Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.161
1.161 ! djm 1: .\" $OpenBSD: ssh-keygen.1,v 1.160 2019/05/20 06:01:59 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: .\"
1.160 jmc 38: .Dd $Mdocdate: May 20 2019 $
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
1.155 djm 53: .Op Fl m Ar format
1.2 deraadt 54: .Nm ssh-keygen
55: .Fl p
56: .Op Fl P Ar old_passphrase
57: .Op Fl N Ar new_passphrase
1.9 markus 58: .Op Fl f Ar keyfile
1.155 djm 59: .Op Fl m Ar format
1.2 deraadt 60: .Nm ssh-keygen
1.37 markus 61: .Fl i
1.95 djm 62: .Op Fl m Ar key_format
1.20 markus 63: .Op Fl f Ar input_keyfile
1.16 deraadt 64: .Nm ssh-keygen
1.37 markus 65: .Fl e
1.95 djm 66: .Op Fl m Ar key_format
1.20 markus 67: .Op Fl f Ar input_keyfile
1.16 deraadt 68: .Nm ssh-keygen
1.17 markus 69: .Fl y
1.20 markus 70: .Op Fl f Ar input_keyfile
1.17 markus 71: .Nm ssh-keygen
1.2 deraadt 72: .Fl c
73: .Op Fl P Ar passphrase
74: .Op Fl C Ar comment
1.9 markus 75: .Op Fl f Ar keyfile
76: .Nm ssh-keygen
77: .Fl l
1.125 naddy 78: .Op Fl v
1.124 djm 79: .Op Fl E Ar fingerprint_hash
1.35 markus 80: .Op Fl f Ar input_keyfile
81: .Nm ssh-keygen
82: .Fl B
1.20 markus 83: .Op Fl f Ar input_keyfile
1.48 jakob 84: .Nm ssh-keygen
1.82 jmc 85: .Fl D Ar pkcs11
1.48 jakob 86: .Nm ssh-keygen
1.64 djm 87: .Fl F Ar hostname
88: .Op Fl f Ar known_hosts_file
1.79 sthen 89: .Op Fl l
1.64 djm 90: .Nm ssh-keygen
91: .Fl H
92: .Op Fl f Ar known_hosts_file
93: .Nm ssh-keygen
94: .Fl R Ar hostname
95: .Op Fl f Ar known_hosts_file
1.57 jakob 96: .Nm ssh-keygen
97: .Fl r Ar hostname
98: .Op Fl f Ar input_keyfile
99: .Op Fl g
1.60 djm 100: .Nm ssh-keygen
101: .Fl G Ar output_file
1.61 djm 102: .Op Fl v
1.60 djm 103: .Op Fl b Ar bits
104: .Op Fl M Ar memory
105: .Op Fl S Ar start_point
106: .Nm ssh-keygen
107: .Fl T Ar output_file
108: .Fl f Ar input_file
1.61 djm 109: .Op Fl v
1.117 djm 110: .Op Fl a Ar rounds
1.109 dtucker 111: .Op Fl J Ar num_lines
112: .Op Fl j Ar start_line
1.108 dtucker 113: .Op Fl K Ar checkpt
1.60 djm 114: .Op Fl W Ar generator
1.84 djm 115: .Nm ssh-keygen
116: .Fl s Ar ca_key
117: .Fl I Ar certificate_identity
118: .Op Fl h
1.142 djm 119: .Op Fl U
120: .Op Fl D Ar pkcs11_provider
1.84 djm 121: .Op Fl n Ar principals
1.93 djm 122: .Op Fl O Ar option
1.84 djm 123: .Op Fl V Ar validity_interval
1.93 djm 124: .Op Fl z Ar serial_number
1.84 djm 125: .Ar
1.86 djm 126: .Nm ssh-keygen
127: .Fl L
128: .Op Fl f Ar input_keyfile
1.102 stevesk 129: .Nm ssh-keygen
130: .Fl A
1.143 djm 131: .Op Fl f Ar prefix_path
1.111 djm 132: .Nm ssh-keygen
133: .Fl k
134: .Fl f Ar krl_file
135: .Op Fl u
1.112 jmc 136: .Op Fl s Ar ca_public
137: .Op Fl z Ar version_number
1.111 djm 138: .Ar
139: .Nm ssh-keygen
140: .Fl Q
141: .Fl f Ar krl_file
142: .Ar
1.85 jmc 143: .Ek
1.13 aaron 144: .Sh DESCRIPTION
1.2 deraadt 145: .Nm
1.37 markus 146: generates, manages and converts authentication keys for
1.2 deraadt 147: .Xr ssh 1 .
