Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.227
1.227 ! djm 1: .\" $OpenBSD: ssh-keygen.1,v 1.226 2022/09/10 08:50:53 jsg 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: .\"
1.227 ! djm 38: .Dd $Mdocdate: September 10 2022 $
1.2 deraadt 39: .Dt SSH-KEYGEN 1
40: .Os
41: .Sh NAME
42: .Nm ssh-keygen
1.179 jmc 43: .Nd OpenSSH authentication key utility
1.2 deraadt 44: .Sh SYNOPSIS
45: .Nm ssh-keygen
1.25 markus 46: .Op Fl q
1.205 solene 47: .Op Fl a Ar rounds
1.2 deraadt 48: .Op Fl b Ar bits
49: .Op Fl C Ar comment
1.20 markus 50: .Op Fl f Ar output_keyfile
1.155 djm 51: .Op Fl m Ar format
1.171 jmc 52: .Op Fl N Ar new_passphrase
1.191 naddy 53: .Op Fl O Ar option
1.205 solene 54: .Op Fl t Cm dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa
1.173 naddy 55: .Op Fl w Ar provider
1.212 dtucker 56: .Op Fl Z Ar cipher
1.2 deraadt 57: .Nm ssh-keygen
58: .Fl p
1.205 solene 59: .Op Fl a Ar rounds
1.9 markus 60: .Op Fl f Ar keyfile
1.155 djm 61: .Op Fl m Ar format
1.171 jmc 62: .Op Fl N Ar new_passphrase
63: .Op Fl P Ar old_passphrase
1.212 dtucker 64: .Op Fl Z Ar cipher
1.2 deraadt 65: .Nm ssh-keygen
1.37 markus 66: .Fl i
1.171 jmc 67: .Op Fl f Ar input_keyfile
1.95 djm 68: .Op Fl m Ar key_format
1.16 deraadt 69: .Nm ssh-keygen
1.37 markus 70: .Fl e
1.171 jmc 71: .Op Fl f Ar input_keyfile
1.95 djm 72: .Op Fl m Ar key_format
1.16 deraadt 73: .Nm ssh-keygen
1.17 markus 74: .Fl y
1.20 markus 75: .Op Fl f Ar input_keyfile
1.17 markus 76: .Nm ssh-keygen
1.2 deraadt 77: .Fl c
1.205 solene 78: .Op Fl a Ar rounds
1.2 deraadt 79: .Op Fl C Ar comment
1.9 markus 80: .Op Fl f Ar keyfile
1.171 jmc 81: .Op Fl P Ar passphrase
1.9 markus 82: .Nm ssh-keygen
83: .Fl l
1.125 naddy 84: .Op Fl v
1.124 djm 85: .Op Fl E Ar fingerprint_hash
1.35 markus 86: .Op Fl f Ar input_keyfile
87: .Nm ssh-keygen
88: .Fl B
1.20 markus 89: .Op Fl f Ar input_keyfile
1.48 jakob 90: .Nm ssh-keygen
1.82 jmc 91: .Fl D Ar pkcs11
1.48 jakob 92: .Nm ssh-keygen
1.64 djm 93: .Fl F Ar hostname
1.170 jmc 94: .Op Fl lv
1.64 djm 95: .Op Fl f Ar known_hosts_file
96: .Nm ssh-keygen
97: .Fl H
98: .Op Fl f Ar known_hosts_file
99: .Nm ssh-keygen
1.187 djm 100: .Fl K
1.205 solene 101: .Op Fl a Ar rounds
1.187 djm 102: .Op Fl w Ar provider
103: .Nm ssh-keygen
1.64 djm 104: .Fl R Ar hostname
105: .Op Fl f Ar known_hosts_file
1.57 jakob 106: .Nm ssh-keygen
107: .Fl r Ar hostname
1.170 jmc 108: .Op Fl g
1.57 jakob 109: .Op Fl f Ar input_keyfile
1.60 djm 110: .Nm ssh-keygen
1.184 djm 111: .Fl M Cm generate
112: .Op Fl O Ar option
1.191 naddy 113: .Ar output_file
1.60 djm 114: .Nm ssh-keygen
1.184 djm 115: .Fl M Cm screen
1.191 naddy 116: .Op Fl f Ar input_file
1.184 djm 117: .Op Fl O Ar option
1.191 naddy 118: .Ar output_file
1.84 djm 119: .Nm ssh-keygen
1.171 jmc 120: .Fl I Ar certificate_identity
1.84 djm 121: .Fl s Ar ca_key
1.170 jmc 122: .Op Fl hU
1.142 djm 123: .Op Fl D Ar pkcs11_provider
1.84 djm 124: .Op Fl n Ar principals
1.93 djm 125: .Op Fl O Ar option
1.84 djm 126: .Op Fl V Ar validity_interval
1.93 djm 127: .Op Fl z Ar serial_number
1.84 djm 128: .Ar
1.86 djm 129: .Nm ssh-keygen
130: .Fl L
131: .Op Fl f Ar input_keyfile
1.102 stevesk 132: .Nm ssh-keygen
133: .Fl A
1.205 solene 134: .Op Fl a Ar rounds
1.143 djm 135: .Op Fl f Ar prefix_path
1.111 djm 136: .Nm ssh-keygen
137: .Fl k
138: .Fl f Ar krl_file
139: .Op Fl u
1.112 jmc 140: .Op Fl s Ar ca_public
141: .Op Fl z Ar version_number
1.111 djm 142: .Ar
143: .Nm ssh-keygen
144: .Fl Q
1.203 djm 145: .Op Fl l
1.111 djm 146: .Fl f Ar krl_file
147: .Ar
1.163 djm 148: .Nm ssh-keygen
1.196 djm 149: .Fl Y Cm find-principals
1.214 djm 150: .Op Fl O Ar option
1.194 djm 151: .Fl s Ar signature_file
152: .Fl f Ar allowed_signers_file
153: .Nm ssh-keygen
1.217 djm 154: .Fl Y Cm match-principals
155: .Fl I Ar signer_identity
156: .Fl f Ar allowed_signers_file
157: .Nm ssh-keygen
1.171 jmc 158: .Fl Y Cm check-novalidate
1.214 djm 159: .Op Fl O Ar option
1.171 jmc 160: .Fl n Ar namespace
161: .Fl s Ar signature_file
162: .Nm ssh-keygen
1.163 djm 163: .Fl Y Cm sign
1.219 djm 164: .Op Fl O Ar option
1.163 djm 165: .Fl f Ar key_file
166: .Fl n Ar namespace
167: .Ar
168: .Nm ssh-keygen
169: .Fl Y Cm verify
1.214 djm 170: .Op Fl O Ar option
1.171 jmc 171: .Fl f Ar allowed_signers_file
1.163 djm 172: .Fl I Ar signer_identity
173: .Fl n Ar namespace
174: .Fl s Ar signature_file
175: .Op Fl r Ar revocation_file
1.13 aaron 176: .Sh DESCRIPTION
1.2 deraadt 177: .Nm
1.37 markus 178: generates, manages and converts authentication keys for
1.2 deraadt 179: .Xr ssh 1 .
