Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.142
1.142 ! djm 1: .\" $OpenBSD: ssh-keygen.1,v 1.141 2017/05/05 10:41:58 naddy 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: .\"
1.142 ! djm 38: .Dd $Mdocdate: May 5 2017 $
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
1.111 djm 129: .Nm ssh-keygen
130: .Fl k
131: .Fl f Ar krl_file
132: .Op Fl u
1.112 jmc 133: .Op Fl s Ar ca_public
134: .Op Fl z Ar version_number
1.111 djm 135: .Ar
136: .Nm ssh-keygen
137: .Fl Q
138: .Fl f Ar krl_file
139: .Ar
1.85 jmc 140: .Ek
1.13 aaron 141: .Sh DESCRIPTION
1.2 deraadt 142: .Nm
1.37 markus 143: generates, manages and converts authentication keys for
1.2 deraadt 144: .Xr ssh 1 .
1.15 deraadt 145: .Nm
1.140 jmc 146: can create keys for use by SSH protocol version 2.
1.130 jmc 147: .Pp
1.58 jmc 148: The type of key to be generated is specified with the
1.25 markus 149: .Fl t
1.52 djm 150: option.
1.70 djm 151: If invoked without any arguments,
152: .Nm
1.141 naddy 153: will generate an RSA key.
1.15 deraadt 154: .Pp
1.60 djm 155: .Nm
156: is also used to generate groups for use in Diffie-Hellman group
157: exchange (DH-GEX).
158: See the
159: .Sx MODULI GENERATION
160: section for details.
161: .Pp
1.111 djm 162: Finally,
163: .Nm
164: can be used to generate and update Key Revocation Lists, and to test whether
1.112 jmc 165: given keys have been revoked by one.
166: See the
1.111 djm 167: .Sx KEY REVOCATION LISTS
168: section for details.
169: .Pp
1.2 deraadt 170: Normally each user wishing to use SSH
1.99 djm 171: with public key authentication runs this once to create the authentication
1.1 deraadt 172: key in
1.118 naddy 173: .Pa ~/.ssh/id_dsa ,
1.99 djm 174: .Pa ~/.ssh/id_ecdsa ,
1.118 naddy 175: .Pa ~/.ssh/id_ed25519
1.15 deraadt 176: or
1.68 djm 177: .Pa ~/.ssh/id_rsa .
1.15 deraadt 178: Additionally, the system administrator may use this to generate host keys,
179: as seen in
180: .Pa /etc/rc .
1.2 deraadt 181: .Pp
1.1 deraadt 182: Normally this program generates the key and asks for a file in which
1.12 aaron 183: to store the private key.
184: The public key is stored in a file with the same name but
1.2 deraadt 185: .Dq .pub
1.12 aaron 186: appended.
187: The program also asks for a passphrase.
188: The passphrase may be empty to indicate no passphrase
1.26 markus 189: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 190: arbitrary length.
1.51 stevesk 191: A passphrase is similar to a password, except it can be a phrase with a
192: series of words, punctuation, numbers, whitespace, or any string of
193: characters you want.
194: Good passphrases are 10-30 characters long, are
1.1 deraadt 195: not simple sentences or otherwise easily guessable (English
1.42 markus 196: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 197: passphrases), and contain a mix of upper and lowercase letters,
198: numbers, and non-alphanumeric characters.
1.12 aaron 199: The passphrase can be changed later by using the
1.2 deraadt 200: .Fl p
1.1 deraadt 201: option.
1.2 deraadt 202: .Pp
1.12 aaron 203: There is no way to recover a lost passphrase.
1.105 djm 204: If the passphrase is lost or forgotten, a new key must be generated
205: and the corresponding public key copied to other machines.
1.2 deraadt 206: .Pp
1.136 djm 207: For keys stored in the newer OpenSSH format,
1.37 markus 208: there is also a comment field in the key file that is only for
1.12 aaron 209: convenience to the user to help identify the key.
210: The comment can tell what the key is for, or whatever is useful.
211: The comment is initialized to
1.2 deraadt 212: .Dq user@host
213: when the key is created, but can be changed using the
214: .Fl c
1.1 deraadt 215: option.
1.2 deraadt 216: .Pp
1.15 deraadt 217: After a key is generated, instructions below detail where the keys
218: should be placed to be activated.
