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 libresolv_hidden_def (b64_ntop)
 190
 191 /* skips all whitespace anywhere.
 192    converts characters, four at a time, starting at (or after)
 193    src from base - 64 numbers into three 8 bit bytes in the target area.
 194    it returns the number of data bytes stored at the target, or -1 on error.
 195  */
 196
 197 int
 198 b64_pton(src, target, targsize)
 199         char const *src;
 200         u_char *target;
 201         size_t targsize;
 202 {
 203         int tarindex, state, ch;
 204         char *pos;
 205
 206         state = 0;
 207         tarindex = 0;
 208
 209         while ((ch = *src++) != '\0') {
 210                 if (isspace(ch))        /* Skip whitespace anywhere. */
 211                         continue;
 212
 213                 if (ch == Pad64)
 214                         break;
 215
 216                 pos = strchr(Base64, ch);
 217                 if (pos == 0)           /* A non-base64 character. */
 218                         return (-1);
 219
 220                 switch (state) {
 221                 case 0:
 222                         if (target) {
 223                                 if ((size_t)tarindex >= targsize)
 224                                         return (-1);
 225                                 target[tarindex] = (pos - Base64) << 2;
 226                         }
 227                         state = 1;
 228                         break;
 229                 case 1:
 230                         if (target) {
 231                                 if ((size_t)tarindex + 1 >= targsize)
 232                                         return (-1);
 233                                 target[tarindex]   |=  (pos - Base64) >> 4;
 234                                 target[tarindex+1]  = ((pos - Base64) & 0x0f)
 235                                                         << 4 ;
 236                         }
 237                         tarindex++;
 238                         state = 2;
 239                         break;
 240                 case 2:
 241                         if (target) {
 242                                 if ((size_t)tarindex + 1 >= targsize)
 243                                         return (-1);
 244                                 target[tarindex]   |=  (pos - Base64) >> 2;
 245                                 target[tarindex+1]  = ((pos - Base64) & 0x03)
 246                                                         << 6;
 247                         }
 248                         tarindex++;
 249                         state = 3;
 250                         break;
 251                 case 3:
 252                         if (target) {
 253                                 if ((size_t)tarindex >= targsize)
 254                                         return (-1);
 255                                 target[tarindex] |= (pos - Base64);
 256                         }
 257                         tarindex++;
 258                         state = 0;
 259                         break;
 260                 default:
 261                         abort();
 262                 }
 263         }
 264
 265         /*
 266          * We are done decoding Base-64 chars.  Let's see if we ended
 267          * on a byte boundary, and/or with erroneous trailing characters.
 268          */
 269
 270         if (ch == Pad64) {              /* We got a pad char. */
 271                 ch = *src++;            /* Skip it, get next. */
 272                 switch (state) {
 273                 case 0:         /* Invalid = in first position */
 274                 case 1:         /* Invalid = in second position */
 275                         return (-1);
 276
 277                 case 2:         /* Valid, means one byte of info */
 278                         /* Skip any number of spaces. */
 279                         for ((void)NULL; ch != '\0'; ch = *src++)
 280                                 if (!isspace(ch))
 281                                         break;
 282                         /* Make sure there is another trailing = sign. */
 283                         if (ch != Pad64)
 284                                 return (-1);
 285                         ch = *src++;            /* Skip the = */
 286                         /* Fall through to "single trailing =" case. */
 287                         /* FALLTHROUGH */
 288
 289                 case 3:         /* Valid, means two bytes of info */
 290                         /*
 291                          * We know this char is an =.  Is there anything but
 292                          * whitespace after it?
 293                          */
 294                         for ((void)NULL; ch != '\0'; ch = *src++)
 295                                 if (!isspace(ch))
 296                                         return (-1);
 297
 298                         /*
 299                          * Now make sure for cases 2 and 3 that the "extra"
 300                          * bits that slopped past the last full byte were
 301                          * zeros.  If we don't check them, they become a
 302                          * subliminal channel.
 303                          */
 304                         if (target && target[tarindex] != 0)
 305                                 return (-1);
 306                 }
 307         } else {
 308                 /*
 309                  * We ended by seeing the end of the string.  Make sure we
 310                  * have no partial bytes lying around.
 311                  */
 312                 if (state != 0)
 313                         return (-1);
 314         }
 315
 316         return (tarindex);
 317 }