bsd/kern/mach_process.c

   1 /*
   2  * Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
  29 /*-
  30  * Copyright (c) 1982, 1986, 1989, 1993
  31  *      The Regents of the University of California.  All rights reserved.
  32  * (c) UNIX System Laboratories, Inc.
  33  * All or some portions of this file are derived from material licensed
  34  * to the University of California by American Telephone and Telegraph
  35  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
  36  * the permission of UNIX System Laboratories, Inc.
  37  *
  38  * Redistribution and use in source and binary forms, with or without
  39  * modification, are permitted provided that the following conditions
  40  * are met:
  41  * 1. Redistributions of source code must retain the above copyright
  42  *    notice, this list of conditions and the following disclaimer.
  43  * 2. Redistributions in binary form must reproduce the above copyright
  44  *    notice, this list of conditions and the following disclaimer in the
  45  *    documentation and/or other materials provided with the distribution.
  46  * 3. All advertising materials mentioning features or use of this software
  47  *    must display the following acknowledgement:
  48  *      This product includes software developed by the University of
  49  *      California, Berkeley and its contributors.
  50  * 4. Neither the name of the University nor the names of its contributors
  51  *    may be used to endorse or promote products derived from this software
  52  *    without specific prior written permission.
  53  *
  54  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  55  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  56  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  57  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  58  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  59  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  60  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  61  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  62  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  63  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  64  * SUCH DAMAGE.
  65  *
  66  *      from: @(#)sys_process.c 8.1 (Berkeley) 6/10/93
  67  */
  68
  69 #include <machine/reg.h>
  70 #include <machine/psl.h>
  71
  72 #include <sys/param.h>
  73 #include <sys/systm.h>
  74 #include <sys/proc_internal.h>
  75 #include <sys/kauth.h>
  76 #include <sys/errno.h>
  77 #include <sys/ptrace.h>
  78 #include <sys/uio.h>
  79 #include <sys/user.h>
  80 #include <sys/sysctl.h>
  81 #include <sys/wait.h>
  82
  83 #include <sys/mount_internal.h>
  84 #include <sys/sysproto.h>
  85 #include <sys/kdebug.h>
  86 #include <sys/codesign.h>               /* cs_allow_invalid() */
  87
  88 #include <security/audit/audit.h>
  89
  90 #include <kern/task.h>
  91 #include <kern/thread.h>
  92
  93 #include <mach/task.h>                  /* for task_resume() */
  94 #include <kern/sched_prim.h>            /* for thread_exception_return() */
  95
  96 #include <pexpert/pexpert.h>
  97
  98 #if CONFIG_MACF
  99 #include <security/mac_framework.h>
 100 #endif
 101
 102 /* XXX ken/bsd_kern.c - prototype should be in common header */
 103 int get_task_userstop(task_t);
 104
 105 /* Macros to clear/set/test flags. */
 106 #define SET(t, f)       (t) |= (f)
 107 #define CLR(t, f)       (t) &= ~(f)
 108 #define ISSET(t, f)     ((t) & (f))
 109
 110 extern thread_t get_firstthread(task_t);
 111
 112
 113 /*
 114  * sys-trace system call.
 115  */
 116
 117 int
 118 ptrace(struct proc *p, struct ptrace_args *uap, int32_t *retval)
 119 {
 120         struct proc *t = current_proc();        /* target process */
 121         task_t          task;
 122         thread_t        th_act;
 123         struct uthread  *ut;
 124         int tr_sigexc = 0;
 125         int error = 0;
 126         int stopped = 0;
 127
 128         AUDIT_ARG(cmd, uap->req);
 129         AUDIT_ARG(pid, uap->pid);
 130         AUDIT_ARG(addr, uap->addr);
 131         AUDIT_ARG(value32, uap->data);
 132
 133         if (uap->req == PT_DENY_ATTACH) {
 134 #if (DEVELOPMENT || DEBUG) && CONFIG_EMBEDDED
 135                 if (PE_i_can_has_debugger(NULL)) {
 136                         return 0;
 137                 }
 138 #endif
 139                 proc_lock(p);
 140                 if (ISSET(p->p_lflag, P_LTRACED)) {
 141                         proc_unlock(p);
 142                         KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_FRCEXIT) | DBG_FUNC_NONE,
 143                             p->p_pid, W_EXITCODE(ENOTSUP, 0), 4, 0, 0);
 144                         exit1(p, W_EXITCODE(ENOTSUP, 0), retval);
 145
 146                         thread_exception_return();
 147                         /* NOTREACHED */
 148                 }
 149                 SET(p->p_lflag, P_LNOATTACH);
 150                 proc_unlock(p);
 151
 152                 return 0;
 153         }
 154
 155         if (uap->req == PT_FORCEQUOTA) {
 156                 if (kauth_cred_issuser(kauth_cred_get())) {
 157                         OSBitOrAtomic(P_FORCEQUOTA, &t->p_flag);
 158                         return 0;
 159                 } else {
 160                         return EPERM;
 161                 }
 162         }
 163
 164         /*
 165          *      Intercept and deal with "please trace me" request.
