Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.123
1.123 ! sobrado 1: .\" $OpenBSD: ssh-keygen.1,v 1.122 2014/03/31 13:39:34 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
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36: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 37: .\"
1.123 ! sobrado 38: .Dd $Mdocdate: March 31 2014 $
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
1.121 deraadt 49: .Op Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1
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
1.117 djm 106: .Op Fl a Ar rounds
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
1.111 djm 125: .Nm ssh-keygen
126: .Fl k
127: .Fl f Ar krl_file
128: .Op Fl u
1.112 jmc 129: .Op Fl s Ar ca_public
130: .Op Fl z Ar version_number
1.111 djm 131: .Ar
132: .Nm ssh-keygen
133: .Fl Q
134: .Fl f Ar krl_file
135: .Ar
1.85 jmc 136: .Ek
1.13 aaron 137: .Sh DESCRIPTION
1.2 deraadt 138: .Nm
1.37 markus 139: generates, manages and converts authentication keys for
1.2 deraadt 140: .Xr ssh 1 .
1.15 deraadt 141: .Nm
1.118 naddy 142: can create RSA keys for use by SSH protocol version 1 and
1.123 ! sobrado 143: DSA, ECDSA, Ed25519 or RSA keys for use by SSH protocol version 2.
1.58 jmc 144: The type of key to be generated is specified with the
1.25 markus 145: .Fl t
1.52 djm 146: option.
1.70 djm 147: If invoked without any arguments,
148: .Nm
1.71 jmc 149: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 150: .Pp
1.60 djm 151: .Nm
152: is also used to generate groups for use in Diffie-Hellman group
153: exchange (DH-GEX).
154: See the
155: .Sx MODULI GENERATION
156: section for details.
157: .Pp
1.111 djm 158: Finally,
159: .Nm
160: can be used to generate and update Key Revocation Lists, and to test whether
1.112 jmc 161: given keys have been revoked by one.
162: See the
1.111 djm 163: .Sx KEY REVOCATION LISTS
164: section for details.
165: .Pp
1.2 deraadt 166: Normally each user wishing to use SSH
1.99 djm 167: with public key authentication runs this once to create the authentication
1.1 deraadt 168: key in
1.68 djm 169: .Pa ~/.ssh/identity ,
1.118 naddy 170: .Pa ~/.ssh/id_dsa ,
1.99 djm 171: .Pa ~/.ssh/id_ecdsa ,
1.118 naddy 172: .Pa ~/.ssh/id_ed25519
1.15 deraadt 173: or
1.68 djm 174: .Pa ~/.ssh/id_rsa .
1.15 deraadt 175: Additionally, the system administrator may use this to generate host keys,
176: as seen in
177: .Pa /etc/rc .
1.2 deraadt 178: .Pp
1.1 deraadt 179: Normally this program generates the key and asks for a file in which
1.12 aaron 180: to store the private key.
181: The public key is stored in a file with the same name but
1.2 deraadt 182: .Dq .pub
1.12 aaron 183: appended.
184: The program also asks for a passphrase.
185: The passphrase may be empty to indicate no passphrase
1.26 markus 186: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 187: arbitrary length.
1.51 stevesk 188: A passphrase is similar to a password, except it can be a phrase with a
189: series of words, punctuation, numbers, whitespace, or any string of
190: characters you want.
191: Good passphrases are 10-30 characters long, are
1.1 deraadt 192: not simple sentences or otherwise easily guessable (English
1.42 markus 193: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 194: passphrases), and contain a mix of upper and lowercase letters,
195: numbers, and non-alphanumeric characters.
1.12 aaron 196: The passphrase can be changed later by using the
1.2 deraadt 197: .Fl p
1.1 deraadt 198: option.
1.2 deraadt 199: .Pp
1.12 aaron 200: There is no way to recover a lost passphrase.
1.105 djm 201: If the passphrase is lost or forgotten, a new key must be generated
202: and the corresponding public key copied to other machines.
1.2 deraadt 203: .Pp
1.37 markus 204: For RSA1 keys,
205: there is also a comment field in the key file that is only for
1.12 aaron 206: convenience to the user to help identify the key.
