X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/036eddfb3ea7dabc26c17608ce18bb4d3fe8689b..62ddb51e0424dd4bd1098b024f2427959aefc729:/sshbn.c diff --git a/sshbn.c b/sshbn.c index 14cdd05e..ba3d5b63 100644 --- a/sshbn.c +++ b/sshbn.c @@ -9,6 +9,20 @@ #include "misc.h" +/* + * Usage notes: + * * Do not call the DIVMOD_WORD macro with expressions such as array + * subscripts, as some implementations object to this (see below). + * * Note that none of the division methods below will cope if the + * quotient won't fit into BIGNUM_INT_BITS. Callers should be careful + * to avoid this case. + * If this condition occurs, in the case of the x86 DIV instruction, + * an overflow exception will occur, which (according to a correspondent) + * will manifest on Windows as something like + * 0xC0000095: Integer overflow + * The C variant won't give the right answer, either. + */ + #if defined __GNUC__ && defined __i386__ typedef unsigned long BignumInt; typedef unsigned long long BignumDblInt; @@ -27,26 +41,16 @@ typedef unsigned __int64 BignumDblInt; #define BIGNUM_TOP_BIT 0x80000000UL #define BIGNUM_INT_BITS 32 #define MUL_WORD(w1, w2) ((BignumDblInt)w1 * w2) -typedef struct { - unsigned __int32 quot; - unsigned __int32 remd; -} msvc_quorem; -static __declspec(naked) msvc_quorem __stdcall msvc_divmod( - unsigned __int32 hi, - unsigned __int32 lo, - unsigned __int32 w) -{ - __asm { - mov edx, dword ptr [esp+4] - mov eax, dword ptr [esp+8] - div dword ptr [esp+12] - ret 12 - }; -} +/* Note: MASM interprets array subscripts in the macro arguments as + * assembler syntax, which gives the wrong answer. Don't supply them. + * */ #define DIVMOD_WORD(q, r, hi, lo, w) do { \ - const msvc_quorem qr = msvc_divmod((hi), (lo), (w)); \ - (q) = qr.quot; (r) = qr.remd; \ -} while (0) + __asm mov edx, hi \ + __asm mov eax, lo \ + __asm div w \ + __asm mov r, edx \ + __asm mov q, eax \ +} while(0) #else typedef unsigned short BignumInt; typedef unsigned long BignumDblInt; @@ -230,7 +234,10 @@ static void internal_mod(BignumInt *a, int alen, */ q = BIGNUM_INT_MASK; } else { - DIVMOD_WORD(q, r, h, a[i], m0); + /* Macro doesn't want an array subscript expression passed + * into it (see definition), so use a temporary. */ + BignumInt tmplo = a[i]; + DIVMOD_WORD(q, r, h, tmplo, m0); /* Refine our estimate of q by looking at h:a[i]:a[i+1] / m0:m1 */ @@ -249,7 +256,7 @@ static void internal_mod(BignumInt *a, int alen, for (k = mlen - 1; k >= 0; k--) { t = MUL_WORD(q, m[k]); t += c; - c = t >> BIGNUM_INT_BITS; + c = (unsigned)(t >> BIGNUM_INT_BITS); if ((BignumInt) t > a[i + k]) c++; a[i + k] -= (BignumInt) t; @@ -315,7 +322,7 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) i = mlen - base[0]; for (j = 0; j < i; j++) n[j] = 0; - for (j = 0; j < base[0]; j++) + for (j = 0; j < (int)base[0]; j++) n[i + j] = base[base[0] - j]; /* Allocate a and b of size 2*mlen. Set a = 1 */ @@ -328,7 +335,7 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) /* Skip leading zero bits of exp. */ i = 0; j = BIGNUM_INT_BITS-1; - while (i < exp[0] && (exp[exp[0] - i] & (1 << j)) == 0) { + while (i < (int)exp[0] && (exp[exp[0] - i] & (1 << j)) == 0) { j--; if (j < 0) { i++; @@ -337,7 +344,7 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) } /* Main computation */ - while (i < exp[0]) { + while (i < (int)exp[0]) { while (j >= 0) { internal_mul(a + mlen, a + mlen, b, mlen); internal_mod(b, mlen * 2, m, mlen, NULL, 0); @@ -428,7 +435,7 @@ Bignum modmul(Bignum p, Bignum q, Bignum mod) i = pqlen - p[0]; for (j = 0; j < i; j++) n[j] = 0; - for (j = 0; j < p[0]; j++) + for (j = 0; j < (int)p[0]; j++) n[i + j] = p[p[0] - j]; /* Allocate o of size pqlen, copy q to o */ @@ -436,7 +443,7 @@ Bignum modmul(Bignum p, Bignum q, Bignum mod) i = pqlen - q[0]; for (j = 0; j < i; j++) o[j] = 0; - for (j = 0; j < q[0]; j++) + for (j = 0; j < (int)q[0]; j++) o[i + j] = q[q[0] - j]; /* Allocate a of size 2*pqlen for result */ @@ -520,7 +527,7 @@ static void bigdivmod(Bignum p, Bignum mod, Bignum result, Bignum quotient) n = snewn(plen, BignumInt); for (j = 0; j < plen; j++) n[j] = 0; - for (j = 1; j <= p[0]; j++) + for (j = 1; j <= (int)p[0]; j++) n[plen - j] = p[j]; /* Main computation */ @@ -538,7 +545,7 @@ static void bigdivmod(Bignum p, Bignum mod, Bignum result, Bignum quotient) /* Copy result to buffer */ if (result) { - for (i = 1; i <= result[0]; i++) { + for (i = 1; i <= (int)result[0]; i++) { int j = plen - i; result[i] = j >= 0 ? n[j] : 0; } @@ -559,7 +566,7 @@ static void bigdivmod(Bignum p, Bignum mod, Bignum result, Bignum quotient) void decbn(Bignum bn) { int i = 1; - while (i < bn[0] && bn[i] == 0) + while (i < (int)bn[0] && bn[i] == 0) bn[i++] = BIGNUM_INT_MASK; bn[i]--; } @@ -645,7 +652,7 @@ int ssh2_bignum_length(Bignum bn) */ int bignum_byte(Bignum bn, int i) { - if (i >= BIGNUM_INT_BYTES * bn[0]) + if (i >= (int)(BIGNUM_INT_BYTES * bn[0])) return 0; /* beyond the end */ else return (bn[i / BIGNUM_INT_BYTES + 1] >> @@ -657,7 +664,7 @@ int bignum_byte(Bignum bn, int i) */ int bignum_bit(Bignum bn, int i) { - if (i >= BIGNUM_INT_BITS * bn[0]) + if (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; @@ -668,7 +675,7 @@ int bignum_bit(Bignum bn, int i) */ void bignum_set_bit(Bignum bn, int bitnum, int value) { - if (bitnum >= BIGNUM_INT_BITS * bn[0]) + if (bitnum >= (int)(BIGNUM_INT_BITS * bn[0])) abort(); /* beyond the end */ else { int v = bitnum / BIGNUM_INT_BITS + 1; @@ -735,9 +742,9 @@ Bignum bignum_rshift(Bignum a, int shift) shiftbb = BIGNUM_INT_BITS - shiftb; ai1 = a[shiftw + 1]; - for (i = 1; i <= ret[0]; i++) { + for (i = 1; i <= (int)ret[0]; i++) { ai = ai1; - ai1 = (i + shiftw + 1 <= a[0] ? a[i + shiftw + 1] : 0); + ai1 = (i + shiftw + 1 <= (int)a[0] ? a[i + shiftw + 1] : 0); ret[i] = ((ai >> shiftb) | (ai1 << shiftbb)) & BIGNUM_INT_MASK; } } @@ -759,8 +766,8 @@ Bignum bigmuladd(Bignum a, Bignum b, Bignum addend) /* mlen space for a, mlen space for b, 2*mlen for result */ workspace = snewn(mlen * 4, BignumInt); for (i = 0; i < mlen; i++) { - workspace[0 * mlen + i] = (mlen - i <= a[0] ? a[mlen - i] : 0); - workspace[1 * mlen + i] = (mlen - i <= b[0] ? b[mlen - i] : 0); + workspace[0 * mlen + i] = (mlen - i <= (int)a[0] ? a[mlen - i] : 0); + workspace[1 * mlen + i] = (mlen - i <= (int)b[0] ? b[mlen - i] : 0); } internal_mul(workspace + 0 * mlen, workspace + 1 * mlen, @@ -768,11 +775,11 @@ Bignum bigmuladd(Bignum a, Bignum b, Bignum addend) /* now just copy the result back */ rlen = alen + blen + 1; - if (addend && rlen <= addend[0]) + if (addend && rlen <= (int)addend[0]) rlen = addend[0] + 1; ret = newbn(rlen); maxspot = 0; - for (i = 1; i <= ret[0]; i++) { + for (i = 1; i <= (int)ret[0]; i++) { ret[i] = (i <= 2 * mlen ? workspace[4 * mlen - i] : 0); if (ret[i] != 0) maxspot = i; @@ -783,8 +790,8 @@ Bignum bigmuladd(Bignum a, Bignum b, Bignum addend) if (addend) { BignumDblInt carry = 0; for (i = 1; i <= rlen; i++) { - carry += (i <= ret[0] ? ret[i] : 0); - carry += (i <= addend[0] ? addend[i] : 0); + carry += (i <= (int)ret[0] ? ret[i] : 0); + carry += (i <= (int)addend[0] ? addend[i] : 0); ret[i] = (BignumInt) carry & BIGNUM_INT_MASK; carry >>= BIGNUM_INT_BITS; if (ret[i] != 0 && i > maxspot) @@ -855,9 +862,9 @@ Bignum bignum_add_long(Bignum number, unsigned long addendx) int i, maxspot = 0; BignumDblInt carry = 0, addend = addendx; - for (i = 1; i <= ret[0]; i++) { + for (i = 1; i <= (int)ret[0]; i++) { carry += addend & BIGNUM_INT_MASK; - carry += (i <= number[0] ? number[i] : 0); + carry += (i <= (int)number[0] ? number[i] : 0); addend >>= BIGNUM_INT_BITS; ret[i] = (BignumInt) carry & BIGNUM_INT_MASK; carry >>= BIGNUM_INT_BITS; @@ -988,9 +995,9 @@ Bignum modinv(Bignum number, Bignum modulus) int maxspot = 1; int i; - for (i = 1; i <= newx[0]; i++) { - BignumInt aword = (i <= modulus[0] ? modulus[i] : 0); - BignumInt bword = (i <= x[0] ? x[i] : 0); + for (i = 1; i <= (int)newx[0]; i++) { + BignumInt aword = (i <= (int)modulus[0] ? modulus[i] : 0); + BignumInt bword = (i <= (int)x[0] ? x[i] : 0); newx[i] = aword - bword - carry; bword = ~bword; carry = carry ? (newx[i] >= bword) : (newx[i] > bword); @@ -1030,9 +1037,14 @@ char *bignum_decimal(Bignum x) * round up (rounding down might make it less than x again). * Therefore if we multiply the bit count by 28/93, rounding * up, we will have enough digits. + * + * i=0 (i.e., x=0) is an irritating special case. */ i = bignum_bitcount(x); - ndigits = (28 * i + 92) / 93; /* multiply by 28/93 and round up */ + if (!i) + ndigits = 1; /* x = 0 */ + else + ndigits = (28 * i + 92) / 93; /* multiply by 28/93 and round up */ ndigits++; /* allow for trailing \0 */ ret = snewn(ndigits, char); @@ -1042,7 +1054,7 @@ char *bignum_decimal(Bignum x) * big-endian form of the number. */ workspace = snewn(x[0], BignumInt); - for (i = 0; i < x[0]; i++) + for (i = 0; i < (int)x[0]; i++) workspace[i] = x[x[0] - i]; /* @@ -1055,7 +1067,7 @@ char *bignum_decimal(Bignum x) do { iszero = 1; carry = 0; - for (i = 0; i < x[0]; i++) { + for (i = 0; i < (int)x[0]; i++) { carry = (carry << BIGNUM_INT_BITS) + workspace[i]; workspace[i] = (BignumInt) (carry / 10); if (workspace[i])