lib/libc/net/base64.c

   1 /*      $NetBSD: base64.c,v 1.12 2009/04/12 17:07:17 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 1.12 2009/04/12 17:07:17 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         return (datalength);
 207 }
 208
 209 /* skips all whitespace anywhere.
 210    converts characters, four at a time, starting at (or after)
 211    src from base - 64 numbers into three 8 bit bytes in the target area.
 212    it returns the number of data bytes stored at the target, or -1 on error.
 213  */
 214
 215 int
 216 b64_pton(src, target, targsize)
 217         char const *src;
 218         u_char *target;
 219         size_t targsize;
 220 {
 221         size_t tarindex;
 222         int state, ch;
 223         char *pos;
 224
 225         _DIAGASSERT(src != NULL);
 226         _DIAGASSERT(target != NULL);
 227
 228         state = 0;
 229         tarindex = 0;
 230
 231         while ((ch = (u_char) *src++) != '\0') {
 232                 if (isspace(ch))        /*%< Skip whitespace anywhere. */
 233                         continue;
 234
 235                 if (ch == Pad64)
 236                         break;
 237
 238                 pos = strchr(Base64, ch);
 239                 if (pos == 0)           /*%< A non-base64 character. */
 240                         return (-1);
 241
 242                 switch (state) {
 243                 case 0:
 244                         if (target) {
 245                                 if ((size_t)tarindex >= targsize)
 246                                         return (-1);
 247                                 target[tarindex] = (pos - Base64) << 2;
 248                         }
 249                         state = 1;
 250                         break;
 251                 case 1:
 252                         if (target) {
 253                                 if ((size_t)tarindex + 1 >= targsize)
 254                                         return (-1);
 255                                 target[tarindex] |=
 256                                     (u_int32_t)(pos - Base64) >> 4;
 257                                 target[tarindex+1]  = ((pos - Base64) & 0x0f)
 258                                                         << 4 ;
 259                         }
 260                         tarindex++;
 261                         state = 2;
 262                         break;
 263                 case 2:
 264                         if (target) {
 265                                 if ((size_t)tarindex + 1 >= targsize)
 266                                         return (-1);
 267                                 target[tarindex] |=
 268                                         (u_int32_t)(pos - Base64) >> 2;
 269                                 target[tarindex+1] = ((pos - Base64) & 0x03)
 270                                                         << 6;
 271                         }
 272                         tarindex++;
 273                         state = 3;
 274                         break;
 275                 case 3:
 276                         if (target) {
 277                                 if ((size_t)tarindex >= targsize)
 278                                         return (-1);
 279                                 target[tarindex] |= (pos - Base64);
 280                         }
 281                         tarindex++;
 282                         state = 0;
 283                         break;
 284                 default:
 285                         abort();
 286                 }
 287         }
 288
 289         /*
 290          * We are done decoding Base-64 chars.  Let's see if we ended
 291          * on a byte boundary, and/or with erroneous trailing characters.
 292          */
 293
 294         if (ch == Pad64) {              /*%< We got a pad char. */
 295                 ch = *src++;            /*%< Skip it, get next. */
 296                 switch (state) {
 297                 case 0:         /*%< Invalid = in first position */
 298                 case 1:         /*%< Invalid = in second position */
 299                         return (-1);
 300
 301                 case 2:         /*%< Valid, means one byte of info */
 302                         /* Skip any number of spaces. */
 303                         for (; ch != '\0'; ch = (u_char) *src++)
 304                                 if (!isspace(ch))
 305                                         break;
 306                         /* Make sure there is another trailing = sign. */
 307                         if (ch != Pad64)
 308                                 return (-1);
 309                         ch = *src++;            /*%< Skip the = */
 310                         /* Fall through to "single trailing =" case. */
 311                         /* FALLTHROUGH */
 312
 313                 case 3:         /*%< Valid, means two bytes of info */
 314                         /*
 315                          * We know this char is an =.  Is there anything but
 316                          * whitespace after it?
 317                          */
 318                         for (; ch != '\0'; ch = (u_char) *src++)
 319                                 if (!isspace(ch))
 320                                         return (-1);
 321
 322                         /*
 323                          * Now make sure for cases 2 and 3 that the "extra"
 324                          * bits that slopped past the last full byte were
 325                          * zeros.  If we don't check them, they become a
 326                          * subliminal channel.
 327                          */
 328                         if (target && target[tarindex] != 0)
 329                                 return (-1);
 330                 }
 331         } else {
 332                 /*
 333                  * We ended by seeing the end of the string.  Make sure we
 334                  * have no partial bytes lying around.
 335                  */
 336                 if (state != 0)
 337                         return (-1);
 338         }
 339
 340         return (tarindex);
 341 }
 342
 343 /*! \file */