Ubuntu Manpage: debsig-verify - Verify signatures for a Debian format package

NAME

       debsig-verify - Verify signatures for a Debian format package

SYNOPSIS

       debsig-verify [option...] deb

DESCRIPTION

This program is part of a security model that verifies the source and validity of a Debian format package
(commonly referred to as a deb).

This program implements the verification specs defined in the document, "Package Verification with dpkg:
Implementation", which is a more complete reference for the verification procedure.

The program generally takes one argument, the deb file to be verified. It will then check the origin
signature of the deb, find its Public Key ID (long format), and use that as the name for a policy
subdirectory. If this subdirectory does not exist, then the verification fails immediately.

In this subdirectory, the program finds one or more files named with the .pol file extension, which
signifies an XML format policy definition. This file contains three main parts.

Origin Information about the origin of this policy.

Selection
Rules used to decide if this policy is pertinent to this deb's verification.

Verification
Rules that are used to actually verify the deb.

The policy files will reference OpenPGP keyrings by a filename. These OpenPGP keyrings will be looked
for in a subdirectory of the OpenPGP keyring directory. The subdirectory has the same name as the policy
subdirectory (previously determined by the Origin's Public Key ID).

The program will, after first parsing the entire file, check the Origin ID against the Public Key ID of
the origin signature in the deb. If these match (which they should, else something is really wrong),
then it will proceed to the Selection rules.

The Selection rules decide whether this policy is suitable for verifying this deb. If these rules fail,
then the program will proceed to the next policy. If it passes, then the program commits to using this
policy for verification, and no other policies will be referenced.

The last verification step relies on the Verification rules. These are similar in format to the Selection
rules, but are usually more constrained. If these rules fail, the program exits with a non-zero status.
If they pass, then it exits with a zero status.

OPTIONS

-q, --quiet
Causes the program to send no output, other than fatal errors. This is useful when being called
from another program, where you rely on the exit value only.

-v, --verbose
Causes the program to send more output on execution, so as to follow the steps it is taking while
trying to verify the deb.

-d, --debug
Outputs even more info than the -v option. This is mainly for debugging.

--help Outputs the usage information for the program.

--version
Outputs the version information for the program. This includes the policy format version. This
option does not require any other arguments.

--list-policies
Outputs a list of the policies that passed the Selection phase of the verification process. In
other words, those that could potentially verify the deb. The output is one line showing the
directory selected by the origin signature, and then a single line for any policy files in that
directory that pass the Selection rules. This option will NOT verify the deb.

--use-policy policy
This option takes one argument, which is the name of the policy file (as shown by the
--list-policies option). Note, this is just a file, and not a full path. You cannot specify
arbitrary policies. This option is useful if more than one policy applies to potentially
verifying the deb. The program will then use this policy, and only this policy, to try and verify
the deb.

--policies-dir directory
Use a different directory when looking up for policies.

--keyrings-dir directory
Use a different directory when looking up for OpenPGP keyrings.

--root directory
Use a different root directory when looking up for policies and OpenPGP keyrings.

EXIT STATUS

       0      The requested operation completed successfully.

       1      General non-success exit value. This occurs for non-verification operations.

       10     Either no signatures are contained in the deb or no origin signature was found.

       11     An  origin  signature was found, but it does not have a corresponding subdirectory in the policies
              directory.

       12     The origin was found, and is present. However, no policies were found that  passed  the  selection
              phase of the process. Thus, no verification was performed.

       13     The  package  failed the verification phase of the process. More than likely, this occurs due to a
              bad signature, or because not all criteria of the verification block of the policy were passed.

       14     An internal error occurred. This is an unrecoverable error. Either the deb is corrupt, the OpenPGP
              backend failed abnormally, or some other uncontrollable failure.

ENVIRONMENT

       DEBSIG_GNUPG_PROGRAM
              The name (or pathname) of the GnuPG program to use.

FILES

       /etc/debsig/policies/
              Directory containing the policy (.pol) definitions.

       /etc/debsig/policies/*/*.pol
              XML format policy files.

       /usr/share/debsig/keyrings/
              Directory containing the OpenPGP keyrings (*.pgp) that coincide with the policies.

       /usr/share/debsig/keyrings/*/*.pgp
       /usr/share/debsig/keyrings/*/*.gpg
              OpenPGP format keyrings for use by the policies.  Note: The .gpg extensions are the  legacy  names
              used  due  to  the  prevalence  of  one  of the OpenPGP implementation.  These keyrings must be in
              OpenPGP keyring format, and not some tool specific format (such as GnuPG keybox databases).