diff options
Diffstat (limited to 'util/libreboot-utils/lib')
| -rw-r--r-- | util/libreboot-utils/lib/rand.c | 57 |
1 files changed, 35 insertions, 22 deletions
diff --git a/util/libreboot-utils/lib/rand.c b/util/libreboot-utils/lib/rand.c index 63cb3fcd..58cb211e 100644 --- a/util/libreboot-utils/lib/rand.c +++ b/util/libreboot-utils/lib/rand.c @@ -72,49 +72,62 @@ * or your program dies. */ -#ifndef BUFSIZ -#define BUFSIZ 8192 /* reasonably on modern 64-bit systems */ -#elif (BUFSIZ <= 0) -#error defined buffer size BUFSIZ below or equal to zero -#endif +#define MAX_ALLOC (2 << 16) int -win_lottery(char **buf) /* are u lucky? */ +win_lottery(void) /* are u lucky? */ { - size_t size = 0; - int rval; + size_t size = rsize(); + size_t size2 = rsize(); + char *s = NULL; + + if (size && + size == size2 && + size <= MAX_ALLOC << 1) { + + if (!memcmp(s = mkrbuf(size << 1), + s + size, size)) + size2 = 1; /* winner! */ + else + size2 = 0; + } else { + return 0; + } - char *s1 = rmalloc(&size); - char *s2 = rmalloc(&size); + free_if_null(&s); + return (int)size2; +} - if (scmp(s1, s2, BUFSIZ + 1, &rval) >= 0 && - rval == 0) - rval = 1; /* winner! */ - else - rval = 0; +size_t +rsize(void) +{ + size_t rval = 0; - (void) scat(s1, s2, BUFSIZ << 1, buf); + /* clamp rand to prevent modulo bias */ + size_t limit = SIZE_MAX - (SIZE_MAX % MAX_ALLOC); - free_if_null(&s1); - free_if_null(&s2); + do { + rset(&rval, sizeof(rval)); + } while (rval >= limit); - return rval; + return rval % MAX_ALLOC; } + void * rmalloc(size_t *rval) { /* clamp rand to prevent modulo bias */ - size_t limit = SIZE_MAX - (SIZE_MAX % BUFSIZ); + size_t limit = SIZE_MAX - (SIZE_MAX % MAX_ALLOC); if (if_err(rval == NULL, EFAULT)) return NULL; do { rset(rval, sizeof(*rval)); - } while (*rval >= limit); + } while (*rval >= limit || *rval == 0); - return mkrstr(*rval %= BUFSIZ); + return mkrstr(*rval %= MAX_ALLOC); } char * |