X-Git-Url: https://git.distorted.org.uk/~mdw/sgt/putty/blobdiff_plain/5a502a193f88c484cff9872bdbf0e2143d96294b..4d9b8cfde347c30066cdcf1002fb6d4b02bdc808:/sshbn.c diff --git a/sshbn.c b/sshbn.c index 6cab8962..a5e0552f 100644 --- a/sshbn.c +++ b/sshbn.c @@ -6,6 +6,7 @@ #include #include #include +#include #include "misc.h" @@ -120,7 +121,11 @@ Bignum Zero = bnZero, One = bnOne; 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)); @@ -148,13 +153,17 @@ void freebn(Bignum b) /* * Burn the evidence, just in case. */ - memset(b, 0, sizeof(b[0]) * (b[0] + 1)); + smemclr(b, sizeof(b[0]) * (b[0] + 1)); sfree(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; } @@ -221,10 +230,8 @@ static int mul_compute_scratch(int len) static void internal_mul(const BignumInt *a, const BignumInt *b, BignumInt *c, int len, BignumInt *scratch) { - int i, j; - BignumDblInt t; - if (len > KARATSUBA_THRESHOLD) { + int i; /* * Karatsuba divide-and-conquer algorithm. Cut each input in @@ -311,9 +318,9 @@ static void internal_mul(const BignumInt *a, const BignumInt *b, * copied over. */ scratch[0] = scratch[1] = scratch[midlen] = scratch[midlen+1] = 0; - for (j = 0; j < toplen; j++) { - scratch[midlen - toplen + j] = a[j]; /* a_1 */ - scratch[2*midlen - toplen + j] = b[j]; /* b_1 */ + for (i = 0; i < toplen; i++) { + scratch[midlen - toplen + i] = a[i]; /* a_1 */ + scratch[2*midlen - toplen + i] = b[i]; /* b_1 */ } /* compute a_1 + a_0 */ @@ -355,8 +362,8 @@ static void internal_mul(const BignumInt *a, const BignumInt *b, * product to obtain the middle one. */ scratch[0] = scratch[1] = scratch[2] = scratch[3] = 0; - for (j = 0; j < 2*toplen; j++) - scratch[2*midlen - 2*toplen + j] = c[j]; + for (i = 0; i < 2*toplen; i++) + scratch[2*midlen - 2*toplen + i] = c[i]; scratch[1] = internal_add(scratch+2, c + 2*toplen, scratch+2, 2*botlen); #ifdef KARA_DEBUG @@ -386,13 +393,13 @@ static void internal_mul(const BignumInt *a, const BignumInt *b, carry = internal_add(c + 2*len - botlen - 2*midlen, scratch + 2*midlen, c + 2*len - botlen - 2*midlen, 2*midlen); - j = 2*len - botlen - 2*midlen - 1; + i = 2*len - botlen - 2*midlen - 1; while (carry) { - assert(j >= 0); - carry += c[j]; - c[j] = (BignumInt)carry; + assert(i >= 0); + carry += c[i]; + c[i] = (BignumInt)carry; carry >>= BIGNUM_INT_BITS; - j--; + i--; } #ifdef KARA_DEBUG printf("ab = 0x"); @@ -403,23 +410,27 @@ static void internal_mul(const BignumInt *a, const BignumInt *b, #endif } else { + int i; + BignumInt carry; + BignumDblInt t; + const BignumInt *ap, *bp; + BignumInt *cp, *cps; /* * Multiply in the ordinary O(N^2) way. */ - for (j = 0; j < 2 * len; j++) - c[j] = 0; + for (i = 0; i < 2 * len; i++) + c[i] = 0; - for (i = len - 1; i >= 0; i--) { - t = 0; - for (j = len - 1; j >= 0; j--) { - t += MUL_WORD(a[i], (BignumDblInt) b[j]); - t += (BignumDblInt) c[i + j + 1]; - c[i + j + 1] = (BignumInt) t; - t = t >> BIGNUM_INT_BITS; + for (cps = c + 2*len, ap = a + len; ap-- > a; cps--) { + carry = 0; + for (cp = cps, bp = b + len; cp--, bp-- > b ;) { + t = (MUL_WORD(*ap, *bp) + carry) + *cp; + *cp = (BignumInt) t; + carry = (BignumInt)(t >> BIGNUM_INT_BITS); } - c[i] = (BignumInt) t; + *cp = carry; } } } @@ -432,10 +443,8 @@ static void internal_mul(const BignumInt *a, const BignumInt *b, static void internal_mul_low(const BignumInt *a, const BignumInt *b, BignumInt *c, int len, BignumInt *scratch) { - int i, j; - BignumDblInt t; - if (len > KARATSUBA_THRESHOLD) { + int i; /* * Karatsuba-aware version of internal_mul_low. As before, we @@ -492,8 +501,8 @@ static void internal_mul_low(const BignumInt *a, const BignumInt *b, scratch + 2*len); /* Copy the bottom half of the big coefficient into place */ - for (j = 0; j < botlen; j++) - c[toplen + j] = scratch[2*toplen + botlen + j]; + for (i = 0; i < botlen; i++) + c[toplen + i] = scratch[2*toplen + botlen + i]; /* Add the two small coefficients, throwing away the returned carry */ internal_add(scratch, scratch + toplen, scratch, toplen); @@ -503,20 +512,27 @@ static void internal_mul_low(const BignumInt *a, const BignumInt *b, c, toplen); } else { + int i; + BignumInt carry; + BignumDblInt t; + const BignumInt *ap, *bp; + BignumInt *cp, *cps; - for (j = 0; j < len; j++) - c[j] = 0; + /* + * Multiply in the ordinary O(N^2) way. + */ - for (i = len - 1; i >= 0; i--) { - t = 0; - for (j = len - 1; j >= len - i - 1; j--) { - t += MUL_WORD(a[i], (BignumDblInt) b[j]); - t += (BignumDblInt) c[i + j + 1 - len]; - c[i + j + 1 - len] = (BignumInt) t; - t = t >> BIGNUM_INT_BITS; + for (i = 0; i < len; i++) + c[i] = 0; + + for (cps = c + len, ap = a + len; ap-- > a; cps--) { + carry = 0; + for (cp = cps, bp = b + len; bp--, cp-- > c ;) { + t = (MUL_WORD(*ap, *bp) + carry) + *cp; + *cp = (BignumInt) t; + carry = (BignumInt)(t >> BIGNUM_INT_BITS); } } - } } @@ -591,6 +607,7 @@ static void internal_add_shifted(BignumInt *number, addend = (BignumDblInt)n << bshift; while (addend) { + assert(word <= number[0]); addend += number[word]; number[word] = (BignumInt) addend & BIGNUM_INT_MASK; addend >>= BIGNUM_INT_BITS; @@ -617,6 +634,7 @@ static void internal_mod(BignumInt *a, int alen, int i, k; m0 = m[0]; + assert(m0 >> (BIGNUM_INT_BITS-1) == 1); if (mlen > 1) m1 = m[1]; else @@ -808,20 +826,15 @@ Bignum modpow_simple(Bignum base_in, Bignum exp, Bignum mod) result[0]--; /* Free temporary arrays */ - for (i = 0; i < 2 * mlen; i++) - a[i] = 0; + smemclr(a, 2 * mlen * sizeof(*a)); sfree(a); - for (i = 0; i < scratchlen; i++) - scratch[i] = 0; + smemclr(scratch, scratchlen * sizeof(*scratch)); sfree(scratch); - for (i = 0; i < 2 * mlen; i++) - b[i] = 0; + smemclr(b, 2 * mlen * sizeof(*b)); sfree(b); - for (i = 0; i < mlen; i++) - m[i] = 0; + smemclr(m, mlen * sizeof(*m)); sfree(m); - for (i = 0; i < mlen; i++) - n[i] = 0; + smemclr(n, mlen * sizeof(*n)); sfree(n); freebn(base); @@ -866,6 +879,7 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) 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 @@ -890,7 +904,7 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) mninv = snewn(len, BignumInt); for (j = 0; j < len; j++) - mninv[len - 1 - j] = (j < inv[0] ? inv[j + 1] : 0); + mninv[len - 1 - j] = (j < (int)inv[0] ? inv[j + 1] : 0); freebn(inv); /* we don't need this copy of it any more */ /* Now negate mninv mod r, so it's the inverse of -n rather than +n. */ x = snewn(len, BignumInt); @@ -900,13 +914,13 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) /* x = snewn(len, BignumInt); */ /* already done above */ for (j = 0; j < len; j++) - x[len - 1 - j] = (j < base[0] ? base[j + 1] : 0); + x[len - 1 - j] = (j < (int)base[0] ? base[j + 1] : 0); freebn(base); /* we don't need this copy of it any more */ a = snewn(2*len, BignumInt); b = snewn(2*len, BignumInt); for (j = 0; j < len; j++) - a[2*len - 1 - j] = (j < rn[0] ? rn[j + 1] : 0); + a[2*len - 1 - j] = (j < (int)rn[0] ? rn[j + 1] : 0); freebn(rn); /* Scratch space for multiplies */ @@ -958,23 +972,17 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) result[0]--; /* Free temporary arrays */ - for (i = 0; i < scratchlen; i++) - scratch[i] = 0; + smemclr(scratch, scratchlen * sizeof(*scratch)); sfree(scratch); - for (i = 0; i < 2 * len; i++) - a[i] = 0; + smemclr(a, 2 * len * sizeof(*a)); sfree(a); - for (i = 0; i < 2 * len; i++) - b[i] = 0; + smemclr(b, 2 * len * sizeof(*b)); sfree(b); - for (i = 0; i < len; i++) - mninv[i] = 0; + smemclr(mninv, len * sizeof(*mninv)); sfree(mninv); - for (i = 0; i < len; i++) - n[i] = 0; + smemclr(n, len * sizeof(*n)); sfree(n); - for (i = 0; i < len; i++) - x[i] = 0; + smemclr(x, len * sizeof(*x)); sfree(x); return result; @@ -992,6 +1000,12 @@ Bignum modmul(Bignum p, Bignum q, Bignum mod) int pqlen, mlen, rlen, i, j; Bignum result; + /* + * The most significant word of mod needs to be non-zero. It + * should already be, but let's make sure. + */ + assert(mod[mod[0]] != 0); + /* Allocate m of size mlen, copy mod to m */ /* We use big endian internally */ mlen = mod[0]; @@ -1011,6 +1025,13 @@ Bignum modmul(Bignum p, Bignum q, Bignum mod) pqlen = (p[0] > q[0] ? p[0] : q[0]); + /* + * Make sure that we're allowing enough space. The shifting below + * will underflow the vectors we allocate if pqlen is too small. + */ + if (2*pqlen <= mlen) + pqlen = mlen/2 + 1; + /* Allocate n of size pqlen, copy p to n */ n = snewn(pqlen, BignumInt); i = pqlen - p[0]; @@ -1057,20 +1078,15 @@ Bignum modmul(Bignum p, Bignum q, Bignum mod) result[0]--; /* Free temporary arrays */ - for (i = 0; i < scratchlen; i++) - scratch[i] = 0; + smemclr(scratch, scratchlen * sizeof(*scratch)); sfree(scratch); - for (i = 0; i < 2 * pqlen; i++) - a[i] = 0; + smemclr(a, 2 * pqlen * sizeof(*a)); sfree(a); - for (i = 0; i < mlen; i++) - m[i] = 0; + smemclr(m, mlen * sizeof(*m)); sfree(m); - for (i = 0; i < pqlen; i++) - n[i] = 0; + smemclr(n, pqlen * sizeof(*n)); sfree(n); - for (i = 0; i < pqlen; i++) - o[i] = 0; + smemclr(o, pqlen * sizeof(*o)); sfree(o); return result; @@ -1089,6 +1105,12 @@ static void bigdivmod(Bignum p, Bignum mod, Bignum result, Bignum quotient) int mshift; int plen, mlen, i, j; + /* + * The most significant word of mod needs to be non-zero. It + * should already be, but let's make sure. + */ + assert(mod[mod[0]] != 0); + /* Allocate m of size mlen, copy mod to m */ /* We use big endian internally */ mlen = mod[0]; @@ -1140,11 +1162,9 @@ static void bigdivmod(Bignum p, Bignum mod, Bignum result, Bignum quotient) } /* Free temporary arrays */ - for (i = 0; i < mlen; i++) - m[i] = 0; + smemclr(m, mlen * sizeof(*m)); sfree(m); - for (i = 0; i < plen; i++) - n[i] = 0; + smemclr(n, plen * sizeof(*n)); sfree(n); } @@ -1164,6 +1184,8 @@ Bignum bignum_from_bytes(const unsigned char *data, int nbytes) 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); @@ -1240,7 +1262,7 @@ int ssh2_bignum_length(Bignum bn) */ 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] >> @@ -1252,7 +1274,7 @@ int bignum_byte(Bignum bn, int i) */ 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; @@ -1263,7 +1285,7 @@ int bignum_bit(Bignum bn, int i) */ 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; @@ -1299,7 +1321,18 @@ int ssh1_write_bignum(void *data, Bignum bn) 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]); @@ -1321,6 +1354,8 @@ Bignum bignum_rshift(Bignum a, int shift) 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); @@ -1391,8 +1426,7 @@ Bignum bigmuladd(Bignum a, Bignum b, Bignum addend) } ret[0] = maxspot; - for (i = 0; i < wslen; i++) - workspace[i] = 0; + smemclr(workspace, wslen * sizeof(*workspace)); sfree(workspace); return ret; } @@ -1622,9 +1656,26 @@ Bignum modinv(Bignum number, Bignum modulus) Bignum x = copybn(One); int sign = +1; + assert(number[number[0]] != 0); + 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]--; @@ -1743,6 +1794,7 @@ char *bignum_decimal(Bignum x) /* * Done. */ + smemclr(workspace, x[0] * sizeof(*workspace)); sfree(workspace); return ret; } @@ -1754,7 +1806,7 @@ char *bignum_decimal(Bignum x) #include /* - * gcc -g -O0 -DTESTBN -o testbn sshbn.c misc.c -I unix -I charset + * gcc -Wall -g -O0 -DTESTBN -o testbn sshbn.c misc.c conf.c tree234.c unix/uxmisc.c -I. -I unix -I charset * * Then feed to this program's standard input the output of * testdata/bignum.py . @@ -1828,7 +1880,7 @@ int main(int argc, char **argv) Bignum a, b, c, p; if (ptrnum != 3) { - printf("%d: mul with %d parameters, expected 3\n", line); + printf("%d: mul with %d parameters, expected 3\n", line, ptrnum); exit(1); } a = bignum_from_bytes(ptrs[0], ptrs[1]-ptrs[0]); @@ -1857,11 +1909,49 @@ int main(int argc, char **argv) freebn(b); freebn(c); freebn(p); + } else if (!strcmp(buf, "modmul")) { + Bignum a, b, m, c, p; + + if (ptrnum != 4) { + printf("%d: modmul with %d parameters, expected 4\n", + line, ptrnum); + exit(1); + } + a = bignum_from_bytes(ptrs[0], ptrs[1]-ptrs[0]); + b = bignum_from_bytes(ptrs[1], ptrs[2]-ptrs[1]); + m = bignum_from_bytes(ptrs[2], ptrs[3]-ptrs[2]); + c = bignum_from_bytes(ptrs[3], ptrs[4]-ptrs[3]); + p = modmul(a, b, m); + + if (bignum_cmp(c, p) == 0) { + passes++; + } else { + char *as = bignum_decimal(a); + char *bs = bignum_decimal(b); + char *ms = bignum_decimal(m); + char *cs = bignum_decimal(c); + char *ps = bignum_decimal(p); + + printf("%d: fail: %s * %s mod %s gave %s expected %s\n", + line, as, bs, ms, ps, cs); + fails++; + + sfree(as); + sfree(bs); + sfree(ms); + sfree(cs); + sfree(ps); + } + freebn(a); + freebn(b); + freebn(m); + freebn(c); + freebn(p); } else if (!strcmp(buf, "pow")) { Bignum base, expt, modulus, expected, answer; if (ptrnum != 4) { - printf("%d: mul with %d parameters, expected 3\n", line); + printf("%d: mul with %d parameters, expected 4\n", line, ptrnum); exit(1); }