[PATCH 3/3 v2] filter and verify keyserver responses
Stefan Tomanek
tomanek at internet-sicherheit.de
Sun Sep 15 22:57:48 CEST 2013
This 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.
It also prevents the accidental import of secret keys through key server
responses.
Signed-off-by: Stefan Tomanek <tomanek at internet-sicherheit.de>
---
g10/import.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++------
g10/keyserver.c | 45 ++++++++++++++++++++++++++++++--
g10/main.h | 4 +++
3 files changed, 117 insertions(+), 10 deletions(-)
diff --git a/g10/import.c b/g10/import.c
index 90fc2d6..c08dd1e 100644
--- a/g10/import.c
+++ b/g10/import.c
@@ -58,6 +58,9 @@ struct stats_s {
};
+static int import_constr( IOBUF inp, const char* fname,struct stats_s *stats,
+ unsigned char **fpr,size_t *fpr_len,unsigned int options,
+ import_filter filter, void *filter_arg );
static int import( IOBUF inp, const char* fname,struct stats_s *stats,
unsigned char **fpr,size_t *fpr_len,unsigned int options );
static int read_block( IOBUF a, PACKET **pending_pkt, KBNODE *ret_root );
@@ -65,8 +68,16 @@ static void revocation_present(KBNODE keyblock);
static int import_one(const char *fname, KBNODE keyblock,struct stats_s *stats,
unsigned char **fpr,size_t *fpr_len,
unsigned int options,int from_sk);
+static int import_one_constr(const char *fname, KBNODE keyblock,struct stats_s *stats,
+ unsigned char **fpr,size_t *fpr_len,
+ unsigned int options,int from_sk,
+ import_filter filter, void *filter_arg);
+
static int import_secret_one( const char *fname, KBNODE keyblock,
struct stats_s *stats, unsigned int options);
+static int import_secret_one_constr( const char *fname, KBNODE keyblock,
+ struct stats_s *stats, unsigned int options,
+ import_filter filter, void *filter_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,
@@ -161,9 +172,10 @@ import_release_stats_handle (void *p)
*
*/
static int
-import_keys_internal( IOBUF inp, char **fnames, int nnames,
+import_keys_internal_constr( IOBUF inp, char **fnames, int nnames,
void *stats_handle, unsigned char **fpr, size_t *fpr_len,
- unsigned int options )
+ unsigned int options,
+ import_filter filter, void *filter_arg )
{
int i, rc = 0;
struct stats_s *stats = stats_handle;
@@ -172,7 +184,7 @@ import_keys_internal( IOBUF inp, char **fnames, int nnames,
stats = import_new_stats_handle ();
if (inp) {
- rc = import( inp, "[stream]", stats, fpr, fpr_len, options);
+ rc = import_constr( inp, "[stream]", stats, fpr, fpr_len, options, filter, filter_arg);
}
else {
int once = (!fnames && !nnames);
@@ -219,6 +231,14 @@ import_keys_internal( IOBUF inp, char **fnames, int nnames,
return rc;
}
+static int
+import_keys_internal( IOBUF inp, char **fnames, int nnames,
+ void *stats_handle, unsigned char **fpr, size_t *fpr_len,
+ unsigned int options )
+{
+ return import_keys_internal_constr(inp, fnames, nnames, stats_handle, fpr, fpr_len, options, NULL, NULL);
+}
+
void
import_keys( char **fnames, int nnames,
void *stats_handle, unsigned int options )
@@ -227,15 +247,24 @@ import_keys( char **fnames, int nnames,
}
int
+import_keys_stream_constr( IOBUF inp, void *stats_handle,
