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* keygen.c (make_backsig): If DO_BACKSIGS is not defined, do not create

Browse source 
backsigs.

* getkey.c (merge_selfsigs_subkey): Find 0x19 backsigs on subkey selfsigs
and verify they are valid.  If DO_BACKSIGS is not defined, fake this as
always valid.

* packet.h, parse-packet.c (parse_signature): Make parse_signature
non-static so we can parse 0x19s in self-sigs.

* main.h, sig-check.c (check_backsig): Check a 0x19 signature.
(signature_check2): Give a backsig warning if there is no or a bad 0x19
with signatures from a subkey.
This commit is contained in:
David Shaw 2004-04-23 03:01:53 +00:00
parent 8030362eae
commit 4a07655935
7 changed files with 123 additions and 7 deletions
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54
g10/sig-check.c
View file

@ -75,11 +75,29 @@ signature_check2( PKT_signature *sig, MD_HANDLE digest,
else if(!pk->is_valid && !pk->is_primary)
rc=G10ERR_BAD_PUBKEY; /* you cannot have a good sig from an
invalid subkey */
else {
else
{
if(r_expiredate)
*r_expiredate = pk->expiredate;
rc = do_check( pk, sig, digest, r_expired, r_revoked );
}
/* Check the backsig. This is a 0x19 signature from the
subkey on the primary key. The idea here is that it should
not be possible for someone to "steal" subkeys and claim
them as their own. The attacker couldn't actually use the
subkey, but they could try and claim ownership of any
signaures issued by it. */
if(rc==0 && !pk->is_primary && pk->backsig<2)
{
if(pk->backsig==0)
log_info(_("WARNING: signing subkey %08lX is not"
" cross-certified\n"),(ulong)keyid_from_pk(pk,NULL));
else
log_info(_("WARNING: signing subkey %08lX has an invalid"
" cross-certification\n"),
(ulong)keyid_from_pk(pk,NULL));
}
}
free_public_key( pk );
@ -473,6 +491,38 @@ check_revocation_keys(PKT_public_key *pk,PKT_signature *sig)
return rc;
}
/* Backsigs (0x19) have the same format as binding sigs (0x18), but
this function is simpler than check_key_signature in a few ways.
For example, there is no support for expiring backsigs since it is
questionable what such a thing actually means. Note also that the
sig cache check here, unlike other sig caches in GnuPG, is not
persistent. */
int
check_backsig(PKT_public_key *main_pk,PKT_public_key *sub_pk,
PKT_signature *backsig)
{
MD_HANDLE md;
int rc;
if(!opt.no_sig_cache && backsig->flags.checked)
{
if((rc=check_digest_algo(backsig->digest_algo)))
return rc;
return backsig->flags.valid? 0 : G10ERR_BAD_SIGN;
}
md=md_open(backsig->digest_algo,0);
hash_public_key(md,main_pk);
hash_public_key(md,sub_pk);
rc=do_check(sub_pk,backsig,md,NULL,NULL);
cache_sig_result(backsig,rc);
md_close(md);
return rc;
}
/****************
* check the signature pointed to by NODE. This is a key signature.
* If the function detects a self-signature, it uses the PK from