#include <assert.h>
#include <stdlib.h>
#include <string.h>
+#include <limits.h>
#include "misc.h"
static Bignum newbn(int length)
{
- Bignum b = snewn(length + 1, BignumInt);
+ Bignum b;
+
+ assert(length >= 0 && length < INT_MAX / BIGNUM_INT_BITS);
+
+ b = snewn(length + 1, BignumInt);
if (!b)
abort(); /* FIXME */
memset(b, 0, (length + 1) * sizeof(*b));
Bignum bn_power_2(int n)
{
- Bignum ret = newbn(n / BIGNUM_INT_BITS + 1);
+ Bignum ret;
+
+ assert(n >= 0);
+
+ ret = newbn(n / BIGNUM_INT_BITS + 1);
bignum_set_bit(ret, n, 1);
return ret;
}
addend = (BignumDblInt)n << bshift;
while (addend) {
+ assert(word <= number[0]);
addend += number[word];
number[word] = (BignumInt) addend & BIGNUM_INT_MASK;
addend >>= BIGNUM_INT_BITS;
len = mod[0];
r = bn_power_2(BIGNUM_INT_BITS * len);
inv = modinv(mod, r);
+ assert(inv); /* cannot fail, since mod is odd and r is a power of 2 */
/*
* Multiply the base by r mod n, to get it into Montgomery
return result;
}
+Bignum modsub(const Bignum a, const Bignum b, const Bignum n)
+{
+ Bignum a1, b1, ret;
+
+ if (bignum_cmp(a, n) >= 0) a1 = bigmod(a, n);
+ else a1 = a;
+ if (bignum_cmp(b, n) >= 0) b1 = bigmod(b, n);
+ else b1 = b;
+
+ if (bignum_cmp(a1, b1) >= 0) /* a >= b */
+ {
+ ret = bigsub(a1, b1);
+ }
+ else
+ {
+ /* Handle going round the corner of the modulus without having
+ * negative support in Bignum */
+ Bignum tmp = bigsub(n, b1);
+ if (tmp) {
+ ret = bigadd(tmp, a1);
+ freebn(tmp);
+ } else {
+ ret = NULL;
+ }
+ }
+
+ if (a != a1) freebn(a1);
+ if (b != b1) freebn(b1);
+
+ return ret;
+}
+
/*
* Compute p % mod.
* The most significant word of mod MUST be non-zero.
Bignum result;
int w, i;
+ assert(nbytes >= 0 && nbytes < INT_MAX/8);
+
w = (nbytes + BIGNUM_INT_BYTES - 1) / BIGNUM_INT_BYTES; /* bytes->words */
result = newbn(w);
return result;
}
+Bignum bignum_random_in_range(const Bignum lower, const Bignum upper)
+{
+ Bignum ret = NULL;
+ unsigned char *bytes;
+ int upper_len = bignum_bitcount(upper);
+ int upper_bytes = upper_len / 8;
+ int upper_bits = upper_len % 8;
+ if (upper_bits) ++upper_bytes;
+
+ bytes = snewn(upper_bytes, unsigned char);
+ do {
+ int i;
+
+ if (ret) freebn(ret);
+
+ for (i = 0; i < upper_bytes; ++i)
+ {
+ bytes[i] = (unsigned char)random_byte();
+ }
+ /* Mask the top to reduce failure rate to 50/50 */
+ if (upper_bits)
+ {
+ bytes[i - 1] &= 0xFF >> (8 - upper_bits);
+ }
+
+ ret = bignum_from_bytes(bytes, upper_bytes);
+ } while (bignum_cmp(ret, lower) < 0 || bignum_cmp(ret, upper) > 0);
+ smemclr(bytes, upper_bytes);
+ sfree(bytes);
+
+ return ret;
+}
+
/*
* Read an SSH-1-format bignum from a data buffer. Return the number
* of bytes consumed, or -1 if there wasn't enough data.
*/
int bignum_byte(Bignum bn, int i)
{
- if (i >= (int)(BIGNUM_INT_BYTES * bn[0]))
+ if (i < 0 || i >= (int)(BIGNUM_INT_BYTES * bn[0]))
return 0; /* beyond the end */
else
return (bn[i / BIGNUM_INT_BYTES + 1] >>
*/
int bignum_bit(Bignum bn, int i)
{
- if (i >= (int)(BIGNUM_INT_BITS * bn[0]))
+ if (i < 0 || i >= (int)(BIGNUM_INT_BITS * bn[0]))
return 0; /* beyond the end */
else
return (bn[i / BIGNUM_INT_BITS + 1] >> (i % BIGNUM_INT_BITS)) & 1;
*/
void bignum_set_bit(Bignum bn, int bitnum, int value)
{
- if (bitnum >= (int)(BIGNUM_INT_BITS * bn[0]))
+ if (bitnum < 0 || bitnum >= (int)(BIGNUM_INT_BITS * bn[0]))
abort(); /* beyond the end */
else {
int v = bitnum / BIGNUM_INT_BITS + 1;
int bignum_cmp(Bignum a, Bignum b)
{
int amax = a[0], bmax = b[0];
- int i = (amax > bmax ? amax : bmax);
+ int i;
+
+ /* Annoyingly we have two representations of zero */
+ if (amax == 1 && a[amax] == 0)
+ amax = 0;
+ if (bmax == 1 && b[bmax] == 0)
+ bmax = 0;
+
+ assert(amax == 0 || a[amax] != 0);
+ assert(bmax == 0 || b[bmax] != 0);
+
+ i = (amax > bmax ? amax : bmax);
while (i) {
BignumInt aval = (i > amax ? 0 : a[i]);
BignumInt bval = (i > bmax ? 0 : b[i]);
int i, shiftw, shiftb, shiftbb, bits;
BignumInt ai, ai1;
+ assert(shift >= 0);
+
bits = bignum_bitcount(a) - shift;
ret = newbn((bits + BIGNUM_INT_BITS - 1) / BIGNUM_INT_BITS);
return ret;
}
+/*
+ * Left-shift one bignum to form another.
+ */
+Bignum bignum_lshift(Bignum a, int shift)
+{
+ Bignum ret;
+ int bits, shiftWords, shiftBits;
+
+ assert(shift >= 0);
+
+ bits = bignum_bitcount(a) + shift;
+ ret = newbn((bits + BIGNUM_INT_BITS - 1) / BIGNUM_INT_BITS);
+ if (!ret) return NULL;
+
+ shiftWords = shift / BIGNUM_INT_BITS;
+ shiftBits = shift % BIGNUM_INT_BITS;
+
+ if (shiftBits == 0)
+ {
+ memcpy(&ret[1 + shiftWords], &a[1], sizeof(BignumInt) * a[0]);
+ }
+ else
+ {
+ int i;
+ BignumInt carry = 0;
+
+ /* Remember that Bignum[0] is length, so add 1 */
+ for (i = shiftWords + 1; i < ((int)a[0]) + shiftWords + 1; ++i)
+ {
+ BignumInt from = a[i - shiftWords];
+ ret[i] = (from << shiftBits) | carry;
+ carry = from >> (BIGNUM_INT_BITS - shiftBits);
+ }
+ if (carry) ret[i] = carry;
+ }
+
+ return ret;
+}
+
/*
* Non-modular multiplication and addition.
*/
{
Bignum q = newbn(a[0]);
bigdivmod(a, b, NULL, q);
+ while (q[0] > 1 && q[q[0]] == 0)
+ q[0]--;
return q;
}
{
Bignum r = newbn(b[0]);
bigdivmod(a, b, r, NULL);
+ while (r[0] > 1 && r[r[0]] == 0)
+ r[0]--;
return r;
}
assert(modulus[modulus[0]] != 0);
while (bignum_cmp(b, One) != 0) {
- Bignum t = newbn(b[0]);
- Bignum q = newbn(a[0]);
+ Bignum t, q;
+
+ if (bignum_cmp(b, Zero) == 0) {
+ /*
+ * Found a common factor between the inputs, so we cannot
+ * return a modular inverse at all.
+ */
+ freebn(b);
+ freebn(a);
+ freebn(xp);
+ freebn(x);
+ return NULL;
+ }
+
+ t = newbn(b[0]);
+ q = newbn(a[0]);
bigdivmod(a, b, t, q);
while (t[0] > 1 && t[t[0]] == 0)
t[0]--;
+ while (q[0] > 1 && q[q[0]] == 0)
+ q[0]--;
freebn(a);
a = b;
b = t;
projects / PuTTY.git / blobdiff