Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.141
1.141 ! naddy 1: .\" $OpenBSD: ssh-keygen.1,v 1.140 2017/05/03 06:32:02 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: .\"
1.141 ! naddy 38: .Dd $Mdocdate: May 3 2017 $
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
1.139 jmc 49: .Op Fl t Cm dsa | ecdsa | ed25519 | rsa
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
1.140 jmc 144: can create keys for use by SSH protocol version 2.
1.130 jmc 145: .Pp
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
1.141 ! naddy 151: will generate an RSA key.
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
1.118 naddy 171: .Pa ~/.ssh/id_dsa ,
1.99 djm 172: .Pa ~/.ssh/id_ecdsa ,
1.118 naddy 173: .Pa ~/.ssh/id_ed25519
1.15 deraadt 174: or
1.68 djm 175: .Pa ~/.ssh/id_rsa .
1.15 deraadt 176: Additionally, the system administrator may use this to generate host keys,
177: as seen in
178: .Pa /etc/rc .
1.2 deraadt 179: .Pp
1.1 deraadt 180: Normally this program generates the key and asks for a file in which
1.12 aaron 181: to store the private key.
182: The public key is stored in a file with the same name but
1.2 deraadt 183: .Dq .pub
1.12 aaron 184: appended.
185: The program also asks for a passphrase.
186: The passphrase may be empty to indicate no passphrase
1.26 markus 187: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 188: arbitrary length.
1.51 stevesk 189: A passphrase is similar to a password, except it can be a phrase with a
190: series of words, punctuation, numbers, whitespace, or any string of
191: characters you want.
192: Good passphrases are 10-30 characters long, are
1.1 deraadt 193: not simple sentences or otherwise easily guessable (English
1.42 markus 194: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 195: passphrases), and contain a mix of upper and lowercase letters,
196: numbers, and non-alphanumeric characters.
1.12 aaron 197: The passphrase can be changed later by using the
1.2 deraadt 198: .Fl p
1.1 deraadt 199: option.
1.2 deraadt 200: .Pp
1.12 aaron 201: There is no way to recover a lost passphrase.
1.105 djm 202: If the passphrase is lost or forgotten, a new key must be generated
203: and the corresponding public key copied to other machines.
1.2 deraadt 204: .Pp
1.136 djm 205: For keys stored in the newer OpenSSH format,
1.37 markus 206: there is also a comment field in the key file that is only for
1.12 aaron 207: convenience to the user to help identify the key.
208: The comment can tell what the key is for, or whatever is useful.
209: The comment is initialized to
1.2 deraadt 210: .Dq user@host
211: when the key is created, but can be changed using the
212: .Fl c
1.1 deraadt 213: option.
1.2 deraadt 214: .Pp
1.15 deraadt 215: After a key is generated, instructions below detail where the keys
216: should be placed to be activated.
217: .Pp
1.2 deraadt 218: The options are as follows:
219: .Bl -tag -width Ds
1.102 stevesk 220: .It Fl A
1.139 jmc 221: For each of the key types (rsa, dsa, ecdsa and ed25519)
1.118 naddy 222: for which host keys
1.102 stevesk 223: do not exist, generate the host keys with the default key file path,
224: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 225: This is used by
1.102 stevesk 226: .Pa /etc/rc
227: to generate new host keys.
1.117 djm 228: .It Fl a Ar rounds
1.140 jmc 229: When saving a new-format private key (i.e. an ed25519 key or when the
1.117 djm 230: .Fl o
231: flag is set), this option specifies the number of KDF (key derivation function)
232: rounds used.
233: Higher numbers result in slower passphrase verification and increased
234: resistance to brute-force password cracking (should the keys be stolen).
235: .Pp
1.140 jmc 236: When screening DH-GEX candidates (using the
1.60 djm 237: .Fl T
1.117 djm 238: command).
239: This option specifies the number of primality tests to perform.
