util: add secure pseudorandom number generator

headers/private/kernel/util/Random.h

@@ -15,9 +15,11 @@
 
 #define MAX_FAST_RANDOM_VALUE		0x7fff
 #define MAX_RANDOM_VALUE			0x7fffffffu
+#define MAX_SECURE_RANDOM_VALUE		0xffffffffu
 
 static const int	kFastRandomShift		= 15;
 static const int	kRandomShift			= 31;
+static const int	kSecureRandomShift		= 32;
 
 #ifdef __cplusplus
 extern "C" {
@@ -25,6 +27,7 @@ extern "C" {
 
 unsigned int	fast_random_value(void);
 unsigned int	random_value(void);
+unsigned int	secure_random_value(void);
 
 #ifdef __cplusplus
 }
@@ -63,6 +66,21 @@ get_random()
 }
 
 
+template<typename T>
+T
+secure_get_random()
+{
+	size_t shift = 0;
+	T random = 0;
+	while (shift < sizeof(T) * 8) {
+		random |= (T)secure_random_value() << shift;
+		shift += kSecureRandomShift;
+	}
+
+	return random;
+}
+
+
 #endif	// __cplusplus
 
 #endif	// KERNEL_UTIL_RANDOM_H

src/system/kernel/util/Random.cpp

@@ -14,6 +14,59 @@
 
 static uint32	sFastLast	= 0;
 static uint32	sLast		= 0;
+static uint32	sSecureLast	= 0;
+
+// MD4 helper definitions, based on RFC 1320
+#define F(x, y, z)	(((x) & (y)) | (~(x) & (z)))
+#define G(x, y, z)	(((x) & (y)) | ((x) & (z)) | ((y) & (z)))
+#define H(x, y, z)	((x) ^ (y) ^ (z))
+
+#define STEP(f, a, b, c, d, xk, s)	\
+	(a += f((b), (c), (d)) + (xk), a = (a << (s)) | (a >> (32 - (s))))
+
+
+// MD4 based hash function. Simplified in order to improve performance.
+static uint32
+hash(uint32* data)
+{
+		const uint32 kMD4Round2 = 0x5a827999;
+		const uint32 kMD4Round3 = 0x6ed9eba1;
+
+		uint32 a = 0x67452301;
+		uint32 b = 0xefcdab89;
+		uint32 c = 0x98badcfe;
+		uint32 d = 0x10325476;
+
+		STEP(F, a, b, c, d, data[0], 3);
+		STEP(F, d, a, b, c, data[1], 7);
+		STEP(F, c, d, a, b, data[2], 11);
+		STEP(F, b, c, d, a, data[3], 19);
+		STEP(F, a, b, c, d, data[4], 3);
+		STEP(F, d, a, b, c, data[5], 7);
+		STEP(F, c, d, a, b, data[6], 11);
+		STEP(F, b, c, d, a, data[7], 19);
+
+		STEP(G, a, b, c, d, data[1] + kMD4Round2, 3);
+		STEP(G, d, a, b, c, data[5] + kMD4Round2, 5);
+		STEP(G, c, d, a, b, data[6] + kMD4Round2, 9);
+		STEP(G, b, c, d, a, data[2] + kMD4Round2, 13);
+		STEP(G, a, b, c, d, data[3] + kMD4Round2, 3);
+		STEP(G, d, a, b, c, data[7] + kMD4Round2, 5);
+		STEP(G, c, d, a, b, data[4] + kMD4Round2, 9);
+		STEP(G, b, c, d, a, data[0] + kMD4Round2, 13);
+
+		STEP(H, a, b, c, d, data[1] + kMD4Round3, 3);
+		STEP(H, d, a, b, c, data[6] + kMD4Round3, 9);
+		STEP(H, c, d, a, b, data[5] + kMD4Round3, 11);
+		STEP(H, b, c, d, a, data[2] + kMD4Round3, 15);
+		STEP(H, a, b, c, d, data[3] + kMD4Round3, 3);
+		STEP(H, d, a, b, c, data[4] + kMD4Round3, 9);
+		STEP(H, c, d, a, b, data[7] + kMD4Round3, 11);
+		STEP(H, b, c, d, a, data[0] + kMD4Round3, 15);
+
+		return b;
+}
+
 
 // In the following functions there are race conditions when many threads
 // attempt to update static variable last. However, since such conflicts
@@ -52,3 +105,24 @@ random_value()
 	return random % (MAX_RANDOM_VALUE + 1);
 }
 
+
+unsigned int
+secure_random_value()
+{
+	static vint32 count = 0;
+
+	uint32 data[8];
+	data[0] = atomic_add(&count, 1);
+	data[1] = system_time();
+	data[2] = find_thread(NULL);
+	data[3] = smp_get_current_cpu();
+	data[4] = smp_get_num_cpus();
+	data[5] = sFastLast;
+	data[6] = sLast;
+	data[7] = sSecureLast;
+
+	uint32 random = hash(data);
+	sSecureLast = random;
+	return random;
+}
+