协助 openssl blowfish 插入垃圾字符的简单示例

Question

如果您有一个使用 openssl 简单加密文件的好例子，它比我遇到的问题更好，我将非常感激。

更新：作者Myabe是正确的。 在我没有分配的东西上使用 memset 让我想起了 strtok 对非堆栈变量的阻塞。

更新2：使用malloc停止核心转储。 更新了代码。 控制 H 仍然出现。 更新代码以反映这一点。

更新3：示例中的循环结构看起来不正确。 我不确定后续读取的大小如何大于初始读取的大小。

更新4：我想我找到了。 解密循环有一个 olen += tlen ，缓冲区应该丢弃该组位。 :( 不是。

Update99988: 在这里我已经放弃了所有的希望。 我想我需要扔掉这个例子并从 Openssl 书中的一些内容开始。 解密后，中间层缓冲区会预先附加 ^H，但由于传入了指针，我开始怀疑对齐问题。

我认为从一个坏例子开始可能比从头开始更糟糕。 我必须做出一些更正（原文在下面的代码中注释）。 原作者在错误地传递地址时遇到了一些问题。 我的思绪被作者使用的 1024 和 1032 不同大小的缓冲区所困扰，但我认为这与 8 位种子和链式加密调用有关。

我在（控制 Hs）中收到垃圾字符，并且像解密这样的核心转储正在破坏堆栈。 我对加密、openssl 相当陌生，而且我对 gdb 不太熟悉。

我已尽一切努力简化

1. gcc --version reports 4.3.2
2. Open SU​​SE 11

compile.sh

gcc -g -o blowfish blowfish.c -lcrypto

run.sh

ulimit -c unlimited
./blowfish example.txt encrypted_example decrypted_example
echo diff example.txt decrypted_example
diff example.txt decrypted_example

clean.sh

rm -rf blowfish encrypted_example decrypted_example core

example.txt

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor 
incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis 
nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. 
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu 
fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in 
culpa qui officia deserunt mollit anim id est laborum.

Hydrogen H
Helium H
Lithium L
Beryllium B
Boron B
Carbon C
Nitrogen N
Oxygen O
Fluorine F
Neon N
Sodium N
Magnesium M
Aluminium A
Silicon S
Phosphorus P
Sulfur S
Chlorine C
Argon A
Potassium K
Calcium C
Scandium S
Titanium T
Vanadium V
Chromium C
Manganese M
Iron F
Cobalt C
Nickel N
Copper C
Zinc Z
Gallium G
Germanium G
Arsenic A
Selenium S
Bromine B
Krypton K
Rubidium R
Strontium S
Yttrium Y
Zirconium Z
Niobium N
Molybdenum M
Technetium T
Ruthenium R
Rhodium R
Palladium P
Silver A
Cadmium C
Indium I
Tin S
Antimony S
Tellurium T
Iodine I
Xenon X
Caesium C
Barium B
Lanthanum L
Cerium C
Praseodymium P
Neodymium N
Promethium P
Samarium S
Europium E
Gadolinium G
Terbium T
Dysprosium D
Holmium H
Erbium E
Thulium T
Ytterbium Y
Lutetium L
Hafnium H
Tantalum T
Tungsten W
Rhenium R
Osmium O
Iridium I
Platinum P
Gold A
Mercury H
Thallium T
Lead P
Bismuth B
Polonium P
Astatine A
Radon R
Francium F
Radium R
Actinium A
Thorium T
Protactinium P
Uranium U
Neptunium N
Plutonium P
Americium A
Curium C
Berkelium B
Californium C
Einsteinium E
Fermium F
Mendelevium M
Nobelium N
Lawrencium L
Rutherfordium R
Dubnium D
Seaborgium S
Bohrium B
Hassium H
Meitnerium M
Darmstadtium D
Roentgenium R
Ununbium U
Ununtrium U
Ununquadium U
Ununpentium U
Ununhexium U
Ununseptium U
Ununoctium U

错误代码警告错误代码使用所选答案blowfish.c中的代码

#include <openssl/blowfish.h>
#include <openssl/evp.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#define IP_SIZE 1024
#define OP_SIZE 1032
unsigned char key[16];
unsigned char iv[8];

int
generate_key ()
{
  int i, j, fd;
  if ((fd = open ("/dev/random", O_RDONLY)) == -1)
    perror ("open error");

  if ((read (fd, key, 16)) == -1)
    perror ("read key error");

  if ((read (fd, iv, 8)) == -1)
    perror ("read iv error");

  printf ("128 bit key:\n");
  for (i = 0; i < 16; i++)
    printf ("%4d ", key[i]);

  printf ("\nInitialization vector\n");
  for (i = 0; i < 8; i++)
    printf ("%4d ", iv[i]);
  printf ("\n");


  close (fd);
  return 0;
}

int
decrypt (int infd, int outfd)
{
  char *inbuff, *outbuf;
  int olen, tlen, n;
  EVP_CIPHER_CTX ctx;
  EVP_CIPHER_CTX_init (&ctx);
  EVP_DecryptInit (&ctx, EVP_bf_cbc (), key, iv);

  outbuf = (unsigned char *) malloc ( sizeof(unsigned char) * IP_SIZE );
  inbuff = (unsigned char *) malloc ( sizeof(unsigned char) * OP_SIZE );