1.66 jmc 240: .It Fl B
241: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 242: .It Fl b Ar bits
1.12 aaron 243: Specifies the number of bits in the key to create.
1.126 djm 244: For RSA keys, the minimum size is 1024 bits and the default is 2048 bits.
1.69 djm 245: Generally, 2048 bits is considered sufficient.
1.72 dtucker 246: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 247: For ECDSA keys, the
248: .Fl b
1.107 deraadt 249: flag determines the key length by selecting from one of three elliptic
1.106 djm 250: curve sizes: 256, 384 or 521 bits.
251: Attempting to use bit lengths other than these three values for ECDSA keys
252: will fail.
1.123 sobrado 253: Ed25519 keys have a fixed length and the
1.118 naddy 254: .Fl b
255: flag will be ignored.
1.66 jmc 256: .It Fl C Ar comment
257: Provides a new comment.
1.2 deraadt 258: .It Fl c
1.1 deraadt 259: Requests changing the comment in the private and public key files.
1.136 djm 260: This operation is only supported for keys stored in the
1.133 jmc 261: newer OpenSSH format.
1.1 deraadt 262: The program will prompt for the file containing the private keys, for
1.41 stevesk 263: the passphrase if the key has one, and for the new comment.
1.81 markus 264: .It Fl D Ar pkcs11
1.83 markus 265: Download the RSA public keys provided by the PKCS#11 shared library
266: .Ar pkcs11 .
1.98 djm 267: When used in combination with
268: .Fl s ,
269: this option indicates that a CA key resides in a PKCS#11 token (see the
270: .Sx CERTIFICATES
271: section for details).
1.124 djm 272: .It Fl E Ar fingerprint_hash
273: Specifies the hash algorithm used when displaying key fingerprints.
274: Valid options are:
275: .Dq md5
276: and
277: .Dq sha256 .
278: The default is
279: .Dq sha256 .
1.37 markus 280: .It Fl e
1.40 markus 281: This option will read a private or public OpenSSH key file and
1.95 djm 282: print to stdout the key in one of the formats specified by the
283: .Fl m
284: option.
285: The default export format is
286: .Dq RFC4716 .
1.96 jmc 287: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 288: several commercial SSH implementations.
1.66 jmc 289: .It Fl F Ar hostname
290: Search for the specified
291: .Ar hostname
292: in a
293: .Pa known_hosts
294: file, listing any occurrences found.
295: This option is useful to find hashed host names or addresses and may also be
296: used in conjunction with the
297: .Fl H
298: option to print found keys in a hashed format.
299: .It Fl f Ar filename
300: Specifies the filename of the key file.
301: .It Fl G Ar output_file
302: Generate candidate primes for DH-GEX.
303: These primes must be screened for
304: safety (using the
305: .Fl T
306: option) before use.
1.57 jakob 307: .It Fl g
1.62 jakob 308: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 309: .Fl r
1.62 jakob 310: command.
1.66 jmc 311: .It Fl H
312: Hash a
313: .Pa known_hosts
1.67 dtucker 314: file.
315: This replaces all hostnames and addresses with hashed representations
316: within the specified file; the original content is moved to a file with
317: a .old suffix.
1.66 jmc 318: These hashes may be used normally by
319: .Nm ssh
320: and
321: .Nm sshd ,
322: but they do not reveal identifying information should the file's contents
323: be disclosed.
324: This option will not modify existing hashed hostnames and is therefore safe
325: to use on files that mix hashed and non-hashed names.
1.84 djm 326: .It Fl h
327: When signing a key, create a host certificate instead of a user
328: certificate.
329: Please see the
330: .Sx CERTIFICATES
331: section for details.
1.85 jmc 332: .It Fl I Ar certificate_identity
1.84 djm 333: Specify the key identity when signing a public key.
334: Please see the
335: .Sx CERTIFICATES
336: section for details.
1.37 markus 337: .It Fl i
338: This option will read an unencrypted private (or public) key file
1.95 djm 339: in the format specified by the
340: .Fl m
341: option and print an OpenSSH compatible private
1.37 markus 342: (or public) key to stdout.
