mirror of
https://github.com/vim/vim
synced 2025-03-16 06:47:52 +01:00
aae583441b
Problem: Decrypting with libsodium may fail if the library changes.
Solution: Add parameters used to the encrypted file header. (Christian
Brabandt, closes #12279)
154 lines
3.2 KiB
C
154 lines
3.2 KiB
C
/* vi:set ts=8 sts=4 sw=4 noet:
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*
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* VIM - Vi IMproved by Bram Moolenaar
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*
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* Do ":help uganda" in Vim to read copying and usage conditions.
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* Do ":help credits" in Vim to see a list of people who contributed.
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* See README.txt for an overview of the Vim source code.
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*/
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/*
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* crypt_zip.c: Zip encryption support.
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*/
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#include "vim.h"
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#if defined(FEAT_CRYPT) || defined(PROTO)
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/*
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* Optional encryption support.
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* Mohsin Ahmed, mosh@sasi.com, 98-09-24
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* Based on zip/crypt sources.
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*
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* NOTE FOR USA: Since 2000 exporting this code from the USA is allowed to
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* most countries. There are a few exceptions, but that still should not be a
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* problem since this code was originally created in Europe and India.
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*/
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// Need a type that should be 32 bits. 64 also works but wastes space.
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typedef unsigned int u32_T; // int is at least 32 bits
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// The state of encryption, referenced by cryptstate_T.
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typedef struct {
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u32_T keys[3];
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} zip_state_T;
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static u32_T crc_32_table[256];
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/*
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* Fill the CRC table, if not done already.
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*/
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static void
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make_crc_tab(void)
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{
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u32_T s, t, v;
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static int done = FALSE;
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if (done)
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return;
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for (t = 0; t < 256; t++)
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{
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v = t;
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for (s = 0; s < 8; s++)
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v = (v >> 1) ^ ((v & 1) * (u32_T)0xedb88320L);
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crc_32_table[t] = v;
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}
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done = TRUE;
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}
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#define CRC32(c, b) (crc_32_table[((int)(c) ^ (b)) & 0xff] ^ ((c) >> 8))
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/*
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* Return the next byte in the pseudo-random sequence.
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*/
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#define DECRYPT_BYTE_ZIP(keys, t) \
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{ \
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short_u temp = (short_u)keys[2] | 2; \
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t = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff); \
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}
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/*
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* Update the encryption keys with the next byte of plain text.
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*/
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#define UPDATE_KEYS_ZIP(keys, c) do { \
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keys[0] = CRC32(keys[0], (c)); \
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keys[1] += keys[0] & 0xff; \
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keys[1] = keys[1] * 134775813L + 1; \
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keys[2] = CRC32(keys[2], (int)(keys[1] >> 24)); \
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} while (0)
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/*
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* Initialize for encryption/decryption.
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*/
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int
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crypt_zip_init(
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cryptstate_T *state,
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char_u *key,
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crypt_arg_T *arg UNUSED)
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{
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char_u *p;
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zip_state_T *zs;
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zs = ALLOC_ONE(zip_state_T);
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if (zs == NULL)
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return FAIL;
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state->method_state = zs;
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make_crc_tab();
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zs->keys[0] = 305419896L;
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zs->keys[1] = 591751049L;
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zs->keys[2] = 878082192L;
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for (p = key; *p != NUL; ++p)
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UPDATE_KEYS_ZIP(zs->keys, (int)*p);
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return OK;
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}
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/*
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* Encrypt "from[len]" into "to[len]".
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* "from" and "to" can be equal to encrypt in place.
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*/
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void
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crypt_zip_encode(
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cryptstate_T *state,
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char_u *from,
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size_t len,
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char_u *to,
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int last UNUSED)
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{
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zip_state_T *zs = state->method_state;
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size_t i;
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int ztemp, t;
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for (i = 0; i < len; ++i)
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{
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ztemp = from[i];
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DECRYPT_BYTE_ZIP(zs->keys, t);
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UPDATE_KEYS_ZIP(zs->keys, ztemp);
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to[i] = t ^ ztemp;
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}
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}
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/*
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* Decrypt "from[len]" into "to[len]".
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*/
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void
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crypt_zip_decode(
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cryptstate_T *state,
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char_u *from,
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size_t len,
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char_u *to,
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int last UNUSED)
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{
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zip_state_T *zs = state->method_state;
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size_t i;
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short_u temp;
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for (i = 0; i < len; ++i)
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{
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temp = (short_u)zs->keys[2] | 2;
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temp = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff);
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UPDATE_KEYS_ZIP(zs->keys, to[i] = from[i] ^ temp);
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}
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}
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#endif // FEAT_CRYPT
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