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1041 lines
38 KiB
Plaintext
@c Copyright (C) 2002 Klar"alvdalens Datakonsult AB
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@c Copyright (C) 2004, 2005, 2006, 2007 g10 Code GmbH
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@c This is part of the GnuPG manual.
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@c For copying conditions, see the file gnupg.texi.
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@node Invoking DIRMNGR
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@chapter Invoking DIRMNGR
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@cindex DIRMNGR command options
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@cindex command options
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@cindex options, DIRMNGR command
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@manpage dirmngr.8
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@ifset manverb
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.B dirmngr
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\- CRL and OCSP daemon
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@end ifset
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@mansect synopsis
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@ifset manverb
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.B dirmngr
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.RI [ options ]
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.I command
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.RI [ args ]
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@end ifset
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@mansect description
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Dirmngr is a server for managing and downloading certificate revocation
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lists (CRLs) for X.509 certificates and for downloading the certificates
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themselves. Dirmngr also handles OCSP requests as an alternative to
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CRLs. Dirmngr is either invoked internally by gpgsm or when running as a
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system daemon through the @command{dirmngr-client} tool.
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If @command{dirmngr} is started in system daemon mode, it uses a
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directory layout as common for system daemons and does not make use of
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the default @file{~/.gnupg} directory.
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@manpause
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@noindent
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@xref{Option Index},for an index to @command{DIRMNGR}'s commands and
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options.
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@mancont
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@menu
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* Dirmngr Commands:: List of all commands.
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* Dirmngr Options:: List of all options.
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* Dirmngr Configuration:: Configuration files.
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* Dirmngr Signals:: Use of signals.
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* Dirmngr Examples:: Some usage examples.
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* Dirmngr Protocol:: The protocol dirmngr uses.
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@end menu
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@node Dirmngr Commands
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@section Commands
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@mansect commands
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Commands are not distinguished from options except for the fact that
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only one command is allowed.
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@table @gnupgtabopt
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@item --version
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@opindex version
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Print the program version and licensing information. Note that you cannot
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abbreviate this command.
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@item --help, -h
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@opindex help
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Print a usage message summarizing the most useful command-line options.
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Not that you cannot abbreviate this command.
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@item --dump-options
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@opindex dump-options
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Print a list of all available options and commands. Note that you cannot
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abbreviate this command.
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@item --server
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@opindex server
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Run in server mode and wait for commands on the @code{stdin}. The
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default mode is to create a socket and listen for commands there.
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@item --daemon
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@opindex daemon
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Run in background daemon mode and listen for commands on a socket.
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Note that this also changes the default home directory and enables the
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internal certificate validation code.
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@item --list-crls
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@opindex list-crls
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List the contents of the CRL cache on @code{stdout}. This is probably
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only useful for debugging purposes.
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@item --load-crl @var{file}
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@opindex load-crl
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This command requires a filename as additional argument, and it will
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make Dirmngr try to import the CRL in @var{file} into it's cache.
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Note, that this is only possible if Dirmngr is able to retrieve the
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CA's certificate directly by its own means. In general it is better
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to use @code{gpgsm}'s @code{--call-dirmngr loadcrl filename} command
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so that @code{gpgsm} can help dirmngr.
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@item --fetch-crl @var{url}
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@opindex fetch-crl
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This command requires an URL as additional argument, and it will make
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dirmngr try to retrieve an import the CRL from that @var{url} into
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it's cache. This is mainly useful for debugging purposes. The
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@command{dirmngr-client} provides the same feature for a running dirmngr.
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@item --shutdown
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@opindex shutdown
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This commands shuts down an running instance of Dirmngr. This command
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has currently no effect.
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@item --flush
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@opindex flush
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This command removes all CRLs from Dirmngr's cache. Client requests
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will thus trigger reading of fresh CRLs.
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@end table
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@mansect options
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@node Dirmngr Options
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@section Option Summary
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@table @gnupgtabopt
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@item --options @var{file}
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@opindex options
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Reads configuration from @var{file} instead of from the default
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per-user configuration file. The default configuration file is named
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@file{dirmngr.conf} and expected in the home directory.
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@item --homedir @var{dir}
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@opindex options
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Set the name of the home directory to @var{dir}. This option is only
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effective when used on the command line. The default depends on the
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running mode:
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@table @asis
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@item With @code{--daemon} given on the commandline
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the directory named @file{/etc/gnupg} for configuration files,
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@file{/var/lib/gnupg/} for extra data and @file{/var/cache/gnupg}
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for cached CRLs.
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@item Without @code{--daemon} given on the commandline
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the directory named @file{.gnupg} directly below the home directory
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of the user unless the environment variable @code{GNUPGHOME} has been set
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in which case its value will be used. All kind of data is stored below
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this directory.
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@end table
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@item -v
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@item --verbose
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@opindex v
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@opindex verbose
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Outputs additional information while running.
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You can increase the verbosity by giving several
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verbose commands to @sc{dirmngr}, such as @option{-vv}.
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@item --log-file @var{file}
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@opindex log-file
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Append all logging output to @var{file}. This is very helpful in
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seeing what the agent actually does.
