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>
70 static const char Base64[] =
71 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
72 static const char Pad64 = '=';
74 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
75 The following encoding technique is taken from RFC 1521 by Borenstein
76 and Freed. It is reproduced here in a slightly edited form for
79 A 65-character subset of US-ASCII is used, enabling 6 bits to be
80 represented per printable character. (The extra 65th character, "=",
81 is used to signify a special processing function.)
83 The encoding process represents 24-bit groups of input bits as output
84 strings of 4 encoded characters. Proceeding from left to right, a
85 24-bit input group is formed by concatenating 3 8-bit input groups.
86 These 24 bits are then treated as 4 concatenated 6-bit groups, each
87 of which is translated into a single digit in the base64 alphabet.
89 Each 6-bit group is used as an index into an array of 64 printable
90 characters. The character referenced by the index is placed in the
93 Table 1: The Base64 Alphabet
95 Value Encoding Value Encoding Value Encoding Value Encoding
110 14 O 31 f 48 w (pad) =
114 Special processing is performed if fewer than 24 bits are available
115 at the end of the data being encoded. A full encoding quantum is
116 always completed at the end of a quantity. When fewer than 24 input
117 bits are available in an input group, zero bits are added (on the
118 right) to form an integral number of 6-bit groups. Padding at the
119 end of the data is performed using the '=' character.
121 Since all base64 input is an integral number of octets, only the
122 -------------------------------------------------
123 following cases can arise:
125 (1) the final quantum of encoding input is an integral
126 multiple of 24 bits; here, the final unit of encoded
127 output will be an integral multiple of 4 characters
129 (2) the final quantum of encoding input is exactly 8 bits;
130 here, the final unit of encoded output will be two
131 characters followed by two "=" padding characters, or
132 (3) the final quantum of encoding input is exactly 16 bits;
133 here, the final unit of encoded output will be three
134 characters followed by one "=" padding character.
137 int b64_encode(const void *_src, size_t srclength,
138 void *dest, size_t targsize)
140 const unsigned char *src = _src;
142 size_t datalength = 0;
147 while (2 < srclength) {
153 output[0] = input[0] >> 2;
154 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
155 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
156 output[3] = input[2] & 0x3f;
158 if (datalength + 4 > targsize)
160 target[datalength++] = Base64[output[0]];
161 target[datalength++] = Base64[output[1]];
162 target[datalength++] = Base64[output[2]];
163 target[datalength++] = Base64[output[3]];
166 /* Now we worry about padding. */
167 if (0 != srclength) {
168 /* Get what's left. */
169 input[0] = input[1] = input[2] = '\0';
170 for (i = 0; i < srclength; i++)
173 output[0] = input[0] >> 2;
174 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
175 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
177 if (datalength + 4 > targsize)
179 target[datalength++] = Base64[output[0]];
180 target[datalength++] = Base64[output[1]];
182 target[datalength++] = Pad64;
184 target[datalength++] = Base64[output[2]];
185 target[datalength++] = Pad64;
187 if (datalength >= targsize)
189 target[datalength] = '\0'; /* Returned value doesn't count \0. */
193 /* skips all whitespace anywhere.
194 converts characters, four at a time, starting at (or after)
195 src from base - 64 numbers into three 8 bit bytes in the target area.
196 it returns the number of data bytes stored at the target, or -1 on error.
199 int b64_decode(const void *_src, void *dest, size_t targsize)
201 const char *src = _src;
202 unsigned char *target = dest;
203 int tarindex, state, ch;
210 while ((ch = (unsigned char)*src++) != '\0') {
211 if (isspace(ch)) /* Skip whitespace anywhere. */
217 pos = strchr(Base64, ch);
218 if (pos == 0) /* A non-base64 character. */
224 if (tarindex >= targsize)
226 target[tarindex] = (pos - Base64) << 2;
232 if (tarindex >= targsize)
234 target[tarindex] |= (pos - Base64) >> 4;
235 nextbyte = ((pos - Base64) & 0x0f) << 4;
236 if (tarindex + 1 < targsize)
237 target[tarindex+1] = nextbyte;
246 if (tarindex >= targsize)
248 target[tarindex] |= (pos - Base64) >> 2;
249 nextbyte = ((pos - Base64) & 0x03) << 6;
250 if (tarindex + 1 < targsize)
251 target[tarindex+1] = nextbyte;
260 if (tarindex >= targsize)
262 target[tarindex] |= (pos - Base64);
271 * We are done decoding Base-64 chars. Let's see if we ended
272 * on a byte boundary, and/or with erroneous trailing characters.
275 if (ch == Pad64) { /* We got a pad char. */
276 ch = (unsigned char)*src++; /* Skip it, get next. */
278 case 0: /* Invalid = in first position */
279 case 1: /* Invalid = in second position */
282 case 2: /* Valid, means one byte of info */
283 /* Skip any number of spaces. */
284 for (; ch != '\0'; ch = (unsigned char)*src++)
287 /* Make sure there is another trailing = sign. */
290 ch = (unsigned char)*src++; /* Skip the = */
291 /* Fall through to "single trailing =" case. */
294 case 3: /* Valid, means two bytes of info */
296 * We know this char is an =. Is there anything but
297 * whitespace after it?
299 for (; ch != '\0'; ch = (unsigned char)*src++)
304 * Now make sure for cases 2 and 3 that the "extra"
305 * bits that slopped past the last full byte were
306 * zeros. If we don't check them, they become a
307 * subliminal channel.
309 if (target && tarindex < targsize &&
310 target[tarindex] != 0)
315 * We ended by seeing the end of the string. Make sure we
316 * have no partial bytes lying around.
322 /* Null-terminate if we have room left */
323 if (tarindex < targsize)
324 target[tarindex] = 0;