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striptag.go
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striptag.go
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/*
Copyright (c) 2009 The Go Authors. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* 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.
* Neither the name of Google Inc. 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.
*/
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the above file.
package helper
import (
"bytes"
"encoding/json"
"fmt"
"html"
"io"
"io/ioutil"
"path/filepath"
"reflect"
"strings"
"sync"
"text/template"
"text/template/parse"
"unicode"
"unicode/utf8"
)
// htmlNospaceEscaper escapes for inclusion in unquoted attribute values.
func htmlNospaceEscaper(args ...interface{}) string {
s, t := stringify(args...)
if t == contentTypeHTML {
return htmlReplacer(StripTags(s), htmlNospaceNormReplacementTable, false)
}
return htmlReplacer(s, htmlNospaceReplacementTable, false)
}
// attrEscaper escapes for inclusion in quoted attribute values.
func attrEscaper(args ...interface{}) string {
s, t := stringify(args...)
if t == contentTypeHTML {
return htmlReplacer(StripTags(s), htmlNormReplacementTable, true)
}
return htmlReplacer(s, htmlReplacementTable, true)
}
// rcdataEscaper escapes for inclusion in an RCDATA element body.
func rcdataEscaper(args ...interface{}) string {
s, t := stringify(args...)
if t == contentTypeHTML {
return htmlReplacer(s, htmlNormReplacementTable, true)
}
return htmlReplacer(s, htmlReplacementTable, true)
}
// htmlEscaper escapes for inclusion in HTML text.
func htmlEscaper(args ...interface{}) string {
s, t := stringify(args...)
if t == contentTypeHTML {
return s
}
return htmlReplacer(s, htmlReplacementTable, true)
}
// htmlReplacementTable contains the runes that need to be escaped
// inside a quoted attribute value or in a text node.
var htmlReplacementTable = []string{
// http://www.w3.org/TR/html5/syntax.html#attribute-value-(unquoted)-state
// U+0000 NULL Parse error. Append a U+FFFD REPLACEMENT
// CHARACTER character to the current attribute's value.
// "
// and similarly
// http://www.w3.org/TR/html5/syntax.html#before-attribute-value-state
0: "\uFFFD",
'"': """,
'&': "&",
'\'': "'",
'+': "+",
'<': "<",
'>': ">",
}
// htmlNormReplacementTable is like htmlReplacementTable but without '&' to
// avoid over-encoding existing entities.
var htmlNormReplacementTable = []string{
0: "\uFFFD",
'"': """,
'\'': "'",
'+': "+",
'<': "<",
'>': ">",
}
// htmlNospaceReplacementTable contains the runes that need to be escaped
// inside an unquoted attribute value.
// The set of runes escaped is the union of the HTML specials and
// those determined by running the JS below in browsers:
// <div id=d></div>
// <script>(function () {
// var a = [], d = document.getElementById("d"), i, c, s;
// for (i = 0; i < 0x10000; ++i) {
// c = String.fromCharCode(i);
// d.innerHTML = "<span title=" + c + "lt" + c + "></span>"
// s = d.getElementsByTagName("SPAN")[0];
// if (!s || s.title !== c + "lt" + c) { a.push(i.toString(16)); }
// }
// document.write(a.join(", "));
// })()</script>
var htmlNospaceReplacementTable = []string{
0: "�",
'\t': "	",
'\n': " ",
'\v': "",
'\f': "",
'\r': " ",
' ': " ",
'"': """,
'&': "&",
'\'': "'",
'+': "+",
'<': "<",
'=': "=",
'>': ">",
// A parse error in the attribute value (unquoted) and
// before attribute value states.
// Treated as a quoting character by IE.
'`': "`",
}
// htmlNospaceNormReplacementTable is like htmlNospaceReplacementTable but
// without '&' to avoid over-encoding existing entities.
var htmlNospaceNormReplacementTable = []string{
0: "�",
'\t': "	",
'\n': " ",
'\v': "",
'\f': "",
'\r': " ",
' ': " ",
'"': """,
'\'': "'",
'+': "+",
'<': "<",
'=': "=",
'>': ">",
// A parse error in the attribute value (unquoted) and
// before attribute value states.
// Treated as a quoting character by IE.
'`': "`",
}
// htmlReplacer returns s with runes replaced according to replacementTable
// and when badRunes is true, certain bad runes are allowed through unescaped.
func htmlReplacer(s string, replacementTable []string, badRunes bool) string {
written, b := 0, new(bytes.Buffer)
for i, r := range s {
if int(r) < len(replacementTable) {
if repl := replacementTable[r]; len(repl) != 0 {
b.WriteString(s[written:i])
b.WriteString(repl)
// Valid as long as replacementTable doesn't
// include anything above 0x7f.
written = i + utf8.RuneLen(r)
}
} else if badRunes {
// No-op.
// IE does not allow these ranges in unquoted attrs.
} else if 0xfdd0 <= r && r <= 0xfdef || 0xfff0 <= r && r <= 0xffff {
fmt.Fprintf(b, "%s&#x%x;", s[written:i], r)
written = i + utf8.RuneLen(r)
}
}
if written == 0 {
return s
}
b.WriteString(s[written:])
return b.String()
}
// StripTags takes a snippet of HTML and returns only the text content.
