Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.54.2.3
1.54.2.3! brad 1: .\" $OpenBSD: ssh-keygen.1,v 1.60 2003/07/28 09:49:56 djm Exp $
1.29 niklas 2: .\"
1.1 deraadt 3: .\" -*- nroff -*-
4: .\"
5: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
6: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7: .\" All rights reserved
8: .\"
1.22 deraadt 9: .\" As far as I am concerned, the code I have written for this software
10: .\" can be used freely for any purpose. Any derived versions of this
11: .\" software must be clearly marked as such, and if the derived work is
12: .\" incompatible with the protocol description in the RFC file, it must be
13: .\" called by a name other than "ssh" or "Secure Shell".
14: .\"
15: .\"
1.33 deraadt 16: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
17: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
18: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
1.22 deraadt 19: .\"
20: .\" Redistribution and use in source and binary forms, with or without
21: .\" modification, are permitted provided that the following conditions
22: .\" are met:
23: .\" 1. Redistributions of source code must retain the above copyright
24: .\" notice, this list of conditions and the following disclaimer.
25: .\" 2. Redistributions in binary form must reproduce the above copyright
26: .\" notice, this list of conditions and the following disclaimer in the
27: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 28: .\"
1.22 deraadt 29: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
30: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
31: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
32: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
33: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
34: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
38: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 39: .\"
1.2 deraadt 40: .Dd September 25, 1999
41: .Dt SSH-KEYGEN 1
42: .Os
43: .Sh NAME
44: .Nm ssh-keygen
1.37 markus 45: .Nd authentication key generation, management and conversion
1.2 deraadt 46: .Sh SYNOPSIS
47: .Nm ssh-keygen
1.54.2.2 margarid 48: .Bk -words
1.25 markus 49: .Op Fl q
1.2 deraadt 50: .Op Fl b Ar bits
1.53 stevesk 51: .Fl t Ar type
1.2 deraadt 52: .Op Fl N Ar new_passphrase
53: .Op Fl C Ar comment
1.20 markus 54: .Op Fl f Ar output_keyfile
1.54.2.2 margarid 55: .Ek
1.2 deraadt 56: .Nm ssh-keygen
57: .Fl p
58: .Op Fl P Ar old_passphrase
59: .Op Fl N Ar new_passphrase
1.9 markus 60: .Op Fl f Ar keyfile
1.2 deraadt 61: .Nm ssh-keygen
1.37 markus 62: .Fl i
1.20 markus 63: .Op Fl f Ar input_keyfile
1.16 deraadt 64: .Nm ssh-keygen
1.37 markus 65: .Fl e
1.20 markus 66: .Op Fl f Ar input_keyfile
1.16 deraadt 67: .Nm ssh-keygen
1.17 markus 68: .Fl y
1.20 markus 69: .Op Fl f Ar input_keyfile
1.17 markus 70: .Nm ssh-keygen
1.2 deraadt 71: .Fl c
72: .Op Fl P Ar passphrase
73: .Op Fl C Ar comment
1.9 markus 74: .Op Fl f Ar keyfile
75: .Nm ssh-keygen
76: .Fl l
1.35 markus 77: .Op Fl f Ar input_keyfile
78: .Nm ssh-keygen
79: .Fl B
1.20 markus 80: .Op Fl f Ar input_keyfile
1.48 jakob 81: .Nm ssh-keygen
82: .Fl D Ar reader
83: .Nm ssh-keygen
84: .Fl U Ar reader
85: .Op Fl f Ar input_keyfile
1.54.2.3! brad 86: .Nm ssh-keygen
! 87: .Fl r Ar hostname
! 88: .Op Fl f Ar input_keyfile
! 89: .Op Fl g
! 90: .Nm ssh-keygen
! 91: .Fl G Ar output_file
! 92: .Op Fl b Ar bits
! 93: .Op Fl M Ar memory
! 94: .Op Fl S Ar start_point
! 95: .Nm ssh-keygen
! 96: .Fl T Ar output_file
! 97: .Fl f Ar input_file
! 98: .Op Fl a Ar num_trials
! 99: .Op Fl W Ar generator
1.13 aaron 100: .Sh DESCRIPTION
1.2 deraadt 101: .Nm
1.37 markus 102: generates, manages and converts authentication keys for
1.2 deraadt 103: .Xr ssh 1 .
1.15 deraadt 104: .Nm
1.54 deraadt 105: can create RSA keys for use by SSH protocol version 1 and RSA or DSA
1.54.2.3! brad 106: keys for use by SSH protocol version 2.
