diff options
Diffstat (limited to 'third_party/bearssl/src/ghash_ctmul.c')
| -rw-r--r-- | third_party/bearssl/src/ghash_ctmul.c | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/third_party/bearssl/src/ghash_ctmul.c b/third_party/bearssl/src/ghash_ctmul.c new file mode 100644 index 0000000..3623202 --- /dev/null +++ b/third_party/bearssl/src/ghash_ctmul.c @@ -0,0 +1,345 @@ +/* + * Copyright (c) 2016 Thomas Pornin <[email protected]> + * + * Permission is hereby granted, free of charge, to any person obtaining + * a copy of this software and associated documentation files (the + * "Software"), to deal in the Software without restriction, including + * without limitation the rights to use, copy, modify, merge, publish, + * distribute, sublicense, and/or sell copies of the Software, and to + * permit persons to whom the Software is furnished to do so, subject to + * the following conditions: + * + * The above copyright notice and this permission notice shall be + * included in all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ + +#include "inner.h" + +/* + * We compute "carryless multiplications" through normal integer + * multiplications, masking out enough bits to create "holes" in which + * carries may expand without altering our bits; we really use 8 data + * bits per 32-bit word, spaced every fourth bit. Accumulated carries + * may not exceed 8 in total, which fits in 4 bits. + * + * It would be possible to use a 3-bit spacing, allowing two operands, + * one with 7 non-zero data bits, the other one with 10 or 11 non-zero + * data bits; this asymmetric splitting makes the overall code more + * complex with thresholds and exceptions, and does not appear to be + * worth the effort. + */ + +/* + * We cannot really autodetect whether multiplications are "slow" or + * not. A typical example is the ARM Cortex M0+, which exists in two + * versions: one with a 1-cycle multiplication opcode, the other with + * a 32-cycle multiplication opcode. They both use exactly the same + * architecture and ABI, and cannot be distinguished from each other + * at compile-time. + * + * Since most modern CPU (even embedded CPU) still have fast + * multiplications, we use the "fast mul" code by default. + */ + +#if BR_SLOW_MUL + +/* + * This implementation uses Karatsuba-like reduction to make fewer + * integer multiplications (9 instead of 16), at the expense of extra + * logical operations (XOR, shifts...). On modern x86 CPU that offer + * fast, pipelined multiplications, this code is about twice slower than + * the simpler code with 16 multiplications. This tendency may be + * reversed on low-end platforms with expensive multiplications. + */ + +#define MUL32(h, l, x, y) do { \ + uint64_t mul32tmp = MUL(x, y); \ + (h) = (uint32_t)(mul32tmp >> 32); \ + (l) = (uint32_t)mul32tmp; \ + } while (0) + +static inline void +bmul(uint32_t *hi, uint32_t *lo, uint32_t x, uint32_t y) +{ + uint32_t x0, x1, x2, x3; + uint32_t y0, y1, y2, y3; + uint32_t a0, a1, a2, a3, a4, a5, a6, a7, a8; + uint32_t b0, b1, b2, b3, b4, b5, b6, b7, b8; + + x0 = x & (uint32_t)0x11111111; + x1 = x & (uint32_t)0x22222222; + x2 = x & (uint32_t)0x44444444; + x3 = x & (uint32_t)0x88888888; + y0 = y & (uint32_t)0x11111111; + y1 = y & (uint32_t)0x22222222; + y2 = y & (uint32_t)0x44444444; + y3 = y & (uint32_t)0x88888888; + + /* + * (x0+W*x1)*(y0+W*y1) -> a0:b0 + * (x2+W*x3)*(y2+W*y3) -> a3:b3 + * ((x0+x2)+W*(x1+x3))*((y0+y2)+W*(y1+y3)) -> a6:b6 + */ + a0 = x0; + b0 = y0; + a1 = x1 >> 1; + b1 = y1 >> 1; + a2 = a0 ^ a1; + b2 = b0 ^ b1; + a3 = x2 >> 2; + b3 = y2 >> 2; + a4 = x3 >> 3; + b4 = y3 >> 3; + a5 = a3 ^ a4; + b5 = b3 ^ b4; + a6 = a0 ^ a3; + b6 = b0 ^ b3; + a7 = a1 ^ a4; + b7 = b1 ^ b4; + a8 = a6 ^ a7; + b8 = b6 ^ b7; + + MUL32(b0, a0, b0, a0); + MUL32(b1, a1, b1, a1); + MUL32(b2, a2, b2, a2); + MUL32(b3, a3, b3, a3); + MUL32(b4, a4, b4, a4); + MUL32(b5, a5, b5, a5); + MUL32(b6, a6, b6, a6); + MUL32(b7, a7, b7, a7); + MUL32(b8, a8, b8, a8); + + a0 &= (uint32_t)0x11111111; + a1 &= (uint32_t)0x11111111; + a2 &= (uint32_t)0x11111111; + a3 &= (uint32_t)0x11111111; + a4 &= (uint32_t)0x11111111; + a5 &= (uint32_t)0x11111111; + a6 &= (uint32_t)0x11111111; + a7 &= (uint32_t)0x11111111; + a8 &= (uint32_t)0x11111111; + b0 &= (uint32_t)0x11111111; + b1 &= (uint32_t)0x11111111; + b2 &= (uint32_t)0x11111111; + b3 &= (uint32_t)0x11111111; + b4 &= (uint32_t)0x11111111; + b5 &= (uint32_t)0x11111111; + b6 &= (uint32_t)0x11111111; + b7 &= (uint32_t)0x11111111; + b8 &= (uint32_t)0x11111111; + + a2 ^= a0 ^ a1; + b2 ^= b0 ^ b1; + a0 ^= (a2 << 1) ^ (a1 << 2); + b0 ^= (b2 << 1) ^ (b1 << 2); + a5 ^= a3 ^ a4; + b5 ^= b3 ^ b4; + a3 ^= (a5 << 1) ^ (a4 << 2); + b3 ^= (b5 << 1) ^ (b4 << 2); + a8 ^= a6 ^ a7; + b8 ^= b6 ^ b7; + a6 ^= (a8 << 1) ^ (a7 << 2); + b6 ^= (b8 << 1) ^ (b7 << 2); + a6 ^= a0 ^ a3; + b6 ^= b0 ^ b3; + *lo = a0 ^ (a6 << 2) ^ (a3 << 4); + *hi = b0 ^ (b6 << 2) ^ (b3 << 4) ^ (a6 >> 30) ^ (a3 >> 28); +} + +#else + +/* + * Simple multiplication in GF(2)[X], using 16 integer multiplications. + */ + +static inline void +bmul(uint32_t *hi, uint32_t *lo, uint32_t x, uint32_t y) +{ + uint32_t x0, x1, x2, x3; + uint32_t y0, y1, y2, y3; + uint64_t z0, z1, z2, z3; + uint64_t z; + + x0 = x & (uint32_t)0x11111111; + x1 = x & (uint32_t)0x22222222; + x2 = x & (uint32_t)0x44444444; + x3 = x & (uint32_t)0x88888888; + y0 = y & (uint32_t)0x11111111; + y1 = y & (uint32_t)0x22222222; + y2 = y & (uint32_t)0x44444444; + y3 = y & (uint32_t)0x88888888; + z0 = MUL(x0, y0) ^ MUL(x1, y3) ^ MUL(x2, y2) ^ MUL(x3, y1); + z1 = MUL(x0, y1) ^ MUL(x1, y0) ^ MUL(x2, y3) ^ MUL(x3, y2); + z2 = MUL(x0, y2) ^ MUL(x1, y1) ^ MUL(x2, y0) ^ MUL(x3, y3); + z3 = MUL(x0, y3) ^ MUL(x1, y2) ^ MUL(x2, y1) ^ MUL(x3, y0); + z0 &= (uint64_t)0x1111111111111111; + z1 &= (uint64_t)0x2222222222222222; + z2 &= (uint64_t)0x4444444444444444; + z3 &= (uint64_t)0x8888888888888888; + z = z0 | z1 | z2 | z3; + *lo = (uint32_t)z; + *hi = (uint32_t)(z >> 32); +} + +#endif + +/* see bearssl_hash.h */ +void +br_ghash_ctmul(void *y, const void *h, const void *data, size_t len) +{ + const unsigned char *buf, *hb; + unsigned char *yb; + uint32_t yw[4]; + uint32_t