Drop GLIBC_TUNABLES for setxid programs when tunables is disabled (bz #21073)

A setxid program that uses a glibc with tunables disabled may pass on
GLIBC_TUNABLES as is to its child processes.  If the child process
ends up using a different glibc that has tunables enabled, it will end
up getting access to unsafe tunables.  To fix this, remove
GLIBC_TUNABLES from the environment for setxid process.

	* sysdeps/generic/unsecvars.h: Add GLIBC_TUNABLES.
	* elf/tst-env-setuid-tunables.c
	(test_child_tunables)[!HAVE_TUNABLES]: Verify that
	GLIBC_TUNABLES is removed in a setgid process.

diff --git a/ChangeLog b/ChangeLog
index aed8764..a210e63 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2017-02-02  Siddhesh Poyarekar  <siddhesh@sourceware.org>
 
+       * sysdeps/generic/unsecvars.h: Add GLIBC_TUNABLES.
+       * elf/tst-env-setuid-tunables.c
+       (test_child_tunables)[!HAVE_TUNABLES]: Verify that
+       GLIBC_TUNABLES is removed in a setgid process.
+
        [BZ #21073]
        * elf/dl-tunable-types.h (tunable_seclevel_t): New enum.
        * elf/dl-tunables.c (tunables_strdup): Remove.

diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index a563f69..a5f0a81 100644 (file)
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -36,6 +36,7 @@ test_child_tunables (void)
 {
   const char *val = getenv ("GLIBC_TUNABLES");
 
+#if HAVE_TUNABLES
   if (val != NULL && strcmp (val, CHILD_VALSTRING_VALUE) == 0)
     return 0;
 
@@ -43,6 +44,14 @@ test_child_tunables (void)
     printf ("Unexpected GLIBC_TUNABLES VALUE %s\n", val);
 
   return 1;
+#else
+  if (val != NULL)
+    {
+      printf ("GLIBC_TUNABLES not cleared\n");
+      return 1;
+    }
+  return 0;
+#endif
 }
 
 static int

diff --git a/sysdeps/generic/unsecvars.h b/sysdeps/generic/unsecvars.h
index d5b8119..a740837 100644 (file)
--- a/sysdeps/generic/unsecvars.h
+++ b/sysdeps/generic/unsecvars.h
@@ -1,9 +1,16 @@
+#if !HAVE_TUNABLES
+# define GLIBC_TUNABLES_ENVVAR "GLIBC_TUNABLES\0"
+#else
+# define GLIBC_TUNABLES_ENVVAR
+#endif
+
 /* Environment variable to be removed for SUID programs.  The names are
    all stuffed in a single string which means they have to be terminated
    with a '\0' explicitly.  */
 #define UNSECURE_ENVVARS \
   "GCONV_PATH\0"                                                             \
   "GETCONF_DIR\0"                                                            \
+  GLIBC_TUNABLES_ENVVAR                                                              \
   "HOSTALIASES\0"                                                            \
   "LD_AUDIT\0"                                                               \
   "LD_DEBUG\0"                                                               \