Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.139
1.139 ! jmc 1: .\" $OpenBSD: ssh-keygen.1,v 1.138 2017/05/02 09:05:58 jmc 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: .\"
1.138 jmc 38: .Dd $Mdocdate: May 2 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
117: .Op Fl n Ar principals
1.93 djm 118: .Op Fl O Ar option
1.84 djm 119: .Op Fl V Ar validity_interval
1.93 djm 120: .Op Fl z Ar serial_number
1.84 djm 121: .Ar
1.86 djm 122: .Nm ssh-keygen
123: .Fl L
124: .Op Fl f Ar input_keyfile
1.102 stevesk 125: .Nm ssh-keygen
126: .Fl A
1.111 djm 127: .Nm ssh-keygen
128: .Fl k
129: .Fl f Ar krl_file
130: .Op Fl u
1.112 jmc 131: .Op Fl s Ar ca_public
132: .Op Fl z Ar version_number
1.111 djm 133: .Ar
134: .Nm ssh-keygen
135: .Fl Q
136: .Fl f Ar krl_file
137: .Ar
1.85 jmc 138: .Ek
1.13 aaron 139: .Sh DESCRIPTION
1.2 deraadt 140: .Nm
1.37 markus 141: generates, manages and converts authentication keys for
1.2 deraadt 142: .Xr ssh 1 .
1.15 deraadt 143: .Nm
1.130 jmc 144: can create keys for use by SSH protocol versions 1 and 2.
145: Protocol 1 should not be used
146: and is only offered to support legacy devices.
147: It suffers from a number of cryptographic weaknesses
148: and doesn't support many of the advanced features available for protocol 2.
149: .Pp
1.58 jmc 150: The type of key to be generated is specified with the
1.25 markus 151: .Fl t
1.52 djm 152: option.
1.70 djm 153: If invoked without any arguments,
154: .Nm
1.71 jmc 155: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 156: .Pp
1.60 djm 157: .Nm
158: is also used to generate groups for use in Diffie-Hellman group
159: exchange (DH-GEX).
160: See the
161: .Sx MODULI GENERATION
162: section for details.
163: .Pp
1.111 djm 164: Finally,
165: .Nm
166: can be used to generate and update Key Revocation Lists, and to test whether
1.112 jmc 167: given keys have been revoked by one.
168: See the
1.111 djm 169: .Sx KEY REVOCATION LISTS
170: section for details.
171: .Pp
1.2 deraadt 172: Normally each user wishing to use SSH
1.99 djm 173: with public key authentication runs this once to create the authentication
1.1 deraadt 174: key in
1.68 djm 175: .Pa ~/.ssh/identity ,
1.118 naddy 176: .Pa ~/.ssh/id_dsa ,
1.99 djm 177: .Pa ~/.ssh/id_ecdsa ,
1.118 naddy 178: .Pa ~/.ssh/id_ed25519
1.15 deraadt 179: or
1.68 djm 180: .Pa ~/.ssh/id_rsa .
1.15 deraadt 181: Additionally, the system administrator may use this to generate host keys,
182: as seen in
183: .Pa /etc/rc .
1.2 deraadt 184: .Pp
1.1 deraadt 185: Normally this program generates the key and asks for a file in which
1.12 aaron 186: to store the private key.
187: The public key is stored in a file with the same name but
1.2 deraadt 188: .Dq .pub
1.12 aaron 189: appended.
190: The program also asks for a passphrase.
191: The passphrase may be empty to indicate no passphrase
1.26 markus 192: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 193: arbitrary length.
1.51 stevesk 194: A passphrase is similar to a password, except it can be a phrase with a
195: series of words, punctuation, numbers, whitespace, or any string of
196: characters you want.
197: Good passphrases are 10-30 characters long, are
1.1 deraadt 198: not simple sentences or otherwise easily guessable (English
1.42 markus 199: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 200: passphrases), and contain a mix of upper and lowercase letters,
201: numbers, and non-alphanumeric characters.
