any occurrences found.
272: This option is useful to find hashed host names or addresses and may also be
273: used in conjunction with the
274: .Fl H
275: option to print found keys in a hashed format.
276: .It Fl f Ar filename
277: Specifies the filename of the key file.
278: .It Fl G Ar output_file
279: Generate candidate primes for DH-GEX.
280: These primes must be screened for
281: safety (using the
282: .Fl T
283: option) before use.
1.57 jakob 284: .It Fl g
1.62 jakob 285: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 286: .Fl r
1.62 jakob 287: command.
1.66 jmc 288: .It Fl H
289: Hash a
290: .Pa known_hosts
1.67 dtucker 291: file.
292: This replaces all hostnames and addresses with hashed representations
293: within the specified file; the original content is moved to a file with
294: a .old suffix.
1.66 jmc 295: These hashes may be used normally by
296: .Nm ssh
297: and
298: .Nm sshd ,
299: but they do not reveal identifying information should the file's contents
300: be disclosed.
301: This option will not modify existing hashed hostnames and is therefore safe
302: to use on files that mix hashed and non-hashed names.
1.84 djm 303: .It Fl h
304: When signing a key, create a host certificate instead of a user
305: certificate.
306: Please see the
307: .Sx CERTIFICATES
308: section for details.
1.85 jmc 309: .It Fl I Ar certificate_identity
1.84 djm 310: Specify the key identity when signing a public key.
311: Please see the
312: .Sx CERTIFICATES
313: section for details.
1.37 markus 314: .It Fl i
315: This option will read an unencrypted private (or public) key file
1.95 djm 316: in the format specified by the
317: .Fl m
318: option and print an OpenSSH compatible private
1.37 markus 319: (or public) key to stdout.
1.109 dtucker 320: .It Fl J Ar num_lines
321: Exit after screening the specified number of lines
322: while performing DH candidate screening using the
323: .Fl T
324: option.
325: .It Fl j Ar start_line
326: Start screening at the specified line number
327: while performing DH candidate screening using the
328: .Fl T
329: option.
1.108 dtucker 330: .It Fl K Ar checkpt
331: Write the last line processed to the file
332: .Ar checkpt
333: while performing DH candidate screening using the
334: .Fl T
335: option.
336: This will be used to skip lines in the input file that have already been
337: processed if the job is restarted.
1.95 djm 338: This option allows importing keys from other software, including several
339: commercial SSH implementations.
340: The default import format is
341: .Dq RFC4716 .
1.111 ! djm 342: .It Fl k
! 343: Generate a KRL file.
! 344: In this mode,
! 345: .Nm
! 346: will generate a KRL file at the location specified via the
! 347: .Fl f
! 348: flag that revokes every key or certificate presented on the command-line.
! 349: Keys/certificates to be revoked may be specified by public key file or
! 350: using the format described in the
! 351: .Sx KEY REVOCATION LISTS
! 352: section.
1.86 djm 353: .It Fl L
354: Prints the contents of a certificate.
1.9 markus 355: .It Fl l
1.77 grunk 356: Show fingerprint of specified public key file.
1.50 markus 357: Private RSA1 keys are also supported.
358: For RSA and DSA keys
359: .Nm
1.78 jmc 360: tries to find the matching public key file and prints its fingerprint.
361: If combined with
362: .Fl v ,
363: an ASCII art representation of the key is supplied with the fingerprint.
1.96 jmc 364: .It Fl M Ar memory
365: Specify the amount of memory to use (in megabytes) when generating
366: candidate moduli for DH-GEX.
1.95 djm 367: .It Fl m Ar key_format
368: Specify a key format for the
369: .Fl i
370: (import) or
371: .Fl e
1.96 jmc 372: (export) conversion options.
1.95 djm 373: The supported key formats are:
374: .Dq RFC4716
1.96 jmc 375: (RFC 4716/SSH2 public or private key),
1.95 djm 376: .Dq PKCS8
377: (PEM PKCS8 public key)
378: or
379: .Dq PEM
380: (PEM public key).
381: The default conversion format is
382: .Dq RFC4716 .
1.66 jmc 383: .It Fl N Ar new_passphrase
384: Provides the new passphrase.
1.84 djm 385: .It Fl n Ar principals
386: Specify one or more principals (user or host names) to be included in
387: a certificate when signing a key.
