Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 1 | SSH-KEYGEN(1) General Commands Manual SSH-KEYGEN(1) |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 2 | |
| 3 | NAME |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 4 | ssh-keygen M-bM-^@M-^S authentication key generation, management and conversion |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 5 | |
| 6 | SYNOPSIS |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 7 | ssh-keygen [-q] [-b bits] [-t dsa | ecdsa | ed25519 | rsa | rsa1] |
| 8 | [-N new_passphrase] [-C comment] [-f output_keyfile] |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 9 | ssh-keygen -p [-P old_passphrase] [-N new_passphrase] [-f keyfile] |
| 10 | ssh-keygen -i [-m key_format] [-f input_keyfile] |
| 11 | ssh-keygen -e [-m key_format] [-f input_keyfile] |
| 12 | ssh-keygen -y [-f input_keyfile] |
| 13 | ssh-keygen -c [-P passphrase] [-C comment] [-f keyfile] |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 14 | ssh-keygen -l [-v] [-E fingerprint_hash] [-f input_keyfile] |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 15 | ssh-keygen -B [-f input_keyfile] |
| 16 | ssh-keygen -D pkcs11 |
| 17 | ssh-keygen -F hostname [-f known_hosts_file] [-l] |
| 18 | ssh-keygen -H [-f known_hosts_file] |
| 19 | ssh-keygen -R hostname [-f known_hosts_file] |
| 20 | ssh-keygen -r hostname [-f input_keyfile] [-g] |
| 21 | ssh-keygen -G output_file [-v] [-b bits] [-M memory] [-S start_point] |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 22 | ssh-keygen -T output_file -f input_file [-v] [-a rounds] [-J num_lines] |
| 23 | [-j start_line] [-K checkpt] [-W generator] |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 24 | ssh-keygen -s ca_key -I certificate_identity [-h] [-n principals] |
| 25 | [-O option] [-V validity_interval] [-z serial_number] file ... |
| 26 | ssh-keygen -L [-f input_keyfile] |
| 27 | ssh-keygen -A |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 28 | ssh-keygen -k -f krl_file [-u] [-s ca_public] [-z version_number] |
| 29 | file ... |
| 30 | ssh-keygen -Q -f krl_file file ... |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 31 | |
| 32 | DESCRIPTION |
| 33 | ssh-keygen generates, manages and converts authentication keys for |
| 34 | ssh(1). ssh-keygen can create RSA keys for use by SSH protocol version 1 |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 35 | and DSA, ECDSA, Ed25519 or RSA keys for use by SSH protocol version 2. |
| 36 | The type of key to be generated is specified with the -t option. If |
| 37 | invoked without any arguments, ssh-keygen will generate an RSA key for |
| 38 | use in SSH protocol 2 connections. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 39 | |
| 40 | ssh-keygen is also used to generate groups for use in Diffie-Hellman |
| 41 | group exchange (DH-GEX). See the MODULI GENERATION section for details. |
| 42 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 43 | Finally, ssh-keygen can be used to generate and update Key Revocation |
| 44 | Lists, and to test whether given keys have been revoked by one. See the |
| 45 | KEY REVOCATION LISTS section for details. |
| 46 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 47 | Normally each user wishing to use SSH with public key authentication runs |
| 48 | this once to create the authentication key in ~/.ssh/identity, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 49 | ~/.ssh/id_dsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ed25519 or ~/.ssh/id_rsa. |
| 50 | Additionally, the system administrator may use this to generate host |
| 51 | keys, as seen in /etc/rc. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 52 | |
| 53 | Normally this program generates the key and asks for a file in which to |
| 54 | store the private key. The public key is stored in a file with the same |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 55 | name but M-bM-^@M-^\.pubM-bM-^@M-^] appended. The program also asks for a passphrase. The |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 56 | passphrase may be empty to indicate no passphrase (host keys must have an |
| 57 | empty passphrase), or it may be a string of arbitrary length. A |
| 58 | passphrase is similar to a password, except it can be a phrase with a |
| 59 | series of words, punctuation, numbers, whitespace, or any string of |
| 60 | characters you want. Good passphrases are 10-30 characters long, are not |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 61 | simple sentences or otherwise easily guessable (English prose has only |
