Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.219
1.219 ! djm 1: .\" $OpenBSD: ssh-keygen.1,v 1.218 2021/11/28 07:15:10 djm Exp $
1.1 deraadt 2: .\"
3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
6: .\"
1.22 deraadt 7: .\" As far as I am concerned, the code I have written for this software
8: .\" can be used freely for any purpose. Any derived versions of this
9: .\" software must be clearly marked as such, and if the derived work is
10: .\" incompatible with the protocol description in the RFC file, it must be
11: .\" called by a name other than "ssh" or "Secure Shell".
12: .\"
13: .\"
1.33 deraadt 14: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
15: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
16: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
1.22 deraadt 17: .\"
18: .\" Redistribution and use in source and binary forms, with or without
19: .\" modification, are permitted provided that the following conditions
20: .\" are met:
21: .\" 1. Redistributions of source code must retain the above copyright
22: .\" notice, this list of conditions and the following disclaimer.
23: .\" 2. Redistributions in binary form must reproduce the above copyright
24: .\" notice, this list of conditions and the following disclaimer in the
25: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 26: .\"
1.22 deraadt 27: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 37: .\"
1.219 ! djm 38: .Dd $Mdocdate: November 28 2021 $
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.
375: Please see the
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.
380: Please see the
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.
1.111 djm 399: .It Fl k
400: Generate a KRL file.
401: In this mode,
402: .Nm
403: will generate a KRL file at the location specified via the
404: .Fl f
1.114 jmc 405: flag that revokes every key or certificate presented on the command line.
1.111 djm 406: Keys/certificates to be revoked may be specified by public key file or
407: using the format described in the
408: .Sx KEY REVOCATION LISTS
409: section.
1.86 djm 410: .It Fl L
1.129 djm 411: Prints the contents of one or more certificates.
1.9 markus 412: .It Fl l
1.77 grunk 413: Show fingerprint of specified public key file.
1.50 markus 414: For RSA and DSA keys
415: .Nm
1.78 jmc 416: tries to find the matching public key file and prints its fingerprint.
417: If combined with
418: .Fl v ,
1.132 jmc 419: a visual ASCII art representation of the key is supplied with the
1.131 djm 420: fingerprint.
1.184 djm 421: .It Fl M Cm generate
422: Generate candidate Diffie-Hellman Group Exchange (DH-GEX) parameters for
423: eventual use by the
424: .Sq diffie-hellman-group-exchange-*
425: key exchange methods.
426: The numbers generated by this operation must be further screened before
427: use.
428: See the
429: .Sx MODULI GENERATION
430: section for more information.
431: .It Fl M Cm screen
432: Screen candidate parameters for Diffie-Hellman Group Exchange.
433: This will accept a list of candidate numbers and test that they are
434: safe (Sophie Germain) primes with acceptable group generators.
435: The results of this operation may be added to the
436: .Pa /etc/moduli
437: file.
438: See the
439: .Sx MODULI GENERATION
440: section for more information.
1.95 djm 441: .It Fl m Ar key_format
1.155 djm 442: Specify a key format for key generation, the
1.95 djm 443: .Fl i
1.155 djm 444: (import),
1.95 djm 445: .Fl e
1.155 djm 446: (export) conversion options, and the
447: .Fl p
448: change passphrase operation.
449: The latter may be used to convert between OpenSSH private key and PEM
450: private key formats.
1.95 djm 451: The supported key formats are:
452: .Dq RFC4716
1.96 jmc 453: (RFC 4716/SSH2 public or private key),
1.95 djm 454: .Dq PKCS8
1.161 djm 455: (PKCS8 public or private key)
1.95 djm 456: or
457: .Dq PEM
458: (PEM public key).
1.161 djm 459: By default OpenSSH will write newly-generated private keys in its own
460: format, but when converting public keys for export the default format is
1.95 djm 461: .Dq RFC4716 .
1.148 djm 462: Setting a format of
463: .Dq PEM
464: when generating or updating a supported private key type will cause the
465: key to be stored in the legacy PEM private key format.
1.66 jmc 466: .It Fl N Ar new_passphrase
467: Provides the new passphrase.
1.84 djm 468: .It Fl n Ar principals
469: Specify one or more principals (user or host names) to be included in
470: a certificate when signing a key.
471: Multiple principals may be specified, separated by commas.
472: Please see the
473: .Sx CERTIFICATES
474: section for details.
1.93 djm 475: .It Fl O Ar option
1.184 djm 476: Specify a key/value option.
477: These are specific to the operation that
478: .Nm
479: has been requested to perform.
