Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.133
1.133 ! jmc 1: .\" $OpenBSD: ssh-keygen.1,v 1.132 2016/05/03 18:38:12 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: .\"
1.132 jmc 38: .Dd $Mdocdate: May 3 2016 $
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
1.125 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
1.133 ! jmc 210: For RSA1 keys and 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
1.118 naddy 226: For each of the key types (rsa1, rsa, dsa, ecdsa and ed25519)
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.
1.133 ! jmc 267: This operation is only supported for RSA1 keys and keys stored in the
! 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: Private RSA1 keys are also supported.
388: For RSA and DSA keys
389: .Nm
1.78 jmc 390: tries to find the matching public key file and prints its fingerprint.
391: If combined with
392: .Fl v ,
1.132 jmc 393: a visual ASCII art representation of the key is supplied with the
1.131 djm 394: fingerprint.
1.96 jmc 395: .It Fl M Ar memory
396: Specify the amount of memory to use (in megabytes) when generating
397: candidate moduli for DH-GEX.
1.95 djm 398: .It Fl m Ar key_format
399: Specify a key format for the
400: .Fl i
401: (import) or
402: .Fl e
1.96 jmc 403: (export) conversion options.
1.95 djm 404: The supported key formats are:
405: .Dq RFC4716
1.96 jmc 406: (RFC 4716/SSH2 public or private key),
1.95 djm 407: .Dq PKCS8
408: (PEM PKCS8 public key)
409: or
410: .Dq PEM
411: (PEM public key).
412: The default conversion format is
413: .Dq RFC4716 .
1.66 jmc 414: .It Fl N Ar new_passphrase
415: Provides the new passphrase.
1.84 djm 416: .It Fl n Ar principals
417: Specify one or more principals (user or host names) to be included in
418: a certificate when signing a key.
419: Multiple principals may be specified, separated by commas.
420: Please see the
421: .Sx CERTIFICATES
422: section for details.
1.93 djm 423: .It Fl O Ar option
424: Specify a certificate option when signing a key.
1.84 djm 425: This option may be specified multiple times.
426: Please see the
427: .Sx CERTIFICATES
428: section for details.
1.93 djm 429: The options that are valid for user certificates are:
1.84 djm 430: .Bl -tag -width Ds
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.
435: .It Ic force-command Ns = Ns Ar command
436: Forces the execution of
437: .Ar command
438: instead of any shell or command specified by the user when
439: the certificate is used for authentication.
1.84 djm 440: .It Ic no-agent-forwarding
441: Disable
442: .Xr ssh-agent 1
1.85 jmc 443: forwarding (permitted by default).
1.84 djm 444: .It Ic no-port-forwarding
1.85 jmc 445: Disable port forwarding (permitted by default).
1.84 djm 446: .It Ic no-pty
1.85 jmc 447: Disable PTY allocation (permitted by default).
1.84 djm 448: .It Ic no-user-rc
449: Disable execution of
450: .Pa ~/.ssh/rc
451: by
1.85 jmc 452: .Xr sshd 8
453: (permitted by default).
1.89 jmc 454: .It Ic no-x11-forwarding
455: Disable X11 forwarding (permitted by default).
1.88 djm 456: .It Ic permit-agent-forwarding
457: Allows
458: .Xr ssh-agent 1
459: forwarding.
1.84 djm 460: .It Ic permit-port-forwarding
461: Allows port forwarding.
462: .It Ic permit-pty
463: Allows PTY allocation.
464: .It Ic permit-user-rc
465: Allows execution of
466: .Pa ~/.ssh/rc
467: by
468: .Xr sshd 8 .
1.89 jmc 469: .It Ic permit-x11-forwarding
470: Allows X11 forwarding.
471: .It Ic source-address Ns = Ns Ar address_list
1.90 jmc 472: Restrict the source addresses from which the certificate is considered valid.
1.84 djm 473: The
474: .Ar address_list
475: is a comma-separated list of one or more address/netmask pairs in CIDR
476: format.
