1 .\" $OpenBSD: ssh-keygen.1,v 1.116 2013/06/27 14:05:37 jmc Exp $
4 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
5 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 .\" All rights reserved
8 .\" As far as I am concerned, the code I have written for this software
9 .\" can be used freely for any purpose. Any derived versions of this
10 .\" software must be clearly marked as such, and if the derived work is
11 .\" incompatible with the protocol description in the RFC file, it must be
12 .\" called by a name other than "ssh" or "Secure Shell".
15 .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
16 .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
17 .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
19 .\" Redistribution and use in source and binary forms, with or without
20 .\" modification, are permitted provided that the following conditions
22 .\" 1. Redistributions of source code must retain the above copyright
23 .\" notice, this list of conditions and the following disclaimer.
24 .\" 2. Redistributions in binary form must reproduce the above copyright
25 .\" notice, this list of conditions and the following disclaimer in the
26 .\" documentation and/or other materials provided with the distribution.
28 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
29 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
31 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
32 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
33 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
37 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
44 .Nd authentication key generation, management and conversion
51 .Op Fl N Ar new_passphrase
53 .Op Fl f Ar output_keyfile
56 .Op Fl P Ar old_passphrase
57 .Op Fl N Ar new_passphrase
61 .Op Fl m Ar key_format
62 .Op Fl f Ar input_keyfile
65 .Op Fl m Ar key_format
66 .Op Fl f Ar input_keyfile
69 .Op Fl f Ar input_keyfile
72 .Op Fl P Ar passphrase
77 .Op Fl f Ar input_keyfile
80 .Op Fl f Ar input_keyfile
85 .Op Fl f Ar known_hosts_file
89 .Op Fl f Ar known_hosts_file
92 .Op Fl f Ar known_hosts_file
95 .Op Fl f Ar input_keyfile
102 .Op Fl S Ar start_point
107 .Op Fl a Ar num_trials
108 .Op Fl J Ar num_lines
109 .Op Fl j Ar start_line
111 .Op Fl W Ar generator
114 .Fl I Ar certificate_identity
116 .Op Fl n Ar principals
118 .Op Fl V Ar validity_interval
119 .Op Fl z Ar serial_number
123 .Op Fl f Ar input_keyfile
130 .Op Fl s Ar ca_public
131 .Op Fl z Ar version_number
140 generates, manages and converts authentication keys for
143 can create RSA keys for use by SSH protocol version 1 and DSA, ECDSA or RSA
144 keys for use by SSH protocol version 2.
145 The type of key to be generated is specified with the
148 If invoked without any arguments,
150 will generate an RSA key for use in SSH protocol 2 connections.
153 is also used to generate groups for use in Diffie-Hellman group
156 .Sx MODULI GENERATION
161 can be used to generate and update Key Revocation Lists, and to test whether
162 given keys have been revoked by one.
164 .Sx KEY REVOCATION LISTS
167 Normally each user wishing to use SSH
168 with public key authentication runs this once to create the authentication
170 .Pa ~/.ssh/identity ,
171 .Pa ~/.ssh/id_ecdsa ,
175 Additionally, the system administrator may use this to generate host keys,
179 Normally this program generates the key and asks for a file in which
180 to store the private key.
181 The public key is stored in a file with the same name but
184 The program also asks for a passphrase.
185 The passphrase may be empty to indicate no passphrase
186 (host keys must have an empty passphrase), or it may be a string of
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
191 Good passphrases are 10-30 characters long, are
192 not simple sentences or otherwise easily guessable (English
193 prose has only 1-2 bits of entropy per character, and provides very bad
194 passphrases), and contain a mix of upper and lowercase letters,
195 numbers, and non-alphanumeric characters.
196 The passphrase can be changed later by using the
200 There is no way to recover a lost passphrase.
201 If the passphrase is lost or forgotten, a new key must be generated
202 and the corresponding public key copied to other machines.
205 there is also a comment field in the key file that is only for
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
210 when the key is created, but can be changed using the
214 After a key is generated, instructions below detail where the keys
215 should be placed to be activated.
217 The options are as follows:
220 For each of the key types (rsa1, rsa, dsa and ecdsa) for which host keys
221 do not exist, generate the host keys with the default key file path,
222 an empty passphrase, default bits for the key type, and default comment.
225 to generate new host keys.
227 Specifies the number of primality tests to perform when screening DH-GEX
232 Show the bubblebabble digest of specified private or public key file.
234 Specifies the number of bits in the key to create.
235 For RSA keys, the minimum size is 768 bits and the default is 2048 bits.
236 Generally, 2048 bits is considered sufficient.
237 DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
240 flag determines the key length by selecting from one of three elliptic
241 curve sizes: 256, 384 or 521 bits.
