Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.127
1.127 ! naddy 1: .\" $OpenBSD: ssh-keygen.1,v 1.126 2015/07/03 03:49:45 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: .\"
1.127 ! naddy 38: .Dd $Mdocdate: July 3 2015 $
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
1.121 deraadt 49: .Op Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1
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
1.125 naddy 76: .Op Fl v
1.124 djm 77: .Op Fl E Ar fingerprint_hash
1.35 markus 78: .Op Fl f Ar input_keyfile
79: .Nm ssh-keygen
80: .Fl B
1.20 markus 81: .Op Fl f Ar input_keyfile
1.48 jakob 82: .Nm ssh-keygen
1.82 jmc 83: .Fl D Ar pkcs11
1.48 jakob 84: .Nm ssh-keygen
1.64 djm 85: .Fl F Ar hostname
86: .Op Fl f Ar known_hosts_file
1.79 sthen 87: .Op Fl l
1.64 djm 88: .Nm ssh-keygen
89: .Fl H
90: .Op Fl f Ar known_hosts_file
91: .Nm ssh-keygen
92: .Fl R Ar hostname
93: .Op Fl f Ar known_hosts_file
1.57 jakob 94: .Nm ssh-keygen
95: .Fl r Ar hostname
96: .Op Fl f Ar input_keyfile
97: .Op Fl g
1.60 djm 98: .Nm ssh-keygen
99: .Fl G Ar output_file
1.61 djm 100: .Op Fl v
1.60 djm 101: .Op Fl b Ar bits
102: .Op Fl M Ar memory
103: .Op Fl S Ar start_point
104: .Nm ssh-keygen
105: .Fl T Ar output_file
106: .Fl f Ar input_file
1.61 djm 107: .Op Fl v
1.117 djm 108: .Op Fl a Ar rounds
1.109 dtucker 109: .Op Fl J Ar num_lines
110: .Op Fl j Ar start_line
1.108 dtucker 111: .Op Fl K Ar checkpt
1.60 djm 112: .Op Fl W Ar generator
1.84 djm 113: .Nm ssh-keygen
114: .Fl s Ar ca_key
115: .Fl I Ar certificate_identity
116: .Op Fl h
117: .Op Fl n Ar principals
1.93 djm 118: .Op Fl O Ar option
1.84 djm 119: .Op Fl V Ar validity_interval
1.93 djm 120: .Op Fl z Ar serial_number
1.84 djm 121: .Ar
1.86 djm 122: .Nm ssh-keygen
123: .Fl L
124: .Op Fl f Ar input_keyfile
1.102 stevesk 125: .Nm ssh-keygen
126: .Fl A
1.111 djm 127: .Nm ssh-keygen
128: .Fl k
129: .Fl f Ar krl_file
130: .Op Fl u
1.112 jmc 131: .Op Fl s Ar ca_public
132: .Op Fl z Ar version_number
1.111 djm 133: .Ar
134: .Nm ssh-keygen
135: .Fl Q
136: .Fl f Ar krl_file
137: .Ar
1.85 jmc 138: .Ek
1.13 aaron 139: .Sh DESCRIPTION
1.2 deraadt 140: .Nm
1.37 markus 141: generates, manages and converts authentication keys for
1.2 deraadt 142: .Xr ssh 1 .
1.15 deraadt 143: .Nm
1.118 naddy 144: can create RSA keys for use by SSH protocol version 1 and
1.123 sobrado 145: DSA, ECDSA, Ed25519 or RSA keys for use by SSH protocol version 2.
1.58 jmc 146: The type of key to be generated is specified with the
1.25 markus 147: .Fl t
1.52 djm 148: option.
1.70 djm 149: If invoked without any arguments,
150: .Nm
1.71 jmc 151: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 152: .Pp
1.60 djm 153: .Nm
154: is also used to generate groups for use in Diffie-Hellman group
155: exchange (DH-GEX).