477: .El
478: .Pp
1.93 djm 479: At present, no options are valid for host keys.
1.117 djm 480: .It Fl o
481: Causes
482: .Nm
1.130 jmc 483: to save private keys using the new OpenSSH format rather than
1.117 djm 484: the more compatible PEM format.
485: The new format has increased resistance to brute-force password cracking
486: but is not supported by versions of OpenSSH prior to 6.5.
487: Ed25519 keys always use the new private key format.
1.66 jmc 488: .It Fl P Ar passphrase
489: Provides the (old) passphrase.
1.2 deraadt 490: .It Fl p
1.1 deraadt 491: Requests changing the passphrase of a private key file instead of
1.12 aaron 492: creating a new private key.
493: The program will prompt for the file
1.1 deraadt 494: containing the private key, for the old passphrase, and twice for the
495: new passphrase.
1.113 jmc 496: .It Fl Q
497: Test whether keys have been revoked in a KRL.
1.5 aaron 498: .It Fl q
499: Silence
500: .Nm ssh-keygen .
1.64 djm 501: .It Fl R Ar hostname
502: Removes all keys belonging to
503: .Ar hostname
1.65 jmc 504: from a
1.64 djm 505: .Pa known_hosts
506: file.
1.65 jmc 507: This option is useful to delete hashed hosts (see the
1.64 djm 508: .Fl H
509: option above).
1.66 jmc 510: .It Fl r Ar hostname
511: Print the SSHFP fingerprint resource record named
512: .Ar hostname
513: for the specified public key file.
1.60 djm 514: .It Fl S Ar start
515: Specify start point (in hex) when generating candidate moduli for DH-GEX.
1.84 djm 516: .It Fl s Ar ca_key
517: Certify (sign) a public key using the specified CA key.
518: Please see the
519: .Sx CERTIFICATES
520: section for details.
1.111 djm 521: .Pp
522: When generating a KRL,
523: .Fl s
1.112 jmc 524: specifies a path to a CA public key file used to revoke certificates directly
1.111 djm 525: by key ID or serial number.
526: See the
527: .Sx KEY REVOCATION LISTS
528: section for details.
1.60 djm 529: .It Fl T Ar output_file
530: Test DH group exchange candidate primes (generated using the
531: .Fl G
532: option) for safety.
1.121 deraadt 533: .It Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1
1.66 jmc 534: Specifies the type of key to create.
535: The possible values are
536: .Dq rsa1
537: for protocol version 1 and
1.100 naddy 538: .Dq dsa ,
1.118 naddy 539: .Dq ecdsa ,
540: .Dq ed25519 ,
1.100 naddy 541: or
1.66 jmc 542: .Dq rsa
543: for protocol version 2.
1.112 jmc 544: .It Fl u
545: Update a KRL.
546: When specified with
547: .Fl k ,
1.114 jmc 548: keys listed via the command line are added to the existing KRL rather than
1.112 jmc 549: a new KRL being created.
1.84 djm 550: .It Fl V Ar validity_interval
551: Specify a validity interval when signing a certificate.
552: A validity interval may consist of a single time, indicating that the
553: certificate is valid beginning now and expiring at that time, or may consist
554: of two times separated by a colon to indicate an explicit time interval.
555: The start time may be specified as a date in YYYYMMDD format, a time
556: in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
557: of a minus sign followed by a relative time in the format described in the
1.116 jmc 558: TIME FORMATS section of
1.90 jmc 559: .Xr sshd_config 5 .
1.84 djm 560: The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
561: a relative time starting with a plus character.
562: .Pp
563: For example:
564: .Dq +52w1d
565: (valid from now to 52 weeks and one day from now),
566: .Dq -4w:+4w
567: (valid from four weeks ago to four weeks from now),
568: .Dq 20100101123000:20110101123000
569: (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
570: .Dq -1d:20110101
571: (valid from yesterday to midnight, January 1st, 2011).
1.61 djm 572: .It Fl v
573: Verbose mode.
