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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 environment 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 con-
firmation 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 corre-
sponding certificates will be removed. Otherwise, the argument list will be inter-
preted as a list of paths to public key files to specify keys and certificates to be
removed from the agent. If no public key is found at a given path, ssh-add will ap-
pend .pub and retry. If the argument 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 fingerprints. 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 destination-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 specific hosts or to spe-
cific 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 for-
warded to a remote host, 'host-b', and is attempting authentication to another host,
'host-c', then the operation will be successful 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. Support in both the re-
mote 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 represented 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 us-
able 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 specified 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 created OpenSSH. Markus Friedl contributed the support
for SSH protocol versions 1.5 and 2.0.
BSD February 4, 2022 BSD
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