OSX/libsecurity_authorization/lib/trampolineClient.cpp

   1 /*
   2  * Copyright (c) 2000-2004,2011-2014 Apple 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 //
  26 // trampolineClient - Authorization trampoline client-side implementation
  27 //
  28 #include <asl.h>
  29 #include <sys/types.h>
  30 #include <unistd.h>
  31 #include <errno.h>
  32 #include <fcntl.h>
  33 #include <stdlib.h>
  34 #include <sys/socket.h>
  35 #include <Security/Authorization.h>
  36 #include <Security/AuthorizationPriv.h>
  37 #include <Security/SecBase.h>
  38 #include <security_utilities/endian.h>
  39 #include <security_utilities/debugging.h>
  40
  41 //
  42 // Where is the trampoline itself?
  43 //
  44 #if !defined(TRAMPOLINE)
  45 # define TRAMPOLINE "/usr/libexec/security_authtrampoline" /* fallback */
  46 #endif
  47
  48
  49 //
  50 // A few names for clarity's sake
  51 //
  52 enum {
  53         READ = 0,               // read end of standard UNIX pipe
  54         WRITE = 1               // write end of standard UNIX pipe
  55 };
  56
  57
  58 //
  59 // Local (static) functions
  60 //
  61 static const char **argVector(const char *trampoline,
  62         const char *tool, const char *commFd,
  63         char *const *arguments);
  64
  65
  66 OSStatus AuthorizationExecuteWithPrivileges(AuthorizationRef authorization,
  67                                             const char *pathToTool,
  68                                             AuthorizationFlags flags,
  69                                             char *const *arguments,
  70                                             FILE **communicationsPipe)
  71 {
  72         // externalize the authorization
  73         AuthorizationExternalForm extForm;
  74         if (OSStatus err = AuthorizationMakeExternalForm(authorization, &extForm))
  75                 return err;
  76
  77     return AuthorizationExecuteWithPrivilegesExternalForm(&extForm, pathToTool, flags, arguments, communicationsPipe);
  78 }
  79
  80 //
  81 // The public client API function.
  82 //
  83 OSStatus AuthorizationExecuteWithPrivilegesExternalForm(const AuthorizationExternalForm * extForm,
  84         const char *pathToTool,
  85         AuthorizationFlags flags,
  86         char *const *arguments,
  87         FILE **communicationsPipe)
  88 {
  89         if (extForm == NULL)
  90         return errAuthorizationInvalidPointer;
  91
  92         // report the caller to the authorities
  93         aslmsg m = asl_new(ASL_TYPE_MSG);
  94         asl_set(m, "com.apple.message.domain", "com.apple.libsecurity_authorization.AuthorizationExecuteWithPrivileges");
  95         asl_set(m, "com.apple.message.signature", getprogname());
  96         asl_log(NULL, m, ASL_LEVEL_NOTICE, "AuthorizationExecuteWithPrivileges!");
  97         asl_free(m);
  98
  99         // flags are currently reserved
 100         if (flags != 0)
 101                 return errAuthorizationInvalidFlags;
 102
 103     // create the mailbox file
 104     FILE *mbox = tmpfile();
 105     if (!mbox)
 106         return errAuthorizationInternal;
 107     if (fwrite(extForm, sizeof(*extForm), 1, mbox) != 1) {
 108         fclose(mbox);
 109         return errAuthorizationInternal;
 110     }
 111     fflush(mbox);
 112
 113         // compute the argument vector here because we can't allocate memory once we fork.
 114
 115     // make text representation of the temp-file descriptor
 116     char mboxFdText[20];
 117     snprintf(mboxFdText, sizeof(mboxFdText), "auth %d", fileno(mbox));
 118
 119         // where is the trampoline?
 120 #if defined(NDEBUG)
 121         const char *trampoline = TRAMPOLINE;
 122 #else //!NDEBUG
 123         const char *trampoline = getenv("AUTHORIZATIONTRAMPOLINE");
 124         if (!trampoline)
 125                 trampoline = TRAMPOLINE;
 126 #endif //NDEBUG
 127
 128         const char **argv = argVector(trampoline, pathToTool, mboxFdText, arguments);
 129
 130         // make a notifier pipe
 131         int notify[2];
 132         if (pipe(notify)) {
 133         fclose(mbox);
 134                 return errAuthorizationToolExecuteFailure;
 135     }
 136
 137         // make the communications pipe if requested
 138         int comm[2];
 139         if (communicationsPipe && socketpair(AF_UNIX, SOCK_STREAM, 0, comm)) {
 140                 close(notify[READ]); close(notify[WRITE]);
 141         fclose(mbox);
 142                 return errAuthorizationToolExecuteFailure;
 143         }
 144
 145         OSStatus status = errSecSuccess;
 146
 147         // do the standard forking tango...
