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44 * $FreeBSD: src/lib/libc/net/base64.c,v 1.4 1999/11/04 04:30:43 ache Exp $
45 * $DragonFly: src/lib/libc/net/base64.c,v 1.4 2005/11/13 02:04:47 swildner Exp $
48 #include <sys/types.h>
49 #include <sys/param.h>
50 #include <sys/socket.h>
52 #include <netinet/in.h>
53 #include <arpa/inet.h>
54 #include <arpa/nameser.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((unsigned char)ch
)) /* Skip whitespace anywhere. */
214 pos
= strchr(Base64
, ch
);
215 if (pos
== 0) /* A non-base64 character. */
221 if ((size_t)tarindex
>= targsize
)
223 target
[tarindex
] = (pos
- Base64
) << 2;
229 if ((size_t)tarindex
+ 1 >= targsize
)
231 target
[tarindex
] |= (pos
- Base64
) >> 4;
232 target
[tarindex
+1] = ((pos
- Base64
) & 0x0f)
240 if ((size_t)tarindex
+ 1 >= targsize
)
242 target
[tarindex
] |= (pos
- Base64
) >> 2;
243 target
[tarindex
+1] = ((pos
- Base64
) & 0x03)
251 if ((size_t)tarindex
>= targsize
)
253 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 ((void)NULL
; ch
!= '\0'; ch
= *src
++)
278 if (!isspace((unsigned char)ch
))
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 ((void)NULL
; ch
!= '\0'; ch
= *src
++)
293 if (!isspace((unsigned char)ch
))
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.