Security-59306.11.20.tar.gz

[apple/security.git] / OSX / utilities / SecPaddingConfigurations.c

diff --git a/OSX/utilities/SecPaddingConfigurations.c b/OSX/utilities/SecPaddingConfigurations.c
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+/*
+ * Copyright (c) 2017 Apple Inc. All Rights Reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#define SecPaddingDomain CFSTR("com.apple.security.padding")
+
+typedef enum {
+       SecPaddingErrorUnknownType     = -1
+} SecPaddingError;
+
+#include "debugging.h"
+#include "SecCFError.h"
+#include "SecCFWrappers.h"
+#include <Security/SecPaddingConfigurationsPriv.h>
+
+#pragma mark Padding Helper Methods
+
+// Compute the next power of two
+// Requires: v <= UINT64_MAX/2
+static uint64_t nextPowerOfTwo(uint64_t v)
+{
+       if (v > (UINT64_MAX>>1)) {
+               secerror("Overflowing uint64_t by requesting nextPowerOfTwo of: %llx", v);
+               assert(0);
+       }
+       if (v & (v - 1)) {
+               // Not already a power of 2
+               return ((uint64_t)1 << ((int)sizeof(v)*8 - __builtin_clzll(v)));
+       } else {
+               // Already a power of 2
+               return v;
+       }
+}
+
+// Round to a multiple of n
+// Requires: v+n <= UINT64_MAX
+static uint64_t nextMultiple(uint64_t v,uint64_t n)
+{
+       // Multiples of 0 are 0. Preventing division by 0.
+       if (n == 0) {
+               return 0;
+       }
+
+       if (n <= 0 || v > (UINT64_MAX-n)) {
+               secerror("Overflowing uint64_t by requesting nextMutiple with parameters v: %llx and n: %llx", v, n);
+               assert(0);
+       }
+       return n*((v+n-1)/n);
+}
+
+#pragma mark Padding Configurations
+
+int64_t SecPaddingCompute(SecPaddingType type, uint32_t size, CFErrorRef *error) {
+       if (type != SecPaddingTypeMMCS) {
+               if (error) {
+                       *error = CFErrorCreate(CFAllocatorGetDefault(), SecPaddingDomain, SecPaddingErrorUnknownType, NULL);
+               }
+               return SecPaddingErrorUnknownType;
+       }
+
+       int64_t paddedSize = 0;
+
+       if (size <= 64){
+               paddedSize = 64;
+       } else if (size <= 1024) {
+               paddedSize = nextPowerOfTwo(size);
+       } else if (size <= 32000) {
+               paddedSize = nextMultiple(size, 1024);
+       } else {
+               paddedSize = nextMultiple(size, 8192);
+       }
+       
+       assert(paddedSize >= size);
+       return paddedSize - size;
+}