1.12 aaron 202: The passphrase can be changed later by using the
1.2 deraadt 203: .Fl p
1.1 deraadt 204: option.
1.2 deraadt 205: .Pp
1.12 aaron 206: There is no way to recover a lost passphrase.
1.105 djm 207: If the passphrase is lost or forgotten, a new key must be generated
208: and the corresponding public key copied to other machines.
1.2 deraadt 209: .Pp
1.136 djm 210: For keys stored in the newer OpenSSH format,
1.37 markus 211: there is also a comment field in the key file that is only for
1.12 aaron 212: convenience to the user to help identify the key.
213: The comment can tell what the key is for, or whatever is useful.
214: The comment is initialized to
1.2 deraadt 215: .Dq user@host
216: when the key is created, but can be changed using the
217: .Fl c
1.1 deraadt 218: option.
1.2 deraadt 219: .Pp
1.15 deraadt 220: After a key is generated, instructions below detail where the keys
221: should be placed to be activated.
222: .Pp
1.2 deraadt 223: The options are as follows:
224: .Bl -tag -width Ds
1.102 stevesk 225: .It Fl A
1.139 ! jmc 226: For each of the key types (rsa, dsa, ecdsa and ed25519)
1.118 naddy 227: for which host keys
1.102 stevesk 228: do not exist, generate the host keys with the default key file path,
229: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 230: This is used by
1.102 stevesk 231: .Pa /etc/rc
232: to generate new host keys.
1.117 djm 233: .It Fl a Ar rounds
234: When saving a new-format private key (i.e. an ed25519 key or any SSH protocol
235: 2 key when the
236: .Fl o
237: flag is set), this option specifies the number of KDF (key derivation function)
238: rounds used.
239: Higher numbers result in slower passphrase verification and increased
240: resistance to brute-force password cracking (should the keys be stolen).
241: .Pp
242: When screening DH-GEX candidates (
243: using the
1.60 djm 244: .Fl T
1.117 djm 245: command).
246: This option specifies the number of primality tests to perform.
1.66 jmc 247: .It Fl B
248: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 249: .It Fl b Ar bits
1.12 aaron 250: Specifies the number of bits in the key to create.
1.126 djm 251: For RSA keys, the minimum size is 1024 bits and the default is 2048 bits.
1.69 djm 252: Generally, 2048 bits is considered sufficient.
1.72 dtucker 253: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 254: For ECDSA keys, the
255: .Fl b
1.107 deraadt 256: flag determines the key length by selecting from one of three elliptic
1.106 djm 257: curve sizes: 256, 384 or 521 bits.
258: Attempting to use bit lengths other than these three values for ECDSA keys
259: will fail.
1.123 sobrado 260: Ed25519 keys have a fixed length and the
1.118 naddy 261: .Fl b
262: flag will be ignored.
1.66 jmc 263: .It Fl C Ar comment
264: Provides a new comment.
1.2 deraadt 265: .It Fl c
1.1 deraadt 266: Requests changing the comment in the private and public key files.
1.136 djm 267: This operation is only supported for keys stored in the
1.133 jmc 268: newer OpenSSH format.
1.1 deraadt 269: The program will prompt for the file containing the private keys, for
1.41 stevesk 270: the passphrase if the key has one, and for the new comment.
1.81 markus 271: .It Fl D Ar pkcs11
1.83 markus 272: Download the RSA public keys provided by the PKCS#11 shared library
273: .Ar pkcs11 .
1.98 djm 274: When used in combination with
275: .Fl s ,
276: this option indicates that a CA key resides in a PKCS#11 token (see the
277: .Sx CERTIFICATES
278: section for details).
1.124 djm 279: .It Fl E Ar fingerprint_hash
280: Specifies the hash algorithm used when displaying key fingerprints.
281: Valid options are:
282: .Dq md5
283: and
284: .Dq sha256 .
285: The default is
286: .Dq sha256 .
