sudo/visudo.c

/*
 *  CU sudo version 1.4
 *
 *  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.
 *
 *  Please send bugs, changes, problems to sudo-bugs@cs.colorado.edu
 *
 *******************************************************************
 *
 *  visudo.c -- locks the sudoers file for safe editing and check
 *  for parse errors.
 *
 *  Todd C. Miller (millert@colorado.edu) Sat Mar 25 21:50:36 MST 1995
 */

#ifndef lint
static char rcsid[] = "$Id$";
#endif /* lint */

#include "config.h"

#include <stdio.h>
#ifdef STDC_HEADERS
#include <stdlib.h>
#endif /* STDC_HEADERS */
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /* HAVE_UNISTD_H */
#ifdef HAVE_STRING_H
#include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif /* HAVE_STRINGS_H */
#if defined(HAVE_MALLOC_H) && !defined(STDC_HEADERS)
#include <malloc.h>
#endif /* HAVE_MALLOC_H && !STDC_HEADERS */
#include <ctype.h>
#include <pwd.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <netinet/in.h>

#include "sudo.h"
#include <options.h>
#include "version.h"

#ifndef STDC_HEADERS
#ifndef __GNUC__	/* gcc has its own malloc */
extern char *malloc	__P((size_t));
#endif /* __GNUC__ */
extern char *getenv	__P((const char *));
extern int stat		__P((const char *, struct stat *));
#endif /* !STDC_HEADERS */

#if defined(POSIX_SIGNALS) && !defined(SA_RESETHAND)
#define SA_RESETHAND    0
#endif /* POSIX_SIGNALS && !SA_RESETHAND */

/*
 * Function prototypes
 */
static void usage		__P((void));
static char whatnow		__P((void));
static void whatnow_help	__P((void));
static RETSIGTYPE Exit		__P((int));
static void setup_signals	__P((void));
int path_matches		__P((char *, char *));
int addr_matches		__P((char *));
int netgr_matches		__P((char *, char *, char *));
int usergr_matches		__P((char *, char *));


/*
 * External globals
 */
extern FILE *yyin, *yyout;
extern int errorlineno, sudolineno;


/*
 * Globals
 */
char **Argv;
char *sudoers = _PATH_SUDO_SUDOERS;
char *stmp = _PATH_SUDO_STMP;
int parse_error = FALSE;


/*
 * For the parsing routines
 */
char host[] = "";
char *cmnd = "";
struct passwd *user_pw_ent;


/********************************************************************
 *
 *  main()
 *
 *  where it all begins...
 */

int main(argc, argv)
    int argc;
    char **argv;
{
    char buf[BUFSIZ];			/* buffer used for copying files */
    char * Editor = EDITOR;		/* editor to use (default is EDITOR */
    int sudoers_fd;			/* sudoers file descriptor */
    int stmp_fd;			/* stmp file descriptor */
    int n;				/* length parameter */
    struct passwd *pwd;			/* to look up info for SUDOERS_OWNER */

    (void) setbuf(stderr, (char *)NULL);	/* unbuffered stderr */

    /*
     * Parse command line options
     */
    Argv = argv;

    /*
     * If passesd -V then print version, else print usage
     * if any other option...
     */
    if (argc == 2)
	if (!strcmp(Argv[1], "-V")) {
	    (void) printf("visudo version %s\n", version);
	    exit(0);
	} else {
	    usage();
	}
    else if (argc != 1)
	usage();

#ifdef ENV_EDITOR
    /*
     * If we are allowing EDITOR and VISUAL envariables set Editor
     * base on whichever exists...
     */
    if (!(Editor = getenv("EDITOR")))
	if (!(Editor = getenv("VISUAL")))
	    Editor = EDITOR;
#endif /* ENV_EDITOR */

    /*
     * Need to find who should own the sudoers file
     */
    if (!(pwd = getpwnam(SUDOERS_OWNER))) {
	(void) fprintf(stderr,
		       "%s:  no passwd entry for sudoers file owner (%s)\n",
		       Argv[0], SUDOERS_OWNER);
	exit(1);
    }

    /* user_pw_ent needs to be defined to _something_, this will do */
    user_pw_ent = pwd;

    /*
     * Copy sudoers file to stmp
     */
    stmp_fd = open(stmp, O_WRONLY | O_CREAT | O_EXCL, 0600);
    if (stmp_fd < 0) {
	if (errno == EEXIST) {
	    (void) fprintf(stderr, "%s: sudoers file busy, try again later.\n",
		Argv[0]);
	    exit(1);
	}
	(void) fprintf(stderr, "%s: ", Argv[0]);
	perror(stmp);
	Exit(1);
    }