// For example, `<b>¡Hi!</b> <script>...</script>` -> `¡Hi! `.
func StripTags(html string) string {
var b bytes.Buffer
s, c, i, allText := []byte(html), context{}, 0, true
// Using the transition funcs helps us avoid mangling
// `<div title="1>2">` or `I <3 Ponies!`.
for i != len(s) {
if c.delim == delimNone {
st := c.state
// Use RCDATA instead of parsing into JS or CSS styles.
if c.element != elementNone && !isInTag(st) {
st = stateRCDATA
}
d, nread := transitionFunc[st](c, s[i:])
i1 := i + nread
if c.state == stateText || c.state == stateRCDATA {
// Emit text up to the start of the tag or comment.
j := i1
if d.state != c.state {
for j1 := j - 1; j1 >= i; j1-- {
if s[j1] == '<' {
j = j1
break
}
}
}
b.Write(s[i:j])
} else {
allText = false
}
c, i = d, i1
continue
}
i1 := i + bytes.IndexAny(s[i:], delimEnds[c.delim])
if i1 < i {
break
}
if c.delim != delimSpaceOrTagEnd {
// Consume any quote.
i1++
}
c, i = context{state: stateTag, element: c.element}, i1
}
if allText {
return html
} else if c.state == stateText || c.state == stateRCDATA {
b.Write(s[i:])
}
return b.String()
}
// htmlNameFilter accepts valid parts of an HTML attribute or tag name or
// a known-safe HTML attribute.
func htmlNameFilter(args ...interface{}) string {
s, t := stringify(args...)
if t == contentTypeHTMLAttr {
return s
}
if len(s) == 0 {
// Avoid violation of structure preservation.
// <input checked {{.K}}={{.V}}>.
// Without this, if .K is empty then .V is the value of
// checked, but otherwise .V is the value of the attribute
// named .K.
return filterFailsafe
}
s = strings.ToLower(s)
if t := attrType(s); t != contentTypePlain {
// TODO: Split attr and element name part filters so we can whitelist
// attributes.
return filterFailsafe
}
for _, r := range s {
switch {
case '0' <= r && r <= '9':
case 'a' <= r && r <= 'z':
default:
return filterFailsafe
}
}
return s
}
// commentEscaper returns the empty string regardless of input.
// Comment content does not correspond to any parsed structure or
// human-readable content, so the simplest and most secure policy is to drop
// content interpolated into comments.
// This approach is equally valid whether or not static comment content is
// removed from the template.
func commentEscaper(args ...interface{}) string {
return ""
}
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// context describes the state an HTML parser must be in when it reaches the
// portion of HTML produced by evaluating a particular template node.
//
// The zero value of type context is the start context for a template that
// produces an HTML fragment as defined at
// http://www.w3.org/TR/html5/syntax.html#the-end
// where the context element is null.
type context struct {
state state
delim delim
urlPart urlPart
jsCtx jsCtx
attr attr
element element
err *Error
}
func (c context) String() string {
return fmt.Sprintf("{%v %v %v %v %v %v %v}", c.state, c.delim, c.urlPart, c.jsCtx, c.attr, c.element, c.err)
}
// eq reports whether two contexts are equal.
func (c context) eq(d context) bool {
return c.state == d.state &&
c.delim == d.delim &&
c.urlPart == d.urlPart &&
c.jsCtx == d.jsCtx &&
c.attr == d.attr &&
c.element == d.element &&
c.err == d.err
}
// mangle produces an identifier that includes a suffix that distinguishes it
// from template names mangled with different contexts.
func (c context) mangle(templateName string) string {
// The mangled name for the default context is the input templateName.
if c.state == stateText {
return templateName
}
s := templateName + "$htmltemplate_" + c.state.String()
if c.delim != 0 {
s += "_" + c.delim.String()
}
if c.urlPart != 0 {
s += "_" + c.urlPart.String()
}
if c.jsCtx != 0 {
s += "_" + c.jsCtx.String()
}
if c.attr != 0 {
s += "_" + c.attr.String()
}
if c.element != 0 {
s += "_" + c.element.String()
}
return s
}
// state describes a high-level HTML parser state.
//
// It bounds the top of the element stack, and by extension the HTML insertion
// mode, but also contains state that does not correspond to anything in the
// HTML5 parsing algorithm because a single token production in the HTML
// grammar may contain embedded actions in a template. For instance, the quoted
// HTML attribute produced by
// <div title="Hello {{.World}}">
// is a single token in HTML's grammar but in a template spans several nodes.
type state uint8
const (
// stateText is parsed character data. An HTML parser is in
// this state when its parse position is outside an HTML tag,
// directive, comment, and special element body.
stateText state = iota
// stateTag occurs before an HTML attribute or the end of a tag.
stateTag
// stateAttrName occurs inside an attribute name.
// It occurs between the ^'s in ` ^name^ = value`.
stateAttrName
// stateAfterName occurs after an attr name has ended but before any
// equals sign. It occurs between the ^'s in ` name^ ^= value`.
stateAfterName
// stateBeforeValue occurs after the equals sign but before the value.
