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/* vi:set ts=8 sts=4 sw=4 noet:
*
* VIM - Vi IMproved by Bram Moolenaar
*
* Do ":help uganda" in Vim to read copying and usage conditions.
* Do ":help credits" in Vim to see a list of people who contributed.
* See README.txt for an overview of the Vim source code.
*/
/*
* crypt_zip.c: Zip encryption support.
*/
#include "vim.h"
#if defined(FEAT_CRYPT) || defined(PROTO)
/*
* Optional encryption support.
* Mohsin Ahmed, mosh@sasi.com, 98-09-24
* Based on zip/crypt sources.
*
* NOTE FOR USA: Since 2000 exporting this code from the USA is allowed to
* most countries. There are a few exceptions, but that still should not be a
* problem since this code was originally created in Europe and India.
*/
// Need a type that should be 32 bits. 64 also works but wastes space.
typedef unsigned int u32_T; // int is at least 32 bits
// The state of encryption, referenced by cryptstate_T.
typedef struct {
u32_T keys[3];
} zip_state_T;
static u32_T crc_32_table[256];
/*
* Fill the CRC table, if not done already.
*/
static void
make_crc_tab(void)
{
u32_T s, t, v;
static int done = FALSE;
if (done)
return;
for (t = 0; t < 256; t++)
{
v = t;
for (s = 0; s < 8; s++)
v = (v >> 1) ^ ((v & 1) * (u32_T)0xedb88320L);
crc_32_table[t] = v;
}
done = TRUE;
}
#define CRC32(c, b) (crc_32_table[((int)(c) ^ (b)) & 0xff] ^ ((c) >> 8))
/*
* Return the next byte in the pseudo-random sequence.
*/
#define DECRYPT_BYTE_ZIP(keys, t) { \
short_u temp = (short_u)keys[2] | 2; \
t = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff); \
}
/*
* Update the encryption keys with the next byte of plain text.
*/
#define UPDATE_KEYS_ZIP(keys, c) do { \
keys[0] = CRC32(keys[0], (c)); \
keys[1] += keys[0] & 0xff; \
keys[1] = keys[1] * 134775813L + 1; \
keys[2] = CRC32(keys[2], (int)(keys[1] >> 24)); \
} while (0)
/*
* Initialize for encryption/decryption.
*/
int
crypt_zip_init(
cryptstate_T *state,
char_u *key,
char_u *salt UNUSED,
int salt_len UNUSED,
char_u *seed UNUSED,
int seed_len UNUSED)
{
char_u *p;
zip_state_T *zs;
zs = ALLOC_ONE(zip_state_T);
if (zs == NULL)
return FAIL;
state->method_state = zs;
make_crc_tab();
zs->keys[0] = 305419896L;
zs->keys[1] = 591751049L;
zs->keys[2] = 878082192L;
for (p = key; *p != NUL; ++p)
UPDATE_KEYS_ZIP(zs->keys, (int)*p);
return OK;
}
/*
* Encrypt "from[len]" into "to[len]".
* "from" and "to" can be equal to encrypt in place.
*/
void
crypt_zip_encode(
cryptstate_T *state,
char_u *from,
size_t len,
char_u *to)
{
zip_state_T *zs = state->method_state;
size_t i;
int ztemp, t;
for (i = 0; i < len; ++i)
{
ztemp = from[i];
DECRYPT_BYTE_ZIP(zs->keys, t);
UPDATE_KEYS_ZIP(zs->keys, ztemp);
to[i] = t ^ ztemp;
}
}
/*
* Decrypt "from[len]" into "to[len]".
*/
void
crypt_zip_decode(
cryptstate_T *state,
char_u *from,
size_t len,
char_u *to)
{
zip_state_T *zs = state->method_state;
size_t i;
short_u temp;
for (i = 0; i < len; ++i)
{
temp = (short_u)zs->keys[2] | 2;
temp = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff);
UPDATE_KEYS_ZIP(zs->keys, to[i] = from[i] ^ temp);
}
}
#endif // FEAT_CRYPT
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