156: See the
157: .Sx MODULI GENERATION
158: section for details.
159: .Pp
1.111 djm 160: Finally,
161: .Nm
162: can be used to generate and update Key Revocation Lists, and to test whether
1.112 jmc 163: given keys have been revoked by one.
164: See the
1.111 djm 165: .Sx KEY REVOCATION LISTS
166: section for details.
167: .Pp
1.2 deraadt 168: Normally each user wishing to use SSH
1.99 djm 169: with public key authentication runs this once to create the authentication
1.1 deraadt 170: key in
1.68 djm 171: .Pa ~/.ssh/identity ,
1.118 naddy 172: .Pa ~/.ssh/id_dsa ,
1.99 djm 173: .Pa ~/.ssh/id_ecdsa ,
1.118 naddy 174: .Pa ~/.ssh/id_ed25519
1.15 deraadt 175: or
1.68 djm 176: .Pa ~/.ssh/id_rsa .
1.15 deraadt 177: Additionally, the system administrator may use this to generate host keys,
178: as seen in
179: .Pa /etc/rc .
1.2 deraadt 180: .Pp
1.1 deraadt 181: Normally this program generates the key and asks for a file in which
1.12 aaron 182: to store the private key.
183: The public key is stored in a file with the same name but
1.2 deraadt 184: .Dq .pub
1.12 aaron 185: appended.
186: The program also asks for a passphrase.
187: The passphrase may be empty to indicate no passphrase
1.26 markus 188: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 189: arbitrary length.
1.51 stevesk 190: A passphrase is similar to a password, except it can be a phrase with a
191: series of words, punctuation, numbers, whitespace, or any string of
192: characters you want.
193: Good passphrases are 10-30 characters long, are
1.1 deraadt 194: not simple sentences or otherwise easily guessable (English
1.42 markus 195: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 196: passphrases), and contain a mix of upper and lowercase letters,
197: numbers, and non-alphanumeric characters.
1.12 aaron 198: The passphrase can be changed later by using the
1.2 deraadt 199: .Fl p
1.1 deraadt 200: option.
1.2 deraadt 201: .Pp
1.12 aaron 202: There is no way to recover a lost passphrase.
1.105 djm 203: If the passphrase is lost or forgotten, a new key must be generated
204: and the corresponding public key copied to other machines.
1.2 deraadt 205: .Pp
1.37 markus 206: For RSA1 keys,
207: there is also a comment field in the key file that is only for
1.12 aaron 208: convenience to the user to help identify the key.
209: The comment can tell what the key is for, or whatever is useful.
210: The comment is initialized to
1.2 deraadt 211: .Dq user@host
212: when the key is created, but can be changed using the
213: .Fl c
1.1 deraadt 214: option.
1.2 deraadt 215: .Pp
1.15 deraadt 216: After a key is generated, instructions below detail where the keys
217: should be placed to be activated.
218: .Pp
1.2 deraadt 219: The options are as follows:
220: .Bl -tag -width Ds
1.102 stevesk 221: .It Fl A
1.118 naddy 222: For each of the key types (rsa1, rsa, dsa, ecdsa and ed25519)
223: for which host keys
1.102 stevesk 224: do not exist, generate the host keys with the default key file path,
225: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 226: This is used by
1.102 stevesk 227: .Pa /etc/rc
228: to generate new host keys.
1.117 djm 229: .It Fl a Ar rounds
230: When saving a new-format private key (i.e. an ed25519 key or any SSH protocol
231: 2 key when the
232: .Fl o
233: flag is set), this option specifies the number of KDF (key derivation function)
234: rounds used.
235: Higher numbers result in slower passphrase verification and increased
236: resistance to brute-force password cracking (should the keys be stolen).
237: .Pp
238: When screening DH-GEX candidates (
239: using the
1.60 djm 240: .Fl T
1.117 djm 241: command).
242: This option specifies the number of primality tests to perform.
