[MOD/WIP] Continue XEP-0421

src/XMPPThread/Bridged.c

@@ -3,6 +3,7 @@
 #include <Cytoplasm/Memory.h>
 #include <Cytoplasm/Str.h>
 #include <Cytoplasm/Log.h>
+#include <Cytoplasm/Sha.h>
 
 #include <string.h>
 
@@ -116,6 +117,7 @@ ParseeVerifyAllStanza(ParseeData *args, XMLElement *stanza)
     return ret;
 }
 
+/* TODO: Cache this information. */
 bool
 ServerHasXEP421(ParseeData *data, char *from)
 {
@@ -153,32 +155,84 @@ ServerHasXEP421(ParseeData *data, char *from)
     Free(server);
     return ret;
 }
+
+/* Scrambles an Occupant ID so that Matrix can use it for MXIDs.
+ * Occupant IDs are to be treated as opaque, therefore, we hash them 
+ * into a SHA-256 value
+ * > "The recipient MUST consider the occupant identifier to be an opaque 
+ * > string.". */
+static char *
+ScrambleOID(ParseeData *data, char *opaque_oid)
+{
+    unsigned char *raw;
+    char *sha, *mxid;
+    const ParseeConfig *c = data->config;
+    if (!opaque_oid)
+    {
+        return NULL;
+    }
+
+    /* Turns this into a 128-byte long, Matrix-safe value. */
+    raw = Sha256(opaque_oid);
+    sha = ShaToHex(raw);
+    Free(raw);
+
+    /* TODO: Either mark this specially, or drop Parsee JID flags 
+     * altogether before any 1.0.0 */
+    mxid = StrConcat(
+        6,
+        "@", c->namespace_base, "_l_", sha, ":",
+        c->homeserver_host
+    );
+    Free(sha);
+    return mxid;
+}
+
+/* TODO: Shove that function everywhere one can see fit. */
 char *
-ParseeGetBridgedUser(ParseeData *data, XMLElement *stanza)
+ParseeGetBridgedUserI(ParseeData *data, XMLElement *stanza, char *force)
 {
     char *user, *xmpp_from, *type;
-    char *decode_from;
+    char *decode_from, *occ_id = NULL;
+    bool is_chat, has_anon = false, is_anon = false;
 
     if (!data || !stanza)
     {
         return NULL;
     }
 
-    xmpp_from = HashMapGet(stanza->attrs, "from");
+    xmpp_from = force ? force : HashMapGet(stanza->attrs, "from");
     type = HashMapGet(stanza->attrs, "type");
     decode_from = ParseeLookupJID(xmpp_from);
 
-    /* TODO: On semi-anonymous MUCs, it might be preferable to use a 
-     * form of the occupant ID as the base, as it is more unique, and 
-     * less prone to trigger the character limit on Matrix. 
-     * I'll need to detect these first....
-     *
-     * See: https://xmpp.org/extensions/xep-0421.html */
-    user = ParseeEncodeJID(
-        data->config, 
-        decode_from, 
-        StrEquals(type, "chat")
-    );
+    is_chat = StrEquals(type, "chat");
+    if (!is_chat)
+    {
+        has_anon = ServerHasXEP421(data, xmpp_from);
+        is_anon = has_anon && StrEquals(xmpp_from, decode_from);
+    }
+
+    if (is_anon)
+    {
+        XMLElement *occupant;
+        occupant = XMLookForTKV(
+            stanza, "occupant-id", 
+            "xmlns", "urn:xmpp:occupant-id:0"
+        );
+        occ_id = occupant ? HashMapGet(occupant->attrs, "id") : NULL;
+    }
+
+    if (!occ_id)
+    {
+        user = ParseeEncodeJID(
+            data->config, 
+            decode_from, 
+            type ? is_chat : false
+        );
+        Free(decode_from);
+        return user;
+    }
+
     Free(decode_from);
-    return user;
+    return ScrambleOID(data, occ_id);
 }