Thread: why is strcmp not returning 0 despite matching strings

Given the following code

Code:

    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    #include <strings.h>
    
    int main(void)
    {
    char buf[1024];
        char **arr1 = NULL;
        char **arr2 = NULL;
        char **arr3 = NULL;
        char **arr4 = NULL;
    
        int size1 = 0;
        int size2 = 0;
        int size3 = 0;
        int size4 = 0;
    
        FILE * f1, *f2;
        f1 = fopen("shadow.txt", "r");
        f2 = fopen("mytab24112.txt", "r");
    
        // Allocate memory for shadow.txt
        while(fgets(buf, 1024, f1))
        {
            size1++;
            arr1 = realloc(arr1, sizeof(char*) * size1);
            arr1[size1 - 1] = strdup(buf);
        }
    
        // Allocate memory for mytab2411.txt
        while(fgets(buf, 1024, f2))
        {
            size2++;
            arr2 = realloc(arr2, sizeof(char*) * size2);
            arr2[size2 - 1] = strdup(buf);
        }
    
            size3++;
            arr3 = realloc(arr3, sizeof(char*) * size3);
            arr3[size3 - 1] = strdup(buf);
    
            size4++;
            arr4 = realloc(arr4, sizeof(char*) * size4);
            arr4[size4 - 1] = strdup(buf);
    
        char line[1000]; //Allocate max number of characters in a line
    
        char hash[1000]; // Allocate max number of characters in a hash (substring of a line) for shadow.txt
        char * hash2; // Define hash for mytab24112.txt
    
        char md5[5]= "$1$$"; // Define string to be searched for md5 in shadow.txt
        char sha512[5]="$6$$"; // Define string to be searched for sha512 in shadow.txt
        char *ret; // Used for shadow.txt
        char *ret2; // Used for shadow.txt
    
        char del='$'; // Delimiter for displaying all hashes in mytab24112.txt
        char * del2; // Delimiter for displaying password text in mytab24112.txt
        char word[sizeof(line)];
    
        // Read shadow.txt line by line
        for(int i = 0; i < size1; i++) {


        memset(hash, '\0', sizeof(hash));
        strcpy(line, arr1[i]);
    
        // Search for md5 in shadow.txt
          md5[4]='\0';
          ret = strstr(line, md5);
    
        // Search for sha512 in shadow.txt
          sha512[4]='\0';
          ret2 = strstr(line, sha512);
    
        // Copies md5 hash to the variable hash if md5 is detected in shadow.txt
        if (ret){
           strncpy(hash, line+5, 26);
           hash[26] = '\0';
   
        }
        // Copies sha512 hash to the variable hash if sha512 is detected in shadow.txt
        else if (ret2){
    
          strncpy(hash, line+5, 90);
           hash[90] = '\0';
           
        }
  
     // Read mytab2411.txt line by line
        for(int j = 0; j < size2; j++){
    
        strcpy(line, arr2[j]);
       
        // Returns all hashes from mytab24112.txt using delimiter '$'
        hash2=strchr(line,del);


     for(int a = 0; a < size3; a++)
           for(int b = 0; b < size4; b++){
    
           strcpy(arr3[a],hash); 
           strcpy(arr4[b],hash2);
          
          printf("Hash in shadow:%s\n",arr3[a]);  
          printf("Hash in mytab24112:%s\n",arr4[b]);
          
          //Compare hash (arr3[a]) and hash 2 (arr4[b])
          int result = strcmp(arr3[a],arr4[b]);                   
            printf("%d\n",result);


    } //End of "for(int a = 0; a < size3; a++)" and "for(int b = 0; b < size4; b++)" loop


         }// End of "for(int j = 0; j < size2; j++)" loop  
  
      }// End of "for (int i = 0; i < size1; i++)" loop
   
        return 0;


    }//End of main

and the following files


shadow.txt

Code:

    
pyc1:$1$$Tnq7a6/C1wwyKyt0V/.BP/:17482:0:99999:7:::
    pyc2:$6$$/xMg2/4CZwMUbah4IhNwCjqzZf0/OByfs6UHmq32jFbsdpbDw9bhLttC7n/bAVlM2NwJ7hBQ3d0H47leLXE6g1:17482:0:99999:7:::
    
pyc3:$1$$zZQKNjRd94GHyYOwXuStf0:17482:0:99999:7:::
    pyc4:$6$iKYSRG68$STdY8TCgoCaNfSUcyCwSBlVekdjs0P3qXtwxSbgpQpMUnHJRRSHOT5amoR24IqZBTPNWuIfO.uhZEnGLuE4q/.:17482:0:99999:7:::
    pyc5:$6$$FDqvMBbQOCyKP9uBL8E6TAEupCh72v.3/ow4fZ5HpZ/0NS7LBifFS9nJdzc/u2OEhUnRF9yC4Lw23hHjD1EmD.:17482:0:99999:7:::
    pyc6:$6$$LfCuhKecDtIfX77LOTWD1PjhF1IC0hBzjxckEthmoT8mVbxKH3qJzFgEi/P9GN1mptR4WPiwuh69X/41M6pHW1:17482:0:99999:7:::

mytab24112.txt

Code:

apple:$1$$Tnq7a6/C1wwyKyt0V/.BP/    
orange:$6$$/xMg2/4CZwMUbah4IhNwCjqzZf0/OByfs6UHmq32jFbsdpbDw9bhLttC7n/bAVlM2NwJ7hBQ3d0H47leLXE6g1  
banana:$1$$zZQKNjRd94GHyYOwXuStf0   
a:$1$$Ij31LCAysPM23KuPlm1wA/    
a:$6$$ek/ucQg0IM8SQLyD2D66mpoW0vAF26eA0/pqoN95V.F0nZh1IFuENNo0OikacRkDBk5frNqziMYMdVVrQ0o.51 
aah:$1$$bh5o1cAKfH43fc/B1.AjF0
aah:$6$$jdxDww2LkNSlQPmWe5iDRAoBBT5IXa9241nN2bcm2Aukdrr4iH27Y6dj801MjLFaDQxbDBNxY4jvlXdIemiCY/
aahed:$1$$zA2Ef92JR9W7kqAf8Km5B0
aahed:$6$$mYQU7f3NL9Dysccvwv2BAyiCb/gxh9lN1gGnC9sa2uwHGX9VVb7jp3b7u/EZbdObqWrRFgiOLcRn7PEW1cOcz.

why is it that "strcmp(arr3[a],arr4[b])" returns "-10" instead of "0" despite matching strings (First 3 lines from shadow.txt and mytab24112.txt should match)? How should I solve this problem?

A few important lines from the output

Code:

    
Hash in shadow:$1$$Tnq7a6/C1wwyKyt0V/.BP/
Hash in mytab24112:$1$$Tnq7a6/C1wwyKyt0V/.BP/
    
-10
    
Hash in shadow:$6$$/xMg2/4CZwMUbah4IhNwCjqzZf0/OByfs6UHmq32jFbsdpbDw9bhLttC7n/bAVlM2NwJ7hBQ3d0H47leLXE6g1
Hash in mytab24112:$6$$/xMg2/4CZwMUbah4IhNwCjqzZf0/OByfs6UHmq32jFbsdpbDw9bhLttC7n/bAVlM2NwJ7hBQ3d0H47leLXE6g1
    
-10
    
Hash in shadow:$1$$zZQKNjRd94GHyYOwXuStf0
Hash in mytab24112:$1$$zZQKNjRd94GHyYOwXuStf0
    
-10