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Message-Id: <201701272353.40452@pali>
Date: Fri, 27 Jan 2017 23:53:29 +0100
From: pali@...n.org
To: oss-security@...ts.openwall.com
Subject: Use after free in libmysqlclient.so
Hello, I would like to report problem related to MySQL/MariaDB and
possibly asking for assigning CVE if this list is the right place.
C client library for MySQL (libmysqlclient.so) has use-after-free defect
which can cause crash of applications using that MySQL client.
Defect occurs by calling mysql_close() function from libmysqlclient.so.
If mysql_close() is called before calling all mysql_stmt_close() (for
all allocated stmts), then following mysql_stmt_close() call try to
write to already released memory. mysql_close() let dangling pointer
exist for prepared statements. Real problem is in function
mysql_prune_stmt_list() which incorrectly iterate over elements.
Function list_add() overwrite ->next pointer of current element which
overwrite next element for iteration.
Basically it is just wrong usage of linked list structure.
Languages in which is not guaranteed order of executing destructor of
created objects have a big problem as such writing to memory pointed by
dangling can cause crash of whole application.
E.g. libmysqlclient.so used by perl DBD::mysql driver cause crash of
whole perl process with simple script:
perl -MDBI -e '
$dbh = DBI->connect("dbi:mysql:", "root", undef,
{RaiseError => 1, mysql_server_prepare => 1});
$sth1 = $dbh->prepare("SELECT 1");
$sth2 = $dbh->prepare("USE mysql");
$dbh->disconnect;
$dbh = undef;
'
Segmentation fault
Tested on amd64 Ubuntu 12.04 LTS with perl 5.14.2. To reproduce change
username, password and host where is running mysql server. Valgrind can
prove that memory corruption really occurs.
This defect was fixed in MySQL 5.6.21 and MySQL 5.7.5 releases. But is
present in all MySQL 5.5 versions (and also older) and appropriate older
5.6 and 5.7 versions. MySQL 5.5 is still used, supported and included in
lot of linux distributions.
Moreover this defect is present also in MariaDB releases. I tested all
last major versions 10.2.3, 10.1.21, 10.0.29, 5.5.54 and all those are
affected.
MySQL and MariaDB provides also standalone package with only C client
library libmysqlclient.so (without server) under name "Connector/C" and
so appropriate versions of it are affected too.
I found that this defected was fixed in MySQL git repository by commit:
https://github.com/mysql/mysql-server/commit/4797ea0b772d5f4c5889bc552424132806f46e93
That commit can be easily applied to last MySQL 5.5.54 version and fixes
this defect.
Looks like problem was already reported and is publically available in
MySQL bug tracker, see more details on links:
https://bugs.mysql.com/bug.php?id=70429
https://bugs.mysql.com/bug.php?id=63363
(tickets are closed despite fact that MySQL 5.5 and older are not fixed)
---
I reported this problem to Oracle secalert_us@...cle.com two months ago,
but they did absolutely nothing for fixing it in MySQL 5.5. Instead they
started resending this problem to some random people with @cpan.org
address for unknown reason. And told me to not disclose information
about this defect. Resending does not look like normal handling of
security related problem! Therefore I suggest other people to not
wasting time reporting problems to Oracle for open source applications.
As two months is really long time to fix such problem which was already
fixed in new versions; it is already publically disclosed in MySQL bug
tracker; fix available in public git; problem is in major MariaDB
versions; fix is small; and this is open source product included in many
linux distributions I decided to send information to oss-security.
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