    /* install signal handler to clean up stmp */
    setup_signals();

    sudoers_fd = open(sudoers, O_RDONLY);
    if (sudoers_fd < 0) {
	(void) fprintf(stderr, "%s: ", Argv[0]);
	perror(sudoers);
	Exit(1);
    }

    /*
     * Copy the data
     */
    while ((n = read(sudoers_fd, buf, sizeof(buf))) > 0)
	if (write(stmp_fd, buf, n) != n) {
	    (void) fprintf(stderr, "%s: Write failed: ", Argv[0]);
	    perror("");
	    Exit(1);
	}

    (void) close(sudoers_fd);
    (void) close(stmp_fd);

    /*
     * Change ownership of temp file to SUDOERS_OWNER
     * so when we move it to sudoers things are kosher.
     */
    if (chown(stmp, pwd -> pw_uid, -1)) {
	(void) fprintf(stderr, "%s: Warning, unable to set owner to %s: ",
	    Argv[0], SUDOERS_OWNER);
	perror("");
    }

    /*
     * Edit the temp file and parse it (for sanity checking)
     */
    do {
	/*
	 * Build up a buffer to execute
	 */
	if (parse_error == TRUE)
	    (void) sprintf(buf, "%s +%d %s", Editor, errorlineno, stmp);
	else
	    (void) sprintf(buf, "%s %s", Editor, stmp);

	/* do the edit */
	if (system(buf) == 0) {
	    struct stat statbuf;	/* for sanity checking */

	    /* make sure stmp exists */
	    if (stat(stmp, &statbuf) < 0) {
		(void) fprintf(stderr,
		    "%s: Can't stat temporary file (%s), %s unchanged.\n",
		    Argv[0], stmp, sudoers);
		Exit(1);
	    }

	    /* check for zero length file */
	    if (statbuf.st_size == 0) {
		(void) fprintf(stderr,
		    "%s: Zero length temporary file (%s), %s unchanged.\n",
		    Argv[0], stmp, sudoers);
		Exit(1);
	    }

	    /*
	     * passed sanity checks so reopen stmp file and check
	     * for parse errors.
	     */
	    yyout = stdout;
	    if (parse_error)
		yyin = freopen(stmp, "r", yyin);
	    else
		yyin = fopen(stmp, "r");
	    if (yyin == NULL) {
		(void) fprintf(stderr,
		    "%s: Can't re-open temporary file (%s), %s unchanged.\n",
		    Argv[0], stmp, sudoers);
		Exit(1);
	    }

	    /* clean slate for each parse */
	    parse_error = FALSE;
	    errorlineno = -1;
	    sudolineno = 1;
	    top = 0;

	    /* parse the sudoers file */
	    if (yyparse()) {
		(void) fprintf(stderr,
		    "%s: Failed to parse temporary file (%s), %s unchanged.\n",
		    Argv[0], stmp, sudoers);
		Exit(1);
	    }
	} else {
	    (void) fprintf(stderr, "%s: Editor (%s) failed, %s unchanged.\n",
		Argv[0], Editor, sudoers);
	    Exit(1);
	}

	/*
	 * Prompt the user for what to do now
	 */
	if (parse_error == TRUE) {
	    switch (whatnow()) {
		case 'q' :	parse_error = FALSE;	/* ignore parse error */
				break;
		case 'x' :	Exit(0);
				break;
	    }
	}
    } while (parse_error == TRUE);

    /*
     * Now that we have a sane stmp file (parse ok) it needs to be
     * rename(2)'d to sudoers.  If the rename(2) fails we try using
     * mv(1) in case stmp and sudoers are on different filesystems.
     */
    if (rename(stmp, sudoers))
	if (errno == EXDEV) {
	    char *tmpbuf;

	    (void) fprintf(stderr,
	      "%s: %s and %s not on the same filesystem, using mv to rename.\n",
	      Argv[0], stmp, sudoers);

	    /* Allocate just enough space for tmpbuf */
	    n = sizeof(char) * (strlen(_PATH_MV) + strlen(stmp) +
		  strlen(sudoers) + 4);
	    if ((tmpbuf = (char *) malloc(n)) == NULL) {
		(void) fprintf(stderr,
			      "%s: Cannot alocate memory, %s unchanged: ",
			      Argv[0], sudoers);
		perror("");
		Exit(1);
	    }

