Tribblix: manual page: gpg-agent.1

GPG-AGENT(1) GNU Privacy Guard 2.2 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] --daemon
[command_line]

DESCRIPTION

gpg-agent is a daemon to manage secret (private) keys independently
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 automatically 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

If you want to manually terminate the currently-running agent, you
can safely do so with:

gpgconf --kill gpg-agent

You should always add the following lines to your .bashrc or whatever
initialization file is used for all shell invocations:

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 dependent) or use the
option pinentry-program to specify the full name of that program. It
is often useful to install a symbolic 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 command-line
options. Note that you cannot abbreviate this command.

--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.

As an alternative you may create a new process as a child of
gpg-agent: gpg-agent --daemon /bin/sh. This way you get a new
shell with the environment setup properly; after you exit from
this shell, gpg-agent terminates within a few seconds.

--supervised
Run in the foreground, sending logs by default to stderr, and
listening on provided file descriptors, which must already be
bound to listening sockets. This command is useful when
running under systemd or other similar process supervision
schemes. This option is not supported on Windows.

In --supervised mode, different file descriptors can be
provided for use as different socket types (e.g. ssh, extra)
as long as they are identified in the environment variable
LISTEN_FDNAMES (see sd_listen_fds(3) on some Linux
distributions for more information on this convention).

OPTIONS

Options may either be used on the command line or, after stripping
off the two leading dashes, in the configuration file.

--options file
Reads configuration from file instead of from the default per-
user configuration file. The default configuration file is
named `gpg-agent.conf' and expected in the `.gnupg' directory
directly below the home directory of the user. This option is
ignored if used in an options file.

--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 Windows systems) by means of the
Registry entry HKCU\Software\GNU\GnuPG:HomeDir.

On Windows systems it is possible to install GnuPG as a
portable application. In this case only this command line
option is considered, all other ways to set a home directory
are ignored.

To install GnuPG as a portable application under Windows,
create an empty file named `gpgconf.ctl' in the same directory
as the tool `gpgconf.exe'. The root of the installation is
then that directory; or, if `gpgconf.exe' has been installed
directly below a directory named `bin', its parent directory.
You also need to make sure that the following directories
exist and are writable: `ROOT/home' for the GnuPG home and
`ROOT/usr/var/cache/gnupg' for internal cache files.

-v
--verbose
Outputs additional information while running. You can
increase the verbosity by giving several verbose commands to
gpg-agent, 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
This option is only useful for debugging and the behavior 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.

--debug-quick-random
This option inhibits the use of the very secure random quality
level (Libgcrypt's GCRY_VERY_STRONG_RANDOM) and degrades all
request down to standard random quality. It is only used for
testing and should not be used for any production quality
keys. This option is only effective when given on the command
line.

On GNU/Linux, another way to quickly generate insecure keys is
to use rngd to fill the kernel's entropy pool with lower
quality random data. rngd is typically provided by the
rng-tools package. It can be run as follows: `sudo rngd -f -r
/dev/urandom'.

--debug-pinentry
This option enables extra debug information pertaining to the
Pinentry. As of now it is only useful when used along with
--debug 1024.

--no-detach
Don't detach the process from the console. This is mainly
useful for debugging.

--steal-socket
In --daemon mode, gpg-agent detects an already running gpg-
agent and does not allow to start a new instance. This option
can be used to override this check: the new gpg-agent process
will try to take over the communication sockets from the
already running process and start anyway. This option should
in general not be used.

-s
--sh
-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 variable SHELL
which is correct in almost all cases.

--grab
--no-grab
Tell the pinentry to grab the keyboard and mouse. This option
should be used on X-Servers to avoid X-sniffing attacks. Any
use of the option --grab overrides an used option --no-grab.
The default is --no-grab.

--log-file file
Append all logging output to file. This is very helpful in
seeing what the agent actually does. Use `socket://' to log to
socket. If neither a log file nor a log file descriptor has
been set on a Windows platform, the Registry entry
HKCU\Software\GNU\GnuPG:DefaultLogFile, if set, is used to
specify the logging output.

--no-allow-mark-trusted
Do not allow clients to mark keys as trusted, i.e. put them
into the `trustlist.txt' file. This makes it harder for users
to inadvertently accept Root-CA keys.

--no-user-trustlist
Entirely ignore the user trust list and consider only the
global trustlist (`/usr/etc/gnupg/trustlist.txt'). This
implies the [option --no-allow-mark-trusted].