219: .Pp
1.2 deraadt 220: The options are as follows:
221: .Bl -tag -width Ds
1.102 stevesk 222: .It Fl A
1.139 jmc 223: For each of the key types (rsa, dsa, ecdsa and ed25519)
1.118 naddy 224: for which host keys
1.102 stevesk 225: do not exist, generate the host keys with the default key file path,
226: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 227: This is used by
1.102 stevesk 228: .Pa /etc/rc
229: to generate new host keys.
1.117 djm 230: .It Fl a Ar rounds
1.140 jmc 231: When saving a new-format private key (i.e. an ed25519 key or when the
1.117 djm 232: .Fl o
233: flag is set), this option specifies the number of KDF (key derivation function)
234: rounds used.
235: Higher numbers result in slower passphrase verification and increased
236: resistance to brute-force password cracking (should the keys be stolen).
237: .Pp
1.140 jmc 238: When screening DH-GEX candidates (using the
1.60 djm 239: .Fl T
1.117 djm 240: command).
241: This option specifies the number of primality tests to perform.
1.66 jmc 242: .It Fl B
243: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 244: .It Fl b Ar bits
1.12 aaron 245: Specifies the number of bits in the key to create.
1.126 djm 246: For RSA keys, the minimum size is 1024 bits and the default is 2048 bits.
1.69 djm 247: Generally, 2048 bits is considered sufficient.
1.72 dtucker 248: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 249: For ECDSA keys, the
250: .Fl b
1.107 deraadt 251: flag determines the key length by selecting from one of three elliptic
1.106 djm 252: curve sizes: 256, 384 or 521 bits.
253: Attempting to use bit lengths other than these three values for ECDSA keys
254: will fail.
1.123 sobrado 255: Ed25519 keys have a fixed length and the
1.118 naddy 256: .Fl b
257: flag will be ignored.
1.66 jmc 258: .It Fl C Ar comment
259: Provides a new comment.
1.2 deraadt 260: .It Fl c
1.1 deraadt 261: Requests changing the comment in the private and public key files.
1.136 djm 262: This operation is only supported for keys stored in the
1.133 jmc 263: newer OpenSSH format.
1.1 deraadt 264: The program will prompt for the file containing the private keys, for
1.41 stevesk 265: the passphrase if the key has one, and for the new comment.
1.81 markus 266: .It Fl D Ar pkcs11
1.83 markus 267: Download the RSA public keys provided by the PKCS#11 shared library
268: .Ar pkcs11 .
1.98 djm 269: When used in combination with
270: .Fl s ,
271: this option indicates that a CA key resides in a PKCS#11 token (see the
272: .Sx CERTIFICATES
273: section for details).
1.124 djm 274: .It Fl E Ar fingerprint_hash
275: Specifies the hash algorithm used when displaying key fingerprints.
276: Valid options are:
277: .Dq md5
278: and
279: .Dq sha256 .
280: The default is
281: .Dq sha256 .
1.37 markus 282: .It Fl e
1.40 markus 283: This option will read a private or public OpenSSH key file and
1.95 djm 284: print to stdout the key in one of the formats specified by the
285: .Fl m
286: option.
287: The default export format is
288: .Dq RFC4716 .
1.96 jmc 289: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 290: several commercial SSH implementations.
1.66 jmc 291: .It Fl F Ar hostname
292: Search for the specified
293: .Ar hostname
294: in a
295: .Pa known_hosts
296: file, listing any occurrences found.
297: This option is useful to find hashed host names or addresses and may also be
298: used in conjunction with the
299: .Fl H
300: option to print found keys in a hashed format.
301: .It Fl f Ar filename
302: Specifies the filename of the key file.
303: .It Fl G Ar output_file
304: Generate candidate primes for DH-GEX.
305: These primes must be screened for
306: safety (using the
307: .Fl T
308: option) before use.
1.57 jakob 309: .It Fl g
1.62 jakob 310: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 311: .Fl r
1.62 jakob 312: command.
1.66 jmc 313: .It Fl H
314: Hash a
315: .Pa known_hosts
1.67 dtucker 316: file.
317: This replaces all hostnames and addresses with hashed representations
318: within the specified file; the original content is moved to a file with
319: a .old suffix.
