[PATCH v2 0/4] tunables and setxid programs

[PATCH v2 0/4] tunables and setxid programs

[Siddhesh Poyarekar]

When parse_tunables tries to erase a tunable marked as SXID_ERASE for
setuid programs, it ends up setting the envvar string iterator
incorrectly, because of which it may parse the next tunable
incorrectly.  Given that currently the implementation allows malformed
and unrecognized tunables pass through, it may even allow SXID_ERASE
tunables to go through.

This change revamps the SXID_ERASE implementation so that:

- Only valid tunables are written back to the tunestr string, because
  of which children of SXID programs will only inherit a clean list of
  identified tunables that are not SXID_ERASE.

- Unrecognized tunables get scrubbed off from the environment and
  subsequently from the child environment.

- This has the side-effect that a tunable that is not identified by
  the setxid binary, will not be passed on to a non-setxid child even
  if the child could have identified that tunable.  This may break
  applications that expect this behaviour but expecting such tunables
  to cross the SXID boundary is wrong.

The setuid test for tunables has been bolstered to test different
combinations of tunable values to ensure that the behaviour is now
consistent.

Siddhesh Poyarekar (4):
  support: Add capability to fork an sgid child
  tst-env-setuid: Use support_capture_subprogram_self_sgid
  Enhance setuid-tunables test
  Fix SXID_ERASE behavior in setuid programs (BZ #27471)

 elf/Makefile                         |   2 -
 elf/dl-tunables.c                    |  56 ++++----
 elf/tst-env-setuid-tunables.c        | 118 +++++++++++++---
 elf/tst-env-setuid.c                 | 197 ++------------------------
 stdlib/tst-secure-getenv.c           | 199 +++------------------------
 support/capture_subprocess.h         |   6 +
 support/check.h                      |  12 ++
 support/subprocess.h                 |   5 +
 support/support_capture_subprocess.c | 114 +++++++++++++++
 support/support_subprocess.c         |  13 ++
 10 files changed, 304 insertions(+), 418 deletions(-)

-- 
2.29.2

[PATCH 1/4] support: Add capability to fork an sgid child

[Siddhesh Poyarekar]

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.
---
 stdlib/tst-secure-getenv.c           | 199 +++------------------------
 support/capture_subprocess.h         |   6 +
 support/check.h                      |  12 ++
 support/subprocess.h                 |   5 +
 support/support_capture_subprocess.c | 114 +++++++++++++++
 support/support_subprocess.c         |  13 ++
 6 files changed, 168 insertions(+), 181 deletions(-)

diff --git a/stdlib/tst-secure-getenv.c b/stdlib/tst-secure-getenv.c
index c9ec03866f..5567c9ae21 100644
--- a/stdlib/tst-secure-getenv.c
+++ b/stdlib/tst-secure-getenv.c
@@ -30,167 +30,12 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+#include <support/check.h>
 #include <support/support.h>
+#include <support/capture_subprocess.h>
 #include <support/test-driver.h>
 
 static char MAGIC_ARGUMENT[] = "run-actual-test";
-#define MAGIC_STATUS 19
-
-/* Return a GID which is not our current GID, but is present in the
-   supplementary group list.  */
-static gid_t
-choose_gid (void)
-{
-  int count = getgroups (0, NULL);
-  if (count < 0)
-    {
-      printf ("getgroups: %m\n");
-      exit (1);
-    }
-  gid_t *groups;
-  groups = xcalloc (count, sizeof (*groups));
-  int ret = getgroups (count, groups);
-  if (ret < 0)
-    {
-      printf ("getgroups: %m\n");
-      exit (1);
-    }
-  gid_t current = getgid ();
-  gid_t not_current = 0;
-  for (int i = 0; i < ret; ++i)
-    {
-      if (groups[i] != current)
-        {
-          not_current = groups[i];
-          break;
-        }
-    }
-  free (groups);
-  return not_current;
-}
-
-
-/* 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
-run_executable_sgid (gid_t target)
-{
-  char *dirname = xasprintf ("%s/secure-getenv.%jd",
-			     test_dir, (intmax_t) getpid ());
-  char *execname = xasprintf ("%s/bin", dirname);
-  int infd = -1;
-  int outfd = -1;
-  int ret = -1;
-  if (mkdir (dirname, 0700) < 0)
-    {
-      printf ("mkdir: %m\n");
-      goto err;
-    }
-  infd = open ("/proc/self/exe", O_RDONLY);
-  if (infd < 0)
-    {
-      printf ("open (/proc/self/exe): %m\n");
-      goto err;
-    }
-  outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700);
-  if (outfd < 0)
-    {
-      printf ("open (%s): %m\n", execname);
-      goto err;
-    }
-  char buf[4096];
-  for (;;)
-    {
-      ssize_t rdcount = read (infd, buf, sizeof (buf));
-      if (rdcount < 0)
-	{
-	  printf ("read: %m\n");
-	  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;
-	  if (wrcount <= 0)
-	    {
-	      printf ("write: %m\n");
-	      goto err;
-	    }
-	  p += wrcount;
-	}
-    }
-  if (fchown (outfd, getuid (), target) < 0)
-    {
-      printf ("fchown (%s): %m\n", execname);
-      goto err;
-    }
-  if (fchmod (outfd, 02750) < 0)
-    {
-      printf ("fchmod (%s): %m\n", execname);
-      goto err;
-    }
-  if (close (outfd) < 0)
-    {
-      printf ("close (outfd): %m\n");
-      goto err;
-    }
-  if (close (infd) < 0)
-    {
-      printf ("close (infd): %m\n");
-      goto err;
-    }
-
-  int kid = fork ();
-  if (kid < 0)
-    {
-      printf ("fork: %m\n");
-      goto err;
-    }
-  if (kid == 0)
-    {
-      /* Child process.  */
-      char *args[] = { execname, MAGIC_ARGUMENT, NULL };
-      execve (execname, args, environ);
-      printf ("execve (%s): %m\n", execname);
-      _exit (1);
-    }
-  int status;
-  if (waitpid (kid, &status, 0) < 0)
-    {
-      printf ("waitpid: %m\n");
-      goto err;
-    }
-  if (!WIFEXITED (status) || WEXITSTATUS (status) != MAGIC_STATUS)
-    {
-      printf ("Unexpected exit status %d from child process\n",
-	      status);
-      goto err;
-    }
-  ret = 0;
-
-err:
-  if (outfd >= 0)
-    close (outfd);
-  if (infd >= 0)
-    close (infd);
-  if (execname)
-    {
-      unlink (execname);
-      free (execname);
-    }
-  if (dirname)
-    {
-      rmdir (dirname);
-      free (dirname);
-    }
-  return ret;
-}
 