480: .Pp
481: When signing certificates, one of the options listed in the
1.183 djm 482: .Sx CERTIFICATES
1.184 djm 483: section may be specified here.
484: .Pp
485: When performing moduli generation or screening, one of the options
486: listed in the
487: .Sx MODULI GENERATION
488: section may be specified.
489: .Pp
1.190 jmc 490: When generating a key that will be hosted on a FIDO authenticator,
491: this flag may be used to specify key-specific options.
492: Those supported at present are:
493: .Bl -tag -width Ds
494: .It Cm application
495: Override the default FIDO application/origin string of
1.189 djm 496: .Dq ssh: .
1.190 jmc 497: This may be useful when generating host or domain-specific resident keys.
1.200 djm 498: The specified application string must begin with
499: .Dq ssh: .
1.199 jmc 500: .It Cm challenge Ns = Ns Ar path
1.198 jmc 501: Specifies a path to a challenge string that will be passed to the
502: FIDO token during key generation.
1.199 jmc 503: The challenge string may be used as part of an out-of-band
504: protocol for key enrollment
505: (a random challenge is used by default).
1.190 jmc 506: .It Cm device
507: Explicitly specify a
1.189 djm 508: .Xr fido 4
509: device to use, rather than letting the token middleware select one.
1.190 jmc 510: .It Cm no-touch-required
511: Indicate that the generated private key should not require touch
1.185 djm 512: events (user presence) when making signatures.
513: Note that
514: .Xr sshd 8
515: will refuse such signatures by default, unless overridden via
516: an authorized_keys option.
1.190 jmc 517: .It Cm resident
518: Indicate that the key should be stored on the FIDO authenticator itself.
1.185 djm 519: Resident keys may be supported on FIDO2 tokens and typically require that
520: a PIN be set on the token prior to generation.
521: Resident keys may be loaded off the token using
522: .Xr ssh-add 1 .
1.190 jmc 523: .It Cm user
524: A username to be associated with a resident key,
1.189 djm 525: overriding the empty default username.
526: Specifying a username may be useful when generating multiple resident keys
527: for the same application name.
1.206 djm 528: .It Cm verify-required
529: Indicate that this private key should require user verification for
530: each signature.
1.208 jmc 531: Not all FIDO tokens support this option.
1.206 djm 532: Currently PIN authentication is the only supported verification method,
533: but other methods may be supported in the future.
1.199 jmc 534: .It Cm write-attestation Ns = Ns Ar path
1.209 djm 535: May be used at key generation time to record the attestation data
1.197 djm 536: returned from FIDO tokens during key generation.
1.209 djm 537: Please note that this information is potentially sensitive.
538: By default, this information is discarded.
1.190 jmc 539: .El
1.185 djm 540: .Pp
1.214 djm 541: When performing signature-related options using the
542: .Fl Y
543: flag, the following options are accepted:
544: .Bl -tag -width Ds
1.219 ! djm 545: .It Cm hashalg Ns = Ns Ar algorithm
! 546: Selects the hash algorithm to use for hashing the message to be signed.
! 547: Valid algorithms are
! 548: .Dq sha256
! 549: and
! 550: .Dq sha512.
! 551: The default is
! 552: .Dq sha512.
1.216 djm 553: .It Cm print-pubkey
554: Print the full public key to standard output after signature verification.
1.214 djm 555: .It Cm verify-time Ns = Ns Ar timestamp
556: Specifies a time to use when validating signatures instead of the current
557: time.
558: The time may be specified as a date in YYYYMMDD format or a time
559: in YYYYMMDDHHMM[SS] format.
560: .El
561: .Pp
1.185 djm 562: The
563: .Fl O
564: option may be specified multiple times.
1.66 jmc 565: .It Fl P Ar passphrase
566: Provides the (old) passphrase.
1.2 deraadt 567: .It Fl p
1.1 deraadt 568: Requests changing the passphrase of a private key file instead of
1.12 aaron 569: creating a new private key.
570: The program will prompt for the file
1.1 deraadt 571: containing the private key, for the old passphrase, and twice for the
572: new passphrase.
1.113 jmc 573: .It Fl Q
574: Test whether keys have been revoked in a KRL.
1.203 djm 575: If the
576: .Fl l
577: option is also specified then the contents of the KRL will be printed.
1.5 aaron 578: .It Fl q
579: Silence
580: .Nm ssh-keygen .
1.152 djm 581: .It Fl R Ar hostname | [hostname]:port
1.151 djm 582: Removes all keys belonging to the specified
1.64 djm 583: .Ar hostname
1.151 djm 584: (with optional port number)
1.65 jmc 585: from a
1.64 djm 586: .Pa known_hosts
587: file.