1.37 markus 287: .It Fl e
1.40 markus 288: This option will read a private or public OpenSSH key file and
1.95 djm 289: print to stdout the key in one of the formats specified by the
290: .Fl m
291: option.
292: The default export format is
293: .Dq RFC4716 .
1.96 jmc 294: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 295: several commercial SSH implementations.
1.66 jmc 296: .It Fl F Ar hostname
297: Search for the specified
298: .Ar hostname
299: in a
300: .Pa known_hosts
301: file, listing any occurrences found.
302: This option is useful to find hashed host names or addresses and may also be
303: used in conjunction with the
304: .Fl H
305: option to print found keys in a hashed format.
306: .It Fl f Ar filename
307: Specifies the filename of the key file.
308: .It Fl G Ar output_file
309: Generate candidate primes for DH-GEX.
310: These primes must be screened for
311: safety (using the
312: .Fl T
313: option) before use.
1.57 jakob 314: .It Fl g
1.62 jakob 315: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 316: .Fl r
1.62 jakob 317: command.
1.66 jmc 318: .It Fl H
319: Hash a
320: .Pa known_hosts
1.67 dtucker 321: file.
322: This replaces all hostnames and addresses with hashed representations
323: within the specified file; the original content is moved to a file with
324: a .old suffix.
1.66 jmc 325: These hashes may be used normally by
326: .Nm ssh
327: and
328: .Nm sshd ,
329: but they do not reveal identifying information should the file's contents
330: be disclosed.
331: This option will not modify existing hashed hostnames and is therefore safe
332: to use on files that mix hashed and non-hashed names.
1.84 djm 333: .It Fl h
334: When signing a key, create a host certificate instead of a user
335: certificate.
336: Please see the
337: .Sx CERTIFICATES
338: section for details.
1.85 jmc 339: .It Fl I Ar certificate_identity
1.84 djm 340: Specify the key identity when signing a public key.
341: Please see the
342: .Sx CERTIFICATES
343: section for details.
1.37 markus 344: .It Fl i
345: This option will read an unencrypted private (or public) key file
1.95 djm 346: in the format specified by the
347: .Fl m
348: option and print an OpenSSH compatible private
1.37 markus 349: (or public) key to stdout.
1.122 jmc 350: This option allows importing keys from other software, including several
351: commercial SSH implementations.
352: The default import format is
353: .Dq RFC4716 .
1.109 dtucker 354: .It Fl J Ar num_lines
355: Exit after screening the specified number of lines
356: while performing DH candidate screening using the
357: .Fl T
358: option.
359: .It Fl j Ar start_line
360: Start screening at the specified line number
361: while performing DH candidate screening using the
362: .Fl T
363: option.
1.108 dtucker 364: .It Fl K Ar checkpt
365: Write the last line processed to the file
366: .Ar checkpt
367: while performing DH candidate screening using the
368: .Fl T
369: option.
370: This will be used to skip lines in the input file that have already been
371: processed if the job is restarted.
1.111 djm 372: .It Fl k
373: Generate a KRL file.
374: In this mode,
375: .Nm
376: will generate a KRL file at the location specified via the
377: .Fl f
1.114 jmc 378: flag that revokes every key or certificate presented on the command line.
1.111 djm 379: Keys/certificates to be revoked may be specified by public key file or
380: using the format described in the
381: .Sx KEY REVOCATION LISTS
382: section.
1.86 djm 383: .It Fl L
1.129 djm 384: Prints the contents of one or more certificates.
1.9 markus 385: .It Fl l
1.77 grunk 386: Show fingerprint of specified public key file.
1.50 markus 387: For RSA and DSA keys
388: .Nm
1.78 jmc 389: tries to find the matching public key file and prints its fingerprint.
390: If combined with
391: .Fl v ,
1.132 jmc 392: a visual ASCII art representation of the key is supplied with the
1.131 djm 393: fingerprint.
1.96 jmc 394: .It Fl M Ar memory
395: Specify the amount of memory to use (in megabytes) when generating
396: candidate moduli for DH-GEX.
