Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.151
1.151 ! djm 1: .\" $OpenBSD: ssh-keygen.1,v 1.150 2018/09/12 06:18:59 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: .\"
1.150 djm 38: .Dd $Mdocdate: September 12 2018 $
1.2 deraadt 39: .Dt SSH-KEYGEN 1
40: .Os
41: .Sh NAME
42: .Nm ssh-keygen
1.37 markus 43: .Nd authentication key generation, management and conversion
1.2 deraadt 44: .Sh SYNOPSIS
1.97 schwarze 45: .Bk -words
1.2 deraadt 46: .Nm ssh-keygen
1.25 markus 47: .Op Fl q
1.2 deraadt 48: .Op Fl b Ar bits
1.139 jmc 49: .Op Fl t Cm dsa | ecdsa | ed25519 | rsa
1.2 deraadt 50: .Op Fl N Ar new_passphrase
51: .Op Fl C Ar comment
1.20 markus 52: .Op Fl f Ar output_keyfile
1.2 deraadt 53: .Nm ssh-keygen
54: .Fl p
55: .Op Fl P Ar old_passphrase
56: .Op Fl N Ar new_passphrase
1.9 markus 57: .Op Fl f Ar keyfile
1.2 deraadt 58: .Nm ssh-keygen
1.37 markus 59: .Fl i
1.95 djm 60: .Op Fl m Ar key_format
1.20 markus 61: .Op Fl f Ar input_keyfile
1.16 deraadt 62: .Nm ssh-keygen
1.37 markus 63: .Fl e
1.95 djm 64: .Op Fl m Ar key_format
1.20 markus 65: .Op Fl f Ar input_keyfile
1.16 deraadt 66: .Nm ssh-keygen
1.17 markus 67: .Fl y
1.20 markus 68: .Op Fl f Ar input_keyfile
1.17 markus 69: .Nm ssh-keygen
1.2 deraadt 70: .Fl c
71: .Op Fl P Ar passphrase
72: .Op Fl C Ar comment
1.9 markus 73: .Op Fl f Ar keyfile
74: .Nm ssh-keygen
75: .Fl l
1.125 naddy 76: .Op Fl v
1.124 djm 77: .Op Fl E Ar fingerprint_hash
1.35 markus 78: .Op Fl f Ar input_keyfile
79: .Nm ssh-keygen
80: .Fl B
1.20 markus 81: .Op Fl f Ar input_keyfile
1.48 jakob 82: .Nm ssh-keygen
1.82 jmc 83: .Fl D Ar pkcs11
1.48 jakob 84: .Nm ssh-keygen
1.64 djm 85: .Fl F Ar hostname
86: .Op Fl f Ar known_hosts_file
1.79 sthen 87: .Op Fl l
1.64 djm 88: .Nm ssh-keygen
89: .Fl H
90: .Op Fl f Ar known_hosts_file
91: .Nm ssh-keygen
92: .Fl R Ar hostname
93: .Op Fl f Ar known_hosts_file
1.57 jakob 94: .Nm ssh-keygen
95: .Fl r Ar hostname
96: .Op Fl f Ar input_keyfile
97: .Op Fl g
1.60 djm 98: .Nm ssh-keygen
99: .Fl G Ar output_file
1.61 djm 100: .Op Fl v
1.60 djm 101: .Op Fl b Ar bits
102: .Op Fl M Ar memory
103: .Op Fl S Ar start_point
104: .Nm ssh-keygen
105: .Fl T Ar output_file
106: .Fl f Ar input_file
1.61 djm 107: .Op Fl v
1.117 djm 108: .Op Fl a Ar rounds
1.109 dtucker 109: .Op Fl J Ar num_lines
110: .Op Fl j Ar start_line
1.108 dtucker 111: .Op Fl K Ar checkpt
1.60 djm 112: .Op Fl W Ar generator
1.84 djm 113: .Nm ssh-keygen
114: .Fl s Ar ca_key
115: .Fl I Ar certificate_identity
116: .Op Fl h
1.142 djm 117: .Op Fl U
118: .Op Fl D Ar pkcs11_provider
1.84 djm 119: .Op Fl n Ar principals
1.93 djm 120: .Op Fl O Ar option
1.84 djm 121: .Op Fl V Ar validity_interval
1.93 djm 122: .Op Fl z Ar serial_number
1.84 djm 123: .Ar
1.86 djm 124: .Nm ssh-keygen
125: .Fl L
126: .Op Fl f Ar input_keyfile
1.102 stevesk 127: .Nm ssh-keygen
128: .Fl A
1.143 djm 129: .Op Fl f Ar prefix_path
1.111 djm 130: .Nm ssh-keygen
131: .Fl k
132: .Fl f Ar krl_file
133: .Op Fl u
1.112 jmc 134: .Op Fl s Ar ca_public
135: .Op Fl z Ar version_number
1.111 djm 136: .Ar
137: .Nm ssh-keygen
138: .Fl Q
139: .Fl f Ar krl_file
140: .Ar
1.85 jmc 141: .Ek
1.13 aaron 142: .Sh DESCRIPTION
1.2 deraadt 143: .Nm
1.37 markus 144: generates, manages and converts authentication keys for
1.2 deraadt 145: .Xr ssh 1 .
