Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.25
1.1 deraadt 1: .\" -*- nroff -*-
2: .\"
3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
6: .\"
1.22 deraadt 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".
12: .\"
13: .\"
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.
17: .\"
18: .\" Redistribution and use in source and binary forms, with or without
19: .\" modification, are permitted provided that the following conditions
20: .\" are met:
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.
1.1 deraadt 26: .\"
1.22 deraadt 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,
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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.
1.1 deraadt 37: .\"
1.2 deraadt 38: .Dd September 25, 1999
39: .Dt SSH-KEYGEN 1
40: .Os
41: .Sh NAME
42: .Nm ssh-keygen
43: .Nd authentication key generation
44: .Sh SYNOPSIS
45: .Nm ssh-keygen
1.25 ! markus 46: .Op Fl q
1.2 deraadt 47: .Op Fl b Ar bits
1.25 ! markus 48: .Op Fl t Ar type
1.2 deraadt 49: .Op Fl N Ar new_passphrase
50: .Op Fl C Ar comment
1.20 markus 51: .Op Fl f Ar output_keyfile
1.2 deraadt 52: .Nm ssh-keygen
53: .Fl p
54: .Op Fl P Ar old_passphrase
55: .Op Fl N Ar new_passphrase
1.9 markus 56: .Op Fl f Ar keyfile
1.2 deraadt 57: .Nm ssh-keygen
1.16 deraadt 58: .Fl x
1.20 markus 59: .Op Fl f Ar input_keyfile
1.16 deraadt 60: .Nm ssh-keygen
61: .Fl X
1.20 markus 62: .Op Fl f Ar input_keyfile
1.16 deraadt 63: .Nm ssh-keygen
1.17 markus 64: .Fl y
1.20 markus 65: .Op Fl f Ar input_keyfile
1.17 markus 66: .Nm ssh-keygen
1.2 deraadt 67: .Fl c
68: .Op Fl P Ar passphrase
69: .Op Fl C Ar comment
1.9 markus 70: .Op Fl f Ar keyfile
71: .Nm ssh-keygen
72: .Fl l
1.20 markus 73: .Op Fl f Ar input_keyfile
1.14 deraadt 74: .Nm ssh-keygen
75: .Fl R
1.13 aaron 76: .Sh DESCRIPTION
1.2 deraadt 77: .Nm
1.13 aaron 78: generates and manages authentication keys for
1.2 deraadt 79: .Xr ssh 1 .
1.15 deraadt 80: .Nm
81: defaults to generating an RSA key for use by protocols 1.3 and 1.5;
82: specifying the
1.25 ! markus 83: .Fl t
! 84: allows you to create a key for use by protocol 2.0.
1.15 deraadt 85: .Pp
1.2 deraadt 86: Normally each user wishing to use SSH
1.15 deraadt 87: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 88: key in
1.15 deraadt 89: .Pa $HOME/.ssh/identity
90: or
91: .Pa $HOME/.ssh/id_dsa .
92: Additionally, the system administrator may use this to generate host keys,
93: as seen in
94: .Pa /etc/rc .
1.2 deraadt 95: .Pp
1.1 deraadt 96: Normally this program generates the key and asks for a file in which
1.12 aaron 97: to store the private key.
98: The public key is stored in a file with the same name but
1.2 deraadt 99: .Dq .pub
1.12 aaron 100: appended.
101: The program also asks for a passphrase.
102: The passphrase may be empty to indicate no passphrase
1.1 deraadt 103: (host keys must have empty passphrase), or it may be a string of
1.12 aaron 104: arbitrary length.
105: Good passphrases are 10-30 characters long and are
1.1 deraadt 106: not simple sentences or otherwise easily guessable (English
107: prose has only 1-2 bits of entropy per word, and provides very bad
1.12 aaron 108: passphrases).
109: The passphrase can be changed later by using the
1.2 deraadt 110: .Fl p
1.1 deraadt 111: option.
1.2 deraadt 112: .Pp
1.12 aaron 113: There is no way to recover a lost passphrase.
114: If the passphrase is
1.1 deraadt 115: lost or forgotten, you will have to generate a new key and copy the
116: corresponding public key to other machines.
1.2 deraadt 117: .Pp
1.15 deraadt 118: For RSA, there is also a comment field in the key file that is only for
1.12 aaron 119: convenience to the user to help identify the key.
120: The comment can tell what the key is for, or whatever is useful.
121: The comment is initialized to
1.2 deraadt 122: .Dq user@host
123: when the key is created, but can be changed using the
124: .Fl c
1.1 deraadt 125: option.
1.2 deraadt 126: .Pp
1.15 deraadt 127: After a key is generated, instructions below detail where the keys
128: should be placed to be activated.
129: .Pp
1.2 deraadt 130: The options are as follows:
131: .Bl -tag -width Ds
132: .It Fl b Ar bits
1.12 aaron 133: Specifies the number of bits in the key to create.
134: Minimum is 512 bits.
135: Generally 1024 bits is considered sufficient, and key sizes
136: above that no longer improve security but make things slower.
137: The default is 1024 bits.
1.2 deraadt 138: .It Fl c
1.1 deraadt 139: Requests changing the comment in the private and public key files.
140: The program will prompt for the file containing the private keys, for
141: passphrase if the key has one, and for the new comment.
