2 * Modified by Kurt D. Zeilenga for inclusion into OpenLDAP
6 * Copyright (c) 1996, 1998 by Internet Software Consortium.
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52 #include <ac/string.h>
54 /* include socket.h to get sys/types.h and/or winsock2.h */
55 #include <ac/socket.h>
59 #define Assert(Cond) if (!(Cond)) abort()
61 static const char Base64[] =
62 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
63 static const char Pad64 = '=';
65 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
66 The following encoding technique is taken from RFC 1521 by Borenstein
67 and Freed. It is reproduced here in a slightly edited form for
70 A 65-character subset of US-ASCII is used, enabling 6 bits to be
71 represented per printable character. (The extra 65th character, "=",
72 is used to signify a special processing function.)
74 The encoding process represents 24-bit groups of input bits as output
75 strings of 4 encoded characters. Proceeding from left to right, a
76 24-bit input group is formed by concatenating 3 8-bit input groups.
77 These 24 bits are then treated as 4 concatenated 6-bit groups, each
78 of which is translated into a single digit in the base64 alphabet.
80 Each 6-bit group is used as an index into an array of 64 printable
81 characters. The character referenced by the index is placed in the
84 Table 1: The Base64 Alphabet
86 Value Encoding Value Encoding Value Encoding Value Encoding
101 14 O 31 f 48 w (pad) =
105 Special processing is performed if fewer than 24 bits are available
106 at the end of the data being encoded. A full encoding quantum is
107 always completed at the end of a quantity. When fewer than 24 input
108 bits are available in an input group, zero bits are added (on the
109 right) to form an integral number of 6-bit groups. Padding at the
110 end of the data is performed using the '=' character.
112 Since all base64 input is an integral number of octets, only the
113 -------------------------------------------------
114 following cases can arise:
116 (1) the final quantum of encoding input is an integral
117 multiple of 24 bits; here, the final unit of encoded
118 output will be an integral multiple of 4 characters
120 (2) the final quantum of encoding input is exactly 8 bits;
121 here, the final unit of encoded output will be two
122 characters followed by two "=" padding characters, or
123 (3) the final quantum of encoding input is exactly 16 bits;
124 here, the final unit of encoded output will be three
125 characters followed by one "=" padding character.
135 size_t datalength = 0;
140 while (2 < srclength) {
146 output[0] = input[0] >> 2;
147 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
148 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
149 output[3] = input[2] & 0x3f;
150 Assert(output[0] < 64);
151 Assert(output[1] < 64);
152 Assert(output[2] < 64);
153 Assert(output[3] < 64);
155 if (datalength + 4 > targsize)
157 target[datalength++] = Base64[output[0]];
158 target[datalength++] = Base64[output[1]];
159 target[datalength++] = Base64[output[2]];
160 target[datalength++] = Base64[output[3]];
163 /* Now we worry about padding. */
164 if (0 != srclength) {
165 /* Get what's left. */
166 input[0] = input[1] = input[2] = '\0';
167 for (i = 0; i < srclength; i++)
170 output[0] = input[0] >> 2;
171 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
172 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
173 Assert(output[0] < 64);
174 Assert(output[1] < 64);
175 Assert(output[2] < 64);
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.
205 int tarindex, state, ch;
211 while ((ch = *src++) != '\0') {
212 if (isspace(ch)) /* Skip whitespace anywhere. */
218 pos = strchr(Base64, ch);
219 if (pos == 0) /* A non-base64 character. */
225 if ((size_t)tarindex >= targsize)
227 target[tarindex] = (pos - Base64) << 2;
233 if ((size_t)tarindex + 1 >= targsize)
235 target[tarindex] |= (pos - Base64) >> 4;
236 target[tarindex+1] = ((pos - Base64) & 0x0f)
244 if ((size_t)tarindex + 1 >= targsize)
246 target[tarindex] |= (pos - Base64) >> 2;
247 target[tarindex+1] = ((pos - Base64) & 0x03)
255 if ((size_t)tarindex >= targsize)
257 target[tarindex] |= (pos - Base64);
268 * We are done decoding Base-64 chars. Let's see if we ended
269 * on a byte boundary, and/or with erroneous trailing characters.
272 if (ch == Pad64) { /* We got a pad char. */
273 ch = *src++; /* Skip it, get next. */
275 case 0: /* Invalid = in first position */
276 case 1: /* Invalid = in second position */
279 case 2: /* Valid, means one byte of info */
280 /* Skip any number of spaces. */
281 for ((void)NULL; ch != '\0'; ch = *src++)
284 /* Make sure there is another trailing = sign. */
287 ch = *src++; /* Skip the = */
288 /* Fall through to "single trailing =" case. */
291 case 3: /* Valid, means two bytes of info */
293 * We know this char is an =. Is there anything but
294 * whitespace after it?
296 for ((void)NULL; ch != '\0'; ch = *src++)
301 * Now make sure for cases 2 and 3 that the "extra"
302 * bits that slopped past the last full byte were
303 * zeros. If we don't check them, they become a
304 * subliminal channel.
306 if (target && target[tarindex] != 0)
311 * We ended by seeing the end of the string. Make sure we
312 * have no partial bytes lying around.