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NetBSD/bin/systrace/intercept.c

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/* $NetBSD: intercept.c,v 1.20 2004/01/24 03:44:46 provos Exp $ */
/* $OpenBSD: intercept.c,v 1.29 2002/08/28 03:30:27 itojun 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/cdefs.h>
__RCSID("$NetBSD: intercept.c,v 1.20 2004/01/24 03:44:46 provos Exp $");
#include <sys/types.h>
#include <sys/param.h>
#include <sys/tree.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <limits.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <poll.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <err.h>
#include <libgen.h>
#include <pwd.h>
#include "intercept.h"
void simplify_path(char *);
struct intercept_syscall {
SPLAY_ENTRY(intercept_syscall) node;
char name[64];
char emulation[16];
short (*cb)(int, pid_t, int, const char *, int, const char *, void *,
int, struct intercept_replace *, struct intercept_tlq *, void *);
void *cb_arg;
struct intercept_tlq tls;
};
static int sccompare(struct intercept_syscall *, struct intercept_syscall *);
static int pidcompare(struct intercept_pid *, struct intercept_pid *);
static struct intercept_syscall *intercept_sccb_find(const char *,
const char *);
static void sigusr1_handler(int);
static SPLAY_HEAD(pidtree, intercept_pid) pids;
static SPLAY_HEAD(sctree, intercept_syscall) scroot;
static volatile int got_sigusr1 = 0;
/* Generic callback functions */
void (*intercept_newimagecb)(int, pid_t, int, const char *, const char *, void *) = NULL;
void *intercept_newimagecbarg = NULL;
short (*intercept_gencb)(int, pid_t, int, const char *, int, const char *, void *, int, void *) = NULL;
void *intercept_gencbarg = NULL;
void (*intercept_pfreecb)(int, void*);
void *intercept_pfreearg = NULL;
int
sccompare(struct intercept_syscall *a, struct intercept_syscall *b)
{
int diff;
diff = strcmp(a->emulation, b->emulation);
if (diff)
return (diff);
return (strcmp(a->name, b->name));
}
int
pidcompare(struct intercept_pid *a, struct intercept_pid *b)
{
int diff = a->pid - b->pid;
if (diff == 0)
return (0);
if (diff > 0)
return (1);
return (-1);
}
SPLAY_PROTOTYPE(sctree, intercept_syscall, node, sccompare);
SPLAY_GENERATE(sctree, intercept_syscall, node, sccompare);
SPLAY_PROTOTYPE(pidtree, intercept_pid, next, pidcompare);
SPLAY_GENERATE(pidtree, intercept_pid, next, pidcompare);
extern struct intercept_system intercept;
int ic_abort;
int
intercept_init(void)
{
SPLAY_INIT(&pids);
SPLAY_INIT(&scroot);
intercept_newimagecb = NULL;
intercept_gencb = NULL;
return (intercept.init());
}
struct intercept_syscall *
intercept_sccb_find(const char *emulation, const char *name)
{
struct intercept_syscall tmp;
strlcpy(tmp.name, name, sizeof(tmp.name));
strlcpy(tmp.emulation, emulation, sizeof(tmp.emulation));
return (SPLAY_FIND(sctree, &scroot, &tmp));
}
struct intercept_translate *
intercept_register_translation(char *emulation, char *name, int offset,
struct intercept_translate *tl)
{
struct intercept_syscall *tmp;
struct intercept_translate *tlnew;
if (offset >= INTERCEPT_MAXSYSCALLARGS)
errx(1, "%s: %s-%s: offset too large",
__func__, emulation, name);
tmp = intercept_sccb_find(emulation, name);
if (tmp == NULL)
errx(1, "%s: %s-%s: can't find call back",
__func__, emulation, name);
tlnew = malloc(sizeof(struct intercept_translate));
