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diff --git a/ssh-keygen.1 b/ssh-keygen.1 index 9b93666c..059c1b03 100644 --- a/ssh-keygen.1 +++ b/ssh-keygen.1 @@ -1,4 +1,4 @@ -.\" $OpenBSD: ssh-keygen.1,v 1.125 2015/02/24 15:24:05 naddy Exp $ +.\" $OpenBSD: ssh-keygen.1,v 1.203 2020/04/03 02:26:56 djm Exp $ .\" .\" Author: Tatu Ylonen <ylo@cs.hut.fi> .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland @@ -35,42 +35,45 @@ .\" (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: February 24 2015 $ +.Dd $Mdocdate: April 3 2020 $ .Dt SSH-KEYGEN 1 .Os .Sh NAME .Nm ssh-keygen -.Nd authentication key generation, management and conversion +.Nd OpenSSH authentication key utility .Sh SYNOPSIS -.Bk -words .Nm ssh-keygen .Op Fl q .Op Fl b Ar bits -.Op Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1 -.Op Fl N Ar new_passphrase .Op Fl C Ar comment .Op Fl f Ar output_keyfile +.Op Fl m Ar format +.Op Fl t Cm dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa +.Op Fl N Ar new_passphrase +.Op Fl O Ar option +.Op Fl w Ar provider .Nm ssh-keygen .Fl p -.Op Fl P Ar old_passphrase -.Op Fl N Ar new_passphrase .Op Fl f Ar keyfile +.Op Fl m Ar format +.Op Fl N Ar new_passphrase +.Op Fl P Ar old_passphrase .Nm ssh-keygen .Fl i -.Op Fl m Ar key_format .Op Fl f Ar input_keyfile +.Op Fl m Ar key_format .Nm ssh-keygen .Fl e -.Op Fl m Ar key_format .Op Fl f Ar input_keyfile +.Op Fl m Ar key_format .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 +.Op Fl P Ar passphrase .Nm ssh-keygen .Fl l .Op Fl v @@ -83,37 +86,35 @@ .Fl D Ar pkcs11 .Nm ssh-keygen .Fl F Ar hostname +.Op Fl lv .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 K +.Op Fl w Ar provider +.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 +.Op Fl f Ar input_keyfile .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 +.Fl M Cm generate +.Op Fl O Ar option +.Ar output_file .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 +.Fl M Cm screen +.Op Fl f Ar input_file +.Op Fl O Ar option +.Ar output_file .Nm ssh-keygen -.Fl s Ar ca_key .Fl I Ar certificate_identity -.Op Fl h +.Fl s Ar ca_key +.Op Fl hU +.Op Fl D Ar pkcs11_provider .Op Fl n Ar principals .Op Fl O Ar option .Op Fl V Ar validity_interval @@ -124,6 +125,7 @@ .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 @@ -133,22 +135,42 @@ .Ar .Nm ssh-keygen .Fl Q +.Op Fl l .Fl f Ar krl_file .Ar -.Ek +.Nm ssh-keygen +.Fl Y Cm find-principals +.Fl s Ar signature_file +.Fl f Ar allowed_signers_file +.Nm ssh-keygen +.Fl Y Cm check-novalidate +.Fl n Ar namespace +.Fl s Ar signature_file +.Nm ssh-keygen +.Fl Y Cm sign +.Fl f Ar key_file +.Fl n Ar namespace +.Ar +.Nm ssh-keygen +.Fl Y Cm verify +.Fl f Ar allowed_signers_file +.Fl I Ar signer_identity +.Fl n Ar namespace +.Fl s Ar signature_file +.Op Fl r Ar revocation_file .Sh DESCRIPTION .Nm generates, manages and converts authentication keys for .Xr ssh 1 . .Nm -can create RSA keys for use by SSH protocol version 1 and -DSA, ECDSA, Ed25519 or RSA keys for use by SSH protocol version 2. +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 for use in SSH protocol 2 connections. +will generate an RSA key. .Pp .Nm is also used to generate groups for use in Diffie-Hellman group @@ -168,10 +190,11 @@ section for details. Normally each user wishing to use SSH with public key authentication runs this once to create the authentication key in -.Pa ~/.ssh/identity , .Pa ~/.ssh/id_dsa , .Pa ~/.ssh/id_ecdsa , -.Pa ~/.ssh/id_ed25519 +.Pa ~/.ssh/id_ecdsa_sk , +.Pa ~/.ssh/id_ed25519 , +.Pa ~/.ssh/id_ed25519_sk or .Pa ~/.ssh/id_rsa . Additionally, the system administrator may use this to generate host keys, @@ -203,49 +226,56 @@ 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 RSA1 keys, -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. +.Nm +will by default write keys in an OpenSSH-specific format. +This format is preferred as it offers better protection for +keys at rest as well as allowing storage of key comments within +the private key file itself. +The key comment may be useful to help identify the key. The comment is initialized to .Dq user@host when the key is created, but can be changed using the .Fl c option. .Pp +It is still possible for +.Nm +to write the previously-used PEM format private keys using the +.Fl m +flag. +This may be used when generating new keys, and existing new-format +keys may be converted using this option in conjunction with the +.Fl p +(change passphrase) flag. +.