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d7d7b7b9 | 1 | /* $Cambridge: exim/src/src/auths/b64decode.c,v 1.3 2006/02/07 11:19:01 ph10 Exp $ */ |
0756eb3c PH |
2 | |
3 | /************************************************* | |
4 | * Exim - an Internet mail transport agent * | |
5 | *************************************************/ | |
6 | ||
d7d7b7b9 | 7 | /* Copyright (c) University of Cambridge 1995 - 2006 */ |
0756eb3c PH |
8 | /* See the file NOTICE for conditions of use and distribution. */ |
9 | ||
10 | #include "../exim.h" | |
11 | ||
12 | ||
13 | /************************************************* | |
14 | * Decode byte-string in base 64 * | |
15 | *************************************************/ | |
16 | ||
17 | /* This function decodes a string in base 64 format as defined in RFC 2045 | |
18 | (MIME) and required by the SMTP AUTH extension (RFC 2554). The decoding | |
19 | algorithm is written out in a straightforward way. Turning it into some kind of | |
20 | compact loop is messy and would probably run more slowly. | |
21 | ||
22 | Arguments: | |
23 | code points to the coded string, zero-terminated | |
24 | ptr where to put the pointer to the result, which is in | |
25 | dynamic store | |
26 | ||
27 | Returns: the number of bytes in the result, | |
28 | or -1 if the input was malformed | |
29 | ||
30 | A zero is added on to the end to make it easy in cases where the result is to | |
31 | be interpreted as text. This is not included in the count. */ | |
32 | ||
33 | static uschar dec64table[] = { | |
34 | 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 0-15 */ | |
35 | 255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255, /* 16-31 */ | |
36 | 255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63, /* 32-47 */ | |
37 | 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,255,255,255, /* 48-63 */ | |
38 | 255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 64-79 */ | |
39 | 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255, /* 80-95 */ | |
40 | 255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, /* 96-111 */ | |
41 | 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255 /* 112-127*/ | |
42 | }; | |
43 | ||
44 | int | |
45 | auth_b64decode(uschar *code, uschar **ptr) | |
46 | { | |
47 | register int x, y; | |
48 | uschar *result = store_get(3*(Ustrlen(code)/4) + 1); | |
49 | ||
50 | *ptr = result; | |
51 | ||
52 | /* Each cycle of the loop handles a quantum of 4 input bytes. For the last | |
53 | quantum this may decode to 1, 2, or 3 output bytes. */ | |
54 | ||
55 | while ((x = (*code++)) != 0) | |
56 | { | |
57 | if (x > 127 || (x = dec64table[x]) == 255) return -1; | |
58 | if ((y = (*code++)) == 0 || (y = dec64table[y]) == 255) | |
59 | return -1; | |
60 | *result++ = (x << 2) | (y >> 4); | |
61 | ||
62 | if ((x = (*code++)) == '=') | |
63 | { | |
64 | if (*code++ != '=' || *code != 0) return -1; | |
65 | } | |
66 | else | |
67 | { | |
68 | if (x > 127 || (x = dec64table[x]) == 255) return -1; | |
69 | *result++ = (y << 4) | (x >> 2); | |
70 | if ((y = (*code++)) == '=') | |
71 | { | |
72 | if (*code != 0) return -1; | |
73 | } | |
74 | else | |
75 | { | |
76 | if (y > 127 || (y = dec64table[y]) == 255) return -1; | |
77 | *result++ = (x << 6) | y; | |
78 | } | |
79 | } | |
80 | } | |
81 | ||
82 | *result = 0; | |
83 | return result - *ptr; | |
84 | } | |
85 | ||
86 | /* End of b64decode.c */ |