1.66 jmc 243: .It Fl B
244: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 245: .It Fl b Ar bits
1.12 aaron 246: Specifies the number of bits in the key to create.
1.126 djm 247: For RSA keys, the minimum size is 1024 bits and the default is 2048 bits.
1.69 djm 248: Generally, 2048 bits is considered sufficient.
1.72 dtucker 249: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 250: For ECDSA keys, the
251: .Fl b
1.107 deraadt 252: flag determines the key length by selecting from one of three elliptic
1.106 djm 253: curve sizes: 256, 384 or 521 bits.
254: Attempting to use bit lengths other than these three values for ECDSA keys
255: will fail.
1.123 sobrado 256: Ed25519 keys have a fixed length and the
1.118 naddy 257: .Fl b
258: flag will be ignored.
1.66 jmc 259: .It Fl C Ar comment
260: Provides a new comment.
1.2 deraadt 261: .It Fl c
1.1 deraadt 262: Requests changing the comment in the private and public key files.
1.50 markus 263: This operation is only supported for RSA1 keys.
1.1 deraadt 264: The program will prompt for the file containing the private keys, for
1.41 stevesk 265: the passphrase if the key has one, and for the new comment.
1.81 markus 266: .It Fl D Ar pkcs11
1.83 markus 267: Download the RSA public keys provided by the PKCS#11 shared library
268: .Ar pkcs11 .
1.98 djm 269: When used in combination with
270: .Fl s ,
271: this option indicates that a CA key resides in a PKCS#11 token (see the
272: .Sx CERTIFICATES
273: section for details).
1.124 djm 274: .It Fl E Ar fingerprint_hash
275: Specifies the hash algorithm used when displaying key fingerprints.
276: Valid options are:
277: .Dq md5
278: and
279: .Dq sha256 .
280: The default is
281: .Dq sha256 .
1.37 markus 282: .It Fl e
1.40 markus 283: This option will read a private or public OpenSSH key file and
1.95 djm 284: print to stdout the key in one of the formats specified by the
285: .Fl m
286: option.
287: The default export format is
288: .Dq RFC4716 .
1.96 jmc 289: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 290: several commercial SSH implementations.
1.66 jmc 291: .It Fl F Ar hostname
292: Search for the specified
293: .Ar hostname
294: in a
295: .Pa known_hosts
296: file, listing any occurrences found.
297: This option is useful to find hashed host names or addresses and may also be
298: used in conjunction with the
299: .Fl H
300: option to print found keys in a hashed format.
301: .It Fl f Ar filename
302: Specifies the filename of the key file.
303: .It Fl G Ar output_file
304: Generate candidate primes for DH-GEX.
305: These primes must be screened for
306: safety (using the
307: .Fl T
308: option) before use.
1.57 jakob 309: .It Fl g
1.62 jakob 310: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 311: .Fl r
1.62 jakob 312: command.
1.66 jmc 313: .It Fl H
314: Hash a
315: .Pa known_hosts
1.67 dtucker 316: file.
317: This replaces all hostnames and addresses with hashed representations
318: within the specified file; the original content is moved to a file with
319: a .old suffix.
1.66 jmc 320: These hashes may be used normally by
321: .Nm ssh
322: and
323: .Nm sshd ,
324: but they do not reveal identifying information should the file's contents
325: be disclosed.
326: This option will not modify existing hashed hostnames and is therefore safe
327: to use on files that mix hashed and non-hashed names.
1.84 djm 328: .It Fl h
329: When signing a key, create a host certificate instead of a user
330: certificate.
331: Please see the
332: .Sx CERTIFICATES
333: section for details.
1.85 jmc 334: .It Fl I Ar certificate_identity
1.84 djm 335: Specify the key identity when signing a public key.
336: Please see the
337: .Sx CERTIFICATES
338: section for details.
1.37 markus 339: .It Fl i
340: This option will read an unencrypted private (or public) key file
1.95 djm 341: in the format specified by the
342: .Fl m
343: option and print an OpenSSH compatible private
1.37 markus 344: (or public) key to stdout.
