Openssl函數無法正常工作而不返回0

Question

我用C寫的函數進行加密/解密。我加密一個字符串並將其保存到文件中。後來我閱讀文件並解密內容。在單獨的函數中執行第二個操作時遇到問題。任何人都可以爲此提出解決方案嗎？

#include <stdio.h> 
#include <unistd.h> 
#include <string.h> 
#include <openssl/des.h> 
#include <fcntl.h> 

char * 
Encrypt(char *Key, char *Msg, int size) 
{ 

     static char* Res; 
     int    n=0; 
     DES_cblock  Key2; 
     DES_key_schedule schedule; 

     Res = (char *) malloc(size); 

     /* Prepare the key for use with DES_cfb64_encrypt */ 
     memcpy(Key2, Key,8); 
     DES_set_odd_parity(&Key2); 
     DES_set_key_checked(&Key2, &schedule); 

     /* Encryption occurs here */ 
     DES_cfb64_encrypt((unsigned char *) Msg, (unsigned char *) Res, 
          size, &schedule, &Key2, &n, DES_ENCRYPT); 

     return (Res); 
} 


char * 
Decrypt(char *Key, char *Msg, int size) 
{ 

     static char* Res; 
     int    n=0; 

     DES_cblock  Key2; 
     DES_key_schedule schedule; 

     Res = (char *) malloc(size); 

     /* Prepare the key for use with DES_cfb64_encrypt */ 
     memcpy(Key2, Key,8); 
     DES_set_odd_parity(&Key2); 
     DES_set_key_checked(&Key2, &schedule); 

     /* Decryption occurs here */ 
     DES_cfb64_encrypt((unsigned char *) Msg, (unsigned char *) Res, 
          size, &schedule, &Key2, &n, DES_DECRYPT); 

     return (Res); 

} 

void test() 
{ 
    char key[]="1234"; 
//  
    char writeBuffer[4096]; 
    char *decrypted; 
// char *encrypted; 
//  
// encrypted=malloc(sizeof(writeBuffer)); 
    decrypted=malloc(sizeof(writeBuffer)); 

    int fp1 = open("encrypted.txt", O_RDONLY); 
    int bytes_read = 0; 
    bytes_read = read(fp1, writeBuffer, sizeof(writeBuffer)-1); 

    memcpy(decrypted,Decrypt(key,writeBuffer,sizeof(writeBuffer)), sizeof(writeBuffer)); 
    printf("Decrypted text\t : %s \n",decrypted); 

} 


int main() { 


    char key[]="1234"; 

    char writeBuffer[4096]; 
    char *decrypted; 
    char *encrypted; 

    encrypted=malloc(sizeof(writeBuffer)); 
    decrypted=malloc(sizeof(writeBuffer)); 

    char clear[]="This is a secret message"; 


    printf("Clear text\t : %s \n",clear); 
    memcpy(encrypted,Encrypt(key,clear,sizeof(writeBuffer)), sizeof(writeBuffer)); 
    printf("Encrypted text\t : %s \n",encrypted); 
    FILE *f = fopen("encrypted.txt", "w"); 
    fwrite(encrypted, sizeof(writeBuffer), 1, f); 
    fclose(f); 

    int i=0; 
    for(i=0;i < 2; i++){ 

// Uncommenting the section below and commenting test() works properly 

// int fp1 = open("encrypted.txt", O_RDONLY); 
// int bytes_read = 0; 
// bytes_read = read(fp1, writeBuffer, sizeof(writeBuffer)-1); 
//  
// memcpy(decrypted,Decrypt(key,writeBuffer,sizeof(writeBuffer)), sizeof(writeBuffer)); 
// printf("Decrypted text\t : %s \n",decrypted); 
     test(); 
    } 

//  close(fp1); 
    return (0); 

} 

Answer 1

問題是這條線，你正在閱讀一個字節不到你正在寫的文件：

bytes_read = read(fp1, writeBuffer, sizeof(writeBuffer)-1); 

