Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.55.2.3
1.55.2.3! brad 1: .\" $OpenBSD: ssh-keygen.1,v 1.61 2003/12/22 09:16:58 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
1.55.2.1 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
1.55.2.1 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
1.55.2.2 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
1.55.2.3! brad 92: .Op Fl v
1.55.2.2 brad 93: .Op Fl b Ar bits
94: .Op Fl M Ar memory
95: .Op Fl S Ar start_point
96: .Nm ssh-keygen
97: .Fl T Ar output_file
98: .Fl f Ar input_file
1.55.2.3! brad 99: .Op Fl v
1.55.2.2 brad 100: .Op Fl a Ar num_trials
101: .Op Fl W Ar generator
1.13 aaron 102: .Sh DESCRIPTION
1.2 deraadt 103: .Nm
1.37 markus 104: generates, manages and converts authentication keys for
1.2 deraadt 105: .Xr ssh 1 .
1.15 deraadt 106: .Nm
1.54 deraadt 107: can create RSA keys for use by SSH protocol version 1 and RSA or DSA
1.55.2.2 brad 108: keys for use by SSH protocol version 2.
109: The type of key to be generated is specified with the
1.25 markus 110: .Fl t
1.52 djm 111: option.
1.15 deraadt 112: .Pp
1.55.2.2 brad 113: .Nm
114: is also used to generate groups for use in Diffie-Hellman group
115: exchange (DH-GEX).
116: See the
117: .Sx MODULI GENERATION
118: section for details.
119: .Pp
1.2 deraadt 120: Normally each user wishing to use SSH
1.15 deraadt 121: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 122: key in
1.36 itojun 123: .Pa $HOME/.ssh/identity ,
124: .Pa $HOME/.ssh/id_dsa
1.15 deraadt 125: or
1.36 itojun 126: .Pa $HOME/.ssh/id_rsa .
1.15 deraadt 127: Additionally, the system administrator may use this to generate host keys,
128: as seen in
129: .Pa /etc/rc .
1.2 deraadt 130: .Pp
1.1 deraadt 131: Normally this program generates the key and asks for a file in which
1.12 aaron 132: to store the private key.
133: The public key is stored in a file with the same name but
1.2 deraadt 134: .Dq .pub
1.12 aaron 135: appended.
136: The program also asks for a passphrase.
137: The passphrase may be empty to indicate no passphrase
1.26 markus 138: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 139: arbitrary length.
1.51 stevesk 140: A passphrase is similar to a password, except it can be a phrase with a
141: series of words, punctuation, numbers, whitespace, or any string of
142: characters you want.
143: Good passphrases are 10-30 characters long, are
1.1 deraadt 144: not simple sentences or otherwise easily guessable (English
1.42 markus 145: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 146: passphrases), and contain a mix of upper and lowercase letters,
147: numbers, and non-alphanumeric characters.
1.12 aaron 148: The passphrase can be changed later by using the
1.2 deraadt 149: .Fl p
1.1 deraadt 150: option.
1.2 deraadt 151: .Pp
1.12 aaron 152: There is no way to recover a lost passphrase.
153: If the passphrase is
1.49 deraadt 154: lost or forgotten, a new key must be generated and copied to the
1.1 deraadt 155: corresponding public key to other machines.
1.2 deraadt 156: .Pp
1.37 markus 157: For RSA1 keys,
158: there is also a comment field in the key file that is only for
1.12 aaron 159: convenience to the user to help identify the key.
160: The comment can tell what the key is for, or whatever is useful.
161: The comment is initialized to
1.2 deraadt 162: .Dq user@host
163: when the key is created, but can be changed using the
164: .Fl c
1.1 deraadt 165: option.
1.2 deraadt 166: .Pp
1.15 deraadt 167: After a key is generated, instructions below detail where the keys
168: should be placed to be activated.
169: .Pp
1.2 deraadt 170: The options are as follows:
171: .Bl -tag -width Ds
1.55.2.2 brad 172: .It Fl a Ar trials
173: Specifies the number of primality tests to perform when screening DH-GEX
174: candidates using the
175: .Fl T
176: command.
1.2 deraadt 177: .It Fl b Ar bits
1.12 aaron 178: Specifies the number of bits in the key to create.
179: Minimum is 512 bits.
1.55 stevesk 180: Generally, 1024 bits is considered sufficient.
1.12 aaron 181: The default is 1024 bits.
1.2 deraadt 182: .It Fl c
1.1 deraadt 183: Requests changing the comment in the private and public key files.
1.50 markus 184: This operation is only supported for RSA1 keys.
1.1 deraadt 185: The program will prompt for the file containing the private keys, for
1.41 stevesk 186: the passphrase if the key has one, and for the new comment.
1.37 markus 187: .It Fl e
1.40 markus 188: This option will read a private or public OpenSSH key file and
189: print the key in a
1.37 markus 190: .Sq SECSH Public Key File Format
191: to stdout.
