CryptoPkg/BaseCryptLib: Fix buffer overflow issue in realloc wrapper

There is one long-standing problem in CRT realloc wrapper, which will
cause the obvious buffer overflow issue when re-allocating one bigger
memory block:
    void *realloc (void *ptr, size_t size)
    {
      //
      // BUG: hardcode OldSize == size! We have no any knowledge about
      // memory size of original pointer ptr.
      //
      return ReallocatePool ((UINTN) size, (UINTN) size, ptr);
    }
This patch introduces one extra header to record the memory buffer size
information when allocating memory block from malloc routine, and re-wrap
the realloc() and free() routines to remove this BUG.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ting Ye <ting.ye@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qin Long <qin.long@intel.com>
Reviewed-by: Jian J Wang <jian.j.wang@intel.com>
Validated-by: Jian J Wang <jian.j.wang@intel.com>

Cherry picked from https://github.com/tianocore/edk2.git, commit
cf8197a39d07179027455421a182598bd6989999. Changes:
* `SIGNATURE_32` -> `EFI_SIGNATURE_32`
* Added definition of `MIN`

Fixes rhboot#538

Signed-off-by: Nicholas Bishop <nicholasbishop@google.com>

Cryptlib/SysCall/BaseMemAllocation.c

@@ -15,34 +15,105 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 
 #include <OpenSslSupport.h>
 
+//
+// Extra header to record the memory buffer size from malloc routine.
+//
+#define CRYPTMEM_HEAD_SIGNATURE    EFI_SIGNATURE_32('c','m','h','d')
+typedef struct {
+  UINT32    Signature;
+  UINT32    Reserved;
+  UINTN     Size;
+} CRYPTMEM_HEAD;
+
+#define CRYPTMEM_OVERHEAD      sizeof(CRYPTMEM_HEAD)
+
+#define MIN(a, b) ({(a) < (b) ? (a) : (b);})
+
 //
 // -- Memory-Allocation Routines --
 //
 
 /* Allocates memory blocks */
 void *malloc (size_t size)
 {
-  return AllocatePool ((UINTN) size);
+  CRYPTMEM_HEAD  *PoolHdr;
+  UINTN          NewSize;
+  VOID           *Data;
+
+  //
+  // Adjust the size by the buffer header overhead
+  //
+  NewSize = (UINTN)(size) + CRYPTMEM_OVERHEAD;
+
+  Data  = AllocatePool (NewSize);
+  if (Data != NULL) {
+    PoolHdr = (CRYPTMEM_HEAD *)Data;
+    //
+    // Record the memory brief information
+    //
+    PoolHdr->Signature = CRYPTMEM_HEAD_SIGNATURE;
+    PoolHdr->Size      = size;
+
+    return (VOID *)(PoolHdr + 1);
+  } else {
+    //
+    // The buffer allocation failed.
+    //
+    return NULL;
+  }
 }
 
 /* Reallocate memory blocks */
 void *realloc (void *ptr, size_t size)
 {
-  //
-  // BUG: hardcode OldSize == size! We have no any knowledge about
-  // memory size of original pointer ptr.
-  //
-  return ReallocatePool (ptr, (UINTN) size, (UINTN) size);
+  CRYPTMEM_HEAD  *OldPoolHdr;
+  CRYPTMEM_HEAD  *NewPoolHdr;
+  UINTN          OldSize;
+  UINTN          NewSize;
+  VOID           *Data;
+
+  NewSize = (UINTN)size + CRYPTMEM_OVERHEAD;
+  Data = AllocatePool (NewSize);
+  if (Data != NULL) {
+    NewPoolHdr = (CRYPTMEM_HEAD *)Data;
+    NewPoolHdr->Signature = CRYPTMEM_HEAD_SIGNATURE;
+    NewPoolHdr->Size      = size;
+    if (ptr != NULL) {
+      //
+      // Retrieve the original size from the buffer header.
+      //
+      OldPoolHdr = (CRYPTMEM_HEAD *)ptr - 1;
+      ASSERT (OldPoolHdr->Signature == CRYPTMEM_HEAD_SIGNATURE);
+      OldSize = OldPoolHdr->Size;
+
+      //
+      // Duplicate the buffer content.
+      //
+      CopyMem ((VOID *)(NewPoolHdr + 1), ptr, MIN (OldSize, size));
+      FreePool ((VOID *)OldPoolHdr);
+    }
+
+    return (VOID *)(NewPoolHdr + 1);
+  } else {
+    //
+    // The buffer allocation failed.
+    //
+    return NULL;
+  }
 }
 
 /* De-allocates or frees a memory block */
 void free (void *ptr)
 {
+  CRYPTMEM_HEAD  *PoolHdr;
+
   //
   // In Standard C, free() handles a null pointer argument transparently. This
   // is not true of FreePool() below, so protect it.
   //
   if (ptr != NULL) {
-    FreePool (ptr);
+    PoolHdr = (CRYPTMEM_HEAD *)ptr - 1;
+    ASSERT (PoolHdr->Signature == CRYPTMEM_HEAD_SIGNATURE);
+    FreePool (PoolHdr);
   }
 }