1.15 deraadt 146: .Nm
1.140 jmc 147: can create keys for use by SSH protocol version 2.
1.130 jmc 148: .Pp
1.58 jmc 149: The type of key to be generated is specified with the
1.25 markus 150: .Fl t
1.52 djm 151: option.
1.70 djm 152: If invoked without any arguments,
153: .Nm
1.141 naddy 154: will generate an RSA key.
1.15 deraadt 155: .Pp
1.60 djm 156: .Nm
157: is also used to generate groups for use in Diffie-Hellman group
158: exchange (DH-GEX).
159: See the
160: .Sx MODULI GENERATION
161: section for details.
162: .Pp
1.111 djm 163: Finally,
164: .Nm
165: can be used to generate and update Key Revocation Lists, and to test whether
1.112 jmc 166: given keys have been revoked by one.
167: See the
1.111 djm 168: .Sx KEY REVOCATION LISTS
169: section for details.
170: .Pp
1.2 deraadt 171: Normally each user wishing to use SSH
1.99 djm 172: with public key authentication runs this once to create the authentication
1.1 deraadt 173: key in
1.118 naddy 174: .Pa ~/.ssh/id_dsa ,
1.99 djm 175: .Pa ~/.ssh/id_ecdsa ,
1.118 naddy 176: .Pa ~/.ssh/id_ed25519
1.15 deraadt 177: or
1.68 djm 178: .Pa ~/.ssh/id_rsa .
1.15 deraadt 179: Additionally, the system administrator may use this to generate host keys,
180: as seen in
181: .Pa /etc/rc .
1.2 deraadt 182: .Pp
1.1 deraadt 183: Normally this program generates the key and asks for a file in which
1.12 aaron 184: to store the private key.
185: The public key is stored in a file with the same name but
1.2 deraadt 186: .Dq .pub
1.12 aaron 187: appended.
188: The program also asks for a passphrase.
189: The passphrase may be empty to indicate no passphrase
1.26 markus 190: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 191: arbitrary length.
1.51 stevesk 192: A passphrase is similar to a password, except it can be a phrase with a
193: series of words, punctuation, numbers, whitespace, or any string of
194: characters you want.
195: Good passphrases are 10-30 characters long, are
1.1 deraadt 196: not simple sentences or otherwise easily guessable (English
1.42 markus 197: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 198: passphrases), and contain a mix of upper and lowercase letters,
199: numbers, and non-alphanumeric characters.
1.12 aaron 200: The passphrase can be changed later by using the
1.2 deraadt 201: .Fl p
1.1 deraadt 202: option.
1.2 deraadt 203: .Pp
1.12 aaron 204: There is no way to recover a lost passphrase.
1.105 djm 205: If the passphrase is lost or forgotten, a new key must be generated
206: and the corresponding public key copied to other machines.
1.2 deraadt 207: .Pp
1.136 djm 208: For keys stored in the newer OpenSSH format,
1.37 markus 209: there is also a comment field in the key file that is only for
1.12 aaron 210: convenience to the user to help identify the key.
211: The comment can tell what the key is for, or whatever is useful.
212: The comment is initialized to
1.2 deraadt 213: .Dq user@host
214: when the key is created, but can be changed using the
215: .Fl c
1.1 deraadt 216: option.
1.2 deraadt 217: .Pp
1.15 deraadt 218: After a key is generated, instructions below detail where the keys
219: should be placed to be activated.