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@item --debug-level @var{level}
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@opindex debug-level
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Select the debug level for investigating problems. @var{level} may be a
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numeric value or by a keyword:
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@table @code
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@item none
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No debugging at all. A value of less than 1 may be used instead of
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the keyword.
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@item basic
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Some basic debug messages. A value between 1 and 2 may be used
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instead of the keyword.
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@item advanced
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More verbose debug messages. A value between 3 and 5 may be used
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instead of the keyword.
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@item expert
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Even more detailed messages. A value between 6 and 8 may be used
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instead of the keyword.
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@item guru
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All of the debug messages you can get. A value greater than 8 may be
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used instead of the keyword. The creation of hash tracing files is
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only enabled if the keyword is used.
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@end table
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How these messages are mapped to the actual debugging flags is not
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specified and may change with newer releases of this program. They are
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however carefully selected to best aid in debugging.
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@item --debug @var{flags}
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@opindex debug
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This option is only useful for debugging and the behaviour may change at
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any time without notice. FLAGS are bit encoded and may be given in
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usual C-Syntax.
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@item --debug-all
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@opindex debug-all
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Same as @code{--debug=0xffffffff}
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@item --debug-wait @var{n}
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@opindex debug-wait
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When running in server mode, wait @var{n} seconds before entering the
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actual processing loop and print the pid. This gives time to attach a
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debugger.
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@item -s
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@itemx --sh
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@itemx -c
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@itemx --csh
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@opindex s
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@opindex sh
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@opindex c
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@opindex csh
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Format the info output in daemon mode for use with the standard Bourne
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shell respective the C-shell . The default ist to guess it based on the
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environment variable @code{SHELL} which is in almost all cases
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sufficient.
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@item --force
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@opindex force
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Enabling this option forces loading of expired CRLs; this is only
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useful for debugging.
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@item --disable-ldap
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@opindex disable-ldap
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Entirely disables the use of LDAP.
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@item --disable-http
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@opindex disable-http
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Entirely disables the use of HTTP.
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@item --ignore-http-dp
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@opindex ignore-http-dp
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When looking for the location of a CRL, the to be tested certificate
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usually contains so called @dfn{CRL Distribution Point} (DP) entries
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which are URLs describing the way to access the CRL. The first found DP
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entry is used. With this option all entries using the @acronym{HTTP}
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scheme are ignored when looking for a suitable DP.
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@item --ignore-ldap-dp
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@opindex ignore-ldap-dp
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This is similar to @option{--ignore-http-dp} but ignores entries using
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the @acronym{LDAP} scheme. Both options may be combined resulting in
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ignoring DPs entirely.
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@item --ignore-ocsp-service-url
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@opindex ignore-ocsp-service-url
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Ignore all OCSP URLs contained in the certificate. The effect is to
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force the use of the default responder.
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@item --honor-http-proxy
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@opindex honor-http-proxy
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If the environment variable @env{http_proxy} has been set, use its
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value to access HTTP servers.
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@item --http-proxy @var{host}[:@var{port}]
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@opindex http-proxy
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Use @var{host} and @var{port} to access HTTP servers. The use of this
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options overrides the environment variable @env{http_proxy} regardless
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whether @option{--honor-http-proxy} has been set.
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@item --ldap-proxy @var{host}[:@var{port}]
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@opindex ldap-proxy
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Use @var{host} and @var{port} to connect to LDAP servers. If @var{port}
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is ommitted, port 389 (standard LDAP port) is used. This overrides any
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specified host and port part in a LDAP URL and will also be used if host
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and port have been ommitted from the URL.
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@item --only-ldap-proxy
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@opindex only-ldap-proxy
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Never use anything else but the LDAP "proxy" as configured with
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@option{--ldap-proxy}. Usually @command{dirmngr} tries to use other
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configured LDAP server if the connection using the "proxy" failed.
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@item --ldapserverlist-file @var{file}
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@opindex ldapserverlist-file
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Read the list of LDAP servers to consult for CRLs and certificates from
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file instead of the default per-user ldap server list file. The default
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value for @var{file} is @file{dirmngr_ldapservers.conf} or
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@file{ldapservers.conf} when running in @option{--daemon} mode.
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This server list file contains one LDAP server per line in the format
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@sc{hostname:port:username:password:base_dn}
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Lines starting with a @samp{#} are comments.
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Note that as usual all strings entered are expected to be UTF-8 encoded.
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Obviously this will lead to problems if the password has orginally been
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encoded as Latin-1. There is no other solution here than to put such a
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password in the binary encoding into the file (i.e. non-ascii characters
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won't show up readable).@footnote{The @command{gpgconf} tool might be
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helpful for frontends as it allows to edit this configuration file using
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percent escaped strings.}
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@item --ldaptimeout @var{secs}
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@opindex ldaptimeout
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Specify the number of seconds to wait for an LDAP query before timing
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out. The default is currently 100 seconds. 0 will never timeout.
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@item --add-servers
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@opindex add-servers
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This options makes dirmngr add any servers it discovers when validating
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certificates against CRLs to the internal list of servers to consult for
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certificates and CRLs.