1.66 jmc 320: These hashes may be used normally by
321: .Nm ssh
322: and
323: .Nm sshd ,
324: but they do not reveal identifying information should the file's contents
325: be disclosed.
326: This option will not modify existing hashed hostnames and is therefore safe
327: to use on files that mix hashed and non-hashed names.
1.84 djm 328: .It Fl h
329: When signing a key, create a host certificate instead of a user
330: certificate.
331: Please see the
332: .Sx CERTIFICATES
333: section for details.
1.85 jmc 334: .It Fl I Ar certificate_identity
1.84 djm 335: Specify the key identity when signing a public key.
336: Please see the
337: .Sx CERTIFICATES
338: section for details.
1.37 markus 339: .It Fl i
340: This option will read an unencrypted private (or public) key file
1.95 djm 341: in the format specified by the
342: .Fl m
343: option and print an OpenSSH compatible private
1.37 markus 344: (or public) key to stdout.
1.122 jmc 345: This option allows importing keys from other software, including several
346: commercial SSH implementations.
347: The default import format is
348: .Dq RFC4716 .
1.109 dtucker 349: .It Fl J Ar num_lines
350: Exit after screening the specified number of lines
351: while performing DH candidate screening using the
352: .Fl T
353: option.
354: .It Fl j Ar start_line
355: Start screening at the specified line number
356: while performing DH candidate screening using the
357: .Fl T
358: option.
1.108 dtucker 359: .It Fl K Ar checkpt
360: Write the last line processed to the file
361: .Ar checkpt
362: while performing DH candidate screening using the
363: .Fl T
364: option.
365: This will be used to skip lines in the input file that have already been
366: processed if the job is restarted.
1.111 djm 367: .It Fl k
368: Generate a KRL file.
369: In this mode,
370: .Nm
371: will generate a KRL file at the location specified via the
372: .Fl f
1.114 jmc 373: flag that revokes every key or certificate presented on the command line.
1.111 djm 374: Keys/certificates to be revoked may be specified by public key file or
375: using the format described in the
376: .Sx KEY REVOCATION LISTS
377: section.
1.86 djm 378: .It Fl L
1.129 djm 379: Prints the contents of one or more certificates.
1.9 markus 380: .It Fl l
1.77 grunk 381: Show fingerprint of specified public key file.
1.50 markus 382: For RSA and DSA keys
383: .Nm
1.78 jmc 384: tries to find the matching public key file and prints its fingerprint.
385: If combined with
386: .Fl v ,
1.132 jmc 387: a visual ASCII art representation of the key is supplied with the
1.131 djm 388: fingerprint.
1.96 jmc 389: .It Fl M Ar memory
390: Specify the amount of memory to use (in megabytes) when generating
391: candidate moduli for DH-GEX.
1.95 djm 392: .It Fl m Ar key_format
393: Specify a key format for the
394: .Fl i
395: (import) or
396: .Fl e
1.96 jmc 397: (export) conversion options.
1.95 djm 398: The supported key formats are:
399: .Dq RFC4716
1.96 jmc 400: (RFC 4716/SSH2 public or private key),
1.95 djm 401: .Dq PKCS8
402: (PEM PKCS8 public key)
403: or
404: .Dq PEM
405: (PEM public key).
406: The default conversion format is
407: .Dq RFC4716 .
1.66 jmc 408: .It Fl N Ar new_passphrase
409: Provides the new passphrase.
1.84 djm 410: .It Fl n Ar principals
411: Specify one or more principals (user or host names) to be included in
412: a certificate when signing a key.
413: Multiple principals may be specified, separated by commas.
414: Please see the
415: .Sx CERTIFICATES
416: section for details.
1.93 djm 417: .It Fl O Ar option
418: Specify a certificate option when signing a key.
1.84 djm 419: This option may be specified multiple times.
1.137 jmc 420: See also the
1.84 djm 421: .Sx CERTIFICATES
1.137 jmc 422: section for further details.
1.93 djm 423: The options that are valid for user certificates are:
1.137 jmc 424: .Pp
425: .Bl -tag -width Ds -compact
1.89 jmc 426: .It Ic clear
427: Clear all enabled permissions.
428: This is useful for clearing the default set of permissions so permissions may
429: be added individually.
