aescrypt.c

linux下完成任意文件的AES加密. 口令可变,加密稳定迅速.

/*
 *  AES Crypt for Linux
 *  Copyright (C) 2007, 2008
 *
 *  Contributors:
 *      Glenn Washburn <[e-mail]>
 *      Paul E. Jones <[e-mail]>
 *      Mauro Gilardi <[e-mail]>
 *
 * This software is licensed as "freeware."  Permission to distribute
 * this software in source and binary forms is hereby granted without a
 * fee.  THIS SOFTWARE IS PROVIDED 'AS IS' AND WITHOUT ANY EXPRESSED OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 * THE AUTHOR SHALL NOT BE HELD LIABLE FOR ANY DAMAGES RESULTING FROM
 * THE USE OF THIS SOFTWARE, EITHER DIRECTLY OR INDIRECTLY, INCLUDING,
 * BUT NOT LIMITED TO, LOSS OF DATA OR DATA BEING RENDERED INACCURATE.
 *
 */

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h> // getopt
#include <assert.h>
#include <stdlib.h> // malloc
#include <time.h> // time
#include <iconv.h> // iconv stuff
#include <langinfo.h> // nl_langinfo
#include <errno.h> // errno

#include "aescrypt.h"
#include "password.h"
#include "version.h"

/*
 *  encrypt_stream
 *
 *  This function is called to encrypt the open data steam "infp".
 */
int encrypt_stream(FILE *infp, FILE *outfp, char* passwd, int passlen)
{
    aes_context                 aes_ctx;
    sha256_context              sha_ctx;
    aescrypt_hdr                aeshdr;
    sha256_t                    digest;
    unsigned char               IV[16];
    unsigned char               iv_key[48];
    int                         i, j, n;
    unsigned char               buffer[32];
    unsigned char               ipad[64], opad[64];
    time_t                      current_time;
    pid_t                       process_id;
    FILE                        *randfp = NULL;
    unsigned char               tag_buffer[256];

    // Open the source for random data.  Note that while the entropy
    // might be lower with /dev/urandom than /dev/random, it will not
    // fail to produce something.  Also, we're going to hash the result
    // anyway.
    if ((randfp = fopen("/dev/urandom", "r")) == NULL)
    {
        perror("Error open /dev/urandom:");
        return  -1;
    }

    // Create the 16-bit IV and 32-bit encryption key
    // used for encrypting the plaintext file.  We do
    // not trust the rand() function, so we improve on
    // that by also hashing the random digits and using
    // only a portion of the hash.  This IV and key
    // generation could be replaced with any good random
    // source of data.
    memset(iv_key, 0, 48);
    for (i=0; i<48; i+=16)
    {
        memset(buffer, 0, 32);
        sha256_starts(&sha_ctx);
        for(j=0; j<256; j++)
        {
            if ((n = fread(buffer, 1, 32, randfp)) != 32)
            {
                fprintf(stderr, "Error: Couldn't read from /dev/urandom : %d\n",n);
                fclose(randfp);
                return  -1;
            }
            sha256_update(&sha_ctx, buffer, 32);
        }
        sha256_finish(&sha_ctx, digest);
        memcpy(iv_key+i, digest, 16);
    }

    // Write an AES signature at the head of the file, along
    // with the AES file format version number.
    buffer[0] = 'A';
    buffer[1] = 'E';
    buffer[2] = 'S';
    buffer[3] = (unsigned char) 0x02;   // Version 2
    buffer[4] = '\0';                   // Reserved for version 0
    if (fwrite(buffer, 1, 5, outfp) != 5)
    {
        fprintf(stderr, "Error: Could not write out header data\n");
        fclose(randfp);
        return  -1;
    }

