test: Add basic test coverage for DBUS_COOKIE_SHA1

We don't actually complete successful authentication, because that
would require us to generate a cookie and compute the correct SHA1,
which is difficult to do in a deterministic authentication script.
However, we do assert that dbus#269 (CVE-2019-12749) has been fixed.

Signed-off-by: Simon McVittie <smcv@collabora.com>

7 files changed, 184 insertions, 3 deletions

diff --git a/dbus/dbus-auth-script.c b/dbus/dbus-auth-script.c
index aaaed30d..9d4345fe 100644
--- a/dbus/dbus-auth-script.c
+++ b/dbus/dbus-auth-script.c
@@ -34,6 +34,8 @@
 #include "dbus-credentials.h"
 #include "dbus-internals.h"
 
+#include "test/test-utils.h"
+
 /**
  * @defgroup DBusAuthScript code for running unit test scripts for DBusAuth
  * @ingroup  DBusInternals
@@ -514,9 +516,43 @@ _dbus_auth_script_run (const DBusString *filename)
           /* Replace USERID_HEX with our username in hex */
           {
             int where;
-            
-            if (_dbus_string_find (&to_send, 0,
-                                   "USERID_HEX", &where))
+
+            if (_dbus_string_find (&to_send, 0, "WRONG_USERID_HEX", &where))
+              {
+                /* This must be checked for before USERID_HEX, because
+                 * that's a substring. */
+                DBusString uid;
+
+                if (!_dbus_string_init (&uid))
+                  {
+                    _dbus_warn ("no memory for uid");
+                    _dbus_string_free (&to_send);
+                    goto out;
+                  }
+
+                if (!_dbus_test_append_different_uid (&uid))
+                  {
+                    _dbus_warn ("no memory for uid");
+                    _dbus_string_free (&to_send);
+                    _dbus_string_free (&uid);
+                    goto out;
+                  }
+
+                _dbus_string_delete (&to_send, where,
+                                     (int) strlen ("WRONG_USERID_HEX"));
+
+                if (!_dbus_string_hex_encode (&uid, 0, &to_send, where))
+                  {
+                    _dbus_warn ("no memory to subst WRONG_USERID_HEX");
+                    _dbus_string_free (&to_send);
+                    _dbus_string_free (&uid);
+                    goto out;
+                  }
+
+                _dbus_string_free (&uid);
+              }
+            else if (_dbus_string_find (&to_send, 0,
+                                        "USERID_HEX", &where))
               {
                 DBusString username;
 
@@ -549,6 +585,51 @@ _dbus_auth_script_run (const DBusString *filename)
                 _dbus_string_free (&username);
               }
             else if (_dbus_string_find (&to_send, 0,
+                                        "WRONG_USERNAME_HEX", &where))
+              {
+                /* This must be checked for before USERNAME_HEX, because
+                 * that's a substring. */
+#ifdef DBUS_UNIX
+                DBusString username;
+
+                if (!_dbus_string_init (&username))
+                  {
+                    _dbus_warn ("no memory for username");
+                    _dbus_string_free (&to_send);
+                    goto out;
+                  }
+
+                if (!_dbus_test_append_different_username (&username))
+                  {
+                    _dbus_warn ("no memory for username");
+                    _dbus_string_free (&to_send);
+                    _dbus_string_free (&username);
+                    goto out;
+                  }
+
+                _dbus_string_delete (&to_send, where,
+                                     (int) strlen ("WRONG_USERNAME_HEX"));
+
+                if (!_dbus_string_hex_encode (&username, 0,
+                                              &to_send, where))
+                  {
+                    _dbus_warn ("no memory to subst WRONG_USERNAME_HEX");
+                    _dbus_string_free (&to_send);
+                    _dbus_string_free (&username);
+                    goto out;
+                  }
+
+                _dbus_string_free (&username);
+#else
+                /* No authentication mechanism uses the login name on
+                 * Windows, so there's no point in it appearing in an
+                 * auth script that is not UNIX_ONLY. */
+                _dbus_warn ("WRONG_USERNAME_HEX cannot be used on Windows");
+                _dbus_string_free (&to_send);
+                goto out;
+#endif
+              }
+            else if (_dbus_string_find (&to_send, 0,
                                         "USERNAME_HEX", &where))
               {
                 DBusString username;
diff --git a/dbus/dbus-sysdeps-util-unix.c b/dbus/dbus-sysdeps-util-unix.c
index 9b724cc9..df3368a2 100644
--- a/dbus/dbus-sysdeps-util-unix.c
+++ b/dbus/dbus-sysdeps-util-unix.c
@@ -1448,3 +1448,43 @@ _dbus_append_session_config_file (DBusString *str)
 {
   return _dbus_string_append (str, DBUS_SESSION_CONFIG_FILE);
 }
+
+#ifdef DBUS_ENABLE_EMBEDDED_TESTS
+
+/*
+ * Set uid to a machine-readable authentication identity (numeric Unix
+ * uid or ConvertSidToStringSid-style Windows SID) that is likely to exist,
+ * and differs from the identity of the current process.
+ *
+ * @param uid Populated with a machine-readable authentication identity
+ *    on success
+ * @returns #FALSE if no memory
+ */
+dbus_bool_t
+_dbus_test_append_different_uid (DBusString *uid)
+{
+  if (geteuid () == 0)
+    return _dbus_string_append (uid, "65534");
+  else
+    return _dbus_string_append (uid, "0");
+}
+
+/*
+ * Set uid to a human-readable authentication identity (login name)
+ * that is likely to exist, and differs from the identity of the current
+ * process. This function currently only exists on Unix platforms.
+ *
+ * @param uid Populated with a machine-readable authentication identity
+ *    on success
+ * @returns #FALSE if no memory
+ */
+dbus_bool_t
+_dbus_test_append_different_username (DBusString *username)
+{
+  if (geteuid () == 0)
+    return _dbus_string_append (username, "nobody");
+  else
+    return _dbus_string_append (username, "root");
+}
+
+#endif
diff --git a/dbus/dbus-sysdeps-util-win.c b/dbus/dbus-sysdeps-util-win.c
index 3b754dbf..54807733 100644
--- a/dbus/dbus-sysdeps-util-win.c
+++ b/dbus/dbus-sysdeps-util-win.c
@@ -1702,3 +1702,28 @@ _dbus_append_session_config_file (DBusString *str)
 {
   return _dbus_get_config_file_name(str, "session.conf");
 }
+
+#ifdef DBUS_ENABLE_EMBEDDED_TESTS
+
+#define ANONYMOUS_SID "S-1-5-7"
+#define LOCAL_SYSTEM_SID "S-1-5-18"
+
+dbus_bool_t
+_dbus_test_append_different_uid (DBusString *uid)
+{
+  char *sid = NULL;
+  dbus_bool_t ret;
+
+  if (!_dbus_getsid (&sid, _dbus_getpid ()))
+    return FALSE;
+
+  if (strcmp (sid, ANONYMOUS_SID) == 0)
+    ret = _dbus_string_append (uid, LOCAL_SYSTEM_SID);
+  else
+    ret = _dbus_string_append (uid, ANONYMOUS_SID);
+
+  LocalFree (sid);
+  return ret;
+}
+
+#endif
diff --git a/dbus/dbus-sysdeps.h b/dbus/dbus-sysdeps.h
index 0ee45c97..8b2836e7 100644
--- a/dbus/dbus-sysdeps.h
+++ b/dbus/dbus-sysdeps.h
@@ -683,6 +683,16 @@ dbus_bool_t     _dbus_rlimit_restore_fd_limit              (DBusRLimit   *saved,
                                                             DBusError    *error);
 void            _dbus_rlimit_free                          (DBusRLimit   *lim);
 
