Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.221
1.221 ! florian 1: .\" $OpenBSD: ssh-keygen.1,v 1.220 2022/02/06 00:29:03 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: .\"
1.221 ! florian 38: .Dd $Mdocdate: February 6 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
1.175 djm 274: For each of the key types (rsa, dsa, ecdsa and ed25519)
1.118 naddy 275: for which host keys
1.102 stevesk 276: do not exist, generate the host keys with the default key file path,
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.
514: The time may be specified as a date in YYYYMMDD format or a time
515: in YYYYMMDDHHMM[SS] format.
516: .El
517: .Pp
1.185 djm 518: The
519: .Fl O
520: option may be specified multiple times.
1.66 jmc 521: .It Fl P Ar passphrase
522: Provides the (old) passphrase.
1.2 deraadt 523: .It Fl p
1.1 deraadt 524: Requests changing the passphrase of a private key file instead of
1.12 aaron 525: creating a new private key.
526: The program will prompt for the file
1.1 deraadt 527: containing the private key, for the old passphrase, and twice for the
528: new passphrase.
1.113 jmc 529: .It Fl Q
530: Test whether keys have been revoked in a KRL.
1.203 djm 531: If the
532: .Fl l
533: option is also specified then the contents of the KRL will be printed.
1.5 aaron 534: .It Fl q
535: Silence
536: .Nm ssh-keygen .
1.152 djm 537: .It Fl R Ar hostname | [hostname]:port
1.151 djm 538: Removes all keys belonging to the specified
1.64 djm 539: .Ar hostname
1.151 djm 540: (with optional port number)
1.65 jmc 541: from a
1.64 djm 542: .Pa known_hosts
543: file.
1.65 jmc 544: This option is useful to delete hashed hosts (see the
1.64 djm 545: .Fl H
546: option above).
1.66 jmc 547: .It Fl r Ar hostname
548: Print the SSHFP fingerprint resource record named
549: .Ar hostname
550: for the specified public key file.
1.84 djm 551: .It Fl s Ar ca_key
552: Certify (sign) a public key using the specified CA key.
1.220 jsg 553: See the
1.84 djm 554: .Sx CERTIFICATES
555: section for details.
1.111 djm 556: .Pp
557: When generating a KRL,
558: .Fl s
1.112 jmc 559: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 560: by key ID or serial number.
561: See the
562: .Sx KEY REVOCATION LISTS
563: section for details.
1.175 djm 564: .It Fl t Cm dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa
1.66 jmc 565: Specifies the type of key to create.
566: The possible values are
1.100 naddy 567: .Dq dsa ,
1.118 naddy 568: .Dq ecdsa ,
1.173 naddy 569: .Dq ecdsa-sk ,
1.118 naddy 570: .Dq ed25519 ,
1.175 djm 571: .Dq ed25519-sk ,
1.100 naddy 572: or
1.139 jmc 573: .Dq rsa .
1.159 djm 574: .Pp
575: This flag may also be used to specify the desired signature type when
1.160 jmc 576: signing certificates using an RSA CA key.
1.159 djm 577: The available RSA signature variants are
578: .Dq ssh-rsa
579: (SHA1 signatures, not recommended),
1.160 jmc 580: .Dq rsa-sha2-256 ,
581: and
1.159 djm 582: .Dq rsa-sha2-512
583: (the default).
1.142 djm 584: .It Fl U
585: When used in combination with
586: .Fl s ,
587: this option indicates that a CA key resides in a
588: .Xr ssh-agent 1 .
589: See the
590: .Sx CERTIFICATES
591: section for more information.
1.112 jmc 592: .It Fl u
593: Update a KRL.
594: When specified with
595: .Fl k ,
1.114 jmc 596: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 597: a new KRL being created.
1.84 djm 598: .It Fl V Ar validity_interval
599: Specify a validity interval when signing a certificate.
600: A validity interval may consist of a single time, indicating that the
601: certificate is valid beginning now and expiring at that time, or may consist
602: of two times separated by a colon to indicate an explicit time interval.
