dav/crypto.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2013 Olaf Wintermann. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/rand.h>

#include "crypto.h"

AESDecrypter* aes_decrypter_new(Key *key, void *stream, dav_write_func write_func) {
    AESDecrypter *dec = malloc(sizeof(AESDecrypter));
    dec->stream = stream;
    dec->write = write_func;
    dec->key = key;
    dec->init = 0;
    dec->ivpos = 0;
    
    return dec;
}

void aes_decrypter_init(AESDecrypter *dec) {
    EVP_CIPHER_CTX_init(&dec->ctx);
    dec->init = 1;
    if(dec->key->type == KEY_AES128) {
        EVP_DecryptInit_ex(
                &dec->ctx,
                EVP_aes_128_cbc(),
                NULL,
                dec->key->data,
                dec->ivtmp);
    } else if(dec->key->type == KEY_AES256) {
        EVP_DecryptInit_ex(
                &dec->ctx,
                EVP_aes_256_cbc(),
                NULL,
                dec->key->data,
                dec->ivtmp);
    } else {
        fprintf(stderr, "unknown key type\n");
        exit(-1);
    }
}

size_t aes_write(const void *buf, size_t s, size_t n, AESDecrypter *dec) {
    int len = s*n;
    if(!dec->init) {
        size_t n = 16 - dec->ivpos;
        size_t cp = n > len ? len : n;
        memcpy(dec->ivtmp + dec->ivpos, buf, cp);
        dec->ivpos += cp;
        if(dec->ivpos >= 16) {
            aes_decrypter_init(dec);
        }
        if(len == cp) {
            return len;
        } else {
            buf = (char*)buf + cp;
            len -= cp;
        }
    }
    
    int outlen = len + 16;
    unsigned char *out = malloc(outlen);
    EVP_DecryptUpdate(&dec->ctx, out, &len, buf, len);
    dec->write(out, 1, len, dec->stream);
    free(out);
    return (s*n) / s;
}

void aes_decrypter_close(AESDecrypter *dec) {
    void *out = malloc(128);
    int len = 0;
    EVP_DecryptFinal_ex(&dec->ctx, out, &len);
    dec->write(out, 1, len, dec->stream);
    free(out);
    EVP_CIPHER_CTX_cleanup(&dec->ctx);
    free(dec);
}


AESEncrypter* aes_encrypter_new(Key *key, void *stream, dav_read_func read_func) {
    unsigned char *iv = malloc(16);
    if(!RAND_bytes(iv, 16)) {
        free(iv);
        return NULL;
    }
    
    AESEncrypter *enc = malloc(sizeof(AESEncrypter));
    enc->stream = stream;
    enc->read = read_func;
    enc->tmp = NULL;
    enc->tmplen = 0;
    enc->tmpoff = 0;
    enc->end = 0;
    //enc->iv = iv;
    enc->iv = iv;
    enc->ivlen = 16;
    
    EVP_CIPHER_CTX_init(&enc->ctx);
    if(key->type == KEY_AES128) {
        EVP_EncryptInit_ex(&enc->ctx, EVP_aes_128_cbc(), NULL, key->data, enc->iv);
    } else if(key->type == KEY_AES256) {
        EVP_EncryptInit_ex(&enc->ctx, EVP_aes_256_cbc(), NULL, key->data, enc->iv);
    } else {
        fprintf(stderr, "unknown key type\n");
        exit(-1);
    }
    return enc;
}

size_t aes_read(void *buf, size_t s, size_t n, AESEncrypter *enc) {
    size_t len = s*n;
    if(enc->tmp) {
        size_t tmp_diff = enc->tmplen - enc->tmpoff;
        size_t cp_len = tmp_diff > len ? len : tmp_diff;
        memcpy(buf, enc->tmp + enc->tmpoff, cp_len);
        enc->tmpoff += cp_len;
        if(enc->tmpoff >= enc->tmplen) {
            free(enc->tmp);
            enc->tmp = NULL;
            enc->tmplen = 0;
            enc->tmpoff = 0;
        }
        return cp_len / s;
    }
    
    if(enc->end) {
        return 0;
    }
    
    void *in = malloc(len);
    size_t in_len = enc->read(in, 1, len, enc->stream);
    
    unsigned char *out = NULL;
    int outlen = 0;
    size_t ivl = enc->ivlen;
    if(in_len != 0) {
        outlen = len + 16;
        out = malloc(outlen + ivl);
        if(enc->iv) {
            memcpy(out, enc->iv, ivl);
        }
        EVP_EncryptUpdate(&enc->ctx, out + ivl, &outlen, in, in_len);
        free(in);
    } else {
        out = malloc(16);
        EVP_EncryptFinal_ex(&enc->ctx, out, &outlen);
        enc->end = 1;
    }
    enc->tmp = (char*)out;
    enc->tmplen = outlen + ivl;
    enc->tmpoff = 0;
    
    if(enc->iv) {
        enc->iv = NULL;
        enc->ivlen = 0;
    }
    
    return aes_read(buf, s, n, enc);
}

void aes_encrypter_close(AESEncrypter *enc) {
    if(enc->tmp) {
        free(enc->tmp);
    }
    EVP_CIPHER_CTX_cleanup(&enc->ctx);
    free(enc);
}