1.65 jmc 588: This option is useful to delete hashed hosts (see the
1.64 djm 589: .Fl H
590: option above).
1.66 jmc 591: .It Fl r Ar hostname
592: Print the SSHFP fingerprint resource record named
593: .Ar hostname
594: for the specified public key file.
1.84 djm 595: .It Fl s Ar ca_key
596: Certify (sign) a public key using the specified CA key.
597: Please see the
598: .Sx CERTIFICATES
599: section for details.
1.111 djm 600: .Pp
601: When generating a KRL,
602: .Fl s
1.112 jmc 603: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 604: by key ID or serial number.
605: See the
606: .Sx KEY REVOCATION LISTS
607: section for details.
1.175 djm 608: .It Fl t Cm dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa
1.66 jmc 609: Specifies the type of key to create.
610: The possible values are
1.100 naddy 611: .Dq dsa ,
1.118 naddy 612: .Dq ecdsa ,
1.173 naddy 613: .Dq ecdsa-sk ,
1.118 naddy 614: .Dq ed25519 ,
1.175 djm 615: .Dq ed25519-sk ,
1.100 naddy 616: or
1.139 jmc 617: .Dq rsa .
1.159 djm 618: .Pp
619: This flag may also be used to specify the desired signature type when
1.160 jmc 620: signing certificates using an RSA CA key.
1.159 djm 621: The available RSA signature variants are
622: .Dq ssh-rsa
623: (SHA1 signatures, not recommended),
1.160 jmc 624: .Dq rsa-sha2-256 ,
625: and
1.159 djm 626: .Dq rsa-sha2-512
627: (the default).
1.142 djm 628: .It Fl U
629: When used in combination with
630: .Fl s ,
631: this option indicates that a CA key resides in a
632: .Xr ssh-agent 1 .
633: See the
634: .Sx CERTIFICATES
635: section for more information.
1.112 jmc 636: .It Fl u
637: Update a KRL.
638: When specified with
639: .Fl k ,
1.114 jmc 640: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 641: a new KRL being created.
1.84 djm 642: .It Fl V Ar validity_interval
643: Specify a validity interval when signing a certificate.
644: A validity interval may consist of a single time, indicating that the
645: certificate is valid beginning now and expiring at that time, or may consist
646: of two times separated by a colon to indicate an explicit time interval.
1.145 djm 647: .Pp
648: The start time may be specified as the string
649: .Dq always
650: to indicate the certificate has no specified start time,
1.147 djm 651: a date in YYYYMMDD format, a time in YYYYMMDDHHMM[SS] format,
1.145 djm 652: a relative time (to the current time) consisting of a minus sign followed by
653: an interval in the format described in the
1.116 jmc 654: TIME FORMATS section of
1.90 jmc 655: .Xr sshd_config 5 .
1.145 djm 656: .Pp
1.147 djm 657: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMM[SS] time,
1.145 djm 658: a relative time starting with a plus character or the string
659: .Dq forever
1.202 dtucker 660: to indicate that the certificate has no expiry date.
1.84 djm 661: .Pp
662: For example:
663: .Dq +52w1d
664: (valid from now to 52 weeks and one day from now),
665: .Dq -4w:+4w
666: (valid from four weeks ago to four weeks from now),
667: .Dq 20100101123000:20110101123000
668: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
669: .Dq -1d:20110101
1.210 dtucker 670: (valid from yesterday to midnight, January 1st, 2011),
1.145 djm 671: .Dq -1m:forever
672: (valid from one minute ago and never expiring).
1.61 djm 673: .It Fl v
674: Verbose mode.
675: Causes
676: .Nm
677: to print debugging messages about its progress.
678: This is helpful for debugging moduli generation.
679: Multiple
680: .Fl v
681: options increase the verbosity.
682: The maximum is 3.
1.173 naddy 683: .It Fl w Ar provider
1.180 naddy 684: Specifies a path to a library that will be used when creating
685: FIDO authenticator-hosted keys, overriding the default of using
686: the internal USB HID support.
1.196 djm 687: .It Fl Y Cm find-principals
688: Find the principal(s) associated with the public key of a signature,
1.194 djm 689: provided using the
690: .Fl s
691: flag in an authorized signers file provided using the
692: .Fl f
693: flag.
694: The format of the allowed signers file is documented in the
695: .Sx ALLOWED SIGNERS
1.195 jmc 696: section below.
1.217 djm 697: If one or more matching principals are found, they are returned on
698: standard output.
699: .It Fl Y Cm match-principals
700: Find principal matching the principal name provided using the
701: .Fl I
702: flag in the authorized signers file specified using the
703: .Fl f
704: flag.
