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Diffstat (limited to 'src/crypt_zip.c')
| -rw-r--r-- | src/crypt_zip.c | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/src/crypt_zip.c b/src/crypt_zip.c new file mode 100644 index 0000000..91bbd7b --- /dev/null +++ b/src/crypt_zip.c @@ -0,0 +1,157 @@ +/* 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, + int last UNUSED) +{ + 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, + int last UNUSED) +{ + 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 |