base64.c

/*
 * Copyright (C), 2000-2007 by the monit project group.
 * All Rights Reserved.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "rdup-tr.h"
#include "base64.h"

/* See Section 4 of RFC 3548, be URL safe, modified by Miek Gieben, 2009 */

/* Private prototypes */
static int is_base64(char c);
static char encode(unsigned char u);
static unsigned char decode(char c);

/**
 *  Implementation of base64 encoding/decoding.
 *  @author Jan-Henrik Haukeland, <hauk@tildeslash.com>
 *  @version \$Id: base64.c,v 1.19 2007/07/25 12:54:31 hauk Exp $
 *
 */

/**
 * Base64 encode and return size data in 'src'. The caller must free the
 * returned string.
 * @param size The size of the data in src
 * @param src The data to be base64 encode
 * @return encoded string otherwise NULL
 */
char
*encode_base64(int size, unsigned char *src)
{
	int i;
	char *out, *p;

	if (!src)
		return NULL;

	if (!size)
		size = strlen((char *)src);

	out = g_malloc0(size * 4 / 3 + 4);
	p = out;

	for (i = 0; i < size; i += 3) {

		unsigned char b1 = 0, b2 = 0, b3 = 0, b4 = 0, b5 = 0, b6 =
		    0, b7 = 0;

		b1 = src[i];

		if (i + 1 < size)
			b2 = src[i + 1];

		if (i + 2 < size)
			b3 = src[i + 2];

		b4 = b1 >> 2;
		b5 = ((b1 & 0x3) << 4) | (b2 >> 4);
		b6 = ((b2 & 0xf) << 2) | (b3 >> 6);
		b7 = b3 & 0x3f;

		*p++ = encode(b4);
		*p++ = encode(b5);

		if (i + 1 < size) {
			*p++ = encode(b6);
		} else {
			*p++ = '=';
		}

		if (i + 2 < size) {
			*p++ = encode(b7);
		} else {
			*p++ = '=';
		}
	}
	return out;
}

/**
 * Decode the base64 encoded string 'src' into the memory pointed to by
 * 'dest'. The dest buffer is <b>not</b> NUL terminated.
 * @param dest Pointer to memory for holding the decoded string.
 * Must be large enough to recieve the decoded string.
 * @param src A base64 encoded string.
 * @return (the length of the decoded string) if decode
 * succeeded otherwise FALSE.
 */
int decode_base64(unsigned char *dest, const char *src)
{
	if (src && *src) {

		unsigned char *p = dest;
		int k, l = strlen(src) + 1;
		unsigned char *buf = g_malloc0(l);

		/* Ignore non base64 chars as per the POSIX standard */
		for (k = 0, l = 0; src[k]; k++) {
			if (is_base64(src[k])) {
				buf[l++] = src[k];
			}
		}

		for (k = 0; k < l; k += 4) {
			char c1 = 'A', c2 = 'A', c3 = 'A', c4 = 'A';
			unsigned char b1 = 0, b2 = 0, b3 = 0, b4 = 0;

			c1 = buf[k];
			if (k + 1 < l) {
				c2 = buf[k + 1];
			}

			if (k + 2 < l) {
				c3 = buf[k + 2];
			}

			if (k + 3 < l) {
				c4 = buf[k + 3];
			}

			b1 = decode(c1);
			b2 = decode(c2);
			b3 = decode(c3);
			b4 = decode(c4);

			*p++ = ((b1 << 2) | (b2 >> 4));

			if (c3 != '=') {
				*p++ = (((b2 & 0xf) << 4) | (b3 >> 2));
			}
			if (c4 != '=') {
				*p++ = (((b3 & 0x3) << 6) | b4);
			}
		}

		g_free(buf);
		return (p - dest);
	}
	return FALSE;
}

/**
 * Base64 encode one byte
 */
static char encode(unsigned char u)
{
	if (u < 26)
		return 'A' + u;
	if (u < 52)
		return 'a' + (u - 26);
	if (u < 62)
		return '0' + (u - 52);
	if (u == 62)
		return '-';	/* was + */

	/* return '/'; */
	return '_';
}

/**
 * Decode a base64 character
 */
static unsigned char decode(char c)
{
	if (c >= 'A' && c <= 'Z')
		return (c - 'A');
	if (c >= 'a' && c <= 'z')
		return (c - 'a' + 26);
	if (c >= '0' && c <= '9')
		return (c - '0' + 52);
	if (c == '-')
		return 62;	/* was '+' */
	return 63;
}

/**
 * Return TRUE if 'c' is a valid base64 character, otherwise FALSE
 */
static int is_base64(char c)
{
	if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') ||
	    (c >= '0' && c <= '9') || (c == '-') || (c == '_') || (c == '=')) {
		return TRUE;
	}
	return FALSE;
}