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;;; 822.scm - parsing RFC2822 style message
;;;
;;; Copyright (c) 2000-2014 Shiro Kawai <shiro@acm.org>
;;;
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;;
;;; 1. Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;;
;;; 2. Redistributions in binary form must reproduce the above copyright
;;; notice, this list of conditions and the following disclaimer in the
;;; documentation and/or other materials provided with the distribution.
;;;
;;; 3. Neither the name of the authors nor the names of its contributors
;;; may be used to endorse or promote products derived from this
;;; software without specific prior written permission.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;;; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
;;; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
;;; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
;;; OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
;;; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
;;; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
;;; PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
;;; LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;;
;; Parser and constructor of the message defined in
;; RFC2822 Internet Message Format
;; http://www.ietf.org/rfc/rfc2822.txt
(define-module rfc.822
(use srfi-1)
(use srfi-13)
(use srfi-19)
(use text.parse)
(use gauche.regexp)
(use util.match)
(export <rfc822-parse-error> rfc822-parse-errorf
rfc822-read-headers rfc822-header->list rfc822-header-ref
rfc822-skip-cfws
*rfc822-atext-chars* *rfc822-standard-tokenizers*
rfc822-atom rfc822-dot-atom rfc822-quoted-string
rfc822-next-token rfc822-field->tokens
rfc822-parse-date rfc822-date->date date->rfc822-date
rfc822-invalid-header-field rfc822-write-headers
)
)
(select-module rfc.822)
;;=================================================================
;; Parsers
;;
;;-----------------------------------------------------------------
;; A condition reported when rfc822 parser finds an error.
;;
;; For most practical applications, it is useful to handle
;; rfc822 syntax errors gracefully. So the rfc822 and mime procedures
;; tries to return a reasonable value even if the input is not strictly
;; conforming the RFCs. Some routines have an option to be more strict,
;; and they raise <rfc822-parse-error> when the option is given and
;; they find a violation.
;;
;; TODO: We need some consistent way to switch these 'graceful' and
;; 'strict' modes throughout the libraries; otherwise the API would be
;; pretty confusing. Something to consider as we add more high-level
;; parsers.
(define-condition-type <rfc822-parse-error> <error> #f
(header-field-name)
(header-field-body))
(define (rfc822-parse-errorf name body fmt . args)
(apply errorf <rfc822-parse-error>
:header-field-name name
:header-field-body body
fmt args))
;;-----------------------------------------------------------------
;; Generic header parser. Returns ((name body) ...)
;; Does process unfolding.
;; May throw <rfc822-parse-error> if :strict? is true.
(define (rfc822-read-headers iport :key (strict? #f)
(reader (cut read-line <> #t)))
(define (accum name bodies r)
(cons (list name (string-concatenate-reverse bodies)) r))
(define (drop-leading-fws body)
(if (string-incomplete? body)
body ;; this message is not RFC2822 compliant anyway
(string-trim body)))
(let loop ([r '()]
[line (reader iport)])
(cond
[(eof-object? line) (reverse! r)]
[(string-null? line) (reverse! r)]
[else
(receive (n body) (string-scan line #\: 'both)
(let1 name (and-let* ([ (string? n) ]
[name (string-incomplete->complete n)]
[name (string-trim-both name)]
[ (string-every #[\u0021-\u0039\u003b-\u007e] name) ])
(string-downcase name))
(cond
[name
(let loop2 ([nline (reader iport)]
[bodies (list (drop-leading-fws body))])
(cond [(eof-object? nline)
;; maybe premature end of the message
(if strict?
(rfc822-parse-errorf
#f #f "premature end of message header")
(reverse! (accum name bodies r)))]
[(string-null? nline) ;; end of the header
(reverse! (accum name bodies r))]
[(memv (string-byte-ref nline 0) '(9 32))
;; careful for byte strings
(loop2 (reader iport) (cons nline bodies))]
[else
(loop (accum name bodies r) nline)]))]
[strict? (rfc822-parse-errorf #f #f "bad header line: ~s" line)]
[else (loop r (reader iport))])))])
))
(define (rfc822-header-ref header field-name :optional (default #f))
(cond [(assoc field-name header) => cadr]
[else default]))
;; backward compatibility
(define rfc822-header->list rfc822-read-headers)
;;------------------------------------------------------------------
;; Comments, quoted pairs, atoms and quoted string. Section 3.2
;;
;; skip comments and white spaces, then returns the head char.
