1 ;;; Scratchy gopher server
3 ;; Requires Chicken 5.0.0.
17 (chicken process-context)
18 (chicken process-context posix)
19 srfi-1 srfi-13 matchable)
23 (define scratchy-version "1.2.0")
25 (define scratchy-footer
27 "--------------------------------------------------\n"
28 "This gopher hole was dug using Scratchy v" scratchy-version ".\n"
29 "Powered by Chicken Scheme!"))
31 (define gopher-index-filename "index")
35 ;; We don't yet use worker threads here to handle requests,
36 ;; the server just blocks until the first request is finished.
37 ;; While we should fix this, it's actually probably okay, as
38 ;; we genuinely don't expect a huge flood of gopher traffic. :-(
41 root-dir host port display-footer user group)
43 (define (run-server config)
44 (set-buffering-mode! (current-output-port) #:line)
45 (let ((listener (tcp-listen (config-port config) 10 "::")))
46 (print "Gopher server listening on port " (config-port config) " ...")
48 (server-loop listener config))
51 (define (drop-privs config)
52 (let ((uid (config-user config))
53 (gid (config-group config)))
54 (if (not (null? gid)) ; Group first, since only root can switch groups.
55 (set! (current-group-id) gid))
57 (set! (current-user-id) uid))))
59 (define (server-loop listener config)
60 (let-values (((in-port out-port) (tcp-accept listener)))
61 (let-values (((local-ip remote-ip) (tcp-addresses in-port)))
62 (print "Accepted connection from " remote-ip
63 " on " (seconds->string)))
65 (let* ((line (read-line in-port))
66 (selector (string-trim-both line)))
69 (with-output-to-port out-port
71 (serve-selector (if (= (string-length selector) 0)
75 (print "... served selector '" selector "'. Closing connection."))
77 (print-error-message o out-port)
78 (print-error-message o)
79 (print "Error while attempting to serve selector " selector "."))))
81 (print-error-message o)))
82 (close-input-port in-port)
83 (close-output-port out-port))
84 (server-loop listener config))
86 ;;; Selector type inference
88 (define (true-for-one? predicate values)
91 (if (predicate (car values))
93 (true-for-one? predicate (cdr values)))))
95 (define (has-suffix? selector . suffixes)
96 (true-for-one? (lambda (suffix)
97 (string-suffix? suffix selector))
100 (define (has-prefix? selector . prefixes)
101 (true-for-one? (lambda (prefix)
102 (string-prefix? prefix selector))
105 (define (infer-selector-type selector)
106 (let ((l (string-downcase selector)))
108 ((or (= (string-length l) 0)
109 (string-suffix? "/" l)) 1)
110 ((has-suffix? l ".txt" ".org" ".md") 0)
111 ((has-suffix? l ".png" ".jpg" ".gif" ".bmp" ".tif" ".tga") 'I)
112 ((has-suffix? l "?" "%3f") 7)
113 ((has-prefix? l "url:" "/url:") 'h)
117 ;;; Selector retrieval
119 (define (serve-selector raw-selector config)
120 (let* ((selector-list (string-split raw-selector "\t"))
121 (selector (car selector-list))
122 (arguments (cdr selector-list)))
123 (if (string-contains selector "|")
124 (let ((l (string-split selector "|")))
125 (serve-script (car l) (cdr l) config))
126 (case (infer-selector-type selector)
127 ((1) (serve-directory-file selector config))
128 ((7) (let ((l (string-split selector "?")))
129 (serve-script (car l) arguments config)))
130 ((0) (serve-text-file selector config))
131 ((h) (serve-url selector config))
132 (else (serve-binary-file selector config))))))
134 (define (legal-filename? filename config)
135 (and (string-prefix? (config-root-dir config)
136 (normalize-pathname filename))
137 (file-exists? filename)
138 (not (directory-exists? filename))
139 (file-readable? filename)))
141 (define (legal-script-filename? filename config)
142 (and (legal-filename? filename config)
143 (string-suffix? ".scm" filename)
144 (file-executable? filename)))
146 (define (serve-directory-file selector config)
147 (let ((filename (make-pathname (list (config-root-dir config) selector)
148 gopher-index-filename)))
149 (if (legal-filename? filename config)
151 (with-input-from-file filename
153 (let loop ((c (peek-char)))
160 (serve-record (read) selector config)
162 (serve-info-records (read-line)))
163 (loop (peek-char)))))))
164 (if (config-display-footer config)
165 (serve-info-records scratchy-footer))
167 (error "No legal index file not found."))))
