diff options
Diffstat (limited to 'sys/libkern')
-rw-r--r-- | sys/libkern/arc4random.c | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/sys/libkern/arc4random.c b/sys/libkern/arc4random.c new file mode 100644 index 0000000..3c4c06b --- /dev/null +++ b/sys/libkern/arc4random.c @@ -0,0 +1,89 @@ +/*- + * THE BEER-WARE LICENSE + * + * <dan@FreeBSD.ORG> wrote this file. As long as you retain this notice you + * can do whatever you want with this stuff. If we meet some day, and you + * think this stuff is worth it, you can buy me a beer in return. + * + * Dan Moschuk + * + * $FreeBSD$ + */ + +#include <sys/libkern.h> +#include <sys/time.h> + +static u_int8_t arc4_i, arc4_j; +static int arc4_initialized = 0; +static u_int8_t arc4_sbox[256]; + +static __inline void +arc4_swap(u_int8_t *a, u_int8_t *b) +{ + u_int8_t c; + + c = *a; + *a = *b; + *b = c; +} + +/* + * Initialize our S-box to its beginning defaults. + */ +static void +arc4_init(void) +{ + struct timespec ts; + u_int8_t key[256]; + int n; + + for (n = 0; n < 256; n++) + arc4_sbox[n] = (u_int8_t) n; + + nanotime(&ts); + srandom(ts.tv_sec ^ ts.tv_nsec); + for (n = 0; n < 256; n++) + key[n] = random() % 256; + + arc4_i = arc4_j = 0; + for (n = 0; n < 256; n++) + { + arc4_j = arc4_j + arc4_sbox[n] + key[n]; + arc4_swap(&arc4_sbox[n], &arc4_sbox[arc4_j]); + } + arc4_initialized = 1; +} + +/* + * Generate a random byte. + */ +static u_int8_t +arc4_randbyte(void) +{ + u_int8_t arc4_t; + + arc4_i = (arc4_i + 1) % 256; + arc4_j = (arc4_j + arc4_sbox[arc4_i]) % 256; + + arc4_swap(&arc4_sbox[arc4_i], &arc4_sbox[arc4_j]); + + arc4_t = (arc4_sbox[arc4_i] + arc4_sbox[arc4_j]) % 256; + return arc4_sbox[arc4_t]; +} + +u_int32_t +arc4random(void) +{ + u_int32_t ret; + + /* Initialize array if needed. */ + if (!arc4_initialized) + arc4_init(); + + ret = arc4_randbyte(); + ret |= arc4_randbyte() << 8; + ret |= arc4_randbyte() << 16; + ret |= arc4_randbyte() << 24; + + return ret; +} |