Patchwork [2/2] Drop GLIBC_TUNABLES for setxid programs when tunables is disabled

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Submitter Siddhesh Poyarekar
Date Feb. 1, 2017, 11:37 a.m.
Message ID <1485949078-30635-3-git-send-email-siddhesh@sourceware.org>
Download mbox | patch
Permalink /patch/19078/
State New
Headers show

Comments

Siddhesh Poyarekar - Feb. 1, 2017, 11:37 a.m.
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.
---
 elf/tst-env-setuid-tunables.c | 9 +++++++++
 sysdeps/generic/unsecvars.h   | 7 +++++++
 2 files changed, 16 insertions(+)
Florian Weimer - Feb. 1, 2017, 12:16 p.m.
On 02/01/2017 12:37 PM, Siddhesh Poyarekar wrote:
> 	* 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.

Looks reasonable.  Thanks.

Florian

Patch

diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index a563f69..a5f0a81 100644
--- 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
--- 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"								      \