Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.132
1.132 ! jmc 1: .\" $OpenBSD: ssh-keygen.1,v 1.131 2016/05/03 14:54:08 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: .\"
1.132 ! jmc 38: .Dd $Mdocdate: May 3 2016 $
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
1.130 jmc 144: can create keys for use by SSH protocol versions 1 and 2.
145: Protocol 1 should not be used
146: and is only offered to support legacy devices.
147: It suffers from a number of cryptographic weaknesses
148: and doesn't support many of the advanced features available for protocol 2.
149: .Pp
1.58 jmc 150: The type of key to be generated is specified with the
1.25 markus 151: .Fl t
1.52 djm 152: option.
1.70 djm 153: If invoked without any arguments,
154: .Nm
1.71 jmc 155: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 156: .Pp
1.60 djm 157: .Nm
158: is also used to generate groups for use in Diffie-Hellman group
159: exchange (DH-GEX).
160: See the
161: .Sx MODULI GENERATION
162: section for details.
163: .Pp
1.111 djm 164: Finally,
165: .Nm
166: can be used to generate and update Key Revocation Lists, and to test whether
1.112 jmc 167: given keys have been revoked by one.
168: See the
1.111 djm 169: .Sx KEY REVOCATION LISTS
170: section for details.
171: .Pp
1.2 deraadt 172: Normally each user wishing to use SSH
1.99 djm 173: with public key authentication runs this once to create the authentication
1.1 deraadt 174: key in
1.68 djm 175: .Pa ~/.ssh/identity ,
1.118 naddy 176: .Pa ~/.ssh/id_dsa ,
1.99 djm 177: .Pa ~/.ssh/id_ecdsa ,
1.118 naddy 178: .Pa ~/.ssh/id_ed25519
1.15 deraadt 179: or
1.68 djm 180: .Pa ~/.ssh/id_rsa .
1.15 deraadt 181: Additionally, the system administrator may use this to generate host keys,
182: as seen in
183: .Pa /etc/rc .
1.2 deraadt 184: .Pp
1.1 deraadt 185: Normally this program generates the key and asks for a file in which
1.12 aaron 186: to store the private key.
187: The public key is stored in a file with the same name but
1.2 deraadt 188: .Dq .pub
1.12 aaron 189: appended.
190: The program also asks for a passphrase.
191: The passphrase may be empty to indicate no passphrase
1.26 markus 192: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 193: arbitrary length.
1.51 stevesk 194: A passphrase is similar to a password, except it can be a phrase with a
195: series of words, punctuation, numbers, whitespace, or any string of
196: characters you want.
197: Good passphrases are 10-30 characters long, are
1.1 deraadt 198: not simple sentences or otherwise easily guessable (English
1.42 markus 199: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 200: passphrases), and contain a mix of upper and lowercase letters,
201: numbers, and non-alphanumeric characters.
1.12 aaron 202: The passphrase can be changed later by using the
1.2 deraadt 203: .Fl p
1.1 deraadt 204: option.
1.2 deraadt 205: .Pp
1.12 aaron 206: There is no way to recover a lost passphrase.
1.105 djm 207: If the passphrase is lost or forgotten, a new key must be generated
208: and the corresponding public key copied to other machines.
1.2 deraadt 209: .Pp
1.37 markus 210: For RSA1 keys,
211: there is also a comment field in the key file that is only for
1.12 aaron 212: convenience to the user to help identify the key.
213: The comment can tell what the key is for, or whatever is useful.
214: The comment is initialized to
1.2 deraadt 215: .Dq user@host
216: when the key is created, but can be changed using the
217: .Fl c
1.1 deraadt 218: option.
1.2 deraadt 219: .Pp
1.15 deraadt 220: After a key is generated, instructions below detail where the keys
221: should be placed to be activated.
222: .Pp
1.2 deraadt 223: The options are as follows:
224: .Bl -tag -width Ds
1.102 stevesk 225: .It Fl A
1.118 naddy 226: For each of the key types (rsa1, rsa, dsa, ecdsa and ed25519)
227: for which host keys
1.102 stevesk 228: do not exist, generate the host keys with the default key file path,
229: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 230: This is used by
1.102 stevesk 231: .Pa /etc/rc
232: to generate new host keys.