1.137 jmc 430: .Pp
431: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
432: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
433: Includes an arbitrary certificate critical option or extension.
434: The specified
435: .Ar name
436: should include a domain suffix, e.g.\&
437: .Dq name@example.com .
438: If
439: .Ar contents
440: is specified then it is included as the contents of the extension/option
441: encoded as a string, otherwise the extension/option is created with no
442: contents (usually indicating a flag).
443: Extensions may be ignored by a client or server that does not recognise them,
444: whereas unknown critical options will cause the certificate to be refused.
1.138 jmc 445: .Pp
446: At present, no standard options are valid for host keys.
1.137 jmc 447: .Pp
1.89 jmc 448: .It Ic force-command Ns = Ns Ar command
449: Forces the execution of
450: .Ar command
451: instead of any shell or command specified by the user when
452: the certificate is used for authentication.
1.137 jmc 453: .Pp
1.84 djm 454: .It Ic no-agent-forwarding
455: Disable
456: .Xr ssh-agent 1
1.85 jmc 457: forwarding (permitted by default).
1.137 jmc 458: .Pp
1.84 djm 459: .It Ic no-port-forwarding
1.85 jmc 460: Disable port forwarding (permitted by default).
1.137 jmc 461: .Pp
1.84 djm 462: .It Ic no-pty
1.85 jmc 463: Disable PTY allocation (permitted by default).
1.137 jmc 464: .Pp
1.84 djm 465: .It Ic no-user-rc
466: Disable execution of
467: .Pa ~/.ssh/rc
468: by
1.85 jmc 469: .Xr sshd 8
470: (permitted by default).
1.137 jmc 471: .Pp
1.89 jmc 472: .It Ic no-x11-forwarding
473: Disable X11 forwarding (permitted by default).
1.137 jmc 474: .Pp
1.88 djm 475: .It Ic permit-agent-forwarding
476: Allows
477: .Xr ssh-agent 1
478: forwarding.
1.137 jmc 479: .Pp
1.84 djm 480: .It Ic permit-port-forwarding
481: Allows port forwarding.
1.137 jmc 482: .Pp
1.84 djm 483: .It Ic permit-pty
484: Allows PTY allocation.
1.137 jmc 485: .Pp
1.84 djm 486: .It Ic permit-user-rc
487: Allows execution of
488: .Pa ~/.ssh/rc
489: by
490: .Xr sshd 8 .
1.137 jmc 491: .Pp
1.89 jmc 492: .It Ic permit-x11-forwarding
493: Allows X11 forwarding.
1.137 jmc 494: .Pp
1.89 jmc 495: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 496: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 497: The
498: .Ar address_list
499: is a comma-separated list of one or more address/netmask pairs in CIDR
500: format.
501: .El
1.117 djm 502: .It Fl o
503: Causes
504: .Nm
1.130 jmc 505: to save private keys using the new OpenSSH format rather than
1.117 djm 506: the more compatible PEM format.
507: The new format has increased resistance to brute-force password cracking
508: but is not supported by versions of OpenSSH prior to 6.5.
509: Ed25519 keys always use the new private key format.
1.66 jmc 510: .It Fl P Ar passphrase
511: Provides the (old) passphrase.
1.2 deraadt 512: .It Fl p
1.1 deraadt 513: Requests changing the passphrase of a private key file instead of
1.12 aaron 514: creating a new private key.
515: The program will prompt for the file
1.1 deraadt 516: containing the private key, for the old passphrase, and twice for the
517: new passphrase.
1.113 jmc 518: .It Fl Q
519: Test whether keys have been revoked in a KRL.
1.5 aaron 520: .It Fl q
521: Silence
522: .Nm ssh-keygen .
1.64 djm 523: .It Fl R Ar hostname
524: Removes all keys belonging to
525: .Ar hostname
1.65 jmc 526: from a
1.64 djm 527: .Pa known_hosts
528: file.
1.65 jmc 529: This option is useful to delete hashed hosts (see the
1.64 djm 530: .Fl H
531: option above).
1.66 jmc 532: .It Fl r Ar hostname
533: Print the SSHFP fingerprint resource record named
534: .Ar hostname
535: for the specified public key file.
1.60 djm 536: .It Fl S Ar start
537: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 538: .It Fl s Ar ca_key
539: Certify (sign) a public key using the specified CA key.
