/* * 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]/ be the finite field * used in AES, and let R = F[Y]/ 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; } 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); } 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; } } #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); } SW_ENC_DEC(128) SW_ENC_DEC(192) SW_ENC_DEC(256) AES_EXTRA(_sw); AES_ALL_VTABLES(_sw, "unaccelerated");