fix: OTR/presence/OMEMO correctness, stanza-id disco gate, build hardening

- OTR: strip the whitespace tag by shifting the full message tail incl. the NUL, not tag_length bytes, so the body is no longer duplicated for messages longer than the tag.
- presence: snapshot the resource fields before connection_add_available_resource() takes ownership, removing a use-after-free in the own-presence path.
- OMEMO: propagate _omemo_finalize_identity_load() failure on connect (log + cons_show_error + stop) instead of leaving OMEMO silently unavailable.
- OMEMO: guard NULL fingerprint decode in _omemo_fingerprint_decode / omemo_is_trusted_identity / omemo_trust and log every decode failure instead of failing silently.
- stanza-id: gate XEP-0359 dedup on disco urn:xmpp:sid:0 (the `by` JID or its domain), falling back to no-dedup when caps are unknown; add functional tests for trusted vs untrusted server.
- accounts: narrow the group-name sanitizer to the characters GKeyFile forbids in headers ([ ] \n \r), keeping `=` and `#`, so read/write stays symmetric.
- build: re-introduce compiler/sanitizer flags in a Pikaur-safe form (opt-in sanitizers, -Wsign-compare) and fix the resulting -Wsign-compare warnings (incl. proftest _mkdir_recursive).fix: OTR/presence/OMEMO correctness, stanza-id disco gate, build hardening

Author: jabber.developer2 <jabber.developer2@jabber.space>

src/xmpp/jid.c

@@ -117,7 +117,7 @@ jid_is_valid(const gchar* const str)
 
     // Localpart validation
     if (at) {
-        size_t local_len = at - str;
+        size_t local_len = g_diff_to_gsize(at, str);
         if (local_len == 0 || local_len > JID_MAX_PART_LEN) {
             return FALSE;
         }
@@ -135,7 +135,7 @@ jid_is_valid(const gchar* const str)
 
     // Resourcepart validation if present
     if (slash) {
-        domain_len = slash - domain_start;
+        domain_len = g_diff_to_gsize(slash, domain_start);
         size_t resource_len = strlen(slash + 1);
         if (resource_len > JID_MAX_PART_LEN) {
             return FALSE;

src/xmpp/message.c

@@ -65,6 +65,7 @@ static void _handle_pubsub(xmpp_stanza_t* const stanza, xmpp_stanza_t* const eve
 static gboolean _handle_form(xmpp_stanza_t* const stanza);
 static gboolean _handle_jingle_message(xmpp_stanza_t* const stanza);
 static gboolean _should_ignore_based_on_silence(xmpp_stanza_t* const stanza);
+static gboolean _stanza_id_by_trusted(const char* by);
 #ifdef HAVE_OMEMO
 static void _receive_omemo(xmpp_stanza_t* const stanza, ProfMessage* message);
 #endif
@@ -1088,7 +1089,7 @@ _handle_groupchat(xmpp_stanza_t* const stanza)
     xmpp_stanza_t* stanzaidst = xmpp_stanza_get_child_by_name_and_ns(stanza, STANZA_NAME_STANZA_ID, STANZA_NS_STABLE_ID);
     if (stanzaidst) {
         const char* by = xmpp_stanza_get_attribute(stanzaidst, "by");
-        if (by && (g_strcmp0(by, from_jid->barejid) == 0)) {
+        if (by && g_strcmp0(by, from_jid->barejid) == 0 && _stanza_id_by_trusted(by)) {
             stanzaid = (char*)xmpp_stanza_get_attribute(stanzaidst, STANZA_ATTR_ID);
             if (stanzaid) {
                 message->stanzaid = strdup(stanzaid);
@@ -1397,7 +1398,7 @@ _handle_chat(xmpp_stanza_t* const stanza, gboolean is_mam, gboolean is_carbon, c
         xmpp_stanza_t* stanzaidst = xmpp_stanza_get_child_by_name_and_ns(stanza, STANZA_NAME_STANZA_ID, STANZA_NS_STABLE_ID);
         if (stanzaidst) {
             const char* by = xmpp_stanza_get_attribute(stanzaidst, "by");
-            if (by && equals_our_barejid(by)) {
+            if (by && equals_our_barejid(by) && _stanza_id_by_trusted(by)) {
                 stanzaid = (char*)xmpp_stanza_get_attribute(stanzaidst, STANZA_ATTR_ID);
                 if (stanzaid) {
                     message->stanzaid = strdup(stanzaid);
@@ -1735,3 +1736,22 @@ _should_ignore_based_on_silence(xmpp_stanza_t* const stanza)
     }
     return FALSE;
 }
+
+// XEP-0359 §6 disco-gate; falls back to domain since that's what disco is run against.
+static gboolean
+_stanza_id_by_trusted(const char* by)
+{
+    if (!by) {
+        return FALSE;
+    }
+    GHashTable* features = connection_get_features(by);
+    if (features && g_hash_table_contains(features, STANZA_NS_STABLE_ID)) {
+        return TRUE;
+    }
+    const char* at = strchr(by, '@');
+    if (!at) {
+        return FALSE;
+    }
+    features = connection_get_features(at + 1);
+    return features && g_hash_table_contains(features, STANZA_NS_STABLE_ID);
+}

src/xmpp/muc.c

@@ -707,7 +707,7 @@ muc_autocomplete(ProfWin* window, const char* const input, gboolean previous)
     } else {
         search_str = last_space + 1;
         if (!chat_room->autocomplete_prefix) {
-            chat_room->autocomplete_prefix = g_strndup(input, search_str - input);
+            chat_room->autocomplete_prefix = g_strndup(input, g_diff_to_gsize(search_str, input));
         }
     }
 

src/xmpp/presence.c

@@ -621,15 +621,20 @@ _available_handler(xmpp_stanza_t* const stanza)
     }
 
     if (g_strcmp0(xmpp_presence->jid->barejid, my_jid->barejid) == 0) {
-        connection_add_available_resource(resource);
+        // Copy what we read before connection_add_available_resource() takes ownership.
         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 +644,14 @@ _available_handler(xmpp_stanza_t* const stanza)
                 }
                 notify(message, 10000, "Security alert");
 
-                const char* resource_presence = string_from_resource_presence(resource->presence);
-                win_print(console, THEME_DEFAULT, "|", "New device info: \n    %s (%d), %s", resource->name, resource->priority, 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_str);
 
-                if (resource->status) {
-                    win_append(console, THEME_DEFAULT, ", \"%s\"", resource->status);
+                if (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) {