gpg-agent
(1)
Name
gpg-agent - Secret key management for GnuPG
Synopsis
gpg-agent [--homedir dir] [--options file] [options]
gpg-agent [--homedir dir] [--options file] [options]
--server
gpg-agent [--homedir dir] [--options file] [options] --dae-
mon [command_line]
Description
GNU Privacy Guard GPG-AGENT(1)
NAME
gpg-agent - Secret key management for GnuPG
SYNOPSIS
gpg-agent [--homedir dir] [--options file] [options]
gpg-agent [--homedir dir] [--options file] [options]
--server
gpg-agent [--homedir dir] [--options file] [options] --dae-
mon [command_line]
DESCRIPTION
gpg-agent is a daemon to manage secret (private) keys inde-
pendently from any protocol. It is used as a backend for
gpg and gpgsm as well as for a couple of other utilities.
The agent is usualy started on demand by gpg, gpgsm, gpgconf
or gpg-connect-agent. Thus there is no reason to start it
manually. In case you want to use the included Secure Shell
Agent you may start the agent using:
gpg-connect-agent /bye
The usual way to run the agent is from the ~/.xsession file:
eval $(gpg-agent --daemon)
If you don't use an X server, you can also put this into
your regular startup file ~/.profile or .bash_profile. It
is best not to run multiple instance of the gpg-agent, so
you should make sure that only one is running: gpg-agent
uses an environment variable to inform clients about the
communication parameters. You can write the content of this
environment variable to a file so that you can test for a
running agent. Here is an example using Bourne shell syn-
tax:
gpg-agent --daemon --enable-ssh-support \
--write-env-file "${HOME}/.gpg-agent-info"
This code should only be run once per user session to ini-
tially fire up the agent. In the example the optional sup-
port for the included Secure Shell agent is enabled and the
information about the agent is written to a file in the HOME
directory. Note that by running gpg-agent without arguments
you may test whether an agent is already running; however
such a test may lead to a race condition, thus it is not
suggested.
The second script needs to be run for each interactive
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session:
if [ -f "${HOME}/.gpg-agent-info" ]; then
. "${HOME}/.gpg-agent-info"
export GPG_AGENT_INFO
export SSH_AUTH_SOCK
fi
It reads the data out of the file and exports the variables.
If you don't use Secure Shell, you don't need the last two
export statements.
You should always add the following lines to your .bashrc or
whatever initialization file is used for all shell invoca-
tions:
GPG_TTY=$(tty)
export GPG_TTY
It is important that this environment variable always
reflects the output of the tty command. For W32 systems
this option is not required.
Please make sure that a proper pinentry program has been
installed under the default filename (which is system depen-
dant) or use the option pinentry-program to specify the full
name of that program. It is often useful to install a sym-
bolic link from the actual used pinentry (e.g.
`/usr/bin/pinentry-gtk') to the expected one (e.g.
`/usr/bin/pinentry').
COMMANDS
Commands are not distinguished from options except for the
fact that only one command is allowed.
--version
Print the program version and licensing information.
Note that you cannot abbreviate this command.
--help
-h Print a usage message summarizing the most useful com-
mand-line options. Note that you cannot abbreviate
this command.
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--dump-options
Print a list of all available options and commands.
Note that you cannot abbreviate this command.
--server
Run in server mode and wait for commands on the stdin.
The default mode is to create a socket and listen for
commands there.
--daemon [command line]
Start the gpg-agent as a daemon; that is, detach it
from the console and run it in the background. Because
gpg-agent prints out important information required for
further use, a common way of invoking gpg-agent is:
eval $(gpg-agent --daemon) to setup the environment
variables. The option --write-env-file is another way
commonly used to do this. Yet another way is creating
a new process as a child of gpg-agent: gpg-agent --dae-
mon /bin/sh. This way you get a new shell with the
environment setup properly; if you exit from this
shell, gpg-agent terminates as well.
OPTIONS
--options file
Reads configuration from file instead of from the
default per-user configuration file. The default con-
figuration file is named `gpg-agent.conf' and expected
in the `.gnupg' directory directly below the home
directory of the user.