1.145 djm 603: .Pp
604: The start time may be specified as the string
605: .Dq always
606: to indicate the certificate has no specified start time,
1.147 djm 607: a date in YYYYMMDD format, a time in YYYYMMDDHHMM[SS] format,
1.145 djm 608: a relative time (to the current time) consisting of a minus sign followed by
609: an interval in the format described in the
1.116 jmc 610: TIME FORMATS section of
1.90 jmc 611: .Xr sshd_config 5 .
1.145 djm 612: .Pp
1.147 djm 613: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMM[SS] time,
1.145 djm 614: a relative time starting with a plus character or the string
615: .Dq forever
1.202 dtucker 616: to indicate that the certificate has no expiry date.
1.84 djm 617: .Pp
618: For example:
619: .Dq +52w1d
620: (valid from now to 52 weeks and one day from now),
621: .Dq -4w:+4w
622: (valid from four weeks ago to four weeks from now),
623: .Dq 20100101123000:20110101123000
624: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
625: .Dq -1d:20110101
1.210 dtucker 626: (valid from yesterday to midnight, January 1st, 2011),
1.145 djm 627: .Dq -1m:forever
628: (valid from one minute ago and never expiring).
1.61 djm 629: .It Fl v
630: Verbose mode.
631: Causes
632: .Nm
633: to print debugging messages about its progress.
634: This is helpful for debugging moduli generation.
635: Multiple
636: .Fl v
637: options increase the verbosity.
638: The maximum is 3.
1.173 naddy 639: .It Fl w Ar provider
1.180 naddy 640: Specifies a path to a library that will be used when creating
641: FIDO authenticator-hosted keys, overriding the default of using
642: the internal USB HID support.
1.196 djm 643: .It Fl Y Cm find-principals
644: Find the principal(s) associated with the public key of a signature,
1.194 djm 645: provided using the
646: .Fl s
647: flag in an authorized signers file provided using the
648: .Fl f
649: flag.
650: The format of the allowed signers file is documented in the
651: .Sx ALLOWED SIGNERS
1.195 jmc 652: section below.
1.217 djm 653: If one or more matching principals are found, they are returned on
654: standard output.
655: .It Fl Y Cm match-principals
656: Find principal matching the principal name provided using the
657: .Fl I
658: flag in the authorized signers file specified using the
659: .Fl f
660: flag.
1.196 djm 661: If one or more matching principals are found, they are returned on
662: standard output.
1.182 jmc 663: .It Fl Y Cm check-novalidate
664: Checks that a signature generated using
665: .Nm
666: .Fl Y Cm sign
667: has a valid structure.
668: This does not validate if a signature comes from an authorized signer.
669: When testing a signature,
670: .Nm
671: accepts a message on standard input and a signature namespace using
672: .Fl n .
673: A file containing the corresponding signature must also be supplied using the
674: .Fl s
675: flag.
676: Successful testing of the signature is signalled by
677: .Nm
678: returning a zero exit status.
1.166 jmc 679: .It Fl Y Cm sign
1.163 djm 680: Cryptographically sign a file or some data using a SSH key.
681: When signing,
682: .Nm
683: accepts zero or more files to sign on the command-line - if no files
684: are specified then
685: .Nm
686: will sign data presented on standard input.
687: Signatures are written to the path of the input file with
688: .Dq .sig
689: appended, or to standard output if the message to be signed was read from
690: standard input.
691: .Pp
692: The key used for signing is specified using the
693: .Fl f
694: option and may refer to either a private key, or a public key with the private
695: half available via
696: .Xr ssh-agent 1 .
697: An additional signature namespace, used to prevent signature confusion across
698: different domains of use (e.g. file signing vs email signing) must be provided
699: via the
700: .Fl n
701: flag.
702: Namespaces are arbitrary strings, and may include:
703: .Dq file
704: for file signing,
705: .Dq email
706: for email signing.
707: For custom uses, it is recommended to use names following a
708: NAMESPACE@YOUR.DOMAIN pattern to generate unambiguous namespaces.
1.166 jmc 709: .It Fl Y Cm verify
1.163 djm 710: Request to verify a signature generated using
711: .Nm
1.166 jmc 712: .Fl Y Cm sign
1.163 djm 713: as described above.
