Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.148
1.148 ! djm 1: .\" $OpenBSD: ssh-keygen.1,v 1.147 2018/03/12 00:52:01 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: .\"
1.148 ! djm 38: .Dd $Mdocdate: March 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.
1.66 jmc 292: .It Fl F Ar hostname
293: Search for the specified
294: .Ar hostname
295: in a
296: .Pa known_hosts
297: file, listing any occurrences found.
298: This option is useful to find hashed host names or addresses and may also be
299: used in conjunction with the
300: .Fl H
301: option to print found keys in a hashed format.
302: .It Fl f Ar filename
303: Specifies the filename of the key file.
304: .It Fl G Ar output_file
305: Generate candidate primes for DH-GEX.
306: These primes must be screened for
307: safety (using the
308: .Fl T
309: option) before use.
1.57 jakob 310: .It Fl g
1.62 jakob 311: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 312: .Fl r
1.62 jakob 313: command.
1.66 jmc 314: .It Fl H
315: Hash a
316: .Pa known_hosts
1.67 dtucker 317: file.
318: This replaces all hostnames and addresses with hashed representations
319: within the specified file; the original content is moved to a file with
320: a .old suffix.
1.66 jmc 321: These hashes may be used normally by
322: .Nm ssh
323: and
324: .Nm sshd ,
325: but they do not reveal identifying information should the file's contents
326: be disclosed.
327: This option will not modify existing hashed hostnames and is therefore safe
328: to use on files that mix hashed and non-hashed names.
1.84 djm 329: .It Fl h
330: When signing a key, create a host certificate instead of a user
331: certificate.
332: Please see the
333: .Sx CERTIFICATES
334: section for details.
1.85 jmc 335: .It Fl I Ar certificate_identity
1.84 djm 336: Specify the key identity when signing a public key.
337: Please see the
338: .Sx CERTIFICATES
339: section for details.
1.37 markus 340: .It Fl i
341: This option will read an unencrypted private (or public) key file
1.95 djm 342: in the format specified by the
343: .Fl m
344: option and print an OpenSSH compatible private
1.37 markus 345: (or public) key to stdout.
1.122 jmc 346: This option allows importing keys from other software, including several
347: commercial SSH implementations.
348: The default import format is
349: .Dq RFC4716 .
1.109 dtucker 350: .It Fl J Ar num_lines
351: Exit after screening the specified number of lines
352: while performing DH candidate screening using the
353: .Fl T
354: option.
355: .It Fl j Ar start_line
356: Start screening at the specified line number
357: while performing DH candidate screening using the
358: .Fl T
359: option.
1.108 dtucker 360: .It Fl K Ar checkpt
361: Write the last line processed to the file
362: .Ar checkpt
363: while performing DH candidate screening using the
364: .Fl T
365: option.
366: This will be used to skip lines in the input file that have already been
367: processed if the job is restarted.
1.111 djm 368: .It Fl k
369: Generate a KRL file.
370: In this mode,
371: .Nm
372: will generate a KRL file at the location specified via the
373: .Fl f
1.114 jmc 374: flag that revokes every key or certificate presented on the command line.
1.111 djm 375: Keys/certificates to be revoked may be specified by public key file or
376: using the format described in the
377: .Sx KEY REVOCATION LISTS
378: section.
1.86 djm 379: .It Fl L
1.129 djm 380: Prints the contents of one or more certificates.
1.9 markus 381: .It Fl l
1.77 grunk 382: Show fingerprint of specified public key file.
1.50 markus 383: For RSA and DSA keys
384: .Nm
1.78 jmc 385: tries to find the matching public key file and prints its fingerprint.
386: If combined with
387: .Fl v ,
1.132 jmc 388: a visual ASCII art representation of the key is supplied with the
1.131 djm 389: fingerprint.
1.96 jmc 390: .It Fl M Ar memory
391: Specify the amount of memory to use (in megabytes) when generating
392: candidate moduli for DH-GEX.
1.95 djm 393: .It Fl m Ar key_format
394: Specify a key format for the
395: .Fl i
396: (import) or
397: .Fl e
1.96 jmc 398: (export) conversion options.
1.95 djm 399: The supported key formats are:
400: .Dq RFC4716
1.96 jmc 401: (RFC 4716/SSH2 public or private key),
1.95 djm 402: .Dq PKCS8
403: (PEM PKCS8 public key)
404: or
405: .Dq PEM
406: (PEM public key).
407: The default conversion format is
408: .Dq RFC4716 .