if (tlnew == NULL)
err(1, "%s: %s-%s: malloc",
__func__, emulation, name);
memcpy(tlnew, tl, sizeof(struct intercept_translate));
tlnew->off = offset;
TAILQ_INSERT_TAIL(&tmp->tls, tlnew, next);
return (tlnew);
}
void *
intercept_sccb_cbarg(char *emulation, char *name)
{
struct intercept_syscall *tmp;
if ((tmp = intercept_sccb_find(emulation, name)) == NULL)
return (NULL);
return (tmp->cb_arg);
}
int
intercept_register_sccb(char *emulation, char *name,
short (*cb)(int, pid_t, int, const char *, int, const char *, void *, int,
struct intercept_replace *, struct intercept_tlq *, void *),
void *cbarg)
{
struct intercept_syscall *tmp;
if (intercept_sccb_find(emulation, name))
return (-1);
if (intercept.getsyscallnumber(emulation, name) == -1) {
warnx("%s: %d: unknown syscall: %s-%s", __func__, __LINE__,
emulation, name);
return (-1);
}
if ((tmp = calloc(1, sizeof(struct intercept_syscall))) == NULL) {
warn("%s:%d: malloc", __func__, __LINE__);
return (-1);
}
TAILQ_INIT(&tmp->tls);
strlcpy(tmp->name, name, sizeof(tmp->name));
strlcpy(tmp->emulation, emulation, sizeof(tmp->emulation));
tmp->cb = cb;
tmp->cb_arg = cbarg;
SPLAY_INSERT(sctree, &scroot, tmp);
return (0);
}
int
intercept_register_gencb(short (*cb)(int, pid_t, int, const char *, int, const char *, void *, int, void *), void *arg)
{
intercept_gencb = cb;
intercept_gencbarg = arg;
return (0);
}
int
intercept_register_execcb(void (*cb)(int, pid_t, int, const char *, const char *, void *), void *arg)
{
intercept_newimagecb = cb;
intercept_newimagecbarg = arg;
return (0);
}
int
intercept_register_pfreecb(void (*cb)(int, void *), void *arg)
{
intercept_pfreecb = cb;
intercept_pfreearg = arg;
return (0);
}
static void
sigusr1_handler(int signum)
{
/* all we need to do is pretend to handle it */
got_sigusr1 = 1;
}
void
intercept_setpid(struct intercept_pid *icpid, uid_t uid, gid_t gid)
{
struct passwd *pw;
icpid->uid = uid;
icpid->gid = gid;
if ((pw = getpwuid(icpid->uid)) == NULL) {
snprintf(icpid->username, sizeof(icpid->username),
"unknown(%d)", icpid->uid);
strlcpy(icpid->home, "/var/empty", sizeof(icpid->home));
} else {
strlcpy(icpid->username, pw->pw_name, sizeof(icpid->username));
strlcpy(icpid->home, pw->pw_dir, sizeof(icpid->home));
}
}
pid_t
intercept_run(int bg, int fd, uid_t uid, gid_t gid,
char *path, char *const argv[])
{
struct intercept_pid *icpid;
sigset_t none, set, oset;
sig_t ohandler;
pid_t pid, cpid;
int status;
/* Block signals so that timeing on signal delivery does not matter */
sigemptyset(&none);
sigemptyset(&set);
sigaddset(&set, SIGUSR1);
if (sigprocmask(SIG_BLOCK, &set, &oset) == -1)
err(1, "sigprocmask");
ohandler = signal(SIGUSR1, sigusr1_handler);
if (ohandler == SIG_ERR)
err(1, "signal");
pid = getpid();
cpid = fork();
if (cpid == -1)
return (-1);
/*
* If the systrace process should be in the background and we're
* the parent, or vice versa.
*/
if ((!bg && cpid == 0) || (bg && cpid != 0)) {
/* Needs to be closed */
close(fd);
if (bg) {
/* Wait for child to "detach" */
cpid = wait(&status);
if (cpid == -1)
err(1, "wait");
if (status != 0)
errx(1, "wait: child gave up");
}
/* Sleep */
sigsuspend(&none);
if (!got_sigusr1)
errx(1, "wrong signal");
/*
* Woken up, restore signal handling state.
*
* Note that there is either no child or we have no idea
* what pid it might have at this point. If we fail.
