NAME¶
gpgsm - CMS encryption and signing tool
SYNOPSIS¶
gpgsm [
--homedir dir] [
--options file]
[
options]
command [
args]
DESCRIPTION¶
gpgsm is a tool similar to
gpg to provide digital encryption and
signing services on X.509 certificates and the CMS protocol. It is mainly used
as a backend for S/MIME mail processing.
gpgsm includes a full featured
certificate management and complies with all rules defined for the German
Sphinx project.
COMMANDS¶
Commands are not distinguished from options except for the fact that only one
command is allowed.
Commands not specific to the function¶
- --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.
- --warranty
- Print warranty information. 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.
Commands to select the type of operation¶
- --encrypt
- Perform an encryption. The keys the data is encrypted too
must be set using the option --recipient.
- --decrypt
- Perform a decryption; the type of input is automatically
determined. It may either be in binary form or PEM encoded; automatic
determination of base-64 encoding is not done.
- --sign
- Create a digital signature. The key used is either the fist
one found in the keybox or those set with the --local-user option.
- --verify
- Check a signature file for validity. Depending on the
arguments a detached signature may also be checked.
- --server
- Run in server mode and wait for commands on the
stdin.
- --call-dirmngr command [args]
- Behave as a Dirmngr client issuing the request
command with the optional list of args. The output of the
Dirmngr is printed stdout. Please note that file names given as arguments
should have an absolute file name (i.e. commencing with / because
they are passed verbatim to the Dirmngr and the working directory of the
Dirmngr might not be the same as the one of this client. Currently it is
not possible to pass data via stdin to the Dirmngr. command should
not contain spaces.
This is command is required for certain maintaining tasks of the dirmngr
where a dirmngr must be able to call back to gpgsm. See the Dirmngr
manual for details.
- --call-protect-tool arguments
- Certain maintenance operations are done by an external
program call gpg-protect-tool; this is usually not installed in a
directory listed in the PATH variable. This command provides a simple
wrapper to access this tool. arguments are passed verbatim to this
command; use '--help' to get a list of supported operations.
How to manage the certificates and keys¶
- --gen-key
- -This command allows the creation of a certificate signing
request. It -is commonly used along with the --output option to
save the -created CSR into a file. If used with the --batch a
parameter -file is used to create the CSR.
- --list-keys
- -k
- List all available certificates stored in the local key
database. Note that the displayed data might be reformatted for better
human readability and illegal characters are replaced by safe substitutes.
- --list-secret-keys
- -K
- List all available certificates for which a corresponding a
secret key is available.
- --list-external-keys pattern
- List certificates matching pattern using an external
server. This utilizes the dirmngr service.
- --list-chain
- Same as --list-keys but also prints all keys making
up the chain.
- --dump-cert
- --dump-keys
- List all available certificates stored in the local key
database using a format useful mainly for debugging.
- --dump-chain
- Same as --dump-keys but also prints all keys making
up the chain.
- --dump-secret-keys
- List all available certificates for which a corresponding a
secret key is available using a format useful mainly for debugging.
- --dump-external-keys pattern
- List certificates matching pattern using an external
server. This utilizes the dirmngr service. It uses a format useful
mainly for debugging.
- --keydb-clear-some-cert-flags
- This is a debugging aid to reset certain flags in the key
database which are used to cache certain certificate stati. It is
especially useful if a bad CRL or a weird running OCSP responder did
accidentally revoke certificate. There is no security issue with this
command because gpgsm always make sure that the validity of a
certificate is checked right before it is used.
- --delete-keys pattern
- Delete the keys matching pattern. Note that there is
no command to delete the secret part of the key directly. In case you need
to do this, you should run the command gpgsm --dump-secret-keys
KEYID before you delete the key, copy the string of hex-digits in the
``keygrip'' line and delete the file consisting of these hex-digits and
the suffix .key from the ‘private-keys-v1.d’
directory below our GnuPG home directory (usually ‘
~/.gnupg’).
- --export [pattern]
- Export all certificates stored in the Keybox or those
specified by the optional pattern. Those pattern consist of a list
of user ids (see: [how-to-specify-a-user-id]). When used along with the
--armor option a few informational lines are prepended before each
block. There is one limitation: As there is no commonly agreed upon way to
pack more than one certificate into an ASN.1 structure, the binary export
(i.e. without using armor) works only for the export of one
certificate. Thus it is required to specify a pattern which yields
exactly one certificate. Ephemeral certificate are only exported if all
pattern are given as fingerprints or keygrips.