220: .Pp
1.2 deraadt 221: The options are as follows:
222: .Bl -tag -width Ds
1.102 stevesk 223: .It Fl A
1.139 jmc 224: For each of the key types (rsa, dsa, ecdsa and ed25519)
1.118 naddy 225: for which host keys
1.102 stevesk 226: do not exist, generate the host keys with the default key file path,
227: an empty passphrase, default bits for the key type, and default comment.
1.144 jmc 228: If
1.143 djm 229: .Fl f
1.144 jmc 230: has also been specified, its argument is used as a prefix to the
1.143 djm 231: default path for the resulting host key files.
1.104 jmc 232: This is used by
1.102 stevesk 233: .Pa /etc/rc
234: to generate new host keys.
1.117 djm 235: .It Fl a Ar rounds
1.148 djm 236: When saving a private key this option specifies the number of KDF
237: (key derivation function) rounds used.
1.117 djm 238: Higher numbers result in slower passphrase verification and increased
239: resistance to brute-force password cracking (should the keys be stolen).
240: .Pp
1.140 jmc 241: When screening DH-GEX candidates (using the
1.60 djm 242: .Fl T
1.117 djm 243: command).
244: This option specifies the number of primality tests to perform.
1.66 jmc 245: .It Fl B
246: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 247: .It Fl b Ar bits
1.12 aaron 248: Specifies the number of bits in the key to create.
1.126 djm 249: For RSA keys, the minimum size is 1024 bits and the default is 2048 bits.
1.69 djm 250: Generally, 2048 bits is considered sufficient.
1.72 dtucker 251: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 252: For ECDSA keys, the
253: .Fl b
1.107 deraadt 254: flag determines the key length by selecting from one of three elliptic
1.106 djm 255: curve sizes: 256, 384 or 521 bits.
256: Attempting to use bit lengths other than these three values for ECDSA keys
257: will fail.
1.123 sobrado 258: Ed25519 keys have a fixed length and the
1.118 naddy 259: .Fl b
260: flag will be ignored.
1.66 jmc 261: .It Fl C Ar comment
262: Provides a new comment.
1.2 deraadt 263: .It Fl c
1.1 deraadt 264: Requests changing the comment in the private and public key files.
265: The program will prompt for the file containing the private keys, for
1.41 stevesk 266: the passphrase if the key has one, and for the new comment.
1.81 markus 267: .It Fl D Ar pkcs11
1.83 markus 268: Download the RSA public keys provided by the PKCS#11 shared library
269: .Ar pkcs11 .
1.98 djm 270: When used in combination with
271: .Fl s ,
272: this option indicates that a CA key resides in a PKCS#11 token (see the
273: .Sx CERTIFICATES
274: section for details).
1.124 djm 275: .It Fl E Ar fingerprint_hash
276: Specifies the hash algorithm used when displaying key fingerprints.
277: Valid options are:
278: .Dq md5
279: and
280: .Dq sha256 .
281: The default is
282: .Dq sha256 .
1.37 markus 283: .It Fl e
1.40 markus 284: This option will read a private or public OpenSSH key file and
1.95 djm 285: print to stdout the key in one of the formats specified by the
286: .Fl m
287: option.
288: The default export format is
289: .Dq RFC4716 .
1.96 jmc 290: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 291: several commercial SSH implementations.
1.151 ! djm 292: .It Fl F Ar hostname | [hostname]:port
1.66 jmc 293: Search for the specified
294: .Ar hostname
1.151 ! djm 295: (with optional port number)
1.66 jmc 296: in a
297: .Pa known_hosts
298: file, listing any occurrences found.
299: This option is useful to find hashed host names or addresses and may also be
300: used in conjunction with the
301: .Fl H
302: option to print found keys in a hashed format.
303: .It Fl f Ar filename
304: Specifies the filename of the key file.
305: .It Fl G Ar output_file
306: Generate candidate primes for DH-GEX.
307: These primes must be screened for
308: safety (using the
309: .Fl T
310: option) before use.
1.57 jakob 311: .It Fl g
1.62 jakob 312: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 313: .Fl r
1.62 jakob 314: command.
1.66 jmc 315: .It Fl H
316: Hash a
317: .Pa known_hosts
1.67 dtucker 318: file.
319: This replaces all hostnames and addresses with hashed representations
320: within the specified file; the original content is moved to a file with
321: a .old suffix.
1.66 jmc 322: These hashes may be used normally by
323: .Nm ssh
324: and
325: .Nm sshd ,
326: but they do not reveal identifying information should the file's contents
327: be disclosed.