 static int
 do_test (void)
@@ -212,15 +57,15 @@ do_test (void)
       exit (1);
     }
 
-  gid_t target = choose_gid ();
-  if (target == 0)
-    {
-      fprintf (stderr,
-	       "Could not find a suitable GID for user %jd, skipping test\n",
-	       (intmax_t) getuid ());
-      exit (0);
-    }
-  return run_executable_sgid (target);
+  int status = support_capture_subprogram_self_sgid (MAGIC_ARGUMENT);
+
+  if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
+    return EXIT_UNSUPPORTED;
+
+  if (!WIFEXITED (status))
+    FAIL_EXIT1 ("Unexpected exit status %d from child process\n", status);
+
+  return 0;
 }
 
 static void
@@ -229,23 +74,15 @@ alternative_main (int argc, char **argv)
   if (argc == 2 && strcmp (argv[1], MAGIC_ARGUMENT) == 0)
     {
       if (getgid () == getegid ())
-	{
-	  /* This can happen if the file system is mounted nosuid.  */
-	  fprintf (stderr, "SGID failed: GID and EGID match (%jd)\n",
-		  (intmax_t) getgid ());
-	  exit (MAGIC_STATUS);
-	}
+	/* This can happen if the file system is mounted nosuid.  */
+	FAIL_UNSUPPORTED ("SGID failed: GID and EGID match (%jd)\n",
+		   (intmax_t) getgid ());
       if (getenv ("PATH") == NULL)
-	{
-	  printf ("PATH variable not present\n");
-	  exit (3);
-	}
+	FAIL_EXIT (3, "PATH variable not present\n");
       if (secure_getenv ("PATH") != NULL)
-	{
-	  printf ("PATH variable not filtered out\n");
-	  exit (4);
-	}
-      exit (MAGIC_STATUS);
+	FAIL_EXIT (4, "PATH variable not filtered out\n");
+
+      exit (EXIT_SUCCESS);
     }
 }
 
diff --git a/support/capture_subprocess.h b/support/capture_subprocess.h
index 8969d4a99a..4be430f099 100644
--- a/support/capture_subprocess.h
+++ b/support/capture_subprocess.h
@@ -41,6 +41,12 @@ struct support_capture_subprocess support_capture_subprocess
 struct support_capture_subprocess support_capture_subprogram
   (const char *file, char *const argv[]);
 
+/* Copy the running program into a setgid binary and run it with CHILD_ID
+   argument.  If execution is successful, return the exit status of the child
+   program, otherwise return a non-zero failure exit code.  */
+int support_capture_subprogram_self_sgid
+  (char *child_id);
+
 /* Deallocate the subprocess data captured by
    support_capture_subprocess.  */
 void support_capture_subprocess_free (struct support_capture_subprocess *);
diff --git a/support/check.h b/support/check.h
index 83662b2d10..801e34e943 100644
--- a/support/check.h
+++ b/support/check.h
@@ -54,6 +54,18 @@ __BEGIN_DECLS
       support_test_verify_impl (__FILE__, __LINE__, #expr);     \
   })
 