- --export-secret-key-p12 key-id
- Export the private key and the certificate identified by
key-id in a PKCS#12 format. When used with the --armor
option a few informational lines are prepended to the output. Note, that
the PKCS#12 format is not very secure and this command is only provided if
there is no other way to exchange the private key. (see: [option
--p12-charset])
- --import [files]
- Import the certificates from the PEM or binary encoded
files as well as from signed-only messages. This command may also be used
to import a secret key from a PKCS#12 file.
- --learn-card
- Read information about the private keys from the smartcard
and import the certificates from there. This command utilizes the
gpg-agent and in turn the scdaemon.
- --passwd user_id
- Change the passphrase of the private key belonging to the
certificate specified as user_id. Note, that changing the
passphrase/PIN of a smartcard is not yet supported.
OPTIONS¶
GPGSM features a bunch of options to control the exact behaviour and to
change the default configuration.
How to change the configuration¶
These options are used to change the configuration and are usually found in the
option file.
- --options file
- Reads configuration from file instead of from the
default per-user configuration file. The default configuration file is
named ‘ gpgsm.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 commands to gpgsm,
such as '-vv'.
- --policy-file filename
- Change the default name of the policy file to
filename.
- --agent-program file
- Specify an agent program to be used for secret key
operations. The default value is the ‘
/usr/local/bin/gpg-agent’. This is only used as a fallback
when the environment variable GPG_AGENT_INFO is not set or a
running agent cannot be connected.
- --dirmngr-program file
- Specify a dirmngr program to be used for CRL checks. The
default value is ‘ /usr/sbin/dirmngr’. This is only
used as a fallback when the environment variable DIRMNGR_INFO is
not set or a running dirmngr cannot be connected.
- --prefer-system-dirmngr
- If a system wide dirmngr is running in daemon mode,
first try to connect to this one. Fallback to a pipe based server if this
does not work. Under Windows this option is ignored because the system
dirmngr is always used.
- --disable-dirmngr
- Entirely disable the use of the Dirmngr.
- --no-secmem-warning
- Do not print a warning when the so called "secure
memory" cannot be used.
- --log-file file
- When running in server mode, append all logging output to
file.
- --enable-policy-checks
- --disable-policy-checks
- By default policy checks are enabled. These options may be
used to change it.
- --enable-crl-checks
- --disable-crl-checks
- By default the CRL checks are enabled and the DirMngr is
used to check for revoked certificates. The disable option is most useful
with an off-line network connection to suppress this check.
- --enable-trusted-cert-crl-check
- --disable-trusted-cert-crl-check
- By default the CRL for trusted root certificates are
checked like for any other certificates. This allows a CA to revoke its
own certificates voluntary without the need of putting all ever issued
certificates into a CRL. The disable option may be used to switch this
extra check off. Due to the caching done by the Dirmngr, there will not be
any noticeable performance gain. Note, that this also disables possible
OCSP checks for trusted root certificates. A more specific way of
disabling this check is by adding the ``relax'' keyword to the root CA
line of the ‘ trustlist.txt’
- --force-crl-refresh
- Tell the dirmngr to reload the CRL for each request. For
better performance, the dirmngr will actually optimize this by suppressing
the loading for short time intervals (e.g. 30 minutes). This option is
useful to make sure that a fresh CRL is available for certificates hold in
the keybox. The suggested way of doing this is by using it along with the
option --with-validation for a key listing command. This option
should not be used in a configuration file.
- --enable-ocsp
- --disable-ocsp
- By default OCSP checks are disabled. The enable option may
be used to enable OCSP checks via Dirmngr. If CRL checks are also enabled,
CRLs will be used as a fallback if for some reason an OCSP request will
not succeed. Note, that you have to allow OCSP requests in Dirmngr's
configuration too (option --allow-ocsp) and configure Dirmngr
properly. If you do not do so you will get the error code 'Not supported'.
- --auto-issuer-key-retrieve
- If a required certificate is missing while validating the
chain of certificates, try to load that certificate from an external
location. This usually means that Dirmngr is employed to search for the
certificate. Note that this option makes a "web bug" like
behavior possible. LDAP server operators can see which keys you request,
so by sending you a message signed by a brand new key (which you naturally
will not have on your local keybox), the operator can tell both your IP
address and the time when you verified the signature.
- --validation-model name
- This option changes the default validation model. The only
possible values are "shell" (which is the default),
"chain" which forces the use of the chain model and
"steed" for a new simplified model. The chain model is also used
if an option in the ‘ trustlist.txt’ or an attribute of
the certificate requests it. However the standard model (shell) is in that
case always tried first.