1.122 jmc 343: This option allows importing keys from other software, including several
344: commercial SSH implementations.
345: The default import format is
346: .Dq RFC4716 .
1.109 dtucker 347: .It Fl J Ar num_lines
348: Exit after screening the specified number of lines
349: while performing DH candidate screening using the
350: .Fl T
351: option.
352: .It Fl j Ar start_line
353: Start screening at the specified line number
354: while performing DH candidate screening using the
355: .Fl T
356: option.
1.108 dtucker 357: .It Fl K Ar checkpt
358: Write the last line processed to the file
359: .Ar checkpt
360: while performing DH candidate screening using the
361: .Fl T
362: option.
363: This will be used to skip lines in the input file that have already been
364: processed if the job is restarted.
1.111 djm 365: .It Fl k
366: Generate a KRL file.
367: In this mode,
368: .Nm
369: will generate a KRL file at the location specified via the
370: .Fl f
1.114 jmc 371: flag that revokes every key or certificate presented on the command line.
1.111 djm 372: Keys/certificates to be revoked may be specified by public key file or
373: using the format described in the
374: .Sx KEY REVOCATION LISTS
375: section.
1.86 djm 376: .It Fl L
1.129 djm 377: Prints the contents of one or more certificates.
1.9 markus 378: .It Fl l
1.77 grunk 379: Show fingerprint of specified public key file.
1.50 markus 380: For RSA and DSA keys
381: .Nm
1.78 jmc 382: tries to find the matching public key file and prints its fingerprint.
383: If combined with
384: .Fl v ,
1.132 jmc 385: a visual ASCII art representation of the key is supplied with the
1.131 djm 386: fingerprint.
1.96 jmc 387: .It Fl M Ar memory
388: Specify the amount of memory to use (in megabytes) when generating
389: candidate moduli for DH-GEX.
1.95 djm 390: .It Fl m Ar key_format
391: Specify a key format for the
392: .Fl i
393: (import) or
394: .Fl e
1.96 jmc 395: (export) conversion options.
1.95 djm 396: The supported key formats are:
397: .Dq RFC4716
1.96 jmc 398: (RFC 4716/SSH2 public or private key),
1.95 djm 399: .Dq PKCS8
400: (PEM PKCS8 public key)
401: or
402: .Dq PEM
403: (PEM public key).
404: The default conversion format is
405: .Dq RFC4716 .
1.66 jmc 406: .It Fl N Ar new_passphrase
407: Provides the new passphrase.
1.84 djm 408: .It Fl n Ar principals
409: Specify one or more principals (user or host names) to be included in
410: a certificate when signing a key.
411: Multiple principals may be specified, separated by commas.
412: Please see the
413: .Sx CERTIFICATES
414: section for details.
1.93 djm 415: .It Fl O Ar option
416: Specify a certificate option when signing a key.
1.84 djm 417: This option may be specified multiple times.
1.137 jmc 418: See also the
1.84 djm 419: .Sx CERTIFICATES
1.137 jmc 420: section for further details.
1.93 djm 421: The options that are valid for user certificates are:
1.137 jmc 422: .Pp
423: .Bl -tag -width Ds -compact
1.89 jmc 424: .It Ic clear
425: Clear all enabled permissions.
426: This is useful for clearing the default set of permissions so permissions may
427: be added individually.
1.137 jmc 428: .Pp
429: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
430: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
431: Includes an arbitrary certificate critical option or extension.
432: The specified
433: .Ar name
434: should include a domain suffix, e.g.\&
435: .Dq name@example.com .
436: If
437: .Ar contents
438: is specified then it is included as the contents of the extension/option
439: encoded as a string, otherwise the extension/option is created with no
440: contents (usually indicating a flag).
441: Extensions may be ignored by a client or server that does not recognise them,
442: whereas unknown critical options will cause the certificate to be refused.