328: This option will not modify existing hashed hostnames and is therefore safe
329: to use on files that mix hashed and non-hashed names.
1.84 djm 330: .It Fl h
331: When signing a key, create a host certificate instead of a user
332: certificate.
333: Please see the
334: .Sx CERTIFICATES
335: section for details.
1.85 jmc 336: .It Fl I Ar certificate_identity
1.84 djm 337: Specify the key identity when signing a public key.
338: Please see the
339: .Sx CERTIFICATES
340: section for details.
1.37 markus 341: .It Fl i
342: This option will read an unencrypted private (or public) key file
1.95 djm 343: in the format specified by the
344: .Fl m
345: option and print an OpenSSH compatible private
1.37 markus 346: (or public) key to stdout.
1.122 jmc 347: This option allows importing keys from other software, including several
348: commercial SSH implementations.
349: The default import format is
350: .Dq RFC4716 .
1.109 dtucker 351: .It Fl J Ar num_lines
352: Exit after screening the specified number of lines
353: while performing DH candidate screening using the
354: .Fl T
355: option.
356: .It Fl j Ar start_line
357: Start screening at the specified line number
358: while performing DH candidate screening using the
359: .Fl T
360: option.
1.108 dtucker 361: .It Fl K Ar checkpt
362: Write the last line processed to the file
363: .Ar checkpt
364: while performing DH candidate screening using the
365: .Fl T
366: option.
367: This will be used to skip lines in the input file that have already been
368: processed if the job is restarted.
1.111 djm 369: .It Fl k
370: Generate a KRL file.
371: In this mode,
372: .Nm
373: will generate a KRL file at the location specified via the
374: .Fl f
1.114 jmc 375: flag that revokes every key or certificate presented on the command line.
1.111 djm 376: Keys/certificates to be revoked may be specified by public key file or
377: using the format described in the
378: .Sx KEY REVOCATION LISTS
379: section.
1.86 djm 380: .It Fl L
1.129 djm 381: Prints the contents of one or more certificates.
1.9 markus 382: .It Fl l
1.77 grunk 383: Show fingerprint of specified public key file.
1.50 markus 384: For RSA and DSA keys
385: .Nm
1.78 jmc 386: tries to find the matching public key file and prints its fingerprint.
387: If combined with
388: .Fl v ,
1.132 jmc 389: a visual ASCII art representation of the key is supplied with the
1.131 djm 390: fingerprint.
1.96 jmc 391: .It Fl M Ar memory
392: Specify the amount of memory to use (in megabytes) when generating
393: candidate moduli for DH-GEX.
1.95 djm 394: .It Fl m Ar key_format
395: Specify a key format for the
396: .Fl i
397: (import) or
398: .Fl e
1.96 jmc 399: (export) conversion options.
1.95 djm 400: The supported key formats are:
401: .Dq RFC4716
1.96 jmc 402: (RFC 4716/SSH2 public or private key),
1.95 djm 403: .Dq PKCS8
404: (PEM PKCS8 public key)
405: or
406: .Dq PEM
407: (PEM public key).
408: The default conversion format is
409: .Dq RFC4716 .
1.148 djm 410: Setting a format of
411: .Dq PEM
412: when generating or updating a supported private key type will cause the
413: key to be stored in the legacy PEM private key format.
1.66 jmc 414: .It Fl N Ar new_passphrase
415: Provides the new passphrase.
1.84 djm 416: .It Fl n Ar principals
417: Specify one or more principals (user or host names) to be included in
418: a certificate when signing a key.
419: Multiple principals may be specified, separated by commas.
420: Please see the
421: .Sx CERTIFICATES
422: section for details.
1.93 djm 423: .It Fl O Ar option
424: Specify a certificate option when signing a key.
1.84 djm 425: This option may be specified multiple times.
1.137 jmc 426: See also the
1.84 djm 427: .Sx CERTIFICATES
1.137 jmc 428: section for further details.
1.146 djm 429: .Pp
430: At present, no standard options are valid for host keys.
1.93 djm 431: The options that are valid for user certificates are:
1.137 jmc 432: .Pp
433: .Bl -tag -width Ds -compact
1.89 jmc 434: .It Ic clear
435: Clear all enabled permissions.
436: This is useful for clearing the default set of permissions so permissions may
437: be added individually.
1.137 jmc 438: .Pp
439: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
440: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
441: Includes an arbitrary certificate critical option or extension.
