2 * Modified by Kurt D. Zeilenga for inclusion into OpenLDAP
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50 #include <sys/types.h>
54 #define Assert(Cond) if (!(Cond)) abort()
56 static const char Base64[] =
57 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
58 static const char Pad64 = '=';
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
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.)
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.
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
79 Table 1: The Base64 Alphabet
81 Value Encoding Value Encoding Value Encoding Value Encoding
96 14 O 31 f 48 w (pad) =
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.
107 Since all base64 input is an integral number of octets, only the
108 -------------------------------------------------
109 following cases can arise:
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
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.
130 size_t datalength = 0;
135 while (2 < srclength) {
141 output[0] = input[0] >> 2;
142 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
143 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
144 output[3] = input[2] & 0x3f;
145 Assert(output[0] < 64);
146 Assert(output[1] < 64);
147 Assert(output[2] < 64);
148 Assert(output[3] < 64);
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);
168 Assert(output[0] < 64);
169 Assert(output[1] < 64);
170 Assert(output[2] < 64);
172 if (datalength + 4 > targsize)
174 target[datalength++] = Base64[output[0]];
175 target[datalength++] = Base64[output[1]];
177 target[datalength++] = Pad64;
179 target[datalength++] = Base64[output[2]];
180 target[datalength++] = Pad64;
182 if (datalength >= targsize)
184 target[datalength] = '\0'; /* Returned value doesn't count \0. */
188 /* skips all whitespace anywhere.
189 converts characters, four at a time, starting at (or after)
190 src from base - 64 numbers into three 8 bit bytes in the target area.
191 it returns the number of data bytes stored at the target, or -1 on error.
200 int tarindex, state, ch;
206 while ((ch = *src++) != '\0') {
207 if (isspace(ch)) /* Skip whitespace anywhere. */
213 pos = strchr(Base64, ch);
214 if (pos == 0) /* A non-base64 character. */
220 if ((size_t)tarindex >= targsize)
222 target[tarindex] = (pos - Base64) << 2;
228 if ((size_t)tarindex + 1 >= targsize)
230 target[tarindex] |= (pos - Base64) >> 4;
231 target[tarindex+1] = ((pos - Base64) & 0x0f)
239 if ((size_t)tarindex + 1 >= targsize)
241 target[tarindex] |= (pos - Base64) >> 2;
242 target[tarindex+1] = ((pos - Base64) & 0x03)
250 if ((size_t)tarindex >= targsize)
252 target[tarindex] |= (pos - Base64);
263 * We are done decoding Base-64 chars. Let's see if we ended
264 * on a byte boundary, and/or with erroneous trailing characters.
267 if (ch == Pad64) { /* We got a pad char. */
268 ch = *src++; /* Skip it, get next. */
270 case 0: /* Invalid = in first position */
271 case 1: /* Invalid = in second position */
274 case 2: /* Valid, means one byte of info */
275 /* Skip any number of spaces. */
276 for ((void)NULL; ch != '\0'; ch = *src++)
279 /* Make sure there is another trailing = sign. */
282 ch = *src++; /* Skip the = */
283 /* Fall through to "single trailing =" case. */
286 case 3: /* Valid, means two bytes of info */
288 * We know this char is an =. Is there anything but
289 * whitespace after it?
291 for ((void)NULL; ch != '\0'; ch = *src++)
296 * Now make sure for cases 2 and 3 that the "extra"
297 * bits that slopped past the last full byte were
298 * zeros. If we don't check them, they become a
299 * subliminal channel.
301 if (target && target[tarindex] != 0)
306 * We ended by seeing the end of the string. Make sure we
307 * have no partial bytes lying around.