Remove the built-in memory guard support.

* configure.ac (--enable-m-guard): Remove.
* src/global.c (_gcry_vcontrol): Return GPG_ERR_NOT_SUPPORTED for
GCRYCTL_ENABLE_M_GUARD.
* src/stdmem.c (use_m_guard, _gcry_private_enable_m_guard): Remove.
(_gcry_private_malloc): Remove the code path with use_m_guard==1.
(_gcry_private_malloc_secure): Likewise.
(_gcry_private_realloc, _gcry_private_free): Likewise.
(_gcry_private_check_heap): Remove.
* src/stdmem.h: Remove declarations for memory guard functions.

--

GnuPG-bug-id: T5822
Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>

7 files changed, 12 insertions, 149 deletions

diff --git a/NEWS b/NEWS
index c46b3470..2a6384e3 100644
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,10 @@
 Noteworthy changes in version 1.11.0 (unreleased)  [C25/A5/R0]
 -------------------------------------------------
 
+ * Other features:
+
+   - The control code GCRYCTL_ENABLE_M_GUARD is deprecated and not
+     supported any more.  Please use valgrind or other tools.
 
 
 Noteworthy changes in version 1.10.0 (2022-02-01)  [C24/A4/R0]
diff --git a/README b/README
index 436b6cd4..3b465c1b 100644
--- a/README
+++ b/README
@@ -90,12 +90,6 @@
                      With this option a "make check" will take really
                      long due to extra checks for the hash algorithms.
 
-     --enable-m-guard
-                     Enable the integrated malloc checking code. Please
-                     note that this feature does not work on all CPUs
-                     (e.g. SunOS 5.7 on UltraSparc-2) and might give
-                     you a bus error.
-
      --disable-asm
                      Do not use assembler modules.  It is not possible
                      to use this on some CPU types.
diff --git a/configure.ac b/configure.ac
index 0667484e..a9350c9c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -363,8 +363,6 @@ AC_CHECK_SIZEOF(unsigned long, 4)
 AC_CHECK_SIZEOF(unsigned long long, 0)
 AC_CHECK_SIZEOF(void *, 0)
 
-AC_CHECK_ALIGNOF(long double)
-
 AC_TYPE_UINTPTR_T
 
 if test "$ac_cv_sizeof_unsigned_short" = "0" \
@@ -539,17 +537,6 @@ if test "$try_asm_modules" != yes ; then
     AC_DEFINE(ASM_DISABLED,1,[Defined if --disable-asm was used to configure])
 fi
 
-# Implementation of the --enable-m-guard switch.
-AC_MSG_CHECKING([whether memory guard is requested])
-AC_ARG_ENABLE(m-guard,
-              AS_HELP_STRING([--enable-m-guard],
-                             [Enable memory guard facility]),
-              [use_m_guard=$enableval], [use_m_guard=no])
-AC_MSG_RESULT($use_m_guard)
-if test "$use_m_guard" = yes ; then
-    AC_DEFINE(M_GUARD,1,[Define to use the (obsolete) malloc guarding feature])
-fi
-
 # Implementation of the --enable-large-data-tests switch.
 AC_MSG_CHECKING([whether to run large data tests])
 AC_ARG_ENABLE(large-data-tests,
diff --git a/doc/gcrypt.texi b/doc/gcrypt.texi
index 92eb5024..25d2f951 100644
--- a/doc/gcrypt.texi
+++ b/doc/gcrypt.texi
@@ -652,12 +652,8 @@ arguments can or have to be provided.
 
 @table @code
 @item GCRYCTL_ENABLE_M_GUARD; Arguments: none
-This command enables the built-in memory guard.  It must not be used
-to activate the memory guard after the memory management has already
-been used; therefore it can ONLY be used before
-@code{gcry_check_version}.  Note that the memory guard is NOT used
-when the user of the library has set his own memory management
-callbacks.
+This command was to enable the built-in memory guard, but not supported
+any more.
 
 @item GCRYCTL_ENABLE_QUICK_RANDOM; Arguments: none
 This command inhibits the use the very secure random quality level
diff --git a/src/global.c b/src/global.c
index 7cf40e4a..956043c4 100644
--- a/src/global.c
+++ b/src/global.c
@@ -523,7 +523,7 @@ _gcry_vcontrol (enum gcry_ctl_cmds cmd, va_list arg_ptr)
   switch (cmd)
     {
     case GCRYCTL_ENABLE_M_GUARD:
-      _gcry_private_enable_m_guard ();
+      rc = GPG_ERR_NOT_SUPPORTED;
       break;
 
     case GCRYCTL_ENABLE_QUICK_RANDOM:
@@ -1043,8 +1043,6 @@ _gcry_check_heap( const void *a )
 #if 0
     if( some_handler )
 	some_handler(a)
-    else
-	_gcry_private_check_heap(a)
 #endif
 }
 
diff --git a/src/stdmem.c b/src/stdmem.c
index f657ddcc..d0ebef0c 100644
--- a/src/stdmem.c
+++ b/src/stdmem.c
@@ -57,32 +57,6 @@
 
 
 
