sudo/visudo.c

/*
 * Copyright (c) 1996, 1998, 1999 Todd C. Miller <Todd.Miller@courtesan.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * 4. Products derived from this software may not be called "Sudo" nor
 *    may "Sudo" appear in their names without specific prior written
 *    permission from the author.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Lock the sudoers file for safe editing (ala vipw) and check for parse errors.
 */

#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 <time.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 "sudo.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 */

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

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

/*
 * External globals exported by the parser
 */
extern FILE *yyin, *yyout;
extern int errorlineno;
extern int pedantic;

/*
 * Globals
 */
char **Argv;
char *sudoers = _PATH_SUDOERS;
char *stmp = _PATH_SUDOERS_TMP;
struct sudo_user sudo_user;
int parse_error = FALSE;


int
main(argc, argv)
    int argc;
    char **argv;
{
    char buf[MAXPATHLEN*2];		/* 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 */
    time_t now;				/* time now */
    struct stat stmp_sb, sudoers_sb;	/* to check for changes */

    /* Warn about aliases that are used before being defined. */
    pedantic = 1;

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

    /*
     * Arg handling.
     */
    while (--argc) {
	if (!strcmp(argv[argc], "-V")) {
	    (void) printf("visudo version %s\n", version);
	    exit(0);
	} else if (!strcmp(argv[argc], "-s")) {
	    pedantic++;			/* strict mode */
	} else {
	    usage();
	}
    }

    /* Mock up a fake sudo_user struct. */
    user_runas = RUNAS_DEFAULT;
    user_host = user_shost = user_cmnd = "";
    if ((sudo_user.pw = getpwuid(getuid())) == NULL) {
	(void) fprintf(stderr, "%s: Can't find you in the passwd database.\n",
	    Argv[0]);
	exit(1);
    }

#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 */

    /*
     * Open sudoers temp file and grab a lock.
     */
    stmp_fd = open(stmp, O_WRONLY | O_CREAT, 0600);
    if (stmp_fd < 0) {
	(void) fprintf(stderr, "%s: %s\n", Argv[0], strerror(errno));
	exit(1);
    }
    if (!lock_file(stmp_fd, SUDO_TLOCK)) {
	(void) fprintf(stderr, "%s: sudoers file busy, try again later.\n",
	    Argv[0]);
	exit(1);
    }
#ifdef HAVE_FTRUNCATE
    if (ftruncate(stmp_fd, 0) == -1) {
#else
    if (truncate(stmp, 0) == -1) {
#endif
	(void) fprintf(stderr, "%s: can't truncate %s: %s\n", Argv[0],
	    stmp, strerror(errno));
	Exit(-1);
    }

    /* Install signal handlers to clean up stmp if we are killed. */
    setup_signals();

    (void) memset(&sudoers_sb, 0, sizeof(sudoers_sb));
    if (stat(sudoers, &sudoers_sb) == -1 && errno != ENOENT) {
	(void) fprintf(stderr, "%s: %s\n", Argv[0], strerror(errno));
	Exit(-1);
    }
    sudoers_fd = open(sudoers, O_RDONLY);
    if (sudoers_fd == -1 && errno != ENOENT) {
	(void) fprintf(stderr, "%s: %s\n", Argv[0], strerror(errno));
	Exit(-1);
    }

    /* Copy sudoers -> stmp and reset the mtime */
    if (sudoers_fd != -1) {
	while ((n = read(sudoers_fd, buf, sizeof(buf))) > 0)
	    if (write(stmp_fd, buf, n) != n) {
		(void) fprintf(stderr, "%s: Write failed: %s\n", Argv[0],
		strerror(errno));
		Exit(-1);
	    }

	(void) close(sudoers_fd);
    }
    (void) close(stmp_fd);
    (void) touch(stmp, sudoers_sb.st_mtime);

    /*
     * Edit the temp file and parse it (for sanity checking)
     */
    do {
	/*
	 * Build up a buffer to execute
	 */
	if (strlen(Editor) + strlen(stmp) + 30 > sizeof(buf)) {
	    (void) fprintf(stderr, "%s: Buffer too short (line %d).\n",
			   Argv[0], __LINE__);
	    Exit(-1);
	}
	if (parse_error == TRUE)
	    (void) sprintf(buf, "%s +%d %s", Editor, errorlineno, stmp);
	else
	    (void) sprintf(buf, "%s %s", Editor, stmp);

	/* Do the edit -- some SYSV editors exit with 1 instead of 0 */
	now = time(NULL);
	n = system(buf);
	if (n != -1 && ((n >> 8) == 0 || (n >> 8) == 1)) {
	    /*
	     * Sanity checks.
	     */
	    if (stat(stmp, &stmp_sb) < 0) {
		(void) fprintf(stderr,
		    "%s: Can't stat temporary file (%s), %s unchanged.\n",
		    Argv[0], stmp, sudoers);
		Exit(-1);
	    }
	    if (stmp_sb.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 */
	    init_parser();