1.196 djm 705: If one or more matching principals are found, they are returned on
706: standard output.
1.182 jmc 707: .It Fl Y Cm check-novalidate
708: Checks that a signature generated using
709: .Nm
710: .Fl Y Cm sign
711: has a valid structure.
712: This does not validate if a signature comes from an authorized signer.
713: When testing a signature,
714: .Nm
715: accepts a message on standard input and a signature namespace using
716: .Fl n .
717: A file containing the corresponding signature must also be supplied using the
718: .Fl s
719: flag.
720: Successful testing of the signature is signalled by
721: .Nm
722: returning a zero exit status.
1.166 jmc 723: .It Fl Y Cm sign
1.163 djm 724: Cryptographically sign a file or some data using a SSH key.
725: When signing,
726: .Nm
727: accepts zero or more files to sign on the command-line - if no files
728: are specified then
729: .Nm
730: will sign data presented on standard input.
731: Signatures are written to the path of the input file with
732: .Dq .sig
733: appended, or to standard output if the message to be signed was read from
734: standard input.
735: .Pp
736: The key used for signing is specified using the
737: .Fl f
738: option and may refer to either a private key, or a public key with the private
739: half available via
740: .Xr ssh-agent 1 .
741: An additional signature namespace, used to prevent signature confusion across
742: different domains of use (e.g. file signing vs email signing) must be provided
743: via the
744: .Fl n
745: flag.
746: Namespaces are arbitrary strings, and may include:
747: .Dq file
748: for file signing,
749: .Dq email
750: for email signing.
751: For custom uses, it is recommended to use names following a
752: NAMESPACE@YOUR.DOMAIN pattern to generate unambiguous namespaces.
1.166 jmc 753: .It Fl Y Cm verify
1.163 djm 754: Request to verify a signature generated using
755: .Nm
1.166 jmc 756: .Fl Y Cm sign
1.163 djm 757: as described above.
758: When verifying a signature,
759: .Nm
760: accepts a message on standard input and a signature namespace using
761: .Fl n .
762: A file containing the corresponding signature must also be supplied using the
763: .Fl s
764: flag, along with the identity of the signer using
765: .Fl I
766: and a list of allowed signers via the
767: .Fl f
768: flag.
769: The format of the allowed signers file is documented in the
770: .Sx ALLOWED SIGNERS
771: section below.
772: A file containing revoked keys can be passed using the
773: .Fl r
1.165 jmc 774: flag.
775: The revocation file may be a KRL or a one-per-line list of public keys.
1.163 djm 776: Successful verification by an authorized signer is signalled by
777: .Nm
778: returning a zero exit status.
1.181 jmc 779: .It Fl y
780: This option will read a private
781: OpenSSH format file and print an OpenSSH public key to stdout.
1.212 dtucker 782: .It Fl Z Ar cipher
783: Specifies the cipher to use for encryption when writing an OpenSSH-format
784: private key file.
785: The list of available ciphers may be obtained using
786: .Qq ssh -Q cipher .
787: The default is
788: .Dq aes256-ctr .
1.93 djm 789: .It Fl z Ar serial_number
790: Specifies a serial number to be embedded in the certificate to distinguish
791: this certificate from others from the same CA.
1.156 djm 792: If the
793: .Ar serial_number
794: is prefixed with a
795: .Sq +
796: character, then the serial number will be incremented for each certificate
797: signed on a single command-line.
1.93 djm 798: The default serial number is zero.
1.111 djm 799: .Pp
800: When generating a KRL, the
801: .Fl z
802: flag is used to specify a KRL version number.
1.2 deraadt 803: .El
1.60 djm 804: .Sh MODULI GENERATION
805: .Nm
806: may be used to generate groups for the Diffie-Hellman Group Exchange
807: (DH-GEX) protocol.
808: Generating these groups is a two-step process: first, candidate
809: primes are generated using a fast, but memory intensive process.
810: These candidate primes are then tested for suitability (a CPU-intensive
811: process).
812: .Pp
813: Generation of primes is performed using the
1.184 djm 814: .Fl M Cm generate
1.60 djm 815: option.
816: The desired length of the primes may be specified by the
1.184 djm 817: .Fl O Cm bits
1.60 djm 818: option.
819: For example:
820: .Pp
1.184 djm 821: .Dl # ssh-keygen -M generate -O bits=2048 moduli-2048.candidates
1.60 djm 822: .Pp
823: By default, the search for primes begins at a random point in the
824: desired length range.
825: This may be overridden using the
1.184 djm 826: .Fl O Cm start
1.60 djm 827: option, which specifies a different start point (in hex).