1.95 djm 397: .It Fl m Ar key_format
398: Specify a key format for the
399: .Fl i
400: (import) or
401: .Fl e
1.96 jmc 402: (export) conversion options.
1.95 djm 403: The supported key formats are:
404: .Dq RFC4716
1.96 jmc 405: (RFC 4716/SSH2 public or private key),
1.95 djm 406: .Dq PKCS8
407: (PEM PKCS8 public key)
408: or
409: .Dq PEM
410: (PEM public key).
411: The default conversion format is
412: .Dq RFC4716 .
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.
1.93 djm 428: The options that are valid for user certificates are:
1.137 jmc 429: .Pp
430: .Bl -tag -width Ds -compact
1.89 jmc 431: .It Ic clear
432: Clear all enabled permissions.
433: This is useful for clearing the default set of permissions so permissions may
434: be added individually.
1.137 jmc 435: .Pp
436: .It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents
437: .It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents
438: Includes an arbitrary certificate critical option or extension.
439: The specified
440: .Ar name
441: should include a domain suffix, e.g.\&
442: .Dq name@example.com .
443: If
444: .Ar contents
445: is specified then it is included as the contents of the extension/option
446: encoded as a string, otherwise the extension/option is created with no
447: contents (usually indicating a flag).
448: Extensions may be ignored by a client or server that does not recognise them,
449: whereas unknown critical options will cause the certificate to be refused.
1.138 jmc 450: .Pp
451: At present, no standard options are valid for host keys.
1.137 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
1.89 jmc 497: .It Ic permit-x11-forwarding
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
1.117 djm 507: .It Fl o
508: Causes
509: .Nm
1.130 jmc 510: to save private keys using the new OpenSSH format rather than
1.117 djm 511: the more compatible PEM format.
512: The new format has increased resistance to brute-force password cracking
513: but is not supported by versions of OpenSSH prior to 6.5.
514: Ed25519 keys always use the new private key format.
1.66 jmc 515: .It Fl P Ar passphrase
516: Provides the (old) passphrase.
1.2 deraadt 517: .It Fl p
1.1 deraadt 518: Requests changing the passphrase of a private key file instead of
1.12 aaron 519: creating a new private key.
520: The program will prompt for the file
1.1 deraadt 521: containing the private key, for the old passphrase, and twice for the
522: new passphrase.
1.113 jmc 523: .It Fl Q
524: Test whether keys have been revoked in a KRL.
1.5 aaron 525: .It Fl q
526: Silence
527: .Nm ssh-keygen .
1.64 djm 528: .It Fl R Ar hostname
529: Removes all keys belonging to
530: .Ar hostname
1.65 jmc 531: from a
1.64 djm 532: .Pa known_hosts
533: file.
1.65 jmc 534: This option is useful to delete hashed hosts (see the
1.64 djm 535: .Fl H
536: option above).
1.66 jmc 537: .It Fl r Ar hostname
538: Print the SSHFP fingerprint resource record named
539: .Ar hostname
540: for the specified public key file.
1.60 djm 541: .It Fl S Ar start
542: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 543: .It Fl s Ar ca_key
544: Certify (sign) a public key using the specified CA key.
545: Please see the
546: .Sx CERTIFICATES
547: section for details.
1.111 djm 548: .Pp
549: When generating a KRL,
550: .Fl s
1.112 jmc 551: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 552: by key ID or serial number.
553: See the
554: .Sx KEY REVOCATION LISTS
555: section for details.
1.60 djm 556: .It Fl T Ar output_file
557: Test DH group exchange candidate primes (generated using the
558: .Fl G
559: option) for safety.
1.139 ! jmc 560: .It Fl t Cm dsa | ecdsa | ed25519 | rsa
1.66 jmc 561: Specifies the type of key to create.
