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Diffstat (limited to 'crypto/des.c')
| -rw-r--r-- | crypto/des.c | 1053 |
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diff --git a/crypto/des.c b/crypto/des.c new file mode 100644 index 00000000..1cbec8fa --- /dev/null +++ b/crypto/des.c @@ -0,0 +1,1053 @@ +/* + * Implementation of DES. + */ + +/* + * Background + * ---------- + * + * The basic structure of DES is a Feistel network: the 64-bit cipher + * block is divided into two 32-bit halves L and R, and in each round, + * a mixing function is applied to one of them, the result is XORed + * into the other, and then the halves are swapped so that the other + * one will be the input to the mixing function next time. (This + * structure guarantees reversibility no matter whether the mixing + * function itself is bijective.) + * + * The mixing function for DES goes like this: + * + Extract eight contiguous 6-bit strings from the 32-bit word. + * They start at positions 4 bits apart, so each string overlaps + * the next one by one bit. At least one has to wrap cyclically + * round the end of the word. + * + XOR each of those strings with 6 bits of data from the key + * schedule (which consists of 8 x 6-bit strings per round). + * + Use the resulting 6-bit numbers as the indices into eight + * different lookup tables ('S-boxes'), each of which delivers a + * 4-bit output. + * + Concatenate those eight 4-bit values into a 32-bit word. + * + Finally, apply a fixed permutation P to that word. + * + * DES adds one more wrinkle on top of this structure, which is to + * conjugate it by a bitwise permutation of the cipher block. That is, + * before starting the main cipher rounds, the input bits are permuted + * according to a 64-bit permutation called IP, and after the rounds + * are finished, the output bits are permuted back again by applying + * the inverse of IP. + * + * This gives a lot of leeway to redefine the components of the cipher + * without actually changing the input and output. You could permute + * the bits in the output of any or all of the S-boxes, or reorder the + * S-boxes among themselves, and adjust the following permutation P to + * compensate. And you could adjust IP by post-composing a rotation of + * each 32-bit half, and adjust the starting offsets of the 6-bit + * S-box indices to compensate. + * + * test/desref.py demonstrates this by providing two equivalent forms + * of the cipher, called DES and SGTDES, which give the same output. + * DES is the form described in the original spec: if you make it + * print diagnostic output during the cipher and check it against the + * original, you should recognise the S-box outputs as matching the + * ones you expect. But SGTDES, which I egotistically name after + * myself, is much closer to the form implemented here: I've changed + * the permutation P to suit my implementation strategy and + * compensated by permuting the S-boxes, and also I've added a + * rotation right by 1 bit to IP so that only one S-box index has to + * wrap round the word and also so that the indices are nicely aligned + * for the constant-time selection system I'm using. + */ + +#include <stdio.h> + +#include "ssh.h" +#include "mpint_i.h" /* we reuse the BignumInt system */ + +/* If you compile with -DDES_DIAGNOSTICS, intermediate results will be + * sent to debug() (so you also need to compile with -DDEBUG). + * Otherwise this ifdef will condition away all the debug() calls. */ +#ifndef DES_DIAGNOSTICS +#undef debug +#define debug(...) ((void)0) +#endif + +/* + * General utility functions. + */ +static inline uint32_t rol(uint32_t x, unsigned c) +{ + return (x << (31 & c)) | (x >> (31 & -c)); +} +static inline uint32_t ror(uint32_t x, unsigned c) +{ + return rol(x, -c); +} + +/* + * The hard part of doing DES in constant time is the S-box lookup. + * + * My strategy is to iterate over the whole lookup table! That's slow, + * but I don't see any way to avoid _something_ along those lines: in + * every round, every entry in every S-box is potentially needed, and + * if you can't change your memory access pattern based on the input + * data, it follows that you have to read a quantity of information + * equal to the size of all the S-boxes. (Unless they were to turn out + * to be significantly compressible, but I for one couldn't show them + * to be.) + * + * In more detail, I construct a sort of counter-based 'selection + * gadget', which is 15 bits wide and starts off with the top bit + * zero, the next eight bits all 1, and the bottom six set to the + * input S-box index: + * + * 