714: When verifying a signature,
715: .Nm
716: accepts a message on standard input and a signature namespace using
717: .Fl n .
718: A file containing the corresponding signature must also be supplied using the
719: .Fl s
720: flag, along with the identity of the signer using
721: .Fl I
722: and a list of allowed signers via the
723: .Fl f
724: flag.
725: The format of the allowed signers file is documented in the
726: .Sx ALLOWED SIGNERS
727: section below.
728: A file containing revoked keys can be passed using the
729: .Fl r
1.165 jmc 730: flag.
731: The revocation file may be a KRL or a one-per-line list of public keys.
1.163 djm 732: Successful verification by an authorized signer is signalled by
733: .Nm
734: returning a zero exit status.
1.181 jmc 735: .It Fl y
736: This option will read a private
737: OpenSSH format file and print an OpenSSH public key to stdout.
1.212 dtucker 738: .It Fl Z Ar cipher
739: Specifies the cipher to use for encryption when writing an OpenSSH-format
740: private key file.
741: The list of available ciphers may be obtained using
742: .Qq ssh -Q cipher .
743: The default is
744: .Dq aes256-ctr .
1.93 djm 745: .It Fl z Ar serial_number
746: Specifies a serial number to be embedded in the certificate to distinguish
747: this certificate from others from the same CA.
1.156 djm 748: If the
749: .Ar serial_number
750: is prefixed with a
751: .Sq +
752: character, then the serial number will be incremented for each certificate
753: signed on a single command-line.
1.93 djm 754: The default serial number is zero.
1.111 djm 755: .Pp
756: When generating a KRL, the
757: .Fl z
758: flag is used to specify a KRL version number.
1.2 deraadt 759: .El
1.60 djm 760: .Sh MODULI GENERATION
761: .Nm
762: may be used to generate groups for the Diffie-Hellman Group Exchange
763: (DH-GEX) protocol.
764: Generating these groups is a two-step process: first, candidate
765: primes are generated using a fast, but memory intensive process.
766: These candidate primes are then tested for suitability (a CPU-intensive
767: process).
768: .Pp
769: Generation of primes is performed using the
1.184 djm 770: .Fl M Cm generate
1.60 djm 771: option.
772: The desired length of the primes may be specified by the
1.184 djm 773: .Fl O Cm bits
1.60 djm 774: option.
775: For example:
776: .Pp
1.184 djm 777: .Dl # ssh-keygen -M generate -O bits=2048 moduli-2048.candidates
1.60 djm 778: .Pp
779: By default, the search for primes begins at a random point in the
780: desired length range.
781: This may be overridden using the
1.184 djm 782: .Fl O Cm start
1.60 djm 783: option, which specifies a different start point (in hex).
784: .Pp
1.109 dtucker 785: Once a set of candidates have been generated, they must be screened for
1.60 djm 786: suitability.
787: This may be performed using the
1.184 djm 788: .Fl M Cm screen
1.60 djm 789: option.
790: In this mode
791: .Nm
792: will read candidates from standard input (or a file specified using the
793: .Fl f
794: option).
795: For example:
796: .Pp
1.184 djm 797: .Dl # ssh-keygen -M screen -f moduli-2048.candidates moduli-2048
1.60 djm 798: .Pp
799: By default, each candidate will be subjected to 100 primality tests.
800: This may be overridden using the
1.184 djm 801: .Fl O Cm prime-tests
1.60 djm 802: option.
803: The DH generator value will be chosen automatically for the
804: prime under consideration.
805: If a specific generator is desired, it may be requested using the
1.184 djm 806: .Fl O Cm generator
1.60 djm 807: option.
1.66 jmc 808: Valid generator values are 2, 3, and 5.
1.60 djm 809: .Pp
810: Screened DH groups may be installed in
811: .Pa /etc/moduli .
1.213 dtucker 812: It is important that this file contains moduli of a range of bit lengths.
1.184 djm 813: .Pp
814: A number of options are available for moduli generation and screening via the
815: .Fl O
816: flag:
1.186 jmc 817: .Bl -tag -width Ds
1.184 djm 818: .It Ic lines Ns = Ns Ar number
819: Exit after screening the specified number of lines while performing DH
820: candidate screening.