+/* Record a test failure and jump to LABEL if EXPR evaluates to false.  */
+#define TEST_VERIFY_GOTO(expr, label)                           \
+  ({                                                            \
+    if ((expr))                                                   \
+      ;                                                         \
+    else                                                        \
+      {                                                         \
+        support_test_verify_impl (__FILE__, __LINE__, #expr);   \
+        goto label;                                             \
+      }                                                         \
+  })
+
 /* Record a test failure and exit if EXPR evaluates to false.  */
 #define TEST_VERIFY_EXIT(expr)                                  \
   ({                                                            \
diff --git a/support/subprocess.h b/support/subprocess.h
index 11cfc6a07f..40d82c7e4d 100644
--- a/support/subprocess.h
+++ b/support/subprocess.h
@@ -38,6 +38,11 @@ struct support_subprocess support_subprocess
 struct support_subprocess support_subprogram
   (const char *file, char *const argv[]);
 
+/* Invoke program FILE with ARGV arguments by using posix_spawn and wait for it
+   to complete.  Return program exit status.  */
+int support_subprogram_wait
+  (const char *file, char *const argv[]);
+
 /* Wait for the subprocess indicated by PROC::PID.  Return the status
    indicate by waitpid call.  */
 int support_process_wait (struct support_subprocess *proc);
diff --git a/support/support_capture_subprocess.c b/support/support_capture_subprocess.c
index 3eb825b9af..bb61fecaaf 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 +105,117 @@ 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_GOTO (mkdir (dirname, 0700) >= 0, 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_GOTO (outfd >= 0, err);
+
+  char buf[4096];
+  for (;;)
+    {
+      ssize_t rdcount = read (infd, buf, sizeof (buf));
+      TEST_VERIFY_GOTO (rdcount >= 0, 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_GOTO (wrcount > 0, err);
+	  p += wrcount;
+	}
+    }
+  int goto_ret = fchown (outfd, getuid (), gid);
+  TEST_VERIFY_GOTO (goto_ret == 0, err);
+  goto_ret = fchmod (outfd, 02750);
+  TEST_VERIFY_GOTO (goto_ret == 0, err);
+  goto_ret = close (outfd);
+  TEST_VERIFY_GOTO (goto_ret == 0, err);
+  goto_ret = close (infd);
+  TEST_VERIFY_GOTO (goto_ret == 0, 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)
 {
diff --git a/support/support_subprocess.c b/support/support_subprocess.c
index 2acfc57b7e..89e767ae47 100644
--- a/support/support_subprocess.c
+++ b/support/support_subprocess.c
@@ -92,6 +92,19 @@ support_subprogram (const char *file, char *const argv[])
   return result;
 }
 
+int
+support_subprogram_wait (const char *file, char *const argv[])
+{
+  posix_spawn_file_actions_t fa;
+
+  posix_spawn_file_actions_init (&fa);
+  struct support_subprocess res = support_subprocess_init ();
+
+  res.pid = xposix_spawn (file, &fa, NULL, argv, environ);
+
+  return support_process_wait (&res);
+}
+
 int
 support_process_wait (struct support_subprocess *proc)
 {
-- 
2.29.2

[PATCH 2/4] tst-env-setuid: Use support_capture_subprogram_self_sgid

[Siddhesh Poyarekar]

Use the support_capture_subprogram_self_sgid to spawn an sgid child.
---
 elf/tst-env-setuid.c | 197 +++----------------------------------------
 1 file changed, 14 insertions(+), 183 deletions(-)

diff --git a/elf/tst-env-setuid.c b/elf/tst-env-setuid.c
index 60ae0ca380..49b5e319e2 100644
--- a/elf/tst-env-setuid.c
+++ b/elf/tst-env-setuid.c
@@ -29,173 +29,12 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+#include <support/check.h>
 #include <support/support.h>
 #include <support/test-driver.h>
+#include <support/capture_subprocess.h>
 
