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SSH-ADD(1) BSD General Commands Manual SSH-ADD(1)
NAME
ssh-add -- adds private key identities to the OpenSSH authentication
agent
SYNOPSIS
ssh-add [-cDdKkLlqvXx] [-E fingerprint_hash] [-H hostkey_file]
[-h destination_constraint] [-S provider] [-t life] [file ...]
ssh-add -s pkcs11
ssh-add -e pkcs11
ssh-add -T pubkey ...
DESCRIPTION
ssh-add adds private key identities to the authentication agent,
ssh-agent(1). When run without arguments, it adds the files
~/.ssh/id_rsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ecdsa_sk, ~/.ssh/id_ed25519,
~/.ssh/id_ed25519_sk, and ~/.ssh/id_dsa. After loading a private key,
ssh-add will try to load corresponding certificate information from the
filename obtained by appending -cert.pub to the name of the private key
file. Alternative file names can be given on the command line.
If any file requires a passphrase, ssh-add asks for the passphrase from
the user. The passphrase is read from the user's tty. ssh-add retries
the last passphrase if multiple identity files are given.
The authentication agent must be running and the SSH_AUTH_SOCK environ-
ment variable must contain the name of its socket for ssh-add to work.
The options are as follows:
-c Indicates that added identities should be subject to confirmation
before being used for authentication. Confirmation is performed
by ssh-askpass(1). Successful confirmation is signaled by a zero
exit status from ssh-askpass(1), rather than text entered into
the requester.
-D Deletes all identities from the agent.
-d Instead of adding identities, removes identities from the agent.
If ssh-add has been run without arguments, the keys for the
default identities and their corresponding certificates will be
removed. Otherwise, the argument list will be interpreted as a
list of paths to public key files to specify keys and certifi-
cates to be removed from the agent. If no public key is found at
a given path, ssh-add will append .pub and retry. If the argu-
ment list consists of ``-'' then ssh-add will read public keys to
be removed from standard input.
-E fingerprint_hash
Specifies the hash algorithm used when displaying key finger-
prints. Valid options are: ``md5'' and ``sha256''. The default
is ``sha256''.
-e pkcs11
Remove keys provided by the PKCS#11 shared library pkcs11.
-H hostkey_file
Specifies a known hosts file to look up hostkeys when using des-
tination-constrained keys via the -h flag. This option may be
specified multiple times to allow multiple files to be searched.
If no files are specified, ssh-add will use the default
ssh_config(5) known hosts files: ~/.ssh/known_hosts,
~/.ssh/known_hosts2, /etc/ssh/ssh_known_hosts, and
/etc/ssh/ssh_known_hosts2.
-h destination_constraint
When adding keys, constrain them to be usable only through spe-
cific hosts or to specific destinations.
Destination constraints of the form `[user@]dest-hostname' permit
use of the key only from the origin host (the one running
ssh-agent(1)) to the listed destination host, with optional user
name.
Constraints of the form `src-hostname>[user@]dst-hostname' allow
a key available on a forwarded ssh-agent(1) to be used through a
particular host (as specified by `src-hostname') to authenticate
to a further host, specified by `dst-hostname'.
Multiple destination constraints may be added when loading keys.
When attempting authentication with a key that has destination
constraints, the whole connection path, including ssh-agent(1)
forwarding, is tested against those constraints and each hop must
be permitted for the attempt to succeed. For example, if key is
forwarded to a remote host, `host-b', and is attempting authenti-
cation to another host, `host-c', then the operation will be suc-
cessful only if `host-b' was permitted from the origin host and
the subsequent `host-b>host-c' hop is also permitted by destina-
tion constraints.
Hosts are identified by their host keys, and are looked up from
known hosts files by ssh-add. Wildcards patterns may be used for
hostnames and certificate host keys are supported. By default,
keys added by ssh-add are not destination constrained.
Destination constraints were added in OpenSSH release 8.9. Sup-
port in both the remote SSH client and server is required when
using destination-constrained keys over a forwarded ssh-agent(1)
channel.
It is also important to note that destination constraints can
only be enforced by ssh-agent(1) when a key is used, or when it
is forwarded by a cooperating ssh(1). Specifically, it does not
prevent an attacker with access to a remote SSH_AUTH_SOCK from
forwarding it again and using it on a different host (but only to
a permitted destination).
-K Load resident keys from a FIDO authenticator.
-k When loading keys into or deleting keys from the agent, process
plain private keys only and skip certificates.
-L Lists public key parameters of all identities currently repre-
sented by the agent.
-l Lists fingerprints of all identities currently represented by the
agent.
-q Be quiet after a successful operation.
-S provider
Specifies a path to a library that will be used when adding FIDO
authenticator-hosted keys, overriding the default of using the
internal USB HID support.
-s pkcs11
Add keys provided by the PKCS#11 shared library pkcs11.
-T pubkey ...
Tests whether the private keys that correspond to the specified
pubkey files are usable by performing sign and verify operations
on each.
-t life
Set a maximum lifetime when adding identities to an agent. The
lifetime may be specified in seconds or in a time format speci-
fied in sshd_config(5).
-v Verbose mode. Causes ssh-add to print debugging messages about
its progress. This is helpful in debugging problems. Multiple
-v options increase the verbosity. The maximum is 3.
-X Unlock the agent.
-x Lock the agent with a password.
ENVIRONMENT
DISPLAY, SSH_ASKPASS and SSH_ASKPASS_REQUIRE
If ssh-add needs a passphrase, it will read the passphrase from
the current terminal if it was run from a terminal. If ssh-add
does not have a terminal associated with it but DISPLAY and
SSH_ASKPASS are set, it will execute the program specified by
SSH_ASKPASS (by default ``ssh-askpass'') and open an X11 window
to read the passphrase. This is particularly useful when calling
ssh-add from a .xsession or related script.
SSH_ASKPASS_REQUIRE allows further control over the use of an
askpass program. If this variable is set to ``never'' then
ssh-add will never attempt to use one. If it is set to
``prefer'', then ssh-add will prefer to use the askpass program
instead of the TTY when requesting passwords. Finally, if the
variable is set to ``force'', then the askpass program will be
used for all passphrase input regardless of whether DISPLAY is
set.
SSH_AUTH_SOCK
Identifies the path of a UNIX-domain socket used to communicate
with the agent.
SSH_SK_PROVIDER
Specifies a path to a library that will be used when loading any
FIDO authenticator-hosted keys, overriding the default of using
the built-in USB HID support.
FILES
~/.ssh/id_dsa
~/.ssh/id_ecdsa
~/.ssh/id_ecdsa_sk
~/.ssh/id_ed25519
~/.ssh/id_ed25519_sk
~/.ssh/id_rsa
Contains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519,
authenticator-hosted Ed25519 or RSA authentication identity of
the user.
Identity files should not be readable by anyone but the user. Note that
ssh-add ignores identity files if they are accessible by others.
EXIT STATUS
Exit status is 0 on success, 1 if the specified command fails, and 2 if
ssh-add is unable to contact the authentication agent.
SEE ALSO
ssh(1), ssh-agent(1), ssh-askpass(1), ssh-keygen(1), sshd(8)
AUTHORS
OpenSSH is a derivative of the original and free ssh 1.2.12 release by
Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
de Raadt and Dug Song removed many bugs, re-added newer features and cre-
ated OpenSSH. Markus Friedl contributed the support for SSH protocol
versions 1.5 and 2.0.
BSD September 20, 2024 BSD
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