fix(xmpp): obfuscate client identity in protocol exchanges

Modify version responses to return a generic client name and omit
version strings. Drop the "profanity." prefix from dynamically
generated JID resources. Spoof the XEP-0115 capabilities node URI to
prevent service discovery/presence fingerprinting. These adjustments
reduce the client's attack surface by minimizing identifiable metadata.

src/xmpp/stanza.c

@@ -32,6 +32,7 @@
 
 static void _stanza_add_unique_id(xmpp_stanza_t* stanza);
 static gchar* _stanza_create_sha1_hash(char* str);
+static const char* _stanza_get_caps_node(const char* const client);
 
 #if 0
 xmpp_stanza_t*
@@ -930,23 +931,22 @@ stanza_create_caps_query_element(xmpp_ctx_t* ctx)
 
     xmpp_stanza_t* identity = xmpp_stanza_new(ctx);
     xmpp_stanza_set_name(identity, "identity");
+    xmpp_stanza_set_type(identity, "pc");
     xmpp_stanza_set_attribute(identity, "category", "client");
 
     ProfAccount* account = accounts_get_account(session_get_account_name());
-    gchar* client = account->client;
-    bool is_custom_client = client != NULL;
 
-    GString* name_str = g_string_new(is_custom_client ? client : "Profanity ");
-    if (!is_custom_client) {
-        xmpp_stanza_set_type(identity, "console");
-        auto_gchar gchar* prof_version = prof_get_version();
-        g_string_append(name_str, prof_version);
+    auto_gchar gchar* name = g_strdup(account->client ? account->client : "Pidgin");
+
+    if (account->client) {
+        gchar* space = strchr(name, ' ');
+        if (space) {
+            *space = '\0';
+        }
     }
-
     account_free(account);
 
-    xmpp_stanza_set_attribute(identity, "name", name_str->str);
-    g_string_free(name_str, TRUE);
+    xmpp_stanza_set_attribute(identity, "name", name);
     xmpp_stanza_add_child(query, identity);
     xmpp_stanza_release(identity);
 
@@ -1994,6 +1994,42 @@ stanza_attach_last_activity(xmpp_ctx_t* const ctx,
     xmpp_stanza_release(query);
 }
 
+static const char*
+_stanza_get_caps_node(const char* const client)
+{
+    if (!client || g_strcmp0(client, "") == 0) {
+        return "http://pidgin.im";
+    }
+
+    auto_gchar gchar* lower = g_ascii_strdown(client, -1);
+
+    if (g_str_has_prefix(lower, "pidgin")) {
+        return "http://pidgin.im";
+    }
+
+    if (g_str_has_prefix(lower, "gajim")) {
+        return "https://gajim.org";
+    }
+
+    if (g_str_has_prefix(lower, "conversations")) {
+        return "https://conversations.im";
+    }
+
+    if (g_str_has_prefix(lower, "psi+")) {
+        return "http://psi-plus.com";
+    }
+
+    if (g_str_has_prefix(lower, "psi")) {
+        return "http://psi-im.org";
+    }
+
+    if (g_str_has_prefix(lower, "profanity")) {
+        return "http://profanity-im.github.io";
+    }
+
+    return "";
+}
+
 void
 stanza_attach_caps(xmpp_ctx_t* const ctx, xmpp_stanza_t* const presence)
 {
@@ -2002,9 +2038,13 @@ stanza_attach_caps(xmpp_ctx_t* const ctx, xmpp_stanza_t* const presence)
     xmpp_stanza_set_ns(caps, STANZA_NS_CAPS);
     xmpp_stanza_t* query = stanza_create_caps_query_element(ctx);
 
+    ProfAccount* account = accounts_get_account(session_get_account_name());
+    const char* node = _stanza_get_caps_node(account->client);
+    account_free(account);
+
     char* sha1 = caps_get_my_sha1(ctx);
     xmpp_stanza_set_attribute(caps, STANZA_ATTR_HASH, "sha-1");
-    xmpp_stanza_set_attribute(caps, STANZA_ATTR_NODE, "http://profanity-im.github.io");
+    xmpp_stanza_set_attribute(caps, STANZA_ATTR_NODE, node);
     xmpp_stanza_set_attribute(caps, STANZA_ATTR_VER, sha1);
     xmpp_stanza_add_child(presence, caps);
     xmpp_stanza_release(caps);