** Description changed: - [Impact] + [Impact] There is a timeout bug in the openvpn-auth-ldap package that causes OpenVPN to crash when the network timeout is exceeded. The openvpn-auth-ldap plugin is not correctly checking the error codes from ldap_result. As a result, it is not catching timeouts, and proceeds as if ldap_result was successful. This results in a segfault when access to the result (which is set to Null) is attempted. Network timeouts are somewhat common and services should be resilient to it. Having a service as a whole crash because of such an occurrence is not acceptable. This upload fixes the problem by simply including the timeout error case in an existing check. It was clearly just an oversight in that one call, as the remainder of the code does handle timeout errors. It was just never reached. [Test Case] + To reproduce the problem, configure an openvpn server as usual with + certificates and: + - add the plugin configuration line: + plugin /usr/lib/openvpn/openvpn-auth-ldap.so /etc/openvpn/ldap.conf + - in /etc/openvpn/ldap.conf: + <LDAP> + BindDN uid=john,ou=people,dc=example + Password something + URL ldap://localhost + Timeout 1 + TLSEnable no + FollowReferrals yes + </LDAP> + # no need for an <Authorization> section + - start nc on port 389: + nc -l -p 389 + - start the openvpn server - * detailed instructions how to reproduce the bug + Next you will need an openvpn client, also configured with the SSL certs + as usual, plus "auth-user-pass". - * these should allow someone who is not familiar with the affected - package to reproduce the bug and verify that the updated package fixes - the problem. + When you start this openvpn client, it will prompt you for username and + password. The values you provide are irrelevant: + (...) + Enter Auth Username: asd + Enter Auth Password: *** - [Regression Potential] + The vulnerable server will crash: + root@trusty-openvpn-1602813:/etc/openvpn# openvpn --config server.conf + Tue Jun 20 13:56:55 2017 OpenVPN 2.3.2 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [eurephia] [MH] [IPv6] built on Dec 1 2014 + Tue Jun 20 13:56:55 2017 TUN/TAP device tun0 opened + Tue Jun 20 13:56:55 2017 Note: Cannot set tx queue length on tun0: Operation not permitted (errno=1) + Tue Jun 20 13:56:55 2017 do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0 + Tue Jun 20 13:56:55 2017 /sbin/ip link set dev tun0 up mtu 1500 + Tue Jun 20 13:56:55 2017 /sbin/ip addr add dev tun0 local 10.8.0.1 peer 10.8.0.2 + Tue Jun 20 13:56:55 2017 UDPv4 link local (bound): [undef] + Tue Jun 20 13:56:55 2017 UDPv4 link remote: [undef] + Tue Jun 20 13:56:55 2017 Initialization Sequence Completed + openvpn: sasl.c:257: ldap_parse_sasl_bind_result: Assertion `res != ((void *)0)' failed. + Aborted (core dumped) + + The fixed version will just complain about a timeout error. + + + [Regression Potential] The patch is very focused. I believe the biggest regression potential lies in the fact that this package hasn't been rebuilt very often. This new build will be done with the surrounding system libraries having changed a lot since the last time this package was built. [Other Info] There are two places in the code which mishandled the return code of ldap_result(). They are essentially identical, but the test case I provided only covers one of them. I believe that to be good enough, as the other code path will require setting up an LDAP server with a populated directory.
-- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to the bug report. https://bugs.launchpad.net/bugs/1602813 Title: openvpn-auth-ldap causing segfault on network timeout To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openvpn-auth-ldap/+bug/1602813/+subscriptions -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
