1 ;;; Burrower 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 burrower-version "1.0.0")
25 (define burrower-footer
27 "--------------------------------------------------\n"
28 "This gopher hole was dug using Burrower v" burrower-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))))
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* ((line (read-line in-port))
62 (selector (string-trim-both line)))
63 (let-values (((local-ip remote-ip) (tcp-addresses in-port)))
64 (print "Accepted connection from " remote-ip
65 " on " (seconds->string))
68 (with-output-to-port out-port
70 (serve-selector (if (= (string-length selector) 0)
74 (print "... served selector '" selector "'. Closing connection."))
76 (print-error-message o out-port)
77 (print-error-message o)
78 (print "Error while attempting to serve selector " selector ".")))))
79 (close-input-port in-port)
80 (close-output-port out-port))
81 (server-loop listener config))
83 ;;; Selector type inference
85 (define (true-for-one? predicate values)
88 (if (predicate (car values))
90 (true-for-one? predicate (cdr values)))))
92 (define (has-suffix? selector . suffixes)
93 (true-for-one? (lambda (suffix)
94 (string-suffix? suffix selector))
97 (define (has-prefix? selector . prefixes)
98 (true-for-one? (lambda (prefix)
99 (string-prefix? prefix selector))
102 (define (infer-selector-type selector)
103 (let ((l (string-downcase selector)))
105 ((or (= (string-length l) 0)
106 (string-suffix? "/" l)) 1)
107 ((has-suffix? l ".txt" ".org" ".md") 0)
108 ((has-suffix? l ".png" ".jpg" ".gif" ".bmp" ".tif" ".tga") 'I)
109 ((has-suffix? l "?" "%3f") 7)
110 ((has-prefix? l "url:" "/url:") 'h)
114 ;;; Selector retrieval
116 (define (serve-selector raw-selector config)
117 (let* ((selector-list (string-split raw-selector "\t"))
118 (selector (car selector-list))
119 (arguments (cdr selector-list)))
120 (if (string-contains selector "|")
121 (let ((l (string-split selector "|")))
122 (serve-script (car l) (cdr l) config))
123 (case (infer-selector-type selector)
124 ((1) (serve-directory-file selector config))
125 ((7) (let ((l (string-split selector "?")))
126 (serve-script (car l) arguments config)))
127 ((0) (serve-text-file selector config))
128 ((h) (serve-url selector config))
129 (else (serve-binary-file selector config))))))
131 (define (legal-filename? filename config)
132 (and (string-prefix? (config-root-dir config)
133 (normalize-pathname filename))
134 (file-exists? filename)
135 (not (directory-exists? filename))
136 (file-readable? filename)))
138 (define (legal-script-filename? filename config)
139 (and (legal-filename? filename config)
140 (string-suffix? ".scm" filename)
141 (file-executable? filename)))
143 (define (serve-directory-file selector config)
144 (let ((filename (make-pathname (list (config-root-dir config) selector)
145 gopher-index-filename)))
146 (if (legal-filename? filename config)
148 (with-input-from-file filename
150 (let loop ((c (peek-char)))
157 (serve-record (read) selector config)
159 (serve-info-records (read-line)))
160 (loop (peek-char)))))))
161 (if (config-display-footer config)
162 (serve-info-records burrower-footer))
164 (error "No legal index file not found."))))
