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 # if VIM_SIZEOF_INT >= 4 28 typedef unsigned int u32_T; /* int is at least 32 bits */ 29 # else 30 typedef unsigned long u32_T; /* long should be 32 bits or more */ 31 # endif 32 33 /* The state of encryption, referenced by cryptstate_T. */ 34 typedef struct { 35 u32_T keys[3]; 36 } zip_state_T; 37 38 39 static u32_T crc_32_table[256]; 40 41 /* 42 * Fill the CRC table, if not done already. 43 */ 44 static void 45 make_crc_tab(void) 46 { 47 u32_T s, t, v; 48 static int done = FALSE; 49 50 if (done) 51 return; 52 for (t = 0; t < 256; t++) 53 { 54 v = t; 55 for (s = 0; s < 8; s++) 56 v = (v >> 1) ^ ((v & 1) * (u32_T)0xedb88320L); 57 crc_32_table[t] = v; 58 } 59 done = TRUE; 60 } 61 62 #define CRC32(c, b) (crc_32_table[((int)(c) ^ (b)) & 0xff] ^ ((c) >> 8)) 63 64 /* 65 * Return the next byte in the pseudo-random sequence. 66 */ 67 #define DECRYPT_BYTE_ZIP(keys, t) { \ 68 short_u temp = (short_u)keys[2] | 2; \ 69 t = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff); \ 70 } 71 72 /* 73 * Update the encryption keys with the next byte of plain text. 74 */ 75 #define UPDATE_KEYS_ZIP(keys, c) { \ 76 keys[0] = CRC32(keys[0], (c)); \ 77 keys[1] += keys[0] & 0xff; \ 78 keys[1] = keys[1] * 134775813L + 1; \ 79 keys[2] = CRC32(keys[2], (int)(keys[1] >> 24)); \ 80 } 81 82 /* 83 * Initialize for encryption/decryption. 84 */ 85 void 86 crypt_zip_init( 87 cryptstate_T *state, 88 char_u *key, 89 char_u *salt UNUSED, 90 int salt_len UNUSED, 91 char_u *seed UNUSED, 92 int seed_len UNUSED) 93 { 94 char_u *p; 95 zip_state_T *zs; 96 97 zs = (zip_state_T *)alloc(sizeof(zip_state_T)); 98 state->method_state = zs; 99 100 make_crc_tab(); 101 zs->keys[0] = 305419896L; 102 zs->keys[1] = 591751049L; 103 zs->keys[2] = 878082192L; 104 for (p = key; *p != NUL; ++p) 105 { 106 UPDATE_KEYS_ZIP(zs->keys, (int)*p); 107 } 108 } 109 110 /* 111 * Encrypt "from[len]" into "to[len]". 112 * "from" and "to" can be equal to encrypt in place. 113 */ 114 void 115 crypt_zip_encode( 116 cryptstate_T *state, 117 char_u *from, 118 size_t len, 119 char_u *to) 120 { 121 zip_state_T *zs = state->method_state; 122 size_t i; 123 int ztemp, t; 124 125 for (i = 0; i < len; ++i) 126 { 127 ztemp = from[i]; 128 DECRYPT_BYTE_ZIP(zs->keys, t); 129 UPDATE_KEYS_ZIP(zs->keys, ztemp); 130 to[i] = t ^ ztemp; 131 } 132 } 133 134 /* 135 * Decrypt "from[len]" into "to[len]". 136 */ 137 void 138 crypt_zip_decode( 139 cryptstate_T *state, 140 char_u *from, 141 size_t len, 142 char_u *to) 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