我沒有-1測試你的代碼和它的作品。

此外，你的代碼有幾個問題，你的函數應該採取const參數，一些內存得到分配，永遠不會釋放。某些代碼可以更好地寫，例如：

int bytes_read = 0; 
bytes_read = read(fp1, writeBuffer, sizeof(writeBuffer)-1); 

應該是：

int bytes_read = read(fp1, writeBuffer, sizeof(writeBuffer)-1); 

代碼也並不一致，您使用一次fopen和FILE這是在標準C庫，一旦open和作爲POSIX一部分的文件描述符。

編輯： 這是我測試您的修改後的代碼（你必須編譯它與C99被激活， 「-std = C99」）：

#include <stdio.h> 
#include <unistd.h> 
#include <string.h> 
#include <openssl/des.h> 
#include <fcntl.h> 

char * 
Encrypt(const char *Key, const char *Msg, int size) 
{ 
    /* Prepare the key for use with DES_cfb64_encrypt */ 
    DES_cblock Key2; 
    memcpy(Key2, Key, 8); 
    DES_set_odd_parity(&Key2); 
    DES_key_schedule schedule; 
    DES_set_key_checked(&Key2, &schedule); 

    /* Encryption occurs here */ 
    int n = 0; 
    char *Res = malloc(size); 
    DES_cfb64_encrypt((unsigned char *) Msg, (unsigned char *) Res, 
      size, &schedule, &Key2, &n, DES_ENCRYPT); 
    return Res; 
} 

char * 
Decrypt(const char *Key, const char *Msg, int size) 
{ 
    /* Prepare the key for use with DES_cfb64_encrypt */ 
    DES_cblock  Key2; 
    memcpy(Key2, Key,8); 
    DES_set_odd_parity(&Key2); 
    DES_key_schedule schedule; 
    DES_set_key_checked(&Key2, &schedule); 

    /* Decryption occurs here */ 
    int n = 0; 
    char *Res = malloc(size); 
    DES_cfb64_encrypt((unsigned char *) Msg, (unsigned char *) Res, 
      size, &schedule, &Key2, &n, DES_DECRYPT); 
    return (Res); 
} 

void test() 
{ 
    char key[] = "12345678"; 
    char writeBuffer[4096]; 
    char *decrypted = malloc(sizeof(writeBuffer)); 

    int fp1 = open("encrypted.txt", O_RDONLY); 
    int bytes_read = read(fp1, writeBuffer, sizeof(writeBuffer)); 

    memcpy(decrypted, 
     Decrypt(key,writeBuffer,sizeof(writeBuffer)), 
     sizeof(writeBuffer)); 
    printf("Decrypted text\t : %s \n",decrypted); 

} 


int main() { 
    char key[]="12345678"; 
    char writeBuffer[4096]; 

    char clear[] = "This is a secret message"; 
    printf("Clear text\t : %s \n",clear); 

    char *encrypted = malloc(sizeof(writeBuffer)); 
    memcpy(encrypted, Encrypt(key, clear, sizeof(writeBuffer)), sizeof(writeBuffer)); 
    printf("Encrypted text\t : %s \n",encrypted); 

    FILE *f = fopen("encrypted.txt", "w"); 
    fwrite(encrypted, sizeof(writeBuffer), 1, f); 
    fclose(f); 

    for(int i = 0; i < 2; i++) { 
     // Uncommenting the section below and commenting test() works properly 
     if (0) { 
      int fp1 = open("encrypted.txt", O_RDONLY); 
      int bytes_read = read(fp1, writeBuffer, sizeof(writeBuffer)); 

      char *decrypted = malloc(sizeof(writeBuffer)); 
      memcpy(decrypted, 
        Decrypt(key, writeBuffer, sizeof(writeBuffer)), 
        sizeof(writeBuffer)); 
      printf("Decrypted text\t : %s \n",decrypted); 
      close(fp1); 
     } 
     else { 
      test(); 
     } 
    } 

    return (0); 

}