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base64.c revision 1.13 
      1 /*	$NetBSD: base64.c,v 1.13 2012/03/13 21:13:40 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
      5  * Copyright (c) 1996-1999 by Internet Software Consortium.
      6  *
      7  * Permission to use, copy, modify, and distribute this software for any
      8  * purpose with or without fee is hereby granted, provided that the above
      9  * copyright notice and this permission notice appear in all copies.
     10  *
     11  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
     12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     13  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
     14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
     17  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     18  */
     19 
     20 /*
     21  * Portions Copyright (c) 1995 by International Business Machines, Inc.
     22  *
     23  * International Business Machines, Inc. (hereinafter called IBM) grants
     24  * permission under its copyrights to use, copy, modify, and distribute this
     25  * Software with or without fee, provided that the above copyright notice and
     26  * all paragraphs of this notice appear in all copies, and that the name of IBM
     27  * not be used in connection with the marketing of any product incorporating
     28  * the Software or modifications thereof, without specific, written prior
     29  * permission.
     30  *
     31  * To the extent it has a right to do so, IBM grants an immunity from suit
     32  * under its patents, if any, for the use, sale or manufacture of products to
     33  * the extent that such products are used for performing Domain Name System
     34  * dynamic updates in TCP/IP networks by means of the Software.  No immunity is
     35  * granted for any product per se or for any other function of any product.
     36  *
     37  * THE SOFTWARE IS PROVIDED "AS IS", AND IBM DISCLAIMS ALL WARRANTIES,
     38  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
     39  * PARTICULAR PURPOSE.  IN NO EVENT SHALL IBM BE LIABLE FOR ANY SPECIAL,
     40  * DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER ARISING
     41  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE, EVEN
     42  * IF IBM IS APPRISED OF THE POSSIBILITY OF SUCH DAMAGES.
     43  */
     44 
     45 #include <sys/cdefs.h>
     46 #if defined(LIBC_SCCS) && !defined(lint)
     47 #if 0
     48 static const char rcsid[] = "Id: base64.c,v 1.4 2005/04/27 04:56:34 sra Exp";
     49 #else
     50 __RCSID("$NetBSD: base64.c,v 1.13 2012/03/13 21:13:40 christos Exp $");
     51 #endif
     52 #endif /* LIBC_SCCS and not lint */
     53 
     54 #include "port_before.h"
     55 
     56 #include <sys/types.h>
     57 #include <sys/param.h>
     58 #include <sys/socket.h>
     59 
     60 #include <netinet/in.h>
     61 #include <arpa/inet.h>
     62 #include <arpa/nameser.h>
     63 
     64 #include <assert.h>
     65 #include <ctype.h>
     66 #include <resolv.h>
     67 #include <stdio.h>
     68 #include <stdlib.h>
     69 #include <string.h>
     70 
     71 #include "port_after.h"
     72 
     73 #define Assert(Cond) if (!(Cond)) abort()
     74 
     75 static const char Base64[] =
     76 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
     77 static const char Pad64 = '=';
     78 
     79 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
     80    The following encoding technique is taken from RFC1521 by Borenstein
     81    and Freed.  It is reproduced here in a slightly edited form for
     82    convenience.
     83 
     84    A 65-character subset of US-ASCII is used, enabling 6 bits to be
     85    represented per printable character. (The extra 65th character, "=",
     86    is used to signify a special processing function.)
     87 
     88    The encoding process represents 24-bit groups of input bits as output
     89    strings of 4 encoded characters. Proceeding from left to right, a
     90    24-bit input group is formed by concatenating 3 8-bit input groups.
     91    These 24 bits are then treated as 4 concatenated 6-bit groups, each
     92    of which is translated into a single digit in the base64 alphabet.
     93 
     94    Each 6-bit group is used as an index into an array of 64 printable
     95    characters. The character referenced by the index is placed in the
     96    output string.
     97 
     98                          Table 1: The Base64 Alphabet
     99 
    100       Value Encoding  Value Encoding  Value Encoding  Value Encoding
    101           0 A            17 R            34 i            51 z
    102           1 B            18 S            35 j            52 0
    103           2 C            19 T            36 k            53 1
    104           3 D            20 U            37 l            54 2
    105           4 E            21 V            38 m            55 3
    106           5 F            22 W            39 n            56 4
    107           6 G            23 X            40 o            57 5
    108           7 H            24 Y            41 p            58 6
    109           8 I            25 Z            42 q            59 7
    110           9 J            26 a            43 r            60 8
    111          10 K            27 b            44 s            61 9
    112          11 L            28 c            45 t            62 +
    113          12 M            29 d            46 u            63 /
    114          13 N            30 e            47 v
    115          14 O            31 f            48 w         (pad) =
    116          15 P            32 g            49 x
    117          16 Q            33 h            50 y
    118 
    119    Special processing is performed if fewer than 24 bits are available
    120    at the end of the data being encoded.  A full encoding quantum is
    121    always completed at the end of a quantity.  When fewer than 24 input
    122    bits are available in an input group, zero bits are added (on the
    123    right) to form an integral number of 6-bit groups.  Padding at the
    124    end of the data is performed using the '=' character.
