shelestov lab3

23213/k.shelestov/lab3/Makefile

@@ -0,0 +1,9 @@
+all: lab3.out file
+
+file:
+	touch file
+	chmod 600 file
+
+lab3.out: lab3.c
+	cc lab3.c -v -o lab3.out
+	chmod u+s lab3.out

23213/k.shelestov/lab3/lab3.c

@@ -0,0 +1,37 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+
+int main(){
+
+    uid_t real_id = getuid();
+    uid_t effective_id = geteuid();
+
+    printf("real id: %d\n effective id: %d\n", real_id, effective_id);
+
+    FILE* file = fopen("file", "r");
+    if (file == NULL){
+        perror("Error while opening file");
+    }
+    else{
+        fclose(file);
+    }
+
+    if (setuid(real_id) == -1)
+        perror("Error setting id");
+
+    effective_id = geteuid();
+
+    printf("real id: %d\n effective id: %d\n", real_id, effective_id);
+
+    file = fopen("file", "r");
+    if (file == NULL){
+        perror("Error while opening file");
+    }
+    else{
+        fclose(file);
+    }
+
+    return 0;
+}