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42 #include <ldns/config.h>
47 static const char Base64[] =
48 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
49 static const char Pad64 = '=';
51 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
52 The following encoding technique is taken from RFC 1521 by Borenstein
53 and Freed. It is reproduced here in a slightly edited form for
56 A 65-character subset of US-ASCII is used, enabling 6 bits to be
57 represented per printable character. (The extra 65th character, "=",
58 is used to signify a special processing function.)
60 The encoding process represents 24-bit groups of input bits as output
61 strings of 4 encoded characters. Proceeding from left to right, a
62 24-bit input group is formed by concatenating 3 8-bit input groups.
63 These 24 bits are then treated as 4 concatenated 6-bit groups, each
64 of which is translated into a single digit in the base64 alphabet.
66 Each 6-bit group is used as an index into an array of 64 printable
67 characters. The character referenced by the index is placed in the
70 Table 1: The Base64 Alphabet
72 Value Encoding Value Encoding Value Encoding Value Encoding
87 14 O 31 f 48 w (pad) =
91 Special processing is performed if fewer than 24 bits are available
92 at the end of the data being encoded. A full encoding quantum is
93 always completed at the end of a quantity. When fewer than 24 input
94 bits are available in an input group, zero bits are added (on the
95 right) to form an integral number of 6-bit groups. Padding at the
96 end of the data is performed using the '=' character.
98 Since all base64 input is an integral number of octets, only the
99 -------------------------------------------------
100 following cases can arise:
102 (1) the final quantum of encoding input is an integral
103 multiple of 24 bits; here, the final unit of encoded
104 output will be an integral multiple of 4 characters
106 (2) the final quantum of encoding input is exactly 8 bits;
107 here, the final unit of encoded output will be two
108 characters followed by two "=" padding characters, or
109 (3) the final quantum of encoding input is exactly 16 bits;
110 here, the final unit of encoded output will be three
111 characters followed by one "=" padding character.
114 /* skips all whitespace anywhere.
115 converts characters, four at a time, starting at (or after)
116 src from base - 64 numbers into three 8 bit bytes in the target area.
117 it returns the number of data bytes stored at the target, or -1 on error.
121 ldns_b64_pton(char const *src, uint8_t *target, size_t targsize)
123 int tarindex, state, ch;
129 if (strlen(src) == 0) {
133 while ((ch = *src++) != '\0') {
134 if (isspace((unsigned char)ch)) /* Skip whitespace anywhere. */
140 pos = strchr(Base64, ch);
142 /* A non-base64 character. */
149 if ((size_t)tarindex >= targsize)
151 target[tarindex] = (pos - Base64) << 2;
157 if ((size_t)tarindex + 1 >= targsize)
159 target[tarindex] |= (pos - Base64) >> 4;
160 target[tarindex+1] = ((pos - Base64) & 0x0f)
168 if ((size_t)tarindex + 1 >= targsize)
170 target[tarindex] |= (pos - Base64) >> 2;
171 target[tarindex+1] = ((pos - Base64) & 0x03)
179 if ((size_t)tarindex >= targsize)
181 target[tarindex] |= (pos - Base64);
192 * We are done decoding Base-64 chars. Let's see if we ended
193 * on a byte boundary, and/or with erroneous trailing characters.
196 if (ch == Pad64) { /* We got a pad char. */
197 ch = *src++; /* Skip it, get next. */
199 case 0: /* Invalid = in first position */
200 case 1: /* Invalid = in second position */
203 case 2: /* Valid, means one byte of info */
204 /* Skip any number of spaces. */
205 for ((void)NULL; ch != '\0'; ch = *src++)
206 if (!isspace((unsigned char)ch))
208 /* Make sure there is another trailing = sign. */
211 ch = *src++; /* Skip the = */
212 /* Fall through to "single trailing =" case. */
215 case 3: /* Valid, means two bytes of info */
217 * We know this char is an =. Is there anything but
218 * whitespace after it?
220 for ((void)NULL; ch != '\0'; ch = *src++)
221 if (!isspace((unsigned char)ch))
225 * Now make sure for cases 2 and 3 that the "extra"
226 * bits that slopped past the last full byte were
227 * zeros. If we don't check them, they become a
228 * subliminal channel.
230 if (target && target[tarindex] != 0)
235 * We ended by seeing the end of the string. Make sure we
236 * have no partial bytes lying around.