*/
if (signal(SIGUSR1, ohandler) == SIG_ERR)
err(1, "signal");
if (sigprocmask(SIG_SETMASK, &oset, NULL) == -1)
err(1, "sigprocmask");
/* Change to different user */
if (uid || gid) {
if (setgroups(1, &gid) == -1)
err(1, "setgroups");
if (setgid(gid) == -1)
err(1, "setgid");
if (setegid(gid) == -1)
err(1, "setegid");
if (setuid(uid) == -1)
err(1, "setuid");
if (seteuid(uid) == -1)
err(1, "seteuid");
}
execvp(path, argv);
/* Error */
err(1, "execvp");
}
/* Choose the pid of the systraced process */
pid = bg ? pid : cpid;
icpid = intercept_getpid(pid);
/* Set up user related information */
if (!uid && !gid) {
uid = getuid();
gid = getgid();
}
intercept_setpid(icpid, uid, gid);
/* Setup done, restore signal handling state */
if (signal(SIGUSR1, ohandler) == SIG_ERR) {
kill(pid, SIGKILL);
err(1, "signal");
}
if (sigprocmask(SIG_SETMASK, &oset, NULL) == -1) {
kill(pid, SIGKILL);
err(1, "sigprocmask");
}
if (bg) {
if (daemon(1, 1) == -1) {
kill(pid, SIGKILL);
err(1, "daemon");
}
}
return (pid);
}
int
intercept_existpids(void)
{
return (SPLAY_ROOT(&pids) != NULL);
}
void
intercept_freepid(pid_t pidnr)
{
struct intercept_pid *pid, tmp2;
tmp2.pid = pidnr;
pid = SPLAY_FIND(pidtree, &pids, &tmp2);
if (pid == NULL)
return;
intercept.freepid(pid);
SPLAY_REMOVE(pidtree, &pids, pid);
if (pid->name)
free(pid->name);
if (pid->newname)
free(pid->newname);
free(pid);
}
struct intercept_pid *
intercept_getpid(pid_t pid)
{
struct intercept_pid *tmp, tmp2;
tmp2.pid = pid;
tmp = SPLAY_FIND(pidtree, &pids, &tmp2);
if (tmp)
return (tmp);
if ((tmp = malloc(sizeof(struct intercept_pid))) == NULL)
err(1, "%s: malloc", __func__);
memset(tmp, 0, sizeof(struct intercept_pid));
tmp->pid = pid;
SPLAY_INSERT(pidtree, &pids, tmp);
return (tmp);
}
int
intercept_open(void)
{
int fd;
if ((fd = intercept.open()) == -1)
return (-1);
if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1)
warn("fcntl(O_NONBLOCK)");
return (fd);
}
int
intercept_attach(int fd, pid_t pid)
{
return (intercept.attach(fd, pid));
}
int
intercept_attachpid(int fd, pid_t pid, char *name)
{
struct intercept_pid *icpid;
int res;
res = intercept.attach(fd, pid);
if (res == -1)
return (-1);
icpid = intercept_getpid(pid);
if ((icpid->newname = strdup(name)) == NULL)
err(1, "strdup");
if (intercept.report(fd, pid) == -1)
return (-1);
/* Indicates a running attach */
icpid->execve_code = -1;
return (0);
}
int
intercept_detach(int fd, pid_t pid)
{
int res;
res = intercept.detach(fd, pid);
if (res != -1)
intercept_freepid(pid);
return (res);
}
int
intercept_read(int fd)
{
struct pollfd pollfd;
int n;
pollfd.fd = fd;
pollfd.events = POLLIN;
do {
n = poll(&pollfd, 1, -1);
if (n == -1) {
if (errno != EINTR && errno != EAGAIN)
return (-1);
}
} while (n <= 0);
if (!(pollfd.revents & (POLLIN|POLLRDNORM)))
return (-1);
return (intercept.read(fd));
}
int
intercept_replace_init(struct intercept_replace *repl)
{
memset(repl, 0, sizeof(struct intercept_replace));
return (0);
}
int
intercept_replace_add(struct intercept_replace *repl, int off,
u_char *addr, size_t len, u_int flags)
{
int ind = repl->num;
if (ind >= INTERCEPT_MAXSYSCALLARGS)
return (-1);
repl->ind[ind] = off;
repl->address[ind] = addr;
repl->len[ind] = len;
repl->flags[ind] = flags;
repl->num++;
return (0);
}
int
intercept_replace(int fd, pid_t pid, u_int16_t seqnr,
struct intercept_replace *repl)
{
if (repl->num == 0)
return (0);
return (intercept.replace(fd, pid, seqnr, repl));
}
char *
intercept_get_string(int fd, pid_t pid, void *addr)
{
static char name[8192];
int off = 0, done = 0, stride;
stride = 32;
do {
if (intercept.io(fd, pid, INTERCEPT_READ, (char *)addr + off,
&name[off], stride) == -1) {
/* Did the current system call get interrupted? */
if (errno == EBUSY)
return (NULL);
if (errno != EINVAL || stride == 4) {
warn("%s: ioctl", __func__);
return (NULL);
}
/* Try smaller stride */
stride /= 2;
continue;
}
off += stride;
name[off] = '\0';
if (strlen(name) < off)
done = 1;
} while (!done && off + stride + 1 < sizeof(name));
if (!done) {
warnx("%s: string too long", __func__);
return (NULL);
}
return (name);
}
char *
intercept_filename(int fd, pid_t pid, void *addr, int userp)
{
char *name;
if ((name = intercept_get_string(fd, pid, addr)) == NULL)
goto abort;
if ((name = normalize_filename(fd, pid, name, userp)) == NULL)
goto abort;
return (name);
abort:
ic_abort = 1;
return (NULL);
}
/*
* Normalizes a pathname so that Systrace policies entries are
* invariant to symlinks.
