SecurityServer/Authorization/trampolineClient.cpp

   1 /*
   2  * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 //
  20 // trampolineClient - Authorization trampoline client-side implementation
  21 //
  22 #include <sys/types.h>
  23 #include <unistd.h>
  24 #include <errno.h>
  25 #include <fcntl.h>
  26 #include <stdlib.h>
  27 #include <sys/socket.h>
  28 #include <Security/Authorization.h>
  29 #include <Security/debugging.h>
  30
  31 //
  32 // Where is the trampoline itself?
  33 //
  34 #if !defined(TRAMPOLINE)
  35 # define TRAMPOLINE "/System/Library/CoreServices/AuthorizationTrampoline" /* fallback */
  36 #endif
  37
  38
  39 //
  40 // A few names for clarity's sake
  41 //
  42 enum {
  43         READ = 0,               // read end of standard UNIX pipe
  44         WRITE = 1               // write end of standard UNIX pipe
  45 };
  46
  47
  48 //
  49 // Local (static) functions
  50 //
  51 static const char **argVector(const char *trampoline,
  52         const char *tool, const char *commFd,
  53         char *const *arguments);
  54
  55
  56 //
  57 // The public client API function.
  58 //
  59 OSStatus AuthorizationExecuteWithPrivileges(AuthorizationRef authorization,
  60         const char *pathToTool,
  61         unsigned long flags,
  62         char *const *arguments,
  63         FILE **communicationsPipe)
  64 {
  65         // flags are currently reserved
  66         if (flags != 0)
  67                 return errAuthorizationInvalidFlags;
  68
  69         // externalize the authorization
  70         AuthorizationExternalForm extForm;
  71         if (OSStatus err = AuthorizationMakeExternalForm(authorization, &extForm))
  72                 return err;
  73
  74     // create the mailbox file
  75     FILE *mbox = tmpfile();
  76     if (!mbox)
  77         return errAuthorizationInternal;
  78     if (fwrite(&extForm, sizeof(extForm), 1, mbox) != 1) {
  79         fclose(mbox);
  80         return errAuthorizationInternal;
  81     }
  82     fflush(mbox);
  83
  84     // make text representation of the temp-file descriptor
  85     char mboxFdText[20];
  86     snprintf(mboxFdText, sizeof(mboxFdText), "auth %d", fileno(mbox));
  87
  88         // make a notifier pipe
  89         int notify[2];
  90         if (pipe(notify)) {
  91         fclose(mbox);
  92                 return errAuthorizationToolExecuteFailure;
  93     }
  94
  95         // make the communications pipe if requested
  96         int comm[2];
  97         if (communicationsPipe && socketpair(AF_UNIX, SOCK_STREAM, 0, comm)) {
  98                 close(notify[READ]); close(notify[WRITE]);
  99         fclose(mbox);
 100                 return errAuthorizationToolExecuteFailure;
 101         }
 102
 103         // do the standard forking tango...
 104         int delay = 1;
 105         for (int n = 5;; n--, delay *= 2) {
 106                 switch (pid_t pid = fork()) {
 107                 case -1:        // error
 108                         if (errno == EAGAIN) {
 109                                 // potentially recoverable resource shortage
 110                                 if (n > 0) {
 111                                         debug("authexec", "resource shortage (EAGAIN), delaying %d seconds", delay);
 112                                         sleep(delay);
 113                                         continue;
 114                                 }
 115                         }
 116                         debug("authexec", "fork failed (errno=%d)", errno);
 117                         close(notify[READ]); close(notify[WRITE]);
 118                         return errAuthorizationToolExecuteFailure;
 119
 120                 default:        // parent
 121                         // close foreign side of pipes
 122                         close(notify[WRITE]);
 123                         if (communicationsPipe)
 124                                 close(comm[WRITE]);
 125
 126             // close mailbox file (child has it open now)
 127             fclose(mbox);
 128
 129                         // get status notification from child
 130                         OSStatus status;
 131                         debug("authexec", "parent waiting for status");
 132                         switch (ssize_t rc = read(notify[READ], &status, sizeof(status))) {
 133                         default:                                // weird result of read: post error
 134                                 debug("authexec", "unexpected read return value %ld", long(rc));
 135                                 status = errAuthorizationToolEnvironmentError;
 136                                 // fall through
 137                         case sizeof(status):    // read succeeded: child reported an error
 138                                 debug("authexec", "parent received status=%ld", status);
 139                                 close(notify[READ]);
 140                                 if (communicationsPipe) { close(comm[READ]); close(comm[WRITE]); }
 141                                 return status;
 142                         case 0:                                 // end of file: exec succeeded
 143                                 close(notify[READ]);
 144                                 if (communicationsPipe)
 145                                         *communicationsPipe = fdopen(comm[READ], "r+");
 146                                 debug("authexec", "parent resumes (no error)");
 147                                 return noErr;
 148                         }
 149
 150                 case 0:         // child
 151                         // close foreign side of pipes
 152                         close(notify[READ]);
 153                         if (communicationsPipe)
 154                                 close(comm[READ]);
 155
 156                         // fd 1 (stdout) holds the notify write end
 157                         dup2(notify[WRITE], 1);
 158                         close(notify[WRITE]);
 159
 160                         // fd 0 (stdin) holds either the comm-link write-end or /dev/null
 161                         if (communicationsPipe) {
 162                                 dup2(comm[WRITE], 0);
 163                                 close(comm[WRITE]);
 164                         } else {
 165                                 close(0);
 166                                 open("/dev/null", O_RDWR);
 167                         }
 168
 169                         // where is the trampoline?
 170 #if defined(NDEBUG)
 171                         const char *trampoline = TRAMPOLINE;
 172 #else //!NDEBUG
 173                         const char *trampoline = getenv("AUTHORIZATIONTRAMPOLINE");
 174                         if (!trampoline)
 175                                 trampoline = TRAMPOLINE;
 176 #endif //NDEBUG
 177
 178                         // okay, execute the trampoline
 179                         debug("authexec", "child exec(%s:%s)",
 180                                 trampoline, pathToTool);
 181                         if (const char **argv = argVector(trampoline, pathToTool, mboxFdText, arguments))
 182                                 execv(trampoline, (char *const*)argv);
 183                         debug("authexec", "trampoline exec failed (errno=%d)", errno);
 184
 185                         // execute failed - tell the parent
 186                         {
 187                                 OSStatus error = errAuthorizationToolExecuteFailure;
 188                                 write(1, &error, sizeof(error));
 189                                 _exit(1);
 190                         }
 191                 }
 192         }
 193 }
 194
 195
 196 //
 197 // Build an argv vector
 198 //
 199 static const char **argVector(const char *trampoline, const char *pathToTool,
 200         const char *mboxFdText, char *const *arguments)
 201 {
 202         int length = 0;
 203         if (arguments) {
 204                 for (char *const *p = arguments; *p; p++)
 205                         length++;
 206         }
 207         if (const char **args = (const char **)malloc(sizeof(const char *) * (length + 4))) {
 208                 args[0] = trampoline;
 209                 args[1] = pathToTool;
 210                 args[2] = mboxFdText;
 211                 if (arguments)
 212                         for (int n = 0; arguments[n]; n++)
 213                                 args[n + 3] = arguments[n];
 214                 args[length + 3] = NULL;
 215                 return args;
 216         }
 217         return NULL;
 218 }