1.148 ! djm 409: Setting a format of
! 410: .Dq PEM
! 411: when generating or updating a supported private key type will cause the
! 412: key to be stored in the legacy PEM private key format.
1.66 jmc 413: .It Fl N Ar new_passphrase
414: Provides the new passphrase.
1.84 djm 415: .It Fl n Ar principals
416: Specify one or more principals (user or host names) to be included in
417: a certificate when signing a key.
418: Multiple principals may be specified, separated by commas.
419: Please see the
420: .Sx CERTIFICATES
421: section for details.
1.93 djm 422: .It Fl O Ar option
423: Specify a certificate option when signing a key.
1.84 djm 424: This option may be specified multiple times.
1.137 jmc 425: See also the
1.84 djm 426: .Sx CERTIFICATES
1.137 jmc 427: section for further details.
1.146 djm 428: .Pp
429: At present, no standard options are valid for host keys.
1.93 djm 430: The options that are valid for user certificates are:
1.137 jmc 431: .Pp
432: .Bl -tag -width Ds -compact
1.89 jmc 433: .It Ic clear
434: Clear all enabled permissions.
435: This is useful for clearing the default set of permissions so permissions may
436: be added individually.
1.137 jmc 437: .Pp
438: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
439: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
440: Includes an arbitrary certificate critical option or extension.
441: The specified
442: .Ar name
443: should include a domain suffix, e.g.\&
444: .Dq name@example.com .
445: If
446: .Ar contents
447: is specified then it is included as the contents of the extension/option
448: encoded as a string, otherwise the extension/option is created with no
449: contents (usually indicating a flag).
450: Extensions may be ignored by a client or server that does not recognise them,
451: whereas unknown critical options will cause the certificate to be refused.
1.138 jmc 452: .Pp
1.89 jmc 453: .It Ic force-command Ns = Ns Ar command
454: Forces the execution of
455: .Ar command
456: instead of any shell or command specified by the user when
457: the certificate is used for authentication.
1.137 jmc 458: .Pp
1.84 djm 459: .It Ic no-agent-forwarding
460: Disable
461: .Xr ssh-agent 1
1.85 jmc 462: forwarding (permitted by default).
1.137 jmc 463: .Pp
1.84 djm 464: .It Ic no-port-forwarding
1.85 jmc 465: Disable port forwarding (permitted by default).
1.137 jmc 466: .Pp
1.84 djm 467: .It Ic no-pty
1.85 jmc 468: Disable PTY allocation (permitted by default).
1.137 jmc 469: .Pp
1.84 djm 470: .It Ic no-user-rc
471: Disable execution of
472: .Pa ~/.ssh/rc
473: by
1.85 jmc 474: .Xr sshd 8
475: (permitted by default).
1.137 jmc 476: .Pp
1.89 jmc 477: .It Ic no-x11-forwarding
478: Disable X11 forwarding (permitted by default).
1.137 jmc 479: .Pp
1.88 djm 480: .It Ic permit-agent-forwarding
481: Allows
482: .Xr ssh-agent 1
483: forwarding.
1.137 jmc 484: .Pp
1.84 djm 485: .It Ic permit-port-forwarding
486: Allows port forwarding.
1.137 jmc 487: .Pp
1.84 djm 488: .It Ic permit-pty
489: Allows PTY allocation.
1.137 jmc 490: .Pp
1.84 djm 491: .It Ic permit-user-rc
492: Allows execution of
493: .Pa ~/.ssh/rc
494: by
495: .Xr sshd 8 .
1.137 jmc 496: .Pp
1.146 djm 497: .It Ic permit-X11-forwarding
1.89 jmc 498: Allows X11 forwarding.
1.137 jmc 499: .Pp
1.89 jmc 500: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 501: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 502: The
503: .Ar address_list
504: is a comma-separated list of one or more address/netmask pairs in CIDR
505: format.
506: .El
1.66 jmc 507: .It Fl P Ar passphrase
508: Provides the (old) passphrase.
1.2 deraadt 509: .It Fl p
1.1 deraadt 510: Requests changing the passphrase of a private key file instead of
1.12 aaron 511: creating a new private key.
512: The program will prompt for the file
1.1 deraadt 513: containing the private key, for the old passphrase, and twice for the
514: new passphrase.
1.113 jmc 515: .It Fl Q
516: Test whether keys have been revoked in a KRL.
1.5 aaron 517: .It Fl q
518: Silence
519: .Nm ssh-keygen .
1.64 djm 520: .It Fl R Ar hostname
521: Removes all keys belonging to
522: .Ar hostname
1.65 jmc 523: from a
1.64 djm 524: .Pa known_hosts
525: file.