1.117 djm 233: .It Fl a Ar rounds
234: When saving a new-format private key (i.e. an ed25519 key or any SSH protocol
235: 2 key when the
236: .Fl o
237: flag is set), this option specifies the number of KDF (key derivation function)
238: rounds used.
239: Higher numbers result in slower passphrase verification and increased
240: resistance to brute-force password cracking (should the keys be stolen).
241: .Pp
242: When screening DH-GEX candidates (
243: using the
1.60 djm 244: .Fl T
1.117 djm 245: command).
246: This option specifies the number of primality tests to perform.
1.66 jmc 247: .It Fl B
248: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 249: .It Fl b Ar bits
1.12 aaron 250: Specifies the number of bits in the key to create.
1.126 djm 251: For RSA keys, the minimum size is 1024 bits and the default is 2048 bits.
1.69 djm 252: Generally, 2048 bits is considered sufficient.
1.72 dtucker 253: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 254: For ECDSA keys, the
255: .Fl b
1.107 deraadt 256: flag determines the key length by selecting from one of three elliptic
1.106 djm 257: curve sizes: 256, 384 or 521 bits.
258: Attempting to use bit lengths other than these three values for ECDSA keys
259: will fail.
1.123 sobrado 260: Ed25519 keys have a fixed length and the
1.118 naddy 261: .Fl b
262: flag will be ignored.
1.66 jmc 263: .It Fl C Ar comment
264: Provides a new comment.
1.2 deraadt 265: .It Fl c
1.1 deraadt 266: Requests changing the comment in the private and public key files.
1.50 markus 267: This operation is only supported for RSA1 keys.
1.1 deraadt 268: The program will prompt for the file containing the private keys, for
1.41 stevesk 269: the passphrase if the key has one, and for the new comment.
1.81 markus 270: .It Fl D Ar pkcs11
1.83 markus 271: Download the RSA public keys provided by the PKCS#11 shared library
272: .Ar pkcs11 .
1.98 djm 273: When used in combination with
274: .Fl s ,
275: this option indicates that a CA key resides in a PKCS#11 token (see the
276: .Sx CERTIFICATES
277: section for details).
1.124 djm 278: .It Fl E Ar fingerprint_hash
279: Specifies the hash algorithm used when displaying key fingerprints.
280: Valid options are:
281: .Dq md5
282: and
283: .Dq sha256 .
284: The default is
285: .Dq sha256 .
1.37 markus 286: .It Fl e
1.40 markus 287: This option will read a private or public OpenSSH key file and
1.95 djm 288: print to stdout the key in one of the formats specified by the
289: .Fl m
290: option.
291: The default export format is
292: .Dq RFC4716 .
1.96 jmc 293: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 294: several commercial SSH implementations.
1.66 jmc 295: .It Fl F Ar hostname
296: Search for the specified
297: .Ar hostname
298: in a
299: .Pa known_hosts
300: file, listing any occurrences found.
301: This option is useful to find hashed host names or addresses and may also be
302: used in conjunction with the
303: .Fl H
304: option to print found keys in a hashed format.
305: .It Fl f Ar filename
306: Specifies the filename of the key file.
307: .It Fl G Ar output_file
308: Generate candidate primes for DH-GEX.
309: These primes must be screened for
310: safety (using the
311: .Fl T
312: option) before use.
1.57 jakob 313: .It Fl g
1.62 jakob 314: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 315: .Fl r
1.62 jakob 316: command.
1.66 jmc 317: .It Fl H
318: Hash a
319: .Pa known_hosts
1.67 dtucker 320: file.
321: This replaces all hostnames and addresses with hashed representations
322: within the specified file; the original content is moved to a file with
323: a .old suffix.
1.66 jmc 324: These hashes may be used normally by
325: .Nm ssh
326: and
327: .Nm sshd ,
328: but they do not reveal identifying information should the file's contents
329: be disclosed.
