不执行下一个任务自动调用退出函数 [英] Automatically Calling The Exit Function Without Performing the Next Task

问题描述

参考我的

解决方案

您写道:

 if(c==1){第一个读者()；}如果(c==2){第二个读者()；}别的{printf(应用程序退出...");退出(1)；}

意思是:

• 如果 c 为 1，则调用 firstReader.
• 如果 c 为 2，则调用 secondReader，否则退出.

如果 c 为 1，则它调用 firstReader，然后退出，因为 c 不是 2.计算机不够聪明，无法弄清楚您的实际意思.您可能打算编写 else if(c==2) 将两个 if 链接在一起，以便最终的 else 仅在两者都没有时运行一个是真的.

In reference to my previous question I just have to change most part of the code and use function call. Now the file can read and print as expected, but I noticed that after when it goes to the expected fileReader and prints the file, it automatically exited by calling choiceReader(case: else ) function which is not the expected function to call. My expectation is that algorithm() will be the next call. Please what am I missing here again?

The new code is:

#include <openssl/ssl.h>
#include <openssl/err.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int success = 0;
char counter[1000];//used to monitor the read file length
int c;

size_t cipher_len; // size_t is sizeof(type)
unsigned char* ciphertext;
unsigned char plainpassword[] = "00000";
unsigned char* password = &plainpassword[0];

unsigned char salt[8];

unsigned char key[16];
unsigned char iv[16];

FILE *fp;
FILE *fptr;

char* plaintext = "To be or not to be is the question.";
char dict[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

int decryptedtext_len, ciphertext_len, dict_len;

char* ciphertext_base64;

unsigned char *plaintexts;
int len;
int plaintext_len;

void handleOpenSSLErrors(void)
{
    ERR_print_errors_fp(stderr);
    abort();
}

unsigned char* decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key, unsigned char *iv ){

    EVP_CIPHER_CTX *ctx;
    
    unsigned char* plaintext = malloc(ciphertext_len);
    bzero(plaintext,ciphertext_len);

    /* Create and initialise the context */
  
    if(!(ctx = EVP_CIPHER_CTX_new())) handleOpenSSLErrors();

    /* Initialise the decryption operation. IMPORTANT - ensure you use a key
    * and IV size appropriate for your cipher
    * IV size for *most* modes is the same as the block size. For AES this
    * is 128 bits */
    
    if(1 != EVP_DecryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv))
        handleOpenSSLErrors();

  
    EVP_CIPHER_CTX_set_key_length(ctx, EVP_MAX_KEY_LENGTH);

    /* Provide the message to be decrypted, and obtain the plaintext output.
    * EVP_DecryptUpdate can be called multiple times if necessary
    */
    if(1 != EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len))
        handleOpenSSLErrors();
   
    plaintext_len = len;

    /* Finalise the decryption. Further plaintext bytes may be written at
    * this stage.
    */
    
    // return 1 if decryption successful, otherwise 0
    if(1 == EVP_DecryptFinal_ex(ctx, plaintext + len, &len)) 
        success = 1;
    plaintext_len += len;

   
    /* Add the null terminator */
    plaintext[plaintext_len] = 0;

    /* Clean up */
    EVP_CIPHER_CTX_free(ctx);
    //delete [] plaintext;
    return plaintext;
}


size_t calcDecodeLength(char* b64input) {
    size_t len = strlen(b64input), padding = 0;

    if (b64input[len-1] == '=' && b64input[len-2] == '=') //last two chars are =
        padding = 2;
    else if (b64input[len-1] == '=') //last char is =
        padding = 1;
    return (len*3)/4 - padding;
}

void Base64Decode( char* b64message, unsigned char** buffer, size_t* length) {

    
    BIO *bio, *b64;  // A BIO is an I/O strean abstraction

    int decodeLen = calcDecodeLength(b64message);
    *buffer = (unsigned char*)malloc(decodeLen + 1);
    (*buffer)[decodeLen] = '\0';

    bio = BIO_new_mem_buf(b64message, -1);
    b64 = BIO_new(BIO_f_base64());
    bio = BIO_push(b64, bio);

