putty/mpunsafe.c at master · github/putty · GitHub

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#include <assert.h>

#include <limits.h>

#include <stdio.h>

#include "defs.h"

#include "misc.h"

#include "puttymem.h"

#include "mpint.h"

#include "mpint_i.h"

* This global symbol is also defined in ssh2kex-client.c, to ensure

* that these unsafe non-constant-time mp_int functions can't end up

* accidentally linked in to any PuTTY tool that actually makes an SSH

* client connection.

* (Only _client_ connections, however. Uppity, being a test server

* only, is exempt.)

const int deliberate_symbol_clash = 12345;

static size_t mp_unsafe_words_needed(mp_int *x)

{

size_t words = x->nw;

while (words > 1 && !x->w[words-1])

words--;

return words;

}

mp_int *mp_unsafe_shrink(mp_int *x)

{

x->nw = mp_unsafe_words_needed(x);

/* This potentially leaves some allocated words between the new

* and old values of x->nw, which won't be wiped by mp_free now

* that x->nw doesn't mention that they exist. But we've just

* checked they're all zero, so we don't need to wipe them now

* either. */

return x;

}

mp_int *mp_unsafe_copy(mp_int *x)

{

mp_int *copy = mp_make_sized(mp_unsafe_words_needed(x));

mp_copy_into(copy, x);

return copy;

}

uint32_t mp_unsafe_mod_integer(mp_int *x, uint32_t modulus)

{

uint64_t accumulator = 0;

for (size_t i = mp_max_bytes(x); i-- > 0 ;) {

accumulator = 0x100 * accumulator + mp_get_byte(x, i);

accumulator %= modulus;

}

return accumulator;

}

putty/mpunsafe.c at master · github/putty · GitHub

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