uac_auth(): Fix corner-case with missing "algorithm=" in 401

Make sure to convert ALG_UNSPEC to ALG_MD5 before doing the bitmask
conversion, as otherwise the matching will fail!

Partial revert of commit 977ce90.

lib/digest_auth/digest_auth.c

@@ -67,7 +67,8 @@ int dauth_algorithm_check(const struct authenticate_body *auth,
 	if (!digest_algorithm_available(auth->algorithm))
 		return (0);
 	damp = (const struct dauth_algorithm_match *)mdp->argp;
-	return (ALG2ALGFLG(auth->algorithm) & damp->algmask);
+	return (ALG2ALGFLG(auth->algorithm==ALG_UNSPEC ? ALG_MD5:auth->algorithm)
+				& damp->algmask);
 }
 
 int dauth_fixup_algorithms(void** param)

modules/uac/auth.c

@@ -307,7 +307,7 @@ int uac_auth( struct sip_msg *msg, unsigned algmask)
 	}
 
 	if (auth == NULL) {
-		LM_ERR("Unable to extract authentication info\n");
+		LM_ERR("Unable to extract a compatible authentication challenge\n");
 		goto error;
 	}
 

modules/uac/uac.c

@@ -488,7 +488,8 @@ static int w_replace_to(struct sip_msg* msg, str *dsp, str *uri)
 
 static int w_uac_auth(struct sip_msg* msg, intptr_t _alg)
 {
-	return (uac_auth(msg, !_alg ? 0U:*(unsigned *)_alg)==0)?1:-1;
+
+	return (uac_auth(msg, _alg)==0)?1:-1;
 }