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This options is useful when trying to validate a certificate that has
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a CRL distribution point that points to a server that is not already
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listed in the ldapserverlist. Dirmngr will always go to this server and
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try to download the CRL, but chances are high that the certificate used
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to sign the CRL is located on the same server. So if dirmngr doesn't add
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that new server to list, it will often not be able to verify the
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signature of the CRL unless the @code{--add-servers} option is used.
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Note: The current version of dirmngr has this option disabled by default.
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@item --allow-ocsp
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@opindex allow-ocsp
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This option enables OCSP support if requested by the client.
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OCSP requests are rejected by default because they may violate the
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privacy of the user; for example it is possible to track the time when
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a user is reading a mail.
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@item --ocsp-responder @var{url}
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@opindex ocsp-responder
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Use @var{url} as the default OCSP Responder if the certificate does
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not contain information about an assigned responder. Note, that
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@code{--ocsp-signer} must also be set to a valid certificate.
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@item --ocsp-signer @var{fpr}|@var{file}
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@opindex ocsp-signer
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Use the certificate with the fingerprint @var{fpr} to check the
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responses of the default OCSP Responder. Alternativly a filename can be
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given in which case the respinse is expected to be signed by one of the
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certificates described in that file. Any argument which contains a
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slash, dot or tilde is considered a filename. Usual filename expansion
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takes place: A tilde at the start followed by a slash is replaced by the
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content of @env{HOME}, no slash at start describes a relative filename
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which will be searched at the home directory. To make sure that the
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@var{file} is searched in the home directory, either prepend the name
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with "./" or use a name which contains a dot.
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If a response has been signed by a certificate described by these
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fingerprints no further check upon the validity of this certificate is
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done.
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The format of the @var{FILE} is a list of SHA-1 fingerprint, one per
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line with optional colons between the bytes. Empty lines and lines
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prefix with a hash mark are ignored.
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@item --ocsp-max-clock-skew @var{n}
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@opindex ocsp-max-clock-skew
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The number of seconds a skew between the OCSP responder and them local
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clock is accepted. Default is 600 (20 minutes).
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@item --ocsp-max-period @var{n}
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@opindex ocsp-max-period
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Seconds a response is at maximum considered valid after the time given
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in the thisUpdate field. Default is 7776000 (90 days).
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@item --ocsp-current-period @var{n}
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@opindex ocsp-current-period
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The number of seconds an OCSP response is considered valid after the
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time given in the NEXT_UPDATE datum. Default is 10800 (3 hours).
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@item --max-replies @var{n}
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@opindex max-replies
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Do not return more that @var{n} items in one query. The default is
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10.
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@item --ignore-cert-extension @var{oid}
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@opindex ignore-cert-extension
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Add @var{oid} to the list of ignored certificate extensions. The
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@var{oid} is expected to be in dotted decimal form, like
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@code{2.5.29.3}. This option may be used more than once. Critical
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flagged certificate extensions matching one of the OIDs in the list
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are treated as if they are actually handled and thus the certificate
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won't be rejected due to an unknown critical extension. Use this
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option with care because extensions are usually flagged as critical
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for a reason.
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@end table
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@c
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@c Dirmngr Configuration
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@c
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@mansect files
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@node Dirmngr Configuration
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@section Configuration
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Dirmngr makes use of several directories when running in daemon mode:
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@table @file
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@item /etc/gnupg
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This is where all the configuration files are expected by default.
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@item /etc/gnupg/trusted-certs
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This directory should be filled with certificates of Root CAs you are
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trusting in checking the CRLS and signing OCSP Reponses. Usually
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these are the same certificates you use with the applications making
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use of dirmngr. It is expected that each of these certificate files
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contain exactly one @acronym{DER} encoded certificate in a file with
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the suffix @file{.crt} or @file{.der}. @command{dirmngr} reads those
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certificates on startup and when given a SIGHUP. Certificates which
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are not readable or do not make up a proper X.509 certificate are
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ignored; see the log file for details.
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Note that for OCSP responses the certificate specified using the option
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@option{--ocsp-signer} is always considered valid to sign OCSP requests.
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@item /var/lib/gnupg/extra-certs
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This directory may contain extra certificates which are preloaded into
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the interal cache on startup. This is convenient in cases you have a
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couple intermediate CA certificates or certificates ususally used to
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sign OCSP reponses. These certificates are first tried before going out
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to the net to look for them. These certificates must also be
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@acronym{DER} encoded and suffixed with @file{.crt} or @file{.der}.
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@item /var/run/gnupg
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This directory keeps the socket file for accsing @command{dirmngr} services.
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The name of the socket file will be @file{S.dirmngr}. Make sure that this
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directory has the proper permissions to let @command{dirmngr} create the
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socket file and that eligible users may read and write to that socket.
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@item /var/cache/gnupg/crls.d
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This directory is used to store cached CRLs. The @file{crls.d} part
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will be created by dirmngr if it does not exists but you need to make
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sure that the upper directory exists.
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@end table
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@manpause
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To be able to see what's going on you should create the configure file
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@file{/etc/dirmngr/dirmngr.conf} with at least one line:
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@example
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log-file /var/log/gnupg/dirmngr.log
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@end example
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To be able to perform OCSP requests you probably want to add the line:
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@example
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allow-ocsp
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@end example
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Now you may start dirmngr as a system daemon using:
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@example
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dirmngr --daemon
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@end example
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Please ignore the output; it is not needed anymore. Check the log file
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to see whether all trusted root certificates have been loaded correctly.