 static char SETGID_CHILD[] = "setgid-child";
-#define CHILD_STATUS 42
-
-/* Return a GID which is not our current GID, but is present in the
-   supplementary group list.  */
-static gid_t
-choose_gid (void)
-{
-  const int count = 64;
-  gid_t groups[count];
-  int ret = getgroups (count, groups);
-  if (ret < 0)
-    {
-      printf ("getgroups: %m\n");
-      exit (1);
-    }
-  gid_t current = getgid ();
-  for (int i = 0; i < ret; ++i)
-    {
-      if (groups[i] != current)
-	return groups[i];
-    }
-  return 0;
-}
-
-/* Spawn and execute a program and verify that it returns the CHILD_STATUS.  */
-static pid_t
-do_execve (char **args)
-{
-  pid_t kid = vfork ();
-
-  if (kid < 0)
-    {
-      printf ("vfork: %m\n");
-      return -1;
-    }
-
-  if (kid == 0)
-    {
-      /* Child process.  */
-      execve (args[0], args, environ);
-      _exit (-errno);
-    }
-
-  if (kid < 0)
-    return 1;
-
-  int status;
-
-  if (waitpid (kid, &status, 0) < 0)
-    {
-      printf ("waitpid: %m\n");
-      return 1;
-    }
-
-  if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
-    return EXIT_UNSUPPORTED;
-
-  if (!WIFEXITED (status) || WEXITSTATUS (status) != CHILD_STATUS)
-    {
-      printf ("Unexpected exit status %d from child process\n",
-	      WEXITSTATUS (status));
-      return 1;
-    }
-  return 0;
-}
-
-/* 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
-run_executable_sgid (gid_t target)
-{
-  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 = 0;
-  if (mkdir (dirname, 0700) < 0)
-    {
-      printf ("mkdir: %m\n");
-      goto err;
-    }
-  infd = open ("/proc/self/exe", O_RDONLY);
-  if (infd < 0)
-    {
-      printf ("open (/proc/self/exe): %m\n");
-      goto err;
-    }
-  outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700);
-  if (outfd < 0)
-    {
-      printf ("open (%s): %m\n", execname);
-      goto err;
-    }
-  char buf[4096];
-  for (;;)
-    {
-      ssize_t rdcount = read (infd, buf, sizeof (buf));
-      if (rdcount < 0)
-	{
-	  printf ("read: %m\n");
-	  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;
-	  if (wrcount <= 0)
-	    {
-	      printf ("write: %m\n");
-	      goto err;
-	    }
-	  p += wrcount;
-	}
-    }
-  if (fchown (outfd, getuid (), target) < 0)
-    {
-      printf ("fchown (%s): %m\n", execname);
-      goto err;
-    }
-  if (fchmod (outfd, 02750) < 0)
-    {
-      printf ("fchmod (%s): %m\n", execname);
-      goto err;
-    }
-  if (close (outfd) < 0)
-    {
-      printf ("close (outfd): %m\n");
-      goto err;
-    }
-  if (close (infd) < 0)
-    {
-      printf ("close (infd): %m\n");
-      goto err;
-    }
-
-  char *args[] = {execname, SETGID_CHILD, NULL};
-
-  ret = do_execve (args);
-
-err:
-  if (outfd >= 0)
-    close (outfd);
-  if (infd >= 0)
-    close (infd);
-  if (execname)
-    {
-      unlink (execname);
-      free (execname);
-    }
-  if (dirname)
-    {
-      rmdir (dirname);
-      free (dirname);
-    }
-  return ret;
-}
 
 #ifndef test_child
 static int
@@ -256,40 +95,32 @@ do_test (int argc, char **argv)
   if (argc == 2 && strcmp (argv[1], SETGID_CHILD) == 0)
     {
       if (getgid () == getegid ())
-	{
-	  /* This can happen if the file system is mounted nosuid.  */
-	  fprintf (stderr, "SGID failed: GID and EGID match (%jd)\n",
-		   (intmax_t) getgid ());
-	  exit (EXIT_UNSUPPORTED);
-	}
+	/* This can happen if the file system is mounted nosuid.  */
+	FAIL_UNSUPPORTED ("SGID failed: GID and EGID match (%jd)\n",
+			  (intmax_t) getgid ());
 
       int ret = test_child ();
 
       if (ret != 0)
 	exit (1);
 
-      exit (CHILD_STATUS);
+      exit (EXIT_SUCCESS);
     }
   else
     {
       if (test_parent () != 0)
 	exit (1);
 
-      /* Try running a setgid program.  */
-      gid_t target = choose_gid ();
-      if (target == 0)
-	{
-	  fprintf (stderr,
-		   "Could not find a suitable GID for user %jd, skipping test\n",
-		   (intmax_t) getuid ());
-	  exit (0);
-	}
+      int status = support_capture_subprogram_self_sgid (SETGID_CHILD);
 
-      return run_executable_sgid (target);
-    }
+      if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
+	return EXIT_UNSUPPORTED;
+
+      if (!WIFEXITED (status))
+	FAIL_EXIT1 ("Unexpected exit status %d from child process\n", status);
 
-  /* Something went wrong and our argv was corrupted.  */
-  _exit (1);
+      return 0;
+    }
 }
 
 #define TEST_FUNCTION_ARGV do_test
-- 
2.29.2

[PATCH 3/4] Enhance setuid-tunables test

[Siddhesh Poyarekar]

Instead of passing GLIBC_TUNABLES via the environment, pass the
environment variable from parent to child.  This allows us to test
multiple variables to ensure better coverage.