+ unsigned char **fpr, size_t *fpr_len,unsigned int options,
+ import_filter filter, void *filter_arg )
+{
+ return import_keys_internal_constr(inp,NULL,0,stats_handle,fpr,fpr_len,options,filter,filter_arg);
+}
+
+int
import_keys_stream( IOBUF inp, void *stats_handle,
unsigned char **fpr, size_t *fpr_len,unsigned int options )
{
- return import_keys_internal(inp,NULL,0,stats_handle,fpr,fpr_len,options);
+ return import_keys_stream_constr(inp,stats_handle,fpr,fpr_len,options,NULL,NULL);
}
static int
-import( IOBUF inp, const char* fname,struct stats_s *stats,
- unsigned char **fpr,size_t *fpr_len,unsigned int options )
+import_constr( IOBUF inp, const char* fname,struct stats_s *stats,
+ unsigned char **fpr,size_t *fpr_len,unsigned int options,
+ import_filter filter, void *filter_arg )
{
PACKET *pending_pkt = NULL;
KBNODE keyblock = NULL;
@@ -252,9 +281,10 @@ import( 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( fname, keyblock, stats, fpr, fpr_len, options, 0);
+ rc = import_one_constr( fname, keyblock, stats, fpr, fpr_len, options, 0,
+ filter, filter_arg);
else if( keyblock->pkt->pkttype == PKT_SECRET_KEY )
- rc = import_secret_one( fname, keyblock, stats, options );
+ rc = import_secret_one_constr( fname, keyblock, stats, options, filter, filter_arg );
else if( keyblock->pkt->pkttype == PKT_SIGNATURE
&& keyblock->pkt->pkt.signature->sig_class == 0x20 )
rc = import_revoke_cert( fname, keyblock, stats );
@@ -278,6 +308,12 @@ import( IOBUF inp, const char* fname,struct stats_s *stats,
return rc;
}
+static int
+import( IOBUF inp, const char* fname,struct stats_s *stats,
+ unsigned char **fpr,size_t *fpr_len,unsigned int options )
+{
+ return import_constr(inp, fname, stats, fpr, fpr_len, options, NULL, NULL);
+}
void
import_print_stats (void *hd)
@@ -740,6 +776,15 @@ import_one( const char *fname, KBNODE keyblock, struct stats_s *stats,
unsigned char **fpr,size_t *fpr_len,unsigned int options,
int from_sk )
{
+ return import_one_constr(fname, keyblock, stats, fpr,
+ fpr_len, options, from_sk, NULL, NULL);
+}
+
+static int
+import_one_constr( const char *fname, KBNODE keyblock, struct stats_s *stats,
+ unsigned char **fpr,size_t *fpr_len,unsigned int options,
+ int from_sk, import_filter filter, void *filter_arg)
+{
PKT_public_key *pk;
PKT_public_key *pk_orig;
KBNODE node, uidnode;
@@ -778,6 +823,10 @@ import_one( const char *fname, KBNODE keyblock, struct stats_s *stats,
return 0;
}
+ if (filter && filter(pk, NULL, filter_arg)) {
+ log_error( _("key %s: rejected by import filter\n"), keystr_from_pk(pk));
+ return 0;
+ }
if (opt.interactive) {
if(is_status_enabled())
print_import_check (pk, uidnode->pkt->pkt.user_id);
@@ -1148,6 +1197,14 @@ static int
import_secret_one( const char *fname, KBNODE keyblock,
struct stats_s *stats, unsigned int options)
{
+ return import_secret_one_constr(fname, keyblock, stats, options, NULL, NULL);
+}
+
+static int
+import_secret_one_constr( const char *fname, KBNODE keyblock,
+ struct stats_s *stats, unsigned int options,
+ import_filter filter, void *filter_arg )
+{
PKT_secret_key *sk;
KBNODE node, uidnode;
u32 keyid[2];
@@ -1162,6 +1219,11 @@ import_secret_one( const char *fname, KBNODE keyblock,
