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)
107 (string-contains l ":")) 1)
108 ((has-suffix? l ".txt" ".org" ".md") 0)
109 ((has-suffix? l ".png" ".jpg" ".gif" ".bmp" ".tif" ".tga") 'I)
110 ((has-suffix? l "?" "%3f") 7)
111 ((has-prefix? l "url:" "/url:") 'h)
115 ;;; Selector retrieval
117 (define (serve-selector raw-selector config)
118 (let* ((selector-list (string-split raw-selector "\t"))
119 (selector (car selector-list))
120 (arguments (cdr selector-list)))
121 (if (string-contains selector ":")
122 (let ((l (string-split selector ":")))
123 (serve-script (car l) (cdr l) config))
124 (case (infer-selector-type selector)
125 ((1) (serve-directory-file selector config))
126 ((7) (let ((l (string-split selector "?")))
127 (serve-script (car l) arguments config)))
128 ((0) (serve-text-file selector config))
129 ((h) (serve-url selector config))
130 (else (serve-binary-file selector config))))))
132 (define (legal-filename? filename config)
133 (and (string-prefix? (config-root-dir config)
134 (normalize-pathname filename))
135 (file-exists? filename)
136 (not (directory-exists? filename))
137 (file-readable? filename)))
139 (define (legal-script-filename? filename config)
140 (and (legal-filename? filename config)
141 (string-suffix? ".scm" filename)
142 (file-executable? filename)))
144 (define (serve-directory-file selector config)
145 (let ((filename (make-pathname (list (config-root-dir config) selector)
146 gopher-index-filename)))
147 (if (legal-filename? filename config)
149 (with-input-from-file filename
151 (let loop ((c (peek-char)))
158 (serve-record (read) selector config)
160 (serve-info-records (read-line)))
161 (loop (peek-char)))))))
162 (if (config-display-footer config)
163 (serve-info-records burrower-footer))
165 (error "No legal index file not found."))))
167 (define (serve-text-file selector config)
168 (let ((filename (make-pathname (config-root-dir config) selector)))
169 (if (legal-filename? filename config)
171 (with-input-from-file filename
178 (error "File not found." filename))))
180 (define (serve-binary-file selector config)
181 (let ((filename (make-pathname (config-root-dir config) selector)))
182 (if (legal-filename? filename config)
183 (with-input-from-file filename
185 (let loop ((b (read-byte)))
190 (loop (read-byte)))))))
191 (error "File not found." filename))))
193 (define (serve-url selector config)
194 (let ((url (substring selector 4)))
196 "<html><head><title>Redirection</title>"
197 "<meta http-equiv=\"refresh\" content=\"10; URL='" url "'\" />"
199 "<p>If you are seeing this page, your gopher browser does not "
200 "properly support URL directory entries or cannot follow such "
202 "<p>If you are viewing this page using a web browser, you should "
203 "be redirected shortly. Otherwise, you can manually open the "
204 "the follwing url:\n"
206 "<a href=\"" url "\">" url "</a>\n"
209 (define (serve-script selector arguments config)
210 (let ((filename (make-pathname (config-root-dir config) selector)))
211 (if (legal-script-filename? filename config)
212 (let* ((sexp (with-input-from-file filename read))
213 (script-result (with-selector-dir
216 (apply (eval sexp) arguments)))))
217 (when (pair? script-result)
218 (serve-records script-result
219 (pathname-directory selector) config)
221 (error "No legal index script not found." filename))))
226 (define (serve-records records dir-selector config)
229 (serve-record record dir-selector config))
232 (define (serve-info-records string)
236 (for-each (lambda (char)
237 (print* (if (eq? char #\tab)
241 (print "\tfake\tfake\t1\r"))
242 (string-split string "\n" #t)))
244 (define (serve-record record dir-selector config)
246 ((? string?) (serve-info-records record))
247 (('shell command) (serve-shell-command command dir-selector config))
248 (('eval expression) (serve-expression expression dir-selector config))
249 (('url display-string url)
250 (print #\h display-string "\tURL:" url
251 "\t" (config-host config)
252 "\t" (config-port config) "\r"))
253 ((type display-string selector host port)
254 (print type display-string "\t" selector "\t" host "\t" port "\r"))
255 ((type display-string selector host)
256 (serve-record (list type display-string selector host 70)
257 dir-selector config))
258 ((type display-string selector)
259 (serve-record (list type display-string
260 (make-pathname dir-selector selector)
261 (config-host config) (config-port config))
262 dir-selector config))
263 ((display-string selector)
264 (serve-record (list (infer-selector-type selector) display-string selector)
265 dir-selector config))
267 (serve-record (list (infer-selector-type selector) selector)
268 dir-selector config))
269 (else (error "Unknown record type."))))
271 (define (serve-shell-command command dir-selector config)
275 (let-values (((in-port out-port id) (process command)))
276 (let ((string (read-string #f in-port)))
277 (if (and (not (eof-object? string))
278 (> (string-length string) 0))
279 (serve-info-records (string-chomp string "\n")))
280 (close-input-port in-port)
281 (close-output-port out-port))))))
283 (define (serve-expression expression dir-selector config)
287 (serve-records (eval expression) dir-selector config))))
292 (define (with-current-working-directory directory thunk)
293 (let ((old-wd (current-directory))
297 (change-directory directory)
298 (set! result (thunk))
299 (change-directory old-wd)
302 (change-directory old-wd)
305 (define (with-selector-dir selector config thunk)
306 (with-current-working-directory
307 (make-pathname (config-root-dir config)
308 (pathname-directory selector)) thunk))
313 (define (print-usage progname)
315 progname " -h/--help\n"
316 progname " [-n/--no-footer] [-u/--user UID] [-g/--group GID] root-dir hostname [port]\n"
318 "The -n option tells the server to not display a directory footer."
319 "The -u and -g can be used to set the UID and GID of the process following"
320 "the creation of the TCP port listener (which often requires root)."))
323 (let* ((progname (car (argv)))
324 (config (make-config '() '() 70 #t '() '())))
325 (if (null? (cdr (argv)))
326 (print-usage progname)
327 (let loop ((args (cdr (argv))))
328 (let ((this-arg (car args))
329 (rest-args (cdr args)))
330 (if (string-prefix? "-" this-arg)
332 ((or (equal? this-arg "-h")
333 (equal? this-arg "--help"))
334 (print-usage progname))
335 ((or (equal? this-arg "-n")
336 (equal? this-arg "--no-footer"))
337 (config-display-footer-set! config #f)
339 ((or (equal? this-arg "-u")
340 (equal? this-arg "--user"))
341 (config-user-set! config (string->number (car rest-args)))
342 (loop (cdr rest-args)))
343 ((or (equal? this-arg "-g")
344 (equal? this-arg "--group"))
345 (config-group-set! config (string->number (car rest-args)))
346 (loop (cdr rest-args)))
348 (print-usage progname)))
350 (config-root-dir-set! config (car args))
351 (config-host-set! config (cadr args))
352 (if (>= (length rest-args) 2)
353 (config-port-set! config (string->number (caddr args))))
354 (run-server config))))))))
359 ;; (run-server (make-config "gopher-root" "localhost" 70 #t '() '())))