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 (rsa1, rsa, dsa, ecdsa and ed25519) +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 new-format private key (i.e. an ed25519 key or any SSH protocol -2 key when the -.Fl o -flag is set), this option specifies the number of KDF (key derivation function) -rounds used. +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 768 bits and the default is 2048 bits. -Generally, 2048 bits is considered sufficient. +For RSA keys, the minimum size is 1024 bits and the default is 3072 bits. +Generally, 3072 bits is considered sufficient. DSA keys must be exactly 1024 bits as specified by FIPS 186-2. For ECDSA keys, the .Fl b @@ -253,18 +283,17 @@ 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 +ECDSA-SK, Ed25519 and Ed25519-SK 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. -This operation is only supported for RSA1 keys. 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 +Download the public keys provided by the PKCS#11 shared library .Ar pkcs11 . When used in combination with .Fl s , @@ -281,16 +310,17 @@ 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 +print to stdout a public 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 +.It Fl F Ar hostname | [hostname]:port Search for the specified .Ar hostname +(with optional port number) in a .Pa known_hosts file, listing any occurrences found. @@ -300,12 +330,6 @@ used in conjunction with the 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 @@ -346,24 +370,10 @@ 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 +Download resident keys from a FIDO authenticator. +Public and private key files will be written to the current directory for +each downloaded key. .It Fl k Generate a KRL file. In this mode, @@ -376,35 +386,61 @@ using the format described in the .Sx KEY REVOCATION LISTS section. .It Fl L -Prints the contents of a certificate. +Prints the contents of one or more certificates. .It Fl l Show fingerprint of specified public key file. -Private RSA1 keys are also supported. For RSA and DSA keys .Nm tries to find the matching public key file and prints its fingerprint. If combined with .Fl v , -an 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. +a visual ASCII art representation of the key is supplied with the +fingerprint. +.It Fl M Cm generate +Generate candidate Diffie-Hellman Group Exchange (DH-GEX) parameters for +eventual use by the +.Sq diffie-hellman-group-exchange-* +key exchange methods. +The numbers generated by this operation must be further screened before +use. +See the +.Sx MODULI GENERATION +section for more information. +.It Fl M Cm screen +Screen candidate parameters for Diffie-Hellman Group Exchange. +This will accept a list of candidate numbers and test that they are +safe (Sophie Germain) primes with acceptable group generators. +The results of this operation may be added to the +.Pa /etc/moduli +file. +See the +.Sx MODULI GENERATION +section for more information. .It Fl m Ar key_format -Specify a key format for the +Specify a key format for key generation, the .Fl i -(import) or +(import), .Fl e -(export) conversion options. +(export) conversion options, and the +.Fl p +change passphrase operation. +The latter may be used to convert between OpenSSH private key and PEM +private key formats. The supported key formats are: .Dq RFC4716 (RFC 4716/SSH2 public or private key), .Dq PKCS8 -(PEM PKCS8 public key) +(PKCS8 public or private key) or .Dq PEM (PEM public key). -The default conversion format is +By default OpenSSH will write newly-generated private keys in its own +format, but when converting public keys for export the default 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 @@ -415,70 +451,67 @@ 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. -Please see the +Specify a key/value option. +These are specific to the operation that +.Nm +has been requested to perform. +.Pp +When signing certificates, one of the options listed in the .Sx CERTIFICATES -section for details. -The options that are valid for user certificates are: +section may be specified here. +.Pp +When performing moduli generation or screening, one of the options +listed in the +.Sx MODULI GENERATION +section may be specified. +.Pp +When generating a key that will be hosted on a FIDO authenticator, +this flag may be used to specify key-specific options. +Those supported at present are: .Bl -tag -width Ds -.It Ic clear -Clear all enabled permissions. -This is useful for clearing the default set of permissions so permissions may -be added individually. -.