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-rw-r--r--src/crypt_zip.c157
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diff --git a/src/crypt_zip.c b/src/crypt_zip.c
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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,
+ 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