! 107: The type of key to be generated is specified with the
1.25 markus 108: .Fl t
1.52 djm 109: option.
1.15 deraadt 110: .Pp
1.54.2.3! brad 111: .Nm
! 112: is also used to generate groups for use in Diffie-Hellman group
! 113: exchange (DH-GEX).
! 114: See the
! 115: .Sx MODULI GENERATION
! 116: section for details.
! 117: .Pp
1.2 deraadt 118: Normally each user wishing to use SSH
1.15 deraadt 119: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 120: key in
1.36 itojun 121: .Pa $HOME/.ssh/identity ,
122: .Pa $HOME/.ssh/id_dsa
1.15 deraadt 123: or
1.36 itojun 124: .Pa $HOME/.ssh/id_rsa .
1.15 deraadt 125: Additionally, the system administrator may use this to generate host keys,
126: as seen in
127: .Pa /etc/rc .
1.2 deraadt 128: .Pp
1.1 deraadt 129: Normally this program generates the key and asks for a file in which
1.12 aaron 130: to store the private key.
131: The public key is stored in a file with the same name but
1.2 deraadt 132: .Dq .pub
1.12 aaron 133: appended.
134: The program also asks for a passphrase.
135: The passphrase may be empty to indicate no passphrase
1.26 markus 136: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 137: arbitrary length.
1.51 stevesk 138: A passphrase is similar to a password, except it can be a phrase with a
139: series of words, punctuation, numbers, whitespace, or any string of
140: characters you want.
141: Good passphrases are 10-30 characters long, are
1.1 deraadt 142: not simple sentences or otherwise easily guessable (English
1.42 markus 143: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 144: passphrases), and contain a mix of upper and lowercase letters,
145: numbers, and non-alphanumeric characters.
1.12 aaron 146: The passphrase can be changed later by using the
1.2 deraadt 147: .Fl p
1.1 deraadt 148: option.
1.2 deraadt 149: .Pp
1.12 aaron 150: There is no way to recover a lost passphrase.
151: If the passphrase is
1.49 deraadt 152: lost or forgotten, a new key must be generated and copied to the
1.1 deraadt 153: corresponding public key to other machines.
1.2 deraadt 154: .Pp
1.37 markus 155: For RSA1 keys,
156: there is also a comment field in the key file that is only for
1.12 aaron 157: convenience to the user to help identify the key.
158: The comment can tell what the key is for, or whatever is useful.
159: The comment is initialized to
1.2 deraadt 160: .Dq user@host
161: when the key is created, but can be changed using the
162: .Fl c
1.1 deraadt 163: option.
1.2 deraadt 164: .Pp
1.15 deraadt 165: After a key is generated, instructions below detail where the keys
166: should be placed to be activated.
167: .Pp
1.2 deraadt 168: The options are as follows:
169: .Bl -tag -width Ds
1.54.2.3! brad 170: .It Fl a Ar trials
! 171: Specifies the number of primality tests to perform when screening DH-GEX
! 172: candidates using the
! 173: .Fl T
! 174: command.
1.2 deraadt 175: .It Fl b Ar bits
1.12 aaron 176: Specifies the number of bits in the key to create.
177: Minimum is 512 bits.
1.54.2.1 margarid 178: Generally, 1024 bits is considered sufficient.
1.12 aaron 179: The default is 1024 bits.
1.2 deraadt 180: .It Fl c
1.1 deraadt 181: Requests changing the comment in the private and public key files.
1.50 markus 182: This operation is only supported for RSA1 keys.
1.1 deraadt 183: The program will prompt for the file containing the private keys, for
1.41 stevesk 184: the passphrase if the key has one, and for the new comment.
1.37 markus 185: .It Fl e
1.40 markus 186: This option will read a private or public OpenSSH key file and
187: print the key in a
1.37 markus 188: .Sq SECSH Public Key File Format
189: to stdout.
190: This option allows exporting keys for use by several commercial
191: SSH implementations.
1.54.2.3! brad 192: .It Fl g
! 193: Use generic DNS resource record format.
1.48 jakob 194: .It Fl f Ar filename
1.9 markus 195: Specifies the filename of the key file.
1.37 markus 196: .It Fl i
197: This option will read an unencrypted private (or public) key file
198: in SSH2-compatible format and print an OpenSSH compatible private
199: (or public) key to stdout.
200: .Nm
1.38 markus 201: also reads the
1.37 markus 202: .Sq SECSH Public Key File Format .