574: Causes
575: .Nm
576: to print debugging messages about its progress.
577: This is helpful for debugging moduli generation.
578: Multiple
579: .Fl v
580: options increase the verbosity.
581: The maximum is 3.
1.66 jmc 582: .It Fl W Ar generator
583: Specify desired generator when testing candidate moduli for DH-GEX.
584: .It Fl y
585: This option will read a private
586: OpenSSH format file and print an OpenSSH public key to stdout.
1.93 djm 587: .It Fl z Ar serial_number
588: Specifies a serial number to be embedded in the certificate to distinguish
589: this certificate from others from the same CA.
590: The default serial number is zero.
1.111 djm 591: .Pp
592: When generating a KRL, the
593: .Fl z
594: flag is used to specify a KRL version number.
1.2 deraadt 595: .El
1.60 djm 596: .Sh MODULI GENERATION
597: .Nm
598: may be used to generate groups for the Diffie-Hellman Group Exchange
599: (DH-GEX) protocol.
600: Generating these groups is a two-step process: first, candidate
601: primes are generated using a fast, but memory intensive process.
602: These candidate primes are then tested for suitability (a CPU-intensive
603: process).
604: .Pp
605: Generation of primes is performed using the
606: .Fl G
607: option.
608: The desired length of the primes may be specified by the
609: .Fl b
610: option.
611: For example:
612: .Pp
1.66 jmc 613: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 614: .Pp
615: By default, the search for primes begins at a random point in the
616: desired length range.
617: This may be overridden using the
618: .Fl S
619: option, which specifies a different start point (in hex).
620: .Pp
1.109 dtucker 621: Once a set of candidates have been generated, they must be screened for
1.60 djm 622: suitability.
623: This may be performed using the
624: .Fl T
625: option.
626: In this mode
627: .Nm
628: will read candidates from standard input (or a file specified using the
629: .Fl f
630: option).
631: For example:
632: .Pp
1.66 jmc 633: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 634: .Pp
635: By default, each candidate will be subjected to 100 primality tests.
636: This may be overridden using the
637: .Fl a
638: option.
639: The DH generator value will be chosen automatically for the
640: prime under consideration.
641: If a specific generator is desired, it may be requested using the
642: .Fl W
643: option.
1.66 jmc 644: Valid generator values are 2, 3, and 5.
1.60 djm 645: .Pp
646: Screened DH groups may be installed in
647: .Pa /etc/moduli .
648: It is important that this file contains moduli of a range of bit lengths and
649: that both ends of a connection share common moduli.
1.84 djm 650: .Sh CERTIFICATES
651: .Nm
652: supports signing of keys to produce certificates that may be used for
653: user or host authentication.
654: Certificates consist of a public key, some identity information, zero or
1.94 jmc 655: more principal (user or host) names and a set of options that
1.84 djm 656: are signed by a Certification Authority (CA) key.
657: Clients or servers may then trust only the CA key and verify its signature
658: on a certificate rather than trusting many user/host keys.
659: Note that OpenSSH certificates are a different, and much simpler, format to
660: the X.509 certificates used in
661: .Xr ssl 8 .
662: .Pp
663: .Nm
664: supports two types of certificates: user and host.
665: User certificates authenticate users to servers, whereas host certificates
1.85 jmc 666: authenticate server hosts to users.
667: To generate a user certificate:
1.84 djm 668: .Pp
669: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
670: .Pp
671: The resultant certificate will be placed in
1.91 djm 672: .Pa /path/to/user_key-cert.pub .
1.84 djm 673: A host certificate requires the
674: .Fl h
675: option:
676: .Pp
677: .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
678: .Pp
679: The host certificate will be output to
1.91 djm 680: .Pa /path/to/host_key-cert.pub .
