126 lines
5.4 KiB
Scheme
126 lines
5.4 KiB
Scheme
(module dispatch-passwords mzscheme
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(require (lib "kw.ss")
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(lib "url.ss" "net")
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(lib "contract.ss"))
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(require "dispatch.ss"
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"../private/util.ss"
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"../configuration/responders.ss"
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"../private/request-structs.ss"
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"../servlet/basic-auth.ss"
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"../private/response.ss")
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(provide/contract
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[interface-version dispatcher-interface-version?])
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(provide make)
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(define interface-version 'v1)
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(define/kw (make #:key
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; XXX Take authorized? function
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[password-file "passwords"]
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[authentication-responder
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(gen-authentication-responder "forbidden.html")])
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(define last-read-time (box #f))
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(define password-cache (box #f))
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(define (update-password-cache!)
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(when (and (file-exists? password-file) (memq 'read (file-or-directory-permissions password-file)))
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(let ([cur-mtime (file-or-directory-modify-seconds password-file)])
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(when (or (not (unbox last-read-time))
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(cur-mtime . > . (unbox last-read-time))
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(not (unbox password-cache)))
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(set-box! last-read-time cur-mtime)
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(set-box! password-cache (read-passwords password-file))))))
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(define (read-password-cache)
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(update-password-cache!)
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(unbox password-cache))
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(define (dispatch conn req)
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(define uri (request-uri req))
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(define path (url-path->string (url-path uri)))
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(define method (request-method req))
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(define denied? (read-password-cache))
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(cond
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[(and denied?
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(access-denied? method path (request-headers/raw req) denied?))
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=> (lambda (realm)
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(request-authentication conn method uri
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authentication-responder
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realm))]
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[else
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(next-dispatcher)]))
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(values update-password-cache!
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dispatch))
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;; ****************************************
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;; ****************************************
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;; ACCESS CONTROL
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;; pass-entry = (make-pass-entry str regexp (list sym str))
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(define-struct pass-entry (domain pattern users))
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;; access-denied? : Method string x-table denied? -> (or/c false str)
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;; denied?: str sym str -> (or/c str #f)
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;; the return string is the prompt for authentication
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(define (access-denied? method uri-str headers denied?)
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(define user-pass (extract-user-pass headers))
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(if user-pass
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(denied? uri-str (lowercase-symbol! (car user-pass)) (cdr user-pass))
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(denied? uri-str fake-user "")))
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(define-struct (exn:password-file exn) ())
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;; : host -> (str sym str -> (or/c str #f))
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;; to produce a function that checks if a given url path is accessible by a given user with a given
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;; password. If not, the produced function returns a string, prompting for the password.
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;; If the password file does not exist, all accesses are allowed. If the file is malformed, an
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;; exn:password-file is raised.
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(define (read-passwords password-path)
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(with-handlers ([void (lambda (exn)
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(raise (make-exn:password-file
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(format "could not load password file ~a" password-path)
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(current-continuation-marks))))])
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(let ([passwords
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(let ([raw (load password-path)])
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(unless (password-list? raw)
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(raise "malformed passwords"))
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(map (lambda (x) (make-pass-entry (car x) (regexp (cadr x)) (cddr x)))
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raw))])
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;; string symbol bytes -> (or/c #f string)
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(lambda (request-path user-name password)
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(ormap (lambda (x)
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(and (regexp-match (pass-entry-pattern x) request-path)
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(let ([name-pass (assq user-name (pass-entry-users x))])
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(if (and name-pass
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(string=?
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(cadr name-pass)
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(bytes->string/utf-8 password)))
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#f
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(pass-entry-domain x)))))
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passwords)))))
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(define fake-user (gensym))
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;; password-list? : TST -> bool
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;; Note: andmap fails for dotted pairs at end.
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;; This is okay, since #f ends up raising a caught exception anyway.
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(define (password-list? passwords)
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(and (list? passwords)
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(andmap (lambda (domain)
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(and (pair? domain) (pair? (cdr domain)) (list (cddr domain))
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(string? (car domain))
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(string? (cadr domain))
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(andmap (lambda (x)
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(and (pair? x) (pair? (cdr x)) (null? (cddr x))
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(symbol? (car x)) (string? (cadr x))))
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(cddr domain))))
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passwords)))
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;; request-authentication : connection Method URL iport oport host str bool -> bool
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;; GregP: at first look, it seems that this gets called when the user
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;; has supplied bad authentication credentials.
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(define (request-authentication conn method uri authentication-responder realm)
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(output-response/method
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conn
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(authentication-responder
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uri
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(make-header #"WWW-Authenticate" (string->bytes/utf-8 (format " Basic realm=\"~a\"" realm))))
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method))) |