The test list currently only includes the case that's already being
tested.  More tests will be added later.
---
 elf/Makefile                  |  2 -
 elf/tst-env-setuid-tunables.c | 90 +++++++++++++++++++++++++++--------
 2 files changed, 69 insertions(+), 23 deletions(-)

diff --git a/elf/Makefile b/elf/Makefile
index 3b8e13e066..4e04c26eea 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -1653,8 +1653,6 @@ $(objpfx)tst-nodelete-dlclose.out: $(objpfx)tst-nodelete-dlclose-dso.so \
 
 tst-env-setuid-ENV = MALLOC_CHECK_=2 MALLOC_MMAP_THRESHOLD_=4096 \
 		     LD_HWCAP_MASK=0x1
-tst-env-setuid-tunables-ENV = \
-	GLIBC_TUNABLES=glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096
 
 $(objpfx)tst-debug1: $(libdl)
 $(objpfx)tst-debug1.out: $(objpfx)tst-debug1mod1.so
diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index 50bef8683d..3d523875b1 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -25,35 +25,50 @@
 #include "config.h"
 #undef _LIBC
 
-#define test_parent test_parent_tunables
-#define test_child test_child_tunables
-
-static int test_child_tunables (void);
-static int test_parent_tunables (void);
-
-#include "tst-env-setuid.c"
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <intprops.h>
+#include <array_length.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+#include <support/capture_subprocess.h>
+
+const char *teststrings[] =
+{
+  "glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096",
+};
 
-#define CHILD_VALSTRING_VALUE "glibc.malloc.mmap_threshold=4096"
-#define PARENT_VALSTRING_VALUE \
-  "glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096"
+const char *resultstrings[] =
+{
+  "glibc.malloc.mmap_threshold=4096",
+};
 
 static int
-test_child_tunables (void)
+test_child (int off)
 {
   const char *val = getenv ("GLIBC_TUNABLES");
 
 #if HAVE_TUNABLES
-  if (val != NULL && strcmp (val, CHILD_VALSTRING_VALUE) == 0)
+  if (val != NULL && strcmp (val, resultstrings[off]) == 0)
     return 0;
 
   if (val != NULL)
-    printf ("Unexpected GLIBC_TUNABLES VALUE %s\n", val);
+    printf ("[%d] Unexpected GLIBC_TUNABLES VALUE %s\n", off, val);
 
   return 1;
 #else
   if (val != NULL)
     {
-      printf ("GLIBC_TUNABLES not cleared\n");
+      printf ("[%d] GLIBC_TUNABLES not cleared\n", off);
       return 1;
     }
   return 0;
@@ -61,15 +76,48 @@ test_child_tunables (void)
 }
 
 static int
-test_parent_tunables (void)
+do_test (int argc, char **argv)
 {
-  const char *val = getenv ("GLIBC_TUNABLES");
+  /* Setgid child process.  */
+  if (argc == 2)
+    {
+      if (getgid () == getegid ())
+	/* This can happen if the file system is mounted nosuid.  */
+	FAIL_UNSUPPORTED ("SGID failed: GID and EGID match (%jd)\n",
+			  (intmax_t) getgid ());
 
-  if (val != NULL && strcmp (val, PARENT_VALSTRING_VALUE) == 0)
-    return 0;
+      int ret = test_child (atoi (argv[1]));
 
-  if (val != NULL)
-    printf ("Unexpected GLIBC_TUNABLES VALUE %s\n", val);
+      if (ret != 0)
+	exit (1);
 
-  return 1;
+      exit (EXIT_SUCCESS);
+    }
+  else
+    {
+      int ret = 0;
+
+      /* Spawn tests.  */
+      for (int i = 0; i < array_length (teststrings); i++)
+	{
+	  char buf[INT_BUFSIZE_BOUND (int)];
+
+	  printf ("Spawned test for %s (%d)\n", teststrings[i], i);
+	  snprintf (buf, sizeof (buf), "%d\n", i);
+	  if (setenv ("GLIBC_TUNABLES", teststrings[i], 1) != 0)
+	    exit (1);
+
+	  int status = support_capture_subprogram_self_sgid (buf);
+
+	  /* Bail out early if unsupported.  */
+	  if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
+	    return EXIT_UNSUPPORTED;
+
+	  ret |= status;
+	}
+      return ret;
+    }
 }
+
+#define TEST_FUNCTION_ARGV do_test
+#include <support/test-driver.c>
-- 
2.29.2

[PATCH 4/4] Fix SXID_ERASE behavior in setuid programs (BZ #27471)

[Siddhesh Poyarekar]

When parse_tunables tries to erase a tunable marked as SXID_ERASE for
setuid programs, it ends up setting the envvar string iterator
incorrectly, because of which it may parse the next tunable
incorrectly.  Given that currently the implementation allows malformed
and unrecognized tunables pass through, it may even allow SXID_ERASE
tunables to go through.

This change revamps the SXID_ERASE implementation so that:

- Only valid tunables are written back to the tunestr string, because
  of which children of SXID programs will only inherit a clean list of
  identified tunables that are not SXID_ERASE.

- Unrecognized tunables get scrubbed off from the environment and
  subsequently from the child environment.

