freebsd-dev/sys/kern/kern_jail.c
2007-03-09 05:22:10 +00:00

744 lines
17 KiB
C

/*-
* ----------------------------------------------------------------------------
* "THE BEER-WARE LICENSE" (Revision 42):
* <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
* this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
* ----------------------------------------------------------------------------
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_mac.h"
#include <sys/param.h>
#include <sys/types.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/sysproto.h>
#include <sys/malloc.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/taskqueue.h>
#include <sys/jail.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/mount.h>
#include <sys/queue.h>
#include <sys/socket.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <net/if.h>
#include <netinet/in.h>
#include <security/mac/mac_framework.h>
MALLOC_DEFINE(M_PRISON, "prison", "Prison structures");
SYSCTL_NODE(_security, OID_AUTO, jail, CTLFLAG_RW, 0,
"Jail rules");
int jail_set_hostname_allowed = 1;
SYSCTL_INT(_security_jail, OID_AUTO, set_hostname_allowed, CTLFLAG_RW,
&jail_set_hostname_allowed, 0,
"Processes in jail can set their hostnames");
int jail_socket_unixiproute_only = 1;
SYSCTL_INT(_security_jail, OID_AUTO, socket_unixiproute_only, CTLFLAG_RW,
&jail_socket_unixiproute_only, 0,
"Processes in jail are limited to creating UNIX/IPv4/route sockets only");
int jail_sysvipc_allowed = 0;
SYSCTL_INT(_security_jail, OID_AUTO, sysvipc_allowed, CTLFLAG_RW,
&jail_sysvipc_allowed, 0,
"Processes in jail can use System V IPC primitives");
static int jail_enforce_statfs = 2;
SYSCTL_INT(_security_jail, OID_AUTO, enforce_statfs, CTLFLAG_RW,
&jail_enforce_statfs, 0,
"Processes in jail cannot see all mounted file systems");
int jail_allow_raw_sockets = 0;
SYSCTL_INT(_security_jail, OID_AUTO, allow_raw_sockets, CTLFLAG_RW,
&jail_allow_raw_sockets, 0,
"Prison root can create raw sockets");
int jail_chflags_allowed = 0;
SYSCTL_INT(_security_jail, OID_AUTO, chflags_allowed, CTLFLAG_RW,
&jail_chflags_allowed, 0,
"Processes in jail can alter system file flags");
/* allprison, lastprid, and prisoncount are protected by allprison_mtx. */
struct prisonlist allprison;
struct mtx allprison_mtx;
int lastprid = 0;
int prisoncount = 0;
static void init_prison(void *);
static void prison_complete(void *context, int pending);
static struct prison *prison_find(int);
static int sysctl_jail_list(SYSCTL_HANDLER_ARGS);
static void
init_prison(void *data __unused)
{
mtx_init(&allprison_mtx, "allprison", NULL, MTX_DEF);
LIST_INIT(&allprison);
}
SYSINIT(prison, SI_SUB_INTRINSIC, SI_ORDER_ANY, init_prison, NULL);
/*
* struct jail_args {
* struct jail *jail;
* };
*/
int
jail(struct thread *td, struct jail_args *uap)
{
struct nameidata nd;
struct prison *pr, *tpr;
struct jail j;
struct jail_attach_args jaa;
int vfslocked, error, tryprid;
error = copyin(uap->jail, &j, sizeof(j));
if (error)
return (error);
if (j.version != 0)
return (EINVAL);
MALLOC(pr, struct prison *, sizeof(*pr), M_PRISON, M_WAITOK | M_ZERO);
