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Diffstat (limited to 'crypto/aes-sw.c')
| -rw-r--r-- | crypto/aes-sw.c | 1133 |
1 files changed, 1133 insertions, 0 deletions
diff --git a/crypto/aes-sw.c b/crypto/aes-sw.c new file mode 100644 index 00000000..aaa3c475 --- /dev/null +++ b/crypto/aes-sw.c @@ -0,0 +1,1133 @@ +/* + * Software implementation of AES. + * + * This implementation uses a bit-sliced representation. Instead of + * the obvious approach of storing the cipher state so that each byte + * (or field element, or entry in the cipher matrix) occupies 8 + * contiguous bits in a machine integer somewhere, we organise the + * cipher state as an array of 8 integers, in such a way that each + * logical byte of the cipher state occupies one bit in each integer, + * all at the same position. This allows us to do parallel logic on + * all bytes of the state by doing bitwise operations between the 8 + * integers; in particular, the S-box (SubBytes) lookup is done this + * way, which takes about 110 operations - but for those 110 bitwise + * ops you get 64 S-box lookups, not just one. + */ + +#include "ssh.h" +#include "aes.h" +#include "mpint_i.h" /* we reuse the BignumInt system */ + +static bool aes_sw_available(void) +{ + /* Software AES is always available */ + return true; +} + +#define SLICE_PARALLELISM (BIGNUM_INT_BYTES / 2) + +#ifdef BITSLICED_DEBUG +/* Dump function that undoes the bitslicing transform, so you can see + * the logical data represented by a set of slice words. */ +static inline void dumpslices_uint16_t( + const char *prefix, const uint16_t slices[8]) +{ + printf("%-30s", prefix); + for (unsigned byte = 0; byte < 16; byte++) { + unsigned byteval = 0; + for (unsigned bit = 0; bit < 8; bit++) + byteval |= (1 & (slices[bit] >> byte)) << bit; + printf("%02x", byteval); + } + printf("\n"); +} + +static inline void dumpslices_BignumInt( + const char *prefix, const BignumInt slices[8]) +{ + printf("%-30s", prefix); + for (unsigned iter = 0; iter < SLICE_PARALLELISM; iter++) { + for (unsigned byte = 0; byte < 16; byte++) { + unsigned byteval = 0; + for (unsigned bit = 0; bit < 8; bit++) + byteval |= (1 & (slices[bit] >> (iter*16+byte))) << bit; + printf("%02x", byteval); + } + if (iter+1 < SLICE_PARALLELISM) + printf(" "); + } + printf("\n"); +} +#else +#define dumpslices_uintN_t(prefix, slices) ((void)0) +#define dumpslices_BignumInt(prefix, slices) ((void)0) +#endif + +/* ----- + * Bit-slicing transformation: convert between an array of 16 uint8_t + * and an array of 8 uint16_t, so as to interchange the bit index + * within each element and the element index within the array. (That + * is, bit j of input[i] == bit i of output[j]. + */ + +#define SWAPWORDS(shift) do \ + { \ + uint64_t mask = ~(uint64_t)0 / ((1ULL << shift) + 1); \ + uint64_t diff = ((i0 >> shift) ^ i1) & mask; \ + i0 ^= diff << shift; \ + i1 ^= diff; \ + } while (0) + +#define SWAPINWORD(i, bigshift, smallshift) do \ + { \ + uint64_t mask = ~(uint64_t)0; \ + mask /= ((1ULL << bigshift) + 1); \ + mask /= ((1ULL << smallshift) + 1); \ + mask <<= smallshift; \ + unsigned shift = bigshift - smallshift; \ + uint64_t diff = ((i >> shift) ^ i) & mask; \ + i ^= diff ^ (diff << shift); \ + } while (0) + +#define TO_BITSLICES(slices, bytes, uintN_t, assign_op, shift) do \ + { \ + uint64_t i0 = GET_64BIT_LSB_FIRST(bytes); \ + uint64_t i1 = GET_64BIT_LSB_FIRST(bytes + 8); \ + SWAPINWORD(i0, 8, 1); \ + SWAPINWORD(i1, 8, 1); \ + SWAPINWORD(i0, 16, 2); \ + SWAPINWORD(i1, 16, 2); \ + SWAPINWORD(i0, 32, 4); \ + SWAPINWORD(i1, 32, 4); \ + SWAPWORDS(8); \ + slices[0] assign_op (uintN_t)((i0 >> 0) & 0xFFFF) << (shift); \ + slices[2] assign_op (uintN_t)((i0 >> 16) & 0xFFFF) << (shift); \ + slices[4] assign_op (uintN_t)((i0 >> 32) & 0xFFFF) << (shift); \ + slices[6] assign_op (uintN_t)((i0 >> 48) & 0xFFFF) << (shift); \ + slices[1] assign_op (uintN_t)((i1 >> 0) & 0xFFFF) << (shift); \ + slices[3] assign_op (uintN_t)((i1 >> 16) & 0xFFFF) << (shift); \ + slices[5] assign_op (uintN_t)((i1 >> 32) & 0xFFFF) << (shift); \ + slices[7] assign_op (uintN_t)((i1 >> 48) & 0xFFFF) << (shift); \ + } while (0) + +#define FROM_BITSLICES(bytes, slices, shift) do \ + { \ + uint64_t i1 = ((slices[7] >> (shift)) & 0xFFFF); \ + i1 = (i1 << 16) | ((slices[5] >> (shift)) & 0xFFFF); \ + i1 = (i1 << 16) | ((slices[3] >> (shift)) & 0xFFFF); \ + i1 = (i1 << 16) | ((slices[1] >> (shift)) & 0xFFFF); \ + uint64_t i0 = ((slices[6] >> (shift)) & 0xFFFF); \ + i0 = (i0 << 16) | ((slices[4] >> (shift)) & 0xFFFF); \ + i0 = (i0 << 16) | ((slices[2] >> (shift)) & 