207: The comment can tell what the key is for, or whatever is useful.
208: The comment is initialized to
1.2 deraadt 209: .Dq user@host
210: when the key is created, but can be changed using the
211: .Fl c
1.1 deraadt 212: option.
1.2 deraadt 213: .Pp
1.15 deraadt 214: After a key is generated, instructions below detail where the keys
215: should be placed to be activated.
216: .Pp
1.2 deraadt 217: The options are as follows:
218: .Bl -tag -width Ds
1.102 stevesk 219: .It Fl A
1.118 naddy 220: For each of the key types (rsa1, rsa, dsa, ecdsa and ed25519)
221: for which host keys
1.102 stevesk 222: do not exist, generate the host keys with the default key file path,
223: an empty passphrase, default bits for the key type, and default comment.
1.104 jmc 224: This is used by
1.102 stevesk 225: .Pa /etc/rc
226: to generate new host keys.
1.117 djm 227: .It Fl a Ar rounds
228: When saving a new-format private key (i.e. an ed25519 key or any SSH protocol
229: 2 key when the
230: .Fl o
231: flag is set), this option specifies the number of KDF (key derivation function)
232: rounds used.
233: Higher numbers result in slower passphrase verification and increased
234: resistance to brute-force password cracking (should the keys be stolen).
235: .Pp
236: When screening DH-GEX candidates (
237: using the
1.60 djm 238: .Fl T
1.117 djm 239: command).
240: This option specifies the number of primality tests to perform.
1.66 jmc 241: .It Fl B
242: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 243: .It Fl b Ar bits
1.12 aaron 244: Specifies the number of bits in the key to create.
1.72 dtucker 245: For RSA keys, the minimum size is 768 bits and the default is 2048 bits.
1.69 djm 246: Generally, 2048 bits is considered sufficient.
1.72 dtucker 247: DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
1.106 djm 248: For ECDSA keys, the
249: .Fl b
1.107 deraadt 250: flag determines the key length by selecting from one of three elliptic
1.106 djm 251: curve sizes: 256, 384 or 521 bits.
252: Attempting to use bit lengths other than these three values for ECDSA keys
253: will fail.
1.123 ! sobrado 254: Ed25519 keys have a fixed length and the
1.118 naddy 255: .Fl b
256: flag will be ignored.
1.66 jmc 257: .It Fl C Ar comment
258: Provides a new comment.
1.2 deraadt 259: .It Fl c
1.1 deraadt 260: Requests changing the comment in the private and public key files.
1.50 markus 261: This operation is only supported for RSA1 keys.
1.1 deraadt 262: The program will prompt for the file containing the private keys, for
1.41 stevesk 263: the passphrase if the key has one, and for the new comment.
1.81 markus 264: .It Fl D Ar pkcs11
1.83 markus 265: Download the RSA public keys provided by the PKCS#11 shared library
266: .Ar pkcs11 .
1.98 djm 267: When used in combination with
268: .Fl s ,
269: this option indicates that a CA key resides in a PKCS#11 token (see the
270: .Sx CERTIFICATES
271: section for details).
1.37 markus 272: .It Fl e
1.40 markus 273: This option will read a private or public OpenSSH key file and
1.95 djm 274: print to stdout the key in one of the formats specified by the
275: .Fl m
276: option.
277: The default export format is
278: .Dq RFC4716 .
1.96 jmc 279: This option allows exporting OpenSSH keys for use by other programs, including
1.95 djm 280: several commercial SSH implementations.
1.66 jmc 281: .It Fl F Ar hostname
282: Search for the specified
283: .Ar hostname
284: in a
285: .Pa known_hosts
286: file, listing any occurrences found.
287: This option is useful to find hashed host names or addresses and may also be
288: used in conjunction with the
289: .Fl H
290: option to print found keys in a hashed format.
291: .It Fl f Ar filename
292: Specifies the filename of the key file.
293: .It Fl G Ar output_file
294: Generate candidate primes for DH-GEX.
295: These primes must be screened for
296: safety (using the
297: .Fl T
298: option) before use.
1.57 jakob 299: .It Fl g
1.62 jakob 300: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 301: .Fl r
1.62 jakob 302: command.