1.138 jmc 443: .Pp
444: At present, no standard options are valid for host keys.
1.137 jmc 445: .Pp
1.89 jmc 446: .It Ic force-command Ns = Ns Ar command
447: Forces the execution of
448: .Ar command
449: instead of any shell or command specified by the user when
450: the certificate is used for authentication.
1.137 jmc 451: .Pp
1.84 djm 452: .It Ic no-agent-forwarding
453: Disable
454: .Xr ssh-agent 1
1.85 jmc 455: forwarding (permitted by default).
1.137 jmc 456: .Pp
1.84 djm 457: .It Ic no-port-forwarding
1.85 jmc 458: Disable port forwarding (permitted by default).
1.137 jmc 459: .Pp
1.84 djm 460: .It Ic no-pty
1.85 jmc 461: Disable PTY allocation (permitted by default).
1.137 jmc 462: .Pp
1.84 djm 463: .It Ic no-user-rc
464: Disable execution of
465: .Pa ~/.ssh/rc
466: by
1.85 jmc 467: .Xr sshd 8
468: (permitted by default).
1.137 jmc 469: .Pp
1.89 jmc 470: .It Ic no-x11-forwarding
471: Disable X11 forwarding (permitted by default).
1.137 jmc 472: .Pp
1.88 djm 473: .It Ic permit-agent-forwarding
474: Allows
475: .Xr ssh-agent 1
476: forwarding.
1.137 jmc 477: .Pp
1.84 djm 478: .It Ic permit-port-forwarding
479: Allows port forwarding.
1.137 jmc 480: .Pp
1.84 djm 481: .It Ic permit-pty
482: Allows PTY allocation.
1.137 jmc 483: .Pp
1.84 djm 484: .It Ic permit-user-rc
485: Allows execution of
486: .Pa ~/.ssh/rc
487: by
488: .Xr sshd 8 .
1.137 jmc 489: .Pp
1.89 jmc 490: .It Ic permit-x11-forwarding
491: Allows X11 forwarding.
1.137 jmc 492: .Pp
1.89 jmc 493: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 494: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 495: The
496: .Ar address_list
497: is a comma-separated list of one or more address/netmask pairs in CIDR
498: format.
499: .El
1.117 djm 500: .It Fl o
501: Causes
502: .Nm
1.130 jmc 503: to save private keys using the new OpenSSH format rather than
1.117 djm 504: the more compatible PEM format.
505: The new format has increased resistance to brute-force password cracking
506: but is not supported by versions of OpenSSH prior to 6.5.
507: Ed25519 keys always use the new private key format.
1.66 jmc 508: .It Fl P Ar passphrase
509: Provides the (old) passphrase.
1.2 deraadt 510: .It Fl p
1.1 deraadt 511: Requests changing the passphrase of a private key file instead of
1.12 aaron 512: creating a new private key.
513: The program will prompt for the file
1.1 deraadt 514: containing the private key, for the old passphrase, and twice for the
515: new passphrase.
1.113 jmc 516: .It Fl Q
517: Test whether keys have been revoked in a KRL.
1.5 aaron 518: .It Fl q
519: Silence
520: .Nm ssh-keygen .
1.64 djm 521: .It Fl R Ar hostname
522: Removes all keys belonging to
523: .Ar hostname
1.65 jmc 524: from a
1.64 djm 525: .Pa known_hosts
526: file.
1.65 jmc 527: This option is useful to delete hashed hosts (see the
1.64 djm 528: .Fl H
529: option above).
1.66 jmc 530: .It Fl r Ar hostname
531: Print the SSHFP fingerprint resource record named
532: .Ar hostname
533: for the specified public key file.
1.60 djm 534: .It Fl S Ar start
535: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 536: .It Fl s Ar ca_key
537: Certify (sign) a public key using the specified CA key.
538: Please see the
539: .Sx CERTIFICATES
540: section for details.
1.111 djm 541: .Pp
542: When generating a KRL,
543: .Fl s
1.112 jmc 544: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 545: by key ID or serial number.