--homedir dir
Set the name of the home directory to dir. If this
option is not used, the home directory defaults to
`~/.gnupg'. It is only recognized when given on the
command line. It also overrides any home directory
stated through the environment variable `GNUPGHOME' or
(on W32 systems) by means of the Registry entry
HKCU\Software\GNU\GnuPG:HomeDir.
-v
--verbose
Outputs additional information while running. You can
increase the verbosity by giving several verbose
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commands to gpgsm, such as '-vv'.
-q
--quiet
Try to be as quiet as possible.
--batch
Don't invoke a pinentry or do any other thing requiring
human interaction.
--faked-system-time epoch
This option is only useful for testing; it sets the
system time back or forth to epoch which is the number
of seconds elapsed since the year 1970.
--debug-level level
Select the debug level for investigating problems.
level may be a numeric value or a keyword:
none No debugging at all. A value of less than 1 may
be used instead of the keyword.
basic
Some basic debug messages. A value between 1 and
2 may be used instead of the keyword.
advanced
More verbose debug messages. A value between 3
and 5 may be used instead of the keyword.
expert
Even more detailed messages. A value between 6
and 8 may be used instead of the keyword.
guru All of the debug messages you can get. A value
greater than 8 may be used instead of the keyword.
The creation of hash tracing files is only enabled
if the keyword is used.
How these messages are mapped to the actual debugging flags
is not specified and may change with newer releases of this
program. They are however carefully selected to best aid in
debugging.
--debug flags
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This option is only useful for debugging and the behav-
iour may change at any time without notice. FLAGS are
bit encoded and may be given in usual C-Syntax. The
currently defined bits are:
0 (1)
X.509 or OpenPGP protocol related data
1 (2)
values of big number integers
2 (4)
low level crypto operations
5 (32)
memory allocation
6 (64)
caching
7 (128)
show memory statistics.
9 (512)
write hashed data to files named dbgmd-000*
10 (1024)
trace Assuan protocol
12 (4096)
bypass all certificate validation
--debug-all
Same as --debug=0xffffffff
--debug-wait n
When running in server mode, wait n seconds before
entering the actual processing loop and print the pid.
This gives time to attach a debugger.
--no-detach
Don't detach the process from the console. This is
mainly useful for debugging.
-s
--sh
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-c
--csh
Format the info output in daemon mode for use with the
standard Bourne shell or the C-shell respectively. The
default is to guess it based on the environment vari-
able SHELL which is correct in almost all cases.
--write-env-file file
Often it is required to connect to the agent from a
process not being an inferior of gpg-agent and thus the
environment variable with the socket name is not avail-
able. To help setting up those variables in other ses-
sions, this option may be used to write the information
into file. If file is not specified the default name
`${HOME}/.gpg-agent-info' will be used. The format is
suitable to be evaluated by a Bourne shell like in this
simple example:
eval $(cat file)
eval $(cut -d= -f 1 < file | xargs echo export)
--no-grab
Tell the pinentry not to grab the keyboard and mouse.
This option should in general not be used to avoid X-
sniffing attacks.
--log-file file
Append all logging output to file. This is very help-
ful in seeing what the agent actually does. If neither
a log file nor a log file descriptor has been set on a
Windows platform, the Registry entry HKCU\Soft-
ware\GNU\GnuPG:DefaultLogFile, if set, is used to spec-
ify the logging output.
--allow-mark-trusted
Allow clients to mark keys as trusted, i.e. put them
into the `trustlist.txt' file. This is by default not
allowed to make it harder for users to inadvertently
accept Root-CA keys.
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--allow-loopback-pinentry
Allow clients to use the loopback pinentry features;
see the option pinentry-mode for details.
--ignore-cache-for-signing
This option will let gpg-agent bypass the passphrase
cache for all signing operation. Note that there is
also a per-session option to control this behaviour but
this command line option takes precedence.
--default-cache-ttl n
Set the time a cache entry is valid to n seconds. The
default is 600 seconds.
