fix: address issue #112 follow-ups (OTR strip, presence UAF, OMEMO load)

- otr: strip the OTR whitespace tag by shifting the full remaining tail
  (including the trailing NUL) instead of tag_length bytes, which duplicated
  the body for messages longer than the tag (#8).
- xmpp: snapshot resource name/status/priority/presence before
  connection_add_available_resource() transfers ownership of the Resource, so
  the later reads can no longer become a use-after-free (#9).
- omemo: propagate _omemo_finalize_identity_load failure on connect — mark the
  context unloaded, log it, surface a cons_show_error, and stop instead of
  silently leaving OMEMO unavailable (#10).

Refs #112

src/omemo/omemo.c

@@ -260,7 +260,12 @@ omemo_on_connect(ProfAccount* account)
             return;
     }
 
-    _omemo_finalize_identity_load(account);
+    if (!_omemo_finalize_identity_load(account)) {
+        omemo_ctx.loaded = FALSE;
+        log_error("[OMEMO] failed to load OMEMO state from disk for %s", account->jid);
+        cons_show_error("OMEMO: could not load encryption state from disk; OMEMO will be unavailable this session.");
+        return;
+    }
 
     wins_omemo_trust_changed(NULL);
 }

src/otr/otr.c

@@ -278,7 +278,10 @@ otr_on_message_recv(const char* const barejid, const char* const resource, const
                 if (strstr(message, OTRL_MESSAGE_TAG_V2) && strstr(message, OTRL_MESSAGE_TAG_V1)) {
                     tag_length = 32;
                 }
-                memmove(whitespace_base, whitespace_base + tag_length, tag_length);
+                // Shift the remainder of the message (including the trailing NUL)
+                // left over the tag, not just the next tag_length bytes — otherwise
+                // the tail is left in place and the body is duplicated/truncated.
+                memmove(whitespace_base, whitespace_base + tag_length, strlen(whitespace_base + tag_length) + 1);
                 char* otr_query_message = otr_start_query();
                 cons_show("OTR Whitespace pattern detected. Attempting to start OTR session…");
                 free(message_send_chat_otr(barejid, otr_query_message, FALSE, NULL));

src/xmpp/presence.c

@@ -621,15 +621,23 @@ _available_handler(xmpp_stanza_t* const stanza)
     }
 
     if (g_strcmp0(xmpp_presence->jid->barejid, my_jid->barejid) == 0) {
-        connection_add_available_resource(resource);
+        // Snapshot everything we read from `resource` before ownership is
+        // transferred to the available-resources table; dereferencing it
+        // afterwards would be a use-after-free should the same resource name
+        // ever be re-added between the transfer and the reads below.
         Resource* resource_for_roster = resource_copy(resource);
+        auto_gchar gchar* resource_name = g_strdup(resource->name);
+        auto_gchar gchar* resource_status = resource->status ? g_strdup(resource->status) : NULL;
+        int resource_priority = resource->priority;
+        resource_presence_t resource_presence = resource->presence;
+        connection_add_available_resource(resource);
         sv_ev_contact_online(xmpp_presence->jid->barejid, resource_for_roster, xmpp_presence->last_activity, pgpsig);
         const char* account_name = session_get_account_name();
         int max_sessions = accounts_get_max_sessions(account_name);
         if (max_sessions > 0) {
             auto_gchar gchar* cur_resource = accounts_get_resource(account_name);
             int res_count = connection_count_available_resources();
-            if (res_count > max_sessions && g_strcmp0(cur_resource, resource->name)) {
+            if (res_count > max_sessions && g_strcmp0(cur_resource, resource_name)) {
                 ProfWin* console = wins_get_console();
                 ProfWin* current_window = wins_get_current();
                 auto_gchar gchar* message = g_strdup_printf("Max sessions alarm! (%d/%d devices in use)", res_count, max_sessions);
@@ -639,14 +647,14 @@ _available_handler(xmpp_stanza_t* const stanza)
                 }
                 notify(message, 10000, "Security alert");
 
-                const char* resource_presence = string_from_resource_presence(resource->presence);
+                const char* resource_presence_str = string_from_resource_presence(resource_presence);
-                win_print(console, THEME_DEFAULT, "|", "New device info: \n    %s (%d), %s", resource->name, resource->priority, resource_presence);
+                win_print(console, THEME_DEFAULT, "|", "New device info: \n    %s (%d), %s", resource_name, resource_priority, resource_presence_str);
 
-                if (resource->status) {
+                if (resource_status) {
-                    win_append(console, THEME_DEFAULT, ", \"%s\"", resource->status);
+                    win_append(console, THEME_DEFAULT, ", \"%s\"", resource_status);
                 }
                 win_appendln(console, THEME_DEFAULT, "");
-                auto_jid Jid* jidp = jid_create_from_bare_and_resource(my_jid->barejid, resource->name);
+                auto_jid Jid* jidp = jid_create_from_bare_and_resource(my_jid->barejid, resource_name);
                 EntityCapabilities* caps = caps_lookup(jidp->fulljid);
 
                 if (caps) {