lib/libc/net/base64.c

   1 /*
   2  * Copyright (c) 1996, 1998 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 /*
  44  * $FreeBSD: src/lib/libc/net/base64.c,v 1.4 1999/11/04 04:30:43 ache Exp $
  45  */
  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 {
 133         size_t datalength = 0;
 134         u_char input[3];
 135         u_char output[4];
 136         size_t i;
 137
 138         while (2 < srclength) {
 139                 input[0] = *src++;
 140                 input[1] = *src++;
 141                 input[2] = *src++;
 142                 srclength -= 3;
 143
 144                 output[0] = input[0] >> 2;
 145                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 146                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 147                 output[3] = input[2] & 0x3f;
 148                 Assert(output[0] < 64);
 149                 Assert(output[1] < 64);
 150                 Assert(output[2] < 64);
 151                 Assert(output[3] < 64);
 152
 153                 if (datalength + 4 > targsize)
 154                         return (-1);
 155                 target[datalength++] = Base64[output[0]];
 156                 target[datalength++] = Base64[output[1]];
 157                 target[datalength++] = Base64[output[2]];
 158                 target[datalength++] = Base64[output[3]];
 159         }
 160
 161         /* Now we worry about padding. */
 162         if (0 != srclength) {
 163                 /* Get what's left. */
 164                 input[0] = input[1] = input[2] = '\0';
 165                 for (i = 0; i < srclength; i++)
 166                         input[i] = *src++;
 167
 168                 output[0] = input[0] >> 2;
 169                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 170                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 171                 Assert(output[0] < 64);
 172                 Assert(output[1] < 64);
 173                 Assert(output[2] < 64);
 174
 175                 if (datalength + 4 > targsize)
 176                         return (-1);
 177                 target[datalength++] = Base64[output[0]];
 178                 target[datalength++] = Base64[output[1]];
 179                 if (srclength == 1)
 180                         target[datalength++] = Pad64;
 181                 else
 182                         target[datalength++] = Base64[output[2]];
 183                 target[datalength++] = Pad64;
 184         }
 185         if (datalength >= targsize)
 186                 return (-1);
 187         target[datalength] = '\0';      /* Returned value doesn't count \0. */
 188         return (datalength);
 189 }
 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(char const *src, u_char *target, size_t targsize)
 199 {
 200         int tarindex, state, ch;
 201         char *pos;
 202
 203         state = 0;
 204         tarindex = 0;
 205
 206         while ((ch = *src++) != '\0') {
 207                 if (isspace((unsigned char)ch))        /* Skip whitespace anywhere. */
 208                         continue;
 209
 210                 if (ch == Pad64)
 211                         break;
 212
 213                 pos = strchr(Base64, ch);
 214                 if (pos == NULL)                /* A non-base64 character. */
 215                         return (-1);
 216
 217                 switch (state) {
 218                 case 0:
 219                         if (target) {
 220                                 if ((size_t)tarindex >= targsize)
 221                                         return (-1);
 222                                 target[tarindex] = (pos - Base64) << 2;
 223                         }
 224                         state = 1;
 225                         break;
 226                 case 1:
 227                         if (target) {
 228                                 if ((size_t)tarindex + 1 >= targsize)
 229                                         return (-1);
 230                                 target[tarindex]   |=  (pos - Base64) >> 4;
 231                                 target[tarindex+1]  = ((pos - Base64) & 0x0f)
 232                                                         << 4 ;
 233                         }
 234                         tarindex++;
 235                         state = 2;
 236                         break;
 237                 case 2:
 238                         if (target) {
 239                                 if ((size_t)tarindex + 1 >= targsize)
 240                                         return (-1);
 241                                 target[tarindex]   |=  (pos - Base64) >> 2;
 242                                 target[tarindex+1]  = ((pos - Base64) & 0x03)
 243                                                         << 6;
 244                         }
 245                         tarindex++;
 246                         state = 3;
 247                         break;
 248                 case 3:
 249                         if (target) {
 250                                 if ((size_t)tarindex >= targsize)
 251                                         return (-1);
 252                                 target[tarindex] |= (pos - Base64);
 253                         }
 254                         tarindex++;
 255                         state = 0;
 256                         break;
 257                 default:
 258                         abort();
 259                 }
 260         }
 261
 262         /*
 263          * We are done decoding Base-64 chars.  Let's see if we ended
 264          * on a byte boundary, and/or with erroneous trailing characters.
 265          */
 266
 267         if (ch == Pad64) {              /* We got a pad char. */
 268                 ch = *src++;            /* Skip it, get next. */
 269                 switch (state) {
 270                 case 0:         /* Invalid = in first position */
 271                 case 1:         /* Invalid = in second position */
 272                         return (-1);
 273
 274                 case 2:         /* Valid, means one byte of info */
 275                         /* Skip any number of spaces. */
 276                         for ((void)NULL; ch != '\0'; ch = *src++)
 277                                 if (!isspace((unsigned char)ch))
 278                                         break;
 279                         /* Make sure there is another trailing = sign. */
 280                         if (ch != Pad64)
 281                                 return (-1);
 282                         ch = *src++;            /* Skip the = */
 283                         /* Fall through to "single trailing =" case. */
 284                         /* FALLTHROUGH */
 285
 286                 case 3:         /* Valid, means two bytes of info */
 287                         /*
 288                          * We know this char is an =.  Is there anything but
 289                          * whitespace after it?
 290                          */
 291                         for ((void)NULL; ch != '\0'; ch = *src++)
 292                                 if (!isspace((unsigned char)ch))
 293                                         return (-1);
 294
 295                         /*
 296                          * Now make sure for cases 2 and 3 that the "extra"
 297                          * bits that slopped past the last full byte were
 298                          * zeros.  If we don't check them, they become a
 299                          * subliminal channel.
 300                          */
 301                         if (target && target[tarindex] != 0)
 302                                 return (-1);
 303                 }
 304         } else {
 305                 /*
 306                  * We ended by seeing the end of the string.  Make sure we
 307                  * have no partial bytes lying around.
 308                  */
 309                 if (state != 0)
 310                         return (-1);
 311         }
 312
 313         return (tarindex);
 314 }