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@c
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@c Dirmngr Signals
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@c
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@mansect signals
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@node Dirmngr Signals
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@section Use of signals.
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A running @command{dirmngr} may be controlled by signals, i.e. using
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the @command{kill} command to send a signal to the process.
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Here is a list of supported signals:
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@table @gnupgtabopt
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@item SIGHUP
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@cpindex SIGHUP
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This signals flushes all internally cached CRLs as well as any cached
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certificates. Then the certificate cache is reinitialized as on
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startup. Options are re-read from the configuration file.
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@item SIGTERM
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@cpindex SIGTERM
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Shuts down the process but waits until all current requests are
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fulfilled. If the process has received 3 of these signals and requests
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are still pending, a shutdown is forced.
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@item SIGINT
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@cpindex SIGINT
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Shuts down the process immediately.
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@item SIGUSR1
|
|
@cpindex SIGUSR1
|
|
This prints some caching statistics to the log file.
|
|
|
|
@end table
|
|
|
|
|
|
|
|
@c
|
|
@c Examples
|
|
@c
|
|
@mansect examples
|
|
@node Dirmngr Examples
|
|
@section Examples
|
|
|
|
|
|
Dirmngr is supposed to be used as a system wide daemon, it should be
|
|
started like:
|
|
|
|
@example
|
|
dirmngr --daemon
|
|
@end example
|
|
|
|
This will force it to go into the backround, read the default
|
|
certificates (including the trusted root certificates) and listen on a
|
|
socket for client requests. It does also print information about the
|
|
socket used but they are only for compatibilty reasons with old GnuPG
|
|
versions and may be ignored.
|
|
|
|
For debugging purposes it is also possible to start Dirmngr in the
|
|
foreground:
|
|
|
|
@example
|
|
dirmngr --server -v
|
|
@end example
|
|
|
|
|
|
|
|
@c
|
|
@c Assuan Protocol
|
|
@c
|
|
@manpause
|
|
@node Dirmngr Protocol
|
|
@section Dirmngr's Assuan Protocol
|
|
|
|
Assuan is the IPC protocol used to access dirmngr. This is a
|
|
description of the commands implemented by dirmngr.
|
|
|
|
@menu
|
|
* Dirmngr LOOKUP:: Look up a certificate via LDAP
|
|
* Dirmngr ISVALID:: Validate a certificate using a CRL or OCSP.
|
|
* Dirmngr CHECKCRL:: Validate a certificate using a CRL.
|
|
* Dirmngr CHECKOCSP:: Validate a certificate using OCSP.
|
|
* Dirmngr CACHECERT:: Put a certificate into the internal cache.
|
|
* Dirmngr VALIDATE:: Validate a certificate for debugging.
|
|
@end menu
|
|
|
|
@node Dirmngr LOOKUP
|
|
@subsection Return the certificate(s) found
|
|
|
|
Lookup certificate. To allow multiple patterns (which are ORed)
|
|
quoting is required: Spaces are to be translated into "+" or into
|
|
"%20"; obviously this requires that the usual escape quoting rules
|
|
are applied. The server responds with:
|
|
|
|
@example
|
|
S: D <DER encoded certificate>
|
|
S: END
|
|
S: D <second DER encoded certificate>
|
|
S: END
|
|
S: OK
|
|
@end example
|
|
|
|
In this example 2 certificates are returned. The server may return
|
|
any number of certificates; OK will also be returned when no
|
|
certificates were found. The dirmngr might return a status line
|
|
|
|
@example
|
|
S: S TRUNCATED <n>
|
|
@end example
|
|
|
|
|
|
To indicate that the output was truncated to N items due to a
|
|
limitation of the server or by an arbitrary set limit.
|
|
|
|
The option @option{--url} may be used if instead of a search pattern a
|
|
complete URL to the certificate is known:
|
|
|
|
@example
|
|
C: LOOKUP --url CN%3DWerner%20Koch,o%3DIntevation%20GmbH,c%3DDE?userCertificate
|
|
@end example
|
|
|
|
If the option @option{--cache-only} is given, no external lookup is done
|
|
so that only certificates from the cache are returned.
|
|
|
|
With the option @option{--single}, the first and only the first match
|
|
will be returned. Unless option @option{--cache-only} is also used, no
|
|
local lookup will be done in this case.
|
|
|
|
|
|
|
|
@node Dirmngr ISVALID
|
|
@subsection Validate a certificate using a CRL or OCSP
|
|
|
|
@example
|
|
ISVALID [--only-ocsp] [--force-default-responder] @var{certid}|@var{certfpr}
|
|
@end example
|
|
|
|
Check whether the certificate described by the @var{certid} has been
|
|
revoked. Due to caching, the Dirmngr is able to answer immediately in
|
|
most cases.
|
|
|
|
The @var{certid} is a hex encoded string consisting of two parts,
|
|
delimited by a single dot. The first part is the SHA-1 hash of the
|
|
issuer name and the second part the serial number.
