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@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@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 */
base64_decode(const unsigned char * in,unsigned long inlen,unsigned char * out,unsigned long * outlen)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