keyid_from_sk( sk, keyid );
uidnode = find_next_kbnode( keyblock, PKT_USER_ID );
+ if (filter && filter(NULL, sk, filter_arg)) {
+ log_error( _("secret key %s: rejected by import filter\n"), keystr_from_sk(sk));
+ return 0;
+ }
+
if( opt.verbose )
{
log_info( "sec %4u%c/%s %s ",
diff --git a/g10/keyserver.c b/g10/keyserver.c
index 440c6a1..caa64b5 100644
--- a/g10/keyserver.c
+++ b/g10/keyserver.c
@@ -971,6 +971,46 @@ direct_uri_map(const char *scheme,unsigned int is_direct)
#define KEYSERVER_ARGS_KEEP " -o \"%O\" \"%I\""
#define KEYSERVER_ARGS_NOKEEP " -o \"%o\" \"%i\""
+static int
+keyserver_retrieval_filter(PKT_public_key *pk, PKT_secret_key *sk, void *arg)
+{
+ KEYDB_SEARCH_DESC *desc = arg;
+ u32 keyid[2];
+ byte fpr[MAX_FINGERPRINT_LEN];
+ size_t fpr_len = 0;
+
+ /* we definitely do not want to import secret keys! */
+ if (sk) {
+ return 1;
+ }
+
+ fingerprint_from_pk(pk, fpr, &fpr_len);
+ keyid_from_pk(pk, keyid);
+
+ /* compare requested and returned fingerprints if available */
+ if (desc->mode == KEYDB_SEARCH_MODE_FPR20) {
+ if (fpr_len != 20 || memcmp(fpr, desc->u.fpr, 20)) {
+ return 1;
+ }
+ }
+ else if (desc->mode == KEYDB_SEARCH_MODE_FPR16) {
+ if (fpr_len != 16 || memcmp(fpr, desc->u.fpr, 16)) {
+ return 1;
+ }
+ }
+ else if (desc->mode == KEYDB_SEARCH_MODE_LONG_KID) {
+ if (memcmp(keyid, desc->u.kid, sizeof(keyid))) {
+ return 1;
+ }
+ }
+ else if (desc->mode == KEYDB_SEARCH_MODE_SHORT_KID) {
+ if (memcmp(&keyid[1], &desc->u.kid[1], 1)) {
+ return 1;
+ }
+ }
+ return 0;
+}
+
static int
keyserver_spawn(enum ks_action action,STRLIST list,KEYDB_SEARCH_DESC *desc,
int count,int *prog,unsigned char **fpr,size_t *fpr_len,
@@ -1517,8 +1557,9 @@ keyserver_spawn(enum ks_action action,STRLIST list,KEYDB_SEARCH_DESC *desc,
way to do this could be to continue parsing this
line-by-line and make a temp iobuf for each key. */
- import_keys_stream(spawn->fromchild,stats_handle,fpr,fpr_len,
- opt.keyserver_options.import_options);
+ import_keys_stream_constr(spawn->fromchild,stats_handle,fpr,fpr_len,
+ opt.keyserver_options.import_options,
+ &keyserver_retrieval_filter, desc);
import_print_stats(stats_handle);
import_release_stats_handle(stats_handle);
diff --git a/g10/main.h b/g10/main.h
index eadac1f..a729327 100644
--- a/g10/main.h
+++ b/g10/main.h
@@ -207,11 +207,15 @@ MPI encode_md_value( PKT_public_key *pk, PKT_secret_key *sk,
MD_HANDLE md, int hash_algo );
/*-- import.c --*/
+typedef int (*import_filter)(PKT_public_key *pk, PKT_secret_key *sk, void *arg);
int parse_import_options(char *str,unsigned int *options,int noisy);
void import_keys( char **fnames, int nnames,
void *stats_hd, unsigned int options );
int import_keys_stream( IOBUF inp,void *stats_hd,unsigned char **fpr,
size_t *fpr_len,unsigned int options );
+int import_keys_stream_constr( IOBUF inp,void *stats_hd,unsigned char **fpr,
+ size_t *fpr_len,unsigned int options,
+ import_filter constr, void *filter_arg);
void *import_new_stats_handle (void);
void import_release_stats_handle (void *p);
void import_print_stats (void *hd);
--
1.7.10.4
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