hw[4]; + + /* + * Throughout the loop we handle the y and h values as arrays + * of 32-bit words. + */ + buf = data; + yb = y; + hb = h; + yw[3] = br_dec32be(yb); + yw[2] = br_dec32be(yb + 4); + yw[1] = br_dec32be(yb + 8); + yw[0] = br_dec32be(yb + 12); + hw[3] = br_dec32be(hb); + hw[2] = br_dec32be(hb + 4); + hw[1] = br_dec32be(hb + 8); + hw[0] = br_dec32be(hb + 12); + while (len > 0) { + const unsigned char *src; + unsigned char tmp[16]; + int i; + uint32_t a[9], b[9], zw[8]; + uint32_t c0, c1, c2, c3, d0, d1, d2, d3, e0, e1, e2, e3; + + /* + * Get the next 16-byte block (using zero-padding if + * necessary). + */ + if (len >= 16) { + src = buf; + buf += 16; + len -= 16; + } else { + memcpy(tmp, buf, len); + memset(tmp + len, 0, (sizeof tmp) - len); + src = tmp; + len = 0; + } + + /* + * Decode the block. The GHASH standard mandates + * big-endian encoding. + */ + yw[3] ^= br_dec32be(src); + yw[2] ^= br_dec32be(src + 4); + yw[1] ^= br_dec32be(src + 8); + yw[0] ^= br_dec32be(src + 12); + + /* + * We multiply two 128-bit field elements. We use + * Karatsuba to turn that into three 64-bit + * multiplications, which are themselves done with a + * total of nine 32-bit multiplications. + */ + + /* + * y[0,1]*h[0,1] -> 0..2 + * y[2,3]*h[2,3] -> 3..5 + * (y[0,1]+y[2,3])*(h[0,1]+h[2,3]) -> 6..8 + */ + a[0] = yw[0]; + b[0] = hw[0]; + a[1] = yw[1]; + b[1] = hw[1]; + a[2] = a[0] ^ a[1]; + b[2] = b[0] ^ b[1]; + + a[3] = yw[2]; + b[3] = hw[2]; + a[4] = yw[3]; + b[4] = hw[3]; + a[5] = a[3] ^ a[4]; + b[5] = b[3] ^ b[4]; + + a[6] = a[0] ^ a[3]; + b[6] = b[0] ^ b[3]; + a[7] = a[1] ^ a[4]; + b[7] = b[1] ^ b[4]; + a[8] = a[6] ^ a[7]; + b[8] = b[6] ^ b[7]; + + for (i = 0; i < 9; i ++) { + bmul(&b[i], &a[i], b[i], a[i]); + } + + c0 = a[0]; + c1 = b[0] ^ a[2] ^ a[0] ^ a[1]; + c2 = a[1] ^ b[2] ^ b[0] ^ b[1]; + c3 = b[1]; + d0 = a[3]; + d1 = b[3] ^ a[5] ^ a[3] ^ a[4]; + d2 = a[4] ^ b[5] ^ b[3] ^ b[4]; + d3 = b[4]; + e0 = a[6]; + e1 = b[6] ^ a[8] ^ a[6] ^ a[7]; + e2 = a[7] ^ b[8] ^ b[6] ^ b[7]; + e3 = b[7]; + + e0 ^= c0 ^ d0; + e1 ^= c1 ^ d1; + e2 ^= c2 ^ d2; + e3 ^= c3 ^ d3; + c2 ^= e0; + c3 ^= e1; + d0 ^= e2; + d1 ^= e3; + + /* + * GHASH specification has the bits "reversed" (most + * significant is in fact least significant), which does + * not matter for a carryless multiplication, except that + * the 255-bit result must be shifted by 1 bit. + */ + zw[0] = c0 << 1; + zw[1] = (c1 << 1) | (c0 >> 31); + zw[2] = (c2 << 1) | (c1 >> 31); + zw[3] = (c3 << 1) | (c2 >> 31); + zw[4] = (d0 << 1) | (c3 >> 31); + zw[5] = (d1 << 1) | (d0 >> 31); + zw[6] = (d2 << 1) | (d1 >> 31); + zw[7] = (d3 << 1) | (d2 >> 31); + + /* + * We now do the reduction modulo the field polynomial + * to get back to 128 bits. + */ + for (i = 0; i < 4; i ++) { + uint32_t lw; + + lw = zw[i]; + zw[i + 4] ^= lw ^ (lw >> 1) ^ (lw >> 2) ^ (lw >> 7); + zw[i + 3] ^= (lw << 31) ^ (lw << 30) ^ (lw << 25); + } + memcpy(yw, zw + 4, sizeof yw); + } + + /* + * Encode back the result. + */ + br_enc32be(yb, yw[3]); + br_enc32be(yb + 4, yw[2]); + br_enc32be(yb + 8, yw[1]); + br_enc32be(yb + 12, yw[0]); +} |