77 lines
2.5 KiB
Racket
77 lines
2.5 KiB
Racket
#lang racket
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(define memory (make-vector 1024 #\nul))
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(define (write-to-memory! str memory-start-index)
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(define str-length (string-length str))
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(define (loop str-index)
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(when (< str-index str-length)
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(vector-set! memory (+ memory-start-index str-index) (string-ref str str-index))
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(loop (+ str-index 1))))
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(loop 0))
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(define (init-memory!)
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(write-to-memory! "admin\0" 8)
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(write-to-memory! "<PASSWORD>\0" 14))
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(init-memory!)
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(define (read-from-memory memory-start-index)
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(define (loop str curr-index)
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(if (equal? (vector-ref memory curr-index) #\nul)
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str
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(loop (string-append str (string (vector-ref memory curr-index))) (+ curr-index 1))))
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(loop "" memory-start-index))
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(define (find-in-memory value)
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(define (loop memory-index value-index)
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(cond
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((>= memory-index (vector-length memory))
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#f)
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((>= value-index (string-length value))
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(if (equal? (vector-ref memory memory-index) #\nul)
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(- memory-index (string-length value))
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(loop (+ memory-index 1) 0)))
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((equal? (vector-ref memory memory-index) (string-ref value value-index))
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(loop (+ memory-index 1) (+ value-index 1)))
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(else
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(loop (+ memory-index 1) 0))))
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(loop 8 0))
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(define (find-next-value-in-memory-after start-memory-index-previous)
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(define (loop memory-index)
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(if (equal? (vector-ref memory memory-index) #\nul)
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(+ memory-index 1)
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(loop (+ memory-index 1))))
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(loop start-memory-index-previous))
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(define (get-password-for username)
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(define username-in-memory (find-in-memory username))
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(if username-in-memory
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(read-from-memory (find-next-value-in-memory-after username-in-memory))
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#f))
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(define (receive-login-attempt-username username)
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(write-to-memory! username 0))
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(define (passwords-match? received-password)
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(define login-username (read-from-memory 0))
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(define password-in-memory (get-password-for login-username))
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(equal? received-password password-in-memory))
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(define (accept-null-termination str)
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(string-replace str "\\0" "\0"))
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; Using \0 in your username or password string will be interpreted as the null character. Surely this is very safe and secure and will certainly not cause potential leaks
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(define (main)
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(display "username: ")
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(receive-login-attempt-username (accept-null-termination (read-line (current-input-port) 'any)))
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(display "password: ")
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(if (passwords-match? (read-line (current-input-port) 'any))
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(flag-or-something-idk)
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(display "Incorrect password!!!1!! >:(")))
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(main)
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