-#define MAGIC_NOR_BYTE 0x55
-#define MAGIC_SEC_BYTE 0xcc
-#define MAGIC_END_BYTE 0xaa
-
-#ifdef ALIGNOF_LONG_DOUBLE
-#define EXTRA_ALIGN (ALIGNOF_LONG_DOUBLE-4)
-#elif SIZEOF_UNSIGNED_LONG == 8
-#define EXTRA_ALIGN 4
-#else
-#define EXTRA_ALIGN 0
-#endif
-
-
-static int use_m_guard = 0;
-
-/****************
- * Warning: Never use this function after any of the functions
- * here have been used.
- */
-void
-_gcry_private_enable_m_guard (void)
-{
-  use_m_guard = 1;
-}
-
-
 /*
  * Allocate memory of size n.
  * Return NULL if we are out of memory.
@@ -97,23 +71,7 @@ _gcry_private_malloc (size_t n)
                       an error to detect such coding errors.  */
     }
 
-  if (use_m_guard)
-    {
-      char *p;
-
-      if ( !(p = malloc (n + EXTRA_ALIGN+5)) )
-        return NULL;
-      ((byte*)p)[EXTRA_ALIGN+0] = n;
-      ((byte*)p)[EXTRA_ALIGN+1] = n >> 8 ;
-      ((byte*)p)[EXTRA_ALIGN+2] = n >> 16 ;
-      ((byte*)p)[EXTRA_ALIGN+3] = MAGIC_NOR_BYTE;
-      p[4+EXTRA_ALIGN+n] = MAGIC_END_BYTE;
-      return p+EXTRA_ALIGN+4;
-    }
-  else
-    {
-      return malloc( n );
-    }
+  return malloc( n );
 }
 
 
@@ -132,23 +90,7 @@ _gcry_private_malloc_secure (size_t n, int xhint)
                       error to detect such coding errors.  */
     }
 
-  if (use_m_guard)
-    {
-      char *p;
-
-      if (!(p = _gcry_secmem_malloc (n + EXTRA_ALIGN + 5, xhint)))
-        return NULL;
-      ((byte*)p)[EXTRA_ALIGN+0] = n;
-      ((byte*)p)[EXTRA_ALIGN+1] = n >> 8 ;
-      ((byte*)p)[EXTRA_ALIGN+2] = n >> 16 ;
-      ((byte*)p)[EXTRA_ALIGN+3] = MAGIC_SEC_BYTE;
-      p[4+EXTRA_ALIGN+n] = MAGIC_END_BYTE;
-      return p+EXTRA_ALIGN+4;
-    }
-  else
-    {
-      return _gcry_secmem_malloc (n, xhint);
-    }
+  return _gcry_secmem_malloc (n, xhint);
 }
 
 
@@ -160,33 +102,7 @@ _gcry_private_malloc_secure (size_t n, int xhint)
 void *
 _gcry_private_realloc (void *a, size_t n, int xhint)
 {
-  if (use_m_guard)
-    {
-      unsigned char *p = a;
-      char *b;
-      size_t len;
-
-      if (!a)
-        return _gcry_private_malloc(n);
-
-      _gcry_private_check_heap(p);
-      len  = p[-4];
-      len |= p[-3] << 8;
-      len |= p[-2] << 16;
-      if( len >= n ) /* We don't shrink for now. */
-        return a;
-      if (p[-1] == MAGIC_SEC_BYTE)
-        b = _gcry_private_malloc_secure (n, xhint);
-      else
-        b = _gcry_private_malloc(n);
-      if (!b)
-        return NULL;
-      memcpy (b, a, len);
-      memset (b+len, 0, n-len);
-      _gcry_private_free (p);
-      return b;
-    }
-  else if ( _gcry_private_is_secure(a) )
+  if ( _gcry_private_is_secure(a) )
     {
       return _gcry_secmem_realloc (a, n, xhint);
     }
@@ -197,28 +113,6 @@ _gcry_private_realloc (void *a, size_t n, int xhint)
 }
 
 
-void
-_gcry_private_check_heap (const void *a)
-{
-  if (use_m_guard)
-    {
-      const byte *p = a;
-      size_t len;
-
-      if (!p)
-        return;
-
-      if ( !(p[-1] == MAGIC_NOR_BYTE || p[-1] == MAGIC_SEC_BYTE) )
-        _gcry_log_fatal ("memory at %p corrupted (underflow=%02x)\n", p, p[-1]);
-      len  = p[-4];
-      len |= p[-3] << 8;
-      len |= p[-2] << 16;
-      if ( p[len] != MAGIC_END_BYTE )
-        _gcry_log_fatal ("memory at %p corrupted (overflow=%02x)\n", p, p[-1]);
-    }
-}
-
-
 /*
  * Free a memory block allocated by this or the secmem module
  */
@@ -230,15 +124,8 @@ _gcry_private_free (void *a)
 
   if (!p)
     return;
-  if (use_m_guard)
-    {
-      _gcry_private_check_heap (p);
-      freep = p - EXTRA_ALIGN - 4;
-    }
-  else
-    {
-      freep = p;
-    }
+
+  freep = p;
 
   if (!_gcry_private_is_secure (freep) ||
       !_gcry_secmem_free (freep))
diff --git a/src/stdmem.h b/src/stdmem.h
index c52aab54..ba885005 100644
--- a/src/stdmem.h
+++ b/src/stdmem.h
@@ -21,12 +21,9 @@
 #ifndef G10_STDMEM_H
 #define G10_STDMEM_H 1
 
-void _gcry_private_enable_m_guard(void);
-
 void *_gcry_private_malloc (size_t n) _GCRY_GCC_ATTR_MALLOC;
 void *_gcry_private_malloc_secure (size_t n, int xhint) _GCRY_GCC_ATTR_MALLOC;
 void *_gcry_private_realloc (void *a, size_t n, int xhint);
-void _gcry_private_check_heap (const void *a);
 void _gcry_private_free (void *a);
 
 #endif /* G10_STDMEM_H */