resolv/base64.c

   1 /*
   2  * Copyright (c) 1996 by Internet Software Consortium.
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
   9  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  10  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  11  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  12  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  13  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  14  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  15  * SOFTWARE.
  16  */
  17
  18 /*
  19  * Portions Copyright (c) 1995 by International Business Machines, Inc.
  20  *
  21  * International Business Machines, Inc. (hereinafter called IBM) grants
  22  * permission under its copyrights to use, copy, modify, and distribute this
  23  * Software with or without fee, provided that the above copyright notice and
  24  * all paragraphs of this notice appear in all copies, and that the name of IBM
  25  * not be used in connection with the marketing of any product incorporating
  26  * the Software or modifications thereof, without specific, written prior
  27  * permission.
  28  *
  29  * To the extent it has a right to do so, IBM grants an immunity from suit
  30  * under its patents, if any, for the use, sale or manufacture of products to
  31  * the extent that such products are used for performing Domain Name System
  32  * dynamic updates in TCP/IP networks by means of the Software.  No immunity is
  33  * granted for any product per se or for any other function of any product.
  34  *
  35  * THE SOFTWARE IS PROVIDED "AS IS", AND IBM DISCLAIMS ALL WARRANTIES,
  36  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  37  * PARTICULAR PURPOSE.  IN NO EVENT SHALL IBM BE LIABLE FOR ANY SPECIAL,
  38  * DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER ARISING
  39  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE, EVEN
  40  * IF IBM IS APPRISED OF THE POSSIBILITY OF SUCH DAMAGES.
  41  */
  42
  43 #include <sys/types.h>
  44 #include <sys/param.h>
  45 #include <sys/socket.h>
  46 #include <netinet/in.h>
  47 #include <arpa/inet.h>
  48 #include <arpa/nameser.h>
  49
  50 #include <ctype.h>
  51 #include <resolv.h>
  52 #include <stdio.h>
  53
  54 #if defined(BSD) && (BSD >= 199103) && defined(AF_INET6)
  55 # include <stdlib.h>
  56 # include <string.h>
  57 #else
  58 # include "../conf/portability.h"
  59 #endif
  60
  61 #define Assert(Cond) if (!(Cond)) abort()
  62
  63 static const char Base64[] =
  64         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  65 static const char Pad64 = '=';
  66
  67 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
  68    The following encoding technique is taken from RFC 1521 by Borenstein
  69    and Freed.  It is reproduced here in a slightly edited form for
  70    convenience.
  71
  72    A 65-character subset of US-ASCII is used, enabling 6 bits to be
  73    represented per printable character. (The extra 65th character, "=",
  74    is used to signify a special processing function.)
  75
  76    The encoding process represents 24-bit groups of input bits as output
  77    strings of 4 encoded characters. Proceeding from left to right, a
  78    24-bit input group is formed by concatenating 3 8-bit input groups.
  79    These 24 bits are then treated as 4 concatenated 6-bit groups, each
  80    of which is translated into a single digit in the base64 alphabet.
  81
  82    Each 6-bit group is used as an index into an array of 64 printable
  83    characters. The character referenced by the index is placed in the
  84    output string.
  85
  86                          Table 1: The Base64 Alphabet
  87
  88       Value Encoding  Value Encoding  Value Encoding  Value Encoding
  89           0 A            17 R            34 i            51 z
  90           1 B            18 S            35 j            52 0
  91           2 C            19 T            36 k            53 1
  92           3 D            20 U            37 l            54 2
  93           4 E            21 V            38 m            55 3
  94           5 F            22 W            39 n            56 4
  95           6 G            23 X            40 o            57 5
  96           7 H            24 Y            41 p            58 6
  97           8 I            25 Z            42 q            59 7
  98           9 J            26 a            43 r            60 8
  99          10 K            27 b            44 s            61 9
 100          11 L            28 c            45 t            62 +
 101          12 M            29 d            46 u            63 /
 102          13 N            30 e            47 v
 103          14 O            31 f            48 w         (pad) =
 104          15 P            32 g            49 x
 105          16 Q            33 h            50 y
 106
 107    Special processing is performed if fewer than 24 bits are available
 108    at the end of the data being encoded.  A full encoding quantum is
 109    always completed at the end of a quantity.  When fewer than 24 input
 110    bits are available in an input group, zero bits are added (on the
 111    right) to form an integral number of 6-bit groups.  Padding at the
 112    end of the data is performed using the '=' character.
 113
 114    Since all base64 input is an integral number of octets, only the
 115          -------------------------------------------------
 116    following cases can arise:
 117
 118        (1) the final quantum of encoding input is an integral
 119            multiple of 24 bits; here, the final unit of encoded
 120            output will be an integral multiple of 4 characters
 121            with no "=" padding,
 122        (2) the final quantum of encoding input is exactly 8 bits;
 123            here, the final unit of encoded output will be two
 124            characters followed by two "=" padding characters, or
 125        (3) the final quantum of encoding input is exactly 16 bits;
 126            here, the final unit of encoded output will be three
 127            characters followed by one "=" padding character.
