SystemConfiguration.fproj/SCDPlugin.c

   1 /*
   2  * Copyright (c) 2002-2006, 2013, 2015, 2017, 2018 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_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. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 /*
  25  * Modification History
  26  *
  27  * October 12, 2001             Allan Nathanson <ajn@apple.com>
  28  * - initial revision
  29  */
  30
  31 #include <fcntl.h>
  32 #include <paths.h>
  33 #include <pwd.h>
  34 #include <pthread.h>
  35 #include <unistd.h>
  36 #include <sysexits.h>
  37 #include <sys/types.h>
  38 #include <sys/ioctl.h>
  39 #include <sys/socket.h>
  40 #include <sys/wait.h>
  41 #include <mach/mach.h>
  42 #include <mach/mach_error.h>
  43
  44 #include <CoreFoundation/CoreFoundation.h>
  45 #include <SystemConfiguration/SCDPlugin.h>
  46 #include <SystemConfiguration/SCPrivate.h>
  47
  48
  49
  50 typedef struct childInfo *childInfoRef;
  51
  52 struct childInfo {
  53         pid_t                   pid;
  54         SCDPluginExecCallBack   callout;
  55         void                    *context;
  56         int                     status;
  57         struct rusage           rusage;
  58         childInfoRef            next;
  59 };
  60
  61
  62 /*
  63  * Mach port used to notify runloop when a child process
  64  * has been reaped.
  65  */
  66 static CFMachPortRef    childReaped     = NULL;
  67
  68 /*
  69  * The following dictionaries contain information about child
  70  * processes, reaped processes, and any associated callback
  71  * information.
  72  *
  73  * Important: Access to these dictionaries should only be
  74  *            made when in a SIGCHLD handler (or when the
  75  *            childLock mutex is held *AND* the signal
  76  *            has been blocked).
  77  */
  78 static childInfoRef     activeChildren  = NULL;
  79 static pthread_mutex_t  lock            = PTHREAD_MUTEX_INITIALIZER;
  80
  81
  82 static __inline__ void
  83 blockSignal()
  84 {
  85         sigset_t        mask    = sigmask(SIGCHLD);
  86
  87         // block SIGCHLD
  88         if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1) {
  89                 perror("sigprocmask(SIG_BLOCK)");
  90         }
  91
  92         return;
  93 }
  94
  95
  96 static __inline__ void
  97 unblockSignal()
  98 {
  99         sigset_t        mask    = sigmask(SIGCHLD);
 100
 101         // unblock SIGCHLD
 102         if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1) {
 103                 perror("sigprocmask(SIG_UNBLOCK)");
 104         }
 105
 106         return;
 107 }
 108
 109
 110 static void
 111 reaper(int sigraised)
 112 {
 113 #pragma unused(sigraised)
 114         /*
 115          * block additional SIGCHLD's until current children have
 116          * been reaped.
 117          */
 118         blockSignal();
 119
 120         /*
 121          * send message to indicate that at least one child is ready
 122          * to be reaped.