--default-cache-ttl-ssh n
Set the time a cache entry used for SSH keys is valid
to n seconds. The default is 1800 seconds.
--max-cache-ttl n
Set the maximum time a cache entry is valid to n sec-
onds. After this time a cache entry will be expired
even if it has been accessed recently. The default is
2 hours (7200 seconds).
--max-cache-ttl-ssh n
Set the maximum time a cache entry used for SSH keys is
valid to n seconds. After this time a cache entry will
be expired even if it has been accessed recently. The
default is 2 hours (7200 seconds).
--enforce-passphrase-constraints
Enforce the passphrase constraints by not allowing the
user to bypass them using the ``Take it anyway'' but-
ton.
--min-passphrase-len n
Set the minimal length of a passphrase. When entering
a new passphrase shorter than this value a warning will
be displayed. Defaults to 8.
--min-passphrase-nonalpha n
Set the minimal number of digits or special characters
required in a passphrase. When entering a new
passphrase with less than this number of digits or
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special characters a warning will be displayed.
Defaults to 1.
--check-passphrase-pattern file
Check the passphrase against the pattern given in file.
When entering a new passphrase matching one of these
pattern a warning will be displayed. file should be an
absolute filename. The default is not to use any pat-
tern file.
Security note: It is known that checking a passphrase
against a list of pattern or even against a complete
dictionary is not very effective to enforce good
passphrases. Users will soon figure up ways to bypass
such a policy. A better policy is to educate users on
good security behavior and optionally to run a
passphrase cracker regularly on all users passphrases
to catch the very simple ones.
--max-passphrase-days n
Ask the user to change the passphrase if n days have
passed since the last change. With --enforce-
passphrase-constraints set the user may not bypass this
check.
--enable-passphrase-history
This option does nothing yet.
--pinentry-program filename
Use program filename as the PIN entry. The default is
installation dependent.
--pinentry-touch-file filename
By default the filename of the socket gpg-agent is lis-
tening for requests is passed to Pinentry, so that it
can touch that file before exiting (it does this only
in curses mode). This option changes the file passed
to Pinentry to filename. The special name /dev/null
may be used to completely disable this feature. Note
that Pinentry will not create that file, it will only
change the modification and access time.
--scdaemon-program filename
Use program filename as the Smartcard daemon. The
default is installation dependent and can be shown with
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the gpgconf command.
--disable-scdaemon
Do not make use of the scdaemon tool. This option has
the effect of disabling the ability to do smartcard
operations. Note, that enabling this option at runtime
does not kill an already forked scdaemon.
--disable-check-own-socket
gpg-agent employs a periodic self-test to detect a
stolen socket. This usually means a second instance of
gpg-agent has taken over the socket and gpg-agent will
then terminate itself. This option may be used to dis-
able this self-test for debugging purposes.
--use-standard-socket
--no-use-standard-socket
By enabling this option gpg-agent will listen on the
socket named `S.gpg-agent', located in the home direc-
tory, and not create a random socket below a temporary
directory. Tools connecting to gpg-agent should first
try to connect to the socket given in environment vari-
able GPG_AGENT_INFO and then fall back to this socket.
This option may not be used if the home directory is
mounted on a remote file system which does not support
special files like fifos or sockets. Note, that --use-
standard-socket is the default on all systems since
GnuPG 2.1. Note, that --use-standard-socket is the
default on Windows systems. The default may be changed
at build time. It is possible to test at runtime
whether the agent has been configured for use with the
standard socket by issuing the command gpg-agent --use-
standard-socket-p which returns success if the standard
socket option has been enabled.
--display string
--ttyname string
--ttytype string
--lc-ctype string
--lc-messages string
--xauthority string
These options are used with the server mode to pass
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localization information.
--keep-tty
--keep-display
Ignore requests to change the current tty or X window
system's DISPLAY variable respectively. This is useful
to lock the pinentry to pop up at the tty or display
you started the agent.
--enable-ssh-support
Enable the OpenSSH Agent protocol.
In this mode of operation, the agent does not only
implement the gpg-agent protocol, but also the agent
protocol used by OpenSSH (through a separate socket).
