1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis 2 * 3 * LibTomCrypt is a library that provides various cryptographic 4 * algorithms in a highly modular and flexible manner. 5 * 6 * The library is free for all purposes without any express 7 * guarantee it works. 8 * 9 * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 #include "tomcrypt.h" 12 13 /** 14 @file base64_decode.c 15 Compliant base64 code donated by Wayne Scott (wscott (at) bitmover.com) 16 */ 17 18 19 #ifdef BASE64 20 21 static const unsigned char map[256] = { 22 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 23 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 24 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 25 255, 255, 255, 255, 255, 255, 255, 62, 255, 255, 255, 63, 26 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255, 255, 27 255, 254, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6, 28 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 29 19, 20, 21, 22, 23, 24, 25, 255, 255, 255, 255, 255, 30 255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 31 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 32 49, 50, 51, 255, 255, 255, 255, 255, 255, 255, 255, 255, 33 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 34 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 35 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 36 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 37 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 38 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 39 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 40 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 41 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 42 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 43 255, 255, 255, 255 }; 44 45 /** 46 base64 decode a block of memory 47 @param in The base64 data to decode 48 @param inlen The length of the base64 data 49 @param out [out] The destination of the binary decoded data 50 @param outlen [in/out] The max size and resulting size of the decoded data 51 @return CRYPT_OK if successful 52 */ 53 int base64_decode(const unsigned char *in, unsigned long inlen, 54 unsigned char *out, unsigned long *outlen) 55 { 56 unsigned long t, x, y, z; 57 unsigned char c; 58 int g; 59 60 LTC_ARGCHK(in != NULL); 61 LTC_ARGCHK(out != NULL); 62 LTC_ARGCHK(outlen != NULL); 63 64 g = 3; 65 for (x = y = z = t = 0; x < inlen; x++) { 66 c = map[in[x]&0xFF]; 67 if (c == 255) continue; 68 /* the final = symbols are read and used to trim the remaining bytes */ 69 if (c == 254) { 70 c = 0; 71 /* prevent g < 0 which would potentially allow an overflow later */ 72 if (--g < 0) { 73 return CRYPT_INVALID_PACKET; 74 } 75 } else if (g != 3) { 76 /* we only allow = to be at the end */ 77 return CRYPT_INVALID_PACKET; 78 } 79 80 t = (t<<6)|c; 81 82 if (++y == 4) { 83 if (z + g > *outlen) { 84 return CRYPT_BUFFER_OVERFLOW; 85 } 86 out[z++] = (unsigned char)((t>>16)&255); 87 if (g > 1) out[z++] = (unsigned char)((t>>8)&255); 88 if (g > 2) out[z++] = (unsigned char)(t&255); 89 y = t = 0; 90 } 91 } 92 if (y != 0) { 93 return CRYPT_INVALID_PACKET; 94 } 95 *outlen = z; 96 return CRYPT_OK; 97 } 98 99 #endif 100 101 102 /* $Source: /cvs/libtom/libtomcrypt/src/misc/base64/base64_decode.c,v $ */ 103 /* $Revision: 1.4 $ */ 104 /* $Date: 2006/03/31 14:15:35 $ */ 105