- --ignore-cert-extension oid
- Add oid to the list of ignored certificate
extensions. The oid is expected to be in dotted decimal form, like
2.5.29.3. This option may be used more than once. Critical flagged
certificate extensions matching one of the OIDs in the list are treated as
if they are actually handled and thus the certificate will not be rejected
due to an unknown critical extension. Use this option with care because
extensions are usually flagged as critical for a reason.
- --armor
- -a
- Create PEM encoded output. Default is binary output.
- --base64
- Create Base-64 encoded output; i.e. PEM without the header
lines.
- --assume-armor
- Assume the input data is PEM encoded. Default is to
autodetect the encoding but this is may fail.
- --assume-base64
- Assume the input data is plain base-64 encoded.
- --assume-binary
- Assume the input data is binary encoded.
- --p12-charset name
- gpgsm uses the UTF-8 encoding when encoding
passphrases for PKCS#12 files. This option may be used to force the
passphrase to be encoded in the specified encoding name. This is
useful if the application used to import the key uses a different encoding
and thus will not be able to import a file generated by gpgsm.
Commonly used values for name are Latin1 and CP850.
Note that gpgsm itself automagically imports any file with a
passphrase encoded to the most commonly used encodings.
- --default-key user_id
- Use user_id as the standard key for signing. This
key is used if no other key has been defined as a signing key. Note, that
the first --local-users option also sets this key if it has not yet
been set; however --default-key always overrides this.
- --local-user user_id
- -u user_id
- Set the user(s) to be used for signing. The default is the
first secret key found in the database.
- --recipient name
- -r
- Encrypt to the user id name. There are several ways
a user id may be given (see: [how-to-specify-a-user-id]).
- --output file
- -o file
- Write output to file. The default is to write it to
stdout.
- --with-key-data
- Displays extra information with the --list-keys
commands. Especially a line tagged grp is printed which tells you
the keygrip of a key. This string is for example used as the file name of
the secret key.
- --with-validation
- When doing a key listing, do a full validation check for
each key and print the result. This is usually a slow operation because it
requires a CRL lookup and other operations.
When used along with --import, a validation of the certificate to import is
done and only imported if it succeeds the test. Note that this does not
affect an already available certificate in the DB. This option is
therefore useful to simply verify a certificate.
- --with-md5-fingerprint
- For standard key listings, also print the MD5 fingerprint
of the certificate.
- --with-keygrip
- Include the keygrip in standard key listings. Note that the
keygrip is always listed in --with-colons mode.
How to change how the CMS is created.¶
- --include-certs n
- Using n of -2 includes all certificate except for
the root cert, -1 includes all certs, 0 does not include any certs, 1
includes only the signers cert and all other positive values include up to
n certificates starting with the signer cert. The default is -2.
- --cipher-algo oid
- Use the cipher algorithm with the ASN.1 object identifier
oid for encryption. For convenience the strings 3DES,
AES and AES256 may be used instead of their OIDs. The
default is 3DES (1.2.840.113549.3.7).
- --digest-algo name
- Use name as the message digest algorithm. Usually
this algorithm is deduced from the respective signing certificate. This
option forces the use of the given algorithm and may lead to severe
interoperability problems.
Doing things one usually do not want to do.¶
- --extra-digest-algo name
- Sometimes signatures are broken in that they announce a
different digest algorithm than actually used. gpgsm uses a
one-pass data processing model and thus needs to rely on the announced
digest algorithms to properly hash the data. As a workaround this option
may be used to tell gpg to also hash the data using the algorithm
name; this slows processing down a little bit but allows to verify
such broken signatures. If gpgsm prints an error like ``digest algo
8 has not been enabled'' you may want to try this option, with 'SHA256'
for name.
- --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. Alternatively epoch may be given as a full ISO
time string (e.g. "20070924T154812").
- --with-ephemeral-keys
- Include ephemeral flagged keys in the output of key
listings. Note that they are included anyway if the key specification for
a listing is given as fingerprint or keygrip.
- --debug-level level
- Select the debug level for investigating problems.
level may be a numeric value or by 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 behaviour
may change at any time without notice; using --debug-levels is the
preferred method to select the debug verbosity. 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
Note, that all flags set using this option may get overridden by
--debug-level.
