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gpg: Disable an MD5 workaround for pgp2 by default.

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* g10/sig-check.c (do_check): Move some code to ...
* g10/misc.c (print_md5_rejected_note): new function.
* g10/mainproc.c (proc_tree, proc_plaintext): Enable MD5 workaround
only if option --allow-weak-digest-algos is used.
This commit is contained in:
Werner Koch 2014-08-12 10:36:30 +02:00
parent 2b8d8369d5
commit ae29b52119
4 changed files with 32 additions and 22 deletions
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1
g10/main.h
View File

@ -74,6 +74,7 @@ extern int g10_errors_seen;
void print_pubkey_algo_note (pubkey_algo_t algo); void print_pubkey_algo_note (pubkey_algo_t algo);
void print_cipher_algo_note (cipher_algo_t algo); void print_cipher_algo_note (cipher_algo_t algo);
void print_digest_algo_note (digest_algo_t algo); void print_digest_algo_note (digest_algo_t algo);
void print_md5_rejected_note (void);
/*-- armor.c --*/ /*-- armor.c --*/
char *make_radix64_string( const byte *data, size_t len ); char *make_radix64_string( const byte *data, size_t len );

25
g10/mainproc.c
View File

@ -694,7 +694,8 @@ proc_plaintext( CTX c, PACKET *pkt )
gcry_md_enable( c->mfx.md, DIGEST_ALGO_SHA1 ); gcry_md_enable( c->mfx.md, DIGEST_ALGO_SHA1 );
gcry_md_enable( c->mfx.md, DIGEST_ALGO_MD5 ); gcry_md_enable( c->mfx.md, DIGEST_ALGO_MD5 );
} }
if( opt.pgp2_workarounds && only_md5 && !opt.skip_verify ) { if (opt.pgp2_workarounds && only_md5 && !opt.skip_verify
&& opt.flags.allow_weak_digest_algos) {
/* This is a kludge to work around a bug in pgp2. It does only /* This is a kludge to work around a bug in pgp2. It does only
* catch those mails which are armored. To catch the non-armored * catch those mails which are armored. To catch the non-armored
* pgp mails we could see whether there is the signature packet * pgp mails we could see whether there is the signature packet
@ -2132,7 +2133,8 @@ proc_tree( CTX c, KBNODE node )
if( !opt.pgp2_workarounds ) if( !opt.pgp2_workarounds )
; ;
else if( sig->digest_algo == DIGEST_ALGO_MD5 else if( sig->digest_algo == DIGEST_ALGO_MD5
&& is_RSA( sig->pubkey_algo ) ) { && is_RSA( sig->pubkey_algo)
&& opt.flags.allow_weak_digest_algos) {
/* enable a workaround for a pgp2 bug */ /* enable a workaround for a pgp2 bug */
if (gcry_md_open (&c->mfx.md2, DIGEST_ALGO_MD5, 0)) if (gcry_md_open (&c->mfx.md2, DIGEST_ALGO_MD5, 0))
BUG (); BUG ();
@ -2145,16 +2147,17 @@ proc_tree( CTX c, KBNODE node )
if (gcry_md_open (&c->mfx.md2, sig->digest_algo, 0 )) if (gcry_md_open (&c->mfx.md2, sig->digest_algo, 0 ))
BUG (); BUG ();
} }
#if 0 /* workaround disabled */
/* Here we have another hack to work around a pgp 2 bug /* Here we used to have another hack to work around a pgp
* It works by not using the textmode for detached signatures; * 2 bug: It worked by not using the textmode for detached
* this will let the first signature check (on md) fail * signatures; this would let the first signature check
* but the second one (on md2) which adds an extra CR should * (on md) fail but the second one (on md2), which adds an
* then produce the "correct" hash. This is very, very ugly * extra CR would then have produced the "correct" hash.
* hack but it may help in some cases (and break others) * This is very, very ugly hack but it may haved help in
* some cases (and break others).
* c->mfx.md2? 0 :(sig->sig_class == 0x01)
*/ */
/* c->mfx.md2? 0 :(sig->sig_class == 0x01) */
#endif
if ( DBG_HASHING ) { if ( DBG_HASHING ) {
gcry_md_debug( c->mfx.md, "verify" ); gcry_md_debug( c->mfx.md, "verify" );
if ( c->mfx.md2 ) if ( c->mfx.md2 )

15
g10/misc.c
View File

@ -342,6 +342,21 @@ print_digest_algo_note (digest_algo_t algo)
} }
void
print_md5_rejected_note (void)
{
static int shown;
if (!shown)
{
log_info
(_("Note: signatures using the %s algorithm are rejected\n"),
"MD5");
shown = 1;
}
}
/* Map OpenPGP algo numbers to those used by Libgcrypt. We need to do /* Map OpenPGP algo numbers to those used by Libgcrypt. We need to do
this for algorithms we implemented in Libgcrypt after they become this for algorithms we implemented in Libgcrypt after they become
part of OpenPGP. */ part of OpenPGP. */

11
g10/sig-check.c
View File

@ -269,16 +269,7 @@ do_check( PKT_public_key *pk, PKT_signature *sig, gcry_md_hd_t digest,
if (sig->digest_algo == GCRY_MD_MD5 if (sig->digest_algo == GCRY_MD_MD5
&& !opt.flags.allow_weak_digest_algos) && !opt.flags.allow_weak_digest_algos)
{ {
static int shown; print_md5_rejected_note ();
if (!shown)
{
log_info
(_("Note: signatures using the %s algorithm are rejected\n"),
"MD5");
shown = 1;
}
return GPG_ERR_DIGEST_ALGO; return GPG_ERR_DIGEST_ALGO;
} }