mtx_init(&pr->pr_mtx, "jail mutex", NULL, MTX_DEF);
pr->pr_ref = 1;
error = copyinstr(j.path, &pr->pr_path, sizeof(pr->pr_path), 0);
if (error)
goto e_killmtx;
NDINIT(&nd, LOOKUP, MPSAFE | FOLLOW | LOCKLEAF, UIO_SYSSPACE,
pr->pr_path, td);
error = namei(&nd);
if (error)
goto e_killmtx;
vfslocked = NDHASGIANT(&nd);
pr->pr_root = nd.ni_vp;
VOP_UNLOCK(nd.ni_vp, 0, td);
NDFREE(&nd, NDF_ONLY_PNBUF);
VFS_UNLOCK_GIANT(vfslocked);
error = copyinstr(j.hostname, &pr->pr_host, sizeof(pr->pr_host), 0);
if (error)
goto e_dropvnref;
pr->pr_ip = j.ip_number;
pr->pr_linux = NULL;
pr->pr_securelevel = securelevel;
/* Determine next pr_id and add prison to allprison list. */
mtx_lock(&allprison_mtx);
tryprid = lastprid + 1;
if (tryprid == JAIL_MAX)
tryprid = 1;
next:
LIST_FOREACH(tpr, &allprison, pr_list) {
if (tpr->pr_id == tryprid) {
tryprid++;
if (tryprid == JAIL_MAX) {
mtx_unlock(&allprison_mtx);
error = EAGAIN;
goto e_dropvnref;
}
goto next;
}
}
pr->pr_id = jaa.jid = lastprid = tryprid;
LIST_INSERT_HEAD(&allprison, pr, pr_list);
prisoncount++;
mtx_unlock(&allprison_mtx);
error = jail_attach(td, &jaa);
if (error)
goto e_dropprref;
mtx_lock(&pr->pr_mtx);
pr->pr_ref--;
mtx_unlock(&pr->pr_mtx);
td->td_retval[0] = jaa.jid;
return (0);
e_dropprref:
mtx_lock(&allprison_mtx);
LIST_REMOVE(pr, pr_list);
prisoncount--;
mtx_unlock(&allprison_mtx);
e_dropvnref:
vfslocked = VFS_LOCK_GIANT(pr->pr_root->v_mount);
vrele(pr->pr_root);
VFS_UNLOCK_GIANT(vfslocked);
e_killmtx:
mtx_destroy(&pr->pr_mtx);
FREE(pr, M_PRISON);
return (error);
}
/*
* struct jail_attach_args {
* int jid;
* };
*/
int
jail_attach(struct thread *td, struct jail_attach_args *uap)
{
struct proc *p;
struct ucred *newcred, *oldcred;
struct prison *pr;
int vfslocked, error;
/*
* XXX: Note that there is a slight race here if two threads
* in the same privileged process attempt to attach to two
* different jails at the same time. It is important for
* user processes not to do this, or they might end up with
* a process root from one prison, but attached to the jail
* of another.
*/
error = priv_check(td, PRIV_JAIL_ATTACH);
if (error)
return (error);
p = td->td_proc;
mtx_lock(&allprison_mtx);
pr = prison_find(uap->jid);
if (pr == NULL) {
mtx_unlock(&allprison_mtx);
return (EINVAL);
}
pr->pr_ref++;
mtx_unlock(&pr->pr_mtx);
mtx_unlock(&allprison_mtx);
vfslocked = VFS_LOCK_GIANT(pr->pr_root->v_mount);
vn_lock(pr->pr_root, LK_EXCLUSIVE | LK_RETRY, td);
if ((error = change_dir(pr->pr_root, td)) != 0)
goto e_unlock;
#ifdef MAC
if ((error = mac_check_vnode_chroot(td->td_ucred, pr->pr_root)))
goto e_unlock;
#endif
VOP_UNLOCK(pr->pr_root, 0, td);
change_root(pr->pr_root, td);
VFS_UNLOCK_GIANT(vfslocked);
newcred = crget();
PROC_LOCK(p);
oldcred = p->p_ucred;
setsugid(p);
crcopy(newcred, oldcred);
newcred->cr_prison = pr;
p->p_ucred = newcred;
PROC_UNLOCK(p);
crfree(oldcred);
return (0);
e_unlock:
VOP_UNLOCK(pr->pr_root, 0, td);
VFS_UNLOCK_GIANT(vfslocked);
mtx_lock(&pr->pr_mtx);
pr->pr_ref--;
mtx_unlock(&pr->pr_mtx);
return (error);
}
/*
* Returns a locked prison instance, or NULL on failure.
