[libmicrohttpd] Issue getting escaped binary data in MHD_KeyValueIterator

[Joe Cossette]

Have been using libmicrohttpd for some time and it performs great. Currently using version 0.9.59.

 

I’ve encountered a situation I’m not sure how to solve using the library and hoping someone may be able to help.

 

The issue is likely a corner case, but valid nonetheless.

 

It involves getting escaped binary data using the function MHD_get_connection_values with the MHD_GET_ARGUMENT_KIND option.

 

A simplified example of a submitted URI looks like this:

 

            http://n.n.n.n/sendsms?to=123456789&udh=%06%05%04%0f%ea%00%03&text=Hello

 

As you can see, there is a binary zero before the end of the escaped key udh, but RFC1738 appears to mention that binary zero’s are valid in escaped strings.

 

The problem arises in the MHD_KeyValueIterator callback routine.  The library correctly delivers the decoded binary string value, but there doesn’t seem to be a way to get the correct length of this argument because a normal strlen() function returns a truncated length value due to the presence of a NULL character value.

 

It seems to me that since binary data is a valid payload in the URI that instead of a const char* for the value of the MHD_KeyValueIterator callback, that perhaps the callback prototype should look something more like the following:

 

typedef int (*MHD_KeyValueIterator) (void *cls,

                         enum MHD_ValueKind kind,

                         const char *key,

                         const unsigned char *value,

  int value_length);

 

If it did even this corner case could get covered properly.

 

The only other solution I can think of is to parse the complete URI myself, which negates some of the library’s functionality.

 

Any other suggestion?