546: See the
547: .Sx KEY REVOCATION LISTS
548: section for details.
1.60 djm 549: .It Fl T Ar output_file
550: Test DH group exchange candidate primes (generated using the
551: .Fl G
552: option) for safety.
1.139 jmc 553: .It Fl t Cm dsa | ecdsa | ed25519 | rsa
1.66 jmc 554: Specifies the type of key to create.
555: The possible values are
1.100 naddy 556: .Dq dsa ,
1.118 naddy 557: .Dq ecdsa ,
558: .Dq ed25519 ,
1.100 naddy 559: or
1.139 jmc 560: .Dq rsa .
1.112 jmc 561: .It Fl u
562: Update a KRL.
563: When specified with
564: .Fl k ,
1.114 jmc 565: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 566: a new KRL being created.
1.84 djm 567: .It Fl V Ar validity_interval
568: Specify a validity interval when signing a certificate.
569: A validity interval may consist of a single time, indicating that the
570: certificate is valid beginning now and expiring at that time, or may consist
571: of two times separated by a colon to indicate an explicit time interval.
572: The start time may be specified as a date in YYYYMMDD format, a time
573: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
574: of a minus sign followed by a relative time in the format described in the
1.116 jmc 575: TIME FORMATS section of
1.90 jmc 576: .Xr sshd_config 5 .
1.84 djm 577: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
578: a relative time starting with a plus character.
579: .Pp
580: For example:
581: .Dq +52w1d
582: (valid from now to 52 weeks and one day from now),
583: .Dq -4w:+4w
584: (valid from four weeks ago to four weeks from now),
585: .Dq 20100101123000:20110101123000
586: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
587: .Dq -1d:20110101
588: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 589: .It Fl v
590: Verbose mode.
591: Causes
592: .Nm
593: to print debugging messages about its progress.
594: This is helpful for debugging moduli generation.
595: Multiple
596: .Fl v
597: options increase the verbosity.
598: The maximum is 3.
1.66 jmc 599: .It Fl W Ar generator
600: Specify desired generator when testing candidate moduli for DH-GEX.
601: .It Fl y
602: This option will read a private
603: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 604: .It Fl z Ar serial_number
605: Specifies a serial number to be embedded in the certificate to distinguish
606: this certificate from others from the same CA.
607: The default serial number is zero.
1.111 djm 608: .Pp
609: When generating a KRL, the
610: .Fl z
611: flag is used to specify a KRL version number.
1.2 deraadt 612: .El
1.60 djm 613: .Sh MODULI GENERATION
614: .Nm
615: may be used to generate groups for the Diffie-Hellman Group Exchange
616: (DH-GEX) protocol.
617: Generating these groups is a two-step process: first, candidate
618: primes are generated using a fast, but memory intensive process.
619: These candidate primes are then tested for suitability (a CPU-intensive
620: process).
621: .Pp
622: Generation of primes is performed using the
623: .Fl G
624: option.
625: The desired length of the primes may be specified by the
626: .Fl b
627: option.
628: For example:
629: .Pp
1.66 jmc 630: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 631: .Pp
632: By default, the search for primes begins at a random point in the
633: desired length range.
634: This may be overridden using the
635: .Fl S
636: option, which specifies a different start point (in hex).
637: .Pp
1.109 dtucker 638: Once a set of candidates have been generated, they must be screened for
1.60 djm 639: suitability.
640: This may be performed using the
641: .Fl T
642: option.
643: In this mode
644: .Nm
645: will read candidates from standard input (or a file specified using the
646: .Fl f
647: option).
648: For example:
649: .Pp
1.66 jmc 650: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 651: .Pp
652: By default, each candidate will be subjected to 100 primality tests.
653: This may be overridden using the
654: .Fl a
655: option.
656: The DH generator value will be chosen automatically for the
657: prime under consideration.
658: If a specific generator is desired, it may be requested using the
659: .Fl W
660: option.