011111111xxxxxx + * + * Now if you add 1 in the lowest bit position, then either it carries + * into the top section (resetting it to 100000000), or it doesn't do + * that yet. If you do that 64 times, then it will _guarantee_ to have + * ticked over into 100000000. In between those increments, the eight + * bits that started off as 11111111 will have stayed that way for + * some number of iterations and then become 00000000, and exactly how + * many iterations depends on the input index. + * + * The purpose of the 0 bit at the top is to absorb the carry when the + * switch happens, which means you can pack more than one gadget into + * the same machine word and have them all work in parallel without + * each one intefering with the next. + * + * The next step is to use each of those 8-bit segments as a bit mask: + * each one is ANDed with a lookup table entry, and all the results + * are XORed together. So you end up with the bitwise XOR of some + * initial segment of the table entries. And the stored S-box tables + * are transformed in such a way that the real S-box values are given + * not by the individual entries, but by the cumulative XORs + * constructed in this way. + * + * A refinement is that I increment each gadget by 2 rather than 1 + * each time, so I only iterate 32 times instead of 64. That's why + * there are 8 selection bits instead of 4: each gadget selects enough + * bits to reconstruct _two_ S-box entries, for a pair of indices + * (2n,2n+1), and then finally I use the low bit of the index to do a + * parallel selection between each of those pairs. + * + * The selection gadget is not quite 16 bits wide. So you can fit four + * of them across a 64-bit word at 16-bit intervals, which is also + * convenient because the place the S-box indices are coming from also + * has pairs of them separated by 16-bit distances, so it's easy to + * copy them into the gadgets in the first place. + */ + +/* + * The S-box data. Each pair of nonzero columns here describes one of + * the S-boxes, corresponding to the SGTDES tables in test/desref.py, + * under the following transformation. + * + * Take S-box #3 as an example. Its values in successive rows of this + * table are eb,e8,54,3d, ... So the cumulative XORs of initial + * sequences of those values are eb,(eb^e8),(eb^e8^54), ... which + * comes to eb,03,57,... Of _those_ values, the top nibble (e,0,5,...) + * gives the even-numbered entries in the S-box, in _reverse_ order + * (because a lower input index selects the XOR of a longer + * subsequence). The odd-numbered entries are given by XORing the two + * digits together: (e^b),(0^3),(5^7),... = 5,3,2,... And indeed, if + * you check SGTDES.sboxes[3] you find it ends ... 52 03 e5. + */ +#define SBOX_ITERATION(X) \ + /* 66 22 44 00 77 33 55 11 */ \ + X(0xf600970083008500, 0x0e00eb007b002e00) \ + X(0xda00e4009000e000, 0xad00e800a700b400) \ + X(0x1a009d003f003600, 0xf60054004300cd00) \ + X(0xaf00c500e900a900, 0x63003d00f2005900) \ + X(0xf300750079001400, 0x80005000a2008900) \ + X(0xa100d400d6007b00, 0xd3009000d300e100) \ + X(0x450087002600ac00, 0xae003c0031009c00) \ + X(0xd000b100b6003600, 0x3e006f0092005900) \ + X(0x4d008a0026001000, 0x89007a00b8004a00) \ + X(0xca00f5003f00ac00, 0x6f00f0003c009400) \ + X(0x92008d0090001000, 0x8c00c600ce004a00) \ + X(0xe2005900e9006d00, 0x790078007800fa00) \ + X(0x1300b10090008d00, 0xa300170027001800) \ + X(0xc70058005f006a00, 0x9c00c100e0006300) \ + X(0x9b002000f000f000, 0xf70057001600f900) \ + X(0xeb00b0009000af00, 0xa9006300b0005800) \ + X(0xa2001d00cf000000, 0x3800b00066000000) \ + X(0xf100da007900d000, 0xbc00790094007900) \ + X(0x570015001900ad00, 0x6f00ef005100cb00) \ + X(0xc3006100e9006d00, 0xc000b700f800f200) \ + X(0x1d005800b600d000, 0x67004d00cd002c00) \ + X(0xf400b800d600e000, 0x5e00a900b000e700) \ + X(0x5400d1003f009c00, 0xc90069002c005300) \ + X(0xe200e50060005900, 0x6a00b800c500f200) \ + X(0xdf0047007900d500, 0x7000ec004c00ea00) \ + X(0x7100d10060009c00, 0x3f00b10095005e00) \ + X(0x82008200f0002000, 0x87001d00cd008000) \ + X(0xd0007000af00c000, 0xe200be006100f200) \ + X(0x8000930060001000, 0x36006e0081001200) \ + X(0x6500a300d600ac00, 0xcf003d007d00c000) \ + X(0x9000700060009800, 0x62008100ad009200) \ + X(0xe000e4003f00f400, 0x5a00ed009000f200) \ + /* end of list */ + +/* + * The S-box mapping function. Expects two 32-bit input words: si6420 + * contains the table indices for S-boxes 0,2,4,6 with their low bits + * starting at position 2 (for S-box 0) and going up in steps of 8. + * si7531 has indices 1,3,5,7 in the same bit positions. + */ +static inline uint32_t des_S(uint32_t