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freebsd-dev/sys/kern/sys_process.c
Robert Watson 387d2c036b o Centralize inter-process access control, introducing: 
int p_can(p1, p2, operation, privused)

  which allows specification of subject process, object process,
  inter-process operation, and an optional call-by-reference privused
  flag, allowing the caller to determine if privilege was required
  for the call to succeed.  This allows jail, kern.ps_showallprocs and
  regular credential-based interaction checks to occur in one block of
  code.  Possible operations are P_CAN_SEE, P_CAN_SCHED, P_CAN_KILL,
  and P_CAN_DEBUG.  p_can currently breaks out as a wrapper to a
  series of static function checks in kern_prot, which should not
  be invoked directly.

o Commented out capabilities entries are included for some checks.

o Update most inter-process authorization to make use of p_can() instead
  of manual checks, PRISON_CHECK(), P_TRESPASS(), and
  kern.ps_showallprocs.

o Modify suser{,_xxx} to use const arguments, as it no longer modifies
  process flags due to the disabling of ASU.

o Modify some checks/errors in procfs so that ENOENT is returned instead
  of ESRCH, further improving concealment of processes that should not
  be visible to other processes.  Also introduce new access checks to
  improve hiding of processes for procfs_lookup(), procfs_getattr(),
  procfs_readdir().  Correct a bug reported by bp concerning not
  handling the CREATE case in procfs_lookup().  Remove volatile flag in
  procfs that caused apparently spurious qualifier warnigns (approved by
  bde).

o Add comment noting that ktrace() has not been updated, as its access
  control checks are different from ptrace(), whereas they should
  probably be the same.  Further discussion should happen on this topic.

Reviewed by:	bde, green, phk, freebsd-security, others
Approved by:	bde
Obtained from:	TrustedBSD Project
2000-08-30 04:49:09 +00:00

