pgcrypto: Detect and report too-short crypt() salts.

Certain short salts crashed the backend or disclosed a few bytes of
backend memory.  For existing salt-induced error conditions, emit a
message saying as much.  Back-patch to 9.0 (all supported versions).

Josh Kupershmidt

Security: CVE-2015-5288

contrib/pgcrypto/expected/crypt-blowfish.out

@@ -13,6 +13,15 @@ SELECT crypt('foox', '$2a$06$RQiOJ.3ELirrXwxIZY8q0O');
  $2a$06$RQiOJ.3ELirrXwxIZY8q0OR3CVJrAfda1z26CCHPnB6mmVZD8p0/C
 (1 row)
 
+-- error, salt too short:
+SELECT crypt('foox', '$2a$');
+ERROR:  invalid salt
+-- error, first digit of count in salt invalid
+SELECT crypt('foox', '$2a$40$RQiOJ.3ELirrXwxIZY8q0O');
+ERROR:  invalid salt
+-- error, count in salt too small
+SELECT crypt('foox', '$2a$00$RQiOJ.3ELirrXwxIZY8q0O');
+ERROR:  invalid salt
 CREATE TABLE ctest (data text, res text, salt text);
 INSERT INTO ctest VALUES ('password', '', '');
 UPDATE ctest SET salt = gen_salt('bf', 8);

contrib/pgcrypto/expected/crypt-des.out

@@ -13,6 +13,10 @@ SELECT crypt('foox', 'NB');
  NB53EGGqrrb5E
 (1 row)
 
+-- We are supposed to pass in a 2-character salt.
+-- error since salt is too short:
+SELECT crypt('password', 'a');
+ERROR:  invalid salt
 CREATE TABLE ctest (data text, res text, salt text);
 INSERT INTO ctest VALUES ('password', '', '');
 UPDATE ctest SET salt = gen_salt('des');

contrib/pgcrypto/expected/crypt-xdes.out

@@ -13,6 +13,30 @@ SELECT crypt('foox', '_J9..j2zz');
  _J9..j2zzAYKMvO2BYRY
 (1 row)
 
+-- check XDES handling of keys longer than 8 chars
+SELECT crypt('longlongpassword', '_J9..j2zz');
+        crypt         
+----------------------
+ _J9..j2zz4BeseiQNwUg
+(1 row)
+
+-- error, salt too short
+SELECT crypt('foox', '_J9..BWH');
+ERROR:  invalid salt
+-- error, count specified in the second argument is 0
+SELECT crypt('password', '_........');
+ERROR:  crypt(3) returned NULL
+-- error, count will wind up still being 0 due to invalid encoding
+-- of the count: only chars ``./0-9A-Za-z' are valid
+SELECT crypt('password', '_..!!!!!!');
+ERROR:  crypt(3) returned NULL
+-- count should be non-zero here, will work
+SELECT crypt('password', '_/!!!!!!!');
+        crypt         
+----------------------
+ _/!!!!!!!zqM49hRzxko
+(1 row)
+
 CREATE TABLE ctest (data text, res text, salt text);
 INSERT INTO ctest VALUES ('password', '', '');
 UPDATE ctest SET salt = gen_salt('xdes', 1001);