Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.115
1.115 ! jmc 1: .\" $OpenBSD: ssh-keygen.1,v 1.114 2013/01/18 21:48:43 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: .\"
1.113 jmc 38: .Dd $Mdocdate: January 18 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
1.114 jmc 349: flag that revokes every key or certificate presented on the command line.
1.111 djm 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.
1.113 jmc 458: .It Fl Q
459: Test whether keys have been revoked in a KRL.
1.5 aaron 460: .It Fl q
461: Silence
462: .Nm ssh-keygen .
1.64 djm 463: .It Fl R Ar hostname
464: Removes all keys belonging to
465: .Ar hostname
1.65 jmc 466: from a
1.64 djm 467: .Pa known_hosts
468: file.
1.65 jmc 469: This option is useful to delete hashed hosts (see the
1.64 djm 470: .Fl H
471: option above).
1.66 jmc 472: .It Fl r Ar hostname
473: Print the SSHFP fingerprint resource record named
474: .Ar hostname
475: for the specified public key file.
1.60 djm 476: .It Fl S Ar start
477: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 478: .It Fl s Ar ca_key
479: Certify (sign) a public key using the specified CA key.
480: Please see the
481: .Sx CERTIFICATES
482: section for details.
1.111 djm 483: .Pp
484: When generating a KRL,
485: .Fl s
1.112 jmc 486: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 487: by key ID or serial number.
488: See the
489: .Sx KEY REVOCATION LISTS
490: section for details.
1.60 djm 491: .It Fl T Ar output_file
492: Test DH group exchange candidate primes (generated using the
493: .Fl G
494: option) for safety.
1.66 jmc 495: .It Fl t Ar type
496: Specifies the type of key to create.
497: The possible values are
498: .Dq rsa1
499: for protocol version 1 and
1.100 naddy 500: .Dq dsa ,
501: .Dq ecdsa
502: or
1.66 jmc 503: .Dq rsa
504: for protocol version 2.
1.112 jmc 505: .It Fl u
506: Update a KRL.
507: When specified with
508: .Fl k ,
1.114 jmc 509: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 510: a new KRL being created.
1.84 djm 511: .It Fl V Ar validity_interval
512: Specify a validity interval when signing a certificate.
513: A validity interval may consist of a single time, indicating that the
514: certificate is valid beginning now and expiring at that time, or may consist
515: of two times separated by a colon to indicate an explicit time interval.
516: The start time may be specified as a date in YYYYMMDD format, a time
517: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
518: of a minus sign followed by a relative time in the format described in the
519: .Sx TIME FORMATS
520: section of
1.90 jmc 521: .Xr sshd_config 5 .
1.84 djm 522: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
523: a relative time starting with a plus character.
524: .Pp
525: For example:
526: .Dq +52w1d
527: (valid from now to 52 weeks and one day from now),
528: .Dq -4w:+4w
529: (valid from four weeks ago to four weeks from now),
530: .Dq 20100101123000:20110101123000
531: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
532: .Dq -1d:20110101
533: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 534: .It Fl v
535: Verbose mode.
536: Causes
537: .Nm
538: to print debugging messages about its progress.
539: This is helpful for debugging moduli generation.
540: Multiple
541: .Fl v
542: options increase the verbosity.
543: The maximum is 3.
1.66 jmc 544: .It Fl W Ar generator
545: Specify desired generator when testing candidate moduli for DH-GEX.
546: .It Fl y
547: This option will read a private
548: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 549: .It Fl z Ar serial_number
550: Specifies a serial number to be embedded in the certificate to distinguish
551: this certificate from others from the same CA.
552: The default serial number is zero.
1.111 djm 553: .Pp
554: When generating a KRL, the
555: .Fl z
556: flag is used to specify a KRL version number.
1.2 deraadt 557: .El
1.60 djm 558: .Sh MODULI GENERATION
559: .Nm
560: may be used to generate groups for the Diffie-Hellman Group Exchange
561: (DH-GEX) protocol.
562: Generating these groups is a two-step process: first, candidate
563: primes are generated using a fast, but memory intensive process.
564: These candidate primes are then tested for suitability (a CPU-intensive
565: process).
566: .Pp
567: Generation of primes is performed using the
568: .Fl G
569: option.
570: The desired length of the primes may be specified by the
571: .Fl b
572: option.
573: For example:
574: .Pp
1.66 jmc 575: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 576: .Pp
577: By default, the search for primes begins at a random point in the
578: desired length range.
579: This may be overridden using the
580: .Fl S
581: option, which specifies a different start point (in hex).
582: .Pp
1.109 dtucker 583: Once a set of candidates have been generated, they must be screened for
1.60 djm 584: suitability.
585: This may be performed using the
586: .Fl T
587: option.