	    /* Parse the sudoers file */
	    if (yyparse() && parse_error != TRUE) {
		(void) fprintf(stderr,
		    "%s: Failed to parse temporary file (%s), unknown error.\n",
		    Argv[0], stmp);
		parse_error = TRUE;
	    }
	} else {
	    (void) fprintf(stderr,
		"%s: Editor (%s) failed with exit status %d, %s unchanged.\n",
		Argv[0], Editor, n, sudoers);
	    Exit(-1);
	}

	/*
	 * Got an error, 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);

    /*
     * If the user didn't change the temp file, just unlink it.
     */
    if (sudoers_sb.st_mtime != now && sudoers_sb.st_mtime == stmp_sb.st_mtime &&
	sudoers_sb.st_size == stmp_sb.st_size) {
	(void) fprintf(stderr, "%s: sudoers file unchanged.\n", Argv[0]);
	Exit(0);
    }

    /*
     * Change mode and ownership of temp file so when
     * we move it to sudoers things are kosher.
     */
    if (chown(stmp, SUDOERS_UID, SUDOERS_GID)) {
	(void) fprintf(stderr,
	    "%s: Unable to set (uid, gid) of %s to (%d, %d): %s\n",
	    Argv[0], stmp, SUDOERS_UID, SUDOERS_GID, strerror(errno));
	Exit(-1);
    }
    if (chmod(stmp, SUDOERS_MODE)) {
	(void) fprintf(stderr,
	    "%s: Unable to change mode of %s to %o: %s\n",
	    Argv[0], stmp, SUDOERS_MODE, strerror(errno));
	Exit(-1);
    }

    /*
     * Now that we have a sane stmp file (parses 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: %s\n",
			      Argv[0], sudoers, strerror(errno));
		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);
	    }
	    free(tmpbuf);
	} else {
	    (void) fprintf(stderr, "%s: Error renaming %s, %s unchanged: %s\n",
				   Argv[0], stmp, sudoers, strerror(errno));
	    Exit(-1);
	}
    }

    return(0);
}

/*
 * Dummy *_matches routines.
 * These exist to allow us to use the same parser as sudo(8).
 */
int
command_matches(cmnd, cmnd_args, path, sudoers_args)
    char *cmnd;
    char *cmnd_args;
    char *path;
    char *sudoers_args;
{
    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);
}

/*
 * Assuming a parse error occurred, prompt the user for what they want
 * to do now.  Returns the first letter of their choice.
 */
static char
whatnow()
{
    int choice, c;

    for (;;) {
	(void) fputs("What now? ", stdout);
	choice = getchar();
	for (c = choice; c != '\n' && c != EOF;)
	    c = getchar();

	if (choice == 'e' || choice == 'x' || choice == 'Q')
	    break;
	else {
	    (void) puts("Options are:");
	    (void) puts("  (e)dit sudoers file again");
	    (void) puts("  e(x)it without saving changes to sudoers file");
	    (void) puts("  (Q)uit and save changes to sudoers file (DANGER!)\n");
	}
    }

    return(choice);
}

/*
 * Install signal handlers for visudo.
 */
static void
setup_signals()
{
#ifdef POSIX_SIGNALS
	struct sigaction action;		/* POSIX signal structure */
#endif /* POSIX_SIGNALS */

	/*
	 * Setup signal handlers to cleanup nicely.
	 */
#ifdef POSIX_SIGNALS
	(void) memset((VOID *)&action, 0, sizeof(action));
	action.sa_handler = Exit;
	action.sa_flags = SA_RESETHAND;
	(void) sigaction(SIGTERM, &action, NULL);
	(void) sigaction(SIGHUP, &action, NULL);
	(void) sigaction(SIGINT, &action, NULL);
	(void) sigaction(SIGQUIT, &action, NULL);
#else
	(void) signal(SIGTERM, Exit);
	(void) signal(SIGHUP, Exit);
	(void) signal(SIGINT, Exit);
	(void) signal(SIGQUIT, Exit);
#endif /* POSIX_SIGNALS */
}

/*
 * Unlink the sudoers temp file (if it exists) and exit.
 * Used in place of a normal exit() and as a signal handler.
 * A positive parameter is considered to be a signal and is reported.
 */
static RETSIGTYPE
Exit(sig)
    int sig;
{
    (void) unlink(stmp);

    if (sig > 0)
	(void) fprintf(stderr, "%s exiting, caught signal %d.\n", Argv[0], sig);

    exit(-sig);
}

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