- This has the side-effect that a tunable that is not identified by
  the setxid binary, will not be passed on to a non-setxid child even
  if the child could have identified that tunable.  This may break
  applications that expect this behaviour but expecting such tunables
  to cross the SXID boundary is wrong.
---
 elf/dl-tunables.c             | 56 ++++++++++++++++-------------------
 elf/tst-env-setuid-tunables.c | 26 ++++++++++++++++
 2 files changed, 52 insertions(+), 30 deletions(-)

diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index a2be9cde2f..1aedb9bd36 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -171,6 +171,7 @@ parse_tunables (char *tunestr, char *valstring)
     return;
 
   char *p = tunestr;
+  size_t off = 0;
 
   while (true)
     {
@@ -184,7 +185,11 @@ parse_tunables (char *tunestr, char *valstring)
       /* If we reach the end of the string before getting a valid name-value
 	 pair, bail out.  */
       if (p[len] == '\0')
-	return;
+	{
+	  if (__libc_enable_secure)
+	    tunestr[off] = '\0';
+	  return;
+	}
 
       /* We did not find a valid name-value pair before encountering the
 	 colon.  */
@@ -210,35 +215,28 @@ parse_tunables (char *tunestr, char *valstring)
 
 	  if (tunable_is_name (cur->name, name))
 	    {
-	      /* If we are in a secure context (AT_SECURE) then ignore the tunable
-		 unless it is explicitly marked as secure.  Tunable values take
-		 precedence over their envvar aliases.  */
+	      /* If we are in a secure context (AT_SECURE) then ignore the
+		 tunable unless it is explicitly marked as secure.  Tunable
+		 values take precedence over their envvar aliases.  We write
+		 the tunables that are not SXID_ERASE back to TUNESTR, thus
+		 dropping all SXID_ERASE tunables and any invalid or
+		 unrecognized tunables.  */
 	      if (__libc_enable_secure)
 		{
-		  if (cur->security_level == TUNABLE_SECLEVEL_SXID_ERASE)
+		  if (cur->security_level != TUNABLE_SECLEVEL_SXID_ERASE)
 		    {
-		      if (p[len] == '\0')
-			{
-			  /* Last tunable in the valstring.  Null-terminate and
-			     return.  */
-			  *name = '\0';
-			  return;
-			}
-		      else
-			{
-			  /* Remove the current tunable from the string.  We do
-			     this by overwriting the string starting from NAME
-			     (which is where the current tunable begins) with
-			     the remainder of the string.  We then have P point
-			     to NAME so that we continue in the correct
-			     position in the valstring.  */
-			  char *q = &p[len + 1];
-			  p = name;
-			  while (*q != '\0')
-			    *name++ = *q++;
-			  name[0] = '\0';
-			  len = 0;
-			}
+		      if (off > 0)
+			tunestr[off++] = ':';
+
+		      const char *n = cur->name;
+
+		      while (*n != '\0')
+			tunestr[off++] = *n++;
+
+		      tunestr[off++] = '=';
+
+		      for (size_t j = 0; j < len; j++)
+			tunestr[off++] = value[j];
 		    }
 
 		  if (cur->security_level != TUNABLE_SECLEVEL_NONE)
@@ -251,9 +249,7 @@ parse_tunables (char *tunestr, char *valstring)
 	    }
 	}
 
-      if (p[len] == '\0')
-	return;
-      else
+      if (p[len] != '\0')
 	p += len + 1;
     }
 }
diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index 3d523875b1..05619c9adc 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -45,11 +45,37 @@
 const char *teststrings[] =
 {
   "glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.check=2:glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096:glibc.malloc.check=2",
+  "glibc.malloc.perturb=0x800",
+  "glibc.malloc.perturb=0x800:glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.perturb=0x800:not_valid.malloc.check=2:glibc.malloc.mmap_threshold=4096",
+  "glibc.not_valid.check=2:glibc.malloc.mmap_threshold=4096",
+  "not_valid.malloc.check=2:glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.garbage=2:glibc.maoc.mmap_threshold=4096:glibc.malloc.check=2",
+  "glibc.malloc.check=4:glibc.malloc.garbage=2:glibc.maoc.mmap_threshold=4096",
+  ":glibc.malloc.garbage=2:glibc.malloc.check=1",
+  "glibc.malloc.check=1:glibc.malloc.check=2",
+  "not_valid.malloc.check=2",
+  "glibc.not_valid.check=2",
 };
 
 const char *resultstrings[] =
 {
   "glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.perturb=0x800",
+  "glibc.malloc.perturb=0x800:glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.perturb=0x800:glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.mmap_threshold=4096",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "",
 };
 
 static int
-- 
2.29.2

[ignore][PATCH v2 0/4] tunables and setxid programs

[Siddhesh Poyarekar]

I ended up sending the series twice; please ignore this since it 
misspells Adhemerval's email address.

Siddhesh

Re: [PATCH 3/4] Enhance setuid-tunables test

[Carlos O'Donell]

On 3/16/21 3:07 AM, Siddhesh Poyarekar via Libc-alpha wrote:
> Instead of passing GLIBC_TUNABLES via the environment, pass the
> environment variable from parent to child.  This allows us to test
> multiple variables to ensure better coverage.
> 
> The test list currently only includes the case that's already being
> tested.  More tests will be added later.