1.9 markus 142: .It Fl f
143: Specifies the filename of the key file.
144: .It Fl l
145: Show fingerprint of specified private or public key file.
1.2 deraadt 146: .It Fl p
1.1 deraadt 147: Requests changing the passphrase of a private key file instead of
1.12 aaron 148: creating a new private key.
149: The program will prompt for the file
1.1 deraadt 150: containing the private key, for the old passphrase, and twice for the
151: new passphrase.
1.5 aaron 152: .It Fl q
153: Silence
154: .Nm ssh-keygen .
155: Used by
156: .Pa /etc/rc
157: when creating a new key.
1.25 ! markus 158: .It Fl t Ar type
! 159: Specifies the type of the key to create.
! 160: The possible values are
! 161: .Dq rsa1
! 162: for protocol version 1 and
! 163: .Dq rsa
! 164: or
! 165: .Dq dsa
! 166: for protocol version 2.
! 167: The default is
! 168: .Dq rsa .
1.2 deraadt 169: .It Fl C Ar comment
1.1 deraadt 170: Provides the new comment.
1.2 deraadt 171: .It Fl N Ar new_passphrase
1.1 deraadt 172: Provides the new passphrase.
1.2 deraadt 173: .It Fl P Ar passphrase
1.1 deraadt 174: Provides the (old) passphrase.
1.14 deraadt 175: .It Fl R
176: If RSA support is functional, immediately exits with code 0. If RSA
177: support is not functional, exits with code 1. This flag will be
178: removed once the RSA patent expires.
1.16 deraadt 179: .It Fl x
1.17 markus 180: This option will read a private
1.18 hugh 181: OpenSSH DSA format file and print a SSH2-compatible public key to stdout.
1.16 deraadt 182: .It Fl X
1.23 markus 183: This option will read a unencrypted
184: SSH2-compatible private (or public) key file and
185: print an OpenSSH compatible private (or public) key to stdout.
1.17 markus 186: .It Fl y
187: This option will read a private
1.25 ! markus 188: OpenSSH format file and print an OpenSSH public key to stdout.
1.2 deraadt 189: .El
190: .Sh FILES
191: .Bl -tag -width Ds
192: .It Pa $HOME/.ssh/identity
1.12 aaron 193: Contains the RSA authentication identity of the user.
194: This file should not be readable by anyone but the user.
195: It is possible to
1.1 deraadt 196: specify a passphrase when generating the key; that passphrase will be
1.12 aaron 197: used to encrypt the private part of this file using 3DES.
198: This file is not automatically accessed by
1.2 deraadt 199: .Nm
1.1 deraadt 200: but it is offered as the default file for the private key.
1.15 deraadt 201: .Xr sshd 8
202: will read this file when a login attempt is made.
1.2 deraadt 203: .It Pa $HOME/.ssh/identity.pub
1.12 aaron 204: Contains the public key for authentication.
205: The contents of this file should be added to
1.2 deraadt 206: .Pa $HOME/.ssh/authorized_keys
207: on all machines
1.12 aaron 208: where you wish to log in using RSA authentication.
1.15 deraadt 209: There is no need to keep the contents of this file secret.
210: .It Pa $HOME/.ssh/id_dsa
211: Contains the DSA authentication identity of the user.
212: This file should not be readable by anyone but the user.
213: It is possible to
214: specify a passphrase when generating the key; that passphrase will be
215: used to encrypt the private part of this file using 3DES.
216: This file is not automatically accessed by
217: .Nm
218: but it is offered as the default file for the private key.
219: .Xr sshd 8
220: will read this file when a login attempt is made.
221: .It Pa $HOME/.ssh/id_dsa.pub
222: Contains the public key for authentication.
223: The contents of this file should be added to
224: .Pa $HOME/.ssh/authorized_keys2
225: on all machines
1.25 ! markus 226: where you wish to log in using public key authentication.
1.12 aaron 227: There is no need to keep the contents of this file secret.
1.19 aaron 228: .El
1.24 aaron 229: .Sh AUTHORS
1.1 deraadt 230: Tatu Ylonen <ylo@cs.hut.fi>
1.4 deraadt 231: .Pp
1.6 deraadt 232: OpenSSH
233: is a derivative of the original (free) ssh 1.2.12 release, but with bugs
1.12 aaron 234: removed and newer features re-added.
235: Rapidly after the 1.2.12 release,
236: newer versions bore successively more restrictive licenses.
237: This version of OpenSSH
1.6 deraadt 238: .Bl -bullet
239: .It
1.11 aaron 240: has all components of a restrictive nature (i.e., patents, see
1.6 deraadt 241: .Xr ssl 8 )
242: directly removed from the source code; any licensed or patented components
243: are chosen from
244: external libraries.
245: .It
246: has been updated to support ssh protocol 1.5.
247: .It
1.13 aaron 248: contains added support for
1.6 deraadt 249: .Xr kerberos 8
250: authentication and ticket passing.
251: .It
252: supports one-time password authentication with
253: .Xr skey 1 .
254: .El
1.2 deraadt 255: .Sh SEE ALSO
256: .Xr ssh 1 ,
257: .Xr ssh-add 1 ,
1.8 ericj 258: .Xr ssh-agent 1 ,
1.4 deraadt 259: .Xr sshd 8 ,
260: .Xr ssl 8
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