[paho-dev] Paho Java Client SSL Security Vulnerability

[Alex Helder <alexrhelder@xxxxxxxxxxx>]

The Paho Java client does not perform peer verification on the connected socket. This allows peer spoofing / MITM attacks.

Proposed Solution #1

Like HttpsURLConnection, the IMQTTClient interface could get something like the following:

void setHostnameVerifier(HostnameVerifier hv);

where Java5 built-in HostNameVerifier interface is either reused as-is or inspires a Paho equivalent.

http://docs.oracle.com/javase/1.5.0/docs/api/javax/net/ssl/HostnameVerifier.html

Proposed Solution #2

Instead of SSLNetworkModule / TCPNetworkModule creating a disconnected socket via

SocketFactory.createSocket(), use SocketFactory.createSocket(String hostname, int port)

A custom SSLFactory implementation could look like:

class MySSLSocketFactory {

    SSLSocketFactory delegate;

    SSLSocket createSocket(String hostname, int port) throws IOException {

        SSLSocket s = delegate.createSocket(hostname, port);

        s.startHandshake();

        verifyHostName(s, host);

    }

    void verifyHostName(Socket s, String host) {

        // Throw exception if fail verification

    }

}

In any case, I think the Paho client should not create a disconnected socket; this allows the SSLSocketFactory to apply alternative settings and policies on the created socket.

Note: Java 7 has X509ExtendedTrustManager which is a connection-sensitive trust manager. This may also be leveraged in the future, but is relatively new.