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tests: Cope with having CAP_DAC_OVERRIDE, even if not euid 0

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Some CI platforms invoke these tests with euid != 0 but with
capabilities. Detect whether we have Linux CAP_DAC_OVERRIDE or other
OSs' equivalents, and skip tests that rely on DAC permissions being
denied if we do have that privilege.

Signed-off-by: Simon McVittie <smcv@collabora.com>
Fixes: https://gitlab.gnome.org/GNOME/glib/issues/2027
Fixes: https://gitlab.gnome.org/GNOME/glib/issues/2028
This commit is contained in:
Simon McVittie
2020-02-13 12:53:13 +00:00
parent 6e28ce2860
commit b9d04b37b0
2 changed files with 172 additions and 20 deletions
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104
glib/tests/fileutils.c
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@@ -522,6 +522,65 @@ test_mkdir_with_parents (void)
g_assert_cmpint (errno, ==, EINVAL);
}
#ifdef G_OS_UNIX
/*
* check_cap_dac_override:
* @tmpdir: A temporary directory in which we can create and delete files
*
* Check whether the current process can bypass DAC permissions.
*
* Traditionally, "privileged" processes (those with effective uid 0)
* could do this (and bypass many other checks), and "unprivileged"
* processes could not.
*
* In Linux, the special powers of euid 0 are divided into many
* capabilities: see `capabilities(7)`. The one we are interested in
* here is `CAP_DAC_OVERRIDE`.
*
* We do this generically instead of actually looking at the capability
* bits, so that the right thing will happen on non-Linux Unix
* implementations, in particular if they have something equivalent to
* but not identical to Linux permissions.
*
* Returns: %TRUE if we have Linux `CAP_DAC_OVERRIDE` or equivalent
* privileges
*/
static gboolean
check_cap_dac_override (const char *tmpdir)
{
gchar *dac_denies_write;
gchar *inside;
gboolean have_cap;
dac_denies_write = g_build_filename (tmpdir, "dac-denies-write", NULL);
inside = g_build_filename (dac_denies_write, "inside", NULL);
g_assert_cmpint (mkdir (dac_denies_write, S_IRWXU) == 0 ? 0 : errno, ==, 0);
g_assert_cmpint (chmod (dac_denies_write, 0) == 0 ? 0 : errno, ==, 0);
if (mkdir (inside, S_IRWXU) == 0)
{
g_test_message ("Looks like we have CAP_DAC_OVERRIDE or equivalent");
g_assert_cmpint (rmdir (inside) == 0 ? 0 : errno, ==, 0);
have_cap = TRUE;
}
else
{
int saved_errno = errno;
g_test_message ("We do not have CAP_DAC_OVERRIDE or equivalent");
g_assert_cmpint (saved_errno, ==, EACCES);
have_cap = FALSE;
}
g_assert_cmpint (chmod (dac_denies_write, S_IRWXU) == 0 ? 0 : errno, ==, 0);
g_assert_cmpint (rmdir (dac_denies_write) == 0 ? 0 : errno, ==, 0);
g_free (dac_denies_write);
g_free (inside);
return have_cap;
}
#endif
/* Reproducer for https://gitlab.gnome.org/GNOME/glib/issues/1852 */
static void
test_mkdir_with_parents_permission (void)
@@ -534,21 +593,23 @@ test_mkdir_with_parents_permission (void)
GError *error = NULL;
int result;
int saved_errno;
gboolean have_cap_dac_override;
tmpdir = g_dir_make_tmp ("test-fileutils.XXXXXX", &error);
g_assert_no_error (error);
g_assert_nonnull (tmpdir);
have_cap_dac_override = check_cap_dac_override (tmpdir);
subdir = g_build_filename (tmpdir, "sub", NULL);
subdir2 = g_build_filename (subdir, "sub2", NULL);
subdir3 = g_build_filename (subdir2, "sub3", NULL);
g_assert_cmpint (g_mkdir (subdir, 0700) == 0 ? 0 : errno, ==, 0);
g_assert_cmpint (g_chmod (subdir, 0) == 0 ? 0 : errno, ==, 0);
if (g_mkdir (subdir2, 0700) == 0)
if (have_cap_dac_override)
{
g_test_skip ("have CAP_DAC_OVERRIDE or equivalent, cannot test");
g_remove (subdir2);
}
else
{
@@ -949,14 +1010,8 @@ test_stdio_wrappers (void)
GError *error = NULL;
GStatBuf path_statbuf, cwd_statbuf;
time_t now;
/* The permissions tests here don’t work when running as root. */
#ifdef G_OS_UNIX
if (getuid () == 0 || geteuid () == 0)
{
g_test_skip ("File permissions tests cannot be run as root");
return;
}
gboolean have_cap_dac_override;
#endif
g_remove ("mkdir-test/test-create");
@@ -973,13 +1028,32 @@ test_stdio_wrappers (void)
cwd = g_get_current_dir ();
path = g_build_filename (cwd, "mkdir-test", NULL);
g_free (cwd);
#ifndef G_OS_WIN32
/* 0666 on directories means nothing to Windows, it only obeys ACLs */
ret = g_chdir (path);
g_assert_cmpint (errno, ==, EACCES);
g_assert_cmpint (ret, ==, -1);
#ifdef G_OS_UNIX
have_cap_dac_override = check_cap_dac_override (cwd);
#endif
g_free (cwd);
/* 0666 on directories means nothing to Windows, it only obeys ACLs.
* It doesn't necessarily mean anything on Unix either: if we have
* Linux CAP_DAC_OVERRIDE or equivalent (in particular if we're root),
* then we ignore filesystem permissions. */
#ifdef G_OS_UNIX
if (have_cap_dac_override)
{
g_test_message ("Cannot test g_chdir() failing with EACCES: we "
"probably have CAP_DAC_OVERRIDE or equivalent");
}
else
{
ret = g_chdir (path);
g_assert_cmpint (ret == 0 ? 0 : errno, ==, EACCES);
g_assert_cmpint (ret, ==, -1);
}
#else
g_test_message ("Cannot test g_chdir() failing with EACCES: "
"it's Unix-specific behaviour");
#endif
ret = g_chmod (path, 0777);
g_assert_cmpint (ret, ==, 0);
ret = g_chdir (path);