Consequently, it should be possible to use the gpg-
agent as a drop-in replacement for the well known ssh-
agent.
SSH Keys, which are to be used through the agent, need
to be added to the gpg-agent initially through the ssh-
add utility. When a key is added, ssh-add will ask for
the password of the provided key file and send the
unprotected key material to the agent; this causes the
gpg-agent to ask for a passphrase, which is to be used
for encrypting the newly received key and storing it in
a gpg-agent specific directory.
Once a key has been added to the gpg-agent this way,
the gpg-agent will be ready to use the key.
Note: in case the gpg-agent receives a signature
request, the user might need to be prompted for a
passphrase, which is necessary for decrypting the
stored key. Since the ssh-agent protocol does not con-
tain a mechanism for telling the agent on which dis-
play/terminal it is running, gpg-agent's ssh-support
will use the TTY or X display where gpg-agent has been
started. To switch this display to the current one,
the following command may be used:
gpg-connect-agent updatestartuptty /bye
Although all GnuPG components try to start the gpg-agent as
needed, this is not possible for the ssh support because ssh
does not know about it. Thus if no GnuPG tool which
accesses the agent has been run, there is no guarantee that
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ssh is abale to use gpg-agent for authentication. To fix
this you may start gpg-agent if needed using this simple
command:
gpg-connect-agent /bye
Adding the --verbose shows the progress of starting the
agent.
All the long options may also be given in the configuration
file after stripping off the two leading dashes.
EXAMPLES
The usual way to invoke gpg-agent is
$ eval $(gpg-agent --daemon)
An alternative way is by replacing ssh-agent with gpg-agent.
If for example ssh-agent is started as part of the Xsession
initialization, you may simply replace ssh-agent by a script
like:
#!/bin/sh
exec /usr/local/bin/gpg-agent --enable-ssh-support --daemon \
--write-env-file ${HOME}/.gpg-agent-info "$@"
and add something like (for Bourne shells)
if [ -f "${HOME}/.gpg-agent-info" ]; then
. "${HOME}/.gpg-agent-info"
export GPG_AGENT_INFO
export SSH_AUTH_SOCK
fi
to your shell initialization file (e.g. `~/.bashrc').
FILES
There are a few configuration files needed for the operation
of the agent. By default they may all be found in the cur-
rent home directory (see: [option --homedir]).
gpg-agent.conf
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This is the standard configuration file read by gpg-
agent on
startup. It may contain any valid long option; the
leading
two dashes may not be entered and the option may not
be abbreviated.
This file is also read after a SIGHUP however only a
few
options will actually have an effect. This default
name may be
changed on the command line (see: [option
--options]).
You should backup this file.
trustlist.txt
This is the list of trusted keys. You should backup
this file.
Comment lines, indicated by a leading hash mark, as
well as empty
lines are ignored. To mark a key as trusted you need
to enter its
fingerprint followed by a space and a capital letter
S. Colons
may optionally be used to separate the bytes of a
fingerprint; this
allows to cut and paste the fingerprint from a key
listing output. If
the line is prefixed with a ! the key is explicitly
marked as
not trusted.
Here is an example where two keys are marked as ulti-
mately trusted
and one as not trusted:
.RS 2
# CN=Wurzel ZS 3,O=Intevation GmbH,C=DE
A6935DD34EF3087973C706FC311AA2CCF733765B S
# CN=PCA-1-Verwaltung-02/O=PKI-1-Verwaltung/C=DE
DC:BD:69:25:48:BD:BB:7E:31:6E:BB:80:D3:00:80:35:D4:F8:A6:CD S
# CN=Root-CA/O=Schlapphuete/L=Pullach/C=DE
!14:56:98:D3:FE:9C:CA:5A:31:6E:BC:81:D3:11:4E:00:90:A3:44:C2 S
.fi
Before entering a key into this file, you need to ensure its
authenticity. How to do this depends on your organisation; your
administrator might have already entered those keys which are deemed
trustworthy enough into this file. Places where to look for the
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fingerprint of a root certificate are letters received from the CA or
the website of the CA (after making 100% sure that this is indeed the
website of that CA). You may want to consider allowing interactive
updates of this file by using the see: [option --allow-mark-trusted].