1.15 deraadt 148: .Nm
1.140 jmc 149: can create keys for use by SSH protocol version 2.
1.130 jmc 150: .Pp
1.58 jmc 151: The type of key to be generated is specified with the
1.25 markus 152: .Fl t
1.52 djm 153: option.
1.70 djm 154: If invoked without any arguments,
155: .Nm
1.141 naddy 156: will generate an RSA key.
1.15 deraadt 157: .Pp
1.60 djm 158: .Nm
159: is also used to generate groups for use in Diffie-Hellman group
160: exchange (DH-GEX).
161: See the
162: .Sx MODULI GENERATION
163: section for details.
164: .Pp
1.111 djm 165: Finally,
166: .Nm
167: can be used to generate and update Key Revocation Lists, and to test whether
1.112 jmc 168: given keys have been revoked by one.
169: See the
1.111 djm 170: .Sx KEY REVOCATION LISTS
171: section for details.
172: .Pp
1.2 deraadt 173: Normally each user wishing to use SSH
1.99 djm 174: with public key authentication runs this once to create the authentication
1.1 deraadt 175: key in
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
1.153 djm 210: .Nm
211: will by default write keys in an OpenSSH-specific format.
212: This format is preferred as it offers better protection for
213: keys at rest as well as allowing storage of key comments within
214: the private key file itself.
215: The key comment may be useful to help identify the key.
1.12 aaron 216: The comment is initialized to
1.2 deraadt 217: .Dq user@host
218: when the key is created, but can be changed using the
219: .Fl c
1.1 deraadt 220: option.
1.153 djm 221: .Pp
222: It is still possible for
223: .Nm
224: to write the previously-used PEM format private keys using the
225: .Fl m
226: flag.
227: This may be used when generating new keys, and existing new-format
228: keys may be converted using this option in conjunction with the
229: .Fl p
230: (change passphrase) flag.
1.2 deraadt 231: .Pp
1.15 deraadt 232: After a key is generated, instructions below detail where the keys
233: should be placed to be activated.
234: .Pp
1.2 deraadt 235: The options are as follows:
236: .Bl -tag -width Ds
1.102 stevesk 237: .It Fl A
1.139 jmc 238: For each of the key types (rsa, dsa, ecdsa and ed25519)
1.118 naddy 239: for which host keys
1.102 stevesk 240: do not exist, generate the host keys with the default key file path,
241: an empty passphrase, default bits for the key type, and default comment.
1.144 jmc 242: If
1.143 djm 243: .Fl f
1.144 jmc 244: has also been specified, its argument is used as a prefix to the
1.143 djm 245: default path for the resulting host key files.
1.104 jmc 246: This is used by
1.102 stevesk 247: .Pa /etc/rc
248: to generate new host keys.
1.117 djm 249: .It Fl a Ar rounds
1.148 djm 250: When saving a private key this option specifies the number of KDF
251: (key derivation function) rounds used.
1.117 djm 252: Higher numbers result in slower passphrase verification and increased
253: resistance to brute-force password cracking (should the keys be stolen).
254: .Pp
1.140 jmc 255: When screening DH-GEX candidates (using the
1.60 djm 256: .Fl T
1.117 djm 257: command).
258: This option specifies the number of primality tests to perform.
1.66 jmc 259: .It Fl B
260: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 261: .It Fl b Ar bits
1.12 aaron 262: Specifies the number of bits in the key to create.
1.158 dtucker 263: For RSA keys, the minimum size is 1024 bits and the default is 3072 bits.
264: Generally, 3072 bits is considered sufficient.
1.72 dtucker 265: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 266: For ECDSA keys, the
267: .Fl b
1.107 deraadt 268: flag determines the key length by selecting from one of three elliptic
1.106 djm 269: curve sizes: 256, 384 or 521 bits.
270: Attempting to use bit lengths other than these three values for ECDSA keys
271: will fail.