192: This option allows exporting keys for use by several commercial
193: SSH implementations.
1.55.2.2 brad 194: .It Fl g
195: Use generic DNS resource record format.
1.48 jakob 196: .It Fl f Ar filename
1.9 markus 197: Specifies the filename of the key file.
1.37 markus 198: .It Fl i
199: This option will read an unencrypted private (or public) key file
200: in SSH2-compatible format and print an OpenSSH compatible private
201: (or public) key to stdout.
202: .Nm
1.38 markus 203: also reads the
1.37 markus 204: .Sq SECSH Public Key File Format .
205: This option allows importing keys from several commercial
206: SSH implementations.
1.9 markus 207: .It Fl l
1.50 markus 208: Show fingerprint of specified public key file.
209: Private RSA1 keys are also supported.
210: For RSA and DSA keys
211: .Nm
212: tries to find the matching public key file and prints its fingerprint.
1.2 deraadt 213: .It Fl p
1.1 deraadt 214: Requests changing the passphrase of a private key file instead of
1.12 aaron 215: creating a new private key.
216: The program will prompt for the file
1.1 deraadt 217: containing the private key, for the old passphrase, and twice for the
218: new passphrase.
1.5 aaron 219: .It Fl q
220: Silence
221: .Nm ssh-keygen .
222: Used by
223: .Pa /etc/rc
224: when creating a new key.
1.37 markus 225: .It Fl y
226: This option will read a private
227: OpenSSH format file and print an OpenSSH public key to stdout.
1.25 markus 228: .It Fl t Ar type
229: Specifies the type of the key to create.
230: The possible values are
231: .Dq rsa1
232: for protocol version 1 and
233: .Dq rsa
234: or
235: .Dq dsa
236: for protocol version 2.
1.35 markus 237: .It Fl B
238: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 239: .It Fl C Ar comment
1.1 deraadt 240: Provides the new comment.
1.48 jakob 241: .It Fl D Ar reader
242: Download the RSA public key stored in the smartcard in
243: .Ar reader .
1.55.2.2 brad 244: .It Fl G Ar output_file
245: Generate candidate primes for DH-GEX.
246: These primes must be screened for
247: safety (using the
248: .Fl T
249: option) before use.
250: .It Fl M Ar memory
251: Specify the amount of memory to use (in megabytes) when generating
252: candidate moduli for DH-GEX.
1.2 deraadt 253: .It Fl N Ar new_passphrase
1.1 deraadt 254: Provides the new passphrase.
1.2 deraadt 255: .It Fl P Ar passphrase
1.1 deraadt 256: Provides the (old) passphrase.
1.55.2.2 brad 257: .It Fl S Ar start
258: Specify start point (in hex) when generating candidate moduli for DH-GEX.
259: .It Fl T Ar output_file
260: Test DH group exchange candidate primes (generated using the
261: .Fl G
262: option) for safety.
263: .It Fl W Ar generator
264: Specify desired generator when testing candidate moduli for DH-GEX.
1.48 jakob 265: .It Fl U Ar reader
266: Upload an existing RSA private key into the smartcard in
267: .Ar reader .
1.55.2.3! brad 268: .It Fl v
! 269: Verbose mode.
! 270: Causes
! 271: .Nm
! 272: to print debugging messages about its progress.
! 273: This is helpful for debugging moduli generation.
! 274: Multiple
! 275: .Fl v
! 276: options increase the verbosity.
! 277: The maximum is 3.
1.55.2.2 brad 278: .It Fl r Ar hostname
279: Print DNS resource record with the specified
280: .Ar hostname .
1.2 deraadt 281: .El
1.55.2.2 brad 282: .Sh MODULI GENERATION
283: .Nm
284: may be used to generate groups for the Diffie-Hellman Group Exchange
285: (DH-GEX) protocol.
286: Generating these groups is a two-step process: first, candidate
287: primes are generated using a fast, but memory intensive process.
288: These candidate primes are then tested for suitability (a CPU-intensive
289: process).
290: .Pp
291: Generation of primes is performed using the
292: .Fl G
293: option.
294: The desired length of the primes may be specified by the
295: .Fl b
296: option.
297: For example:
298: .Pp
299: .Dl ssh-keygen -G moduli-2048.candidates -b 2048
300: .Pp
301: By default, the search for primes begins at a random point in the
302: desired length range.
303: This may be overridden using the
304: .Fl S
305: option, which specifies a different start point (in hex).
306: .Pp
307: Once a set of candidates have been generated, they must be tested for
308: suitability.
309: This may be performed using the
310: .Fl T
311: option.
312: In this mode
313: .Nm
314: will read candidates from standard input (or a file specified using the
315: .Fl f
316: option).
