Merge branch 'master' of https://github.com/failedxyz/easyctf

20xx/description.md

@@ -1 +1 @@
-What is this file saying? Help me.
+My friend sent me this file and told me to git gud.

doubly-dangerous/doubly_dangerous.c

@@ -0,0 +1,39 @@
+//compile with:
+//gcc -m32 -std=c99 -Wall -fno-stack-protector doubly_dangerous.c -o doubly_dangerous
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+
+void give_flag() {
+    FILE *f = fopen("flag.txt", "r");
+    if (f != NULL) {
+        char c;
+
+        while ((c = fgetc(f)) != EOF) {
+            putchar(c);
+        }
+        fclose(f);
+    }
+    else {
+        printf("Failed to open flag file!\n");
+    }
+}
+
+int main(int argc, char **argv){
+  volatile float modified;
+  char buffer[64];
+
+  modified = 0;
+  printf("Give me a string: \n");
+  gets(buffer);
+
+  if (modified == 11.28125) {
+      printf("Success! Here is your flag:\n");
+      give_flag();
+  } 
+  else {
+      printf("nope!\n");
+  }
+}

library/grader.py

@@ -1,3 +1,9 @@
+# Very easy problem. Compute a few values w/ brute force or something, then check OEIS.
+# Part of: https://oeis.org/A001333
+# Tells us:  f(n) = (1/4) * Trace( [[0,0,1,0],[0,1,0,1],[1,0,2,0],[0,2,0,1]] )
+# just write a program to compute this quickly 
+# this sol takes something like ~O(log n) i think?
+
 x = input() + 1
 
 mat = [[0,0,1,0],[0,1,0,1],[1,0,2,0],[0,2,0,1]]

library/problem.yml

@@ -3,7 +3,7 @@ title: library
 category: Programming
 autogen: false
 programming: true
-value: 75
+value: 175
 
 test_cases: 10
 time_limit: 1000