base64.c

/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* util/support/base64.c - base64 encoder and decoder */
/*
 * Copyright (c) 1995-2001 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

//#include <k5-platform.h>
//#include <k5-base64.h>
#include <string.h>
#include <stdlib.h>

#ifndef SIZE_MAX
#define SIZE_MAX ((size_t)((size_t)0 - 1))
#endif

static const char base64_chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

char *
k5_base64_encode(const void *data, size_t len)
{
	char *s, *p;
	size_t i;
	unsigned int c;
	const unsigned char *q;

	if (len > SIZE_MAX / 4)
		return NULL;

	p = s = malloc(len * 4 / 3 + 4);
	if (p == NULL)
		return NULL;
	q = (const unsigned char *)data;

	for (i = 0; i < len;) {
		c = q[i++];
		c *= 256;
		if (i < len)
			c += q[i];
		i++;
		c *= 256;
		if (i < len)
			c += q[i];
		i++;
		p[0] = base64_chars[(c & 0x00fc0000) >> 18];
		p[1] = base64_chars[(c & 0x0003f000) >> 12];
		p[2] = base64_chars[(c & 0x00000fc0) >> 6];
		p[3] = base64_chars[(c & 0x0000003f) >> 0];
		if (i > len)
			p[3] = '=';
		if (i > len + 1)
			p[2] = '=';
		p += 4;
	}
	*p = '\0';
	return s;
}

#define DECODE_ERROR 0xffffffff

/* Decode token, which must be four bytes long. */
static unsigned int
decode_token(const char *token)
{
	int i, marker = 0;
	unsigned int val = 0;
	const char *p;

	for (i = 0; i < 4; i++) {
		val *= 64;
		if (token[i] == '=') {
			marker++;
		} else if (marker > 0) {
			return DECODE_ERROR;
		} else {
			p = strchr(base64_chars, token[i]);
			if (p == NULL)
				return DECODE_ERROR;
			val += p - base64_chars;
		}
	}
	if (marker > 2)
		return DECODE_ERROR;
	return (marker << 24) | val;
}

void *
k5_base64_decode(const char *str, size_t *len_out)
{
	unsigned char *data, *q;
	unsigned int val, marker;
	size_t len;

	*len_out = SIZE_MAX;

	/* Allocate the output buffer. */
	len = strlen(str);
	if (len % 4)
		return NULL;
	q = data = malloc(len / 4 * 3);
	if (data == NULL) {
		*len_out = 0;
		return NULL;
	}

	/* Decode the string. */
	for (; *str != '\0'; str += 4) {
		val = decode_token(str);
		if (val == DECODE_ERROR) {
			free(data);
			return NULL;
		}
		marker = (val >> 24) & 0xff;
		*q++ = (val >> 16) & 0xff;
		if (marker < 2)
			*q++ = (val >> 8) & 0xff;
		if (marker < 1)
			*q++ = val & 0xff;
	}
	*len_out = q - data;
	return data;
}