fix(xmpp): treat disco#info result without 'from' as from the server

RFC 6120 §8.1.2.1: a stanza received over a c2s stream without a 'from'
attribute must be treated as coming from the server itself. The
on-connect disco#info handler passed the absent attribute as NULL into
connection_features_received(), where g_str_hash() dereferenced the NULL
key and crashed (remotely triggerable DoS on connect).

Substitute connection_get_domain() at both disco#info handler
boundaries, and make connection_features_received() and
connection_get_features() NULL-safe as defense in depth. Add a stabber
regression test answering the on-connect disco#info with a from-less
result.

Fixes #168

src/config/theme.c

@@ -87,7 +87,6 @@ theme_init(const char* const theme_name)
     g_hash_table_insert(defaults, strdup("main.help.header"), strdup("default"));
     g_hash_table_insert(defaults, strdup("main.trackbar"), strdup("default"));
     g_hash_table_insert(defaults, strdup("error"), strdup("red"));
-    g_hash_table_insert(defaults, strdup("warning"), strdup("yellow"));
     g_hash_table_insert(defaults, strdup("incoming"), strdup("yellow"));
     g_hash_table_insert(defaults, strdup("mention"), strdup("yellow"));
     g_hash_table_insert(defaults, strdup("trigger"), strdup("yellow"));
@@ -704,9 +703,6 @@ theme_attrs(theme_item_t attrs)
     case THEME_ERROR:
         _theme_prep_fgnd("error", lookup_str, &bold);
         break;
-    case THEME_WARNING:
-        _theme_prep_fgnd("warning", lookup_str, &bold);
-        break;
     case THEME_INCOMING:
         _theme_prep_fgnd("incoming", lookup_str, &bold);
         break;

src/config/theme.h

@@ -23,7 +23,6 @@ typedef enum {
     THEME_SPLASH,
     THEME_HELP_HEADER,
     THEME_ERROR,
-    THEME_WARNING,
     THEME_INCOMING,
     THEME_MENTION,
     THEME_TRIGGER,

src/ui/console.c

@@ -155,20 +155,6 @@ cons_show_error(const char* const msg, ...)
     cons_alert(NULL);
 }
 
-void
-cons_show_warning(const char* const msg, ...)
-{
-    va_list arg;
-    va_start(arg, msg);
-    GString* fmt_msg = g_string_new(NULL);
-    g_string_vprintf(fmt_msg, msg, arg);
-    win_println(wins_get_console(), THEME_WARNING, "-", "Warning: %s", fmt_msg->str);
-    g_string_free(fmt_msg, TRUE);
-    va_end(arg);
-
-    cons_alert(NULL);
-}
-
 void
 cons_show_tlscert_summary(const TLSCertificate* cert)
 {

src/ui/ui.h

@@ -252,8 +252,6 @@ G_GNUC_PRINTF(1, 2)
 void cons_debug(const char* const msg, ...);
 G_GNUC_PRINTF(1, 2)
 void cons_show_error(const char* const cmd, ...);
-G_GNUC_PRINTF(1, 2)
-void cons_show_warning(const char* const msg, ...);
 void cons_show_contacts(GSList* list);
 void cons_show_roster(GSList* list);
 void cons_show_roster_group(const char* const group, GSList* list);

src/xmpp/connection.c

@@ -749,21 +749,14 @@ connection_get_user(void)
     return connection_get_jid()->localpart;
 }
 
-// NULL 'from' means the server (RFC 6120 §8.1.2.1)
-static const char*
-_get_from_via_jid(const char* const jid)
-{
-    return jid ? jid : conn.domain;
-}
-
 void
 connection_features_received(const char* const jid)
 {
-    const char* key = _get_from_via_jid(jid);
+    log_info("[CONNECTION] connection_features_received %s", jid);
+    const char* key = jid ? jid : conn.domain; // g_str_hash crashes on NULL; NULL 'from' means the server (RFC 6120 §8.1.2.1)
     if (!key) {
         return;
     }
-    log_info("[CONNECTION] connection_features_received %s", key);
     if (g_hash_table_remove(conn.requested_features, key) && g_hash_table_size(conn.requested_features) == 0) {
         sv_ev_connection_features_received();
     }
@@ -772,7 +765,7 @@ connection_features_received(const char* const jid)
 GHashTable*
 connection_get_features(const char* const jid)
 {
-    const char* key = _get_from_via_jid(jid);
+    const char* key = jid ? jid : conn.domain;
     if (!key || !conn.features_by_jid) {
         return NULL;
     }

tests/unittests/ui/stub_ui.c

@@ -49,18 +49,6 @@ expect_any_cons_show_error(void)
     expect_any(cons_show_error, output);
 }
 
-void
-expect_cons_show_warning(char* expected)
-{
-    expect_string(cons_show_warning, output, expected);
-}
-
-void
-expect_any_cons_show_warning(void)
-{
-    expect_any(cons_show_warning, output);
-}
-
 void
 expect_win_println(char* message)
 {
@@ -857,16 +845,6 @@ cons_show_error(const char* const cmd, ...)
     va_end(args);
 }
 
-void
-cons_show_warning(const char* const msg, ...)
-{
-    va_list args;
-    va_start(args, msg);
-    vsnprintf(output, sizeof(output), msg, args);
-    check_expected(output);
-    va_end(args);
-}
-
 void
 cons_show_contacts(GSList* list)
 {

tests/unittests/ui/stub_ui.h

@@ -10,6 +10,4 @@ void expect_cons_show(char* expected);
 void expect_any_cons_show(void);
 void expect_cons_show_error(char* expected);
 void expect_any_cons_show_error(void);
-void expect_cons_show_warning(char* expected);
-void expect_any_cons_show_warning(void);
 void expect_win_println(char* message);