Fix buffer overrun after incomplete read in pullf_read_max().

Most callers pass a stack buffer.  The ensuing stack smash can crash the
server, and we have not ruled out the viability of attacks that lead to
privilege escalation.  Back-patch to 9.0 (all supported versions).

Marko Tiikkaja

Security: CVE-2015-0243

Author: nmisch

contrib/pgcrypto/expected/pgp-info.out

@@ -74,5 +74,6 @@ from encdata order by id;
  2C226E1FFE5CC7D4
  B68504FD128E1FF9
  FD0206C409B74875
-(4 rows)
+ FD0206C409B74875
+(5 rows)
 

contrib/pgcrypto/expected/pgp-pubkey-decrypt.out

@@ -564,6 +564,27 @@ GQ==
 =XHkF
 -----END PGP MESSAGE-----
 ');
+-- rsaenc2048 / aes128 (not from gnupg)
+insert into encdata (id, data) values (5, '
+-----BEGIN PGP MESSAGE-----
+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=
+=PHJ1
+-----END PGP MESSAGE-----
+');
 -- successful decrypt
 select pgp_pub_decrypt(dearmor(data), dearmor(seckey))
 from keytbl, encdata where keytbl.id=1 and encdata.id=1;
@@ -629,3 +650,7 @@ from keytbl, encdata where keytbl.id=5 and encdata.id=1;
  Secret msg
 (1 row)
 
+-- test for a short read from prefix_init
+select pgp_pub_decrypt(dearmor(data), dearmor(seckey))
+from keytbl, encdata where keytbl.id=6 and encdata.id=5;
+ERROR:  Wrong key or corrupt data

contrib/pgcrypto/mbuf.c

@@ -305,6 +305,7 @@ pullf_read_max(PullFilter *pf, int len, uint8 **data_p, uint8 *tmpbuf)
 			break;
 		memcpy(tmpbuf + total, tmp, res);
 		total += res;
+		len -= res;
 	}
 	return total;
 }

contrib/pgcrypto/sql/pgp-pubkey-decrypt.sql

@@ -579,6 +579,28 @@ GQ==
 -----END PGP MESSAGE-----
 ');
 
+-- rsaenc2048 / aes128 (not from gnupg)
+insert into encdata (id, data) values (5, '
+-----BEGIN PGP MESSAGE-----
+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=
+=PHJ1
+-----END PGP MESSAGE-----
+');
+
 -- successful decrypt
 select pgp_pub_decrypt(dearmor(data), dearmor(seckey))
 from keytbl, encdata where keytbl.id=1 and encdata.id=1;
@@ -619,3 +641,7 @@ from keytbl, encdata where keytbl.id=5 and encdata.id=1;
 -- password-protected secret key, right password
 select pgp_pub_decrypt(dearmor(data), dearmor(seckey), 'parool')
 from keytbl, encdata where keytbl.id=5 and encdata.id=1;
+
+-- test for a short read from prefix_init
+select pgp_pub_decrypt(dearmor(data), dearmor(seckey))
+from keytbl, encdata where keytbl.id=6 and encdata.id=5;