1.122 jmc 345: This option allows importing keys from other software, including several
346: commercial SSH implementations.
347: The default import format is
348: .Dq RFC4716 .
1.109 dtucker 349: .It Fl J Ar num_lines
350: Exit after screening the specified number of lines
351: while performing DH candidate screening using the
352: .Fl T
353: option.
354: .It Fl j Ar start_line
355: Start screening at the specified line number
356: while performing DH candidate screening using the
357: .Fl T
358: option.
1.108 dtucker 359: .It Fl K Ar checkpt
360: Write the last line processed to the file
361: .Ar checkpt
362: while performing DH candidate screening using the
363: .Fl T
364: option.
365: This will be used to skip lines in the input file that have already been
366: processed if the job is restarted.
1.111 djm 367: .It Fl k
368: Generate a KRL file.
369: In this mode,
370: .Nm
371: will generate a KRL file at the location specified via the
372: .Fl f
1.114 jmc 373: flag that revokes every key or certificate presented on the command line.
1.111 djm 374: Keys/certificates to be revoked may be specified by public key file or
375: using the format described in the
376: .Sx KEY REVOCATION LISTS
377: section.
1.86 djm 378: .It Fl L
379: Prints the contents of a certificate.
1.9 markus 380: .It Fl l
1.77 grunk 381: Show fingerprint of specified public key file.
1.50 markus 382: Private RSA1 keys are also supported.
383: For RSA and DSA keys
384: .Nm
1.78 jmc 385: tries to find the matching public key file and prints its fingerprint.
386: If combined with
387: .Fl v ,
388: an ASCII art representation of the key is supplied with the fingerprint.
1.96 jmc 389: .It Fl M Ar memory
390: Specify the amount of memory to use (in megabytes) when generating
391: candidate moduli for DH-GEX.
1.95 djm 392: .It Fl m Ar key_format
393: Specify a key format for the
394: .Fl i
395: (import) or
396: .Fl e
1.96 jmc 397: (export) conversion options.
1.95 djm 398: The supported key formats are:
399: .Dq RFC4716
1.96 jmc 400: (RFC 4716/SSH2 public or private key),
1.95 djm 401: .Dq PKCS8
402: (PEM PKCS8 public key)
403: or
404: .Dq PEM
405: (PEM public key).
406: The default conversion format is
407: .Dq RFC4716 .
1.66 jmc 408: .It Fl N Ar new_passphrase
409: Provides the new passphrase.
1.84 djm 410: .It Fl n Ar principals
411: Specify one or more principals (user or host names) to be included in
412: a certificate when signing a key.
413: Multiple principals may be specified, separated by commas.
414: Please see the
415: .Sx CERTIFICATES
416: section for details.
1.93 djm 417: .It Fl O Ar option
418: Specify a certificate option when signing a key.
1.84 djm 419: This option may be specified multiple times.
420: Please see the
421: .Sx CERTIFICATES
422: section for details.
1.93 djm 423: The options that are valid for user certificates are:
1.84 djm 424: .Bl -tag -width Ds
1.89 jmc 425: .It Ic clear
426: Clear all enabled permissions.
427: This is useful for clearing the default set of permissions so permissions may
428: be added individually.
429: .It Ic force-command Ns = Ns Ar command
430: Forces the execution of
431: .Ar command
432: instead of any shell or command specified by the user when
433: the certificate is used for authentication.
1.84 djm 434: .It Ic no-agent-forwarding
435: Disable
436: .Xr ssh-agent 1
1.85 jmc 437: forwarding (permitted by default).
1.84 djm 438: .It Ic no-port-forwarding
1.85 jmc 439: Disable port forwarding (permitted by default).
1.84 djm 440: .It Ic no-pty
1.85 jmc 441: Disable PTY allocation (permitted by default).