562: The possible values are
1.100 naddy 563: .Dq dsa ,
1.118 naddy 564: .Dq ecdsa ,
565: .Dq ed25519 ,
1.100 naddy 566: or
1.139 ! jmc 567: .Dq rsa .
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.
579: The start time may be specified as a date in YYYYMMDD format, a time
580: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
581: of a minus sign followed by a relative time in the format described in the
1.116 jmc 582: TIME FORMATS section of
1.90 jmc 583: .Xr sshd_config 5 .
1.84 djm 584: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
585: a relative time starting with a plus character.
586: .Pp
587: For example:
588: .Dq +52w1d
589: (valid from now to 52 weeks and one day from now),
590: .Dq -4w:+4w
591: (valid from four weeks ago to four weeks from now),
592: .Dq 20100101123000:20110101123000
593: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
594: .Dq -1d:20110101
595: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 596: .It Fl v
597: Verbose mode.
598: Causes
599: .Nm
600: to print debugging messages about its progress.
601: This is helpful for debugging moduli generation.
602: Multiple
603: .Fl v
604: options increase the verbosity.
605: The maximum is 3.
1.66 jmc 606: .It Fl W Ar generator
607: Specify desired generator when testing candidate moduli for DH-GEX.
608: .It Fl y
609: This option will read a private
610: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 611: .It Fl z Ar serial_number
612: Specifies a serial number to be embedded in the certificate to distinguish
613: this certificate from others from the same CA.
614: The default serial number is zero.
1.111 djm 615: .Pp
616: When generating a KRL, the
617: .Fl z
618: flag is used to specify a KRL version number.
1.2 deraadt 619: .El
1.60 djm 620: .Sh MODULI GENERATION
621: .Nm
622: may be used to generate groups for the Diffie-Hellman Group Exchange
623: (DH-GEX) protocol.
624: Generating these groups is a two-step process: first, candidate
625: primes are generated using a fast, but memory intensive process.
626: These candidate primes are then tested for suitability (a CPU-intensive
627: process).
628: .Pp
629: Generation of primes is performed using the
630: .Fl G
631: option.
632: The desired length of the primes may be specified by the
633: .Fl b
634: option.
635: For example:
636: .Pp
1.66 jmc 637: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 638: .Pp
639: By default, the search for primes begins at a random point in the
640: desired length range.
641: This may be overridden using the
642: .Fl S
643: option, which specifies a different start point (in hex).
644: .Pp
1.109 dtucker 645: Once a set of candidates have been generated, they must be screened for
1.60 djm 646: suitability.
647: This may be performed using the
648: .Fl T
649: option.
650: In this mode
651: .Nm
652: will read candidates from standard input (or a file specified using the
653: .Fl f
654: option).
655: For example:
656: .Pp
1.66 jmc 657: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 658: .Pp
659: By default, each candidate will be subjected to 100 primality tests.
660: This may be overridden using the
661: .Fl a
662: option.
663: The DH generator value will be chosen automatically for the
664: prime under consideration.
665: If a specific generator is desired, it may be requested using the
666: .Fl W
667: option.
1.66 jmc 668: Valid generator values are 2, 3, and 5.
1.60 djm 669: .Pp
670: Screened DH groups may be installed in
671: .Pa /etc/moduli .
672: It is important that this file contains moduli of a range of bit lengths and
673: that both ends of a connection share common moduli.
1.84 djm 674: .Sh CERTIFICATES
675: .Nm
676: supports signing of keys to produce certificates that may be used for
677: user or host authentication.
678: Certificates consist of a public key, some identity information, zero or
1.94 jmc 679: more principal (user or host) names and a set of options that
1.84 djm 680: are signed by a Certification Authority (CA) key.
681: Clients or servers may then trust only the CA key and verify its signature
682: on a certificate rather than trusting many user/host keys.
683: Note that OpenSSH certificates are a different, and much simpler, format to
684: the X.509 certificates used in
685: .Xr ssl 8 .
686: .Pp
687: .Nm
688: supports two types of certificates: user and host.
