Tuesday, May 17, 2011

Decrypting SSL using tshark/wireshark

I was banging my head on the keyboard last week trying to figure out why wireshar/tshark was not decrypting my SSL packets. Turns out that you cannot do this if the key exchange is Diffie-Hellman. You can get around this by telling the server to ignore DH, In apache's case, changing the SSLCipherSuite to something like:

The server hello changes from
Cipher Suite: TLS_DHE_RSA_WITH_AES_256_CBC_SHA (0x0039)


Cipher Suite: TLS_RSA_WITH_RC4_128_SHA (0x0005)

 tshark   -o "ssl.desegment_ssl_records: TRUE" -o "ssl.desegment_ssl_application_data: TRUE" -o "ssl.keys_list:,443,http,/path/to/server.key.pem" -o "ssl.debug_file: /tmp/wireshark-log" -r /path/to/example.pcap  -V| awk '/^Frame.*/;/Source: 2/;/Secure Socket Layer.*/,/^$/;' |tail -n 40

     Version: TLS 1.0 (0x0301)
        Length: 61
        Encrypted Application Data: 6C6423B17A7211C8F8E9E60B5F726D0C7C40B5645B234A36...
    SSL segment data (41 bytes)
[Reassembled SSL Segments (227 bytes): #60(186), #60(41)]
    [Frame: 60, payload: 0-185 (186 bytes)]
    [Frame: 60, payload: 186-226 (41 bytes)]
Hypertext Transfer Protocol
    HTTP/1.1 200 Script output follows\r\n
        [Expert Info (Chat/Sequence): HTTP/1.1 200 Script output follows\r\n]
            [Message: HTTP/1.1 200 Script output follows\r\n]
            [Severity level: Chat]
            [Group: Sequence]
        Request Version: HTTP/1.1
        Response Code: 200
    Date: Mon, 16 May 2011 13:41:11 GMT\r\n
    Server: Apache/2.2.8 (CentOS)\r\n
    Content-Length: 41\r\n
        [Content length: 41]
    Connection: close\r\n
    Content-Type: application/mercurial-0.1\r\n
Media Type
    Media Type: application/mercurial-0.1 (41 bytes)

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