chan_sip: On authentication, pick MD5 for sure.

RFC 8760 added new digest-access-authentication schemes. Testing
revealed that chan_sip does not pick MD5 if several schemes are offered
by the User Agent Server (UAS). This change does not implement any of
the new schemes like SHA-256. This change makes sure, MD5 is picked so
UAS with SHA-2 enabled, like the service www.linphone.org/freesip, can
still be used. This should have worked since day one because SIP/2.0
already envisioned several schemes (see RFC 3261 and its augmented BNF
for 'algorithm' which includes 'token' as third alternative; note: if
'algorithm' was not present, MD5 is still assumed even in RFC 7616).

Change-Id: I61ca0b1f74b5ec2b5f3062c2d661cafeaf597fcd

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index e506d35fdd584358bf33a6e97b83608e732df95b..d6f4a473e102bed300b3f5aa58b9b8d584d1f7ae 100644 (file)
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -23078,6 +23078,7 @@ static int reply_digest(struct sip_pvt *p, struct sip_request *req, char *header
        char tmp[512];
        char *c;
        char oldnonce[256];
+       int start = 0;
 
        /* table of recognised keywords, and places where they should be copied */
        const struct x {
@@ -23092,9 +23093,11 @@ static int reply_digest(struct sip_pvt *p, struct sip_request *req, char *header
                { NULL, 0 },
        };
 
-       ast_copy_string(tmp, sip_get_header(req, header), sizeof(tmp));
-       if (ast_strlen_zero(tmp))
-               return -1;
+       do {
+               ast_copy_string(tmp, __get_header(req, header, &start), sizeof(tmp));
+               if (ast_strlen_zero(tmp))
+                       return -1;
+       } while (strcasestr(tmp, "algorithm=") && !strcasestr(tmp, "algorithm=MD5"));
        if (strncasecmp(tmp, "Digest ", strlen("Digest "))) {
                ast_log(LOG_WARNING, "missing Digest.\n");
                return -1;