1 /* $OpenBSD: base64.c,v 1.3 1997/11/08 20:46:55 deraadt Exp $ */
4 * Copyright (c) 1996 by Internet Software Consortium.
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21 * Portions Copyright (c) 1995 by International Business Machines, Inc.
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25 * Software with or without fee, provided that the above copyright notice and
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33 * the extent that such products are used for performing Domain Name System
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49 #include <sys/types.h>
50 #include <sys/param.h>
51 #include <sys/socket.h>
52 #include <netinet/in.h>
53 #include <arpa/inet.h>
62 #define Assert(Cond) if (!(Cond)) abort()
64 static const char Base64[] =
65 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
66 static const char Pad64 = '=';
68 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
69 The following encoding technique is taken from RFC 1521 by Borenstein
70 and Freed. It is reproduced here in a slightly edited form for
73 A 65-character subset of US-ASCII is used, enabling 6 bits to be
74 represented per printable character. (The extra 65th character, "=",
75 is used to signify a special processing function.)
77 The encoding process represents 24-bit groups of input bits as output
78 strings of 4 encoded characters. Proceeding from left to right, a
79 24-bit input group is formed by concatenating 3 8-bit input groups.
80 These 24 bits are then treated as 4 concatenated 6-bit groups, each
81 of which is translated into a single digit in the base64 alphabet.
83 Each 6-bit group is used as an index into an array of 64 printable
84 characters. The character referenced by the index is placed in the
87 Table 1: The Base64 Alphabet
89 Value Encoding Value Encoding Value Encoding Value Encoding
104 14 O 31 f 48 w (pad) =
108 Special processing is performed if fewer than 24 bits are available
109 at the end of the data being encoded. A full encoding quantum is
110 always completed at the end of a quantity. When fewer than 24 input
111 bits are available in an input group, zero bits are added (on the
112 right) to form an integral number of 6-bit groups. Padding at the
113 end of the data is performed using the '=' character.
115 Since all base64 input is an integral number of octets, only the
116 -------------------------------------------------
117 following cases can arise:
119 (1) the final quantum of encoding input is an integral
120 multiple of 24 bits; here, the final unit of encoded
121 output will be an integral multiple of 4 characters
123 (2) the final quantum of encoding input is exactly 8 bits;
124 here, the final unit of encoded output will be two
125 characters followed by two "=" padding characters, or
126 (3) the final quantum of encoding input is exactly 16 bits;
127 here, the final unit of encoded output will be three
128 characters followed by one "=" padding character.
132 b64_ntop(u_char const *src, size_t srclength, char *target, size_t 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;
149 Assert(output[0] < 64);
150 Assert(output[1] < 64);
151 Assert(output[2] < 64);
152 Assert(output[3] < 64);
154 if (datalength + 4 > targsize)
156 target[datalength++] = Base64[output[0]];
157 target[datalength++] = Base64[output[1]];
158 target[datalength++] = Base64[output[2]];
159 target[datalength++] = Base64[output[3]];
162 /* Now we worry about padding. */
163 if (0 != srclength) {
164 /* Get what's left. */
165 input[0] = input[1] = input[2] = '\0';
166 for (i = 0; i < srclength; i++)
169 output[0] = input[0] >> 2;
170 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
171 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
172 Assert(output[0] < 64);
173 Assert(output[1] < 64);
174 Assert(output[2] < 64);
176 if (datalength + 4 > targsize)
178 target[datalength++] = Base64[output[0]];
179 target[datalength++] = Base64[output[1]];
181 target[datalength++] = Pad64;
183 target[datalength++] = Base64[output[2]];
184 target[datalength++] = Pad64;
186 if (datalength >= targsize)
188 target[datalength] = '\0'; /* Returned value doesn't count \0. */
192 /* skips all whitespace anywhere.
193 converts characters, four at a time, starting at (or after)
194 src from base - 64 numbers into three 8 bit bytes in the target area.
195 it returns the number of data bytes stored at the target, or -1 on error.
199 b64_pton(char const *src, u_char *target, size_t targsize)
201 int tarindex, state, ch;
207 while ((ch = *src++) != '\0') {
208 if (isspace(ch)) /* Skip whitespace anywhere. */
214 pos = strchr(Base64, ch);
215 if (pos == 0) /* A non-base64 character. */
221 if (tarindex >= targsize)
223 target[tarindex] = (pos - Base64) << 2;
229 if (tarindex + 1 >= targsize)
231 target[tarindex] |= (pos - Base64) >> 4;
232 target[tarindex+1] = ((pos - Base64) & 0x0f)
240 if (tarindex + 1 >= targsize)
242 target[tarindex] |= (pos - Base64) >> 2;
243 target[tarindex+1] = ((pos - Base64) & 0x03)
251 if (tarindex >= targsize)
253 target[tarindex] |= (pos - Base64);
262 * We are done decoding Base-64 chars. Let's see if we ended
263 * on a byte boundary, and/or with erroneous trailing characters.
266 if (ch == Pad64) { /* We got a pad char. */
267 ch = *src++; /* Skip it, get next. */
269 case 0: /* Invalid = in first position */
270 case 1: /* Invalid = in second position */
273 case 2: /* Valid, means one byte of info */
274 /* Skip any number of spaces. */
275 for (; ch != '\0'; ch = *src++)
278 /* Make sure there is another trailing = sign. */
281 ch = *src++; /* Skip the = */
282 /* Fall through to "single trailing =" case. */
285 case 3: /* Valid, means two bytes of info */
287 * We know this char is an =. Is there anything but
288 * whitespace after it?
290 for (; ch != '\0'; ch = *src++)
295 * Now make sure for cases 2 and 3 that the "extra"
296 * bits that slopped past the last full byte were
297 * zeros. If we don't check them, they become a
298 * subliminal channel.
300 if (target && target[tarindex] != 0)
305 * We ended by seeing the end of the string. Make sure we
306 * have no partial bytes lying around.
315 #endif /* HAVE_B64_NTOP */