1.84 djm 442: .It Ic no-user-rc
443: Disable execution of
444: .Pa ~/.ssh/rc
445: by
1.85 jmc 446: .Xr sshd 8
447: (permitted by default).
1.89 jmc 448: .It Ic no-x11-forwarding
449: Disable X11 forwarding (permitted by default).
1.88 djm 450: .It Ic permit-agent-forwarding
451: Allows
452: .Xr ssh-agent 1
453: forwarding.
1.84 djm 454: .It Ic permit-port-forwarding
455: Allows port forwarding.
456: .It Ic permit-pty
457: Allows PTY allocation.
458: .It Ic permit-user-rc
459: Allows execution of
460: .Pa ~/.ssh/rc
461: by
462: .Xr sshd 8 .
1.89 jmc 463: .It Ic permit-x11-forwarding
464: Allows X11 forwarding.
465: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 466: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 467: The
468: .Ar address_list
469: is a comma-separated list of one or more address/netmask pairs in CIDR
470: format.
471: .El
472: .Pp
1.93 djm 473: At present, no options are valid for host keys.
1.117 djm 474: .It Fl o
475: Causes
476: .Nm
477: to save SSH protocol 2 private keys using the new OpenSSH format rather than
478: the more compatible PEM format.
479: The new format has increased resistance to brute-force password cracking
480: but is not supported by versions of OpenSSH prior to 6.5.
481: Ed25519 keys always use the new private key format.
1.66 jmc 482: .It Fl P Ar passphrase
483: Provides the (old) passphrase.
1.2 deraadt 484: .It Fl p
1.1 deraadt 485: Requests changing the passphrase of a private key file instead of
1.12 aaron 486: creating a new private key.
487: The program will prompt for the file
1.1 deraadt 488: containing the private key, for the old passphrase, and twice for the
489: new passphrase.
1.113 jmc 490: .It Fl Q
491: Test whether keys have been revoked in a KRL.
1.5 aaron 492: .It Fl q
493: Silence
494: .Nm ssh-keygen .
1.64 djm 495: .It Fl R Ar hostname
496: Removes all keys belonging to
497: .Ar hostname
1.65 jmc 498: from a
1.64 djm 499: .Pa known_hosts
500: file.
1.65 jmc 501: This option is useful to delete hashed hosts (see the
1.64 djm 502: .Fl H
503: option above).
1.66 jmc 504: .It Fl r Ar hostname
505: Print the SSHFP fingerprint resource record named
506: .Ar hostname
507: for the specified public key file.
1.60 djm 508: .It Fl S Ar start
509: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 510: .It Fl s Ar ca_key
511: Certify (sign) a public key using the specified CA key.
512: Please see the
513: .Sx CERTIFICATES
514: section for details.
1.111 djm 515: .Pp
516: When generating a KRL,
517: .Fl s
1.112 jmc 518: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 519: by key ID or serial number.
520: See the
521: .Sx KEY REVOCATION LISTS
522: section for details.
1.60 djm 523: .It Fl T Ar output_file
524: Test DH group exchange candidate primes (generated using the
525: .Fl G
526: option) for safety.
1.121 deraadt 527: .It Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1
1.66 jmc 528: Specifies the type of key to create.
529: The possible values are
530: .Dq rsa1
531: for protocol version 1 and
1.100 naddy 532: .Dq dsa ,
1.118 naddy 533: .Dq ecdsa ,
534: .Dq ed25519 ,
1.100 naddy 535: or
1.66 jmc 536: .Dq rsa
537: for protocol version 2.
1.112 jmc 538: .It Fl u
539: Update a KRL.
540: When specified with
541: .Fl k ,
1.114 jmc 542: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 543: a new KRL being created.
1.84 djm 544: .It Fl V Ar validity_interval
545: Specify a validity interval when signing a certificate.
546: A validity interval may consist of a single time, indicating that the
547: certificate is valid beginning now and expiring at that time, or may consist
548: of two times separated by a colon to indicate an explicit time interval.
