2 * base64 - libubox base64 functions
4 * Copyright (C) 2015 Felix Fietkau <nbd@openwrt.org>
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19 /* $OpenBSD: base64.c,v 1.7 2013/12/31 02:32:56 tedu Exp $ */
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63 #include <sys/types.h>
72 static const char Base64[] =
73 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
74 static const char Pad64 = '=';
76 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
77 The following encoding technique is taken from RFC 1521 by Borenstein
78 and Freed. It is reproduced here in a slightly edited form for
81 A 65-character subset of US-ASCII is used, enabling 6 bits to be
82 represented per printable character. (The extra 65th character, "=",
83 is used to signify a special processing function.)
85 The encoding process represents 24-bit groups of input bits as output
86 strings of 4 encoded characters. Proceeding from left to right, a
87 24-bit input group is formed by concatenating 3 8-bit input groups.
88 These 24 bits are then treated as 4 concatenated 6-bit groups, each
89 of which is translated into a single digit in the base64 alphabet.
91 Each 6-bit group is used as an index into an array of 64 printable
92 characters. The character referenced by the index is placed in the
95 Table 1: The Base64 Alphabet
97 Value Encoding Value Encoding Value Encoding Value Encoding
112 14 O 31 f 48 w (pad) =
116 Special processing is performed if fewer than 24 bits are available
117 at the end of the data being encoded. A full encoding quantum is
118 always completed at the end of a quantity. When fewer than 24 input
119 bits are available in an input group, zero bits are added (on the
120 right) to form an integral number of 6-bit groups. Padding at the
121 end of the data is performed using the '=' character.
123 Since all base64 input is an integral number of octets, only the
124 -------------------------------------------------
125 following cases can arise:
127 (1) the final quantum of encoding input is an integral
128 multiple of 24 bits; here, the final unit of encoded
129 output will be an integral multiple of 4 characters
131 (2) the final quantum of encoding input is exactly 8 bits;
132 here, the final unit of encoded output will be two
133 characters followed by two "=" padding characters, or
134 (3) the final quantum of encoding input is exactly 16 bits;
135 here, the final unit of encoded output will be three
136 characters followed by one "=" padding character.
139 int b64_encode(const void *_src, size_t srclength,
140 void *dest, size_t targsize)
142 const unsigned char *src = _src;
144 size_t datalength = 0;
145 u_char input[3] = {0};
149 assert(dest && targsize > 0);
151 while (2 < srclength) {
157 output[0] = input[0] >> 2;
158 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
159 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
160 output[3] = input[2] & 0x3f;
162 if (datalength + 4 > targsize)
164 target[datalength++] = Base64[output[0]];
165 target[datalength++] = Base64[output[1]];
166 target[datalength++] = Base64[output[2]];
167 target[datalength++] = Base64[output[3]];
170 /* Now we worry about padding. */
171 if (0 != srclength) {
172 /* Get what's left. */
173 input[0] = input[1] = input[2] = '\0';
174 for (i = 0; i < srclength; i++)
177 output[0] = input[0] >> 2;
178 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
179 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
181 if (datalength + 4 > targsize)
183 target[datalength++] = Base64[output[0]];
184 target[datalength++] = Base64[output[1]];
186 target[datalength++] = Pad64;
188 target[datalength++] = Base64[output[2]];
189 target[datalength++] = Pad64;
191 if (datalength >= targsize)
193 target[datalength] = '\0'; /* Returned value doesn't count \0. */
197 /* skips all whitespace anywhere.
198 converts characters, four at a time, starting at (or after)
199 src from base - 64 numbers into three 8 bit bytes in the target area.
200 it returns the number of data bytes stored at the target, or -1 on error.
203 int b64_decode(const void *_src, void *dest, size_t targsize)
205 const char *src = _src;
206 unsigned char *target = dest;
215 assert(dest && targsize > 0);
217 while ((ch = (unsigned char)*src++) != '\0') {
218 if (isspace(ch)) /* Skip whitespace anywhere. */
224 pos = strchr(Base64, ch);
225 if (pos == 0) /* A non-base64 character. */
231 if (tarindex >= targsize)
233 target[tarindex] = (pos - Base64) << 2;
239 if (tarindex >= targsize)
241 target[tarindex] |= (pos - Base64) >> 4;
242 nextbyte = ((pos - Base64) & 0x0f) << 4;
243 if (tarindex + 1 < targsize)
244 target[tarindex+1] = nextbyte;
253 if (tarindex >= targsize)
255 target[tarindex] |= (pos - Base64) >> 2;
256 nextbyte = ((pos - Base64) & 0x03) << 6;
257 if (tarindex + 1 < targsize)
258 target[tarindex+1] = nextbyte;
267 if (tarindex >= targsize)
269 target[tarindex] |= (pos - Base64);
278 * We are done decoding Base-64 chars. Let's see if we ended
279 * on a byte boundary, and/or with erroneous trailing characters.
282 if (ch == Pad64) { /* We got a pad char. */
283 ch = (unsigned char)*src++; /* Skip it, get next. */
285 case 0: /* Invalid = in first position */
286 case 1: /* Invalid = in second position */
289 case 2: /* Valid, means one byte of info */
290 /* Skip any number of spaces. */
291 for (; ch != '\0'; ch = (unsigned char)*src++)
294 /* Make sure there is another trailing = sign. */
297 ch = (unsigned char)*src++; /* Skip the = */
298 /* Fall through to "single trailing =" case. */
301 case 3: /* Valid, means two bytes of info */
303 * We know this char is an =. Is there anything but
304 * whitespace after it?
306 for (; ch != '\0'; ch = (unsigned char)*src++)
311 * Now make sure for cases 2 and 3 that the "extra"
312 * bits that slopped past the last full byte were
313 * zeros. If we don't check them, they become a
314 * subliminal channel.
316 if (target && tarindex < targsize &&
317 target[tarindex] != 0)
322 * We ended by seeing the end of the string. Make sure we
323 * have no partial bytes lying around.
329 /* Null-terminate if we have room left */
330 if (tarindex < targsize)
331 target[tarindex] = 0;