visudo.c

A* sudo sudo/* B* adduser script adduser C* rmuser script rmuser E* tout tout/*

/*
 *  sudo version 1.1 allows users to execute commands as root
 *  Copyright (C) 1991  The Root Group, Inc.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 1, or (at your option)
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *  If you make modifications to the source, we would be happy to have
 *  them to include in future releases.  Feel free to send them to:
 *      Jeff Nieusma                       [e-mail]
 *      3959 Arbol CT                      [phone]
 *      Boulder, CO 80301-1752             
 *
********************************************************************************
* visudo.c, sudo project
* David R. Hieb
* March 18, 1991
*
* edit, lock and parse the sudoers file in a fashion similiar to /etc/vipw.
*******************************************************************************/
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <stdio.h>
#include <errno.h>
#include <signal.h>

#include "sudo.h"

extern	FILE *yyin, *yyout;
extern	int errno, yylineno;

char	buffer[BUFSIZ];
char	*sudoers = SUDOERS;
int	status = 0, err_line_no = 0;
char	*sudoers_tmp_file = TMPSUDOERS;
FILE	*sudoers_tmp_fp, *sudoers_fp;

void Exit()
{
fclose(sudoers_tmp_fp);
unlink(sudoers_tmp_file);
exit(1);
}

main(argc, argv)
int argc;
char **argv;
{
int fd;
struct stat sbuf;

/* handle the signals */
signal(SIGILL, Exit);
signal(SIGTRAP, Exit);
signal(SIGBUS, Exit);
signal(SIGSEGV, Exit);
signal(SIGTERM, Exit);

signal(SIGHUP, SIG_IGN);
signal(SIGINT, SIG_IGN);
signal(SIGQUIT, SIG_IGN);

setbuf(stderr, NULL);

/* we only want root to be able to read/write the sudoers_tmp_file */
umask(077);

/* open the sudoers file read only */
if ((sudoers_fp = fopen(sudoers, "r")) == NULL) {
    fprintf(stderr, "%s: ", *argv); 
    perror(sudoers);
    Exit();
    }

/* open the temporary sudoers file with the correct flags */
if ((fd = open(sudoers_tmp_file, O_WRONLY|O_CREAT|O_EXCL, 0600)) < 0) {
    if (errno == EEXIST) {
        fprintf(stderr, "%s: sudoers file busy\n", *argv);
        exit(1);
        }
    fprintf(stderr, "%s: ", *argv); 
    perror(sudoers_tmp_file);
    exit(1);
    }

/* get a STREAM file pointer to the temporary sudoers file */
if ((sudoers_tmp_fp = fdopen(fd, "w")) == NULL) {
    fprintf(stderr, "%s: ", *argv); 
    perror(sudoers_tmp_file);
    Exit();
    }

/* transfer the contents of the sudoers file to the temporary sudoers file */
while (fgets(buffer, sizeof(buffer) - 1, sudoers_fp) != NULL) {
    fputs(buffer, sudoers_tmp_fp);
    }

fclose(sudoers_fp);
fclose(sudoers_tmp_fp);

do {
    /* build strings in buffer to be executed by system() */
    sprintf(buffer, "%s +%d %s", EDITOR, err_line_no, sudoers_tmp_file);

    /* edit the file */
    if (system(buffer) == 0) {

        /* can't stat file */
        if (stat(sudoers_tmp_file, &sbuf) < 0) {
            fprintf(stderr, "%s: can't stat temporary file, %s unchanged\n", 
                sudoers, *argv);
            Exit();
            }
        /* file has size == 0 */
        if (sbuf.st_size == 0) {
            fprintf(stderr, "%s: bad temporary file, %s unchanged\n", 
                sudoers, *argv);
            Exit();
            }
        /* re-open the sudoers file for parsing */
        if ((sudoers_tmp_fp = fopen(sudoers_tmp_file, "r")) == NULL) {
            fprintf(stderr, "%s: can't re-open temporary file, %s unchanged\n", 
                sudoers, *argv);
            Exit();
            }

        yyin = sudoers_tmp_fp;
        yyout = stdout;
         
        /* parse the file */
        if (yyparse()) {
            fprintf(stderr, "yyparse() failed\n");
            Exit();
            }

        /*
         * the first time we get an error, set status to yylineno which
         * will be the line number after the line with the error.
         * then, if we have gotten an error, set err_line_no to the
         * correct line so that when we edit the file err_line_no will
         * be correct. at this time we also reset status and yylineno
         * to their default values so that the next time yyparse() is
         * called, they will be initialized correctly.
         */
        err_line_no = (status == 0) ? 0 : status - 1;
        status = 0;
        yylineno = 1;

        fclose(sudoers_tmp_fp);
        }
    } while (err_line_no);

/* once the temporary sudoers file is gramatically correct, we can 
 * rename it to the real sudoers file.
 */
if (rename(sudoers_tmp_file, sudoers) != 0) {
    fprintf(stderr, "%s: ", *argv), perror("rename");
    }
else {
    if (chmod(sudoers, 0400) != 0) {
        perror("chmod: failed");
        }
    exit(0);
    }
}