330: This option will not modify existing hashed hostnames and is therefore safe
331: to use on files that mix hashed and non-hashed names.
1.84 djm 332: .It Fl h
333: When signing a key, create a host certificate instead of a user
334: certificate.
335: Please see the
336: .Sx CERTIFICATES
337: section for details.
1.85 jmc 338: .It Fl I Ar certificate_identity
1.84 djm 339: Specify the key identity when signing a public key.
340: Please see the
341: .Sx CERTIFICATES
342: section for details.
1.37 markus 343: .It Fl i
344: This option will read an unencrypted private (or public) key file
1.95 djm 345: in the format specified by the
346: .Fl m
347: option and print an OpenSSH compatible private
1.37 markus 348: (or public) key to stdout.
1.122 jmc 349: This option allows importing keys from other software, including several
350: commercial SSH implementations.
351: The default import format is
352: .Dq RFC4716 .
1.109 dtucker 353: .It Fl J Ar num_lines
354: Exit after screening the specified number of lines
355: while performing DH candidate screening using the
356: .Fl T
357: option.
358: .It Fl j Ar start_line
359: Start screening at the specified line number
360: while performing DH candidate screening using the
361: .Fl T
362: option.
1.108 dtucker 363: .It Fl K Ar checkpt
364: Write the last line processed to the file
365: .Ar checkpt
366: while performing DH candidate screening using the
367: .Fl T
368: option.
369: This will be used to skip lines in the input file that have already been
370: processed if the job is restarted.
1.111 djm 371: .It Fl k
372: Generate a KRL file.
373: In this mode,
374: .Nm
375: will generate a KRL file at the location specified via the
376: .Fl f
1.114 jmc 377: flag that revokes every key or certificate presented on the command line.
1.111 djm 378: Keys/certificates to be revoked may be specified by public key file or
379: using the format described in the
380: .Sx KEY REVOCATION LISTS
381: section.
1.86 djm 382: .It Fl L
1.129 djm 383: Prints the contents of one or more certificates.
1.9 markus 384: .It Fl l
1.77 grunk 385: Show fingerprint of specified public key file.
1.50 markus 386: Private RSA1 keys are also supported.
387: For RSA and DSA keys
388: .Nm
1.78 jmc 389: tries to find the matching public key file and prints its fingerprint.
390: If combined with
391: .Fl v ,
1.132 ! jmc 392: a visual ASCII art representation of the key is supplied with the
1.131 djm 393: fingerprint.
1.96 jmc 394: .It Fl M Ar memory
395: Specify the amount of memory to use (in megabytes) when generating
396: candidate moduli for DH-GEX.
1.95 djm 397: .It Fl m Ar key_format
398: Specify a key format for the
399: .Fl i
400: (import) or
401: .Fl e
1.96 jmc 402: (export) conversion options.
1.95 djm 403: The supported key formats are:
404: .Dq RFC4716
1.96 jmc 405: (RFC 4716/SSH2 public or private key),
1.95 djm 406: .Dq PKCS8
407: (PEM PKCS8 public key)
408: or
409: .Dq PEM
410: (PEM public key).
411: The default conversion format is
412: .Dq RFC4716 .
1.66 jmc 413: .It Fl N Ar new_passphrase
414: Provides the new passphrase.
1.84 djm 415: .It Fl n Ar principals
416: Specify one or more principals (user or host names) to be included in
417: a certificate when signing a key.
418: Multiple principals may be specified, separated by commas.
419: Please see the
420: .Sx CERTIFICATES
421: section for details.
1.93 djm 422: .It Fl O Ar option
423: Specify a certificate option when signing a key.
1.84 djm 424: This option may be specified multiple times.
425: Please see the
426: .Sx CERTIFICATES
427: section for details.
1.93 djm 428: The options that are valid for user certificates are:
1.84 djm 429: .Bl -tag -width Ds
1.89 jmc 430: .It Ic clear
431: Clear all enabled permissions.
432: This is useful for clearing the default set of permissions so permissions may
433: be added individually.