549: The start time may be specified as a date in YYYYMMDD format, a time
550: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
551: of a minus sign followed by a relative time in the format described in the
1.116 jmc 552: TIME FORMATS section of
1.90 jmc 553: .Xr sshd_config 5 .
1.84 djm 554: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
555: a relative time starting with a plus character.
556: .Pp
557: For example:
558: .Dq +52w1d
559: (valid from now to 52 weeks and one day from now),
560: .Dq -4w:+4w
561: (valid from four weeks ago to four weeks from now),
562: .Dq 20100101123000:20110101123000
563: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
564: .Dq -1d:20110101
565: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 566: .It Fl v
567: Verbose mode.
568: Causes
569: .Nm
570: to print debugging messages about its progress.
571: This is helpful for debugging moduli generation.
572: Multiple
573: .Fl v
574: options increase the verbosity.
575: The maximum is 3.
1.66 jmc 576: .It Fl W Ar generator
577: Specify desired generator when testing candidate moduli for DH-GEX.
578: .It Fl y
579: This option will read a private
580: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 581: .It Fl z Ar serial_number
582: Specifies a serial number to be embedded in the certificate to distinguish
583: this certificate from others from the same CA.
584: The default serial number is zero.
1.111 djm 585: .Pp
586: When generating a KRL, the
587: .Fl z
588: flag is used to specify a KRL version number.
1.2 deraadt 589: .El
1.60 djm 590: .Sh MODULI GENERATION
591: .Nm
592: may be used to generate groups for the Diffie-Hellman Group Exchange
593: (DH-GEX) protocol.
594: Generating these groups is a two-step process: first, candidate
595: primes are generated using a fast, but memory intensive process.
596: These candidate primes are then tested for suitability (a CPU-intensive
597: process).
598: .Pp
599: Generation of primes is performed using the
600: .Fl G
601: option.
602: The desired length of the primes may be specified by the
603: .Fl b
604: option.
605: For example:
606: .Pp
1.66 jmc 607: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 608: .Pp
609: By default, the search for primes begins at a random point in the
610: desired length range.
611: This may be overridden using the
612: .Fl S
613: option, which specifies a different start point (in hex).
614: .Pp
1.109 dtucker 615: Once a set of candidates have been generated, they must be screened for
1.60 djm 616: suitability.
617: This may be performed using the
618: .Fl T
619: option.
620: In this mode
621: .Nm
622: will read candidates from standard input (or a file specified using the
623: .Fl f
624: option).
625: For example:
626: .Pp
1.66 jmc 627: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 628: .Pp
629: By default, each candidate will be subjected to 100 primality tests.
630: This may be overridden using the
631: .Fl a
632: option.
633: The DH generator value will be chosen automatically for the
634: prime under consideration.
635: If a specific generator is desired, it may be requested using the
636: .Fl W
637: option.
1.66 jmc 638: Valid generator values are 2, 3, and 5.
1.60 djm 639: .Pp
640: Screened DH groups may be installed in
641: .Pa /etc/moduli .
642: It is important that this file contains moduli of a range of bit lengths and
643: that both ends of a connection share common moduli.
1.84 djm 644: .Sh CERTIFICATES
645: .Nm
646: supports signing of keys to produce certificates that may be used for
647: user or host authentication.
648: Certificates consist of a public key, some identity information, zero or
1.94 jmc 649: more principal (user or host) names and a set of options that
1.84 djm 650: are signed by a Certification Authority (CA) key.
651: Clients or servers may then trust only the CA key and verify its signature
652: on a certificate rather than trusting many user/host keys.
653: Note that OpenSSH certificates are a different, and much simpler, format to
654: the X.509 certificates used in
655: .Xr ssl 8 .
656: .Pp
657: .Nm
658: supports two types of certificates: user and host.
659: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 660: authenticate server hosts to users.