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/*
* Copyright (c) 1994, Sean Eric Fagan
* 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 Sean Eric Fagan.
* 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
*
* $FreeBSD$
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/ptrace.h>
#include <machine/reg.h>
#include <vm/vm.h>
#include <sys/lock.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <sys/user.h>
#include <miscfs/procfs/procfs.h>
/* use the equivalent procfs code */
#if 0
static int
pread (struct proc *procp, unsigned int addr, unsigned int *retval) {
int rv;
vm_map_t map, tmap;
vm_object_t object;
vm_offset_t kva = 0;
int page_offset; /* offset into page */
vm_offset_t pageno; /* page number */
vm_map_entry_t out_entry;
vm_prot_t out_prot;
boolean_t wired;
vm_pindex_t pindex;
/* Map page into kernel space */
map = &procp->p_vmspace->vm_map;
page_offset = addr - trunc_page(addr);
pageno = trunc_page(addr);
tmap = map;
rv = vm_map_lookup (&tmap, pageno, VM_PROT_READ, &out_entry,
&object, &pindex, &out_prot, &wired);
if (rv != KERN_SUCCESS)
return EINVAL;
vm_map_lookup_done (tmap, out_entry);
/* Find space in kernel_map for the page we're interested in */
rv = vm_map_find (kernel_map, object, IDX_TO_OFF(pindex),
&kva, PAGE_SIZE, 0, VM_PROT_ALL, VM_PROT_ALL, 0);
if (!rv) {
vm_object_reference (object);
rv = vm_map_pageable (kernel_map, kva, kva + PAGE_SIZE, 0);
if (!rv) {
*retval = 0;
bcopy ((caddr_t)kva + page_offset,
retval, sizeof *retval);
}
vm_map_remove (kernel_map, kva, kva + PAGE_SIZE);
}
return rv;
}
static int
pwrite (struct proc *procp, unsigned int addr, unsigned int datum) {
int rv;
vm_map_t map, tmap;
vm_object_t object;
vm_offset_t kva = 0;
int page_offset; /* offset into page */
vm_offset_t pageno; /* page number */
vm_map_entry_t out_entry;
vm_prot_t out_prot;
boolean_t wired;
vm_pindex_t pindex;
boolean_t fix_prot = 0;
/* Map page into kernel space */
map = &procp->p_vmspace->vm_map;
page_offset = addr - trunc_page(addr);
pageno = trunc_page(addr);
/*
* Check the permissions for the area we're interested in.
*/
if (vm_map_check_protection (map, pageno, pageno + PAGE_SIZE,
VM_PROT_WRITE) == FALSE) {
/*
* If the page was not writable, we make it so.
* XXX It is possible a page may *not* be read/executable,
* if a process changes that!
*/
fix_prot = 1;
/* The page isn't writable, so let's try making it so... */
if ((rv = vm_map_protect (map, pageno, pageno + PAGE_SIZE,
VM_PROT_ALL, 0)) != KERN_SUCCESS)
return EFAULT; /* I guess... */
}
/*
* Now we need to get the page. out_entry, out_prot, wired, and
* single_use aren't used. One would think the vm code would be
* a *bit* nicer... We use tmap because vm_map_lookup() can
* change the map argument.
*/
tmap = map;
rv = vm_map_lookup (&tmap, pageno, VM_PROT_WRITE, &out_entry,
&object, &pindex, &out_prot, &wired);
if (rv != KERN_SUCCESS) {
return EINVAL;
}
/*
* Okay, we've got the page. Let's release tmap.
*/
vm_map_lookup_done (tmap, out_entry);
/*
* Fault the page in...
*/
rv = vm_fault(map, pageno, VM_PROT_WRITE|VM_PROT_READ, FALSE);
if (rv != KERN_SUCCESS)
return EFAULT;
/* Find space in kernel_map for the page we're interested in */
rv = vm_map_find (kernel_map, object, IDX_TO_OFF(pindex),
&kva, PAGE_SIZE, 0,
VM_PROT_ALL, VM_PROT_ALL, 0);
if (!rv) {
vm_object_reference (object);
rv = vm_map_pageable (kernel_map, kva, kva + PAGE_SIZE, 0);
if (!rv) {
bcopy (&datum, (caddr_t)kva + page_offset, sizeof datum);
}
vm_map_remove (kernel_map, kva, kva + PAGE_SIZE);
}
if (fix_prot)
vm_map_protect (map, pageno, pageno + PAGE_SIZE,
VM_PROT_READ|VM_PROT_EXECUTE, 0);
return rv;