1.15 deraadt 180: .Nm
1.140 jmc 181: can create keys for use by SSH protocol version 2.
1.130 jmc 182: .Pp
1.58 jmc 183: The type of key to be generated is specified with the
1.25 markus 184: .Fl t
1.52 djm 185: option.
1.70 djm 186: If invoked without any arguments,
187: .Nm
1.141 naddy 188: will generate an RSA key.
1.15 deraadt 189: .Pp
1.60 djm 190: .Nm
191: is also used to generate groups for use in Diffie-Hellman group
192: exchange (DH-GEX).
193: See the
194: .Sx MODULI GENERATION
195: section for details.
196: .Pp
1.111 djm 197: Finally,
198: .Nm
199: can be used to generate and update Key Revocation Lists, and to test whether
1.112 jmc 200: given keys have been revoked by one.
201: See the
1.111 djm 202: .Sx KEY REVOCATION LISTS
203: section for details.
204: .Pp
1.2 deraadt 205: Normally each user wishing to use SSH
1.99 djm 206: with public key authentication runs this once to create the authentication
1.1 deraadt 207: key in
1.118 naddy 208: .Pa ~/.ssh/id_dsa ,
1.99 djm 209: .Pa ~/.ssh/id_ecdsa ,
1.173 naddy 210: .Pa ~/.ssh/id_ecdsa_sk ,
1.176 naddy 211: .Pa ~/.ssh/id_ed25519 ,
212: .Pa ~/.ssh/id_ed25519_sk
1.15 deraadt 213: or
1.68 djm 214: .Pa ~/.ssh/id_rsa .
1.15 deraadt 215: Additionally, the system administrator may use this to generate host keys,
216: as seen in
217: .Pa /etc/rc .
1.2 deraadt 218: .Pp
1.1 deraadt 219: Normally this program generates the key and asks for a file in which
1.12 aaron 220: to store the private key.
221: The public key is stored in a file with the same name but
1.2 deraadt 222: .Dq .pub
1.12 aaron 223: appended.
224: The program also asks for a passphrase.
225: The passphrase may be empty to indicate no passphrase
1.26 markus 226: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 227: arbitrary length.
1.51 stevesk 228: A passphrase is similar to a password, except it can be a phrase with a
229: series of words, punctuation, numbers, whitespace, or any string of
230: characters you want.
231: Good passphrases are 10-30 characters long, are
1.1 deraadt 232: not simple sentences or otherwise easily guessable (English
1.42 markus 233: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 234: passphrases), and contain a mix of upper and lowercase letters,
235: numbers, and non-alphanumeric characters.
1.12 aaron 236: The passphrase can be changed later by using the
1.2 deraadt 237: .Fl p
1.1 deraadt 238: option.
1.2 deraadt 239: .Pp
1.12 aaron 240: There is no way to recover a lost passphrase.
1.105 djm 241: If the passphrase is lost or forgotten, a new key must be generated
242: and the corresponding public key copied to other machines.
1.2 deraadt 243: .Pp
1.153 djm 244: .Nm
245: will by default write keys in an OpenSSH-specific format.
246: This format is preferred as it offers better protection for
247: keys at rest as well as allowing storage of key comments within
248: the private key file itself.
249: The key comment may be useful to help identify the key.
1.12 aaron 250: The comment is initialized to
1.2 deraadt 251: .Dq user@host
252: when the key is created, but can be changed using the
253: .Fl c
1.1 deraadt 254: option.
1.153 djm 255: .Pp
256: It is still possible for
257: .Nm
258: to write the previously-used PEM format private keys using the
259: .Fl m
260: flag.
261: This may be used when generating new keys, and existing new-format
262: keys may be converted using this option in conjunction with the
263: .Fl p
264: (change passphrase) flag.
1.2 deraadt 265: .Pp
1.205 solene 266: After a key is generated,
267: .Nm
268: will ask where the keys
1.15 deraadt 269: should be placed to be activated.
270: .Pp
1.2 deraadt 271: The options are as follows:
272: .Bl -tag -width Ds
1.102 stevesk 273: .It Fl A
1.223 dtucker 274: Generate host keys of all default key types (rsa, ecdsa, and
275: ed25519) if they do not already exist.
276: The host keys are generated with the default key file path,
1.102 stevesk 277: an empty passphrase, default bits for the key type, and default comment.
1.144 jmc 278: If
1.143 djm 279: .Fl f
1.144 jmc 280: has also been specified, its argument is used as a prefix to the
1.143 djm 281: default path for the resulting host key files.
1.104 jmc 282: This is used by
1.102 stevesk 283: .Pa /etc/rc
284: to generate new host keys.
1.117 djm 285: .It Fl a Ar rounds
1.169 jmc 286: When saving a private key, this option specifies the number of KDF
1.211 dtucker 287: (key derivation function, currently
288: .Xr bcrypt_pbkdf 3 )
289: rounds used.
1.117 djm 290: Higher numbers result in slower passphrase verification and increased
291: resistance to brute-force password cracking (should the keys be stolen).
1.204 dtucker 292: The default is 16 rounds.
1.66 jmc 293: .It Fl B
294: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 295: .It Fl b Ar bits
1.12 aaron 296: Specifies the number of bits in the key to create.
1.158 dtucker 297: For RSA keys, the minimum size is 1024 bits and the default is 3072 bits.
298: Generally, 3072 bits is considered sufficient.
1.72 dtucker 299: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 300: For ECDSA keys, the
301: .Fl b
1.107 deraadt 302: flag determines the key length by selecting from one of three elliptic
1.106 djm 303: curve sizes: 256, 384 or 521 bits.
304: Attempting to use bit lengths other than these three values for ECDSA keys
305: will fail.
1.176 naddy 306: ECDSA-SK, Ed25519 and Ed25519-SK keys have a fixed length and the
1.118 naddy 307: .Fl b
308: flag will be ignored.
1.66 jmc 309: .It Fl C Ar comment
310: Provides a new comment.
1.2 deraadt 311: .It Fl c
1.1 deraadt 312: Requests changing the comment in the private and public key files.
313: The program will prompt for the file containing the private keys, for
1.41 stevesk 314: the passphrase if the key has one, and for the new comment.
1.81 markus 315: .It Fl D Ar pkcs11
1.157 naddy 316: Download the public keys provided by the PKCS#11 shared library
1.83 markus 317: .Ar pkcs11 .
1.98 djm 318: When used in combination with
319: .Fl s ,
320: this option indicates that a CA key resides in a PKCS#11 token (see the
321: .Sx CERTIFICATES
322: section for details).
1.124 djm 323: .It Fl E Ar fingerprint_hash
324: Specifies the hash algorithm used when displaying key fingerprints.
325: Valid options are:
326: .Dq md5
327: and
328: .Dq sha256 .