1.123 sobrado 272: Ed25519 keys have a fixed length and the
1.118 naddy 273: .Fl b
274: flag will be ignored.
1.66 jmc 275: .It Fl C Ar comment
276: Provides a new comment.
1.2 deraadt 277: .It Fl c
1.1 deraadt 278: Requests changing the comment in the private and public key files.
279: The program will prompt for the file containing the private keys, for
1.41 stevesk 280: the passphrase if the key has one, and for the new comment.
1.81 markus 281: .It Fl D Ar pkcs11
1.157 naddy 282: Download the public keys provided by the PKCS#11 shared library
1.83 markus 283: .Ar pkcs11 .
1.98 djm 284: When used in combination with
285: .Fl s ,
286: this option indicates that a CA key resides in a PKCS#11 token (see the
287: .Sx CERTIFICATES
288: section for details).
1.124 djm 289: .It Fl E Ar fingerprint_hash
290: Specifies the hash algorithm used when displaying key fingerprints.
291: Valid options are:
292: .Dq md5
293: and
294: .Dq sha256 .
295: The default is
296: .Dq sha256 .
1.37 markus 297: .It Fl e
1.40 markus 298: This option will read a private or public OpenSSH key file and
1.154 djm 299: print to stdout a public key in one of the formats specified by the
1.95 djm 300: .Fl m
301: option.
302: The default export format is
303: .Dq RFC4716 .
1.96 jmc 304: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 305: several commercial SSH implementations.
1.151 djm 306: .It Fl F Ar hostname | [hostname]:port
1.66 jmc 307: Search for the specified
308: .Ar hostname
1.151 djm 309: (with optional port number)
1.66 jmc 310: in a
311: .Pa known_hosts
312: file, listing any occurrences found.
313: This option is useful to find hashed host names or addresses and may also be
314: used in conjunction with the
315: .Fl H
316: option to print found keys in a hashed format.
317: .It Fl f Ar filename
318: Specifies the filename of the key file.
319: .It Fl G Ar output_file
320: Generate candidate primes for DH-GEX.
321: These primes must be screened for
322: safety (using the
323: .Fl T
324: option) before use.
1.57 jakob 325: .It Fl g
1.62 jakob 326: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 327: .Fl r
1.62 jakob 328: command.
1.66 jmc 329: .It Fl H
330: Hash a
331: .Pa known_hosts
1.67 dtucker 332: file.
333: This replaces all hostnames and addresses with hashed representations
334: within the specified file; the original content is moved to a file with
335: a .old suffix.
1.66 jmc 336: These hashes may be used normally by
337: .Nm ssh
338: and
339: .Nm sshd ,
340: but they do not reveal identifying information should the file's contents
341: be disclosed.
342: This option will not modify existing hashed hostnames and is therefore safe
343: to use on files that mix hashed and non-hashed names.
1.84 djm 344: .It Fl h
345: When signing a key, create a host certificate instead of a user
346: certificate.
347: Please see the
348: .Sx CERTIFICATES
349: section for details.
1.85 jmc 350: .It Fl I Ar certificate_identity
1.84 djm 351: Specify the key identity when signing a public key.
352: Please see the
353: .Sx CERTIFICATES
354: section for details.
1.37 markus 355: .It Fl i
356: This option will read an unencrypted private (or public) key file
1.95 djm 357: in the format specified by the
358: .Fl m
359: option and print an OpenSSH compatible private
1.37 markus 360: (or public) key to stdout.
1.122 jmc 361: This option allows importing keys from other software, including several
362: commercial SSH implementations.
363: The default import format is
364: .Dq RFC4716 .
1.109 dtucker 365: .It Fl J Ar num_lines
366: Exit after screening the specified number of lines
367: while performing DH candidate screening using the
368: .Fl T
369: option.
370: .It Fl j Ar start_line
371: Start screening at the specified line number
372: while performing DH candidate screening using the
373: .Fl T
374: option.
1.108 dtucker 375: .It Fl K Ar checkpt
376: Write the last line processed to the file
377: .Ar checkpt
378: while performing DH candidate screening using the
379: .Fl T
380: option.
381: This will be used to skip lines in the input file that have already been
382: processed if the job is restarted.
1.111 djm 383: .It Fl k
384: Generate a KRL file.