1.65 jmc 526: This option is useful to delete hashed hosts (see the
1.64 djm 527: .Fl H
528: option above).
1.66 jmc 529: .It Fl r Ar hostname
530: Print the SSHFP fingerprint resource record named
531: .Ar hostname
532: for the specified public key file.
1.60 djm 533: .It Fl S Ar start
534: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 535: .It Fl s Ar ca_key
536: Certify (sign) a public key using the specified CA key.
537: Please see the
538: .Sx CERTIFICATES
539: section for details.
1.111 djm 540: .Pp
541: When generating a KRL,
542: .Fl s
1.112 jmc 543: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 544: by key ID or serial number.
545: See the
546: .Sx KEY REVOCATION LISTS
547: section for details.
1.60 djm 548: .It Fl T Ar output_file
549: Test DH group exchange candidate primes (generated using the
550: .Fl G
551: option) for safety.
1.139 jmc 552: .It Fl t Cm dsa | ecdsa | ed25519 | rsa
1.66 jmc 553: Specifies the type of key to create.
554: The possible values are
1.100 naddy 555: .Dq dsa ,
1.118 naddy 556: .Dq ecdsa ,
557: .Dq ed25519 ,
1.100 naddy 558: or
1.139 jmc 559: .Dq rsa .
1.142 djm 560: .It Fl U
561: When used in combination with
562: .Fl s ,
563: this option indicates that a CA key resides in a
564: .Xr ssh-agent 1 .
565: See the
566: .Sx CERTIFICATES
567: section for more information.
1.112 jmc 568: .It Fl u
569: Update a KRL.
570: When specified with
571: .Fl k ,
1.114 jmc 572: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 573: a new KRL being created.
1.84 djm 574: .It Fl V Ar validity_interval
575: Specify a validity interval when signing a certificate.
576: A validity interval may consist of a single time, indicating that the
577: certificate is valid beginning now and expiring at that time, or may consist
578: of two times separated by a colon to indicate an explicit time interval.
1.145 djm 579: .Pp
580: The start time may be specified as the string
581: .Dq always
582: to indicate the certificate has no specified start time,
1.147 djm 583: a date in YYYYMMDD format, a time in YYYYMMDDHHMM[SS] format,
1.145 djm 584: a relative time (to the current time) consisting of a minus sign followed by
585: an interval in the format described in the
1.116 jmc 586: TIME FORMATS section of
1.90 jmc 587: .Xr sshd_config 5 .
1.145 djm 588: .Pp
1.147 djm 589: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMM[SS] time,
1.145 djm 590: a relative time starting with a plus character or the string
591: .Dq forever
592: to indicate that the certificate has no expirty date.
1.84 djm 593: .Pp
594: For example:
595: .Dq +52w1d
596: (valid from now to 52 weeks and one day from now),
597: .Dq -4w:+4w
598: (valid from four weeks ago to four weeks from now),
599: .Dq 20100101123000:20110101123000
600: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
601: .Dq -1d:20110101
602: (valid from yesterday to midnight, January 1st, 2011).
1.145 djm 603: .Dq -1m:forever
604: (valid from one minute ago and never expiring).
1.61 djm 605: .It Fl v
606: Verbose mode.
607: Causes
608: .Nm
609: to print debugging messages about its progress.
610: This is helpful for debugging moduli generation.
611: Multiple
612: .Fl v
613: options increase the verbosity.
614: The maximum is 3.
1.66 jmc 615: .It Fl W Ar generator
616: Specify desired generator when testing candidate moduli for DH-GEX.
617: .It Fl y
618: This option will read a private
619: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 620: .It Fl z Ar serial_number
621: Specifies a serial number to be embedded in the certificate to distinguish
622: this certificate from others from the same CA.
623: The default serial number is zero.
1.111 djm 624: .Pp
625: When generating a KRL, the
626: .Fl z
627: flag is used to specify a KRL version number.
1.2 deraadt 628: .El
1.60 djm 629: .Sh MODULI GENERATION
630: .Nm
631: may be used to generate groups for the Diffie-Hellman Group Exchange
632: (DH-GEX) protocol.
633: Generating these groups is a two-step process: first, candidate
634: primes are generated using a fast, but memory intensive process.
635: These candidate primes are then tested for suitability (a CPU-intensive
636: process).
637: .Pp
638: Generation of primes is performed using the
639: .Fl G
640: option.
641: The desired length of the primes may be specified by the
642: .Fl b
643: option.