821: .It Ic start-line Ns = Ns Ar line-number
822: Start screening at the specified line number while performing DH candidate
823: screening.
824: .It Ic checkpoint Ns = Ns Ar filename
825: Write the last line processed to the specified file while performing DH
826: candidate screening.
827: This will be used to skip lines in the input file that have already been
828: processed if the job is restarted.
829: .It Ic memory Ns = Ns Ar mbytes
830: Specify the amount of memory to use (in megabytes) when generating
831: candidate moduli for DH-GEX.
832: .It Ic start Ns = Ns Ar hex-value
833: Specify start point (in hex) when generating candidate moduli for DH-GEX.
834: .It Ic generator Ns = Ns Ar value
835: Specify desired generator (in decimal) when testing candidate moduli for DH-GEX.
836: .El
1.84 djm 837: .Sh CERTIFICATES
838: .Nm
839: supports signing of keys to produce certificates that may be used for
840: user or host authentication.
841: Certificates consist of a public key, some identity information, zero or
1.94 jmc 842: more principal (user or host) names and a set of options that
1.84 djm 843: are signed by a Certification Authority (CA) key.
844: Clients or servers may then trust only the CA key and verify its signature
845: on a certificate rather than trusting many user/host keys.
846: Note that OpenSSH certificates are a different, and much simpler, format to
847: the X.509 certificates used in
848: .Xr ssl 8 .
849: .Pp
850: .Nm
851: supports two types of certificates: user and host.
852: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 853: authenticate server hosts to users.
854: To generate a user certificate:
1.84 djm 855: .Pp
856: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
857: .Pp
858: The resultant certificate will be placed in
1.91 djm 859: .Pa /path/to/user_key-cert.pub .
1.84 djm 860: A host certificate requires the
861: .Fl h
862: option:
863: .Pp
864: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
865: .Pp
866: The host certificate will be output to
1.91 djm 867: .Pa /path/to/host_key-cert.pub .
1.98 djm 868: .Pp
869: It is possible to sign using a CA key stored in a PKCS#11 token by
870: providing the token library using
871: .Fl D
872: and identifying the CA key by providing its public half as an argument
873: to
874: .Fl s :
875: .Pp
1.127 naddy 876: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.142 djm 877: .Pp
878: Similarly, it is possible for the CA key to be hosted in a
879: .Xr ssh-agent 1 .
880: This is indicated by the
881: .Fl U
882: flag and, again, the CA key must be identified by its public half.
883: .Pp
884: .Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
1.98 djm 885: .Pp
886: In all cases,
1.84 djm 887: .Ar key_id
888: is a "key identifier" that is logged by the server when the certificate
889: is used for authentication.
890: .Pp
891: Certificates may be limited to be valid for a set of principal (user/host)
892: names.
893: By default, generated certificates are valid for all users or hosts.
894: To generate a certificate for a specified set of principals:
895: .Pp
896: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 897: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 898: .Pp
899: Additional limitations on the validity and use of user certificates may
1.94 jmc 900: be specified through certificate options.
1.93 djm 901: A certificate option may disable features of the SSH session, may be
1.84 djm 902: valid only when presented from particular source addresses or may
903: force the use of a specific command.
1.183 djm 904: .Pp
905: The options that are valid for user certificates are:
906: .Pp
907: .Bl -tag -width Ds -compact
908: .It Ic clear
909: Clear all enabled permissions.
910: This is useful for clearing the default set of permissions so permissions may
911: be added individually.
912: .Pp
913: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
914: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
915: Includes an arbitrary certificate critical option or extension.
916: The specified
917: .Ar name
918: should include a domain suffix, e.g.\&
919: .Dq name@example.com .
920: If
921: .Ar contents
922: is specified then it is included as the contents of the extension/option
923: encoded as a string, otherwise the extension/option is created with no
924: contents (usually indicating a flag).
925: Extensions may be ignored by a client or server that does not recognise them,
926: whereas unknown critical options will cause the certificate to be refused.