}
#endif
/*
* Process debugging system call.
*/
#ifndef _SYS_SYSPROTO_H_
struct ptrace_args {
int req;
pid_t pid;
caddr_t addr;
int data;
};
#endif
int
ptrace(curp, uap)
struct proc *curp;
struct ptrace_args *uap;
{
struct proc *p;
struct iovec iov;
struct uio uio;
int error = 0;
int write;
int s;
write = 0;
if (uap->req == PT_TRACE_ME)
p = curp;
else {
if ((p = pfind(uap->pid)) == NULL)
return ESRCH;
}
if (p_can(curp, p, P_CAN_SEE, NULL))
return (ESRCH);
/*
* Permissions check
*/
switch (uap->req) {
case PT_TRACE_ME:
/* Always legal. */
break;
case PT_ATTACH:
/* Self */
if (p->p_pid == curp->p_pid)
return EINVAL;
/* Already traced */
if (p->p_flag & P_TRACED)
return EBUSY;
if ((error = p_can(curp, p, P_CAN_DEBUG, NULL)))
return error;
/* OK */
break;
case PT_READ_I:
case PT_READ_D:
case PT_READ_U:
case PT_WRITE_I:
case PT_WRITE_D:
case PT_WRITE_U:
case PT_CONTINUE:
case PT_KILL:
case PT_STEP:
case PT_DETACH:
#ifdef PT_GETREGS
case PT_GETREGS:
#endif
#ifdef PT_SETREGS
case PT_SETREGS:
#endif
#ifdef PT_GETFPREGS
case PT_GETFPREGS:
#endif
#ifdef PT_SETFPREGS
case PT_SETFPREGS:
#endif
#ifdef PT_GETDBREGS
case PT_GETDBREGS:
#endif
#ifdef PT_SETDBREGS
case PT_SETDBREGS:
#endif
/* not being traced... */
if ((p->p_flag & P_TRACED) == 0)
return EPERM;
/* not being traced by YOU */
if (p->p_pptr != curp)
return EBUSY;
/* not currently stopped */
if (p->p_stat != SSTOP || (p->p_flag & P_WAITED) == 0)
return EBUSY;
/* OK */
break;
default:
return EINVAL;
}
#ifdef FIX_SSTEP
/*
* Single step fixup ala procfs
*/
FIX_SSTEP(p);
#endif
/*
* Actually do the requests
*/
curp->p_retval[0] = 0;
switch (uap->req) {
case PT_TRACE_ME:
/* set my trace flag and "owner" so it can read/write me */
p->p_flag |= P_TRACED;
p->p_oppid = p->p_pptr->p_pid;
return 0;
case PT_ATTACH:
/* security check done above */
p->p_flag |= P_TRACED;
p->p_oppid = p->p_pptr->p_pid;
if (p->p_pptr != curp)
proc_reparent(p, curp);
uap->data = SIGSTOP;
goto sendsig; /* in PT_CONTINUE below */
case PT_STEP:
case PT_CONTINUE:
case PT_DETACH:
if ((unsigned)uap->data >= NSIG)
return EINVAL;
PHOLD(p);
if (uap->req == PT_STEP) {
if ((error = ptrace_single_step (p))) {
PRELE(p);
return error;
}
}
if (uap->addr != (caddr_t)1) {
fill_eproc (p, &p->p_addr->u_kproc.kp_eproc);
if ((error = ptrace_set_pc (p,
(u_long)(uintfptr_t)uap->addr))) {
PRELE(p);
return error;
}
}
PRELE(p);
if (uap->req == PT_DETACH) {
/* reset process parent */
if (p->p_oppid != p->p_pptr->p_pid) {
struct proc *pp;
pp = pfind(p->p_oppid);
proc_reparent(p, pp ? pp : initproc);
}
p->p_flag &= ~(P_TRACED | P_WAITED);
p->p_oppid = 0;
/* should we send SIGCHLD? */
}
sendsig:
/* deliver or queue signal */
s = splhigh();
if (p->p_stat == SSTOP) {
p->p_xstat = uap->data;
setrunnable(p);
} else if (uap->data) {
psignal(p, uap->data);
}
splx(s);
return 0;
case PT_WRITE_I:
case PT_WRITE_D:
write = 1;
/* fallthrough */
case PT_READ_I:
case PT_READ_D:
/* write = 0 set above */
iov.iov_base = write ? (caddr_t)&uap->data : (caddr_t)curp->p_retval;
iov.iov_len = sizeof(int);
uio.uio_iov = &iov;
uio.uio_iovcnt = 1;
uio.uio_offset = (off_t)(uintptr_t)uap->addr;
uio.uio_resid = sizeof(int);
uio.uio_segflg = UIO_SYSSPACE; /* ie: the uap */
uio.uio_rw = write ? UIO_WRITE : UIO_READ;
uio.uio_procp = p;
error = procfs_domem(curp, p, NULL, &uio);
if (uio.uio_resid != 0) {
/*
* XXX procfs_domem() doesn't currently return ENOSPC,
* so I think write() can bogusly return 0.
* XXX what happens for short writes? We don't want
* to write partial data.
* XXX procfs_domem() returns EPERM for other invalid
* addresses. Convert this to EINVAL. Does this
* clobber returns of EPERM for other reasons?
