From 965cb60a21674edb8e20b1a2a41297bcd4622361 Mon Sep 17 00:00:00 2001
From: Ulrich Drepper <drepper@redhat.com>
Date: Sun, 11 Jan 2009 04:44:06 +0000
Subject: [PATCH] * sysdeps/generic/dl-osinfo.h (_dl_setup_stack_chk_guard)

diff --git a/elf/dl-support.c b/elf/dl-support.c
index 6bd573ec57..7b3ccf3d4d 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -84,6 +84,9 @@ struct r_scope_elem _dl_initial_searchlist;
 int _dl_starting_up = 1;
 #endif
 
+/* Random data provided by the kernel.  */
+void *_dl_random;
+
 /* Get architecture specific initializer.  */
 #include <dl-procinfo.c>
 
@@ -216,6 +219,9 @@ _dl_aux_init (ElfW(auxv_t) *av)
 	__libc_enable_secure = av->a_un.a_val;
 	__libc_enable_secure_decided = 1;
 	break;
+      case AT_RANDOM:
+	_dl_random = (void *) av->a_un.a_val;
+	break;
 # ifdef DL_PLATFORM_AUXV
       DL_PLATFORM_AUXV
 # endif
diff --git a/elf/dl-sysdep.c b/elf/dl-sysdep.c
index e6f4272a63..29ae895473 100644
--- a/elf/dl-sysdep.c
+++ b/elf/dl-sysdep.c
@@ -62,6 +62,7 @@ int __libc_multiple_libcs = 0;	/* Defining this here avoids the inclusion
 void *__libc_stack_end attribute_relro = NULL;
 rtld_hidden_data_def(__libc_stack_end)
 static ElfW(auxv_t) *_dl_auxv attribute_relro;
+void *_dl_random attribute_relro = NULL;
 
 #ifndef DL_FIND_ARG_COMPONENTS
 # define DL_FIND_ARG_COMPONENTS(cookie, argc, argv, envp, auxp)	\
@@ -173,6 +174,9 @@ _dl_sysdep_start (void **start_argptr,
 	GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
 	break;
 #endif
+      case AT_RANDOM:
+	_dl_random = (void *) av->a_un.a_val;
+	break;
 #ifdef DL_PLATFORM_AUXV
       DL_PLATFORM_AUXV
 #endif
@@ -294,6 +298,7 @@ _dl_show_auxv (void)
 	  [AT_SECURE - 2] =		{ "AT_SECURE:       ", dec },
 	  [AT_SYSINFO - 2] =		{ "AT_SYSINFO:      0x", hex },
 	  [AT_SYSINFO_EHDR - 2] =	{ "AT_SYSINFO_EHDR: 0x", hex },
+	  [AT_RANDOM - 2] =		{ "AT_RANDOM:       0x", hex },
 	};
       unsigned int idx = (unsigned int) (av->a_type - 2);
 
diff --git a/elf/rtld.c b/elf/rtld.c
index 46bece7fa3..60d414d637 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -841,7 +841,7 @@ static void
 security_init (void)
 {
   /* Set up the stack checker's canary.  */
-  uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard ();
+  uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
 #ifdef THREAD_SET_STACK_GUARD
   THREAD_SET_STACK_GUARD (stack_chk_guard);
 #else
@@ -851,18 +851,18 @@ security_init (void)
   /* Set up the pointer guard as well, if necessary.  */
   if (GLRO(dl_pointer_guard))
     {
-      // XXX If it is cheap, we should use a separate value.
-      uintptr_t pointer_chk_guard = stack_chk_guard;
-#ifndef HP_TIMING_NONAVAIL
-      hp_timing_t now;
-      HP_TIMING_NOW (now);
-      pointer_chk_guard ^= now;
-#endif
+      uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
+							     stack_chk_guard);
 #ifdef THREAD_SET_POINTER_GUARD
       THREAD_SET_POINTER_GUARD (pointer_chk_guard);
 #endif
       __pointer_chk_guard_local = pointer_chk_guard;
     }
+
+  /* We do not need the _dl_random value anymore.  The less
+     information we leave behind, the better, so clear the
+     variable.  */
+  _dl_random = NULL;
 }
 
