1 /* $OpenBSD: base64.c,v 1.4 2002/01/02 23:00:10 deraadt Exp $ */
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47 #if !defined(HAVE_B64_NTOP) && !defined(HAVE___B64_NTOP)
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>
63 /* XXX abort illegal in library */
64 #define Assert(Cond) if (!(Cond)) abort()
66 static const char Base64[] =
67 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
68 static const char Pad64 = '=';
70 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
71 The following encoding technique is taken from RFC 1521 by Borenstein
72 and Freed. It is reproduced here in a slightly edited form for
75 A 65-character subset of US-ASCII is used, enabling 6 bits to be
76 represented per printable character. (The extra 65th character, "=",
77 is used to signify a special processing function.)
79 The encoding process represents 24-bit groups of input bits as output
80 strings of 4 encoded characters. Proceeding from left to right, a
81 24-bit input group is formed by concatenating 3 8-bit input groups.
82 These 24 bits are then treated as 4 concatenated 6-bit groups, each
83 of which is translated into a single digit in the base64 alphabet.
85 Each 6-bit group is used as an index into an array of 64 printable
86 characters. The character referenced by the index is placed in the
89 Table 1: The Base64 Alphabet
91 Value Encoding Value Encoding Value Encoding Value Encoding
106 14 O 31 f 48 w (pad) =
110 Special processing is performed if fewer than 24 bits are available
111 at the end of the data being encoded. A full encoding quantum is
112 always completed at the end of a quantity. When fewer than 24 input
113 bits are available in an input group, zero bits are added (on the
114 right) to form an integral number of 6-bit groups. Padding at the
115 end of the data is performed using the '=' character.
117 Since all base64 input is an integral number of octets, only the
118 -------------------------------------------------
119 following cases can arise:
121 (1) the final quantum of encoding input is an integral
122 multiple of 24 bits; here, the final unit of encoded
123 output will be an integral multiple of 4 characters
125 (2) the final quantum of encoding input is exactly 8 bits;
126 here, the final unit of encoded output will be two
127 characters followed by two "=" padding characters, or
128 (3) the final quantum of encoding input is exactly 16 bits;
129 here, the final unit of encoded output will be three
130 characters followed by one "=" padding character.
134 b64_ntop(u_char const *src, size_t srclength, char *target, size_t targsize)
136 size_t datalength = 0;
141 while (2 < srclength) {
147 output[0] = input[0] >> 2;
148 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
149 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
150 output[3] = input[2] & 0x3f;
151 Assert(output[0] < 64);
152 Assert(output[1] < 64);
153 Assert(output[2] < 64);
154 Assert(output[3] < 64);
156 if (datalength + 4 > targsize)
158 target[datalength++] = Base64[output[0]];
159 target[datalength++] = Base64[output[1]];
160 target[datalength++] = Base64[output[2]];
161 target[datalength++] = Base64[output[3]];
164 /* Now we worry about padding. */
165 if (0 != srclength) {
166 /* Get what's left. */
167 input[0] = input[1] = input[2] = '\0';
168 for (i = 0; i < srclength; i++)
171 output[0] = input[0] >> 2;
172 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
173 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
174 Assert(output[0] < 64);
175 Assert(output[1] < 64);
176 Assert(output[2] < 64);
178 if (datalength + 4 > targsize)
180 target[datalength++] = Base64[output[0]];
181 target[datalength++] = Base64[output[1]];
183 target[datalength++] = Pad64;
185 target[datalength++] = Base64[output[2]];
186 target[datalength++] = Pad64;
188 if (datalength >= targsize)
190 target[datalength] = '\0'; /* Returned value doesn't count \0. */
194 /* skips all whitespace anywhere.
195 converts characters, four at a time, starting at (or after)
196 src from base - 64 numbers into three 8 bit bytes in the target area.
197 it returns the number of data bytes stored at the target, or -1 on error.
201 b64_pton(char const *src, u_char *target, size_t targsize)
203 int tarindex, state, ch;
209 while ((ch = *src++) != '\0') {
210 if (isspace(ch)) /* Skip whitespace anywhere. */
216 pos = strchr(Base64, ch);
217 if (pos == 0) /* A non-base64 character. */
223 if (tarindex >= targsize)
225 target[tarindex] = (pos - Base64) << 2;
231 if (tarindex + 1 >= targsize)
233 target[tarindex] |= (pos - Base64) >> 4;
234 target[tarindex+1] = ((pos - Base64) & 0x0f)
242 if (tarindex + 1 >= targsize)
244 target[tarindex] |= (pos - Base64) >> 2;
245 target[tarindex+1] = ((pos - Base64) & 0x03)
253 if (tarindex >= targsize)
255 target[tarindex] |= (pos - Base64);
264 * We are done decoding Base-64 chars. Let's see if we ended
265 * on a byte boundary, and/or with erroneous trailing characters.
268 if (ch == Pad64) { /* We got a pad char. */
269 ch = *src++; /* Skip it, get next. */
271 case 0: /* Invalid = in first position */
272 case 1: /* Invalid = in second position */
275 case 2: /* Valid, means one byte of info */
276 /* Skip any number of spaces. */
277 for (; ch != '\0'; ch = *src++)
280 /* Make sure there is another trailing = sign. */
283 ch = *src++; /* Skip the = */
284 /* Fall through to "single trailing =" case. */
287 case 3: /* Valid, means two bytes of info */
289 * We know this char is an =. Is there anything but
290 * whitespace after it?
292 for (; ch != '\0'; ch = *src++)
297 * Now make sure for cases 2 and 3 that the "extra"
298 * bits that slopped past the last full byte were
299 * zeros. If we don't check them, they become a
300 * subliminal channel.
302 if (target && target[tarindex] != 0)
307 * We ended by seeing the end of the string. Make sure we
308 * have no partial bytes lying around.
317 #endif /* !defined(HAVE_B64_NTOP) && !defined(HAVE___B64_NTOP) */