|
|
|
|
Alternatively the certificate's SHA-1 fingerprint @var{certfpr} may be
|
|
given in which case an OCSP request is done before consulting the CRL.
|
|
If the option @option{--only-ocsp} is given, no fallback to a CRL check
|
|
will be used. If the option @option{--force-default-responder} is
|
|
given, only the default OCSP responder will be used and any other
|
|
methods of obtaining an OCSP responder URL won't be used.
|
|
|
|
@noindent
|
|
Common return values are:
|
|
|
|
@table @code
|
|
@item GPG_ERR_NO_ERROR (0)
|
|
This is the positive answer: The certificate is not revoked and we have
|
|
an up-to-date revocation list for that certificate. If OCSP was used
|
|
the responder confirmed that the certificate has not been revoked.
|
|
|
|
@item GPG_ERR_CERT_REVOKED
|
|
This is the negative answer: The certificate has been revoked. Either
|
|
it is in a CRL and that list is up to date or an OCSP responder informed
|
|
us that it has been revoked.
|
|
|
|
@item GPG_ERR_NO_CRL_KNOWN
|
|
No CRL is known for this certificate or the CRL is not valid or out of
|
|
date.
|
|
|
|
@item GPG_ERR_NO_DATA
|
|
The OCSP responder returned an ``unknown'' status. This means that it
|
|
is not aware of the certificate's status.
|
|
|
|
@item GPG_ERR_NOT_SUPPORTED
|
|
This is commonly seen if OCSP support has not been enabled in the
|
|
configuration.
|
|
@end table
|
|
|
|
If DirMngr has not enough information about the given certificate (which
|
|
is the case for not yet cached certificates), it will will inquire the
|
|
missing data:
|
|
|
|
@example
|
|
S: INQUIRE SENDCERT <CertID>
|
|
C: D <DER encoded certificate>
|
|
C: END
|
|
@end example
|
|
|
|
A client should be aware that DirMngr may ask for more than one
|
|
certificate.
|
|
|
|
If Dirmngr has a certificate but the signature of the certificate
|
|
could not been validated because the root certificate is not known to
|
|
dirmngr as trusted, it may ask back to see whether the client trusts
|
|
this the root certificate:
|
|
|
|
@example
|
|
S: INQUIRE ISTRUSTED <CertHexfpr>
|
|
C: D 1
|
|
C: END
|
|
@end example
|
|
|
|
Only this answer will let Dirmngr consider the CRL as valid.
|
|
|
|
|
|
@node Dirmngr CHECKCRL
|
|
@subsection Validate a certificate using a CRL
|
|
|
|
Check whether the certificate with FINGERPRINT (SHA-1 hash of the
|
|
entire X.509 certificate blob) is valid or not by consulting the CRL
|
|
responsible for this certificate. If the fingerprint has not been
|
|
given or the certificate is not know, the function inquires the
|
|
certificate using:
|
|
|
|
@example
|
|
S: INQUIRE TARGETCERT
|
|
C: D <DER encoded certificate>
|
|
C: END
|
|
@end example
|
|
|
|
Thus the caller is expected to return the certificate for the request
|
|
(which should match FINGERPRINT) as a binary blob. Processing then
|
|
takes place without further interaction; in particular dirmngr tries
|
|
to locate other required certificate by its own mechanism which
|
|
includes a local certificate store as well as a list of trusted root
|
|
certificates.
|
|
|
|
@noindent
|
|
The return code is 0 for success; i.e. the certificate has not been
|
|
revoked or one of the usual error codes from libgpg-error.
|
|
|
|
@node Dirmngr CHECKOCSP
|
|
@subsection Validate a certificate using OCSP
|
|
|
|
@example
|
|
CHECKOCSP [--force-default-responder] [@var{fingerprint}]
|
|
@end example
|
|
|
|
Check whether the certificate with @var{fingerprint} (the SHA-1 hash of
|
|
the entire X.509 certificate blob) is valid by consulting the appropiate
|
|
OCSP responder. If the fingerprint has not been given or the
|
|
certificate is not known by Dirmngr, the function inquires the
|
|
certificate using:
|
|
|
|
@example
|
|
S: INQUIRE TARGETCERT
|
|
C: D <DER encoded certificate>
|
|
C: END
|
|
@end example
|
|
|
|
Thus the caller is expected to return the certificate for the request
|
|
(which should match @var{fingerprint}) as a binary blob. Processing
|
|
then takes place without further interaction; in particular dirmngr
|
|
tries to locate other required certificates by its own mechanism which
|
|
includes a local certificate store as well as a list of trusted root
|
|
certificates.
|
|
|
|
If the option @option{--force-default-responder} is given, only the
|
|
default OCSP responder is used. This option is the per-command variant
|
|
of the global option @option{--ignore-ocsp-service-url}.
|
|
|
|
|
|
@noindent
|
|
The return code is 0 for success; i.e. the certificate has not been
|
|
revoked or one of the usual error codes from libgpg-error.
