X-Git-Url: https://git.saurik.com/apple/security.git/blobdiff_plain/72a12576750f52947eb043106ba5c12c0d07decf..b1ab9ed8d0e0f1c3b66d7daa8fd5564444c56195:/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