1 .\" $OpenBSD: ssh-keygen.1,v 1.127 2015/08/20 19:20:06 naddy Exp $
3 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 .\" All rights reserved
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".
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.
18 .\" Redistribution and use in source and binary forms, with or without
19 .\" modification, are permitted provided that the following conditions
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.
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.
38 .Dd $Mdocdate: August 20 2015 $
43 .Nd authentication key generation, management and conversion
49 .Op Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1
50 .Op Fl N Ar new_passphrase
52 .Op Fl f Ar output_keyfile
55 .Op Fl P Ar old_passphrase
56 .Op Fl N Ar new_passphrase
60 .Op Fl m Ar key_format
61 .Op Fl f Ar input_keyfile
64 .Op Fl m Ar key_format
65 .Op Fl f Ar input_keyfile
68 .Op Fl f Ar input_keyfile
71 .Op Fl P Ar passphrase
77 .Op Fl E Ar fingerprint_hash
78 .Op Fl f Ar input_keyfile
81 .Op Fl f Ar input_keyfile
86 .Op Fl f Ar known_hosts_file
90 .Op Fl f Ar known_hosts_file
93 .Op Fl f Ar known_hosts_file
96 .Op Fl f Ar input_keyfile
103 .Op Fl S Ar start_point
109 .Op Fl J Ar num_lines
110 .Op Fl j Ar start_line
112 .Op Fl W Ar generator
115 .Fl I Ar certificate_identity
117 .Op Fl n Ar principals
119 .Op Fl V Ar validity_interval
120 .Op Fl z Ar serial_number
124 .Op Fl f Ar input_keyfile
131 .Op Fl s Ar ca_public
132 .Op Fl z Ar version_number
141 generates, manages and converts authentication keys for
144 can create RSA keys for use by SSH protocol version 1 and
145 DSA, ECDSA, Ed25519 or RSA keys for use by SSH protocol version 2.
146 The type of key to be generated is specified with the
149 If invoked without any arguments,
151 will generate an RSA key for use in SSH protocol 2 connections.
154 is also used to generate groups for use in Diffie-Hellman group
157 .Sx MODULI GENERATION
162 can be used to generate and update Key Revocation Lists, and to test whether
163 given keys have been revoked by one.
165 .Sx KEY REVOCATION LISTS
168 Normally each user wishing to use SSH
169 with public key authentication runs this once to create the authentication
171 .Pa ~/.ssh/identity ,
173 .Pa ~/.ssh/id_ecdsa ,
174 .Pa ~/.ssh/id_ed25519
177 Additionally, the system administrator may use this to generate host keys,
181 Normally this program generates the key and asks for a file in which
182 to store the private key.
183 The public key is stored in a file with the same name but
186 The program also asks for a passphrase.
187 The passphrase may be empty to indicate no passphrase
188 (host keys must have an empty passphrase), or it may be a string of
190 A passphrase is similar to a password, except it can be a phrase with a
191 series of words, punctuation, numbers, whitespace, or any string of
193 Good passphrases are 10-30 characters long, are
194 not simple sentences or otherwise easily guessable (English
195 prose has only 1-2 bits of entropy per character, and provides very bad
196 passphrases), and contain a mix of upper and lowercase letters,
197 numbers, and non-alphanumeric characters.
198 The passphrase can be changed later by using the
202 There is no way to recover a lost passphrase.
203 If the passphrase is lost or forgotten, a new key must be generated
204 and the corresponding public key copied to other machines.
207 there is also a comment field in the key file that is only for
208 convenience to the user to help identify the key.
209 The comment can tell what the key is for, or whatever is useful.
210 The comment is initialized to
212 when the key is created, but can be changed using the
216 After a key is generated, instructions below detail where the keys
217 should be placed to be activated.
219 The options are as follows:
222 For each of the key types (rsa1, rsa, dsa, ecdsa and ed25519)
224 do not exist, generate the host keys with the default key file path,
225 an empty passphrase, default bits for the key type, and default comment.
228 to generate new host keys.
230 When saving a new-format private key (i.e. an ed25519 key or any SSH protocol
233 flag is set), this option specifies the number of KDF (key derivation function)
235 Higher numbers result in slower passphrase verification and increased
236 resistance to brute-force password cracking (should the keys be stolen).
238 When screening DH-GEX candidates (
242 This option specifies the number of primality tests to perform.
244 Show the bubblebabble digest of specified private or public key file.
246 Specifies the number of bits in the key to create.
247 For RSA keys, the minimum size is 1024 bits and the default is 2048 bits.
248 Generally, 2048 bits is considered sufficient.
249 DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
252 flag determines the key length by selecting from one of three elliptic
253 curve sizes: 256, 384 or 521 bits.