434: .It Ic force-command Ns = Ns Ar command
435: Forces the execution of
436: .Ar command
437: instead of any shell or command specified by the user when
438: the certificate is used for authentication.
1.84 djm 439: .It Ic no-agent-forwarding
440: Disable
441: .Xr ssh-agent 1
1.85 jmc 442: forwarding (permitted by default).
1.84 djm 443: .It Ic no-port-forwarding
1.85 jmc 444: Disable port forwarding (permitted by default).
1.84 djm 445: .It Ic no-pty
1.85 jmc 446: Disable PTY allocation (permitted by default).
1.84 djm 447: .It Ic no-user-rc
448: Disable execution of
449: .Pa ~/.ssh/rc
450: by
1.85 jmc 451: .Xr sshd 8
452: (permitted by default).
1.89 jmc 453: .It Ic no-x11-forwarding
454: Disable X11 forwarding (permitted by default).
1.88 djm 455: .It Ic permit-agent-forwarding
456: Allows
457: .Xr ssh-agent 1
458: forwarding.
1.84 djm 459: .It Ic permit-port-forwarding
460: Allows port forwarding.
461: .It Ic permit-pty
462: Allows PTY allocation.
463: .It Ic permit-user-rc
464: Allows execution of
465: .Pa ~/.ssh/rc
466: by
467: .Xr sshd 8 .
1.89 jmc 468: .It Ic permit-x11-forwarding
469: Allows X11 forwarding.
470: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 471: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 472: The
473: .Ar address_list
474: is a comma-separated list of one or more address/netmask pairs in CIDR
475: format.
476: .El
477: .Pp
1.93 djm 478: At present, no options are valid for host keys.
1.117 djm 479: .It Fl o
480: Causes
481: .Nm
1.130 jmc 482: to save private keys using the new OpenSSH format rather than
1.117 djm 483: the more compatible PEM format.
484: The new format has increased resistance to brute-force password cracking
485: but is not supported by versions of OpenSSH prior to 6.5.
486: Ed25519 keys always use the new private key format.
1.66 jmc 487: .It Fl P Ar passphrase
488: Provides the (old) passphrase.
1.2 deraadt 489: .It Fl p
1.1 deraadt 490: Requests changing the passphrase of a private key file instead of
1.12 aaron 491: creating a new private key.
492: The program will prompt for the file
1.1 deraadt 493: containing the private key, for the old passphrase, and twice for the
494: new passphrase.
1.113 jmc 495: .It Fl Q
496: Test whether keys have been revoked in a KRL.
1.5 aaron 497: .It Fl q
498: Silence
499: .Nm ssh-keygen .
1.64 djm 500: .It Fl R Ar hostname
501: Removes all keys belonging to
502: .Ar hostname
1.65 jmc 503: from a
1.64 djm 504: .Pa known_hosts
505: file.
1.65 jmc 506: This option is useful to delete hashed hosts (see the
1.64 djm 507: .Fl H
508: option above).
1.66 jmc 509: .It Fl r Ar hostname
510: Print the SSHFP fingerprint resource record named
511: .Ar hostname
512: for the specified public key file.
1.60 djm 513: .It Fl S Ar start
514: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 515: .It Fl s Ar ca_key
516: Certify (sign) a public key using the specified CA key.
517: Please see the
518: .Sx CERTIFICATES
519: section for details.
1.111 djm 520: .Pp
521: When generating a KRL,
522: .Fl s
1.112 jmc 523: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 524: by key ID or serial number.
525: See the
526: .Sx KEY REVOCATION LISTS
527: section for details.
1.60 djm 528: .It Fl T Ar output_file
529: Test DH group exchange candidate primes (generated using the
530: .Fl G
531: option) for safety.
1.121 deraadt 532: .It Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1
1.66 jmc 533: Specifies the type of key to create.
534: The possible values are
535: .Dq rsa1
536: for protocol version 1 and
1.100 naddy 537: .Dq dsa ,
1.118 naddy 538: .Dq ecdsa ,
539: .Dq ed25519 ,
1.100 naddy 540: or
1.66 jmc 541: .Dq rsa
542: for protocol version 2.
