Whant to write an entry in /etc/passwd (putpwent) Post: 302211357

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Top Forums Programming Whant to write an entry in /etc/passwd (putpwent) Post 302211357 by nighter on Thursday 3rd of July 2008 06:33:31 AM

07-03-2008

Registered User

/etc/shadow update password entry (putspent?)

Hi i just whant to update an password entry in /etc/shadow.
But dosen't get it to work. Something is wrong! in this code.

What i try do do is if user kalle exist in shadow.
I whant it to update it's password for just that entry.

Code:

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <string.h>
#include <shadow.h>
//#include <userpw.h>

int main()
{
     // -------------------------- //
     // ------- passwd file ------ //
     // -------------------------- //
     FILE* fp;
     struct passwd *p;

     memset(&p, 0, sizeof(p));

     if (!(fp = fopen("/etc/passwd", "a"))) {
           perror("Problem ");
           return(1);
     }

     // --------------------------- //
     // ----- Password Crypt ------ //
     // --------------------------- //
     char salt[2];
     char password[8] = "password";
     char t[11];

     salt[0] = 'W'; salt[1] = 'M';
     strcpy(t,(char *)crypt(password, salt));

    // --------------------------- //
     // ------ shadow file -------- //
     // --------------------------- //

     FILE* fps;
     struct spwd *sp;
     memset(&sp, 0, sizeof(sp));
     if (!(fps = fopen("/etc/shadow", "rw"))) {
        perror("Problem");
        return(1);
     }

     char user[20] = "kalle";

     /* Loop thru passwd file */
     while ((p = getpwent()) != NULL) {
                printf("%s\n",p->pw_name);

                //IF user found 
                if (strcmp(p->pw_name, user) == 0 ) {

                        if(!(sp=getspnam(p->pw_name))){
                                printf("user missing in shadow file");
                        } else {
                                strcpy(sp->sp_pwdp,t);
                                prinf("run the train %s\n",sp->sp_pwdp);
                                putspent(sp,fps);
                        }

                    
                }

    }

       
    fclose(fps);
  
 return( EXIT_SUCCESS );
}

nighter

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LEARN ABOUT MINIX

crypt

CRYPT(3)						     Library Functions Manual							  CRYPT(3)

NAME

       crypt - one-way password encryption function

SYNOPSIS

       #define _MINIX_SOURCE 1
       #include <unistd.h>

       char *crypt(const char *key, const char *salt)

DESCRIPTION

       The  first  use	of  crypt()  is  to encrypt a password.  Its second use is to authenticate a shadow password.  In both cases crypt() calls
       pwdauth(8) to do the real work.

       Crypt() encrypts a password if called with a user typed key, and a salt whose first two characters  are	in  the  set  [./0-9A-Za-z].   The
       result  is  a  character  string in the [./0-9A-Za-z] alphabet of which the first two characters are equal to the salt, and the rest is the
       result of encrypting the key and the salt.

       If crypt() is called with a salt that has the form ##user then the key is encrypted and compared to the encrypted password of user  in  the
       shadow  password  file.	If they are equal then crypt() returns the ##user argument, if not then some other string is returned.	This trick
       assures that the normal way to authenticate a password still works:

	      if (strcmp(pw->pw_passwd, crypt(key, pw->pw_passwd))) ...

       If key is a null string, and the shadow password is a null string or the salt is a null string then  the  result  equals  salt.	 (This	is
       because the caller can't tell if a password field is empty in the shadow password file.)

       The key and salt are limited to 1024 bytes total including the null bytes.

FILES

       /usr/lib/pwdauth 	The password authentication program

SEE ALSO

       getpass(3), getpwent(3), passwd(5), pwdauth(8).

NOTES

       The result of an encryption is returned in a static array that is overwritten by each call.  The return value should not be modified.

AUTHOR

       Kees J. Bot (kjb@cs.vu.nl)

																	  CRYPT(3)

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