- --debug-all
- Same as --debug=0xffffffff
- --debug-allow-core-dump
- Usually gpgsm tries to avoid dumping core by well
written code and by disabling core dumps for security reasons. However,
bugs are pretty durable beasts and to squash them it is sometimes useful
to have a core dump. This option enables core dumps unless the Bad Thing
happened before the option parsing.
- --debug-no-chain-validation
- This is actually not a debugging option but only useful as
such. It lets gpgsm bypass all certificate chain validation checks.
- --debug-ignore-expiration
- This is actually not a debugging option but only useful as
such. It lets gpgsm ignore all notAfter dates, this is used by the
regression tests.
- --fixed-passphrase string
- Supply the passphrase string to the
gpg-protect-tool. This option is only useful for the regression tests
included with this package and may be revised or removed at any time
without notice.
- --no-common-certs-import
- Suppress the import of common certificates on keybox
creation.
All the long options may also be given in the configuration file after
stripping off the two leading dashes.
HOW TO SPECIFY A USER ID¶
There are different ways to specify a user ID to GnuPG. Some of them are only
valid for
gpg others are only good for
gpgsm. Here is the entire
list of ways to specify a key:
- By key Id.
- This format is deduced from the length of the string and
its content or 0x prefix. The key Id of an X.509 certificate are
the low 64 bits of its SHA-1 fingerprint. The use of key Ids is just a
shortcut, for all automated processing the fingerprint should be used.
When using gpg an exclamation mark (!) may be appended to force using
the specified primary or secondary key and not to try and calculate which
primary or secondary key to use.
The last four lines of the example give the key ID in their long form as
internally used by the OpenPGP protocol. You can see the long key ID using
the option --with-colons.
234567C4
0F34E556E
01347A56A
0xAB123456
234AABBCC34567C4
0F323456784E56EAB
01AB3FED1347A5612
0x234AABBCC34567C4
- By fingerprint.
- This format is deduced from the length of the string and
its content or the 0x prefix. Note, that only the 20 byte version
fingerprint is available with gpgsm (i.e. the SHA-1 hash of the
certificate).
When using gpg an exclamation mark (!) may be appended to force using
the specified primary or secondary key and not to try and calculate which
primary or secondary key to use.
The best way to specify a key Id is by using the fingerprint. This avoids
any ambiguities in case that there are duplicated key IDs.
1234343434343434C434343434343434
123434343434343C3434343434343734349A3434
0E12343434343434343434EAB3484343434343434
0xE12343434343434343434EAB3484343434343434
(
gpgsm also accepts colons between each pair of hexadecimal digits
because this is the de-facto standard on how to present X.509 fingerprints.)
- By exact match on OpenPGP user ID.
- This is denoted by a leading equal sign. It does not make
sense for X.509 certificates.
=Heinrich Heine <heinrichh@uni-duesseldorf.de>
- By exact match on an email address.
- This is indicated by enclosing the email address in the
usual way with left and right angles.
<heinrichh@uni-duesseldorf.de>
- By word match.
- All words must match exactly (not case sensitive) but can
appear in any order in the user ID or a subjects name. Words are any
sequences of letters, digits, the underscore and all characters with bit 7
set.
+Heinrich Heine duesseldorf
- By exact match on the subject's DN.
- This is indicated by a leading slash, directly followed by
the RFC-2253 encoded DN of the subject. Note that you can't use the string
printed by "gpgsm --list-keys" because that one as been
reordered and modified for better readability; use --with-colons to print
the raw (but standard escaped) RFC-2253 string
/CN=Heinrich Heine,O=Poets,L=Paris,C=FR
- By exact match on the issuer's DN.
- This is indicated by a leading hash mark, directly followed
by a slash and then directly followed by the rfc2253 encoded DN of the
issuer. This should return the Root cert of the issuer. See note above.
#/CN=Root Cert,O=Poets,L=Paris,C=FR
- By exact match on serial number and issuer's
DN.
- This is indicated by a hash mark, followed by the
hexadecimal representation of the serial number, then followed by a slash
and the RFC-2253 encoded DN of the issuer. See note above.
#4F03/CN=Root Cert,O=Poets,L=Paris,C=FR
- By keygrip
- This is indicated by an ampersand followed by the 40 hex
digits of a keygrip. gpgsm prints the keygrip when using the
command --dump-cert. It does not yet work for OpenPGP keys.
&D75F22C3F86E355877348498CDC92BD21010A480
- By substring match.
- This is the default mode but applications may want to
explicitly indicate this by putting the asterisk in front. Match is not
case sensitive.
Please note that we have reused the hash mark identifier which was used in old
GnuPG versions to indicate the so called local-id. It is not anymore used and
there should be no conflict when used with X.509 stuff.