540: Please see the
541: .Sx CERTIFICATES
542: section for details.
1.111 djm 543: .Pp
544: When generating a KRL,
545: .Fl s
1.112 jmc 546: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 547: by key ID or serial number.
548: See the
549: .Sx KEY REVOCATION LISTS
550: section for details.
1.60 djm 551: .It Fl T Ar output_file
552: Test DH group exchange candidate primes (generated using the
553: .Fl G
554: option) for safety.
1.139 jmc 555: .It Fl t Cm dsa | ecdsa | ed25519 | rsa
1.66 jmc 556: Specifies the type of key to create.
557: The possible values are
1.100 naddy 558: .Dq dsa ,
1.118 naddy 559: .Dq ecdsa ,
560: .Dq ed25519 ,
1.100 naddy 561: or
1.139 jmc 562: .Dq rsa .
1.142 ! djm 563: .It Fl U
! 564: When used in combination with
! 565: .Fl s ,
! 566: this option indicates that a CA key resides in a
! 567: .Xr ssh-agent 1 .
! 568: See the
! 569: .Sx CERTIFICATES
! 570: section for more information.
1.112 jmc 571: .It Fl u
572: Update a KRL.
573: When specified with
574: .Fl k ,
1.114 jmc 575: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 576: a new KRL being created.
1.84 djm 577: .It Fl V Ar validity_interval
578: Specify a validity interval when signing a certificate.
579: A validity interval may consist of a single time, indicating that the
580: certificate is valid beginning now and expiring at that time, or may consist
581: of two times separated by a colon to indicate an explicit time interval.
582: The start time may be specified as a date in YYYYMMDD format, a time
583: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
584: of a minus sign followed by a relative time in the format described in the
1.116 jmc 585: TIME FORMATS section of
1.90 jmc 586: .Xr sshd_config 5 .
1.84 djm 587: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
588: a relative time starting with a plus character.
589: .Pp
590: For example:
591: .Dq +52w1d
592: (valid from now to 52 weeks and one day from now),
593: .Dq -4w:+4w
594: (valid from four weeks ago to four weeks from now),
595: .Dq 20100101123000:20110101123000
596: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
597: .Dq -1d:20110101
598: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 599: .It Fl v
600: Verbose mode.
601: Causes
602: .Nm
603: to print debugging messages about its progress.
604: This is helpful for debugging moduli generation.
605: Multiple
606: .Fl v
607: options increase the verbosity.
608: The maximum is 3.
1.66 jmc 609: .It Fl W Ar generator
610: Specify desired generator when testing candidate moduli for DH-GEX.
611: .It Fl y
612: This option will read a private
613: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 614: .It Fl z Ar serial_number
615: Specifies a serial number to be embedded in the certificate to distinguish
616: this certificate from others from the same CA.
617: The default serial number is zero.
1.111 djm 618: .Pp
619: When generating a KRL, the
620: .Fl z
621: flag is used to specify a KRL version number.
1.2 deraadt 622: .El
1.60 djm 623: .Sh MODULI GENERATION
624: .Nm
625: may be used to generate groups for the Diffie-Hellman Group Exchange
626: (DH-GEX) protocol.
627: Generating these groups is a two-step process: first, candidate
628: primes are generated using a fast, but memory intensive process.
629: These candidate primes are then tested for suitability (a CPU-intensive
630: process).
631: .Pp
632: Generation of primes is performed using the
633: .Fl G
634: option.
635: The desired length of the primes may be specified by the
636: .Fl b
637: option.
638: For example:
639: .Pp
1.66 jmc 640: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 641: .Pp
642: By default, the search for primes begins at a random point in the
643: desired length range.
644: This may be overridden using the
645: .Fl S
646: option, which specifies a different start point (in hex).
647: .Pp
1.109 dtucker 648: Once a set of candidates have been generated, they must be screened for
1.60 djm 649: suitability.
650: This may be performed using the
651: .Fl T
652: option.
653: In this mode
654: .Nm
655: will read candidates from standard input (or a file specified using the
656: .Fl f
657: option).
658: For example:
659: .Pp
1.66 jmc 660: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 661: .Pp
662: By default, each candidate will be subjected to 100 primality tests.
663: This may be overridden using the
664: .Fl a
665: option.
