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jeremybenn |
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package template
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import (
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"bytes"
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"fmt"
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"strings"
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)
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// urlFilter returns its input unless it contains an unsafe protocol in which
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// case it defangs the entire URL.
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func urlFilter(args ...interface{}) string {
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s, t := stringify(args...)
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if t == contentTypeURL {
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return s
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}
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if i := strings.IndexRune(s, ':'); i >= 0 && strings.IndexRune(s[:i], '/') < 0 {
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protocol := strings.ToLower(s[:i])
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if protocol != "http" && protocol != "https" && protocol != "mailto" {
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return "#" + filterFailsafe
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}
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}
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return s
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}
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// urlEscaper produces an output that can be embedded in a URL query.
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// The output can be embedded in an HTML attribute without further escaping.
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func urlEscaper(args ...interface{}) string {
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return urlProcessor(false, args...)
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}
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// urlEscaper normalizes URL content so it can be embedded in a quote-delimited
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// string or parenthesis delimited url(...).
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// The normalizer does not encode all HTML specials. Specifically, it does not
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// encode '&' so correct embedding in an HTML attribute requires escaping of
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// '&' to '&'.
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func urlNormalizer(args ...interface{}) string {
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return urlProcessor(true, args...)
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}
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// urlProcessor normalizes (when norm is true) or escapes its input to produce
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// a valid hierarchical or opaque URL part.
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func urlProcessor(norm bool, args ...interface{}) string {
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s, t := stringify(args...)
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if t == contentTypeURL {
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norm = true
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}
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var b bytes.Buffer
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written := 0
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// The byte loop below assumes that all URLs use UTF-8 as the
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// content-encoding. This is similar to the URI to IRI encoding scheme
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// defined in section 3.1 of RFC 3987, and behaves the same as the
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// EcmaScript builtin encodeURIComponent.
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// It should not cause any misencoding of URLs in pages with
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// Content-type: text/html;charset=UTF-8.
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for i, n := 0, len(s); i < n; i++ {
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c := s[i]
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switch c {
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// Single quote and parens are sub-delims in RFC 3986, but we
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// escape them so the output can be embedded in in single
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// quoted attributes and unquoted CSS url(...) constructs.
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// Single quotes are reserved in URLs, but are only used in
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// the obsolete "mark" rule in an appendix in RFC 3986
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// so can be safely encoded.
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case '!', '#', '$', '&', '*', '+', ',', '/', ':', ';', '=', '?', '@', '[', ']':
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if norm {
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continue
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}
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// Unreserved according to RFC 3986 sec 2.3
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// "For consistency, percent-encoded octets in the ranges of
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// ALPHA (%41-%5A and %61-%7A), DIGIT (%30-%39), hyphen (%2D),
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// period (%2E), underscore (%5F), or tilde (%7E) should not be
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// created by URI producers
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case '-', '.', '_', '~':
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continue
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case '%':
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// When normalizing do not re-encode valid escapes.
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if norm && i+2 < len(s) && isHex(s[i+1]) && isHex(s[i+2]) {
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continue
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}
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default:
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// Unreserved according to RFC 3986 sec 2.3
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if 'a' <= c && c <= 'z' {
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continue
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}
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if 'A' <= c && c <= 'Z' {
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continue
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}
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if '0' <= c && c <= '9' {
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continue
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}
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}
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b.WriteString(s[written:i])
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fmt.Fprintf(&b, "%%%02x", c)
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written = i + 1
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}
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if written == 0 {
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return s
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}
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b.WriteString(s[written:])
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return b.String()
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}
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