927: .Pp
928: .It Ic force-command Ns = Ns Ar command
929: Forces the execution of
930: .Ar command
931: instead of any shell or command specified by the user when
932: the certificate is used for authentication.
933: .Pp
934: .It Ic no-agent-forwarding
935: Disable
936: .Xr ssh-agent 1
937: forwarding (permitted by default).
938: .Pp
939: .It Ic no-port-forwarding
940: Disable port forwarding (permitted by default).
941: .Pp
942: .It Ic no-pty
943: Disable PTY allocation (permitted by default).
944: .Pp
945: .It Ic no-user-rc
946: Disable execution of
947: .Pa ~/.ssh/rc
948: by
949: .Xr sshd 8
950: (permitted by default).
951: .Pp
952: .It Ic no-x11-forwarding
953: Disable X11 forwarding (permitted by default).
954: .Pp
955: .It Ic permit-agent-forwarding
956: Allows
957: .Xr ssh-agent 1
958: forwarding.
959: .Pp
960: .It Ic permit-port-forwarding
961: Allows port forwarding.
962: .Pp
963: .It Ic permit-pty
964: Allows PTY allocation.
965: .Pp
966: .It Ic permit-user-rc
967: Allows execution of
968: .Pa ~/.ssh/rc
969: by
970: .Xr sshd 8 .
971: .Pp
972: .It Ic permit-X11-forwarding
973: Allows X11 forwarding.
974: .Pp
975: .It Ic no-touch-required
1.206 djm 976: Do not require signatures made using this key include demonstration
1.193 naddy 977: of user presence (e.g. by having the user touch the authenticator).
1.192 naddy 978: This option only makes sense for the FIDO authenticator algorithms
1.183 djm 979: .Cm ecdsa-sk
980: and
981: .Cm ed25519-sk .
982: .Pp
983: .It Ic source-address Ns = Ns Ar address_list
984: Restrict the source addresses from which the certificate is considered valid.
985: The
986: .Ar address_list
987: is a comma-separated list of one or more address/netmask pairs in CIDR
988: format.
1.206 djm 989: .Pp
990: .It Ic verify-required
991: Require signatures made using this key indicate that the user was first
992: verified.
993: This option only makes sense for the FIDO authenticator algorithms
994: .Cm ecdsa-sk
995: and
996: .Cm ed25519-sk .
997: Currently PIN authentication is the only supported verification method,
998: but other methods may be supported in the future.
1.183 djm 999: .El
1000: .Pp
1001: At present, no standard options are valid for host keys.
1.84 djm 1002: .Pp
1003: Finally, certificates may be defined with a validity lifetime.
1004: The
1005: .Fl V
1006: option allows specification of certificate start and end times.
1007: A certificate that is presented at a time outside this range will not be
1008: considered valid.
1.210 dtucker 1009: By default, certificates are valid from the
1.110 jmc 1010: .Ux
1011: Epoch to the distant future.
1.84 djm 1012: .Pp
1013: For certificates to be used for user or host authentication, the CA
1014: public key must be trusted by
1015: .Xr sshd 8
1016: or
1017: .Xr ssh 1 .
1.220 jsg 1018: Refer to those manual pages for details.
1.221 ! florian 1019: .Sh FIDO AUTHENTICATOR
! 1020: .Nm
! 1021: is able to to generate FIDO authenticator-backed keys, after which
! 1022: they may be used much like any other key type supported by OpenSSH, so
! 1023: long as the hardware authenticator is attached when the keys are used.
! 1024: FIDO authenticators generally require the user to explicitly authorise
! 1025: operations by touching or tapping them.
! 1026: FIDO keys consist of two parts: a key handle part stored in the
! 1027: private key file on disk, and a per-device private key that is unique
! 1028: to each FIDO authenticator and that cannot be exported from the
! 1029: authenticator hardware.
! 1030: These are combined by the hardware at authentication time to derive
! 1031: the real key that is used to sign authentication challenges.
! 1032: Supported key types are
! 1033: .Cm ecdsa-sk
! 1034: and
! 1035: .Cm ed25519-sk .