644: For example:
645: .Pp
1.66 jmc 646: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 647: .Pp
648: By default, the search for primes begins at a random point in the
649: desired length range.
650: This may be overridden using the
651: .Fl S
652: option, which specifies a different start point (in hex).
653: .Pp
1.109 dtucker 654: Once a set of candidates have been generated, they must be screened for
1.60 djm 655: suitability.
656: This may be performed using the
657: .Fl T
658: option.
659: In this mode
660: .Nm
661: will read candidates from standard input (or a file specified using the
662: .Fl f
663: option).
664: For example:
665: .Pp
1.66 jmc 666: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 667: .Pp
668: By default, each candidate will be subjected to 100 primality tests.
669: This may be overridden using the
670: .Fl a
671: option.
672: The DH generator value will be chosen automatically for the
673: prime under consideration.
674: If a specific generator is desired, it may be requested using the
675: .Fl W
676: option.
1.66 jmc 677: Valid generator values are 2, 3, and 5.
1.60 djm 678: .Pp
679: Screened DH groups may be installed in
680: .Pa /etc/moduli .
681: It is important that this file contains moduli of a range of bit lengths and
682: that both ends of a connection share common moduli.
1.84 djm 683: .Sh CERTIFICATES
684: .Nm
685: supports signing of keys to produce certificates that may be used for
686: user or host authentication.
687: Certificates consist of a public key, some identity information, zero or
1.94 jmc 688: more principal (user or host) names and a set of options that
1.84 djm 689: are signed by a Certification Authority (CA) key.
690: Clients or servers may then trust only the CA key and verify its signature
691: on a certificate rather than trusting many user/host keys.
692: Note that OpenSSH certificates are a different, and much simpler, format to
693: the X.509 certificates used in
694: .Xr ssl 8 .
695: .Pp
696: .Nm
697: supports two types of certificates: user and host.
698: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 699: authenticate server hosts to users.
700: To generate a user certificate:
1.84 djm 701: .Pp
702: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
703: .Pp
704: The resultant certificate will be placed in
1.91 djm 705: .Pa /path/to/user_key-cert.pub .
1.84 djm 706: A host certificate requires the
707: .Fl h
708: option:
709: .Pp
710: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
711: .Pp
712: The host certificate will be output to
1.91 djm 713: .Pa /path/to/host_key-cert.pub .
1.98 djm 714: .Pp
715: It is possible to sign using a CA key stored in a PKCS#11 token by
716: providing the token library using
717: .Fl D
718: and identifying the CA key by providing its public half as an argument
719: to
720: .Fl s :
721: .Pp
1.127 naddy 722: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.142 djm 723: .Pp
724: Similarly, it is possible for the CA key to be hosted in a
725: .Xr ssh-agent 1 .
726: This is indicated by the
727: .Fl U
728: flag and, again, the CA key must be identified by its public half.
729: .Pp
730: .Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
1.98 djm 731: .Pp
732: In all cases,
1.84 djm 733: .Ar key_id
734: is a "key identifier" that is logged by the server when the certificate
735: is used for authentication.
736: .Pp
737: Certificates may be limited to be valid for a set of principal (user/host)
738: names.
739: By default, generated certificates are valid for all users or hosts.
740: To generate a certificate for a specified set of principals:
741: .Pp
742: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 743: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 744: .Pp
745: Additional limitations on the validity and use of user certificates may
1.94 jmc 746: be specified through certificate options.
1.93 djm 747: A certificate option may disable features of the SSH session, may be
1.84 djm 748: valid only when presented from particular source addresses or may
749: force the use of a specific command.
1.93 djm 750: For a list of valid certificate options, see the documentation for the
1.84 djm 751: .Fl O
752: option above.
753: .Pp
754: Finally, certificates may be defined with a validity lifetime.
755: The
756: .Fl V
757: option allows specification of certificate start and end times.
758: A certificate that is presented at a time outside this range will not be
759: considered valid.
1.110 jmc 760: By default, certificates are valid from
761: .Ux
762: Epoch to the distant future.
1.84 djm 763: .Pp
764: For certificates to be used for user or host authentication, the CA
765: public key must be trusted by
766: .Xr sshd 8
767: or
768: .Xr ssh 1 .
769: Please refer to those manual pages for details.
1.111 djm 770: .Sh KEY REVOCATION LISTS
771: .Nm
772: is able to manage OpenSSH format Key Revocation Lists (KRLs).
773: These binary files specify keys or certificates to be revoked using a
1.119 tedu 774: compact format, taking as little as one bit per certificate if they are being
1.111 djm 775: revoked by serial number.
