Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.109
1.109 ! dtucker 1: .\" $OpenBSD: ssh-keygen.1,v 1.108 2011/10/16 11:02:46 dtucker 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: .\"
1.109 ! dtucker 38: .Dd $Mdocdate: October 16 2011 $
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
1.53 stevesk 49: .Fl t Ar type
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
1.35 markus 76: .Op Fl f Ar input_keyfile
77: .Nm ssh-keygen
78: .Fl B
1.20 markus 79: .Op Fl f Ar input_keyfile
1.48 jakob 80: .Nm ssh-keygen
1.82 jmc 81: .Fl D Ar pkcs11
1.48 jakob 82: .Nm ssh-keygen
1.64 djm 83: .Fl F Ar hostname
84: .Op Fl f Ar known_hosts_file
1.79 sthen 85: .Op Fl l
1.64 djm 86: .Nm ssh-keygen
87: .Fl H
88: .Op Fl f Ar known_hosts_file
89: .Nm ssh-keygen
90: .Fl R Ar hostname
91: .Op Fl f Ar known_hosts_file
1.57 jakob 92: .Nm ssh-keygen
93: .Fl r Ar hostname
94: .Op Fl f Ar input_keyfile
95: .Op Fl g
1.60 djm 96: .Nm ssh-keygen
97: .Fl G Ar output_file
1.61 djm 98: .Op Fl v
1.60 djm 99: .Op Fl b Ar bits
100: .Op Fl M Ar memory
101: .Op Fl S Ar start_point
102: .Nm ssh-keygen
103: .Fl T Ar output_file
104: .Fl f Ar input_file
1.61 djm 105: .Op Fl v
1.60 djm 106: .Op Fl a Ar num_trials
1.109 ! dtucker 107: .Op Fl J Ar num_lines
! 108: .Op Fl j Ar start_line
1.108 dtucker 109: .Op Fl K Ar checkpt
1.60 djm 110: .Op Fl W Ar generator
1.84 djm 111: .Nm ssh-keygen
112: .Fl s Ar ca_key
113: .Fl I Ar certificate_identity
114: .Op Fl h
115: .Op Fl n Ar principals
1.93 djm 116: .Op Fl O Ar option
1.84 djm 117: .Op Fl V Ar validity_interval
1.93 djm 118: .Op Fl z Ar serial_number
1.84 djm 119: .Ar
1.86 djm 120: .Nm ssh-keygen
121: .Fl L
122: .Op Fl f Ar input_keyfile
1.102 stevesk 123: .Nm ssh-keygen
124: .Fl A
1.85 jmc 125: .Ek
1.13 aaron 126: .Sh DESCRIPTION
1.2 deraadt 127: .Nm
1.37 markus 128: generates, manages and converts authentication keys for
1.2 deraadt 129: .Xr ssh 1 .
1.15 deraadt 130: .Nm
1.100 naddy 131: can create RSA keys for use by SSH protocol version 1 and DSA, ECDSA or RSA
1.58 jmc 132: keys for use by SSH protocol version 2.
133: The type of key to be generated is specified with the
1.25 markus 134: .Fl t
1.52 djm 135: option.
1.70 djm 136: If invoked without any arguments,
137: .Nm
1.71 jmc 138: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 139: .Pp
1.60 djm 140: .Nm
141: is also used to generate groups for use in Diffie-Hellman group
142: exchange (DH-GEX).
143: See the
144: .Sx MODULI GENERATION
145: section for details.
146: .Pp
1.2 deraadt 147: Normally each user wishing to use SSH
1.99 djm 148: with public key authentication runs this once to create the authentication
1.1 deraadt 149: key in
1.68 djm 150: .Pa ~/.ssh/identity ,
1.99 djm 151: .Pa ~/.ssh/id_ecdsa ,
1.68 djm 152: .Pa ~/.ssh/id_dsa
1.15 deraadt 153: or
1.68 djm 154: .Pa ~/.ssh/id_rsa .
1.15 deraadt 155: Additionally, the system administrator may use this to generate host keys,
156: as seen in
157: .Pa /etc/rc .
1.2 deraadt 158: .Pp
1.1 deraadt 159: Normally this program generates the key and asks for a file in which
1.12 aaron 160: to store the private key.