385: In this mode,
386: .Nm
387: will generate a KRL file at the location specified via the
388: .Fl f
1.114 jmc 389: flag that revokes every key or certificate presented on the command line.
1.111 djm 390: Keys/certificates to be revoked may be specified by public key file or
391: using the format described in the
392: .Sx KEY REVOCATION LISTS
393: section.
1.86 djm 394: .It Fl L
1.129 djm 395: Prints the contents of one or more certificates.
1.9 markus 396: .It Fl l
1.77 grunk 397: Show fingerprint of specified public key file.
1.50 markus 398: For RSA and DSA keys
399: .Nm
1.78 jmc 400: tries to find the matching public key file and prints its fingerprint.
401: If combined with
402: .Fl v ,
1.132 jmc 403: a visual ASCII art representation of the key is supplied with the
1.131 djm 404: fingerprint.
1.96 jmc 405: .It Fl M Ar memory
406: Specify the amount of memory to use (in megabytes) when generating
407: candidate moduli for DH-GEX.
1.95 djm 408: .It Fl m Ar key_format
1.155 djm 409: Specify a key format for key generation, the
1.95 djm 410: .Fl i
1.155 djm 411: (import),
1.95 djm 412: .Fl e
1.155 djm 413: (export) conversion options, and the
414: .Fl p
415: change passphrase operation.
416: The latter may be used to convert between OpenSSH private key and PEM
417: private key formats.
1.95 djm 418: The supported key formats are:
419: .Dq RFC4716
1.96 jmc 420: (RFC 4716/SSH2 public or private key),
1.95 djm 421: .Dq PKCS8
1.161 ! djm 422: (PKCS8 public or private key)
1.95 djm 423: or
424: .Dq PEM
425: (PEM public key).
1.161 ! djm 426: By default OpenSSH will write newly-generated private keys in its own
! 427: format, but when converting public keys for export the default format is
1.95 djm 428: .Dq RFC4716 .
1.148 djm 429: Setting a format of
430: .Dq PEM
431: when generating or updating a supported private key type will cause the
432: key to be stored in the legacy PEM private key format.
1.66 jmc 433: .It Fl N Ar new_passphrase
434: Provides the new passphrase.
1.84 djm 435: .It Fl n Ar principals
436: Specify one or more principals (user or host names) to be included in
437: a certificate when signing a key.
438: Multiple principals may be specified, separated by commas.
439: Please see the
440: .Sx CERTIFICATES
441: section for details.
1.93 djm 442: .It Fl O Ar option
443: Specify a certificate option when signing a key.
1.84 djm 444: This option may be specified multiple times.
1.137 jmc 445: See also the
1.84 djm 446: .Sx CERTIFICATES
1.137 jmc 447: section for further details.
1.146 djm 448: .Pp
449: At present, no standard options are valid for host keys.
1.93 djm 450: The options that are valid for user certificates are:
1.137 jmc 451: .Pp
452: .Bl -tag -width Ds -compact
1.89 jmc 453: .It Ic clear
454: Clear all enabled permissions.
455: This is useful for clearing the default set of permissions so permissions may
456: be added individually.
1.137 jmc 457: .Pp
458: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
459: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
460: Includes an arbitrary certificate critical option or extension.
461: The specified
462: .Ar name
463: should include a domain suffix, e.g.\&
464: .Dq name@example.com .
465: If
466: .Ar contents
467: is specified then it is included as the contents of the extension/option
468: encoded as a string, otherwise the extension/option is created with no
469: contents (usually indicating a flag).
470: Extensions may be ignored by a client or server that does not recognise them,
471: whereas unknown critical options will cause the certificate to be refused.
1.138 jmc 472: .Pp
1.89 jmc 473: .It Ic force-command Ns = Ns Ar command
474: Forces the execution of
475: .Ar command
476: instead of any shell or command specified by the user when
477: the certificate is used for authentication.
1.137 jmc 478: .Pp
1.84 djm 479: .It Ic no-agent-forwarding
480: Disable
481: .Xr ssh-agent 1
1.85 jmc 482: forwarding (permitted by default).
1.137 jmc 483: .Pp
1.84 djm 484: .It Ic no-port-forwarding
1.85 jmc 485: Disable port forwarding (permitted by default).
1.137 jmc 486: .Pp
1.84 djm 487: .It Ic no-pty
1.85 jmc 488: Disable PTY allocation (permitted by default).