776: .Pp
777: KRLs may be generated using the
778: .Fl k
779: flag.
1.114 jmc 780: This option reads one or more files from the command line and generates a new
1.111 djm 781: KRL.
782: The files may either contain a KRL specification (see below) or public keys,
783: listed one per line.
784: Plain public keys are revoked by listing their hash or contents in the KRL and
785: certificates revoked by serial number or key ID (if the serial is zero or
786: not available).
787: .Pp
788: Revoking keys using a KRL specification offers explicit control over the
789: types of record used to revoke keys and may be used to directly revoke
790: certificates by serial number or key ID without having the complete original
791: certificate on hand.
792: A KRL specification consists of lines containing one of the following directives
793: followed by a colon and some directive-specific information.
794: .Bl -tag -width Ds
1.115 jmc 795: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 796: Revokes a certificate with the specified serial number.
1.112 jmc 797: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 798: in decimal, hex or octal.
799: If two serial numbers are specified separated by a hyphen, then the range
800: of serial numbers including and between each is revoked.
801: The CA key must have been specified on the
802: .Nm
1.114 jmc 803: command line using the
1.111 djm 804: .Fl s
805: option.
806: .It Cm id : Ar key_id
807: Revokes a certificate with the specified key ID string.
808: The CA key must have been specified on the
809: .Nm
1.114 jmc 810: command line using the
1.111 djm 811: .Fl s
812: option.
813: .It Cm key : Ar public_key
814: Revokes the specified key.
1.112 jmc 815: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 816: .It Cm sha1 : Ar public_key
817: Revokes the specified key by its SHA1 hash.
818: .El
819: .Pp
820: KRLs may be updated using the
821: .Fl u
822: flag in addition to
823: .Fl k .
1.114 jmc 824: When this option is specified, keys listed via the command line are merged into
1.111 djm 825: the KRL, adding to those already there.
826: .Pp
827: It is also possible, given a KRL, to test whether it revokes a particular key
828: (or keys).
829: The
830: .Fl Q
1.128 jmc 831: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 832: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 833: then
834: .Nm
835: will exit with a non-zero exit status.
836: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 837: .Sh FILES
1.100 naddy 838: .Bl -tag -width Ds -compact
1.68 djm 839: .It Pa ~/.ssh/id_dsa
1.100 naddy 840: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 841: .It Pa ~/.ssh/id_ed25519
1.100 naddy 842: .It Pa ~/.ssh/id_rsa
1.141 naddy 843: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 844: authentication identity of the user.
1.15 deraadt 845: This file should not be readable by anyone but the user.
846: It is possible to
847: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 848: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 849: This file is not automatically accessed by
850: .Nm
851: but it is offered as the default file for the private key.
1.46 markus 852: .Xr ssh 1
1.15 deraadt 853: will read this file when a login attempt is made.
1.100 naddy 854: .Pp
1.68 djm 855: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 856: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 857: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 858: .It Pa ~/.ssh/id_rsa.pub
1.141 naddy 859: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 860: public key for authentication.
1.15 deraadt 861: The contents of this file should be added to
1.68 djm 862: .Pa ~/.ssh/authorized_keys
1.15 deraadt 863: on all machines
1.49 deraadt 864: where the user wishes to log in using public key authentication.
1.12 aaron 865: There is no need to keep the contents of this file secret.
1.100 naddy 866: .Pp
1.60 djm 867: .It Pa /etc/moduli
868: Contains Diffie-Hellman groups used for DH-GEX.
869: The file format is described in
870: .Xr moduli 5 .
1.19 aaron 871: .El
1.2 deraadt 872: .Sh SEE ALSO
873: .Xr ssh 1 ,
874: .Xr ssh-add 1 ,
1.8 ericj 875: .Xr ssh-agent 1 ,
1.60 djm 876: .Xr moduli 5 ,
1.30 itojun 877: .Xr sshd 8
1.37 markus 878: .Rs
1.73 markus 879: .%R RFC 4716
880: .%T "The Secure Shell (SSH) Public Key File Format"
881: .%D 2006
1.37 markus 882: .Re
1.59 jmc 883: .Sh AUTHORS
884: OpenSSH is a derivative of the original and free
885: ssh 1.2.12 release by Tatu Ylonen.
886: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
887: Theo de Raadt and Dug Song
888: removed many bugs, re-added newer features and
889: created OpenSSH.
890: Markus Friedl contributed the support for SSH
891: protocol versions 1.5 and 2.0.
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