-.\" -*- nroff -*-
+.\" $OpenBSD: ssh-keygen.1,v 1.80 2009/10/24 00:48:34 dtucker Exp $
.\"
-.\" ssh-keygen.1
+.\" -*- nroff -*-
.\"
.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
-.\"
.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
.\" All rights reserved
.\"
-.\" Created: Sat Apr 22 23:55:14 1995 ylo
+.\" 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".
+.\"
.\"
-.\" $Id$
+.\" 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.
.\"
-.Dd September 25, 1999
+.\" 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 $Mdocdate$
.Dt SSH-KEYGEN 1
.Os
.Sh NAME
.Nm ssh-keygen
-.Nd authentication key generation
+.Nd authentication key generation, management and conversion
.Sh SYNOPSIS
.Nm ssh-keygen
+.Bk -words
.Op Fl q
.Op Fl b Ar bits
+.Fl t Ar type
.Op Fl N Ar new_passphrase
.Op Fl C Ar comment
+.Op Fl f Ar output_keyfile
+.Ek
.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 f Ar input_keyfile
+.Nm ssh-keygen
+.Fl e
+.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
-.Sh DESCRIPTION
+.Op Fl f Ar keyfile
+.Nm ssh-keygen
+.Fl l
+.Op Fl f Ar input_keyfile
+.Nm ssh-keygen
+.Fl B
+.Op Fl f Ar input_keyfile
+.Nm ssh-keygen
+.Fl D Ar reader
+.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 U Ar reader
+.Op Fl f Ar input_keyfile
+.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 num_trials
+.Op Fl W Ar generator
+.Sh DESCRIPTION
.Nm
-generates and manages authentication keys for
+generates, manages and converts authentication keys for
.Xr ssh 1 .
+.Nm
+can create RSA keys for use by SSH protocol version 1 and RSA or DSA
+keys for use by SSH protocol version 2.
+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.
+.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
Normally each user wishing to use SSH
-with RSA authentication runs this once to create the authentication
+with RSA or DSA authentication runs this once to create the authentication
key in
-.Pa $HOME/.ssh/identity .
-Additionally, the system administrator may use this to generate host keys.
+.Pa ~/.ssh/identity ,
+.Pa ~/.ssh/id_dsa
+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
+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 empty passphrase), or it may be a string of
-arbitrary length. Good passphrases are 10-30 characters long and are
+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 word, and provides very bad
-passphrases). The passphrase can be changed later by using the
+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, you will have to generate a new key and copy the
+There is no way to recover a lost passphrase.
+If the passphrase is
+lost or forgotten, a new key must be generated and copied to the
corresponding public key to other machines.
.Pp
-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
+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.
+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 Ar trials
+Specifies the number of primality tests to perform when screening DH-GEX
+candidates using the
+.Fl T
+command.
+.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. Minimum is 512
-bits. Generally 1024 bits is considered sufficient, and key sizes
-above that no longer improve security but make things slower. The
-default is 1024 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.
+DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
+.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
-passphrase if the key has one, and for the new comment.
+the passphrase if the key has one, and for the new comment.
+.It Fl D Ar reader
+Download the RSA public key stored in the smartcard in
+.Ar reader .
+.It Fl e
+This option will read a private or public OpenSSH key file and
+print the key in
+RFC 4716 SSH Public Key File Format
+to stdout.
+This option allows exporting keys for use by 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 i
+This option will read an unencrypted private (or public) key file
+in SSH2-compatible format and print an OpenSSH compatible private
+(or public) key to stdout.
+.Nm
+also reads the
+RFC 4716 SSH Public Key File Format.
+This option allows importing keys from several commercial
+SSH implementations.
+.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.
+.It Fl N Ar new_passphrase
+Provides the new passphrase.
+.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
+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
Used by
.Pa /etc/rc
when creating a new key.
-.It Fl C Ar comment
-Provides the new comment.
-.It Fl N Ar new_passphrase
-Provides the new passphrase.
-.It Fl P Ar passphrase
-Provides the (old) passphrase.
+.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 T Ar output_file
+Test DH group exchange candidate primes (generated using the
+.Fl G
+option) for safety.
+.It Fl t Ar type
+Specifies the type of key to create.
+The possible values are
+.Dq rsa1
+for protocol version 1 and
+.Dq rsa
+or
+.Dq dsa
+for protocol version 2.
+.It Fl U Ar reader
+Upload an existing RSA private key into the smartcard in
+.Ar reader .
+.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.
.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 tested 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 FILES
.Bl -tag -width Ds
-.It Pa $HOME/.ssh/random_seed
-Used for seeding the random number generator. This file should not be
-readable by anyone but the user. This file is created the first time
-the program is run, and is updated every time.
-.It Pa $HOME/.ssh/identity
-Contains the RSA authentication identity of the user. This file
-should not be readable by anyone but the user. It is possible to
+.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
+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.
-.It Pa $HOME/.ssh/identity.pub
-Contains the public key for authentication. The contents of this file
-should be added to
-.Pa $HOME/.ssh/authorized_keys
+.Xr ssh 1
+will read this file when a login attempt is made.
+.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 you wish to log in using RSA authentication. There is no
-need to keep the contents of this file secret.
-.Sh AUTHOR
-Tatu Ylonen <ylo@cs.hut.fi>
-.Pp
-OpenSSH
-is a derivative of the original (free) ssh 1.2.12 release, but with bugs
-removed and newer features re-added. Rapidly after the 1.2.12 release,
-newer versions bore successively more restrictive licenses. This version
-of OpenSSH
-.Bl -bullet
-.It
-has all components of a restrictive nature (ie. patents, see
-.Xr ssl 8 )
-directly removed from the source code; any licensed or patented components
-are chosen from
-external libraries.
-.It
-has been updated to support ssh protocol 1.5.
-.It
-contains added support for
-.Xr kerberos 8
-authentication and ticket passing.
-.It
-supports one-time password authentication with
-.Xr skey 1 .
+where the user wishes to log in using RSA authentication.
+There is no need to keep the contents of this file secret.
+.It Pa ~/.ssh/id_dsa
+Contains the protocol version 2 DSA 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.
+.It Pa ~/.ssh/id_dsa.pub
+Contains the protocol version 2 DSA 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.
+.It Pa ~/.ssh/id_rsa
+Contains the protocol version 2 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.
+.It Pa ~/.ssh/id_rsa.pub
+Contains the protocol version 2 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.
+.It Pa /etc/moduli
+Contains Diffie-Hellman groups used for DH-GEX.
+The file format is described in
+.Xr moduli 5 .
.El
-.Pp
-The libraries described in
-.Xr ssl 8
-are required for proper operation.
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr ssh-add 1 ,
-.Xr ssh-agent 1,
-.Xr sshd 8 ,
-.Xr ssl 8
+.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.
andersk / openssh.git / blobdiff