1 .\" $OpenBSD: ssh-add.1,v 1.84 2022/02/04 02:49:17 dtucker Exp $
3 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 .\" All rights reserved
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".
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.
18 .\" Redistribution and use in source and binary forms, with or without
19 .\" modification, are permitted provided that the following conditions
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.
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,
33 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.
38 .Dd $Mdocdate: February 4 2022 $
43 .Nd adds private key identities to the OpenSSH authentication agent
47 .Op Fl E Ar fingerprint_hash
48 .Op Fl H Ar hostkey_file
49 .Op Fl h Ar destination_constraint
62 adds private key identities to the authentication agent,
64 When run without arguments, it adds the files
67 .Pa ~/.ssh/id_ecdsa_sk ,
68 .Pa ~/.ssh/id_ed25519 ,
69 .Pa ~/.ssh/id_ed25519_sk ,
72 After loading a private key,
74 will try to load corresponding certificate information from the
75 filename obtained by appending
77 to the name of the private key file.
78 Alternative file names can be given on the command line.
80 If any file requires a passphrase,
82 asks for the passphrase from the user.
83 The passphrase is read from the user's tty.
85 retries the last passphrase if multiple identity files are given.
87 The authentication agent must be running and the
89 environment variable must contain the name of its socket for
93 The options are as follows:
96 Indicates that added identities should be subject to confirmation before
97 being used for authentication.
98 Confirmation is performed by
100 Successful confirmation is signaled by a zero exit status from
102 rather than text entered into the requester.
104 Deletes all identities from the agent.
106 Instead of adding identities, removes identities from the agent.
109 has been run without arguments, the keys for the default identities and
110 their corresponding certificates will be removed.
111 Otherwise, the argument list will be interpreted as a list of paths to
112 public key files to specify keys and certificates to be removed from the agent.
113 If no public key is found at a given path,
118 If the argument list consists of
122 will read public keys to be removed from standard input.
123 .It Fl E Ar fingerprint_hash
124 Specifies the hash algorithm used when displaying key fingerprints.
132 Remove keys provided by the PKCS#11 shared library
134 .It Fl H Ar hostkey_file
135 Specifies a known hosts file to look up hostkeys when using
136 destination-constrained keys via the
139 This option may be specified multiple times to allow multiple files to be
141 If no files are specified,
146 .Pa ~/.ssh/known_hosts ,
147 .Pa ~/.ssh/known_hosts2 ,
148 .Pa /etc/ssh/ssh_known_hosts ,
150 .Pa /etc/ssh/ssh_known_hosts2 .
151 .It Fl h Ar destination_constraint
152 When adding keys, constrain them to be usable only through specific hosts or to
153 specific destinations.
155 Destination constraints of the form
156 .Sq [user@]dest-hostname
157 permit use of the key only from the origin host (the one running
159 to the listed destination host, with optional user name.
161 Constraints of the form
162 .Sq src-hostname>[user@]dst-hostname
163 allow a key available on a forwarded
165 to be used through a particular host (as specified by
167 to authenticate to a further host,
171 Multiple destination constraints may be added when loading keys.
172 When attempting authentication with a key that has destination constraints,
173 the whole connection path, including
175 forwarding, is tested against those constraints and each
176 hop must be permitted for the attempt to succeed.
177 For example, if key is forwarded to a remote host,
179 and is attempting authentication to another host,
181 then the operation will be successful only if
183 was permitted from the origin host and the subsequent
185 hop is also permitted by destination constraints.
187 Hosts are identified by their host keys, and are looked up from known hosts
190 Wildcards patterns may be used for hostnames and certificate host
192 By default, keys added by
194 are not destination constrained.
196 Destination constraints were added in OpenSSH release 8.9.
197 Support in both the remote SSH client and server is required when using
198 destination-constrained keys over a forwarded
202 It is also important to note that destination constraints can only be
205 when a key is used, or when it is forwarded by a
208 Specifically, it does not prevent an attacker with access to a remote
210 from forwarding it again and using it on a different host (but only to
211 a permitted destination).
213 Load resident keys from a FIDO authenticator.
215 When loading keys into or deleting keys from the agent, process plain private
216 keys only and skip certificates.
218 Lists public key parameters of all identities currently represented
221 Lists fingerprints of all identities currently represented by the agent.
223 Be quiet after a successful operation.
225 Specifies a path to a library that will be used when adding
226 FIDO authenticator-hosted keys, overriding the default of using the
227 internal USB HID support.
229 Add keys provided by the PKCS#11 shared library
231 .It Fl T Ar pubkey ...
232 Tests whether the private keys that correspond to the specified
234 files are usable by performing sign and verify operations on each.
236 Set a maximum lifetime when adding identities to an agent.
237 The lifetime may be specified in seconds or in a time format
244 to print debugging messages about its progress.
245 This is helpful in debugging problems.
248 options increase the verbosity.
253 Lock the agent with a password.
257 .It Ev "DISPLAY", "SSH_ASKPASS" and "SSH_ASKPASS_REQUIRE"
260 needs a passphrase, it will read the passphrase from the current
261 terminal if it was run from a terminal.
264 does not have a terminal associated with it but
268 are set, it will execute the program specified by
272 and open an X11 window to read the passphrase.
273 This is particularly useful when calling
279 .Ev SSH_ASKPASS_REQUIRE
280 allows further control over the use of an askpass program.
281 If this variable is set to
285 will never attempt to use one.
290 will prefer to use the askpass program instead of the TTY when requesting
292 Finally, if the variable is set to
294 then the askpass program will be used for all passphrase input regardless
299 Identifies the path of a
301 socket used to communicate with the agent.
302 .It Ev SSH_SK_PROVIDER
303 Specifies a path to a library that will be used when loading any
304 FIDO authenticator-hosted keys, overriding the default of using
305 the built-in USB HID support.
308 .Bl -tag -width Ds -compact
310 .It Pa ~/.ssh/id_ecdsa
311 .It Pa ~/.ssh/id_ecdsa_sk
312 .It Pa ~/.ssh/id_ed25519
313 .It Pa ~/.ssh/id_ed25519_sk
315 Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
316 authenticator-hosted Ed25519 or RSA authentication identity of the user.
319 Identity files should not be readable by anyone but the user.
322 ignores identity files if they are accessible by others.
324 Exit status is 0 on success, 1 if the specified command fails,
327 is unable to contact the authentication agent.
335 OpenSSH is a derivative of the original and free
336 ssh 1.2.12 release by Tatu Ylonen.
337 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
338 Theo de Raadt and Dug Song
339 removed many bugs, re-added newer features and
341 Markus Friedl contributed the support for SSH
342 protocol versions 1.5 and 2.0.