si6420, uint32_t si7531) +{ + debug("sindices: %02x %02x %02x %02x %02x %02x %02x %02x\n", + 0x3F & (si6420 >> 2), 0x3F & (si7531 >> 2), + 0x3F & (si6420 >> 10), 0x3F & (si7531 >> 10), + 0x3F & (si6420 >> 18), 0x3F & (si7531 >> 18), + 0x3F & (si6420 >> 26), 0x3F & (si7531 >> 26)); + +#ifdef SIXTY_FOUR_BIT + /* + * On 64-bit machines, we store the table in exactly the form + * shown above, and make two 64-bit words containing four + * selection gadgets each. + */ + + /* Set up the gadgets. The 'cNNNN' variables will be gradually + * incremented, and the bits in positions FF00FF00FF00FF00 will + * act as selectors for the words in the table. + * + * A side effect of moving the input indices further apart is that + * they change order, because it's easier to keep a pair that were + * originally 16 bits apart still 16 bits apart, which now makes + * them adjacent instead of separated by one. So the fact that + * si6420 turns into c6240 (with the 2,4 reversed) is not a typo! + * This will all be undone when we rebuild the output word later. + */ + uint64_t c6240 = ((si6420 | ((uint64_t)si6420 << 24)) + & 0x00FC00FC00FC00FC) | 0xFF00FF00FF00FF00; + uint64_t c7351 = ((si7531 | ((uint64_t)si7531 << 24)) + & 0x00FC00FC00FC00FC) | 0xFF00FF00FF00FF00; + debug("S in: c6240=%016"PRIx64" c7351=%016"PRIx64"\n", c6240, c7351); + + /* Iterate over the table. The 'sNNNN' variables accumulate the + * XOR of all the table entries not masked out. */ + static const struct tbl { uint64_t t6240, t7351; } tbl[32] = { +#define TABLE64(a, b) { a, b }, + SBOX_ITERATION(TABLE64) +#undef TABLE64 + }; + uint64_t s6240 = 0, s7351 = 0; + for (const struct tbl *t = tbl, *limit = tbl + 32; t < limit; t++) { + s6240 ^= c6240 & t->t6240; c6240 += 0x0008000800080008; + s7351 ^= c7351 & t->t7351; c7351 += 0x0008000800080008; + } + debug("S out: s6240=%016"PRIx64" s7351=%016"PRIx64"\n", s6240, s7351); + + /* Final selection between each even/odd pair: mask off the low + * bits of all the input indices (which haven't changed throughout + * the iteration), and multiply by a bit mask that will turn each + * set bit into a mask covering the upper nibble of the selected + * pair. Then use those masks to control which set of lower + * nibbles is XORed into the upper nibbles. */ + s6240 ^= (s6240 << 4) & ((0xf000/0x004) * (c6240 & 0x0004000400040004)); + s7351 ^= (s7351 << 4) & ((0xf000/0x004) * (c7351 & 0x0004000400040004)); + + /* Now the eight final S-box outputs are in the upper nibble of + * each selection position. Mask away the rest of the clutter. */ + s6240 &= 0xf000f000f000f000; + s7351 &= 0xf000f000f000f000; + debug("s0=%x s1=%x s2=%x s3=%x s4=%x s5=%x s6=%x s7=%x\n", + (unsigned)(0xF & (s6240 >> 12)), + (unsigned)(0xF & (s7351 >> 12)), + (unsigned)(0xF & (s6240 >> 44)), + (unsigned)(0xF & (s7351 >> 44)), + (unsigned)(0xF & (s6240 >> 28)), + (unsigned)(0xF & (s7351 >> 28)), + (unsigned)(0xF & (s6240 >> 60)), + (unsigned)(0xF & (s7351 >> 60))); + + /* Combine them all into a single 32-bit output word, which will + * come out in the order 76543210. */ + uint64_t combined = (s6240 >> 12) | (s7351 >> 8); + return combined | (combined >> 24); + +#else /* SIXTY_FOUR_BIT */ + /* + * For 32-bit platforms, we do the same thing but in four 32-bit + * words instead of two 64-bit ones, so the CPU doesn't have to + * waste time propagating carries or shifted bits between the two + * halves of a uint64 that weren't needed anyway. + */ + + /* Set up the gadgets */ + uint32_t c40 = ((si6420 ) & 0x00FC00FC) | 0xFF00FF00; + uint32_t c62 = ((si6420 >> 8) & 0x00FC00FC) | 0xFF00FF00; + uint32_t c51 = ((si7531 ) & 0x00FC00FC) | 0xFF00FF00; + uint32_t c73 = ((si7531 >> 8) & 0x00FC00FC) | 0xFF00FF00; + debug("S in: c40=%08"PRIx32" c62=%08"PRIx32 + " c51=%08"PRIx32" c73=%08"PRIx32"\n", c40, c62, c51, c73); + + /* Iterate over the table */ + static const struct tbl { uint32_t t40, t62, t51, t73; } tbl[32] = { +#define TABLE32(a, b) { ((uint32_t)a), (a>>32), ((uint32_t)b), (b>>32) }, + SBOX_ITERATION(TABLE32) +#undef TABLE32 + }; + uint32_t s40 = 0, s62 = 0, s51 = 0, s73 = 0; + for (const struct tbl *t = tbl, *limit = tbl + 32; t < limit; t++) { + s40 ^= c40 & t->t40; c40 += 0x00080008; + s62 ^= c62 & t->t62; c62 += 0x00080008; + s51 ^= c51 & t->t51; c51 += 0x00080008; + s73 ^= c73 & t->t73; c73 += 0x00080008; + } + debug("S out: s40=%08"PRIx32" s62=%08"PRIx32 + " s51=%08"PRIx32" s73=%08"PRIx32"\n", s40, s62, s51, s73); + + /* Final selection within each pair */ + s40 ^= (s40 << 4) & ((0xf000/0x004) * (c40 & 0x00040004)); + s62 ^= (s62 << 4) & ((0xf000/0x004) * (c62 & 0x00040004)); + s51 ^= (s51 << 4) & ((0xf000/0x004) * (c51 & 0x00040004)); + s73 ^= (s73 << 4) & ((0xf000/0x004) * (c73 & 0x00040004)); + + /* Clean up the clutter */ + s40 &= 0xf000f000; + s62 &= 0xf000f000; + s51 &= 0xf000f000; + s73 &= 0xf000f000; + debug("s0=%x s1=%x s2=%x s3=%x s4=%x s5=%x s6=%x s7=%x\n", + (unsigned)(0xF & (s40 >> 12)), + (unsigned)(0xF & (s51 >> 12)), + (unsigned)(0xF & (s62 >> 12)), + (unsigned)(0xF & (s73 >> 12)), + (unsigned)(0xF & (s40 >> 28)), + (unsigned)(0xF & (s51 >> 28)), + (unsigned)(0xF & (s62 >> 28)), + (unsigned)(0xF & (s73 >> 28))); + + /* Recombine and return */ + return (s40 >> 12) | (s62 >> 4) | (s51 >> 8) | (s73); + +#endif /* SIXTY_FOUR_BIT */ + +} + +/* + * Now for the permutation P. The basic strategy here is to use a + * Benes network: in each stage, the bit at position i is allowed to + * either stay where it is or swap with i ^ D, where D is a power of 2 + * that varies with each phase. (So when D=1, pairs of the form + * {2n,2n+1} can swap; when D=2, the pairs are {4n+j,4n+j+2} for + * j={0,1}, and so on.) + * + * You can recursively construct a Benes network for an arbitrary + * permutation, in which the values of D iterate across all the powers + * of 2 less than the permutation size and then go back again. For + * example, the typical presentation for 32 bits would have D iterate + * over 16,8,4,2,1,2,4,8,16, and there's an easy algorithm that can + * express any permutation in that form by deciding which pairs of + * bits to swap in the outer pair of stages and then recursing to do + * all the stages in between. + * + * Actually implementing the swaps is easy when they're all between + * bits at the same separation: make the value x ^ (x >> D), mask out + * just the bits in the low position of a pair that needs to swap, and + * then use the resulting value y to make x ^ y ^ (y << D) which is + * the swapped version. + * + * In this particular case, I processed the bit indices in the other + * order (going 1,2,4,8,16,8,4,2,1), which makes no significant + * difference to the construction algorithm (it's just a relabelling), + * but it now means that the first two steps only permute entries + * within the output of each S-box - and therefore we can leave them + * completely out, in favour of just defining the S-boxes so that + * those permutation steps are already applied. Furthermore, by + * exhaustive search over the rest of the possible bit-orders for each + * S-box, I was able to find a version of P which could be represented + * in such a way that two further phases had all their control bits + * zero and could be skipped. So the number of swap stages is reduced + * to 5 from the 9 that might have been needed. + */ + +static inline uint32_t des_benes_step(uint32_t v, unsigned D, uint32_t mask) +{ + uint32_t diff = (v ^ (v >> D)) & mask; + return v ^ diff ^ (diff << D); +} + +static inline uint32_t des_P(uint32_t v_orig) +{ + uint32_t v = v_orig; + + /* initial stages with distance 1,2 are part of the S-box data table */ + v = des_benes_step(v, 4, 0x07030702); + v = des_benes_step(v, 8, 0x004E009E); + v = des_benes_step(v, 16, 0x0000D9D3); +/* v = des_benes_step(v, 8, 0x00000000); no-op, so we can skip it */ + v = des_benes_step(v, 4, 0x05040004); +/* v = des_benes_step(v, 2, 0x00000000); no-op, so we can skip it */ + v = des_benes_step(v, 1, 0x04045015); + + debug("P(%08"PRIx32") = %08"PRIx32"\n", v_orig, v); + + return v; +} + +/* + * Putting the S and P functions together, and adding in the round key + * as well, gives us the full mixing function f. + */ + +static inline uint32_t des_f(uint32_t R, uint32_t K7531, uint32_t K6420) +{ + uint32_t s7531 = R ^ K7531, s6420 = rol(R, 4) ^ K6420; + return des_P(des_S(s6420, s7531)); +} + +/* + * The key schedule, and the function to set it up. + */ + +typedef struct des_keysched des_keysched; +struct des_keysched { + uint32_t k7531[16], k6420[16]; +}; + +/* + * Simplistic function to select an arbitrary sequence of bits from + * one value and glue them together into another value. bitnums[] + * gives the sequence of bit indices of the input, from the highest + * output bit downwards. An index of -1 means that output bit is left + * at zero. + * + * This function is only used during key setup, so it doesn't need to + * be highly optimised. + */ +static inline uint64_t bitsel( + uint64_t input, const int8_t *bitnums, size_t size) +{ + uint64_t ret = 0; + while (size-- > 0) { + int bitpos = *bitnums++; + ret <<= 1; + if (bitpos >= 0) + ret |= 1 & (input >> bitpos); + } + return ret; +} + +static void des_key_setup(uint64_t key, des_keysched *sched) +{ + static const int8_t PC1[] = { + 7, 15, 23, 31, 39, 47, 55, 63, 6, 14, 22, 30, 38, 46, + 54, 62, 5, 13, 21, 29, 37, 45, 53, 61, 4, 12, 20, 28, + -1, -1, -1, -1, + 1, 9, 17, 25, 33, 41, 49, 57, 2, 10, 18, 26, 34, 42, + 50, 58, 3, 11, 19, 27, 35, 43, 51, 59, 36, 44, 52, 60, + }; + static const int8_t PC2_7531[] = { + 46, 43, 49, 36, 59, 55, -1, -1, /* index into S-box 7 */ + 37, 41, 48, 56, 34, 52, -1, -1, /* index into S-box 5 */ + 15, 4, 25, 19, 9, 1, -1, -1, /* index into S-box 3 */ + 12, 7, 17, 0, 22, 3, -1, -1, /* index into S-box 1 */ + }; + static const int8_t PC2_6420[] = { + 57, 32, 45, 54, 39, 50, -1, -1, /* index into S-box 6 */ + 44, 53, 33, 40, 47, 58, -1, -1, /* index into S-box 4 */ + 26, 16, 5, 11, 23, 8, -1, -1, /* index into S-box 2 */ + 10, 14, 6, 20, 27, 24, -1, -1, /* index into S-box 0 */ + }; + static const int leftshifts[] = {1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1}; + + /* Select 56 bits from the 64-bit input key integer (the low bit + * of each input byte is unused), into a word consisting of two + * 28-bit integers starting at bits 0 and 32. */ + uint64_t CD = bitsel(key, PC1, lenof(PC1)); + + for (size_t i = 0; i < 16; i++) { + /* Rotate each 28-bit half of CD left by 1 or 2 bits (varying + * between rounds) */ + CD <<= leftshifts[i]; + CD = (CD & 0x0FFFFFFF0FFFFFFF) | ((CD & 0xF0000000F0000000) >> 28); + + /* Select key bits from the rotated word to use during the + * actual cipher */ + sched->k7531[i] = bitsel(CD, PC2_7531, lenof(PC2_7531)); + sched->k6420[i] = bitsel(CD, PC2_6420, lenof(PC2_6420)); + } +} + +/* + * Helper routines for dealing with 64-bit blocks in the form of an L + * and R word. + */ + +typedef struct LR LR; +struct LR { uint32_t L, R; }; + +static inline LR des_load_lr(const void *vp) +{ + const uint8_t *p = (const uint8_t *)vp; + LR out; + out.L = GET_32BIT_MSB_FIRST(p); + out.R = GET_32BIT_MSB_FIRST(p+4); + return out; +} + +static inline void des_store_lr(void *vp, LR lr) +{ + uint8_t *p = (uint8_t *)vp; + PUT_32BIT_MSB_FIRST(p, lr.L); + PUT_32BIT_MSB_FIRST(p+4, lr.R); +} + +static inline LR des_xor_lr(LR a, LR b) +{ + a.L ^= b.L; + a.R ^= b.R; + return a; +} + +static inline LR des_swap_lr(LR in) +{ + LR out; + out.L = in.R; + out.R = in.L; + return out; +} + +/* + * The initial and final permutations of official DES are in a + * restricted form, in which the 'before' and 'after' positions of a + * given data bit are derived from each other by permuting the bits of + * the _index_ and flipping some of them. This allows the permutation + * to be performed effectively by a method that looks rather like + * _half_ of a general Benes network, because the restricted form + * means only half of it is actually needed. + * + * _Our_ initial and final permutations include a rotation by 1 bit, + * but it's still easier to just suffix that to the standard IP/FP + * than to regenerate everything using a more general method. + * + * Because we're permuting 64 bits in this case, between two 32-bit + * words, there's a separate helper function for this code that + * doesn't look quite like des_benes_step() above. + */ + +static inline void des_bitswap_IP_FP(uint32_t *L, uint32_t *R, + unsigned D, uint32_t mask) +{ + uint32_t diff = mask & ((*R >> D) ^ *L); + *R ^= diff << D; + *L ^= diff; +} + +static inline LR des_IP(LR lr) +{ + des_bitswap_IP_FP(&lr.R, &lr.L, 4, 0x0F0F0F0F); + des_bitswap_IP_FP(&lr.R, &lr.L, 16, 0x0000FFFF); + des_bitswap_IP_FP(&lr.L, &lr.R, 2, 0x33333333); + des_bitswap_IP_FP(&lr.L, &lr.R, 8, 0x00FF00FF); + des_bitswap_IP_FP(&lr.R, &lr.L, 1, 0x55555555); + + lr.L = ror(lr.L, 1); + lr.R = ror(lr.R, 1); + + return lr; +} + +static inline LR des_FP(LR lr) +{ + lr.L = rol(lr.L, 1); + lr.R = rol(lr.R, 1); + + des_bitswap_IP_FP(&lr.R, &lr.L, 1, 0x55555555); + des_bitswap_IP_FP(&lr.L, &lr.R, 8, 0x00FF00FF); + des_bitswap_IP_FP(&lr.L, &lr.R, 2, 0x33333333); + des_bitswap_IP_FP(&lr.R, &lr.L, 16, 0x0000FFFF); + des_bitswap_IP_FP(&lr.R, &lr.L, 4, 0x0F0F0F0F); + + return lr; +} + +/* + * The main cipher functions, which are identical except that they use + * the key schedule in opposite orders. + * + * We provide a version without the initial and final permutations, + * for use in triple-DES mode (no sense undoing and redoing it in + * between the phases). + */ + +static inline LR des_round(LR in, const des_keysched *sched, size_t round) +{ + LR out; + out.L = in.R; + out.R = in.L ^ des_f(in.R, sched->k7531[round], sched->k6420[round]); + return out; +} + +static inline LR des_inner_cipher(LR lr, const des_keysched *sched, + size_t start, size_t step) +{ + lr = des_round(lr, sched, start+0x0*step); + lr = des_round(lr, sched, start+0x1*step); + lr = des_round(lr, sched, start+0x2*step); + lr = des_round(lr, sched, start+0x3*step); + lr = des_round(lr, sched, start+0x4*step); + lr = des_round(lr, sched, start+0x5*step); + lr = des_round(lr, sched, start+0x6*step); + lr = des_round(lr, sched, start+0x7*step); + lr = des_round(lr, sched, start+0x8*step); + lr = des_round(lr, sched, start+0x9*step); + lr = des_round(lr, sched, start+0xa*step); + lr = des_round(lr, sched, start+0xb*step); + lr = des_round(lr, sched, start+0xc*step); + lr = des_round(lr, sched, start+0xd*step); + lr = des_round(lr, sched, start+0xe*step); + lr = des_round(lr, sched, start+0xf*step); + return des_swap_lr(lr); +} + +static inline LR des_full_cipher(LR lr, const des_keysched *sched, + size_t start, size_t step) +{ + lr = des_IP(lr); + lr = des_inner_cipher(lr, sched, start, step); + lr = des_FP(lr); + return lr; +} + +/* + * Parameter pairs for the start,step arguments to the cipher routines + * above, causing them to use the same key schedule in opposite orders. + */ +#define ENCIPHER 0, 1 /* for encryption */ +#define DECIPHER 15, -1 /* for decryption */ + +/* ---------------------------------------------------------------------- + * Single-DES + */ + +struct des_cbc_ctx { + des_keysched sched; + LR iv; + ssh_cipher ciph; +}; + +static ssh_cipher *des_cbc_new(const ssh_cipheralg *alg) +{ + struct des_cbc_ctx *ctx = snew(struct des_cbc_ctx); + ctx->ciph.vt = alg; + return &ctx->ciph; +} + +static void des_cbc_free(ssh_cipher *ciph) +{ + struct des_cbc_ctx *ctx = container_of(ciph, struct des_cbc_ctx, ciph); + smemclr(ctx, sizeof(*ctx)); + sfree(ctx); +} + +static void des_cbc_setkey(ssh_cipher *ciph, const void *vkey) +{ + struct des_cbc_ctx *ctx = container_of(ciph, struct des_cbc_ctx, ciph); + const uint8_t *key = (const uint8_t *)vkey; + des_key_setup(GET_64BIT_MSB_FIRST(key), &ctx->sched); +} + +static void des_cbc_setiv(ssh_cipher *ciph, const void *iv) +{ + struct des_cbc_ctx *ctx = container_of(ciph, struct des_cbc_ctx, ciph); + ctx->iv = des_load_lr(iv); +} + +static void des_cbc_encrypt(ssh_cipher *ciph, void *vdata, int len) +{ + struct des_cbc_ctx *ctx = container_of(ciph, struct des_cbc_ctx, ciph); + uint8_t *data = (uint8_t *)vdata; + for (; len > 0; len -= 8, data += 8) { + LR plaintext = des_load_lr(data); + LR cipher_in = des_xor_lr(plaintext, ctx->iv); + LR ciphertext = des_full_cipher(cipher_in, &ctx->sched, ENCIPHER); + des_store_lr(data, ciphertext); + ctx->iv = ciphertext; + } +} + +static void des_cbc_decrypt(ssh_cipher *ciph, void *vdata, int len) +{ + struct des_cbc_ctx *ctx = container_of(ciph, struct des_cbc_ctx, ciph); + uint8_t *data = (uint8_t *)vdata; + for (; len > 0; len -= 8, data += 8) { + LR ciphertext = des_load_lr(data); + LR cipher_out = des_full_cipher(ciphertext, &ctx->sched, DECIPHER); + LR plaintext = des_xor_lr(cipher_out, ctx->iv); + des_store_lr(data, plaintext); + ctx->iv = ciphertext; + } +} + +const ssh_cipheralg ssh_des = { + .new = des_cbc_new, + .free = des_cbc_free, + .setiv = des_cbc_setiv, + .setkey = des_cbc_setkey, + .encrypt = des_cbc_encrypt, + .decrypt = des_cbc_decrypt, + .next_message = nullcipher_next_message, + .ssh2_id = "des-cbc", + .blksize = 8, + .real_keybits = 56, + .padded_keybytes = 8, + .flags = SSH_CIPHER_IS_CBC, + .text_name = "single-DES CBC", +}; + +const ssh_cipheralg ssh_des_sshcom_ssh2 = { + /* Same as ssh_des_cbc, but with a different SSH-2 ID */ + .new = des_cbc_new, + .free = des_cbc_free, + .setiv = des_cbc_setiv, + .setkey = des_cbc_setkey, + .encrypt = des_cbc_encrypt, + .decrypt = des_cbc_decrypt, + .next_message = nullcipher_next_message, + .ssh2_id = "des-cbc@ssh.com", + .blksize = 8, + .real_keybits = 56, + .padded_keybytes = 8, + .flags = SSH_CIPHER_IS_CBC, + .text_name = "single-DES CBC", +}; + +static const ssh_cipheralg *const des_list[] = { + &ssh_des, + &ssh_des_sshcom_ssh2 +}; + +const ssh2_ciphers ssh2_des = { lenof(des_list), des_list }; + +/* ---------------------------------------------------------------------- + * Triple-DES CBC, SSH-2 style. The CBC mode treats the three + * invocations of DES as a single unified cipher, and surrounds it + * with just one layer of CBC, so only one IV is needed. + */ + +struct des3_cbc1_ctx { + des_keysched sched[3]; + LR iv; + ssh_cipher ciph; +}; + +static ssh_cipher *des3_cbc1_new(const ssh_cipheralg *alg) +{ + struct des3_cbc1_ctx *ctx = snew(struct des3_cbc1_ctx); + ctx->ciph.vt = alg; + return &ctx->ciph; +} + +static void des3_cbc1_free(ssh_cipher *ciph) +{ + struct