libdigest

Libdigest is a small C library for parsing and generating HTTP Digest Access Authentication (rfc2617) header strings, both server side and client side.

Only supports qop="auth" and algorithm="MD5" for now. If they are not supplied, auth and MD5 are assumed.

Please note that this library is under development and should not be used yet.

To do

• Finish implementing server functionality.
• Function documentation.
• Function tests.
• Unit tests.

Build it

$ make && make install

How to use it

Client side

First, include the header files:

#include <stdio.h>
#include <digest.h>
#include <digest/client.h>

Create a new digest object with the value of the WWW-Authenticate header:

digest_t d;
digest_init(&d);
digest_client_parse(&d, "Digest realm=\"api\", qop=\"auth,auth-int\", nonce=\"dcd98b7102dd2f0e8b11d0f600bfb0c093\"");

Then supply the username, password, URI and HTTP method like below:

digest_set_attr(&d, D_ATTR_USERNAME, (digest_attr_value_t) "jack");
digest_set_attr(&d, D_ATTR_PASSWORD, (digest_attr_value_t) "Passw0rd");
digest_set_attr(&d, D_ATTR_URI, (digest_attr_value_t) "/api/resource");
digest_set_attr(&d, D_ATTR_METHOD, (digest_attr_value_t) DIGEST_METHOD_POST);

To generate the string to use in the Authorization header, call digest_client_generate_header(), as below:

char result[1024];
digest_client_generate_header(&d, result, sizeof (result));

All the code (compile with -ldigest):

#include <stdio.h>
#include <digest.h>
#include <digest/client.h>

int
main(int argc, char **argv)
{
	digest_t d;
	char result[1024];
	char digest_str[] = "Digest realm=\"api\", qop=\"auth-int,auth\", nonce=\"dcd98b7102dd2f0e8b11d0f600bfb0c093\"";
	printf("WWW-Authentication: %s\n", digest_str);

	digest_init(&d);
	digest_client_parse(&d, digest_str);
	digest_set_attr(&d, D_ATTR_USERNAME, (digest_attr_value_t) "jack");
	digest_set_attr(&d, D_ATTR_PASSWORD, (digest_attr_value_t) "Passw0rd");
	digest_set_attr(&d, D_ATTR_URI, (digest_attr_value_t) "/api/resource");
	digest_set_attr(&d, D_ATTR_METHOD, (digest_attr_value_t) DIGEST_METHOD_POST);

	digest_client_generate_header(&d, result, sizeof (result));
	printf("Authorization: %s\n", result);

	return 0;
}

Attributes

Attribute	Data Type	Header Attr	Default	Mandatory
D_ATTR_USERNAME	char *	username	NULL	Yes
D_ATTR_PASSWORD	char *	response (hashed)	NULL	Yes
D_ATTR_REALM	char *	realm	Parsed value
D_ATTR_NONCE	char *	nonce	Parsed value
D_ATTR_CNONCE	int	cnonce	Random value
D_ATTR_OPAQUE	char *	opaque	Parsed value
D_ATTR_URI	char *	uri	NULL	Yes
D_ATTR_METHOD	int	response (hashed)		Yes
D_ATTR_ALGORITHM	int	algorithm	DIGEST_ALGORITHM_MD5
D_ATTR_QOP	int	qop	auth
D_ATTR_NONCE_COUNT	int	nc	1