+#ifdef DBUS_ENABLE_EMBEDDED_TESTS
+_DBUS_GNUC_WARN_UNUSED_RESULT
+dbus_bool_t _dbus_test_append_different_uid (DBusString *uid);
+
+#ifdef DBUS_UNIX
+_DBUS_GNUC_WARN_UNUSED_RESULT
+dbus_bool_t _dbus_test_append_different_username (DBusString *username);
+#endif
+#endif  /* DBUS_ENABLE_EMBEDDED_TESTS */
+
 /** @} */
 
 DBUS_END_DECLS
diff --git a/test/Makefile.am b/test/Makefile.am
index ecf5aed7..db07c1e2 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -370,6 +370,8 @@ static_data = \
 	data/auth/anonymous-server-successful.auth-script \
 	data/auth/cancel.auth-script \
 	data/auth/client-out-of-mechanisms.auth-script \
+	data/auth/cookie-sha1-username.auth-script \
+	data/auth/cookie-sha1.auth-script \
 	data/auth/external-failed.auth-script \
 	data/auth/external-root.auth-script \
 	data/auth/external-silly.auth-script \
diff --git a/test/data/auth/cookie-sha1-username.auth-script b/test/data/auth/cookie-sha1-username.auth-script
new file mode 100644
index 00000000..45668294
--- /dev/null
+++ b/test/data/auth/cookie-sha1-username.auth-script
@@ -0,0 +1,12 @@
+UNIX_ONLY
+SERVER
+SEND 'AUTH DBUS_COOKIE_SHA1 WRONG_USERNAME_HEX'
+EXPECT_COMMAND REJECTED
+EXPECT_STATE WAITING_FOR_INPUT
+EXPECT_HAVE_NO_CREDENTIALS
+SEND 'AUTH DBUS_COOKIE_SHA1 USERNAME_HEX'
+EXPECT_COMMAND DATA
+EXPECT_STATE WAITING_FOR_INPUT
+EXPECT_HAVE_NO_CREDENTIALS
+# We don't actually complete DBUS_COOKIE_SHA1 authentication, because
+# it's non-trivial.
diff --git a/test/data/auth/cookie-sha1.auth-script b/test/data/auth/cookie-sha1.auth-script
new file mode 100644
index 00000000..f0dd33d7
--- /dev/null
+++ b/test/data/auth/cookie-sha1.auth-script
@@ -0,0 +1,11 @@
+SERVER
+SEND 'AUTH DBUS_COOKIE_SHA1 WRONG_USERID_HEX'
+EXPECT_COMMAND REJECTED
+EXPECT_STATE WAITING_FOR_INPUT
+EXPECT_HAVE_NO_CREDENTIALS
+SEND 'AUTH DBUS_COOKIE_SHA1 USERID_HEX'
+EXPECT_COMMAND DATA
+EXPECT_STATE WAITING_FOR_INPUT
+EXPECT_HAVE_NO_CREDENTIALS
+# We don't actually complete DBUS_COOKIE_SHA1 authentication, because
+# it's non-trivial.