Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.71
1.71 ! jmc 1: .\" $OpenBSD: ssh-keygen.1,v 1.70 2005/10/31 11:12:49 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
1.56 jmc 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
1.56 jmc 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
1.64 djm 84: .Fl F Ar hostname
85: .Op Fl f Ar known_hosts_file
86: .Nm ssh-keygen
87: .Fl H
88: .Op Fl f Ar known_hosts_file
89: .Nm ssh-keygen
90: .Fl R Ar hostname
91: .Op Fl f Ar known_hosts_file
92: .Nm ssh-keygen
1.48 jakob 93: .Fl U Ar reader
94: .Op Fl f Ar input_keyfile
1.57 jakob 95: .Nm ssh-keygen
96: .Fl r Ar hostname
97: .Op Fl f Ar input_keyfile
98: .Op Fl g
1.60 djm 99: .Nm ssh-keygen
100: .Fl G Ar output_file
1.61 djm 101: .Op Fl v
1.60 djm 102: .Op Fl b Ar bits
103: .Op Fl M Ar memory
104: .Op Fl S Ar start_point
105: .Nm ssh-keygen
106: .Fl T Ar output_file
107: .Fl f Ar input_file
1.61 djm 108: .Op Fl v
1.60 djm 109: .Op Fl a Ar num_trials
110: .Op Fl W Ar generator
1.13 aaron 111: .Sh DESCRIPTION
1.2 deraadt 112: .Nm
1.37 markus 113: generates, manages and converts authentication keys for
1.2 deraadt 114: .Xr ssh 1 .
1.15 deraadt 115: .Nm
1.54 deraadt 116: can create RSA keys for use by SSH protocol version 1 and RSA or DSA
1.58 jmc 117: keys for use by SSH protocol version 2.
118: The type of key to be generated is specified with the
1.25 markus 119: .Fl t
1.52 djm 120: option.
1.70 djm 121: If invoked without any arguments,
122: .Nm
1.71 ! jmc 123: will generate an RSA key for use in SSH protocol 2 connections.
1.15 deraadt 124: .Pp
1.60 djm 125: .Nm
126: is also used to generate groups for use in Diffie-Hellman group
127: exchange (DH-GEX).
128: See the
129: .Sx MODULI GENERATION
130: section for details.
131: .Pp
1.2 deraadt 132: Normally each user wishing to use SSH
1.15 deraadt 133: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 134: key in
1.68 djm 135: .Pa ~/.ssh/identity ,
136: .Pa ~/.ssh/id_dsa
1.15 deraadt 137: or
1.68 djm 138: .Pa ~/.ssh/id_rsa .
1.15 deraadt 139: Additionally, the system administrator may use this to generate host keys,
140: as seen in
141: .Pa /etc/rc .
1.2 deraadt 142: .Pp
1.1 deraadt 143: Normally this program generates the key and asks for a file in which
1.12 aaron 144: to store the private key.
145: The public key is stored in a file with the same name but
1.2 deraadt 146: .Dq .pub
1.12 aaron 147: appended.
148: The program also asks for a passphrase.
149: The passphrase may be empty to indicate no passphrase
1.26 markus 150: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 151: arbitrary length.
1.51 stevesk 152: A passphrase is similar to a password, except it can be a phrase with a
153: series of words, punctuation, numbers, whitespace, or any string of
154: characters you want.
155: Good passphrases are 10-30 characters long, are
1.1 deraadt 156: not simple sentences or otherwise easily guessable (English
1.42 markus 157: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 158: passphrases), and contain a mix of upper and lowercase letters,
159: numbers, and non-alphanumeric characters.
1.12 aaron 160: The passphrase can be changed later by using the
1.2 deraadt 161: .Fl p
1.1 deraadt 162: option.
1.2 deraadt 163: .Pp
1.12 aaron 164: There is no way to recover a lost passphrase.
165: If the passphrase is
1.49 deraadt 166: lost or forgotten, a new key must be generated and copied to the
1.1 deraadt 167: corresponding public key to other machines.
