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* g10/options.h: Add weak_digests linked list to opts. * g10/main.h: Declare weakhash linked list struct and additional_weak_digest() function to insert newly-declared weak digests into opts. * g10/misc.c: (additional_weak_digest): New function. (print_digest_algo_note): Check for deprecated digests. * g10/sig-check.c: (do_check): Reject all weak digests. * g10/gpg.c: Add --weak-digest option to gpg. * doc/gpg.texi: Document gpg --weak-digest option. * g10/gpgv.c: Add --weak-digest option to gpgv. * doc/gpgv.texi: Document gpgv --weak-digest option. -- gpg and gpgv treat signatures made over MD5 as unreliable, unless the user supplies --allow-weak-digests to gpg. Signatures over any other digest are considered acceptable. Despite SHA-1 being a mandatory-to-implement digest algorithm in RFC 4880, the collision-resistance of SHA-1 is weaker than anyone would like it to be. Some operators of high-value targets that depend on OpenPGP signatures may wish to require their signers to use a stronger digest algorithm than SHA1, even if the OpenPGP ecosystem at large cannot deprecate SHA1 entirely today. This changeset adds a new "--weak-digest DIGEST" option for both gpg and gpgv, which makes it straightforward for anyone to treat any signature or certification made over the specified digest as unreliable. This option can be supplied multiple times if the operator wishes to deprecate multiple digest algorithms, and will be ignored completely if the operator supplies --allow-weak-digests (as before). MD5 is always considered weak, regardless of any further --weak-digest options supplied. Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net> (this is a rough cherry-pick of applying the following commits to STABLE-BRANCH-1-4:76afaed65eb98939812a91015d021b)
177 lines
4.3 KiB
Plaintext
177 lines
4.3 KiB
Plaintext
@c Copyright (C) 2004 Free Software Foundation, Inc.
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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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@c
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@c This is included by tools.texi.
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@c
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@c Begin GnuPG 1.x specific stuff
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@ifset gpgone
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@macro gpgvname
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gpgv
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@end macro
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@manpage gpgv.1
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@node gpgv
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@section Verify OpenPGP signatures
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@ifset manverb
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.B gpgv
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\- Verify OpenPGP signatures
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@end ifset
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@mansect synopsis
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@ifset manverb
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.B gpgv
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.RI [ options ]
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.I signed_files
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@end ifset
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@end ifset
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@c End GnuPG 1.x specific stuff
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@c Begin GnuPG 2 specific stuff
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@ifclear gpgone
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@macro gpgvname
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gpgv2
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@end macro
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@manpage gpgv2.1
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@node gpgv
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@section Verify OpenPGP signatures
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@ifset manverb
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.B gpgv2
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\- Verify OpenPGP signatures
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@end ifset
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@mansect synopsis
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@ifset manverb
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.B gpgv2
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.RI [ options ]
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.I signed_files
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@end ifset
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@end ifclear
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@c End GnuPG 2 specific stuff
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@mansect description
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@code{@gpgvname} is an OpenPGP signature verification tool.
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This program is actually a stripped-down version of @code{gpg} which is
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only able to check signatures. It is somewhat smaller than the fully-blown
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@code{gpg} and uses a different (and simpler) way to check that
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the public keys used to make the signature are valid. There are
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no configuration files and only a few options are implemented.
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@code{@gpgvname} assumes that all keys in the keyring are trustworthy.
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That does also mean that it does not check for expired or revoked
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keys.
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By default a keyring named @file{trustedkeys.gpg} is used. This
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default keyring is assumed to be in the home directory of GnuPG,
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either the default home directory or the one set by an option or an
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environment variable. The option @code{--keyring} may be used to
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specify a different keyring or even multiple keyrings.
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@noindent
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@mansect options
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@code{@gpgvname} recognizes these options:
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@table @gnupgtabopt
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@item --verbose
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@itemx -v
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@opindex verbose
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Gives more information during processing. If used
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twice, the input data is listed in detail.
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@item --quiet
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@itemx -q
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@opindex quiet
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Try to be as quiet as possible.
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@item --keyring @var{file}
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@opindex keyring
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Add @var{file} to the list of keyrings.
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If @var{file} begins with a tilde and a slash, these
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are replaced by the HOME directory. If the filename
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does not contain a slash, it is assumed to be in the
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home-directory ("~/.gnupg" if --homedir is not used).
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@item --status-fd @var{n}
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@opindex status-fd
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Write special status strings to the file descriptor @var{n}. See the
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file DETAILS in the documentation for a listing of them.
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@item --logger-fd @code{n}
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@opindex logger-fd
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Write log output to file descriptor @code{n} and not to stderr.
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@item --ignore-time-conflict
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@opindex ignore-time-conflict
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GnuPG normally checks that the timestamps associated with keys and
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signatures have plausible values. However, sometimes a signature seems to
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be older than the key due to clock problems. This option turns these
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checks into warnings.
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@include opt-homedir.texi
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@item --weak-digest @code{name}
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@opindex weak-digest
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Treat the specified digest algorithm as weak. Signatures made over
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weak digests algorithms are normally rejected. This option can be
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supplied multiple times if multiple algorithms should be considered
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weak. MD5 is always considered weak, and does not need to be listed
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explicitly.
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@end table
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@mansect return value
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The program returns 0 if everything is fine, 1 if at least
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one signature was bad, and other error codes for fatal errors.
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@mansect examples
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@subsection Examples
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@table @asis
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@item @gpgvname @code{pgpfile}
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@itemx @gpgvname @code{sigfile} [@code{datafile}]
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Verify the signature of the file. The second form is used for detached
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signatures, where @code{sigfile} is the detached signature (either
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ASCII-armored or binary) and @code{datafile} contains the signed data;
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if @code{datafile} is "-" the signed data is expected on
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@code{stdin}; if @code{datafile} is not given the name of the file
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holding the signed data is constructed by cutting off the extension
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(".asc", ".sig" or ".sign") from @code{sigfile}.
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@end table
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@mansect environment
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@subsection Environment
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@table @asis
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@item HOME
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Used to locate the default home directory.
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@item GNUPGHOME
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If set directory used instead of "~/.gnupg".
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@end table
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@mansect files
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@subsection FILES
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@table @asis
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@item ~/.gnupg/trustedkeys.gpg
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The default keyring with the allowed keys.
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@end table
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@mansect see also
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@command{gpg2}(1)
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@include see-also-note.texi
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