    125 
    126    Since all base64 input is an integral number of octets, only the
    127          -------------------------------------------------
    128    following cases can arise:
    129 
    130        (1) the final quantum of encoding input is an integral
    131            multiple of 24 bits; here, the final unit of encoded
    132 	   output will be an integral multiple of 4 characters
    133 	   with no "=" padding,
    134        (2) the final quantum of encoding input is exactly 8 bits;
    135            here, the final unit of encoded output will be two
    136 	   characters followed by two "=" padding characters, or
    137        (3) the final quantum of encoding input is exactly 16 bits;
    138            here, the final unit of encoded output will be three
    139 	   characters followed by one "=" padding character.
    140    */
    141 
    142 int
    143 b64_ntop(u_char const *src, size_t srclength, char *target, size_t targsize) {
    144 	size_t datalength = 0;
    145 	u_char input[3];
    146 	u_char output[4];
    147 	size_t i;
    148 
    149 	_DIAGASSERT(src != NULL);
    150 	_DIAGASSERT(target != NULL);
    151 
    152 	while (2U < srclength) {
    153 		input[0] = *src++;
    154 		input[1] = *src++;
    155 		input[2] = *src++;
    156 		srclength -= 3;
    157 
    158 		output[0] = (u_int32_t)input[0] >> 2;
    159 		output[1] = ((u_int32_t)(input[0] & 0x03) << 4) +
    160 		    ((u_int32_t)input[1] >> 4);
    161 		output[2] = ((u_int32_t)(input[1] & 0x0f) << 2) +
    162 		    ((u_int32_t)input[2] >> 6);
    163 		output[3] = input[2] & 0x3f;
    164 		Assert(output[0] < 64);
    165 		Assert(output[1] < 64);
    166 		Assert(output[2] < 64);
    167 		Assert(output[3] < 64);
    168 
    169 		if (datalength + 4 > targsize)
    170 			return (-1);
    171 		target[datalength++] = Base64[output[0]];
    172 		target[datalength++] = Base64[output[1]];
    173 		target[datalength++] = Base64[output[2]];
    174 		target[datalength++] = Base64[output[3]];
    175 	}
    176 
    177 	/* Now we worry about padding. */
    178 	if (0U != srclength) {
    179 		/* Get what's left. */
    180 		input[0] = input[1] = input[2] = '\0';
    181 		for (i = 0; i < srclength; i++)
    182 			input[i] = *src++;
    183 
    184 		output[0] = (u_int32_t)input[0] >> 2;
    185 		output[1] = ((u_int32_t)(input[0] & 0x03) << 4) +
    186 		    ((u_int32_t)input[1] >> 4);
    187 		output[2] = ((u_int32_t)(input[1] & 0x0f) << 2) +
    188 		    ((u_int32_t)input[2] >> 6);
    189 		Assert(output[0] < 64);
    190 		Assert(output[1] < 64);
    191 		Assert(output[2] < 64);
    192 
    193 		if (datalength + 4 > targsize)
    194 			return (-1);
    195 		target[datalength++] = Base64[output[0]];
    196 		target[datalength++] = Base64[output[1]];
    197 		if (srclength == 1U)
    198 			target[datalength++] = Pad64;
    199 		else
    200 			target[datalength++] = Base64[output[2]];
    201 		target[datalength++] = Pad64;
    202 	}
    203 	if (datalength >= targsize)
    204 		return (-1);
    205 	target[datalength] = '\0';	/*%< Returned value doesn't count \\0. */
    206 	_DIAGASSERT(__type_fit(int, datalength));
    207 	return (int)datalength;
    208 }
    209 
    210 /* skips all whitespace anywhere.
    211    converts characters, four at a time, starting at (or after)
    212    src from base - 64 numbers into three 8 bit bytes in the target area.
    213    it returns the number of data bytes stored at the target, or -1 on error.