I like that you turn this into a data-driven test and move the env vars
out of make.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  elf/Makefile                  |  2 -
>  elf/tst-env-setuid-tunables.c | 90 +++++++++++++++++++++++++++--------
>  2 files changed, 69 insertions(+), 23 deletions(-)
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index 3b8e13e066..4e04c26eea 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -1653,8 +1653,6 @@ $(objpfx)tst-nodelete-dlclose.out: $(objpfx)tst-nodelete-dlclose-dso.so \
>  
>  tst-env-setuid-ENV = MALLOC_CHECK_=2 MALLOC_MMAP_THRESHOLD_=4096 \
>  		     LD_HWCAP_MASK=0x1
> -tst-env-setuid-tunables-ENV = \
> -	GLIBC_TUNABLES=glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096

OK.

>  
>  $(objpfx)tst-debug1: $(libdl)
>  $(objpfx)tst-debug1.out: $(objpfx)tst-debug1mod1.so
> diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
> index 50bef8683d..3d523875b1 100644
> --- a/elf/tst-env-setuid-tunables.c
> +++ b/elf/tst-env-setuid-tunables.c
> @@ -25,35 +25,50 @@
>  #include "config.h"
>  #undef _LIBC
>  
> -#define test_parent test_parent_tunables
> -#define test_child test_child_tunables
> -
> -static int test_child_tunables (void);
> -static int test_parent_tunables (void);
> -
> -#include "tst-env-setuid.c"
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <string.h>
> +#include <sys/stat.h>
> +#include <sys/wait.h>
> +#include <unistd.h>
> +#include <intprops.h>
> +#include <array_length.h>
> +
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <support/test-driver.h>
> +#include <support/capture_subprocess.h>
> +
> +const char *teststrings[] =
> +{
> +  "glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096",

OK.

> +};
>  
> -#define CHILD_VALSTRING_VALUE "glibc.malloc.mmap_threshold=4096"
> -#define PARENT_VALSTRING_VALUE \
> -  "glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096"
> +const char *resultstrings[] =
> +{
> +  "glibc.malloc.mmap_threshold=4096",

OK. SXID_IGNORE.

> +};
>  
>  static int
> -test_child_tunables (void)
> +test_child (int off)
>  {
>    const char *val = getenv ("GLIBC_TUNABLES");
>  
>  #if HAVE_TUNABLES
> -  if (val != NULL && strcmp (val, CHILD_VALSTRING_VALUE) == 0)
> +  if (val != NULL && strcmp (val, resultstrings[off]) == 0)
>      return 0;
>  
>    if (val != NULL)
> -    printf ("Unexpected GLIBC_TUNABLES VALUE %s\n", val);
> +    printf ("[%d] Unexpected GLIBC_TUNABLES VALUE %s\n", off, val);
>  
>    return 1;
>  #else
>    if (val != NULL)
>      {
> -      printf ("GLIBC_TUNABLES not cleared\n");
> +      printf ("[%d] GLIBC_TUNABLES not cleared\n", off);
>        return 1;
>      }
>    return 0;
> @@ -61,15 +76,48 @@ test_child_tunables (void)
>  }
>  
>  static int
> -test_parent_tunables (void)
> +do_test (int argc, char **argv)
>  {
> -  const char *val = getenv ("GLIBC_TUNABLES");
> +  /* Setgid child process.  */
> +  if (argc == 2)
> +    {
> +      if (getgid () == getegid ())
> +	/* This can happen if the file system is mounted nosuid.  */
> +	FAIL_UNSUPPORTED ("SGID failed: GID and EGID match (%jd)\n",
> +			  (intmax_t) getgid ());
>  
> -  if (val != NULL && strcmp (val, PARENT_VALSTRING_VALUE) == 0)
> -    return 0;
> +      int ret = test_child (atoi (argv[1]));
>  
> -  if (val != NULL)
> -    printf ("Unexpected GLIBC_TUNABLES VALUE %s\n", val);
> +      if (ret != 0)
> +	exit (1);
>  
> -  return 1;
> +      exit (EXIT_SUCCESS);
> +    }
> +  else
> +    {
> +      int ret = 0;
> +
> +      /* Spawn tests.  */
> +      for (int i = 0; i < array_length (teststrings); i++)
> +	{
> +	  char buf[INT_BUFSIZE_BOUND (int)];
> +
> +	  printf ("Spawned test for %s (%d)\n", teststrings[i], i);
> +	  snprintf (buf, sizeof (buf), "%d\n", i);
> +	  if (setenv ("GLIBC_TUNABLES", teststrings[i], 1) != 0)

OK. Put env vars into test as a data-driven test rather than Make-driven.

> +	    exit (1);
> +
> +	  int status = support_capture_subprogram_self_sgid (buf);
> +
> +	  /* Bail out early if unsupported.  */
> +	  if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
> +	    return EXIT_UNSUPPORTED;
> +
> +	  ret |= status;
> +	}
> +      return ret;
> +    }
>  }
> +
> +#define TEST_FUNCTION_ARGV do_test
> +#include <support/test-driver.c>
> 


-- 
Cheers,
Carlos.