1.66 jmc 303: .It Fl H
304: Hash a
305: .Pa known_hosts
1.67 dtucker 306: file.
307: This replaces all hostnames and addresses with hashed representations
308: within the specified file; the original content is moved to a file with
309: a .old suffix.
1.66 jmc 310: These hashes may be used normally by
311: .Nm ssh
312: and
313: .Nm sshd ,
314: but they do not reveal identifying information should the file's contents
315: be disclosed.
316: This option will not modify existing hashed hostnames and is therefore safe
317: to use on files that mix hashed and non-hashed names.
1.84 djm 318: .It Fl h
319: When signing a key, create a host certificate instead of a user
320: certificate.
321: Please see the
322: .Sx CERTIFICATES
323: section for details.
1.85 jmc 324: .It Fl I Ar certificate_identity
1.84 djm 325: Specify the key identity when signing a public key.
326: Please see the
327: .Sx CERTIFICATES
328: section for details.
1.37 markus 329: .It Fl i
330: This option will read an unencrypted private (or public) key file
1.95 djm 331: in the format specified by the
332: .Fl m
333: option and print an OpenSSH compatible private
1.37 markus 334: (or public) key to stdout.
1.122 jmc 335: This option allows importing keys from other software, including several
336: commercial SSH implementations.
337: The default import format is
338: .Dq RFC4716 .
1.109 dtucker 339: .It Fl J Ar num_lines
340: Exit after screening the specified number of lines
341: while performing DH candidate screening using the
342: .Fl T
343: option.
344: .It Fl j Ar start_line
345: Start screening at the specified line number
346: while performing DH candidate screening using the
347: .Fl T
348: option.
1.108 dtucker 349: .It Fl K Ar checkpt
350: Write the last line processed to the file
351: .Ar checkpt
352: while performing DH candidate screening using the
353: .Fl T
354: option.
355: This will be used to skip lines in the input file that have already been
356: processed if the job is restarted.
1.111 djm 357: .It Fl k
358: Generate a KRL file.
359: In this mode,
360: .Nm
361: will generate a KRL file at the location specified via the
362: .Fl f
1.114 jmc 363: flag that revokes every key or certificate presented on the command line.
1.111 djm 364: Keys/certificates to be revoked may be specified by public key file or
365: using the format described in the
366: .Sx KEY REVOCATION LISTS
367: section.
1.86 djm 368: .It Fl L
369: Prints the contents of a certificate.
1.9 markus 370: .It Fl l
1.77 grunk 371: Show fingerprint of specified public key file.
1.50 markus 372: Private RSA1 keys are also supported.
373: For RSA and DSA keys
374: .Nm
1.78 jmc 375: tries to find the matching public key file and prints its fingerprint.
376: If combined with
377: .Fl v ,
378: an ASCII art representation of the key is supplied with the fingerprint.
1.96 jmc 379: .It Fl M Ar memory
380: Specify the amount of memory to use (in megabytes) when generating
381: candidate moduli for DH-GEX.
1.95 djm 382: .It Fl m Ar key_format
383: Specify a key format for the
384: .Fl i
385: (import) or
386: .Fl e
1.96 jmc 387: (export) conversion options.
1.95 djm 388: The supported key formats are:
389: .Dq RFC4716
1.96 jmc 390: (RFC 4716/SSH2 public or private key),
1.95 djm 391: .Dq PKCS8
392: (PEM PKCS8 public key)
393: or
394: .Dq PEM
395: (PEM public key).
396: The default conversion format is
397: .Dq RFC4716 .
1.66 jmc 398: .It Fl N Ar new_passphrase
399: Provides the new passphrase.
1.84 djm 400: .It Fl n Ar principals
401: Specify one or more principals (user or host names) to be included in
402: a certificate when signing a key.
403: Multiple principals may be specified, separated by commas.
404: Please see the
405: .Sx CERTIFICATES
406: section for details.
1.93 djm 407: .It Fl O Ar option
408: Specify a certificate option when signing a key.
1.84 djm 409: This option may be specified multiple times.
410: Please see the
411: .Sx CERTIFICATES
412: section for details.
