NetBSD/bin/systrace/systrace.c

/*	$NetBSD: systrace.c,v 1.21 2003/06/03 04:33:44 provos Exp $	*/
/*	$OpenBSD: systrace.c,v 1.32 2002/08/05 23:27:53 provos Exp $	*/
/*
 * Copyright 2002 Niels Provos <provos@citi.umich.edu>
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Niels Provos.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/wait.h>
#include <sys/tree.h>
#include <sys/socket.h>
#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <signal.h>
#include <syslog.h>
#include <string.h>
#include <err.h>
#include <errno.h>
#include <grp.h>
#include <pwd.h>

#include "intercept.h"
#include "systrace.h"
#include "util.h"

pid_t trpid;
int trfd;
int connected = 0;		/* Connected to GUI */
int inherit = 0;		/* Inherit policy to childs */
int automatic = 0;		/* Do not run interactively */
int allow = 0;			/* Allow all and generate */
int userpolicy = 1;		/* Permit user defined policies */
int noalias = 0;		/* Do not do system call aliasing */
int iamroot = 0;		/* Set if we are running as root */
char cwd[MAXPATHLEN];		/* Current working directory */
char home[MAXPATHLEN];		/* Home directory of user */
char username[LOGIN_NAME_MAX];	/* Username: predicate match and expansion */

static void child_handler(int);
static void usage(void);
static int requestor_start(char *);

void
systrace_parameters(void)
{
	struct passwd *pw;
	uid_t uid = getuid();

	iamroot = getuid() == 0;

	/* Find out current username. */
	if ((pw = getpwuid(uid)) == NULL)
		snprintf(username, sizeof(username), "uid %u", uid);
	else
		snprintf(username, sizeof(username), "%s", pw->pw_name);

	strlcpy(home, pw->pw_dir, sizeof(home));

	/* Determine current working directory for filtering */
	if (getcwd(cwd, sizeof(cwd)) == NULL)
		err(1, "getcwd");
}

/*
 * Generate human readable output and setup replacements if available.
 */

void
make_output(char *output, size_t outlen, const char *binname,
    pid_t pid, pid_t ppid,
    int policynr, const char *policy, int nfilters, const char *emulation,
    const char *name, int code, struct intercept_tlq *tls,
    struct intercept_replace *repl)
{
	struct intercept_translate *tl;
	char *p, *line;
	int size;

	snprintf(output, outlen,
	    "%s, pid: %d(%d)[%d], policy: %s, filters: %d, syscall: %s-%s(%d)",
	    binname, pid, policynr, ppid, policy, nfilters,
	    emulation, name, code);

	p = output + strlen(output);
	size = outlen - strlen(output);

	if (repl != NULL)
		intercept_replace_init(repl);

	if (tls == NULL)
		return;

	TAILQ_FOREACH(tl, tls, next) {
		if (!tl->trans_valid)
			break;
		line = intercept_translate_print(tl);
		if (line == NULL)
			continue;

		snprintf(p, size, ", %s: %s", tl->name, strescape(line));
		p = output + strlen(output);
		size = outlen - strlen(output);

		if (repl != NULL && tl->trans_size)
			intercept_replace_add(repl, tl->off,
			    tl->trans_data, tl->trans_size);
	}
}

short
trans_cb(int fd, pid_t pid, int policynr,
    const char *name, int code, const char *emulation,
    void *args, int argsize, struct intercept_tlq *tls, void *cbarg)
{
	short action, future;
	struct policy *policy;
	struct intercept_pid *ipid;
	struct intercept_replace repl;
	struct intercept_tlq alitls;
	struct intercept_translate alitl[SYSTRACE_MAXALIAS];
	struct systrace_alias *alias = NULL;
	struct filterq *pflq = NULL;
	const char *binname = NULL;
	char output[_POSIX2_LINE_MAX];
	pid_t ppid;
	int dolog = 0;

	action = ICPOLICY_PERMIT;

	if (policynr == -1)
		goto out;

	if ((policy = systrace_findpolnr(policynr)) == NULL)
		errx(1, "%s:%d: find %d", __func__, __LINE__,
		    policynr);

	ipid = intercept_getpid(pid);
	ipid->uflags = 0;
	binname = ipid->name != NULL ? ipid->name : policy->name;
	ppid = ipid->ppid;