[PATCH 3/4] Enhance setuid-tunables test

[Siddhesh Poyarekar]

Instead of passing GLIBC_TUNABLES via the environment, pass the
environment variable from parent to child.  This allows us to test
multiple variables to ensure better coverage.

The test list currently only includes the case that's already being
tested.  More tests will be added later.
---
 elf/Makefile                  |  2 -
 elf/tst-env-setuid-tunables.c | 90 +++++++++++++++++++++++++++--------
 2 files changed, 69 insertions(+), 23 deletions(-)

diff --git a/elf/Makefile b/elf/Makefile
index 3b8e13e066..4e04c26eea 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -1653,8 +1653,6 @@ $(objpfx)tst-nodelete-dlclose.out: $(objpfx)tst-nodelete-dlclose-dso.so \
 
 tst-env-setuid-ENV = MALLOC_CHECK_=2 MALLOC_MMAP_THRESHOLD_=4096 \
 		     LD_HWCAP_MASK=0x1
-tst-env-setuid-tunables-ENV = \
-	GLIBC_TUNABLES=glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096
 
 $(objpfx)tst-debug1: $(libdl)
 $(objpfx)tst-debug1.out: $(objpfx)tst-debug1mod1.so
diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index 50bef8683d..3d523875b1 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -25,35 +25,50 @@
 #include "config.h"
 #undef _LIBC
 
-#define test_parent test_parent_tunables
-#define test_child test_child_tunables
-
-static int test_child_tunables (void);
-static int test_parent_tunables (void);
-
-#include "tst-env-setuid.c"
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <intprops.h>
+#include <array_length.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+#include <support/capture_subprocess.h>
+
+const char *teststrings[] =
+{
+  "glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096",
+};
 
-#define CHILD_VALSTRING_VALUE "glibc.malloc.mmap_threshold=4096"
-#define PARENT_VALSTRING_VALUE \
-  "glibc.malloc.check=2:glibc.malloc.mmap_threshold=4096"
+const char *resultstrings[] =
+{
+  "glibc.malloc.mmap_threshold=4096",
+};
 
 static int
-test_child_tunables (void)
+test_child (int off)
 {
   const char *val = getenv ("GLIBC_TUNABLES");
 
 #if HAVE_TUNABLES
-  if (val != NULL && strcmp (val, CHILD_VALSTRING_VALUE) == 0)
+  if (val != NULL && strcmp (val, resultstrings[off]) == 0)
     return 0;
 
   if (val != NULL)
-    printf ("Unexpected GLIBC_TUNABLES VALUE %s\n", val);
+    printf ("[%d] Unexpected GLIBC_TUNABLES VALUE %s\n", off, val);
 
   return 1;
 #else
   if (val != NULL)
     {
-      printf ("GLIBC_TUNABLES not cleared\n");
+      printf ("[%d] GLIBC_TUNABLES not cleared\n", off);
       return 1;
     }
   return 0;
@@ -61,15 +76,48 @@ test_child_tunables (void)
 }
 
 static int
-test_parent_tunables (void)
+do_test (int argc, char **argv)
 {
-  const char *val = getenv ("GLIBC_TUNABLES");
+  /* Setgid child process.  */
+  if (argc == 2)
+    {
+      if (getgid () == getegid ())
+	/* This can happen if the file system is mounted nosuid.  */
+	FAIL_UNSUPPORTED ("SGID failed: GID and EGID match (%jd)\n",
+			  (intmax_t) getgid ());
 
-  if (val != NULL && strcmp (val, PARENT_VALSTRING_VALUE) == 0)
-    return 0;
+      int ret = test_child (atoi (argv[1]));
 
-  if (val != NULL)
-    printf ("Unexpected GLIBC_TUNABLES VALUE %s\n", val);
+      if (ret != 0)
+	exit (1);
 
-  return 1;
+      exit (EXIT_SUCCESS);
+    }
+  else
+    {
+      int ret = 0;
+
+      /* Spawn tests.  */
+      for (int i = 0; i < array_length (teststrings); i++)
+	{
+	  char buf[INT_BUFSIZE_BOUND (int)];
+
+	  printf ("Spawned test for %s (%d)\n", teststrings[i], i);
+	  snprintf (buf, sizeof (buf), "%d\n", i);
+	  if (setenv ("GLIBC_TUNABLES", teststrings[i], 1) != 0)
+	    exit (1);
+
+	  int status = support_capture_subprogram_self_sgid (buf);
+
+	  /* Bail out early if unsupported.  */
+	  if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
+	    return EXIT_UNSUPPORTED;
+
+	  ret |= status;
+	}
+      return ret;
+    }
 }
+
+#define TEST_FUNCTION_ARGV do_test
+#include <support/test-driver.c>
-- 
2.29.2