shadow/libmisc/suauth.c

#include <config.h>

#ifdef SU_ACCESS

#include <stdio.h>
#include <pwd.h>
#include <grp.h>
#include <sys/types.h>
#include <errno.h>
#include "prototypes.h"
#include "defines.h"

#ifndef SUAUTHFILE
#define SUAUTHFILE "/etc/suauth"
#endif

#define	NOACTION	0
#define	NOPWORD		1
#define	DENY		-1
#define	OWNPWORD	2

/* Really, I could do with a few const char's here defining all the 
 * strings output to the user or the syslog. -- chris
 */

static int applies(const char *, char *);

int check_su_auth(const char *, const char *);
int isgrp(const char *, const char *);

static int lines = 0;

extern struct passwd pwent;

int
check_su_auth(const char *actual_id, const char *wanted_id)
{
	int	posn, endline;
	const	char    field[] = ":";
	FILE    *authfile_fd;
	char	temp[1024];
	char	*to_users;
	char	*from_users;
	char	*action;

	if (!(authfile_fd = fopen(SUAUTHFILE, "r"))) {
		/*
		 * If the file doesn't exist - default to the standard su
		 * behaviour (no access control).  If open fails for some
		 * other reason - maybe someone is trying to fool us with
		 * file descriptors limit etc., so deny access.  --marekm
		 */
		if (errno == ENOENT)
			return NOACTION;
		SYSLOG((LOG_ERR, "could not open/read config file '%s': %m\n",
			SUAUTHFILE));
		return DENY;
	}

	while (fgets(temp, sizeof(temp), authfile_fd) != NULL) {
		lines++;

		if (temp[endline = strlen(temp) - 1] != '\n') {
			SYSLOG((LOG_ERR,
				"%s, line %d: line too long or missing newline",
				SUAUTHFILE, lines));
			continue;
		}

		while (endline > 0 && (temp[endline-1] == ' ' 
			|| temp[endline-1] == '\t' || temp[endline-1] == '\n'))
			endline--;
		temp[endline] = '\0';

		posn = 0;
		while (temp[posn] == ' ' || temp[posn] == '\t')
			posn++;

		if (temp[posn] == '\n' || temp[posn] == '#' || temp[posn] == '\0') {
			continue;
		}
		if (!(to_users = strtok(temp + posn, field))
			|| !(from_users = strtok((char *)NULL, field))
			|| !(action = strtok((char *)NULL, field))
			|| strtok((char *)NULL, field)) {
			SYSLOG((LOG_ERR, "%s, line %d. Bad number of fields.\n",
				SUAUTHFILE, lines));
			continue;
		}

		if (!applies(wanted_id, to_users))
			continue;
		if (!applies(actual_id, from_users))
			continue;
		if (!strcmp(action, "DENY")) {
			SYSLOG((pwent.pw_uid ? LOG_NOTICE : LOG_WARN,
				"DENIED su from `%s' to `%s' (%s)\n",
				actual_id, wanted_id, SUAUTHFILE));
			fprintf(stderr, _("Access to su to that account DENIED.\n"));
			fclose(authfile_fd);
			return DENY;
		} else if (!strcmp(action, "NOPASS")) {
			SYSLOG((pwent.pw_uid ? LOG_INFO : LOG_NOTICE,
				"NO password asked for su from `%s' to `%s' (%s)\n",
				actual_id, wanted_id, SUAUTHFILE));
			fprintf(stderr, _("Password authentication bypassed.\n"));
			fclose(authfile_fd);
			return NOPWORD;
		} else if (!strcmp(action, "OWNPASS")) {
			SYSLOG((pwent.pw_uid ? LOG_INFO : LOG_NOTICE,
				"su from `%s' to `%s': asking for user's own password (%s)\n",
				actual_id, wanted_id, SUAUTHFILE));
			fprintf(stderr, _("Please enter your OWN password as authentication.\n"));
			fclose(authfile_fd);
			return OWNPWORD;
		} else {
			SYSLOG((LOG_ERR, "%s, line %d: unrecognised action!\n",
				SUAUTHFILE, lines));
		}
	}
	fclose(authfile_fd);
	return NOACTION;
}

static int
applies(const char *single, char *list)
{
	const	char	split[] = ", ";
	char	*tok;

	int state = 0;

	for (tok = strtok(list, split); tok != NULL; tok = strtok(NULL, split)) {

		if (!strcmp(tok, "ALL")) {
			if (state != 0) {
				SYSLOG((LOG_ERR,
					"%s, line %d: ALL in bad place\n",
					SUAUTHFILE, lines));
				return 0;
			}
			state = 1;
		} else if (!strcmp(tok, "EXCEPT")) {
			if (state != 1) {
				SYSLOG((LOG_ERR,
					"%s, line %d: EXCEPT in bas place\n",
					SUAUTHFILE, lines));
				return 0;
			}
			state = 2;
		} else if (!strcmp(tok, "GROUP")) {
			if ((state != 0) && (state != 2)) {
				SYSLOG((LOG_ERR,
					"%s, line %d: GROUP in bad place\n",
					SUAUTHFILE, lines));
				return 0;
			}
			state = (state == 0) ? 3 : 4;
		} else {
			switch (state) {
				case 0: /* No control words yet */
					if (!strcmp(tok, single))
						return 1;
					break;
				case 1: /* An all */
        		                SYSLOG((LOG_ERR, "%s, line %d: expect another token after ALL\n",
						SUAUTHFILE, lines));
					return 0;
				case 2: /* All except */
					if (!strcmp(tok, single))
						return 0;
					break;
				case 3: /* Group */
					if (isgrp(single, tok))
						return 1;
					break;
				case 4: /* All except group */
					if (isgrp(single, tok))
						return 0;
					/* FALL THRU */
			}
		}
	}
	if ((state != 0) && (state != 3))
		return 1;
	return 0;
}

int
isgrp(const char *name, const char *group)
{
	struct	group	*grp;

	grp = getgrnam(group);

	if (!grp || !grp->gr_mem)
		return 0;

	return is_on_list(grp->gr_mem, name);
}
#endif /* SU_ACCESS */