	/* Required to set up replacements */
	make_output(output, sizeof(output), binname, pid, ppid, policynr,
	    policy->name, policy->nfilters, emulation, name, code,
	    tls, &repl);

	if ((pflq = systrace_policyflq(policy, emulation, name)) == NULL)
		errx(1, "%s:%d: no filter queue", __func__, __LINE__);

	action = filter_evaluate(tls, pflq, ipid);
	if (action != ICPOLICY_ASK)
		goto replace;

	/* Do aliasing here */
	if (!noalias)
		alias = systrace_find_alias(emulation, name);
	if (alias != NULL) {
		int i;

		/* Set up variables for further filter actions */
		tls = &alitls;
		emulation = alias->aemul;
		name = alias->aname;

		/* Create an aliased list for filter_evaluate */
		TAILQ_INIT(tls);
		for (i = 0; i < alias->nargs; i++) {
			memcpy(&alitl[i], alias->arguments[i], 
			    sizeof(struct intercept_translate));
			TAILQ_INSERT_TAIL(tls, &alitl[i], next);
		}

		if ((pflq = systrace_policyflq(policy,
			 alias->aemul, alias->aname)) == NULL)
			errx(1, "%s:%d: no filter queue", __func__, __LINE__);

		action = filter_evaluate(tls, pflq, ipid);
		if (action != ICPOLICY_ASK)
			goto replace;

		make_output(output, sizeof(output), binname, pid, ppid,
		    policynr, policy->name, policy->nfilters,
		    alias->aemul, alias->aname, code, tls, NULL);
	}

	if (policy->flags & POLICY_UNSUPERVISED) {
		action = ICPOLICY_NEVER;
		dolog = 1;
		goto out;
	}

	action = filter_ask(fd, tls, pflq, policynr, emulation, name,
	    output, &future, ipid);
	if (future != ICPOLICY_ASK)
		filter_modifypolicy(fd, policynr, emulation, name, future);

	if (policy->flags & POLICY_DETACHED) {
		if (intercept_detach(fd, pid) == -1)
			err(1, "intercept_detach");
		return (action);
	} else if (action == ICPOLICY_KILL) {
		kill(pid, SIGKILL);
		return (ICPOLICY_NEVER);
	}
 replace:
	if (ipid->uflags & SYSCALL_LOG)
		dolog = 1;

	if (action < ICPOLICY_NEVER) {
		/* If we can not rewrite the arguments, system call fails */
		if (intercept_replace(fd, pid, &repl) == -1)
			action = ICPOLICY_NEVER;
	}
 out:
	if (dolog)
		syslog(LOG_WARNING, "%s user: %s, prog: %s",
		    action < ICPOLICY_NEVER ? "permit" : "deny",
		    ipid->username, output);

	return (action);
}

short
gen_cb(int fd, pid_t pid, int policynr, const char *name, int code,
    const char *emulation, void *args, int argsize, void *cbarg)
{
	char output[_POSIX2_LINE_MAX];
	struct policy *policy;
	struct intercept_pid *ipid;
	struct filterq *pflq = NULL;
	short action = ICPOLICY_PERMIT;
	short future;
	int len, off, dolog = 0;

	if (policynr == -1)
		goto out;

	if ((policy = systrace_findpolnr(policynr)) == NULL)
		errx(1, "%s:%d: find %d", __func__, __LINE__,
		    policynr);

	ipid = intercept_getpid(pid);
	ipid->uflags = 0;

	make_output(output, sizeof(output),
	    ipid->name != NULL ? ipid->name : policy->name,
	    pid, ipid->ppid, policynr,
	    policy->name, policy->nfilters, emulation, name, code,
	    NULL, NULL);

	off = strlen(output);
	len = sizeof(output) - off;
	if (len > 0)
		snprintf(output + off, len, ", args: %d", argsize);

	if ((pflq = systrace_policyflq(policy, emulation, name)) == NULL)
		errx(1, "%s:%d: no filter queue", __func__, __LINE__);

	action = filter_evaluate(NULL, pflq, ipid);

	if (ipid->uflags & SYSCALL_LOG)
		dolog = 1;
	
	if (action != ICPOLICY_ASK)
		goto out;

	if (policy->flags & POLICY_UNSUPERVISED) {
		action = ICPOLICY_NEVER;
		dolog = 1;
		goto out;
	}

	action = filter_ask(fd, NULL, pflq, policynr, emulation, name,
	    output, &future, ipid);
	if (future != ICPOLICY_ASK)
		systrace_modifypolicy(fd, policynr, name, future);

