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diff --git a/ssh-keygen.1 b/ssh-keygen.1 new file mode 100644 index 0000000..bfa2eb5 --- /dev/null +++ b/ssh-keygen.1 @@ -0,0 +1,904 @@ +.\" $OpenBSD: ssh-keygen.1,v 1.150 2018/09/12 06:18:59 djm Exp $ +.\" +.\" Author: Tatu Ylonen <ylo@cs.hut.fi> +.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland +.\" All rights reserved +.\" +.\" As far as I am concerned, the code I have written for this software +.\" can be used freely for any purpose. Any derived versions of this +.\" software must be clearly marked as such, and if the derived work is +.\" incompatible with the protocol description in the RFC file, it must be +.\" called by a name other than "ssh" or "Secure Shell". +.\" +.\" +.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. +.\" Copyright (c) 1999 Aaron Campbell. All rights reserved. +.\" Copyright (c) 1999 Theo de Raadt. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR +.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES +.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. +.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, +.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT +.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF +.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.Dd $Mdocdate: September 12 2018 $ +.Dt SSH-KEYGEN 1 +.Os +.Sh NAME +.Nm ssh-keygen +.Nd authentication key generation, management and conversion +.Sh SYNOPSIS +.Bk -words +.Nm ssh-keygen +.Op Fl q +.Op Fl b Ar bits +.Op Fl t Cm dsa | ecdsa | ed25519 | rsa +.Op Fl N Ar new_passphrase +.Op Fl C Ar comment +.Op Fl f Ar output_keyfile +.Nm ssh-keygen +.Fl p +.Op Fl P Ar old_passphrase +.Op Fl N Ar new_passphrase +.Op Fl f Ar keyfile +.Nm ssh-keygen +.Fl i +.Op Fl m Ar key_format +.Op Fl f Ar input_keyfile +.Nm ssh-keygen +.Fl e +.Op Fl m Ar key_format +.Op Fl f Ar input_keyfile +.Nm ssh-keygen +.Fl y +.Op Fl f Ar input_keyfile +.Nm ssh-keygen +.Fl c +.Op Fl P Ar passphrase +.Op Fl C Ar comment +.Op Fl f Ar keyfile +.Nm ssh-keygen +.Fl l +.Op Fl v +.Op Fl E Ar fingerprint_hash +.Op Fl f Ar input_keyfile +.Nm ssh-keygen +.Fl B +.Op Fl f Ar input_keyfile +.Nm ssh-keygen +.Fl D Ar pkcs11 +.Nm ssh-keygen +.Fl F Ar hostname +.Op Fl f Ar known_hosts_file +.Op Fl l +.Nm ssh-keygen +.Fl H +.Op Fl f Ar known_hosts_file +.Nm ssh-keygen +.Fl R Ar hostname +.Op Fl f Ar known_hosts_file +.Nm ssh-keygen +.Fl r Ar hostname +.Op Fl f Ar input_keyfile +.Op Fl g +.Nm ssh-keygen +.Fl G Ar output_file +.Op Fl v +.Op Fl b Ar bits +.Op Fl M Ar memory +.Op Fl S Ar start_point +.Nm ssh-keygen +.Fl T Ar output_file +.Fl f Ar input_file +.Op Fl v +.Op Fl a Ar rounds +.Op Fl J Ar num_lines +.Op Fl j Ar start_line +.Op Fl K Ar checkpt +.Op Fl W Ar generator +.Nm ssh-keygen +.Fl s Ar ca_key +.Fl I Ar certificate_identity +.Op Fl h +.Op Fl U +.Op Fl D Ar pkcs11_provider +.Op Fl n Ar principals +.Op Fl O Ar option +.Op Fl V Ar validity_interval +.Op Fl z Ar serial_number +.Ar +.Nm ssh-keygen +.Fl L +.Op Fl f Ar input_keyfile +.Nm ssh-keygen +.Fl A +.Op Fl f Ar prefix_path +.Nm ssh-keygen +.Fl k +.Fl f Ar krl_file +.Op Fl u +.Op Fl s Ar ca_public +.Op Fl z Ar version_number +.Ar +.Nm ssh-keygen +.Fl Q +.Fl f Ar krl_file +.Ar +.Ek +.Sh DESCRIPTION +.Nm +generates, manages and converts authentication keys for +.Xr ssh 1 . +.Nm +can create keys for use by SSH protocol version 2. +.Pp +The type of key to be generated is specified with the +.Fl t +option. +If invoked without any arguments, +.Nm +will generate an RSA key. +.Pp +.Nm +is also used to generate groups for use in Diffie-Hellman group +exchange (DH-GEX). +See the +.Sx MODULI GENERATION +section for details. +.Pp +Finally, +.Nm +can be used to generate and update Key Revocation Lists, and to test whether +given keys have been revoked by one. +See the +.Sx KEY REVOCATION LISTS +section for details. +.Pp +Normally each user wishing to use SSH +with public key authentication runs this once to create the authentication +key in +.Pa ~/.ssh/id_dsa , +.Pa ~/.ssh/id_ecdsa , +.Pa ~/.ssh/id_ed25519 +or +.Pa ~/.ssh/id_rsa . +Additionally, the system administrator may use this to generate host keys, +as seen in +.Pa /etc/rc . +.Pp +Normally this program generates the key and asks for a file in which +to store the private key. +The public key is stored in a file with the same name but +.Dq .pub +appended. +The program also asks for a passphrase. +The passphrase may be empty to indicate no passphrase +(host keys must have an empty passphrase), or it may be a string