329: The default is
330: .Dq sha256 .
1.37 markus 331: .It Fl e
1.40 markus 332: This option will read a private or public OpenSSH key file and
1.154 djm 333: print to stdout a public key in one of the formats specified by the
1.95 djm 334: .Fl m
335: option.
336: The default export format is
337: .Dq RFC4716 .
1.96 jmc 338: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 339: several commercial SSH implementations.
1.151 djm 340: .It Fl F Ar hostname | [hostname]:port
1.66 jmc 341: Search for the specified
342: .Ar hostname
1.151 djm 343: (with optional port number)
1.66 jmc 344: in a
345: .Pa known_hosts
346: file, listing any occurrences found.
347: This option is useful to find hashed host names or addresses and may also be
348: used in conjunction with the
349: .Fl H
350: option to print found keys in a hashed format.
351: .It Fl f Ar filename
352: Specifies the filename of the key file.
1.57 jakob 353: .It Fl g
1.62 jakob 354: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 355: .Fl r
1.62 jakob 356: command.
1.66 jmc 357: .It Fl H
358: Hash a
359: .Pa known_hosts
1.67 dtucker 360: file.
361: This replaces all hostnames and addresses with hashed representations
362: within the specified file; the original content is moved to a file with
363: a .old suffix.
1.66 jmc 364: These hashes may be used normally by
365: .Nm ssh
366: and
367: .Nm sshd ,
368: but they do not reveal identifying information should the file's contents
369: be disclosed.
370: This option will not modify existing hashed hostnames and is therefore safe
371: to use on files that mix hashed and non-hashed names.
1.84 djm 372: .It Fl h
373: When signing a key, create a host certificate instead of a user
374: certificate.
1.220 jsg 375: See the
1.84 djm 376: .Sx CERTIFICATES
377: section for details.
1.85 jmc 378: .It Fl I Ar certificate_identity
1.84 djm 379: Specify the key identity when signing a public key.
1.220 jsg 380: See the
1.84 djm 381: .Sx CERTIFICATES
382: section for details.
1.37 markus 383: .It Fl i
384: This option will read an unencrypted private (or public) key file
1.95 djm 385: in the format specified by the
386: .Fl m
387: option and print an OpenSSH compatible private
1.37 markus 388: (or public) key to stdout.
1.122 jmc 389: This option allows importing keys from other software, including several
390: commercial SSH implementations.
391: The default import format is
392: .Dq RFC4716 .
1.188 jmc 393: .It Fl K
1.187 djm 394: Download resident keys from a FIDO authenticator.
395: Public and private key files will be written to the current directory for
396: each downloaded key.
1.207 djm 397: If multiple FIDO authenticators are attached, keys will be downloaded from
398: the first touched authenticator.
1.221 florian 399: See the
400: .Sx FIDO AUTHENTICATOR
401: section for more information.
1.111 djm 402: .It Fl k
403: Generate a KRL file.
404: In this mode,
405: .Nm
406: will generate a KRL file at the location specified via the
407: .Fl f
1.114 jmc 408: flag that revokes every key or certificate presented on the command line.
1.111 djm 409: Keys/certificates to be revoked may be specified by public key file or
410: using the format described in the
411: .Sx KEY REVOCATION LISTS
412: section.
1.86 djm 413: .It Fl L
1.129 djm 414: Prints the contents of one or more certificates.
1.9 markus 415: .It Fl l
1.77 grunk 416: Show fingerprint of specified public key file.
1.50 markus 417: For RSA and DSA keys
418: .Nm
1.78 jmc 419: tries to find the matching public key file and prints its fingerprint.
420: If combined with
421: .Fl v ,
1.132 jmc 422: a visual ASCII art representation of the key is supplied with the
1.131 djm 423: fingerprint.
1.184 djm 424: .It Fl M Cm generate
425: Generate candidate Diffie-Hellman Group Exchange (DH-GEX) parameters for
426: eventual use by the
427: .Sq diffie-hellman-group-exchange-*
428: key exchange methods.
429: The numbers generated by this operation must be further screened before
430: use.
431: See the
432: .Sx MODULI GENERATION
433: section for more information.
434: .It Fl M Cm screen
435: Screen candidate parameters for Diffie-Hellman Group Exchange.
436: This will accept a list of candidate numbers and test that they are
437: safe (Sophie Germain) primes with acceptable group generators.
438: The results of this operation may be added to the
439: .Pa /etc/moduli
440: file.
441: See the
442: .Sx MODULI GENERATION
443: section for more information.
1.95 djm 444: .It Fl m Ar key_format
1.155 djm 445: Specify a key format for key generation, the
1.95 djm 446: .Fl i
1.155 djm 447: (import),
1.95 djm 448: .Fl e
1.155 djm 449: (export) conversion options, and the
450: .Fl p
451: change passphrase operation.
452: The latter may be used to convert between OpenSSH private key and PEM
453: private key formats.
1.95 djm 454: The supported key formats are:
455: .Dq RFC4716
1.96 jmc 456: (RFC 4716/SSH2 public or private key),
1.95 djm 457: .Dq PKCS8
1.161 djm 458: (PKCS8 public or private key)
1.95 djm 459: or
460: .Dq PEM
461: (PEM public key).
1.161 djm 462: By default OpenSSH will write newly-generated private keys in its own
463: format, but when converting public keys for export the default format is
1.95 djm 464: .Dq RFC4716 .
1.148 djm 465: Setting a format of
466: .Dq PEM
467: when generating or updating a supported private key type will cause the
468: key to be stored in the legacy PEM private key format.
1.66 jmc 469: .It Fl N Ar new_passphrase
470: Provides the new passphrase.
1.84 djm 471: .It Fl n Ar principals
472: Specify one or more principals (user or host names) to be included in
473: a certificate when signing a key.
474: Multiple principals may be specified, separated by commas.
1.220 jsg 475: See the
1.84 djm 476: .Sx CERTIFICATES
477: section for details.
1.93 djm 478: .It Fl O Ar option
1.184 djm 479: Specify a key/value option.
480: These are specific to the operation that
481: .Nm
482: has been requested to perform.
483: .Pp
484: When signing certificates, one of the options listed in the
1.183 djm 485: .Sx CERTIFICATES
1.184 djm 486: section may be specified here.
487: .Pp
488: When performing moduli generation or screening, one of the options
489: listed in the
490: .Sx MODULI GENERATION
491: section may be specified.
492: .Pp
1.221 florian 493: When generating FIDO authenticator-backed keys, the options listed in the
494: .Sx FIDO AUTHENTICATOR
495: section may be specified.
1.185 djm 496: .Pp
1.214 djm 497: When performing signature-related options using the
498: .Fl Y
499: flag, the following options are accepted:
500: .Bl -tag -width Ds
1.219 djm 501: .It Cm hashalg Ns = Ns Ar algorithm
502: Selects the hash algorithm to use for hashing the message to be signed.
