sudo/plugins/sudoers/visudo.c

/*
 * Copyright (c) 1996, 1998-2005, 2007-2011
 *	Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Sponsored in part by the Defense Advanced Research Projects
 * Agency (DARPA) and Air Force Research Laboratory, Air Force
 * Materiel Command, USAF, under agreement number F39502-99-1-0512.
 */

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

#define _SUDO_MAIN

#ifdef __TANDEM
# include <floss.h>
#endif

#include <config.h>

#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/time.h>
#ifndef __TANDEM
# include <sys/file.h>
#endif
#include <sys/wait.h>
#include <stdio.h>
#ifdef STDC_HEADERS
# include <stdlib.h>
# include <stddef.h>
#else
# ifdef HAVE_STDLIB_H
#  include <stdlib.h>
# endif
#endif /* STDC_HEADERS */
#ifdef HAVE_STRING_H
# include <string.h>
#endif /* HAVE_STRING_H */
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif /* HAVE_STRINGS_H */
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /* HAVE_UNISTD_H */
#include <ctype.h>
#include <pwd.h>
#include <grp.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#if TIME_WITH_SYS_TIME
# include <time.h>
#endif
#ifdef __STDC__
# include <stdarg.h>
#else
# include <varargs.h>
#endif

#include "sudoers.h"
#include "interfaces.h"
#include "parse.h"
#include "redblack.h"
#include <gram.h>

struct sudoersfile {
    struct sudoersfile *prev, *next;
    char *path;
    char *tpath;
    int fd;
    int modified;
    int doedit;
};
TQ_DECLARE(sudoersfile)

/*
 * Function prototypes
 */
static void quit(int);
static char *get_args(char *);
static char *get_editor(char **);
static void get_hostname(void);
static char whatnow(void);
static int check_aliases(int, int);
static int check_syntax(char *, int, int);
static int edit_sudoers(struct sudoersfile *, char *, char *, int);
static int install_sudoers(struct sudoersfile *, int);
static int print_unused(void *, void *);
static int reparse_sudoers(char *, char *, int, int);
static int run_command(char *, char **);
static int visudo_printf(int msg_type, const char *fmt, ...);
static void print_selfref(char *name, int, int, int);
static void print_undefined(char *name, int, int, int);
static void setup_signals(void);
static void help(void) __attribute__((__noreturn__));
static void usage(int);

void cleanup(int);

extern void yyerror(const char *);
extern void yyrestart(FILE *);

/*
 * External globals exported by the parser
 */
extern struct rbtree *aliases;
extern FILE *yyin;
extern char *sudoers, *errorfile;
extern int errorlineno, parse_error;
/* For getopt(3) */
extern char *optarg;
extern int optind;

/*
 * Globals
 */
struct interface *interfaces;
struct sudo_user sudo_user;
struct passwd *list_pw;
sudo_printf_t sudo_printf = visudo_printf;
static struct sudoersfile_list sudoerslist;
static struct rbtree *alias_freelist;

int
main(int argc, char *argv[])
{
    struct sudoersfile *sp;
    char *args, *editor, *sudoers_path;
    int ch, checkonly, quiet, strict, oldperms;
#if defined(SUDO_DEVEL) && defined(__OpenBSD__)
    extern char *malloc_options;
    malloc_options = "AFGJPR";
#endif

#if !defined(HAVE_GETPROGNAME) && !defined(HAVE___PROGNAME)
    setprogname(argc > 0 ? argv[0] : "visudo");
#endif
    if (argc < 1)
	usage(1);

    /*
     * Arg handling.
     */
    checkonly = oldperms = quiet = strict = FALSE;
    sudoers_path = _PATH_SUDOERS;
    while ((ch = getopt(argc, argv, "Vcf:sq")) != -1) {
	switch (ch) {
	    case 'V':
		(void) printf("%s version %s\n", getprogname(), PACKAGE_VERSION);
		exit(0);
	    case 'c':
		checkonly++;		/* check mode */
		break;
	    case 'f':
		sudoers_path = optarg;	/* sudoers file path */
		oldperms = TRUE;
		break;
	    case 'h':
		help();
		break;
	    case 's':
		strict++;		/* strict mode */
		break;
	    case 'q':
		quiet++;		/* quiet mode */
		break;
	    default:
		usage(1);
	}
    }
    argc -= optind;
    argv += optind;
    if (argc)
	usage(1);

    sudo_setpwent();
    sudo_setgrent();