of +arbitrary length. +A passphrase is similar to a password, except it can be a phrase with a +series of words, punctuation, numbers, whitespace, or any string of +characters you want. +Good passphrases are 10-30 characters long, are +not simple sentences or otherwise easily guessable (English +prose has only 1-2 bits of entropy per character, and provides very bad +passphrases), and contain a mix of upper and lowercase letters, +numbers, and non-alphanumeric characters. +The passphrase can be changed later by using the +.Fl p +option. +.Pp +There is no way to recover a lost passphrase. +If the passphrase is lost or forgotten, a new key must be generated +and the corresponding public key copied to other machines. +.Pp +For keys stored in the newer OpenSSH format, +there is also a comment field in the key file that is only for +convenience to the user to help identify the key. +The comment can tell what the key is for, or whatever is useful. +The comment is initialized to +.Dq user@host +when the key is created, but can be changed using the +.Fl c +option. +.Pp +After a key is generated, instructions below detail where the keys +should be placed to be activated. +.Pp +The options are as follows: +.Bl -tag -width Ds +.It Fl A +For each of the key types (rsa, dsa, ecdsa and ed25519) +for which host keys +do not exist, generate the host keys with the default key file path, +an empty passphrase, default bits for the key type, and default comment. +If +.Fl f +has also been specified, its argument is used as a prefix to the +default path for the resulting host key files. +This is used by +.Pa /etc/rc +to generate new host keys. +.It Fl a Ar rounds +When saving a private key this option specifies the number of KDF +(key derivation function) rounds used. +Higher numbers result in slower passphrase verification and increased +resistance to brute-force password cracking (should the keys be stolen). +.Pp +When screening DH-GEX candidates (using the +.Fl T +command). +This option specifies the number of primality tests to perform. +.It Fl B +Show the bubblebabble digest of specified private or public key file. +.It Fl b Ar bits +Specifies the number of bits in the key to create. +For RSA keys, the minimum size is 1024 bits and the default is 2048 bits. +Generally, 2048 bits is considered sufficient. +DSA keys must be exactly 1024 bits as specified by FIPS 186-2. +For ECDSA keys, the +.Fl b +flag determines the key length by selecting from one of three elliptic +curve sizes: 256, 384 or 521 bits. +Attempting to use bit lengths other than these three values for ECDSA keys +will fail. +Ed25519 keys have a fixed length and the +.Fl b +flag will be ignored. +.It Fl C Ar comment +Provides a new comment. +.It Fl c +Requests changing the comment in the private and public key files. +The program will prompt for the file containing the private keys, for +the passphrase if the key has one, and for the new comment. +.It Fl D Ar pkcs11 +Download the RSA public keys provided by the PKCS#11 shared library +.Ar pkcs11 . +When used in combination with +.Fl s , +this option indicates that a CA key resides in a PKCS#11 token (see the +.Sx CERTIFICATES +section for details). +.It Fl E Ar fingerprint_hash +Specifies the hash algorithm used when displaying key fingerprints. +Valid options are: +.Dq md5 +and +.Dq sha256 . +The default is +.Dq sha256 . +.It Fl e +This option will read a private or public OpenSSH key file and +print to stdout the key in one of the formats specified by the +.Fl m +option. +The default export format is +.Dq RFC4716 . +This option allows exporting OpenSSH keys for use by other programs, including +several commercial SSH implementations. +.It Fl F Ar hostname +Search for the specified +.Ar hostname +in a +.Pa known_hosts +file, listing any occurrences found. +This option is useful to find hashed host names or addresses and may also be +used in conjunction with the +.Fl H +option to print found keys in a hashed format. +.It Fl f Ar filename +Specifies the filename of the key file. +.It Fl G Ar output_file +Generate candidate primes for DH-GEX. +These primes must be screened for +safety (using the +.Fl T +option) before use. +.It Fl g +Use generic DNS format when printing fingerprint resource records using the +.Fl r +command. +.It Fl H +Hash a +.Pa known_hosts +file. +This replaces all hostnames and addresses with hashed representations +within the specified file; the original content is moved to a file with +a .old suffix. +These hashes may be used normally