1.2 deraadt 168: .Pp
1.37 markus 169: For RSA1 keys,
170: there is also a comment field in the key file that is only for
1.12 aaron 171: convenience to the user to help identify the key.
172: The comment can tell what the key is for, or whatever is useful.
173: The comment is initialized to
1.2 deraadt 174: .Dq user@host
175: when the key is created, but can be changed using the
176: .Fl c
1.1 deraadt 177: option.
1.2 deraadt 178: .Pp
1.15 deraadt 179: After a key is generated, instructions below detail where the keys
180: should be placed to be activated.
181: .Pp
1.2 deraadt 182: The options are as follows:
183: .Bl -tag -width Ds
1.60 djm 184: .It Fl a Ar trials
185: Specifies the number of primality tests to perform when screening DH-GEX
186: candidates using the
187: .Fl T
188: command.
1.66 jmc 189: .It Fl B
190: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 191: .It Fl b Ar bits
1.12 aaron 192: Specifies the number of bits in the key to create.
193: Minimum is 512 bits.
1.69 djm 194: Generally, 2048 bits is considered sufficient.
195: The default is 2048 bits.
1.66 jmc 196: .It Fl C Ar comment
197: Provides a new comment.
1.2 deraadt 198: .It Fl c
1.1 deraadt 199: Requests changing the comment in the private and public key files.
1.50 markus 200: This operation is only supported for RSA1 keys.
1.1 deraadt 201: The program will prompt for the file containing the private keys, for
1.41 stevesk 202: the passphrase if the key has one, and for the new comment.
1.66 jmc 203: .It Fl D Ar reader
204: Download the RSA public key stored in the smartcard in
205: .Ar reader .
1.37 markus 206: .It Fl e
1.40 markus 207: This option will read a private or public OpenSSH key file and
208: print the key in a
1.37 markus 209: .Sq SECSH Public Key File Format
210: to stdout.
211: This option allows exporting keys for use by several commercial
212: SSH implementations.
1.66 jmc 213: .It Fl F Ar hostname
214: Search for the specified
215: .Ar hostname
216: in a
217: .Pa known_hosts
218: file, listing any occurrences found.
219: This option is useful to find hashed host names or addresses and may also be
220: used in conjunction with the
221: .Fl H
222: option to print found keys in a hashed format.
223: .It Fl f Ar filename
224: Specifies the filename of the key file.
225: .It Fl G Ar output_file
226: Generate candidate primes for DH-GEX.
227: These primes must be screened for
228: safety (using the
229: .Fl T
230: option) before use.
1.57 jakob 231: .It Fl g
1.62 jakob 232: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 233: .Fl r
1.62 jakob 234: command.
1.66 jmc 235: .It Fl H
236: Hash a
237: .Pa known_hosts
1.67 dtucker 238: file.
239: This replaces all hostnames and addresses with hashed representations
240: within the specified file; the original content is moved to a file with
241: a .old suffix.
1.66 jmc 242: These hashes may be used normally by
243: .Nm ssh
244: and
245: .Nm sshd ,
246: but they do not reveal identifying information should the file's contents
247: be disclosed.
248: This option will not modify existing hashed hostnames and is therefore safe
249: to use on files that mix hashed and non-hashed names.
1.37 markus 250: .It Fl i
251: This option will read an unencrypted private (or public) key file
252: in SSH2-compatible format and print an OpenSSH compatible private
253: (or public) key to stdout.
254: .Nm
1.38 markus 255: also reads the
1.37 markus 256: .Sq SECSH Public Key File Format .
257: This option allows importing keys from several commercial
258: SSH implementations.
1.9 markus 259: .It Fl l
1.50 markus 260: Show fingerprint of specified public key file.
261: Private RSA1 keys are also supported.
262: For RSA and DSA keys
263: .Nm
264: tries to find the matching public key file and prints its fingerprint.
1.66 jmc 265: .It Fl M Ar memory
266: Specify the amount of memory to use (in megabytes) when generating
267: candidate moduli for DH-GEX.
268: .It Fl N Ar new_passphrase
269: Provides the new passphrase.