 123          */
 124         _SC_sendMachMessage(CFMachPortGetPort(childReaped), 0);
 125
 126         return;
 127 }
 128
 129
 130 static void
 131 childrenReaped(CFMachPortRef port, void *msg, CFIndex size, void *info)
 132 {
 133 #pragma unused(port)
 134 #pragma unused(msg)
 135 #pragma unused(size)
 136 #pragma unused(info)
 137         pid_t           pid             = 0;
 138         childInfoRef    reapedChildren  = NULL;
 139
 140         do {
 141                 struct rusage   rusage;
 142                 int             status;
 143
 144                 pid = wait4(-1, &status, WNOHANG, &rusage);
 145                 switch (pid) {
 146                         case -1 :       // if error
 147                                 if (errno != ECHILD) {
 148                                         perror("wait4");
 149                                 }
 150                                 break;
 151
 152                         case  0 :       // if no more children
 153                                 break;
 154
 155                         default : {
 156                                 childInfoRef    last;
 157                                 childInfoRef    this;
 158
 159                                 // grab the activeChildren mutex
 160                                 pthread_mutex_lock(&lock);
 161
 162                                 last = NULL;
 163                                 this = activeChildren;
 164                                 while (this) {
 165                                         if (this->pid == pid) {
 166                                                 /* save exit status & usage */
 167                                                 this->status = status;
 168                                                 this->rusage = rusage;
 169
 170                                                 /* remove from activeChildren */
 171                                                 if (last) {
 172                                                         last->next = this->next;
 173                                                 } else {
 174                                                         activeChildren = this->next;
 175                                                 }
 176
 177                                                 /* add to reapedChildren */
 178                                                 this->next = reapedChildren;
 179                                                 reapedChildren = this;
 180
 181                                                 break;
 182                                         } else {
 183                                                 /* if not this child */
 184                                                 last = this;
 185                                                 this = this->next;
 186                                         }
 187                                 }
 188
 189                                 // release the activeChildren mutex
 190                                 pthread_mutex_unlock(&lock);
 191
 192                                 break;
 193                         }
 194                 }
 195         } while (pid > 0);
 196
 197         /*
 198          * we need to know about any new children waiting to be reaped so
 199          * re-enable the SIGCHLD handler.
 200
 201          */
 202         unblockSignal();
 203
 204         while (reapedChildren) {
 205                 childInfoRef    child = reapedChildren;
 206
 207                 reapedChildren = reapedChildren->next;
 208                 (*child->callout)(child->pid,
 209                                   child->status,
 210                                   &child->rusage,
 211                                   child->context);
 212                 CFAllocatorDeallocate(NULL, child);
 213         }
 214
 215         return;
 216 }
 217
 218
 219 static CFStringRef
 220 childReapedMPCopyDescription(const void *info)
 221 {
 222 #pragma unused(info)
 223         return CFStringCreateWithFormat(NULL, NULL, CFSTR("<SIGCHLD MP>"));
 224 }
 225
 226
 227 void
 228 _SCDPluginExecInit(void)
 229 {
 230         struct sigaction        act;
 231         CFMachPortContext       context = { 0
 232                                           , (void *)1
 233                                           , NULL
 234                                           , NULL
 235                                           , childReapedMPCopyDescription
 236                                           };
 237
 238         CFRunLoopSourceRef      rls;
 239
 240         // create the "a child has been reaped" notification port
 241         childReaped = CFMachPortCreate(NULL, childrenReaped, &context, NULL);
 242
 243         // set queue limit
 244         {
 245                 mach_port_limits_t      limits;
 246                 kern_return_t           status;
 247
 248                 limits.mpl_qlimit = 1;
 249                 status = mach_port_set_attributes(mach_task_self(),
 250                                                   CFMachPortGetPort(childReaped),
 251                                                   MACH_PORT_LIMITS_INFO,
 252                                                   (mach_port_info_t)&limits,
 253                                                   MACH_PORT_LIMITS_INFO_COUNT);
 254                 if (status != KERN_SUCCESS) {
 255                         perror("mach_port_set_attributes");
 256                 }
 257         }
 258
 259         // add to our runloop
 260         rls = CFMachPortCreateRunLoopSource(NULL, childReaped, 0);
 261         CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopDefaultMode);
 262         CFRelease(rls);
 263
 264         // enable signal handler
 265         act.sa_handler = reaper;
 266         sigemptyset(&act.sa_mask);
 267         act.sa_flags = SA_RESTART|SA_NOCLDSTOP;
 268         if (sigaction(SIGCHLD, &act, NULL) == -1) {
 269                 perror("sigaction");
 270         }
 271
 272         return;
 273 }
 274
 275
 276 pid_t
 277 _SCDPluginExecCommand2(SCDPluginExecCallBack    callout,
 278                        void                     *context,
 279                        uid_t                    uid,
 280                        gid_t                    gid,
 281                        const char               *path,
 282                        char * const             argv[],
 283                        SCDPluginExecSetup       setup,
 284                        void                     *setupContext
 285                        )
 286 {
 287         char            buf[1024];
 288         pid_t           pid;
 289         struct passwd   pwd;
 290         struct passwd   *result = NULL;
 291         char            *username = NULL;
 292
 293         // grab the activeChildren mutex
 294         pthread_mutex_lock(&lock);
 295
 296         // cache the getpwuid_r result here to avoid spinning that can happen
 297         // when calling it between fork and execv.
