SystemConfiguration.fproj/SCDPlugin.c

   1 /*
   2  * Copyright (c) 2002-2006, 2013 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         /*
 114          * block additional SIGCHLD's until current children have
 115          * been reaped.
 116          */
 117         blockSignal();
 118
 119         /*
 120          * send message to indicate that at least one child is ready
 121          * to be reaped.
 122          */
 123         _SC_sendMachMessage(CFMachPortGetPort(childReaped), 0);
 124
 125         return;
 126 }
 127
 128
 129 static void
 130 childrenReaped(CFMachPortRef port, void *msg, CFIndex size, void *info)
 131 {
 132         pid_t           pid             = 0;
 133         childInfoRef    reapedChildren  = NULL;
 134
 135         do {
 136                 struct rusage   rusage;
 137                 int             status;
 138
 139                 pid = wait4(-1, &status, WNOHANG, &rusage);
 140                 switch (pid) {
 141                         case -1 :       // if error
 142                                 if (errno != ECHILD) {
 143                                         perror("wait4");
 144                                 }
 145                                 break;
 146
 147                         case  0 :       // if no more children
 148                                 break;
 149
 150                         default : {
 151                                 childInfoRef    last;
 152                                 childInfoRef    this;
 153
 154                                 // grab the activeChildren mutex
 155                                 pthread_mutex_lock(&lock);
 156
 157                                 last = NULL;
 158                                 this = activeChildren;
 159                                 while (this) {
 160                                         if (this->pid == pid) {
 161                                                 /* save exit status & usage */
 162                                                 this->status = status;
 163                                                 this->rusage = rusage;
 164
 165                                                 /* remove from activeChildren */
 166                                                 if (last) {
 167                                                         last->next = this->next;
 168                                                 } else {
 169                                                         activeChildren = this->next;
 170                                                 }
 171
 172                                                 /* add to reapedChildren */
 173                                                 this->next = reapedChildren;
 174                                                 reapedChildren = this;
 175
 176                                                 break;
 177                                         } else {
 178                                                 /* if not this child */
 179                                                 last = this;
 180                                                 this = this->next;
 181                                         }
 182                                 }
 183
 184                                 // release the activeChildren mutex
 185                                 pthread_mutex_unlock(&lock);
 186
 187                                 break;
 188                         }
 189                 }
 190         } while (pid > 0);
 191
 192         /*
 193          * we need to know about any new children waiting to be reaped so
 194          * re-enable the SIGCHLD handler.
 195
 196          */
 197         unblockSignal();
 198
 199         while (reapedChildren) {
 200                 childInfoRef    child = reapedChildren;
 201
 202                 reapedChildren = reapedChildren->next;
 203                 (*child->callout)(child->pid,
 204                                   child->status,
 205                                   &child->rusage,
 206                                   child->context);
 207                 CFAllocatorDeallocate(NULL, child);
 208         }
 209
 210         return;
 211 }
 212
 213
 214 static CFStringRef
 215 childReapedMPCopyDescription(const void *info)
 216 {
 217         return CFStringCreateWithFormat(NULL, NULL, CFSTR("<SIGCHLD MP>"));
 218 }
 219
 220
 221 void
 222 _SCDPluginExecInit()
 223 {
 224         struct sigaction        act;
 225         CFMachPortContext       context = { 0
 226                                           , (void *)1
 227                                           , NULL
 228                                           , NULL
 229                                           , childReapedMPCopyDescription
 230                                           };
 231
 232         CFRunLoopSourceRef      rls;
 233
 234         // create the "a child has been reaped" notification port
 235         childReaped = CFMachPortCreate(NULL, childrenReaped, &context, NULL);
 236
 237         // set queue limit
 238         {
 239                 mach_port_limits_t      limits;
 240                 kern_return_t           status;
 241
 242                 limits.mpl_qlimit = 1;
 243                 status = mach_port_set_attributes(mach_task_self(),
 244                                                   CFMachPortGetPort(childReaped),
 245                                                   MACH_PORT_LIMITS_INFO,
 246                                                   (mach_port_info_t)&limits,
 247                                                   MACH_PORT_LIMITS_INFO_COUNT);
 248                 if (status != KERN_SUCCESS) {
 249                         perror("mach_port_set_attributes");
 250                 }
 251         }
 252
 253         // add to our runloop
 254         rls = CFMachPortCreateRunLoopSource(NULL, childReaped, 0);
 255         CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopDefaultMode);
 256         CFRelease(rls);
 257
 258         // enable signal handler
 259         act.sa_handler = reaper;
 260         sigemptyset(&act.sa_mask);
 261         act.sa_flags = SA_RESTART|SA_NOCLDSTOP;
 262         if (sigaction(SIGCHLD, &act, NULL) == -1) {
 263                 perror("sigaction");
 264         }
 265
 266         return;
 267 }
 268
 269
 270 pid_t
 271 _SCDPluginExecCommand2(SCDPluginExecCallBack    callout,
 272                        void                     *context,
 273                        uid_t                    uid,
 274                        gid_t                    gid,
 275                        const char               *path,
 276                        char * const             argv[],
 277                        SCDPluginExecSetup       setup,
 278                        void                     *setupContext
 279                        )
 280 {
 281         char            buf[1024];
 282         pid_t           pid;
 283         struct passwd   pwd;
 284         struct passwd   *result = NULL;
 285         char            *username = NULL;
 286
 287         // grab the activeChildren mutex
 288         pthread_mutex_lock(&lock);
 289
 290         // cache the getpwuid_r result here to avoid spinning that can happen
 291         // when calling it between fork and execv.