*/
static struct prison *
prison_find(int prid)
{
struct prison *pr;
mtx_assert(&allprison_mtx, MA_OWNED);
LIST_FOREACH(pr, &allprison, pr_list) {
if (pr->pr_id == prid) {
mtx_lock(&pr->pr_mtx);
return (pr);
}
}
return (NULL);
}
void
prison_free(struct prison *pr)
{
mtx_lock(&allprison_mtx);
mtx_lock(&pr->pr_mtx);
pr->pr_ref--;
if (pr->pr_ref == 0) {
LIST_REMOVE(pr, pr_list);
mtx_unlock(&pr->pr_mtx);
prisoncount--;
mtx_unlock(&allprison_mtx);
TASK_INIT(&pr->pr_task, 0, prison_complete, pr);
taskqueue_enqueue(taskqueue_thread, &pr->pr_task);
return;
}
mtx_unlock(&pr->pr_mtx);
mtx_unlock(&allprison_mtx);
}
static void
prison_complete(void *context, int pending)
{
struct prison *pr;
int vfslocked;
pr = (struct prison *)context;
vfslocked = VFS_LOCK_GIANT(pr->pr_root->v_mount);
vrele(pr->pr_root);
VFS_UNLOCK_GIANT(vfslocked);
mtx_destroy(&pr->pr_mtx);
if (pr->pr_linux != NULL)
FREE(pr->pr_linux, M_PRISON);
FREE(pr, M_PRISON);
}
void
prison_hold(struct prison *pr)
{
mtx_lock(&pr->pr_mtx);
pr->pr_ref++;
mtx_unlock(&pr->pr_mtx);
}
u_int32_t
prison_getip(struct ucred *cred)
{
return (cred->cr_prison->pr_ip);
}
int
prison_ip(struct ucred *cred, int flag, u_int32_t *ip)
{
u_int32_t tmp;
if (!jailed(cred))
return (0);
if (flag)
tmp = *ip;
else
tmp = ntohl(*ip);
if (tmp == INADDR_ANY) {
if (flag)
*ip = cred->cr_prison->pr_ip;
else
*ip = htonl(cred->cr_prison->pr_ip);
return (0);
}
if (tmp == INADDR_LOOPBACK) {
if (flag)
*ip = cred->cr_prison->pr_ip;
else
*ip = htonl(cred->cr_prison->pr_ip);
return (0);
}
if (cred->cr_prison->pr_ip != tmp)
return (1);
return (0);
}
void
prison_remote_ip(struct ucred *cred, int flag, u_int32_t *ip)
{
u_int32_t tmp;
if (!jailed(cred))
return;
if (flag)
tmp = *ip;
else
tmp = ntohl(*ip);
if (tmp == INADDR_LOOPBACK) {
if (flag)
*ip = cred->cr_prison->pr_ip;
else
*ip = htonl(cred->cr_prison->pr_ip);
return;
}
return;
}
int
prison_if(struct ucred *cred, struct sockaddr *sa)
{
struct sockaddr_in *sai;
int ok;
sai = (struct sockaddr_in *)sa;
if ((sai->sin_family != AF_INET) && jail_socket_unixiproute_only)
ok = 1;
else if (sai->sin_family != AF_INET)
ok = 0;
else if (cred->cr_prison->pr_ip != ntohl(sai->sin_addr.s_addr))
ok = 1;
else
ok = 0;
return (ok);
}
/*
* Return 0 if jails permit p1 to frob p2, otherwise ESRCH.
*/
int
prison_check(struct ucred *cred1, struct ucred *cred2)
{
if (jailed(cred1)) {
if (!jailed(cred2))
return (ESRCH);
if (cred2->cr_prison != cred1->cr_prison)
return (ESRCH);
}
return (0);
}
/*
* Return 1 if the passed credential is in a jail, otherwise 0.
*/
int
jailed(struct ucred *cred)
{
return (cred->cr_prison != NULL);
}
/*
* Return the correct hostname for the passed credential.
*/
void
getcredhostname(struct ucred *cred, char *buf, size_t size)
{
if (jailed(cred)) {
mtx_lock(&cred->cr_prison->pr_mtx);
strlcpy(buf, cred->cr_prison->pr_host, size);
mtx_unlock(&cred->cr_prison->pr_mtx);
} else
strlcpy(buf, hostname, size);
}
/*
* Determine whether the subject represented by cred can "see"
* status of a mount point.
* Returns: 0 for permitted, ENOENT otherwise.
* XXX: This function should be called cr_canseemount() and should be
* placed in kern_prot.c.
*/
int
prison_canseemount(struct ucred *cred, struct mount *mp)
{
struct prison *pr;
struct statfs *sp;
size_t len;
if (!jailed(cred) || jail_enforce_statfs == 0)
return (0);
pr = cred->cr_prison;
if (pr->pr_root->v_mount == mp)
return (0);
if (jail_enforce_statfs == 2)
return (ENOENT);
/*
* If jail's chroot directory is set to "/" we should be able to see
* all mount-points from inside a jail.
