Java 7 and Could not generate DH keypair

Question

I read a previous post regarding the error \'Could not generate DH keypair\' fired when the server sents a key longer than 1024 bits. Downloading the JCE unlimited jars shou

Answer 1

I stumbled on the same issue with SSLScokets and I think I identified the reason for this regression with Java 7. The reason comes to the ciphers negotiated between the client and the server.

By default Java 6 enables these ciphers for a TLS connection (in priority order) :

SSL_RSA_WITH_RC4_128_MD5
SSL_RSA_WITH_RC4_128_SHA
TLS_RSA_WITH_AES_128_CBC_SHA
TLS_DHE_RSA_WITH_AES_128_CBC_SHA
TLS_DHE_DSS_WITH_AES_128_CBC_SHA
SSL_RSA_WITH_3DES_EDE_CBC_SHA
SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA
SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA
SSL_RSA_WITH_DES_CBC_SHA
SSL_DHE_RSA_WITH_DES_CBC_SHA
SSL_DHE_DSS_WITH_DES_CBC_SHA
SSL_RSA_EXPORT_WITH_RC4_40_MD5
SSL_RSA_EXPORT_WITH_DES40_CBC_SHA
SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA
SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA
TLS_EMPTY_RENEGOTIATION_INFO_SCSV

And Java 7 enables these ciphers:

TLS_DHE_RSA_WITH_AES_128_CBC_SHA
TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA
SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA
SSL_RSA_WITH_RC4_128_SHA
TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA
TLS_ECDHE_RSA_WITH_RC4_128_SHA
TLS_ECDH_ECDSA_WITH_RC4_128_SHA
TLS_ECDHE_ECDSA_WITH_RC4_128_SHA
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA
TLS_ECDH_RSA_WITH_RC4_128_SHA
TLS_EMPTY_RENEGOTIATION_INFO_SCSV
TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA
TLS_ECDH_RSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
TLS_RSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
SSL_RSA_WITH_RC4_128_MD5
TLS_DHE_DSS_WITH_AES_128_CBC_SHA
SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA
SSL_RSA_WITH_3DES_EDE_CBC_SHA

Ciphers using Diffie-Hellman come in higher priority on Java 7, but they don't seem to support keys longer than 1024 bits unless the strong crypto package is installed.

The workaround I used was to specify the ciphers enabled by Java 6 on the SSLSocket:

SSLSocketFactory socketFactory = SSLContext.getInstance("TLS").getSocketFactory();
SSLSocket socket = (SSLSocket) socketFactory.createSocket(InetAddress.getByName(hostname), port);
socket.setEnabledCipherSuites(new String[] {
        "SSL_RSA_WITH_RC4_128_MD5",
        "SSL_RSA_WITH_RC4_128_SHA",
        "TLS_RSA_WITH_AES_128_CBC_SHA",
        "TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
        "TLS_DHE_DSS_WITH_AES_128_CBC_SHA",
        "SSL_RSA_WITH_3DES_EDE_CBC_SHA",
        "SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA",
        "SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA",
        "SSL_RSA_WITH_DES_CBC_SHA",
        "SSL_DHE_RSA_WITH_DES_CBC_SHA",
        "SSL_DHE_DSS_WITH_DES_CBC_SHA",
        "SSL_RSA_EXPORT_WITH_RC4_40_MD5",
        "SSL_RSA_EXPORT_WITH_DES40_CBC_SHA",
        "SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA",
        "SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA",
        "TLS_EMPTY_RENEGOTIATION_INFO_SCSV"});

socket.startHandshake();