[Dovecot] Bug in driver-mysql.c + fix

[Alain Williams]

I tried to use MySQL stored procedures from dovecot:

	password_query = CALL user_pass_check('%n', '%d', '%w')

	user_query = CALL user_info('%n', '%d')

This failed with the message:
	User query failed: PROCEDURE imap.user_info can't return a result set in the given context

The root of this problem is that mysql_real_connect() needs to be called with option CLIENT_MULTI_RESULTS
and mysql_next_result() called to retrieve extra results (that will not exist in the way that we use it).
I attach a patch that fixes this problem -- the patch is against dovecot-1.2.10.
This works for me ... but could probably do with testing by other people.

BTW: I got the same problem with exim this morning, wrote a patch that has now been accepted.
The dovecot patch is similar.


I am looking to use mysql procedures, there are some interesting things that can be done.
Two suggestions that I have will help with this:

1) There be variable (say) %o - this be the obscured password, ie what password_query returns.

2) that dovecot look for either ''password_query'' as above, or ''password_check''.
   password_check would NOT return a password, but would be given %o and determine
   itself if the password is correct.
   It would return the other values (user, userdb_home, ...) and auth_result
   that would encode success/retry/fail (0, 1, 2 - or maybe more structured [**])
   and auth_reason some human readable reason.
   The ''nologin'' value encodes some of this.

The motivation for this is that my stored procedure will record the number of successive
login failures and lock the account after 3 of them. It would also be possible to
do time based restrictions & the such.

Also: by passing %o the password is not sent in plain to the database server - which
will increase security.

I will publish my stored procedures when done.

Regards

[**] eg taking ideas from the HTTP codes:
200 - OK
300 5 - try again in 5 minutes
301 2 9 - try again on tuesday at 9am
400 - Login forbidden, no reason given
401 - bad username and/or password
402 - account locked administratively
403 - too many failed login attempts
500 - authentication system error
The above would allow a native language version of auth_reason to be produced

-- 
Alain Williams
Linux/GNU Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer.
+44 (0) 787 668 0256  http://www.phcomp.co.uk/
Parliament Hill Computers Ltd. Registration Information: http://www.phcomp.co.uk/contact.php
Past chairman of UKUUG: http://www.ukuug.org/
#include <std_disclaimer.h>
-------------- next part --------------
--- driver-mysql.c	2010-03-05 19:38:10.512212871 +0000
+++ driver-mysql.c	2010-03-05 19:38:17.000000000 +0000
@@ -132,9 +132,10 @@
 	}
 
 	alarm(MYSQL_CONNECT_FAILURE_TIMEOUT);
+	/* CLIENT_MULTI_RESULTS allows the use of stored procedures */
 	failed = mysql_real_connect(conn->mysql, host, db->user, db->password,
 				    db->dbname, db->port, unix_socket,
-				    db->client_flags) == NULL;
+				    db->client_flags | CLIENT_MULTI_RESULTS) == NULL;
 	alarm(0);
 	if (failed) {
 		if (conn->connect_failure_count > 0) {
@@ -429,6 +430,7 @@
 	struct mysql_db *db = (struct mysql_db *)_db;
 	struct mysql_connection *conn;
 	struct mysql_result *result;
+	int nr;
 
 	result = i_new(struct mysql_result, 1);
 	result->api = driver_mysql_result;
@@ -442,6 +444,17 @@
 	case 1:
 		/* query ok */
 		result->result = mysql_store_result(conn->mysql);
+		while((nr = mysql_next_result(conn->mysql)) >= 0) {
+			/* more results? -1 = no, >0 = error, 0 = yes
+			 * Because of the CLIENT_MULTI_RESULTS on mysql_real_connect()
+			 * we need to read extra results - there should not be any.
+			 */
+			if(nr == 0)   /* Just ignore more results */
+				continue;
+
+			result->api = driver_mysql_error_result;
+			goto off;
+		}
 		if (result->result != NULL || mysql_errno(conn->mysql) == 0)
 			break;
 		/* fallback */
@@ -451,6 +464,7 @@
 		break;
 	}
 
+off:
 	result->conn = conn;
 	return &result->api;
 }