661: To generate a user certificate:
1.84 djm 662: .Pp
663: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
664: .Pp
665: The resultant certificate will be placed in
1.91 djm 666: .Pa /path/to/user_key-cert.pub .
1.84 djm 667: A host certificate requires the
668: .Fl h
669: option:
670: .Pp
671: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
672: .Pp
673: The host certificate will be output to
1.91 djm 674: .Pa /path/to/host_key-cert.pub .
1.98 djm 675: .Pp
676: It is possible to sign using a CA key stored in a PKCS#11 token by
677: providing the token library using
678: .Fl D
679: and identifying the CA key by providing its public half as an argument
680: to
681: .Fl s :
682: .Pp
1.127 ! naddy 683: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.98 djm 684: .Pp
685: In all cases,
1.84 djm 686: .Ar key_id
687: is a "key identifier" that is logged by the server when the certificate
688: is used for authentication.
689: .Pp
690: Certificates may be limited to be valid for a set of principal (user/host)
691: names.
692: By default, generated certificates are valid for all users or hosts.
693: To generate a certificate for a specified set of principals:
694: .Pp
695: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 ! naddy 696: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 697: .Pp
698: Additional limitations on the validity and use of user certificates may
1.94 jmc 699: be specified through certificate options.
1.93 djm 700: A certificate option may disable features of the SSH session, may be
1.84 djm 701: valid only when presented from particular source addresses or may
702: force the use of a specific command.
1.93 djm 703: For a list of valid certificate options, see the documentation for the
1.84 djm 704: .Fl O
705: option above.
706: .Pp
707: Finally, certificates may be defined with a validity lifetime.
708: The
709: .Fl V
710: option allows specification of certificate start and end times.
711: A certificate that is presented at a time outside this range will not be
712: considered valid.
1.110 jmc 713: By default, certificates are valid from
714: .Ux
715: Epoch to the distant future.
1.84 djm 716: .Pp
717: For certificates to be used for user or host authentication, the CA
718: public key must be trusted by
719: .Xr sshd 8
720: or
721: .Xr ssh 1 .
722: Please refer to those manual pages for details.
1.111 djm 723: .Sh KEY REVOCATION LISTS
724: .Nm
725: is able to manage OpenSSH format Key Revocation Lists (KRLs).
726: These binary files specify keys or certificates to be revoked using a
1.119 tedu 727: compact format, taking as little as one bit per certificate if they are being
1.111 djm 728: revoked by serial number.
729: .Pp
730: KRLs may be generated using the
731: .Fl k
732: flag.
1.114 jmc 733: This option reads one or more files from the command line and generates a new
1.111 djm 734: KRL.
735: The files may either contain a KRL specification (see below) or public keys,
736: listed one per line.
737: Plain public keys are revoked by listing their hash or contents in the KRL and
738: certificates revoked by serial number or key ID (if the serial is zero or
739: not available).
740: .Pp
741: Revoking keys using a KRL specification offers explicit control over the
742: types of record used to revoke keys and may be used to directly revoke
743: certificates by serial number or key ID without having the complete original
744: certificate on hand.
745: A KRL specification consists of lines containing one of the following directives
746: followed by a colon and some directive-specific information.
747: .Bl -tag -width Ds
1.115 jmc 748: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 749: Revokes a certificate with the specified serial number.
1.112 jmc 750: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 751: in decimal, hex or octal.
752: If two serial numbers are specified separated by a hyphen, then the range
753: of serial numbers including and between each is revoked.
754: The CA key must have been specified on the
755: .Nm
1.114 jmc 756: command line using the
1.111 djm 757: .Fl s
758: option.
759: .It Cm id : Ar key_id
760: Revokes a certificate with the specified key ID string.
761: The CA key must have been specified on the
762: .Nm
1.114 jmc 763: command line using the
1.111 djm 764: .Fl s
765: option.
766: .It Cm key : Ar public_key
767: Revokes the specified key.
1.112 jmc 768: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 769: .It Cm sha1 : Ar public_key
770: Revokes the specified key by its SHA1 hash.