828: .Pp
1.109 dtucker 829: Once a set of candidates have been generated, they must be screened for
1.60 djm 830: suitability.
831: This may be performed using the
1.184 djm 832: .Fl M Cm screen
1.60 djm 833: option.
834: In this mode
835: .Nm
836: will read candidates from standard input (or a file specified using the
837: .Fl f
838: option).
839: For example:
840: .Pp
1.184 djm 841: .Dl # ssh-keygen -M screen -f moduli-2048.candidates moduli-2048
1.60 djm 842: .Pp
843: By default, each candidate will be subjected to 100 primality tests.
844: This may be overridden using the
1.184 djm 845: .Fl O Cm prime-tests
1.60 djm 846: option.
847: The DH generator value will be chosen automatically for the
848: prime under consideration.
849: If a specific generator is desired, it may be requested using the
1.184 djm 850: .Fl O Cm generator
1.60 djm 851: option.
1.66 jmc 852: Valid generator values are 2, 3, and 5.
1.60 djm 853: .Pp
854: Screened DH groups may be installed in
855: .Pa /etc/moduli .
1.213 dtucker 856: It is important that this file contains moduli of a range of bit lengths.
1.184 djm 857: .Pp
858: A number of options are available for moduli generation and screening via the
859: .Fl O
860: flag:
1.186 jmc 861: .Bl -tag -width Ds
1.184 djm 862: .It Ic lines Ns = Ns Ar number
863: Exit after screening the specified number of lines while performing DH
864: candidate screening.
865: .It Ic start-line Ns = Ns Ar line-number
866: Start screening at the specified line number while performing DH candidate
867: screening.
868: .It Ic checkpoint Ns = Ns Ar filename
869: Write the last line processed to the specified file while performing DH
870: candidate screening.
871: This will be used to skip lines in the input file that have already been
872: processed if the job is restarted.
873: .It Ic memory Ns = Ns Ar mbytes
874: Specify the amount of memory to use (in megabytes) when generating
875: candidate moduli for DH-GEX.
876: .It Ic start Ns = Ns Ar hex-value
877: Specify start point (in hex) when generating candidate moduli for DH-GEX.
878: .It Ic generator Ns = Ns Ar value
879: Specify desired generator (in decimal) when testing candidate moduli for DH-GEX.
880: .El
1.84 djm 881: .Sh CERTIFICATES
882: .Nm
883: supports signing of keys to produce certificates that may be used for
884: user or host authentication.
885: Certificates consist of a public key, some identity information, zero or
1.94 jmc 886: more principal (user or host) names and a set of options that
1.84 djm 887: are signed by a Certification Authority (CA) key.
888: Clients or servers may then trust only the CA key and verify its signature
889: on a certificate rather than trusting many user/host keys.
890: Note that OpenSSH certificates are a different, and much simpler, format to
891: the X.509 certificates used in
892: .Xr ssl 8 .
893: .Pp
894: .Nm
895: supports two types of certificates: user and host.
896: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 897: authenticate server hosts to users.
898: To generate a user certificate:
1.84 djm 899: .Pp
900: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
901: .Pp
902: The resultant certificate will be placed in
1.91 djm 903: .Pa /path/to/user_key-cert.pub .
1.84 djm 904: A host certificate requires the
905: .Fl h
906: option:
907: .Pp
908: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
909: .Pp
910: The host certificate will be output to
1.91 djm 911: .Pa /path/to/host_key-cert.pub .
1.98 djm 912: .Pp
913: It is possible to sign using a CA key stored in a PKCS#11 token by
914: providing the token library using
915: .Fl D
916: and identifying the CA key by providing its public half as an argument
917: to
918: .Fl s :
919: .Pp
1.127 naddy 920: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.142 djm 921: .Pp
922: Similarly, it is possible for the CA key to be hosted in a
923: .Xr ssh-agent 1 .
924: This is indicated by the
925: .Fl U
926: flag and, again, the CA key must be identified by its public half.
927: .Pp
928: .Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
1.98 djm 929: .Pp
930: In all cases,
1.84 djm 931: .Ar key_id
932: is a "key identifier" that is logged by the server when the certificate
933: is used for authentication.
934: .Pp
935: Certificates may be limited to be valid for a set of principal (user/host)
936: names.
937: By default, generated certificates are valid for all users or hosts.
938: To generate a certificate for a specified set of principals:
939: .Pp
940: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 941: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 942: .Pp
943: Additional limitations on the validity and use of user certificates may
1.94 jmc 944: be specified through certificate options.
1.93 djm 945: A certificate option may disable features of the SSH session, may be
1.84 djm 946: valid only when presented from particular source addresses or may
947: force the use of a specific command.
