1 /* vi:set ts=8 sts=4 sw=4: 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 void make_crc_tab(void); 40 41 static u32_T crc_32_table[256]; 42 43 /* 44 * Fill the CRC table, if not done already. 45 */ 46 static void 47 make_crc_tab(void) 48 { 49 u32_T s, t, v; 50 static int done = FALSE; 51 52 if (done) 53 return; 54 for (t = 0; t < 256; t++) 55 { 56 v = t; 57 for (s = 0; s < 8; s++) 58 v = (v >> 1) ^ ((v & 1) * (u32_T)0xedb88320L); 59 crc_32_table[t] = v; 60 } 61 done = TRUE; 62 } 63 64 #define CRC32(c, b) (crc_32_table[((int)(c) ^ (b)) & 0xff] ^ ((c) >> 8)) 65 66 /* 67 * Return the next byte in the pseudo-random sequence. 68 */ 69 #define DECRYPT_BYTE_ZIP(keys, t) { \ 70 short_u temp = (short_u)keys[2] | 2; \ 71 t = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff); \ 72 } 73 74 /* 75 * Update the encryption keys with the next byte of plain text. 76 */ 77 #define UPDATE_KEYS_ZIP(keys, c) { \ 78 keys[0] = CRC32(keys[0], (c)); \ 79 keys[1] += keys[0] & 0xff; \ 80 keys[1] = keys[1] * 134775813L + 1; \ 81 keys[2] = CRC32(keys[2], (int)(keys[1] >> 24)); \ 82 } 83 84 /* 85 * Initialize for encryption/decryption. 86 */ 87 void 88 crypt_zip_init( 89 cryptstate_T *state, 90 char_u *key, 91 char_u *salt UNUSED, 92 int salt_len UNUSED, 93 char_u *seed UNUSED, 94 int seed_len UNUSED) 95 { 96 char_u *p; 97 zip_state_T *zs; 98 99 zs = (zip_state_T *)alloc(sizeof(zip_state_T)); 100 state->method_state = zs; 101 102 make_crc_tab(); 103 zs->keys[0] = 305419896L; 104 zs->keys[1] = 591751049L; 105 zs->keys[2] = 878082192L; 106 for (p = key; *p != NUL; ++p) 107 { 108 UPDATE_KEYS_ZIP(zs->keys, (int)*p); 109 } 110 } 111 112 /* 113 * Encrypt "from[len]" into "to[len]". 114 * "from" and "to" can be equal to encrypt in place. 115 */ 116 void 117 crypt_zip_encode( 118 cryptstate_T *state, 119 char_u *from, 120 size_t len, 121 char_u *to) 122 { 123 zip_state_T *zs = state->method_state; 124 size_t i; 125 int ztemp, t; 126 127 for (i = 0; i < len; ++i) 128 { 129 ztemp = from[i]; 130 DECRYPT_BYTE_ZIP(zs->keys, t); 131 UPDATE_KEYS_ZIP(zs->keys, ztemp); 132 to[i] = t ^ ztemp; 133 } 134 } 135 136 /* 137 * Decrypt "from[len]" into "to[len]". 138 */ 139 void 140 crypt_zip_decode( 141 cryptstate_T *state, 142 char_u *from, 143 size_t len, 144 char_u *to) 145 { 146 zip_state_T *zs = state->method_state; 147 size_t i; 148 short_u temp; 149 150 for (i = 0; i < len; ++i) 151 { 152 temp = (short_u)zs->keys[2] | 2; 153 temp = (int)(((unsigned)(temp * (temp ^ 1U)) >> 8) & 0xff); 154 UPDATE_KEYS_ZIP(zs->keys, to[i] = from[i] ^ temp); 155 } 156 } 157 158 #endif /* FEAT_CRYPT */ 159