0xFFFF); \ + i0 = (i0 << 16) | ((slices[0] >> (shift)) & 0xFFFF); \ + SWAPWORDS(8); \ + SWAPINWORD(i0, 32, 4); \ + SWAPINWORD(i1, 32, 4); \ + SWAPINWORD(i0, 16, 2); \ + SWAPINWORD(i1, 16, 2); \ + SWAPINWORD(i0, 8, 1); \ + SWAPINWORD(i1, 8, 1); \ + PUT_64BIT_LSB_FIRST(bytes, i0); \ + PUT_64BIT_LSB_FIRST((bytes) + 8, i1); \ + } while (0) + +/* ----- + * Some macros that will be useful repeatedly. + */ + +/* Iterate a unary transformation over all 8 slices. */ +#define ITERATE(MACRO, output, input, uintN_t) do \ + { \ + MACRO(output[0], input[0], uintN_t); \ + MACRO(output[1], input[1], uintN_t); \ + MACRO(output[2], input[2], uintN_t); \ + MACRO(output[3], input[3], uintN_t); \ + MACRO(output[4], input[4], uintN_t); \ + MACRO(output[5], input[5], uintN_t); \ + MACRO(output[6], input[6], uintN_t); \ + MACRO(output[7], input[7], uintN_t); \ + } while (0) + +/* Simply add (i.e. XOR) two whole sets of slices together. */ +#define BITSLICED_ADD(output, lhs, rhs) do \ + { \ + output[0] = lhs[0] ^ rhs[0]; \ + output[1] = lhs[1] ^ rhs[1]; \ + output[2] = lhs[2] ^ rhs[2]; \ + output[3] = lhs[3] ^ rhs[3]; \ + output[4] = lhs[4] ^ rhs[4]; \ + output[5] = lhs[5] ^ rhs[5]; \ + output[6] = lhs[6] ^ rhs[6]; \ + output[7] = lhs[7] ^ rhs[7]; \ + } while (0) + +/* ----- + * The AES S-box, in pure bitwise logic so that it can be run in + * parallel on whole words full of bit-sliced field elements. + * + * Source: 'A new combinational logic minimization technique with + * applications to cryptology', https://eprint.iacr.org/2009/191 + * + * As a minor speed optimisation, I use a modified version of the + * S-box which omits the additive constant 0x63, i.e. this S-box + * consists of only the field inversion and linear map components. + * Instead, the addition of the constant is deferred until after the + * subsequent ShiftRows and MixColumns stages, so that it happens at + * the same time as adding the next round key - and then we just make + * it _part_ of the round key, so it doesn't cost any extra + * instructions to add. + * + * (Obviously adding a constant to each byte commutes with ShiftRows, + * which only permutes the bytes. It also commutes with MixColumns: + * that's not quite so obvious, but since the effect of MixColumns is + * to multiply a constant polynomial M into each column, it is obvious + * that adding some polynomial K and then multiplying by M is + * equivalent to multiplying by M and then adding the product KM. And + * in fact, since the coefficients of M happen to sum to 1, it turns + * out that KM = K, so we don't even have to change the constant when + * we move it to the far side of MixColumns.) + * + * Of course, one knock-on effect of this is that the use of the S-box + * *during* key setup has to be corrected by manually adding on the + * constant afterwards! + */ + +/* Initial linear transformation for the forward S-box, from Fig 2 of + * the paper. */ +#define SBOX_FORWARD_TOP_TRANSFORM(input, uintN_t) \ + uintN_t y14 = input[4] ^ input[2]; \ + uintN_t y13 = input[7] ^ input[1]; \ + uintN_t y9 = input[7] ^ input[4]; \ + uintN_t y8 = input[7] ^ input[2]; \ + uintN_t t0 = input[6] ^ input[5]; \ + uintN_t y1 = t0 ^ input[0]; \ + uintN_t y4 = y1 ^ input[4]; \ + uintN_t y12 = y13 ^ y14; \ + uintN_t y2 = y1 ^ input[7]; \ + uintN_t y5 = y1 ^ input[1]; \ + uintN_t y3 = y5 ^ y8; \ + uintN_t t1 = input[3] ^ y12; \ + uintN_t y15 = t1 ^ input[2]; \ + uintN_t y20 = t1 ^ input[6]; \ + uintN_t y6 = y15 ^ input[0]; \ + uintN_t y10 = y15 ^ t0; \ + uintN_t y11 = y20 ^ y9; \ + uintN_t y7 = input[0] ^ y11; \ + uintN_t y17 = y10 ^ y11; \ + uintN_t y19 = y10 ^ y8; \ + uintN_t y16 = t0 ^ y11; \ + uintN_t y21 = y13 ^ y16; \ + uintN_t y18 = input[7] ^ y16; \ + /* Make a copy of input[0] under a new name, because the core + * will refer to it, and in the inverse version of the S-box + * the corresponding value will be one of the calculated ones + * and not in input[0] itself. */ \ + uintN_t i0 = input[0]; \ + /* end */ + +/* Core nonlinear component, from Fig 3 of the paper. */ +#define SBOX_CORE(uintN_t) \ + uintN_t t2 = y12 & y15; \ + uintN_t t3 = y3 & y6; \ + uintN_t t4 = t3 ^ t2; \ + uintN_t t5 = y4 & i0; \ + uintN_t t6 = t5 ^ t2; \ + uintN_t t7 = y13 & y16; \ + uintN_t t8 = y5 & y1; \ + uintN_t t9 = t8 ^ t7; \ + uintN_t t10 = y2 & y7; \ + uintN_t t11 = t10 ^ t7; \ + uintN_t t12 = y9 & y11; \ + uintN_t t13 = y14 & y17; \ + uintN_t t14 = t13 ^ t12; \ + uintN_t t15 = y8 & y10; \ + uintN_t t16 = t15 ^ t12; \ + uintN_t t17 = t4 ^ t14; \ + uintN_t t18 = t6 ^ t16; \ + uintN_t t19 = t9 ^ t14; \ + uintN_t t20 = t11 ^ t16; \ + uintN_t t21 = t17 ^ y20; \ + uintN_t t22 = t18 ^ y19; \ + uintN_t t23 = t19 ^ y21; \ + uintN_t t24 = t20 ^ y18; \ + uintN_t t25 = t21 ^ t22; \ + uintN_t t26 = t21 & t23; \ + uintN_t t27 = t24 ^ t26; \ + uintN_t t28 = t25 & t27; \ + uintN_t t29 = t28 ^ t22; \ + uintN_t t30 = t23 ^ t24; \ + uintN_t t31 = t22 ^ t26; \ + uintN_t t32 = t31 & t30; \ + uintN_t t33 = t32 ^ t24; \ + uintN_t t34 = t23 ^ t33; \ + uintN_t t35 = t27 ^ t33; \ + uintN_t t36 = t24 & t35; \ + uintN_t t37 = t36 ^ t34; \ + uintN_t t38 = t27 ^ t36; \ + uintN_t t39 = t29 & t38; \ + uintN_t t40 = t25 ^ t39; \ + uintN_t t41 = t40 ^ t37; \ + uintN_t t42 = t29 ^ t33; \ + uintN_t t43 = t29 ^ t40; \ + uintN_t t44 = t33 ^ t37; \ + uintN_t t45 = t42 ^ t41; \ + uintN_t z0 = t44 & y15; \ + uintN_t z1 = t37 & y6; \ + uintN_t z2 = t33 & i0; \ + uintN_t z3 = t43 & y16; \ + uintN_t z4 = t40 & y1; \ + uintN_t z5 = t29 & y7; \ + uintN_t z6 = t42 & y11; \ + uintN_t z7 = t45 & y17; \ + uintN_t z8 = t41 & y10; \ + uintN_t z9 = t44 & y12; \ + uintN_t z10 = t37 & y3; \ + uintN_t z11 = t33 & y4; \ + uintN_t z12 = t43 & y13; \ + uintN_t z13 = t40 & y5; \ + uintN_t z14 = t29 & y2; \ + uintN_t z15 = t42 & y9; \ + uintN_t z16 = t45 & y14; \ + uintN_t z17 = t41 & y8; \ + /* end */ + +/* Final linear transformation for the forward S-box, from Fig 4 of + * the paper. */ +#define SBOX_FORWARD_BOTTOM_TRANSFORM(output, uintN_t) \ + uintN_t t46 = z15 ^ z16; \ + uintN_t t47 = z10 ^ z11; \ + uintN_t t48 = z5 ^ z13; \ + uintN_t t49 = z9 ^ z10; \ + uintN_t t50 = z2 ^ z12; \ + uintN_t t51 = z2 ^ z5; \ + uintN_t t52 = z7 ^ z8; \ + uintN_t t53 = z0 ^ z3; \ + uintN_t t54 = z6 ^ z7; \ + uintN_t t55 = z16 ^ z17; \ + uintN_t t56 = z12 ^ t48; \ + uintN_t t57 = t50 ^ t53; \ + uintN_t t58 = z4 ^ t46; \ + uintN_t t59 = z3 ^ t54; \ + uintN_t t60 = t46 ^ t57; \ + uintN_t t61 = z14 ^ t57; \ + uintN_t t62 = t52 ^ t58; \ + uintN_t t63 = t49 ^ t58; \ + uintN_t t64 = z4 ^ t59; \ + uintN_t t65 = t61 ^ t62; \ + uintN_t t66 = z1 ^ t63; \ + output[7] = t59 ^ t63; \ + output[1] = t56 ^ t62; \ + output[0] = t48 ^ t60; \ + uintN_t t67 = t64 ^ t65; \ + output[4] = t53 ^ t66; \ + output[3] = t51 ^ t66; \ + output[2] = t47 ^ t65; \ + output[6] = t64 ^ output[4]; \ + output[5] = t55 ^ t67; \ + /* end */ + +#define BITSLICED_SUBBYTES(output, input, uintN_t) do { \ + SBOX_FORWARD_TOP_TRANSFORM(input, uintN_t); \ + SBOX_CORE(uintN_t); \ + SBOX_FORWARD_BOTTOM_TRANSFORM(output, uintN_t); \ + } while (0) + +/* + * Initial and final linear transformations for the backward S-box. I + * generated these myself, by implementing the linear-transform + * optimisation algorithm in the paper, and applying it to the + * matrices calculated by _their_ top and bottom transformations, pre- + * and post-multiplied as appropriate by the linear map in the inverse + * S_box. + */ +#define SBOX_BACKWARD_TOP_TRANSFORM(input, uintN_t) \ + uintN_t y5 = input[4] ^ input[6]; \ + uintN_t y19 = input[3] ^ input[0]; \ + uintN_t itmp8 = y5 ^ input[0]; \ + uintN_t y4 = itmp8 ^ input[1]; \ + uintN_t y9 = input[4] ^ input[3]; \ + uintN_t y2 = y9 ^ y4; \ + uintN_t itmp9 = y2 ^ input[7]; \ + uintN_t y1 = y9 ^ input[0]; \ + uintN_t y6 = y5 ^ input[7]; \ + uintN_t y18 = y9 ^ input[5]; \ + uintN_t y7 = y18 ^ y2; \ + uintN_t y16 = y7 ^ y1; \ + uintN_t y21 = y7 ^ input[1]; \ + uintN_t y3 = input[4] ^ input[7]; \ + uintN_t y13 = y16 ^ y21; \ + uintN_t y8 = input[4] ^ y6; \ + uintN_t y10 = y8 ^ y19; \ + uintN_t y14 = y8 ^ y9; \ + uintN_t y20 = itmp9 ^ input[2]; \ + uintN_t y11 = y9 ^ y20; \ + uintN_t i0 = y11 ^ y7; \ + uintN_t y15 = i0 ^ y6; \ + uintN_t y17 = y16 ^ y15; \ + uintN_t y12 = itmp9 ^ input[3]; \ + /* end */ +#define SBOX_BACKWARD_BOTTOM_TRANSFORM(output, uintN_t) \ + uintN_t otmp18 = z15 ^ z6; \ + uintN_t otmp19 = z13 ^ otmp18; \ + uintN_t otmp20 = z12 ^ otmp19; \ + uintN_t otmp21 = z16 ^ otmp20; \ + uintN_t otmp22 = z8 ^ otmp21; \ + uintN_t otmp23 = z0 ^ otmp22; \ + uintN_t otmp24 = otmp22 ^ z3; \ + uintN_t otmp25 = otmp24 ^ z4; \ + uintN_t otmp26 = otmp25 ^ z2; \ + uintN_t otmp27 = z1 ^ otmp26; \ + uintN_t otmp28 = z14 ^ otmp27; \ + uintN_t otmp29 = otmp28 ^ z10; \ + output[4] = z2 ^ otmp23; \ + output[7] = z5 ^ otmp24; \ + uintN_t otmp30 = z11 ^ otmp29; \ + output[5] = z13 ^ otmp30; \ + uintN_t otmp31 = otmp25 ^ z8; \ + output[1] = z7 ^ otmp31; \ + uintN_t otmp32 = z11 ^ z9; \ + uintN_t otmp33 = z17 ^ otmp32; \ + uintN_t otmp34 = otmp30 ^ otmp33; \ + output[0] = z15 ^ otmp33; \ + uintN_t otmp35 = z12 ^ otmp34; \ + output[6] = otmp35 ^ z16; \ + uintN_t otmp36 = z1 ^ otmp23; \ + uintN_t otmp37 = z5 ^ otmp36; \ + output[2] = z4 ^ otmp37; \ + uintN_t otmp38 = z11 ^ output[1]; \ + uintN_t otmp39 = z2 ^ otmp38; \ + uintN_t otmp40 = z17 ^ otmp39; \ + uintN_t otmp41 = z0 ^ otmp40; \ + uintN_t otmp42 = z5 ^ otmp41; \ + uintN_t otmp43 = otmp42 ^ z10; \ + uintN_t otmp44 = otmp43 ^ z3; \ + output[3] = otmp44 ^ z16; \ + /* end */ + +#define BITSLICED_INVSUBBYTES(output, input, uintN_t) do { \ + SBOX_BACKWARD_TOP_TRANSFORM(input, uintN_t); \ + SBOX_CORE(uintN_t); \ + SBOX_BACKWARD_BOTTOM_TRANSFORM(output, uintN_t); \ + } while (0) + + +/* ----- + * The ShiftRows transformation. This operates independently on each + * bit slice. + */ + +#define SINGLE_BITSLICE_SHIFTROWS(output, input, uintN_t) do \ + { \ + uintN_t mask, mask2, mask3, diff, x = (input); \ + /* Rotate rows 2 and 3 by 16 bits */ \ + mask = 0x00CC * (((uintN_t)~(uintN_t)0) / 0xFFFF); \ + diff = ((x >> 8) ^ x) & mask; \ + x ^= diff ^ (diff << 8); \ + /* Rotate rows 1 and 3 by 8 bits */ \ + mask = 0x0AAA * (((uintN_t)~(uintN_t)0) / 0xFFFF); \ + mask2 = 0xA000 * (((uintN_t)~(uintN_t)0) / 0xFFFF); \ + mask3 = 0x5555 * (((uintN_t)~(uintN_t)0) / 0xFFFF); \ + x = ((x >> 4) & mask) | ((x << 12) & mask2) | (x & mask3); \ + /* Write output */ \ + (output) = x; \ + } while (0) + +#define SINGLE_BITSLICE_INVSHIFTROWS(output, input, uintN_t) do \ + { \ + uintN_t mask, mask2, mask3, diff, x = (input); \ + /* Rotate rows 2 and 3 by 16 bits */ \ + mask = 0x00CC * (((uintN_t)~(uintN_t)0) / 0xFFFF); \ + diff = ((x >> 8) ^ x) & mask; \ + x ^= diff ^ (diff << 8); \ + /* Rotate rows 1 and 3 by 8 bits, the opposite way to ShiftRows */ \ + mask = 0x000A * (((uintN_t)~(uintN_t)0) / 0xFFFF); \ + mask2 = 0xAAA0 * (((uintN_t)~(uintN_t)0) / 0xFFFF); \ + mask3 = 0x5555 * (((uintN_t)~(uintN_t)0) / 0xFFFF); \ + x = ((x >> 12) & mask) | ((x << 4) & mask2) | (x & mask3); \ + /* Write output */ \ + (output) = x; \ + } while (0) + +#define BITSLICED_SHIFTROWS(output, input, uintN_t) do \ + { \ + ITERATE(SINGLE_BITSLICE_SHIFTROWS, output, input, uintN_t); \ + } while (0) + +#define BITSLICED_INVSHIFTROWS(output, input, uintN_t) do \ + { \ + ITERATE(SINGLE_BITSLICE_INVSHIFTROWS, output, input, uintN_t); \ + } while (0) + +/* ----- + * The MixColumns transformation. This has to operate on all eight bit + * slices at once, and also passes data back and forth between the + * bits in an adjacent group of 4 within each slice. + * + * Notation: let F = GF(2)[X]/<X^8+X^4+X^3+X+1> be the finite field + * used in AES, and let R = F[Y]/<Y^4+1> be the ring whose elements + * represent the possible contents of a column of the matrix. I use X + * and Y below in those senses, i.e. X is the value in F that + * represents the byte 0x02, and Y is the value in R that cycles the + * four bytes around by one if you multiply by it. + */ + +/* Multiply every column by Y^3, i.e. cycle it round one place to the + * right. Operates on one bit slice at a time; you have to wrap it in + * ITERATE to affect all the data at once. */ +#define BITSLICED_MUL_BY_Y3(output, input, uintN_t) do \ + { \ + uintN_t mask, mask2, x; \ + mask = 0x8 * (((uintN_t)~(uintN_t)0) / 0xF); \ + mask2 = 0x7 * (((uintN_t)~(uintN_t)0) / 0xF); \ + x = input; \ + output = ((x << 3) & mask) ^ ((x >> 1) & mask2); \ + } while (0) + +/* Multiply every column by Y^2. */ +#define BITSLICED_MUL_BY_Y2(output, input, uintN_t) do \ + { \ + uintN_t mask, mask2, x; \ + mask = 0xC * (((uintN_t)~(uintN_t)0) / 0xF); \ + mask2 = 0x3 * (((uintN_t)~(uintN_t)0) / 0xF); \ + x = input; \ + output = ((x << 2) & mask) ^ ((x >> 2) & mask2); \ + } while (0) + +#define BITSLICED_MUL_BY_1_Y3(output, input, uintN_t) do \ + { \ + uintN_t tmp = input; \ + BITSLICED_MUL_BY_Y3(tmp, input, uintN_t); \ + output = input ^ tmp; \ + } while (0) + +/* Multiply every column by 1+Y^2. */ +#define BITSLICED_MUL_BY_1_Y2(output, input, uintN_t) do \ + { \ + uintN_t tmp = input; \ + BITSLICED_MUL_BY_Y2(tmp, input, uintN_t); \ + output = input ^ tmp; \ + } while (0) + +/* Multiply every field element by X. This has to feed data between + * slices, so it does the whole job in one go without needing ITERATE. */ +#define BITSLICED_MUL_BY_X(output, input, uintN_t) do \ + { \ + uintN_t bit7 = input[7]; \ + output[7] = input[6]; \ + output[6] = input[5]; \ + output[5] = input[4]; \ + output[4] = input[3] ^ bit7; \ + output[3] = input[2] ^ bit7; \ + output[2] = input[1]; \ + output[1] = input[0] ^ bit7; \ + output[0] = bit7; \ + } while (0) + +/* + * The MixColumns constant is + * M = X + Y + Y^2 + (X+1)Y^3 + * which we construct by rearranging it into + * M = 1 + (1+Y^3) [ X + (1+Y^2) ] + */ +#define BITSLICED_MIXCOLUMNS(output, input, uintN_t) do \ + { \ + uintN_t a[8], aX[8], b[8]; \ + /* a = input * (1+Y^3) */ \ + ITERATE(BITSLICED_MUL_BY_1_Y3, a, input, uintN_t); \ + /* aX = a * X */ \ + BITSLICED_MUL_BY_X(aX, a, uintN_t); \ + /* b = a * (1+Y^2) = input * (1+Y+Y^2+Y^3) */ \ + ITERATE(BITSLICED_MUL_BY_1_Y2, b, a, uintN_t); \ + /* output = input + aX + b (reusing a as a temp */ \ + BITSLICED_ADD(a, aX, b); \ + BITSLICED_ADD(output, input, a); \ + } while (0) + +/* + * The InvMixColumns constant, written out longhand, is + * I = (X^3+X^2+X) + (X^3+1)Y + (X^3+X^2+1)Y^2 + (X^3+X+1)Y^3 + * We represent this as + * I = (X^3+X^2+X+1)(Y^3+Y^2+Y+1) + 1 + X(Y+Y^2) + X^2(Y+Y^3) + */ +#define BITSLICED_INVMIXCOLUMNS(output, input, uintN_t) do \ + { \ + /* We need input * X^i for i=1,...,3 */ \ + uintN_t X[8], X2[8], X3[8]; \ + BITSLICED_MUL_BY_X(X, input, uintN_t); \ + BITSLICED_MUL_BY_X(X2, X, uintN_t); \ + BITSLICED_MUL_BY_X(X3, X2, uintN_t); \ + /* Sum them all and multiply by 1+Y+Y^2+Y^3. */ \ + uintN_t S[8]; \ + BITSLICED_ADD(S, input, X); \ + BITSLICED_ADD(S, S, X2); \ + BITSLICED_ADD(S, S, X3); \ + ITERATE(BITSLICED_MUL_BY_1_Y3, S, S, uintN_t); \ + ITERATE(BITSLICED_MUL_BY_1_Y2, S, S, uintN_t); \ + /* Compute the X(Y+Y^2) term. */ \ + uintN_t A[8]; \ + ITERATE(BITSLICED_MUL_BY_1_Y3, A, X, uintN_t); \ + ITERATE(BITSLICED_MUL_BY_Y2, A, A, uintN_t); \ + /* Compute the X^2(Y+Y^3) term. */ \ + uintN_t B[8]; \ + ITERATE(BITSLICED_MUL_BY_1_Y2, B, X2, uintN_t); \ + ITERATE(BITSLICED_MUL_BY_Y3, B, B, uintN_t); \ + /* And add all the pieces together. */ \ + BITSLICED_ADD(S, S, input); \ + BITSLICED_ADD(S, S, A); \ + BITSLICED_ADD(output, S, B); \ + } while (0) + +/* ----- + * Put it all together into a cipher round. + */ + +/* Dummy macro to get rid of the MixColumns in the final round. */ +#define NO_MIXCOLUMNS(out, in, uintN_t) do {} while (0) + +#define ENCRYPT_ROUND_FN(suffix, uintN_t, mixcol_macro) \ + static void aes_sliced_round_e_##suffix( \ + uintN_t output[8], const uintN_t input[8], const uintN_t roundkey[8]) \ + { \ + BITSLICED_SUBBYTES(output, input, uintN_t); \ + BITSLICED_SHIFTROWS(output, output, uintN_t); \ + mixcol_macro(output, output, uintN_t); \ + BITSLICED_ADD(output, output, roundkey); \ + } + +ENCRYPT_ROUND_FN(serial, uint16_t, BITSLICED_MIXCOLUMNS) +ENCRYPT_ROUND_FN(serial_last, uint16_t, NO_MIXCOLUMNS) +ENCRYPT_ROUND_FN(parallel, BignumInt, BITSLICED_MIXCOLUMNS) +ENCRYPT_ROUND_FN(parallel_last, BignumInt, NO_MIXCOLUMNS) + +#define DECRYPT_ROUND_FN(suffix, uintN_t, mixcol_macro) \ + static void aes_sliced_round_d_##suffix( \ + uintN_t output[8], const uintN_t input[8], const uintN_t roundkey[8]) \ + { \ + BITSLICED_ADD(output, input, roundkey); \ + mixcol_macro(output, output, uintN_t); \ + BITSLICED_INVSUBBYTES(output, output, uintN_t); \ + BITSLICED_INVSHIFTROWS(output, output, uintN_t); \ + } + +#if 0 /* no cipher mode we support requires serial decryption */ +DECRYPT_ROUND_FN(serial, uint16_t, BITSLICED_INVMIXCOLUMNS) +DECRYPT_ROUND_FN(serial_first, uint16_t, NO_MIXCOLUMNS) +#endif +DECRYPT_ROUND_FN(parallel, BignumInt, BITSLICED_INVMIXCOLUMNS) +DECRYPT_ROUND_FN(parallel_first, BignumInt, NO_MIXCOLUMNS) + +/* ----- + * Key setup function. + */ + +typedef struct aes_sliced_key aes_sliced_key; +struct aes_sliced_key { + BignumInt roundkeys_parallel[MAXROUNDKEYS * 8]; + uint16_t roundkeys_serial[MAXROUNDKEYS * 8]; + unsigned rounds; +}; + +static void aes_sliced_key_setup( + aes_sliced_key *sk, const void *vkey, size_t keybits) +{ + const unsigned char *key = (const unsigned char *)vkey; + + size_t key_words = keybits / 32; + sk->rounds = key_words + 6; + size_t sched_words = (sk->rounds + 1) * 4; + + unsigned rconpos = 0; + + uint16_t *outslices = sk->roundkeys_serial; + unsigned outshift = 0; + + memset(sk->roundkeys_serial, 0, sizeof(sk->roundkeys_serial)); + + uint8_t inblk[16]; + memset(inblk, 0, 16); + uint16_t slices[8]; + + for (size_t i = 0; i < sched_words; i++) { + /* + * Prepare a word of round key in the low 4 bits of each + * integer in slices[]. + */ + if (i < key_words) { + memcpy(inblk, key + 4*i, 4); + TO_BITSLICES(slices, inblk, uint16_t, =, 0); + } else { + unsigned wordindex, bitshift; + uint16_t *prevslices; + + /* Fetch the (i-1)th key word */ + wordindex = i-1; + bitshift = 4 * (wordindex & 3); + prevslices = sk->roundkeys_serial + 8 * (wordindex >> 2); + for (size_t i = 0; i < 8; i++) + slices[i] = prevslices[i] >> bitshift; + + /* Decide what we're doing in this expansion stage */ + bool rotate_and_round_constant = (i % key_words == 0); + bool