771: .El
772: .Pp
773: KRLs may be updated using the
774: .Fl u
775: flag in addition to
776: .Fl k .
1.114 jmc 777: When this option is specified, keys listed via the command line are merged into
1.111 djm 778: the KRL, adding to those already there.
779: .Pp
780: It is also possible, given a KRL, to test whether it revokes a particular key
781: (or keys).
782: The
783: .Fl Q
784: flag will query an existing KRL, testing each key specified on the commandline.
1.114 jmc 785: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 786: then
787: .Nm
788: will exit with a non-zero exit status.
789: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 790: .Sh FILES
1.100 naddy 791: .Bl -tag -width Ds -compact
1.68 djm 792: .It Pa ~/.ssh/identity
1.36 itojun 793: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 794: This file should not be readable by anyone but the user.
795: It is possible to
1.1 deraadt 796: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 797: used to encrypt the private part of this file using 3DES.
1.12 aaron 798: This file is not automatically accessed by
1.2 deraadt 799: .Nm
1.1 deraadt 800: but it is offered as the default file for the private key.
1.46 markus 801: .Xr ssh 1
1.15 deraadt 802: will read this file when a login attempt is made.
1.100 naddy 803: .Pp
1.68 djm 804: .It Pa ~/.ssh/identity.pub
1.36 itojun 805: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 806: The contents of this file should be added to
1.68 djm 807: .Pa ~/.ssh/authorized_keys
1.2 deraadt 808: on all machines
1.49 deraadt 809: where the user wishes to log in using RSA authentication.
1.15 deraadt 810: There is no need to keep the contents of this file secret.
1.100 naddy 811: .Pp
1.68 djm 812: .It Pa ~/.ssh/id_dsa
1.100 naddy 813: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 814: .It Pa ~/.ssh/id_ed25519
1.100 naddy 815: .It Pa ~/.ssh/id_rsa
1.123 sobrado 816: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 817: authentication identity of the user.
1.15 deraadt 818: This file should not be readable by anyone but the user.
819: It is possible to
820: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 821: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 822: This file is not automatically accessed by
823: .Nm
824: but it is offered as the default file for the private key.
1.46 markus 825: .Xr ssh 1
1.15 deraadt 826: will read this file when a login attempt is made.
1.100 naddy 827: .Pp
1.68 djm 828: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 829: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 830: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 831: .It Pa ~/.ssh/id_rsa.pub
1.123 sobrado 832: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 833: public key for authentication.
1.15 deraadt 834: The contents of this file should be added to
1.68 djm 835: .Pa ~/.ssh/authorized_keys
1.15 deraadt 836: on all machines
1.49 deraadt 837: where the user wishes to log in using public key authentication.
1.12 aaron 838: There is no need to keep the contents of this file secret.
1.100 naddy 839: .Pp
1.60 djm 840: .It Pa /etc/moduli
841: Contains Diffie-Hellman groups used for DH-GEX.
842: The file format is described in
843: .Xr moduli 5 .
1.19 aaron 844: .El
1.2 deraadt 845: .Sh SEE ALSO
846: .Xr ssh 1 ,
847: .Xr ssh-add 1 ,
1.8 ericj 848: .Xr ssh-agent 1 ,
1.60 djm 849: .Xr moduli 5 ,
1.30 itojun 850: .Xr sshd 8
1.37 markus 851: .Rs
1.73 markus 852: .%R RFC 4716
853: .%T "The Secure Shell (SSH) Public Key File Format"
854: .%D 2006
1.37 markus 855: .Re
1.59 jmc 856: .Sh AUTHORS
857: OpenSSH is a derivative of the original and free
858: ssh 1.2.12 release by Tatu Ylonen.
859: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
860: Theo de Raadt and Dug Song
861: removed many bugs, re-added newer features and
862: created OpenSSH.
863: Markus Friedl contributed the support for SSH
864: 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