security-and-privacy/gnupg
security-and-privacy/gnupg
1
0
Fork 0
mirror of git://git.gnupg.org/gnupg.git synced 2025-07-02 22:46:30 +02:00
Code Activity

gpg: Add option --weak-digest to gpg and gpgv.

Browse source 
* 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:
  76afaed65e
  b98939812a
  91015d021b
)
This commit is contained in:
Daniel Kahn Gillmor 2015-10-27 00:01:32 -04:00 • committed by Werner Koch
parent 43e5d28c6d
commit 924518b10d
No known key found for this signature in database
GPG key ID: E3FDFF218E45B72B
8 changed files with 92 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

9
g10/main.h
View file

@ -60,6 +60,14 @@ struct groupitem
struct groupitem *next;
};
struct weakhash
{
int algo;
int rejection_shown;
struct weakhash *next;
};
/*-- gpg.c --*/
extern int g10_errors_seen;
@ -71,6 +79,7 @@ extern int g10_errors_seen;
void print_pubkey_algo_note( int algo );
void print_cipher_algo_note( int algo );
void print_digest_algo_note( int algo );
void additional_weak_digest (const char* digestname);
/*-- armor.c --*/
char *make_radix64_string( const byte *data, size_t len );