588: In this mode
589: .Nm
590: will read candidates from standard input (or a file specified using the
591: .Fl f
592: option).
593: For example:
594: .Pp
1.66 jmc 595: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 596: .Pp
597: By default, each candidate will be subjected to 100 primality tests.
598: This may be overridden using the
599: .Fl a
600: option.
601: The DH generator value will be chosen automatically for the
602: prime under consideration.
603: If a specific generator is desired, it may be requested using the
604: .Fl W
605: option.
1.66 jmc 606: Valid generator values are 2, 3, and 5.
1.60 djm 607: .Pp
608: Screened DH groups may be installed in
609: .Pa /etc/moduli .
610: It is important that this file contains moduli of a range of bit lengths and
611: that both ends of a connection share common moduli.
1.84 djm 612: .Sh CERTIFICATES
613: .Nm
614: supports signing of keys to produce certificates that may be used for
615: user or host authentication.
616: Certificates consist of a public key, some identity information, zero or
1.94 jmc 617: more principal (user or host) names and a set of options that
1.84 djm 618: are signed by a Certification Authority (CA) key.
619: Clients or servers may then trust only the CA key and verify its signature
620: on a certificate rather than trusting many user/host keys.
621: Note that OpenSSH certificates are a different, and much simpler, format to
622: the X.509 certificates used in
623: .Xr ssl 8 .
624: .Pp
625: .Nm
626: supports two types of certificates: user and host.
627: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 628: authenticate server hosts to users.
629: To generate a user certificate:
1.84 djm 630: .Pp
631: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
632: .Pp
633: The resultant certificate will be placed in
1.91 djm 634: .Pa /path/to/user_key-cert.pub .
1.84 djm 635: A host certificate requires the
636: .Fl h
637: option:
638: .Pp
639: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
640: .Pp
641: The host certificate will be output to
1.91 djm 642: .Pa /path/to/host_key-cert.pub .
1.98 djm 643: .Pp
644: It is possible to sign using a CA key stored in a PKCS#11 token by
645: providing the token library using
646: .Fl D
647: and identifying the CA key by providing its public half as an argument
648: to
649: .Fl s :
650: .Pp
651: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id host_key.pub
652: .Pp
653: In all cases,
1.84 djm 654: .Ar key_id
655: is a "key identifier" that is logged by the server when the certificate
656: is used for authentication.
657: .Pp
658: Certificates may be limited to be valid for a set of principal (user/host)
659: names.
660: By default, generated certificates are valid for all users or hosts.
661: To generate a certificate for a specified set of principals:
662: .Pp
663: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.92 jmc 664: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub"
1.84 djm 665: .Pp
666: Additional limitations on the validity and use of user certificates may
1.94 jmc 667: be specified through certificate options.
1.93 djm 668: A certificate option may disable features of the SSH session, may be
1.84 djm 669: valid only when presented from particular source addresses or may
670: force the use of a specific command.
1.93 djm 671: For a list of valid certificate options, see the documentation for the
1.84 djm 672: .Fl O
673: option above.
674: .Pp
675: Finally, certificates may be defined with a validity lifetime.
676: The
677: .Fl V
678: option allows specification of certificate start and end times.
679: A certificate that is presented at a time outside this range will not be
680: considered valid.
1.110 jmc 681: By default, certificates are valid from
682: .Ux
683: Epoch to the distant future.
1.84 djm 684: .Pp
685: For certificates to be used for user or host authentication, the CA
686: public key must be trusted by
687: .Xr sshd 8
688: or
689: .Xr ssh 1 .
690: Please refer to those manual pages for details.
1.111 djm 691: .Sh KEY REVOCATION LISTS
692: .Nm
693: is able to manage OpenSSH format Key Revocation Lists (KRLs).
694: These binary files specify keys or certificates to be revoked using a
1.112 jmc 695: compact format, taking as little a one bit per certificate if they are being
1.111 djm 696: revoked by serial number.
697: .Pp
698: KRLs may be generated using the
699: .Fl k
700: flag.
1.114 jmc 701: This option reads one or more files from the command line and generates a new
1.111 djm 702: KRL.
703: The files may either contain a KRL specification (see below) or public keys,
704: listed one per line.
705: Plain public keys are revoked by listing their hash or contents in the KRL and
706: certificates revoked by serial number or key ID (if the serial is zero or
707: not available).
708: .Pp
709: Revoking keys using a KRL specification offers explicit control over the
710: types of record used to revoke keys and may be used to directly revoke
711: certificates by serial number or key ID without having the complete original
712: certificate on hand.
713: A KRL specification consists of lines containing one of the following directives
714: followed by a colon and some directive-specific information.
715: .Bl -tag -width Ds
1.115 ! jmc 716: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 717: Revokes a certificate with the specified serial number.