    // Write out the CREATED-BY tag
    j = 11 +                   // "CREATED-BY\0"
        strlen(PROG_NAME) +    // Program name
        1 +                    // Space
        strlen(PROG_VERSION);  // Program version ID
    // Our extension buffer is only 256 octets long, so
    // let's not write an extension if it is too big
    if (j < 256)
    {
        buffer[0] = '\0';
        buffer[1] = (unsigned char) (j & 0xff);
        if (fwrite(buffer, 1, 2, outfp) != 2)
        {
            fprintf(stderr, "Error: Could not write tag to AES file (1)\n");
            fclose(randfp);
            return  -1;
        }

        strncpy(tag_buffer, "CREATED_BY", 255);
        tag_buffer[255] = '\0';
        if (fwrite(tag_buffer, 1, 11, outfp) != 11)
        {
            fprintf(stderr, "Error: Could not write tag to AES file (2)\n");
            fclose(randfp);
            return  -1;
        }

        sprintf(tag_buffer, "%s %s", PROG_NAME, PROG_VERSION);
        j = strlen(tag_buffer);
        if (fwrite(tag_buffer, 1, j, outfp) != j)
        {
            fprintf(stderr, "Error: Could not write tag to AES file (3)\n");
            fclose(randfp);
            return  -1;
        }
    }

    // Write out the "container" extension
    buffer[0] = '\0';
    buffer[1] = (unsigned char) 128;
    if (fwrite(buffer, 1, 2, outfp) != 2)
    {
        fprintf(stderr, "Error: Could not write tag to AES file (4)\n");
        fclose(randfp);
        return  -1;
    }
    bzero(tag_buffer, 128);
    if (fwrite(tag_buffer, 1, 128, outfp) != 128)
    {
        fprintf(stderr, "Error: Could not write tag to AES file (5)\n");
        fclose(randfp);
        return  -1;
    }

    // Write out 0x0000 to indicate that no more extensions exist
    buffer[0] = '\0';
    buffer[1] = '\0';
    if (fwrite(buffer, 1, 2, outfp) != 2)
    {
        fprintf(stderr, "Error: Could not write tag to AES file (6)\n");
        fclose(randfp);
        return  -1;
    }

    // We will use an initialization vector comprised of the current time
    // process ID, and random data, all hashed together with SHA-256.
    current_time = time(NULL);
    for(i = 0; i < 8; i++)
    {
        buffer[i] = (unsigned char)
                        (current_time >> (i * 8));
    }
    process_id = getpid();
    for(i = 0; i < 8; i++)
    {
        buffer[i+8] = (unsigned char)
                        (process_id >> (i * 8));
    }

    sha256_starts(  &sha_ctx);
    sha256_update(  &sha_ctx, buffer, 16);

    for (i=0; i<256; i++)
    {
        if (fread(buffer, 1, 32, randfp) != 32)
        {
            fprintf(stderr, "Error: Couldn't read from /dev/random\n");
            fclose(randfp);
            return  -1;
        }
        sha256_update(  &sha_ctx,
                        buffer,
                        32);
    }

    sha256_finish(  &sha_ctx, digest);

    memcpy(IV, digest, 16);

    // We're finished collecting random data
    fclose(randfp);

    // Write the initialization vector to the file
    if (fwrite(IV, 1, 16, outfp) != 16)
    {
        fprintf(stderr, "Error: Could not write out initialization vector\n");
        return  -1;
    }
    
    // Hash the IV and password 8192 times
    memset(digest, 0, 32);
    memcpy(digest, IV, 16);
    for(i=0; i<8192; i++)
    {
        sha256_starts(  &sha_ctx);
        sha256_update(  &sha_ctx, digest, 32);
        sha256_update(  &sha_ctx,
                        (unsigned char*)passwd,
                        (unsigned long)passlen);
        sha256_finish(  &sha_ctx,
                        digest);
    }

    // Set the AES encryption key
    aes_set_key(&aes_ctx, digest, 256);

    // Set the ipad and opad arrays with values as
    // per RFC 2104 (HMAC).  HMAC is defined as
    //   H(K XOR opad, H(K XOR ipad, text))
    memset(ipad, 0x36, 64);
    memset(opad, 0x5C, 64);

    for(i=0; i<32; i++)
    {
        ipad[i] ^= digest[i];
        opad[i] ^= digest[i];
    }

    sha256_starts(&sha_ctx);
    sha256_update(&sha_ctx, ipad, 64);