242 Attempting to use bit lengths other than these three values for ECDSA keys
245 Provides a new comment.
247 Requests changing the comment in the private and public key files.
248 This operation is only supported for RSA1 keys.
249 The program will prompt for the file containing the private keys, for
250 the passphrase if the key has one, and for the new comment.
252 Download the RSA public keys provided by the PKCS#11 shared library
254 When used in combination with
256 this option indicates that a CA key resides in a PKCS#11 token (see the
258 section for details).
260 This option will read a private or public OpenSSH key file and
261 print to stdout the key in one of the formats specified by the
264 The default export format is
266 This option allows exporting OpenSSH keys for use by other programs, including
267 several commercial SSH implementations.
269 Search for the specified
273 file, listing any occurrences found.
274 This option is useful to find hashed host names or addresses and may also be
275 used in conjunction with the
277 option to print found keys in a hashed format.
279 Specifies the filename of the key file.
280 .It Fl G Ar output_file
281 Generate candidate primes for DH-GEX.
282 These primes must be screened for
287 Use generic DNS format when printing fingerprint resource records using the
294 This replaces all hostnames and addresses with hashed representations
295 within the specified file; the original content is moved to a file with
297 These hashes may be used normally by
301 but they do not reveal identifying information should the file's contents
303 This option will not modify existing hashed hostnames and is therefore safe
304 to use on files that mix hashed and non-hashed names.
306 When signing a key, create a host certificate instead of a user
311 .It Fl I Ar certificate_identity
312 Specify the key identity when signing a public key.
317 This option will read an unencrypted private (or public) key file
318 in the format specified by the
320 option and print an OpenSSH compatible private
321 (or public) key to stdout.
322 .It Fl J Ar num_lines
323 Exit after screening the specified number of lines
324 while performing DH candidate screening using the
327 .It Fl j Ar start_line
328 Start screening at the specified line number
329 while performing DH candidate screening using the
333 Write the last line processed to the file
335 while performing DH candidate screening using the
338 This will be used to skip lines in the input file that have already been
339 processed if the job is restarted.
340 This option allows importing keys from other software, including several
341 commercial SSH implementations.
342 The default import format is
348 will generate a KRL file at the location specified via the
350 flag that revokes every key or certificate presented on the command line.
351 Keys/certificates to be revoked may be specified by public key file or
352 using the format described in the
353 .Sx KEY REVOCATION LISTS
356 Prints the contents of a certificate.
358 Show fingerprint of specified public key file.
359 Private RSA1 keys are also supported.
362 tries to find the matching public key file and prints its fingerprint.
365 an ASCII art representation of the key is supplied with the fingerprint.
367 Specify the amount of memory to use (in megabytes) when generating
368 candidate moduli for DH-GEX.
369 .It Fl m Ar key_format
370 Specify a key format for the
374 (export) conversion options.
375 The supported key formats are:
377 (RFC 4716/SSH2 public or private key),
379 (PEM PKCS8 public key)
383 The default conversion format is
385 .It Fl N Ar new_passphrase
386 Provides the new passphrase.
387 .It Fl n Ar principals
388 Specify one or more principals (user or host names) to be included in
389 a certificate when signing a key.
390 Multiple principals may be specified, separated by commas.
395 Specify a certificate option when signing a key.
396 This option may be specified multiple times.
400 The options that are valid for user certificates are:
403 Clear all enabled permissions.
404 This is useful for clearing the default set of permissions so permissions may
405 be added individually.
406 .It Ic force-command Ns = Ns Ar command
407 Forces the execution of
409 instead of any shell or command specified by the user when
410 the certificate is used for authentication.
411 .It Ic no-agent-forwarding
414 forwarding (permitted by default).
415 .It Ic no-port-forwarding
416 Disable port forwarding (permitted by default).
418 Disable PTY allocation (permitted by default).
424 (permitted by default).
425 .It Ic no-x11-forwarding
426 Disable X11 forwarding (permitted by default).
427 .It Ic permit-agent-forwarding
431 .It Ic permit-port-forwarding
432 Allows port forwarding.
434 Allows PTY allocation.
435 .It Ic permit-user-rc
440 .It Ic permit-x11-forwarding
441 Allows X11 forwarding.
442 .It Ic source-address Ns = Ns Ar address_list
443 Restrict the source addresses from which the certificate is considered valid.
446 is a comma-separated list of one or more address/netmask pairs in CIDR
450 At present, no options are valid for host keys.
451 .It Fl P Ar passphrase
452 Provides the (old) passphrase.
454 Requests changing the passphrase of a private key file instead of
455 creating a new private key.