! 1036: .Pp
! 1037: The options that are valid for FIDO keys are:
! 1038: .Bl -tag -width Ds
! 1039: .It Cm application
! 1040: Override the default FIDO application/origin string of
! 1041: .Dq ssh: .
! 1042: This may be useful when generating host or domain-specific resident keys.
! 1043: The specified application string must begin with
! 1044: .Dq ssh: .
! 1045: .It Cm challenge Ns = Ns Ar path
! 1046: Specifies a path to a challenge string that will be passed to the
! 1047: FIDO authenticator during key generation.
! 1048: The challenge string may be used as part of an out-of-band
! 1049: protocol for key enrollment
! 1050: (a random challenge is used by default).
! 1051: .It Cm device
! 1052: Explicitly specify a
! 1053: .Xr fido 4
! 1054: device to use, rather than letting the authenticator middleware select one.
! 1055: .It Cm no-touch-required
! 1056: Indicate that the generated private key should not require touch
! 1057: events (user presence) when making signatures.
! 1058: Note that
! 1059: .Xr sshd 8
! 1060: will refuse such signatures by default, unless overridden via
! 1061: an authorized_keys option.
! 1062: .It Cm resident
! 1063: Indicate that the key handle should be stored on the FIDO
! 1064: authenticator itself.
! 1065: This makes it easier to use the authenticator on multiple computers.
! 1066: Resident keys may be supported on FIDO2 authenticators and typically
! 1067: require that a PIN be set on the authenticator prior to generation.
! 1068: Resident keys may be loaded off the authenticator using
! 1069: .Xr ssh-add 1 .
! 1070: Storing both parts of a key on a FIDO authenticator increases the likelihood
! 1071: of an attacker being able to use a stolen authenticator device.
! 1072: .It Cm user
! 1073: A username to be associated with a resident key,
! 1074: overriding the empty default username.
! 1075: Specifying a username may be useful when generating multiple resident keys
! 1076: for the same application name.
! 1077: .It Cm verify-required
! 1078: Indicate that this private key should require user verification for
! 1079: each signature.
! 1080: Not all FIDO authenticators support this option.
! 1081: Currently PIN authentication is the only supported verification method,
! 1082: but other methods may be supported in the future.
! 1083: .It Cm write-attestation Ns = Ns Ar path
! 1084: May be used at key generation time to record the attestation data
! 1085: returned from FIDO authenticators during key generation.
! 1086: This information is potentially sensitive.
! 1087: By default, this information is discarded.
! 1088: .El
1.111 djm 1089: .Sh KEY REVOCATION LISTS
1090: .Nm
1091: is able to manage OpenSSH format Key Revocation Lists (KRLs).
1092: These binary files specify keys or certificates to be revoked using a
1.119 tedu 1093: compact format, taking as little as one bit per certificate if they are being
1.111 djm 1094: revoked by serial number.
1095: .Pp
1096: KRLs may be generated using the
1097: .Fl k
1098: flag.
1.114 jmc 1099: This option reads one or more files from the command line and generates a new
1.111 djm 1100: KRL.
1101: The files may either contain a KRL specification (see below) or public keys,
1102: listed one per line.
1103: Plain public keys are revoked by listing their hash or contents in the KRL and
1104: certificates revoked by serial number or key ID (if the serial is zero or
1105: not available).
1106: .Pp
1107: Revoking keys using a KRL specification offers explicit control over the
1108: types of record used to revoke keys and may be used to directly revoke
1109: certificates by serial number or key ID without having the complete original
1110: certificate on hand.
1111: A KRL specification consists of lines containing one of the following directives
1112: followed by a colon and some directive-specific information.
1113: .Bl -tag -width Ds
1.115 jmc 1114: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 1115: Revokes a certificate with the specified serial number.
1.112 jmc 1116: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 1117: in decimal, hex or octal.
1118: If two serial numbers are specified separated by a hyphen, then the range
1119: of serial numbers including and between each is revoked.
1120: The CA key must have been specified on the
1121: .Nm
1.114 jmc 1122: command line using the
1.111 djm 1123: .Fl s
1124: option.
1125: .It Cm id : Ar key_id
1126: Revokes a certificate with the specified key ID string.