1.137 jmc 489: .Pp
1.84 djm 490: .It Ic no-user-rc
491: Disable execution of
492: .Pa ~/.ssh/rc
493: by
1.85 jmc 494: .Xr sshd 8
495: (permitted by default).
1.137 jmc 496: .Pp
1.89 jmc 497: .It Ic no-x11-forwarding
498: Disable X11 forwarding (permitted by default).
1.137 jmc 499: .Pp
1.88 djm 500: .It Ic permit-agent-forwarding
501: Allows
502: .Xr ssh-agent 1
503: forwarding.
1.137 jmc 504: .Pp
1.84 djm 505: .It Ic permit-port-forwarding
506: Allows port forwarding.
1.137 jmc 507: .Pp
1.84 djm 508: .It Ic permit-pty
509: Allows PTY allocation.
1.137 jmc 510: .Pp
1.84 djm 511: .It Ic permit-user-rc
512: Allows execution of
513: .Pa ~/.ssh/rc
514: by
515: .Xr sshd 8 .
1.137 jmc 516: .Pp
1.146 djm 517: .It Ic permit-X11-forwarding
1.89 jmc 518: Allows X11 forwarding.
1.137 jmc 519: .Pp
1.89 jmc 520: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 521: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 522: The
523: .Ar address_list
524: is a comma-separated list of one or more address/netmask pairs in CIDR
525: format.
526: .El
1.66 jmc 527: .It Fl P Ar passphrase
528: Provides the (old) passphrase.
1.2 deraadt 529: .It Fl p
1.1 deraadt 530: Requests changing the passphrase of a private key file instead of
1.12 aaron 531: creating a new private key.
532: The program will prompt for the file
1.1 deraadt 533: containing the private key, for the old passphrase, and twice for the
534: new passphrase.
1.113 jmc 535: .It Fl Q
536: Test whether keys have been revoked in a KRL.
1.5 aaron 537: .It Fl q
538: Silence
539: .Nm ssh-keygen .
1.152 djm 540: .It Fl R Ar hostname | [hostname]:port
1.151 djm 541: Removes all keys belonging to the specified
1.64 djm 542: .Ar hostname
1.151 djm 543: (with optional port number)
1.65 jmc 544: from a
1.64 djm 545: .Pa known_hosts
546: file.
1.65 jmc 547: This option is useful to delete hashed hosts (see the
1.64 djm 548: .Fl H
549: option above).
1.66 jmc 550: .It Fl r Ar hostname
551: Print the SSHFP fingerprint resource record named
552: .Ar hostname
553: for the specified public key file.
1.60 djm 554: .It Fl S Ar start
555: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 556: .It Fl s Ar ca_key
557: Certify (sign) a public key using the specified CA key.
558: Please see the
559: .Sx CERTIFICATES
560: section for details.
1.111 djm 561: .Pp
562: When generating a KRL,
563: .Fl s
1.112 jmc 564: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 565: by key ID or serial number.
566: See the
567: .Sx KEY REVOCATION LISTS
568: section for details.
1.60 djm 569: .It Fl T Ar output_file
570: Test DH group exchange candidate primes (generated using the
571: .Fl G
572: option) for safety.
1.139 jmc 573: .It Fl t Cm dsa | ecdsa | ed25519 | rsa
1.66 jmc 574: Specifies the type of key to create.
575: The possible values are
1.100 naddy 576: .Dq dsa ,
1.118 naddy 577: .Dq ecdsa ,
578: .Dq ed25519 ,
1.100 naddy 579: or
1.139 jmc 580: .Dq rsa .
1.159 djm 581: .Pp
582: This flag may also be used to specify the desired signature type when
1.160 jmc 583: signing certificates using an RSA CA key.
1.159 djm 584: The available RSA signature variants are
585: .Dq ssh-rsa
586: (SHA1 signatures, not recommended),
1.160 jmc 587: .Dq rsa-sha2-256 ,
588: and
1.159 djm 589: .Dq rsa-sha2-512
590: (the default).
1.142 djm 591: .It Fl U
592: When used in combination with
593: .Fl s ,
594: this option indicates that a CA key resides in a
595: .Xr ssh-agent 1 .
596: See the
597: .Sx CERTIFICATES
598: section for more information.