    /* Mock up a fake sudo_user struct. */
    user_cmnd = "";
    if ((sudo_user.pw = sudo_getpwuid(getuid())) == NULL)
	errorx(1, "you don't exist in the passwd database");
    get_hostname();

    /* Setup defaults data structures. */
    init_defaults();

    if (checkonly)
	exit(check_syntax(sudoers_path, quiet, strict));

    /*
     * Parse the existing sudoers file(s) in quiet mode to highlight any
     * existing errors and to pull in editor and env_editor conf values.
     */
    if ((yyin = open_sudoers(sudoers_path, TRUE, NULL)) == NULL) {
	error(1, "%s", sudoers_path);
    }
    init_parser(sudoers_path, 0);
    yyparse();
    (void) update_defaults(SETDEF_GENERIC|SETDEF_HOST|SETDEF_USER);

    editor = get_editor(&args);

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

    /* Edit the sudoers file(s) */
    tq_foreach_fwd(&sudoerslist, sp) {
	if (!sp->doedit)
	    continue;
	if (sp != tq_first(&sudoerslist)) {
	    printf("press return to edit %s: ", sp->path);
	    while ((ch = getchar()) != EOF && ch != '\n')
		    continue;
	}
	edit_sudoers(sp, editor, args, -1);
    }

    /* Check edited files for a parse error and re-edit any that fail. */
    reparse_sudoers(editor, args, strict, quiet);

    /* Install the sudoers temp files. */
    tq_foreach_fwd(&sudoerslist, sp) {
	if (!sp->modified)
	    (void) unlink(sp->tpath);
	else
	    (void) install_sudoers(sp, oldperms);
    }

    exit(0);
}

/*
 * Edit each sudoers file.
 * Returns TRUE on success, else FALSE.
 */
static int
edit_sudoers(struct sudoersfile *sp, char *editor, char *args, int lineno)
{
    int tfd;				/* sudoers temp file descriptor */
    int modified;			/* was the file modified? */
    int ac;				/* argument count */
    char **av;				/* argument vector for run_command */
    char *cp;				/* scratch char pointer */
    char buf[PATH_MAX*2];		/* buffer used for copying files */
    char linestr[64];			/* string version of lineno */
    struct timeval tv, tv1, tv2;	/* time before and after edit */
    struct timeval orig_mtim;		/* starting mtime of sudoers file */
    off_t orig_size;			/* starting size of sudoers file */
    ssize_t nread;			/* number of bytes read */
    struct stat sb;			/* stat buffer */

#ifdef HAVE_FSTAT
    if (fstat(sp->fd, &sb) == -1)
#else
    if (stat(sp->path, &sb) == -1)
#endif
	error(1, "can't stat %s", sp->path);
    orig_size = sb.st_size;
    mtim_get(&sb, &orig_mtim);

    /* Create the temp file if needed and set timestamp. */
    if (sp->tpath == NULL) {
	easprintf(&sp->tpath, "%s.tmp", sp->path);
	tfd = open(sp->tpath, O_WRONLY | O_CREAT | O_TRUNC, 0600);
	if (tfd < 0)
	    error(1, "%s", sp->tpath);

	/* Copy sp->path -> sp->tpath and reset the mtime. */
	if (orig_size != 0) {
	    (void) lseek(sp->fd, (off_t)0, SEEK_SET);
	    while ((nread = read(sp->fd, buf, sizeof(buf))) > 0)
		if (write(tfd, buf, nread) != nread)
		    error(1, "write error");

	    /* Add missing newline at EOF if needed. */
	    if (nread > 0 && buf[nread - 1] != '\n') {
		buf[0] = '\n';
		if (write(tfd, buf, 1) != 1)
		    error(1, "write error");
	    }
	}
	(void) close(tfd);
    }
    (void) touch(-1, sp->tpath, &orig_mtim);

    /* Find the length of the argument vector */
    ac = 3 + (lineno > 0);
    if (args) {
        int wasblank;

        ac++;
        for (wasblank = FALSE, cp = args; *cp; cp++) {
            if (isblank((unsigned char) *cp))
                wasblank = TRUE;
            else if (wasblank) {
                wasblank = FALSE;
                ac++;
            }
        }
    }

