Re: [libmicrohttpd] Question regarding HTTP basic auth example

[Christian Grothoff]

I think simply adding a

if (*upload_data_size > 0)
{
  *upload_data_size = 0; // consume
  return MHD_YES;
}

just before

const char *page = "Not Authorized!\n\n";

will do the trick (untested).  This will cause MHD to process (and throw
away) all upload data before you queue a response.  If you do not do this,

ret = MHD_queue_basic_auth_fail_response

will set 'ret' to MHD_NO (response queued too early, before
processing all upload data) and returning MHD_NO from the
callback will then cause MHD to close the connection.

Happy hacking!

Christian

On 02/17/2014 01:47 PM, Sebastian Hammerl wrote:
> Hi,
> 
> I just started experimenting with libmicrohttpd and followed the
> tutorial with all the examples. When I implemented HTTP basic auth,
> I experienced the following problem:
> 
> When I send a request with invalid auth credentials and no additional
> (e.g. POST) data everything works well and I get the "Not Authorized!"
> response correctly. But when I additionally attach data to my request
> I get an empty reply from the server.
> 
> I figured out that "MHD_queue_basic_auth_fail_response" returns 0 in
> the case that additional data is attached to the request which causes
> the ending of the connection.
> 
> However I could not figure out how to solve this problem. My goal is to
> get a valid response from the server when sending invalid credentials
> with extra data.
> 
> I stripped down the example code to the minimum, this is what I am
> testing with, compile with "g++ basicauth.c -lmicrohttpd":
> 
> 
> basicauth.cpp:
> 
> #include <microhttpd.h>
> #include <string.h>
> #include <stdio.h>
> 
> static int answer_to_connection (void *cls,
>                                  struct MHD_Connection *connection,
>                                  const char *url,
>                                  const char *method,
>                                  const char *version,
>                                  const char *upload_data,
>                                  size_t *upload_data_size,
>                                  void **con_cls) {
>     int ret;
>     struct MHD_Response *response;
> 
>     if (NULL == *con_cls) {
>         *con_cls = connection;
>         return MHD_YES;
>     }
> 
>     const char *page = "Not Authorized!\n\n";
>     response = MHD_create_response_from_buffer(strlen (page),
>                                                (void *) page,
> MHD_RESPMEM_PERSISTENT);
>     ret = MHD_queue_basic_auth_fail_response(connection,
>                                              "my realm",
>                                              response);
> 
>     MHD_destroy_response (response);
>     return ret;
> }
> 
> 
> int main () {
>     struct MHD_Daemon *d = MHD_start_daemon (MHD_USE_SELECT_INTERNALLY,
>                                            8888, NULL, NULL,
> &answer_to_connection, NULL,
>                                            MHD_OPTION_END);
>     if (NULL == d)
>         return 1;
>     getchar ();
>     MHD_stop_daemon (d);
>     return 0;
> }
> 
> 
> Here are the two request examples I am using with curl:
> 
> :~> curl -X POST localhost:8888
> Not Authorized!
> :~> curl -X POST -d a=b localhost:8888
> curl: (52) Empty reply from server
> 
> 
> Can anyone help me with this problem?
> 
> Thank you very much,
>     Sebastian
> 
>

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