1127: The CA key must have been specified on the
1128: .Nm
1.114 jmc 1129: command line using the
1.111 djm 1130: .Fl s
1131: option.
1132: .It Cm key : Ar public_key
1133: Revokes the specified key.
1.112 jmc 1134: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 1135: .It Cm sha1 : Ar public_key
1.149 djm 1136: Revokes the specified key by including its SHA1 hash in the KRL.
1137: .It Cm sha256 : Ar public_key
1138: Revokes the specified key by including its SHA256 hash in the KRL.
1139: KRLs that revoke keys by SHA256 hash are not supported by OpenSSH versions
1140: prior to 7.9.
1141: .It Cm hash : Ar fingerprint
1.150 djm 1142: Revokes a key using a fingerprint hash, as obtained from a
1.149 djm 1143: .Xr sshd 8
1144: authentication log message or the
1145: .Nm
1146: .Fl l
1147: flag.
1148: Only SHA256 fingerprints are supported here and resultant KRLs are
1149: not supported by OpenSSH versions prior to 7.9.
1.111 djm 1150: .El
1151: .Pp
1152: KRLs may be updated using the
1153: .Fl u
1154: flag in addition to
1155: .Fl k .
1.114 jmc 1156: When this option is specified, keys listed via the command line are merged into
1.111 djm 1157: the KRL, adding to those already there.
1158: .Pp
1159: It is also possible, given a KRL, to test whether it revokes a particular key
1160: (or keys).
1161: The
1162: .Fl Q
1.128 jmc 1163: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 1164: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 1165: then
1166: .Nm
1167: will exit with a non-zero exit status.
1168: A zero exit status will only be returned if no key was revoked.
1.163 djm 1169: .Sh ALLOWED SIGNERS
1170: When verifying signatures,
1171: .Nm
1172: uses a simple list of identities and keys to determine whether a signature
1173: comes from an authorized source.
1174: This "allowed signers" file uses a format patterned after the
1175: AUTHORIZED_KEYS FILE FORMAT described in
1.165 jmc 1176: .Xr sshd 8 .
1.163 djm 1177: Each line of the file contains the following space-separated fields:
1178: principals, options, keytype, base64-encoded key.
1179: Empty lines and lines starting with a
1180: .Ql #
1181: are ignored as comments.
1182: .Pp
1.210 dtucker 1183: The principals field is a pattern-list (see PATTERNS in
1.163 djm 1184: .Xr ssh_config 5 )
1185: consisting of one or more comma-separated USER@DOMAIN identity patterns
1186: that are accepted for signing.
1187: When verifying, the identity presented via the
1.172 jmc 1188: .Fl I
1189: option must match a principals pattern in order for the corresponding key to be
1.163 djm 1190: considered acceptable for verification.
1191: .Pp
1192: The options (if present) consist of comma-separated option specifications.
1193: No spaces are permitted, except within double quotes.
1194: The following option specifications are supported (note that option keywords
1195: are case-insensitive):
1196: .Bl -tag -width Ds
1197: .It Cm cert-authority
1198: Indicates that this key is accepted as a certificate authority (CA) and
1199: that certificates signed by this CA may be accepted for verification.
1.214 djm 1200: .It Cm namespaces Ns = Ns "namespace-list"
1.163 djm 1201: Specifies a pattern-list of namespaces that are accepted for this key.
1.164 djm 1202: If this option is present, the signature namespace embedded in the
1.163 djm 1203: signature object and presented on the verification command-line must
1204: match the specified list before the key will be considered acceptable.
1.214 djm 1205: .It Cm valid-after Ns = Ns "timestamp"
1206: Indicates that the key is valid for use at or after the specified timestamp,
1.215 jmc 1207: which may be a date in YYYYMMDD format or a time in YYYYMMDDHHMM[SS] format.
1.214 djm 1208: .It Cm valid-before Ns = Ns "timestamp"
1209: Indicates that the key is valid for use at or before the specified timestamp.
1.163 djm 1210: .El
1211: .Pp
1212: When verifying signatures made by certificates, the expected principal
1213: name must match both the principals pattern in the allowed signers file and
1214: the principals embedded in the certificate itself.