*/
char *
normalize_filename(int fd, pid_t pid, char *name, int userp)
{
static char cwd[2*MAXPATHLEN];
int havecwd = 0;
/*
* The empty filename does not receive normalization.
* System calls are supposed to fail on it.
*/
if (strcmp(name, "") == 0)
return (name);
if (fd != -1 && intercept.setcwd(fd, pid) == -1) {
if (errno == EBUSY)
return (NULL);
getcwderr:
if (strcmp(name, "/") == 0)
return (name);
err(1, "%s: getcwd", __func__);
}
if (userp == ICLINK_NONE) {
if (getcwd(cwd, sizeof(cwd)) == NULL)
goto getcwderr;
havecwd = 1;
}
/* Need concatenated path for simplifypath */
if (havecwd && name[0] != '/') {
if (strlcat(cwd, "/", sizeof(cwd)) >= sizeof(cwd))
goto error;
if (strlcat(cwd, name, sizeof(cwd)) >= sizeof(cwd))
goto error;
} else {
if (strlcpy(cwd, name, sizeof(cwd)) >= sizeof(cwd))
goto error;
}
if (userp != ICLINK_NONE) {
static char rcwd[2*MAXPATHLEN];
char *base = basename(cwd);
int failed = 0;
/* The dot may be used by rmdir("/tmp/something/.") */
if (strcmp(base, ".") == 0)
goto nolast;
if (userp == ICLINK_NOLAST) {
/* Check if the last component has special meaning */
if (strcmp(base, "..") == 0 || strcmp(base, "/") == 0)
userp = ICLINK_ALL;
else
goto nolast;
}
/* If realpath fails then the filename does not exist,
* or we are supposed to not resolve the last component */
if (realpath(cwd, rcwd) == NULL) {
char *dir, *file;
struct stat st;
if (errno != EACCES) {
failed = 1;
goto out;
}
nolast:
/* Component of path could not be entered */
if (strlcpy(rcwd, cwd, sizeof(rcwd)) >= sizeof(rcwd))
goto error;
if ((file = basename(rcwd)) == NULL)
goto error;
if ((dir = dirname(rcwd)) == NULL)
goto error;
/* So, try again */
if (realpath(dir, rcwd) == NULL) {
failed = 1;
goto out;
}
/* If path is not "/" append a "/" */
if (strlen(rcwd) > 1 &&
strlcat(rcwd, "/", sizeof(rcwd)) >= sizeof(rcwd))
goto error;
if (strlcat(rcwd, file, sizeof(rcwd)) >= sizeof(rcwd))
goto error;
/*
* At this point, filename has to exist and has to
* be a directory.
*/
if (userp != ICLINK_NOLAST) {
if (lstat(rcwd, &st) == -1 ||
!(st.st_mode & S_IFDIR))
failed = 1;
}
}
out:
if (failed)
snprintf(rcwd, sizeof(rcwd),
"/<non-existent filename>: %s", cwd);
name = rcwd;
} else {
simplify_path(cwd);
name = cwd;
}
/* Restore working directory and change root space after realpath */
if (fd != -1 && intercept.restcwd(fd) == -1)
err(1, "%s: restcwd", __func__);
return (name);
error:
errx(1, "%s: filename too long", __func__);
/* NOTREACHED */
}
void
intercept_syscall(int fd, pid_t pid, u_int16_t seqnr, int policynr,
const char *name, int code, const char *emulation, void *args, int argsize)
{
short action, flags = 0;
struct intercept_syscall *sc;
struct intercept_pid *icpid;
struct elevate *elevate = NULL;
int error = 0;
action = ICPOLICY_PERMIT;
flags = 0;
icpid = intercept_getpid(pid);
/* Special handling for the exec call */
if (!strcmp(name, "execve")) {
void *addr;
char *argname;
icpid->execve_code = code;
icpid->policynr = policynr;
if (icpid->newname)
free(icpid->newname);
intercept.getarg(0, args, argsize, &addr);
argname = intercept_filename(fd, pid, addr, ICLINK_ALL);
if (argname == NULL)
err(1, "%s:%d: intercept_filename",
__func__, __LINE__);
icpid->newname = strdup(argname);
if (icpid->newname == NULL)
err(1, "%s:%d: strdup", __func__, __LINE__);
/* We need to know the result from this system call */
flags = ICFLAGS_RESULT;
}
icpid->elevate = NULL;
sc = intercept_sccb_find(emulation, name);
if (sc != NULL) {
struct intercept_translate *tl;
ic_abort = 0;
TAILQ_FOREACH(tl, &sc->tls, next) {
if (intercept_translate(tl, fd, pid, tl->off,
args, argsize) == -1)
break;
}
if (!ic_abort) {
struct intercept_replace repl;
intercept_replace_init(&repl);
action = (*sc->cb)(fd, pid, policynr, name, code,
emulation, args, argsize, &repl,
&sc->tls, sc->cb_arg);
if (action < ICPOLICY_NEVER) {
/* If we can not rewrite the arguments,
* system call fails.