| 62 | 1-2 bits of entropy per character, and provides very bad passphrases), |
| 63 | and contain a mix of upper and lowercase letters, numbers, and non- |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 64 | alphanumeric characters. The passphrase can be changed later by using |
| 65 | the -p option. |
| 66 | |
| 67 | There is no way to recover a lost passphrase. If the passphrase is lost |
| 68 | or forgotten, a new key must be generated and the corresponding public |
| 69 | key copied to other machines. |
| 70 | |
| 71 | For RSA1 keys, there is also a comment field in the key file that is only |
| 72 | for convenience to the user to help identify the key. The comment can |
| 73 | tell what the key is for, or whatever is useful. The comment is |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 74 | initialized to M-bM-^@M-^\user@hostM-bM-^@M-^] when the key is created, but can be changed |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 75 | using the -c option. |
| 76 | |
| 77 | After a key is generated, instructions below detail where the keys should |
| 78 | be placed to be activated. |
| 79 | |
| 80 | The options are as follows: |
| 81 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 82 | -A For each of the key types (rsa1, rsa, dsa, ecdsa and ed25519) for |
| 83 | which host keys do not exist, generate the host keys with the |
| 84 | default key file path, an empty passphrase, default bits for the |
| 85 | key type, and default comment. This is used by /etc/rc to |
| 86 | generate new host keys. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 87 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 88 | -a rounds |
| 89 | When saving a new-format private key (i.e. an ed25519 key or any |
| 90 | SSH protocol 2 key when the -o flag is set), this option |
| 91 | specifies the number of KDF (key derivation function) rounds |
| 92 | used. Higher numbers result in slower passphrase verification |
| 93 | and increased resistance to brute-force password cracking (should |
| 94 | the keys be stolen). |
| 95 | |
| 96 | When screening DH-GEX candidates ( using the -T command). This |
| 97 | option specifies the number of primality tests to perform. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 98 | |
| 99 | -B Show the bubblebabble digest of specified private or public key |
| 100 | file. |
| 101 | |
| 102 | -b bits |
| 103 | Specifies the number of bits in the key to create. For RSA keys, |
| 104 | the minimum size is 768 bits and the default is 2048 bits. |
| 105 | Generally, 2048 bits is considered sufficient. DSA keys must be |
| 106 | exactly 1024 bits as specified by FIPS 186-2. For ECDSA keys, |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 107 | the -b flag determines the key length by selecting from one of |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 108 | three elliptic curve sizes: 256, 384 or 521 bits. Attempting to |
| 109 | use bit lengths other than these three values for ECDSA keys will |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 110 | fail. Ed25519 keys have a fixed length and the -b flag will be |
| 111 | ignored. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 112 | |
| 113 | -C comment |
| 114 | Provides a new comment. |
| 115 | |
| 116 | -c Requests changing the comment in the private and public key |
| 117 | files. This operation is only supported for RSA1 keys. The |
| 118 | program will prompt for the file containing the private keys, for |
| 119 | the passphrase if the key has one, and for the new comment. |
| 120 | |
| 121 | -D pkcs11 |
| 122 | Download the RSA public keys provided by the PKCS#11 shared |
| 123 | library pkcs11. When used in combination with -s, this option |
| 124 | indicates that a CA key resides in a PKCS#11 token (see the |
| 125 | CERTIFICATES section for details). |
| 126 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 127 | -E fingerprint_hash |
| 128 | Specifies the hash algorithm used when displaying key |
| 129 | fingerprints. Valid options are: M-bM-^@M-^\md5M-bM-^@M-^] and M-bM-^@M-^\sha256M-bM-^@M-^]. The |
| 130 | default is M-bM-^@M-^\sha256M-bM-^@M-^]. |
| 131 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 132 | -e This option will read a private or public OpenSSH key file and |
| 133 | print to stdout the key in one of the formats specified by the -m |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 134 | option. The default export format is M-bM-^@M-^\RFC4716M-bM-^@M-^]. This option |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 135 | allows exporting OpenSSH keys for use by other programs, |