    /* Build up argument vector for the command */
    av = emalloc2(ac, sizeof(char *));
    if ((av[0] = strrchr(editor, '/')) != NULL)
	av[0]++;
    else
	av[0] = editor;
    ac = 1;
    if (lineno > 0) {
	(void) snprintf(linestr, sizeof(linestr), "+%d", lineno);
	av[ac++] = linestr;
    }
    if (args) {
	for ((cp = strtok(args, " \t")); cp; (cp = strtok(NULL, " \t")))
	    av[ac++] = cp;
    }
    av[ac++] = sp->tpath;
    av[ac++] = NULL;

    /*
     * Do the edit:
     *  We cannot check the editor's exit value against 0 since
     *  XPG4 specifies that vi's exit value is a function of the
     *  number of errors during editing (?!?!).
     */
    gettimeofday(&tv1, NULL);
    if (run_command(editor, av) != -1) {
	gettimeofday(&tv2, NULL);
	/*
	 * Sanity checks.
	 */
	if (stat(sp->tpath, &sb) < 0) {
	    warningx("cannot stat temporary file (%s), %s unchanged",
		sp->tpath, sp->path);
	    return FALSE;
	}
	if (sb.st_size == 0 && orig_size != 0) {
	    warningx("zero length temporary file (%s), %s unchanged",
		sp->tpath, sp->path);
	    sp->modified = TRUE;
	    return FALSE;
	}
    } else {
	warningx("editor (%s) failed, %s unchanged", editor, sp->path);
	return FALSE;
    }

    /* Set modified bit if use changed the file. */
    modified = TRUE;
    mtim_get(&sb, &tv);
    if (orig_size == sb.st_size && timevalcmp(&orig_mtim, &tv, ==)) {
	/*
	 * If mtime and size match but the user spent no measurable
	 * time in the editor we can't tell if the file was changed.
	 */
	timevalsub(&tv1, &tv2);
	if (timevalisset(&tv2))
	    modified = FALSE;
    }

    /*
     * If modified in this edit session, mark as modified.
     */
    if (modified)
	sp->modified = modified;
    else
	warningx("%s unchanged", sp->tpath);

    return TRUE;
}

/*
 * Parse sudoers after editing and re-edit any ones that caused a parse error.
 * Returns TRUE on success, else FALSE.
 */
static int
reparse_sudoers(char *editor, char *args, int strict, int quiet)
{
    struct sudoersfile *sp, *last;
    FILE *fp;
    int ch;

    /*
     * Parse the edited sudoers files and do sanity checking
     */
    do {
	sp = tq_first(&sudoerslist);
	last = tq_last(&sudoerslist);
	fp = fopen(sp->tpath, "r+");
	if (fp == NULL)
	    errorx(1, "can't re-open temporary file (%s), %s unchanged.",
		sp->tpath, sp->path);

	/* Clean slate for each parse */
	init_defaults();
	init_parser(sp->path, quiet);

	/* Parse the sudoers temp file */
	yyrestart(fp);
	if (yyparse() && !parse_error) {
	    warningx("unabled to parse temporary file (%s), unknown error",
		sp->tpath);
	    parse_error = TRUE;
	    errorfile = sp->path;
	}
	fclose(yyin);
	if (!parse_error) {
	    if (!update_defaults(SETDEF_GENERIC|SETDEF_HOST|SETDEF_USER) ||
		check_aliases(strict, quiet) != 0) {
		parse_error = TRUE;
		errorfile = sp->path;
	    }
	}

	/*
	 * Got an error, prompt the user for what to do now
	 */
	if (parse_error) {
	    switch (whatnow()) {
		case 'Q' :	parse_error = FALSE;	/* ignore parse error */
				break;
		case 'x' :	cleanup(0);
				exit(0);
				break;
	    }
	}
	if (parse_error) {
	    /* Edit file with the parse error */
	    tq_foreach_fwd(&sudoerslist, sp) {
		if (errorfile == NULL || strcmp(sp->path, errorfile) == 0) {
		    edit_sudoers(sp, editor, args, errorlineno);
		    break;
		}
	    }
	    if (sp == NULL)
		errorx(1, "internal error, can't find %s in list!", sudoers);
	}