254 Attempting to use bit lengths other than these three values for ECDSA keys
256 Ed25519 keys have a fixed length and the
258 flag will be ignored.
260 Provides a new comment.
262 Requests changing the comment in the private and public key files.
263 This operation is only supported for RSA1 keys.
264 The program will prompt for the file containing the private keys, for
265 the passphrase if the key has one, and for the new comment.
267 Download the RSA public keys provided by the PKCS#11 shared library
269 When used in combination with
271 this option indicates that a CA key resides in a PKCS#11 token (see the
273 section for details).
274 .It Fl E Ar fingerprint_hash
275 Specifies the hash algorithm used when displaying key fingerprints.
283 This option will read a private or public OpenSSH key file and
284 print to stdout the key in one of the formats specified by the
287 The default export format is
289 This option allows exporting OpenSSH keys for use by other programs, including
290 several commercial SSH implementations.
292 Search for the specified
296 file, listing any occurrences found.
297 This option is useful to find hashed host names or addresses and may also be
298 used in conjunction with the
300 option to print found keys in a hashed format.
302 Specifies the filename of the key file.
303 .It Fl G Ar output_file
304 Generate candidate primes for DH-GEX.
305 These primes must be screened for
310 Use generic DNS format when printing fingerprint resource records using the
317 This replaces all hostnames and addresses with hashed representations
318 within the specified file; the original content is moved to a file with
320 These hashes may be used normally by
324 but they do not reveal identifying information should the file's contents
326 This option will not modify existing hashed hostnames and is therefore safe
327 to use on files that mix hashed and non-hashed names.
329 When signing a key, create a host certificate instead of a user
334 .It Fl I Ar certificate_identity
335 Specify the key identity when signing a public key.
340 This option will read an unencrypted private (or public) key file
341 in the format specified by the
343 option and print an OpenSSH compatible private
344 (or public) key to stdout.
345 This option allows importing keys from other software, including several
346 commercial SSH implementations.
347 The default import format is
349 .It Fl J Ar num_lines
350 Exit after screening the specified number of lines
351 while performing DH candidate screening using the
354 .It Fl j Ar start_line
355 Start screening at the specified line number
356 while performing DH candidate screening using the
360 Write the last line processed to the file
362 while performing DH candidate screening using the
365 This will be used to skip lines in the input file that have already been
366 processed if the job is restarted.
371 will generate a KRL file at the location specified via the
373 flag that revokes every key or certificate presented on the command line.
374 Keys/certificates to be revoked may be specified by public key file or
375 using the format described in the
376 .Sx KEY REVOCATION LISTS
379 Prints the contents of a certificate.
381 Show fingerprint of specified public key file.
382 Private RSA1 keys are also supported.
385 tries to find the matching public key file and prints its fingerprint.
388 an ASCII art representation of the key is supplied with the fingerprint.
390 Specify the amount of memory to use (in megabytes) when generating
391 candidate moduli for DH-GEX.
392 .It Fl m Ar key_format
393 Specify a key format for the
397 (export) conversion options.
398 The supported key formats are:
400 (RFC 4716/SSH2 public or private key),
402 (PEM PKCS8 public key)
406 The default conversion format is
408 .It Fl N Ar new_passphrase
409 Provides the new passphrase.
410 .It Fl n Ar principals
411 Specify one or more principals (user or host names) to be included in
412 a certificate when signing a key.
413 Multiple principals may be specified, separated by commas.
418 Specify a certificate option when signing a key.
419 This option may be specified multiple times.
423 The options that are valid for user certificates are:
426 Clear all enabled permissions.
427 This is useful for clearing the default set of permissions so permissions may
428 be added individually.
429 .It Ic force-command Ns = Ns Ar command
430 Forces the execution of
432 instead of any shell or command specified by the user when
433 the certificate is used for authentication.
434 .It Ic no-agent-forwarding
437 forwarding (permitted by default).
438 .It Ic no-port-forwarding
439 Disable port forwarding (permitted by default).
441 Disable PTY allocation (permitted by default).
447 (permitted by default).
448 .It Ic no-x11-forwarding
449 Disable X11 forwarding (permitted by default).
450 .It Ic permit-agent-forwarding
454 .It Ic permit-port-forwarding
455 Allows port forwarding.
457 Allows PTY allocation.
458 .It Ic permit-user-rc
463 .It Ic permit-x11-forwarding
464 Allows X11 forwarding.
465 .It Ic source-address Ns = Ns Ar address_list
466 Restrict the source addresses from which the certificate is considered valid.
469 is a comma-separated list of one or more address/netmask pairs in CIDR
473 At present, no options are valid for host keys.
477 to save SSH protocol 2 private keys using the new OpenSSH format rather than
478 the more compatible PEM format.