442: The specified
443: .Ar name
444: should include a domain suffix, e.g.\&
445: .Dq name@example.com .
446: If
447: .Ar contents
448: is specified then it is included as the contents of the extension/option
449: encoded as a string, otherwise the extension/option is created with no
450: contents (usually indicating a flag).
451: Extensions may be ignored by a client or server that does not recognise them,
452: whereas unknown critical options will cause the certificate to be refused.
1.138 jmc 453: .Pp
1.89 jmc 454: .It Ic force-command Ns = Ns Ar command
455: Forces the execution of
456: .Ar command
457: instead of any shell or command specified by the user when
458: the certificate is used for authentication.
1.137 jmc 459: .Pp
1.84 djm 460: .It Ic no-agent-forwarding
461: Disable
462: .Xr ssh-agent 1
1.85 jmc 463: forwarding (permitted by default).
1.137 jmc 464: .Pp
1.84 djm 465: .It Ic no-port-forwarding
1.85 jmc 466: Disable port forwarding (permitted by default).
1.137 jmc 467: .Pp
1.84 djm 468: .It Ic no-pty
1.85 jmc 469: Disable PTY allocation (permitted by default).
1.137 jmc 470: .Pp
1.84 djm 471: .It Ic no-user-rc
472: Disable execution of
473: .Pa ~/.ssh/rc
474: by
1.85 jmc 475: .Xr sshd 8
476: (permitted by default).
1.137 jmc 477: .Pp
1.89 jmc 478: .It Ic no-x11-forwarding
479: Disable X11 forwarding (permitted by default).
1.137 jmc 480: .Pp
1.88 djm 481: .It Ic permit-agent-forwarding
482: Allows
483: .Xr ssh-agent 1
484: forwarding.
1.137 jmc 485: .Pp
1.84 djm 486: .It Ic permit-port-forwarding
487: Allows port forwarding.
1.137 jmc 488: .Pp
1.84 djm 489: .It Ic permit-pty
490: Allows PTY allocation.
1.137 jmc 491: .Pp
1.84 djm 492: .It Ic permit-user-rc
493: Allows execution of
494: .Pa ~/.ssh/rc
495: by
496: .Xr sshd 8 .
1.137 jmc 497: .Pp
1.146 djm 498: .It Ic permit-X11-forwarding
1.89 jmc 499: Allows X11 forwarding.
1.137 jmc 500: .Pp
1.89 jmc 501: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 502: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 503: The
504: .Ar address_list
505: is a comma-separated list of one or more address/netmask pairs in CIDR
506: format.
507: .El
1.66 jmc 508: .It Fl P Ar passphrase
509: Provides the (old) passphrase.
1.2 deraadt 510: .It Fl p
1.1 deraadt 511: Requests changing the passphrase of a private key file instead of
1.12 aaron 512: creating a new private key.
513: The program will prompt for the file
1.1 deraadt 514: containing the private key, for the old passphrase, and twice for the
515: new passphrase.
1.113 jmc 516: .It Fl Q
517: Test whether keys have been revoked in a KRL.
1.5 aaron 518: .It Fl q
519: Silence
520: .Nm ssh-keygen .
1.151 ! djm 521: .It Fl F Ar hostname | [hostname]:port
! 522: Removes all keys belonging to the specified
1.64 djm 523: .Ar hostname
1.151 ! djm 524: (with optional port number)
1.65 jmc 525: from a
1.64 djm 526: .Pa known_hosts
527: file.
1.65 jmc 528: This option is useful to delete hashed hosts (see the
1.64 djm 529: .Fl H
530: option above).
1.66 jmc 531: .It Fl r Ar hostname
532: Print the SSHFP fingerprint resource record named
533: .Ar hostname
534: for the specified public key file.
1.60 djm 535: .It Fl S Ar start
536: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 537: .It Fl s Ar ca_key
538: Certify (sign) a public key using the specified CA key.
539: Please see the
540: .Sx CERTIFICATES
541: section for details.
1.111 djm 542: .Pp
543: When generating a KRL,
544: .Fl s
1.112 jmc 545: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 546: by key ID or serial number.
547: See the
548: .Sx KEY REVOCATION LISTS
549: section for details.
1.60 djm 550: .It Fl T Ar output_file
551: Test DH group exchange candidate primes (generated using the
552: .Fl G
553: option) for safety.