689: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 690: authenticate server hosts to users.
691: To generate a user certificate:
1.84 djm 692: .Pp
693: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
694: .Pp
695: The resultant certificate will be placed in
1.91 djm 696: .Pa /path/to/user_key-cert.pub .
1.84 djm 697: A host certificate requires the
698: .Fl h
699: option:
700: .Pp
701: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
702: .Pp
703: The host certificate will be output to
1.91 djm 704: .Pa /path/to/host_key-cert.pub .
1.98 djm 705: .Pp
706: It is possible to sign using a CA key stored in a PKCS#11 token by
707: providing the token library using
708: .Fl D
709: and identifying the CA key by providing its public half as an argument
710: to
711: .Fl s :
712: .Pp
1.127 naddy 713: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.98 djm 714: .Pp
715: In all cases,
1.84 djm 716: .Ar key_id
717: is a "key identifier" that is logged by the server when the certificate
718: is used for authentication.
719: .Pp
720: Certificates may be limited to be valid for a set of principal (user/host)
721: names.
722: By default, generated certificates are valid for all users or hosts.
723: To generate a certificate for a specified set of principals:
724: .Pp
725: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 726: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 727: .Pp
728: Additional limitations on the validity and use of user certificates may
1.94 jmc 729: be specified through certificate options.
1.93 djm 730: A certificate option may disable features of the SSH session, may be
1.84 djm 731: valid only when presented from particular source addresses or may
732: force the use of a specific command.
1.93 djm 733: For a list of valid certificate options, see the documentation for the
1.84 djm 734: .Fl O
735: option above.
736: .Pp
737: Finally, certificates may be defined with a validity lifetime.
738: The
739: .Fl V
740: option allows specification of certificate start and end times.
741: A certificate that is presented at a time outside this range will not be
742: considered valid.
1.110 jmc 743: By default, certificates are valid from
744: .Ux
745: Epoch to the distant future.
1.84 djm 746: .Pp
747: For certificates to be used for user or host authentication, the CA
748: public key must be trusted by
749: .Xr sshd 8
750: or
751: .Xr ssh 1 .
752: Please refer to those manual pages for details.
1.111 djm 753: .Sh KEY REVOCATION LISTS
754: .Nm
755: is able to manage OpenSSH format Key Revocation Lists (KRLs).
756: These binary files specify keys or certificates to be revoked using a
1.119 tedu 757: compact format, taking as little as one bit per certificate if they are being
1.111 djm 758: revoked by serial number.
759: .Pp
760: KRLs may be generated using the
761: .Fl k
762: flag.
1.114 jmc 763: This option reads one or more files from the command line and generates a new
1.111 djm 764: KRL.
765: The files may either contain a KRL specification (see below) or public keys,
766: listed one per line.
767: Plain public keys are revoked by listing their hash or contents in the KRL and
768: certificates revoked by serial number or key ID (if the serial is zero or
769: not available).
770: .Pp
771: Revoking keys using a KRL specification offers explicit control over the
772: types of record used to revoke keys and may be used to directly revoke
773: certificates by serial number or key ID without having the complete original
774: certificate on hand.
775: A KRL specification consists of lines containing one of the following directives
776: followed by a colon and some directive-specific information.
777: .Bl -tag -width Ds
1.115 jmc 778: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 779: Revokes a certificate with the specified serial number.
1.112 jmc 780: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 781: in decimal, hex or octal.
782: If two serial numbers are specified separated by a hyphen, then the range
783: of serial numbers including and between each is revoked.
784: The CA key must have been specified on the
785: .Nm
1.114 jmc 786: command line using the
1.111 djm 787: .Fl s
788: option.
789: .It Cm id : Ar key_id
790: Revokes a certificate with the specified key ID string.
791: The CA key must have been specified on the
792: .Nm
1.114 jmc 793: command line using the
1.111 djm 794: .Fl s
795: option.
796: .It Cm key : Ar public_key
797: Revokes the specified key.
