ssh-addadds 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-addwill 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,
asks for the passphrase from the user. The passphrase is read from the
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:
ssh-addhas 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-addwill append .pub and retry. If the argument list consists of “-” then
ssh-addwill read public keys to be removed from standard input.
-hflag. This option may be specified multiple times to allow multiple files to be searched. If no files are specified,
ssh-addwill 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.
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
patterns may be used for hostnames and certificate host keys are
supported. By default, keys added by
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).
ssh-addto print debugging messages about its progress. This is helpful in debugging problems. Multiple
-voptions increase the verbosity. The maximum is 3.
SSH_ASKPASS and SSH_ASKPASS_REQUIRE
ssh-addneeds a passphrase, it will read the passphrase from the current terminal if it was run from a terminal. If
ssh-adddoes not have a terminal associated with it but
SSH_ASKPASSare 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-addfrom a .xsession or related script.
SSH_ASKPASS_REQUIRE allows further
control over the use of an askpass program. If this variable is set to
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.
Identity files should not be readable by anyone but the user. Note
ssh-add ignores identity files if they are
accessible by others.
ssh-addis unable to contact the authentication agent.
|February 4, 2022||OmniOS|