1.93 djm 413: The options that are valid for user certificates are:
1.84 djm 414: .Bl -tag -width Ds
1.89 jmc 415: .It Ic clear
416: Clear all enabled permissions.
417: This is useful for clearing the default set of permissions so permissions may
418: be added individually.
419: .It Ic force-command Ns = Ns Ar command
420: Forces the execution of
421: .Ar command
422: instead of any shell or command specified by the user when
423: the certificate is used for authentication.
1.84 djm 424: .It Ic no-agent-forwarding
425: Disable
426: .Xr ssh-agent 1
1.85 jmc 427: forwarding (permitted by default).
1.84 djm 428: .It Ic no-port-forwarding
1.85 jmc 429: Disable port forwarding (permitted by default).
1.84 djm 430: .It Ic no-pty
1.85 jmc 431: Disable PTY allocation (permitted by default).
1.84 djm 432: .It Ic no-user-rc
433: Disable execution of
434: .Pa ~/.ssh/rc
435: by
1.85 jmc 436: .Xr sshd 8
437: (permitted by default).
1.89 jmc 438: .It Ic no-x11-forwarding
439: Disable X11 forwarding (permitted by default).
1.88 djm 440: .It Ic permit-agent-forwarding
441: Allows
442: .Xr ssh-agent 1
443: forwarding.
1.84 djm 444: .It Ic permit-port-forwarding
445: Allows port forwarding.
446: .It Ic permit-pty
447: Allows PTY allocation.
448: .It Ic permit-user-rc
449: Allows execution of
450: .Pa ~/.ssh/rc
451: by
452: .Xr sshd 8 .
1.89 jmc 453: .It Ic permit-x11-forwarding
454: Allows X11 forwarding.
455: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 456: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 457: The
458: .Ar address_list
459: is a comma-separated list of one or more address/netmask pairs in CIDR
460: format.
461: .El
462: .Pp
1.93 djm 463: At present, no options are valid for host keys.
1.117 djm 464: .It Fl o
465: Causes
466: .Nm
467: to save SSH protocol 2 private keys using the new OpenSSH format rather than
468: the more compatible PEM format.
469: The new format has increased resistance to brute-force password cracking
470: but is not supported by versions of OpenSSH prior to 6.5.
471: Ed25519 keys always use the new private key format.
1.66 jmc 472: .It Fl P Ar passphrase
473: Provides the (old) passphrase.
1.2 deraadt 474: .It Fl p
1.1 deraadt 475: Requests changing the passphrase of a private key file instead of
1.12 aaron 476: creating a new private key.
477: The program will prompt for the file
1.1 deraadt 478: containing the private key, for the old passphrase, and twice for the
479: new passphrase.
1.113 jmc 480: .It Fl Q
481: Test whether keys have been revoked in a KRL.
1.5 aaron 482: .It Fl q
483: Silence
484: .Nm ssh-keygen .
1.64 djm 485: .It Fl R Ar hostname
486: Removes all keys belonging to
487: .Ar hostname
1.65 jmc 488: from a
1.64 djm 489: .Pa known_hosts
490: file.
1.65 jmc 491: This option is useful to delete hashed hosts (see the
1.64 djm 492: .Fl H
493: option above).
1.66 jmc 494: .It Fl r Ar hostname
495: Print the SSHFP fingerprint resource record named
496: .Ar hostname
497: for the specified public key file.
1.60 djm 498: .It Fl S Ar start
499: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 500: .It Fl s Ar ca_key
501: Certify (sign) a public key using the specified CA key.
502: Please see the
503: .Sx CERTIFICATES
504: section for details.
1.111 djm 505: .Pp
506: When generating a KRL,
507: .Fl s
1.112 jmc 508: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 509: by key ID or serial number.
510: See the
511: .Sx KEY REVOCATION LISTS
512: section for details.
1.60 djm 513: .It Fl T Ar output_file
514: Test DH group exchange candidate primes (generated using the
515: .Fl G
516: option) for safety.
1.121 deraadt 517: .It Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1
1.66 jmc 518: Specifies the type of key to create.
