/*	$OpenBSD: base64.c,v 1.8 2015/01/16 16:48:51 deraadt Exp $	*/

/*
 * Copyright (c) 1996 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.
 */

static const char b64_Base64[] =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
	"abcdefghijklmnopqrstuvwxyz0123456789+/";
static const char b64_Pad64 = '=';

static int
b64_ntop(unsigned char *src, size_t srclength,
	char *target, size_t targsize)
{
	size_t 		 datalength = 0;
	unsigned char 	 input[3];
	unsigned char 	 output[4];
	size_t 		 i;

	while (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;

		if (datalength + 4 > targsize)
			return (-1);
		target[datalength++] = b64_Base64[output[0]];
		target[datalength++] = b64_Base64[output[1]];
		target[datalength++] = b64_Base64[output[2]];
		target[datalength++] = b64_Base64[output[3]];
	}

	if (0 != srclength) {
		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);
		output[2] = ((input[1] & 0x0f) << 2) + (input[2] >> 6);

		if (datalength + 4 > targsize)
			return (-1);
		target[datalength++] = b64_Base64[output[0]];
		target[datalength++] = b64_Base64[output[1]];
		if (srclength == 1)
			target[datalength++] = b64_Pad64;
		else
			target[datalength++] = b64_Base64[output[2]];
		target[datalength++] = b64_Pad64;
	}
	if (datalength >= targsize)
		return (-1);
	target[datalength] = '\0';
	return (datalength);
}

/* 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.
 */

static int
b64_pton(const char *src, u_char *target, size_t targsize)
{
	int 	 state = 0, ch;
	size_t 	 tarindex = 0;
	u_char 	 nextbyte;
	char 	*pos;

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

		if (ch == b64_Pad64)
			break;

		pos = strchr(b64_Base64, ch);
		if (pos == 0) 		/* A non-base64 character. */
			return (-1);

		switch (state) {
		case 0:
			if (target) {
				if (tarindex >= targsize)
					return (-1);
				target[tarindex] = (pos - b64_Base64) << 2;
			}
			state = 1;
			break;
		case 1:
			if (target) {
				if (tarindex >= targsize)
					return (-1);
				target[tarindex]   |=  (pos - b64_Base64) >> 4;
				nextbyte = ((pos - b64_Base64) & 0x0f) << 4;
				if (tarindex + 1 < targsize)
					target[tarindex+1] = nextbyte;
				else if (nextbyte)
					return (-1);
			}
			tarindex++;
			state = 2;
			break;
		case 2:
			if (target) {
				if (tarindex >= targsize)
					return (-1);
				target[tarindex]   |=  (pos - b64_Base64) >> 2;
				nextbyte = ((pos - b64_Base64) & 0x03) << 6;
				if (tarindex + 1 < targsize)
					target[tarindex+1] = nextbyte;
				else if (nextbyte)
					return (-1);
			}
			tarindex++;
			state = 3;
			break;
		case 3:
			if (target) {
				if (tarindex >= targsize)
					return (-1);
				target[tarindex] |= (pos - b64_Base64);
			}
			tarindex++;
			state = 0;
			break;
		}
	}

	/*
	 * 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 == b64_Pad64) {			/* We got a pad char. */
		ch = (unsigned char)*src++;	/* 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 (; ch != '\0'; ch = (unsigned char)*src++)
				if (!isspace(ch))
					break;
			/* Make sure there is another trailing = sign. */
			if (ch != b64_Pad64)
				return (-1);
			ch = (unsigned char)*src++;		/* 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 (; ch != '\0'; ch = (unsigned char)*src++)
				if (!isspace(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 && tarindex < targsize &&
			    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);
}
