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 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 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 113 crypt_zip_encode( 114 cryptstate_T *state, 115 char_u *from, 116 size_t len, 117 char_u *to) 118 { 119 zip_state_T *zs = state->method_state; 120 size_t i; 121 int ztemp, t; 122 123 for (i = 0; i < len; ++i) 124 { 125 ztemp = from[i]; 126 DECRYPT_BYTE_ZIP(zs->keys, t); 127 UPDATE_KEYS_ZIP(zs->keys, ztemp); 128 to[i] = t ^ ztemp; 129 } 130 } 131 132 /* 133 * Decrypt "from[len]" into "to[len]". 134 */ 135 void 136 crypt_zip_decode( 137 cryptstate_T *state, 138 char_u *from, 139 size_t len, 140 char_u *to) 141 { 142 zip_state_T *zs = state->method_state; 143 size_t i; 144 short_u temp; 145 146 for (i = 0; i < len; ++i) 147 { 148 temp = (short_u)zs->keys[2] | 2; 149 temp = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff); 150 UPDATE_KEYS_ZIP(zs->keys, to[i] = from[i] ^ temp); 151 } 152 } 153 154 #endif /* FEAT_CRYPT */ 155