/*
 * 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 "base64.h"

#include <assert.h>
#include <ctype.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.
 */

int
p11_b64_pton (const char *src,
              size_t length,
              unsigned char *target,
              size_t targsize)
{
	int tarindex, state, ch;
	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);
}

int
p11_b64_ntop (const unsigned char *src,
              size_t srclength,
              char *target,
              size_t targsize,
              int breakl)
{
	size_t len = 0;
	unsigned char input[3];
	unsigned char output[4];
	size_t i;

	while (srclength > 0) {
		if (2 < srclength) {
			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 if (0 != srclength) {
			/* 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++) {
			if (breakl && len % (breakl + 1) == 0) {
				assert (len + 1 < targsize);
				target[len++] = '\n';
			}

			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;
}
