SSH-AGENT(1) | User Commands | SSH-AGENT(1) |
ssh-agent
—
ssh-agent |
[-c | -s ]
[-Dd ] [-a
bind_address] [-E
fingerprint_hash] [-P
allowed_providers] [-t
life] |
ssh-agent |
[-a bind_address]
[-E fingerprint_hash]
[-P allowed_providers]
[-t life]
command [arg ...] |
ssh-agent |
[-c | -s ]
-k |
ssh-agent
is a program to hold private keys used for
public key authentication. Through use of environment variables the agent can
be located and automatically used for authentication when logging in to other
machines using ssh(1).
The options are as follows:
-a
bind_address-c
stdout
. This is the
default if SHELL
looks like it's a csh style of
shell.-D
ssh-agent
will not fork.-d
ssh-agent
will not fork and will write debug
information to standard error.-E
fingerprint_hash-k
SSH_AGENT_PID
environment variable).-P
allowed_providers-S
or -s
options to
ssh-add(1). Libraries that do not
match the pattern list will be refused. See PATTERNS in
ssh_config(5) for a description
of pattern-list syntax. The default list is
“/usr/lib/*,/usr/local/lib/*”.-s
stdout
. This is
the default if SHELL
does not look like it's a csh
style of shell.-t
lifeThere are two main ways to get an agent set up. The first is at
the start of an X session, where all other windows or programs are started
as children of the ssh-agent
program. The agent
starts a command under which its environment variables are exported, for
example ssh-agent xterm &
. When the command
terminates, so does the agent.
The second method is used for a login session. When
ssh-agent
is started, it prints the shell commands
required to set its environment variables, which in turn can be evaluated in
the calling shell, for example eval `ssh-agent
-s`
.
In both cases, ssh(1) looks at these environment variables and uses them to establish a connection to the agent.
The agent initially does not have any private keys. Keys are added
using ssh-add(1) or by
ssh(1) when
AddKeysToAgent
is set in
ssh_config(5). Multiple identities
may be stored in ssh-agent
concurrently and
ssh(1) will automatically use them if
present. ssh-add(1) is also used to
remove keys from ssh-agent
and to query the keys
that are held in one.
Connections to ssh-agent
may be forwarded
from further remote hosts using the -A
option to
ssh(1) (but see the caveats documented
therein), avoiding the need for authentication data to be stored on other
machines. Authentication passphrases and private keys never go over the
network: the connection to the agent is forwarded over SSH remote
connections and the result is returned to the requester, allowing the user
access to their identities anywhere in the network in a secure fashion.
SSH_AGENT_PID
ssh-agent
starts, it stores the name of the
agent's process ID (PID) in this variable.SSH_AUTH_SOCK
ssh-agent
starts, it creates a
UNIX-domain socket and stores its pathname in this
variable. It is accessible only to the current user, but is easily abused
by root or another instance of the same user.March 31, 2022 | OmniOS |