|
|
|
|
@node Dirmngr CACHECERT
|
|
@subsection Put a certificate into the internal cache
|
|
|
|
Put a certificate into the internal cache. This command might be
|
|
useful if a client knows in advance certificates required for a test and
|
|
wnats to make sure they get added to the internal cache. It is also
|
|
helpful for debugging. To get the actual certificate, this command
|
|
immediately inquires it using
|
|
|
|
@example
|
|
S: INQUIRE TARGETCERT
|
|
C: D <DER encoded certificate>
|
|
C: END
|
|
@end example
|
|
|
|
Thus the caller is expected to return the certificate for the request
|
|
as a binary blob.
|
|
|
|
@noindent
|
|
The return code is 0 for success; i.e. the certificate has not been
|
|
succesfully cached or one of the usual error codes from libgpg-error.
|
|
|
|
@node Dirmngr VALIDATE
|
|
@subsection Validate a certificate for debugging
|
|
|
|
Validate a certificate using the certificate validation function used
|
|
internally by dirmngr. This command is only useful for debugging. To
|
|
get the actual certificate, this command immediately inquires it using
|
|
|
|
@example
|
|
S: INQUIRE TARGETCERT
|
|
C: D <DER encoded certificate>
|
|
C: END
|
|
@end example
|
|
|
|
Thus the caller is expected to return the certificate for the request
|
|
as a binary blob.
|
|
|
|
|
|
@mansect see also
|
|
@ifset isman
|
|
@command{gpgsm}(1),
|
|
@command{dirmngr-client}(1)
|
|
@end ifset
|
|
@include see-also-note.texi
|
|
|
|
@c
|
|
@c !!! UNDER CONSTRUCTION !!!
|
|
@c
|
|
@c
|
|
@c @section Verifying a Certificate
|
|
@c
|
|
@c There are several ways to request services from Dirmngr. Almost all of
|
|
@c them are done using the Assuan protocol. What we describe here is the
|
|
@c Assuan command CHECKCRL as used for example by the dirmnr-client tool if
|
|
@c invoked as
|
|
@c
|
|
@c @example
|
|
@c dirmngr-client foo.crt
|
|
@c @end example
|
|
@c
|
|
@c This command will send an Assuan request to an already running Dirmngr
|
|
@c instance. foo.crt is expected to be a standard X.509 certificate and
|
|
@c dirmngr will receive the Assuan command
|
|
@c
|
|
@c @example
|
|
@c CHECKCRL @var [{fingerprint}]
|
|
@c @end example
|
|
@c
|
|
@c @var{fingerprint} is optional and expected to be the SHA-1 has of the
|
|
@c DER encoding of the certificate under question. It is to be HEX
|
|
@c encoded. The rationale for sending the fingerprint is that it allows
|
|
@c dirmngr to reply immediatly if it has already cached such a request. If
|
|
@c this is not the case and no certificate has been found in dirmngr's
|
|
@c internal certificate storage, dirmngr will request the certificate using
|
|
@c the Assuan inquiry
|
|
@c
|
|
@c @example
|
|
@c INQUIRE TARGETCERT
|
|
@c @end example
|
|
@c
|
|
@c The caller (in our example dirmngr-client) is then expected to return
|
|
@c the certificate for the request (which should match @var{fingerprint})
|
|
@c as a binary blob.
|
|
@c
|
|
@c Dirmngr now passes control to @code{crl_cache_cert_isvalid}. This
|
|
@c function checks whether a CRL item exists for target certificate. These
|
|
@c CRL items are kept in a database of already loaded and verified CRLs.
|
|
@c This mechanism is called the CRL cache. Obviously timestamps are kept
|
|
@c there with each item to cope with the expiration date of the CRL. The
|
|
@c possible return values are: @code{0} to indicate that a valid CRL is
|
|
@c available for the certificate and the certificate itself is not listed
|
|
@c in this CRL, @code{GPG_ERR_CERT_REVOKED} to indicate that the certificate is
|
|
@c listed in the CRL or @code{GPG_ERR_NO_CRL_KNOWN} in cases where no CRL or no
|
|
@c information is available. The first two codes are immediatly returned to
|
|
@c the caller and the processing of this request has been done.
|
|
@c
|
|
@c Only the @code{GPG_ERR_NO_CRL_KNOWN} needs more attention: Dirmngr now
|
|
@c calls @code{clr_cache_reload_crl} and if this succeeds calls
|
|
@c @code{crl_cache_cert_isvald) once more. All further errors are
|
|
@c immediately returned to the caller.
|
|
@c
|
|
@c @code{crl_cache_reload_crl} is the actual heart of the CRL management.
|
|
@c It locates the corresponding CRL for the target certificate, reads and
|
|
@c verifies this CRL and stores it in the CRL cache. It works like this:
|
|
@c
|
|
@c * Loop over all crlDPs in the target certificate.
|
|
@c * If the crlDP is invalid immediately terminate the loop.
|
|
@c * Loop over all names in the current crlDP.
|
|
@c * If the URL scheme is unknown or not enabled
|
|
@c (--ignore-http-dp, --ignore-ldap-dp) continues with
|
|
@c the next name.
|
|
@c * @code{crl_fetch} is called to actually retrieve the CRL.
|
|
@c In case of problems this name is ignore and we continue with
|
|
@c the next name. Note that @code{crl_fetch} does only return
|
|
@c a descriptor for the CRL for further reading so does the CRL
|
|
@c does not yet end up in memory.
