resolv/base64.c

   1 /*
   2  * Copyright (c) 1996-1999 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 #if !defined(LINT) && !defined(CODECENTER)
  44 static const char rcsid[] = "$BINDId: base64.c,v 8.7 1999/10/13 16:39:33 vixie Exp $";
  45 #endif /* not lint */
  46
  47 #include <sys/types.h>
  48 #include <sys/param.h>
  49 #include <sys/socket.h>
  50
  51 #include <netinet/in.h>
  52 #include <arpa/inet.h>
  53 #include <arpa/nameser.h>
  54
  55 #include <ctype.h>
  56 #include <resolv.h>
  57 #include <stdio.h>
  58 #include <stdlib.h>
  59 #include <string.h>
  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(u_char const *src, size_t srclength, char *target, size_t targsize) {
 132         size_t datalength = 0;
 133         u_char input[3];
 134         u_char output[4];
 135         size_t i;
 136
 137         while (2 < srclength) {
 138                 input[0] = *src++;
 139                 input[1] = *src++;
 140                 input[2] = *src++;
 141                 srclength -= 3;
 142
 143                 output[0] = input[0] >> 2;
 144                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 145                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 146                 output[3] = input[2] & 0x3f;
 147                 Assert(output[0] < 64);
 148                 Assert(output[1] < 64);
 149                 Assert(output[2] < 64);
 150                 Assert(output[3] < 64);
 151
 152                 if (datalength + 4 > targsize)
 153                         return (-1);
 154                 target[datalength++] = Base64[output[0]];
 155                 target[datalength++] = Base64[output[1]];
 156                 target[datalength++] = Base64[output[2]];
 157                 target[datalength++] = Base64[output[3]];
 158         }
 159
 160         /* Now we worry about padding. */
 161         if (0 != srclength) {
 162                 /* Get what's left. */
 163                 input[0] = input[1] = input[2] = '\0';
 164                 for (i = 0; i < srclength; i++)
 165                         input[i] = *src++;
 166
 167                 output[0] = input[0] >> 2;
 168                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 169                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 170                 Assert(output[0] < 64);
 171                 Assert(output[1] < 64);
 172                 Assert(output[2] < 64);
 173
 174                 if (datalength + 4 > targsize)
 175                         return (-1);
 176                 target[datalength++] = Base64[output[0]];
 177                 target[datalength++] = Base64[output[1]];
 178                 if (srclength == 1)
 179                         target[datalength++] = Pad64;
 180                 else
 181                         target[datalength++] = Base64[output[2]];
 182                 target[datalength++] = Pad64;
 183         }
 184         if (datalength >= targsize)
 185                 return (-1);
 186         target[datalength] = '\0';      /* Returned value doesn't count \0. */
 187         return (datalength);
 188 }
 189
 190 /* skips all whitespace anywhere.
 191    converts characters, four at a time, starting at (or after)
 192    src from base - 64 numbers into three 8 bit bytes in the target area.
 193    it returns the number of data bytes stored at the target, or -1 on error.
 194  */
 195
 196 int
 197 b64_pton(src, target, targsize)
 198         char const *src;
 199         u_char *target;
 200         size_t targsize;
 201 {
 202         int tarindex, state, ch;
 203         char *pos;
 204
 205         state = 0;
 206         tarindex = 0;
 207
 208         while ((ch = *src++) != '\0') {
 209                 if (isspace(ch))        /* Skip whitespace anywhere. */
 210                         continue;
 211
 212                 if (ch == Pad64)
 213                         break;
 214
 215                 pos = strchr(Base64, ch);
 216                 if (pos == 0)           /* A non-base64 character. */
 217                         return (-1);
 218
 219                 switch (state) {
 220                 case 0:
 221                         if (target) {
 222                                 if ((size_t)tarindex >= targsize)
 223                                         return (-1);
 224                                 target[tarindex] = (pos - Base64) << 2;
 225                         }
 226                         state = 1;
 227                         break;
 228                 case 1:
 229                         if (target) {
 230                                 if ((size_t)tarindex + 1 >= targsize)
 231                                         return (-1);
 232                                 target[tarindex]   |=  (pos - Base64) >> 4;
 233                                 target[tarindex+1]  = ((pos - Base64) & 0x0f)
 234                                                         << 4 ;
 235                         }
 236                         tarindex++;
 237                         state = 2;
 238                         break;
 239                 case 2:
 240                         if (target) {
 241                                 if ((size_t)tarindex + 1 >= targsize)
 242                                         return (-1);
 243                                 target[tarindex]   |=  (pos - Base64) >> 2;
 244                                 target[tarindex+1]  = ((pos - Base64) & 0x03)
 245                                                         << 6;
 246                         }
 247                         tarindex++;
 248                         state = 3;
 249                         break;
 250                 case 3:
 251                         if (target) {
 252                                 if ((size_t)tarindex >= targsize)
 253                                         return (-1);
 254                                 target[tarindex] |= (pos - Base64);
 255                         }
 256                         tarindex++;
 257                         state = 0;
 258                         break;
 259                 default:
 260                         abort();
 261                 }
 262         }
 263
 264         /*
 265          * We are done decoding Base-64 chars.  Let's see if we ended
 266          * on a byte boundary, and/or with erroneous trailing characters.
 267          */
 268
 269         if (ch == Pad64) {              /* We got a pad char. */
 270                 ch = *src++;            /* Skip it, get next. */
 271                 switch (state) {
 272                 case 0:         /* Invalid = in first position */
 273                 case 1:         /* Invalid = in second position */
 274                         return (-1);
 275
 276                 case 2:         /* Valid, means one byte of info */
 277                         /* Skip any number of spaces. */
 278                         for ((void)NULL; ch != '\0'; ch = *src++)
 279                                 if (!isspace(ch))
 280                                         break;
 281                         /* Make sure there is another trailing = sign. */
 282                         if (ch != Pad64)
 283                                 return (-1);
 284                         ch = *src++;            /* Skip the = */
 285                         /* Fall through to "single trailing =" case. */
 286                         /* FALLTHROUGH */
 287
 288                 case 3:         /* Valid, means two bytes of info */
 289                         /*
 290                          * We know this char is an =.  Is there anything but
 291                          * whitespace after it?
 292                          */
 293                         for ((void)NULL; ch != '\0'; ch = *src++)
 294                                 if (!isspace(ch))
 295                                         return (-1);
 296
 297                         /*
 298                          * Now make sure for cases 2 and 3 that the "extra"
 299                          * bits that slopped past the last full byte were
 300                          * zeros.  If we don't check them, they become a
 301                          * subliminal channel.
 302                          */
 303                         if (target && target[tarindex] != 0)
 304                                 return (-1);
 305                 }
 306         } else {
 307                 /*
 308                  * We ended by seeing the end of the string.  Make sure we
 309                  * have no partial bytes lying around.
 310                  */
 311                 if (state != 0)
 312                         return (-1);
 313         }
 314
 315         return (tarindex);
 316 }