wp_get_http, discover_pingback_server_uri does not consider HTTP chuck format

[lilyfan]

wp_get_http() at wp-includes/functions.php, discover_pingback_server_uri() at wp-includes/comment.php speaks HTTP with fcoskopen(), fputs(), fgets(), fread(). But, thease codes does not consider HTTP chunk format.
If the server returns chunk format, received data will be malformed.
The chunk format is described in ​http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html

To handle chunk format, check Transfer-Encoding field in HTTP header, and read chunk-size and the content.

Patch for discover_pingback_server_uri()

Patch for discover_pingback_server_uri()

HTTP/1.0 does not understand chunked-encoding, therefore, should not accept the header and ignore it. If it is received, then the standard states that we must send a 501 response back.

HTTP/1.0 does not understand chunked-encoding

The function in question should be set to use 1.0, I believe the function in question uses HTTP/1.1, which is probably the reason the server is returning that content type.

I think the easiest way to fix this problem is to use HTTP 1.0 instead.

This can use the new HTTP API WP_Http method for decoding chunked transfer-encoding messages. I'm not sure if the team wants to convert those functions over to the new HTTP API yet. I think the HTTP API is stable enough, but there does seem to still be problems.

Superceded by #7793.