 166          */
 167         if (uap->req == PT_TRACE_ME) {
 168 retry_trace_me: ;
 169                 proc_t pproc = proc_parent(p);
 170                 if (pproc == NULL) {
 171                         return EINVAL;
 172                 }
 173 #if CONFIG_MACF
 174                 /*
 175                  * NB: Cannot call kauth_authorize_process(..., KAUTH_PROCESS_CANTRACE, ...)
 176                  *     since that assumes the process being checked is the current process
 177                  *     when, in this case, it is the current process's parent.
 178                  *     Most of the other checks in cantrace() don't apply either.
 179                  */
 180                 if ((error = mac_proc_check_debug(pproc, p)) == 0) {
 181 #endif
 182                 proc_lock(p);
 183                 /* Make sure the process wasn't re-parented. */
 184                 if (p->p_ppid != pproc->p_pid) {
 185                         proc_unlock(p);
 186                         proc_rele(pproc);
 187                         goto retry_trace_me;
 188                 }
 189                 SET(p->p_lflag, P_LTRACED);
 190                 /* Non-attached case, our tracer is our parent. */
 191                 p->p_oppid = p->p_ppid;
 192                 proc_unlock(p);
 193                 /* Child and parent will have to be able to run modified code. */
 194                 cs_allow_invalid(p);
 195                 cs_allow_invalid(pproc);
 196 #if CONFIG_MACF
 197         }
 198 #endif
 199                 proc_rele(pproc);
 200                 return error;
 201         }
 202         if (uap->req == PT_SIGEXC) {
 203                 proc_lock(p);
 204                 if (ISSET(p->p_lflag, P_LTRACED)) {
 205                         SET(p->p_lflag, P_LSIGEXC);
 206                         proc_unlock(p);
 207                         return 0;
 208                 } else {
 209                         proc_unlock(p);
 210                         return EINVAL;
 211                 }
 212         }
 213
 214         /*
 215          * We do not want ptrace to do anything with kernel or launchd
 216          */
 217         if (uap->pid < 2) {
 218                 return EPERM;
 219         }
 220
 221         /*
 222          *      Locate victim, and make sure it is traceable.
 223          */
 224         if ((t = proc_find(uap->pid)) == NULL) {
 225                 return ESRCH;
 226         }
 227
 228         AUDIT_ARG(process, t);
 229
 230         task = t->task;
 231         if (uap->req == PT_ATTACHEXC) {
 232 #pragma clang diagnostic push
 233 #pragma clang diagnostic ignored "-Wdeprecated-declarations"
 234                 uap->req = PT_ATTACH;
 235                 tr_sigexc = 1;
 236         }
 237         if (uap->req == PT_ATTACH) {
 238 #pragma clang diagnostic pop
 239                 int             err;
 240
 241 #if CONFIG_EMBEDDED
 242                 if (tr_sigexc == 0) {
 243                         error = ENOTSUP;
 244                         goto out;
 245                 }
 246 #endif
 247
 248                 if (kauth_authorize_process(proc_ucred(p), KAUTH_PROCESS_CANTRACE,
 249                     t, (uintptr_t)&err, 0, 0) == 0) {
 250                         /* it's OK to attach */
 251                         proc_lock(t);
 252                         SET(t->p_lflag, P_LTRACED);
 253                         if (tr_sigexc) {
 254                                 SET(t->p_lflag, P_LSIGEXC);
 255                         }
 256
 257                         t->p_oppid = t->p_ppid;
 258                         /* Check whether child and parent are allowed to run modified
 259                          * code (they'll have to) */
 260                         proc_unlock(t);
 261                         cs_allow_invalid(t);
 262                         cs_allow_invalid(p);
 263                         if (t->p_pptr != p) {
 264                                 proc_reparentlocked(t, p, 1, 0);
 265                         }
 266
 267                         proc_lock(t);
 268                         if (get_task_userstop(task) > 0) {
 269                                 stopped = 1;
 270                         }
 271                         t->p_xstat = 0;
 272                         proc_unlock(t);
 273                         psignal(t, SIGSTOP);
 274                         /*
 275                          * If the process was stopped, wake up and run through
 276                          * issignal() again to properly connect to the tracing
 277                          * process.