This is however not as secure as maintaining this file manually. It is
even advisable to change the permissions to read-only so that this file
can't be changed inadvertently.
As a special feature a line include-default will include a global
list of trusted certificates (e.g. `/etc/gnupg/trustlist.txt').
This global list is also used if the local list is not available.
It is possible to add further flags after the S for use by the
caller:
relax
Relax checking of some root certificate requirements. As of now this
flag allows the use of root certificates with a missing basicConstraints
attribute (despite that it is a MUST for CA certificates) and disables
CRL checking for the root certificate.
cm If validation of a certificate finally issued by a CA with this flag set
fails, try again using the chain validation model.
sshcontrol
This file is used when support for the secure shell agent protocol has
been enabled (see: [option --enable-ssh-support]). Only keys present in
this file are used in the SSH protocol. You should backup this file.
The ssh-add tool may be used to add new entries to this file;
you may also add them manually. Comment lines, indicated by a leading
hash mark, as well as empty lines are ignored. An entry starts with
optional whitespace, followed by the keygrip of the key given as 40 hex
digits, optionally followed by the caching TTL in seconds and another
optional field for arbitrary flags. A non-zero TTL overrides the global
default as set by --default-cache-ttl-ssh.
The only flag support is confirm. If this flag is found for a
key, each use of the key will pop up a pinentry to confirm the use of
that key. The flag is automatically set if a new key was loaded into
gpg-agent using the option -c of the ssh-add
command.
The keygrip may be prefixed with a ! to disable an entry entry.
The following example lists exactly one key. Note that keys available
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through a OpenPGP smartcard in the active smartcard reader are
implicitly added to this list; i.e. there is no need to list them.
.RS 2
# Key added on: 2011-07-20 20:38:46
# Fingerprint: 5e:8d:c4:ad:e7:af:6e:27:8a:d6:13:e4:79:ad:0b:81
34B62F25E277CF13D3C6BCEBFD3F85D08F0A864B 0 confirm
.fi
private-keys-v1.d/
This is the directory where gpg-agent stores the private keys. Each
key is stored in a file with the name made up of the keygrip and the
suffix `key'. You should backup all files in this directory
and take great care to keep this backup closed away.
Note that on larger installations, it is useful to put predefined
files into the directory `/etc/skel/.gnupg/' so that newly created
users start up with a working configuration. For existing users the
a small helper script is provided to create these files (see: [addgnupghome]).
SIGNALS
A running gpg-agent may be controlled by signals, i.e. using
the kill command to send a signal to the process.
Here is a list of supported signals:
SIGHUP
This signal flushes all cached passphrases and if the
program has been started with a configuration file, the
configuration file is read again. Only certain options
are honored: quiet, verbose, debug, debug-all, debug-
level, no-grab, pinentry-program, default-cache-ttl,
max-cache-ttl, ignore-cache-for-signing, allow-mark-
trusted, disable-scdaemon, and disable-check-own-
socket. scdaemon-program is also supported but due to
the current implementation, which calls the scdaemon
only once, it is not of much use unless you manually
kill the scdaemon.
SIGTERM
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Shuts down the process but waits until all current
requests are fulfilled. If the process has received 3
of these signals and requests are still pending, a
shutdown is forced.
SIGINT
Shuts down the process immediately.
SIGUSR1
Dump internal information to the log file.
SIGUSR2
This signal is used for internal purposes.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | crypto/gnupg |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
SEE ALSO
gpg2(1), gpgsm(1), gpg-connect-agent(1), scdaemon(1)
The full documentation for this tool is maintained as a Tex-
info manual. If GnuPG and the info program are properly
installed at your site, the command
info gnupg
should give you access to the complete manual including a
menu structure and an index.
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
ftp://ftp.gnupg.org/gcrypt/gnupg/gnupg-2.0.22.tar.bz2
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Further information about this software can be found on the
open source community website at http://www.gnupg.org/.
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