270: .It Fl P Ar passphrase
271: Provides the (old) passphrase.
1.2 deraadt 272: .It Fl p
1.1 deraadt 273: Requests changing the passphrase of a private key file instead of
1.12 aaron 274: creating a new private key.
275: The program will prompt for the file
1.1 deraadt 276: containing the private key, for the old passphrase, and twice for the
277: new passphrase.
1.5 aaron 278: .It Fl q
279: Silence
280: .Nm ssh-keygen .
281: Used by
282: .Pa /etc/rc
283: when creating a new key.
1.64 djm 284: .It Fl R Ar hostname
285: Removes all keys belonging to
286: .Ar hostname
1.65 jmc 287: from a
1.64 djm 288: .Pa known_hosts
289: file.
1.65 jmc 290: This option is useful to delete hashed hosts (see the
1.64 djm 291: .Fl H
292: option above).
1.66 jmc 293: .It Fl r Ar hostname
294: Print the SSHFP fingerprint resource record named
295: .Ar hostname
296: for the specified public key file.
1.60 djm 297: .It Fl S Ar start
298: Specify start point (in hex) when generating candidate moduli for DH-GEX.
299: .It Fl T Ar output_file
300: Test DH group exchange candidate primes (generated using the
301: .Fl G
302: option) for safety.
1.66 jmc 303: .It Fl t Ar type
304: Specifies the type of key to create.
305: The possible values are
306: .Dq rsa1
307: for protocol version 1 and
308: .Dq rsa
309: or
310: .Dq dsa
311: for protocol version 2.
1.48 jakob 312: .It Fl U Ar reader
313: Upload an existing RSA private key into the smartcard in
314: .Ar reader .
1.61 djm 315: .It Fl v
316: Verbose mode.
317: Causes
318: .Nm
319: to print debugging messages about its progress.
320: This is helpful for debugging moduli generation.
321: Multiple
322: .Fl v
323: options increase the verbosity.
324: The maximum is 3.
1.66 jmc 325: .It Fl W Ar generator
326: Specify desired generator when testing candidate moduli for DH-GEX.
327: .It Fl y
328: This option will read a private
329: OpenSSH format file and print an OpenSSH public key to stdout.
1.2 deraadt 330: .El
1.60 djm 331: .Sh MODULI GENERATION
332: .Nm
333: may be used to generate groups for the Diffie-Hellman Group Exchange
334: (DH-GEX) protocol.
335: Generating these groups is a two-step process: first, candidate
336: primes are generated using a fast, but memory intensive process.
337: These candidate primes are then tested for suitability (a CPU-intensive
338: process).
339: .Pp
340: Generation of primes is performed using the
341: .Fl G
342: option.
343: The desired length of the primes may be specified by the
344: .Fl b
345: option.
346: For example:
347: .Pp
1.66 jmc 348: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 349: .Pp
350: By default, the search for primes begins at a random point in the
351: desired length range.
352: This may be overridden using the
353: .Fl S
354: option, which specifies a different start point (in hex).
355: .Pp
356: Once a set of candidates have been generated, they must be tested for
357: suitability.
358: This may be performed using the
359: .Fl T
360: option.
361: In this mode
362: .Nm
363: will read candidates from standard input (or a file specified using the
364: .Fl f
365: option).
366: For example:
367: .Pp
1.66 jmc 368: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 369: .Pp
370: By default, each candidate will be subjected to 100 primality tests.
371: This may be overridden using the
372: .Fl a
373: option.
374: The DH generator value will be chosen automatically for the
375: prime under consideration.
376: If a specific generator is desired, it may be requested using the
377: .Fl W
378: option.
1.66 jmc 379: Valid generator values are 2, 3, and 5.
1.60 djm 380: .Pp
381: Screened DH groups may be installed in
382: .Pa /etc/moduli .
383: It is important that this file contains moduli of a range of bit lengths and
384: that both ends of a connection share common moduli.
1.2 deraadt 385: .Sh FILES
386: .Bl -tag -width Ds
1.68 djm 387: .It Pa ~/.ssh/identity
1.36 itojun 388: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 389: This file should not be readable by anyone but the user.
