From 08c30d1a3d2256b2e613c4d5d8c68d6819be6a85 Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Mon, 1 Feb 2021 10:49:11 -0500
Subject: first draft of front-end

---
 privexec/Makefile   | 26 +++++++++++++++++++
 privexec/privexec.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 98 insertions(+)
 create mode 100644 privexec/Makefile
 create mode 100644 privexec/privexec.c

diff --git a/privexec/Makefile b/privexec/Makefile
new file mode 100644
index 0000000..26cafe6
--- /dev/null
+++ b/privexec/Makefile
@@ -0,0 +1,26 @@
+.POSIX:
+
+# This Makefile was generated by maje
+# See https://gitlab.com/jkaivo/maje/ for more information
+# Do not edit this Makefile by hand
+
+CC=c99
+LD=$(CC)
+CFLAGS=-Wall -Wextra -Wpedantic -Werror -g
+LDFLAGS=
+LDLIBS=
+SRCDIR=.
+OBJDIR=.
+BINDIR=$(OBJDIR)
+
+all: $(BINDIR)/privexec
+
+clean:
+	rm -f $(BINDIR)/privexec $(OBJDIR)/*.o
+
+$(BINDIR)/privexec: $(OBJDIR)/privexec.o
+$(OBJDIR)/privexec.o: $(SRCDIR)/privexec.c
+	$(CC) $(CFLAGS) -o $@ -c $(SRCDIR)/privexec.c
+
+$(BINDIR)/privexec:
+	$(LD) $(LDFLAGS) -o $@ $(OBJDIR)/*.o $(LDLIBS)
diff --git a/privexec/privexec.c b/privexec/privexec.c
new file mode 100644
index 0000000..1b7a54e
--- /dev/null
+++ b/privexec/privexec.c
@@ -0,0 +1,72 @@
+#define _POSIX_C_SOURCE 200809L
+#include <spawn.h>
+#include <stdio.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#ifndef PATH_CHECK
+#define PATH_CHECK	"/usr/local/lib/privexec/check"
+#endif
+
+#ifndef PATH_EXEC
+#define PATH_EXEC	"/usr/local/lib/privexec/exec"
+#endif
+
+static int exec_with_privileges(char *argv[])
+{
+	argv[0] = PATH_EXEC;
+	execv(argv[0], argv);
+	perror(argv[0]);
+	return 1;
+}
+
+static int check_privileges(char *argv[])
+{
+	argv[0] = PATH_CHECK;
+	pid_t pid = 0;
+	if (posix_spawn(&pid, argv[0], NULL, NULL, argv, NULL) != 0) {
+		perror(PATH_CHECK);
+		return 1;
+	}
+
+	int status = 1;
+	if (waitpid(pid, &status, 0) != 0) {
+		perror(PATH_CHECK);
+		return 1;
+	}
+
+	return status;
+}
+
+int main(int argc, char *argv[])
+{
+	const char *name = argv[0];
+	if (name == NULL) {
+		fprintf(stderr, "NULL execution not supported\n");
+		return 1;
+	}
+
+	/* no options, but allow for -- */
+	int c;
+	while ((c = getopt(argc, argv, "")) != -1) {
+		switch (c) {
+		default:
+			return 1;
+		}
+	}
+
+	argc -= (optind - 1);
+	argv += (optind - 1);
+
+	if (argc < 2) {
+		printf("%s: missing operands\n", name);
+		return 1;
+	}
+
+	if (check_privileges(argv) == 0) {
+		return exec_with_privileges(argv);
+	}
+
+	/* error message already displayed by check_privileges() */
+	return 1;
+}
-- 
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