 128    */
 129
 130 int
 131 b64_ntop(src, srclength, target, targsize)
 132         u_char const *src;
 133         size_t srclength;
 134         char *target;
 135         size_t targsize;
 136 {
 137         size_t datalength = 0;
 138         u_char input[3];
 139         u_char output[4];
 140         int i;
 141
 142         while (2 < srclength) {
 143                 input[0] = *src++;
 144                 input[1] = *src++;
 145                 input[2] = *src++;
 146                 srclength -= 3;
 147
 148                 output[0] = input[0] >> 2;
 149                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 150                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 151                 output[3] = input[2] & 0x3f;
 152                 Assert(output[0] < 64);
 153                 Assert(output[1] < 64);
 154                 Assert(output[2] < 64);
 155                 Assert(output[3] < 64);
 156
 157                 if (datalength + 4 > targsize)
 158                         return (-1);
 159                 target[datalength++] = Base64[output[0]];
 160                 target[datalength++] = Base64[output[1]];
 161                 target[datalength++] = Base64[output[2]];
 162                 target[datalength++] = Base64[output[3]];
 163         }
 164
 165         /* Now we worry about padding. */
 166         if (0 != srclength) {
 167                 /* Get what's left. */
 168                 input[0] = input[1] = input[2] = '\0';
 169                 for (i = 0; i < srclength; i++)
 170                         input[i] = *src++;
 171
 172                 output[0] = input[0] >> 2;
 173                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 174                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 175                 Assert(output[0] < 64);
 176                 Assert(output[1] < 64);
 177                 Assert(output[2] < 64);
 178
 179                 if (datalength + 4 > targsize)
 180                         return (-1);
 181                 target[datalength++] = Base64[output[0]];
 182                 target[datalength++] = Base64[output[1]];
 183                 if (srclength == 1)
 184                         target[datalength++] = Pad64;
 185                 else
 186                         target[datalength++] = Base64[output[2]];
 187                 target[datalength++] = Pad64;
 188         }
 189         if (datalength >= targsize)
 190                 return (-1);
 191         target[datalength] = '\0';      /* Returned value doesn't count \0. */
 192         return (datalength);
 193 }
 194
 195 /* skips all whitespace anywhere.
 196    converts characters, four at a time, starting at (or after)
 197    src from base - 64 numbers into three 8 bit bytes in the target area.
 198    it returns the number of data bytes stored at the target, or -1 on error.
 199  */
 200
 201 int
 202 b64_pton(src, target, targsize)
 203         char const *src;
 204         u_char *target;
 205         size_t targsize;
 206 {
 207         int tarindex, state, ch;
 208         char *pos;
 209
 210         state = 0;
 211         tarindex = 0;
 212
 213         while ((ch = *src++) != '\0') {
 214                 if (isspace(ch))        /* Skip whitespace anywhere. */
 215                         continue;
 216
 217                 if (ch == Pad64)
 218                         break;
 219
 220                 pos = strchr(Base64, ch);
 221                 if (pos == 0)           /* A non-base64 character. */
 222                         return (-1);
 223
 224                 switch (state) {
 225                 case 0:
 226                         if (target) {
 227                                 if (tarindex >= targsize)
 228                                         return (-1);
 229                                 target[tarindex] = (pos - Base64) << 2;
 230                         }
 231                         state = 1;
 232                         break;
 233                 case 1:
 234                         if (target) {
 235                                 if (tarindex + 1 >= targsize)
 236                                         return (-1);
 237                                 target[tarindex]   |=  (pos - Base64) >> 4;
 238                                 target[tarindex+1]  = ((pos - Base64) & 0x0f)
 239                                                         << 4 ;
 240                         }
 241                         tarindex++;
 242                         state = 2;
 243                         break;
 244                 case 2:
 245                         if (target) {
 246                                 if (tarindex + 1 >= targsize)
 247                                         return (-1);
 248                                 target[tarindex]   |=  (pos - Base64) >> 2;
 249                                 target[tarindex+1]  = ((pos - Base64) & 0x03)
 250                                                         << 6;
 251                         }
 252                         tarindex++;
 253                         state = 3;
 254                         break;
 255                 case 3:
 256                         if (target) {
 257                                 if (tarindex >= targsize)
 258                                         return (-1);
 259                                 target[tarindex] |= (pos - Base64);
 260                         }
 261                         tarindex++;
 262                         state = 0;
 263                         break;
 264                 default:
 265                         abort();
 266                 }
 267         }
 268
 269         /*
 270          * We are done decoding Base-64 chars.  Let's see if we ended
 271          * on a byte boundary, and/or with erroneous trailing characters.
 272          */
 273
 274         if (ch == Pad64) {              /* We got a pad char. */
 275                 ch = *src++;            /* Skip it, get next. */
 276                 switch (state) {
 277                 case 0:         /* Invalid = in first position */
 278                 case 1:         /* Invalid = in second position */
 279                         return (-1);
 280
 281                 case 2:         /* Valid, means one byte of info */
 282                         /* Skip any number of spaces. */
 283                         for ( ; ch != '\0'; ch = *src++)
 284                                 if (!isspace(ch))
 285                                         break;
 286                         /* Make sure there is another trailing = sign. */
 287                         if (ch != Pad64)
 288                                 return (-1);
 289                         ch = *src++;            /* Skip the = */
 290                         /* Fall through to "single trailing =" case. */
 291                         /* FALLTHROUGH */
 292
 293                 case 3:         /* Valid, means two bytes of info */
 294                         /*
 295                          * We know this char is an =.  Is there anything but
 296                          * whitespace after it?
 297                          */
 298                         for ( ; ch != '\0'; ch = *src++)
 299                                 if (!isspace(ch))
 300                                         return (-1);
 301
 302                         /*
 303                          * Now make sure for cases 2 and 3 that the "extra"
 304                          * bits that slopped past the last full byte were
 305                          * zeros.  If we don't check them, they become a
 306                          * subliminal channel.
 307                          */
 308                         if (target && target[tarindex] != 0)
 309                                 return (-1);
 310                 }
 311         } else {
 312                 /*
 313                  * We ended by seeing the end of the string.  Make sure we
 314                  * have no partial bytes lying around.
 315                  */
 316                 if (state != 0)
 317                         return (-1);
 318         }
 319
 320         return (tarindex);
 321 }