161: The public key is stored in a file with the same name but
1.2 deraadt 162: .Dq .pub
1.12 aaron 163: appended.
164: The program also asks for a passphrase.
165: The passphrase may be empty to indicate no passphrase
1.26 markus 166: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 167: arbitrary length.
1.51 stevesk 168: A passphrase is similar to a password, except it can be a phrase with a
169: series of words, punctuation, numbers, whitespace, or any string of
170: characters you want.
171: Good passphrases are 10-30 characters long, are
1.1 deraadt 172: not simple sentences or otherwise easily guessable (English
1.42 markus 173: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 174: passphrases), and contain a mix of upper and lowercase letters,
175: numbers, and non-alphanumeric characters.
1.12 aaron 176: The passphrase can be changed later by using the
1.2 deraadt 177: .Fl p
1.1 deraadt 178: option.
1.2 deraadt 179: .Pp
1.12 aaron 180: There is no way to recover a lost passphrase.
1.105 djm 181: If the passphrase is lost or forgotten, a new key must be generated
182: and the corresponding public key copied to other machines.
1.2 deraadt 183: .Pp
1.37 markus 184: For RSA1 keys,
185: there is also a comment field in the key file that is only for
1.12 aaron 186: convenience to the user to help identify the key.
187: The comment can tell what the key is for, or whatever is useful.
188: The comment is initialized to
1.2 deraadt 189: .Dq user@host
190: when the key is created, but can be changed using the
191: .Fl c
1.1 deraadt 192: option.
1.2 deraadt 193: .Pp
1.15 deraadt 194: After a key is generated, instructions below detail where the keys
195: should be placed to be activated.
196: .Pp
1.2 deraadt 197: The options are as follows:
198: .Bl -tag -width Ds
1.102 stevesk 199: .It Fl A
200: For each of the key types (rsa1, rsa, dsa and ecdsa) for which host keys
201: do not exist, generate the host keys with the default key file path,
202: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 203: This is used by
1.102 stevesk 204: .Pa /etc/rc
205: to generate new host keys.
1.60 djm 206: .It Fl a Ar trials
207: Specifies the number of primality tests to perform when screening DH-GEX
208: candidates using the
209: .Fl T
210: command.
1.66 jmc 211: .It Fl B
212: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 213: .It Fl b Ar bits
1.12 aaron 214: Specifies the number of bits in the key to create.
1.72 dtucker 215: For RSA keys, the minimum size is 768 bits and the default is 2048 bits.
1.69 djm 216: Generally, 2048 bits is considered sufficient.
1.72 dtucker 217: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 218: For ECDSA keys, the
219: .Fl b
1.107 deraadt 220: flag determines the key length by selecting from one of three elliptic
1.106 djm 221: curve sizes: 256, 384 or 521 bits.
222: Attempting to use bit lengths other than these three values for ECDSA keys
223: will fail.
1.66 jmc 224: .It Fl C Ar comment
225: Provides a new comment.
1.2 deraadt 226: .It Fl c
1.1 deraadt 227: Requests changing the comment in the private and public key files.
1.50 markus 228: This operation is only supported for RSA1 keys.
1.1 deraadt 229: The program will prompt for the file containing the private keys, for
1.41 stevesk 230: the passphrase if the key has one, and for the new comment.
1.81 markus 231: .It Fl D Ar pkcs11
1.83 markus 232: Download the RSA public keys provided by the PKCS#11 shared library
233: .Ar pkcs11 .
1.98 djm 234: When used in combination with
235: .Fl s ,
236: this option indicates that a CA key resides in a PKCS#11 token (see the
237: .Sx CERTIFICATES
238: section for details).
1.37 markus 239: .It Fl e
1.40 markus 240: This option will read a private or public OpenSSH key file and
1.95 djm 241: print to stdout the key in one of the formats specified by the
242: .Fl m
243: option.
244: The default export format is
245: .Dq RFC4716 .
1.96 jmc 246: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 247: several commercial SSH implementations.
1.66 jmc 248: .It Fl F Ar hostname
249: Search for the specified
250: .Ar hostname
251: in a
252: .Pa known_hosts
253: file, listing any occurrences found.
254: This option is useful to find hashed host names or addresses and may also be
255: used in conjunction with the
256: .Fl H
257: option to print found keys in a hashed format.
258: .It Fl f Ar filename
259: Specifies the filename of the key file.