388: Multiple principals may be specified, separated by commas.
389: Please see the
390: .Sx CERTIFICATES
391: section for details.
1.93 djm 392: .It Fl O Ar option
393: Specify a certificate option when signing a key.
1.84 djm 394: This option may be specified multiple times.
395: Please see the
396: .Sx CERTIFICATES
397: section for details.
1.93 djm 398: The options that are valid for user certificates are:
1.84 djm 399: .Bl -tag -width Ds
1.89 jmc 400: .It Ic clear
401: Clear all enabled permissions.
402: This is useful for clearing the default set of permissions so permissions may
403: be added individually.
404: .It Ic force-command Ns = Ns Ar command
405: Forces the execution of
406: .Ar command
407: instead of any shell or command specified by the user when
408: the certificate is used for authentication.
1.84 djm 409: .It Ic no-agent-forwarding
410: Disable
411: .Xr ssh-agent 1
1.85 jmc 412: forwarding (permitted by default).
1.84 djm 413: .It Ic no-port-forwarding
1.85 jmc 414: Disable port forwarding (permitted by default).
1.84 djm 415: .It Ic no-pty
1.85 jmc 416: Disable PTY allocation (permitted by default).
1.84 djm 417: .It Ic no-user-rc
418: Disable execution of
419: .Pa ~/.ssh/rc
420: by
1.85 jmc 421: .Xr sshd 8
422: (permitted by default).
1.89 jmc 423: .It Ic no-x11-forwarding
424: Disable X11 forwarding (permitted by default).
1.88 djm 425: .It Ic permit-agent-forwarding
426: Allows
427: .Xr ssh-agent 1
428: forwarding.
1.84 djm 429: .It Ic permit-port-forwarding
430: Allows port forwarding.
431: .It Ic permit-pty
432: Allows PTY allocation.
433: .It Ic permit-user-rc
434: Allows execution of
435: .Pa ~/.ssh/rc
436: by
437: .Xr sshd 8 .
1.89 jmc 438: .It Ic permit-x11-forwarding
439: Allows X11 forwarding.
440: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 441: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 442: The
443: .Ar address_list
444: is a comma-separated list of one or more address/netmask pairs in CIDR
445: format.
446: .El
447: .Pp
1.93 djm 448: At present, no options are valid for host keys.
1.66 jmc 449: .It Fl P Ar passphrase
450: Provides the (old) passphrase.
1.2 deraadt 451: .It Fl p
1.1 deraadt 452: Requests changing the passphrase of a private key file instead of
1.12 aaron 453: creating a new private key.
454: The program will prompt for the file
1.1 deraadt 455: containing the private key, for the old passphrase, and twice for the
456: new passphrase.
1.5 aaron 457: .It Fl q
458: Silence
459: .Nm ssh-keygen .
1.64 djm 460: .It Fl R Ar hostname
461: Removes all keys belonging to
462: .Ar hostname
1.65 jmc 463: from a
1.64 djm 464: .Pa known_hosts
465: file.
1.65 jmc 466: This option is useful to delete hashed hosts (see the
1.64 djm 467: .Fl H
468: option above).
1.66 jmc 469: .It Fl r Ar hostname
470: Print the SSHFP fingerprint resource record named
471: .Ar hostname
472: for the specified public key file.
1.60 djm 473: .It Fl S Ar start
474: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 475: .It Fl s Ar ca_key
476: Certify (sign) a public key using the specified CA key.
477: Please see the
478: .Sx CERTIFICATES
479: section for details.
1.111 ! djm 480: .Pp
! 481: When generating a KRL,
! 482: .Fl s
! 483: specifies a path to a CA public key file used to revoke certificated directly
! 484: by key ID or serial number.
! 485: See the
! 486: .Sx KEY REVOCATION LISTS
! 487: section for details.
1.60 djm 488: .It Fl T Ar output_file
489: Test DH group exchange candidate primes (generated using the
490: .Fl G
491: option) for safety.
1.66 jmc 492: .It Fl t Ar type
493: Specifies the type of key to create.
494: The possible values are
495: .Dq rsa1
496: for protocol version 1 and
1.100 naddy 497: .Dq dsa ,
498: .Dq ecdsa
499: or
1.66 jmc 500: .Dq rsa
501: for protocol version 2.