1.66 jmc 661: Valid generator values are 2, 3, and 5.
1.60 djm 662: .Pp
663: Screened DH groups may be installed in
664: .Pa /etc/moduli .
665: It is important that this file contains moduli of a range of bit lengths and
666: that both ends of a connection share common moduli.
1.84 djm 667: .Sh CERTIFICATES
668: .Nm
669: supports signing of keys to produce certificates that may be used for
670: user or host authentication.
671: Certificates consist of a public key, some identity information, zero or
1.94 jmc 672: more principal (user or host) names and a set of options that
1.84 djm 673: are signed by a Certification Authority (CA) key.
674: Clients or servers may then trust only the CA key and verify its signature
675: on a certificate rather than trusting many user/host keys.
676: Note that OpenSSH certificates are a different, and much simpler, format to
677: the X.509 certificates used in
678: .Xr ssl 8 .
679: .Pp
680: .Nm
681: supports two types of certificates: user and host.
682: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 683: authenticate server hosts to users.
684: To generate a user certificate:
1.84 djm 685: .Pp
686: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
687: .Pp
688: The resultant certificate will be placed in
1.91 djm 689: .Pa /path/to/user_key-cert.pub .
1.84 djm 690: A host certificate requires the
691: .Fl h
692: option:
693: .Pp
694: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
695: .Pp
696: The host certificate will be output to
1.91 djm 697: .Pa /path/to/host_key-cert.pub .
1.98 djm 698: .Pp
699: It is possible to sign using a CA key stored in a PKCS#11 token by
700: providing the token library using
701: .Fl D
702: and identifying the CA key by providing its public half as an argument
703: to
704: .Fl s :
705: .Pp
1.127 naddy 706: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.98 djm 707: .Pp
708: In all cases,
1.84 djm 709: .Ar key_id
710: is a "key identifier" that is logged by the server when the certificate
711: is used for authentication.
712: .Pp
713: Certificates may be limited to be valid for a set of principal (user/host)
714: names.
715: By default, generated certificates are valid for all users or hosts.
716: To generate a certificate for a specified set of principals:
717: .Pp
718: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 719: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 720: .Pp
721: Additional limitations on the validity and use of user certificates may
1.94 jmc 722: be specified through certificate options.
1.93 djm 723: A certificate option may disable features of the SSH session, may be
1.84 djm 724: valid only when presented from particular source addresses or may
725: force the use of a specific command.
1.93 djm 726: For a list of valid certificate options, see the documentation for the
1.84 djm 727: .Fl O
728: option above.
729: .Pp
730: Finally, certificates may be defined with a validity lifetime.
731: The
732: .Fl V
733: option allows specification of certificate start and end times.
734: A certificate that is presented at a time outside this range will not be
735: considered valid.
1.110 jmc 736: By default, certificates are valid from
737: .Ux
738: Epoch to the distant future.
1.84 djm 739: .Pp
740: For certificates to be used for user or host authentication, the CA
741: public key must be trusted by
742: .Xr sshd 8
743: or
744: .Xr ssh 1 .
745: Please refer to those manual pages for details.
1.111 djm 746: .Sh KEY REVOCATION LISTS
747: .Nm
748: is able to manage OpenSSH format Key Revocation Lists (KRLs).
749: These binary files specify keys or certificates to be revoked using a
1.119 tedu 750: compact format, taking as little as one bit per certificate if they are being
1.111 djm 751: revoked by serial number.
752: .Pp
753: KRLs may be generated using the
754: .Fl k
755: flag.
1.114 jmc 756: This option reads one or more files from the command line and generates a new
1.111 djm 757: KRL.
758: The files may either contain a KRL specification (see below) or public keys,
759: listed one per line.
760: Plain public keys are revoked by listing their hash or contents in the KRL and
761: certificates revoked by serial number or key ID (if the serial is zero or
762: not available).
