*** 3000userlogin.c	2021-02-06 13:11:42.000000000 -0500
--- 3000userlogin-passwd.c	2021-02-13 01:54:39.103644826 -0500
***************
*** 6,19 ****
  #include <unistd.h>
  #include <stdlib.h>
  #include <pwd.h>
  
  int main(int argc, char *argv[])
  {
          int result;
          char *shell_argv[3];
!         char *username;
          extern char **environ;
!         struct passwd *pw_entry;
                  
          if (argc < 2) {
                  fprintf(stderr, "Usage: %s <username>\n", argv[0]);
--- 6,22 ----
  #include <unistd.h>
  #include <stdlib.h>
  #include <pwd.h>
+ #include <shadow.h>
+ #include <string.h>
  
  int main(int argc, char *argv[])
  {
          int result;
          char *shell_argv[3];
!         char *username, *s, *salt, full[128], *index, computed[128], openssl_cmd[128];
          extern char **environ;
!         struct spwd *sp_entry;
! 	struct passwd *pw_entry;
                  
          if (argc < 2) {
                  fprintf(stderr, "Usage: %s <username>\n", argv[0]);
***************
*** 26,36 ****
          username = argv[1];
          
          pw_entry = getpwnam(username);
!         if (pw_entry == NULL) {
                  fprintf(stderr, "Could not find user %s.\n", username);
                  exit(-2);
          }
!                        
          result = setgid(pw_entry->pw_gid);
          if (result != 0) {
                  fprintf(stderr, "Failed to change to gid %d\n",
--- 29,57 ----
          username = argv[1];
          
          pw_entry = getpwnam(username);
! 	sp_entry = getspnam(username);
!         if (pw_entry == NULL || sp_entry == NULL) {
                  fprintf(stderr, "Could not find user %s.\n", username);
                  exit(-2);
          }
!                       
! 	memcpy(full, sp_entry->sp_pwdp, strlen(sp_entry->sp_pwdp)+1); // save a copy of the entire line
! 	index = strtok(sp_entry->sp_pwdp, "$"); // get the algorithm index
! 	salt = strtok(NULL, "$"); 
! 
! 	snprintf(openssl_cmd, 128, "openssl passwd -%s -salt %s\n", index, salt); 
! 	FILE *fp = popen(openssl_cmd, "r"); // this sends the command above and returns a pointer to its stdout
! 	if (!fp) {
! 		fprintf(stderr, "openssl command failed.\n");
! 		exit(-2);
! 	}
! 	s = fgets(computed, 128, fp); //read the computed result
! 	pclose(fp);
! 	if(strncmp(full, s, strlen(full))) {
! 		fprintf(stderr, "authentication failed.\n");
! 		exit(-2);
! 	}
! 	
          result = setgid(pw_entry->pw_gid);
          if (result != 0) {
                  fprintf(stderr, "Failed to change to gid %d\n",