avr-crypto-lib/base64/base64_dec.c

/* base64_dec.c */
/*
 *   This file is part of the AVR-Crypto-Lib.
 *   Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)
 *
 *   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/>.
 */

/**
 * base64 decoder (RFC3548)
 * Author: Daniel Otte
 * License: GPLv3
 * 
 * 
 */

#include <stdint.h>
#include "base64_dec.h"

#include "cli.h"

/*
 #define USE_GCC_EXTENSION
 */
#if 1

#ifdef USE_GCC_EXTENSION

static
int ascii2bit6(char a) {
    switch(a) {
        case 'A'...'Z':
        return a-'A';
        case 'a'...'z':
        return a-'a'+26;
        case '0'...'9':
        return a-'0'+52;
        case '+':
        case '-':
        return 62;
        case '/':
        case '_':
        return 63;
        default:
        return -1;
    }
}

#else

static uint8_t ascii2bit6(char a)
{
    int r;
    switch (a >> 4) {
    case 0x5:
        case 0x4:
        r = a - 'A';
        if (r < 0 || r > 25) {
            return -1;
        } else {
            return r;
        }
    case 0x7:
        case 0x6:
        r = a - 'a';
        if (r < 0 || r > 25) {
            return -1;
        } else {
            return r + 26;
        }
        break;
    case 0x3:
        if (a > '9')
            return -1;
        return a - '0' + 52;
    default:
        break;
    }
    switch (a) {
    case '+':
        case '-':
        return 62;
    case '/':
        case '_':
        return 63;
    default:
        return 0xff;
    }
}

#endif

#else

static
uint8_t ascii2bit6(uint8_t a) {
    if(a>='A' && a<='Z') {
        return a-'A';
    } else {
        if(a>='a' && a<= 'z') {
            return a-'a'+26;
        } else {
            if(a>='0' && a<='9') {
                return a-'0'+52;
            } else {
                if(a=='+' || a=='-') {
                    return 62;
                } else {
                    if(a=='/' || a=='_') {
                        return 63;
                    } else {
                        return 0xff;
                    }
                }
            }
        }
    }
}

#endif

int base64_binlength(char *str, uint8_t strict)
{
    int l = 0;
    uint8_t term = 0;
    for (;;) {
        if (*str == '\0')
            break;
        if (*str == '\n' || *str == '\r') {
            str++;
            continue;
        }
        if (*str == '=') {
            term++;
            str++;
            if (term == 2) {
                break;
            }
            continue;
        }
        if (term)
            return -1;
        if (ascii2bit6(*str) == -1) {
            if (strict)
                return -1;
        } else {
            l++;
        }
        str++;
    }
    switch (term) {
    case 0:
        if (l % 4 != 0)
            return -1;
        return l / 4 * 3;
    case 1:
        if (l % 4 != 3)
            return -1;
        return (l + 1) / 4 * 3 - 1;
    case 2:
        if (l % 4 != 2)
            return -1;
        return (l + 2) / 4 * 3 - 2;
    default:
        return -1;
    }
}

/*
 |543210543210543210543210|
 |765432107654321076543210|

 .      .      .     .
 |54321054|32105432|10543210|
 |76543210|76543210|76543210|

 */

int base64dec(void *dest, const char *b64str, uint8_t strict)
{
    uint8_t buffer[4];
    uint8_t idx = 0;
    uint8_t term = 0;
    for (;;) {
//		cli_putstr_P(PSTR("\r\n  DBG: got 0x"));
//		cli_hexdump(b64str, 1);
        buffer[idx] = ascii2bit6(*b64str);
//		cli_putstr_P(PSTR(" --> 0x"));
//		cli_hexdump(buffer+idx, 1);

        if (buffer[idx] == 0xFF) {
            if (*b64str == '=') {
                term++;
                b64str++;
                if (term == 2)
                    goto finalize;
                /* definitly the end */
            } else {
                if (*b64str == '\0') {
                    goto finalize;
                    /* definitly the end */
                } else {
                    if (*b64str == '\r' || *b64str == '\n' || !(strict)) {
                        b64str++; /* charcters that we simply ignore */
                    } else {
                        return -1;
                    }
                }
            }
        } else {
            if (term)
                return -1; /* this happens if we get a '=' in the stream */
            idx++;
            b64str++;
        }
        if (idx == 4) {
            ((uint8_t*) dest)[0] = buffer[0] << 2 | buffer[1] >> 4;
            ((uint8_t*) dest)[1] = buffer[1] << 4 | buffer[2] >> 2;
            ((uint8_t*) dest)[2] = buffer[2] << 6 | buffer[3];
            dest = (uint8_t*) dest + 3;
            idx = 0;
        }
    }
    finalize:
    /* the final touch */
    if (idx == 0)
        return 0;
    if (term == 1) {
        ((uint8_t*) dest)[0] = buffer[0] << 2 | buffer[1] >> 4;
        ((uint8_t*) dest)[1] = buffer[1] << 4 | buffer[2] >> 2;
        return 0;
    }
    if (term == 2) {
        ((uint8_t*) dest)[0] = buffer[0] << 2 | buffer[1] >> 4;
        return 0;
    }
    return -1;
}