519: The possible values are
520: .Dq rsa1
521: for protocol version 1 and
1.100 naddy 522: .Dq dsa ,
1.118 naddy 523: .Dq ecdsa ,
524: .Dq ed25519 ,
1.100 naddy 525: or
1.66 jmc 526: .Dq rsa
527: for protocol version 2.
1.112 jmc 528: .It Fl u
529: Update a KRL.
530: When specified with
531: .Fl k ,
1.114 jmc 532: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 533: a new KRL being created.
1.84 djm 534: .It Fl V Ar validity_interval
535: Specify a validity interval when signing a certificate.
536: A validity interval may consist of a single time, indicating that the
537: certificate is valid beginning now and expiring at that time, or may consist
538: of two times separated by a colon to indicate an explicit time interval.
539: The start time may be specified as a date in YYYYMMDD format, a time
540: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
541: of a minus sign followed by a relative time in the format described in the
1.116 jmc 542: TIME FORMATS section of
1.90 jmc 543: .Xr sshd_config 5 .
1.84 djm 544: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
545: a relative time starting with a plus character.
546: .Pp
547: For example:
548: .Dq +52w1d
549: (valid from now to 52 weeks and one day from now),
550: .Dq -4w:+4w
551: (valid from four weeks ago to four weeks from now),
552: .Dq 20100101123000:20110101123000
553: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
554: .Dq -1d:20110101
555: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 556: .It Fl v
557: Verbose mode.
558: Causes
559: .Nm
560: to print debugging messages about its progress.
561: This is helpful for debugging moduli generation.
562: Multiple
563: .Fl v
564: options increase the verbosity.
565: The maximum is 3.
1.66 jmc 566: .It Fl W Ar generator
567: Specify desired generator when testing candidate moduli for DH-GEX.
568: .It Fl y
569: This option will read a private
570: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 571: .It Fl z Ar serial_number
572: Specifies a serial number to be embedded in the certificate to distinguish
573: this certificate from others from the same CA.
574: The default serial number is zero.
1.111 djm 575: .Pp
576: When generating a KRL, the
577: .Fl z
578: flag is used to specify a KRL version number.
1.2 deraadt 579: .El
1.60 djm 580: .Sh MODULI GENERATION
581: .Nm
582: may be used to generate groups for the Diffie-Hellman Group Exchange
583: (DH-GEX) protocol.
584: Generating these groups is a two-step process: first, candidate
585: primes are generated using a fast, but memory intensive process.
586: These candidate primes are then tested for suitability (a CPU-intensive
587: process).
588: .Pp
589: Generation of primes is performed using the
590: .Fl G
591: option.
592: The desired length of the primes may be specified by the
593: .Fl b
594: option.
595: For example:
596: .Pp
1.66 jmc 597: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 598: .Pp
599: By default, the search for primes begins at a random point in the
600: desired length range.
601: This may be overridden using the
602: .Fl S
603: option, which specifies a different start point (in hex).
604: .Pp
1.109 dtucker 605: Once a set of candidates have been generated, they must be screened for
1.60 djm 606: suitability.
607: This may be performed using the
608: .Fl T
609: option.
610: In this mode
611: .Nm
612: will read candidates from standard input (or a file specified using the
613: .Fl f
614: option).
615: For example:
616: .Pp
1.66 jmc 617: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 618: .Pp
619: By default, each candidate will be subjected to 100 primality tests.
620: This may be overridden using the
621: .Fl a
622: option.
623: The DH generator value will be chosen automatically for the
624: prime under consideration.
625: If a specific generator is desired, it may be requested using the
626: .Fl W
627: option.
1.66 jmc 628: Valid generator values are 2, 3, and 5.
1.60 djm 629: .Pp
630: Screened DH groups may be installed in
631: .Pa /etc/moduli .
632: It is important that this file contains moduli of a range of bit lengths and
633: that both ends of a connection share common moduli.
1.84 djm 634: .Sh CERTIFICATES
635: .Nm
636: supports signing of keys to produce certificates that may be used for
637: user or host authentication.
638: Certificates consist of a public key, some identity information, zero or
1.94 jmc 639: more principal (user or host) names and a set of options that
1.84 djm 640: are signed by a Certification Authority (CA) key.
641: Clients or servers may then trust only the CA key and verify its signature
642: on a certificate rather than trusting many user/host keys.
