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gpg: Screen keyserver responses. 

* g10/main.h (import_screener_t): New.
* g10/import.c (import): Add screener callbacks to param list.
(import_one): Ditto.
(import_secret_one): Ditto.
(import_keys_internal): Ditto.
(import_keys_stream): Ditto.
* g10/keyserver.c (struct ks_retrieval_screener_arg_s): New.
(keyserver_retrieval_screener): New.
(keyserver_get): Pass screener to import_keys_es_stream().
--
These changes introduces import functions that apply a constraining
filter to imported keys. These filters can verify the fingerprints of
the keys returned before importing them into the keyring, ensuring
that the keys fetched from the keyserver are in fact those selected by
the user beforehand.

Signed-off-by: Stefan Tomanek <tomanek@internet-sicherheit.de>

This is an extended and fixed versions of Stefan's patch.  In addition
to the changes done in gnupg 2.0, namely the commits

  5e933008be
  044847a0e2
  088f82c0b5

the symbol names have been changed to "screener" to void mixing them
up with the iobuf filter feature and it has been changed to be used
with the dirmngr based keyserver lookup.

Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2014-08-14 15:20:53 +02:00
parent a61b28df1f
commit c23c18c154
3 changed files with 143 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

69
g10/import.c
View File

@ -63,16 +63,19 @@ struct stats_s {
static int import (ctrl_t ctrl,
IOBUF inp, const char* fname, struct stats_s *stats,
unsigned char **fpr, size_t *fpr_len, unsigned int options);
unsigned char **fpr, size_t *fpr_len, unsigned int options,
import_screener_t screener, void *screener_arg);
static int read_block( IOBUF a, PACKET **pending_pkt, KBNODE *ret_root );
static void revocation_present (ctrl_t ctrl, kbnode_t keyblock);
static int import_one (ctrl_t ctrl,
const char *fname, KBNODE keyblock,struct stats_s *stats,
unsigned char **fpr,size_t *fpr_len,
unsigned int options,int from_sk, int silent);
unsigned char **fpr, size_t *fpr_len,
unsigned int options, int from_sk, int silent,
import_screener_t screener, void *screener_arg);
static int import_secret_one (ctrl_t ctrl, const char *fname, KBNODE keyblock,
struct stats_s *stats, int batch,
unsigned int options, int for_migration);
unsigned int options, int for_migration,
import_screener_t screener, void *screener_arg);
static int import_revoke_cert( const char *fname, KBNODE node,
struct stats_s *stats);
static int chk_self_sigs( const char *fname, KBNODE keyblock,
@ -169,7 +172,8 @@ import_release_stats_handle (void *p)
static int
import_keys_internal (ctrl_t ctrl, iobuf_t inp, char **fnames, int nnames,
void *stats_handle, unsigned char **fpr, size_t *fpr_len,
unsigned int options )
unsigned int options,
import_screener_t screener, void *screener_arg)
{
int i, rc = 0;
struct stats_s *stats = stats_handle;
@ -178,7 +182,8 @@ import_keys_internal (ctrl_t ctrl, iobuf_t inp, char **fnames, int nnames,
stats = import_new_stats_handle ();
if (inp) {
rc = import (ctrl, inp, "[stream]", stats, fpr, fpr_len, options);
rc = import (ctrl, inp, "[stream]", stats, fpr, fpr_len, options,
screener, screener_arg);
}
else {
if( !fnames && !nnames )
@ -199,7 +204,8 @@ import_keys_internal (ctrl_t ctrl, iobuf_t inp, char **fnames, int nnames,
log_error(_("can't open '%s': %s\n"), fname, strerror(errno) );
else
{
rc = import (ctrl, inp2, fname, stats, fpr, fpr_len, options);
rc = import (ctrl, inp2, fname, stats, fpr, fpr_len, options,
screener, screener_arg);
iobuf_close(inp2);
/* Must invalidate that ugly cache to actually close it. */
iobuf_ioctl (NULL, IOBUF_IOCTL_INVALIDATE_CACHE,
@ -235,15 +241,15 @@ import_keys (ctrl_t ctrl, char **fnames, int nnames,
void *stats_handle, unsigned int options )
{
import_keys_internal (ctrl, NULL, fnames, nnames, stats_handle,
NULL, NULL, options);
NULL, NULL, options, NULL, NULL);
}
int
import_keys_stream (ctrl_t ctrl, IOBUF inp, void *stats_handle,
unsigned char **fpr, size_t *fpr_len,unsigned int options)
unsigned char **fpr, size_t *fpr_len, unsigned int options)
