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util: add secure pseudorandom number generator

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This commit is contained in:
Pawel Dziepak
2013-04-11 12:31:58 +02:00
parent 69042ecd1b
commit 87d1bdb87c
2 changed files with 92 additions and 0 deletions
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headers/private/kernel/util/Random.h
+18
View File
@@ -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
+74
View File
@@ -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;
}