by +.Nm ssh +and +.Nm sshd , +but they do not reveal identifying information should the file's contents +be disclosed. +This option will not modify existing hashed hostnames and is therefore safe +to use on files that mix hashed and non-hashed names. +.It Fl h +When signing a key, create a host certificate instead of a user +certificate. +Please see the +.Sx CERTIFICATES +section for details. +.It Fl I Ar certificate_identity +Specify the key identity when signing a public key. +Please see the +.Sx CERTIFICATES +section for details. +.It Fl i +This option will read an unencrypted private (or public) key file +in the format specified by the +.Fl m +option and print an OpenSSH compatible private +(or public) key to stdout. +This option allows importing keys from other software, including several +commercial SSH implementations. +The default import format is +.Dq RFC4716 . +.It Fl J Ar num_lines +Exit after screening the specified number of lines +while performing DH candidate screening using the +.Fl T +option. +.It Fl j Ar start_line +Start screening at the specified line number +while performing DH candidate screening using the +.Fl T +option. +.It Fl K Ar checkpt +Write the last line processed to the file +.Ar checkpt +while performing DH candidate screening using the +.Fl T +option. +This will be used to skip lines in the input file that have already been +processed if the job is restarted. +.It Fl k +Generate a KRL file. +In this mode, +.Nm +will generate a KRL file at the location specified via the +.Fl f +flag that revokes every key or certificate presented on the command line. +Keys/certificates to be revoked may be specified by public key file or +using the format described in the +.Sx KEY REVOCATION LISTS +section. +.It Fl L +Prints the contents of one or more certificates. +.It Fl l +Show fingerprint of specified public key file. +For RSA and DSA keys +.Nm +tries to find the matching public key file and prints its fingerprint. +If combined with +.Fl v , +a visual ASCII art representation of the key is supplied with the +fingerprint. +.It Fl M Ar memory +Specify the amount of memory to use (in megabytes) when generating +candidate moduli for DH-GEX. +.It Fl m Ar key_format +Specify a key format for the +.Fl i +(import) or +.Fl e +(export) conversion options. +The supported key formats are: +.Dq RFC4716 +(RFC 4716/SSH2 public or private key), +.Dq PKCS8 +(PEM PKCS8 public key) +or +.Dq PEM +(PEM public key). +The default conversion format is +.Dq RFC4716 . +Setting a format of +.Dq PEM +when generating or updating a supported private key type will cause the +key to be stored in the legacy PEM private key format. +.It Fl N Ar new_passphrase +Provides the new passphrase. +.It Fl n Ar principals +Specify one or more principals (user or host names) to be included in +a certificate when signing a key. +Multiple principals may be specified, separated by commas. +Please see the +.Sx CERTIFICATES +section for details. +.It Fl O Ar option +Specify a certificate option when signing a key. +This option may be specified multiple times. +See also the +.Sx CERTIFICATES +section for further details. +.Pp +At present, no standard options are valid for host keys. +The options that are valid for user certificates are: +.Pp +.Bl -tag -width Ds -compact +.It Ic clear +Clear all enabled permissions. +This is useful for clearing the default set of permissions so permissions may +be added individually. +.Pp +.It Ic critical : Ns Ar name Ns Op Ns = Ns Ar contents +.It Ic extension : Ns Ar name Ns Op Ns = Ns Ar contents +Includes an arbitrary certificate critical option or extension. +The specified +.Ar name +should include a domain suffix, e.g.\& +.Dq name@example.com . +If +.Ar contents +is specified then it is included as the contents of the extension/option +encoded as a string, otherwise the extension/option is created with no +contents (usually indicating a flag). +Extensions may be ignored by a client or server that does not recognise them, +whereas unknown critical options will cause the certificate to be refused. +.Pp +.It Ic force-command Ns = Ns Ar command +Forces the execution of +.Ar command +instead of any shell or command specified by the user when +the certificate is used for authentication. +.Pp +.It Ic no-agent-forwarding +Disable +.Xr ssh-agent 1 +forwarding (permitted by default). +.Pp +.It Ic no-port-forwarding +Disable port forwarding (permitted by default). +.Pp +.It Ic no-pty +Disable PTY allocation (permitted by default). +.Pp +.It Ic