1.112 jmc 543: .It Fl u
544: Update a KRL.
545: When specified with
546: .Fl k ,
1.114 jmc 547: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 548: a new KRL being created.
1.84 djm 549: .It Fl V Ar validity_interval
550: Specify a validity interval when signing a certificate.
551: A validity interval may consist of a single time, indicating that the
552: certificate is valid beginning now and expiring at that time, or may consist
553: of two times separated by a colon to indicate an explicit time interval.
554: The start time may be specified as a date in YYYYMMDD format, a time
555: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
556: of a minus sign followed by a relative time in the format described in the
1.116 jmc 557: TIME FORMATS section of
1.90 jmc 558: .Xr sshd_config 5 .
1.84 djm 559: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
560: a relative time starting with a plus character.
561: .Pp
562: For example:
563: .Dq +52w1d
564: (valid from now to 52 weeks and one day from now),
565: .Dq -4w:+4w
566: (valid from four weeks ago to four weeks from now),
567: .Dq 20100101123000:20110101123000
568: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
569: .Dq -1d:20110101
570: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 571: .It Fl v
572: Verbose mode.
573: Causes
574: .Nm
575: to print debugging messages about its progress.
576: This is helpful for debugging moduli generation.
577: Multiple
578: .Fl v
579: options increase the verbosity.
580: The maximum is 3.
1.66 jmc 581: .It Fl W Ar generator
582: Specify desired generator when testing candidate moduli for DH-GEX.
583: .It Fl y
584: This option will read a private
585: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 586: .It Fl z Ar serial_number
587: Specifies a serial number to be embedded in the certificate to distinguish
588: this certificate from others from the same CA.
589: The default serial number is zero.
1.111 djm 590: .Pp
591: When generating a KRL, the
592: .Fl z
593: flag is used to specify a KRL version number.
1.2 deraadt 594: .El
1.60 djm 595: .Sh MODULI GENERATION
596: .Nm
597: may be used to generate groups for the Diffie-Hellman Group Exchange
598: (DH-GEX) protocol.
599: Generating these groups is a two-step process: first, candidate
600: primes are generated using a fast, but memory intensive process.
601: These candidate primes are then tested for suitability (a CPU-intensive
602: process).
603: .Pp
604: Generation of primes is performed using the
605: .Fl G
606: option.
607: The desired length of the primes may be specified by the
608: .Fl b
609: option.
610: For example:
611: .Pp
1.66 jmc 612: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 613: .Pp
614: By default, the search for primes begins at a random point in the
615: desired length range.
616: This may be overridden using the
617: .Fl S
618: option, which specifies a different start point (in hex).
619: .Pp
1.109 dtucker 620: Once a set of candidates have been generated, they must be screened for
1.60 djm 621: suitability.
622: This may be performed using the
623: .Fl T
624: option.
625: In this mode
626: .Nm
627: will read candidates from standard input (or a file specified using the
628: .Fl f
629: option).
630: For example:
631: .Pp
1.66 jmc 632: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 633: .Pp
634: By default, each candidate will be subjected to 100 primality tests.
635: This may be overridden using the
636: .Fl a
637: option.
638: The DH generator value will be chosen automatically for the
639: prime under consideration.
640: If a specific generator is desired, it may be requested using the
641: .Fl W
642: option.
1.66 jmc 643: Valid generator values are 2, 3, and 5.
1.60 djm 644: .Pp
645: Screened DH groups may be installed in
646: .Pa /etc/moduli .
647: It is important that this file contains moduli of a range of bit lengths and
648: that both ends of a connection share common moduli.
1.84 djm 649: .Sh CERTIFICATES
650: .Nm
651: supports signing of keys to produce certificates that may be used for
652: user or host authentication.
653: Certificates consist of a public key, some identity information, zero or
1.94 jmc 654: more principal (user or host) names and a set of options that
1.84 djm 655: are signed by a Certification Authority (CA) key.
656: Clients or servers may then trust only the CA key and verify its signature
657: on a certificate rather than trusting many user/host keys.
