From 11c12539d9ee64b816ad2e734b499d7ce1e83ac9 Mon Sep 17 00:00:00 2001
From: Nathan Wagner <nw@hydaspes.if.org>
Date: Wed, 13 Feb 2013 20:43:09 +0000
Subject: [PATCH] initial commit

---
 Makefile  |  7 ++++++
 chdir.c   | 19 ++++++++++++++++
 chids.c   | 26 +++++++++++++++++++++
 daemon.c  | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 exec.c    | 26 +++++++++++++++++++++
 monitor.c | 48 +++++++++++++++++++++++++++++++++++++++
 6 files changed, 194 insertions(+)
 create mode 100644 Makefile
 create mode 100644 chdir.c
 create mode 100644 chids.c
 create mode 100644 daemon.c
 create mode 100644 exec.c
 create mode 100644 monitor.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..f57d26b
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,7 @@
+PRG=daemon chdir chids
+CFLAGS=-Wall -Wno-parentheses
+
+all:	$(PRG)
+
+clean:
+	rm -f *.o $(PRG)
diff --git a/chdir.c b/chdir.c
new file mode 100644
index 0000000..32c0e82
--- /dev/null
+++ b/chdir.c
@@ -0,0 +1,19 @@
+/*
+ * daemonize and exec
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "exec.c"
+
+int main(int ac, char *av[]) {
+	if (chdir(av[1]) < 0) {
+		exit(EXIT_FAILURE);
+	}
+
+	do_exec(2, ac, av);
+
+	/* shouldn't get here... */
+	return EXIT_FAILURE;
+}
diff --git a/chids.c b/chids.c
new file mode 100644
index 0000000..61e7226
--- /dev/null
+++ b/chids.c
@@ -0,0 +1,26 @@
+/*
+ * daemonize and exec
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <pwd.h>
+
+#include "exec.c"
+
+int main(int ac, char *av[]) {
+	struct passwd *pw;
+
+	pw = getpwnam(av[1]);
+	if (!pw) {
+		exit(EXIT_FAILURE);
+	}
+	
+	seteuid(pw->pw_uid);
+
+	do_exec(2, ac, av);
+
+	/* shouldn't get here... */
+	return EXIT_FAILURE;
+}
diff --git a/daemon.c b/daemon.c
new file mode 100644
index 0000000..cdafbf6
--- /dev/null
+++ b/daemon.c
@@ -0,0 +1,68 @@
+/*
+ * daemonize and exec
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include <unistd.h>
+
+#include "exec.c"
+
+int main(int ac, char *av[]) {
+	pid_t pid, sid;
+
+	pid = fork();
+	if (pid < 0) {
+		fprintf(stderr, "fork fail!\n");
+		exit(EXIT_FAILURE);
+	}
+
+	if (pid > 0) {
+		exit(EXIT_SUCCESS);
+	}
+
+	umask(0);
+
+	sid = setsid();
+	if (sid < 0) {
+		exit(EXIT_SUCCESS);
+	}
+
+	pid = fork();
+	if (pid < 0) {
+		fprintf(stderr, "fork fail!\n");
+		exit(EXIT_FAILURE);
+	}
+	if (pid > 0) {
+		/* fprintf(stderr, "pid = %d\n", pid); */
+		exit(EXIT_SUCCESS);
+	}
+
+	/* reset the file descriptors */
+	if (isatty(0)) {
+		close(0);
+		open("/dev/null", O_RDONLY);
+	}
+	if (isatty(1)) {
+		close(0);
+		open("/dev/null", O_WRONLY);
+	}
+	if (isatty(2)) {
+		close(0);
+		open("/dev/null", O_WRONLY);
+	}
+
+	if (chdir("/") < 0) {
+		exit(EXIT_FAILURE);
+	}
+
+	do_exec(1, ac, av);
+
+	/* shouldn't get here... */
+	return EXIT_FAILURE;
+}
diff --git a/exec.c b/exec.c
new file mode 100644
index 0000000..94f319f
--- /dev/null
+++ b/exec.c
@@ -0,0 +1,26 @@
+/*
+ * exec
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <string.h>
+
+#include <unistd.h>
+
+void do_exec(int skip, int ac, char *av[]) {
+	int i;
+
+	for (i=0;i<ac-skip;i++) {
+		av[i] = av[i+skip];
+	}
+	av[i] = 0;
+
+	if (i = execvp(av[0], av) < 0) {
+		fprintf(stderr, "exec returned %d: %s\n", i, strerror(i));
+	}
+}
diff --git a/monitor.c b/monitor.c
new file mode 100644
index 0000000..fcceeb6
--- /dev/null
+++ b/monitor.c
@@ -0,0 +1,48 @@
+/*
+ * daemonize and exec
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <unistd.h>
+
+#include "exec.c"
+
+int main(int ac, char *av[]) {
+	pid_t child = 0;
+
+	/* create the child */
+	child = fork();
+	if (child < 0) {
+		fprintf(stderr, "fork fail!\n");
+		exit(EXIT_FAILURE);
+	}
+
+	/* parent, actually does the monitoring */
+	if (child > 0) {
+		exit(EXIT_SUCCESS);
+	}
+
+	pid = fork();
+	if (pid < 0) {
+		fprintf(stderr, "fork fail!\n");
+		exit(EXIT_FAILURE);
+	}
+	if (pid > 0) {
+		/* fprintf(stderr, "pid = %d\n", pid); */
+		exit(EXIT_SUCCESS);
+	}
+
+	if (chdir("/") < 0) {
+		exit(EXIT_FAILURE);
+	}
+
+	do_exec(1, ac, av);
+
+	/* shouldn't get here... */
+	return EXIT_FAILURE;
+}
-- 
2.40.0