des3_cbc1_ctx *ctx = container_of(ciph, struct des3_cbc1_ctx, ciph); + smemclr(ctx, sizeof(*ctx)); + sfree(ctx); +} + +static void des3_cbc1_setkey(ssh_cipher *ciph, const void *vkey) +{ + struct des3_cbc1_ctx *ctx = container_of(ciph, struct des3_cbc1_ctx, ciph); + const uint8_t *key = (const uint8_t *)vkey; + for (size_t i = 0; i < 3; i++) + des_key_setup(GET_64BIT_MSB_FIRST(key + 8*i), &ctx->sched[i]); +} + +static void des3_cbc1_setiv(ssh_cipher *ciph, const void *iv) +{ + struct des3_cbc1_ctx *ctx = container_of(ciph, struct des3_cbc1_ctx, ciph); + ctx->iv = des_load_lr(iv); +} + +static void des3_cbc1_cbc_encrypt(ssh_cipher *ciph, void *vdata, int len) +{ + struct des3_cbc1_ctx *ctx = container_of(ciph, struct des3_cbc1_ctx, ciph); + uint8_t *data = (uint8_t *)vdata; + for (; len > 0; len -= 8, data += 8) { + LR plaintext = des_load_lr(data); + LR cipher_in = des_xor_lr(plaintext, ctx->iv); + + /* Run three copies of the cipher, without undoing and redoing + * IP/FP in between. */ + LR lr = des_IP(cipher_in); + lr = des_inner_cipher(lr, &ctx->sched[0], ENCIPHER); + lr = des_inner_cipher(lr, &ctx->sched[1], DECIPHER); + lr = des_inner_cipher(lr, &ctx->sched[2], ENCIPHER); + LR ciphertext = des_FP(lr); + + des_store_lr(data, ciphertext); + ctx->iv = ciphertext; + } +} + +static void des3_cbc1_cbc_decrypt(ssh_cipher *ciph, void *vdata, int len) +{ + struct des3_cbc1_ctx *ctx = container_of(ciph, struct des3_cbc1_ctx, ciph); + uint8_t *data = (uint8_t *)vdata; + for (; len > 0; len -= 8, data += 8) { + LR ciphertext = des_load_lr(data); + + /* Similarly to encryption, but with the order reversed. */ + LR lr = des_IP(ciphertext); + lr = des_inner_cipher(lr, &ctx->sched[2], DECIPHER); + lr = des_inner_cipher(lr, &ctx->sched[1], ENCIPHER); + lr = des_inner_cipher(lr, &ctx->sched[0], DECIPHER); + LR cipher_out = des_FP(lr); + + LR plaintext = des_xor_lr(cipher_out, ctx->iv); + des_store_lr(data, plaintext); + ctx->iv = ciphertext; + } +} + +const ssh_cipheralg ssh_3des_ssh2 = { + .new = des3_cbc1_new, + .free = des3_cbc1_free, + .setiv = des3_cbc1_setiv, + .setkey = des3_cbc1_setkey, + .encrypt = des3_cbc1_cbc_encrypt, + .decrypt = des3_cbc1_cbc_decrypt, + .next_message = nullcipher_next_message, + .ssh2_id = "3des-cbc", + .blksize = 8, + .real_keybits = 168, + .padded_keybytes = 24, + .flags = SSH_CIPHER_IS_CBC, + .text_name = "triple-DES CBC", +}; + +/* ---------------------------------------------------------------------- + * Triple-DES in SDCTR mode. Again, the three DES instances are + * treated as one big cipher, with a single counter encrypted through + * all three. + */ + +#define SDCTR_WORDS (8 / BIGNUM_INT_BYTES) + +struct des3_sdctr_ctx { + des_keysched sched[3]; + BignumInt counter[SDCTR_WORDS]; + ssh_cipher ciph; +}; + +static ssh_cipher *des3_sdctr_new(const ssh_cipheralg *alg) +{ + struct des3_sdctr_ctx *ctx = snew(struct des3_sdctr_ctx); + ctx->ciph.vt = alg; + return &ctx->ciph; +} + +static void des3_sdctr_free(ssh_cipher *ciph) +{ + struct des3_sdctr_ctx *ctx = container_of( + ciph, struct des3_sdctr_ctx, ciph); + smemclr(ctx, sizeof(*ctx)); + sfree(ctx); +} + +static void des3_sdctr_setkey(ssh_cipher *ciph, const void *vkey) +{ + struct des3_sdctr_ctx *ctx = container_of( + ciph, struct des3_sdctr_ctx, ciph); + const uint8_t *key = (const uint8_t *)vkey; + for (size_t i = 0; i < 3; i++) + des_key_setup(GET_64BIT_MSB_FIRST(key + 8*i), &ctx->sched[i]); +} + +static void des3_sdctr_setiv(ssh_cipher *ciph, const void *viv) +{ + struct des3_sdctr_ctx *ctx = container_of( + ciph, struct des3_sdctr_ctx, 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->counter[i] = GET_BIGNUMINT_MSB_FIRST( + iv + 8 - BIGNUM_INT_BYTES - i*BIGNUM_INT_BYTES); +} + +static void des3_sdctr_encrypt_decrypt(ssh_cipher *ciph, void *vdata, int len) +{ + struct des3_sdctr_ctx *ctx = container_of( + ciph, struct des3_sdctr_ctx, ciph); + uint8_t *data = (uint8_t *)vdata; + uint8_t iv_buf[8]; + for (; len > 0; len -= 8, data += 8) { + /* Format the counter value into the buffer. */ + for (unsigned i = 0; i < SDCTR_WORDS; i++) + PUT_BIGNUMINT_MSB_FIRST( + iv_buf + 8 - BIGNUM_INT_BYTES - i*BIGNUM_INT_BYTES, + ctx->counter[i]); + + /* Increment the counter. */ + BignumCarry carry = 1; + for (unsigned i = 0; i < SDCTR_WORDS; i++) + BignumADC(ctx->counter[i], carry, ctx->counter[i], 0, carry); + + /* Triple-encrypt the counter value from the IV. */ + LR lr = des_IP(des_load_lr(iv_buf)); + lr = des_inner_cipher(lr, &ctx->sched[0], ENCIPHER); + lr = des_inner_cipher(lr, &ctx->sched[1], DECIPHER); + lr = des_inner_cipher(lr, &ctx->sched[2], ENCIPHER); + LR