1.112 jmc 599: .It Fl u
600: Update a KRL.
601: When specified with
602: .Fl k ,
1.114 jmc 603: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 604: a new KRL being created.
1.84 djm 605: .It Fl V Ar validity_interval
606: Specify a validity interval when signing a certificate.
607: A validity interval may consist of a single time, indicating that the
608: certificate is valid beginning now and expiring at that time, or may consist
609: of two times separated by a colon to indicate an explicit time interval.
1.145 djm 610: .Pp
611: The start time may be specified as the string
612: .Dq always
613: to indicate the certificate has no specified start time,
1.147 djm 614: a date in YYYYMMDD format, a time in YYYYMMDDHHMM[SS] format,
1.145 djm 615: a relative time (to the current time) consisting of a minus sign followed by
616: an interval in the format described in the
1.116 jmc 617: TIME FORMATS section of
1.90 jmc 618: .Xr sshd_config 5 .
1.145 djm 619: .Pp
1.147 djm 620: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMM[SS] time,
1.145 djm 621: a relative time starting with a plus character or the string
622: .Dq forever
623: to indicate that the certificate has no expirty date.
1.84 djm 624: .Pp
625: For example:
626: .Dq +52w1d
627: (valid from now to 52 weeks and one day from now),
628: .Dq -4w:+4w
629: (valid from four weeks ago to four weeks from now),
630: .Dq 20100101123000:20110101123000
631: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
632: .Dq -1d:20110101
633: (valid from yesterday to midnight, January 1st, 2011).
1.145 djm 634: .Dq -1m:forever
635: (valid from one minute ago and never expiring).
1.61 djm 636: .It Fl v
637: Verbose mode.
638: Causes
639: .Nm
640: to print debugging messages about its progress.
641: This is helpful for debugging moduli generation.
642: Multiple
643: .Fl v
644: options increase the verbosity.
645: The maximum is 3.
1.66 jmc 646: .It Fl W Ar generator
647: Specify desired generator when testing candidate moduli for DH-GEX.
648: .It Fl y
649: This option will read a private
650: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 651: .It Fl z Ar serial_number
652: Specifies a serial number to be embedded in the certificate to distinguish
653: this certificate from others from the same CA.
1.156 djm 654: If the
655: .Ar serial_number
656: is prefixed with a
657: .Sq +
658: character, then the serial number will be incremented for each certificate
659: signed on a single command-line.
1.93 djm 660: The default serial number is zero.
1.111 djm 661: .Pp
662: When generating a KRL, the
663: .Fl z
664: flag is used to specify a KRL version number.
1.2 deraadt 665: .El
1.60 djm 666: .Sh MODULI GENERATION
667: .Nm
668: may be used to generate groups for the Diffie-Hellman Group Exchange
669: (DH-GEX) protocol.
670: Generating these groups is a two-step process: first, candidate
671: primes are generated using a fast, but memory intensive process.
672: These candidate primes are then tested for suitability (a CPU-intensive
673: process).
674: .Pp
675: Generation of primes is performed using the
676: .Fl G
677: option.
678: The desired length of the primes may be specified by the
679: .Fl b
680: option.
681: For example:
682: .Pp
1.66 jmc 683: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 684: .Pp
685: By default, the search for primes begins at a random point in the
686: desired length range.
687: This may be overridden using the
688: .Fl S
689: option, which specifies a different start point (in hex).
690: .Pp
1.109 dtucker 691: Once a set of candidates have been generated, they must be screened for
1.60 djm 692: suitability.
693: This may be performed using the
694: .Fl T
695: option.
696: In this mode
697: .Nm
698: will read candidates from standard input (or a file specified using the
699: .Fl f
700: option).
701: For example:
702: .Pp
1.66 jmc 703: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 704: .Pp
705: By default, each candidate will be subjected to 100 primality tests.
706: This may be overridden using the
707: .Fl a
708: option.
709: The DH generator value will be chosen automatically for the
710: prime under consideration.
711: If a specific generator is desired, it may be requested using the
712: .Fl W
713: option.
1.66 jmc 714: Valid generator values are 2, 3, and 5.
1.60 djm 715: .Pp
716: Screened DH groups may be installed in
717: .Pa /etc/moduli .
718: It is important that this file contains moduli of a range of bit lengths and
719: that both ends of a connection share common moduli.
