Default to sane cipher suite

[jsyeo]

http.rb defaults to insecure ciphers like RC4, allowing attackers to decrypt encrypted data.

When tested against https://www.howsmyssl.com/a/check, the api returns this for http.rb:

HTTP.get('https://www.howsmyssl.com/a/check').body.to_s

{
  "given_cipher_suites": [
    "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
    "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
    "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
    "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
    "TLS_DHE_RSA_WITH_AES_128_GCM_SHA256",
    "TLS_DHE_DSS_WITH_AES_128_GCM_SHA256",
    "TLS_DHE_RSA_WITH_AES_256_GCM_SHA384",
    "TLS_DHE_DSS_WITH_AES_256_GCM_SHA384",
    "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256",
    "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
    "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
    "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
    "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384",
    "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384",
    "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
    "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
    "TLS_DHE_RSA_WITH_AES_128_CBC_SHA256",
    "TLS_DHE_RSA_WITH_AES_256_CBC_SHA256",
    "TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
    "TLS_DHE_RSA_WITH_AES_256_CBC_SHA",
    "TLS_DHE_DSS_WITH_AES_128_CBC_SHA256",
    "TLS_DHE_DSS_WITH_AES_256_CBC_SHA256",
    "TLS_DHE_DSS_WITH_AES_128_CBC_SHA",
    "TLS_DHE_DSS_WITH_AES_256_CBC_SHA",
    "TLS_RSA_WITH_AES_128_GCM_SHA256",
    "TLS_RSA_WITH_AES_256_GCM_SHA384",
    "TLS_RSA_WITH_AES_128_CBC_SHA256",
    "TLS_RSA_WITH_AES_256_CBC_SHA256",
    "TLS_RSA_WITH_AES_128_CBC_SHA",
    "TLS_RSA_WITH_AES_256_CBC_SHA",
    "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
    "TLS_ECDHE_RSA_WITH_RC4_128_SHA",
    "TLS_RSA_WITH_RC4_128_SHA",
    "TLS_EMPTY_RENEGOTIATION_INFO_SCSV"
  ],
  "ephemeral_keys_supported": true,
  "session_ticket_supported": true,
  "tls_compression_supported": false,
  "unknown_cipher_suite_supported": false,
  "beast_vuln": false,
  "able_to_detect_n_minus_one_splitting": false,
  "insecure_cipher_suites": {
    "TLS_ECDHE_ECDSA_WITH_RC4_128_SHA": [
      "uses RC4 which has insecure biases in its output"
    ],
    "TLS_ECDHE_RSA_WITH_RC4_128_SHA": [
      "uses RC4 which has insecure biases in its output"
    ],
    "TLS_RSA_WITH_RC4_128_SHA": [
      "uses RC4 which has insecure biases in its output"
    ]
  },
  "tls_version": "TLS 1.2",
  "rating": "Bad"
}

This commit sets a default cipher suite and avoids using the RC4 encryption algorithm. For more information about RC4 deprecation, see https://tools.ietf.org/html/rfc7465. 😸

[tarcieri]

http.rb isn't opinionated about the ciphersuite list and uses the Ruby OpenSSL extensions's defaults. If you think the default ciphersuite is bad, the appropriate place to fix it is https://github.com/ruby/openssl

I'm not opposed to http.rb being opinionated about it, however the appropriate ciphersuite list to include by default is Brian Smith's (we can omit RC4 from that as well):

https://briansmith.org/browser-ciphersuites-01

BTW, I designed this t-shirt, I'm well aware of the issues with RC4 😜

https://cryptosphere.spreadshirt.com/unknown-ciphers-v2-men-s-premium-A16680438/customize/color/2

[jsyeo]

You're right. I've made a PR to remove RC4 from ruby/openssl.

ruby/openssl#50

Nice t-shirt by the way. 👍