;; -*- mode: scheme; coding: utf-8 -*- ;; Copyright © 2009, 2010, 2012, 2013 Göran Weinholt ;; Permission is hereby granted, free of charge, to any person obtaining a ;; copy of this software and associated documentation files (the "Software"), ;; to deal in the Software without restriction, including without limitation ;; the rights to use, copy, modify, merge, publish, distribute, sublicense, ;; and/or sell copies of the Software, and to permit persons to whom the ;; Software is furnished to do so, subject to the following conditions: ;; The above copyright notice and this permission notice shall be included in ;; all copies or substantial portions of the Software. ;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR ;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, ;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL ;; THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER ;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING ;; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER ;; DEALINGS IN THE SOFTWARE. #!r6rs ;; RFC 4648 Base-N Encodings (library (8sync contrib base64) (export base64-encode base64-decode base64-alphabet base64url-alphabet get-delimited-base64 put-delimited-base64) (import (rnrs) (only (srfi :13 strings) string-index string-prefix? string-suffix? string-concatenate string-trim-both)) (define base64-alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/") (define base64url-alphabet "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_") (define base64-encode (case-lambda ;; Simple interface. Returns a string containing the canonical ;; base64 representation of the given bytevector. ((bv) (base64-encode bv 0 (bytevector-length bv) #f #f base64-alphabet #f)) ((bv start) (base64-encode bv start (bytevector-length bv) #f #f base64-alphabet #f)) ((bv start end) (base64-encode bv start end #f #f base64-alphabet #f)) ((bv start end line-length) (base64-encode bv start end line-length #f base64-alphabet #f)) ((bv start end line-length no-padding) (base64-encode bv start end line-length no-padding base64-alphabet #f)) ((bv start end line-length no-padding alphabet) (base64-encode bv start end line-length no-padding alphabet #f)) ;; Base64 encodes the bytes [start,end[ in the given bytevector. ;; Lines are limited to line-length characters (unless #f), ;; which must be a multiple of four. To omit the padding ;; characters (#\=) set no-padding to a true value. If port is ;; #f, returns a string. ((bv start end line-length no-padding alphabet port) (assert (or (not line-length) (zero? (mod line-length 4)))) (let-values (((p extract) (if port (values port (lambda () (values))) (open-string-output-port)))) (letrec ((put (if line-length (let ((chars 0)) (lambda (p c) (when (fx=? chars line-length) (set! chars 0) (put-char p #\linefeed)) (set! chars (fx+ chars 1)) (put-char p c))) put-char))) (let lp ((i start)) (cond ((= i end)) ((<= (+ i 3) end) (let ((x (bytevector-uint-ref bv i (endianness big) 3))) (put p (string-ref alphabet (fxbit-field x 18 24))) (put p (string-ref alphabet (fxbit-field x 12 18))) (put p (string-ref alphabet (fxbit-field x 6 12))) (put p (string-ref alphabet (fxbit-field x 0 6))) (lp (+ i 3)))) ((<= (+ i 2) end) (let ((x (fxarithmetic-shift-left (bytevector-u16-ref bv i (endianness big)) 8))) (put p (string-ref alphabet (fxbit-field x 18 24))) (put p (string-ref alphabet (fxbit-field x 12 18))) (put p (string-ref alphabet (fxbit-field x 6 12))) (unless no-padding (put p #\=)))) (else (let ((x (fxarithmetic-shift-left (bytevector-u8-ref bv i) 16))) (put p (string-ref alphabet (fxbit-field x 18 24))) (put p (string-ref alphabet (fxbit-field x 12 18))) (unless no-padding (put p #\=) (put p #\=))))))) (extract))))) ;; Create a lookup table for the alphabet and remember the latest table. (define get-decode-table (let ((ascii-table #f) (extra-table '()) ;in the unlikely case of unicode chars (table-alphabet #f)) (lambda (alphabet) (unless (eq? alphabet table-alphabet) ;; Rebuild the table. (do ((ascii (make-vector 128 #f)) (extra '()) (i 0 (+ i 1))) ((= i (string-length alphabet)) (set! ascii-table ascii) (set! extra-table extra)) (let ((c (char->integer (string-ref alphabet i)))) (if (fx<=? c 127) (vector-set! ascii c i) (set! extra (cons (cons c i) extra))))) (set! table-alphabet alphabet)) (values ascii-table extra-table)))) ;; Decodes a correctly padded base64 string, optionally ignoring ;; non-alphabet characters. (define base64-decode (case-lambda ((str) (base64-decode str base64-alphabet #f)) ((str alphabet) (base64-decode str alphabet #f)) ((str alphabet port) (base64-decode str