	/* If any new #include directives were added, edit them too. */
	for (sp = last->next; sp != NULL; sp = sp->next) {
	    printf("press return to edit %s: ", sp->path);
	    while ((ch = getchar()) != EOF && ch != '\n')
		    continue;
	    edit_sudoers(sp, editor, args, errorlineno);
	}
    } while (parse_error);

    return TRUE;
}

/*
 * Set the owner and mode on a sudoers temp file and
 * move it into place.  Returns TRUE on success, else FALSE.
 */
static int
install_sudoers(struct sudoersfile *sp, int oldperms)
{
    struct stat sb;

    /*
     * Change mode and ownership of temp file so when
     * we move it to sp->path things are kosher.
     */
    if (oldperms) {
	/* Use perms of the existing file.  */
#ifdef HAVE_FSTAT
	if (fstat(sp->fd, &sb) == -1)
#else
	if (stat(sp->path, &sb) == -1)
#endif
	    error(1, "can't stat %s", sp->path);
	if (chown(sp->tpath, sb.st_uid, sb.st_gid) != 0) {
	    warning("unable to set (uid, gid) of %s to (%d, %d)",
		sp->tpath, sb.st_uid, sb.st_gid);
	}
	if (chmod(sp->tpath, sb.st_mode & 0777) != 0) {
	    warning("unable to change mode of %s to 0%o", sp->tpath,
		(sb.st_mode & 0777));
	}
    } else {
	if (chown(sp->tpath, SUDOERS_UID, SUDOERS_GID) != 0) {
	    warning("unable to set (uid, gid) of %s to (%d, %d)",
		sp->tpath, SUDOERS_UID, SUDOERS_GID);
	    return FALSE;
	}
	if (chmod(sp->tpath, SUDOERS_MODE) != 0) {
	    warning("unable to change mode of %s to 0%o", sp->tpath,
		SUDOERS_MODE);
	    return FALSE;
	}
    }

    /*
     * Now that sp->tpath is sane (parses ok) it needs to be
     * rename(2)'d to sp->path.  If the rename(2) fails we try using
     * mv(1) in case sp->tpath and sp->path are on different file systems.
     */
    if (rename(sp->tpath, sp->path) == 0) {
	efree(sp->tpath);
	sp->tpath = NULL;
    } else {
	if (errno == EXDEV) {
	    char *av[4];
	    warningx("%s and %s not on the same file system, using mv to rename",
	      sp->tpath, sp->path);

	    /* Build up argument vector for the command */
	    if ((av[0] = strrchr(_PATH_MV, '/')) != NULL)
		av[0]++;
	    else
		av[0] = _PATH_MV;
	    av[1] = sp->tpath;
	    av[2] = sp->path;
	    av[3] = NULL;

	    /* And run it... */
	    if (run_command(_PATH_MV, av)) {
		warningx("command failed: '%s %s %s', %s unchanged",
		    _PATH_MV, sp->tpath, sp->path, sp->path);
		(void) unlink(sp->tpath);
		efree(sp->tpath);
		sp->tpath = NULL;
		return FALSE;
	    }
	    efree(sp->tpath);
	    sp->tpath = NULL;
	} else {
	    warning("error renaming %s, %s unchanged", sp->tpath, sp->path);
	    (void) unlink(sp->tpath);
	    return FALSE;
	}
    }
    return TRUE;
}

/* STUB */
void
set_fqdn(void)
{
    return;
}

/* STUB */
void
init_envtables(void)
{
    return;
}

/* STUB */
int
user_is_exempt(void)
{
    return FALSE;
}

/* STUB */
void
sudo_setspent(void)
{
    return;
}

/* STUB */
void
sudo_endspent(void)
{
    return;
}

/* STUB */
int
group_plugin_query(const char *user, const char *group, const struct passwd *pw)
{
    return FALSE;
}

/*
 * 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(void)
{
    int choice, c;

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

	switch (choice) {
	    case EOF:
		choice = 'x';
		/* FALLTHROUGH */
	    case 'e':
	    case 'x':
	    case 'Q':
		return choice;
	    default:
		(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");
	}
    }
}

/*
 * Install signal handlers for visudo.
 */
static void
setup_signals(void)
{
	sigaction_t sa;