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. -.It Ic no-agent-forwarding -Disable -.Xr ssh-agent 1 -forwarding (permitted by default). -.It Ic no-port-forwarding -Disable port forwarding (permitted by default). -.It Ic no-pty -Disable PTY allocation (permitted by default). -.It Ic no-user-rc -Disable execution of -.Pa ~/.ssh/rc -by +.It Cm application +Override the default FIDO application/origin string of +.Dq ssh: . +This may be useful when generating host or domain-specific resident keys. +The specified application string must begin with +.Dq ssh: . +.It Cm challenge Ns = Ns Ar path +Specifies a path to a challenge string that will be passed to the +FIDO token during key generation. +The challenge string may be used as part of an out-of-band +protocol for key enrollment +(a random challenge is used by default). +.It Cm device +Explicitly specify a +.Xr fido 4 +device to use, rather than letting the token middleware select one. +.It Cm no-touch-required +Indicate that the generated private key should not require touch +events (user presence) when making signatures. +Note that .Xr sshd 8 -(permitted by default). -.It Ic no-x11-forwarding -Disable X11 forwarding (permitted by default). -.It Ic permit-agent-forwarding -Allows -.Xr ssh-agent 1 -forwarding. -.It Ic permit-port-forwarding -Allows port forwarding. -.It Ic permit-pty -Allows PTY allocation. -.It Ic permit-user-rc -Allows execution of -.Pa ~/.ssh/rc -by -.Xr sshd 8 . -.It Ic permit-x11-forwarding -Allows X11 forwarding. -.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. +will refuse such signatures by default, unless overridden via +an authorized_keys option. +.It Cm resident +Indicate that the key should be stored on the FIDO authenticator itself. +Resident keys may be supported on FIDO2 tokens and typically require that +a PIN be set on the token prior to generation. +Resident keys may be loaded off the token using +.Xr ssh-add 1 . +.It Cm user +A username to be associated with a resident key, +overriding the empty default username. +Specifying a username may be useful when generating multiple resident keys +for the same application name. +.It Cm write-attestation Ns = Ns Ar path +May be used at key generation time to record the attestation certificate +returned from FIDO tokens during key generation. +By default this information is discarded. .El .Pp -At present, no options are valid for host keys. -.It Fl o -Causes -.Nm -to save SSH protocol 2 private keys using the new OpenSSH format rather than -the more compatible PEM format. -The new format has increased resistance to brute-force password cracking -but is not supported by versions of OpenSSH prior to 6.5. -Ed25519 keys always use the new private key format. +The +.Fl O +option may be specified multiple times. .It Fl P Ar passphrase Provides the (old) passphrase. .It Fl p @@ -489,12 +522,16 @@ 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. +If the +.Fl l +option is also specified then the contents of the KRL will be printed. .It Fl q Silence .Nm ssh-keygen . -.It Fl R Ar hostname -Removes all keys belonging to +.It Fl R Ar hostname | [hostname]:port +Removes all keys belonging to the specified .Ar hostname +(with optional port number) from a .Pa known_hosts file. @@ -505,8 +542,6 @@ option above). 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 @@ -520,21 +555,34 @@ 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 | rsa1 +.It Fl t Cm dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa Specifies the type of key to create. The possible values are -.Dq rsa1 -for protocol version 1 and .Dq dsa , .Dq ecdsa , +.Dq ecdsa-sk , .Dq ed25519 , +.Dq ed25519-sk , or -.Dq rsa -for protocol version 2. +.Dq rsa . +.Pp +This flag may also be used to specify the desired signature type when +signing certificates using an RSA CA key. +The available RSA signature variants are +.Dq ssh-rsa +(SHA1 signatures, not recommended), +.Dq rsa-sha2-256 , +and +.Dq rsa-sha2-512 +(the default). +.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 @@ -546,13 +594,20 @@ 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. -The start time may be specified as a date in YYYYMMDD format, a time -in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting -of a minus sign followed by a relative time in the format described in the +.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 . -The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or -a relative time starting with a plus character. +.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 expiry date. .Pp For example: .Dq +52w1d @@ -563,6 +618,8 @@ For example: (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 @@ -573,14 +630,106 @@ 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 w Ar provider +Specifies a path to a library that will be used when creating +FIDO authenticator-hosted keys, overriding the default of using +the internal USB HID support. +.It Fl Y Cm find-principals +Find the principal(s) associated with the public key of a signature, +provided using the +.Fl s +flag in an authorized signers file provided using the +.Fl f +flag. +The format of the allowed signers file is documented in the +.Sx ALLOWED SIGNERS +section below. +If one or more matching principals are found, they are returned on +standard output. +.It Fl Y Cm check-novalidate +Checks that a signature generated using +.Nm +.Fl Y Cm sign +has a valid structure. +This does not validate if a signature comes from an authorized signer. +When testing a signature, +.Nm +accepts a message on standard input and a signature namespace using +.Fl n . +A file containing the corresponding signature must also be supplied using the +.Fl s +flag. +Successful testing of the signature is signalled by +.Nm +returning a zero exit status. +.It Fl Y Cm sign +Cryptographically sign a file or some data using a SSH key. +When signing, +.Nm +accepts zero or more files to sign on the command-line - if no files +are specified then +.Nm +will sign data presented on standard input. +Signatures are written to the path of the input file with +.Dq .sig +appended, or to standard output if the message to be signed was read from +standard input. +.Pp +The key used for signing is specified using the +.Fl f +option and may refer to either a private key, or a public key with the private +half available via +.Xr ssh-agent 1 . +An additional signature namespace, used to prevent signature confusion across +different domains of use (e.g. file signing vs email signing) must be provided +via the +.Fl n +flag. +Namespaces are arbitrary strings, and may include: +.Dq file +for file signing, +.Dq email +for email signing. +For custom uses, it is recommended to use names following a +NAMESPACE@YOUR.DOMAIN pattern to generate unambiguous namespaces. +.It Fl Y Cm verify +Request to verify a signature generated using +.Nm +.Fl Y Cm sign +as described above. +When verifying a signature, +.Nm +accepts a message on standard input and a signature namespace using +.Fl n . +A file containing the corresponding signature must also be supplied using the +.Fl s +flag, along with the identity of the signer using +.Fl I +and a list of allowed signers via the +.Fl f +flag. +The format of the allowed signers file is documented in the +.Sx ALLOWED SIGNERS +section below. +A file containing revoked keys can be passed using the +.Fl r +flag. +The revocation file may be a KRL or a one-per-line list of public keys. +Successful verification by an authorized signer is signalled by +.Nm +returning a zero exit status. .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. +If the +.Ar serial_number +is prefixed with a +.Sq + +character, then the serial number will be incremented for each certificate +signed on a single command-line. The default serial number is zero. .Pp When generating a KRL, the @@ -597,25 +746,25 @@ These candidate primes are then tested for suitability (a CPU-intensive process). .Pp Generation of primes is performed using the -.Fl G +.Fl M Cm generate option. The desired length of the primes may be specified by the -.Fl b +.Fl O Cm bits option. For example: .Pp -.Dl # ssh-keygen -G moduli-2048.candidates -b 2048 +.Dl # ssh-keygen -M generate -O bits=2048 moduli-2048.candidates .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 +.Fl O Cm start 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 +.Fl M Cm screen option. In this mode .Nm @@ -624,16 +773,16 @@ will read candidates from standard input (or a file specified using the option). For example: .Pp -.Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates +.Dl # ssh-keygen -M screen -f moduli-2048.candidates moduli-2048 .Pp By default, each candidate will be subjected to 100 primality tests. This may be overridden using the -.Fl a +.Fl O Cm prime-tests 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 +.Fl O Cm generator option. Valid generator values are 2, 3, and 5. .Pp @@ -641,6 +790,30 @@ 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. +.Pp +A number of options are available for moduli generation and screening via the +.Fl O +flag: +.Bl -tag -width Ds +.It Ic lines Ns = Ns Ar number +Exit after screening the specified number of lines while performing DH +candidate screening. +.It Ic start-line Ns = Ns Ar line-number +Start screening at the specified line number while performing DH candidate +screening. +.It Ic checkpoint Ns = Ns Ar filename +Write the last line processed to the specified file while performing DH +candidate screening. +This will be used to skip lines in the input file that have already been +processed if the job is restarted. +.It Ic memory Ns = Ns Ar mbytes +Specify the amount of memory to use (in megabytes) when generating +candidate moduli for DH-GEX. +.It Ic start Ns = Ns Ar hex-value +Specify start point (in hex) when generating candidate moduli for DH-GEX. +.It Ic generator Ns = Ns Ar value +Specify desired generator (in decimal) when testing candidate moduli for DH-GEX. +.El .Sh CERTIFICATES .Nm supports signing of keys to produce certificates that may be used for @@ -680,7 +853,15 @@ 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 host_key.pub +.