From bde87883f667d86a64b67ce7e793c33890b00f3e Mon Sep 17 00:00:00 2001
From: Donald Buczek <buczek@molgen.mpg.de>
Date: Fri, 2 Nov 2018 10:21:00 +0100
Subject: [PATCH] Add tool setuid

Add a simple tool to execute a command with another uid.
---
 .gitignore      |  1 +
 Makefile        | 10 ++++++----
 install.sh      |  1 +
 setuid/setuid.c | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 40 insertions(+), 4 deletions(-)
 create mode 100644 .gitignore
 create mode 100644 setuid/setuid.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2f683ef
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+setuid/setuid
diff --git a/Makefile b/Makefile
index baa247b..ef0ff8e 100644
--- a/Makefile
+++ b/Makefile
@@ -64,10 +64,12 @@ INSTALL=install -v
 INSTALL_PROGRAM = $(INSTALL)
 INSTALL_DATA = $(INSTALL) -m 644
 
-all:
-	@echo 'Nothing to be done. Ready for "make install"'
+all:	setuid/setuid
 
-install:
+clean:
+	@rm setuid/setuid 2>/dev/null || true
+
+install: all
 	@prefix="$(prefix)" usr_prefix="$(usr_prefix)" usrlocal_prefix="$(usrlocal_prefix)" \
 	root_exec_prefix="$(root_exec_prefix)"         root_bindir="$(root_bindir)"    root_sbindir="$(root_sbindir)" \
 	usr_exec_prefix="$(usr_exec_prefix)"           use_bindir="$(usr_bindir)"      usr_sbindir="$(usr_sbindir)" \
@@ -79,6 +81,6 @@ install:
 	DESTDIR="$(DESTDIR)" \
 	./install.sh
 
-.PHONY: all install
+.PHONY: all install clean
 
 
diff --git a/install.sh b/install.sh
index 798c1f6..c5a45ed 100755
--- a/install.sh
+++ b/install.sh
@@ -125,4 +125,5 @@ install_data blink/blinkd.service                        "$DESTDIR$systemdunitdi
 install_data blink/51-blink.rules                        "$DESTDIR$udev_rulesdir/51-blink.rules"
 install_data clusterd/clusterd.service                   "$DESTDIR$systemdunitdir/clusterd.service"
 install_exec clusterd/clusterd                           "$DESTDIR$usr_sbindir/clusterd"
+install_exec setuid/setuid                               "$DESTDIR$usr_sbindir/setuid"
 exit
diff --git a/setuid/setuid.c b/setuid/setuid.c
new file mode 100644
index 0000000..3480c9d
--- /dev/null
+++ b/setuid/setuid.c
@@ -0,0 +1,32 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+int main(int argc,char **argv) {
+	uid_t uid;
+	char *end;
+	int status;
+
+	if (argc<3) {
+		fprintf(stderr,"usage: %s uid cmd...\n",argv[0]);
+		exit(1);
+	}
+	uid=strtoul(argv[1],&end,10);
+	if (end==argv[1] || *end != '\0') {
+		fprintf(stderr,"%s: %s: invalid uid\n",argv[0],argv[1]);
+		exit(1);
+	}
+	status=setuid(uid);
+	if (status==-1) {
+		perror(argv[0]);
+		exit(1);
+	}
+
+	status=execvp(argv[2],&argv[2]);
+	if (status==-1) {
+		perror(argv[0]);
+		exit(1);
+	}
+	exit(0);
+}