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author | phk <phk@FreeBSD.org> | 2002-10-11 13:13:08 +0000 |
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committer | phk <phk@FreeBSD.org> | 2002-10-11 13:13:08 +0000 |
commit | 775372e52e220ea57ea15373e6c1778c9b1e2885 (patch) | |
tree | 5c4b8bec4ec8c16f1f1c6a313fa7d665fc8e8ad1 /sys/libkern | |
parent | 50fb07a0692e71731aa2dc5776ea519ad91490ef (diff) | |
download | FreeBSD-src-775372e52e220ea57ea15373e6c1778c9b1e2885.zip FreeBSD-src-775372e52e220ea57ea15373e6c1778c9b1e2885.tar.gz |
Slight overhaul of arc4random() and friends.
One bug fixed: Use getmicrouptime() to trigger reseeds so that we
cannot be tricked by a clock being stepped backwards.
Express parameters in natural units and with natural names.
Don't use struct timeval more than we need to.
Various stylistic and readability polishing.
Introduce arc4rand(void *ptr, u_int len, int reseed) function which
returns a stream of pseudo-random bytes, observing the automatic
reseed criteria as well as allowing forced reseeds.
Rewrite arc4random() in terms of arc4rand().
Sponsored by: DARPA & NAI Labs.
Diffstat (limited to 'sys/libkern')
-rw-r--r-- | sys/libkern/arc4random.c | 49 |
1 files changed, 27 insertions, 22 deletions
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; } |