479 The new format has increased resistance to brute-force password cracking
480 but is not supported by versions of OpenSSH prior to 6.5.
481 Ed25519 keys always use the new private key format.
482 .It Fl P Ar passphrase
483 Provides the (old) passphrase.
485 Requests changing the passphrase of a private key file instead of
486 creating a new private key.
487 The program will prompt for the file
488 containing the private key, for the old passphrase, and twice for the
491 Test whether keys have been revoked in a KRL.
496 Removes all keys belonging to
501 This option is useful to delete hashed hosts (see the
505 Print the SSHFP fingerprint resource record named
507 for the specified public key file.
509 Specify start point (in hex) when generating candidate moduli for DH-GEX.
511 Certify (sign) a public key using the specified CA key.
516 When generating a KRL,
518 specifies a path to a CA public key file used to revoke certificates directly
519 by key ID or serial number.
521 .Sx KEY REVOCATION LISTS
523 .It Fl T Ar output_file
524 Test DH group exchange candidate primes (generated using the
527 .It Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1
528 Specifies the type of key to create.
529 The possible values are
531 for protocol version 1 and
537 for protocol version 2.
542 keys listed via the command line are added to the existing KRL rather than
543 a new KRL being created.
544 .It Fl V Ar validity_interval
545 Specify a validity interval when signing a certificate.
546 A validity interval may consist of a single time, indicating that the
547 certificate is valid beginning now and expiring at that time, or may consist
548 of two times separated by a colon to indicate an explicit time interval.
549 The start time may be specified as a date in YYYYMMDD format, a time
550 in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting
551 of a minus sign followed by a relative time in the format described in the
552 TIME FORMATS section of
554 The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or
555 a relative time starting with a plus character.
559 (valid from now to 52 weeks and one day from now),
561 (valid from four weeks ago to four weeks from now),
562 .Dq 20100101123000:20110101123000
563 (valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011),
565 (valid from yesterday to midnight, January 1st, 2011).
570 to print debugging messages about its progress.
571 This is helpful for debugging moduli generation.
574 options increase the verbosity.
576 .It Fl W Ar generator
577 Specify desired generator when testing candidate moduli for DH-GEX.
579 This option will read a private
580 OpenSSH format file and print an OpenSSH public key to stdout.
581 .It Fl z Ar serial_number
582 Specifies a serial number to be embedded in the certificate to distinguish
583 this certificate from others from the same CA.
584 The default serial number is zero.
586 When generating a KRL, the
588 flag is used to specify a KRL version number.
590 .Sh MODULI GENERATION
592 may be used to generate groups for the Diffie-Hellman Group Exchange
594 Generating these groups is a two-step process: first, candidate
595 primes are generated using a fast, but memory intensive process.
596 These candidate primes are then tested for suitability (a CPU-intensive
599 Generation of primes is performed using the
602 The desired length of the primes may be specified by the
607 .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
609 By default, the search for primes begins at a random point in the
610 desired length range.
611 This may be overridden using the
613 option, which specifies a different start point (in hex).
615 Once a set of candidates have been generated, they must be screened for
617 This may be performed using the
622 will read candidates from standard input (or a file specified using the
627 .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
629 By default, each candidate will be subjected to 100 primality tests.
630 This may be overridden using the
633 The DH generator value will be chosen automatically for the
634 prime under consideration.
635 If a specific generator is desired, it may be requested using the
638 Valid generator values are 2, 3, and 5.
640 Screened DH groups may be installed in
642 It is important that this file contains moduli of a range of bit lengths and
643 that both ends of a connection share common moduli.
646 supports signing of keys to produce certificates that may be used for
647 user or host authentication.
648 Certificates consist of a public key, some identity information, zero or
649 more principal (user or host) names and a set of options that
650 are signed by a Certification Authority (CA) key.
651 Clients or servers may then trust only the CA key and verify its signature
652 on a certificate rather than trusting many user/host keys.
653 Note that OpenSSH certificates are a different, and much simpler, format to
654 the X.509 certificates used in
658 supports two types of certificates: user and host.
659 User certificates authenticate users to servers, whereas host certificates
660 authenticate server hosts to users.
661 To generate a user certificate:
663 .Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
665 The resultant certificate will be placed in
666 .Pa /path/to/user_key-cert.pub .
667 A host certificate requires the
671 .Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
673 The host certificate will be output to
674 .Pa /path/to/host_key-cert.pub .
676 It is possible to sign using a CA key stored in a PKCS#11 token by
677 providing the token library using
679 and identifying the CA key by providing its public half as an argument
683 .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
687 is a "key identifier" that is logged by the server when the certificate
688 is used for authentication.