390: It is possible to
1.1 deraadt 391: specify a passphrase when generating the key; that passphrase will be
1.12 aaron 392: used to encrypt the private part of this file using 3DES.
393: This file is not automatically accessed by
1.2 deraadt 394: .Nm
1.1 deraadt 395: but it is offered as the default file for the private key.
1.46 markus 396: .Xr ssh 1
1.15 deraadt 397: will read this file when a login attempt is made.
1.68 djm 398: .It Pa ~/.ssh/identity.pub
1.36 itojun 399: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 400: The contents of this file should be added to
1.68 djm 401: .Pa ~/.ssh/authorized_keys
1.2 deraadt 402: on all machines
1.49 deraadt 403: where the user wishes to log in using RSA authentication.
1.15 deraadt 404: There is no need to keep the contents of this file secret.
1.68 djm 405: .It Pa ~/.ssh/id_dsa
1.36 itojun 406: Contains the protocol version 2 DSA authentication identity of the user.
1.15 deraadt 407: This file should not be readable by anyone but the user.
408: It is possible to
409: specify a passphrase when generating the key; that passphrase will be
410: used to encrypt the private part of this file using 3DES.
411: This file is not automatically accessed by
412: .Nm
413: but it is offered as the default file for the private key.
1.46 markus 414: .Xr ssh 1
1.15 deraadt 415: will read this file when a login attempt is made.
1.68 djm 416: .It Pa ~/.ssh/id_dsa.pub
1.36 itojun 417: Contains the protocol version 2 DSA public key for authentication.
418: The contents of this file should be added to
1.68 djm 419: .Pa ~/.ssh/authorized_keys
1.36 itojun 420: on all machines
1.49 deraadt 421: where the user wishes to log in using public key authentication.
1.36 itojun 422: There is no need to keep the contents of this file secret.
1.68 djm 423: .It Pa ~/.ssh/id_rsa
1.36 itojun 424: Contains the protocol version 2 RSA authentication identity of the user.
425: This file should not be readable by anyone but the user.
426: It is possible to
427: specify a passphrase when generating the key; that passphrase will be
428: used to encrypt the private part of this file using 3DES.
429: This file is not automatically accessed by
430: .Nm
431: but it is offered as the default file for the private key.
1.46 markus 432: .Xr ssh 1
1.36 itojun 433: will read this file when a login attempt is made.
1.68 djm 434: .It Pa ~/.ssh/id_rsa.pub
1.36 itojun 435: Contains the protocol version 2 RSA public key for authentication.
1.15 deraadt 436: The contents of this file should be added to
1.68 djm 437: .Pa ~/.ssh/authorized_keys
1.15 deraadt 438: on all machines
1.49 deraadt 439: where the user wishes to log in using public key authentication.
1.12 aaron 440: There is no need to keep the contents of this file secret.
1.60 djm 441: .It Pa /etc/moduli
442: Contains Diffie-Hellman groups used for DH-GEX.
443: The file format is described in
444: .Xr moduli 5 .
1.19 aaron 445: .El
1.2 deraadt 446: .Sh SEE ALSO
447: .Xr ssh 1 ,
448: .Xr ssh-add 1 ,
1.8 ericj 449: .Xr ssh-agent 1 ,
1.60 djm 450: .Xr moduli 5 ,
1.30 itojun 451: .Xr sshd 8
1.37 markus 452: .Rs
1.45 deraadt 453: .%A J. Galbraith
454: .%A R. Thayer
1.37 markus 455: .%T "SECSH Public Key File Format"
456: .%N draft-ietf-secsh-publickeyfile-01.txt
457: .%D March 2001
458: .%O work in progress material
459: .Re
1.59 jmc 460: .Sh AUTHORS
461: OpenSSH is a derivative of the original and free
462: ssh 1.2.12 release by Tatu Ylonen.
463: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
464: Theo de Raadt and Dug Song
465: removed many bugs, re-added newer features and
466: created OpenSSH.
467: Markus Friedl contributed the support for SSH
468: protocol versions 1.5 and 2.0.
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