1.139 jmc 554: .It Fl t Cm dsa | ecdsa | ed25519 | rsa
1.66 jmc 555: Specifies the type of key to create.
556: The possible values are
1.100 naddy 557: .Dq dsa ,
1.118 naddy 558: .Dq ecdsa ,
559: .Dq ed25519 ,
1.100 naddy 560: or
1.139 jmc 561: .Dq rsa .
1.142 djm 562: .It Fl U
563: When used in combination with
564: .Fl s ,
565: this option indicates that a CA key resides in a
566: .Xr ssh-agent 1 .
567: See the
568: .Sx CERTIFICATES
569: section for more information.
1.112 jmc 570: .It Fl u
571: Update a KRL.
572: When specified with
573: .Fl k ,
1.114 jmc 574: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 575: a new KRL being created.
1.84 djm 576: .It Fl V Ar validity_interval
577: Specify a validity interval when signing a certificate.
578: A validity interval may consist of a single time, indicating that the
579: certificate is valid beginning now and expiring at that time, or may consist
580: of two times separated by a colon to indicate an explicit time interval.
1.145 djm 581: .Pp
582: The start time may be specified as the string
583: .Dq always
584: to indicate the certificate has no specified start time,
1.147 djm 585: a date in YYYYMMDD format, a time in YYYYMMDDHHMM[SS] format,
1.145 djm 586: a relative time (to the current time) consisting of a minus sign followed by
587: an interval in the format described in the
1.116 jmc 588: TIME FORMATS section of
1.90 jmc 589: .Xr sshd_config 5 .
1.145 djm 590: .Pp
1.147 djm 591: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMM[SS] time,
1.145 djm 592: a relative time starting with a plus character or the string
593: .Dq forever
594: to indicate that the certificate has no expirty date.
1.84 djm 595: .Pp
596: For example:
597: .Dq +52w1d
598: (valid from now to 52 weeks and one day from now),
599: .Dq -4w:+4w
600: (valid from four weeks ago to four weeks from now),
601: .Dq 20100101123000:20110101123000
602: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
603: .Dq -1d:20110101
604: (valid from yesterday to midnight, January 1st, 2011).
1.145 djm 605: .Dq -1m:forever
606: (valid from one minute ago and never expiring).
1.61 djm 607: .It Fl v
608: Verbose mode.
609: Causes
610: .Nm
611: to print debugging messages about its progress.
612: This is helpful for debugging moduli generation.
613: Multiple
614: .Fl v
615: options increase the verbosity.
616: The maximum is 3.
1.66 jmc 617: .It Fl W Ar generator
618: Specify desired generator when testing candidate moduli for DH-GEX.
619: .It Fl y
620: This option will read a private
621: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 622: .It Fl z Ar serial_number
623: Specifies a serial number to be embedded in the certificate to distinguish
624: this certificate from others from the same CA.
625: The default serial number is zero.
1.111 djm 626: .Pp
627: When generating a KRL, the
628: .Fl z
629: flag is used to specify a KRL version number.
1.2 deraadt 630: .El
1.60 djm 631: .Sh MODULI GENERATION
632: .Nm
633: may be used to generate groups for the Diffie-Hellman Group Exchange
634: (DH-GEX) protocol.
635: Generating these groups is a two-step process: first, candidate
636: primes are generated using a fast, but memory intensive process.
637: These candidate primes are then tested for suitability (a CPU-intensive
638: process).
639: .Pp
640: Generation of primes is performed using the
641: .Fl G
642: option.
643: The desired length of the primes may be specified by the
644: .Fl b
645: option.
646: For example:
647: .Pp
1.66 jmc 648: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 649: .Pp
650: By default, the search for primes begins at a random point in the
651: desired length range.
652: This may be overridden using the
653: .Fl S
654: option, which specifies a different start point (in hex).
655: .Pp
1.109 dtucker 656: Once a set of candidates have been generated, they must be screened for
1.60 djm 657: suitability.
658: This may be performed using the
659: .Fl T
660: option.
661: In this mode
662: .Nm
663: will read candidates from standard input (or a file specified using the
664: .Fl f
665: option).
666: For example:
667: .Pp
1.66 jmc 668: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 669: .Pp
670: By default, each candidate will be subjected to 100 primality tests.
671: This may be overridden using the
672: .Fl a
673: option.
674: The DH generator value will be chosen automatically for the
675: prime under consideration.
676: If a specific generator is desired, it may be requested using the
677: .Fl W
678: option.