169 (define (serve-text-file selector config)
170 (let ((filename (make-pathname (config-root-dir config) selector)))
171 (if (legal-filename? filename config)
173 (with-input-from-file filename
180 (error "File not found." filename))))
182 (define (serve-binary-file selector config)
183 (let ((filename (make-pathname (config-root-dir config) selector)))
184 (if (legal-filename? filename config)
185 (with-input-from-file filename
187 (let loop ((b (read-byte)))
192 (loop (read-byte)))))))
193 (error "File not found." filename))))
195 (define (serve-url selector config)
196 (let ((url (substring selector 4)))
198 "<html><head><title>Redirection</title>"
199 "<meta http-equiv=\"refresh\" content=\"10; URL='" url "'\" />"
201 "<p>If you are seeing this page, your gopher browser does not "
202 "properly support URL directory entries or cannot follow such "
204 "<p>If you are viewing this page using a web browser, you should "
205 "be redirected shortly. Otherwise, you can manually open the "
206 "the follwing url:\n"
208 "<a href=\"" url "\">" url "</a>\n"
211 (define (serve-script selector arguments config)
212 (let ((filename (make-pathname (config-root-dir config) selector)))
213 (if (legal-script-filename? filename config)
214 (let* ((sexp (with-input-from-file filename read))
215 (script-result (with-selector-dir
218 (apply (eval sexp) arguments)))))
219 (when (pair? script-result)
220 (serve-records script-result
221 (pathname-directory selector) config)
223 (error "No legal index script not found." filename))))
228 (define (serve-records records dir-selector config)
231 (serve-record record dir-selector config))
234 (define (serve-info-records string)
238 (for-each (lambda (char)
239 (print* (if (eq? char #\tab)
243 (print "\tfake\tfake\t1\r"))
244 (string-split string "\n" #t)))
246 (define (serve-record record dir-selector config)
248 ((? string?) (serve-info-records record))
249 (('shell command) (serve-shell-command command dir-selector config))
250 (('eval expression) (serve-expression expression dir-selector config))
251 (('url display-string url)
252 (print #\h display-string "\tURL:" url
253 "\t" (config-host config)
254 "\t" (config-port config) "\r"))
255 ((type display-string selector host port)
256 (print type display-string "\t" selector "\t" host "\t" port "\r"))
257 ((type display-string selector host)
258 (serve-record (list type display-string selector host 70)
259 dir-selector config))
260 ((type display-string selector)
261 (serve-record (list type display-string
262 (make-pathname dir-selector selector)
263 (config-host config) (config-port config))
264 dir-selector config))
265 ((display-string selector)
266 (serve-record (list (infer-selector-type selector) display-string selector)
267 dir-selector config))
269 (serve-record (list (infer-selector-type selector) selector)
270 dir-selector config))
271 (else (error "Unknown record type."))))
273 (define (serve-shell-command command dir-selector config)
277 (let-values (((in-port out-port id) (process command)))
278 (let ((string (read-string #f in-port)))
279 (if (and (not (eof-object? string))
280 (> (string-length string) 0))
281 (serve-info-records (string-chomp string "\n")))
282 (close-input-port in-port)
283 (close-output-port out-port))))))
285 (define (serve-expression expression dir-selector config)
289 (serve-records (eval expression) dir-selector config))))
294 (define (with-current-working-directory directory thunk)
295 (let ((old-wd (current-directory))
299 (change-directory directory)
300 (set! result (thunk))
301 (change-directory old-wd)
304 (change-directory old-wd)
307 (define (with-selector-dir selector config thunk)
308 (with-current-working-directory
309 (make-pathname (config-root-dir config)
310 (pathname-directory selector)) thunk))
315 (define (print-usage progname)
317 progname " -h/--help\n"
318 progname " [-n/--no-footer] [-u/--user UID] [-g/--group GID] root-dir hostname [port]\n"
320 "The -n option tells the server to not display a directory footer.\n"
321 "The -u and -g can be used to set the UID and GID of the process following\n"
322 "the creation of the TCP port listener (which often requires root)."))
325 (let* ((progname (pathname-file (car (argv))))
326 (config (make-config '() '() 70 #t '() '())))
327 (if (null? (cdr (argv)))
328 (print-usage progname)
329 (let loop ((args (cdr (argv))))
330 (let ((this-arg (car args))
331 (rest-args (cdr args)))
332 (if (string-prefix? "-" this-arg)
334 ((or (equal? this-arg "-h")
335 (equal? this-arg "--help"))
336 (print-usage progname))
337 ((or (equal? this-arg "-n")
338 (equal? this-arg "--no-footer"))
339 (config-display-footer-set! config #f)
341 ((or (equal? this-arg "-u")
342 (equal? this-arg "--user"))
343 (config-user-set! config (string->number (car rest-args)))
344 (loop (cdr rest-args)))
345 ((or (equal? this-arg "-g")
346 (equal? this-arg "--group"))
347 (config-group-set! config (string->number (car rest-args)))
348 (loop (cdr rest-args)))
350 (print-usage progname)))
352 (config-root-dir-set! config (car args))
353 (config-host-set! config (cadr args))
354 (if (>= (length rest-args) 2)
355 (config-port-set! config (string->number (caddr args))))
356 (run-server config))))))))
361 ;; (run-server (make-config "gopher-root" "localhost" 70 #t '() '())))