503: Valid algorithms are
504: .Dq sha256
505: and
506: .Dq sha512.
507: The default is
508: .Dq sha512.
1.216 djm 509: .It Cm print-pubkey
510: Print the full public key to standard output after signature verification.
1.214 djm 511: .It Cm verify-time Ns = Ns Ar timestamp
512: Specifies a time to use when validating signatures instead of the current
513: time.
1.224 djm 514: The time may be specified as a date or time in the YYYYMMDD[Z] or
515: in YYYYMMDDHHMM[SS][Z] formats.
516: Dates and times will be interpreted in the current system time zone unless
517: suffixed with a Z character, which causes them to be interpreted in the
518: UTC time zone.
1.227 ! djm 519: .El
! 520: .Pp
! 521: When generating SSHFP DNS records from public keys using the
! 522: .Fl r
! 523: flag, the following options are accepted:
! 524: .Bl -tag -width Ds
! 525: .It Cm hashalg Ns = Ns Ar algorithm
! 526: Selects a hash algorithm to use when printing SSHFP records using the
! 527: .Fl D
! 528: flag.
! 529: Valid algorithms are
! 530: .Dq sha1
! 531: and
! 532: .Dq sha256.
! 533: The default is to print both.
1.214 djm 534: .El
535: .Pp
1.185 djm 536: The
537: .Fl O
538: option may be specified multiple times.
1.66 jmc 539: .It Fl P Ar passphrase
540: Provides the (old) passphrase.
1.2 deraadt 541: .It Fl p
1.1 deraadt 542: Requests changing the passphrase of a private key file instead of
1.12 aaron 543: creating a new private key.
544: The program will prompt for the file
1.1 deraadt 545: containing the private key, for the old passphrase, and twice for the
546: new passphrase.
1.113 jmc 547: .It Fl Q
548: Test whether keys have been revoked in a KRL.
1.203 djm 549: If the
550: .Fl l
551: option is also specified then the contents of the KRL will be printed.
1.5 aaron 552: .It Fl q
553: Silence
554: .Nm ssh-keygen .
1.152 djm 555: .It Fl R Ar hostname | [hostname]:port
1.151 djm 556: Removes all keys belonging to the specified
1.64 djm 557: .Ar hostname
1.151 djm 558: (with optional port number)
1.65 jmc 559: from a
1.64 djm 560: .Pa known_hosts
561: file.
1.65 jmc 562: This option is useful to delete hashed hosts (see the
1.64 djm 563: .Fl H
564: option above).
1.66 jmc 565: .It Fl r Ar hostname
566: Print the SSHFP fingerprint resource record named
567: .Ar hostname
568: for the specified public key file.
1.84 djm 569: .It Fl s Ar ca_key
570: Certify (sign) a public key using the specified CA key.
1.220 jsg 571: See the
1.84 djm 572: .Sx CERTIFICATES
573: section for details.
1.111 djm 574: .Pp
575: When generating a KRL,
576: .Fl s
1.112 jmc 577: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 578: by key ID or serial number.
579: See the
580: .Sx KEY REVOCATION LISTS
581: section for details.
1.175 djm 582: .It Fl t Cm dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa
1.66 jmc 583: Specifies the type of key to create.
584: The possible values are
1.100 naddy 585: .Dq dsa ,
1.118 naddy 586: .Dq ecdsa ,
1.173 naddy 587: .Dq ecdsa-sk ,
1.118 naddy 588: .Dq ed25519 ,
1.175 djm 589: .Dq ed25519-sk ,
1.100 naddy 590: or
1.139 jmc 591: .Dq rsa .
1.159 djm 592: .Pp
593: This flag may also be used to specify the desired signature type when
1.160 jmc 594: signing certificates using an RSA CA key.
1.159 djm 595: The available RSA signature variants are
596: .Dq ssh-rsa
597: (SHA1 signatures, not recommended),
1.160 jmc 598: .Dq rsa-sha2-256 ,
599: and
1.159 djm 600: .Dq rsa-sha2-512
601: (the default).
1.142 djm 602: .It Fl U
603: When used in combination with
1.222 djm 604: .Fl s
605: or
1.225 jmc 606: .Fl Y Cm sign ,
1.142 djm 607: this option indicates that a CA key resides in a
608: .Xr ssh-agent 1 .
609: See the
610: .Sx CERTIFICATES
611: section for more information.
1.112 jmc 612: .It Fl u
613: Update a KRL.
614: When specified with
615: .Fl k ,
1.114 jmc 616: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 617: a new KRL being created.
1.84 djm 618: .It Fl V Ar validity_interval
619: Specify a validity interval when signing a certificate.
620: A validity interval may consist of a single time, indicating that the
621: certificate is valid beginning now and expiring at that time, or may consist
622: of two times separated by a colon to indicate an explicit time interval.
1.145 djm 623: .Pp
1.224 djm 624: The start time may be specified as:
625: .Bl -bullet -compact
626: .It
627: The string
1.145 djm 628: .Dq always
1.224 djm 629: to indicate the certificate has no specified start time.
630: .It
631: A date or time in the system time zone formatted as YYYYMMDD or
632: YYYYMMDDHHMM[SS].
633: .It
634: A date or time in the UTC time zone as YYYYMMDDZ or YYYYMMDDHHMM[SS]Z.
635: .It
636: A relative time before the current system time consisting of a minus sign
637: followed by an interval in the format described in the
1.116 jmc 638: TIME FORMATS section of
1.90 jmc 639: .Xr sshd_config 5 .
1.224 djm 640: .It
641: A raw seconds since epoch (Jan 1 1970 00:00:00 UTC) as a hexadecimal
642: number beginning with
643: .Dq 0x .
644: .El
1.145 djm 645: .Pp
1.224 djm 646: The end time may be specified similarly to the start time:
647: .Bl -bullet -compact
648: .It
649: The string
1.145 djm 650: .Dq forever
1.224 djm 651: to indicate the certificate has no specified end time.
652: .It
653: A date or time in the system time zone formatted as YYYYMMDD or
654: YYYYMMDDHHMM[SS].
655: .It
656: A date or time in the UTC time zone as YYYYMMDDZ or YYYYMMDDHHMM[SS]Z.
657: .It
658: A relative time after the current system time consisting of a plus sign
659: followed by an interval in the format described in the
660: TIME FORMATS section of
661: .Xr sshd_config 5 .
662: .It
663: A raw seconds since epoch (Jan 1 1970 00:00:00 UTC) as a hexadecimal
664: number beginning with
665: .Dq 0x .
666: .El
1.84 djm 667: .Pp
668: For example:
1.224 djm 669: .Bl -tag -width Ds
670: .It +52w1d
671: Valid from now to 52 weeks and one day from now.
672: .It -4w:+4w
673: Valid from four weeks ago to four weeks from now.
674: .It 20100101123000:20110101123000
675: Valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011.
676: .It 20100101123000Z:20110101123000Z
677: Similar, but interpreted in the UTC time zone rather than the system time zone.