(define (rfc822-skip-cfws input)
(define (scan c)
(cond [(eof-object? c) c]
[(char=? c #\( ) (in-comment (peek-next-char input))]
[(char-whitespace? c) (scan (peek-next-char input))]
[else c]))
(define (in-comment c)
(cond [(eof-object? c) c]
[(char=? c #\) ) (scan (peek-next-char input))]
[(char=? c #\\ ) (read-char input) (in-comment (peek-next-char input))]
[(char=? c #\( ) (in-comment (in-comment (peek-next-char input)))]
[else (in-comment (peek-next-char input))]))
(scan (peek-char input)))
;; Basic tokenizers. Supposed to be used for higher-level parsers.
(define-constant *rfc822-atext-chars* #[A-Za-z0-9!#$%&'*+/=?^_`{|}~-])
(define (rfc822-atom input)
(next-token-of *rfc822-atext-chars* input))
;; NB: this is loose, but usually OK.
(define (rfc822-dot-atom input)
(next-token-of `(,*rfc822-atext-chars* #\.) input))
;; Assuming the first char in input is DQUOTE
(define (rfc822-quoted-string input)
(let1 r (open-output-string :private? #t)
(define (finish) (get-output-string r))
(let loop ([c (peek-next-char input)])
(cond [(eof-object? c) (finish)];; tolerate missing closing DQUOTE
[(char=? c #\") (read-char input) (finish)] ;; discard DQUOTE
[(char=? c #\\)
(let1 c (peek-next-char input)
(cond [(eof-object? c) (finish)] ;; tolerate stray backslash
[else (write-char c r) (loop (peek-next-char input))]))]
[else (write-char c r) (loop (peek-next-char input))]))))
;; Default tokenizer table
(define-constant *rfc822-standard-tokenizers*
`((#[\"] . ,rfc822-quoted-string)
(,*rfc822-atext-chars* . ,rfc822-dot-atom)))
;; Returns the next token or EOF
(define (rfc822-next-token input :optional (table *rfc822-standard-tokenizers*))
(let ([toktab (map (^e (if (char-set? e)
(cons e (cut next-token-of e <>))
e))
table)]
[c (rfc822-skip-cfws input)])
(cond [(eof-object? c) c]
[(find (^e (char-set-contains? (car e) c)) toktab)
=> (^e ((cdr e) input))]
[else (read-char input)])))
;; returns a list of tokens, for convenience
(define (rfc822-field->tokens field . opts)
(call-with-input-string field
(cut port->list (cut apply rfc822-next-token <> opts) <>)))
;;------------------------------------------------------------------
;; Date and time, section 3.3
;;
;; Takes RFC-822 type date string, and returns eight values:
;; year, month, day-of-month, hour, minutes, seconds, timezone, day-of-week.
;; Timezone is an offset from UT in minutes. Day-of-week is a day from
;; sunday, and may be #f if that information is not available.
;; If the string is not parsable, all the elements are #f.
;; NB: This function follows the new definition of date format in RFC2822,
;; but may fail to recognize "obsolete" format, which allows arbitrary
;; comments appear between words.