sub = rotate_and_round_constant || + (key_words == 8 && i % 8 == 4); + + if (rotate_and_round_constant) { + for (size_t i = 0; i < 8; i++) + slices[i] = ((slices[i] << 3) | (slices[i] >> 1)) & 0xF; + } + + if (sub) { + /* Apply the SubBytes transform to the key word. But + * here we need to apply the _full_ SubBytes from the + * spec, including the constant which our S-box leaves + * out. */ + BITSLICED_SUBBYTES(slices, slices, uint16_t); + slices[0] ^= 0xFFFF; + slices[1] ^= 0xFFFF; + slices[5] ^= 0xFFFF; + slices[6] ^= 0xFFFF; + } + + if (rotate_and_round_constant) { + assert(rconpos < lenof(aes_key_setup_round_constants)); + uint8_t rcon = aes_key_setup_round_constants[rconpos++]; + for (size_t i = 0; i < 8; i++) + slices[i] ^= 1 & (rcon >> i); + } + + /* Combine with the (i-Nk)th key word */ + wordindex = i - key_words; + bitshift = 4 * (wordindex & 3); + prevslices = sk->roundkeys_serial + 8 * (wordindex >> 2); + for (size_t i = 0; i < 8; i++) + slices[i] ^= prevslices[i] >> bitshift; + } + + /* + * Now copy it into sk. + */ + for (unsigned b = 0; b < 8; b++) + outslices[b] |= (slices[b] & 0xF) << outshift; + outshift += 4; + if (outshift == 16) { + outshift = 0; + outslices += 8; + } + } + + smemclr(inblk, sizeof(inblk)); + smemclr(slices, sizeof(slices)); + + /* + * Add the S-box constant to every round key after the first one, + * compensating for it being left out in the main cipher. + */ + for (size_t i = 8; i < 8 * (sched_words/4); i += 8) { + sk->roundkeys_serial[i+0] ^= 0xFFFF; + sk->roundkeys_serial[i+1] ^= 0xFFFF; + sk->roundkeys_serial[i+5] ^= 0xFFFF; + sk->roundkeys_serial[i+6] ^= 0xFFFF; + } + + /* + * Replicate that set of round keys into larger integers for the + * parallel versions of the cipher. + */ + for (size_t i = 0; i < 8 * (sched_words / 4); i++) { + sk->roundkeys_parallel[i] = sk->roundkeys_serial[i] * + ((BignumInt)~(BignumInt)0 / 0xFFFF); + } +} + +/* ----- + * The full cipher primitive, including transforming the input and + * output to/from bit-sliced form. + */ + +#define ENCRYPT_FN(suffix, uintN_t, nblocks) \ + static void aes_sliced_e_##suffix( \ + uint8_t *output, const uint8_t *input, const aes_sliced_key *sk) \ + { \ + uintN_t state[8]; \ + TO_BITSLICES(state, input, uintN_t, =, 0); \ + for (unsigned i = 1; i < nblocks; i++) { \ + input += 16; \ + TO_BITSLICES(state, input, uintN_t, |=, i*16); \ + } \ + const uintN_t *keys = sk->roundkeys_##suffix; \ + BITSLICED_ADD(state, state, keys); \ + keys += 8; \ + for (unsigned i = 0; i < sk->rounds-1; i++) { \ + aes_sliced_round_e_##suffix(state, state, keys); \ + keys += 8; \ + } \ + aes_sliced_round_e_##suffix##_last(state, state, keys); \ + for (unsigned i = 0; i < nblocks; i++) { \ + FROM_BITSLICES(output, state, i*16); \ + output += 16; \ + } \ + } + +#define DECRYPT_FN(suffix, uintN_t, nblocks) \ + static void aes_sliced_d_##suffix( \ + uint8_t *output, const uint8_t *input, const aes_sliced_key *sk) \ + { \ + uintN_t state[8]; \ + TO_BITSLICES(state, input, uintN_t, =, 0); \ + for (unsigned i = 1; i < nblocks; i++) { \ + input += 16; \ + TO_BITSLICES(state, input, uintN_t, |=, i*16); \ + } \ + const uintN_t *keys = sk->roundkeys_##suffix + 8*sk->rounds; \ + aes_sliced_round_d_##suffix##_first(state, state, keys); \ + keys -= 8; \ + for (unsigned i = 0; i < sk->rounds-1; i++) { \ + aes_sliced_round_d_##suffix(state, state, keys); \ + keys -= 8; \ + } \ + BITSLICED_ADD(state, state, keys); \ + for (unsigned i = 0; i < nblocks; i++) { \ + FROM_BITSLICES(output, state, i*16); \ + output += 16; \ + } \ + } + +ENCRYPT_FN(serial, uint16_t, 1) +#if 0 /* no cipher mode we support requires serial decryption */ +DECRYPT_FN(serial, uint16_t, 1) +#endif +ENCRYPT_FN(parallel, BignumInt, SLICE_PARALLELISM) +DECRYPT_FN(parallel, BignumInt, SLICE_PARALLELISM) + +/* ----- + * The SSH interface and the cipher modes. + */ + +#define SDCTR_WORDS (16 / BIGNUM_INT_BYTES) + +typedef struct aes_sw_context aes_sw_context; +struct aes_sw_context { + aes_sliced_key sk; + union { + struct { + /* In CBC mode, the IV is just a copy of the last seen + * cipher block. */ + uint8_t prevblk[16]; + } cbc; + struct { + /* In SDCTR mode, we keep the counter itself in a form + * that's easy to increment. We also use the parallel + * version of the core AES function, so we'll encrypt + * multiple counter values in one go. That won't align + * nicely with the sizes of data we're asked to encrypt, + * so we must also store a cache of the last set of + * keystream blocks we generated, and our current position + * within that cache. */ + BignumInt