1.183 djm 948: .Pp
949: The options that are valid for user certificates are:
950: .Pp
951: .Bl -tag -width Ds -compact
952: .It Ic clear
953: Clear all enabled permissions.
954: This is useful for clearing the default set of permissions so permissions may
955: be added individually.
956: .Pp
957: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
958: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
959: Includes an arbitrary certificate critical option or extension.
960: The specified
961: .Ar name
962: should include a domain suffix, e.g.\&
963: .Dq name@example.com .
964: If
965: .Ar contents
966: is specified then it is included as the contents of the extension/option
967: encoded as a string, otherwise the extension/option is created with no
968: contents (usually indicating a flag).
969: Extensions may be ignored by a client or server that does not recognise them,
970: whereas unknown critical options will cause the certificate to be refused.
971: .Pp
972: .It Ic force-command Ns = Ns Ar command
973: Forces the execution of
974: .Ar command
975: instead of any shell or command specified by the user when
976: the certificate is used for authentication.
977: .Pp
978: .It Ic no-agent-forwarding
979: Disable
980: .Xr ssh-agent 1
981: forwarding (permitted by default).
982: .Pp
983: .It Ic no-port-forwarding
984: Disable port forwarding (permitted by default).
985: .Pp
986: .It Ic no-pty
987: Disable PTY allocation (permitted by default).
988: .Pp
989: .It Ic no-user-rc
990: Disable execution of
991: .Pa ~/.ssh/rc
992: by
993: .Xr sshd 8
994: (permitted by default).
995: .Pp
996: .It Ic no-x11-forwarding
997: Disable X11 forwarding (permitted by default).
998: .Pp
999: .It Ic permit-agent-forwarding
1000: Allows
1001: .Xr ssh-agent 1
1002: forwarding.
1003: .Pp
1004: .It Ic permit-port-forwarding
1005: Allows port forwarding.
1006: .Pp
1007: .It Ic permit-pty
1008: Allows PTY allocation.
1009: .Pp
1010: .It Ic permit-user-rc
1011: Allows execution of
1012: .Pa ~/.ssh/rc
1013: by
1014: .Xr sshd 8 .
1015: .Pp
1016: .It Ic permit-X11-forwarding
1017: Allows X11 forwarding.
1018: .Pp
1019: .It Ic no-touch-required
1.206 djm 1020: Do not require signatures made using this key include demonstration
1.193 naddy 1021: of user presence (e.g. by having the user touch the authenticator).
1.192 naddy 1022: This option only makes sense for the FIDO authenticator algorithms
1.183 djm 1023: .Cm ecdsa-sk
1024: and
1025: .Cm ed25519-sk .
1026: .Pp
1027: .It Ic source-address Ns = Ns Ar address_list
1028: Restrict the source addresses from which the certificate is considered valid.
1029: The
1030: .Ar address_list
1031: is a comma-separated list of one or more address/netmask pairs in CIDR
1032: format.
1.206 djm 1033: .Pp
1034: .It Ic verify-required
1035: Require signatures made using this key indicate that the user was first
1036: verified.
1037: This option only makes sense for the FIDO authenticator algorithms
1038: .Cm ecdsa-sk
1039: and
1040: .Cm ed25519-sk .
1041: Currently PIN authentication is the only supported verification method,
1042: but other methods may be supported in the future.
1.183 djm 1043: .El
1044: .Pp
1045: At present, no standard options are valid for host keys.
1.84 djm 1046: .Pp
1047: Finally, certificates may be defined with a validity lifetime.
1048: The
1049: .Fl V
1050: option allows specification of certificate start and end times.
1051: A certificate that is presented at a time outside this range will not be
1052: considered valid.
1.210 dtucker 1053: By default, certificates are valid from the
1.110 jmc 1054: .Ux
1055: Epoch to the distant future.
1.84 djm 1056: .Pp
1057: For certificates to be used for user or host authentication, the CA
1058: public key must be trusted by
1059: .Xr sshd 8
1060: or
1061: .Xr ssh 1 .
1062: Please refer to those manual pages for details.
1.111 djm 1063: .Sh KEY REVOCATION LISTS
1064: .Nm
1065: is able to manage OpenSSH format Key Revocation Lists (KRLs).
1066: These binary files specify keys or certificates to be revoked using a
1.119 tedu 1067: compact format, taking as little as one bit per certificate if they are being
1.111 djm 1068: revoked by serial number.
1069: .Pp
1070: KRLs may be generated using the
1071: .Fl k
1072: flag.
1.114 jmc 1073: This option reads one or more files from the command line and generates a new
1.111 djm 1074: KRL.