alphabet port #t)) ((str alphabet port strict?) (define (pad? c) (eqv? c (char->integer #\=))) (let-values (((p extract) (if port (values port (lambda () (values))) (open-bytevector-output-port))) ((ascii extra) (get-decode-table alphabet))) (define-syntax lookup (syntax-rules () ((_ c) (or (and (fx<=? c 127) (vector-ref ascii c)) (cond ((assv c extra) => cdr) (else #f)))))) (let* ((len (if strict? (string-length str) (let lp ((i (fx- (string-length str) 1))) ;; Skip trailing invalid chars. (cond ((fxzero? i) 0) ((let ((c (char->integer (string-ref str i)))) (or (lookup c) (pad? c))) (fx+ i 1)) (else (lp (fx- i 1)))))))) (let lp ((i 0)) (cond ((fx=? i len) (extract)) ((fx<=? i (fx- len 4)) (let lp* ((c1 (char->integer (string-ref str i))) (c2 (char->integer (string-ref str (fx+ i 1)))) (c3 (char->integer (string-ref str (fx+ i 2)))) (c4 (char->integer (string-ref str (fx+ i 3)))) (i i)) (let ((i1 (lookup c1)) (i2 (lookup c2)) (i3 (lookup c3)) (i4 (lookup c4))) (cond ((and i1 i2 i3 i4) ;; All characters present and accounted for. ;; The most common case. (let ((x (fxior (fxarithmetic-shift-left i1 18) (fxarithmetic-shift-left i2 12) (fxarithmetic-shift-left i3 6) i4))) (put-u8 p (fxbit-field x 16 24)) (put-u8 p (fxbit-field x 8 16)) (put-u8 p (fxbit-field x 0 8)) (lp (fx+ i 4)))) ((and i1 i2 i3 (pad? c4) (= i (- len 4))) ;; One padding character at the end of the input. (let ((x (fxior (fxarithmetic-shift-left i1 18) (fxarithmetic-shift-left i2 12) (fxarithmetic-shift-left i3 6)))) (put-u8 p (fxbit-field x 16 24)) (put-u8 p (fxbit-field x 8 16)) (lp (fx+ i 4)))) ((and i1 i2 (pad? c3) (pad? c4) (= i (- len 4))) ;; Two padding characters. (let ((x (fxior (fxarithmetic-shift-left i1 18) (fxarithmetic-shift-left i2 12)))) (put-u8 p (fxbit-field x 16 24)) (lp (fx+ i 4)))) ((not strict?) ;; Non-alphabet characters. (let lp ((i i) (c* '()) (n 4)) (cond ((fxzero? n) ;; Found four valid characters. (lp* (cadddr c*) (caddr c*) (cadr c*) (car c*) (fx- i 4))) ((fx=? i len) (error 'base64-decode "Invalid input in non-strict mode." i c*)) (else ;; Gather alphabetic (or valid ;; padding) characters. (let ((c (char->integer (string-ref str i)))) (cond ((or (lookup c) (and (pad? c) (fx<=? n 2) (fx=? i (fx- len n)))) (lp (fx+ i 1) (cons c c*) (fx- n 1))) (else (lp (fx+ i 1) c* n)))))))) (else (error 'base64-decode "Invalid input in strict mode." c1 c2 c3 c4)))))) (else (error 'base64-decode "The input is too short, it may be missing padding." i))))))))) (define (get-line-comp f port) (if (port-eof? port) (eof-object) (f (get-line port)))) ;; Reads the common -----BEGIN/END type----- delimited format from ;; the given port. Returns two values: a string with the type and a ;; bytevector containing the base64 decoded data. The second value ;; is the eof object if there is an eof before the BEGIN delimiter. (define get-delimited-base64 (case-lambda ((port) (get-delimited-base64 port #t)) ((port strict) (define (get-first-data-line port) ;; Some MIME data has header fields in the same format as mail ;; or http. These are ignored. (let ((line (get-line-comp string-trim-both port))) (cond ((eof-object? line) line) ((string-index line #\:) (let lp () ;read until empty line (let ((line (get-line-comp string-trim-both port))) (if (string=? line "") (get-line-comp string-trim-both port) (lp))))) (else line)))) (let ((line (get-line-comp string-trim-both port))) (cond ((eof-object? line) (values "" (eof-object))) ((string=? line "") (get-delimited-base64 port)) ((and (string-prefix? "-----BEGIN " line) (string-suffix? "-----" line)) (let* ((type (substring line 11 (- (string-length line) 5))) (endline (string-append "-----END " type "-----"))) (let-values (((outp extract) (open-bytevector-output-port))) (let lp ((line (get-first-data-line port))) (cond ((eof-object? line) (error 'get-delimited-base64 "unexpected end of file")) ((string-prefix? "-" line) (unless (string=? line endline) (error 'get-delimited-base64 "bad end delimiter" type line)) (values type (extract))) (else (unless (and (= (string-length line) 5) (string-prefix? "=" line)) ;Skip Radix-64 checksum (base64-decode line base64-alphabet outp)) (lp (get-line-comp string-trim-both port)))))))) (else ;skip garbage (like in openssl x509 -in foo -text output). (get-delimited-base64 port))))))) (define put-delimited-base64 (case-lambda ((port type bv line-length) (display (string-append "-----BEGIN " type "-----\n") port) (base64-encode bv 0 (bytevector-length bv) line-length #f base64-alphabet port) (display (string-append "\n-----END " type "-----\n") port)) ((port type bv) (put-delimited-base64 port type bv 76)))))