678: .It -1d:20110101
679: Valid from yesterday to midnight, January 1st, 2011.
680: .It 0x1:0x2000000000
681: Valid from roughly early 1970 to May 2033.
682: .It -1m:forever
683: Valid from one minute ago and never expiring.
684: .El
1.61 djm 685: .It Fl v
686: Verbose mode.
687: Causes
688: .Nm
689: to print debugging messages about its progress.
690: This is helpful for debugging moduli generation.
691: Multiple
692: .Fl v
693: options increase the verbosity.
694: The maximum is 3.
1.173 naddy 695: .It Fl w Ar provider
1.180 naddy 696: Specifies a path to a library that will be used when creating
697: FIDO authenticator-hosted keys, overriding the default of using
698: the internal USB HID support.
1.196 djm 699: .It Fl Y Cm find-principals
700: Find the principal(s) associated with the public key of a signature,
1.194 djm 701: provided using the
702: .Fl s
703: flag in an authorized signers file provided using the
704: .Fl f
705: flag.
706: The format of the allowed signers file is documented in the
707: .Sx ALLOWED SIGNERS
1.195 jmc 708: section below.
1.217 djm 709: If one or more matching principals are found, they are returned on
710: standard output.
711: .It Fl Y Cm match-principals
712: Find principal matching the principal name provided using the
713: .Fl I
714: flag in the authorized signers file specified using the
715: .Fl f
716: flag.
1.196 djm 717: If one or more matching principals are found, they are returned on
718: standard output.
1.182 jmc 719: .It Fl Y Cm check-novalidate
720: Checks that a signature generated using
721: .Nm
722: .Fl Y Cm sign
723: has a valid structure.
724: This does not validate if a signature comes from an authorized signer.
725: When testing a signature,
726: .Nm
727: accepts a message on standard input and a signature namespace using
728: .Fl n .
729: A file containing the corresponding signature must also be supplied using the
730: .Fl s
731: flag.
732: Successful testing of the signature is signalled by
733: .Nm
734: returning a zero exit status.
1.166 jmc 735: .It Fl Y Cm sign
1.163 djm 736: Cryptographically sign a file or some data using a SSH key.
737: When signing,
738: .Nm
739: accepts zero or more files to sign on the command-line - if no files
740: are specified then
741: .Nm
742: will sign data presented on standard input.
743: Signatures are written to the path of the input file with
744: .Dq .sig
745: appended, or to standard output if the message to be signed was read from
746: standard input.
747: .Pp
748: The key used for signing is specified using the
749: .Fl f
750: option and may refer to either a private key, or a public key with the private
751: half available via
752: .Xr ssh-agent 1 .
753: An additional signature namespace, used to prevent signature confusion across
754: different domains of use (e.g. file signing vs email signing) must be provided
755: via the
756: .Fl n
757: flag.
758: Namespaces are arbitrary strings, and may include:
759: .Dq file
760: for file signing,
761: .Dq email
762: for email signing.
763: For custom uses, it is recommended to use names following a
764: NAMESPACE@YOUR.DOMAIN pattern to generate unambiguous namespaces.
1.166 jmc 765: .It Fl Y Cm verify
1.163 djm 766: Request to verify a signature generated using
767: .Nm
1.166 jmc 768: .Fl Y Cm sign
1.163 djm 769: as described above.
770: When verifying a signature,
771: .Nm
772: accepts a message on standard input and a signature namespace using
773: .Fl n .
774: A file containing the corresponding signature must also be supplied using the
775: .Fl s
776: flag, along with the identity of the signer using
777: .Fl I
778: and a list of allowed signers via the
779: .Fl f
780: flag.
781: The format of the allowed signers file is documented in the
782: .Sx ALLOWED SIGNERS
783: section below.
784: A file containing revoked keys can be passed using the
785: .Fl r
1.165 jmc 786: flag.
787: The revocation file may be a KRL or a one-per-line list of public keys.
1.163 djm 788: Successful verification by an authorized signer is signalled by
789: .Nm
790: returning a zero exit status.
1.181 jmc 791: .It Fl y
792: This option will read a private
793: OpenSSH format file and print an OpenSSH public key to stdout.
1.212 dtucker 794: .It Fl Z Ar cipher
795: Specifies the cipher to use for encryption when writing an OpenSSH-format
796: private key file.
797: The list of available ciphers may be obtained using
798: .Qq ssh -Q cipher .
799: The default is
800: .Dq aes256-ctr .
1.93 djm 801: .It Fl z Ar serial_number
802: Specifies a serial number to be embedded in the certificate to distinguish
803: this certificate from others from the same CA.
1.156 djm 804: If the
805: .Ar serial_number
806: is prefixed with a
807: .Sq +
808: character, then the serial number will be incremented for each certificate
809: signed on a single command-line.
1.93 djm 810: The default serial number is zero.
1.111 djm 811: .Pp
812: When generating a KRL, the
813: .Fl z
814: flag is used to specify a KRL version number.
1.2 deraadt 815: .El
1.60 djm 816: .Sh MODULI GENERATION
817: .Nm
818: may be used to generate groups for the Diffie-Hellman Group Exchange
819: (DH-GEX) protocol.
820: Generating these groups is a two-step process: first, candidate
821: primes are generated using a fast, but memory intensive process.
822: These candidate primes are then tested for suitability (a CPU-intensive
823: process).
824: .Pp
825: Generation of primes is performed using the
1.184 djm 826: .Fl M Cm generate
1.60 djm 827: option.
828: The desired length of the primes may be specified by the
1.184 djm 829: .Fl O Cm bits
1.60 djm 830: option.
831: For example:
832: .Pp
1.184 djm 833: .Dl # ssh-keygen -M generate -O bits=2048 moduli-2048.candidates
1.60 djm 834: .Pp
835: By default, the search for primes begins at a random point in the
836: desired length range.
837: This may be overridden using the
1.184 djm 838: .Fl O Cm start
1.60 djm 839: option, which specifies a different start point (in hex).
840: .Pp
1.109 dtucker 841: Once a set of candidates have been generated, they must be screened for
1.60 djm 842: suitability.
843: This may be performed using the
1.184 djm 844: .Fl M Cm screen
1.60 djm 845: option.
846: In this mode
847: .Nm
848: will read candidates from standard input (or a file specified using the
849: .Fl f
850: option).
851: For example:
852: .Pp
1.184 djm 853: .Dl # ssh-keygen -M screen -f moduli-2048.candidates moduli-2048
1.60 djm 854: .Pp
855: By default, each candidate will be subjected to 100 primality tests.
856: This may be overridden using the
1.184 djm 857: .Fl O Cm prime-tests
1.60 djm 858: option.
859: The DH generator value will be chosen automatically for the
860: prime under consideration.
861: If a specific generator is desired, it may be requested using the
1.184 djm 862: .Fl O Cm generator
1.60 djm 863: option.
