diff options
| -rw-r--r-- | share/man/man9/random.9 | 30 | ||||
| -rw-r--r-- | sys/libkern/arc4random.c | 49 | ||||
| -rw-r--r-- | sys/sys/libkern.h | 3 |
3 files changed, 53 insertions, 29 deletions
diff --git a/share/man/man9/random.9 b/share/man/man9/random.9 index 734e583..98d0ffa 100644 --- a/share/man/man9/random.9 +++ b/share/man/man9/random.9 @@ -41,6 +41,8 @@ .Fn srandom "u_long seed" .Ft u_long .Fn random "void" +.Ft void +.Fn arc4rand "void *ptr" "u_int length" "int reseed" .Ft u_int32_t .Fn arc4random "void" .Pp @@ -68,12 +70,17 @@ function is entirely predictable, and is therefore not of use where knowledge of the sequence of numbers may be of benefit to an attacker. .Pp The -.Fn arc4random +.Fn arc4rand function will return very good quality random numbers, slightly better suited for security-related purposes. The random numbers from -.Fn arc4random +.Fn arc4rand are seeded from the entropy device if it is available. +Automatic reseeds happen after a certain timeinterval and after a +certain number of bytes have been delivered. +A forced reseed can be forced by passing a non-zero value in the +.Ar reseed +argument. .Pp The .Fn read_random @@ -90,16 +97,22 @@ is filled with no more than bytes. It is advised that .Fn read_random is not used; instead use -.Fn arc4random . +.Fn arc4rand .Pp All the bits generated by .Fn random , -.Fn arc4random +.Fn arc4rand and .Fn read_random are usable. For example, .Sq Li random()&01 will produce a random binary value. +.Pp +The +.Fn arc4random +is a convenience function which calls +.Fn arc4rand +to return a 32 bit pseudo-random integer. .Sh RETURN VALUES The .Fn random @@ -114,10 +127,15 @@ The period of this random number generator is very large, approximately .if n 16*((2**31)\(mi1). .Pp The +.Fn arc4rand +function uses the RC4 algorithm to generate successive pseudo-random +bytes. +The .Fn arc4random function -uses the RC4 algorithm to generate successive pseudo-random -numbers in the range from 0 to +uses +.Fn arc4rand +to generate pseudo-random numbers in the range from 0 to .if t 2\u\s732\s10\d\(mi1. .if n (2**32)\(mi1. .Pp diff --git a/sys/libkern/arc4random.c b/sys/libkern/arc4random.c index 993f764..6d6ed22 100644 --- a/sys/libkern/arc4random.c +++ b/sys/libkern/arc4random.c @@ -15,15 +15,15 @@ #include <sys/libkern.h> #include <sys/time.h> -#define ARC4_MAXRUNS 16384 +#define ARC4_RESEED_BYTES 65536 #define ARC4_RESEED_SECONDS 300 -#define ARC4_KEYBYTES 32 /* 256 bit key */ +#define ARC4_KEYBYTES (256 / 8) static u_int8_t arc4_i, arc4_j; static int arc4_initialized = 0; static int arc4_numruns = 0; static u_int8_t arc4_sbox[256]; -static struct timeval arc4_tv_nextreseed; +static time_t arc4_t_reseed; static u_int8_t arc4_randbyte(void); @@ -45,6 +45,7 @@ arc4_randomstir (void) { u_int8_t key[256]; int r, n; + struct timeval tv_now; /* * XXX read_random() returns unsafe numbers if the entropy @@ -52,21 +53,19 @@ arc4_randomstir (void) */ r = read_random(key, ARC4_KEYBYTES); /* If r == 0 || -1, just use what was on the stack. */ - if (r > 0) - { + if (r > 0) { for (n = r; n < sizeof(key); n++) key[n] = key[n % r]; } - for (n = 0; n < 256; n++) - { + for (n = 0; n < 256; n++) { arc4_j = (arc4_j + arc4_sbox[n] + key[n]) % 256; arc4_swap(&arc4_sbox[n], &arc4_sbox[arc4_j]); } /* Reset for next reseed cycle. */ - getmicrotime(&arc4_tv_nextreseed); - arc4_tv_nextreseed.tv_sec += ARC4_RESEED_SECONDS; + getmicrouptime(&tv_now); + arc4_t_reseed = tv_now.tv_sec + ARC4_RESEED_SECONDS; arc4_numruns = 0; } @@ -111,27 +110,33 @@ arc4_randbyte(void) return arc4_sbox[arc4_t]; } -u_int32_t -arc4random(void) +void +arc4rand(void *ptr, u_int len, int reseed) { - u_int32_t ret; - struct timeval tv_now; + u_char *p; + struct timeval tv; /* Initialize array if needed. */ if (!arc4_initialized) arc4_init(); - getmicrotime(&tv_now); - if ((++arc4_numruns > ARC4_MAXRUNS) || - (tv_now.tv_sec > arc4_tv_nextreseed.tv_sec)) - { + getmicrouptime(&tv); + arc4_numruns += len; + if (reseed || + (arc4_numruns > ARC4_RESEED_BYTES) || + (tv.tv_sec > arc4_t_reseed)) arc4_randomstir(); - } - ret = arc4_randbyte(); - ret |= arc4_randbyte() << 8; - ret |= arc4_randbyte() << 16; - ret |= arc4_randbyte() << 24; + p = ptr; + while (len--) + *p++ = arc4_randbyte(); +} + +uint32_t +arc4random(void) +{ + uint32_t ret; + arc4rand(&ret, sizeof ret, 0); return ret; } diff --git a/sys/sys/libkern.h b/sys/sys/libkern.h index 0471840..65ab341 100644 --- a/sys/sys/libkern.h +++ b/sys/sys/libkern.h @@ -64,7 +64,8 @@ static __inline u_long ulmax(u_long a, u_long b) { return (a > b ? a : b); } static __inline u_long ulmin(u_long a, u_long b) { return (a < b ? a : b); } /* Prototypes for non-quad routines. */ -u_int32_t arc4random(void); +uint32_t arc4random(void); +void arc4rand(void *ptr, u_int len, int reseed); int bcmp(const void *, const void *, size_t); void *bsearch(const void *, const void *, size_t, size_t, int (*)(const void *, const void *)); |