 148         int delay = 1;
 149         for (int n = 5;; n--, delay *= 2) {
 150                 switch (fork()) {
 151                 case -1:        // error
 152                         if (errno == EAGAIN) {
 153                                 // potentially recoverable resource shortage
 154                                 if (n > 0) {
 155                                         secinfo("authexec", "resource shortage (EAGAIN), delaying %d seconds", delay);
 156                                         sleep(delay);
 157                                         continue;
 158                                 }
 159                         }
 160                         secinfo("authexec", "fork failed (errno=%d)", errno);
 161                         close(notify[READ]); close(notify[WRITE]);
 162                         return errAuthorizationToolExecuteFailure;
 163
 164                 default: {      // parent
 165                         // close foreign side of pipes
 166                         close(notify[WRITE]);
 167                         if (communicationsPipe)
 168                                 close(comm[WRITE]);
 169
 170             // close mailbox file (child has it open now)
 171             fclose(mbox);
 172
 173                         // get status notification from child
 174                         secinfo("authexec", "parent waiting for status");
 175                         ssize_t rc = read(notify[READ], &status, sizeof(status));
 176                         status = n2h(status);
 177                         switch (rc) {
 178                         default:                                // weird result of read: post error
 179                                 secinfo("authexec", "unexpected read return value %ld", long(rc));
 180                                 status = errAuthorizationToolEnvironmentError;
 181                                 // fall through
 182                         case sizeof(status):    // read succeeded: child reported an error
 183                                 secinfo("authexec", "parent received status=%d", (int)status);
 184                                 close(notify[READ]);
 185                                 if (communicationsPipe) { close(comm[READ]); close(comm[WRITE]); }
 186                                 goto exit_point;
 187                         case 0:                                 // end of file: exec succeeded
 188                                 close(notify[READ]);
 189                                 if (communicationsPipe)
 190                                         *communicationsPipe = fdopen(comm[READ], "r+");
 191                                 secinfo("authexec", "parent resumes (no error)");
 192                                 status = errSecSuccess;
 193                                 goto exit_point;
 194                         }
 195         }
 196                 break;
 197
 198                 case 0:         // child
 199                         // close foreign side of pipes
 200                         close(notify[READ]);
 201                         if (communicationsPipe)
 202                                 close(comm[READ]);
 203
 204                         // fd 1 (stdout) holds the notify write end
 205                         dup2(notify[WRITE], 1);
 206                         close(notify[WRITE]);
 207
 208                         // fd 0 (stdin) holds either the comm-link write-end or /dev/null
 209                         if (communicationsPipe) {
 210                                 dup2(comm[WRITE], 0);
 211                                 close(comm[WRITE]);
 212                         } else {
 213                                 close(0);
 214                                 open("/dev/null", O_RDWR);
 215                         }
 216
 217                         // okay, execute the trampoline
 218                         if (argv)
 219                                 execv(trampoline, (char *const*)argv);
 220
 221                         // execute failed - tell the parent
 222                         {
 223                                 OSStatus error = errAuthorizationToolExecuteFailure;
 224                                 error = h2n(error);
 225                                 write(1, &error, sizeof(error));
 226                                 _exit(1);
 227                         }
 228                 }
 229         }
 230
 231 exit_point:
 232         free(argv);
 233         return status;
 234 }
 235
 236
 237 //
 238 // Build an argv vector
 239 //
 240 static const char **argVector(const char *trampoline, const char *pathToTool,
 241         const char *mboxFdText, char *const *arguments)
 242 {
 243         int length = 0;
 244         if (arguments) {
 245                 for (char *const *p = arguments; *p; p++)
 246                         length++;
 247         }
 248         if (const char **args = (const char **)malloc(sizeof(const char *) * (length + 4))) {
 249                 args[0] = trampoline;
 250                 args[1] = pathToTool;
 251                 args[2] = mboxFdText;
 252                 if (arguments)
 253                         for (int n = 0; arguments[n]; n++)
 254                                 args[n + 3] = arguments[n];
 255                 args[length + 3] = NULL;
 256                 return args;
 257         }
 258         return NULL;
 259 }