456 The program will prompt for the file
457 containing the private key, for the old passphrase, and twice for the
460 Test whether keys have been revoked in a KRL.
465 Removes all keys belonging to
470 This option is useful to delete hashed hosts (see the
474 Print the SSHFP fingerprint resource record named
476 for the specified public key file.
478 Specify start point (in hex) when generating candidate moduli for DH-GEX.
480 Certify (sign) a public key using the specified CA key.
485 When generating a KRL,
487 specifies a path to a CA public key file used to revoke certificates directly
488 by key ID or serial number.
490 .Sx KEY REVOCATION LISTS
492 .It Fl T Ar output_file
493 Test DH group exchange candidate primes (generated using the
497 Specifies the type of key to create.
498 The possible values are
500 for protocol version 1 and
505 for protocol version 2.
510 keys listed via the command line are added to the existing KRL rather than
511 a new KRL being created.
512 .It Fl V Ar validity_interval
513 Specify a validity interval when signing a certificate.
514 A validity interval may consist of a single time, indicating that the
515 certificate is valid beginning now and expiring at that time, or may consist
516 of two times separated by a colon to indicate an explicit time interval.
517 The start time may be specified as a date in YYYYMMDD format, a time
518 in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
519 of a minus sign followed by a relative time in the format described in the
520 TIME FORMATS section of
522 The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
523 a relative time starting with a plus character.
527 (valid from now to 52 weeks and one day from now),
529 (valid from four weeks ago to four weeks from now),
530 .Dq 20100101123000:20110101123000
531 (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
533 (valid from yesterday to midnight, January 1st, 2011).
538 to print debugging messages about its progress.
539 This is helpful for debugging moduli generation.
542 options increase the verbosity.
544 .It Fl W Ar generator
545 Specify desired generator when testing candidate moduli for DH-GEX.
547 This option will read a private
548 OpenSSH format file and print an OpenSSH public key to stdout.
549 .It Fl z Ar serial_number
550 Specifies a serial number to be embedded in the certificate to distinguish
551 this certificate from others from the same CA.
552 The default serial number is zero.
554 When generating a KRL, the
556 flag is used to specify a KRL version number.
558 .Sh MODULI GENERATION
560 may be used to generate groups for the Diffie-Hellman Group Exchange
562 Generating these groups is a two-step process: first, candidate
563 primes are generated using a fast, but memory intensive process.
564 These candidate primes are then tested for suitability (a CPU-intensive
567 Generation of primes is performed using the
570 The desired length of the primes may be specified by the
575 .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
577 By default, the search for primes begins at a random point in the
578 desired length range.
579 This may be overridden using the
581 option, which specifies a different start point (in hex).
583 Once a set of candidates have been generated, they must be screened for
585 This may be performed using the
590 will read candidates from standard input (or a file specified using the
595 .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
597 By default, each candidate will be subjected to 100 primality tests.
598 This may be overridden using the
601 The DH generator value will be chosen automatically for the
602 prime under consideration.
603 If a specific generator is desired, it may be requested using the
606 Valid generator values are 2, 3, and 5.
608 Screened DH groups may be installed in
610 It is important that this file contains moduli of a range of bit lengths and
611 that both ends of a connection share common moduli.
614 supports signing of keys to produce certificates that may be used for
615 user or host authentication.
616 Certificates consist of a public key, some identity information, zero or
617 more principal (user or host) names and a set of options that
618 are signed by a Certification Authority (CA) key.
619 Clients or servers may then trust only the CA key and verify its signature
620 on a certificate rather than trusting many user/host keys.
621 Note that OpenSSH certificates are a different, and much simpler, format to
622 the X.509 certificates used in
626 supports two types of certificates: user and host.
627 User certificates authenticate users to servers, whereas host certificates
628 authenticate server hosts to users.
629 To generate a user certificate:
631 .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
633 The resultant certificate will be placed in
634 .Pa /path/to/user_key-cert.pub .
635 A host certificate requires the
639 .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
641 The host certificate will be output to
642 .Pa /path/to/host_key-cert.pub .
644 It is possible to sign using a CA key stored in a PKCS#11 token by
645 providing the token library using
647 and identifying the CA key by providing its public half as an argument
651 .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id host_key.pub
655 is a "key identifier" that is logged by the server when the certificate
656 is used for authentication.
658 Certificates may be limited to be valid for a set of principal (user/host)
660 By default, generated certificates are valid for all users or hosts.
661 To generate a certificate for a specified set of principals:
663 .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
664 .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub"
666 Additional limitations on the validity and use of user certificates may
667 be specified through certificate options.