1.84 djm 502: .It Fl V Ar validity_interval
503: Specify a validity interval when signing a certificate.
504: A validity interval may consist of a single time, indicating that the
505: certificate is valid beginning now and expiring at that time, or may consist
506: of two times separated by a colon to indicate an explicit time interval.
507: The start time may be specified as a date in YYYYMMDD format, a time
508: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
509: of a minus sign followed by a relative time in the format described in the
510: .Sx TIME FORMATS
511: section of
1.90 jmc 512: .Xr sshd_config 5 .
1.84 djm 513: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
514: a relative time starting with a plus character.
515: .Pp
516: For example:
517: .Dq +52w1d
518: (valid from now to 52 weeks and one day from now),
519: .Dq -4w:+4w
520: (valid from four weeks ago to four weeks from now),
521: .Dq 20100101123000:20110101123000
522: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
523: .Dq -1d:20110101
524: (valid from yesterday to midnight, January 1st, 2011).
1.111 ! djm 525: .It Fl u
! 526: Update a KRL.
! 527: When specified with
! 528: .Fl k ,
! 529: keys listed via the command-line are added to the existing KRL rather than
! 530: a new KRL being created.
1.61 djm 531: .It Fl v
532: Verbose mode.
533: Causes
534: .Nm
535: to print debugging messages about its progress.
536: This is helpful for debugging moduli generation.
537: Multiple
538: .Fl v
539: options increase the verbosity.
540: The maximum is 3.
1.66 jmc 541: .It Fl W Ar generator
542: Specify desired generator when testing candidate moduli for DH-GEX.
543: .It Fl y
544: This option will read a private
545: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 546: .It Fl z Ar serial_number
547: Specifies a serial number to be embedded in the certificate to distinguish
548: this certificate from others from the same CA.
549: The default serial number is zero.
1.111 ! djm 550: .Pp
! 551: When generating a KRL, the
! 552: .Fl z
! 553: flag is used to specify a KRL version number.
1.2 deraadt 554: .El
1.60 djm 555: .Sh MODULI GENERATION
556: .Nm
557: may be used to generate groups for the Diffie-Hellman Group Exchange
558: (DH-GEX) protocol.
559: Generating these groups is a two-step process: first, candidate
560: primes are generated using a fast, but memory intensive process.
561: These candidate primes are then tested for suitability (a CPU-intensive
562: process).
563: .Pp
564: Generation of primes is performed using the
565: .Fl G
566: option.
567: The desired length of the primes may be specified by the
568: .Fl b
569: option.
570: For example:
571: .Pp
1.66 jmc 572: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 573: .Pp
574: By default, the search for primes begins at a random point in the
575: desired length range.
576: This may be overridden using the
577: .Fl S
578: option, which specifies a different start point (in hex).
579: .Pp
1.109 dtucker 580: Once a set of candidates have been generated, they must be screened for
1.60 djm 581: suitability.
582: This may be performed using the
583: .Fl T
584: option.
585: In this mode
586: .Nm
587: will read candidates from standard input (or a file specified using the
588: .Fl f
589: option).
590: For example:
591: .Pp
1.66 jmc 592: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 593: .Pp
594: By default, each candidate will be subjected to 100 primality tests.
595: This may be overridden using the
596: .Fl a
597: option.
598: The DH generator value will be chosen automatically for the
599: prime under consideration.
600: If a specific generator is desired, it may be requested using the
601: .Fl W
602: option.
1.66 jmc 603: Valid generator values are 2, 3, and 5.
1.60 djm 604: .Pp
605: Screened DH groups may be installed in
606: .Pa /etc/moduli .
607: It is important that this file contains moduli of a range of bit lengths and
608: that both ends of a connection share common moduli.
1.84 djm 609: .Sh CERTIFICATES
610: .Nm
611: supports signing of keys to produce certificates that may be used for
612: user or host authentication.
613: Certificates consist of a public key, some identity information, zero or
1.94 jmc 614: more principal (user or host) names and a set of options that
1.84 djm 615: are signed by a Certification Authority (CA) key.
616: Clients or servers may then trust only the CA key and verify its signature
617: on a certificate rather than trusting many user/host keys.
618: Note that OpenSSH certificates are a different, and much simpler, format to
619: the X.509 certificates used in
620: .Xr ssl 8 .