1.84 djm 720: .Sh CERTIFICATES
721: .Nm
722: supports signing of keys to produce certificates that may be used for
723: user or host authentication.
724: Certificates consist of a public key, some identity information, zero or
1.94 jmc 725: more principal (user or host) names and a set of options that
1.84 djm 726: are signed by a Certification Authority (CA) key.
727: Clients or servers may then trust only the CA key and verify its signature
728: on a certificate rather than trusting many user/host keys.
729: Note that OpenSSH certificates are a different, and much simpler, format to
730: the X.509 certificates used in
731: .Xr ssl 8 .
732: .Pp
733: .Nm
734: supports two types of certificates: user and host.
735: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 736: authenticate server hosts to users.
737: To generate a user certificate:
1.84 djm 738: .Pp
739: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
740: .Pp
741: The resultant certificate will be placed in
1.91 djm 742: .Pa /path/to/user_key-cert.pub .
1.84 djm 743: A host certificate requires the
744: .Fl h
745: option:
746: .Pp
747: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
748: .Pp
749: The host certificate will be output to
1.91 djm 750: .Pa /path/to/host_key-cert.pub .
1.98 djm 751: .Pp
752: It is possible to sign using a CA key stored in a PKCS#11 token by
753: providing the token library using
754: .Fl D
755: and identifying the CA key by providing its public half as an argument
756: to
757: .Fl s :
758: .Pp
1.127 naddy 759: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.142 djm 760: .Pp
761: Similarly, it is possible for the CA key to be hosted in a
762: .Xr ssh-agent 1 .
763: This is indicated by the
764: .Fl U
765: flag and, again, the CA key must be identified by its public half.
766: .Pp
767: .Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
1.98 djm 768: .Pp
769: In all cases,
1.84 djm 770: .Ar key_id
771: is a "key identifier" that is logged by the server when the certificate
772: is used for authentication.
773: .Pp
774: Certificates may be limited to be valid for a set of principal (user/host)
775: names.
776: By default, generated certificates are valid for all users or hosts.
777: To generate a certificate for a specified set of principals:
778: .Pp
779: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 780: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 781: .Pp
782: Additional limitations on the validity and use of user certificates may
1.94 jmc 783: be specified through certificate options.
1.93 djm 784: A certificate option may disable features of the SSH session, may be
1.84 djm 785: valid only when presented from particular source addresses or may
786: force the use of a specific command.
1.93 djm 787: For a list of valid certificate options, see the documentation for the
1.84 djm 788: .Fl O
789: option above.
790: .Pp
791: Finally, certificates may be defined with a validity lifetime.
792: The
793: .Fl V
794: option allows specification of certificate start and end times.
795: A certificate that is presented at a time outside this range will not be
796: considered valid.
1.110 jmc 797: By default, certificates are valid from
798: .Ux
799: Epoch to the distant future.
1.84 djm 800: .Pp
801: For certificates to be used for user or host authentication, the CA
802: public key must be trusted by
803: .Xr sshd 8
804: or
805: .Xr ssh 1 .
806: Please refer to those manual pages for details.
1.111 djm 807: .Sh KEY REVOCATION LISTS
808: .Nm
809: is able to manage OpenSSH format Key Revocation Lists (KRLs).
810: These binary files specify keys or certificates to be revoked using a
1.119 tedu 811: compact format, taking as little as one bit per certificate if they are being
1.111 djm 812: revoked by serial number.
813: .Pp
814: KRLs may be generated using the
815: .Fl k
816: flag.
1.114 jmc 817: This option reads one or more files from the command line and generates a new
1.111 djm 818: KRL.
819: The files may either contain a KRL specification (see below) or public keys,
820: listed one per line.
821: Plain public keys are revoked by listing their hash or contents in the KRL and
822: certificates revoked by serial number or key ID (if the serial is zero or
823: not available).
824: .Pp
825: Revoking keys using a KRL specification offers explicit control over the
826: types of record used to revoke keys and may be used to directly revoke
827: certificates by serial number or key ID without having the complete original
828: certificate on hand.
829: A KRL specification consists of lines containing one of the following directives
830: followed by a colon and some directive-specific information.
831: .Bl -tag -width Ds
1.115 jmc 832: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 833: Revokes a certificate with the specified serial number.