keystream = des_FP(lr); + + LR input = des_load_lr(data); + LR output = des_xor_lr(input, keystream); + des_store_lr(data, output); + } + smemclr(iv_buf, sizeof(iv_buf)); +} + +const ssh_cipheralg ssh_3des_ssh2_ctr = { + .new = des3_sdctr_new, + .free = des3_sdctr_free, + .setiv = des3_sdctr_setiv, + .setkey = des3_sdctr_setkey, + .encrypt = des3_sdctr_encrypt_decrypt, + .decrypt = des3_sdctr_encrypt_decrypt, + .next_message = nullcipher_next_message, + .ssh2_id = "3des-ctr", + .blksize = 8, + .real_keybits = 168, + .padded_keybytes = 24, + .flags = 0, + .text_name = "triple-DES SDCTR", +}; + +static const ssh_cipheralg *const des3_list[] = { + &ssh_3des_ssh2_ctr, + &ssh_3des_ssh2 +}; + +const ssh2_ciphers ssh2_3des = { lenof(des3_list), des3_list }; + +/* ---------------------------------------------------------------------- + * Triple-DES, SSH-1 style. SSH-1 replicated the whole CBC structure + * three times, so there have to be three separate IVs, one in each + * layer. + */ + +struct des3_cbc3_ctx { + des_keysched sched[3]; + LR iv[3]; + ssh_cipher ciph; +}; + +static ssh_cipher *des3_cbc3_new(const ssh_cipheralg *alg) +{ + struct des3_cbc3_ctx *ctx = snew(struct des3_cbc3_ctx); + ctx->ciph.vt = alg; + return &ctx->ciph; +} + +static void des3_cbc3_free(ssh_cipher *ciph) +{ + struct des3_cbc3_ctx *ctx = container_of(ciph, struct des3_cbc3_ctx, ciph); + smemclr(ctx, sizeof(*ctx)); + sfree(ctx); +} + +static void des3_cbc3_setkey(ssh_cipher *ciph, const void *vkey) +{ + struct des3_cbc3_ctx *ctx = container_of(ciph, struct des3_cbc3_ctx, ciph); + const uint8_t *key = (const uint8_t *)vkey; + for (size_t i = 0; i < 3; i++) + des_key_setup(GET_64BIT_MSB_FIRST(key + 8*i), &ctx->sched[i]); +} + +static void des3_cbc3_setiv(ssh_cipher *ciph, const void *viv) +{ + struct des3_cbc3_ctx *ctx = container_of(ciph, struct des3_cbc3_ctx, ciph); + + /* + * In principle, we ought to provide an interface for the user to + * input 24 instead of 8 bytes of IV. But that would make this an + * ugly exception to the otherwise universal rule that IV size = + * cipher block size, and there's really no need to violate that + * rule given that this is a historical one-off oddity and SSH-1 + * always initialises all three IVs to zero anyway. So we fudge it + * by just setting all the IVs to the same value. + */ + + LR iv = des_load_lr(viv); + + /* But we store the IVs in permuted form, so that we can handle + * all three CBC layers without having to do IP/FP in between. */ + iv = des_IP(iv); + for (size_t i = 0; i < 3; i++) + ctx->iv[i] = iv; +} + +static void des3_cbc3_cbc_encrypt(ssh_cipher *ciph, void *vdata, int len) +{ + struct des3_cbc3_ctx *ctx = container_of(ciph, struct des3_cbc3_ctx, ciph); + uint8_t *data = (uint8_t *)vdata; + for (; len > 0; len -= 8, data += 8) { + /* Load and IP the input. */ + LR plaintext = des_IP(des_load_lr(data)); + LR lr = plaintext; + + /* Do three passes of CBC, with the middle one inverted. */ + + lr = des_xor_lr(lr, ctx->iv[0]); + lr = des_inner_cipher(lr, &ctx->sched[0], ENCIPHER); + ctx->iv[0] = lr; + + LR ciphertext = lr; + lr = des_inner_cipher(ciphertext, &ctx->sched[1], DECIPHER); + lr = des_xor_lr(lr, ctx->iv[1]); + ctx->iv[1] = ciphertext; + + lr = des_xor_lr(lr, ctx->iv[2]); + lr = des_inner_cipher(lr, &ctx->sched[2], ENCIPHER); + ctx->iv[2] = lr; + + des_store_lr(data, des_FP(lr)); + } +} + +static void des3_cbc3_cbc_decrypt(ssh_cipher *ciph, void *vdata, int len) +{ + struct des3_cbc3_ctx *ctx = container_of(ciph, struct des3_cbc3_ctx, ciph); + uint8_t *data = (uint8_t *)vdata; + for (; len > 0; len -= 8, data += 8) { + /* Load and IP the input */ + LR lr = des_IP(des_load_lr(data)); + LR ciphertext; + + /* Do three passes of CBC, with the middle one inverted. */ + ciphertext = lr; + lr = des_inner_cipher(ciphertext, &ctx->sched[2], DECIPHER); + lr = des_xor_lr(lr, ctx->iv[2]); + ctx->iv[2] = ciphertext; + + lr = des_xor_lr(lr, ctx->iv[1]); + lr = des_inner_cipher(lr, &ctx->sched[1], ENCIPHER); + ctx->iv[1] = lr; + + ciphertext = lr; + lr = des_inner_cipher(ciphertext, &ctx->sched[0], DECIPHER); + lr = des_xor_lr(lr, ctx->iv[0]); + ctx->iv[0] = ciphertext; + + des_store_lr(data, des_FP(lr)); + } +} + +const ssh_cipheralg ssh_3des_ssh1 = { + .new = des3_cbc3_new, + .free = des3_cbc3_free, + .setiv = des3_cbc3_setiv, + .setkey = des3_cbc3_setkey, + .encrypt = des3_cbc3_cbc_encrypt, + .decrypt = des3_cbc3_cbc_decrypt, + .next_message = nullcipher_next_message, + .blksize = 8, + .real_keybits = 168, + .padded_keybytes = 24, + .flags = SSH_CIPHER_IS_CBC, + .text_name = "triple-DES inner-CBC", +}; |