Bug #13708485: malformed resultset packet crashes client

Several fixes :

* sql-common/client.c
Added a validity check of the fields metadata packet sent 
by the server.
Now libmysql will check if the length of the data sent by
the server matches what's expected by the protocol before
using the data.

* client/mysqltest.cc
Fixed the error handling code in mysqltest to avoid sending
new commands when the reading the result set failed (and 
there are unread data in the pipe).

* sql_common.h + libmysql/libmysql.c + sql-common/client.c
unpack_fields() now generates a proper error when it fails.
Added a new argument to this function to support the error 
generation.

* sql/protocol.cc
Added a debug trigger to cause the server to send a NULL
insted of the packet expected by the client for testing 
purposes.

1 files changed, 12 insertions, 3 deletions

diff --git a/sql-common/client.c b/sql-common/client.c
index 0df7c242969..51911d913c7 100644
--- a/sql-common/client.c
+++ b/sql-common/client.c
@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1268,7 +1268,7 @@ static void cli_fetch_lengths(ulong *to, MYSQL_ROW column,
 ***************************************************************************/
 
 MYSQL_FIELD *
-unpack_fields(MYSQL_DATA *data,MEM_ROOT *alloc,uint fields,
+unpack_fields(MYSQL *mysql, MYSQL_DATA *data,MEM_ROOT *alloc,uint fields,
 	      my_bool default_value, uint server_capabilities)
 {
   MYSQL_ROWS	*row;
@@ -1281,6 +1281,7 @@ unpack_fields(MYSQL_DATA *data,MEM_ROOT *alloc,uint fields,
   if (!result)
   {
     free_rows(data);				/* Free old data */
+    set_mysql_error(mysql, CR_OUT_OF_MEMORY, unknown_sqlstate);
     DBUG_RETURN(0);
   }
   bzero((char*) field, (uint) sizeof(MYSQL_FIELD)*fields);
@@ -1308,6 +1309,14 @@ unpack_fields(MYSQL_DATA *data,MEM_ROOT *alloc,uint fields,
       field->org_name_length=	lengths[5];
 
       /* Unpack fixed length parts */
+      if (lengths[6] != 12)
+      {
+        /* malformed packet. signal an error. */
+        free_rows(data);			/* Free old data */
+        set_mysql_error(mysql, CR_MALFORMED_PACKET, unknown_sqlstate);
+        DBUG_RETURN(0);
+      }
+
       pos= (uchar*) row->data[6];
       field->charsetnr= uint2korr(pos);
       field->length=	(uint) uint4korr(pos+2);
@@ -2868,7 +2877,7 @@ get_info:
 
   if (!(fields=cli_read_rows(mysql,(MYSQL_FIELD*)0, protocol_41(mysql) ? 7:5)))
     DBUG_RETURN(1);
-  if (!(mysql->fields=unpack_fields(fields,&mysql->field_alloc,
+  if (!(mysql->fields=unpack_fields(mysql, fields,&mysql->field_alloc,
 				    (uint) field_count,0,
 				    mysql->server_capabilities)))
     DBUG_RETURN(1);