lib/password.c

/* pwdutils.c - password read/update helper functions.
 *
 * Copyright 2012 Ashwini Kumar <ak.ashwini@gmail.com>
 */

#include "toys.h"
#include <time.h>

int read_password(char * buff, int buflen, char* mesg)
{
  int i = 0;
  struct termios termio, oldtermio;
  tcgetattr(0, &oldtermio);
  tcflush(0, TCIFLUSH);
  termio = oldtermio;

  termio.c_iflag &= ~(IUCLC|IXON|IXOFF|IXANY);
  termio.c_lflag &= ~(ECHO|ECHOE|ECHOK|ECHONL|TOSTOP);
  tcsetattr(0, TCSANOW, &termio);

  fputs(mesg, stdout);
  fflush(stdout);

  while (1) {
    int ret = read(0, &buff[i], 1);
    if ( ret < 0 ) {
      buff[0] = 0;
      tcsetattr(0, TCSANOW, &oldtermio);
      return 1;
    } else if (ret == 0 || buff[i] == '\n' || buff[i] == '\r' || buflen == i+1)
    {
      buff[i] = '\0';
      break;
    }
    i++;
  }

  tcsetattr(0, TCSANOW, &oldtermio);
  puts("");
  fflush(stdout);
  return 0;
}

static char *get_nextcolon(const char *line, char delim)
{
  char *current_ptr = NULL;
  if((current_ptr = strchr(line, ':')) == NULL) error_exit("Invalid Entry\n");
  return current_ptr;
}

int update_password(char *filename, char* username, char* encrypted)
{
  char *filenamesfx = NULL, *namesfx = NULL;
  char *shadow = NULL, *sfx = NULL;
  FILE *exfp, *newfp;
  int ret = -1; //fail
  struct flock lock;
  char *line = NULL;

  shadow = strstr(filename, "shadow");
  filenamesfx = xmsprintf("%s+", filename);
  sfx = strchr(filenamesfx, '+');

  exfp = fopen(filename, "r+");
  if(!exfp) {
    perror_msg("Couldn't open file %s",filename);
    goto free_storage;
  }

  *sfx = '-';
  ret = unlink(filenamesfx);
  ret = link(filename, filenamesfx);
  if(ret < 0) error_msg("can't create backup file");

  *sfx = '+';
  lock.l_type = F_WRLCK;
  lock.l_whence = SEEK_SET;
  lock.l_start = 0;
  lock.l_len = 0;

  ret = fcntl(fileno(exfp), F_SETLK, &lock);
  if(ret < 0) perror_msg("Couldn't lock file %s",filename);

  lock.l_type = F_UNLCK; //unlocking at a later stage

  newfp = fopen(filenamesfx, "w+");
  if(!newfp) {
    error_msg("couldn't open file for writing");
    ret = -1;
    fclose(exfp);
    goto free_storage;
  }

  ret = 0;
  namesfx = xmsprintf("%s:",username);
  while((line = get_line(fileno(exfp))) != NULL)
  {
    if(strncmp(line, namesfx, strlen(namesfx)) != 0)
      fprintf(newfp, "%s\n", line);
    else {
      char *current_ptr = NULL;
      fprintf(newfp, "%s%s:",namesfx,encrypted);
      current_ptr = get_nextcolon(line, ':'); //past username
      current_ptr++; //past colon ':' after username
      current_ptr = get_nextcolon(current_ptr, ':'); //past passwd
      current_ptr++; //past colon ':' after passwd
      if(shadow) {
        fprintf(newfp, "%u:",(unsigned)(time(NULL))/(24*60*60));
        current_ptr = get_nextcolon(current_ptr, ':');
        current_ptr++; //past time stamp colon.
        fprintf(newfp, "%s\n",current_ptr);
      }
      else fprintf(newfp, "%s\n",current_ptr);
    }

    free(line);
  }
  free(namesfx);
  fcntl(fileno(exfp), F_SETLK, &lock);
  fclose(exfp);

  errno = 0;
  fflush(newfp);
  fsync(fileno(newfp));
  fclose(newfp);
  rename(filenamesfx, filename);
  if(errno) {
    perror_msg("File Writing/Saving failed: ");
    unlink(filenamesfx);
    ret = -1;
  }

free_storage:
  free(filenamesfx);
  return ret;
}