    //BIO_set_flags(bio, BIO_FLAGS_BASE64_NO_NL); //Do not use newlines to flush buffer
    *length = BIO_read(bio, *buffer, strlen(b64message));
    BIO_free_all(bio);
}

void initAES(const unsigned char *pass, unsigned char* salt, unsigned char* key, unsigned char* iv )
{
    //initialisatio of key and iv with 0
    bzero(key,sizeof(key)); 
    bzero(iv,sizeof(iv));
  
    EVP_BytesToKey(EVP_aes_128_cbc(), EVP_sha1(), salt, pass, strlen(pass), 1, key, iv);
}


int checkPlaintext(char* plaintext, char* result){

    int length = 10; // we just check the first then characters
    return strncmp(plaintext, result, length);

}

//this tries to crack the password.
int algorithm(){
    time_t begin = time(NULL);

    for(int i=0; i<dict_len; i++)
        for(int j=0; j<dict_len; j++)
            for(int k=0; k<dict_len; k++)
                for(int l=0; l<dict_len; l++)
                    for(int m=0; m<dict_len; m++){
                        *password = dict[i];
                        *(password+1) = dict[j];
                        *(password+2) = dict[k];
                        *(password+3) = dict[l];
                        *(password+4) = dict[m];

                        
                        initAES(password, salt, key, iv);
                        unsigned char* result = decrypt(ciphertext, cipher_len, key, iv);
                        
                        if (success == 1){
                            if(checkPlaintext(plaintext, result)==0){
                                
                                printf("Password is %s\n", password);
                                
                                time_t end = time(NULL);
                                printf("Time elpased is %ld seconds", (end - begin));
 
                                return 0;
                            }

                        }
                       
                        free(result);           
     }
}

// this given cipher text
int firstReader(){
    if ((fp = fopen("givenfile.txt", "r")) == NULL) {
        printf("Error! File cannot be opened.");
        exit(1);
    }
    fscanf(fp, "%[^\n]", counter);
    
    printf("Cipher text is:\n%s", counter);
    printf("\nCracking cipher text one in progress ....\n");

    algorithm();//calls the algorithm function
}

int secondReader(){

    if ((fptr = fopen("cipher1.txt", "r")) == NULL) {
    printf("Error! File cannot be opened.");
    // Program exits if the file pointer returns NULL.
    exit(1);
    }
    fscanf(fptr, "%[^\n]", counter);
    
    printf("Cipher text is:\n%s", counter);
    printf("\nCracking cipher text tow in progress ....\n");

    algorithm(); // calls the algorithm function

}

// reads user's choice and performs the next operation accordingly
void choiceReader(){

    printf("User's application guide.\nIst cipher decryption = 1\nSecond cipher decryption = 2\nQuit = Any other input\n");
    scanf("%d", &c);
    
    if(c==1){
        firstReader();
    }
    if(c==2){
        secondReader();
    }

    else{
        printf("Application Exited ...");
        exit(1);
    }

}

int main (void)
{
    //the core function that controls the user's action.
    choiceReader();

    dict_len = strlen(dict);

    if (c==1){
        ciphertext_base64 = (char*) fp;
    }
    if (c==2){
        ciphertext_base64 = (char*) fptr;
    }
    
    printf(ciphertext_base64);

    ERR_load_crypto_strings();
    
    Base64Decode(ciphertext_base64, &ciphertext, &cipher_len);

    
    // retrive the slater from ciphertext (binary)
    if (strncmp((const char*)ciphertext,"Salted__",8) == 0) { // find the keyword "Salted__"
        
        memcpy(salt,&ciphertext[8],8);
        ciphertext += 16; 
        cipher_len -= 16;
    
    }
            
    // Clean up
    fclose(fptr);
    EVP_cleanup();
    ERR_free_strings();


    return 0;
}

The output is screenshot below:

解决方案

You wrote:

    if(c==1){
        firstReader();
    }
    if(c==2){
        secondReader();
    }
    else{
        printf("Application Exited ...");
        exit(1);
    }

which means:

• If c is 1, call firstReader.
• If c is 2, call secondReader, otherwise exit.

If c is 1, then it calls firstReader, and then exits because c is not 2. The computer is not smart enough to figure out what you actually meant. You probably meant to write else if(c==2) which links the two ifs together so that the final else only runs if neither one is true.

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