317: For example:
318: .Pp
319: .Dl ssh-keygen -T moduli-2048 -f moduli-2048.candidates
320: .Pp
321: By default, each candidate will be subjected to 100 primality tests.
322: This may be overridden using the
323: .Fl a
324: option.
325: The DH generator value will be chosen automatically for the
326: prime under consideration.
327: If a specific generator is desired, it may be requested using the
328: .Fl W
329: option.
330: Valid generator values are 2, 3 and 5.
331: .Pp
332: Screened DH groups may be installed in
333: .Pa /etc/moduli .
334: It is important that this file contains moduli of a range of bit lengths and
335: that both ends of a connection share common moduli.
1.2 deraadt 336: .Sh FILES
337: .Bl -tag -width Ds
338: .It Pa $HOME/.ssh/identity
1.36 itojun 339: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 340: This file should not be readable by anyone but the user.
341: It is possible to
1.1 deraadt 342: specify a passphrase when generating the key; that passphrase will be
1.12 aaron 343: used to encrypt the private part of this file using 3DES.
344: This file is not automatically accessed by
1.2 deraadt 345: .Nm
1.1 deraadt 346: but it is offered as the default file for the private key.
1.46 markus 347: .Xr ssh 1
1.15 deraadt 348: will read this file when a login attempt is made.
1.2 deraadt 349: .It Pa $HOME/.ssh/identity.pub
1.36 itojun 350: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 351: The contents of this file should be added to
1.2 deraadt 352: .Pa $HOME/.ssh/authorized_keys
353: on all machines
1.49 deraadt 354: where the user wishes to log in using RSA authentication.
1.15 deraadt 355: There is no need to keep the contents of this file secret.
356: .It Pa $HOME/.ssh/id_dsa
1.36 itojun 357: Contains the protocol version 2 DSA authentication identity of the user.
1.15 deraadt 358: This file should not be readable by anyone but the user.
359: It is possible to
360: specify a passphrase when generating the key; that passphrase will be
361: used to encrypt the private part of this file using 3DES.
362: This file is not automatically accessed by
363: .Nm
364: but it is offered as the default file for the private key.
1.46 markus 365: .Xr ssh 1
1.15 deraadt 366: will read this file when a login attempt is made.
367: .It Pa $HOME/.ssh/id_dsa.pub
1.36 itojun 368: Contains the protocol version 2 DSA public key for authentication.
369: The contents of this file should be added to
1.43 markus 370: .Pa $HOME/.ssh/authorized_keys
1.36 itojun 371: on all machines
1.49 deraadt 372: where the user wishes to log in using public key authentication.
1.36 itojun 373: There is no need to keep the contents of this file secret.
374: .It Pa $HOME/.ssh/id_rsa
375: Contains the protocol version 2 RSA authentication identity of the user.
376: This file should not be readable by anyone but the user.
377: It is possible to
378: specify a passphrase when generating the key; that passphrase will be
379: used to encrypt the private part of this file using 3DES.
380: This file is not automatically accessed by
381: .Nm
382: but it is offered as the default file for the private key.
1.46 markus 383: .Xr ssh 1
1.36 itojun 384: will read this file when a login attempt is made.
385: .It Pa $HOME/.ssh/id_rsa.pub
386: Contains the protocol version 2 RSA public key for authentication.
1.15 deraadt 387: The contents of this file should be added to
1.43 markus 388: .Pa $HOME/.ssh/authorized_keys
1.15 deraadt 389: on all machines
1.49 deraadt 390: where the user wishes to log in using public key authentication.
1.12 aaron 391: There is no need to keep the contents of this file secret.
1.55.2.2 brad 392: .It Pa /etc/moduli
393: Contains Diffie-Hellman groups used for DH-GEX.
394: The file format is described in
395: .Xr moduli 5 .
1.19 aaron 396: .El
1.2 deraadt 397: .Sh SEE ALSO
398: .Xr ssh 1 ,
399: .Xr ssh-add 1 ,
1.8 ericj 400: .Xr ssh-agent 1 ,
1.55.2.2 brad 401: .Xr moduli 5 ,
1.30 itojun 402: .Xr sshd 8
1.37 markus 403: .Rs
1.45 deraadt 404: .%A J. Galbraith
405: .%A R. Thayer
1.37 markus 406: .%T "SECSH Public Key File Format"
407: .%N draft-ietf-secsh-publickeyfile-01.txt
408: .%D March 2001
409: .%O work in progress material
410: .Re
1.55.2.2 brad 411: .Sh AUTHORS
412: OpenSSH is a derivative of the original and free
413: ssh 1.2.12 release by Tatu Ylonen.
414: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
415: Theo de Raadt and Dug Song
416: removed many bugs, re-added newer features and
417: created OpenSSH.
418: Markus Friedl contributed the support for SSH
419: protocol versions 1.5 and 2.0.
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