1.66 jmc 864: Valid generator values are 2, 3, and 5.
1.60 djm 865: .Pp
866: Screened DH groups may be installed in
867: .Pa /etc/moduli .
1.213 dtucker 868: It is important that this file contains moduli of a range of bit lengths.
1.184 djm 869: .Pp
870: A number of options are available for moduli generation and screening via the
871: .Fl O
872: flag:
1.186 jmc 873: .Bl -tag -width Ds
1.184 djm 874: .It Ic lines Ns = Ns Ar number
875: Exit after screening the specified number of lines while performing DH
876: candidate screening.
877: .It Ic start-line Ns = Ns Ar line-number
878: Start screening at the specified line number while performing DH candidate
879: screening.
880: .It Ic checkpoint Ns = Ns Ar filename
881: Write the last line processed to the specified file while performing DH
882: candidate screening.
883: This will be used to skip lines in the input file that have already been
884: processed if the job is restarted.
885: .It Ic memory Ns = Ns Ar mbytes
886: Specify the amount of memory to use (in megabytes) when generating
887: candidate moduli for DH-GEX.
888: .It Ic start Ns = Ns Ar hex-value
889: Specify start point (in hex) when generating candidate moduli for DH-GEX.
890: .It Ic generator Ns = Ns Ar value
891: Specify desired generator (in decimal) when testing candidate moduli for DH-GEX.
892: .El
1.84 djm 893: .Sh CERTIFICATES
894: .Nm
895: supports signing of keys to produce certificates that may be used for
896: user or host authentication.
897: Certificates consist of a public key, some identity information, zero or
1.94 jmc 898: more principal (user or host) names and a set of options that
1.84 djm 899: are signed by a Certification Authority (CA) key.
900: Clients or servers may then trust only the CA key and verify its signature
901: on a certificate rather than trusting many user/host keys.
902: Note that OpenSSH certificates are a different, and much simpler, format to
903: the X.509 certificates used in
904: .Xr ssl 8 .
905: .Pp
906: .Nm
907: supports two types of certificates: user and host.
908: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 909: authenticate server hosts to users.
910: To generate a user certificate:
1.84 djm 911: .Pp
912: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
913: .Pp
914: The resultant certificate will be placed in
1.91 djm 915: .Pa /path/to/user_key-cert.pub .
1.84 djm 916: A host certificate requires the
917: .Fl h
918: option:
919: .Pp
920: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
921: .Pp
922: The host certificate will be output to
1.91 djm 923: .Pa /path/to/host_key-cert.pub .
1.98 djm 924: .Pp
925: It is possible to sign using a CA key stored in a PKCS#11 token by
926: providing the token library using
927: .Fl D
928: and identifying the CA key by providing its public half as an argument
929: to
930: .Fl s :
931: .Pp
1.127 naddy 932: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.142 djm 933: .Pp
934: Similarly, it is possible for the CA key to be hosted in a
935: .Xr ssh-agent 1 .
936: This is indicated by the
937: .Fl U
938: flag and, again, the CA key must be identified by its public half.
939: .Pp
940: .Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
1.98 djm 941: .Pp
942: In all cases,
1.84 djm 943: .Ar key_id
944: is a "key identifier" that is logged by the server when the certificate
945: is used for authentication.
946: .Pp
947: Certificates may be limited to be valid for a set of principal (user/host)
948: names.
949: By default, generated certificates are valid for all users or hosts.
950: To generate a certificate for a specified set of principals:
951: .Pp
952: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 953: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 954: .Pp
955: Additional limitations on the validity and use of user certificates may
1.94 jmc 956: be specified through certificate options.
1.93 djm 957: A certificate option may disable features of the SSH session, may be
1.84 djm 958: valid only when presented from particular source addresses or may
959: force the use of a specific command.
1.183 djm 960: .Pp
961: The options that are valid for user certificates are:
962: .Pp
963: .Bl -tag -width Ds -compact
964: .It Ic clear
965: Clear all enabled permissions.
966: This is useful for clearing the default set of permissions so permissions may
967: be added individually.
968: .Pp
969: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
970: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
971: Includes an arbitrary certificate critical option or extension.
972: The specified
973: .Ar name
974: should include a domain suffix, e.g.\&
975: .Dq name@example.com .
976: If
977: .Ar contents
978: is specified then it is included as the contents of the extension/option
979: encoded as a string, otherwise the extension/option is created with no
980: contents (usually indicating a flag).
981: Extensions may be ignored by a client or server that does not recognise them,
982: whereas unknown critical options will cause the certificate to be refused.
983: .Pp
984: .It Ic force-command Ns = Ns Ar command
985: Forces the execution of
986: .Ar command
987: instead of any shell or command specified by the user when
988: the certificate is used for authentication.
989: .Pp
990: .It Ic no-agent-forwarding
991: Disable
992: .Xr ssh-agent 1
993: forwarding (permitted by default).
994: .Pp
995: .It Ic no-port-forwarding
996: Disable port forwarding (permitted by default).
997: .Pp
998: .It Ic no-pty
999: Disable PTY allocation (permitted by default).
1000: .Pp
1001: .It Ic no-user-rc
1002: Disable execution of
1003: .Pa ~/.ssh/rc
1004: by
1005: .Xr sshd 8
1006: (permitted by default).
1007: .Pp
1008: .It Ic no-x11-forwarding
1009: Disable X11 forwarding (permitted by default).
1010: .Pp
1011: .It Ic permit-agent-forwarding
1012: Allows
1013: .Xr ssh-agent 1
1014: forwarding.
1015: .Pp
1016: .It Ic permit-port-forwarding
1017: Allows port forwarding.
1018: .Pp
1019: .It Ic permit-pty
1020: Allows PTY allocation.
1021: .Pp
1022: .It Ic permit-user-rc
1023: Allows execution of
1024: .Pa ~/.ssh/rc
1025: by
1026: .Xr sshd 8 .
1027: .Pp
1028: .It Ic permit-X11-forwarding
1029: Allows X11 forwarding.
1030: .Pp
1031: .It Ic no-touch-required
1.206 djm 1032: Do not require signatures made using this key include demonstration
1.193 naddy 1033: of user presence (e.g. by having the user touch the authenticator).
1.192 naddy 1034: This option only makes sense for the FIDO authenticator algorithms
1.183 djm 1035: .Cm ecdsa-sk
1036: and
1037: .Cm ed25519-sk .
1038: .Pp
1039: .It Ic source-address Ns = Ns Ar address_list
1040: Restrict the source addresses from which the certificate is considered valid.
1041: The
1042: .Ar address_list
1043: is a comma-separated list of one or more address/netmask pairs in CIDR
1044: format.
1.206 djm 1045: .Pp
1046: .It Ic verify-required
1047: Require signatures made using this key indicate that the user was first
1048: verified.
1049: This option only makes sense for the FIDO authenticator algorithms
1050: .Cm ecdsa-sk
1051: and
1052: .Cm ed25519-sk .
