1 /* $OpenBSD: base64.c,v 1.8 2015/01/16 16:48:51 deraadt Exp $ */
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45 #include "got_compat.h"
47 #include <sys/types.h>
48 #include <sys/socket.h>
49 #include <netinet/in.h>
50 #include <arpa/inet.h>
51 #include <arpa/nameser.h>
60 static const char Base64[] =
61 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
62 static const char Pad64 = '=';
64 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
65 The following encoding technique is taken from RFC 1521 by Borenstein
66 and Freed. It is reproduced here in a slightly edited form for
69 A 65-character subset of US-ASCII is used, enabling 6 bits to be
70 represented per printable character. (The extra 65th character, "=",
71 is used to signify a special processing function.)
73 The encoding process represents 24-bit groups of input bits as output
74 strings of 4 encoded characters. Proceeding from left to right, a
75 24-bit input group is formed by concatenating 3 8-bit input groups.
76 These 24 bits are then treated as 4 concatenated 6-bit groups, each
77 of which is translated into a single digit in the base64 alphabet.
79 Each 6-bit group is used as an index into an array of 64 printable
80 characters. The character referenced by the index is placed in the
83 Table 1: The Base64 Alphabet
85 Value Encoding Value Encoding Value Encoding Value Encoding
100 14 O 31 f 48 w (pad) =
104 Special processing is performed if fewer than 24 bits are available
105 at the end of the data being encoded. A full encoding quantum is
106 always completed at the end of a quantity. When fewer than 24 input
107 bits are available in an input group, zero bits are added (on the
108 right) to form an integral number of 6-bit groups. Padding at the
109 end of the data is performed using the '=' character.
111 Since all base64 input is an integral number of octets, only the
112 -------------------------------------------------
113 following cases can arise:
115 (1) the final quantum of encoding input is an integral
116 multiple of 24 bits; here, the final unit of encoded
117 output will be an integral multiple of 4 characters
119 (2) the final quantum of encoding input is exactly 8 bits;
120 here, the final unit of encoded output will be two
121 characters followed by two "=" padding characters, or
122 (3) the final quantum of encoding input is exactly 16 bits;
123 here, the final unit of encoded output will be three
124 characters followed by one "=" padding character.
128 b64_ntop(src, srclength, target, targsize)
134 size_t datalength = 0;
139 while (2 < srclength) {
145 output[0] = input[0] >> 2;
146 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
147 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
148 output[3] = input[2] & 0x3f;
150 if (datalength + 4 > targsize)
152 target[datalength++] = Base64[output[0]];
153 target[datalength++] = Base64[output[1]];
154 target[datalength++] = Base64[output[2]];
155 target[datalength++] = Base64[output[3]];
158 /* Now we worry about padding. */
159 if (0 != srclength) {
160 /* Get what's left. */
161 input[0] = input[1] = input[2] = '\0';
162 for (i = 0; i < srclength; i++)
165 output[0] = input[0] >> 2;
166 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
167 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
169 if (datalength + 4 > targsize)
171 target[datalength++] = Base64[output[0]];
172 target[datalength++] = Base64[output[1]];
174 target[datalength++] = Pad64;
176 target[datalength++] = Base64[output[2]];
177 target[datalength++] = Pad64;
179 if (datalength >= targsize)
181 target[datalength] = '\0'; /* Returned value doesn't count \0. */
185 /* skips all whitespace anywhere.
186 converts characters, four at a time, starting at (or after)
187 src from base - 64 numbers into three 8 bit bytes in the target area.
188 it returns the number of data bytes stored at the target, or -1 on error.
192 b64_pton(src, target, targsize)
197 int tarindex, state, ch;
204 while ((ch = (unsigned char)*src++) != '\0') {
205 if (isspace(ch)) /* Skip whitespace anywhere. */
211 pos = strchr(Base64, ch);
212 if (pos == 0) /* A non-base64 character. */
218 if (tarindex >= targsize)
220 target[tarindex] = (pos - Base64) << 2;
226 if (tarindex >= targsize)
228 target[tarindex] |= (pos - Base64) >> 4;
229 nextbyte = ((pos - Base64) & 0x0f) << 4;
230 if (tarindex + 1 < targsize)
231 target[tarindex+1] = nextbyte;
240 if (tarindex >= targsize)
242 target[tarindex] |= (pos - Base64) >> 2;
243 nextbyte = ((pos - Base64) & 0x03) << 6;
244 if (tarindex + 1 < targsize)
245 target[tarindex+1] = nextbyte;
254 if (tarindex >= targsize)
256 target[tarindex] |= (pos - Base64);
265 * We are done decoding Base-64 chars. Let's see if we ended
266 * on a byte boundary, and/or with erroneous trailing characters.
269 if (ch == Pad64) { /* We got a pad char. */
270 ch = (unsigned char)*src++; /* Skip it, get next. */
272 case 0: /* Invalid = in first position */
273 case 1: /* Invalid = in second position */
276 case 2: /* Valid, means one byte of info */
277 /* Skip any number of spaces. */
278 for (; ch != '\0'; ch = (unsigned char)*src++)
281 /* Make sure there is another trailing = sign. */
284 ch = (unsigned char)*src++; /* Skip the = */
285 /* Fall through to "single trailing =" case. */
288 case 3: /* Valid, means two bytes of info */
290 * We know this char is an =. Is there anything but
291 * whitespace after it?
293 for (; ch != '\0'; ch = (unsigned char)*src++)
298 * Now make sure for cases 2 and 3 that the "extra"
299 * bits that slopped past the last full byte were
300 * zeros. If we don't check them, they become a
301 * subliminal channel.
303 if (target && tarindex < targsize &&
304 target[tarindex] != 0)
309 * We ended by seeing the end of the string. Make sure we
310 * have no partial bytes lying around.