/* We only need assert() when debugging */
# include <assert.h>
+/*
+ * The new BN_FLG_FIXED_TOP flag marks vectors that were not treated with
+ * bn_correct_top, in other words such vectors are permitted to have zeros
+ * in most significant limbs. Such vectors are used internally to achieve
+ * execution time invariance for critical operations with private keys.
+ * It's BN_DEBUG-only flag, because user application is not supposed to
+ * observe it anyway. Moreover, optimizing compiler would actually remove
+ * all operations manipulating the bit in question in non-BN_DEBUG build.
+ */
+# define BN_FLG_FIXED_TOP 0x10000
# ifdef BN_DEBUG_RAND
/* To avoid "make update" cvs wars due to BN_DEBUG, use some tricks */
# ifndef RAND_pseudo_bytes
do { \
const BIGNUM *_bnum2 = (a); \
if (_bnum2 != NULL) { \
- assert((_bnum2->top == 0) || \
- (_bnum2->d[_bnum2->top - 1] != 0)); \
+ int _top = _bnum2->top; \
+ assert((_top == 0) || \
+ (_bnum2->flags & BN_FLG_FIXED_TOP) || \
+ (_bnum2->d[_top - 1] != 0)); \
bn_pollute(_bnum2); \
} \
} while(0)
# else /* !BN_DEBUG */
+# define BN_FLG_FIXED_TOP 0
# define bn_pollute(a)
# define bn_check_top(a)
# define bn_fix_top(a) bn_correct_top(a)
memcpy(a->d, b->d, sizeof(b->d[0]) * b->top);
#endif
- a->top = b->top;
a->neg = b->neg;
+ a->top = b->top;
+ a->flags |= b->flags & BN_FLG_FIXED_TOP;
bn_check_top(a);
return (a);
}
#define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
- | BN_FLG_CONSTTIME))
+ | BN_FLG_CONSTTIME \
+ | BN_FLG_FIXED_TOP))
#define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
void BN_swap(BIGNUM *a, BIGNUM *b)
OPENSSL_cleanse(a->d, a->dmax * sizeof(a->d[0]));
a->top = 0;
a->neg = 0;
+ a->flags &= ~BN_FLG_FIXED_TOP;
}
BN_ULONG BN_get_word(const BIGNUM *a)
a->neg = 0;
a->d[0] = w;
a->top = (w ? 1 : 0);
+ a->flags &= ~BN_FLG_FIXED_TOP;
bn_check_top(a);
return (1);
}
for (k = a->top; k < i + 1; k++)
a->d[k] = 0;
a->top = i + 1;
+ a->flags &= ~BN_FLG_FIXED_TOP;
}
a->d[i] |= (((BN_ULONG)1) << j);
}
rr->neg = 0;
- /*
- * If the most-significant half of the top word of 'a' is zero, then the
- * square of 'a' will max-1 words.
- */
- if (a->d[al - 1] == (a->d[al - 1] & BN_MASK2l))
- rr->top = max - 1;
- else
- rr->top = max;
+ rr->top = max;
+ bn_correct_top(rr);
if (r != rr && BN_copy(r, rr) == NULL)
goto err;