1053: Currently PIN authentication is the only supported verification method,
1054: but other methods may be supported in the future.
1.183 djm 1055: .El
1056: .Pp
1057: At present, no standard options are valid for host keys.
1.84 djm 1058: .Pp
1059: Finally, certificates may be defined with a validity lifetime.
1060: The
1061: .Fl V
1062: option allows specification of certificate start and end times.
1063: A certificate that is presented at a time outside this range will not be
1064: considered valid.
1.210 dtucker 1065: By default, certificates are valid from the
1.110 jmc 1066: .Ux
1067: Epoch to the distant future.
1.84 djm 1068: .Pp
1069: For certificates to be used for user or host authentication, the CA
1070: public key must be trusted by
1071: .Xr sshd 8
1072: or
1073: .Xr ssh 1 .
1.220 jsg 1074: Refer to those manual pages for details.
1.221 florian 1075: .Sh FIDO AUTHENTICATOR
1076: .Nm
1.226 jsg 1077: is able to generate FIDO authenticator-backed keys, after which
1.221 florian 1078: they may be used much like any other key type supported by OpenSSH, so
1079: long as the hardware authenticator is attached when the keys are used.
1080: FIDO authenticators generally require the user to explicitly authorise
1081: operations by touching or tapping them.
1082: FIDO keys consist of two parts: a key handle part stored in the
1083: private key file on disk, and a per-device private key that is unique
1084: to each FIDO authenticator and that cannot be exported from the
1085: authenticator hardware.
1086: These are combined by the hardware at authentication time to derive
1087: the real key that is used to sign authentication challenges.
1088: Supported key types are
1089: .Cm ecdsa-sk
1090: and
1091: .Cm ed25519-sk .
1092: .Pp
1093: The options that are valid for FIDO keys are:
1094: .Bl -tag -width Ds
1095: .It Cm application
1096: Override the default FIDO application/origin string of
1097: .Dq ssh: .
1098: This may be useful when generating host or domain-specific resident keys.
1099: The specified application string must begin with
1100: .Dq ssh: .
1101: .It Cm challenge Ns = Ns Ar path
1102: Specifies a path to a challenge string that will be passed to the
1103: FIDO authenticator during key generation.
1104: The challenge string may be used as part of an out-of-band
1105: protocol for key enrollment
1106: (a random challenge is used by default).
1107: .It Cm device
1108: Explicitly specify a
1109: .Xr fido 4
1110: device to use, rather than letting the authenticator middleware select one.
1111: .It Cm no-touch-required
1112: Indicate that the generated private key should not require touch
1113: events (user presence) when making signatures.
1114: Note that
1115: .Xr sshd 8
1116: will refuse such signatures by default, unless overridden via
1117: an authorized_keys option.
1118: .It Cm resident
1119: Indicate that the key handle should be stored on the FIDO
1120: authenticator itself.
1121: This makes it easier to use the authenticator on multiple computers.
1122: Resident keys may be supported on FIDO2 authenticators and typically
1123: require that a PIN be set on the authenticator prior to generation.
1124: Resident keys may be loaded off the authenticator using
1125: .Xr ssh-add 1 .
1126: Storing both parts of a key on a FIDO authenticator increases the likelihood
1127: of an attacker being able to use a stolen authenticator device.
1128: .It Cm user
1129: A username to be associated with a resident key,
1130: overriding the empty default username.
1131: Specifying a username may be useful when generating multiple resident keys
1132: for the same application name.
1133: .It Cm verify-required
1134: Indicate that this private key should require user verification for
1135: each signature.
1136: Not all FIDO authenticators support this option.
1137: Currently PIN authentication is the only supported verification method,
1138: but other methods may be supported in the future.
1139: .It Cm write-attestation Ns = Ns Ar path
1140: May be used at key generation time to record the attestation data
1141: returned from FIDO authenticators during key generation.
1142: This information is potentially sensitive.
1143: By default, this information is discarded.
1144: .El
1.111 djm 1145: .Sh KEY REVOCATION LISTS
1146: .Nm
1147: is able to manage OpenSSH format Key Revocation Lists (KRLs).
1148: These binary files specify keys or certificates to be revoked using a
1.119 tedu 1149: compact format, taking as little as one bit per certificate if they are being
1.111 djm 1150: revoked by serial number.
1151: .Pp
1152: KRLs may be generated using the
1153: .Fl k
1154: flag.
1.114 jmc 1155: This option reads one or more files from the command line and generates a new
1.111 djm 1156: KRL.
1157: The files may either contain a KRL specification (see below) or public keys,
1158: listed one per line.
1159: Plain public keys are revoked by listing their hash or contents in the KRL and
1160: certificates revoked by serial number or key ID (if the serial is zero or
1161: not available).
1162: .Pp
1163: Revoking keys using a KRL specification offers explicit control over the
1164: types of record used to revoke keys and may be used to directly revoke
1165: certificates by serial number or key ID without having the complete original
1166: certificate on hand.
1167: A KRL specification consists of lines containing one of the following directives
1168: followed by a colon and some directive-specific information.
1169: .Bl -tag -width Ds
1.115 jmc 1170: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 1171: Revokes a certificate with the specified serial number.
1.112 jmc 1172: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 1173: in decimal, hex or octal.
1174: If two serial numbers are specified separated by a hyphen, then the range
1175: of serial numbers including and between each is revoked.
1176: The CA key must have been specified on the
1177: .Nm
1.114 jmc 1178: command line using the
1.111 djm 1179: .Fl s
1180: option.
1181: .It Cm id : Ar key_id
1182: Revokes a certificate with the specified key ID string.
1183: The CA key must have been specified on the
1184: .Nm
1.114 jmc 1185: command line using the
1.111 djm 1186: .Fl s
1187: option.
1188: .It Cm key : Ar public_key
1189: Revokes the specified key.
1.112 jmc 1190: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 1191: .It Cm sha1 : Ar public_key
1.149 djm 1192: Revokes the specified key by including its SHA1 hash in the KRL.
1193: .It Cm sha256 : Ar public_key
1194: Revokes the specified key by including its SHA256 hash in the KRL.
1195: KRLs that revoke keys by SHA256 hash are not supported by OpenSSH versions
1196: prior to 7.9.
1197: .It Cm hash : Ar fingerprint
1.150 djm 1198: Revokes a key using a fingerprint hash, as obtained from a
1.149 djm 1199: .Xr sshd 8
1200: authentication log message or the
1201: .Nm
1202: .Fl l
1203: flag.
1204: Only SHA256 fingerprints are supported here and resultant KRLs are
1205: not supported by OpenSSH versions prior to 7.9.
1.111 djm 1206: .El
1207: .Pp
1208: KRLs may be updated using the
1209: .Fl u
1210: flag in addition to
1211: .Fl k .
1.114 jmc 1212: When this option is specified, keys listed via the command line are merged into
1.111 djm 1213: the KRL, adding to those already there.
