A virtual server may have no SSL context if it does not have certificates defined, so we have to use config of the ngx_http_ssl_module from the SSL context in the certificate callback. To do so, it is now passed as the argument of the callback. The stream module doesn't really need any changes, but was modified as well to match http code.
Dynamic certificates re-introduce problem with incorrect session reuse (AKA "virtual host confusion", CVE-2014-3616), since there are no server certificates to generate session id context from. To prevent this, session id context is now generated from ssl_certificate directives as specified in the configuration. This approach prevents incorrect session reuse in most cases, while still allowing sharing sessions across multiple machines with ssl_session_ticket_key set as long as configurations are identical.
Passwords have to be copied to the configuration pool to be used at runtime. Also, to prevent blocking on stdin (with "daemon off;") an empty password list is provided. To make things simpler, password handling was modified to allow an empty array (with 0 elements and elts set to NULL) as an equivalent of an array with 1 empty password.
To evaluate variables, a request is created in the certificate callback, and then freed. To do this without side effects on the stub_status counters and connection state, an additional function was introduced, ngx_http_alloc_request(). Only works with OpenSSL 1.0.2+, since there is no SSL_CTX_set_cert_cb() in older versions.
Previous interface of ngx_open_dir() assumed that passed directory name has a room for NGX_DIR_MASK at the end (NGX_DIR_MASK_LEN bytes). While all direct users of ngx_dir_open() followed this interface, this also implied similar requirements for indirect uses - in particular, via ngx_walk_tree(). Currently none of ngx_walk_tree() uses provides appropriate space, and fixing this does not look like a right way to go. Instead, ngx_dir_open() interface was changed to not require any additional space and use appropriate allocations instead.
Previously, AF_UNIX addresses misbehaved as AF_INET, which typically resulted in $uid_set composed from the middle of sun_path.
Previously, AF_UNIX client addresses were handled as AF_INET, leading to unexpected results.
On 32-bit platforms mp4->buffer_pos might overflow when a large enough (close to 4 gigabytes) atom is being skipped, resulting in incorrect memory addesses being read further in the code. In most cases this results in harmless errors being logged, though may also result in a segmentation fault if hitting unmapped pages. To address this, ngx_mp4_atom_next() now only increments mp4->buffer_pos up to mp4->buffer_end. This ensures that overflow cannot happen.
This parameter specifies an additional "soft" burst limit at which requests become delayed (but not yet rejected as it happens if "burst=" limit is exceeded). Defaults to 0, i.e., all excess requests are delayed. Originally inspired by Vladislav Shabanov (http://mailman.nginx.org/pipermail/nginx-devel/2016-April/008126.html). Further improved based on a patch by Peter Shchuchkin (http://mailman.nginx.org/pipermail/nginx-devel/2018-October/011522.html).