1.112 jmc 834: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 835: in decimal, hex or octal.
836: If two serial numbers are specified separated by a hyphen, then the range
837: of serial numbers including and between each is revoked.
838: The CA key must have been specified on the
839: .Nm
1.114 jmc 840: command line using the
1.111 djm 841: .Fl s
842: option.
843: .It Cm id : Ar key_id
844: Revokes a certificate with the specified key ID string.
845: The CA key must have been specified on the
846: .Nm
1.114 jmc 847: command line using the
1.111 djm 848: .Fl s
849: option.
850: .It Cm key : Ar public_key
851: Revokes the specified key.
1.112 jmc 852: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 853: .It Cm sha1 : Ar public_key
1.149 djm 854: Revokes the specified key by including its SHA1 hash in the KRL.
855: .It Cm sha256 : Ar public_key
856: Revokes the specified key by including its SHA256 hash in the KRL.
857: KRLs that revoke keys by SHA256 hash are not supported by OpenSSH versions
858: prior to 7.9.
859: .It Cm hash : Ar fingerprint
1.150 djm 860: Revokes a key using a fingerprint hash, as obtained from a
1.149 djm 861: .Xr sshd 8
862: authentication log message or the
863: .Nm
864: .Fl l
865: flag.
866: Only SHA256 fingerprints are supported here and resultant KRLs are
867: not supported by OpenSSH versions prior to 7.9.
1.111 djm 868: .El
869: .Pp
870: KRLs may be updated using the
871: .Fl u
872: flag in addition to
873: .Fl k .
1.114 jmc 874: When this option is specified, keys listed via the command line are merged into
1.111 djm 875: the KRL, adding to those already there.
876: .Pp
877: It is also possible, given a KRL, to test whether it revokes a particular key
878: (or keys).
879: The
880: .Fl Q
1.128 jmc 881: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 882: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 883: then
884: .Nm
885: will exit with a non-zero exit status.
886: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 887: .Sh FILES
1.100 naddy 888: .Bl -tag -width Ds -compact
1.68 djm 889: .It Pa ~/.ssh/id_dsa
1.100 naddy 890: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 891: .It Pa ~/.ssh/id_ed25519
1.100 naddy 892: .It Pa ~/.ssh/id_rsa
1.141 naddy 893: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 894: authentication identity of the user.
1.15 deraadt 895: This file should not be readable by anyone but the user.
896: It is possible to
897: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 898: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 899: This file is not automatically accessed by
900: .Nm
901: but it is offered as the default file for the private key.
1.46 markus 902: .Xr ssh 1
1.15 deraadt 903: will read this file when a login attempt is made.
1.100 naddy 904: .Pp
1.68 djm 905: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 906: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 907: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 908: .It Pa ~/.ssh/id_rsa.pub
1.141 naddy 909: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 910: public key for authentication.
1.15 deraadt 911: The contents of this file should be added to
1.68 djm 912: .Pa ~/.ssh/authorized_keys
1.15 deraadt 913: on all machines
1.49 deraadt 914: where the user wishes to log in using public key authentication.
1.12 aaron 915: There is no need to keep the contents of this file secret.
1.100 naddy 916: .Pp
1.60 djm 917: .It Pa /etc/moduli
918: Contains Diffie-Hellman groups used for DH-GEX.
919: The file format is described in
920: .Xr moduli 5 .
1.19 aaron 921: .El
1.2 deraadt 922: .Sh SEE ALSO
923: .Xr ssh 1 ,
924: .Xr ssh-add 1 ,
1.8 ericj 925: .Xr ssh-agent 1 ,
1.60 djm 926: .Xr moduli 5 ,
1.30 itojun 927: .Xr sshd 8
1.37 markus 928: .Rs
1.73 markus 929: .%R RFC 4716
930: .%T "The Secure Shell (SSH) Public Key File Format"
931: .%D 2006
1.37 markus 932: .Re
1.59 jmc 933: .Sh AUTHORS
934: OpenSSH is a derivative of the original and free
935: ssh 1.2.12 release by Tatu Ylonen.
936: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
937: Theo de Raadt and Dug Song
938: removed many bugs, re-added newer features and
939: created OpenSSH.
940: Markus Friedl contributed the support for SSH
941: protocol versions 1.5 and 2.0.
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