Fix combo_decrypt() to throw an error for zero-length input when using a

padded encryption scheme.  Formerly it would try to access res[(unsigned) -1],
which resulted in core dumps on 64-bit machines, and was certainly trouble
waiting to happen on 32-bit machines (though in at least the known case
it was harmless because that byte would be overwritten after return).
Per report from Ken Colson; fix by Marko Kreen.

diff --git a/contrib/pgcrypto/px.c b/contrib/pgcrypto/px.c
index 49c4bdc7317d518759c9f9c7f9ce9dff5697af59..30b02646201e74951d287f813cf19c18074c9dc1 100644 (file)
--- a/contrib/pgcrypto/px.c
+++ b/contrib/pgcrypto/px.c
@@ -26,7 +26,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * $PostgreSQL: pgsql/contrib/pgcrypto/px.c,v 1.9 2004/05/07 00:24:57 tgl Exp $
+ * $PostgreSQL: pgsql/contrib/pgcrypto/px.c,v 1.9.4.1 2007/08/23 16:16:11 tgl Exp $
  */
 
 #include <postgres.h>
@@ -185,6 +185,18 @@ combo_decrypt(PX_Combo * cx, const uint8 *data, unsigned dlen,
 
    PX_Cipher  *c = cx->cipher;
 
+   /* decide whether zero-length input is allowed */
+   if (dlen == 0)
+   {
+       /* with padding, empty ciphertext is not allowed */
+       if (cx->padding)
+           return -1;
+       
+       /* without padding, report empty result */
+       *rlen = 0;
+       return 0;
+   }
+
    bs = px_cipher_block_size(c);
    if (bs > 1 && (dlen % bs) != 0)
        goto block_error;