1.98 djm 681: .Pp
682: It is possible to sign using a CA key stored in a PKCS#11 token by
683: providing the token library using
684: .Fl D
685: and identifying the CA key by providing its public half as an argument
686: to
687: .Fl s :
688: .Pp
1.127 naddy 689: .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
1.98 djm 690: .Pp
691: In all cases,
1.84 djm 692: .Ar key_id
693: is a "key identifier" that is logged by the server when the certificate
694: is used for authentication.
695: .Pp
696: Certificates may be limited to be valid for a set of principal (user/host)
697: names.
698: By default, generated certificates are valid for all users or hosts.
699: To generate a certificate for a specified set of principals:
700: .Pp
701: .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
1.127 naddy 702: .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
1.84 djm 703: .Pp
704: Additional limitations on the validity and use of user certificates may
1.94 jmc 705: be specified through certificate options.
1.93 djm 706: A certificate option may disable features of the SSH session, may be
1.84 djm 707: valid only when presented from particular source addresses or may
708: force the use of a specific command.
1.93 djm 709: For a list of valid certificate options, see the documentation for the
1.84 djm 710: .Fl O
711: option above.
712: .Pp
713: Finally, certificates may be defined with a validity lifetime.
714: The
715: .Fl V
716: option allows specification of certificate start and end times.
717: A certificate that is presented at a time outside this range will not be
718: considered valid.
1.110 jmc 719: By default, certificates are valid from
720: .Ux
721: Epoch to the distant future.
1.84 djm 722: .Pp
723: For certificates to be used for user or host authentication, the CA
724: public key must be trusted by
725: .Xr sshd 8
726: or
727: .Xr ssh 1 .
728: Please refer to those manual pages for details.
1.111 djm 729: .Sh KEY REVOCATION LISTS
730: .Nm
731: is able to manage OpenSSH format Key Revocation Lists (KRLs).
732: These binary files specify keys or certificates to be revoked using a
1.119 tedu 733: compact format, taking as little as one bit per certificate if they are being
1.111 djm 734: revoked by serial number.
735: .Pp
736: KRLs may be generated using the
737: .Fl k
738: flag.
1.114 jmc 739: This option reads one or more files from the command line and generates a new
1.111 djm 740: KRL.
741: The files may either contain a KRL specification (see below) or public keys,
742: listed one per line.
743: Plain public keys are revoked by listing their hash or contents in the KRL and
744: certificates revoked by serial number or key ID (if the serial is zero or
745: not available).
746: .Pp
747: Revoking keys using a KRL specification offers explicit control over the
748: types of record used to revoke keys and may be used to directly revoke
749: certificates by serial number or key ID without having the complete original
750: certificate on hand.
751: A KRL specification consists of lines containing one of the following directives
752: followed by a colon and some directive-specific information.
753: .Bl -tag -width Ds
1.115 jmc 754: .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
1.111 djm 755: Revokes a certificate with the specified serial number.
1.112 jmc 756: Serial numbers are 64-bit values, not including zero and may be expressed
1.111 djm 757: in decimal, hex or octal.
758: If two serial numbers are specified separated by a hyphen, then the range
759: of serial numbers including and between each is revoked.
760: The CA key must have been specified on the
761: .Nm
1.114 jmc 762: command line using the
1.111 djm 763: .Fl s
764: option.
765: .It Cm id : Ar key_id
766: Revokes a certificate with the specified key ID string.
767: The CA key must have been specified on the
768: .Nm
1.114 jmc 769: command line using the
1.111 djm 770: .Fl s
771: option.
772: .It Cm key : Ar public_key
773: Revokes the specified key.
1.112 jmc 774: If a certificate is listed, then it is revoked as a plain public key.
1.111 djm 775: .It Cm sha1 : Ar public_key
776: Revokes the specified key by its SHA1 hash.
777: .El
778: .Pp
779: KRLs may be updated using the
780: .Fl u
781: flag in addition to
782: .Fl k .
1.114 jmc 783: When this option is specified, keys listed via the command line are merged into
1.111 djm 784: the KRL, adding to those already there.
785: .Pp
786: It is also possible, given a KRL, to test whether it revokes a particular key
787: (or keys).
