1 /* $OpenBSD: base64.c,v 1.15 2021/10/25 14:41:09 jca Exp $ */
2
3 /*
4 * Copyright (c) 1996 by Internet Software Consortium.
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
11 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
12 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
13 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
14 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
15 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
16 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
17 * SOFTWARE.
18 */
19
20 /*
21 * Portions Copyright (c) 1995 by International Business Machines, Inc.
22 *
23 * International Business Machines, Inc. (hereinafter called IBM) grants
24 * permission under its copyrights to use, copy, modify, and distribute this
25 * Software with or without fee, provided that the above copyright notice and
26 * all paragraphs of this notice appear in all copies, and that the name of IBM
27 * not be used in connection with the marketing of any product incorporating
28 * the Software or modifications thereof, without specific, written prior
29 * permission.
30 *
31 * To the extent it has a right to do so, IBM grants an immunity from suit
32 * under its patents, if any, for the use, sale or manufacture of products to
33 * the extent that such products are used for performing Domain Name System
34 * dynamic updates in TCP/IP networks by means of the Software. No immunity is
35 * granted for any product per se or for any other function of any product.
36 *
37 * THE SOFTWARE IS PROVIDED "AS IS", AND IBM DISCLAIMS ALL WARRANTIES,
38 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
39 * PARTICULAR PURPOSE. IN NO EVENT SHALL IBM BE LIABLE FOR ANY SPECIAL,
40 * DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER ARISING
41 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE, EVEN
42 * IF IBM IS APPRISED OF THE POSSIBILITY OF SUCH DAMAGES.
43 */
44
45 #include <sys/types.h>
46 #include <sys/socket.h>
47 #include <netinet/in.h>
48 #include <arpa/inet.h>
49
50 #include <ctype.h>
51 #include <resolv.h>
52
53 #include <stdlib.h>
54 #include <string.h>
55
56 static const char Base64[] =
57 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
58 static const char Pad64 = '=';
59
60 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
61 The following encoding technique is taken from RFC 1521 by Borenstein
62 and Freed. It is reproduced here in a slightly edited form for
63 convenience.
64
65 A 65-character subset of US-ASCII is used, enabling 6 bits to be
66 represented per printable character. (The extra 65th character, "=",
67 is used to signify a special processing function.)
68
69 The encoding process represents 24-bit groups of input bits as output
70 strings of 4 encoded characters. Proceeding from left to right, a
71 24-bit input group is formed by concatenating 3 8-bit input groups.
72 These 24 bits are then treated as 4 concatenated 6-bit groups, each
73 of which is translated into a single digit in the base64 alphabet.
74
75 Each 6-bit group is used as an index into an array of 64 printable
76 characters. The character referenced by the index is placed in the
77 output string.
78
79 Table 1: The Base64 Alphabet
80
81 Value Encoding Value Encoding Value Encoding Value Encoding
82 0 A 17 R 34 i 51 z
83 1 B 18 S 35 j 52 0
84 2 C 19 T 36 k 53 1
85 3 D 20 U 37 l 54 2
86 4 E 21 V 38 m 55 3
87 5 F 22 W 39 n 56 4
88 6 G 23 X 40 o 57 5
89 7 H 24 Y 41 p 58 6
90 8 I 25 Z 42 q 59 7
91 9 J 26 a 43 r 60 8
92 10 K 27 b 44 s 61 9
93 11 L 28 c 45 t 62 +
94 12 M 29 d 46 u 63 /
95 13 N 30 e 47 v
96 14 O 31 f 48 w (pad) =
97 15 P 32 g 49 x
98 16 Q 33 h 50 y
99
100 Special processing is performed if fewer than 24 bits are available
101 at the end of the data being encoded. A full encoding quantum is
102 always completed at the end of a quantity. When fewer than 24 input
103 bits are available in an input group, zero bits are added (on the
104 right) to form an integral number of 6-bit groups. Padding at the
105 end of the data is performed using the '=' character.
106
107 Since all base64 input is an integral number of octets, only the
108 -------------------------------------------------
109 following cases can arise:
110
111 (1) the final quantum of encoding input is an integral
112 multiple of 24 bits; here, the final unit of encoded
113 output will be an integral multiple of 4 characters
114 with no "=" padding,
115 (2) the final quantum of encoding input is exactly 8 bits;
116 here, the final unit of encoded output will be two
117 characters followed by two "=" padding characters, or
118 (3) the final quantum of encoding input is exactly 16 bits;
119 here, the final unit of encoded output will be three
120 characters followed by one "=" padding character.
