SSL support for HTTP transport

[bzikarsky]

Issue

The current HTTP transport implementation (see #6, #19) lacks support for SSL/TLS. Some real basic ideas can be taken from the old #6-implementation branch in https://github.com/bzikarsky/gelf-php/blob/issues/6-http-transport/src/Gelf/Transport/HttpTransport.php

Since this is rather big issue, I converted the issue to an internal PR with a custom branch. Please contribute by opening PRs on this branch instead of master.

/cc @steffkes

Tasks

• Extend StreamSocketClient with support for stream-context
• Tests for stream-context-support in StreamSocketClient
• Abstraction for SSL-options (class Gelf\Transport\SslOptions) + tests; possibly relevant options are:
  • verify_peer - default to true
  • allow_self_signed - default to false
  • cafile - lots of people with a custom CA...we also need this for testing
  • ciphers - Allows us to disable certain ciphers, such as SSLv3 (...Poodle-Attack)
• Extend HttpTransport with a SslOptions parameter, when NULL (default) is passed, no SSL is used
• Enable SNI (SNI_enabled and SNI_server_name) when available (OpenSSL 0.9.8j+)
• Enable CN_match on Hostname
• Extend HttpTransportTests with checks for a correct scheme and context generation depending on $sslOptions

[scrutinizer-notifier]

The inspection completed: 12 updated code elements