666: The DH generator value will be chosen automatically for the
667: prime under consideration.
668: If a specific generator is desired, it may be requested using the
669: .Fl W
670: option.
1.66 jmc 671: Valid generator values are 2, 3, and 5.
1.60 djm 672: .Pp
673: Screened DH groups may be installed in
674: .Pa /etc/moduli .
675: It is important that this file contains moduli of a range of bit lengths and
676: that both ends of a connection share common moduli.
1.84 djm 677: .Sh CERTIFICATES
678: .Nm
679: supports signing of keys to produce certificates that may be used for
680: user or host authentication.
681: Certificates consist of a public key, some identity information, zero or
1.94 jmc 682: more principal (user or host) names and a set of options that
1.84 djm 683: are signed by a Certification Authority (CA) key.
684: Clients or servers may then trust only the CA key and verify its signature
685: on a certificate rather than trusting many user/host keys.
686: Note that OpenSSH certificates are a different, and much simpler, format to
687: the X.509 certificates used in
688: .Xr ssl 8 .
689: .Pp
690: .Nm
691: supports two types of certificates: user and host.
692: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 693: authenticate server hosts to users.
694: To generate a user certificate:
1.84 djm 695: .Pp
696: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
697: .Pp
698: The resultant certificate will be placed in
1.91 djm 699: .Pa /path/to/user_key-cert.pub .
1.84 djm 700: A host certificate requires the
701: .Fl h
702: option:
703: .Pp
704: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
705: .Pp
706: The host certificate will be output to
1.91 djm 707: .Pa /path/to/host_key-cert.pub .
1.98 djm 708: .Pp
709: It is possible to sign using a CA key stored in a PKCS#11 token by
710: providing the token library using
711: .Fl D
712: and identifying the CA key by providing its public half as an argument
713: to
714: .Fl s :
715: .Pp
1.127 naddy 716: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.142 ! djm 717: .Pp
! 718: Similarly, it is possible for the CA key to be hosted in a
! 719: .Xr ssh-agent 1 .
! 720: This is indicated by the
! 721: .Fl U
! 722: flag and, again, the CA key must be identified by its public half.
! 723: .Pp
! 724: .Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
1.98 djm 725: .Pp
726: In all cases,
1.84 djm 727: .Ar key_id
728: is a "key identifier" that is logged by the server when the certificate
729: is used for authentication.
730: .Pp
731: Certificates may be limited to be valid for a set of principal (user/host)
732: names.
733: By default, generated certificates are valid for all users or hosts.
734: To generate a certificate for a specified set of principals:
735: .Pp
736: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 737: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 738: .Pp
739: Additional limitations on the validity and use of user certificates may
1.94 jmc 740: be specified through certificate options.
1.93 djm 741: A certificate option may disable features of the SSH session, may be
1.84 djm 742: valid only when presented from particular source addresses or may
743: force the use of a specific command.
1.93 djm 744: For a list of valid certificate options, see the documentation for the
1.84 djm 745: .Fl O
746: option above.
747: .Pp
748: Finally, certificates may be defined with a validity lifetime.
749: The
750: .Fl V
751: option allows specification of certificate start and end times.
752: A certificate that is presented at a time outside this range will not be
753: considered valid.
1.110 jmc 754: By default, certificates are valid from
755: .Ux
756: Epoch to the distant future.
1.84 djm 757: .Pp
758: For certificates to be used for user or host authentication, the CA
759: public key must be trusted by
760: .Xr sshd 8
761: or
762: .Xr ssh 1 .
763: Please refer to those manual pages for details.
1.111 djm 764: .Sh KEY REVOCATION LISTS
765: .Nm
766: is able to manage OpenSSH format Key Revocation Lists (KRLs).
767: These binary files specify keys or certificates to be revoked using a
1.119 tedu 768: compact format, taking as little as one bit per certificate if they are being
1.111 djm 769: revoked by serial number.
770: .Pp
771: KRLs may be generated using the
772: .Fl k
773: flag.
1.114 jmc 774: This option reads one or more files from the command line and generates a new
1.111 djm 775: KRL.
776: The files may either contain a KRL specification (see below) or public keys,
777: listed one per line.
778: Plain public keys are revoked by listing their hash or contents in the KRL and
779: certificates revoked by serial number or key ID (if the serial is zero or
780: not available).
