sslutil: synchronize hostname matching logic with CPython sslutil contains its own hostname matching logic. CPython has code for the same intent. However, it is only available to Python 2.7.9+ (or distributions that have backported 2.7.9's ssl module improvements). This patch effectively imports CPython's hostname matching code from its ssl.py into sslutil.py. The hostname matching code itself is pretty similar. However, the DNS name matching code is much more robust and spec conformant. As the test changes show, this changes some behavior around wildcard handling and IDNA matching. The new behavior allows wildcards in the middle of words (e.g. 'f*.com' matches 'foo.com') This is spec compliant according to RFC 6125 Section 6.5.3 item 3. There is one test where the matcher is more strict. Before, '*.a.com' matched '.a.com'. Now it doesn't match. Strictly speaking this is a security vulnerability.

tests: import CPython's hostname matching tests CPython has a more comprehensive test suite for it's built-in hostname matching functionality. This patch adds its tests so we can improve our hostname matching functionality. Many of the tests have different results from CPython. These will be addressed in a subsequent commit.

i18n-pt_BR: synchronized with dd9175ca81dc

sslutil: emit warning when no CA certificates loaded If no CA certificates are loaded, that is almost certainly a/the reason certificate verification fails when connecting to a server. The modern ssl module in Python 2.7.9+ provides an API to access the list of loaded CA certificates. This patch emits a warning on modern Python when certificate verification fails and there are no loaded CA certificates. There is no way to detect the number of loaded CA certificates unless the modern ssl module is present. Hence the differences in test output depending on whether modern ssl is available. It's worth noting that a test which specifies a CA file still renders this warning. That is because the certificate it is loading is a x509 client certificate and not a CA certificate. This test could be updated if anyone is so inclined.

tests: test case where default ca certs not available I'm not a fan of TLS tests not testing both branches of a possible configuration. While we have test coverage of the inability to validate a cert later in this file, I insist that we add this branch so our testing of security code is extra comprehensive.

sslutil: don't load default certificates when they aren't relevant Before, we would call SSLContext.load_default_certs() when certificate verification wasn't being used. Since SSLContext.verify_mode == ssl.CERT_NONE, this would ideally no-op. However, there is a slim chance the loading of system certs could cause a failure. Furthermore, this behavior interfered with a future patch that aims to provide a more helpful error message when we're unable to load CAs. The lack of test fallout is hopefully a sign that our security code and tests are in a relatively good state.