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Make rekey interval less predictable (#1331)

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Keelan Cannoo 2022-09-12 23:12:47 +04:00 committed by GitHub
parent 039e8d96a4
commit bb41229ff4
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1 changed files with 7 additions and 3 deletions
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10
arc4random.c
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@ -75,8 +75,7 @@
/* Add platform entropy 32 bytes (256 bits) at a time. */ /* Add platform entropy 32 bytes (256 bits) at a time. */
#define ADD_ENTROPY 32 #define ADD_ENTROPY 32
/* Re-seed from the platform RNG after generating this many bytes. */ #define REKEY_BASE (1024*1024) /* NB. should be a power of 2 */
#define BYTES_BEFORE_RESEED 1600000
struct arc4_stream { struct arc4_stream {
unsigned char i; unsigned char i;
@ -343,10 +342,13 @@ arc4_seed(void)
return ok ? 0 : -1; return ok ? 0 : -1;
} }
static inline unsigned int
arc4_getword(void);
static int static int
arc4_stir(void) arc4_stir(void)
{ {
int i; int i;
ARC4RANDOM_UINT32 rekey_fuzz;
if (!rs_initialized) { if (!rs_initialized) {
arc4_init(); arc4_init();
@ -377,7 +379,9 @@ arc4_stir(void)
for (i = 0; i < 12*256; i++) for (i = 0; i < 12*256; i++)
(void)arc4_getbyte(); (void)arc4_getbyte();
arc4_count = BYTES_BEFORE_RESEED; rekey_fuzz = arc4_getword();
/* rekey interval should not be predictable */
arc4_count = REKEY_BASE + (rekey_fuzz % REKEY_BASE);
return 0; return 0;
} }