协助 openssl blowfish 插入垃圾字符的简单示例
https://stackoverflow.com/questions/993780
-
13-09-2019 - |
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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： Myabe 作者是正确的。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： 示例中的循环结构似乎不正确。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 并且缓冲区应该丢弃该组位。：（ 不是。
更新99988： 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。
我已尽一切努力来简化它
- gcc --版本报告 4.3.2
- 打开SUSE 11
编译.sh
gcc -g -o blowfish blowfish.c -lcrypto
运行sh
ulimit -c unlimited
./blowfish example.txt encrypted_example decrypted_example
echo diff example.txt decrypted_example
diff example.txt decrypted_example
干净的sh
rm -rf blowfish encrypted_example decrypted_example core
示例.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中的代码blowfish.c
#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;
}
解决方案
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;
}
其他提示
既然你说错误似乎出现在解密阶段，我会怀疑这些行：
if (EVP_DecryptUpdate (&ctx, outbuf, &olen, inbuff, n) != 1)
...
if (EVP_DecryptFinal (&ctx, outbuf + olen, &tlen) != 1)
...
分配的内存有多大 outbuf 与解密函数将放入其中的内容有关？你确定吗 outbuf + olen 不会带你越过缓冲区的末尾吗？
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