 278                          */
 279                         if (stopped) {
 280                                 task_resume(task);
 281                         }
 282                         error = 0;
 283                         goto out;
 284                 } else {
 285                         /* not allowed to attach, proper error code returned by kauth_authorize_process */
 286                         if (ISSET(t->p_lflag, P_LNOATTACH)) {
 287                                 psignal(p, SIGSEGV);
 288                         }
 289
 290                         error = err;
 291                         goto out;
 292                 }
 293         }
 294
 295         /*
 296          * You can't do what you want to the process if:
 297          *      (1) It's not being traced at all,
 298          */
 299         proc_lock(t);
 300         if (!ISSET(t->p_lflag, P_LTRACED)) {
 301                 proc_unlock(t);
 302                 error = EPERM;
 303                 goto out;
 304         }
 305
 306         /*
 307          *      (2) it's not being traced by _you_, or
 308          */
 309         if (t->p_pptr != p) {
 310                 proc_unlock(t);
 311                 error = EBUSY;
 312                 goto out;
 313         }
 314
 315         /*
 316          *      (3) it's not currently stopped.
 317          */
 318         if (t->p_stat != SSTOP) {
 319                 proc_unlock(t);
 320                 error = EBUSY;
 321                 goto out;
 322         }
 323
 324         /*
 325          *      Mach version of ptrace executes request directly here,
 326          *      thus simplifying the interaction of ptrace and signals.
 327          */
 328         /* proc lock is held here */
 329         switch (uap->req) {
 330         case PT_DETACH:
 331                 if (t->p_oppid != t->p_ppid) {
 332                         struct proc *pp;
 333
 334                         proc_unlock(t);
 335                         pp = proc_find(t->p_oppid);
 336                         if (pp != PROC_NULL) {
 337                                 proc_reparentlocked(t, pp, 1, 0);
 338                                 proc_rele(pp);
 339                         } else {
 340                                 /* original parent exited while traced */
 341                                 proc_list_lock();
 342                                 t->p_listflag |= P_LIST_DEADPARENT;
 343                                 proc_list_unlock();
 344                                 proc_reparentlocked(t, initproc, 1, 0);
 345                         }
 346                         proc_lock(t);
 347                 }
 348
 349                 t->p_oppid = 0;
 350                 CLR(t->p_lflag, P_LTRACED);
 351                 CLR(t->p_lflag, P_LSIGEXC);
 352                 proc_unlock(t);
 353                 goto resume;
 354
 355         case PT_KILL:
 356                 /*
 357                  *      Tell child process to kill itself after it
 358                  *      is resumed by adding NSIG to p_cursig. [see issig]
 359                  */
 360                 proc_unlock(t);
 361 #if CONFIG_MACF
 362                 error = mac_proc_check_signal(p, t, SIGKILL);
 363                 if (0 != error) {
 364                         goto resume;
 365                 }
 366 #endif
 367                 psignal(t, SIGKILL);
 368                 goto resume;
 369
 370         case PT_STEP:                   /* single step the child */
 371         case PT_CONTINUE:               /* continue the child */
 372                 proc_unlock(t);
 373                 th_act = (thread_t)get_firstthread(task);
 374                 if (th_act == THREAD_NULL) {
 375                         error = EINVAL;
 376                         goto out;
 377                 }
 378
 379                 /* force use of Mach SPIs (and task_for_pid security checks) to adjust PC */
 380                 if (uap->addr != (user_addr_t)1) {
 381                         error = ENOTSUP;
 382                         goto out;
 383                 }
 384
 385                 if ((unsigned)uap->data >= NSIG) {
 386                         error = EINVAL;
 387                         goto out;
 388                 }
 389
 390                 if (uap->data != 0) {
 391 #if CONFIG_MACF
 392                         error = mac_proc_check_signal(p, t, uap->data);
 393                         if (0 != error) {
 394                                 goto out;
 395                         }
 396 #endif
 397                         psignal(t, uap->data);
 398                 }
 399
 400                 if (uap->req == PT_STEP) {
 401                         /*
 402                          * set trace bit
 403                          * we use sending SIGSTOP as a comparable security check.