no-user-rc +Disable execution of +.Pa ~/.ssh/rc +by +.Xr sshd 8 +(permitted by default). +.Pp +.It Ic no-x11-forwarding +Disable X11 forwarding (permitted by default). +.Pp +.It Ic permit-agent-forwarding +Allows +.Xr ssh-agent 1 +forwarding. +.Pp +.It Ic permit-port-forwarding +Allows port forwarding. +.Pp +.It Ic permit-pty +Allows PTY allocation. +.Pp +.It Ic permit-user-rc +Allows execution of +.Pa ~/.ssh/rc +by +.Xr sshd 8 . +.Pp +.It Ic permit-X11-forwarding +Allows X11 forwarding. +.Pp +.It Ic source-address Ns = Ns Ar address_list +Restrict the source addresses from which the certificate is considered valid. +The +.Ar address_list +is a comma-separated list of one or more address/netmask pairs in CIDR +format. +.El +.It Fl P Ar passphrase +Provides the (old) passphrase. +.It Fl p +Requests changing the passphrase of a private key file instead of +creating a new private key. +The program will prompt for the file +containing the private key, for the old passphrase, and twice for the +new passphrase. +.It Fl Q +Test whether keys have been revoked in a KRL. +.It Fl q +Silence +.Nm ssh-keygen . +.It Fl R Ar hostname +Removes all keys belonging to +.Ar hostname +from a +.Pa known_hosts +file. +This option is useful to delete hashed hosts (see the +.Fl H +option above). +.It Fl r Ar hostname +Print the SSHFP fingerprint resource record named +.Ar hostname +for the specified public key file. +.It Fl S Ar start +Specify start point (in hex) when generating candidate moduli for DH-GEX. +.It Fl s Ar ca_key +Certify (sign) a public key using the specified CA key. +Please see the +.Sx CERTIFICATES +section for details. +.Pp +When generating a KRL, +.Fl s +specifies a path to a CA public key file used to revoke certificates directly +by key ID or serial number. +See the +.Sx KEY REVOCATION LISTS +section for details. +.It Fl T Ar output_file +Test DH group exchange candidate primes (generated using the +.Fl G +option) for safety. +.It Fl t Cm dsa | ecdsa | ed25519 | rsa +Specifies the type of key to create. +The possible values are +.Dq dsa , +.Dq ecdsa , +.Dq ed25519 , +or +.Dq rsa . +.It Fl U +When used in combination with +.Fl s , +this option indicates that a CA key resides in a +.Xr ssh-agent 1 . +See the +.Sx CERTIFICATES +section for more information. +.It Fl u +Update a KRL. +When specified with +.Fl k , +keys listed via the command line are added to the existing KRL rather than +a new KRL being created. +.It Fl V Ar validity_interval +Specify a validity interval when signing a certificate. +A validity interval may consist of a single time, indicating that the +certificate is valid beginning now and expiring at that time, or may consist +of two times separated by a colon to indicate an explicit time interval. +.Pp +The start time may be specified as the string +.Dq always +to indicate the certificate has no specified start time, +a date in YYYYMMDD format, a time in YYYYMMDDHHMM[SS] format, +a relative time (to the current time) consisting of a minus sign followed by +an interval in the format described in the +TIME FORMATS section of +.Xr sshd_config 5 . +.Pp +The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMM[SS] time, +a relative time starting with a plus character or the string +.Dq forever +to indicate that the certificate has no expirty date. +.Pp +For example: +.Dq +52w1d +(valid from now to 52 weeks and one day from now), +.Dq -4w:+4w +(valid from four weeks ago to four weeks from now), +.Dq 20100101123000:20110101123000 +(valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011), +.Dq -1d:20110101 +(valid from yesterday to midnight, January 1st, 2011). +.Dq -1m:forever +(valid from one minute ago and never expiring). +.It Fl v +Verbose mode. +Causes +.Nm +to print debugging messages about its progress. +This is helpful for debugging moduli generation. +Multiple +.Fl v +options increase the verbosity. +The maximum is 3. +.It Fl W Ar generator +Specify desired generator when testing candidate moduli for DH-GEX. +.It Fl y +This option will read a private +OpenSSH format file and print an OpenSSH public key to stdout. +.It Fl z Ar serial_number +Specifies a serial number to be embedded in the certificate to distinguish +this certificate from others from the same CA. +The default serial number is zero. +.Pp +When generating a KRL, the +.Fl z +flag is used to specify a KRL version number. +.El +.Sh MODULI GENERATION +.Nm +may be used to generate groups for the Diffie-Hellman Group Exchange +(DH-GEX) protocol. +Generating these groups is a