	if (policy->flags & POLICY_DETACHED) {
		if (intercept_detach(fd, pid) == -1)
			err(1, "intercept_detach");
	} else if (action == ICPOLICY_KILL) {
		kill(pid, SIGKILL);
		return (ICPOLICY_NEVER);
	}
 out:
	if (dolog)
		syslog(LOG_WARNING, "%s user: %s, prog: %s",
		    action < ICPOLICY_NEVER ? "permit" : "deny",
		    ipid->username, output);

	return (action);
}

void
execres_cb(int fd, pid_t pid, int policynr, const char *emulation,
    const char *name, void *arg)
{
	struct policy *policy;

	if (policynr != -1) {
		struct intercept_pid *ipid;

		ipid = intercept_getpid(pid);
		if (ipid->uflags & PROCESS_DETACH) {
			if (intercept_detach(fd, pid) == -1)
				err(1, "%s: intercept_detach", __func__);
			return;
		}
		if (inherit)
			return;

		if (ipid->uflags & PROCESS_INHERIT_POLICY)
			return;
	}
	if ((policy = systrace_newpolicy(emulation, name)) == NULL)
		goto error;

	/* See if this policies runs without interactive feedback */
	if (automatic)
		policy->flags |= POLICY_UNSUPERVISED;

	policynr = policy->policynr;

	/* Try to find existing policy in file system */
	if (policynr == -1 && TAILQ_FIRST(&policy->prefilters) == NULL)
		systrace_addpolicy(name);

	if (policy->flags & POLICY_DETACHED) {
		if (intercept_detach(fd, pid) == -1)
			err(1, "intercept_detach");
		return;
	}

	if (policynr == -1) {
		policynr = systrace_newpolicynr(fd, policy);
		if (policynr == -1)
			goto error;
	}

	if (intercept_assignpolicy(fd, pid, policynr) == -1)
		goto error;

	if (TAILQ_FIRST(&policy->prefilters) != NULL)
		filter_prepolicy(fd, policy);

	return;

 error:
	kill(pid, SIGKILL);
	fprintf(stderr, "Terminating %d: %s\n", pid, name);
}

void
policyfree_cb(int policynr, void *arg)
{
	struct policy *policy;

	if ((policy = systrace_findpolnr(policynr)) == NULL)
		errx(1, "%s:%d: find %d", __func__, __LINE__,
		    policynr);

	systrace_freepolicy(policy);
}

static void
child_handler(int sig)
{
	int s = errno, status;

	if (signal(SIGCHLD, child_handler) == SIG_ERR) {
		close(trfd);
	}

	while (wait4(-1, &status, WNOHANG, NULL) > 0)
		;

	errno = s;
}

static void
usage(void)
{
	fprintf(stderr,
	    "Usage: systrace [-AaitUu] [-c uid:gid] [-d policydir] [-f file]\n"
	    "\t [-g gui] [-p pid] command ...\n");
	exit(1);
}

static int
requestor_start(char *path)
{
	char *argv[2];
	int pair[2];
	pid_t pid;

	argv[0] = path;
	argv[1] = NULL;

	if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1)
		err(1, "socketpair");

	pid = fork();
	if (pid == -1)
		err(1, "fork");
	if (pid == 0) {
		close(pair[0]);
		if (dup2(pair[1], fileno(stdin)) == -1)
			err(1, "dup2");
		if (dup2(pair[1], fileno(stdout)) == -1)
			err(1, "dup2");
		setlinebuf(stdout);

		close(pair[1]);

		execvp(path, argv);

		err(1, "execvp: %s", path);
	}

	close(pair[1]);
	if (dup2(pair[0], fileno(stdin)) == -1)
		err(1, "dup2");

	if (dup2(pair[0], fileno(stdout)) == -1)
		err(1, "dup2");

	close(pair[0]);

	setlinebuf(stdout);

	connected = 1;

	return (0);
}

static int
get_uid_gid(const char *argument, uid_t *uid, gid_t *gid)
{
	struct group *gp;
	struct passwd *pw;
	unsigned long ulval;
	char uid_gid_str[128];
	char *endp, *g, *u;

	strlcpy(uid_gid_str, argument, sizeof(uid_gid_str));
	g = uid_gid_str;
	u = strsep(&g, ":");

	if ((pw = getpwnam(u)) != NULL) {
		memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
		*uid = pw->pw_uid;
		*gid = pw->pw_gid;
		/* Ok if group not specified. */
		if (g == NULL)
			return (0);
	} else {
		errno = 0;
		ulval = strtoul(u, &endp, 10);
		if (u[0] == '\0' || *endp != '\0')
			errx(1, "no such user '%s'", u);
		if (errno == ERANGE && ulval == ULONG_MAX)
			errx(1, "invalid uid %s", u);
		*uid = (uid_t)ulval;
	}

