Question

I’m trying to program the tar function but i have some problem.
I want to read my tar file and parse header data.
here is my structure

struct header { 
    char nom[100];
    char droits[3];
    char taille[12];
    char date_modif[12];
    char type[1];
};

And now my code to parse header data :

while ( fread(head.nom, 100, 1, archive) != 0 ){

    printf("NOM : %s\n", head.nom);


    //droits
    fread(head.droits, 3, 1, archive);


    printf("DROITS : %s\n", head.droits);

    //taille
    fread(head.taille, 12, 1, archive);

    printf("TAILLE : %s\n", head.taille);


    //last modif
    fread(head.date_modif, 12, 1, archive);

    printf("MODIF : %s\n", head.date_modif);


    //type
    fread(head.type, 1, 1, archive);

    printf("TYPE : %s\n", head.type);

    printf("NOM : %s\n", head.nom);

    exit(1);
    // on se place a la fin du premier fichier
    fseek(archive, oct2dec(atoi(head.taille)), SEEK_CUR);


    //fprintf(stdout, "%s %d \n", head.nom, oct2dec(atoi(head.taille)));        

    i++;
}

And the result is :

NOM : a.txt...............................................................................................
DROITS : 664
TAILLE : 936.........
MODIF : 1352910882..
TYPE : 1
NOM : a.txt...............................................................................................664936.........1352910882..1

My problem is that the last line display all my data and I want to display only a.txt…. (like in the first line).
How can I do to fix this problem ?

Thanks

Answer 1

This is a buffer overflow issue. You should increase the size of nom to be able to hold the null character. I don’t know about the tar function but an example,

struct header { 
    char nom[200];
    char droits[10];
    char taille[20];
    char date_modif[20];
    char type[5];
};

You should always declare the size of a char string to be 1 more than the maximum expected length to allow for the null character.