BoringSSL has no "openssl/ocsp.h" nor most OCSP related APIs used in
shrpx_tls.cc. This commit add ifdefs to disable related code to allow
building nghttp2 with BoringSSL (again).
It's possible to use !defined(OPENSSL_IS_BORINGSSL), but since BoringSSL
defines OPENSSL_NO_OCSP which is more specific, I chose to go with the
latter one.
At least we should make sure that the OCSP response is targeted to the
expected certificate. This is important because we pass the file path
to the external script, and if the file is replaced because of
renewal, and nghttpx has not reloaded its configuration, the
certificate nghttpx has loaded and the one included in the file
differ. Verifying the OCSP response detects this, and avoids to send
wrong OCSP response.
With this commit, SSL_TLSEXT_ERR_NOACK is returned from
servername_callback, which removes server_name extension from
ServerHello. CertLookupTree is now used even if the number of server
certificate is one. It is better to exercise it regularly.
Tatsuhiro Tsujikawa
Rick Lei