788: The
789: .Fl Q
1.128 jmc 790: flag will query an existing KRL, testing each key specified on the command line.
1.114 jmc 791: If any key listed on the command line has been revoked (or an error encountered)
1.111 djm 792: then
793: .Nm
794: will exit with a non-zero exit status.
795: A zero exit status will only be returned if no key was revoked.
1.2 deraadt 796: .Sh FILES
1.100 naddy 797: .Bl -tag -width Ds -compact
1.68 djm 798: .It Pa ~/.ssh/identity
1.36 itojun 799: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 800: This file should not be readable by anyone but the user.
801: It is possible to
1.1 deraadt 802: specify a passphrase when generating the key; that passphrase will be
1.100 naddy 803: used to encrypt the private part of this file using 3DES.
1.12 aaron 804: This file is not automatically accessed by
1.2 deraadt 805: .Nm
1.1 deraadt 806: but it is offered as the default file for the private key.
1.46 markus 807: .Xr ssh 1
1.15 deraadt 808: will read this file when a login attempt is made.
1.100 naddy 809: .Pp
1.68 djm 810: .It Pa ~/.ssh/identity.pub
1.36 itojun 811: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 812: The contents of this file should be added to
1.68 djm 813: .Pa ~/.ssh/authorized_keys
1.2 deraadt 814: on all machines
1.49 deraadt 815: where the user wishes to log in using RSA authentication.
1.15 deraadt 816: There is no need to keep the contents of this file secret.
1.100 naddy 817: .Pp
1.68 djm 818: .It Pa ~/.ssh/id_dsa
1.100 naddy 819: .It Pa ~/.ssh/id_ecdsa
1.118 naddy 820: .It Pa ~/.ssh/id_ed25519
1.100 naddy 821: .It Pa ~/.ssh/id_rsa
1.123 sobrado 822: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 823: authentication identity of the user.
1.15 deraadt 824: This file should not be readable by anyone but the user.
825: It is possible to
826: specify a passphrase when generating the key; that passphrase will be
1.80 dtucker 827: used to encrypt the private part of this file using 128-bit AES.
1.15 deraadt 828: This file is not automatically accessed by
829: .Nm
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/id_dsa.pub
1.100 naddy 835: .It Pa ~/.ssh/id_ecdsa.pub
1.118 naddy 836: .It Pa ~/.ssh/id_ed25519.pub
1.68 djm 837: .It Pa ~/.ssh/id_rsa.pub
1.123 sobrado 838: Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
1.118 naddy 839: public key for authentication.
1.15 deraadt 840: The contents of this file should be added to
1.68 djm 841: .Pa ~/.ssh/authorized_keys
1.15 deraadt 842: on all machines
1.49 deraadt 843: where the user wishes to log in using public key authentication.
1.12 aaron 844: There is no need to keep the contents of this file secret.
1.100 naddy 845: .Pp
1.60 djm 846: .It Pa /etc/moduli
847: Contains Diffie-Hellman groups used for DH-GEX.
848: The file format is described in
849: .Xr moduli 5 .
1.19 aaron 850: .El
1.2 deraadt 851: .Sh SEE ALSO
852: .Xr ssh 1 ,
853: .Xr ssh-add 1 ,
1.8 ericj 854: .Xr ssh-agent 1 ,
1.60 djm 855: .Xr moduli 5 ,
1.30 itojun 856: .Xr sshd 8
1.37 markus 857: .Rs
1.73 markus 858: .%R RFC 4716
859: .%T "The Secure Shell (SSH) Public Key File Format"
860: .%D 2006
1.37 markus 861: .Re
1.59 jmc 862: .Sh AUTHORS
863: OpenSSH is a derivative of the original and free
864: ssh 1.2.12 release by Tatu Ylonen.
865: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
866: Theo de Raadt and Dug Song
867: removed many bugs, re-added newer features and
868: created OpenSSH.
869: Markus Friedl contributed the support for SSH
870: protocol versions 1.5 and 2.0.
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