* This is ugly check, but this is the only situation when jail's
* directory ends with '/'.
*/
if (strcmp(pr->pr_path, "/") == 0)
return (0);
len = strlen(pr->pr_path);
sp = &mp->mnt_stat;
if (strncmp(pr->pr_path, sp->f_mntonname, len) != 0)
return (ENOENT);
/*
* Be sure that we don't have situation where jail's root directory
* is "/some/path" and mount point is "/some/pathpath".
*/
if (sp->f_mntonname[len] != '\0' && sp->f_mntonname[len] != '/')
return (ENOENT);
return (0);
}
void
prison_enforce_statfs(struct ucred *cred, struct mount *mp, struct statfs *sp)
{
char jpath[MAXPATHLEN];
struct prison *pr;
size_t len;
if (!jailed(cred) || jail_enforce_statfs == 0)
return;
pr = cred->cr_prison;
if (prison_canseemount(cred, mp) != 0) {
bzero(sp->f_mntonname, sizeof(sp->f_mntonname));
strlcpy(sp->f_mntonname, "[restricted]",
sizeof(sp->f_mntonname));
return;
}
if (pr->pr_root->v_mount == mp) {
/*
* Clear current buffer data, so we are sure nothing from
* the valid path left there.
*/
bzero(sp->f_mntonname, sizeof(sp->f_mntonname));
*sp->f_mntonname = '/';
return;
}
/*
* If jail's chroot directory is set to "/" we should be able to see
* all mount-points from inside a jail.
*/
if (strcmp(pr->pr_path, "/") == 0)
return;
len = strlen(pr->pr_path);
strlcpy(jpath, sp->f_mntonname + len, sizeof(jpath));
/*
* Clear current buffer data, so we are sure nothing from
* the valid path left there.
*/
bzero(sp->f_mntonname, sizeof(sp->f_mntonname));
if (*jpath == '\0') {
/* Should never happen. */
*sp->f_mntonname = '/';
} else {
strlcpy(sp->f_mntonname, jpath, sizeof(sp->f_mntonname));
}
}
/*
* Check with permission for a specific privilege is granted within jail. We
* have a specific list of accepted privileges; the rest are denied.
*/
int
prison_priv_check(struct ucred *cred, int priv)
{
if (!jailed(cred))
return (0);
switch (priv) {
/*
* Allow ktrace privileges for root in jail.
*/
case PRIV_KTRACE:
#if 0
/*
* Allow jailed processes to configure audit identity and
* submit audit records (login, etc). In the future we may
* want to further refine the relationship between audit and
* jail.
*/
case PRIV_AUDIT_GETAUDIT:
case PRIV_AUDIT_SETAUDIT:
case PRIV_AUDIT_SUBMIT:
#endif
/*
* Allow jailed processes to manipulate process UNIX
* credentials in any way they see fit.
*/
case PRIV_CRED_SETUID:
case PRIV_CRED_SETEUID:
case PRIV_CRED_SETGID:
case PRIV_CRED_SETEGID:
case PRIV_CRED_SETGROUPS:
case PRIV_CRED_SETREUID:
case PRIV_CRED_SETREGID:
case PRIV_CRED_SETRESUID:
case PRIV_CRED_SETRESGID:
/*
* Jail implements visibility constraints already, so allow
* jailed root to override uid/gid-based constraints.
*/
case PRIV_SEEOTHERGIDS:
case PRIV_SEEOTHERUIDS:
/*
* Jail implements inter-process debugging limits already, so
* allow jailed root various debugging privileges.
*/
case PRIV_DEBUG_DIFFCRED:
case PRIV_DEBUG_SUGID:
case PRIV_DEBUG_UNPRIV:
/*
* Allow jail to set various resource limits and login
* properties, and for now, exceed process resource limits.
*/
case PRIV_PROC_LIMIT:
case PRIV_PROC_SETLOGIN:
case PRIV_PROC_SETRLIMIT:
/*
* System V and POSIX IPC privileges are granted in jail.
*/
case PRIV_IPC_READ:
case PRIV_IPC_WRITE:
case PRIV_IPC_ADMIN:
case PRIV_IPC_MSGSIZE:
case PRIV_MQ_ADMIN:
/*
* Jail implements its own inter-process limits, so allow
* root processes in jail to change scheduling on other
* processes in the same jail. Likewise for signalling.
