summaryrefslogtreecommitdiff
path: root/support/support_capture_subprocess.c
diff options
context:
space:
mode:
authorSiddhesh Poyarekar <siddhesh@sourceware.org>2021-04-09 20:55:45 +0530
committerSiddhesh Poyarekar <siddhesh@sourceware.org>2021-04-12 19:03:19 +0530
commit716a3bdc41b2b4b864dc64475015ba51e35e1273 (patch)
tree103a573114c8263cec174ca7fd655ff4612f0ee9 /support/support_capture_subprocess.c
parent8d4d77f6c848538cfb9e5ad0a14825e7ae4a1657 (diff)
downloadglibc-716a3bdc41b2b4b864dc64475015ba51e35e1273.tar
glibc-716a3bdc41b2b4b864dc64475015ba51e35e1273.tar.gz
glibc-716a3bdc41b2b4b864dc64475015ba51e35e1273.tar.bz2
glibc-716a3bdc41b2b4b864dc64475015ba51e35e1273.zip
support: Add capability to fork an sgid child
Add a new function support_capture_subprogram_self_sgid that spawns an sgid child of the running program with its own image and returns the exit code of the child process. This functionality is used by at least three tests in the testsuite at the moment, so it makes sense to consolidate. There is also a new function support_subprogram_wait which should provide simple system() like functionality that does not set up file actions. This is useful in cases where only the return code of the spawned subprocess is interesting. This patch also ports tst-secure-getenv to this new function. A subsequent patch will port other tests. This also brings an important change to tst-secure-getenv behaviour. Now instead of succeeding, the test fails as UNSUPPORTED if it is unable to spawn a setgid child, which is how it should have been in the first place. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Diffstat (limited to 'support/support_capture_subprocess.c')
-rw-r--r--support/support_capture_subprocess.c126
1 files changed, 126 insertions, 0 deletions
diff --git a/support/support_capture_subprocess.c b/support/support_capture_subprocess.c
index 3eb825b9af..27bfd19c93 100644
--- a/support/support_capture_subprocess.c
+++ b/support/support_capture_subprocess.c
@@ -20,11 +20,14 @@
#include <support/capture_subprocess.h>
#include <errno.h>
+#include <fcntl.h>
#include <stdlib.h>
#include <support/check.h>
#include <support/xunistd.h>
#include <support/xsocket.h>
#include <support/xspawn.h>
+#include <support/support.h>
+#include <support/test-driver.h>
static void
transfer (const char *what, struct pollfd *pfd, struct xmemstream *stream)
@@ -102,6 +105,129 @@ support_capture_subprogram (const char *file, char *const argv[])
return result;
}
+/* Copies the executable into a restricted directory, so that we can
+ safely make it SGID with the TARGET group ID. Then runs the
+ executable. */
+static int
+copy_and_spawn_sgid (char *child_id, gid_t gid)
+{
+ char *dirname = xasprintf ("%s/tst-tunables-setuid.%jd",
+ test_dir, (intmax_t) getpid ());
+ char *execname = xasprintf ("%s/bin", dirname);
+ int infd = -1;
+ int outfd = -1;
+ int ret = 1, status = 1;
+
+ TEST_VERIFY (mkdir (dirname, 0700) == 0);
+ if (support_record_failure_is_failed ())
+ goto err;
+
+ infd = open ("/proc/self/exe", O_RDONLY);
+ if (infd < 0)
+ FAIL_UNSUPPORTED ("unsupported: Cannot read binary from procfs\n");
+
+ outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700);
+ TEST_VERIFY (outfd >= 0);
+ if (support_record_failure_is_failed ())
+ goto err;
+
+ char buf[4096];
+ for (;;)
+ {
+ ssize_t rdcount = read (infd, buf, sizeof (buf));
+ TEST_VERIFY (rdcount >= 0);
+ if (support_record_failure_is_failed ())
+ goto err;
+ if (rdcount == 0)
+ break;
+ char *p = buf;
+ char *end = buf + rdcount;
+ while (p != end)
+ {
+ ssize_t wrcount = write (outfd, buf, end - p);
+ if (wrcount == 0)
+ errno = ENOSPC;
+ TEST_VERIFY (wrcount > 0);
+ if (support_record_failure_is_failed ())
+ goto err;
+ p += wrcount;
+ }
+ }
+ TEST_VERIFY (fchown (outfd, getuid (), gid) == 0);
+ if (support_record_failure_is_failed ())
+ goto err;
+ TEST_VERIFY (fchmod (outfd, 02750) == 0);
+ if (support_record_failure_is_failed ())
+ goto err;
+ TEST_VERIFY (close (outfd) == 0);
+ if (support_record_failure_is_failed ())
+ goto err;
+ TEST_VERIFY (close (infd) == 0);
+ if (support_record_failure_is_failed ())
+ goto err;
+
+ /* We have the binary, now spawn the subprocess. Avoid using
+ support_subprogram because we only want the program exit status, not the
+ contents. */
+ ret = 0;
+
+ char * const args[] = {execname, child_id, NULL};
+
+ status = support_subprogram_wait (args[0], args);
+
+err:
+ if (outfd >= 0)
+ close (outfd);
+ if (infd >= 0)
+ close (infd);
+ if (execname != NULL)
+ {
+ unlink (execname);
+ free (execname);
+ }
+ if (dirname != NULL)
+ {
+ rmdir (dirname);
+ free (dirname);
+ }
+
+ if (ret != 0)
+ FAIL_EXIT1("Failed to make sgid executable for test\n");
+
+ return status;
+}
+
+int
+support_capture_subprogram_self_sgid (char *child_id)
+{
+ gid_t target = 0;
+ const int count = 64;
+ gid_t groups[count];
+
+ /* Get a GID which is not our current GID, but is present in the
+ supplementary group list. */
+ int ret = getgroups (count, groups);
+ if (ret < 0)
+ FAIL_UNSUPPORTED("Could not get group list for user %jd\n",
+ (intmax_t) getuid ());
+
+ gid_t current = getgid ();
+ for (int i = 0; i < ret; ++i)
+ {
+ if (groups[i] != current)
+ {
+ target = groups[i];
+ break;
+ }
+ }
+
+ if (target == 0)
+ FAIL_UNSUPPORTED("Could not find a suitable GID for user %jd\n",
+ (intmax_t) getuid ());
+
+ return copy_and_spawn_sgid (child_id, target);
+}
+
void
support_capture_subprocess_free (struct support_capture_subprocess *p)
{