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gpg: Protect against rogue keyservers sending secret keys.

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* g10/options.h (IMPORT_NO_SECKEY): New.
* g10/keyserver.c (keyserver_spawn, keyserver_import_cert): Set new
flag.
* g10/import.c (import_secret_one): Deny import if flag is set.
--

By modifying a keyserver or a DNS record to send a secret key, an
attacker could trick a user into signing using a different key and
user id.  The trust model should protect against such rogue keys but
we better make sure that secret keys are never received from remote
sources.

Suggested-by: Stefan Tomanek
Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2013-10-04 13:44:39 +02:00
parent dd868acb0d
commit e7abed3448
3 changed files with 22 additions and 10 deletions
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6
g10/import.c
View File

@ -1195,6 +1195,12 @@ import_secret_one( const char *fname, KBNODE keyblock,
}
stats->secret_read++;
if ((options & IMPORT_NO_SECKEY))
{
log_error (_("importing secret keys not allowed\n"));
return 0;
}
if( !uidnode )
{
log_error( _("key %s: no user ID\n"), keystr_from_sk(sk));

15
g10/keyserver.c
View File

@ -1498,10 +1498,14 @@ keyserver_spawn(enum ks_action action,strlist_t list,KEYDB_SEARCH_DESC *desc,
It's harmless to ignore them, but ignoring them does make
gpg complain about "no valid OpenPGP data found". One
way to do this could be to continue parsing this
line-by-line and make a temp iobuf for each key. */
line-by-line and make a temp iobuf for each key. Note
that we don't allow the import of secret keys from a
keyserver. Keyservers should never accept or send them
but we better protect against rogue keyservers. */
import_keys_stream(spawn->fromchild,stats_handle,fpr,fpr_len,
opt.keyserver_options.import_options);
import_keys_stream (spawn->fromchild, stats_handle, fpr, fpr_len,
(opt.keyserver_options.import_options
| IMPORT_NO_SECKEY));
import_print_stats(stats_handle);
import_release_stats_handle(stats_handle);
@ -2039,8 +2043,9 @@ keyserver_import_cert(const char *name,unsigned char **fpr,size_t *fpr_len)
/* CERTs are always in binary format */
opt.no_armor=1;
rc=import_keys_stream(key,NULL,fpr,fpr_len,
opt.keyserver_options.import_options);
rc=import_keys_stream (key, NULL, fpr, fpr_len,
(opt.keyserver_options.import_options
| IMPORT_NO_SECKEY));
opt.no_armor=armor_status;

1
g10/options.h
View File

@ -317,6 +317,7 @@ EXTERN_UNLESS_MAIN_MODULE int memory_stat_debug_mode;
#define IMPORT_MERGE_ONLY (1<<4)
#define IMPORT_MINIMAL (1<<5)
#define IMPORT_CLEAN (1<<6)
#define IMPORT_NO_SECKEY (1<<7)
#define EXPORT_LOCAL_SIGS (1<<0)
#define EXPORT_ATTRIBUTES (1<<1)