1 .\" $OpenBSD: ssh-add.1,v 1.85 2023/12/18 14:46:56 djm 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: December 18 2023 $
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
56 .Op Ar certificate ...
64 adds private key identities to the authentication agent,
66 When run without arguments, it adds the files
69 .Pa ~/.ssh/id_ecdsa_sk ,
70 .Pa ~/.ssh/id_ed25519 ,
71 .Pa ~/.ssh/id_ed25519_sk ,
74 After loading a private key,
76 will try to load corresponding certificate information from the
77 filename obtained by appending
79 to the name of the private key file.
80 Alternative file names can be given on the command line.
82 If any file requires a passphrase,
84 asks for the passphrase from the user.
85 The passphrase is read from the user's tty.
87 retries the last passphrase if multiple identity files are given.
89 The authentication agent must be running and the
91 environment variable must contain the name of its socket for
95 The options are as follows:
98 Indicates that added identities should be subject to confirmation before
99 being used for authentication.
100 Confirmation is performed by
102 Successful confirmation is signaled by a zero exit status from
104 rather than text entered into the requester.
106 When loading keys into or deleting keys from the agent, process
107 certificates only and skip plain keys.
109 Deletes all identities from the agent.
111 Instead of adding identities, removes identities from the agent.
114 has been run without arguments, the keys for the default identities and
115 their corresponding certificates will be removed.
116 Otherwise, the argument list will be interpreted as a list of paths to
117 public key files to specify keys and certificates to be removed from the agent.
118 If no public key is found at a given path,
123 If the argument list consists of
127 will read public keys to be removed from standard input.
128 .It Fl E Ar fingerprint_hash
129 Specifies the hash algorithm used when displaying key fingerprints.
137 Remove keys provided by the PKCS#11 shared library
139 .It Fl H Ar hostkey_file
140 Specifies a known hosts file to look up hostkeys when using
141 destination-constrained keys via the
144 This option may be specified multiple times to allow multiple files to be
146 If no files are specified,
151 .Pa ~/.ssh/known_hosts ,
152 .Pa ~/.ssh/known_hosts2 ,
153 .Pa /etc/ssh/ssh_known_hosts ,
155 .Pa /etc/ssh/ssh_known_hosts2 .
156 .It Fl h Ar destination_constraint
157 When adding keys, constrain them to be usable only through specific hosts or to
158 specific destinations.
160 Destination constraints of the form
161 .Sq [user@]dest-hostname
162 permit use of the key only from the origin host (the one running
164 to the listed destination host, with optional user name.
166 Constraints of the form
167 .Sq src-hostname>[user@]dst-hostname
168 allow a key available on a forwarded
170 to be used through a particular host (as specified by
172 to authenticate to a further host,
176 Multiple destination constraints may be added when loading keys.
177 When attempting authentication with a key that has destination constraints,
178 the whole connection path, including
180 forwarding, is tested against those constraints and each
181 hop must be permitted for the attempt to succeed.
182 For example, if key is forwarded to a remote host,
184 and is attempting authentication to another host,
186 then the operation will be successful only if
188 was permitted from the origin host and the subsequent
190 hop is also permitted by destination constraints.
192 Hosts are identified by their host keys, and are looked up from known hosts
195 Wildcards patterns may be used for hostnames and certificate host
197 By default, keys added by
199 are not destination constrained.
201 Destination constraints were added in OpenSSH release 8.9.
202 Support in both the remote SSH client and server is required when using
203 destination-constrained keys over a forwarded
207 It is also important to note that destination constraints can only be
210 when a key is used, or when it is forwarded by a
213 Specifically, it does not prevent an attacker with access to a remote
215 from forwarding it again and using it on a different host (but only to
216 a permitted destination).
218 Load resident keys from a FIDO authenticator.
220 When loading keys into or deleting keys from the agent, process plain private
221 keys only and skip certificates.
223 Lists public key parameters of all identities currently represented
226 Lists fingerprints of all identities currently represented by the agent.
228 Be quiet after a successful operation.
230 Specifies a path to a library that will be used when adding
231 FIDO authenticator-hosted keys, overriding the default of using the
232 internal USB HID support.
234 Add keys provided by the PKCS#11 shared library
236 Certificate files may optionally be listed as command-line arguments.
237 If these are present, then they will be loaded into the agent using any
238 corresponding private keys loaded from the PKCS#11 token.
239 .It Fl T Ar pubkey ...
240 Tests whether the private keys that correspond to the specified
242 files are usable by performing sign and verify operations on each.
244 Set a maximum lifetime when adding identities to an agent.
245 The lifetime may be specified in seconds or in a time format
252 to print debugging messages about its progress.
253 This is helpful in debugging problems.
256 options increase the verbosity.
261 Lock the agent with a password.
265 .It Ev "DISPLAY", "SSH_ASKPASS" and "SSH_ASKPASS_REQUIRE"
268 needs a passphrase, it will read the passphrase from the current
269 terminal if it was run from a terminal.
272 does not have a terminal associated with it but
276 are set, it will execute the program specified by
280 and open an X11 window to read the passphrase.
281 This is particularly useful when calling
287 .Ev SSH_ASKPASS_REQUIRE
288 allows further control over the use of an askpass program.
289 If this variable is set to
293 will never attempt to use one.
298 will prefer to use the askpass program instead of the TTY when requesting
300 Finally, if the variable is set to
302 then the askpass program will be used for all passphrase input regardless
307 Identifies the path of a
309 socket used to communicate with the agent.
310 .It Ev SSH_SK_PROVIDER
311 Specifies a path to a library that will be used when loading any
312 FIDO authenticator-hosted keys, overriding the default of using
313 the built-in USB HID support.
316 .Bl -tag -width Ds -compact
318 .It Pa ~/.ssh/id_ecdsa
319 .It Pa ~/.ssh/id_ecdsa_sk
320 .It Pa ~/.ssh/id_ed25519
321 .It Pa ~/.ssh/id_ed25519_sk
323 Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
324 authenticator-hosted Ed25519 or RSA authentication identity of the user.
327 Identity files should not be readable by anyone but the user.
330 ignores identity files if they are accessible by others.
332 Exit status is 0 on success, 1 if the specified command fails,
335 is unable to contact the authentication agent.
343 OpenSSH is a derivative of the original and free
344 ssh 1.2.12 release by Tatu Ylonen.
345 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
346 Theo de Raadt and Dug Song
347 removed many bugs, re-added newer features and
349 Markus Friedl contributed the support for SSH
350 protocol versions 1.5 and 2.0.