Using the RFC-2253 format of DNs has the drawback that it is not possible to map
them back to the original encoding, however we don't have to do this because
our key database stores this encoding as meta data.
EXAMPLES¶
$ gpgsm -er goo@bar.net <plaintext >ciphertext
FILES¶
There are a few configuration files to control certain aspects of
gpgsm's
operation. Unless noted, they are expected in the current home directory (see:
[option --homedir]).
- gpgsm.conf
- This is the standard configuration file read by
gpgsm 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
default name may be changed on the command line (see: [gpgsm-option
--options]). You should backup this file.
- policies.txt
- This is a list of allowed CA policies. This file should
list the object identifiers of the policies line by line. Empty lines and
lines starting with a hash mark are ignored. Policies missing in this file
and not marked as critical in the certificate will print only a warning;
certificates with policies marked as critical and not listed in this file
will fail the signature verification. You should backup this file.
For example, to allow only the policy 2.289.9.9, the file should look like
this:
# Allowed policies
2.289.9.9
- qualified.txt
- This is the list of root certificates used for qualified
certificates. They are defined as certificates capable of creating legally
binding signatures in the same way as handwritten signatures are. Comments
start with a hash mark and empty lines are ignored. Lines do have a length
limit but this is not a serious limitation as the format of the entries is
fixed and checked by gpgsm: A non-comment line starts with optional
whitespace, followed by exactly 40 hex character, white space and a
lowercased 2 letter country code. Additional data delimited with by a
white space is current ignored but might late be used for other purposes.
Note that even if a certificate is listed in this file, this does not mean
that the certificate is trusted; in general the certificates listed in
this file need to be listed also in ‘ trustlist.txt’.
This is a global file an installed in the data directory (e.g. ‘
/usr/share/gnupg/qualified.txt’). GnuPG installs a suitable
file with root certificates as used in Germany. As new Root-CA
certificates may be issued over time, these entries may need to be
updated; new distributions of this software should come with an updated
list but it is still the responsibility of the Administrator to check that
this list is correct.
Everytime gpgsm uses a certificate for signing or verification this
file will be consulted to check whether the certificate under question has
ultimately been issued by one of these CAs. If this is the case the user
will be informed that the verified signature represents a legally binding
(``qualified'') signature. When creating a signature using such a
certificate an extra prompt will be issued to let the user confirm that
such a legally binding signature shall really be created.
Because this software has not yet been approved for use with such
certificates, appropriate notices will be shown to indicate this fact.
- help.txt
- This is plain text file with a few help entries used with
pinentry as well as a large list of help items for gpg and
gpgsm. The standard file has English help texts; to install
localized versions use filenames like ‘ help.LL.txt’
with LL denoting the locale. GnuPG comes with a set of predefined help
files in the data directory (e.g. ‘
/usr/share/gnupg/help.de.txt’) and allows overriding of any
help item by help files stored in the system configuration directory (e.g.
‘ /etc/gnupg/help.de.txt’). For a reference of the help
file's syntax, please see the installed ‘ help.txt’
file.
- com-certs.pem
- This file is a collection of common certificates used to
populated a newly created ‘ pubring.kbx’. An
administrator may replace this file with a custom one. The format is a
concatenation of PEM encoded X.509 certificates. This global file is
installed in the data directory (e.g. ‘
/usr/share/gnupg/com-certs.pem’).
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 a small helper
script is provided to create these files (see: [addgnupghome]).
For internal purposes gpgsm creates and maintains a few other files; they all
live in in the current home directory (see: [option --homedir]). Only
gpgsm may modify these files.
- pubring.kbx
- This a database file storing the certificates as well as
meta information. For debugging purposes the tool kbxutil may be
used to show the internal structure of this file. You should backup this
file.
- random_seed
- This content of this file is used to maintain the internal
state of the random number generator across invocations. The same file is
used by other programs of this software too.
- S.gpg-agent
- If this file exists and the environment variable
‘GPG_AGENT_INFO’ is not set, gpgsm will first
try to connect to this socket for accessing gpg-agent before
starting a new gpg-agent instance. Under Windows this socket (which
in reality be a plain file describing a regular TCP listening port) is the
standard way of connecting the gpg-agent.
SEE ALSO¶
gpg2(1),
gpg-agent(1)
The full documentation for this tool is maintained as a Texinfo manual. If GnuPG
and the info program are properly installed at your site, the command
should give you access to the complete manual including a menu structure and an
index.