	if (g == NULL)
		return (-1);

	if ((gp = getgrnam(g)) != NULL)
		*gid = gp->gr_gid;
	else {
		errno = 0;
		ulval = strtoul(g, &endp, 10);
		if (g[0] == '\0' || *endp != '\0')
			errx(1, "no such group '%s'", g);
		if (errno == ERANGE && ulval == ULONG_MAX)
			errx(1, "invalid gid %s", g);
		*gid = (gid_t)ulval;
	}

	return (0);
}

int
main(int argc, char **argv)
{
	int i, c;
	char **args;
	char *filename = NULL;
	char *policypath = NULL;
	char *guipath = _PATH_XSYSTRACE;
	struct timeval tv, tv_wait = {60, 0};
	pid_t pidattach = 0;
	int usex11 = 1, count;
	int background;
	int setcredentials = 0;
	uid_t cr_uid;
	gid_t cr_gid;

	while ((c = getopt(argc, argv, "c:aAituUd:g:f:p:")) != -1) {
		switch (c) {
		case 'c':
			setcredentials = 1;
			if (get_uid_gid(optarg, &cr_uid, &cr_gid) == -1)
				usage();
			break;
		case 'a':
			if (allow)
				usage();
			automatic = 1;
			break;
		case 'd':
			policypath = optarg;
			break;
		case 'A':
			if (automatic)
				usage();
			allow = 1;
			break;
		case 'u':
			noalias = 1;
			break;
		case 'i':
			inherit = 1;
			break;
		case 'g':
			guipath = optarg;
			break;
		case 'f':
			filename = optarg;
			break;
		case 'p':
			if (setcredentials)
				usage();
			if ((pidattach = atoi(optarg)) == 0) {
				warnx("bad pid: %s", optarg);
				usage();
			}
			break;
		case 't':
			usex11 = 0;
			break;
		case 'U':
			userpolicy = 0;
			break;
		default:
			usage();
			break;
		}
	}
	argc -= optind;
	argv += optind;

	if (argc == 0 || (pidattach && *argv[0] != '/'))
		usage();

	systrace_parameters();

	if (setcredentials && !iamroot) {
		fprintf(stderr, "Need to be root to change credentials.\n");
		usage();
	}

	/* Local initalization */
	systrace_initalias();
	systrace_initpolicy(filename, policypath);
	systrace_initcb();

	if ((trfd = intercept_open()) == -1)
		exit(1);

	/* See if we can run the systrace process in the background */
	background = usex11 || automatic || allow;

	if (pidattach == 0) {
		/* Run a command and attach to it */
		if ((args = malloc((argc + 1) * sizeof(char *))) == NULL)
			err(1, "malloc");

		for (i = 0; i < argc; i++)
			args[i] = argv[i];
		args[i] = NULL;

		if (setcredentials)
			trpid = intercept_run(background, trfd,
			    cr_uid, cr_gid, args[0], args);
		else
			trpid = intercept_run(background, trfd, 0, 0,
			    args[0], args);
		if (trpid == -1)
			err(1, "fork");

		if (intercept_attach(trfd, trpid) == -1)
			err(1, "attach");

		if (kill(trpid, SIGUSR1) == -1)
			err(1, "kill");
	} else {
		/* Attach to a running command */
		if (intercept_attachpid(trfd, pidattach, argv[0]) == -1)
			err(1, "attachpid");

		if (background) {
			if (daemon(1, 1) == -1)
				err(1, "daemon");
		}
	}

	if (signal(SIGCHLD, child_handler) == SIG_ERR)
		err(1, "signal");

	/* Start the policy gui if necessary */
	if (usex11 && !automatic && !allow)
		requestor_start(guipath);

	/* Loop on requests */
	count = 0;
	while (intercept_read(trfd) != -1) {
		if (!intercept_existpids())
			break;
		if (userpolicy) {
			/* Periodically save modified policies */
			if (count == 0) {
				/* Set new wait time */
				gettimeofday(&tv, NULL);
				timeradd(&tv, &tv_wait, &tv);
			} else if (count > 10) {
				struct timeval now;
				gettimeofday(&now, NULL);

				count = 0;
				if (timercmp(&now, &tv, >)) {
					/* Dump policy and cause new time */
					systrace_dumppolicy();
					continue;
				}
			}
			count++;
		}
	}

	if (userpolicy)
		systrace_dumppolicy();

	close(trfd);

	exit(0);
}