668 A certificate option may disable features of the SSH session, may be
669 valid only when presented from particular source addresses or may
670 force the use of a specific command.
671 For a list of valid certificate options, see the documentation for the
675 Finally, certificates may be defined with a validity lifetime.
678 option allows specification of certificate start and end times.
679 A certificate that is presented at a time outside this range will not be
681 By default, certificates are valid from
683 Epoch to the distant future.
685 For certificates to be used for user or host authentication, the CA
686 public key must be trusted by
690 Please refer to those manual pages for details.
691 .Sh KEY REVOCATION LISTS
693 is able to manage OpenSSH format Key Revocation Lists (KRLs).
694 These binary files specify keys or certificates to be revoked using a
695 compact format, taking as little a one bit per certificate if they are being
696 revoked by serial number.
698 KRLs may be generated using the
701 This option reads one or more files from the command line and generates a new
703 The files may either contain a KRL specification (see below) or public keys,
705 Plain public keys are revoked by listing their hash or contents in the KRL and
706 certificates revoked by serial number or key ID (if the serial is zero or
709 Revoking keys using a KRL specification offers explicit control over the
710 types of record used to revoke keys and may be used to directly revoke
711 certificates by serial number or key ID without having the complete original
713 A KRL specification consists of lines containing one of the following directives
714 followed by a colon and some directive-specific information.
716 .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
717 Revokes a certificate with the specified serial number.
718 Serial numbers are 64-bit values, not including zero and may be expressed
719 in decimal, hex or octal.
720 If two serial numbers are specified separated by a hyphen, then the range
721 of serial numbers including and between each is revoked.
722 The CA key must have been specified on the
724 command line using the
727 .It Cm id : Ar key_id
728 Revokes a certificate with the specified key ID string.
729 The CA key must have been specified on the
731 command line using the
734 .It Cm key : Ar public_key
735 Revokes the specified key.
736 If a certificate is listed, then it is revoked as a plain public key.
737 .It Cm sha1 : Ar public_key
738 Revokes the specified key by its SHA1 hash.
741 KRLs may be updated using the
745 When this option is specified, keys listed via the command line are merged into
746 the KRL, adding to those already there.
748 It is also possible, given a KRL, to test whether it revokes a particular key
752 flag will query an existing KRL, testing each key specified on the commandline.
753 If any key listed on the command line has been revoked (or an error encountered)
756 will exit with a non-zero exit status.
757 A zero exit status will only be returned if no key was revoked.
759 .Bl -tag -width Ds -compact
760 .It Pa ~/.ssh/identity
761 Contains the protocol version 1 RSA authentication identity of the user.
762 This file should not be readable by anyone but the user.
764 specify a passphrase when generating the key; that passphrase will be
765 used to encrypt the private part of this file using 3DES.
766 This file is not automatically accessed by
768 but it is offered as the default file for the private key.
770 will read this file when a login attempt is made.
772 .It Pa ~/.ssh/identity.pub
773 Contains the protocol version 1 RSA public key for authentication.
774 The contents of this file should be added to
775 .Pa ~/.ssh/authorized_keys
777 where the user wishes to log in using RSA authentication.
778 There is no need to keep the contents of this file secret.
781 .It Pa ~/.ssh/id_ecdsa
783 Contains the protocol version 2 DSA, ECDSA or RSA authentication identity of the user.
784 This file should not be readable by anyone but the user.
786 specify a passphrase when generating the key; that passphrase will be
787 used to encrypt the private part of this file using 128-bit AES.
788 This file is not automatically accessed by
790 but it is offered as the default file for the private key.
792 will read this file when a login attempt is made.
794 .It Pa ~/.ssh/id_dsa.pub
795 .It Pa ~/.ssh/id_ecdsa.pub
796 .It Pa ~/.ssh/id_rsa.pub
797 Contains the protocol version 2 DSA, ECDSA or RSA public key for authentication.
798 The contents of this file should be added to
799 .Pa ~/.ssh/authorized_keys
801 where the user wishes to log in using public key authentication.
802 There is no need to keep the contents of this file secret.
805 Contains Diffie-Hellman groups used for DH-GEX.
806 The file format is described in
817 .%T "The Secure Shell (SSH) Public Key File Format"
821 OpenSSH is a derivative of the original and free
822 ssh 1.2.12 release by Tatu Ylonen.
823 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
824 Theo de Raadt and Dug Song
825 removed many bugs, re-added newer features and
827 Markus Friedl contributed the support for SSH
828 protocol versions 1.5 and 2.0.
projects / FreeBSD / releng / 10.0.git / blob