fix SHA2* cleanups to zero-out the complete context

GCC 4.8 is now clever enough to warn about:

contrib/sha2_internal.cc: In function ‘char* SHA256_End(SHA256_CTX*, char*)’:
contrib/sha2_internal.cc:656:31: warning: argument to ‘sizeof’ in ‘void*
memset(void*, int, size_t)’ call is the same expression as the destination;
did you mean to dereference it? [-Wsizeof-pointer-memaccess]
   MEMSET_BZERO(context, sizeof(context));

So fix it as suggested. Its interesting though that the SHA2*
calculation as far as we need it works even without zeroing out.

Git-Dch: Ignore

apt-pkg/contrib/sha2_internal.cc

@@ -632,7 +632,7 @@ void SHA256_Final(sha2_byte digest[], SHA256_CTX* context) {
 	}
 
 	/* Clean up state data: */
-	MEMSET_BZERO(context, sizeof(context));
+	MEMSET_BZERO(context, sizeof(*context));
 	usedspace = 0;
 }
 
@@ -653,7 +653,7 @@ char *SHA256_End(SHA256_CTX* context, char buffer[]) {
 		}
 		*buffer = (char)0;
 	} else {
-		MEMSET_BZERO(context, sizeof(context));
+		MEMSET_BZERO(context, sizeof(*context));
 	}
 	MEMSET_BZERO(digest, SHA256_DIGEST_LENGTH);
 	return buffer;
@@ -969,7 +969,7 @@ void SHA512_Final(sha2_byte digest[], SHA512_CTX* context) {
 	}
 
 	/* Zero out state data */
-	MEMSET_BZERO(context, sizeof(context));
+	MEMSET_BZERO(context, sizeof(*context));
 }
 
 char *SHA512_End(SHA512_CTX* context, char buffer[]) {
@@ -989,7 +989,7 @@ char *SHA512_End(SHA512_CTX* context, char buffer[]) {
 		}
 		*buffer = (char)0;
 	} else {
-		MEMSET_BZERO(context, sizeof(context));
+		MEMSET_BZERO(context, sizeof(*context));
 	}
 	MEMSET_BZERO(digest, SHA512_DIGEST_LENGTH);
 	return buffer;
@@ -1044,7 +1044,7 @@ void SHA384_Final(sha2_byte digest[], SHA384_CTX* context) {
 	}
 
 	/* Zero out state data */
-	MEMSET_BZERO(context, sizeof(context));
+	MEMSET_BZERO(context, sizeof(*context));
 }
 
 char *SHA384_End(SHA384_CTX* context, char buffer[]) {
@@ -1064,7 +1064,7 @@ char *SHA384_End(SHA384_CTX* context, char buffer[]) {
 		}
 		*buffer = (char)0;
 	} else {
-		MEMSET_BZERO(context, sizeof(context));
+		MEMSET_BZERO(context, sizeof(*context));
 	}
 	MEMSET_BZERO(digest, SHA384_DIGEST_LENGTH);
 	return buffer;