 404                          */
 405 #if CONFIG_MACF
 406                         error = mac_proc_check_signal(p, t, SIGSTOP);
 407                         if (0 != error) {
 408                                 goto out;
 409                         }
 410 #endif
 411                         if (thread_setsinglestep(th_act, 1) != KERN_SUCCESS) {
 412                                 error = ENOTSUP;
 413                                 goto out;
 414                         }
 415                 } else {
 416                         /*
 417                          * clear trace bit if on
 418                          * we use sending SIGCONT as a comparable security check.
 419                          */
 420 #if CONFIG_MACF
 421                         error = mac_proc_check_signal(p, t, SIGCONT);
 422                         if (0 != error) {
 423                                 goto out;
 424                         }
 425 #endif
 426                         if (thread_setsinglestep(th_act, 0) != KERN_SUCCESS) {
 427                                 error = ENOTSUP;
 428                                 goto out;
 429                         }
 430                 }
 431 resume:
 432                 proc_lock(t);
 433                 t->p_xstat = uap->data;
 434                 t->p_stat = SRUN;
 435                 if (t->sigwait) {
 436                         wakeup((caddr_t)&(t->sigwait));
 437                         proc_unlock(t);
 438                         if ((t->p_lflag & P_LSIGEXC) == 0) {
 439                                 task_resume(task);
 440                         }
 441                 } else {
 442                         proc_unlock(t);
 443                 }
 444
 445                 break;
 446
 447         case PT_THUPDATE:  {
 448                 proc_unlock(t);
 449                 if ((unsigned)uap->data >= NSIG) {
 450                         error = EINVAL;
 451                         goto out;
 452                 }
 453                 th_act = port_name_to_thread(CAST_MACH_PORT_TO_NAME(uap->addr),
 454                     PORT_TO_THREAD_NONE);
 455                 if (th_act == THREAD_NULL) {
 456                         error = ESRCH;
 457                         goto out;
 458                 }
 459                 ut = (uthread_t)get_bsdthread_info(th_act);
 460                 if (uap->data) {
 461                         ut->uu_siglist |= sigmask(uap->data);
 462                 }
 463                 proc_lock(t);
 464                 t->p_xstat = uap->data;
 465                 t->p_stat = SRUN;
 466                 proc_unlock(t);
 467                 thread_deallocate(th_act);
 468                 error = 0;
 469         }
 470         break;
 471         default:
 472                 proc_unlock(t);
 473                 error = EINVAL;
 474                 goto out;
 475         }
 476
 477         error = 0;
 478 out:
 479         proc_rele(t);
 480         return error;
 481 }
 482
 483
 484 /*
 485  * determine if one process (cur_procp) can trace another process (traced_procp).
 486  */
 487
 488 int
 489 cantrace(proc_t cur_procp, kauth_cred_t creds, proc_t traced_procp, int *errp)
 490 {
 491         int             my_err;
 492         /*
 493          * You can't trace a process if:
 494          *      (1) it's the process that's doing the tracing,
 495          */
 496         if (traced_procp->p_pid == cur_procp->p_pid) {
 497                 *errp = EINVAL;
 498                 return 0;
 499         }
 500
 501         /*
 502          *      (2) it's already being traced, or
 503          */
 504         if (ISSET(traced_procp->p_lflag, P_LTRACED)) {
 505                 *errp = EBUSY;
 506                 return 0;
 507         }
 508
 509         /*
 510          *      (3) it's not owned by you, or is set-id on exec
 511          *          (unless you're root).
 512          */
 513         if ((kauth_cred_getruid(creds) != kauth_cred_getruid(proc_ucred(traced_procp)) ||
 514             ISSET(traced_procp->p_flag, P_SUGID)) &&
 515             (my_err = suser(creds, &cur_procp->p_acflag)) != 0) {
 516                 *errp = my_err;
 517                 return 0;
 518         }
 519
 520         if ((cur_procp->p_lflag & P_LTRACED) && isinferior(cur_procp, traced_procp)) {
 521                 *errp = EPERM;
 522                 return 0;
 523         }
 524
 525         if (ISSET(traced_procp->p_lflag, P_LNOATTACH)) {
 526                 *errp = EBUSY;
 527                 return 0;
 528         }
 529
 530 #if CONFIG_MACF
 531         if ((my_err = mac_proc_check_debug(cur_procp, traced_procp)) != 0) {
 532                 *errp = my_err;
 533                 return 0;
 534         }
 535 #endif
 536
 537         return 1;
 538 }