(define (rfc822-parse-date string)
(define (dow->number dow)
(list-index (cut string=? <> dow)
'("Sun" "Mon" "Tue" "Wed" "Thu" "Fri" "Sat")))
(define (mon->number mon)
(+ 1 (list-index (cut string=? <> mon)
'("Jan" "Feb" "Mar" "Apr" "May" "Jun"
"Jul" "Aug" "Sep" "Oct" "Nov" "Dec"))))
(define (year->number year) ;; see obs-year definition of RFC2822
(and-let* ([y (string->number year)])
(cond [(< y 50) (+ y 2000)]
[(< y 100) (+ y 1900)]
[else y])))
(define (tz->number tz)
(cond [(equal? tz "-0000") #f] ;;no effective TZ info; see 3.3 of RFC2822
[(string->number tz)]
[(assoc-ref '(("UT" . 0) ("GMT" . 0) ("EDT" . -400) ("EST" . -500)
("CDT" . -500) ("CST" . -600) ("MDT" . -600)
("MST" . -700) ("PDT" . -700) ("PST" . -800)) tz)]
[else #f]))
(rxmatch-case string
(#/((Sun|Mon|Tue|Wed|Thu|Fri|Sat)\s*,)?\s*(\d+)\s*(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\s*(\d\d(\d\d)?)\s+(\d\d)\s*:\s*(\d\d)(\s*:\s*(\d\d))?(\s+([+-]\d\d\d\d|[A-Z][A-Z][A-Z]?))?/
(#f bebe dow dom mon yr #f hour min #f sec #f tz)
(values (year->number yr)
(mon->number mon)
(string->number dom)
(string->number hour)
(string->number min)
(and sec (string->number sec))
(and tz (tz->number tz))
(and dow (dow->number dow))))
(else (values #f #f #f #f #f #f #f #f))))
;; returns it by srfi-19 date
(define (rfc822-date->date string)
(receive (year month day hour min sec tz . rest)
(rfc822-parse-date string)
(and year
(make-date 0 sec min hour day month year
(receive (quot rem) (quotient&remainder tz 100)
(+ (* quot 3600) (* rem 60)))))))
;; inverse of rfc822-date->date. Take srfi-19 date and returns
;; formatted string.
(define (date->rfc822-date date)
(let1 tz (date-zone-offset date)
(format "~a, ~2d ~a ~4d ~2,'0d:~2,'0d:~2,'0d ~a~2,'0d~2,'0d"
(~ '#("Sun" "Mon" "Tue" "Wed" "Thu" "Fri" "Sat")
(date-week-day date))
(date-day date)
(~ '#("" "Jan" "Feb" "Mar" "Apr" "May" "Jun"
"Jul" "Aug" "Sep" "Oct" "Nov" "Dec")
(date-month date))
(date-year date)
(date-hour date) (date-minute date) (date-second date)
(if (>= tz 0) "+" "-")
(quotient (abs tz) 3600)
(modulo (quotient (abs tz) 60) 60))))
;;------------------------------------------------------------------
;; Address specification (Section 3.4)
;;
;; The EBNF syntax in RFC2822 requires arbitrary lookahead,
;; so straight recursive-descent parser won't work.
;;
;; to be written
;;=================================================================
;; Constructors
;;
;; Writes out the header fields specified by HEADERS, which is
;; ((name body) ...).
(define (rfc822-write-headers headers :key
(output (current-output-port))
(check :error) ; #f, :ignore, :error or proc
(continue #f))
(define (process headers)
(dolist [field headers]
(display (car field) output)
(display ": " output)
(display (cadr field) output)
(unless (string-suffix? "\r\n" (cadr field))
(display "\r\n" output)))
(unless continue (display "\r\n" output)))
(define (bad name body reason)
(errorf "Illegal RFC2822 header field data (~a): ~a: ~,,,,80:a" reason name body))
(if (memv check '(#f :ignore))
(process headers)
(let loop ([hs headers]
[hs2 '()])
(match hs
[() (process (reverse hs2))]
[((name body) . rest)
(cond [(rfc822-invalid-header-field (string-append name ": " body))
=> (^[reason]
(if (eq? check :error)
(bad name body reason)
(receive (name2 body2) (check name body reason)
(if (and (equal? name name2) (equal? body body2))
(bad name body reason)
(loop `((,name2 ,body2) . ,rest) hs2)))))]
[else (loop rest `((,name ,body) . ,hs2))])]
[else
(error "Invalid header data:" headers)]))))
(define (rfc822-invalid-header-field body)
(cond [(string-incomplete? body) 'incomplete-string]
[(string-index body #[^\u0001-\u007f]) 'bad-character]
[else
(let1 lines (string-split body "\r\n ")
(cond [(any (^s (> (string-size s) 998)) lines) 'line-too-long]
[(any (^s (string-index s #[\u000d\u000a])) lines) 'stray-crlf]
[else #f]))]))
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