1 /* vi:set ts=8 sts=4 sw=4 noet:
2 *
3 * VIM - Vi IMproved by Bram Moolenaar
4 *
5 * Do ":help uganda" in Vim to read copying and usage conditions.
6 * Do ":help credits" in Vim to see a list of people who contributed.
7 * See README.txt for an overview of the Vim source code.
8 */
9
10 /*
11 * crypt_zip.c: Zip encryption support.
12 */
13 #include "vim.h"
14
15 #if defined(FEAT_CRYPT) || defined(PROTO)
16 /*
17 * Optional encryption support.
18 * Mohsin Ahmed, [email protected], 98-09-24
19 * Based on zip/crypt sources.
20 *
21 * NOTE FOR USA: Since 2000 exporting this code from the USA is allowed to
22 * most countries. There are a few exceptions, but that still should not be a
23 * problem since this code was originally created in Europe and India.
24 */
25
26 // Need a type that should be 32 bits. 64 also works but wastes space.
27 typedef unsigned int u32_T; // int is at least 32 bits
28
29 // The state of encryption, referenced by cryptstate_T.
30 typedef struct {
31 u32_T keys[3];
32 } zip_state_T;
33
34
35 static u32_T crc_32_table[256];
36
37 /*
38 * Fill the CRC table, if not done already.
39 */
40 static void
make_crc_tab(void)41 make_crc_tab(void)
42 {
43 u32_T s, t, v;
44 static int done = FALSE;
45
46 if (done)
47 return;
48 for (t = 0; t < 256; t++)
49 {
50 v = t;
51 for (s = 0; s < 8; s++)
52 v = (v >> 1) ^ ((v & 1) * (u32_T)0xedb88320L);
53 crc_32_table[t] = v;
54 }
55 done = TRUE;
56 }
57
58 #define CRC32(c, b) (crc_32_table[((int)(c) ^ (b)) & 0xff] ^ ((c) >> 8))
59
60 /*
61 * Return the next byte in the pseudo-random sequence.
62 */
63 #define DECRYPT_BYTE_ZIP(keys, t) { \
64 short_u temp = (short_u)keys[2] | 2; \
65 t = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff); \
66 }
67
68 /*
69 * Update the encryption keys with the next byte of plain text.
70 */
71 #define UPDATE_KEYS_ZIP(keys, c) do { \
72 keys[0] = CRC32(keys[0], (c)); \
73 keys[1] += keys[0] & 0xff; \
74 keys[1] = keys[1] * 134775813L + 1; \
75 keys[2] = CRC32(keys[2], (int)(keys[1] >> 24)); \
76 } while (0)
77
78 /*
79 * Initialize for encryption/decryption.
80 */
81 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)82 crypt_zip_init(
83 cryptstate_T *state,
84 char_u *key,
85 char_u *salt UNUSED,
86 int salt_len UNUSED,
87 char_u *seed UNUSED,
88 int seed_len UNUSED)
89 {
90 char_u *p;
91 zip_state_T *zs;
92
93 zs = ALLOC_ONE(zip_state_T);
94 if (zs == NULL)
95 return FAIL;
96 state->method_state = zs;
97
98 make_crc_tab();
99 zs->keys[0] = 305419896L;
100 zs->keys[1] = 591751049L;
101 zs->keys[2] = 878082192L;
102 for (p = key; *p != NUL; ++p)
103 UPDATE_KEYS_ZIP(zs->keys, (int)*p);
104
105 return OK;
106 }
107
108 /*
109 * Encrypt "from[len]" into "to[len]".
110 * "from" and "to" can be equal to encrypt in place.
111 */
112 void
crypt_zip_encode(cryptstate_T * state,char_u * from,size_t len,char_u * to,int last UNUSED)113 crypt_zip_encode(
114 cryptstate_T *state,
115 char_u *from,
116 size_t len,
117 char_u *to,
118 int last UNUSED)
119 {
120 zip_state_T *zs = state->method_state;
121 size_t i;
122 int ztemp, t;
123
124 for (i = 0; i < len; ++i)
125 {
126 ztemp = from[i];
127 DECRYPT_BYTE_ZIP(zs->keys, t);
128 UPDATE_KEYS_ZIP(zs->keys, ztemp);
129 to[i] = t ^ ztemp;
130 }
131 }
132
133 /*
134 * Decrypt "from[len]" into "to[len]".
135 */
136 void
crypt_zip_decode(cryptstate_T * state,char_u * from,size_t len,char_u * to,int last UNUSED)137 crypt_zip_decode(
138 cryptstate_T *state,
139 char_u *from,
140 size_t len,
141 char_u *to,
142 int last UNUSED)
143 {
144 zip_state_T *zs = state->method_state;
145 size_t i;
146 short_u temp;
147
148 for (i = 0; i < len; ++i)
149 {
150 temp = (short_u)zs->keys[2] | 2;
151 temp = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff);
152 UPDATE_KEYS_ZIP(zs->keys, to[i] = from[i] ^ temp);
153 }
154 }
155
156 #endif // FEAT_CRYPT
157