    // Encrypt the IV and key used to encrypt the plaintext file,
    // writing that encrypted text to the output file.
    for(i=0; i<48; i+=16)
    {
        // Place the next 16 octets of IV and key buffer into
        // the input buffer.
        memcpy(buffer, iv_key+i, 16);

        // XOR plain text block with previous encrypted
        // output (i.e., use CBC)
        for(j=0; j<16; j++)
        {
            buffer[j] ^= IV[j];
        }

        // Encrypt the contents of the buffer
        aes_encrypt(&aes_ctx, buffer, buffer);
        
        // Concatenate the "text" as we compute the HMAC
        sha256_update(&sha_ctx, buffer, 16);

        // Write the encrypted block
        if (fwrite(buffer, 1, 16, outfp) != 16)
        {
            fprintf(stderr, "Error: Could not write iv_key data\n");
            return  -1;
        }
        
        // Update the IV (CBC mode)
        memcpy(IV, buffer, 16);
    }

    // Write the HMAC
    sha256_finish(&sha_ctx, digest);
    sha256_starts(&sha_ctx);
    sha256_update(&sha_ctx, opad, 64);
    sha256_update(&sha_ctx, digest, 32);
    sha256_finish(&sha_ctx, digest);
    // Write the encrypted block
    if (fwrite(digest, 1, 32, outfp) != 32)
    {
        fprintf(stderr, "Error: Could not write iv_key HMAC\n");
        return  -1;
    }

    // Re-load the IV and encryption key with the IV and
    // key to now encrypt the datafile.  Also, reset the HMAC
    // computation.
    memcpy(IV, iv_key, 16);

    // Set the AES encryption key
    aes_set_key(&aes_ctx, iv_key+16, 256);

    // Set the ipad and opad arrays with values as
    // per RFC 2104 (HMAC).  HMAC is defined as
    //   H(K XOR opad, H(K XOR ipad, text))
    memset(ipad, 0x36, 64);
    memset(opad, 0x5C, 64);

    for(i=0; i<32; i++)
    {
        ipad[i] ^= iv_key[i+16];
        opad[i] ^= iv_key[i+16];
    }

    // Wipe the IV and encryption mey from memory
    memset(iv_key, 0, 48);

    sha256_starts(&sha_ctx);
    sha256_update(&sha_ctx, ipad, 64);

    while ((n = fread(buffer, 1, 16, infp)) > 0)
    {
        // XOR plain text block with previous encrypted
        // output (i.e., use CBC)
        for(i=0; i<16; i++)
        {
            buffer[i] ^= IV[i];
        }

        // Encrypt the contents of the buffer
        aes_encrypt(&aes_ctx, buffer, buffer);
        
        // Concatenate the "text" as we compute the HMAC
        sha256_update(&sha_ctx, buffer, 16);

        // Write the encrypted block
        if (fwrite(buffer, 1, 16, outfp) != 16)
        {
            fprintf(stderr, "Error: Could not write to output file\n");
            return  -1;
        }
        
        // Update the IV (CBC mode)
        memcpy(IV, buffer, 16);

        // Assume this number of octets is the file modulo
        aeshdr.last_block_size = n;
    }

    // Check to see if we had a read error
    if (n < 0)
    {
        fprintf(stderr, "Error: Couldn't read input file\n");
        return  -1;
    }

    // Write the file size modulo
    buffer[0] = (char) (aeshdr.last_block_size & 0x0F);
    if (fwrite(buffer, 1, 1, outfp) != 1)
    {
        fprintf(stderr, "Error: Could not write the file size modulo\n");
        return  -1;
    }

    // Write the HMAC
    sha256_finish(&sha_ctx, digest);
    sha256_starts(&sha_ctx);
    sha256_update(&sha_ctx, opad, 64);
    sha256_update(&sha_ctx, digest, 32);
    sha256_finish(&sha_ctx, digest);
    if (fwrite(digest, 1, 32, outfp) != 32)
    {
        fprintf(stderr, "Error: Could not write the file HMAC\n");
        return  -1;
    }

    return 0;
}