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putty/sshdes.c

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/*
* sshdes.c: 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;
}
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 = {
des_cbc_new, des_cbc_free, des_cbc_setiv, des_cbc_setkey,
des_cbc_encrypt, des_cbc_decrypt, NULL, NULL, "des-cbc",
8, 56, 8, SSH_CIPHER_IS_CBC, "single-DES CBC", NULL
};
const ssh_cipheralg ssh_des_sshcom_ssh2 = {
/* Same as ssh_des_cbc, but with a different SSH-2 ID */
des_cbc_new, des_cbc_free, des_cbc_setiv, des_cbc_setkey,
des_cbc_encrypt, des_cbc_decrypt, NULL, NULL, "des-cbc@ssh.com",
8, 56, 8, SSH_CIPHER_IS_CBC, "single-DES CBC", NULL
};
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 = {
des3_cbc1_new, des3_cbc1_free, des3_cbc1_setiv, des3_cbc1_setkey,
des3_cbc1_cbc_encrypt, des3_cbc1_cbc_decrypt, NULL, NULL, "3des-cbc",
8, 168, 24, SSH_CIPHER_IS_CBC, "triple-DES CBC", NULL
};
/* ----------------------------------------------------------------------
* 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 = {
des3_sdctr_new, des3_sdctr_free, des3_sdctr_setiv, des3_sdctr_setkey,
des3_sdctr_encrypt_decrypt, des3_sdctr_encrypt_decrypt,
NULL, NULL, "3des-ctr", 8, 168, 24, 0, "triple-DES SDCTR", NULL
};
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 = {
des3_cbc3_new, des3_cbc3_free, des3_cbc3_setiv, des3_cbc3_setkey,
des3_cbc3_cbc_encrypt, des3_cbc3_cbc_decrypt, NULL, NULL, NULL,
8, 168, 24, SSH_CIPHER_IS_CBC, "triple-DES inner-CBC", NULL
};
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