 298         if ((getpwuid_r(uid, &pwd, buf, sizeof(buf), &result) == 0) &&
 299             (result != NULL)) {
 300                 username = result->pw_name;
 301         }
 302
 303         // if needed, initialize
 304         if (childReaped == NULL) {
 305                 _SCDPluginExecInit();
 306         }
 307
 308         pid = fork();
 309
 310         switch (pid) {
 311                 case -1 : {     /* if error */
 312
 313                         int     status;
 314
 315                         status = errno;
 316                         printf("fork() failed: %s\n", strerror(status));
 317                         errno  = status;
 318                         break;
 319                 }
 320
 321                 case 0 : {      /* if child */
 322
 323                         gid_t   egid;
 324                         uid_t   euid;
 325                         int     status;
 326
 327                         if (setup != NULL) {
 328                                 (setup)(pid, setupContext);
 329                         } else {
 330                                 int     fd;
 331                                 int     i;
 332
 333                                 /* close any open FDs */
 334                                 for (i = getdtablesize()-1; i>=0; i--) close(i);
 335
 336                                 /* stdin, stdout, stderr */
 337                                 fd = open(_PATH_DEVNULL, O_RDWR, 0);
 338                                 if (fd != -1) {
 339                                         (void) dup2(fd, STDIN_FILENO);
 340                                         (void) dup2(fd, STDOUT_FILENO);
 341                                         (void) dup2(fd, STDERR_FILENO);
 342                                         if ((fd != STDIN_FILENO) && (fd != STDOUT_FILENO) && (fd != STDERR_FILENO)) {
 343                                                 (void) close(fd);
 344                                         }
 345
 346                                 }
 347                         }
 348
 349                         egid = getegid();
 350                         euid = geteuid();
 351
 352                         if (egid != gid) {
 353                                 (void) setgid(gid);
 354                         }
 355
 356                         if (((euid != uid) || (egid != gid)) && username) {
 357                                 initgroups(username, gid);
 358                         }
 359
 360                         if (euid != uid) {
 361                                 (void) setuid(uid);
 362                         }
 363
 364                         /* ensure that our PATH environment variable is somewhat reasonable */
 365                         if (setenv("PATH", "/bin:/sbin:/usr/bin:/usr/sbin", 0) == -1) {
 366                                 printf("setenv() failed: %s\n", strerror(errno));
 367                                 exit(EX_OSERR);
 368                         }
 369
 370                         /* execute requested command */
 371                         (void) execv(path, argv);
 372
 373                         /* if the execv failed */
 374                         status = W_EXITCODE(errno, 0);
 375                         _exit (WEXITSTATUS(status));
 376                 }
 377
 378                 default : {     /* if parent */
 379                         if (setup != NULL) {
 380                                 (setup)(pid, setupContext);
 381                         }
 382
 383                         if (callout != NULL) {
 384                                 childInfoRef    child;
 385
 386                                 // create child process info
 387                                 child = CFAllocatorAllocate(NULL, sizeof(struct childInfo), 0);
 388                                 memset(child, 0, sizeof(struct childInfo));
 389                                 child->pid     = pid;
 390                                 child->callout = callout;
 391                                 child->context = context;
 392
 393                                 // add the new child to the activeChildren list
 394                                 child->next = activeChildren;
 395                                 activeChildren = child;
 396                         }
 397                         break;
 398                 }
 399         }
 400
 401         // release the activeChildren mutex
 402         pthread_mutex_unlock(&lock);
 403
 404         return pid;
 405 }
 406
 407
 408 pid_t
 409 _SCDPluginExecCommand(SCDPluginExecCallBack     callout,
 410                      void                       *context,
 411                      uid_t                      uid,
 412                      gid_t                      gid,
 413                      const char                 *path,
 414                      char * const               argv[])
 415 {
 416         return _SCDPluginExecCommand2(callout, context, uid, gid, path, argv, NULL, NULL);
 417 }