781: .Pp
782: Revoking keys using a KRL specification offers explicit control over the
783: types of record used to revoke keys and may be used to directly revoke
784: certificates by serial number or key ID without having the complete original
785: certificate on hand.
786: A KRL specification consists of lines containing one of the following directives
787: followed by a colon and some directive-specific information.
788: .Bl -tag -width Ds
1.115 jmc 789: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 790: Revokes a certificate with the specified serial number.
1.112 jmc 791: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 792: in decimal, hex or octal.
793: If two serial numbers are specified separated by a hyphen, then the range
794: of serial numbers including and between each is revoked.
795: The CA key must have been specified on the
796: .Nm
1.114 jmc 797: command line using the
1.111 djm 798: .Fl s
799: option.
800: .It Cm id : Ar key_id
801: Revokes a certificate with the specified key ID string.
802: The CA key must have been specified on the
803: .Nm
1.114 jmc 804: command line using the
1.111 djm 805: .Fl s
806: option.
807: .It Cm key : Ar public_key
808: Revokes the specified key.
1.112 jmc 809: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 810: .It Cm sha1 : Ar public_key
811: Revokes the specified key by its SHA1 hash.
812: .El
813: .Pp
814: KRLs may be updated using the
815: .Fl u
816: flag in addition to
817: .Fl k .
1.114 jmc 818: When this option is specified, keys listed via the command line are merged into
1.111 djm 819: the KRL, adding to those already there.
820: .Pp
821: It is also possible, given a KRL, to test whether it revokes a particular key
822: (or keys).
823: The
824: .Fl Q
1.128 jmc 825: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 826: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 827: then
828: .Nm
829: will exit with a non-zero exit status.
830: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 831: .Sh FILES
1.100 naddy 832: .Bl -tag -width Ds -compact
1.68 djm 833: .It Pa ~/.ssh/id_dsa
1.100 naddy 834: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 835: .It Pa ~/.ssh/id_ed25519
1.100 naddy 836: .It Pa ~/.ssh/id_rsa
1.141 naddy 837: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 838: authentication identity of the user.
1.15 deraadt 839: This file should not be readable by anyone but the user.
840: It is possible to
841: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 842: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 843: This file is not automatically accessed by
844: .Nm
845: but it is offered as the default file for the private key.
1.46 markus 846: .Xr ssh 1
1.15 deraadt 847: will read this file when a login attempt is made.
1.100 naddy 848: .Pp
1.68 djm 849: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 850: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 851: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 852: .It Pa ~/.ssh/id_rsa.pub
1.141 naddy 853: Contains the DSA, ECDSA, Ed25519 or RSA
1.118 naddy 854: public key for authentication.
1.15 deraadt 855: The contents of this file should be added to
1.68 djm 856: .Pa ~/.ssh/authorized_keys
1.15 deraadt 857: on all machines
1.49 deraadt 858: where the user wishes to log in using public key authentication.
1.12 aaron 859: There is no need to keep the contents of this file secret.
1.100 naddy 860: .Pp
1.60 djm 861: .It Pa /etc/moduli
862: Contains Diffie-Hellman groups used for DH-GEX.
863: The file format is described in
864: .Xr moduli 5 .
1.19 aaron 865: .El
1.2 deraadt 866: .Sh SEE ALSO
867: .Xr ssh 1 ,
868: .Xr ssh-add 1 ,
1.8 ericj 869: .Xr ssh-agent 1 ,
1.60 djm 870: .Xr moduli 5 ,
1.30 itojun 871: .Xr sshd 8
1.37 markus 872: .Rs
1.73 markus 873: .%R RFC 4716
874: .%T "The Secure Shell (SSH) Public Key File Format"
875: .%D 2006
1.37 markus 876: .Re
1.59 jmc 877: .Sh AUTHORS
878: OpenSSH is a derivative of the original and free
879: ssh 1.2.12 release by Tatu Ylonen.
880: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
881: Theo de Raadt and Dug Song
882: removed many bugs, re-added newer features and
883: created OpenSSH.
884: Markus Friedl contributed the support for SSH
885: protocol versions 1.5 and 2.0.
![[BACK]](/icons/back.gif){kind=icon}
Return to ssh-keygen.1 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh