X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=blobdiff_plain;f=sshbn.c;h=7aa1069709f774964aa1de309fcb9f3412d528ef;hb=5471539a6738484b48fb938c88dce547a3e4b299;hp=953f06b547042f1e01e249c638025d51b248f573;hpb=e6679d46022a8fb8ddb41af29e5c2684f68a7ef2;p=PuTTY.git diff --git a/sshbn.c b/sshbn.c index 953f06b5..7aa10697 100644 --- a/sshbn.c +++ b/sshbn.c @@ -7,6 +7,7 @@ #include #include #include +#include #include "misc.h" @@ -19,6 +20,7 @@ typedef BignumInt *Bignum; BignumInt bnZero[1] = { 0 }; BignumInt bnOne[2] = { 1, 1 }; +BignumInt bnTen[2] = { 1, 10 }; /* * The Bignum format is an array of `BignumInt'. The first @@ -34,7 +36,7 @@ BignumInt bnOne[2] = { 1, 1 }; * nonzero. */ -Bignum Zero = bnZero, One = bnOne; +Bignum Zero = bnZero, One = bnOne, Ten = bnTen; static Bignum newbn(int length) { @@ -43,8 +45,6 @@ static Bignum newbn(int length) 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)); b[0] = length; return b; @@ -515,7 +515,7 @@ static void monty_reduce(BignumInt *x, const BignumInt *n, } static void internal_add_shifted(BignumInt *number, - unsigned n, int shift) + BignumInt n, int shift) { int word = 1 + (shift / BIGNUM_INT_BITS); int bshift = shift % BIGNUM_INT_BITS; @@ -546,8 +546,7 @@ static void internal_mod(BignumInt *a, int alen, BignumInt *m, int mlen, BignumInt *quot, int qshift) { - BignumInt m0, m1; - unsigned int h; + BignumInt m0, m1, h; int i, k; m0 = m[0]; @@ -559,7 +558,7 @@ static void internal_mod(BignumInt *a, int alen, for (i = 0; i <= alen - mlen; i++) { BignumDblInt t; - unsigned int q, r, c, ai1; + BignumInt q, r, c, ai1; if (i == 0) { h = 0; @@ -614,7 +613,7 @@ static void internal_mod(BignumInt *a, int alen, for (k = mlen - 1; k >= 0; k--) { t = MUL_WORD(q, m[k]); t += c; - c = (unsigned)(t >> BIGNUM_INT_BITS); + c = (BignumInt)(t >> BIGNUM_INT_BITS); if ((BignumInt) t > a[i + k]) c++; a[i + k] -= (BignumInt) t; @@ -697,7 +696,7 @@ Bignum modpow_simple(Bignum base_in, Bignum exp, Bignum mod) /* Skip leading zero bits of exp. */ i = 0; j = BIGNUM_INT_BITS-1; - while (i < (int)exp[0] && (exp[exp[0] - i] & (1 << j)) == 0) { + while (i < (int)exp[0] && (exp[exp[0] - i] & ((BignumInt)1 << j)) == 0) { j--; if (j < 0) { i++; @@ -710,7 +709,7 @@ Bignum modpow_simple(Bignum base_in, Bignum exp, Bignum mod) while (j >= 0) { internal_mul(a + mlen, a + mlen, b, mlen, scratch); internal_mod(b, mlen * 2, m, mlen, NULL, 0); - if ((exp[exp[0] - i] & (1 << j)) != 0) { + if ((exp[exp[0] - i] & ((BignumInt)1 << j)) != 0) { internal_mul(b + mlen, n, a, mlen, scratch); internal_mod(a, mlen * 2, m, mlen, NULL, 0); } else { @@ -847,7 +846,7 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) /* Skip leading zero bits of exp. */ i = 0; j = BIGNUM_INT_BITS-1; - while (i < (int)exp[0] && (exp[exp[0] - i] & (1 << j)) == 0) { + while (i < (int)exp[0] && (exp[exp[0] - i] & ((BignumInt)1 << j)) == 0) { j--; if (j < 0) { i++; @@ -860,7 +859,7 @@ Bignum modpow(Bignum base_in, Bignum exp, Bignum mod) while (j >= 0) { internal_mul(a + len, a + len, b, len, scratch); monty_reduce(b, n, mninv, scratch, len); - if ((exp[exp[0] - i] & (1 << j)) != 0) { + if ((exp[exp[0] - i] & ((BignumInt)1 << j)) != 0) { internal_mul(b + len, x, a, len, scratch); monty_reduce(a, n, mninv, scratch, len); } else { @@ -1009,6 +1008,35 @@ Bignum modmul(Bignum p, Bignum q, Bignum mod) 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); + assert(tmp); + ret = bigadd(tmp, a1); + freebn(tmp); + } + + 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. @@ -1110,14 +1138,93 @@ Bignum bignum_from_bytes(const unsigned char *data, int nbytes) result[i] = 0; for (i = nbytes; i--;) { unsigned char byte = *data++; - result[1 + i / BIGNUM_INT_BYTES] |= byte << (8*i % BIGNUM_INT_BITS); + result[1 + i / BIGNUM_INT_BYTES] |= + (BignumInt)byte << (8*i % BIGNUM_INT_BITS); + } + + bn_restore_invariant(result); + return result; +} + +Bignum bignum_from_bytes_le(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); + for (i = 1; i <= w; i++) + result[i] = 0; + for (i = 0; i < nbytes; ++i) { + unsigned char byte = *data++; + result[1 + i / BIGNUM_INT_BYTES] |= + (BignumInt)byte << (8*i % BIGNUM_INT_BITS); + } + + bn_restore_invariant(result); + return result; +} + +Bignum bignum_from_decimal(const char *decimal) +{ + Bignum result = copybn(Zero); + + while (*decimal) { + Bignum tmp, tmp2; + + if (!isdigit((unsigned char)*decimal)) { + freebn(result); + return 0; + } + + tmp = bigmul(result, Ten); + tmp2 = bignum_from_long(*decimal - '0'); + result = bigadd(tmp, tmp2); + freebn(tmp); + freebn(tmp2); + + decimal++; } - while (result[0] > 1 && result[result[0]] == 0) - result[0]--; 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. @@ -1202,11 +1309,11 @@ int bignum_bit(Bignum bn, int i) */ void bignum_set_bit(Bignum bn, int bitnum, int value) { - if (bitnum < 0 || bitnum >= (int)(BIGNUM_INT_BITS * bn[0])) - abort(); /* beyond the end */ - else { + if (bitnum < 0 || bitnum >= (int)(BIGNUM_INT_BITS * bn[0])) { + if (value) abort(); /* beyond the end */ + } else { int v = bitnum / BIGNUM_INT_BITS + 1; - int mask = 1 << (bitnum % BIGNUM_INT_BITS); + BignumInt mask = (BignumInt)1 << (bitnum % BIGNUM_INT_BITS); if (value) bn[v] |= mask; else @@ -1292,6 +1399,44 @@ Bignum bignum_rshift(Bignum a, int shift) 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); + + 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. */ @@ -1735,7 +1880,7 @@ char *bignum_decimal(Bignum x) * testdata/bignum.py . */ -void modalfatalbox(char *p, ...) +void modalfatalbox(const char *p, ...) { va_list ap; fprintf(stderr, "FATAL ERROR: "); @@ -1746,6 +1891,12 @@ void modalfatalbox(char *p, ...) exit(1); } +int random_byte(void) +{ + modalfatalbox("random_byte called in testbn"); + return 0; +} + #define fromxdigit(c) ( (c)>'9' ? ((c)&0xDF) - 'A' + 10 : (c) - '0' ) int main(int argc, char **argv)