1.66 jmc 679: Valid generator values are 2, 3, and 5.
1.60 djm 680: .Pp
681: Screened DH groups may be installed in
682: .Pa /etc/moduli .
683: It is important that this file contains moduli of a range of bit lengths and
684: that both ends of a connection share common moduli.
1.84 djm 685: .Sh CERTIFICATES
686: .Nm
687: supports signing of keys to produce certificates that may be used for
688: user or host authentication.
689: Certificates consist of a public key, some identity information, zero or
1.94 jmc 690: more principal (user or host) names and a set of options that
1.84 djm 691: are signed by a Certification Authority (CA) key.
692: Clients or servers may then trust only the CA key and verify its signature
693: on a certificate rather than trusting many user/host keys.
694: Note that OpenSSH certificates are a different, and much simpler, format to
695: the X.509 certificates used in
696: .Xr ssl 8 .
697: .Pp
698: .Nm
699: supports two types of certificates: user and host.
700: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 701: authenticate server hosts to users.
702: To generate a user certificate:
1.84 djm 703: .Pp
704: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
705: .Pp
706: The resultant certificate will be placed in
1.91 djm 707: .Pa /path/to/user_key-cert.pub .
1.84 djm 708: A host certificate requires the
709: .Fl h
710: option:
711: .Pp
712: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
713: .Pp
714: The host certificate will be output to
1.91 djm 715: .Pa /path/to/host_key-cert.pub .
1.98 djm 716: .Pp
717: It is possible to sign using a CA key stored in a PKCS#11 token by
718: providing the token library using
719: .Fl D
720: and identifying the CA key by providing its public half as an argument
721: to
722: .Fl s :
723: .Pp
1.127 naddy 724: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.142 djm 725: .Pp
726: Similarly, it is possible for the CA key to be hosted in a
727: .Xr ssh-agent 1 .
728: This is indicated by the
729: .Fl U
730: flag and, again, the CA key must be identified by its public half.
731: .Pp
732: .Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
1.98 djm 733: .Pp
734: In all cases,
1.84 djm 735: .Ar key_id
736: is a "key identifier" that is logged by the server when the certificate
737: is used for authentication.
738: .Pp
739: Certificates may be limited to be valid for a set of principal (user/host)
740: names.
741: By default, generated certificates are valid for all users or hosts.
742: To generate a certificate for a specified set of principals:
743: .Pp
744: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 745: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 746: .Pp
747: Additional limitations on the validity and use of user certificates may
1.94 jmc 748: be specified through certificate options.
1.93 djm 749: A certificate option may disable features of the SSH session, may be
1.84 djm 750: valid only when presented from particular source addresses or may
751: force the use of a specific command.
1.93 djm 752: For a list of valid certificate options, see the documentation for the
1.84 djm 753: .Fl O
754: option above.
755: .Pp
756: Finally, certificates may be defined with a validity lifetime.
757: The
758: .Fl V
759: option allows specification of certificate start and end times.
760: A certificate that is presented at a time outside this range will not be
761: considered valid.
1.110 jmc 762: By default, certificates are valid from
763: .Ux
764: Epoch to the distant future.
1.84 djm 765: .Pp
766: For certificates to be used for user or host authentication, the CA
767: public key must be trusted by
768: .Xr sshd 8
769: or
770: .Xr ssh 1 .
771: Please refer to those manual pages for details.
1.111 djm 772: .Sh KEY REVOCATION LISTS
773: .Nm
774: is able to manage OpenSSH format Key Revocation Lists (KRLs).
775: These binary files specify keys or certificates to be revoked using a
1.119 tedu 776: compact format, taking as little as one bit per certificate if they are being
1.111 djm 777: revoked by serial number.
778: .Pp
779: KRLs may be generated using the
780: .Fl k
781: flag.
1.114 jmc 782: This option reads one or more files from the command line and generates a new
1.111 djm 783: KRL.
784: The files may either contain a KRL specification (see below) or public keys,
785: listed one per line.
786: Plain public keys are revoked by listing their hash or contents in the KRL and
787: certificates revoked by serial number or key ID (if the serial is zero or
788: not available).
789: .Pp
790: Revoking keys using a KRL specification offers explicit control over the
791: types of record used to revoke keys and may be used to directly revoke
792: certificates by serial number or key ID without having the complete original
793: certificate on hand.
794: A KRL specification consists of lines containing one of the following directives
795: followed by a colon and some directive-specific information.