	/*
	 * Setup signal handlers to cleanup nicely.
	 */
	zero_bytes(&sa, sizeof(sa));
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	sa.sa_handler = quit;
	(void) sigaction(SIGTERM, &sa, NULL);
	(void) sigaction(SIGHUP, &sa, NULL);
	(void) sigaction(SIGINT, &sa, NULL);
	(void) sigaction(SIGQUIT, &sa, NULL);
}

static int
run_command(char *path, char **argv)
{
    int status;
    pid_t pid, rv;

    switch (pid = fork()) {
	case -1:
	    error(1, "unable to run %s", path);
	    break;	/* NOTREACHED */
	case 0:
	    sudo_endpwent();
	    sudo_endgrent();
	    closefrom(STDERR_FILENO + 1);
	    execv(path, argv);
	    warning("unable to run %s", path);
	    _exit(127);
	    break;	/* NOTREACHED */
    }

    do {
	rv = waitpid(pid, &status, 0);
    } while (rv == -1 && errno == EINTR);

    if (rv == -1 || !WIFEXITED(status))
	return -1;
    return WEXITSTATUS(status);
}

static int
check_syntax(char *sudoers_path, int quiet, int strict)
{
    struct stat sb;
    int error;

    if (strcmp(sudoers_path, "-") == 0) {
	yyin = stdin;
	sudoers_path = "stdin";
    } else if ((yyin = fopen(sudoers_path, "r")) == NULL) {
	if (!quiet)
	    warning("unable to open %s", sudoers_path);
	exit(1);
    }
    init_parser(sudoers_path, quiet);
    if (yyparse() && !parse_error) {
	if (!quiet)
	    warningx("failed to parse %s file, unknown error", sudoers_path);
	parse_error = TRUE;
	errorfile = sudoers_path;
    }
    if (!parse_error && check_aliases(strict, quiet) != 0) {
	parse_error = TRUE;
	errorfile = sudoers_path;
    }
    error = parse_error;
    if (!quiet) {
	if (parse_error) {
	    if (errorlineno != -1)
		(void) printf("parse error in %s near line %d\n", errorfile,
		    errorlineno);
	    else
		(void) printf("parse error in %s\n", errorfile);
	} else {
	    (void) printf("%s: parsed OK\n", sudoers_path);
	}
    }
    /* Check mode and owner in strict mode. */
#ifdef HAVE_FSTAT
    if (strict && yyin != stdin && fstat(fileno(yyin), &sb) == 0)
#else
    if (strict && yyin != stdin && stat(sudoers_path, &sb) == 0)
#endif
    {
	if (sb.st_uid != SUDOERS_UID || sb.st_gid != SUDOERS_GID) {
	    error = TRUE;
	    if (!quiet) {
		fprintf(stderr, "%s: wrong owner (uid, gid) should be (%d, %d)\n",
		    sudoers_path, SUDOERS_UID, SUDOERS_GID);
		}
	}
	if ((sb.st_mode & 07777) != SUDOERS_MODE) {
	    error = TRUE;
	    if (!quiet) {
		fprintf(stderr, "%s: bad permissions, should be mode 0%o\n",
		    sudoers_path, SUDOERS_MODE);
	    }
	}
    }

    return error;
}

/*
 * Used to open (and lock) the initial sudoers file and to also open
 * any subsequent files #included via a callback from the parser.
 */
FILE *
open_sudoers(const char *path, int doedit, int *keepopen)
{
    struct sudoersfile *entry;
    FILE *fp;

    /* Check for existing entry */
    tq_foreach_fwd(&sudoerslist, entry) {
	if (strcmp(path, entry->path) == 0)
	    break;
    }
    if (entry == NULL) {
	entry = emalloc(sizeof(*entry));
	entry->path = estrdup(path);
	entry->modified = 0;
	entry->prev = entry;
	entry->next = NULL;
	entry->fd = open(entry->path, O_RDWR | O_CREAT, SUDOERS_MODE);
	entry->tpath = NULL;
	entry->doedit = doedit;
	if (entry->fd == -1) {
	    warning("%s", entry->path);
	    efree(entry);
	    return NULL;
	}
	if (!lock_file(entry->fd, SUDO_TLOCK))
	    errorx(1, "%s busy, try again later", entry->path);
	if ((fp = fdopen(entry->fd, "r")) == NULL)
	    error(1, "%s", entry->path);
	tq_append(&sudoerslist, entry);
    } else {
	/* Already exists, open .tmp version if there is one. */
	if (entry->tpath != NULL) {
	    if ((fp = fopen(entry->tpath, "r")) == NULL)
		error(1, "%s", entry->tpath);
	} else {
	    if ((fp = fdopen(entry->fd, "r")) == NULL)
		error(1, "%s", entry->path);
	    rewind(fp);
	}
    }
    if (keepopen != NULL)
	*keepopen = TRUE;
    return fp;
}

static char *
get_editor(char **args)
{
    char *Editor, *EditorArgs, *EditorPath, *UserEditor, *UserEditorArgs;

