X-Git-Url: https://git.saurik.com/apple/security.git/blobdiff_plain/84aacf34eae6543be9f0280b2015385f91e5c2c6..b54c578e17e9bcbd74aa30ea75e25e955b9a6205:/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;
+}