*/
case PRIV_SCHED_DIFFCRED:
case PRIV_SIGNAL_DIFFCRED:
case PRIV_SIGNAL_SUGID:
/*
* Allow jailed processes to write to sysctls marked as jail
* writable.
*/
case PRIV_SYSCTL_WRITEJAIL:
/*
* Allow root in jail to manage a variety of quota
* properties. These should likely be conditional on a
* configuration option.
*/
case PRIV_VFS_GETQUOTA:
case PRIV_VFS_SETQUOTA:
/*
* Since Jail relies on chroot() to implement file system
* protections, grant many VFS privileges to root in jail.
* Be careful to exclude mount-related and NFS-related
* privileges.
*/
case PRIV_VFS_READ:
case PRIV_VFS_WRITE:
case PRIV_VFS_ADMIN:
case PRIV_VFS_EXEC:
case PRIV_VFS_LOOKUP:
case PRIV_VFS_BLOCKRESERVE: /* XXXRW: Slightly surprising. */
case PRIV_VFS_CHFLAGS_DEV:
case PRIV_VFS_CHOWN:
case PRIV_VFS_CHROOT:
case PRIV_VFS_RETAINSUGID:
case PRIV_VFS_FCHROOT:
case PRIV_VFS_LINK:
case PRIV_VFS_SETGID:
case PRIV_VFS_STICKYFILE:
return (0);
/*
* Depending on the global setting, allow privilege of
* setting system flags.
*/
case PRIV_VFS_SYSFLAGS:
if (jail_chflags_allowed)
return (0);
else
return (EPERM);
/*
* Allow jailed root to bind reserved ports.
*/
case PRIV_NETINET_RESERVEDPORT:
return (0);
/*
* Conditionally allow creating raw sockets in jail.
*/
case PRIV_NETINET_RAW:
if (jail_allow_raw_sockets)
return (0);
else
return (EPERM);
/*
* Since jail implements its own visibility limits on netstat
* sysctls, allow getcred. This allows identd to work in
* jail.
*/
case PRIV_NETINET_GETCRED:
return (0);
default:
/*
* In all remaining cases, deny the privilege request. This
* includes almost all network privileges, many system
* configuration privileges.
*/
return (EPERM);
}
}
static int
sysctl_jail_list(SYSCTL_HANDLER_ARGS)
{
struct xprison *xp, *sxp;
struct prison *pr;
int count, error;
if (jailed(req->td->td_ucred))
return (0);
retry:
mtx_lock(&allprison_mtx);
count = prisoncount;
mtx_unlock(&allprison_mtx);
if (count == 0)
return (0);
sxp = xp = malloc(sizeof(*xp) * count, M_TEMP, M_WAITOK | M_ZERO);
mtx_lock(&allprison_mtx);
if (count != prisoncount) {
mtx_unlock(&allprison_mtx);
free(sxp, M_TEMP);
goto retry;
}
LIST_FOREACH(pr, &allprison, pr_list) {
mtx_lock(&pr->pr_mtx);
xp->pr_version = XPRISON_VERSION;
xp->pr_id = pr->pr_id;
strlcpy(xp->pr_path, pr->pr_path, sizeof(xp->pr_path));
strlcpy(xp->pr_host, pr->pr_host, sizeof(xp->pr_host));
xp->pr_ip = pr->pr_ip;
mtx_unlock(&pr->pr_mtx);
xp++;
}
mtx_unlock(&allprison_mtx);
error = SYSCTL_OUT(req, sxp, sizeof(*sxp) * count);
free(sxp, M_TEMP);
return (error);
}
SYSCTL_OID(_security_jail, OID_AUTO, list, CTLTYPE_STRUCT | CTLFLAG_RD,
NULL, 0, sysctl_jail_list, "S", "List of active jails");
static int
sysctl_jail_jailed(SYSCTL_HANDLER_ARGS)
{
int error, injail;
injail = jailed(req->td->td_ucred);
error = SYSCTL_OUT(req, &injail, sizeof(injail));
return (error);
}
SYSCTL_PROC(_security_jail, OID_AUTO, jailed, CTLTYPE_INT | CTLFLAG_RD,
NULL, 0, sysctl_jail_jailed, "I", "Process in jail?");