763: .Pp
764: Revoking keys using a KRL specification offers explicit control over the
765: types of record used to revoke keys and may be used to directly revoke
766: certificates by serial number or key ID without having the complete original
767: certificate on hand.
768: A KRL specification consists of lines containing one of the following directives
769: followed by a colon and some directive-specific information.
770: .Bl -tag -width Ds
1.115 jmc 771: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 772: Revokes a certificate with the specified serial number.
1.112 jmc 773: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 774: in decimal, hex or octal.
775: If two serial numbers are specified separated by a hyphen, then the range
776: of serial numbers including and between each is revoked.
777: The CA key must have been specified on the
778: .Nm
1.114 jmc 779: command line using the
1.111 djm 780: .Fl s
781: option.
782: .It Cm id : Ar key_id
783: Revokes a certificate with the specified key ID string.
784: The CA key must have been specified on the
785: .Nm
1.114 jmc 786: command line using the
1.111 djm 787: .Fl s
788: option.
789: .It Cm key : Ar public_key
790: Revokes the specified key.
1.112 jmc 791: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 792: .It Cm sha1 : Ar public_key
793: Revokes the specified key by its SHA1 hash.
794: .El
795: .Pp
796: KRLs may be updated using the
797: .Fl u
798: flag in addition to
799: .Fl k .
1.114 jmc 800: When this option is specified, keys listed via the command line are merged into
1.111 djm 801: the KRL, adding to those already there.
802: .Pp
803: It is also possible, given a KRL, to test whether it revokes a particular key
804: (or keys).
805: The
806: .Fl Q
1.128 jmc 807: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 808: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 809: then
810: .Nm
811: will exit with a non-zero exit status.
812: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 813: .Sh FILES
1.100 naddy 814: .Bl -tag -width Ds -compact
1.68 djm 815: .It Pa ~/.ssh/id_dsa
1.100 naddy 816: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 817: .It Pa ~/.ssh/id_ed25519
1.100 naddy 818: .It Pa ~/.ssh/id_rsa
1.141 ! naddy 819: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 820: authentication identity of the user.
1.15 deraadt 821: This file should not be readable by anyone but the user.
822: It is possible to
823: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 824: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 825: This file is not automatically accessed by
826: .Nm
827: but it is offered as the default file for the private key.
1.46 markus 828: .Xr ssh 1
1.15 deraadt 829: will read this file when a login attempt is made.
1.100 naddy 830: .Pp
1.68 djm 831: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 832: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 833: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 834: .It Pa ~/.ssh/id_rsa.pub
1.141 ! naddy 835: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 836: public key for authentication.
1.15 deraadt 837: The contents of this file should be added to
1.68 djm 838: .Pa ~/.ssh/authorized_keys
1.15 deraadt 839: on all machines
1.49 deraadt 840: where the user wishes to log in using public key authentication.
1.12 aaron 841: There is no need to keep the contents of this file secret.
1.100 naddy 842: .Pp
1.60 djm 843: .It Pa /etc/moduli
844: Contains Diffie-Hellman groups used for DH-GEX.
845: The file format is described in
846: .Xr moduli 5 .
1.19 aaron 847: .El
1.2 deraadt 848: .Sh SEE ALSO
849: .Xr ssh 1 ,
850: .Xr ssh-add 1 ,
1.8 ericj 851: .Xr ssh-agent 1 ,
1.60 djm 852: .Xr moduli 5 ,
1.30 itojun 853: .Xr sshd 8
1.37 markus 854: .Rs
1.73 markus 855: .%R RFC 4716
856: .%T "The Secure Shell (SSH) Public Key File Format"
857: .%D 2006
1.37 markus 858: .Re
1.59 jmc 859: .Sh AUTHORS
860: OpenSSH is a derivative of the original and free
861: ssh 1.2.12 release by Tatu Ylonen.
862: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
863: Theo de Raadt and Dug Song
864: removed many bugs, re-added newer features and
865: created OpenSSH.
866: Markus Friedl contributed the support for SSH
867: protocol versions 1.5 and 2.0.
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