1.112 jmc 718: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 719: in decimal, hex or octal.
720: If two serial numbers are specified separated by a hyphen, then the range
721: of serial numbers including and between each is revoked.
722: The CA key must have been specified on the
723: .Nm
1.114 jmc 724: command line using the
1.111 djm 725: .Fl s
726: option.
727: .It Cm id : Ar key_id
728: Revokes a certificate with the specified key ID string.
729: The CA key must have been specified on the
730: .Nm
1.114 jmc 731: command line using the
1.111 djm 732: .Fl s
733: option.
734: .It Cm key : Ar public_key
735: Revokes the specified key.
1.112 jmc 736: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 737: .It Cm sha1 : Ar public_key
738: Revokes the specified key by its SHA1 hash.
739: .El
740: .Pp
741: KRLs may be updated using the
742: .Fl u
743: flag in addition to
744: .Fl k .
1.114 jmc 745: When this option is specified, keys listed via the command line are merged into
1.111 djm 746: the KRL, adding to those already there.
747: .Pp
748: It is also possible, given a KRL, to test whether it revokes a particular key
749: (or keys).
750: The
751: .Fl Q
752: flag will query an existing KRL, testing each key specified on the commandline.
1.114 jmc 753: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 754: then
755: .Nm
756: will exit with a non-zero exit status.
757: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 758: .Sh FILES
1.100 naddy 759: .Bl -tag -width Ds -compact
1.68 djm 760: .It Pa ~/.ssh/identity
1.36 itojun 761: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 762: This file should not be readable by anyone but the user.
763: It is possible to
1.1 deraadt 764: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 765: used to encrypt the private part of this file using 3DES.
1.12 aaron 766: This file is not automatically accessed by
1.2 deraadt 767: .Nm
1.1 deraadt 768: but it is offered as the default file for the private key.
1.46 markus 769: .Xr ssh 1
1.15 deraadt 770: will read this file when a login attempt is made.
1.100 naddy 771: .Pp
1.68 djm 772: .It Pa ~/.ssh/identity.pub
1.36 itojun 773: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 774: The contents of this file should be added to
1.68 djm 775: .Pa ~/.ssh/authorized_keys
1.2 deraadt 776: on all machines
1.49 deraadt 777: where the user wishes to log in using RSA authentication.
1.15 deraadt 778: There is no need to keep the contents of this file secret.
1.100 naddy 779: .Pp
1.68 djm 780: .It Pa ~/.ssh/id_dsa
1.100 naddy 781: .It Pa ~/.ssh/id_ecdsa
782: .It Pa ~/.ssh/id_rsa
783: Contains the protocol version 2 DSA, ECDSA or RSA authentication identity of the user.
1.15 deraadt 784: This file should not be readable by anyone but the user.
785: It is possible to
786: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 787: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 788: This file is not automatically accessed by
789: .Nm
790: but it is offered as the default file for the private key.
1.46 markus 791: .Xr ssh 1
1.15 deraadt 792: will read this file when a login attempt is made.
1.100 naddy 793: .Pp
1.68 djm 794: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 795: .It Pa ~/.ssh/id_ecdsa.pub
1.68 djm 796: .It Pa ~/.ssh/id_rsa.pub
1.100 naddy 797: Contains the protocol version 2 DSA, ECDSA or RSA public key for authentication.
1.15 deraadt 798: The contents of this file should be added to
1.68 djm 799: .Pa ~/.ssh/authorized_keys
1.15 deraadt 800: on all machines
1.49 deraadt 801: where the user wishes to log in using public key authentication.
1.12 aaron 802: There is no need to keep the contents of this file secret.
1.100 naddy 803: .Pp
1.60 djm 804: .It Pa /etc/moduli
805: Contains Diffie-Hellman groups used for DH-GEX.
806: The file format is described in
807: .Xr moduli 5 .
1.19 aaron 808: .El
1.2 deraadt 809: .Sh SEE ALSO
810: .Xr ssh 1 ,
811: .Xr ssh-add 1 ,
1.8 ericj 812: .Xr ssh-agent 1 ,
1.60 djm 813: .Xr moduli 5 ,
1.30 itojun 814: .Xr sshd 8
1.37 markus 815: .Rs
1.73 markus 816: .%R RFC 4716
817: .%T "The Secure Shell (SSH) Public Key File Format"
818: .%D 2006
1.37 markus 819: .Re
1.59 jmc 820: .Sh AUTHORS
821: OpenSSH is a derivative of the original and free
822: ssh 1.2.12 release by Tatu Ylonen.
823: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
824: Theo de Raadt and Dug Song
825: removed many bugs, re-added newer features and
826: created OpenSSH.
827: Markus Friedl contributed the support for SSH
828: protocol versions 1.5 and 2.0.
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