counter[SDCTR_WORDS]; + uint8_t keystream[SLICE_PARALLELISM * 16]; + uint8_t *keystream_pos; + } sdctr; + struct { + /* In GCM mode, the cipher preimage consists of three + * sections: one fixed, one that increments per message + * sent and MACed, and one that increments per cipher + * block. */ + uint64_t msg_counter; + uint32_t fixed_iv, block_counter; + /* But we keep the precomputed keystream chunks just like + * SDCTR mode. */ + uint8_t keystream[SLICE_PARALLELISM * 16]; + uint8_t *keystream_pos; + } gcm; + } iv; + ssh_cipher ciph; +}; + +static ssh_cipher *aes_sw_new(const ssh_cipheralg *alg) +{ + aes_sw_context *ctx = snew(aes_sw_context); + ctx->ciph.vt = alg; + return &ctx->ciph; +} + +static void aes_sw_free(ssh_cipher *ciph) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + smemclr(ctx, sizeof(*ctx)); + sfree(ctx); +} + +static void aes_sw_setkey(ssh_cipher *ciph, const void *vkey) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + aes_sliced_key_setup(&ctx->sk, vkey, ctx->ciph.vt->real_keybits); +} + +static void aes_sw_setiv_cbc(ssh_cipher *ciph, const void *iv) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + memcpy(ctx->iv.cbc.prevblk, iv, 16); +} + +static void aes_sw_setiv_sdctr(ssh_cipher *ciph, const void *viv) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + const uint8_t *iv = (const uint8_t *)viv; + + /* Import the initial counter value into the internal representation */ + for (unsigned i = 0; i < SDCTR_WORDS; i++) + ctx->iv.sdctr.counter[i] = + GET_BIGNUMINT_MSB_FIRST( + iv + 16 - BIGNUM_INT_BYTES - i*BIGNUM_INT_BYTES); + + /* Set keystream_pos to indicate that the keystream cache is + * currently empty */ + ctx->iv.sdctr.keystream_pos = + ctx->iv.sdctr.keystream + sizeof(ctx->iv.sdctr.keystream); +} + +static void aes_sw_setiv_gcm(ssh_cipher *ciph, const void *viv) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + const uint8_t *iv = (const uint8_t *)viv; + + ctx->iv.gcm.fixed_iv = GET_32BIT_MSB_FIRST(iv); + ctx->iv.gcm.msg_counter = GET_64BIT_MSB_FIRST(iv + 4); + ctx->iv.gcm.block_counter = 1; + + /* Set keystream_pos to indicate that the keystream cache is + * currently empty */ + ctx->iv.gcm.keystream_pos = + ctx->iv.gcm.keystream + sizeof(ctx->iv.gcm.keystream); +} + +static void aes_sw_next_message_gcm(ssh_cipher *ciph) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + + ctx->iv.gcm.msg_counter++; + ctx->iv.gcm.block_counter = 1; + ctx->iv.gcm.keystream_pos = + ctx->iv.gcm.keystream + sizeof(ctx->iv.gcm.keystream); +} + +typedef void (*aes_sw_fn)(uint32_t v[4], const uint32_t *keysched); + +static inline void memxor16(void *vout, const void *vlhs, const void *vrhs) +{ + uint8_t *out = (uint8_t *)vout; + const uint8_t *lhs = (const uint8_t *)vlhs, *rhs = (const uint8_t *)vrhs; + uint64_t w; + + w = GET_64BIT_LSB_FIRST(lhs); + w ^= GET_64BIT_LSB_FIRST(rhs); + PUT_64BIT_LSB_FIRST(out, w); + w = GET_64BIT_LSB_FIRST(lhs + 8); + w ^= GET_64BIT_LSB_FIRST(rhs + 8); + PUT_64BIT_LSB_FIRST(out + 8, w); +} + +static inline void aes_cbc_sw_encrypt( + ssh_cipher *ciph, void *vblk, int blklen) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + + /* + * CBC encryption has to be done serially, because the input to + * each run of the cipher includes the output from the previous + * run. + */ + + for (uint8_t *blk = (uint8_t *)vblk, *finish = blk + blklen; + blk < finish; blk += 16) { + /* + * We use the IV array itself as the location for the + * encryption, because there's no reason not to. + */ + + /* XOR the new plaintext block into the previous cipher block */ + memxor16(ctx->iv.cbc.prevblk, ctx->iv.cbc.prevblk, blk); + + /* Run the cipher over the result, which leaves it + * conveniently already stored in ctx->iv */ + aes_sliced_e_serial( + ctx->iv.cbc.prevblk, ctx->iv.cbc.prevblk, &ctx->sk); + + /* Copy it to the output location */ + memcpy(blk, ctx->iv.cbc.prevblk, 16); + } +} + +static inline void aes_cbc_sw_decrypt( + ssh_cipher *ciph, void *vblk, int blklen) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + uint8_t *blk = (uint8_t *)vblk; + + /* + * CBC decryption can run in parallel, because all the + * _ciphertext_ blocks are already available. + */ + + size_t blocks_remaining = blklen / 16; + + uint8_t data[SLICE_PARALLELISM * 16]; + /* Zeroing the data array is probably overcautious, but it avoids + * technically undefined behaviour from leaving it uninitialised + * if our very first iteration doesn't include enough cipher + * blocks to populate it fully */ + memset(data, 0, sizeof(data)); + + while (blocks_remaining > 0) { + /* Number