Security-55163.44.tar.gz

[apple/security.git] / libsecurity_utilities / lib / daemon.cpp

diff --git a/libsecurity_utilities/lib/daemon.cpp b/libsecurity_utilities/lib/daemon.cpp
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+/*
+ * Copyright (c) 2000-2004 Apple Computer, Inc. All Rights Reserved.
+ * 
+ * @APPLE_LICENSE_HEADER_START@
+ * 
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ * 
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ * 
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+
+//
+// demon - support code for writing UNIXoid demons
+//
+#include <security_utilities/daemon.h>
+#include <security_utilities/logging.h>
+#include <security_utilities/debugging.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+namespace Security {
+namespace Daemon {
+
+
+//
+// Daemonize this process, the UNIX way.
+//
+bool incarnate(bool doFork /*=true*/)
+{
+       if (doFork) {
+               // fork with slight resilience
+               for (int forkTries = 1; forkTries <= 5; forkTries++) {
+                       switch (fork()) {
+                               case 0:                 // child
+                                                       // we are the daemon process (Har! Har!)
+                                       break;
+                               case -1:                // parent: fork failed
+                                       switch (errno) {
+                                               case EAGAIN:
+                                               case ENOMEM:
+                                                       Syslog::warning("fork() short on resources (errno=%d); retrying", errno);
+                                                       sleep(forkTries);
+                                                       continue;
+                                               default:
+                                                       Syslog::error("fork() failed (errno=%d)", errno);
+                                                       return false;
+                                       }
+                               default:                // parent
+                                                       // @@@ we could close an assurance loop here, but we don't (yet?)
+                                       exit(0);
+                       }
+               }
+               // fork succeeded; we are the child; parent is terminating
+       }
+       
+       // create new session (the magic set-me-apart system call)
+       setsid();
+
+       // redirect standard channels to /dev/null
+       close(0);       // fail silently in case 0 is closed
+       if (open("/dev/null", O_RDWR, 0) == 0) {        // /dev/null could be missing, I suppose...
+               dup2(0, 1);
+               dup2(0, 2);
+       }
+       
+       // ready to roll
+       return true;
+}
+
+
+//
+// Re-execute myself.
+// This is a pretty bad hack for libraries that are pretty broken and (essentially)
+// don't work after a fork() unless you also exec().
+//
+// WARNING: Don't even THINK of doing this in a setuid-anything program.
+//
+bool executeSelf(char **argv)
+{
+       static const char reExecEnv[] = "_RE_EXECUTE";
+       if (getenv(reExecEnv)) {                // was re-executed
+               secdebug("daemon", "self-execution complete");
+               unsetenv(reExecEnv);
+               return true;
+       } else {
+               setenv(reExecEnv, "go", 1);
+               secdebug("daemon", "self-executing (ouch!)");
+               execv(argv[0], argv);
+               perror("re-execution");
+               Syslog::error("Re-execution attempt failed");
+               return false;
+       }
+}
+
+
+} // end namespace Daemon
+} // end namespace Security