1214: .Pp
1215: It is also possible, given a KRL, to test whether it revokes a particular key
1216: (or keys).
1217: The
1218: .Fl Q
1.128 jmc 1219: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 1220: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 1221: then
1222: .Nm
1223: will exit with a non-zero exit status.
1224: A zero exit status will only be returned if no key was revoked.
1.163 djm 1225: .Sh ALLOWED SIGNERS
1226: When verifying signatures,
1227: .Nm
1228: uses a simple list of identities and keys to determine whether a signature
1229: comes from an authorized source.
1230: This "allowed signers" file uses a format patterned after the
1231: AUTHORIZED_KEYS FILE FORMAT described in
1.165 jmc 1232: .Xr sshd 8 .
1.163 djm 1233: Each line of the file contains the following space-separated fields:
1234: principals, options, keytype, base64-encoded key.
1235: Empty lines and lines starting with a
1236: .Ql #
1237: are ignored as comments.
1238: .Pp
1.210 dtucker 1239: The principals field is a pattern-list (see PATTERNS in
1.163 djm 1240: .Xr ssh_config 5 )
1241: consisting of one or more comma-separated USER@DOMAIN identity patterns
1242: that are accepted for signing.
1243: When verifying, the identity presented via the
1.172 jmc 1244: .Fl I
1245: option must match a principals pattern in order for the corresponding key to be
1.163 djm 1246: considered acceptable for verification.
1247: .Pp
1248: The options (if present) consist of comma-separated option specifications.
1249: No spaces are permitted, except within double quotes.
1250: The following option specifications are supported (note that option keywords
1251: are case-insensitive):
1252: .Bl -tag -width Ds
1253: .It Cm cert-authority
1254: Indicates that this key is accepted as a certificate authority (CA) and
1255: that certificates signed by this CA may be accepted for verification.
1.214 djm 1256: .It Cm namespaces Ns = Ns "namespace-list"
1.163 djm 1257: Specifies a pattern-list of namespaces that are accepted for this key.
1.164 djm 1258: If this option is present, the signature namespace embedded in the
1.163 djm 1259: signature object and presented on the verification command-line must
1260: match the specified list before the key will be considered acceptable.
1.214 djm 1261: .It Cm valid-after Ns = Ns "timestamp"
1262: Indicates that the key is valid for use at or after the specified timestamp,
1.224 djm 1263: which may be a date or time in the YYYYMMDD[Z] or YYYYMMDDHHMM[SS][Z] formats.
1264: Dates and times will be interpreted in the current system time zone unless
1265: suffixed with a Z character, which causes them to be interpreted in the UTC
1266: time zone.
1.214 djm 1267: .It Cm valid-before Ns = Ns "timestamp"
1268: Indicates that the key is valid for use at or before the specified timestamp.
1.163 djm 1269: .El
1270: .Pp
1271: When verifying signatures made by certificates, the expected principal
1272: name must match both the principals pattern in the allowed signers file and
1273: the principals embedded in the certificate itself.
1274: .Pp
1275: An example allowed signers file:
1276: .Bd -literal -offset 3n
1277: # Comments allowed at start of line
1278: user1@example.com,user2@example.com ssh-rsa AAAAX1...
1279: # A certificate authority, trusted for all principals in a domain.
1280: *@example.com cert-authority ssh-ed25519 AAAB4...
1281: # A key that is accepted only for file signing.
1282: user2@example.com namespaces="file" ssh-ed25519 AAA41...
1283: .Ed
1.173 naddy 1284: .Sh ENVIRONMENT
1285: .Bl -tag -width Ds
1286: .It Ev SSH_SK_PROVIDER
1.201 djm 1287: Specifies a path to a library that will be used when loading any
1288: FIDO authenticator-hosted keys, overriding the default of using
1289: the built-in USB HID support.
1.173 naddy 1290: .El
1.2 deraadt 1291: .Sh FILES
1.100 naddy 1292: .Bl -tag -width Ds -compact
1.68 djm 1293: .It Pa ~/.ssh/id_dsa
1.100 naddy 1294: .It Pa ~/.ssh/id_ecdsa
1.173 naddy 1295: .It Pa ~/.ssh/id_ecdsa_sk
1.118 naddy 1296: .It Pa ~/.ssh/id_ed25519
1.176 naddy 1297: .It Pa ~/.ssh/id_ed25519_sk
1.100 naddy 1298: .It Pa ~/.ssh/id_rsa
1.180 naddy 1299: Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
1300: authenticator-hosted Ed25519 or RSA authentication identity of the user.
1.15 deraadt 1301: This file should not be readable by anyone but the user.
1302: It is possible to
1303: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 1304: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 1305: This file is not automatically accessed by
1306: .Nm
1307: but it is offered as the default file for the private key.
1.46 markus 1308: .Xr ssh 1
1.15 deraadt 1309: will read this file when a login attempt is made.
1.100 naddy 1310: .Pp
1.68 djm 1311: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 1312: .It Pa ~/.ssh/id_ecdsa.pub
1.173 naddy 1313: .It Pa ~/.ssh/id_ecdsa_sk.pub
1.118 naddy 1314: .It Pa ~/.ssh/id_ed25519.pub
1.176 naddy 1315: .It Pa ~/.ssh/id_ed25519_sk.pub
1.68 djm 1316: .It Pa ~/.ssh/id_rsa.pub
1.180 naddy 1317: Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
1318: authenticator-hosted Ed25519 or RSA public key for authentication.
1.15 deraadt 1319: The contents of this file should be added to
1.68 djm 1320: .Pa ~/.ssh/authorized_keys
1.15 deraadt 1321: on all machines
1.49 deraadt 1322: where the user wishes to log in using public key authentication.
1.12 aaron 1323: There is no need to keep the contents of this file secret.
1.100 naddy 1324: .Pp
1.60 djm 1325: .It Pa /etc/moduli
1326: Contains Diffie-Hellman groups used for DH-GEX.
1327: The file format is described in
1328: .Xr moduli 5 .
1.19 aaron 1329: .El
1.2 deraadt 1330: .Sh SEE ALSO
1331: .Xr ssh 1 ,
1332: .Xr ssh-add 1 ,
1.8 ericj 1333: .Xr ssh-agent 1 ,
1.60 djm 1334: .Xr moduli 5 ,
1.30 itojun 1335: .Xr sshd 8
1.37 markus 1336: .Rs
1.73 markus 1337: .%R RFC 4716
1338: .%T "The Secure Shell (SSH) Public Key File Format"
1339: .%D 2006
1.37 markus 1340: .Re
1.59 jmc 1341: .Sh AUTHORS
1342: OpenSSH is a derivative of the original and free
1343: ssh 1.2.12 release by Tatu Ylonen.
1344: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1345: Theo de Raadt and Dug Song
1346: removed many bugs, re-added newer features and
1347: created OpenSSH.
1348: Markus Friedl contributed the support for SSH
1349: protocol versions 1.5 and 2.0.
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