*/
if (intercept_replace(fd, pid, seqnr, &repl) == -1)
action = ICPOLICY_NEVER;
}
} else
action = ICPOLICY_NEVER;
} else if (intercept_gencb != NULL)
action = (*intercept_gencb)(fd, pid, policynr, name, code,
emulation, args, argsize, intercept_gencbarg);
if (action > 0) {
error = action;
action = ICPOLICY_NEVER;
} else
elevate = icpid->elevate;
/* Resume execution of the process */
intercept.answer(fd, pid, seqnr, action, error, flags, elevate);
}
void
intercept_syscall_result(int fd, pid_t pid, u_int16_t seqnr, int policynr,
const char *name, int code, const char *emulation, void *args, int argsize,
int result, void *rval)
{
struct intercept_pid *icpid;
if (result > 0)
goto out;
icpid = intercept_getpid(pid);
if (!strcmp("execve", name)) {
/* Commit the name of the new image */
if (icpid->name)
free(icpid->name);
icpid->name = icpid->newname;
icpid->newname = NULL;
if (intercept_newimagecb != NULL)
(*intercept_newimagecb)(fd, pid, policynr, emulation,
icpid->name, intercept_newimagecbarg);
}
out:
/* Resume execution of the process */
intercept.answer(fd, pid, seqnr, 0, 0, 0, NULL);
}
int
intercept_newpolicy(int fd)
{
int policynr;
policynr = intercept.newpolicy(fd);
return (policynr);
}
int
intercept_assignpolicy(int fd, pid_t pid, int policynr)
{
return (intercept.assignpolicy(fd, pid, policynr));
}
int
intercept_modifypolicy(int fd, int policynr, const char *emulation,
const char *name, short policy)
{
int code;
code = intercept.getsyscallnumber(emulation, name);
if (code == -1)
return (-1);
return (intercept.policy(fd, policynr, code, policy));
}
void
intercept_child_info(pid_t opid, pid_t npid)
{
struct intercept_pid *ipid, *inpid, tmp;
/* A child just died on us */
if (npid == -1) {
intercept_freepid(opid);
return;
}
tmp.pid = opid;
ipid = SPLAY_FIND(pidtree, &pids, &tmp);
if (ipid == NULL)
return;
inpid = intercept_getpid(npid);
inpid->policynr = ipid->policynr;
if (ipid->name != NULL) {
inpid->name = strdup(ipid->name);
if (inpid->name == NULL)
err(1, "%s:%d: strdup", __func__, __LINE__);
}
/* Process tree */
inpid->ppid = opid;
/* Copy some information */
inpid->uid = ipid->uid;
inpid->gid = ipid->gid;
strlcpy(inpid->username, ipid->username, sizeof(inpid->username));
strlcpy(inpid->home, ipid->home, sizeof(inpid->home));
/* XXX - keeps track of emulation */
intercept.clonepid(ipid, inpid);
}
void
intercept_ugid(struct intercept_pid *icpid, uid_t uid, gid_t gid)
{
/* Update current home dir */
if (icpid->uid != uid) {
struct passwd *pw;
if ((pw = getpwuid(uid)) == NULL) {
snprintf(icpid->username, sizeof(icpid->username),
"uid %d", uid);
strlcpy(icpid->home, "/", sizeof(icpid->home));
} else {
strlcpy(icpid->username, pw->pw_name,
sizeof(icpid->username));
strlcpy(icpid->home, pw->pw_dir, sizeof(icpid->home));
}
}
icpid->uid = uid;
icpid->gid = gid;
}
/*
* Checks if the given emulation has a certain system call.
* This is a very slow function.
*/
int
intercept_isvalidsystemcall(char *emulation, char *name)
{
int res;
res = intercept.getsyscallnumber(emulation, name);
return (res != -1);
}
/*
* Call back when a user has exhausted the number of allowed policies
* in the kernel. The kernel returns the policy number of a policy
* that has been purged.
*/
void
intercept_policy_free(int policynr)
{
(*intercept_pfreecb)(policynr, intercept_pfreearg);
}
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