Some Assembly Required 4

some_assembly_required_4/sol2.py

@@ -0,0 +1,39 @@
+#!/home/maxime/.pyvenv/bin/python3
+from wasmtime import Store, Module, Instance
+import string
+import itertools
+
+store = Store()
+module = Module.from_file(store.engine, "assembly4.wat")
+instance = Instance(store, module, [])
+
+exports = instance.exports(store)
+memory = exports["memory"]
+check_flag = exports["check_flag"]
+
+def init_flag(pair):
+    for i in range(len(flag)):
+        memory.data_ptr(store)[1072+i]=ord(flag[i])
+    for j in range(len(flag_so_far)):
+        memory.data_ptr(store)[1072+8+j]=ord(flag_so_far[j])
+    memory.data_ptr(store)[1072+8+len(flag_so_far)]=ord(pair[0])
+    memory.data_ptr(store)[1072+8+len(flag_so_far)+1]=ord(pair[1])
+
+def count_match():
+    count = 0
+    while memory.data_ptr(store)[1024+count] == memory.data_ptr(store)[1072+count]:
+        count += 1
+    return count
+
+flag = "picoCTF{0123456789abcdef123456789abcdef}"
+flag_chars = string.ascii_lowercase + string.digits + "_}\x00 "
+flag_so_far = ""
+for i in range(24):
+    for j in itertools.product(flag_chars, repeat=2):
+        init_flag(j)
+        check_flag(store)
+        if count_match() >= 10 + len(flag_so_far):
+            flag_so_far += (j[0]+j[1])
+            print("picoCTF{" + flag_so_far)
+            break
+