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#+title: Readme
#+author: Phil Bajsicki
#+options: finline toc:nil
* Intro
This is a coding task from [redacted], which I found
rather fun to tinker with.
This is an org-mode file. The code blocks are tangled using =org-babel= into =cl-secninja.lisp=.
* Dependencies:
- curl
- sbcl with quicklisp
* Usage:
1. Load in SBCL with ~sbcl --load cl-secninja.lisp~.
2. Run ~(four)~
3. Copy the base64 encrypted message into a file called =email=.
4. Run ~(base64)~.
5. Done.
* Code:
** Quicklisp:
#+begin_src lisp :tangle cl-secninja.lisp
(ql:quickload '(:cl-ppcre
:cl-base64
:ironclad
:jsown))
#+end_src
** Defpackage and in-package
#+begin_src lisp :tangle cl-secninja.lisp
(defpackage #:cl-secninja
(:use #:common-lisp #:cl #:uiop #:cl-ppcre #:ironclad #:cl-base64))
(in-package #:cl-secninja)
#+end_src
** URL var
The trailing slash is important for consolidating the URL later.
#+begin_src lisp :tangle cl-secninja.lisp
(defvar *url* "redacted")
#+end_src
** Run cURL
#+begin_src lisp :tangle cl-secninja.lisp
(defun run-curl (command)
(let* ((curl-command (concatenate 'string "curl -i " command))
(result (uiop:run-program curl-command
:output :string
:error-output T)))
result))
#+end_src
** First page
Grab first page, print out the command and result, and return the parameter string.
#+begin_src lisp :tangle cl-secninja.lisp
(defun one ()
(let* ((command *url*)
(result (run-curl *url*)))
(format t "~%COMMAND: curl ~a" command)
(format t "~%RESULT: curl ~a" result)
(car (ppcre:all-matches-as-strings "\\?.*" result))))
#+end_src
** Second page
This function calls ~(one)~, so calling it directly for seeing the second page
works.
Concatenate the URL with the parameter string from the first function, and grab
and return the second page.
#+begin_src lisp :tangle cl-secninja.lisp
(defun two ()
(let* ((command (concatenate 'string
"\"" *url* (one) "\""))
(result (run-curl command)))
result))
#+end_src
** Third
This is where we get interesting. This function calls ~(two)~, which returns the
second page for processing, and then calls ~(run-curl)~ on the command it
constructs, and returns the output.
I wanted to see what the values of the variables are while testing, thus the
print statements and triple let. I know I could consolidate that, but I feel
like this way is more transparent than having a ~(let* (...))~ that does
everything in the background.
The thing that was most tricky here was getting the double quotes to work
properly between this function and ~(run-curl)~, because the =command= string is
being passed around, and it itself includes quotes.
#+begin_src lisp :tangle cl-secninja.lisp
(defun three ()
(let ((headers (ppcre:all-matches-as-strings "X-.*" (two))))
(print headers)
(print (car headers))
(print (cadr headers))
(let ((command (concatenate 'string
"\"" *url* "\?step=2" "\""
" -H \"" (car headers) "\""
" -H \"" (cadr headers) "\"")))
(let ((result (run-curl command)))
(format t "~%RESULT: curl ~a" result)
result))))
#+end_src
** Four
This was the most fun one, given all the processing. I can't say that the loop
worked the first time around.
After running ~(four)~, your terminal will print out the base64 encoded string.
I can't say I want to mess with extracting the base64 string with another
regexp, so I just manually copied the string into a file called =email=.
Then...
#+begin_src lisp :tangle cl-secninja.lisp
(defun four ()
(let*
((data (three))
(input
(car (ppcre:all-matches-as-strings "(?sm)\{.*}$" data)))
(challenge
(string-left-trim "challenge: " (car (ppcre:all-matches-as-strings "challenge:(.*)" data))))
(timestamp
(string-left-trim "timestamp: " (car (ppcre:all-matches-as-strings "timestamp:(.*)" data))))
(sorted (sort (cdr (jsown:parse input)) #'string<= :key #'first))
(connected
(string-right-trim "\&"
(format nil "~{~A~}"
(loop
for item in sorted
collect
(concatenate 'string (car item) "\=" (cdr item) "\&")))))
(hash (sha-256 connected))
(command
(string-right-trim "\-"
(concatenate 'string
"-X POST \"" *url* "\?step=3" "\""
" -H \"Content-Type: application/x-www-form-urlencoded\" "
" -d \"challenge=" challenge "\""
" -d \"timestamp=" timestamp "\""
" -d \"hash=" hash "\""
))))
(terpri)
(print challenge)
(print timestamp)
(print hash)
(terpri)
(format t "~%COMMAND: curl ~a" command)
(terpri)
(let ((result (run-curl command)))
(format t "~%RESULT: curl ~a" result))
(terpri)))
#+end_src
*** Sha256
Util function for the above code.
