Create README.mdx

level11/README.mdx

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+# 11
+
+Login
+
+```b
+> ssh level11@$(ifconfig|grep 'inet '|awk 'NR==2 {print $2}') -p 4242
+> Password: s5cAJpM8ev6XHw998pRWG728z
+```
+
+A lua script
+
+```b
+> ls -l
+-rwsr-sr-x 1 flag11 level11 668 level11.lua
+
+> file level11.lua 
+level11.lua: setuid setgid a lua script, ASCII text executable
+```
+```b
+> strings level11.lua 
+#!/usr/bin/env lua
+local socket = require("socket")
+local server = assert(socket.bind("127.0.0.1", 5151))
+function hash(pass)
+  prog = io.popen("echo "..pass.." | sha1sum", "r")
+  data = prog:read("*all")
+  prog:close()
+  data = string.sub(data, 1, 40)
+  return data
+while 1 do
+  local client = server:accept()
+  client:send("Password: ")
+  client:settimeout(60)
+  local l, err = client:receive()
+  if not err then
+      print("trying " .. l)
+      local h = hash(l)
+      if h ~= "f05d1d066fb246efe0c6f7d095f909a7a0cf34a0" then
+          client:send("Erf nope..\n");
+      else
+          client:send("Gz you dumb*\n")
+      end
+  end
+  client:close()
+```
+```b
+> ltrace ./level11.lua 
+ltrace: Can't open ELF file "./level11.lua"
+
+> ./level11.lua 
+lua: ./level11.lua:3: address already in use
+stack traceback:
+	[C]: in function 'assert'
+	./level11.lua:3: in main chunk
+	[C]: ?
+```