  /* keep reading until a break */
  for (;;)
    {
      memset(inbuff,'\0', OP_SIZE);
      if ((n = read (infd, inbuff, OP_SIZE)) == -1)
    {
      perror ("read error");
      break;
    }
      else if (n == 0)
    break;

      memset(outbuf,'\0', IP_SIZE);

      if (EVP_DecryptUpdate (&ctx, outbuf, &olen, inbuff, n) != 1)
    {
      printf ("error in decrypt update\n");
      return 0;
    }

      if (EVP_DecryptFinal (&ctx, outbuf + olen, &tlen) != 1)
    {
      printf ("error in decrypt final\n");
      return 0;
    }
      olen += tlen;
      if ((n = write (outfd, outbuf, olen)) == -1)
    perror ("write error");
    }

  EVP_CIPHER_CTX_cleanup (&ctx);
  return 1;
}

int
encrypt (int infd, int outfd)
{
  char *inbuff, *outbuf;

  int olen, tlen, n;
  EVP_CIPHER_CTX ctx;
  EVP_CIPHER_CTX_init (&ctx);
  EVP_EncryptInit (&ctx, EVP_bf_cbc (), key, iv);

  outbuf = (unsigned char *) malloc ( sizeof(unsigned char) * OP_SIZE );
  inbuff = (unsigned char *) malloc ( sizeof(unsigned char) * IP_SIZE );

  for (;;)
    {
      memset(inbuff,'\0', IP_SIZE);

      if ((n = read (infd, inbuff, IP_SIZE)) == -1)
    {
      perror ("read error");
      break;
    }
      else if (n == 0)
    break;

      if (EVP_EncryptUpdate (&ctx, outbuf, &olen, inbuff, n) != 1)
    {
      printf ("error in encrypt update\n");
      return 0;
    }

      if (EVP_EncryptFinal (&ctx, outbuf + olen, &tlen) != 1)
    {
      printf ("error in encrypt final\n");
      return 0;
    }
      olen += tlen;
      if ((n = write (outfd, outbuf, olen)) == -1)
    perror ("write error");
    }
  EVP_CIPHER_CTX_cleanup (&ctx);
  return 1;
}

int
main (int argc, char *argv[])
{
  int flags1 = 0, flags2 = 0, outfd, infd, decfd;
  mode_t mode;
  char choice, temp;
  int done = 0, n, olen;

  memset(key,'\0', 16);
  memset(iv,'\0', 8);
  memset(&mode, '\0', sizeof(mode));

  flags1 = flags1 | O_RDONLY;
  flags2 = flags2 | O_RDONLY;
  flags2 = flags2 | O_WRONLY;
  flags2 = flags2 | O_CREAT;

  mode = mode | S_IRUSR;
  mode = mode | S_IWUSR;

  generate_key ();

  if ((infd = open (argv[1], flags1, mode)) == -1)
    perror ("open input file error");

  if ((outfd = open (argv[2], flags2, mode)) == -1)
    perror ("open output file error");

  encrypt (infd, outfd);

  close (infd);
  close (outfd);

  if ((outfd = open (argv[2], flags1, mode)) == -1)
    perror ("open output file error");

  if ((decfd = open (argv[3], flags2, mode)) == -1)
    perror ("open output file error");

  /* After much head scratching reusing the out as an in is correct here */
  decrypt (outfd, decfd);

  close (outfd);
  fsync (decfd);
  close (decfd);

  return 0;
}

Answer 1

错误在于调用 EVP_DecryptFinal 和 EVP_EncryptFinal 的方式。 这些函数应该在 for 循环结束时调用，最后向 olen 添加 tlen 并再次写入的部分是复制输出。 以下是最终的工作版本：