| 136 | including several commercial SSH implementations. |
| 137 | |
| 138 | -F hostname |
| 139 | Search for the specified hostname in a known_hosts file, listing |
| 140 | any occurrences found. This option is useful to find hashed host |
| 141 | names or addresses and may also be used in conjunction with the |
| 142 | -H option to print found keys in a hashed format. |
| 143 | |
| 144 | -f filename |
| 145 | Specifies the filename of the key file. |
| 146 | |
| 147 | -G output_file |
| 148 | Generate candidate primes for DH-GEX. These primes must be |
| 149 | screened for safety (using the -T option) before use. |
| 150 | |
| 151 | -g Use generic DNS format when printing fingerprint resource records |
| 152 | using the -r command. |
| 153 | |
| 154 | -H Hash a known_hosts file. This replaces all hostnames and |
| 155 | addresses with hashed representations within the specified file; |
| 156 | the original content is moved to a file with a .old suffix. |
| 157 | These hashes may be used normally by ssh and sshd, but they do |
| 158 | not reveal identifying information should the file's contents be |
| 159 | disclosed. This option will not modify existing hashed hostnames |
| 160 | and is therefore safe to use on files that mix hashed and non- |
| 161 | hashed names. |
| 162 | |
| 163 | -h When signing a key, create a host certificate instead of a user |
| 164 | certificate. Please see the CERTIFICATES section for details. |
| 165 | |
| 166 | -I certificate_identity |
| 167 | Specify the key identity when signing a public key. Please see |
| 168 | the CERTIFICATES section for details. |
| 169 | |
| 170 | -i This option will read an unencrypted private (or public) key file |
| 171 | in the format specified by the -m option and print an OpenSSH |
| 172 | compatible private (or public) key to stdout. This option allows |
| 173 | importing keys from other software, including several commercial |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 174 | SSH implementations. The default import format is M-bM-^@M-^\RFC4716M-bM-^@M-^]. |
| 175 | |
| 176 | -J num_lines |
| 177 | Exit after screening the specified number of lines while |
| 178 | performing DH candidate screening using the -T option. |
| 179 | |
| 180 | -j start_line |
| 181 | Start screening at the specified line number while performing DH |
| 182 | candidate screening using the -T option. |
| 183 | |
| 184 | -K checkpt |
| 185 | Write the last line processed to the file checkpt while |
| 186 | performing DH candidate screening using the -T option. This will |
| 187 | be used to skip lines in the input file that have already been |
| 188 | processed if the job is restarted. |
| 189 | |
| 190 | -k Generate a KRL file. In this mode, ssh-keygen will generate a |
| 191 | KRL file at the location specified via the -f flag that revokes |
| 192 | every key or certificate presented on the command line. |
| 193 | Keys/certificates to be revoked may be specified by public key |
| 194 | file or using the format described in the KEY REVOCATION LISTS |
| 195 | section. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 196 | |
| 197 | -L Prints the contents of a certificate. |
| 198 | |
| 199 | -l Show fingerprint of specified public key file. Private RSA1 keys |
| 200 | are also supported. For RSA and DSA keys ssh-keygen tries to |
| 201 | find the matching public key file and prints its fingerprint. If |
| 202 | combined with -v, an ASCII art representation of the key is |
| 203 | supplied with the fingerprint. |
| 204 | |
| 205 | -M memory |
| 206 | Specify the amount of memory to use (in megabytes) when |
| 207 | generating candidate moduli for DH-GEX. |
| 208 | |
| 209 | -m key_format |
| 210 | Specify a key format for the -i (import) or -e (export) |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 211 | conversion options. The supported key formats are: M-bM-^@M-^\RFC4716M-bM-^@M-^] |
| 212 | (RFC 4716/SSH2 public or private key), M-bM-^@M-^\PKCS8M-bM-^@M-^] (PEM PKCS8 public |
| 213 | key) or M-bM-^@M-^\PEMM-bM-^@M-^] (PEM public key). The default conversion format is |
| 214 | M-bM-^@M-^\RFC4716M-bM-^@M-^]. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 215 | |
| 216 | -N new_passphrase |
| 217 | Provides the new passphrase. |
| 218 | |
| 219 | -n principals |
| 220 | Specify one or more principals (user or host names) to be |
| 221 | included in a certificate when signing a key. Multiple |
| 222 | principals may be specified, separated by commas. Please see the |
| 223 | CERTIFICATES section for details. |
