/* crypto/des/enc_read.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * 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 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``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 AUTHOR 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.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include <stdio.h>
#include <errno.h>
#include "cryptlib.h"
#include "des_locl.h"

/* This has some uglies in it but it works - even over sockets. */
/*
 * extern int errno;
 */
OPENSSL_IMPLEMENT_GLOBAL(int, DES_rw_mode) = DES_PCBC_MODE;

/*-
 * WARNINGS:
 *
 *  -  The data format used by DES_enc_write() and DES_enc_read()
 *     has a cryptographic weakness: When asked to write more
 *     than MAXWRITE bytes, DES_enc_write will split the data
 *     into several chunks that are all encrypted
 *     using the same IV.  So don't use these functions unless you
 *     are sure you know what you do (in which case you might
 *     not want to use them anyway).
 *
 *  -  This code cannot handle non-blocking sockets.
 *
 *  -  This function uses an internal state and thus cannot be
 *     used on multiple files.
 */

int DES_enc_read(int fd, void *buf, int len, DES_key_schedule *sched,
                 DES_cblock *iv)
{
    /* data to be unencrypted */
    int net_num = 0;
    static unsigned char *net = NULL;
    /*
     * extra unencrypted data for when a block of 100 comes in but is
     * des_read one byte at a time.
     */
    static unsigned char *unnet = NULL;
    static int unnet_start = 0;
    static int unnet_left = 0;
    static unsigned char *tmpbuf = NULL;
    int i;
    long num = 0, rnum;
    unsigned char *p;

    if (tmpbuf == NULL) {
        tmpbuf = OPENSSL_malloc(BSIZE);
        if (tmpbuf == NULL)
            return (-1);
    }
    if (net == NULL) {
        net = OPENSSL_malloc(BSIZE);
        if (net == NULL)
            return (-1);
    }
    if (unnet == NULL) {
        unnet = OPENSSL_malloc(BSIZE);
        if (unnet == NULL)
            return (-1);
    }
    /* left over data from last decrypt */
    if (unnet_left != 0) {
        if (unnet_left < len) {
            /*
             * we still still need more data but will return with the number
             * of bytes we have - should always check the return value
             */
            memcpy(buf, &(unnet[unnet_start]), unnet_left);
            /*
             * eay 26/08/92 I had the next 2 lines reversed :-(
             */
            i = unnet_left;
            unnet_start = unnet_left = 0;
        } else {
            memcpy(buf, &(unnet[unnet_start]), len);
            unnet_start += len;
            unnet_left -= len;
            i = len;
        }
        return (i);
    }

    /* We need to get more data. */
    if (len > MAXWRITE)
        len = MAXWRITE;

    /* first - get the length */
    while (net_num < HDRSIZE) {
#ifndef _WIN32
        i = read(fd, (void *)&(net[net_num]), HDRSIZE - net_num);
#else
        i = _read(fd, (void *)&(net[net_num]), HDRSIZE - net_num);
#endif
#ifdef EINTR
        if ((i == -1) && (errno == EINTR))
            continue;
#endif
        if (i <= 0)
            return (0);
        net_num += i;
    }

    /* we now have at net_num bytes in net */
    p = net;
    /* num=0;  */
    n2l(p, num);
    /*
     * num should be rounded up to the next group of eight we make sure that
     * we have read a multiple of 8 bytes from the net.
     */
    if ((num > MAXWRITE) || (num < 0)) /* error */
        return (-1);
    rnum = (num < 8) ? 8 : ((num + 7) / 8 * 8);

    net_num = 0;
    while (net_num < rnum) {
        i = read(fd, (void *)&(net[net_num]), rnum - net_num);
#ifdef EINTR
        if ((i == -1) && (errno == EINTR))
            continue;
#endif
        if (i <= 0)
            return (0);
        net_num += i;
    }

    /* Check if there will be data left over. */
    if (len < num) {
        if (DES_rw_mode & DES_PCBC_MODE)
            DES_pcbc_encrypt(net, unnet, num, sched, iv, DES_DECRYPT);
        else
            DES_cbc_encrypt(net, unnet, num, sched, iv, DES_DECRYPT);
        memcpy(buf, unnet, len);
        unnet_start = len;
        unnet_left = num - len;

        /*
         * The following line is done because we return num as the number of
         * bytes read.
         */
        num = len;
    } else {
        /*-
         * >output is a multiple of 8 byes, if len < rnum
         * >we must be careful.  The user must be aware that this
         * >routine will write more bytes than he asked for.
         * >The length of the buffer must be correct.
         * FIXED - Should be ok now 18-9-90 - eay */
        if (len < rnum) {

            if (DES_rw_mode & DES_PCBC_MODE)
                DES_pcbc_encrypt(net, tmpbuf, num, sched, iv, DES_DECRYPT);
            else
                DES_cbc_encrypt(net, tmpbuf, num, sched, iv, DES_DECRYPT);

            /*
             * eay 26/08/92 fix a bug that returned more bytes than you asked
             * for (returned len bytes :-(
             */
            memcpy(buf, tmpbuf, num);
        } else {
            if (DES_rw_mode & DES_PCBC_MODE)
                DES_pcbc_encrypt(net, buf, num, sched, iv, DES_DECRYPT);
            else
                DES_cbc_encrypt(net, buf, num, sched, iv, DES_DECRYPT);
        }
    }
    return num;
}