621: .Pp
622: .Nm
623: supports two types of certificates: user and host.
624: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 625: authenticate server hosts to users.
626: To generate a user certificate:
1.84 djm 627: .Pp
628: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
629: .Pp
630: The resultant certificate will be placed in
1.91 djm 631: .Pa /path/to/user_key-cert.pub .
1.84 djm 632: A host certificate requires the
633: .Fl h
634: option:
635: .Pp
636: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
637: .Pp
638: The host certificate will be output to
1.91 djm 639: .Pa /path/to/host_key-cert.pub .
1.98 djm 640: .Pp
641: It is possible to sign using a CA key stored in a PKCS#11 token by
642: providing the token library using
643: .Fl D
644: and identifying the CA key by providing its public half as an argument
645: to
646: .Fl s :
647: .Pp
648: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id host_key.pub
649: .Pp
650: In all cases,
1.84 djm 651: .Ar key_id
652: is a "key identifier" that is logged by the server when the certificate
653: is used for authentication.
654: .Pp
655: Certificates may be limited to be valid for a set of principal (user/host)
656: names.
657: By default, generated certificates are valid for all users or hosts.
658: To generate a certificate for a specified set of principals:
659: .Pp
660: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.92 jmc 661: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub"
1.84 djm 662: .Pp
663: Additional limitations on the validity and use of user certificates may
1.94 jmc 664: be specified through certificate options.
1.93 djm 665: A certificate option may disable features of the SSH session, may be
1.84 djm 666: valid only when presented from particular source addresses or may
667: force the use of a specific command.
1.93 djm 668: For a list of valid certificate options, see the documentation for the
1.84 djm 669: .Fl O
670: option above.
671: .Pp
672: Finally, certificates may be defined with a validity lifetime.
673: The
674: .Fl V
675: option allows specification of certificate start and end times.
676: A certificate that is presented at a time outside this range will not be
677: considered valid.
1.110 jmc 678: By default, certificates are valid from
679: .Ux
680: Epoch to the distant future.
1.84 djm 681: .Pp
682: For certificates to be used for user or host authentication, the CA
683: public key must be trusted by
684: .Xr sshd 8
685: or
686: .Xr ssh 1 .
687: Please refer to those manual pages for details.
1.111 ! djm 688: .Sh KEY REVOCATION LISTS
! 689: .Nm
! 690: is able to manage OpenSSH format Key Revocation Lists (KRLs).
! 691: These binary files specify keys or certificates to be revoked using a
! 692: compact format; taking as little a one bit per certificate if they are being
! 693: revoked by serial number.
! 694: .Pp
! 695: KRLs may be generated using the
! 696: .Fl k
! 697: flag.
! 698: This option reads one or more files from the command-line and generates a new
! 699: KRL.
! 700: The files may either contain a KRL specification (see below) or public keys,
! 701: listed one per line.
! 702: Plain public keys are revoked by listing their hash or contents in the KRL and
! 703: certificates revoked by serial number or key ID (if the serial is zero or
! 704: not available).
! 705: .Pp
! 706: Revoking keys using a KRL specification offers explicit control over the
! 707: types of record used to revoke keys and may be used to directly revoke
! 708: certificates by serial number or key ID without having the complete original
! 709: certificate on hand.
! 710: A KRL specification consists of lines containing one of the following directives
! 711: followed by a colon and some directive-specific information.
! 712: .Bl -tag -width Ds
! 713: .It Cm serial : Ar serial_number Op -serial_number
! 714: Revokes a certificate with the specified serial number.
! 715: Serial numbers are 64 bit values, not including zero and may be expressed
! 716: in decimal, hex or octal.
! 717: If two serial numbers are specified separated by a hyphen, then the range
! 718: of serial numbers including and between each is revoked.
! 719: The CA key must have been specified on the
! 720: .Nm
! 721: command-line using the
! 722: .Fl s
! 723: option.
! 724: .It Cm id : Ar key_id
! 725: Revokes a certificate with the specified key ID string.
! 726: The CA key must have been specified on the
! 727: .Nm
! 728: command-line using the
! 729: .Fl s
! 730: option.
! 731: .It Cm key : Ar public_key
! 732: Revokes the specified key.