1.112 jmc 798: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 799: .It Cm sha1 : Ar public_key
800: Revokes the specified key by its SHA1 hash.
801: .El
802: .Pp
803: KRLs may be updated using the
804: .Fl u
805: flag in addition to
806: .Fl k .
1.114 jmc 807: When this option is specified, keys listed via the command line are merged into
1.111 djm 808: the KRL, adding to those already there.
809: .Pp
810: It is also possible, given a KRL, to test whether it revokes a particular key
811: (or keys).
812: The
813: .Fl Q
1.128 jmc 814: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 815: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 816: then
817: .Nm
818: will exit with a non-zero exit status.
819: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 820: .Sh FILES
1.100 naddy 821: .Bl -tag -width Ds -compact
1.68 djm 822: .It Pa ~/.ssh/identity
1.36 itojun 823: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 824: This file should not be readable by anyone but the user.
825: It is possible to
1.1 deraadt 826: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 827: used to encrypt the private part of this file using 3DES.
1.12 aaron 828: This file is not automatically accessed by
1.2 deraadt 829: .Nm
1.1 deraadt 830: but it is offered as the default file for the private key.
1.46 markus 831: .Xr ssh 1
1.15 deraadt 832: will read this file when a login attempt is made.
1.100 naddy 833: .Pp
1.68 djm 834: .It Pa ~/.ssh/identity.pub
1.36 itojun 835: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 836: The contents of this file should be added to
1.68 djm 837: .Pa ~/.ssh/authorized_keys
1.2 deraadt 838: on all machines
1.49 deraadt 839: where the user wishes to log in using RSA authentication.
1.15 deraadt 840: There is no need to keep the contents of this file secret.
1.100 naddy 841: .Pp
1.68 djm 842: .It Pa ~/.ssh/id_dsa
1.100 naddy 843: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 844: .It Pa ~/.ssh/id_ed25519
1.100 naddy 845: .It Pa ~/.ssh/id_rsa
1.123 sobrado 846: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 847: authentication identity of the user.
1.15 deraadt 848: This file should not be readable by anyone but the user.
849: It is possible to
850: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 851: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 852: This file is not automatically accessed by
853: .Nm
854: but it is offered as the default file for the private key.
1.46 markus 855: .Xr ssh 1
1.15 deraadt 856: will read this file when a login attempt is made.
1.100 naddy 857: .Pp
1.68 djm 858: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 859: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 860: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 861: .It Pa ~/.ssh/id_rsa.pub
1.123 sobrado 862: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 863: public key for authentication.
1.15 deraadt 864: The contents of this file should be added to
1.68 djm 865: .Pa ~/.ssh/authorized_keys
1.15 deraadt 866: on all machines
1.49 deraadt 867: where the user wishes to log in using public key authentication.
1.12 aaron 868: There is no need to keep the contents of this file secret.
1.100 naddy 869: .Pp
1.60 djm 870: .It Pa /etc/moduli
871: Contains Diffie-Hellman groups used for DH-GEX.
872: The file format is described in
873: .Xr moduli 5 .
1.19 aaron 874: .El
1.2 deraadt 875: .Sh SEE ALSO
876: .Xr ssh 1 ,
877: .Xr ssh-add 1 ,
1.8 ericj 878: .Xr ssh-agent 1 ,
1.60 djm 879: .Xr moduli 5 ,
1.30 itojun 880: .Xr sshd 8
1.37 markus 881: .Rs
1.73 markus 882: .%R RFC 4716
883: .%T "The Secure Shell (SSH) Public Key File Format"
884: .%D 2006
1.37 markus 885: .Re
1.59 jmc 886: .Sh AUTHORS
887: OpenSSH is a derivative of the original and free
888: ssh 1.2.12 release by Tatu Ylonen.
889: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
890: Theo de Raadt and Dug Song
891: removed many bugs, re-added newer features and
892: created OpenSSH.
893: Markus Friedl contributed the support for SSH
894: 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