1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 /* util/support/base64.c - base64 encoder and decoder */
3 /*
4 * Copyright (c) 1995-2001 Kungliga Tekniska Högskolan
5 * (Royal Institute of Technology, Stockholm, Sweden).
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * 3. Neither the name of the Institute nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36 #include <k5-platform.h>
37 #include <k5-base64.h>
38
39 static const char base64_chars[] =
40 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
41
42 char *
k5_base64_encode(const void * data,size_t len)43 k5_base64_encode(const void *data, size_t len)
44 {
45 char *s, *p;
46 size_t i;
47 unsigned int c;
48 const unsigned char *q;
49
50 if (len > SIZE_MAX / 4)
51 return NULL;
52
53 p = s = malloc(len * 4 / 3 + 4);
54 if (p == NULL)
55 return NULL;
56 q = (const unsigned char *)data;
57
58 for (i = 0; i < len;) {
59 c = q[i++];
60 c *= 256;
61 if (i < len)
62 c += q[i];
63 i++;
64 c *= 256;
65 if (i < len)
66 c += q[i];
67 i++;
68 p[0] = base64_chars[(c & 0x00fc0000) >> 18];
69 p[1] = base64_chars[(c & 0x0003f000) >> 12];
70 p[2] = base64_chars[(c & 0x00000fc0) >> 6];
71 p[3] = base64_chars[(c & 0x0000003f) >> 0];
72 if (i > len)
73 p[3] = '=';
74 if (i > len + 1)
75 p[2] = '=';
76 p += 4;
77 }
78 *p = '\0';
79 return s;
80 }
81
82 #define DECODE_ERROR 0xffffffff
83
84 /* Decode token, which must be four bytes long. */
85 static unsigned int
decode_token(const char * token)86 decode_token(const char *token)
87 {
88 int i, marker = 0;
89 unsigned int val = 0;
90 const char *p;
91
92 for (i = 0; i < 4; i++) {
93 val *= 64;
94 if (token[i] == '=') {
95 marker++;
96 } else if (marker > 0) {
97 return DECODE_ERROR;
98 } else {
99 p = strchr(base64_chars, token[i]);
100 if (p == NULL)
101 return DECODE_ERROR;
102 val += p - base64_chars;
103 }
104 }
105 if (marker > 2)
106 return DECODE_ERROR;
107 return (marker << 24) | val;
108 }
109
110 void *
k5_base64_decode(const char * str,size_t * len_out)111 k5_base64_decode(const char *str, size_t *len_out)
112 {
113 unsigned char *data, *q;
114 unsigned int val, marker;
115 size_t len;
116
117 *len_out = SIZE_MAX;
118
119 /* Allocate the output buffer. */
120 len = strlen(str);
121 if (len % 4)
122 return NULL;
123 q = data = malloc(len / 4 * 3);
124 if (data == NULL) {
125 *len_out = 0;
126 return NULL;
127 }
128
129 /* Decode the string. */
130 for (; *str != '\0'; str += 4) {
131 val = decode_token(str);
132 if (val == DECODE_ERROR) {
133 free(data);
134 return NULL;
135 }
136 marker = (val >> 24) & 0xff;
137 *q++ = (val >> 16) & 0xff;
138 if (marker < 2)
139 *q++ = (val >> 8) & 0xff;
140 if (marker < 1)
141 *q++ = val & 0xff;
142 }
143 *len_out = q - data;
144 return data;
145 }
146