--sys-trustlist-name file
Changes the default name for the global trustlist from
"trustlist.txt" to file. If file does not contain any slashes
and does not start with "~/" it is searched in the system
configuration directory (`/usr/etc/gnupg').

--allow-preset-passphrase
This option allows the use of gpg-preset-passphrase to seed
the internal cache of gpg-agent with passphrases.

--no-allow-loopback-pinentry

--allow-loopback-pinentry
Disallow or allow clients to use the loopback pinentry
features; see the option pinentry-mode for details. Allow is
the default.

The --force option of the Assuan command DELETE_KEY is also
controlled by this option: The option is ignored if a loopback
pinentry is disallowed.

--no-allow-external-cache
Tell Pinentry not to enable features which use an external
cache for passphrases.

Some desktop environments prefer to unlock all credentials
with one master password and may have installed a Pinentry
which employs an additional external cache to implement such a
policy. By using this option the Pinentry is advised not to
make use of such a cache and instead always ask the user for
the requested passphrase.

--allow-emacs-pinentry
Tell Pinentry to allow features to divert the passphrase entry
to a running Emacs instance. How this is exactly handled
depends on the version of the used Pinentry.

--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 behavior 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. Each time a cache entry is accessed, the
entry's timer is reset. To set an entry's maximum lifetime,
use max-cache-ttl. Note that a cached passphrase may not be
evicted immediately from memory if no client requests a cache
operation. This is due to an internal housekeeping function
which is only run every few 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. Each time a cache
entry is accessed, the entry's timer is reset. To set an
entry's maximum lifetime, use max-cache-ttl-ssh.

--max-cache-ttl n
Set the maximum time a cache entry is valid to n seconds.
After this time a cache entry will be expired even if it has
been accessed recently or has been set using
gpg-preset-passphrase. 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 or has been set using
gpg-preset-passphrase. 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'' button.

--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 special characters a
warning will be displayed. Defaults to 1.

--check-passphrase-pattern file
--check-sym-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. If file does not contain any
slashes and does not start with "~/" it is searched in the
system configuration directory (`/usr/etc/gnupg'). The
default is not to use any pattern file. The second version of
this option is only used when creating a new symmetric key to
allow the use of different patterns for such passphrases.

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-invisible-char char
This option asks the Pinentry to use char for displaying
hidden characters. char must be one character UTF-8 string.
A Pinentry may or may not honor this request.

--pinentry-timeout n
This option asks the Pinentry to timeout after n seconds with
no user input. The default value of 0 does not ask the
pinentry to timeout, however a Pinentry may use its own
default timeout value in this case. A Pinentry may or may not
honor this request.

--pinentry-formatted-passphrase
This option asks the Pinentry to enable passphrase formatting
when asking the user for a new passphrase and masking of the
passphrase is turned off.

If passphrase formatting is enabled, then all non-breaking
space characters are stripped from the entered passphrase.
Passphrase formatting is mostly useful in combination with
passphrases generated with the GENPIN feature of some
Pinentries. Note that such a generated passphrase, if not
modified by the user, skips all passphrase constraints
checking because such constraints would actually weaken the
generated passphrase.

--pinentry-program filename
Use program filename as the PIN entry. The default is
installation dependent. With the default configuration the
name of the default pinentry is `pinentry'; if that file does
not exist but a `pinentry-basic' exist the latter is used.

On a Windows platform the default is to use the first existing
program from this list: `bin\pinentry.exe',
`..\Gpg4win\bin\pinentry.exe', `..\Gpg4win\pinentry.exe',
`..\GNU\GnuPG\pinentry.exe', `..\GNU\bin\pinentry.exe',
`bin\pinentry-basic.exe' where the file names are relative to
the GnuPG installation directory.

--pinentry-touch-file filename
By default the filename of the socket gpg-agent is listening
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 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 disable this self-test for
debugging purposes.

--use-standard-socket
--no-use-standard-socket
--use-standard-socket-p
Since GnuPG 2.1 the standard socket is always used. These
options have no more effect. The command gpg-agent
--use-standard-socket-p will thus always return success.

--display string
--ttyname string
--ttytype string
--lc-ctype string
--lc-messages string
--xauthority string
These options are used with the server mode to pass
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.

--listen-backlog n
Set the size of the queue for pending connections. The
default is 64.

