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  * $DragonFly: src/lib/libc/net/base64.c,v 1.4 2005/11/13 02:04:47 swildner Exp $
  46  */
  47
  48 #include <sys/types.h>
  49 #include <sys/param.h>
  50 #include <sys/socket.h>
  51
  52 #include <netinet/in.h>
  53 #include <arpa/inet.h>
  54 #include <arpa/nameser.h>
  55
  56 #include <ctype.h>
  57 #include <resolv.h>
  58 #include <stdio.h>
  59 #include <stdlib.h>
  60 #include <string.h>
  61
  62 #define Assert(Cond) if (!(Cond)) abort()
  63
  64 static const char Base64[] =
  65         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  66 static const char Pad64 = '=';
  67
  68 /* (From RFC1521 and draft-ietf-dnssec-secext-03.txt)
  69    The following encoding technique is taken from RFC 1521 by Borenstein
  70    and Freed.  It is reproduced here in a slightly edited form for
  71    convenience.
  72
  73    A 65-character subset of US-ASCII is used, enabling 6 bits to be
  74    represented per printable character. (The extra 65th character, "=",
  75    is used to signify a special processing function.)
  76
  77    The encoding process represents 24-bit groups of input bits as output
  78    strings of 4 encoded characters. Proceeding from left to right, a
  79    24-bit input group is formed by concatenating 3 8-bit input groups.
  80    These 24 bits are then treated as 4 concatenated 6-bit groups, each
  81    of which is translated into a single digit in the base64 alphabet.
  82
  83    Each 6-bit group is used as an index into an array of 64 printable
  84    characters. The character referenced by the index is placed in the
  85    output string.
  86
  87                          Table 1: The Base64 Alphabet
  88
  89       Value Encoding  Value Encoding  Value Encoding  Value Encoding
  90           0 A            17 R            34 i            51 z
  91           1 B            18 S            35 j            52 0
  92           2 C            19 T            36 k            53 1
  93           3 D            20 U            37 l            54 2
  94           4 E            21 V            38 m            55 3
  95           5 F            22 W            39 n            56 4
  96           6 G            23 X            40 o            57 5
  97           7 H            24 Y            41 p            58 6
  98           8 I            25 Z            42 q            59 7
  99           9 J            26 a            43 r            60 8
 100          10 K            27 b            44 s            61 9
 101          11 L            28 c            45 t            62 +
 102          12 M            29 d            46 u            63 /
 103          13 N            30 e            47 v
 104          14 O            31 f            48 w         (pad) =
 105          15 P            32 g            49 x
 106          16 Q            33 h            50 y
 107
 108    Special processing is performed if fewer than 24 bits are available
 109    at the end of the data being encoded.  A full encoding quantum is
 110    always completed at the end of a quantity.  When fewer than 24 input
 111    bits are available in an input group, zero bits are added (on the
 112    right) to form an integral number of 6-bit groups.  Padding at the
 113    end of the data is performed using the '=' character.
 114
 115    Since all base64 input is an integral number of octets, only the
 116          -------------------------------------------------
 117    following cases can arise:
 118
 119        (1) the final quantum of encoding input is an integral
 120            multiple of 24 bits; here, the final unit of encoded
 121            output will be an integral multiple of 4 characters
 122            with no "=" padding,
 123        (2) the final quantum of encoding input is exactly 8 bits;
 124            here, the final unit of encoded output will be two
 125            characters followed by two "=" padding characters, or
 126        (3) the final quantum of encoding input is exactly 16 bits;
 127            here, the final unit of encoded output will be three
 128            characters followed by one "=" padding character.
 129    */
 130
 131 int
 132 b64_ntop(u_char const *src, size_t srclength, char *target, size_t targsize)
 133 {
 134         size_t datalength = 0;
 135         u_char input[3];
 136         u_char output[4];
 137         size_t i;
 138
 139         while (2 < srclength) {
 140                 input[0] = *src++;
 141                 input[1] = *src++;
 142                 input[2] = *src++;
 143                 srclength -= 3;
 144
 145                 output[0] = input[0] >> 2;
 146                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 147                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 148                 output[3] = input[2] & 0x3f;
 149                 Assert(output[0] < 64);
 150                 Assert(output[1] < 64);
 151                 Assert(output[2] < 64);
 152                 Assert(output[3] < 64);
 153
 154                 if (datalength + 4 > targsize)
 155                         return (-1);
 156                 target[datalength++] = Base64[output[0]];
 157                 target[datalength++] = Base64[output[1]];
 158                 target[datalength++] = Base64[output[2]];
 159                 target[datalength++] = Base64[output[3]];
 160         }
 161
 162         /* Now we worry about padding. */
 163         if (0 != srclength) {
 164                 /* Get what's left. */
 165                 input[0] = input[1] = input[2] = '\0';
 166                 for (i = 0; i < srclength; i++)
 167                         input[i] = *src++;
 168
 169                 output[0] = input[0] >> 2;
 170                 output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
 171                 output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
 172                 Assert(output[0] < 64);
 173                 Assert(output[1] < 64);
 174                 Assert(output[2] < 64);
 175
 176                 if (datalength + 4 > targsize)
 177                         return (-1);
 178                 target[datalength++] = Base64[output[0]];
 179                 target[datalength++] = Base64[output[1]];
 180                 if (srclength == 1)
 181                         target[datalength++] = Pad64;
 182                 else
 183                         target[datalength++] = Base64[output[2]];
 184                 target[datalength++] = Pad64;
 185         }
 186         if (datalength >= targsize)
 187                 return (-1);
 188         target[datalength] = '\0';      /* Returned value doesn't count \0. */
 189         return (datalength);
 190 }
 191
 192 /* skips all whitespace anywhere.