658: Note that OpenSSH certificates are a different, and much simpler, format to
659: the X.509 certificates used in
660: .Xr ssl 8 .
661: .Pp
662: .Nm
663: supports two types of certificates: user and host.
664: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 665: authenticate server hosts to users.
666: To generate a user certificate:
1.84 djm 667: .Pp
668: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
669: .Pp
670: The resultant certificate will be placed in
1.91 djm 671: .Pa /path/to/user_key-cert.pub .
1.84 djm 672: A host certificate requires the
673: .Fl h
674: option:
675: .Pp
676: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
677: .Pp
678: The host certificate will be output to
1.91 djm 679: .Pa /path/to/host_key-cert.pub .
1.98 djm 680: .Pp
681: It is possible to sign using a CA key stored in a PKCS#11 token by
682: providing the token library using
683: .Fl D
684: and identifying the CA key by providing its public half as an argument
685: to
686: .Fl s :
687: .Pp
1.127 naddy 688: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.98 djm 689: .Pp
690: In all cases,
1.84 djm 691: .Ar key_id
692: is a "key identifier" that is logged by the server when the certificate
693: is used for authentication.
694: .Pp
695: Certificates may be limited to be valid for a set of principal (user/host)
696: names.
697: By default, generated certificates are valid for all users or hosts.
698: To generate a certificate for a specified set of principals:
699: .Pp
700: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 701: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 702: .Pp
703: Additional limitations on the validity and use of user certificates may
1.94 jmc 704: be specified through certificate options.
1.93 djm 705: A certificate option may disable features of the SSH session, may be
1.84 djm 706: valid only when presented from particular source addresses or may
707: force the use of a specific command.
1.93 djm 708: For a list of valid certificate options, see the documentation for the
1.84 djm 709: .Fl O
710: option above.
711: .Pp
712: Finally, certificates may be defined with a validity lifetime.
713: The
714: .Fl V
715: option allows specification of certificate start and end times.
716: A certificate that is presented at a time outside this range will not be
717: considered valid.
1.110 jmc 718: By default, certificates are valid from
719: .Ux
720: Epoch to the distant future.
1.84 djm 721: .Pp
722: For certificates to be used for user or host authentication, the CA
723: public key must be trusted by
724: .Xr sshd 8
725: or
726: .Xr ssh 1 .
727: Please refer to those manual pages for details.
1.111 djm 728: .Sh KEY REVOCATION LISTS
729: .Nm
730: is able to manage OpenSSH format Key Revocation Lists (KRLs).
731: These binary files specify keys or certificates to be revoked using a
1.119 tedu 732: compact format, taking as little as one bit per certificate if they are being
1.111 djm 733: revoked by serial number.
734: .Pp
735: KRLs may be generated using the
736: .Fl k
737: flag.
1.114 jmc 738: This option reads one or more files from the command line and generates a new
1.111 djm 739: KRL.
740: The files may either contain a KRL specification (see below) or public keys,
741: listed one per line.
742: Plain public keys are revoked by listing their hash or contents in the KRL and
743: certificates revoked by serial number or key ID (if the serial is zero or
744: not available).
745: .Pp
746: Revoking keys using a KRL specification offers explicit control over the
747: types of record used to revoke keys and may be used to directly revoke
748: certificates by serial number or key ID without having the complete original
749: certificate on hand.
750: A KRL specification consists of lines containing one of the following directives
751: followed by a colon and some directive-specific information.
752: .Bl -tag -width Ds
1.115 jmc 753: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 754: Revokes a certificate with the specified serial number.
1.112 jmc 755: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 756: in decimal, hex or octal.
757: If two serial numbers are specified separated by a hyphen, then the range
758: of serial numbers including and between each is revoked.
759: The CA key must have been specified on the
760: .Nm
1.114 jmc 761: command line using the
1.111 djm 762: .Fl s
763: option.
764: .It Cm id : Ar key_id
765: Revokes a certificate with the specified key ID string.
766: The CA key must have been specified on the
767: .Nm
1.114 jmc 768: command line using the
1.111 djm 769: .Fl s
770: option.