 292         if ((getpwuid_r(uid, &pwd, buf, sizeof(buf), &result) == 0) &&
 293             (result != NULL)) {
 294                 username = result->pw_name;
 295         }
 296
 297         // if needed, initialize
 298         if (childReaped == NULL) {
 299                 _SCDPluginExecInit();
 300         }
 301
 302         pid = fork();
 303
 304         switch (pid) {
 305                 case -1 : {     /* if error */
 306
 307                         int     status;
 308
 309                         status = errno;
 310                         printf("fork() failed: %s\n", strerror(status));
 311                         errno  = status;
 312                         break;
 313                 }
 314
 315                 case 0 : {      /* if child */
 316
 317                         gid_t   egid;
 318                         uid_t   euid;
 319                         int     i;
 320                         int     status;
 321
 322                         if (setup != NULL) {
 323                                 (setup)(pid, setupContext);
 324                         } else {
 325                                 /* close any open FDs */
 326                                 for (i = getdtablesize()-1; i>=0; i--) close(i);
 327                                 open(_PATH_DEVNULL, O_RDWR, 0);
 328                                 dup(0);
 329                                 dup(0);
 330                         }
 331
 332                         egid = getegid();
 333                         euid = geteuid();
 334
 335                         if (egid != gid) {
 336                                 (void) setgid(gid);
 337                         }
 338
 339                         if (((euid != uid) || (egid != gid)) && username) {
 340                                 initgroups(username, gid);
 341                         }
 342
 343                         if (euid != uid) {
 344                                 (void) setuid(uid);
 345                         }
 346
 347                         /* ensure that our PATH environment variable is somewhat reasonable */
 348                         if (setenv("PATH", "/bin:/sbin:/usr/bin:/usr/sbin", 0) == -1) {
 349                                 printf("setenv() failed: %s\n", strerror(errno));
 350                                 exit(EX_OSERR);
 351                         }
 352
 353                         /* execute requested command */
 354                         (void) execv(path, argv);
 355
 356                         /* if the execv failed */
 357                         status = W_EXITCODE(errno, 0);
 358                         _exit (WEXITSTATUS(status));
 359                 }
 360
 361                 default : {     /* if parent */
 362                         if (setup != NULL) {
 363                                 (setup)(pid, setupContext);
 364                         }
 365
 366                         if (callout != NULL) {
 367                                 childInfoRef    child;
 368
 369                                 // create child process info
 370                                 child = CFAllocatorAllocate(NULL, sizeof(struct childInfo), 0);
 371                                 bzero(child, sizeof(struct childInfo));
 372                                 child->pid     = pid;
 373                                 child->callout = callout;
 374                                 child->context = context;
 375
 376                                 // add the new child to the activeChildren list
 377                                 child->next = activeChildren;
 378                                 activeChildren = child;
 379                         }
 380                         break;
 381                 }
 382         }
 383
 384         // release the activeChildren mutex
 385         pthread_mutex_unlock(&lock);
 386
 387         return pid;
 388 }
 389
 390
 391 pid_t
 392 _SCDPluginExecCommand(SCDPluginExecCallBack     callout,
 393                      void                       *context,
 394                      uid_t                      uid,
 395                      gid_t                      gid,
 396                      const char                 *path,
 397                      char * const               argv[])
 398 {
 399         return _SCDPluginExecCommand2(callout, context, uid, gid, path, argv, NULL, NULL);
 400 }