203: This option allows importing keys from several commercial
204: SSH implementations.
1.9 markus 205: .It Fl l
1.50 markus 206: Show fingerprint of specified public key file.
207: Private RSA1 keys are also supported.
208: For RSA and DSA keys
209: .Nm
210: tries to find the matching public key file and prints its fingerprint.
1.2 deraadt 211: .It Fl p
1.1 deraadt 212: Requests changing the passphrase of a private key file instead of
1.12 aaron 213: creating a new private key.
214: The program will prompt for the file
1.1 deraadt 215: containing the private key, for the old passphrase, and twice for the
216: new passphrase.
1.5 aaron 217: .It Fl q
218: Silence
219: .Nm ssh-keygen .
220: Used by
221: .Pa /etc/rc
222: when creating a new key.
1.37 markus 223: .It Fl y
224: This option will read a private
225: OpenSSH format file and print an OpenSSH public key to stdout.
1.25 markus 226: .It Fl t Ar type
227: Specifies the type of the key to create.
228: The possible values are
229: .Dq rsa1
230: for protocol version 1 and
231: .Dq rsa
232: or
233: .Dq dsa
234: for protocol version 2.
1.35 markus 235: .It Fl B
236: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 237: .It Fl C Ar comment
1.1 deraadt 238: Provides the new comment.
1.48 jakob 239: .It Fl D Ar reader
240: Download the RSA public key stored in the smartcard in
241: .Ar reader .
1.54.2.3! brad 242: .It Fl G Ar output_file
! 243: Generate candidate primes for DH-GEX.
! 244: These primes must be screened for
! 245: safety (using the
! 246: .Fl T
! 247: option) before use.
! 248: .It Fl M Ar memory
! 249: Specify the amount of memory to use (in megabytes) when generating
! 250: candidate moduli for DH-GEX.
1.2 deraadt 251: .It Fl N Ar new_passphrase
1.1 deraadt 252: Provides the new passphrase.
1.2 deraadt 253: .It Fl P Ar passphrase
1.1 deraadt 254: Provides the (old) passphrase.
1.54.2.3! brad 255: .It Fl S Ar start
! 256: Specify start point (in hex) when generating candidate moduli for DH-GEX.
! 257: .It Fl T Ar output_file
! 258: Test DH group exchange candidate primes (generated using the
! 259: .Fl G
! 260: option) for safety.
! 261: .It Fl W Ar generator
! 262: Specify desired generator when testing candidate moduli for DH-GEX.
1.48 jakob 263: .It Fl U Ar reader
264: Upload an existing RSA private key into the smartcard in
265: .Ar reader .
1.54.2.3! brad 266: .It Fl r Ar hostname
! 267: Print DNS resource record with the specified
! 268: .Ar hostname .
1.2 deraadt 269: .El
1.54.2.3! brad 270: .Sh MODULI GENERATION
! 271: .Nm
! 272: may be used to generate groups for the Diffie-Hellman Group Exchange
! 273: (DH-GEX) protocol.
! 274: Generating these groups is a two-step process: first, candidate
! 275: primes are generated using a fast, but memory intensive process.
! 276: These candidate primes are then tested for suitability (a CPU-intensive
! 277: process).
! 278: .Pp
! 279: Generation of primes is performed using the
! 280: .Fl G
! 281: option.
! 282: The desired length of the primes may be specified by the
! 283: .Fl b
! 284: option.
! 285: For example:
! 286: .Pp
! 287: .Dl ssh-keygen -G moduli-2048.candidates -b 2048
! 288: .Pp
! 289: By default, the search for primes begins at a random point in the
! 290: desired length range.
! 291: This may be overridden using the
! 292: .Fl S
! 293: option, which specifies a different start point (in hex).
! 294: .Pp
! 295: Once a set of candidates have been generated, they must be tested for
! 296: suitability.
! 297: This may be performed using the
! 298: .Fl T
! 299: option.
! 300: In this mode
! 301: .Nm
! 302: will read candidates from standard input (or a file specified using the
! 303: .Fl f
! 304: option).
! 305: For example:
! 306: .Pp
! 307: .Dl ssh-keygen -T moduli-2048 -f moduli-2048.candidates
! 308: .Pp
! 309: By default, each candidate will be subjected to 100 primality tests.
! 310: This may be overridden using the
! 311: .Fl a
! 312: option.
! 313: The DH generator value will be chosen automatically for the
! 314: prime under consideration.
! 315: If a specific generator is desired, it may be requested using the
! 316: .Fl W
! 317: option.