643: Note that OpenSSH certificates are a different, and much simpler, format to
644: the X.509 certificates used in
645: .Xr ssl 8 .
646: .Pp
647: .Nm
648: supports two types of certificates: user and host.
649: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 650: authenticate server hosts to users.
651: To generate a user certificate:
1.84 djm 652: .Pp
653: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
654: .Pp
655: The resultant certificate will be placed in
1.91 djm 656: .Pa /path/to/user_key-cert.pub .
1.84 djm 657: A host certificate requires the
658: .Fl h
659: option:
660: .Pp
661: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
662: .Pp
663: The host certificate will be output to
1.91 djm 664: .Pa /path/to/host_key-cert.pub .
1.98 djm 665: .Pp
666: It is possible to sign using a CA key stored in a PKCS#11 token by
667: providing the token library using
668: .Fl D
669: and identifying the CA key by providing its public half as an argument
670: to
671: .Fl s :
672: .Pp
673: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id host_key.pub
674: .Pp
675: In all cases,
1.84 djm 676: .Ar key_id
677: is a "key identifier" that is logged by the server when the certificate
678: is used for authentication.
679: .Pp
680: Certificates may be limited to be valid for a set of principal (user/host)
681: names.
682: By default, generated certificates are valid for all users or hosts.
683: To generate a certificate for a specified set of principals:
684: .Pp
685: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.92 jmc 686: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub"
1.84 djm 687: .Pp
688: Additional limitations on the validity and use of user certificates may
1.94 jmc 689: be specified through certificate options.
1.93 djm 690: A certificate option may disable features of the SSH session, may be
1.84 djm 691: valid only when presented from particular source addresses or may
692: force the use of a specific command.
1.93 djm 693: For a list of valid certificate options, see the documentation for the
1.84 djm 694: .Fl O
695: option above.
696: .Pp
697: Finally, certificates may be defined with a validity lifetime.
698: The
699: .Fl V
700: option allows specification of certificate start and end times.
701: A certificate that is presented at a time outside this range will not be
702: considered valid.
1.110 jmc 703: By default, certificates are valid from
704: .Ux
705: Epoch to the distant future.
1.84 djm 706: .Pp
707: For certificates to be used for user or host authentication, the CA
708: public key must be trusted by
709: .Xr sshd 8
710: or
711: .Xr ssh 1 .
712: Please refer to those manual pages for details.
1.111 djm 713: .Sh KEY REVOCATION LISTS
714: .Nm
715: is able to manage OpenSSH format Key Revocation Lists (KRLs).
716: These binary files specify keys or certificates to be revoked using a
1.119 tedu 717: compact format, taking as little as one bit per certificate if they are being
1.111 djm 718: revoked by serial number.
719: .Pp
720: KRLs may be generated using the
721: .Fl k
722: flag.
1.114 jmc 723: This option reads one or more files from the command line and generates a new
1.111 djm 724: KRL.
725: The files may either contain a KRL specification (see below) or public keys,
726: listed one per line.
727: Plain public keys are revoked by listing their hash or contents in the KRL and
728: certificates revoked by serial number or key ID (if the serial is zero or
729: not available).
730: .Pp
731: Revoking keys using a KRL specification offers explicit control over the
732: types of record used to revoke keys and may be used to directly revoke
733: certificates by serial number or key ID without having the complete original
734: certificate on hand.
735: A KRL specification consists of lines containing one of the following directives
736: followed by a colon and some directive-specific information.
737: .Bl -tag -width Ds
1.115 jmc 738: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 739: Revokes a certificate with the specified serial number.
1.112 jmc 740: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 741: in decimal, hex or octal.
742: If two serial numbers are specified separated by a hyphen, then the range
743: of serial numbers including and between each is revoked.
744: The CA key must have been specified on the
745: .Nm
1.114 jmc 746: command line using the
1.111 djm 747: .Fl s
748: option.
749: .It Cm id : Ar key_id
750: Revokes a certificate with the specified key ID string.
751: The CA key must have been specified on the
752: .Nm
1.114 jmc 753: command line using the
1.111 djm 754: .Fl s
755: option.