|
|
@c * @code{crl_cache_insert} is called with that descriptor to
|
|
@c actually read the CRL into the cache. See below for a
|
|
@c description of this function. If there is any error (e.g. read
|
|
@c problem, CRL not correctly signed or verification of signature
|
|
@c not possible), this descriptor is rejected and we continue
|
|
@c with the next name. If the CRL has been successfully loaded,
|
|
@c the loop is terminated.
|
|
@c * If no crlDP has been found in the previous loop use a default CRL.
|
|
@c Note, that if any crlDP has been found but loading of the CRL failed,
|
|
@c this condition is not true.
|
|
@c * Try to load a CRL from all configured servers (ldapservers.conf)
|
|
@c in turn. The first server returning a CRL is used.
|
|
@c * @code(crl_cache_insert) is then used to actually insert the CRL
|
|
@c into the cache. If this failed we give up immediatley without
|
|
@c checking the rest of the servers from the first step.
|
|
@c * Ready.
|
|
@c
|
|
@c
|
|
@c The @code{crl_cache_insert} function takes care of reading the bulk of
|
|
@c the CRL, parsing it and checking the signature. It works like this: A
|
|
@c new database file is created using a temporary file name. The CRL
|
|
@c parsing machinery is started and all items of the CRL are put into
|
|
@c this database file. At the end the issuer certificate of the CRL
|
|
@c needs to be retrieved. Three cases are to be distinguished:
|
|
@c
|
|
@c a) An authorityKeyIdentifier with an issuer and serialno exits: The
|
|
@c certificate is retrieved using @code{find_cert_bysn}. If
|
|
@c the certificate is in the certificate cache, it is directly
|
|
@c returned. Then the requester (i.e. the client who requested the
|
|
@c CRL check) is asked via the Assuan inquiry ``SENDCERT'' whether
|
|
@c he can provide this certificate. If this succeed the returned
|
|
@c certificate gets cached and returned. Note, that dirmngr does not
|
|
@c verify in any way whether the expected certificate is returned.
|
|
@c It is in the interest of the client to return a useful certificate
|
|
@c as otherwise the service request will fail due to a bad signature.
|
|
@c The last way to get the certificate is by looking it up at
|
|
@c external resources. This is done using the @code{ca_cert_fetch}
|
|
@c and @code{fetch_next_ksba_cert} and comparing the returned
|
|
@c certificate to match the requested issuer and seriano (This is
|
|
@c needed because the LDAP layer may return several certificates as
|
|
@c LDAP as no standard way to retrieve by serial number).
|
|
@c
|
|
@c b) An authorityKeyIdentifier with a key ID exists: The certificate is
|
|
@c retrieved using @code{find_cert_bysubject}. If the certificate is
|
|
@c in the certificate cache, it is directly returned. Then the
|
|
@c requester is asked via the Assuan inquiry ``SENDCERT_SKI'' whether
|
|
@c he can provide this certificate. If this succeed the returned
|
|
@c certificate gets cached and returned. Note, that dirmngr does not
|
|
@c verify in any way whether the expected certificate is returned.
|
|
@c It is in the interest of the client to return a useful certificate
|
|
@c as otherwise the service request will fail due to a bad signature.
|
|
@c The last way to get the certificate is by looking it up at
|
|
@c external resources. This is done using the @code{ca_cert_fetch}
|
|
@c and @code{fetch_next_ksba_cert} and comparing the returned
|
|
@c certificate to match the requested subject and key ID.
|
|
@c
|
|
@c c) No authorityKeyIdentifier exits: The certificate is retrieved
|
|
@c using @code{find_cert_bysubject} without the key ID argument. If
|
|
@c the certificate is in the certificate cache the first one with a
|
|
@c matching subject is is directly returned. Then the requester is
|
|
@c asked via the Assuan inquiry ``SENDCERT'' and an exact
|
|
@c specification of the subject whether he can
|
|
@c provide this certificate. If this succeed the returned
|
|
@c certificate gets cached and returned. Note, that dirmngr does not
|
|
@c verify in any way whether the expected certificate is returned.
|
|
@c It is in the interest of the client to return a useful certificate
|
|
@c as otherwise the service request will fail due to a bad signature.
|
|
@c The last way to get the certificate is by looking it up at
|
|
@c external resources. This is done using the @code{ca_cert_fetch}
|
|
@c and @code{fetch_next_ksba_cert} and comparing the returned
|
|
@c certificate to match the requested subject; the first certificate
|
|
@c with a matching subject is then returned.
|
|
@c
|
|
@c If no certificate was found, the function returns with the error
|
|
@c GPG_ERR_MISSING_CERT. Now the signature is verified. If this fails,
|
|
@c the erro is returned. On success the @code{validate_cert_chain} is
|
|
@c used to verify that the certificate is actually valid.
|
|
@c
|
|
@c Here we may encounter a recursive situation:
|
|
@c @code{validate_cert_chain} needs to look at other certificates and
|
|
@c also at CRLs to check whether tehse other certificates and well, the
|
|
@c CRL issuer certificate itself are not revoked. FIXME: We need to make
|
|
@c sure that @code{validate_cert_chain} does not try to lookup the CRL we
|
|
@c are currently processing. This would be a catch-22 and may indicate a
|
|
@c broken PKI. However, due to overlapping expiring times and imprecise
|
|
@c clocks thsi may actually happen.
