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gdbusprivate: Validate machine ID after loading it

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It’s unlikely that the machine ID will be invalid (it’s system
configuration), but it would be helpful to not propagate invalid IDs
further, since a lot of things rely on it.

It’s not easy to test this (it requires factoring out the code so it can
be used from a test program, or allowing it to load a machine ID from a
custom path), so I haven’t added unit tests. I’ve tested manually by
overriding the loaded machine ID.

Coverity CID: #1430944

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
This commit is contained in:
Philip Withnall 2021-02-24 11:49:47 +00:00
parent ea19358039
commit daa62a35e1
1 changed files with 33 additions and 7 deletions
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40
gio/gdbusprivate.c
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@ -2472,6 +2472,8 @@ _g_dbus_get_machine_id (GError **error)
#else #else
gchar *ret = NULL; gchar *ret = NULL;
GError *first_error = NULL; GError *first_error = NULL;
gsize i;
gboolean non_zero = FALSE;
/* TODO: use PACKAGE_LOCALSTATEDIR ? */ /* TODO: use PACKAGE_LOCALSTATEDIR ? */
if (!g_file_get_contents ("/var/lib/dbus/machine-id", if (!g_file_get_contents ("/var/lib/dbus/machine-id",
@ -2483,17 +2485,41 @@ _g_dbus_get_machine_id (GError **error)
NULL, NULL,
NULL)) NULL))
{ {
g_propagate_prefixed_error (error, first_error, g_propagate_prefixed_error (error, g_steal_pointer (&first_error),
_("Unable to load /var/lib/dbus/machine-id or /etc/machine-id: ")); _("Unable to load /var/lib/dbus/machine-id or /etc/machine-id: "));
return NULL;
} }
else
/* ignore the error from the first try, if any */
g_clear_error (&first_error);
/* Validate the machine ID. From `man 5 machine-id`:
* > The machine ID is a single newline-terminated, hexadecimal, 32-character,
* > lowercase ID. When decoded from hexadecimal, this corresponds to a
* > 16-byte/128-bit value. This ID may not be all zeros.
*/
for (i = 0; ret[i] != '\0' && ret[i] != '\n'; i++)
{ {
/* ignore the error from the first try, if any */ /* Break early if it’s invalid. */
g_clear_error (&first_error); if (!g_ascii_isxdigit (ret[i]) || g_ascii_isupper (ret[i]))
/* TODO: validate value */ break;
g_strstrip (ret);
if (ret[i] != '0')
non_zero = TRUE;
} }
return ret;
if (i != 32 || ret[i] != '\n' || ret[i + 1] != '\0' || !non_zero)
{
g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_FAILED,
"Invalid machine ID in /var/lib/dbus/machine-id or /etc/machine-id");
g_free (ret);
return NULL;
}
/* Strip trailing newline. */
ret[32] = '\0';
return g_steal_pointer (&ret);
#endif #endif
} }