security-and-privacy/gnupg
security-and-privacy/gnupg
1
0
Fork 0
mirror of git://git.gnupg.org/gnupg.git synced 2025-07-03 22:56:33 +02:00
Code Activity

gpg: Fix a verification DoS due to a malicious subkey in the keyring.

Browse source 
* g10/getkey.c (get_pubkey): Factor code out to ...
(get_pubkey_bykid): new.  Add feature to return the keyblock.
(get_pubkey_for_sig): Add arg r_keyblock to return the used keyblock.
Request a signing usage.
(get_pubkeyblock_for_sig): Remove.
(finish_lookup): Improve debug output.
* g10/sig-check.c (check_signature): Add arg r_keyblock and pass it
down.
* g10/mainproc.c (do_check_sig): Ditto.
(check_sig_and_print): Use the keyblock returned by do_check_sig to
show further information instead of looking it up again with
get_pubkeyblock_for_sig.  Also re-check the signature after the import
of an included keyblock.
--

The problem here is that it is possible to import a key from someone
who added a signature subkey from another public key and thus inhibits
that a good signature good be verified.

Such a malicious key signature subkey must have been created w/o the
mandatory backsig which bind a signature subkey to its primary key.
For encryption subkeys this is not an issue because the existence of a
decryption private key is all you need to decrypt something and then
it does not matter if the public subkey or its binding signature has
been put below another primary key; in fact we do the latter for
ADSKs.

GnuPG-bug-id: 7527
This commit is contained in:
Werner Koch 2025-02-21 12:16:17 +01:00
parent 5e87e452e4
commit 48978ccb4e
No known key found for this signature in database
GPG key ID: E3FDFF218E45B72B
7 changed files with 155 additions and 87 deletions
Download patch file Download diff file Expand all files Collapse all files

10
g10/keydb.h
View file

@ -332,9 +332,15 @@ void getkey_disable_caches(void);
/* Return the public key used for signature SIG and store it at PK. */
gpg_error_t get_pubkey_for_sig (ctrl_t ctrl,
PKT_public_key *pk, PKT_signature *sig,
PKT_public_key *forced_pk);
PKT_public_key *forced_pk,
kbnode_t *r_keyblock);
/* Return the public key with the key id KEYID and store it at PK. */
/* Return the public key with the key id KEYID and store it at PK.
* Optionally return the entire keyblock. */
gpg_error_t get_pubkey_bykid (ctrl_t ctrl, PKT_public_key *pk,
kbnode_t *r_keyblock, u32 *keyid);
/* Same as get_pubkey_bykid but w/o r_keyblock. */
int get_pubkey (ctrl_t ctrl, PKT_public_key *pk, u32 *keyid);
/* Same as get_pubkey but with auto LDAP fetch. */