| 224 | |
| 225 | -O option |
| 226 | Specify a certificate option when signing a key. This option may |
| 227 | be specified multiple times. Please see the CERTIFICATES section |
| 228 | for details. The options that are valid for user certificates |
| 229 | are: |
| 230 | |
| 231 | clear Clear all enabled permissions. This is useful for |
| 232 | clearing the default set of permissions so permissions |
| 233 | may be added individually. |
| 234 | |
| 235 | force-command=command |
| 236 | Forces the execution of command instead of any shell or |
| 237 | command specified by the user when the certificate is |
| 238 | used for authentication. |
| 239 | |
| 240 | no-agent-forwarding |
| 241 | Disable ssh-agent(1) forwarding (permitted by default). |
| 242 | |
| 243 | no-port-forwarding |
| 244 | Disable port forwarding (permitted by default). |
| 245 | |
| 246 | no-pty Disable PTY allocation (permitted by default). |
| 247 | |
| 248 | no-user-rc |
| 249 | Disable execution of ~/.ssh/rc by sshd(8) (permitted by |
| 250 | default). |
| 251 | |
| 252 | no-x11-forwarding |
| 253 | Disable X11 forwarding (permitted by default). |
| 254 | |
| 255 | permit-agent-forwarding |
| 256 | Allows ssh-agent(1) forwarding. |
| 257 | |
| 258 | permit-port-forwarding |
| 259 | Allows port forwarding. |
| 260 | |
| 261 | permit-pty |
| 262 | Allows PTY allocation. |
| 263 | |
| 264 | permit-user-rc |
| 265 | Allows execution of ~/.ssh/rc by sshd(8). |
| 266 | |
| 267 | permit-x11-forwarding |
| 268 | Allows X11 forwarding. |
| 269 | |
| 270 | source-address=address_list |
| 271 | Restrict the source addresses from which the certificate |
| 272 | is considered valid. The address_list is a comma- |
| 273 | separated list of one or more address/netmask pairs in |
| 274 | CIDR format. |
| 275 | |
| 276 | At present, no options are valid for host keys. |
| 277 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 278 | -o Causes ssh-keygen to save SSH protocol 2 private keys using the |
| 279 | new OpenSSH format rather than the more compatible PEM format. |
| 280 | The new format has increased resistance to brute-force password |
| 281 | cracking but is not supported by versions of OpenSSH prior to |
| 282 | 6.5. Ed25519 keys always use the new private key format. |
| 283 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 284 | -P passphrase |
| 285 | Provides the (old) passphrase. |
| 286 | |
| 287 | -p Requests changing the passphrase of a private key file instead of |
| 288 | creating a new private key. The program will prompt for the file |
| 289 | containing the private key, for the old passphrase, and twice for |
| 290 | the new passphrase. |
| 291 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 292 | -Q Test whether keys have been revoked in a KRL. |
| 293 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 294 | -q Silence ssh-keygen. |
| 295 | |
| 296 | -R hostname |
| 297 | Removes all keys belonging to hostname from a known_hosts file. |
| 298 | This option is useful to delete hashed hosts (see the -H option |
| 299 | above). |
| 300 | |
| 301 | -r hostname |
| 302 | Print the SSHFP fingerprint resource record named hostname for |
| 303 | the specified public key file. |
| 304 | |
| 305 | -S start |
| 306 | Specify start point (in hex) when generating candidate moduli for |
| 307 | DH-GEX. |
| 308 | |
| 309 | -s ca_key |
| 310 | Certify (sign) a public key using the specified CA key. Please |
| 311 | see the CERTIFICATES section for details. |
| 312 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 313 | When generating a KRL, -s specifies a path to a CA public key |
| 314 | file used to revoke certificates directly by key ID or serial |
| 315 | number. See the KEY REVOCATION LISTS section for details. |
| 316 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 317 | -T output_file |
| 318 | Test DH group exchange candidate primes (generated using the -G |
| 319 | option) for safety. |
| 320 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 321 | -t dsa | ecdsa | ed25519 | rsa | rsa1 |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 322 | Specifies the type of key to create. The possible values are |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 323 | M-bM-^@M-^\rsa1M-bM-^@M-^] for protocol version 1 and M-bM-^@M-^\dsaM-bM-^@M-^], M-bM-^@M-^\ecdsaM-bM-^@M-^], M-bM-^@M-^\ed25519M-bM-^@M-^], or |
| 324 | M-bM-^@M-^\rsaM-bM-^@M-^] for protocol version 2. |
| 325 | |
| 326 | -u Update a KRL. When specified with -k, keys listed via the |
| 327 | command line are added to the existing KRL rather than a new KRL |