*/
if (error == 0 || error == ENOSPC || error == EPERM)
error = EINVAL; /* EOF */
}
return (error);
case PT_READ_U:
if ((uintptr_t)uap->addr > UPAGES * PAGE_SIZE - sizeof(int)) {
return EFAULT;
}
if ((uintptr_t)uap->addr & (sizeof(int) - 1)) {
return EFAULT;
}
if (ptrace_read_u_check(p,(vm_offset_t) uap->addr,
sizeof(int))) {
return EFAULT;
}
error = 0;
PHOLD(p); /* user had damn well better be incore! */
if (p->p_flag & P_INMEM) {
p->p_addr->u_kproc.kp_proc = *p;
fill_eproc (p, &p->p_addr->u_kproc.kp_eproc);
curp->p_retval[0] = *(int *)
((uintptr_t)p->p_addr + (uintptr_t)uap->addr);
} else {
curp->p_retval[0] = 0;
error = EFAULT;
}
PRELE(p);
return error;
case PT_WRITE_U:
PHOLD(p); /* user had damn well better be incore! */
if (p->p_flag & P_INMEM) {
p->p_addr->u_kproc.kp_proc = *p;
fill_eproc (p, &p->p_addr->u_kproc.kp_eproc);
error = ptrace_write_u(p, (vm_offset_t)uap->addr, uap->data);
} else {
error = EFAULT;
}
PRELE(p);
return error;
case PT_KILL:
uap->data = SIGKILL;
goto sendsig; /* in PT_CONTINUE above */
#ifdef PT_SETREGS
case PT_SETREGS:
write = 1;
/* fallthrough */
#endif /* PT_SETREGS */
#ifdef PT_GETREGS
case PT_GETREGS:
/* write = 0 above */
#endif /* PT_SETREGS */
#if defined(PT_SETREGS) || defined(PT_GETREGS)
if (!procfs_validregs(p)) /* no P_SYSTEM procs please */
return EINVAL;
else {
iov.iov_base = uap->addr;
iov.iov_len = sizeof(struct reg);
uio.uio_iov = &iov;
uio.uio_iovcnt = 1;
uio.uio_offset = 0;
uio.uio_resid = sizeof(struct reg);
uio.uio_segflg = UIO_USERSPACE;
uio.uio_rw = write ? UIO_WRITE : UIO_READ;
uio.uio_procp = curp;
return (procfs_doregs(curp, p, NULL, &uio));
}
#endif /* defined(PT_SETREGS) || defined(PT_GETREGS) */
#ifdef PT_SETFPREGS
case PT_SETFPREGS:
write = 1;
/* fallthrough */
#endif /* PT_SETFPREGS */
#ifdef PT_GETFPREGS
case PT_GETFPREGS:
/* write = 0 above */
#endif /* PT_SETFPREGS */
#if defined(PT_SETFPREGS) || defined(PT_GETFPREGS)
if (!procfs_validfpregs(p)) /* no P_SYSTEM procs please */
return EINVAL;
else {
iov.iov_base = uap->addr;
iov.iov_len = sizeof(struct fpreg);
uio.uio_iov = &iov;
uio.uio_iovcnt = 1;
uio.uio_offset = 0;
uio.uio_resid = sizeof(struct fpreg);
uio.uio_segflg = UIO_USERSPACE;
uio.uio_rw = write ? UIO_WRITE : UIO_READ;
uio.uio_procp = curp;
return (procfs_dofpregs(curp, p, NULL, &uio));
}
#endif /* defined(PT_SETFPREGS) || defined(PT_GETFPREGS) */
#ifdef PT_SETDBREGS
case PT_SETDBREGS:
write = 1;
/* fallthrough */
#endif /* PT_SETDBREGS */
#ifdef PT_GETDBREGS
case PT_GETDBREGS:
/* write = 0 above */
#endif /* PT_SETDBREGS */
#if defined(PT_SETDBREGS) || defined(PT_GETDBREGS)
if (!procfs_validdbregs(p)) /* no P_SYSTEM procs please */
return EINVAL;
else {
iov.iov_base = uap->addr;
iov.iov_len = sizeof(struct dbreg);
uio.uio_iov = &iov;
uio.uio_iovcnt = 1;
uio.uio_offset = 0;
uio.uio_resid = sizeof(struct dbreg);
uio.uio_segflg = UIO_USERSPACE;
uio.uio_rw = write ? UIO_WRITE : UIO_READ;
uio.uio_procp = curp;
return (procfs_dodbregs(curp, p, NULL, &uio));
}
#endif /* defined(PT_SETDBREGS) || defined(PT_GETDBREGS) */
default:
break;
}
return 0;
}
int
trace_req(p)
struct proc *p;
{
return 1;
}
/*
* stopevent()
* Stop a process because of a procfs event;
* stay stopped until p->p_step is cleared
* (cleared by PIOCCONT in procfs).
*/
void
stopevent(struct proc *p, unsigned int event, unsigned int val) {
p->p_step = 1;
do {
p->p_xstat = val;
p->p_stype = event; /* Which event caused the stop? */
wakeup(&p->p_stype); /* Wake up any PIOCWAIT'ing procs */
tsleep(&p->p_step, PWAIT, "stopevent", 0);
} while (p->p_step);
}
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