#+begin_src lisp :tangle cl-secninja.lisp
(defun sha-256 (str)
(ironclad:byte-array-to-hex-string
(ironclad:digest-sequence :sha256
(ironclad:ascii-string-to-byte-array str))))
#+end_src
** Base64
Put the contents of the file into a variable.
#+begin_src lisp :tangle cl-secninja.lisp
(defvar *email* (alexandria:read-file-into-string "email"))
#+end_src
Then, run the base64 decoder over it until the string can't be decoded any more.
#+begin_src lisp :tangle cl-secninja.lisp
(defun base64 ()
(let ((email *email*))
(loop repeat 100 do
(if (ppcre:scan "@" email)
(print email)
(setf email (cl-base64:base64-string-to-string email))))))
#+end_src

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(ql:quickload '(:cl-ppcre
:cl-base64
:ironclad
:jsown))
(defpackage #:cl-secninja
(:use #:common-lisp #:cl #:uiop #:cl-ppcre #:ironclad #:cl-base64))
(in-package #:cl-secninja)
(defvar *url* "redacted")
(defun run-curl (command)
(let* ((curl-command (concatenate 'string "curl -i " command))
(result (uiop:run-program curl-command
:output :string
:error-output T)))
result))
(defun one ()
(let* ((command *url*)
(result (run-curl *url*)))
(format t "~%COMMAND: curl ~a" command)
(format t "~%RESULT: curl ~a" result)
(car (ppcre:all-matches-as-strings "\\?.*" result))))
(defun two ()
(let* ((command (concatenate 'string
"\"" *url* (one) "\""))
(result (run-curl command)))
result))
(defun three ()
(let ((headers (ppcre:all-matches-as-strings "X-.*" (two))))
(print headers)
(print (car headers))
(print (cadr headers))
(let ((command (concatenate 'string
"\"" *url* "\?step=2" "\""
" -H \"" (car headers) "\""
" -H \"" (cadr headers) "\"")))
(let ((result (run-curl command)))
(format t "~%RESULT: curl ~a" result)
result))))
(defun four ()
(let*
((data (three))
(input
(car (ppcre:all-matches-as-strings "(?sm)\{.*}$" data)))
(challenge
(string-left-trim "challenge: " (car (ppcre:all-matches-as-strings "challenge:(.*)" data))))
(timestamp
(string-left-trim "timestamp: " (car (ppcre:all-matches-as-strings "timestamp:(.*)" data))))
(sorted (sort (cdr (jsown:parse input)) #'string<= :key #'first))
(connected
(string-right-trim "\&"
(format nil "~{~A~}"
(loop
for item in sorted
collect
(concatenate 'string (car item) "\=" (cdr item) "\&")))))
(hash (sha-256 connected))
(command
(string-right-trim "\-"
(concatenate 'string
"-X POST \"" *url* "\?step=3" "\""
" -H \"Content-Type: application/x-www-form-urlencoded\" "
" -d \"challenge=" challenge "\""
" -d \"timestamp=" timestamp "\""
" -d \"hash=" hash "\""
))))
(terpri)
(print challenge)
(print timestamp)
(print hash)
(terpri)
(format t "~%COMMAND: curl ~a" command)
(terpri)
(let ((result (run-curl command)))
(format t "~%RESULT: curl ~a" result))
(terpri)))
(defun sha-256 (str)
(ironclad:byte-array-to-hex-string
(ironclad:digest-sequence :sha256
(ironclad:ascii-string-to-byte-array str))))
(defvar *email* (alexandria:read-file-into-string "email"))
(defun base64 ()
(let ((email *email*))
(loop repeat 100 do
(if (ppcre:scan "@" email)
(print email)
(setf email (cl-base64:base64-string-to-string email))))))