260: .It Fl G Ar output_file
261: Generate candidate primes for DH-GEX.
262: These primes must be screened for
263: safety (using the
264: .Fl T
265: option) before use.
1.57 jakob 266: .It Fl g
1.62 jakob 267: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 268: .Fl r
1.62 jakob 269: command.
1.66 jmc 270: .It Fl H
271: Hash a
272: .Pa known_hosts
1.67 dtucker 273: file.
274: This replaces all hostnames and addresses with hashed representations
275: within the specified file; the original content is moved to a file with
276: a .old suffix.
1.66 jmc 277: These hashes may be used normally by
278: .Nm ssh
279: and
280: .Nm sshd ,
281: but they do not reveal identifying information should the file's contents
282: be disclosed.
283: This option will not modify existing hashed hostnames and is therefore safe
284: to use on files that mix hashed and non-hashed names.
1.84 djm 285: .It Fl h
286: When signing a key, create a host certificate instead of a user
287: certificate.
288: Please see the
289: .Sx CERTIFICATES
290: section for details.
1.85 jmc 291: .It Fl I Ar certificate_identity
1.84 djm 292: Specify the key identity when signing a public key.
293: Please see the
294: .Sx CERTIFICATES
295: section for details.
1.37 markus 296: .It Fl i
297: This option will read an unencrypted private (or public) key file
1.95 djm 298: in the format specified by the
299: .Fl m
300: option and print an OpenSSH compatible private
1.37 markus 301: (or public) key to stdout.
1.109 ! dtucker 302: .It Fl J Ar num_lines
! 303: Exit after screening the specified number of lines
! 304: while performing DH candidate screening using the
! 305: .Fl T
! 306: option.
! 307: .It Fl j Ar start_line
! 308: Start screening at the specified line number
! 309: while performing DH candidate screening using the
! 310: .Fl T
! 311: option.
1.108 dtucker 312: .It Fl K Ar checkpt
313: Write the last line processed to the file
314: .Ar checkpt
315: while performing DH candidate screening using the
316: .Fl T
317: option.
318: This will be used to skip lines in the input file that have already been
319: processed if the job is restarted.
1.95 djm 320: This option allows importing keys from other software, including several
321: commercial SSH implementations.
322: The default import format is
323: .Dq RFC4716 .
1.86 djm 324: .It Fl L
325: Prints the contents of a certificate.
1.9 markus 326: .It Fl l
1.77 grunk 327: Show fingerprint of specified public key file.
1.50 markus 328: Private RSA1 keys are also supported.
329: For RSA and DSA keys
330: .Nm
1.78 jmc 331: tries to find the matching public key file and prints its fingerprint.
332: If combined with
333: .Fl v ,
334: an ASCII art representation of the key is supplied with the fingerprint.
1.96 jmc 335: .It Fl M Ar memory
336: Specify the amount of memory to use (in megabytes) when generating
337: candidate moduli for DH-GEX.
1.95 djm 338: .It Fl m Ar key_format
339: Specify a key format for the
340: .Fl i
341: (import) or
342: .Fl e
1.96 jmc 343: (export) conversion options.
1.95 djm 344: The supported key formats are:
345: .Dq RFC4716
1.96 jmc 346: (RFC 4716/SSH2 public or private key),
1.95 djm 347: .Dq PKCS8
348: (PEM PKCS8 public key)
349: or
350: .Dq PEM
351: (PEM public key).
352: The default conversion format is
353: .Dq RFC4716 .
1.66 jmc 354: .It Fl N Ar new_passphrase
355: Provides the new passphrase.
1.84 djm 356: .It Fl n Ar principals
357: Specify one or more principals (user or host names) to be included in
358: a certificate when signing a key.
359: Multiple principals may be specified, separated by commas.
360: Please see the
361: .Sx CERTIFICATES
362: section for details.
1.93 djm 363: .It Fl O Ar option
364: Specify a certificate option when signing a key.
1.84 djm 365: This option may be specified multiple times.
366: Please see the
367: .Sx CERTIFICATES
368: section for details.
1.93 djm 369: The options that are valid for user certificates are:
1.84 djm 370: .Bl -tag -width Ds
1.89 jmc 371: .It Ic clear
372: Clear all enabled permissions.
373: This is useful for clearing the default set of permissions so permissions may
374: be added individually.