756: .It Cm key : Ar public_key
757: Revokes the specified key.
1.112 jmc 758: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 759: .It Cm sha1 : Ar public_key
760: Revokes the specified key by its SHA1 hash.
761: .El
762: .Pp
763: KRLs may be updated using the
764: .Fl u
765: flag in addition to
766: .Fl k .
1.114 jmc 767: When this option is specified, keys listed via the command line are merged into
1.111 djm 768: the KRL, adding to those already there.
769: .Pp
770: It is also possible, given a KRL, to test whether it revokes a particular key
771: (or keys).
772: The
773: .Fl Q
774: flag will query an existing KRL, testing each key specified on the commandline.
1.114 jmc 775: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 776: then
777: .Nm
778: will exit with a non-zero exit status.
779: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 780: .Sh FILES
1.100 naddy 781: .Bl -tag -width Ds -compact
1.68 djm 782: .It Pa ~/.ssh/identity
1.36 itojun 783: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 784: This file should not be readable by anyone but the user.
785: It is possible to
1.1 deraadt 786: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 787: used to encrypt the private part of this file using 3DES.
1.12 aaron 788: This file is not automatically accessed by
1.2 deraadt 789: .Nm
1.1 deraadt 790: but it is offered as the default file for the private key.
1.46 markus 791: .Xr ssh 1
1.15 deraadt 792: will read this file when a login attempt is made.
1.100 naddy 793: .Pp
1.68 djm 794: .It Pa ~/.ssh/identity.pub
1.36 itojun 795: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 796: The contents of this file should be added to
1.68 djm 797: .Pa ~/.ssh/authorized_keys
1.2 deraadt 798: on all machines
1.49 deraadt 799: where the user wishes to log in using RSA authentication.
1.15 deraadt 800: There is no need to keep the contents of this file secret.
1.100 naddy 801: .Pp
1.68 djm 802: .It Pa ~/.ssh/id_dsa
1.100 naddy 803: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 804: .It Pa ~/.ssh/id_ed25519
1.100 naddy 805: .It Pa ~/.ssh/id_rsa
1.123 ! sobrado 806: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 807: authentication identity of the user.
1.15 deraadt 808: This file should not be readable by anyone but the user.
809: It is possible to
810: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 811: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 812: This file is not automatically accessed by
813: .Nm
814: but it is offered as the default file for the private key.
1.46 markus 815: .Xr ssh 1
1.15 deraadt 816: will read this file when a login attempt is made.
1.100 naddy 817: .Pp
1.68 djm 818: .It Pa ~/.ssh/id_dsa.pub
1.100 naddy 819: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 820: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 821: .It Pa ~/.ssh/id_rsa.pub
1.123 ! sobrado 822: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 823: public key for authentication.
1.15 deraadt 824: The contents of this file should be added to
1.68 djm 825: .Pa ~/.ssh/authorized_keys
1.15 deraadt 826: on all machines
1.49 deraadt 827: where the user wishes to log in using public key authentication.
1.12 aaron 828: There is no need to keep the contents of this file secret.
1.100 naddy 829: .Pp
1.60 djm 830: .It Pa /etc/moduli
831: Contains Diffie-Hellman groups used for DH-GEX.
832: The file format is described in
833: .Xr moduli 5 .
1.19 aaron 834: .El
1.2 deraadt 835: .Sh SEE ALSO
836: .Xr ssh 1 ,
837: .Xr ssh-add 1 ,
1.8 ericj 838: .Xr ssh-agent 1 ,
1.60 djm 839: .Xr moduli 5 ,
1.30 itojun 840: .Xr sshd 8
1.37 markus 841: .Rs
1.73 markus 842: .%R RFC 4716
843: .%T "The Secure Shell (SSH) Public Key File Format"
844: .%D 2006
1.37 markus 845: .Re
1.59 jmc 846: .Sh AUTHORS
847: OpenSSH is a derivative of the original and free
848: ssh 1.2.12 release by Tatu Ylonen.
849: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
850: Theo de Raadt and Dug Song
851: removed many bugs, re-added newer features and
852: created OpenSSH.
853: Markus Friedl contributed the support for SSH
854: protocol versions 1.5 and 2.0.
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