! 318: Valid generator values are 2, 3 and 5.
! 319: .Pp
! 320: Screened DH groups may be installed in
! 321: .Pa /etc/moduli .
! 322: It is important that this file contains moduli of a range of bit lengths and
! 323: that both ends of a connection share common moduli.
1.2 deraadt 324: .Sh FILES
325: .Bl -tag -width Ds
326: .It Pa $HOME/.ssh/identity
1.36 itojun 327: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 328: This file should not be readable by anyone but the user.
329: It is possible to
1.1 deraadt 330: specify a passphrase when generating the key; that passphrase will be
1.12 aaron 331: used to encrypt the private part of this file using 3DES.
332: This file is not automatically accessed by
1.2 deraadt 333: .Nm
1.1 deraadt 334: but it is offered as the default file for the private key.
1.46 markus 335: .Xr ssh 1
1.15 deraadt 336: will read this file when a login attempt is made.
1.2 deraadt 337: .It Pa $HOME/.ssh/identity.pub
1.36 itojun 338: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 339: The contents of this file should be added to
1.2 deraadt 340: .Pa $HOME/.ssh/authorized_keys
341: on all machines
1.49 deraadt 342: where the user wishes to log in using RSA authentication.
1.15 deraadt 343: There is no need to keep the contents of this file secret.
344: .It Pa $HOME/.ssh/id_dsa
1.36 itojun 345: Contains the protocol version 2 DSA authentication identity of the user.
1.15 deraadt 346: This file should not be readable by anyone but the user.
347: It is possible to
348: specify a passphrase when generating the key; that passphrase will be
349: used to encrypt the private part of this file using 3DES.
350: This file is not automatically accessed by
351: .Nm
352: but it is offered as the default file for the private key.
1.46 markus 353: .Xr ssh 1
1.15 deraadt 354: will read this file when a login attempt is made.
355: .It Pa $HOME/.ssh/id_dsa.pub
1.36 itojun 356: Contains the protocol version 2 DSA public key for authentication.
357: The contents of this file should be added to
1.43 markus 358: .Pa $HOME/.ssh/authorized_keys
1.36 itojun 359: on all machines
1.49 deraadt 360: where the user wishes to log in using public key authentication.
1.36 itojun 361: There is no need to keep the contents of this file secret.
362: .It Pa $HOME/.ssh/id_rsa
363: Contains the protocol version 2 RSA authentication identity of the user.
364: This file should not be readable by anyone but the user.
365: It is possible to
366: specify a passphrase when generating the key; that passphrase will be
367: used to encrypt the private part of this file using 3DES.
368: This file is not automatically accessed by
369: .Nm
370: but it is offered as the default file for the private key.
1.46 markus 371: .Xr ssh 1
1.36 itojun 372: will read this file when a login attempt is made.
373: .It Pa $HOME/.ssh/id_rsa.pub
374: Contains the protocol version 2 RSA public key for authentication.
1.15 deraadt 375: The contents of this file should be added to
1.43 markus 376: .Pa $HOME/.ssh/authorized_keys
1.15 deraadt 377: on all machines
1.49 deraadt 378: where the user wishes to log in using public key authentication.
1.12 aaron 379: There is no need to keep the contents of this file secret.
1.54.2.3! brad 380: .It Pa /etc/moduli
! 381: Contains Diffie-Hellman groups used for DH-GEX.
! 382: The file format is described in
! 383: .Xr moduli 5 .
1.19 aaron 384: .El
1.2 deraadt 385: .Sh SEE ALSO
386: .Xr ssh 1 ,
387: .Xr ssh-add 1 ,
1.8 ericj 388: .Xr ssh-agent 1 ,
1.54.2.3! brad 389: .Xr moduli 5 ,
1.30 itojun 390: .Xr sshd 8
1.37 markus 391: .Rs
1.45 deraadt 392: .%A J. Galbraith
393: .%A R. Thayer
1.37 markus 394: .%T "SECSH Public Key File Format"
395: .%N draft-ietf-secsh-publickeyfile-01.txt
396: .%D March 2001
397: .%O work in progress material
398: .Re
1.54.2.3! brad 399: .Sh AUTHORS
! 400: OpenSSH is a derivative of the original and free
! 401: ssh 1.2.12 release by Tatu Ylonen.
! 402: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
! 403: Theo de Raadt and Dug Song
! 404: removed many bugs, re-added newer features and
! 405: created OpenSSH.
! 406: Markus Friedl contributed the support for SSH
! 407: protocol versions 1.5 and 2.0.
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