771: .It Cm key : Ar public_key
772: Revokes the specified key.
1.112 jmc 773: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 774: .It Cm sha1 : Ar public_key
775: Revokes the specified key by its SHA1 hash.
776: .El
777: .Pp
778: KRLs may be updated using the
779: .Fl u
780: flag in addition to
781: .Fl k .
1.114 jmc 782: When this option is specified, keys listed via the command line are merged into
1.111 djm 783: the KRL, adding to those already there.
784: .Pp
785: It is also possible, given a KRL, to test whether it revokes a particular key
786: (or keys).
787: The
788: .Fl Q
1.128 jmc 789: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 790: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 791: then
792: .Nm
793: will exit with a non-zero exit status.
794: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 795: .Sh FILES
1.100 naddy 796: .Bl -tag -width Ds -compact
1.68 djm 797: .It Pa ~/.ssh/identity
1.36 itojun 798: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 799: This file should not be readable by anyone but the user.
800: It is possible to
1.1 deraadt 801: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 802: used to encrypt the private part of this file using 3DES.
1.12 aaron 803: This file is not automatically accessed by
1.2 deraadt 804: .Nm
1.1 deraadt 805: but it is offered as the default file for the private key.
1.46 markus 806: .Xr ssh 1
1.15 deraadt 807: will read this file when a login attempt is made.
1.100 naddy 808: .Pp
1.68 djm 809: .It Pa ~/.ssh/identity.pub
1.36 itojun 810: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 811: The contents of this file should be added to
1.68 djm 812: .Pa ~/.ssh/authorized_keys
1.2 deraadt 813: on all machines
1.49 deraadt 814: where the user wishes to log in using RSA authentication.
1.15 deraadt 815: There is no need to keep the contents of this file secret.
1.100 naddy 816: .Pp
1.68 djm 817: .It Pa ~/.ssh/id_dsa
1.100 naddy 818: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 819: .It Pa ~/.ssh/id_ed25519
1.100 naddy 820: .It Pa ~/.ssh/id_rsa
1.123 sobrado 821: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 822: authentication identity of the user.
1.15 deraadt 823: This file should not be readable by anyone but the user.
824: It is possible to
825: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 826: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 827: This file is not automatically accessed by
828: .Nm
829: but it is offered as the default file for the private key.
1.46 markus 830: .Xr ssh 1
1.15 deraadt 831: will read this file when a login attempt is made.
1.100 naddy 832: .Pp
1.68 djm 833: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 834: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 835: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 836: .It Pa ~/.ssh/id_rsa.pub
1.123 sobrado 837: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 838: public key for authentication.
1.15 deraadt 839: The contents of this file should be added to
1.68 djm 840: .Pa ~/.ssh/authorized_keys
1.15 deraadt 841: on all machines
1.49 deraadt 842: where the user wishes to log in using public key authentication.
1.12 aaron 843: There is no need to keep the contents of this file secret.
1.100 naddy 844: .Pp
1.60 djm 845: .It Pa /etc/moduli
846: Contains Diffie-Hellman groups used for DH-GEX.
847: The file format is described in
848: .Xr moduli 5 .
1.19 aaron 849: .El
1.2 deraadt 850: .Sh SEE ALSO
851: .Xr ssh 1 ,
852: .Xr ssh-add 1 ,
1.8 ericj 853: .Xr ssh-agent 1 ,
1.60 djm 854: .Xr moduli 5 ,
1.30 itojun 855: .Xr sshd 8
1.37 markus 856: .Rs
1.73 markus 857: .%R RFC 4716
858: .%T "The Secure Shell (SSH) Public Key File Format"
859: .%D 2006
1.37 markus 860: .Re
1.59 jmc 861: .Sh AUTHORS
862: OpenSSH is a derivative of the original and free
863: ssh 1.2.12 release by Tatu Ylonen.
864: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
865: Theo de Raadt and Dug Song
866: removed many bugs, re-added newer features and
867: created OpenSSH.
868: Markus Friedl contributed the support for SSH
869: protocol versions 1.5 and 2.0.
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