{
return import_keys_internal (ctrl, inp, NULL, 0, stats_handle,
fpr, fpr_len, options);
fpr, fpr_len, options, NULL, NULL);
}
@ -251,7 +257,8 @@ import_keys_stream (ctrl_t ctrl, IOBUF inp, void *stats_handle,
int
import_keys_es_stream (ctrl_t ctrl, estream_t fp, void *stats_handle,
unsigned char **fpr, size_t *fpr_len,
unsigned int options)
unsigned int options,
import_screener_t screener, void *screener_arg)
{
int rc;
iobuf_t inp;
@ -265,7 +272,8 @@ import_keys_es_stream (ctrl_t ctrl, estream_t fp, void *stats_handle,
}
rc = import_keys_internal (ctrl, inp, NULL, 0, stats_handle,
fpr, fpr_len, options);
fpr, fpr_len, options,
screener, screener_arg);
iobuf_close (inp);
return rc;
@ -274,7 +282,8 @@ import_keys_es_stream (ctrl_t ctrl, estream_t fp, void *stats_handle,
static int
import (ctrl_t ctrl, IOBUF inp, const char* fname,struct stats_s *stats,
unsigned char **fpr,size_t *fpr_len,unsigned int options )
unsigned char **fpr,size_t *fpr_len, unsigned int options,
import_screener_t screener, void *screener_arg)
{
PACKET *pending_pkt = NULL;
KBNODE keyblock = NULL; /* Need to initialize because gcc can't
@ -296,10 +305,12 @@ import (ctrl_t ctrl, IOBUF inp, const char* fname,struct stats_s *stats,
while( !(rc = read_block( inp, &pending_pkt, &keyblock) )) {
if( keyblock->pkt->pkttype == PKT_PUBLIC_KEY )
rc = import_one (ctrl, fname, keyblock,
stats, fpr, fpr_len, options, 0, 0);
stats, fpr, fpr_len, options, 0, 0,
screener, screener_arg);
else if( keyblock->pkt->pkttype == PKT_SECRET_KEY )
rc = import_secret_one (ctrl, fname, keyblock, stats,
opt.batch, options, 0);
opt.batch, options, 0,
screener, screener_arg);
else if( keyblock->pkt->pkttype == PKT_SIGNATURE
&& keyblock->pkt->pkt.signature->sig_class == 0x20 )
rc = import_revoke_cert( fname, keyblock, stats );
@ -355,7 +366,8 @@ import_old_secring (ctrl_t ctrl, const char *fname)
while (!(err = read_block (inp, &pending_pkt, &keyblock)))
{
if (keyblock->pkt->pkttype == PKT_SECRET_KEY)
err = import_secret_one (ctrl, fname, keyblock, stats, 1, 0, 1);
err = import_secret_one (ctrl, fname, keyblock, stats, 1, 0, 1,
NULL, NULL);
release_kbnode (keyblock);
if (err)
break;
@ -835,8 +847,9 @@ check_prefs (ctrl_t ctrl, kbnode_t keyblock)
static int
import_one (ctrl_t ctrl,
const char *fname, KBNODE keyblock, struct stats_s *stats,
unsigned char **fpr,size_t *fpr_len,unsigned int options,
int from_sk, int silent)
unsigned char **fpr, size_t *fpr_len, unsigned int options,
int from_sk, int silent,
import_screener_t screener, void *screener_arg)
{
PKT_public_key *pk;
PKT_public_key *pk_orig;
@ -880,6 +893,13 @@ import_one (ctrl_t ctrl,
return 0;
}
if (screener && screener (keyblock, screener_arg))
{
log_error (_("key %s: %s\n"), keystr_from_pk (pk),
_("rejected by import screener"));
return 0;
}
if (opt.interactive && !silent) {
if(is_status_enabled())
print_import_check (pk, uidnode->pkt->pkt.user_id);
@ -1519,7 +1539,8 @@ sec_to_pub_keyblock (kbnode_t sec_keyblock)
static int
import_secret_one (ctrl_t ctrl, const char *fname, KBNODE keyblock,
struct stats_s *stats, int batch, unsigned int options,
int for_migration)
int for_migration,
import_screener_t screener, void *screener_arg)
{
PKT_public_key *pk;
struct seckey_info *ski;
@ -1540,6 +1561,13 @@ import_secret_one (ctrl_t ctrl, const char *fname, KBNODE keyblock,
keyid_from_pk (pk, keyid);
uidnode = find_next_kbnode (keyblock, PKT_USER_ID);
if (screener && screener (keyblock, screener_arg))
{
log_error (_("secret key %s: %s\n"), keystr_from_pk (pk),
_("rejected by import screener"));
return 0;
}
if (opt.verbose && !for_migration)
{
log_info ("sec %s/%s %s ",
@ -1610,7 +1638,8 @@ import_secret_one (ctrl_t ctrl, const char *fname, KBNODE keyblock,
public key block, and below we will output another one for
the secret keys. FIXME? */
import_one (ctrl, fname, pub_keyblock, stats,
NULL, NULL, options, 1, for_migration);
NULL, NULL, options, 1, for_migration,
screener, screener_arg);
/* Fixme: We should check for an invalid keyblock and
cancel the secret key import in this case. */

