#73 Hang when server returns 401 and closes connection

[Paul Markham]

Some IIS servers on our intranet are return an http response 401, then closing the connection. According to the comments in direct.c, this behaviour shouldn't happen; unfortunately, it is.

318                         if (loop == 1 && data[1]->code == 401 && hlist_subcmp_all(data[1]->headers, "WWW-Authenticate", "NTLM")) {
319                                 /*
320                                  * Server closing the connection after 401?
321                                  * Should never happen.
322                                  */

Cntlm then closes and re-opens the socket. From there is calls a series of functions, as follows:

www_authenticate
    http_body_drop
        data_send

The data_send funtion executes the following:

334 i = read(src, buf, block);

This call hangs, eventually timing out which causes the connection to fail. I think what's happening is that there isn't any data on the newly opened socket, so the read call blocks.

This is happening on Mac OS X 10.11. I haven't tried in under different versions of OS X or on Linux.

[Paul Markham]

Cntlm version is 0.92.3.