|
|
@c
|
|
@c For historical reasons the Assuan command ISVALID is a bit different
|
|
@c to CHECKCRL but this is mainly due to different calling conventions.
|
|
@c In the end the same fucntionality is used, albeit hidden by a couple
|
|
@c of indirection and argument and result code mangling. It furthere
|
|
@c ingetrages OCSP checking depending on options are the way it is
|
|
@c called. GPGSM still uses this command but might eventuall switch over
|
|
@c to CHECKCRL and CHECKOCSP so that ISVALID can be retired.
|
|
@c
|
|
@c
|
|
@c @section Validating a certificate
|
|
@c
|
|
@c We describe here how the internal function @code{validate_cert_chain}
|
|
@c works. Note that mainly testing purposes this functionality may be
|
|
@c called directly using @cmd{dirmngr-client --validate @file{foo.crt}}.
|
|
@c
|
|
@c For backward compatibility this function returns success if Dirmngr is
|
|
@c not used as a system daemon. Thus not validating the certicates at
|
|
@c all. FIXME: This is definitely not correct and should be fixed ASAP.
|
|
@c
|
|
@c The function takes the target certificate and a mode argument as
|
|
@c parameters and returns an error code and optionally the closes
|
|
@c expiration time of all certificates in the chain.
|
|
@c
|
|
@c We first check that the certificate may be used for the requested
|
|
@c purpose (i.e. OCSP or CRL signing). If this is not the case
|
|
@c GPG_ERR_WRONG_KEY_USAGE is returned.
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@c
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@c The next step is to find the trust anchor (root certificate) and to
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@c assemble the chain in memory: Starting with the target certificate,
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@c the expiration time is checked against the current date, unknown
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@c critical extensions are detected and certificate policies are matched
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@c (We only allow 2.289.9.9 but I have no clue about that OID and from
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@c where I got it - it does not even seem to be assigned - debug cruft?).
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@c
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@c Now if this certificate is a self-signed one, we have reached the
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@c trust anchor. In this case we check that the signature is good, the
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@c certificate is allowed to act as a CA, that it is a trusted one (by
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@c checking whether it is has been put into the trusted-certs
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@c configuration directory) and finally prepend into to our list
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@c representing the certificate chain. This steps ends then.
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@c
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@c If it is not a self-signed certificate, we check that the chain won't
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@c get too long (current limit is 100), if this is the case we terminate
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@c with the error GPG_ERR_BAD_CERT_CHAIN.
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@c
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@c Now the issuer's certificate is looked up: If an
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@c authorityKeyIdentifier is available, this one is used to locate the
|
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@c certificate either using issuer and serialnumber or subject DN
|
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@c (i.e. the issuer's DN) and the keyID. The functions
|
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@c @code{find_cert_bysn) and @code{find_cert_bysubject} are used
|
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@c respectively. The have already been described above under the
|
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@c description of @code{crl_cache_insert}. If no certificate was found
|
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@c or with no authorityKeyIdentifier, only the cache is consulted using
|
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@c @code{get_cert_bysubject}. The latter is is done under the assumption
|
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@c that a matching certificate has explicitly been put into the
|
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@c certificate cache. If the issuer's certificate could not be found,
|
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@c the validation terminates with the error code @code{GPG_ERR_MISSING_CERT}.
|
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@c
|
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@c If the issuer's certificate has been found, the signature of the
|
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@c actual certificate is checked and in case this fails the error
|
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@c #code{GPG_ERR_BAD_CERT_CHAIN} is returned. If the signature checks out, the
|
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@c maximum cahin length of the issueing certificate is checked as well as
|
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@c the capiblity of the certificate (i.e. whether he may be used for
|
|
@c certificate signing). Then the certificate is prepended to our list
|
|
@c representing the certificate chain. Finally the loop is continued now
|
|
@c with the issuer's certificate as the current certificate.
|
|
@c
|
|
@c After the end of the loop and if no error as been encountered
|
|
@c (i.e. the certificate chain has been assempled correctly), a check is
|
|
@c done whether any certificate expired or a critical policy has not been
|
|
@c met. In any of these cases the validation terminates with an
|
|
@c appropriate error.
|
|
@c
|
|
@c Finally the function @code{check_revocations} is called to verify no
|
|
@c certificate in the assempled chain has been revoked: This is an
|
|
@c recursive process because a CRL has to be checked for each certificate
|
|
@c in the chain except for the root certificate, of which we already know
|
|
@c that it is trusted and we avoid checking a CRL here due to common
|
|
@c setup problems and the assumption that a revoked root certifcate has
|
|
@c been removed from the list of trusted certificates.
|
|
@c
|
|
@c
|
|
@c
|
|
@c
|
|
@c @section Looking up certificates through LDAP.
|
|
@c
|
|
@c This describes the LDAP layer to retrieve certificates.
|
|
@c the functions @code{ca_cert_fetch} and @code{fetch_next_ksba_cert} are
|
|
@c used for this. The first one starts a search and the second one is
|
|
@c used to retrieve certificate after certificate.
|
|
@c
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