ssh-add —
adds
private key identities to the OpenSSH authentication agent
ssh-add |
[-cDdKkLlqvXx]
[-E
fingerprint_hash]
[-H
hostkey_file]
[-h
destination_constraint]
[-S
provider]
[-t
life]
[file ...] |
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
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
certificates 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 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 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 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 destination 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 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
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 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 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.
-
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.
- ~/.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 is 0 on success, 1 if the specified command fails, and 2 if
ssh-add is unable to contact the authentication
agent.
ssh(1),
ssh-agent(1),
ssh-askpass(1),
ssh-keygen(1),
sshd(8)
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.