    /*
     * Check VISUAL and EDITOR environment variables to see which editor
     * the user wants to use (we may not end up using it though).
     * If the path is not fully-qualified, make it so and check that
     * the specified executable actually exists.
     */
    UserEditorArgs = NULL;
    if ((UserEditor = getenv("VISUAL")) == NULL || *UserEditor == '\0')
	UserEditor = getenv("EDITOR");
    if (UserEditor && *UserEditor == '\0')
	UserEditor = NULL;
    else if (UserEditor) {
	UserEditorArgs = get_args(UserEditor);
	if (find_path(UserEditor, &Editor, NULL, getenv("PATH"), 0) == FOUND) {
	    UserEditor = Editor;
	} else {
	    if (def_env_editor) {
		/* If we are honoring $EDITOR this is a fatal error. */
		errorx(1, "specified editor (%s) doesn't exist!", UserEditor);
	    } else {
		/* Otherwise, just ignore $EDITOR. */
		UserEditor = NULL;
	    }
	}
    }

    /*
     * See if we can use the user's choice of editors either because
     * we allow any $EDITOR or because $EDITOR is in the allowable list.
     */
    Editor = EditorArgs = EditorPath = NULL;
    if (def_env_editor && UserEditor) {
	Editor = UserEditor;
	EditorArgs = UserEditorArgs;
    } else if (UserEditor) {
	struct stat editor_sb;
	struct stat user_editor_sb;
	char *base, *userbase;

	if (stat(UserEditor, &user_editor_sb) != 0) {
	    /* Should never happen since we already checked above. */
	    error(1, "unable to stat editor (%s)", UserEditor);
	}
	EditorPath = estrdup(def_editor);
	Editor = strtok(EditorPath, ":");
	do {
	    EditorArgs = get_args(Editor);
	    /*
	     * Both Editor and UserEditor should be fully qualified but
	     * check anyway...
	     */
	    if ((base = strrchr(Editor, '/')) == NULL)
		continue;
	    if ((userbase = strrchr(UserEditor, '/')) == NULL) {
		Editor = NULL;
		break;
	    }
	    base++, userbase++;

	    /*
	     * We compare the basenames first and then use stat to match
	     * for sure.
	     */
	    if (strcmp(base, userbase) == 0) {
		if (stat(Editor, &editor_sb) == 0 && S_ISREG(editor_sb.st_mode)
		    && (editor_sb.st_mode & 0000111) &&
		    editor_sb.st_dev == user_editor_sb.st_dev &&
		    editor_sb.st_ino == user_editor_sb.st_ino)
		    break;
	    }
	} while ((Editor = strtok(NULL, ":")));
    }

    /*
     * Can't use $EDITOR, try each element of def_editor until we
     * find one that exists, is regular, and is executable.
     */
    if (Editor == NULL || *Editor == '\0') {
	efree(EditorPath);
	EditorPath = estrdup(def_editor);
	Editor = strtok(EditorPath, ":");
	do {
	    EditorArgs = get_args(Editor);
	    if (sudo_goodpath(Editor, NULL))
		break;
	} while ((Editor = strtok(NULL, ":")));

	/* Bleah, none of the editors existed! */
	if (Editor == NULL || *Editor == '\0')
	    errorx(1, "no editor found (editor path = %s)", def_editor);
    }
    *args = EditorArgs;
    return Editor;
}

/*
 * Split out any command line arguments and return them.
 */
static char *
get_args(char *cmnd)
{
    char *args;

    args = cmnd;
    while (*args && !isblank((unsigned char) *args))
	args++;
    if (*args) {
	*args++ = '\0';
	while (*args && isblank((unsigned char) *args))
	    args++;
    }
    return *args ? args : NULL;
}