375: .It Ic force-command Ns = Ns Ar command
376: Forces the execution of
377: .Ar command
378: instead of any shell or command specified by the user when
379: the certificate is used for authentication.
1.84 djm 380: .It Ic no-agent-forwarding
381: Disable
382: .Xr ssh-agent 1
1.85 jmc 383: forwarding (permitted by default).
1.84 djm 384: .It Ic no-port-forwarding
1.85 jmc 385: Disable port forwarding (permitted by default).
1.84 djm 386: .It Ic no-pty
1.85 jmc 387: Disable PTY allocation (permitted by default).
1.84 djm 388: .It Ic no-user-rc
389: Disable execution of
390: .Pa ~/.ssh/rc
391: by
1.85 jmc 392: .Xr sshd 8
393: (permitted by default).
1.89 jmc 394: .It Ic no-x11-forwarding
395: Disable X11 forwarding (permitted by default).
1.88 djm 396: .It Ic permit-agent-forwarding
397: Allows
398: .Xr ssh-agent 1
399: forwarding.
1.84 djm 400: .It Ic permit-port-forwarding
401: Allows port forwarding.
402: .It Ic permit-pty
403: Allows PTY allocation.
404: .It Ic permit-user-rc
405: Allows execution of
406: .Pa ~/.ssh/rc
407: by
408: .Xr sshd 8 .
1.89 jmc 409: .It Ic permit-x11-forwarding
410: Allows X11 forwarding.
411: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 412: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 413: The
414: .Ar address_list
415: is a comma-separated list of one or more address/netmask pairs in CIDR
416: format.
417: .El
418: .Pp
1.93 djm 419: At present, no options are valid for host keys.
1.66 jmc 420: .It Fl P Ar passphrase
421: Provides the (old) passphrase.
1.2 deraadt 422: .It Fl p
1.1 deraadt 423: Requests changing the passphrase of a private key file instead of
1.12 aaron 424: creating a new private key.
425: The program will prompt for the file
1.1 deraadt 426: containing the private key, for the old passphrase, and twice for the
427: new passphrase.
1.5 aaron 428: .It Fl q
429: Silence
430: .Nm ssh-keygen .
1.64 djm 431: .It Fl R Ar hostname
432: Removes all keys belonging to
433: .Ar hostname
1.65 jmc 434: from a
1.64 djm 435: .Pa known_hosts
436: file.
1.65 jmc 437: This option is useful to delete hashed hosts (see the
1.64 djm 438: .Fl H
439: option above).
1.66 jmc 440: .It Fl r Ar hostname
441: Print the SSHFP fingerprint resource record named
442: .Ar hostname
443: for the specified public key file.
1.60 djm 444: .It Fl S Ar start
445: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 446: .It Fl s Ar ca_key
447: Certify (sign) a public key using the specified CA key.
448: Please see the
449: .Sx CERTIFICATES
450: section for details.
1.60 djm 451: .It Fl T Ar output_file
452: Test DH group exchange candidate primes (generated using the
453: .Fl G
454: option) for safety.
1.66 jmc 455: .It Fl t Ar type
456: Specifies the type of key to create.
457: The possible values are
458: .Dq rsa1
459: for protocol version 1 and
1.100 naddy 460: .Dq dsa ,
461: .Dq ecdsa
462: or
1.66 jmc 463: .Dq rsa
464: for protocol version 2.
1.84 djm 465: .It Fl V Ar validity_interval
466: Specify a validity interval when signing a certificate.
467: A validity interval may consist of a single time, indicating that the
468: certificate is valid beginning now and expiring at that time, or may consist
469: of two times separated by a colon to indicate an explicit time interval.
470: The start time may be specified as a date in YYYYMMDD format, a time
471: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
472: of a minus sign followed by a relative time in the format described in the
473: .Sx TIME FORMATS
474: section of
1.90 jmc 475: .Xr sshd_config 5 .
1.84 djm 476: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
477: a relative time starting with a plus character.
478: .Pp
479: For example:
480: .Dq +52w1d
481: (valid from now to 52 weeks and one day from now),
482: .Dq -4w:+4w
483: (valid from four weeks ago to four weeks from now),
484: .Dq 20100101123000:20110101123000
485: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
486: .Dq -1d:20110101
487: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 488: .It Fl v
489: Verbose mode.