 193    converts characters, four at a time, starting at (or after)
 194    src from base - 64 numbers into three 8 bit bytes in the target area.
 195    it returns the number of data bytes stored at the target, or -1 on error.
 196  */
 197
 198 int
 199 b64_pton(char const *src, u_char *target, size_t targsize)
 200 {
 201         int tarindex, state, ch;
 202         char *pos;
 203
 204         state = 0;
 205         tarindex = 0;
 206
 207         while ((ch = *src++) != '\0') {
 208                 if (isspace((unsigned char)ch))        /* Skip whitespace anywhere. */
 209                         continue;
 210
 211                 if (ch == Pad64)
 212                         break;
 213
 214                 pos = strchr(Base64, ch);
 215                 if (pos == 0)           /* A non-base64 character. */
 216                         return (-1);
 217
 218                 switch (state) {
 219                 case 0:
 220                         if (target) {
 221                                 if ((size_t)tarindex >= targsize)
 222                                         return (-1);
 223                                 target[tarindex] = (pos - Base64) << 2;
 224                         }
 225                         state = 1;
 226                         break;
 227                 case 1:
 228                         if (target) {
 229                                 if ((size_t)tarindex + 1 >= targsize)
 230                                         return (-1);
 231                                 target[tarindex]   |=  (pos - Base64) >> 4;
 232                                 target[tarindex+1]  = ((pos - Base64) & 0x0f)
 233                                                         << 4 ;
 234                         }
 235                         tarindex++;
 236                         state = 2;
 237                         break;
 238                 case 2:
 239                         if (target) {
 240                                 if ((size_t)tarindex + 1 >= targsize)
 241                                         return (-1);
 242                                 target[tarindex]   |=  (pos - Base64) >> 2;
 243                                 target[tarindex+1]  = ((pos - Base64) & 0x03)
 244                                                         << 6;
 245                         }
 246                         tarindex++;
 247                         state = 3;
 248                         break;
 249                 case 3:
 250                         if (target) {
 251                                 if ((size_t)tarindex >= targsize)
 252                                         return (-1);
 253                                 target[tarindex] |= (pos - Base64);
 254                         }
 255                         tarindex++;
 256                         state = 0;
 257                         break;
 258                 default:
 259                         abort();
 260                 }
 261         }
 262
 263         /*
 264          * We are done decoding Base-64 chars.  Let's see if we ended
 265          * on a byte boundary, and/or with erroneous trailing characters.
 266          */
 267
 268         if (ch == Pad64) {              /* We got a pad char. */
 269                 ch = *src++;            /* Skip it, get next. */
 270                 switch (state) {
 271                 case 0:         /* Invalid = in first position */
 272                 case 1:         /* Invalid = in second position */
 273                         return (-1);
 274
 275                 case 2:         /* Valid, means one byte of info */
 276                         /* Skip any number of spaces. */
 277                         for ((void)NULL; ch != '\0'; ch = *src++)
 278                                 if (!isspace((unsigned char)ch))
 279                                         break;
 280                         /* Make sure there is another trailing = sign. */
 281                         if (ch != Pad64)
 282                                 return (-1);
 283                         ch = *src++;            /* Skip the = */
 284                         /* Fall through to "single trailing =" case. */
 285                         /* FALLTHROUGH */
 286
 287                 case 3:         /* Valid, means two bytes of info */
 288                         /*
 289                          * We know this char is an =.  Is there anything but
 290                          * whitespace after it?
 291                          */
 292                         for ((void)NULL; ch != '\0'; ch = *src++)
 293                                 if (!isspace((unsigned char)ch))
 294                                         return (-1);
 295
 296                         /*
 297                          * Now make sure for cases 2 and 3 that the "extra"
 298                          * bits that slopped past the last full byte were
 299                          * zeros.  If we don't check them, they become a
 300                          * subliminal channel.
 301                          */
 302                         if (target && target[tarindex] != 0)
 303                                 return (-1);
 304                 }
 305         } else {
 306                 /*
 307                  * We ended by seeing the end of the string.  Make sure we
 308                  * have no partial bytes lying around.
 309                  */
 310                 if (state != 0)
 311                         return (-1);
 312         }
 313
 314         return (tarindex);
 315 }