1215: .Pp
1216: An example allowed signers file:
1217: .Bd -literal -offset 3n
1218: # Comments allowed at start of line
1219: user1@example.com,user2@example.com ssh-rsa AAAAX1...
1220: # A certificate authority, trusted for all principals in a domain.
1221: *@example.com cert-authority ssh-ed25519 AAAB4...
1222: # A key that is accepted only for file signing.
1223: user2@example.com namespaces="file" ssh-ed25519 AAA41...
1224: .Ed
1.173 naddy 1225: .Sh ENVIRONMENT
1226: .Bl -tag -width Ds
1227: .It Ev SSH_SK_PROVIDER
1.201 djm 1228: Specifies a path to a library that will be used when loading any
1229: FIDO authenticator-hosted keys, overriding the default of using
1230: the built-in USB HID support.
1.173 naddy 1231: .El
1.2 deraadt 1232: .Sh FILES
1.100 naddy 1233: .Bl -tag -width Ds -compact
1.68 djm 1234: .It Pa ~/.ssh/id_dsa
1.100 naddy 1235: .It Pa ~/.ssh/id_ecdsa
1.173 naddy 1236: .It Pa ~/.ssh/id_ecdsa_sk
1.118 naddy 1237: .It Pa ~/.ssh/id_ed25519
1.176 naddy 1238: .It Pa ~/.ssh/id_ed25519_sk
1.100 naddy 1239: .It Pa ~/.ssh/id_rsa
1.180 naddy 1240: Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
1241: authenticator-hosted Ed25519 or RSA authentication identity of the user.
1.15 deraadt 1242: This file should not be readable by anyone but the user.
1243: It is possible to
1244: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 1245: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 1246: This file is not automatically accessed by
1247: .Nm
1248: but it is offered as the default file for the private key.
1.46 markus 1249: .Xr ssh 1
1.15 deraadt 1250: will read this file when a login attempt is made.
1.100 naddy 1251: .Pp
1.68 djm 1252: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 1253: .It Pa ~/.ssh/id_ecdsa.pub
1.173 naddy 1254: .It Pa ~/.ssh/id_ecdsa_sk.pub
1.118 naddy 1255: .It Pa ~/.ssh/id_ed25519.pub
1.176 naddy 1256: .It Pa ~/.ssh/id_ed25519_sk.pub
1.68 djm 1257: .It Pa ~/.ssh/id_rsa.pub
1.180 naddy 1258: Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
1259: authenticator-hosted Ed25519 or RSA public key for authentication.
1.15 deraadt 1260: The contents of this file should be added to
1.68 djm 1261: .Pa ~/.ssh/authorized_keys
1.15 deraadt 1262: on all machines
1.49 deraadt 1263: where the user wishes to log in using public key authentication.
1.12 aaron 1264: There is no need to keep the contents of this file secret.
1.100 naddy 1265: .Pp
1.60 djm 1266: .It Pa /etc/moduli
1267: Contains Diffie-Hellman groups used for DH-GEX.
1268: The file format is described in
1269: .Xr moduli 5 .
1.19 aaron 1270: .El
1.2 deraadt 1271: .Sh SEE ALSO
1272: .Xr ssh 1 ,
1273: .Xr ssh-add 1 ,
1.8 ericj 1274: .Xr ssh-agent 1 ,
1.60 djm 1275: .Xr moduli 5 ,
1.30 itojun 1276: .Xr sshd 8
1.37 markus 1277: .Rs
1.73 markus 1278: .%R RFC 4716
1279: .%T "The Secure Shell (SSH) Public Key File Format"
1280: .%D 2006
1.37 markus 1281: .Re
1.59 jmc 1282: .Sh AUTHORS
1283: OpenSSH is a derivative of the original and free
1284: ssh 1.2.12 release by Tatu Ylonen.
1285: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1286: Theo de Raadt and Dug Song
1287: removed many bugs, re-added newer features and
1288: created OpenSSH.
1289: Markus Friedl contributed the support for SSH
1290: protocol versions 1.5 and 2.0.