490: Causes
491: .Nm
492: to print debugging messages about its progress.
493: This is helpful for debugging moduli generation.
494: Multiple
495: .Fl v
496: options increase the verbosity.
497: The maximum is 3.
1.66 jmc 498: .It Fl W Ar generator
499: Specify desired generator when testing candidate moduli for DH-GEX.
500: .It Fl y
501: This option will read a private
502: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 503: .It Fl z Ar serial_number
504: Specifies a serial number to be embedded in the certificate to distinguish
505: this certificate from others from the same CA.
506: The default serial number is zero.
1.2 deraadt 507: .El
1.60 djm 508: .Sh MODULI GENERATION
509: .Nm
510: may be used to generate groups for the Diffie-Hellman Group Exchange
511: (DH-GEX) protocol.
512: Generating these groups is a two-step process: first, candidate
513: primes are generated using a fast, but memory intensive process.
514: These candidate primes are then tested for suitability (a CPU-intensive
515: process).
516: .Pp
517: Generation of primes is performed using the
518: .Fl G
519: option.
520: The desired length of the primes may be specified by the
521: .Fl b
522: option.
523: For example:
524: .Pp
1.66 jmc 525: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 526: .Pp
527: By default, the search for primes begins at a random point in the
528: desired length range.
529: This may be overridden using the
530: .Fl S
531: option, which specifies a different start point (in hex).
532: .Pp
1.109 ! dtucker 533: Once a set of candidates have been generated, they must be screened for
1.60 djm 534: suitability.
535: This may be performed using the
536: .Fl T
537: option.
538: In this mode
539: .Nm
540: will read candidates from standard input (or a file specified using the
541: .Fl f
542: option).
543: For example:
544: .Pp
1.66 jmc 545: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 546: .Pp
547: By default, each candidate will be subjected to 100 primality tests.
548: This may be overridden using the
549: .Fl a
550: option.
551: The DH generator value will be chosen automatically for the
552: prime under consideration.
553: If a specific generator is desired, it may be requested using the
554: .Fl W
555: option.
1.66 jmc 556: Valid generator values are 2, 3, and 5.
1.60 djm 557: .Pp
558: Screened DH groups may be installed in
559: .Pa /etc/moduli .
560: It is important that this file contains moduli of a range of bit lengths and
561: that both ends of a connection share common moduli.
1.84 djm 562: .Sh CERTIFICATES
563: .Nm
564: supports signing of keys to produce certificates that may be used for
565: user or host authentication.
566: Certificates consist of a public key, some identity information, zero or
1.94 jmc 567: more principal (user or host) names and a set of options that
1.84 djm 568: are signed by a Certification Authority (CA) key.
569: Clients or servers may then trust only the CA key and verify its signature
570: on a certificate rather than trusting many user/host keys.
571: Note that OpenSSH certificates are a different, and much simpler, format to
572: the X.509 certificates used in
573: .Xr ssl 8 .
574: .Pp
575: .Nm
576: supports two types of certificates: user and host.
577: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 578: authenticate server hosts to users.
579: To generate a user certificate:
1.84 djm 580: .Pp
581: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
582: .Pp
583: The resultant certificate will be placed in
1.91 djm 584: .Pa /path/to/user_key-cert.pub .
1.84 djm 585: A host certificate requires the
586: .Fl h
587: option:
588: .Pp
589: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
590: .Pp
591: The host certificate will be output to
1.91 djm 592: .Pa /path/to/host_key-cert.pub .
1.98 djm 593: .Pp
594: It is possible to sign using a CA key stored in a PKCS#11 token by
595: providing the token library using
596: .Fl D
597: and identifying the CA key by providing its public half as an argument
598: to
599: .Fl s :
600: .Pp
601: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id host_key.pub
602: .Pp
603: In all cases,
1.84 djm 604: .Ar key_id
605: is a "key identifier" that is logged by the server when the certificate
606: is used for authentication.
607: .Pp
608: Certificates may be limited to be valid for a set of principal (user/host)
609: names.
610: By default, generated certificates are valid for all users or hosts.
611: To generate a certificate for a specified set of principals:
612: .Pp
613: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.92 jmc 614: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub"
1.84 djm 615: .Pp
616: Additional limitations on the validity and use of user certificates may
1.94 jmc 617: be specified through certificate options.