1075: The files may either contain a KRL specification (see below) or public keys,
1076: listed one per line.
1077: Plain public keys are revoked by listing their hash or contents in the KRL and
1078: certificates revoked by serial number or key ID (if the serial is zero or
1079: not available).
1080: .Pp
1081: Revoking keys using a KRL specification offers explicit control over the
1082: types of record used to revoke keys and may be used to directly revoke
1083: certificates by serial number or key ID without having the complete original
1084: certificate on hand.
1085: A KRL specification consists of lines containing one of the following directives
1086: followed by a colon and some directive-specific information.
1087: .Bl -tag -width Ds
1.115 jmc 1088: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 1089: Revokes a certificate with the specified serial number.
1.112 jmc 1090: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 1091: in decimal, hex or octal.
1092: If two serial numbers are specified separated by a hyphen, then the range
1093: of serial numbers including and between each is revoked.
1094: The CA key must have been specified on the
1095: .Nm
1.114 jmc 1096: command line using the
1.111 djm 1097: .Fl s
1098: option.
1099: .It Cm id : Ar key_id
1100: Revokes a certificate with the specified key ID string.
1101: The CA key must have been specified on the
1102: .Nm
1.114 jmc 1103: command line using the
1.111 djm 1104: .Fl s
1105: option.
1106: .It Cm key : Ar public_key
1107: Revokes the specified key.
1.112 jmc 1108: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 1109: .It Cm sha1 : Ar public_key
1.149 djm 1110: Revokes the specified key by including its SHA1 hash in the KRL.
1111: .It Cm sha256 : Ar public_key
1112: Revokes the specified key by including its SHA256 hash in the KRL.
1113: KRLs that revoke keys by SHA256 hash are not supported by OpenSSH versions
1114: prior to 7.9.
1115: .It Cm hash : Ar fingerprint
1.150 djm 1116: Revokes a key using a fingerprint hash, as obtained from a
1.149 djm 1117: .Xr sshd 8
1118: authentication log message or the
1119: .Nm
1120: .Fl l
1121: flag.
1122: Only SHA256 fingerprints are supported here and resultant KRLs are
1123: not supported by OpenSSH versions prior to 7.9.
1.111 djm 1124: .El
1125: .Pp
1126: KRLs may be updated using the
1127: .Fl u
1128: flag in addition to
1129: .Fl k .
1.114 jmc 1130: When this option is specified, keys listed via the command line are merged into
1.111 djm 1131: the KRL, adding to those already there.
1132: .Pp
1133: It is also possible, given a KRL, to test whether it revokes a particular key
1134: (or keys).
1135: The
1136: .Fl Q
1.128 jmc 1137: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 1138: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 1139: then
1140: .Nm
1141: will exit with a non-zero exit status.
1142: A zero exit status will only be returned if no key was revoked.
1.163 djm 1143: .Sh ALLOWED SIGNERS
1144: When verifying signatures,
1145: .Nm
1146: uses a simple list of identities and keys to determine whether a signature
1147: comes from an authorized source.
1148: This "allowed signers" file uses a format patterned after the
1149: AUTHORIZED_KEYS FILE FORMAT described in
1.165 jmc 1150: .Xr sshd 8 .
1.163 djm 1151: Each line of the file contains the following space-separated fields:
1152: principals, options, keytype, base64-encoded key.
1153: Empty lines and lines starting with a
1154: .Ql #
1155: are ignored as comments.
1156: .Pp
1.210 dtucker 1157: The principals field is a pattern-list (see PATTERNS in
1.163 djm 1158: .Xr ssh_config 5 )
1159: consisting of one or more comma-separated USER@DOMAIN identity patterns
1160: that are accepted for signing.
1161: When verifying, the identity presented via the
1.172 jmc 1162: .Fl I
1163: option must match a principals pattern in order for the corresponding key to be
1.163 djm 1164: considered acceptable for verification.
1165: .Pp
1166: The options (if present) consist of comma-separated option specifications.
1167: No spaces are permitted, except within double quotes.
1168: The following option specifications are supported (note that option keywords
1169: are case-insensitive):
1170: .Bl -tag -width Ds
1171: .It Cm cert-authority
1172: Indicates that this key is accepted as a certificate authority (CA) and
1173: that certificates signed by this CA may be accepted for verification.
1.214 djm 1174: .It Cm namespaces Ns = Ns "namespace-list"
1.163 djm 1175: Specifies a pattern-list of namespaces that are accepted for this key.
1.164 djm 1176: If this option is present, the signature namespace embedded in the
1.163 djm 1177: signature object and presented on the verification command-line must
1178: match the specified list before the key will be considered acceptable.