of blocks we'll handle in this iteration. If we're + * dealing with fewer than the maximum, it doesn't matter - + * it's harmless to run the full parallel cipher function + * anyway. */ + size_t blocks = (blocks_remaining < SLICE_PARALLELISM ? + blocks_remaining : SLICE_PARALLELISM); + + /* Parallel-decrypt the input, in a separate array so we still + * have the cipher stream available for XORing. */ + memcpy(data, blk, 16 * blocks); + aes_sliced_d_parallel(data, data, &ctx->sk); + + /* Write the output and update the IV */ + for (size_t i = 0; i < blocks; i++) { + uint8_t *decrypted = data + 16*i; + uint8_t *output = blk + 16*i; + + memxor16(decrypted, decrypted, ctx->iv.cbc.prevblk); + memcpy(ctx->iv.cbc.prevblk, output, 16); + memcpy(output, decrypted, 16); + } + + /* Advance the input pointer. */ + blk += 16 * blocks; + blocks_remaining -= blocks; + } + + smemclr(data, sizeof(data)); +} + +static inline void aes_sdctr_sw( + ssh_cipher *ciph, void *vblk, int blklen) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + + /* + * SDCTR encrypt/decrypt loops round one block at a time XORing + * the keystream into the user's data, and periodically has to run + * a parallel encryption operation to get more keystream. + */ + + uint8_t *keystream_end = + ctx->iv.sdctr.keystream + sizeof(ctx->iv.sdctr.keystream); + + for (uint8_t *blk = (uint8_t *)vblk, *finish = blk + blklen; + blk < finish; blk += 16) { + + if (ctx->iv.sdctr.keystream_pos == keystream_end) { + /* + * Generate some keystream. + */ + for (uint8_t *block = ctx->iv.sdctr.keystream; + block < keystream_end; block += 16) { + /* Format the counter value into the buffer. */ + for (unsigned i = 0; i < SDCTR_WORDS; i++) + PUT_BIGNUMINT_MSB_FIRST( + block + 16 - BIGNUM_INT_BYTES - i*BIGNUM_INT_BYTES, + ctx->iv.sdctr.counter[i]); + + /* Increment the counter. */ + BignumCarry carry = 1; + for (unsigned i = 0; i < SDCTR_WORDS; i++) + BignumADC(ctx->iv.sdctr.counter[i], carry, + ctx->iv.sdctr.counter[i], 0, carry); + } + + /* Encrypt all those counter blocks. */ + aes_sliced_e_parallel(ctx->iv.sdctr.keystream, + ctx->iv.sdctr.keystream, &ctx->sk); + + /* Reset keystream_pos to the start of the buffer. */ + ctx->iv.sdctr.keystream_pos = ctx->iv.sdctr.keystream; + } + + memxor16(blk, blk, ctx->iv.sdctr.keystream_pos); + ctx->iv.sdctr.keystream_pos += 16; + } +} + +static inline void aes_encrypt_ecb_block_sw(ssh_cipher *ciph, void *blk) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + aes_sliced_e_serial(blk, blk, &ctx->sk); +} + +static inline void aes_gcm_sw( + ssh_cipher *ciph, void *vblk, int blklen) +{ + aes_sw_context *ctx = container_of(ciph, aes_sw_context, ciph); + + /* + * GCM encrypt/decrypt looks just like SDCTR, except that the + * method of generating more keystream varies slightly. + */ + + uint8_t *keystream_end = + ctx->iv.gcm.keystream + sizeof(ctx->iv.gcm.keystream); + + for (uint8_t *blk = (uint8_t *)vblk, *finish = blk + blklen; + blk < finish; blk += 16) { + + if (ctx->iv.gcm.keystream_pos == keystream_end) { + /* + * Generate some keystream. + */ + for (uint8_t *block = ctx->iv.gcm.keystream; + block < keystream_end; block += 16) { + /* Format the counter value into the buffer. */ + PUT_32BIT_MSB_FIRST(block, ctx->iv.gcm.fixed_iv); + PUT_64BIT_MSB_FIRST(block + 4, ctx->iv.gcm.msg_counter); + PUT_32BIT_MSB_FIRST(block + 12, ctx->iv.gcm.block_counter); + + /* Increment the counter. */ + ctx->iv.gcm.block_counter++; + } + + /* Encrypt all those counter blocks. */ + aes_sliced_e_parallel(ctx->iv.gcm.keystream, + ctx->iv.gcm.keystream, &ctx->sk); + + /* Reset keystream_pos to the start of the buffer. */ + ctx->iv.gcm.keystream_pos = ctx->iv.gcm.keystream; + } + + memxor16(blk, blk, ctx->iv.gcm.keystream_pos); + ctx->iv.gcm.keystream_pos += 16; + } +} + +#define SW_ENC_DEC(len) \ + static void aes##len##_sw_cbc_encrypt( \ + ssh_cipher *ciph, void *vblk, int blklen) \ + { aes_cbc_sw_encrypt(ciph, vblk, blklen); } \ + static void aes##len##_sw_cbc_decrypt( \ + ssh_cipher *ciph, void *vblk, int blklen) \ + { aes_cbc_sw_decrypt(ciph, vblk, blklen); } \ + static void aes##len##_sw_sdctr( \ + ssh_cipher *ciph, void *vblk, int blklen) \ + { aes_sdctr_sw(ciph, vblk, blklen); } \ + static void aes##len##_sw_gcm( \ + ssh_cipher *ciph, void *vblk, int blklen) \ + { aes_gcm_sw(ciph, vblk, blklen); } \ + static void aes##len##_sw_encrypt_ecb_block( \ + ssh_cipher *ciph, void *vblk) \ + { aes_encrypt_ecb_block_sw(ciph, vblk); } + +SW_ENC_DEC(128) +SW_ENC_DEC(192) +SW_ENC_DEC(256) + +AES_EXTRA(_sw); +AES_ALL_VTABLES(_sw, "unaccelerated"); |