| 328 | being created. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 329 | |
| 330 | -V validity_interval |
| 331 | Specify a validity interval when signing a certificate. A |
| 332 | validity interval may consist of a single time, indicating that |
| 333 | the certificate is valid beginning now and expiring at that time, |
| 334 | or may consist of two times separated by a colon to indicate an |
| 335 | explicit time interval. The start time may be specified as a |
| 336 | date in YYYYMMDD format, a time in YYYYMMDDHHMMSS format or a |
| 337 | relative time (to the current time) consisting of a minus sign |
| 338 | followed by a relative time in the format described in the TIME |
| 339 | FORMATS section of sshd_config(5). The end time may be specified |
| 340 | as a YYYYMMDD date, a YYYYMMDDHHMMSS time or a relative time |
| 341 | starting with a plus character. |
| 342 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 343 | For example: M-bM-^@M-^\+52w1dM-bM-^@M-^] (valid from now to 52 weeks and one day |
| 344 | from now), M-bM-^@M-^\-4w:+4wM-bM-^@M-^] (valid from four weeks ago to four weeks |
| 345 | from now), M-bM-^@M-^\20100101123000:20110101123000M-bM-^@M-^] (valid from 12:30 PM, |
| 346 | January 1st, 2010 to 12:30 PM, January 1st, 2011), M-bM-^@M-^\-1d:20110101M-bM-^@M-^] |
| 347 | (valid from yesterday to midnight, January 1st, 2011). |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 348 | |
| 349 | -v Verbose mode. Causes ssh-keygen to print debugging messages |
| 350 | about its progress. This is helpful for debugging moduli |
| 351 | generation. Multiple -v options increase the verbosity. The |
| 352 | maximum is 3. |
| 353 | |
| 354 | -W generator |
| 355 | Specify desired generator when testing candidate moduli for DH- |
| 356 | GEX. |
| 357 | |
| 358 | -y This option will read a private OpenSSH format file and print an |
| 359 | OpenSSH public key to stdout. |
| 360 | |
| 361 | -z serial_number |
| 362 | Specifies a serial number to be embedded in the certificate to |
| 363 | distinguish this certificate from others from the same CA. The |
| 364 | default serial number is zero. |
| 365 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 366 | When generating a KRL, the -z flag is used to specify a KRL |
| 367 | version number. |
| 368 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 369 | MODULI GENERATION |
| 370 | ssh-keygen may be used to generate groups for the Diffie-Hellman Group |
| 371 | Exchange (DH-GEX) protocol. Generating these groups is a two-step |
| 372 | process: first, candidate primes are generated using a fast, but memory |
| 373 | intensive process. These candidate primes are then tested for |
| 374 | suitability (a CPU-intensive process). |
| 375 | |
| 376 | Generation of primes is performed using the -G option. The desired |
| 377 | length of the primes may be specified by the -b option. For example: |
| 378 | |
| 379 | # ssh-keygen -G moduli-2048.candidates -b 2048 |
| 380 | |
| 381 | By default, the search for primes begins at a random point in the desired |
| 382 | length range. This may be overridden using the -S option, which |
| 383 | specifies a different start point (in hex). |
| 384 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 385 | Once a set of candidates have been generated, they must be screened for |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 386 | suitability. This may be performed using the -T option. In this mode |
| 387 | ssh-keygen will read candidates from standard input (or a file specified |
| 388 | using the -f option). For example: |
| 389 | |
| 390 | # ssh-keygen -T moduli-2048 -f moduli-2048.candidates |
| 391 | |
| 392 | By default, each candidate will be subjected to 100 primality tests. |
| 393 | This may be overridden using the -a option. The DH generator value will |
| 394 | be chosen automatically for the prime under consideration. If a specific |
| 395 | generator is desired, it may be requested using the -W option. Valid |
| 396 | generator values are 2, 3, and 5. |
| 397 | |
| 398 | Screened DH groups may be installed in /etc/moduli. It is important that |
| 399 | this file contains moduli of a range of bit lengths and that both ends of |
| 400 | a connection share common moduli. |
| 401 | |
| 402 | CERTIFICATES |
| 403 | ssh-keygen supports signing of keys to produce certificates that may be |
| 404 | used for user or host authentication. Certificates consist of a public |
| 405 | key, some identity information, zero or more principal (user or host) |