	    /* Build up command and execute it */
	    (void) sprintf(tmpbuf, "%s %s %s", _PATH_MV, stmp, sudoers);
	    if (system(tmpbuf)) {
		(void) fprintf(stderr,
			       "%s: Command failed: '%s', %s unchanged.\n",
			       Argv[0], tmpbuf, sudoers);
		Exit(1);
	    }
	    (void) free(tmpbuf);
	} else {
	    (void) fprintf(stderr, "%s: Error renaming %s, %s unchanged: ",
				   Argv[0], stmp, sudoers);
	    perror("");
	    Exit(1);
	}

    /*
     * Make the new sudoers file readable only by owner.
     * If this fail it is ok since the file is only least rw owner.
     */
    if (chmod(sudoers, 0400)) {
	(void) fprintf(stderr, "%s: Warning, unable to chmod 0400 %s: ",
	    Argv[0], sudoers);
	perror("");
    }

    return(0);
}


/********************************************************************
 *
 *  dummy *_matches routines
 *
 *  These exist to allow us to use the same parser as sudo(8).
 */

int path_matches(cmnd, path)
    char *cmnd, *path;
{
    return(TRUE);
}


int addr_matches(n)
    char *n;
{
    return(TRUE);
}

int usergr_matches(g, u)
    char *g, *u;
{
    return(TRUE);
}


int netgr_matches(n, h, u)
    char *n, *h, *u;
{
    return(TRUE);
}


/********************************************************************
 *
 *  usage()
 *
 *  Prints a help message and exits w/ exit value of 1.
 */

static void usage()
{
    (void) fprintf(stderr, "usage: %s [-V]\n", Argv[0]);
    Exit(1);
}


/********************************************************************
 *
 *  Exit()
 *
 *  Unlinks the sudoers temp file (if it exists) and exits.
 *  Used in place of a normal exit() and as a signal handler.
 */

static RETSIGTYPE Exit(sig)
    int sig;
{
    (void) unlink(stmp);
    exit(sig);
}


/********************************************************************
 *
 *  whatnow()
 *
 *  Assuming a parse error occurred, prompt the user for what they want
 *  to do now.  Returns first letter of their choice (always lowercase).
 */

static char whatnow()
{
    char choice;
    int ok;

    do {
	ok = FALSE;
	(void) printf("What now? ");
	if ((choice = fgetc(stdin)) != '\n')
	    while (fgetc(stdin) != '\n')
		;

	/* safely force to lower case */
	if (isupper(choice))
	    choice = tolower(choice);

	if (choice == 'e' || choice == 'x' || choice == 'q')
	    ok = TRUE;

	/* help message if they gavce us garbage */
	if (!ok)
	    whatnow_help();

    } while (!ok);

    return(choice);
}


/********************************************************************
 *
 *  whatnow_help()
 *
 *  Print out a help message for whatnow().
 */

static void whatnow_help()
{
    (void) printf("Options are:\n");
    (void) printf("  (e)dit sudoers file again\n");
    (void) printf("  e(x)it without saving changes to sudoers file\n");
    (void) printf("  (q)uit and save changes to sudoers file (DANGER!)\n\n");
}


/********************************************************************
 *
 *  setup_signals()
 *
 *  Install signal handlers for visudo.
 */

static void setup_signals()
{
#ifdef POSIX_SIGNALS
	struct sigaction action;		/* posix signal structure */
#endif /* POSIX_SIGNALS */

	/*
	 * Setup signal handlers
	 */
#ifdef POSIX_SIGNALS
	(void) memset((VOID *)&action, 0, sizeof(action));
	action.sa_handler = Exit;
	action.sa_flags = SA_RESETHAND;
	(void) sigaction(SIGILL, &action, NULL);
	(void) sigaction(SIGTRAP, &action, NULL);
	(void) sigaction(SIGBUS, &action, NULL);
	(void) sigaction(SIGSEGV, &action, NULL);
	(void) sigaction(SIGTERM, &action, NULL);

	action.sa_handler = SIG_IGN;
	action.sa_flags = 0;
	(void) sigaction(SIGHUP, &action, NULL);
	(void) sigaction(SIGINT, &action, NULL);
	(void) sigaction(SIGQUIT, &action, NULL);
#else
	(void) signal(SIGILL, Exit);
	(void) signal(SIGTRAP, Exit);
	(void) signal(SIGBUS, Exit);
	(void) signal(SIGSEGV, Exit);
	(void) signal(SIGTERM, Exit);

	(void) signal(SIGHUP, SIG_IGN);
	(void) signal(SIGINT, SIG_IGN);
	(void) signal(SIGQUIT, SIG_IGN);
#endif /* POSIX_SIGNALS */
}