    214  */
    215 
    216 int
    217 b64_pton(src, target, targsize)
    218 	char const *src;
    219 	u_char *target;
    220 	size_t targsize;
    221 {
    222 	size_t tarindex;
    223 	int state, ch;
    224 	char *pos;
    225 
    226 	_DIAGASSERT(src != NULL);
    227 	_DIAGASSERT(target != NULL);
    228 
    229 	state = 0;
    230 	tarindex = 0;
    231 
    232 	while ((ch = (u_char) *src++) != '\0') {
    233 		if (isspace(ch))	/*%< Skip whitespace anywhere. */
    234 			continue;
    235 
    236 		if (ch == Pad64)
    237 			break;
    238 
    239 		pos = strchr(Base64, ch);
    240 		if (pos == 0) 		/*%< A non-base64 character. */
    241 			return (-1);
    242 
    243 		switch (state) {
    244 		case 0:
    245 			if (target) {
    246 				if ((size_t)tarindex >= targsize)
    247 					return (-1);
    248 				target[tarindex] =
    249 				    (unsigned char)(pos - Base64) << 2;
    250 			}
    251 			state = 1;
    252 			break;
    253 		case 1:
    254 			if (target) {
    255 				if ((size_t)tarindex + 1 >= targsize)
    256 					return (-1);
    257 				target[tarindex] |=
    258 				    (u_int32_t)(pos - Base64) >> 4;
    259 				target[tarindex+1]  =
    260 				    (unsigned char)
    261 				    (((pos - Base64) & 0x0f) << 4);
    262 			}
    263 			tarindex++;
    264 			state = 2;
    265 			break;
    266 		case 2:
    267 			if (target) {
    268 				if ((size_t)tarindex + 1 >= targsize)
    269 					return (-1);
    270 				target[tarindex] |=
    271 					(u_int32_t)(pos - Base64) >> 2;
    272 				target[tarindex+1] =
    273 				    (unsigned char)
    274 				    (((pos - Base64) & 0x03) << 6);
    275 			}
    276 			tarindex++;
    277 			state = 3;
    278 			break;
    279 		case 3:
    280 			if (target) {
    281 				if ((size_t)tarindex >= targsize)
    282 					return (-1);
    283 				target[tarindex] |=
    284 				    (unsigned char)(pos - Base64);
    285 			}
    286 			tarindex++;
    287 			state = 0;
    288 			break;
    289 		default:
    290 			abort();
    291 		}
    292 	}
    293 
    294 	/*
    295 	 * We are done decoding Base-64 chars.  Let's see if we ended
    296 	 * on a byte boundary, and/or with erroneous trailing characters.
    297 	 */
    298 
    299 	if (ch == Pad64) {		/*%< We got a pad char. */
    300 		ch = *src++;		/*%< Skip it, get next. */
    301 		switch (state) {
    302 		case 0:		/*%< Invalid = in first position */
    303 		case 1:		/*%< Invalid = in second position */
    304 			return (-1);
    305 
    306 		case 2:		/*%< Valid, means one byte of info */
    307 			/* Skip any number of spaces. */
    308 			for (; ch != '\0'; ch = (u_char) *src++)
    309 				if (!isspace(ch))
    310 					break;
    311 			/* Make sure there is another trailing = sign. */
    312 			if (ch != Pad64)
    313 				return (-1);
    314 			ch = *src++;		/*%< Skip the = */
    315 			/* Fall through to "single trailing =" case. */
    316 			/* FALLTHROUGH */
    317 
    318 		case 3:		/*%< Valid, means two bytes of info */
    319 			/*
    320 			 * We know this char is an =.  Is there anything but
    321 			 * whitespace after it?
    322 			 */
    323 			for (; ch != '\0'; ch = (u_char) *src++)
    324 				if (!isspace(ch))
    325 					return (-1);
    326 
    327 			/*
    328 			 * Now make sure for cases 2 and 3 that the "extra"
    329 			 * bits that slopped past the last full byte were
    330 			 * zeros.  If we don't check them, they become a
    331 			 * subliminal channel.
    332 			 */
    333 			if (target && target[tarindex] != 0)
    334 				return (-1);
    335 		}
    336 	} else {
    337 		/*
    338 		 * We ended by seeing the end of the string.  Make sure we
    339 		 * have no partial bytes lying around.
    340 		 */
    341 		if (state != 0)
    342 			return (-1);
    343 	}
    344 
    345 	_DIAGASSERT(__type_fit(int, tarindex));
    346 	return (int)tarindex;
    347 }
    348 
    349 /*! \file */
    350