121 */
122
123 int
b64_ntop(unsigned char const * src,size_t srclength,char * target,size_t targsize)124 b64_ntop(unsigned char const *src, size_t srclength, char *target,
125 size_t targsize)
126 {
127 size_t datalength = 0;
128 unsigned char input[3];
129 unsigned char output[4];
130 int i;
131
132 while (2 < srclength) {
133 input[0] = *src++;
134 input[1] = *src++;
135 input[2] = *src++;
136 srclength -= 3;
137
138 output[0] = input[0] >> 2;
139 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
140 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
141 output[3] = input[2] & 0x3f;
142
143 if (datalength + 4 > targsize)
144 return (-1);
145 target[datalength++] = Base64[output[0]];
146 target[datalength++] = Base64[output[1]];
147 target[datalength++] = Base64[output[2]];
148 target[datalength++] = Base64[output[3]];
149 }
150
151 /* Now we worry about padding. */
152 if (0 != srclength) {
153 /* Get what's left. */
154 input[0] = input[1] = input[2] = '\0';
155 for (i = 0; i < srclength; i++)
156 input[i] = *src++;
157
158 output[0] = input[0] >> 2;
159 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
160 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
161
162 if (datalength + 4 > targsize)
163 return (-1);
164 target[datalength++] = Base64[output[0]];
165 target[datalength++] = Base64[output[1]];
166 if (srclength == 1)
167 target[datalength++] = Pad64;
168 else
169 target[datalength++] = Base64[output[2]];
170 target[datalength++] = Pad64;
171 }
172 if (datalength >= targsize)
173 return (-1);
174 target[datalength] = '\0'; /* Returned value doesn't count \0. */
175 return (datalength);
176 }
177
178 /* skips all whitespace anywhere.
179 converts characters, four at a time, starting at (or after)
180 src from base - 64 numbers into three 8 bit bytes in the target area.
181 it returns the number of data bytes stored at the target, or -1 on error.
182 */
183
184 int
b64_pton(char const * src,unsigned char * target,size_t targsize)185 b64_pton(char const *src, unsigned char *target, size_t targsize)
186 {
187 int tarindex, state, ch;
188 unsigned char nextbyte;
189 char *pos;
190
191 state = 0;
192 tarindex = 0;
193
194 while ((ch = (unsigned char)*src++) != '\0') {
195 if (isspace(ch)) /* Skip whitespace anywhere. */
196 continue;
197
198 if (ch == Pad64)
199 break;
200
201 pos = strchr(Base64, ch);
202 if (pos == 0) /* A non-base64 character. */
203 return (-1);
204
205 switch (state) {
206 case 0:
207 if (target) {
208 if (tarindex >= targsize)
209 return (-1);
210 target[tarindex] = (pos - Base64) << 2;
211 }
212 state = 1;
213 break;
214 case 1:
215 if (target) {
216 if (tarindex >= targsize)
217 return (-1);
218 target[tarindex] |= (pos - Base64) >> 4;
219 nextbyte = ((pos - Base64) & 0x0f) << 4;
220 if (tarindex + 1 < targsize)
221 target[tarindex+1] = nextbyte;
222 else if (nextbyte)
223 return (-1);
224 }
225 tarindex++;
226 state = 2;
227 break;
228 case 2:
229 if (target) {
230 if (tarindex >= targsize)
231 return (-1);
232 target[tarindex] |= (pos - Base64) >> 2;
233 nextbyte = ((pos - Base64) & 0x03) << 6;
234 if (tarindex + 1 < targsize)
235 target[tarindex+1] = nextbyte;
236 else if (nextbyte)
237 return (-1);
238 }
239 tarindex++;
240 state = 3;
241 break;
242 case 3:
243 if (target) {
244 if (tarindex >= targsize)
245 return (-1);
246 target[tarindex] |= (pos - Base64);
247 }
248 tarindex++;
249 state = 0;
250 break;
251 }
252 }
253
254 /*
255 * We are done decoding Base-64 chars. Let's see if we ended
256 * on a byte boundary, and/or with erroneous trailing characters.
257 */
258
259 if (ch == Pad64) { /* We got a pad char. */
260 ch = (unsigned char)*src++; /* Skip it, get next. */
261 switch (state) {
262 case 0: /* Invalid = in first position */
263 case 1: /* Invalid = in second position */
264 return (-1);
265
266 case 2: /* Valid, means one byte of info */
267 /* Skip any number of spaces. */
268 for (; ch != '\0'; ch = (unsigned char)*src++)
269 if (!isspace(ch))
270 break;
271 /* Make sure there is another trailing = sign. */
272 if (ch != Pad64)
273 return (-1);
274 ch = (unsigned char)*src++; /* Skip the = */
275 /* Fall through to "single trailing =" case. */
276 /* FALLTHROUGH */
277
278 case 3: /* Valid, means two bytes of info */
279 /*
280 * We know this char is an =. Is there anything but
281 * whitespace after it?
282 */
283 for (; ch != '\0'; ch = (unsigned char)*src++)
284 if (!isspace(ch))
285 return (-1);
286
287 /*
288 * Now make sure for cases 2 and 3 that the "extra"
289 * bits that slopped past the last full byte were
290 * zeros. If we don't check them, they become a
291 * subliminal channel.
292 */
293 if (target && tarindex < targsize &&
294 target[tarindex] != 0)
295 return (-1);
296 }
297 } else {
298 /*
299 * We ended by seeing the end of the string. Make sure we
300 * have no partial bytes lying around.
301 */
302 if (state != 0)
303 return (-1);
304 }
305
306 return (tarindex);
307 }
308