| 406 | names and a set of options that are signed by a Certification Authority |
| 407 | (CA) key. Clients or servers may then trust only the CA key and verify |
| 408 | its signature on a certificate rather than trusting many user/host keys. |
| 409 | Note that OpenSSH certificates are a different, and much simpler, format |
| 410 | to the X.509 certificates used in ssl(8). |
| 411 | |
| 412 | ssh-keygen supports two types of certificates: user and host. User |
| 413 | certificates authenticate users to servers, whereas host certificates |
| 414 | authenticate server hosts to users. To generate a user certificate: |
| 415 | |
| 416 | $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub |
| 417 | |
| 418 | The resultant certificate will be placed in /path/to/user_key-cert.pub. |
| 419 | A host certificate requires the -h option: |
| 420 | |
| 421 | $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub |
| 422 | |
| 423 | The host certificate will be output to /path/to/host_key-cert.pub. |
| 424 | |
| 425 | It is possible to sign using a CA key stored in a PKCS#11 token by |
| 426 | providing the token library using -D and identifying the CA key by |
| 427 | providing its public half as an argument to -s: |
| 428 | |
| 429 | $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id host_key.pub |
| 430 | |
| 431 | In all cases, key_id is a "key identifier" that is logged by the server |
| 432 | when the certificate is used for authentication. |
| 433 | |
| 434 | Certificates may be limited to be valid for a set of principal |
| 435 | (user/host) names. By default, generated certificates are valid for all |
| 436 | users or hosts. To generate a certificate for a specified set of |
| 437 | principals: |
| 438 | |
| 439 | $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub |
| 440 | $ ssh-keygen -s ca_key -I key_id -h -n host.domain user_key.pub |
| 441 | |
| 442 | Additional limitations on the validity and use of user certificates may |
| 443 | be specified through certificate options. A certificate option may |
| 444 | disable features of the SSH session, may be valid only when presented |
| 445 | from particular source addresses or may force the use of a specific |
| 446 | command. For a list of valid certificate options, see the documentation |
| 447 | for the -O option above. |
| 448 | |
| 449 | Finally, certificates may be defined with a validity lifetime. The -V |
| 450 | option allows specification of certificate start and end times. A |
| 451 | certificate that is presented at a time outside this range will not be |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 452 | considered valid. By default, certificates are valid from UNIX Epoch to |
| 453 | the distant future. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 454 | |
| 455 | For certificates to be used for user or host authentication, the CA |
| 456 | public key must be trusted by sshd(8) or ssh(1). Please refer to those |
| 457 | manual pages for details. |
| 458 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 459 | KEY REVOCATION LISTS |
| 460 | ssh-keygen is able to manage OpenSSH format Key Revocation Lists (KRLs). |
| 461 | These binary files specify keys or certificates to be revoked using a |
| 462 | compact format, taking as little as one bit per certificate if they are |
| 463 | being revoked by serial number. |
| 464 | |
| 465 | KRLs may be generated using the -k flag. This option reads one or more |
| 466 | files from the command line and generates a new KRL. The files may |
| 467 | either contain a KRL specification (see below) or public keys, listed one |
| 468 | per line. Plain public keys are revoked by listing their hash or |
| 469 | contents in the KRL and certificates revoked by serial number or key ID |
| 470 | (if the serial is zero or not available). |
| 471 | |
| 472 | Revoking keys using a KRL specification offers explicit control over the |
| 473 | types of record used to revoke keys and may be used to directly revoke |
| 474 | certificates by serial number or key ID without having the complete |
| 475 | original certificate on hand. A KRL specification consists of lines |
| 476 | containing one of the following directives followed by a colon and some |
| 477 | directive-specific information. |
| 478 | |
| 479 | serial: serial_number[-serial_number] |
| 480 | Revokes a certificate with the specified serial number. Serial |
| 481 | numbers are 64-bit values, not including zero and may be |
| 482 | expressed in decimal, hex or octal. If two serial numbers are |
| 483 | specified separated by a hyphen, then the range of serial numbers |