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 @@ -693,16 +874,101 @@ 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 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 +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 no-touch-required +Do not require signatures made using this key require demonstration +of user presence (e.g. by having the user touch the authenticator). +This option only makes sense for the FIDO authenticator algorithms +.Cm ecdsa-sk +and +.Cm ed25519-sk . +.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 +.Pp +At present, no standard options are valid for host keys. .Pp Finally, certificates may be defined with a validity lifetime. The @@ -767,7 +1033,20 @@ option. 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 its SHA1 hash. +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 @@ -781,40 +1060,80 @@ 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 commandline. +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/identity -Contains the protocol version 1 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 3DES. -This file is not automatically accessed by +.Sh ALLOWED SIGNERS +When verifying signatures, .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. +uses a simple list of identities and keys to determine whether a signature +comes from an authorized source. +This "allowed signers" file uses a format patterned after the +AUTHORIZED_KEYS FILE FORMAT described in +.Xr sshd 8 . +Each line of the file contains the following space-separated fields: +principals, options, keytype, base64-encoded key. +Empty lines and lines starting with a +.Ql # +are ignored as comments. .Pp -.It Pa ~/.ssh/identity.pub -Contains the protocol version 1 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 RSA authentication. -There is no need to keep the contents of this file secret. +The principals field is a pattern-list (See PATTERNS in +.Xr ssh_config 5 ) +consisting of one or more comma-separated USER@DOMAIN identity patterns +that are accepted for signing. +When verifying, the identity presented via the +.Fl I +option must match a principals pattern in order for the corresponding key to be +considered acceptable for verification. .Pp +The options (if present) consist of comma-separated option specifications. +No spaces are permitted, except within double quotes. +The following option specifications are supported (note that option keywords +are case-insensitive): +.Bl -tag -width Ds +.It Cm cert-authority +Indicates that this key is accepted as a certificate authority (CA) and +that certificates signed by this CA may be accepted for verification. +.It Cm namespaces="namespace-list" +Specifies a pattern-list of namespaces that are accepted for this key. +If this option is present, the signature namespace embedded in the +signature object and presented on the verification command-line must +match the specified list before the key will be considered acceptable. +.El +.Pp +When verifying signatures made by certificates, the expected principal +name must match both the principals pattern in the allowed signers file and +the principals embedded in the certificate itself. +.Pp +An example allowed signers file: +.Bd -literal -offset 3n +# Comments allowed at start of line +user1@example.com,user2@example.com ssh-rsa AAAAX1... +# A certificate authority, trusted for all principals in a domain. +*@example.com cert-authority ssh-ed25519 AAAB4... +# A key that is accepted only for file signing. +user2@example.com namespaces="file" ssh-ed25519 AAA41... +.Ed +.Sh ENVIRONMENT +.Bl -tag -width Ds +.It Ev SSH_SK_PROVIDER +Specifies a path to a library that will be used when loading any +FIDO authenticator-hosted keys, overriding the default of using +the built-in USB HID support. +.El +.Sh FILES +.Bl -tag -width Ds -compact .It Pa ~/.ssh/id_dsa .It Pa ~/.ssh/id_ecdsa +.It Pa ~/.ssh/id_ecdsa_sk .It Pa ~/.ssh/id_ed25519 +.It Pa ~/.ssh/id_ed25519_sk .It Pa ~/.ssh/id_rsa -Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA -authentication identity of the user. +Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519, +authenticator-hosted 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 @@ -827,10 +1146,12 @@ 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_ecdsa_sk.pub .It Pa ~/.ssh/id_ed25519.pub +.It Pa ~/.ssh/id_ed25519_sk.pub .It Pa ~/.ssh/id_rsa.pub -Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA -public key for authentication. +Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519, +authenticator-hosted Ed25519 or RSA public key for authentication. The contents of this file should be added to .Pa ~/.ssh/authorized_keys on all machines |