 
diff --git a/sysdeps/generic/dl-osinfo.h b/sysdeps/generic/dl-osinfo.h
index 60b84a900d..02ec28d424 100644
--- a/sysdeps/generic/dl-osinfo.h
+++ b/sysdeps/generic/dl-osinfo.h
@@ -1,12 +1,29 @@
 #include <stdint.h>
 
 static inline uintptr_t __attribute__ ((always_inline))
-_dl_setup_stack_chk_guard (void)
+_dl_setup_stack_chk_guard (void *dl_random)
 {
-  uintptr_t ret = 0;
-  unsigned char *p = (unsigned char *) &ret;
-  p[sizeof (ret) - 1] = 255;
-  p[sizeof (ret) - 2] = '\n';
-  p[0] = 0;
+  uintptr_t ret;
+  if (dl_random == NULL)
+    {
+      ret = 0;
+      unsigned char *p = (unsigned char *) &ret;
+      p[sizeof (ret) - 1] = 255;
+      p[sizeof (ret) - 2] = '\n';
+      p[0] = 0;
+    }
+  else
+    memcmp (&ret, dl_random, sizeof (ret));
+  return ret;
+}
+
+static inline uintptr_t __attribute__ ((always_inline))
+_dl_setup_pointer_guard (void *dl_random, uintptr_t stack_chk_guard)
+{
+  uintptr_t ret;
+  if (dl_random == NULL)
+    ret = stack_chk_guard;
+  else
+    memcmp (&ret, (char *) dl_random + sizeof (ret), sizeof (ret));
   return ret;
 }
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 4d857404a3..f5606f373f 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -731,6 +731,9 @@ weak_extern (_dl_starting_up)
 extern int _dl_starting_up_internal attribute_hidden;
 #endif
 
+/* Random data provided by the kernel.  */
+extern void *_dl_random attribute_hidden;
+
 /* OS-dependent function to open the zero-fill device.  */
 extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */
 
diff --git a/sysdeps/unix/sysv/linux/dl-osinfo.h b/sysdeps/unix/sysv/linux/dl-osinfo.h
index 5271d4e4de..ee8eaf20e4 100644
--- a/sysdeps/unix/sysv/linux/dl-osinfo.h
+++ b/sysdeps/unix/sysv/linux/dl-osinfo.h
@@ -60,22 +60,20 @@ dl_fatal (const char *str)
   } while (0)
 
 static inline uintptr_t __attribute__ ((always_inline))
-_dl_setup_stack_chk_guard (void)
+_dl_setup_stack_chk_guard (void *dl_random)
 {
   uintptr_t ret;
-#ifdef ENABLE_STACKGUARD_RANDOMIZE
-  int fd = __open ("/dev/urandom", O_RDONLY);
-  if (fd >= 0)
-    {
-      ssize_t reslen = __read (fd, &ret, sizeof (ret));
-      __close (fd);
-      if (reslen == (ssize_t) sizeof (ret))
-	return ret;
-    }
-#endif
-  ret = 0;
-  unsigned char *p = (unsigned char *) &ret;
-  p[sizeof (ret) - 1] = 255;
-  p[sizeof (ret) - 2] = '\n';
+    /* We need in the moment only 8 bytes on 32-bit platforms and 16
+       bytes on 64-bit platforms.  Therefore we can use the data
+       directly and not use the kernel-provided data to seed a PRNG.  */
+    memcpy (&ret, dl_random, sizeof (ret));
+  return ret;
+}
+
+static inline uintptr_t __attribute__ ((always_inline))
+_dl_setup_pointer_guard (void *dl_random, uintptr_t stack_chk_guard)
+{
+  uintptr_t ret;
+    memcpy (&ret, (char *) dl_random + sizeof (ret), sizeof (ret));
   return ret;
 }
diff --git a/csu/libc-start.c b/csu/libc-start.c
index a14ed71616a..80b672f88d8 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -140,7 +140,7 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
   __pthread_initialize_minimal ();
 
   /* Set up the stack checker's canary.  */
-  uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard ();
+  uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
 # ifdef THREAD_SET_STACK_GUARD
   THREAD_SET_STACK_GUARD (stack_chk_guard);
 # else