/*
 * Look up the hostname and set user_host and user_shost.
 */
static void
get_hostname(void)
{
    char *p, thost[MAXHOSTNAMELEN + 1];

    if (gethostname(thost, sizeof(thost)) != 0) {
	user_host = user_shost = "localhost";
	return;
    }
    thost[sizeof(thost) - 1] = '\0';
    user_host = estrdup(thost);

    if ((p = strchr(user_host, '.'))) {
	*p = '\0';
	user_shost = estrdup(user_host);
	*p = '.';
    } else {
	user_shost = user_host;
    }
}

static int
alias_remove_recursive(char *name, int type, int strict, int quiet)
{
    struct member *m;
    struct alias *a;
    int error = 0;

    if ((a = alias_find(name, type)) != NULL) {
	tq_foreach_fwd(&a->members, m) {
	    if (m->type == ALIAS) {
		if (strcmp(name, m->name) == 0) {
		    print_selfref(m->name, type, strict, quiet);
		    error = 1;
		} else {
		    if (!alias_remove_recursive(m->name, type, strict, quiet))
			error = 1;
		}
	    }
	}
    }
    alias_seqno++;
    a = alias_remove(name, type);
    if (a)
	rbinsert(alias_freelist, a);
    return error;
}

/*
 * Iterate through the sudoers datastructures looking for undefined
 * aliases or unused aliases.
 */
static int
check_aliases(int strict, int quiet)
{
    struct cmndspec *cs;
    struct member *m, *binding;
    struct privilege *priv;
    struct userspec *us;
    struct defaults *d;
    int atype, error = 0;

    alias_freelist = rbcreate(alias_compare);

    /* Forward check. */
    tq_foreach_fwd(&userspecs, us) {
	tq_foreach_fwd(&us->users, m) {
	    if (m->type == ALIAS) {
		alias_seqno++;
		if (alias_find(m->name, USERALIAS) == NULL) {
		    print_undefined(m->name, USERALIAS, strict, quiet);
		    error++;
		}
	    }
	}
	tq_foreach_fwd(&us->privileges, priv) {
	    tq_foreach_fwd(&priv->hostlist, m) {
		if (m->type == ALIAS) {
		    alias_seqno++;
		    if (alias_find(m->name, HOSTALIAS) == NULL) {
			print_undefined(m->name, HOSTALIAS, strict, quiet);
			error++;
		    }
		}
	    }
	    tq_foreach_fwd(&priv->cmndlist, cs) {
		tq_foreach_fwd(&cs->runasuserlist, m) {
		    if (m->type == ALIAS) {
			alias_seqno++;
			if (alias_find(m->name, RUNASALIAS) == NULL) {
			    print_undefined(m->name, RUNASALIAS, strict, quiet);
			    error++;
			}
		    }
		}
		if ((m = cs->cmnd)->type == ALIAS) {
		    alias_seqno++;
		    if (alias_find(m->name, CMNDALIAS) == NULL) {
			print_undefined(m->name, CMNDALIAS, strict, quiet);
			error++;
		    }
		}
	    }
	}
    }

    /* Reverse check (destructive) */
    tq_foreach_fwd(&userspecs, us) {
	tq_foreach_fwd(&us->users, m) {
	    if (m->type == ALIAS) {
		if (!alias_remove_recursive(m->name, USERALIAS, strict, quiet))
		    error++;
	    }
	}
	tq_foreach_fwd(&us->privileges, priv) {
	    tq_foreach_fwd(&priv->hostlist, m) {
		if (m->type == ALIAS)
		    if (!alias_remove_recursive(m->name, HOSTALIAS, strict,
			quiet))
			error++;
	    }
	    tq_foreach_fwd(&priv->cmndlist, cs) {
		tq_foreach_fwd(&cs->runasuserlist, m) {
		    if (m->type == ALIAS)
			if (!alias_remove_recursive(m->name, RUNASALIAS,
			    strict, quiet))
			    error++;
		}
		if ((m = cs->cmnd)->type == ALIAS)
		    if (!alias_remove_recursive(m->name, CMNDALIAS, strict,
			quiet))
			error++;
	    }
	}
    }
    tq_foreach_fwd(&defaults, d) {
	switch (d->type) {
	    case DEFAULTS_HOST:
		atype = HOSTALIAS;
		break;
	    case DEFAULTS_USER:
		atype = USERALIAS;
		break;
	    case DEFAULTS_RUNAS:
		atype = RUNASALIAS;
		break;
	    case DEFAULTS_CMND:
		atype = CMNDALIAS;
		break;
	    default:
		continue; /* not an alias */
	}
	tq_foreach_fwd(&d->binding, binding) {
	    for (m = binding; m != NULL; m = m->next) {
		if (m->type == ALIAS)
		    if (!alias_remove_recursive(m->name, atype, strict, quiet))
			error++;
	    }
	}
    }
    rbdestroy(alias_freelist, alias_free);

