nhyatt/putty-source
1
0
Fork 0
mirror of https://git.tartarus.org/simon/putty.git synced 2025-06-30 19:12:48 -05:00
Code Issues Projects Releases Wiki Activity

Fix mp_{eq,hs}_integer(tiny, huge).

Browse Source 
The comparison functions between an mp_int and an integer worked by
walking along the mp_int, comparing each of its words to the
corresponding word of the integer. When they ran out of mp_int, they'd
stop.

But this overlooks the possibility that they might not have run out of
_integer_ yet! If BIGNUM_INT_BITS is defined to be less than the size
of a uintmax_t, then comparing (say) the uintmax_t 0x8000000000000001
against a one-word mp_int containing 0x0001 would return equality,
because it would never get as far as spotting the high bit of the
integer.

Fixed by iterating up to the max of the number of BignumInts in the
mp_int and the number that cover a uintmax_t. That means we have to
use mp_word() instead of a direct array lookup to get the mp_int words
to compare against, since now the word indices might be out of range.
This commit is contained in:
Simon Tatham
2020-03-02 18:42:31 +00:00
parent 3ea69c290e
commit 289d8873ec
2 changed files with 19 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
mpint.c
View File

@ -877,11 +877,12 @@ unsigned mp_cmp_hs(mp_int *a, mp_int *b)
unsigned mp_hs_integer(mp_int *x, uintmax_t n)
{
BignumInt carry = 1;
for (size_t i = 0; i < x->nw; i++) {
size_t nwords = sizeof(n)/BIGNUM_INT_BYTES;
for (size_t i = 0, e = size_t_max(x->nw, nwords); i < e; i++) {
BignumInt nword = n;
n = shift_right_by_one_word(n);
BignumInt dummy_out;
BignumADC(dummy_out, carry, x->w[i], ~nword, carry);
BignumADC(dummy_out, carry, mp_word(x, i), ~nword, carry);
(void)dummy_out;
}
return carry;
@ -903,10 +904,11 @@ unsigned mp_cmp_eq(mp_int *a, mp_int *b)
unsigned mp_eq_integer(mp_int *x, uintmax_t n)
{
BignumInt diff = 0;
for (size_t i = 0; i < x->nw; i++) {
size_t nwords = sizeof(n)/BIGNUM_INT_BYTES;
for (size_t i = 0, e = size_t_max(x->nw, nwords); i < e; i++) {
BignumInt nword = n;
n = shift_right_by_one_word(n);
diff |= x->w[i] ^ nword;
diff |= mp_word(x, i) ^ nword;
}
return 1 ^ normalise_to_1(diff); /* return 1 if diff _is_ zero */
}