1.214 djm 1179: .It Cm valid-after Ns = Ns "timestamp"
1180: Indicates that the key is valid for use at or after the specified timestamp,
1.215 jmc 1181: which may be a date in YYYYMMDD format or a time in YYYYMMDDHHMM[SS] format.
1.214 djm 1182: .It Cm valid-before Ns = Ns "timestamp"
1183: Indicates that the key is valid for use at or before the specified timestamp.
1.163 djm 1184: .El
1185: .Pp
1186: When verifying signatures made by certificates, the expected principal
1187: name must match both the principals pattern in the allowed signers file and
1188: the principals embedded in the certificate itself.
1189: .Pp
1190: An example allowed signers file:
1191: .Bd -literal -offset 3n
1192: # Comments allowed at start of line
1193: user1@example.com,user2@example.com ssh-rsa AAAAX1...
1194: # A certificate authority, trusted for all principals in a domain.
1195: *@example.com cert-authority ssh-ed25519 AAAB4...
1196: # A key that is accepted only for file signing.
1197: user2@example.com namespaces="file" ssh-ed25519 AAA41...
1198: .Ed
1.173 naddy 1199: .Sh ENVIRONMENT
1200: .Bl -tag -width Ds
1201: .It Ev SSH_SK_PROVIDER
1.201 djm 1202: Specifies a path to a library that will be used when loading any
1203: FIDO authenticator-hosted keys, overriding the default of using
1204: the built-in USB HID support.
1.173 naddy 1205: .El
1.2 deraadt 1206: .Sh FILES
1.100 naddy 1207: .Bl -tag -width Ds -compact
1.68 djm 1208: .It Pa ~/.ssh/id_dsa
1.100 naddy 1209: .It Pa ~/.ssh/id_ecdsa
1.173 naddy 1210: .It Pa ~/.ssh/id_ecdsa_sk
1.118 naddy 1211: .It Pa ~/.ssh/id_ed25519
1.176 naddy 1212: .It Pa ~/.ssh/id_ed25519_sk
1.100 naddy 1213: .It Pa ~/.ssh/id_rsa
1.180 naddy 1214: Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
1215: authenticator-hosted Ed25519 or RSA authentication identity of the user.
1.15 deraadt 1216: This file should not be readable by anyone but the user.
1217: It is possible to
1218: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 1219: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 1220: This file is not automatically accessed by
1221: .Nm
1222: but it is offered as the default file for the private key.
1.46 markus 1223: .Xr ssh 1
1.15 deraadt 1224: will read this file when a login attempt is made.
1.100 naddy 1225: .Pp
1.68 djm 1226: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 1227: .It Pa ~/.ssh/id_ecdsa.pub
1.173 naddy 1228: .It Pa ~/.ssh/id_ecdsa_sk.pub
1.118 naddy 1229: .It Pa ~/.ssh/id_ed25519.pub
1.176 naddy 1230: .It Pa ~/.ssh/id_ed25519_sk.pub
1.68 djm 1231: .It Pa ~/.ssh/id_rsa.pub
1.180 naddy 1232: Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
1233: authenticator-hosted Ed25519 or RSA public key for authentication.
1.15 deraadt 1234: The contents of this file should be added to
1.68 djm 1235: .Pa ~/.ssh/authorized_keys
1.15 deraadt 1236: on all machines
1.49 deraadt 1237: where the user wishes to log in using public key authentication.
1.12 aaron 1238: There is no need to keep the contents of this file secret.
1.100 naddy 1239: .Pp
1.60 djm 1240: .It Pa /etc/moduli
1241: Contains Diffie-Hellman groups used for DH-GEX.
1242: The file format is described in
1243: .Xr moduli 5 .
1.19 aaron 1244: .El
1.2 deraadt 1245: .Sh SEE ALSO
1246: .Xr ssh 1 ,
1247: .Xr ssh-add 1 ,
1.8 ericj 1248: .Xr ssh-agent 1 ,
1.60 djm 1249: .Xr moduli 5 ,
1.30 itojun 1250: .Xr sshd 8
1.37 markus 1251: .Rs
1.73 markus 1252: .%R RFC 4716
1253: .%T "The Secure Shell (SSH) Public Key File Format"
1254: .%D 2006
1.37 markus 1255: .Re
1.59 jmc 1256: .Sh AUTHORS
1257: OpenSSH is a derivative of the original and free
1258: ssh 1.2.12 release by Tatu Ylonen.
1259: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1260: Theo de Raadt and Dug Song
1261: removed many bugs, re-added newer features and
1262: created OpenSSH.
1263: Markus Friedl contributed the support for SSH
1264: protocol versions 1.5 and 2.0.