first and last commit

lib/random/library.mk

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+# Copyright (C) 2014 Apple Inc. All rights reserved.
+#
+# This document is the property of Apple Inc.
+# It is considered confidential and proprietary.
+#
+# This document may not be reproduced or transmitted in any form,
+# in whole or in part, without the express written permission of
+# Apple Inc.
+#
+
+LIBRANDOM_DIR		:=	$(GET_LOCAL_DIR)
+LIBRANDOM_BUILD		:=	$(call TOLIBDIR,$(LIBRANDOM_DIR)/LIBRANDOM.a)
+COMMONLIBS		+=	LIBRANDOM
+
+# Only process the remainder of the makefile if we are building libraries
+#
+ifeq ($(MAKEPHASE),libraries)
+
+LIBRANDOM_OBJS		:=	$(LIBRANDOM_DIR)/random.o
+
+LIBRANDOM_OBJS		:=	$(call TOLIBOBJDIR,$(LIBRANDOM_OBJS))
+
+ALL_DEPS		+=	$(LIBRANDOM_OBJS:%o=%d)
+
+$(LIBRANDOM_BUILD):	$(LIBRANDOM_OBJS)
+
+endif

lib/random/random.c

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+/*
+ * Copyright (C) 2010-2011, 2014 Apple Inc. All rights reserved.
+ *
+ * This document is the property of Apple Inc.
+ * It is considered confidential and proprietary.
+ *
+ * This document may not be reproduced or transmitted in any form,
+ * in whole or in part, without the express written permission of
+ * Apple Inc.
+ */
+#include <debug.h>
+#include <drivers/sha1.h>
+#include <lib/mib.h>
+#include <platform.h>
+
+static int random_get_bytes_internal(uint8_t *buffer, size_t length, uint32_t entropy_ratio, void *entropy_buffer, size_t entropy_buffer_size);
+
+int random_get_bytes(uint8_t *buffer, size_t length)
+{
+	uint32_t entropy_ratio = mib_get_u32(kMIBPlatformEntropyRatio);
+	return random_get_bytes_internal(buffer, length, entropy_ratio, NULL, 0);
+}
+
+// Called when randomness is needed but the heap is not available to store
+// the entropy pool which is instead stored in a caller-provided buffer.
+int random_get_bytes_noheap(uint8_t *buffer, size_t length, void *entropy_buffer, size_t entropy_buffer_size)
+{
+	uint32_t entropy_ratio = mib_get_u32(kMIBPlatformEntropyRatio);
+	return random_get_bytes_internal(buffer, length, entropy_ratio, entropy_buffer, entropy_buffer_size);
+}
+
+#if DEBUG_BUILD
+
+int random_get_bytes_debug(uint8_t *buffer, size_t length, uint32_t entropy_ratio)
+{
+	if (entropy_ratio == 0) {
+		entropy_ratio = mib_get_u32(kMIBPlatformEntropyRatio);
+	}
+
+	return random_get_bytes_internal(buffer, length, entropy_ratio, NULL, 0);
+}
+
+#endif
+
+static uint32_t random_count;
+static uint8_t  random_pool[CCSHA1_OUTPUT_SIZE];
+
+static int random_get_bytes_internal(uint8_t *buffer, size_t length, uint32_t entropy_ratio, void *entropy_buffer, size_t entropy_buffer_size)
+{
+	uint32_t cnt, chunk, entropy_pool_size;
+	uint32_t *entropy_pool = NULL;
+
+	entropy_pool_size = entropy_ratio * CCSHA1_OUTPUT_SIZE;
+
+	RELEASE_ASSERT(entropy_buffer == NULL || entropy_pool_size <= entropy_buffer_size);
+
+	while (length > 0) {
+		// Make random data by calculating a sha-1 hash of entropy data
+		if (random_count == 0) {
+			// lazy intialize: we might need to go to the entropy well
+			// more than once for a big request, or not at all for
+			// small requests we already have whitened randomness for
+			if (entropy_pool == NULL) {
+				if (entropy_buffer == NULL)
+					entropy_pool = malloc(entropy_pool_size);
+				else
+					entropy_pool = entropy_buffer;
+			}
+
+			for (cnt = 0; cnt < (entropy_pool_size / sizeof(uint32_t)); cnt++) {
+				entropy_pool[cnt] = platform_get_entropy();
+			}
+
+			sha1_calculate(entropy_pool, entropy_pool_size, random_pool);
+
+			random_count = CCSHA1_OUTPUT_SIZE;
+		}
+
+		chunk = (length >= random_count) ? random_count : length;
+		memcpy(buffer, random_pool - random_count + CCSHA1_OUTPUT_SIZE, chunk);
+
+		random_count -= chunk;
+
+		buffer += chunk;
+		length -=chunk;
+	}
+
+	if (entropy_pool != NULL) {
+		if (entropy_buffer == NULL) {
+			free(entropy_pool);
+		} else {
+			memset(entropy_buffer, 0, entropy_pool_size);
+		}
+	}
+
+	return 0;
+}

lib/random/rules.mk

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+# Copyright (C) 2010, 2014 Apple Inc. All rights reserved.
+#
+# This document is the property of Apple Inc.
+# It is considered confidential and proprietary.
+#
+# This document may not be reproduced or transmitted in any form,
+# in whole or in part, without the express written permission of
+# Apple Inc.
+#
+
+OPTIONS		+= WITH_RANDOM=1
+LIBRARY_MODULES	+= lib/random
+