/*
 * SPDX-License-Identifier: ISC
 *
 * Copyright (c) 1996, 1998 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

/*
 * Portions Copyright (c) 1995 by International Business Machines, Inc.
 *
 * International Business Machines, Inc. (hereinafter called IBM) grants
 * permission under its copyrights to use, copy, modify, and distribute this
 * Software with or without fee, provided that the above copyright notice and
 * all paragraphs of this notice appear in all copies, and that the name of IBM
 * not be used in connection with the marketing of any product incorporating
 * the Software or modifications thereof, without specific, written prior
 * permission.
 *
 * To the extent it has a right to do so, IBM grants an immunity from suit
 * under its patents, if any, for the use, sale or manufacture of products to
 * the extent that such products are used for performing Domain Name System
 * dynamic updates in TCP/IP networks by means of the Software.  No immunity is
 * granted for any product per se or for any other function of any product.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", AND IBM DISCLAIMS ALL WARRANTIES,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE.  IN NO EVENT SHALL IBM BE LIABLE FOR ANY SPECIAL,
 * DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE, EVEN
 * IF IBM IS APPRISED OF THE POSSIBILITY OF SUCH DAMAGES.
 */

#include "config.h"

#include "cockpitbase64.h"

#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>

static const char Base64[] =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const char Pad64 = '=';

/* skips all whitespace anywhere.
 converts characters, four at a time, starting at (or after)
 src from base - 64 numbers into three 8 bit bytes in the target area.
 it returns the number of data bytes stored at the target, or -1 on error.
 */

ssize_t
cockpit_base64_pton (const char *src,
                     size_t length,
                     unsigned char *target,
                     size_t targsize)
{
  int tarindex, state, ch;
  const char *pos;
  const char *end;

  state = 0;
  tarindex = 0;
  end = src + length;

  /* We can't rely on the null terminator */
  #define next_char(src, end) \
    (((src) == (end)) ? '\0': *(src)++)

  while ((ch = next_char (src, end)) != '\0')
    {
      if (isspace ((unsigned char) ch)) /* Skip whitespace anywhere. */
        continue;

      if (ch == Pad64)
        break;

      pos = strchr (Base64, ch);
      if (pos == 0) /* A non-base64 character */
        return (-1);

      switch (state)
        {
        case 0:
          if (target)
            {
              if ((size_t)tarindex >= targsize)
                return (-1);
              target[tarindex] = (pos - Base64) << 2;
            }
          state = 1;
          break;
        case 1:
          if (target)
            {
              if ((size_t) tarindex + 1 >= targsize)
                return (-1);
              target[tarindex] |= (pos - Base64) >> 4;
              target[tarindex + 1] = ((pos - Base64) & 0x0f) << 4;
            }
          tarindex++;
          state = 2;
          break;
        case 2:
          if (target)
            {
              if ((size_t) tarindex + 1 >= targsize)
                return (-1);
              target[tarindex] |= (pos - Base64) >> 2;
              target[tarindex + 1] = ((pos - Base64) & 0x03) << 6;
            }
          tarindex++;
          state = 3;
          break;
        case 3:
          if (target)
            {
              if ((size_t) tarindex >= targsize)
                return (-1);
              target[tarindex] |= (pos - Base64);
            }
          tarindex++;
          state = 0;
          break;
        default:
          abort();
        }
    }

  /*
   * We are done decoding Base-64 chars.  Let's see if we ended
   * on a byte boundary, and/or with erroneous trailing characters.
   */

  if (ch == Pad64)
    { /* We got a pad char. */
      ch = next_char (src, end); /* Skip it, get next. */
      switch (state)
        {
        case 0: /* Invalid = in first position */
        case 1: /* Invalid = in second position */
          return (-1);

        case 2: /* Valid, means one byte of info */
          /* Skip any number of spaces. */
          for ((void) NULL; ch != '\0'; ch = next_char (src, end))
            {
              if (!isspace((unsigned char) ch))
                break;
            }
          /* Make sure there is another trailing = sign. */
          if (ch != Pad64)
            return (-1);
          ch = next_char (src, end); /* Skip the = */
          /* Fall through to "single trailing =" case. */
          /* FALLTHROUGH */

        case 3: /* Valid, means two bytes of info */
          /*
           * We know this char is an =.  Is there anything but
           * whitespace after it?
           */
          for ((void)NULL; src != end; ch = next_char (src, end))
            {
              if (!isspace((unsigned char) ch))
                return (-1);
            }

          /*
           * Now make sure for cases 2 and 3 that the "extra"
           * bits that slopped past the last full byte were
           * zeros.  If we don't check them, they become a
           * subliminal channel.
           */
          if (target && target[tarindex] != 0)
            return (-1);
        }
    }
  else
    {
      /*
       * We ended by seeing the end of the string.  Make sure we
       * have no partial bytes lying around.
       */
      if (state != 0)
        return (-1);
    }

  return (tarindex);
}

ssize_t
cockpit_base64_ntop (const unsigned char *src,
                     size_t srclength,
                     char *target,
                     size_t targsize)
{
  size_t len = 0;
  unsigned char input[3];
  unsigned char output[4];
  size_t i;

  while (srclength > 0)
    {
      if (srclength >= 3)
        {
          input[0] = *src++;
          input[1] = *src++;
          input[2] = *src++;
          srclength -= 3;

          output[0] = input[0] >> 2;
          output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
          output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
          output[3] = input[2] & 0x3f;

        }
      else
        {
          /* srclength 1 or 2: Get what's left. */
          input[0] = input[1] = input[2] = '\0';
          for (i = 0; i < srclength; i++)
            input[i] = *src++;

          output[0] = input[0] >> 2;
          output[1] = ((input[0] & 0x03) << 4) + (input[1] >> 4);
          if (srclength == 1)
            output[2] = 255;
          else
            output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);
          output[3] = 255;

          srclength = 0;
        }

      for (i = 0; i < 4; i++)
        {
          assert(output[i] == 255 || output[i] < 64);
          assert (len + 1 < targsize);

          if (output[i] == 255)
            target[len++] = Pad64;
          else
            target[len++] = Base64[output[i]];
        }
    }

  assert (len < targsize);
  target[len] = '\0';      /* Returned value doesn't count \0. */
  return len;
}