796: .Bl -tag -width Ds
1.115 jmc 797: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 798: Revokes a certificate with the specified serial number.
1.112 jmc 799: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 800: in decimal, hex or octal.
801: If two serial numbers are specified separated by a hyphen, then the range
802: of serial numbers including and between each is revoked.
803: The CA key must have been specified on the
804: .Nm
1.114 jmc 805: command line using the
1.111 djm 806: .Fl s
807: option.
808: .It Cm id : Ar key_id
809: Revokes a certificate with the specified key ID string.
810: The CA key must have been specified on the
811: .Nm
1.114 jmc 812: command line using the
1.111 djm 813: .Fl s
814: option.
815: .It Cm key : Ar public_key
816: Revokes the specified key.
1.112 jmc 817: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 818: .It Cm sha1 : Ar public_key
1.149 djm 819: Revokes the specified key by including its SHA1 hash in the KRL.
820: .It Cm sha256 : Ar public_key
821: Revokes the specified key by including its SHA256 hash in the KRL.
822: KRLs that revoke keys by SHA256 hash are not supported by OpenSSH versions
823: prior to 7.9.
824: .It Cm hash : Ar fingerprint
1.150 djm 825: Revokes a key using a fingerprint hash, as obtained from a
1.149 djm 826: .Xr sshd 8
827: authentication log message or the
828: .Nm
829: .Fl l
830: flag.
831: Only SHA256 fingerprints are supported here and resultant KRLs are
832: not supported by OpenSSH versions prior to 7.9.
1.111 djm 833: .El
834: .Pp
835: KRLs may be updated using the
836: .Fl u
837: flag in addition to
838: .Fl k .
1.114 jmc 839: When this option is specified, keys listed via the command line are merged into
1.111 djm 840: the KRL, adding to those already there.
841: .Pp
842: It is also possible, given a KRL, to test whether it revokes a particular key
843: (or keys).
844: The
845: .Fl Q
1.128 jmc 846: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 847: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 848: then
849: .Nm
850: will exit with a non-zero exit status.
851: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 852: .Sh FILES
1.100 naddy 853: .Bl -tag -width Ds -compact
1.68 djm 854: .It Pa ~/.ssh/id_dsa
1.100 naddy 855: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 856: .It Pa ~/.ssh/id_ed25519
1.100 naddy 857: .It Pa ~/.ssh/id_rsa
1.141 naddy 858: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 859: authentication identity of the user.
1.15 deraadt 860: This file should not be readable by anyone but the user.
861: It is possible to
862: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 863: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 864: This file is not automatically accessed by
865: .Nm
866: but it is offered as the default file for the private key.
1.46 markus 867: .Xr ssh 1
1.15 deraadt 868: will read this file when a login attempt is made.
1.100 naddy 869: .Pp
1.68 djm 870: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 871: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 872: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 873: .It Pa ~/.ssh/id_rsa.pub
1.141 naddy 874: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 875: public key for authentication.
1.15 deraadt 876: The contents of this file should be added to
1.68 djm 877: .Pa ~/.ssh/authorized_keys
1.15 deraadt 878: on all machines
1.49 deraadt 879: where the user wishes to log in using public key authentication.
1.12 aaron 880: There is no need to keep the contents of this file secret.
1.100 naddy 881: .Pp
1.60 djm 882: .It Pa /etc/moduli
883: Contains Diffie-Hellman groups used for DH-GEX.
884: The file format is described in
885: .Xr moduli 5 .
1.19 aaron 886: .El
1.2 deraadt 887: .Sh SEE ALSO
888: .Xr ssh 1 ,
889: .Xr ssh-add 1 ,
1.8 ericj 890: .Xr ssh-agent 1 ,
1.60 djm 891: .Xr moduli 5 ,
1.30 itojun 892: .Xr sshd 8
1.37 markus 893: .Rs
1.73 markus 894: .%R RFC 4716
895: .%T "The Secure Shell (SSH) Public Key File Format"
896: .%D 2006
1.37 markus 897: .Re
1.59 jmc 898: .Sh AUTHORS
899: OpenSSH is a derivative of the original and free
900: ssh 1.2.12 release by Tatu Ylonen.
901: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
902: Theo de Raadt and Dug Song
903: removed many bugs, re-added newer features and
904: created OpenSSH.
905: Markus Friedl contributed the support for SSH
906: protocol versions 1.5 and 2.0.
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