lib/libc/net/base64.c

   1 /*      $NetBSD: base64.c,v 1.14 2012/06/25 22:32:44 abs 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 1.14 2012/06/25 22:32:44 abs 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(char const *src, u_char *target, size_t targsize)
 218 {
 219         size_t tarindex;
 220         int state, ch;
 221         char *pos;
 222
 223         _DIAGASSERT(src != NULL);
 224         _DIAGASSERT(target != NULL);
 225
 226         state = 0;
 227         tarindex = 0;
 228
 229         while ((ch = (u_char) *src++) != '\0') {
 230                 if (isspace(ch))        /*%< Skip whitespace anywhere. */
 231                         continue;
 232
 233                 if (ch == Pad64)
 234                         break;
 235
 236                 pos = strchr(Base64, ch);
 237                 if (pos == 0)           /*%< A non-base64 character. */
 238                         return (-1);
 239
 240                 switch (state) {
 241                 case 0:
 242                         if (target) {
 243                                 if ((size_t)tarindex >= targsize)
 244                                         return (-1);
 245                                 target[tarindex] =
 246                                     (unsigned char)(pos - Base64) << 2;
 247                         }
 248                         state = 1;
 249                         break;
 250                 case 1:
 251                         if (target) {
 252                                 if ((size_t)tarindex + 1 >= targsize)
 253                                         return (-1);
 254                                 target[tarindex] |=
 255                                     (u_int32_t)(pos - Base64) >> 4;
 256                                 target[tarindex+1]  =
 257                                     (unsigned char)
 258                                     (((pos - Base64) & 0x0f) << 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] =
 270                                     (unsigned char)
 271                                     (((pos - Base64) & 0x03) << 6);
 272                         }
 273                         tarindex++;
 274                         state = 3;
 275                         break;
 276                 case 3:
 277                         if (target) {
 278                                 if ((size_t)tarindex >= targsize)
 279                                         return (-1);
 280                                 target[tarindex] |=
 281                                     (unsigned char)(pos - Base64);
 282                         }
 283                         tarindex++;
 284                         state = 0;
 285                         break;
 286                 default:
 287                         abort();
 288                 }
 289         }
 290
 291         /*
 292          * We are done decoding Base-64 chars.  Let's see if we ended
 293          * on a byte boundary, and/or with erroneous trailing characters.
 294          */
 295
 296         if (ch == Pad64) {              /*%< We got a pad char. */
 297                 ch = *src++;            /*%< Skip it, get next. */
 298                 switch (state) {
 299                 case 0:         /*%< Invalid = in first position */
 300                 case 1:         /*%< Invalid = in second position */
 301                         return (-1);
 302
 303                 case 2:         /*%< Valid, means one byte of info */
 304                         /* Skip any number of spaces. */
 305                         for (; ch != '\0'; ch = (u_char) *src++)
 306                                 if (!isspace(ch))
 307                                         break;
 308                         /* Make sure there is another trailing = sign. */
 309                         if (ch != Pad64)
 310                                 return (-1);
 311                         ch = *src++;            /*%< Skip the = */
 312                         /* Fall through to "single trailing =" case. */
 313                         /* FALLTHROUGH */
 314
 315                 case 3:         /*%< Valid, means two bytes of info */
 316                         /*
 317                          * We know this char is an =.  Is there anything but
 318                          * whitespace after it?
 319                          */
 320                         for (; ch != '\0'; ch = (u_char) *src++)
 321                                 if (!isspace(ch))
 322                                         return (-1);
 323
 324                         /*
 325                          * Now make sure for cases 2 and 3 that the "extra"
 326                          * bits that slopped past the last full byte were
 327                          * zeros.  If we don't check them, they become a
 328                          * subliminal channel.
 329                          */
 330                         if (target && target[tarindex] != 0)
 331                                 return (-1);
 332                 }
 333         } else {
 334                 /*
 335                  * We ended by seeing the end of the string.  Make sure we
 336                  * have no partial bytes lying around.
 337                  */
 338                 if (state != 0)
 339                         return (-1);
 340         }
 341
 342         _DIAGASSERT(__type_fit(int, tarindex));
 343         return (int)tarindex;
 344 }
 345
 346 /*! \file */