166 (define (serve-text-file selector config)
167 (let ((filename (make-pathname (config-root-dir config) selector)))
168 (if (legal-filename? filename config)
170 (with-input-from-file filename
177 (error "File not found." filename))))
179 (define (serve-binary-file selector config)
180 (let ((filename (make-pathname (config-root-dir config) selector)))
181 (if (legal-filename? filename config)
182 (with-input-from-file filename
184 (let loop ((b (read-byte)))
189 (loop (read-byte)))))))
190 (error "File not found." filename))))
192 (define (serve-url selector config)
193 (let ((url (substring selector 4)))
195 "<html><head><title>Redirection</title>"
196 "<meta http-equiv=\"refresh\" content=\"10; URL='" url "'\" />"
198 "<p>If you are seeing this page, your gopher browser does not "
199 "properly support URL directory entries or cannot follow such "
201 "<p>If you are viewing this page using a web browser, you should "
202 "be redirected shortly. Otherwise, you can manually open the "
203 "the follwing url:\n"
205 "<a href=\"" url "\">" url "</a>\n"
208 (define (serve-script selector arguments config)
209 (let ((filename (make-pathname (config-root-dir config) selector)))
210 (if (legal-script-filename? filename config)
211 (let* ((sexp (with-input-from-file filename read))
212 (script-result (with-selector-dir
215 (apply (eval sexp) arguments)))))
216 (when (pair? script-result)
217 (serve-records script-result
218 (pathname-directory selector) config)
220 (error "No legal index script not found." filename))))
225 (define (serve-records records dir-selector config)
228 (serve-record record dir-selector config))
231 (define (serve-info-records string)
235 (for-each (lambda (char)
236 (print* (if (eq? char #\tab)
240 (print "\tfake\tfake\t1\r"))
241 (string-split string "\n" #t)))
243 (define (serve-record record dir-selector config)
245 ((? string?) (serve-info-records record))
246 (('shell command) (serve-shell-command command dir-selector config))
247 (('eval expression) (serve-expression expression dir-selector config))
248 (('url display-string url)
249 (print #\h display-string "\tURL:" url
250 "\t" (config-host config)
251 "\t" (config-port config) "\r"))
252 ((type display-string selector host port)
253 (print type display-string "\t" selector "\t" host "\t" port "\r"))
254 ((type display-string selector host)
255 (serve-record (list type display-string selector host 70)
256 dir-selector config))
257 ((type display-string selector)
258 (serve-record (list type display-string
259 (make-pathname dir-selector selector)
260 (config-host config) (config-port config))
261 dir-selector config))
262 ((display-string selector)
263 (serve-record (list (infer-selector-type selector) display-string selector)
264 dir-selector config))
266 (serve-record (list (infer-selector-type selector) selector)
267 dir-selector config))
268 (else (error "Unknown record type."))))
270 (define (serve-shell-command command dir-selector config)
274 (let-values (((in-port out-port id) (process command)))
275 (let ((string (read-string #f in-port)))
276 (if (and (not (eof-object? string))
277 (> (string-length string) 0))
278 (serve-info-records (string-chomp string "\n")))
279 (close-input-port in-port)
280 (close-output-port out-port))))))
282 (define (serve-expression expression dir-selector config)
286 (serve-records (eval expression) dir-selector config))))
291 (define (with-current-working-directory directory thunk)
292 (let ((old-wd (current-directory))
296 (change-directory directory)
297 (set! result (thunk))
298 (change-directory old-wd)
301 (change-directory old-wd)
304 (define (with-selector-dir selector config thunk)
305 (with-current-working-directory
306 (make-pathname (config-root-dir config)
307 (pathname-directory selector)) thunk))
312 (define (print-usage progname)
314 progname " -h/--help\n"
315 progname " [-n/--no-footer] [-u/--user UID] [-g/--group GID] root-dir hostname [port]\n"
317 "The -n option tells the server to not display a directory footer."
318 "The -u and -g can be used to set the UID and GID of the process following"
319 "the creation of the TCP port listener (which often requires root)."))
322 (let* ((progname (car (argv)))
323 (config (make-config '() '() 70 #t '() '())))
324 (if (null? (cdr (argv)))
325 (print-usage progname)
326 (let loop ((args (cdr (argv))))
327 (let ((this-arg (car args))
328 (rest-args (cdr args)))
329 (if (string-prefix? "-" this-arg)
331 ((or (equal? this-arg "-h")
332 (equal? this-arg "--help"))
333 (print-usage progname))
334 ((or (equal? this-arg "-n")
335 (equal? this-arg "--no-footer"))
336 (config-display-footer-set! config #f)
338 ((or (equal? this-arg "-u")
339 (equal? this-arg "--user"))
340 (config-user-set! config (string->number (car rest-args)))
341 (loop (cdr rest-args)))
342 ((or (equal? this-arg "-g")
343 (equal? this-arg "--group"))
344 (config-group-set! config (string->number (car rest-args)))
345 (loop (cdr rest-args)))
347 (print-usage progname)))
349 (config-root-dir-set! config (car args))
350 (config-host-set! config (cadr args))
351 (if (>= (length rest-args) 2)
352 (config-port-set! config (string->number (caddr args))))
353 (run-server config))))))))
358 ;; (run-server (make-config "gopher-root" "localhost" 70 #t '() '())))