94
g10/keyserver.c
View File

@ -1042,6 +1042,85 @@ keyserver_export (ctrl_t ctrl, strlist_t users)
}
/* Structure to convey the arg to keyserver_retrieval_screener. */
struct ks_retrieval_screener_arg_s
{
KEYDB_SEARCH_DESC *desc;
int ndesc;
};
/* Check whether a key matches the search description. The function
returns 0 if the key shall be imported. */
static gpg_error_t
keyserver_retrieval_screener (kbnode_t keyblock, void *opaque)
{
struct ks_retrieval_screener_arg_s *arg = opaque;
KEYDB_SEARCH_DESC *desc = arg->desc;
int ndesc = arg->ndesc;
kbnode_t node;
PKT_public_key *pk;
int n;
u32 keyid[2];
byte fpr[MAX_FINGERPRINT_LEN];
size_t fpr_len = 0;
/* Secret keys are not expected from a keyserver. We do not
care about secret subkeys because the import code takes care
of skipping them. Not allowing an import of a public key
with a secret subkey would make it too easy to inhibit the
downloading of a public key. Recall that keyservers do only
limited checks. */
node = find_kbnode (keyblock, PKT_SECRET_KEY);
if (node)
return gpg_error (GPG_ERR_GENERAL); /* Do not import. */
if (!ndesc)
return 0; /* Okay if no description given. */
/* Loop over all key packets. */
for (node = keyblock; node; node = node->next)
{
if (node->pkt->pkttype != PKT_PUBLIC_KEY
&& node->pkt->pkttype != PKT_PUBLIC_SUBKEY)
continue;
pk = node->pkt->pkt.public_key;
fingerprint_from_pk (pk, fpr, &fpr_len);
keyid_from_pk (pk, keyid);
/* Compare requested and returned fingerprints if available. */
for (n = 0; n < ndesc; n++)
{
if (desc[n].mode == KEYDB_SEARCH_MODE_FPR20)
{
if (fpr_len == 20 && !memcmp (fpr, desc[n].u.fpr, 20))
return 0;
}
else if (desc[n].mode == KEYDB_SEARCH_MODE_FPR16)
{
if (fpr_len == 16 && !memcmp (fpr, desc[n].u.fpr, 16))
return 0;
}
else if (desc[n].mode == KEYDB_SEARCH_MODE_LONG_KID)
{
if (keyid[0] == desc[n].u.kid[0] && keyid[1] == desc[n].u.kid[1])
return 0;
}
else if (desc[n].mode == KEYDB_SEARCH_MODE_SHORT_KID)
{
if (keyid[1] == desc[n].u.kid[1])
return 0;
}
else /* No keyid or fingerprint - can't check. */
return 0; /* allow import. */
}
}
return gpg_error (GPG_ERR_GENERAL);
}
int
keyserver_import (ctrl_t ctrl, strlist_t users)
{
@ -1601,6 +1680,7 @@ keyserver_get (ctrl_t ctrl, KEYDB_SEARCH_DESC *desc, int ndesc,
if (!err)
{
void *stats_handle;
struct ks_retrieval_screener_arg_s screenerarg;