    /* If all aliases were referenced we will have an empty tree. */
    if (!no_aliases() && !quiet)
	alias_apply(print_unused, strict ? "Error" : "Warning");

    return strict ? error : 0;
}

static void
print_undefined(char *name, int type, int strict, int quiet)
{
    if (!quiet) {
	warningx("%s: %s_Alias `%s' referenced but not defined",
	    strict ? "Error" : "Warning",
	    type == HOSTALIAS ? "Host" : type == CMNDALIAS ? "Cmnd" :
	    type == USERALIAS ? "User" : type == RUNASALIAS ? "Runas" :
	    "Unknown", name);
    }
}

static void
print_selfref(name, type, strict, quiet)
    char *name;
    int type;
    int strict;
    int quiet;
{
    if (!quiet) {
	warningx("%s: %s_Alias `%s' references self",
	    strict ? "Error" : "Warning",
	    type == HOSTALIAS ? "Host" : type == CMNDALIAS ? "Cmnd" :
	    type == USERALIAS ? "User" : type == RUNASALIAS ? "Runas" :
	    "Unknown", name);
    }
}

static int
print_unused(void *v1, void *v2)
{
    struct alias *a = (struct alias *)v1;
    char *prefix = (char *)v2;

    warningx("%s: unused %s_Alias %s", prefix,
	a->type == HOSTALIAS ? "Host" : a->type == CMNDALIAS ? "Cmnd" :
	a->type == USERALIAS ? "User" : a->type == RUNASALIAS ? "Runas" :
	"Unknown", a->name);
    return 0;
}

/*
 * Unlink any sudoers temp files that remain.
 */
void
cleanup(int gotsignal)
{
    struct sudoersfile *sp;

    tq_foreach_fwd(&sudoerslist, sp) {
	if (sp->tpath != NULL)
	    (void) unlink(sp->tpath);
    }
    if (!gotsignal) {
	sudo_endpwent();
	sudo_endgrent();
    }
}

/*
 * Unlink sudoers temp files (if any) and exit.
 */
static void
quit(int signo)
{
    const char *signame, *myname;

    cleanup(signo);
#define	emsg	 " exiting due to signal: "
    myname = getprogname();
    signame = strsignal(signo);
    if (write(STDERR_FILENO, myname, strlen(myname)) == -1 ||
	write(STDERR_FILENO, emsg, sizeof(emsg) - 1) == -1 ||
	write(STDERR_FILENO, signame, strlen(signame)) == -1 ||
	write(STDERR_FILENO, "\n", 1) == -1)
	/* shut up glibc */;
    _exit(signo);
}

static void
usage(int fatal)
{
    (void) fprintf(fatal ? stderr : stdout,
	"usage: %s [-chqsV] [-f sudoers]\n", getprogname());
    if (fatal)
	exit(1);
}

static void
help(void)
{
    (void) printf("%s - safely edit the sudoers file\n\n", getprogname());
    usage(0);
    (void) puts("\nOptions:");
    (void) puts("  -c          check-only mode");
    (void) puts("  -f sudoers  specify sudoers file location");
    (void) puts("  -h          display help message and exit");
    (void) puts("  -q          less verbose (quiet) syntax error messages");
    (void) puts("  -s          strict syntax checking");
    (void) puts("  -V          display version information and exit");
    exit(0);
}

static int
visudo_printf(int msg_type, const char *fmt, ...)
{
    va_list ap;
    FILE *fp;
            
    switch (msg_type) {
    case SUDO_CONV_INFO_MSG:
	fp = stdout;
	break;
    case SUDO_CONV_ERROR_MSG:
	fp = stderr;
	break;
    default:
	errno = EINVAL;
	return -1;
    }
   
    va_start(ap, fmt);
    vfprintf(fp, fmt, ap);
    va_end(ap);
   
    return 0;
}