#include <openssl/blowfish.h>
#include <openssl/evp.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#define IP_SIZE 1024
#define OP_SIZE 1024 + EVP_MAX_BLOCK_LENGTH
unsigned char   key[16];
unsigned char   iv[8];

int
generate_key()
{
    int             i, fd;
    if ((fd = open("/dev/random", O_RDONLY)) == -1)
        perror("open error");

    if ((read(fd, key, 16)) == -1)
        perror("read key error");

    if ((read(fd, iv, 8)) == -1)
        perror("read iv error");

    printf("128 bit key:\n");
    for (i = 0; i < 16; i++)
        printf("%4d ", key[i]);

    printf("\nInitialization vector\n");
    for (i = 0; i < 8; i++)
        printf("%4d ", iv[i]);
    printf("\n");


    close(fd);
    return 0;
}

int
do_decrypt(int infd, int outfd)
{
    unsigned char           *inbuff, *outbuf;
    int             olen=0, tlen=0, n=0;
    EVP_CIPHER_CTX  ctx;
    EVP_CIPHER_CTX_init(&ctx);
    EVP_DecryptInit(&ctx, EVP_bf_cbc(), key, iv);

    outbuf = (unsigned char *) malloc(sizeof(unsigned char) * OP_SIZE);
    inbuff = (unsigned char *) malloc(sizeof(unsigned char) * IP_SIZE);

    /* keep reading until a break */
    for (;;) {
        memset(inbuff, 0, IP_SIZE);
        if ((n = read(infd, inbuff, IP_SIZE)) == -1) {
            perror("read error");
            break;
        } else if (n == 0)
            break;

        memset(outbuf, 0, OP_SIZE);

        if (EVP_DecryptUpdate(&ctx, outbuf, &olen, inbuff, n) != 1) {
            printf("error in decrypt update\n");
            return 0;
        }
        if ((n = write(outfd, outbuf, olen)) == -1)
            perror("write error");
    }

    tlen=0;
    if (EVP_DecryptFinal(&ctx, outbuf + olen, &tlen) != 1) {
        perror("error in decrypt final");
        return 0;
    }

    if ((n = write(outfd, outbuf+olen, tlen)) == -1)
        perror("write error");

    EVP_CIPHER_CTX_cleanup(&ctx);
    return 1;
}

int
do_encrypt(int infd, int outfd)
{
    unsigned char           *inbuff, *outbuf;

    int             olen=0, tlen=0, n=0;
    EVP_CIPHER_CTX  ctx;
    EVP_CIPHER_CTX_init(&ctx);
    EVP_EncryptInit(&ctx, EVP_bf_cbc(), key, iv);

    outbuf = (unsigned char *) malloc(sizeof(unsigned char) * OP_SIZE);
    inbuff = (unsigned char *) malloc(sizeof(unsigned char) * IP_SIZE);

    for (;;) {
        memset(inbuff, 0, IP_SIZE);

        if ((n = read(infd, inbuff, IP_SIZE)) == -1) {
            perror("read error");
            break;
        } else if (n == 0)
            break;

        if (EVP_EncryptUpdate(&ctx, outbuf, &olen, inbuff, n) != 1) {
            printf("error in encrypt update\n");
            return 0;
        }

        if ((n = write(outfd, outbuf, olen)) == -1)
            perror("write error");
    }
    tlen=0;
    if (EVP_EncryptFinal(&ctx, outbuf + olen, &tlen) != 1) {
        printf("error in encrypt final\n");
        return 0;
    }

    if ((n = write(outfd, outbuf+olen, tlen)) == -1)
        perror("write error");

    EVP_CIPHER_CTX_cleanup(&ctx);
    return 1;
}

int
main(int argc, char *argv[])
{
    int             flags1 = 0, flags2 = 0, outfd, infd;
    mode_t          mode;

    memset(key, 0, 16);
    memset(iv, 0, 8);
    memset(&mode, 0, sizeof(mode));

    flags1 = flags1 | O_RDONLY;
    flags2 = flags2 | O_RDONLY;
    flags2 = flags2 | O_WRONLY;
    flags2 = flags2 | O_CREAT;

    mode = mode | S_IRUSR;
    mode = mode | S_IWUSR;


    generate_key();


    if ((infd = open(argv[1], flags1, mode)) == -1)
        perror("open input file error");

    if ((outfd = open(argv[2], flags2, mode)) == -1)
        perror("open output file error");

    do_encrypt(infd, outfd);

    close(infd);
    fsync(outfd);
    close(outfd);

    if ((infd = open(argv[2], flags1, mode)) == -1)
        perror("open output file error");

    if ((outfd = open(argv[3], flags2, mode)) == -1)
        perror("open output file error");

    do_decrypt(infd, outfd);

    close(infd);
    fsync(infd);
    close(outfd);

    return 0;
}

Answer 2

既然你说错误似乎是在解密阶段出现的，我会怀疑地看待这些行：

if (EVP_DecryptUpdate (&ctx, outbuf, &olen, inbuff, n) != 1)
...

if (EVP_DecryptFinal (&ctx, outbuf + olen, &tlen) != 1)
...

相对于解密函数将放入其中的内容，为 outbuf 分配的内存有多大？ 您确定 outbuf + olen 不会超出缓冲区末尾吗？