stats_handle = import_new_stats_handle();
@ -1616,10 +1696,14 @@ keyserver_get (ctrl_t ctrl, KEYDB_SEARCH_DESC *desc, int ndesc,
never accept or send them but we better protect against rogue
keyservers. */
screenerarg.desc = desc;
screenerarg.ndesc = ndesc;
import_keys_es_stream (ctrl, datastream, stats_handle,
r_fpr, r_fprlen,
(opt.keyserver_options.import_options
| IMPORT_NO_SECKEY));
| IMPORT_NO_SECKEY),
keyserver_retrieval_screener, &screenerarg);
import_print_stats (stats_handle);
import_release_stats_handle (stats_handle);
}
@ -1684,7 +1768,7 @@ keyserver_put (ctrl_t ctrl, strlist_t keyspecs,
}
/* Loop over all URLs in STRLIST and fetch the key that URL. Note
/* Loop over all URLs in STRLIST and fetch the key at that URL. Note
that the fetch operation ignores the configured key servers and
instead directly retrieves the keys. */
int
@ -1712,7 +1796,8 @@ keyserver_fetch (ctrl_t ctrl, strlist_t urilist)
stats_handle = import_new_stats_handle();
import_keys_es_stream (ctrl, datastream, stats_handle, NULL, NULL,
opt.keyserver_options.import_options);
opt.keyserver_options.import_options,
NULL, NULL);
import_print_stats (stats_handle);
import_release_stats_handle (stats_handle);
@ -1762,7 +1847,8 @@ keyserver_import_cert (ctrl_t ctrl,
err = import_keys_es_stream (ctrl, key, NULL, fpr, fpr_len,
(opt.keyserver_options.import_options
| IMPORT_NO_SECKEY));
| IMPORT_NO_SECKEY),
NULL, NULL);
opt.no_armor=armor_status;

5
g10/main.h
View File

@ -288,6 +288,8 @@ gcry_mpi_t encode_md_value (PKT_public_key *pk,
gcry_md_hd_t md, int hash_algo );
/*-- import.c --*/
typedef gpg_error_t (*import_screener_t)(kbnode_t keyblock, void *arg);
int parse_import_options(char *str,unsigned int *options,int noisy);
void import_keys (ctrl_t ctrl, char **fnames, int nnames,
void *stats_hd, unsigned int options);
@ -296,7 +298,8 @@ int import_keys_stream (ctrl_t ctrl, iobuf_t inp, void *stats_hd,
size_t *fpr_len, unsigned int options);
int import_keys_es_stream (ctrl_t ctrl, estream_t fp, void *stats_handle,
unsigned char **fpr, size_t *fpr_len,
unsigned int options);
unsigned int options,
import_screener_t screener, void *screener_arg);
gpg_error_t import_old_secring (ctrl_t ctrl, const char *fname);
void *import_new_stats_handle (void);
void import_release_stats_handle (void *p);