security: E2EE and transport correctness (issue #147)

T04: promote security events to warnings — SASL auth failure, TLS
handshake failure, cert-failure details, see-other-host redirect;
DISABLE_TLS, TRUST_TLS and LEGACY_AUTH get a log warning plus a
console notice (REQ-LOG-01, REQ-LOG-02, REQ-AUTH-03)

T05: warn when a session ends up unencrypted without the user having
asked for it; refuse in-band registration on an unencrypted stream;
warn on each HTTP transfer with certificate verification disabled
(REQ-CRY-03, REQ-CFG-01)

T06: pin the update check to https with peer/host verification and no
redirects; strict N.N.N parser for the fetched version, which is
untrusted network input (REQ-VUL-02)

T09: no plaintext logging on failed MUC OMEMO sends; OTR opportunistic
first message passes allow_unencrypted_message(); get_random_string()
draws from a CSPRNG without modulo bias; guard the identity-key length
decrement against unsigned underflow (REQ-CRY-01, REQ-CRY-02,
REQ-CRY-07, REQ-MEM-05)

REQ-VUL-03 and REQ-CRY-09 are already satisfied on master and are
left unchanged.

tests/functionaltests/functionaltests.c

@@ -117,6 +117,7 @@ main(int argc, char* argv[])
         PROF_FUNC_TEST(connect_jid_requests_bookmarks),
         PROF_FUNC_TEST(connect_bad_password),
         PROF_FUNC_TEST(connect_shows_presence_updates),
+        PROF_FUNC_TEST(connect_warns_on_insecure_transport),
 
         /* Ping tests - XEP-0199 XMPP Ping */
         PROF_FUNC_TEST(ping_server),

tests/functionaltests/test_connect.c

@@ -92,3 +92,15 @@ connect_shows_presence_updates(void **state)
     );
     assert_true(prof_output_exact("Buddy1 (mobile) is xa, \"Gone :(\""));
 }
+
+void
+connect_warns_on_insecure_transport(void **state)
+{
+    /* the harness connects with "tls disable auth legacy": both downgrades must reach the console */
+    prof_connect();
+
+    prof_timeout(10);
+    assert_true(prof_output_exact("Security warning: TLS is disabled, this connection is unencrypted."));
+    assert_true(prof_output_exact("Security warning: legacy authentication is enabled for this connection."));
+    prof_timeout_reset();
+}

tests/functionaltests/test_connect.h

@@ -3,3 +3,4 @@ void connect_jid_sends_presence_after_receiving_roster(void **state);
 void connect_jid_requests_bookmarks(void **state);
 void connect_bad_password(void **state);
 void connect_shows_presence_updates(void **state);
+void connect_warns_on_insecure_transport(void **state);

tests/functionaltests/test_export_import.c

@@ -977,6 +977,8 @@ migration_incremental_accumulation(void** state)
     assert_true(prof_output_regex("Database backend switched to 'flatfile'\\."));
 
     prof_input("/msg buddy1@localhost");
+    /* full repaint: incremental redraw may emit only partial line text */
+    prof_input("/redraw");
     assert_true(prof_output_exact("incr-batch1-first"));
     assert_true(prof_output_exact("incr-batch1-second"));
     assert_true(prof_output_exact("incr-batch2-third"));

tests/unittests/test_common.c

@@ -1089,6 +1089,45 @@ release_is_new__tests__various(void** state)
     assert_false(release_is_new("0.16.0", ""));
     assert_false(release_is_new(NULL, "1.0.0"));
     assert_false(release_is_new("1.0.0", NULL));
+
+    // the found version is untrusted network input: nothing but strictly N.N.N may parse
+    assert_false(release_is_new("0.16.0", "  1.0.0"));       // leading whitespace
+    assert_false(release_is_new("0.16.0", "+1.0.0"));        // explicit sign
+    assert_false(release_is_new("0.16.0", "-1.0.0"));        // negative major
+    assert_false(release_is_new("0.16.0", "1.0.0-rc1"));     // trailing garbage
+    assert_false(release_is_new("0.16.0", "1.0.0\n"));       // trailing newline
+    assert_false(release_is_new("0.16.0", "1..0"));          // empty component
+    assert_false(release_is_new("0.16.0", "0x10.0.0"));      // hex is not accepted
+    assert_false(release_is_new("0.16.0", "99999999999.0.0")); // out of int range, must not wrap
+    assert_false(release_is_new("0.16.0", "1.0.0 malicious"));
+
+    // Boundary: the largest still-parsable component is accepted
+    assert_true(release_is_new("0.16.0", "2147483647.0.0"));
+}
+
+void
+get_random_string__generates_valid_ids(void** state)
+{
+    const gchar* alphabet = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    for (size_t len = 1; len <= 40; len++) {
+        gchar* id = get_random_string(len);
+        assert_non_null(id);
+        assert_int_equal(len, strlen(id));
+        for (size_t i = 0; i < len; i++) {
+            assert_non_null(strchr(alphabet, id[i]));
+        }
+        g_free(id);
+    }
+
+    // a collision here would mean a dead random source
+    gchar* a = get_random_string(20);
+    gchar* b = get_random_string(20);
+    assert_non_null(a);
+    assert_non_null(b);
+    assert_string_not_equal(a, b);
+    g_free(a);
+    g_free(b);
 }
 
 void

tests/unittests/test_common.h

@@ -64,5 +64,6 @@ void valid_tls_policy_option__is__correct_for_various_inputs(void** state);
 void get_mentions__tests__various(void** state);
 void release_is_new__tests__various(void** state);
 void str_xml_sanitize__strips_illegal_characters(void** state);
+void get_random_string__generates_valid_ids(void** state);
 
 #endif

tests/unittests/unittests.c

@@ -687,6 +687,7 @@ main(int argc, char* argv[])
         cmocka_unit_test(get_mentions__tests__various),
         cmocka_unit_test(release_is_new__tests__various),
         cmocka_unit_test(str_xml_sanitize__strips_illegal_characters),
+        cmocka_unit_test(get_random_string__generates_valid_ids),
 
         cmocka_unit_test_setup_teardown(plugins_get_command_names__returns__no_commands,
                                         load_preferences,