CVE-2014-5075 MitM Vulnerability in the Smack XMPP Library for Java =================================================================== Smack <http://www.igniterealtime.org/projects/smack/> is an Open Source XMPP (Jabber) client library for instant messaging and presence written in Java. Smack prior to version 4.0.2 is vulnerable to TLS Man-in-the-Middle attacks, as it fails to check if the server certificate matches the hostname of the connection. Affected versions ----------------- - Smack 4.0.0 and 4.0.1 are vulnerable. - Smack 2.x and 3.x are vulnerable if a custom `SSLContext` is supplied via `connectionConfiguration.setCustomSSLContext()`. Details ------- Smack is using Java's `SSLSocket`, which checks the peer certificate using an `X509TrustManager`, but does not perform hostname verification. Therefore, it is possible to redirect the traffic between a Smack-using application and a legitimate XMPP server through the attacker's server, merely by providing a valid certificate for a domain under the attacker's control. In Smack versions 2.2.0 to 3.4.1, a custom `ServerTrustManager` implementation was used, which was supplied with the connection's server name, and performed hostname verification. However, it failed to verify the basicConstraints and nameConstraints of the certificate chain (CVE-2014-0363, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-0363) and has been removed in Smack 4.0.0. Applications using Smack 2.2.0 to 3.4.1 with a custom `TrustManager` did not benefit from `ServerTrustManager` and are vulnerable as well, unless their own `TrustManager` implementation explicitly performs hostname verification. Mitigation ---------- Users of the Smack library are advised to upgrade to Smack 4.0.2, and then use `connectionConfiguration.setHostnameVerifier()` with a reasonable `HostnameVerifier` implementation. A proper hostname verifier **MUST** be configured to close the vulnerability. For Smack 3.x users, a backported commit has been created: https://github.com/ge0rg/smack/commit/8d483b25bda7ae86a3f3e83217c2add6d710798a Here, a `HostnameVerifier` implementation needs to be supplied via `connectionConfiguration.setHostnameVerifier()` as well. When using the official JRE, the internal class `sun.security.util.HostnameChecker` can be wrapped as described here: http://kevinlocke.name/bits/2012/10/03/ssl-certificate-verification-in-dispatch-and-asynchttpclient/ If Apache's HttpClient library is available, its `StrictHostnameVerifier` can be used. On Android, MemorizingTrustManager provides both certificate checking and hostname verification with interactive fallback, allowing the user to decide about the trustworthiness of a server: https://github.com/ge0rg/MemorizingTrustManager/ Affected Applications --------------------- Smack is a library used by different applications. Therefore, the authors of the following Smack-based applications have been contacted to coordinate updated releases: - ChatSecure (fixed in 13.2.0-beta1) - GTalkSMS (contacted on 2014-07-28) - MAXS (fixed in 0.0.1.18) - yaxim and Bruno (fixed in 0.8.8) - *undisclosed Android application* (contacted on 2014-07-21) The following Smack-based applications were not affected: - TransVerse (special interest client) - Xabber (using a custom `TrustManager` performing hostname verification) Timeline -------- - 2014-07-20 Discovery of Smack vulnerability, notification of Smack maintainer - 2014-07-21 Notification of vulnerable apps' authors - 2014-07-27 Release of Smack 4.0.2 - 2014-08-01 Release of MAXS 0.0.1.18 - 2014-08-04 Release of yaxim 0.8.8 - 2014-08-05 Release of ChatSecure 13.2.0 beta 1 - 2014-08-05 Publication of this advisory Links ----- Online version of advisory: http://op-co.de/CVE-2014-5075.html PDF version: http://op-co.de/CVE-2014-5075.pdf -- Dr. Georg Lukas rt-solutions.de GmbH Oberlnder Ufer 190a D-50968 Kln Tel. : (+49)221 93724 0 Fax : (+49)221 93724 50 Mobil: (+49)179 4176591 Web : www.rt-solutions.de