690 Certificates may be limited to be valid for a set of principal (user/host)
692 By default, generated certificates are valid for all users or hosts.
693 To generate a certificate for a specified set of principals:
695 .Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
696 .Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub"
698 Additional limitations on the validity and use of user certificates may
699 be specified through certificate options.
700 A certificate option may disable features of the SSH session, may be
701 valid only when presented from particular source addresses or may
702 force the use of a specific command.
703 For a list of valid certificate options, see the documentation for the
707 Finally, certificates may be defined with a validity lifetime.
710 option allows specification of certificate start and end times.
711 A certificate that is presented at a time outside this range will not be
713 By default, certificates are valid from
715 Epoch to the distant future.
717 For certificates to be used for user or host authentication, the CA
718 public key must be trusted by
722 Please refer to those manual pages for details.
723 .Sh KEY REVOCATION LISTS
725 is able to manage OpenSSH format Key Revocation Lists (KRLs).
726 These binary files specify keys or certificates to be revoked using a
727 compact format, taking as little as one bit per certificate if they are being
728 revoked by serial number.
730 KRLs may be generated using the
733 This option reads one or more files from the command line and generates a new
735 The files may either contain a KRL specification (see below) or public keys,
737 Plain public keys are revoked by listing their hash or contents in the KRL and
738 certificates revoked by serial number or key ID (if the serial is zero or
741 Revoking keys using a KRL specification offers explicit control over the
742 types of record used to revoke keys and may be used to directly revoke
743 certificates by serial number or key ID without having the complete original
745 A KRL specification consists of lines containing one of the following directives
746 followed by a colon and some directive-specific information.
748 .It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number
749 Revokes a certificate with the specified serial number.
750 Serial numbers are 64-bit values, not including zero and may be expressed
751 in decimal, hex or octal.
752 If two serial numbers are specified separated by a hyphen, then the range
753 of serial numbers including and between each is revoked.
754 The CA key must have been specified on the
756 command line using the
759 .It Cm id : Ar key_id
760 Revokes a certificate with the specified key ID string.
761 The CA key must have been specified on the
763 command line using the
766 .It Cm key : Ar public_key
767 Revokes the specified key.
768 If a certificate is listed, then it is revoked as a plain public key.
769 .It Cm sha1 : Ar public_key
770 Revokes the specified key by its SHA1 hash.
773 KRLs may be updated using the
777 When this option is specified, keys listed via the command line are merged into
778 the KRL, adding to those already there.
780 It is also possible, given a KRL, to test whether it revokes a particular key
784 flag will query an existing KRL, testing each key specified on the commandline.
785 If any key listed on the command line has been revoked (or an error encountered)
788 will exit with a non-zero exit status.
789 A zero exit status will only be returned if no key was revoked.
791 .Bl -tag -width Ds -compact
792 .It Pa ~/.ssh/identity
793 Contains the protocol version 1 RSA authentication identity of the user.
794 This file should not be readable by anyone but the user.
796 specify a passphrase when generating the key; that passphrase will be
797 used to encrypt the private part of this file using 3DES.
798 This file is not automatically accessed by
800 but it is offered as the default file for the private key.
802 will read this file when a login attempt is made.
804 .It Pa ~/.ssh/identity.pub
805 Contains the protocol version 1 RSA public key for authentication.
806 The contents of this file should be added to
807 .Pa ~/.ssh/authorized_keys
809 where the user wishes to log in using RSA authentication.
810 There is no need to keep the contents of this file secret.
813 .It Pa ~/.ssh/id_ecdsa
814 .It Pa ~/.ssh/id_ed25519
816 Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
817 authentication identity of the user.
818 This file should not be readable by anyone but the user.
820 specify a passphrase when generating the key; that passphrase will be
821 used to encrypt the private part of this file using 128-bit AES.
822 This file is not automatically accessed by
824 but it is offered as the default file for the private key.
826 will read this file when a login attempt is made.
828 .It Pa ~/.ssh/id_dsa.pub
829 .It Pa ~/.ssh/id_ecdsa.pub
830 .It Pa ~/.ssh/id_ed25519.pub
831 .It Pa ~/.ssh/id_rsa.pub
832 Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA
833 public key for authentication.
834 The contents of this file should be added to
835 .Pa ~/.ssh/authorized_keys
837 where the user wishes to log in using public key authentication.
838 There is no need to keep the contents of this file secret.
841 Contains Diffie-Hellman groups used for DH-GEX.
842 The file format is described in
853 .%T "The Secure Shell (SSH) Public Key File Format"
857 OpenSSH is a derivative of the original and free
858 ssh 1.2.12 release by Tatu Ylonen.
859 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
860 Theo de Raadt and Dug Song
861 removed many bugs, re-added newer features and
863 Markus Friedl contributed the support for SSH
864 protocol versions 1.5 and 2.0.
projects / FreeBSD / releng / 10.3.git / blob