X-Git-Url: http://git.code-monkey.de/?a=blobdiff_plain;f=src%2Fmain.c;h=cef4f605a4d2e88877d7e488dbb83302e378f962;hb=ed9b54bd89b704e6111acbd91b6a7b50e3c30cf5;hp=7bd8a0bfbefdcc2a7e6dadb4a95efbc0744a8582;hpb=0fd109448ce43a6a53866614423463788c278ff6;p=umurmur.git

diff --git a/src/main.c b/src/main.c
index 7bd8a0b..cef4f60 100644
--- a/src/main.c
+++ b/src/main.c
@@ -36,6 +36,8 @@
 #include <sys/stat.h>
 #include <sys/utsname.h>
 #include <fcntl.h>
+#include <pwd.h>
+#include <grp.h>
 #include <signal.h>
 #include <errno.h>
 #include <string.h>
@@ -57,19 +59,105 @@ char *bindaddr;
 
 void lockfile(const char *pidfile)
 {
-	int lfp;
+	int lfp, flags;
 	char str[16];
-	
-	lfp = open(pidfile, O_RDWR|O_CREAT|O_EXCL, 0640);
+
+	/* Don't use O_TRUNC here -- we want to leave the PID file
+	 * unmodified if we cannot lock it.
+	 */
+	lfp = open(pidfile, O_WRONLY|O_CREAT, 0640);
 	
 	if (lfp < 0)
 		Log_fatal("Cannot open PID-file %s for writing", pidfile);
+
+	/* Try to lock the file. */
+	if (lockf(lfp, F_TLOCK, 0) < 0) {
+		close(lfp);
+
+		if (errno == EACCES || errno == EAGAIN)
+			Log_fatal("PID file is locked -- uMurmur already running?");
+
+		Log_fatal("Cannot lock PID file: %s", strerror(errno));
+	}
+
+	/* Now that we locked the file, erase its contents. */
+	if (ftruncate(lfp, 0) < 0) {
+		close(lfp);
+		Log_fatal("Cannot truncate PID file: %s", strerror(errno));
+	}
+
 	snprintf(str,16,"%d\n", getpid());
 	write(lfp, str, strlen(str)); /* record pid to lockfile */
-	close(lfp);
 	Log_info("PID-file: %s", pidfile);
+
+	/* If uMurmur ever starts to fork()+exec(), we don't want it to
+	 * leak the fd to the forked process though. Set the close-on-exec
+	 * flag to prevent leakage.
+	 */
+	flags = fcntl(lfp, F_GETFD, 0);
+	flags |= FD_CLOEXEC;
+	fcntl(lfp, F_SETFD, (long) flags);
+
+	/* Don't close(lfp) here!
+	 * We want the fd to remain opened so the lock is held until the
+	 * process exits.
+	 */
+	lfp = -1;
 }
 
+/* Drops privileges (if configured to do so). */
+static void switch_user(void)
+{
+	struct passwd *pwd;
+	struct group *grp = NULL;
+	const char *username, *groupname;
+	gid_t gid;
+
+	username = getStrConf(USERNAME);
+	groupname = getStrConf(GROUPNAME);
+
+	if (!*username) {
+		/* It's an error to specify groupname
+		 * but leave username empty.
+		 */
+		if (*groupname)
+			Log_fatal("username missing");
+
+		/* Nothing to do. */
+		return;
+	}
+
+	pwd = getpwnam(username);
+	if (!pwd)
+		Log_fatal("Unknown user '%s'", username);
+
+	if (!*groupname)
+		gid = pwd->pw_gid;
+	else {
+		grp = getgrnam(groupname);
+
+		if (!grp)
+			Log_fatal("Unknown group '%s'", groupname);
+
+		gid = grp->gr_gid;
+	}
+
+	if (initgroups(pwd->pw_name, gid))
+		Log_fatal("initgroups() failed: %s", strerror(errno));
+
+	if (setgid(gid))
+		Log_fatal("setgid() failed: %s", strerror(errno));
+
+	if (setuid(pwd->pw_uid))
+		Log_fatal("setuid() failed: %s", strerror(errno));
+	
+	if (!grp)
+		grp = getgrgid(gid);
+	if (!grp)
+		Log_fatal("getgrgid() failed: %s", strerror(errno));
+	
+	Log_info("Switch to user '%s' group '%s'", pwd->pw_name, grp->gr_name);
+}
 
 void signal_handler(int sig)
 {
@@ -189,18 +277,28 @@ int main(int argc, char **argv)
 			break;
 		}
 	}
+
+	/* Logging to terminal if not daemonizing, otherwise to syslog.
+	 * Need to initialize logging before calling Conf_init()
+	 */
+	if (!nodaemon)
+		Log_init(false);
+	else
+		Log_init(true);
 	
+	/* Initialize the config subsystem early;
+	 * switch_user() will need to read some config variables.
+	 */
+	Conf_init(conffile);
+
 	if (!nodaemon) {
-		Log_init(false);
 		daemonize();
 		if (pidfile != NULL)
 			lockfile(pidfile);
+
+		switch_user();
 	}
-	else
-		Log_init(true);
 
-	Conf_init(conffile);
-			
 	signal(SIGCHLD, SIG_IGN); /* ignore child */
 	signal(SIGTSTP, SIG_IGN); /* ignore tty signals */
 	signal(SIGTTOU, SIG_IGN);