! 733: In a certificate is listed, then it is revoked as a plain public key.
! 734: .It Cm sha1 : Ar public_key
! 735: Revokes the specified key by its SHA1 hash.
! 736: .El
! 737: .Pp
! 738: KRLs may be updated using the
! 739: .Fl u
! 740: flag in addition to
! 741: .Fl k .
! 742: When this option is specified, keys listed via the command-line are merged into
! 743: the KRL, adding to those already there.
! 744: .Pp
! 745: It is also possible, given a KRL, to test whether it revokes a particular key
! 746: (or keys).
! 747: The
! 748: .Fl Q
! 749: flag will query an existing KRL, testing each key specified on the commandline.
! 750: If any key listed on the command-line has been revoked (or an error encountered)
! 751: then
! 752: .Nm
! 753: will exit with a non-zero exit status.
! 754: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 755: .Sh FILES
1.100 naddy 756: .Bl -tag -width Ds -compact
1.68 djm 757: .It Pa ~/.ssh/identity
1.36 itojun 758: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 759: This file should not be readable by anyone but the user.
760: It is possible to
1.1 deraadt 761: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 762: used to encrypt the private part of this file using 3DES.
1.12 aaron 763: This file is not automatically accessed by
1.2 deraadt 764: .Nm
1.1 deraadt 765: but it is offered as the default file for the private key.
1.46 markus 766: .Xr ssh 1
1.15 deraadt 767: will read this file when a login attempt is made.
1.100 naddy 768: .Pp
1.68 djm 769: .It Pa ~/.ssh/identity.pub
1.36 itojun 770: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 771: The contents of this file should be added to
1.68 djm 772: .Pa ~/.ssh/authorized_keys
1.2 deraadt 773: on all machines
1.49 deraadt 774: where the user wishes to log in using RSA authentication.
1.15 deraadt 775: There is no need to keep the contents of this file secret.
1.100 naddy 776: .Pp
1.68 djm 777: .It Pa ~/.ssh/id_dsa
1.100 naddy 778: .It Pa ~/.ssh/id_ecdsa
779: .It Pa ~/.ssh/id_rsa
780: Contains the protocol version 2 DSA, ECDSA or RSA authentication identity of the user.
1.15 deraadt 781: This file should not be readable by anyone but the user.
782: It is possible to
783: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 784: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 785: This file is not automatically accessed by
786: .Nm
787: but it is offered as the default file for the private key.
1.46 markus 788: .Xr ssh 1
1.15 deraadt 789: will read this file when a login attempt is made.
1.100 naddy 790: .Pp
1.68 djm 791: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 792: .It Pa ~/.ssh/id_ecdsa.pub
1.68 djm 793: .It Pa ~/.ssh/id_rsa.pub
1.100 naddy 794: Contains the protocol version 2 DSA, ECDSA or RSA public key for authentication.
1.15 deraadt 795: The contents of this file should be added to
1.68 djm 796: .Pa ~/.ssh/authorized_keys
1.15 deraadt 797: on all machines
1.49 deraadt 798: where the user wishes to log in using public key authentication.
1.12 aaron 799: There is no need to keep the contents of this file secret.
1.100 naddy 800: .Pp
1.60 djm 801: .It Pa /etc/moduli
802: Contains Diffie-Hellman groups used for DH-GEX.
803: The file format is described in
804: .Xr moduli 5 .
1.19 aaron 805: .El
1.2 deraadt 806: .Sh SEE ALSO
807: .Xr ssh 1 ,
808: .Xr ssh-add 1 ,
1.8 ericj 809: .Xr ssh-agent 1 ,
1.60 djm 810: .Xr moduli 5 ,
1.30 itojun 811: .Xr sshd 8
1.37 markus 812: .Rs
1.73 markus 813: .%R RFC 4716
814: .%T "The Secure Shell (SSH) Public Key File Format"
815: .%D 2006
1.37 markus 816: .Re
1.59 jmc 817: .Sh AUTHORS
818: OpenSSH is a derivative of the original and free
819: ssh 1.2.12 release by Tatu Ylonen.
820: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
821: Theo de Raadt and Dug Song
822: removed many bugs, re-added newer features and
823: created OpenSSH.
824: Markus Friedl contributed the support for SSH
825: protocol versions 1.5 and 2.0.
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