two-step process: first, candidate +primes are generated using a fast, but memory intensive process. +These candidate primes are then tested for suitability (a CPU-intensive +process). +.Pp +Generation of primes is performed using the +.Fl G +option. +The desired length of the primes may be specified by the +.Fl b +option. +For example: +.Pp +.Dl # ssh-keygen -G moduli-2048.candidates -b 2048 +.Pp +By default, the search for primes begins at a random point in the +desired length range. +This may be overridden using the +.Fl S +option, which specifies a different start point (in hex). +.Pp +Once a set of candidates have been generated, they must be screened for +suitability. +This may be performed using the +.Fl T +option. +In this mode +.Nm +will read candidates from standard input (or a file specified using the +.Fl f +option). +For example: +.Pp +.Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates +.Pp +By default, each candidate will be subjected to 100 primality tests. +This may be overridden using the +.Fl a +option. +The DH generator value will be chosen automatically for the +prime under consideration. +If a specific generator is desired, it may be requested using the +.Fl W +option. +Valid generator values are 2, 3, and 5. +.Pp +Screened DH groups may be installed in +.Pa /etc/moduli . +It is important that this file contains moduli of a range of bit lengths and +that both ends of a connection share common moduli. +.Sh CERTIFICATES +.Nm +supports signing of keys to produce certificates that may be used for +user or host authentication. +Certificates consist of a public key, some identity information, zero or +more principal (user or host) names and a set of options that +are signed by a Certification Authority (CA) key. +Clients or servers may then trust only the CA key and verify its signature +on a certificate rather than trusting many user/host keys. +Note that OpenSSH certificates are a different, and much simpler, format to +the X.509 certificates used in +.Xr ssl 8 . +.Pp +.Nm +supports two types of certificates: user and host. +User certificates authenticate users to servers, whereas host certificates +authenticate server hosts to users. +To generate a user certificate: +.Pp +.Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub +.Pp +The resultant certificate will be placed in +.Pa /path/to/user_key-cert.pub . +A host certificate requires the +.Fl h +option: +.Pp +.Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub +.Pp +The host certificate will be output to +.Pa /path/to/host_key-cert.pub . +.Pp +It is possible to sign using a CA key stored in a PKCS#11 token by +providing the token library using +.Fl D +and identifying the CA key by providing its public half as an argument +to +.Fl s : +.Pp +.Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub +.Pp +Similarly, it is possible for the CA key to be hosted in a +.Xr ssh-agent 1 . +This is indicated by the +.Fl U +flag and, again, the CA key must be identified by its public half. +.Pp +.Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub +.Pp +In all cases, +.Ar key_id +is a "key identifier" that is logged by the server when the certificate +is used for authentication. +.Pp +Certificates may be limited to be valid for a set of principal (user/host) +names. +By default, generated certificates are valid for all users or hosts. +To generate a certificate for a specified set of principals: +.Pp +.Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub +.Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub" +.Pp +Additional limitations on the validity and use of user certificates may +be specified through certificate options. +A certificate option may disable features of the SSH session, may be +valid only when presented from particular source addresses or may +force the use of a specific command. +For a list of valid certificate options, see the documentation for the +.Fl O +option above. +.Pp +Finally, certificates may be defined with a validity lifetime. +The +.Fl V +option allows specification of certificate start and end times. +A certificate that is presented at a time outside this range will not be +considered valid. +By default, certificates are valid from +.Ux +Epoch to the distant future. +.Pp +For certificates to be used for user or host authentication, the CA +public key must be trusted by +.Xr sshd 8 +or +.Xr ssh 1 . +Please refer to those manual pages for details. +.Sh KEY REVOCATION LISTS +.Nm +is able to manage OpenSSH format Key Revocation Lists (KRLs). +These binary files specify keys or certificates to be revoked using a +compact format, taking as little as one bit per certificate if they are being +revoked by serial number. +.Pp +KRLs may be generated using the +.Fl k +flag. +This option reads one or more files from the command line and generates a new +KRL. +The files may either contain a KRL specification (see below) or public keys, +listed one per line. +Plain public keys are revoked by listing their hash or contents in the KRL and +certificates revoked by serial number or key ID (if the serial is zero or +not available). +.Pp +Revoking keys using a KRL specification offers explicit control over the +types of record used to revoke keys and may be used to directly revoke +certificates by serial number or key ID without having the complete original +certificate on hand. +A KRL specification consists of lines containing one of the following directives +followed by a colon and some directive-specific information. +.Bl -tag -width Ds +.It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number +Revokes a certificate with the specified serial number. +Serial numbers are 64-bit values, not including zero and may be expressed +in decimal, hex or octal. +If two serial numbers are specified separated by a hyphen, then the range +of serial numbers including and between each is revoked. +The CA key must have been specified on the +.Nm +command line using the +.Fl s +option. +.It Cm id : Ar key_id +Revokes a certificate with the specified key ID string. +The CA key must have been specified on the +.Nm +command line using the +.Fl s +option. +.It Cm key : Ar public_key +Revokes the specified key. +If a certificate is listed, then it is revoked as a plain public key. +.It Cm sha1 : Ar public_key +Revokes the specified key by including its SHA1 hash in the KRL. +.It Cm sha256 : Ar public_key +Revokes the specified key by including its SHA256 hash in the KRL. +KRLs that revoke keys by SHA256 hash are not supported by OpenSSH versions +prior to 7.9. +.It Cm hash : Ar fingerprint +Revokes a key using a fingerprint hash, as obtained from a +.Xr sshd 8 +authentication log message or the +.Nm +.Fl l +flag. +Only SHA256 fingerprints are supported here and resultant KRLs are +not supported by OpenSSH versions prior to 7.9. +.El +.Pp +KRLs may be updated using the +.Fl u +flag in addition to +.Fl k . +When this option is specified, keys listed via the command line are merged into +the KRL, adding to those already there. +.Pp +It is also possible, given a KRL, to test whether it revokes a particular key +(or keys). +The +.Fl Q +flag will query an existing KRL, testing each key specified on the command line. +If any key listed on the command line has been revoked (or an error encountered) +then +.Nm +will exit with a non-zero exit status. +A zero exit status will only be returned if no key was revoked. +.Sh FILES +.Bl -tag -width Ds -compact +.It Pa ~/.ssh/id_dsa +.It Pa ~/.ssh/id_ecdsa +.It Pa ~/.ssh/id_ed25519 +.It Pa ~/.ssh/id_rsa +Contains the DSA, ECDSA, Ed25519 or RSA +authentication identity of the user. +This file should not be readable by anyone but the user. +It is possible to +specify a passphrase when generating the key; that passphrase will be +used to encrypt the private part of this file using 128-bit AES. +This file is not automatically accessed by +.Nm +but it is offered as the default file for the private key. +.Xr ssh 1 +will read this file when a login attempt is made. +.Pp +.It Pa ~/.ssh/id_dsa.pub +.It Pa ~/.ssh/id_ecdsa.pub +.It Pa ~/.ssh/id_ed25519.pub +.It Pa ~/.ssh/id_rsa.pub +Contains the DSA, ECDSA, Ed25519 or RSA +public key for authentication. +The contents of this file should be added to +.Pa ~/.ssh/authorized_keys +on all machines +where the user wishes to log in using public key authentication. +There is no need to keep the contents of this file secret. +.Pp +.It Pa /etc/moduli +Contains Diffie-Hellman groups used for DH-GEX. +The file format is described in +.Xr moduli 5 . +.El +.Sh SEE ALSO +.Xr ssh 1 , +.Xr ssh-add 1 , +.Xr ssh-agent 1 , +.Xr moduli 5 , +.Xr sshd 8 +.Rs +.%R RFC 4716 +.%T "The Secure Shell (SSH) Public Key File Format" +.%D 2006 +.Re +.Sh AUTHORS +OpenSSH is a derivative of the original and free +ssh 1.2.12 release by Tatu Ylonen. +Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, +Theo de Raadt and Dug Song +removed many bugs, re-added newer features and +created OpenSSH. +Markus Friedl contributed the support for SSH +protocol versions 1.5 and 2.0. |