base64.c

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/*
 * 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.
 */
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include "syshead.h"
 
#include "base64.h"
 
#include "memdbg.h"
 
static char base64_chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
/*
 * base64 encode input data of length size to malloced
 * buffer which is returned as *str.  Returns string
 * length of *str.
 */
int
openvpn_base64_encode(const void *data, int size, char **str)
{
    if (size < 0)
    {
        return -1;
    }
    size_t out_size = (size_t)size * 4 / 3 + 4;
    if (out_size > INT_MAX)
    {
        return -1;
    }
    char *p = (char *)malloc(out_size);
    char *start = p;
    if (p == NULL)
    {
        return -1;
    }
    const unsigned char *q = (const unsigned char *)data;
    for (int i = 0; i < size;)
    {
        unsigned int c = q[i++];
        c <<= 8;
        if (i < size)
        {
            c += q[i];
        }
        i++;
        c <<= 8;
        if (i < size)
        {
            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 > size)
        {
            p[3] = '=';
        }
        if (i > size + 1)
        {
            p[2] = '=';
        }
        p += 4;
    }
    *p = 0;
    *str = start;
    return (int)strlen(start);
}
 
static int
pos(char c)
{
    for (char *p = base64_chars; *p; p++)
    {
        if (*p == c)
        {
            return (int)(p - base64_chars);
        }
    }
    return -1;
}
 
#define DECODE_ERROR 0xffffffff
 
static unsigned int
token_decode(const char *token)
{
    unsigned int val = 0;
    unsigned int marker = 0;
    if (!token[0] || !token[1] || !token[2] || !token[3])
    {
        return DECODE_ERROR;
    }
    for (unsigned int i = 0; i < 4; i++)
    {
        val <<= 6;
        if (token[i] == '=')
        {
            marker++;
        }
        else if (marker > 0)
        {
            return DECODE_ERROR;
        }
        else
        {
            int char_pos = pos(token[i]);
            if (unlikely(char_pos < 0)) /* caller should check */
            {
                return DECODE_ERROR;
            }
            val += (unsigned int)char_pos;
        }
    }
    if (marker > 2)
    {
        return DECODE_ERROR;
    }
    return (marker << 24) | val;
}
/*
 * Decode base64 str, outputting data to buffer
 * at data of length size.  Return length of
 * decoded data written or -1 on error or overflow.
 */
int
openvpn_base64_decode(const char *str, void *data, int size)
{
    const char *p;
    unsigned char *q;
    unsigned char *e = NULL;
 
    q = data;
    if (size >= 0)
    {
        e = q + size;
    }
    for (p = str; *p && (*p == '=' || strchr(base64_chars, *p)); p += 4)
    {
        unsigned int val = token_decode(p);
        unsigned int marker = (val >> 24) & 0xff;
        if (val == DECODE_ERROR)
        {
            return -1;
        }
        if (e && q >= e)
        {
            return -1;
        }
        *q++ = (val >> 16) & 0xff;
        if (marker < 2)
        {
            if (e && q >= e)
            {
                return -1;
            }
            *q++ = (val >> 8) & 0xff;
        }
        if (marker < 1)
        {
            if (e && q >= e)
            {
                return -1;
            }
            *q++ = val & 0xff;
        }
    }
    return (int)(q - (unsigned char *)data);
}