1.93 djm 618: A certificate option may disable features of the SSH session, may be
1.84 djm 619: valid only when presented from particular source addresses or may
620: force the use of a specific command.
1.93 djm 621: For a list of valid certificate options, see the documentation for the
1.84 djm 622: .Fl O
623: option above.
624: .Pp
625: Finally, certificates may be defined with a validity lifetime.
626: The
627: .Fl V
628: option allows specification of certificate start and end times.
629: A certificate that is presented at a time outside this range will not be
630: considered valid.
631: By default, certificates have a maximum validity interval.
632: .Pp
633: For certificates to be used for user or host authentication, the CA
634: public key must be trusted by
635: .Xr sshd 8
636: or
637: .Xr ssh 1 .
638: Please refer to those manual pages for details.
1.2 deraadt 639: .Sh FILES
1.100 naddy 640: .Bl -tag -width Ds -compact
1.68 djm 641: .It Pa ~/.ssh/identity
1.36 itojun 642: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 643: This file should not be readable by anyone but the user.
644: It is possible to
1.1 deraadt 645: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 646: used to encrypt the private part of this file using 3DES.
1.12 aaron 647: This file is not automatically accessed by
1.2 deraadt 648: .Nm
1.1 deraadt 649: but it is offered as the default file for the private key.
1.46 markus 650: .Xr ssh 1
1.15 deraadt 651: will read this file when a login attempt is made.
1.100 naddy 652: .Pp
1.68 djm 653: .It Pa ~/.ssh/identity.pub
1.36 itojun 654: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 655: The contents of this file should be added to
1.68 djm 656: .Pa ~/.ssh/authorized_keys
1.2 deraadt 657: on all machines
1.49 deraadt 658: where the user wishes to log in using RSA authentication.
1.15 deraadt 659: There is no need to keep the contents of this file secret.
1.100 naddy 660: .Pp
1.68 djm 661: .It Pa ~/.ssh/id_dsa
1.100 naddy 662: .It Pa ~/.ssh/id_ecdsa
663: .It Pa ~/.ssh/id_rsa
664: Contains the protocol version 2 DSA, ECDSA or RSA authentication identity of the user.
1.15 deraadt 665: This file should not be readable by anyone but the user.
666: It is possible to
667: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 668: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 669: This file is not automatically accessed by
670: .Nm
671: but it is offered as the default file for the private key.
1.46 markus 672: .Xr ssh 1
1.15 deraadt 673: will read this file when a login attempt is made.
1.100 naddy 674: .Pp
1.68 djm 675: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 676: .It Pa ~/.ssh/id_ecdsa.pub
1.68 djm 677: .It Pa ~/.ssh/id_rsa.pub
1.100 naddy 678: Contains the protocol version 2 DSA, ECDSA or RSA public key for authentication.
1.15 deraadt 679: The contents of this file should be added to
1.68 djm 680: .Pa ~/.ssh/authorized_keys
1.15 deraadt 681: on all machines
1.49 deraadt 682: where the user wishes to log in using public key authentication.
1.12 aaron 683: There is no need to keep the contents of this file secret.
1.100 naddy 684: .Pp
1.60 djm 685: .It Pa /etc/moduli
686: Contains Diffie-Hellman groups used for DH-GEX.
687: The file format is described in
688: .Xr moduli 5 .
1.19 aaron 689: .El
1.2 deraadt 690: .Sh SEE ALSO
691: .Xr ssh 1 ,
692: .Xr ssh-add 1 ,
1.8 ericj 693: .Xr ssh-agent 1 ,
1.60 djm 694: .Xr moduli 5 ,
1.30 itojun 695: .Xr sshd 8
1.37 markus 696: .Rs
1.73 markus 697: .%R RFC 4716
698: .%T "The Secure Shell (SSH) Public Key File Format"
699: .%D 2006
1.37 markus 700: .Re
1.59 jmc 701: .Sh AUTHORS
702: OpenSSH is a derivative of the original and free
703: ssh 1.2.12 release by Tatu Ylonen.
704: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
705: Theo de Raadt and Dug Song
706: removed many bugs, re-added newer features and
707: created OpenSSH.
708: Markus Friedl contributed the support for SSH
709: protocol versions 1.5 and 2.0.
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