diff --git a/compat/arc4random.c b/compat/arc4random.c index b536d3143..486ab89c6 100644 --- a/compat/arc4random.c +++ b/compat/arc4random.c @@ -57,6 +57,8 @@ #define BLOCKSZ 64 #define RSBUFSZ (16*BLOCKSZ) +#define REKEY_BASE (1024*1024) /* NB. should be a power of 2 */ + /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */ static struct { size_t rs_have; /* valid bytes at end of rs_buf */ @@ -179,6 +181,7 @@ static void _rs_stir(void) { u_char rnd[KEYSZ + IVSZ]; + uint32_t rekey_fuzz = 0; if (getentropy(rnd, sizeof rnd) == -1) { if(errno != ENOSYS || @@ -201,7 +204,10 @@ _rs_stir(void) rs->rs_have = 0; memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); - rs->rs_count = 1600000; + /* rekey interval should not be predictable */ + chacha_encrypt_bytes(&rsx->rs_chacha, (uint8_t *)&rekey_fuzz, + (uint8_t *)&rekey_fuzz, sizeof(rekey_fuzz)); + rs->rs_count = REKEY_BASE + (rekey_fuzz % REKEY_BASE); } static inline void