| 484 | including and between each is revoked. The CA key must have been |
| 485 | specified on the ssh-keygen command line using the -s option. |
| 486 | |
| 487 | id: key_id |
| 488 | Revokes a certificate with the specified key ID string. The CA |
| 489 | key must have been specified on the ssh-keygen command line using |
| 490 | the -s option. |
| 491 | |
| 492 | key: public_key |
| 493 | Revokes the specified key. If a certificate is listed, then it |
| 494 | is revoked as a plain public key. |
| 495 | |
| 496 | sha1: public_key |
| 497 | Revokes the specified key by its SHA1 hash. |
| 498 | |
| 499 | KRLs may be updated using the -u flag in addition to -k. When this |
| 500 | option is specified, keys listed via the command line are merged into the |
| 501 | KRL, adding to those already there. |
| 502 | |
| 503 | It is also possible, given a KRL, to test whether it revokes a particular |
| 504 | key (or keys). The -Q flag will query an existing KRL, testing each key |
| 505 | specified on the commandline. If any key listed on the command line has |
| 506 | been revoked (or an error encountered) then ssh-keygen will exit with a |
| 507 | non-zero exit status. A zero exit status will only be returned if no key |
| 508 | was revoked. |
| 509 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 510 | FILES |
| 511 | ~/.ssh/identity |
| 512 | Contains the protocol version 1 RSA authentication identity of |
| 513 | the user. This file should not be readable by anyone but the |
| 514 | user. It is possible to specify a passphrase when generating the |
| 515 | key; that passphrase will be used to encrypt the private part of |
| 516 | this file using 3DES. This file is not automatically accessed by |
| 517 | ssh-keygen but it is offered as the default file for the private |
| 518 | key. ssh(1) will read this file when a login attempt is made. |
| 519 | |
| 520 | ~/.ssh/identity.pub |
| 521 | Contains the protocol version 1 RSA public key for |
| 522 | authentication. The contents of this file should be added to |
| 523 | ~/.ssh/authorized_keys on all machines where the user wishes to |
| 524 | log in using RSA authentication. There is no need to keep the |
| 525 | contents of this file secret. |
| 526 | |
| 527 | ~/.ssh/id_dsa |
| 528 | ~/.ssh/id_ecdsa |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 529 | ~/.ssh/id_ed25519 |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 530 | ~/.ssh/id_rsa |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 531 | Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA |
| 532 | authentication identity of the user. This file should not be |
| 533 | readable by anyone but the user. It is possible to specify a |
| 534 | passphrase when generating the key; that passphrase will be used |
| 535 | to encrypt the private part of this file using 128-bit AES. This |
| 536 | file is not automatically accessed by ssh-keygen but it is |
| 537 | offered as the default file for the private key. ssh(1) will |
| 538 | read this file when a login attempt is made. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 539 | |
| 540 | ~/.ssh/id_dsa.pub |
| 541 | ~/.ssh/id_ecdsa.pub |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 542 | ~/.ssh/id_ed25519.pub |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 543 | ~/.ssh/id_rsa.pub |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 544 | Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA public |
| 545 | key for authentication. The contents of this file should be |
| 546 | added to ~/.ssh/authorized_keys on all machines where the user |
| 547 | wishes to log in using public key authentication. There is no |
| 548 | need to keep the contents of this file secret. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 549 | |
| 550 | /etc/moduli |
| 551 | Contains Diffie-Hellman groups used for DH-GEX. The file format |
| 552 | is described in moduli(5). |
| 553 | |
| 554 | SEE ALSO |
| 555 | ssh(1), ssh-add(1), ssh-agent(1), moduli(5), sshd(8) |
| 556 | |
| 557 | The Secure Shell (SSH) Public Key File Format, RFC 4716, 2006. |
| 558 | |
| 559 | AUTHORS |
| 560 | OpenSSH is a derivative of the original and free ssh 1.2.12 release by |
| 561 | Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo |
| 562 | de Raadt and Dug Song removed many bugs, re-added newer features and |
| 563 | created OpenSSH. Markus Friedl contributed the support for SSH protocol |
| 564 | versions 1.5 and 2.0. |
| 565 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 566 | OpenBSD 5.7 February 24, 2015 OpenBSD 5.7 |