--extra-socket name
The extra socket is created by default, you may use this
option to change the name of the socket. To disable the
creation of the socket use ``none'' or ``/dev/null'' for name.

Also listen on native gpg-agent connections on the given
socket. The intended use for this extra socket is to setup a
Unix domain socket forwarding from a remote machine to this
socket on the local machine. A gpg running on the remote
machine may then connect to the local gpg-agent and use its
private keys. This enables decrypting or signing data on a
remote machine without exposing the private keys to the remote
machine.

--enable-extended-key-format
--disable-extended-key-format
These options are obsolete and have no effect. The extended
key format is used for years now and has been supported since
2.1.12. Existing keys in the old format are migrated to the
new format as soon as they are touched.

--enable-ssh-support
--enable-putty-support

The OpenSSH Agent protocol is always enabled, but gpg-agent
will only set the SSH_AUTH_SOCK variable if this flag is
given.

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 contain a mechanism for telling the agent on
which display/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 ssh is able 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.

The --enable-putty-support is only available under Windows and allows
the use of gpg-agent with the ssh implementation putty. This is
similar to the regular ssh-agent support but makes use of Windows
message queue as required by putty.

--ssh-fingerprint-digest

Select the digest algorithm used to compute ssh fingerprints
that are communicated to the user, e.g. in pinentry dialogs.
OpenSSH has transitioned from using MD5 to the more secure
SHA256.

--auto-expand-secmem n
Allow Libgcrypt to expand its secure memory area as required.
The optional value n is a non-negative integer with a
suggested size in bytes of each additionally allocated secure
memory area. The value is rounded up to the next 32 KiB;
usual C style prefixes are allowed. For an heavy loaded gpg-
agent with many concurrent connection this option avoids sign
or decrypt errors due to out of secure memory error returns.

--s2k-calibration milliseconds
Change the default calibration time to milliseconds. The
given value is capped at 60 seconds; a value of 0 resets to
the compiled-in default. This option is re-read on a SIGHUP
(or gpgconf --reload gpg-agent) and the S2K count is then re-
calibrated.

--s2k-count n
Specify the iteration count used to protect the passphrase.
This option can be used to override the auto-calibration done
by default. The auto-calibration computes a count which
requires by default 100ms to mangle a given passphrase. See
also --s2k-calibration.

To view the actually used iteration count and the milliseconds
required for an S2K operation use:

gpg-connect-agent 'GETINFO s2k_count' /bye
gpg-connect-agent 'GETINFO s2k_time' /bye

To view the auto-calibrated count use:

gpg-connect-agent 'GETINFO s2k_count_cal' /bye

EXAMPLES

It is important to set the environment variable GPG_TTY in your login
shell, for example in the `~/.bashrc' init script:

export GPG_TTY=$(tty)

If you enabled the Ssh Agent Support, you also need to tell ssh about
it by adding this to your init script:

unset SSH_AGENT_PID
if [ "${gnupg_SSH_AUTH_SOCK_by:-0}" -ne $$ ]; then
export SSH_AUTH_SOCK="$(gpgconf --list-dirs agent-ssh-socket)"
fi

FILES

There are a few configuration files needed for the operation of the
agent. By default they may all be found in the current home directory
(see: [option --homedir]).

gpg-agent.conf
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
enables cutting and pasting 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 ultimately
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
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 disallowing interactive
updates of this file by using the [option --no-allow-mark-trusted].
It might even be 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. `/usr/etc/gnupg/trustlist.txt').
This global list is also used if the local list is not available;
the [option --no-user-trustlist] enforces the use of only
this global list.

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.

qual The CA is allowed to issue certificates for qualified signatures.
This flag has an effect only if used in the global list. This is now
the preferred way to mark such CA; the old way of having a separate
file `qualified.txt' is still supported.

de-vs The CA is part of an approved PKI for the German classification level
VS-NfD. It is only valid in the global trustlist. As of now this is
used only for documentation purpose.

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.

The following example lists exactly one key. Note that keys available
through a OpenPGP smartcard in the active smartcard reader are
implicitly added to this list; i.e. there is no need to list them.

# 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

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 `/usr/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, debug-pinentry,
no-grab, pinentry-program, pinentry-invisible-char,
default-cache-ttl, max-cache-ttl, ignore-cache-for-signing,
s2k-count, no-allow-external-cache, allow-emacs-pinentry,
no-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
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.