// It occurs between the ^'s in ` name =^ ^value`.
stateBeforeValue
// stateHTMLCmt occurs inside an <!-- HTML comment -->.
stateHTMLCmt
// stateRCDATA occurs inside an RCDATA element (<textarea> or <title>)
// as described at http://www.w3.org/TR/html5/syntax.html#elements-0
stateRCDATA
// stateAttr occurs inside an HTML attribute whose content is text.
stateAttr
// stateURL occurs inside an HTML attribute whose content is a URL.
stateURL
// stateJS occurs inside an event handler or script element.
stateJS
// stateJSDqStr occurs inside a JavaScript double quoted string.
stateJSDqStr
// stateJSSqStr occurs inside a JavaScript single quoted string.
stateJSSqStr
// stateJSRegexp occurs inside a JavaScript regexp literal.
stateJSRegexp
// stateJSBlockCmt occurs inside a JavaScript /* block comment */.
stateJSBlockCmt
// stateJSLineCmt occurs inside a JavaScript // line comment.
stateJSLineCmt
// stateCSS occurs inside a <style> element or style attribute.
stateCSS
// stateCSSDqStr occurs inside a CSS double quoted string.
stateCSSDqStr
// stateCSSSqStr occurs inside a CSS single quoted string.
stateCSSSqStr
// stateCSSDqURL occurs inside a CSS double quoted url("...").
stateCSSDqURL
// stateCSSSqURL occurs inside a CSS single quoted url('...').
stateCSSSqURL
// stateCSSURL occurs inside a CSS unquoted url(...).
stateCSSURL
// stateCSSBlockCmt occurs inside a CSS /* block comment */.
stateCSSBlockCmt
// stateCSSLineCmt occurs inside a CSS // line comment.
stateCSSLineCmt
// stateError is an infectious error state outside any valid
// HTML/CSS/JS construct.
stateError
)
var stateNames = [...]string{
stateText: "stateText",
stateTag: "stateTag",
stateAttrName: "stateAttrName",
stateAfterName: "stateAfterName",
stateBeforeValue: "stateBeforeValue",
stateHTMLCmt: "stateHTMLCmt",
stateRCDATA: "stateRCDATA",
stateAttr: "stateAttr",
stateURL: "stateURL",
stateJS: "stateJS",
stateJSDqStr: "stateJSDqStr",
stateJSSqStr: "stateJSSqStr",
stateJSRegexp: "stateJSRegexp",
stateJSBlockCmt: "stateJSBlockCmt",
stateJSLineCmt: "stateJSLineCmt",
stateCSS: "stateCSS",
stateCSSDqStr: "stateCSSDqStr",
stateCSSSqStr: "stateCSSSqStr",
stateCSSDqURL: "stateCSSDqURL",
stateCSSSqURL: "stateCSSSqURL",
stateCSSURL: "stateCSSURL",
stateCSSBlockCmt: "stateCSSBlockCmt",
stateCSSLineCmt: "stateCSSLineCmt",
stateError: "stateError",
}
func (s state) String() string {
if int(s) < len(stateNames) {
return stateNames[s]
}
return fmt.Sprintf("illegal state %d", int(s))
}
// isComment is true for any state that contains content meant for template
// authors & maintainers, not for end-users or machines.
func isComment(s state) bool {
switch s {
case stateHTMLCmt, stateJSBlockCmt, stateJSLineCmt, stateCSSBlockCmt, stateCSSLineCmt:
return true
}
return false
}
// isInTag return whether s occurs solely inside an HTML tag.
func isInTag(s state) bool {
switch s {
case stateTag, stateAttrName, stateAfterName, stateBeforeValue, stateAttr:
return true
}
return false
}
// delim is the delimiter that will end the current HTML attribute.
type delim uint8
const (
// delimNone occurs outside any attribute.
delimNone delim = iota
// delimDoubleQuote occurs when a double quote (") closes the attribute.
delimDoubleQuote
// delimSingleQuote occurs when a single quote (') closes the attribute.
delimSingleQuote
// delimSpaceOrTagEnd occurs when a space or right angle bracket (>)
// closes the attribute.
delimSpaceOrTagEnd
)
var delimNames = [...]string{
delimNone: "delimNone",
delimDoubleQuote: "delimDoubleQuote",
delimSingleQuote: "delimSingleQuote",
delimSpaceOrTagEnd: "delimSpaceOrTagEnd",
}
func (d delim) String() string {
if int(d) < len(delimNames) {
return delimNames[d]
}
return fmt.Sprintf("illegal delim %d", int(d))
}
// urlPart identifies a part in an RFC 3986 hierarchical URL to allow different
// encoding strategies.
type urlPart uint8
const (
// urlPartNone occurs when not in a URL, or possibly at the start:
// ^ in "^http://auth/path?k=v#frag".
urlPartNone urlPart = iota
// urlPartPreQuery occurs in the scheme, authority, or path; between the
// ^s in "h^ttp://auth/path^?k=v#frag".
urlPartPreQuery
// urlPartQueryOrFrag occurs in the query portion between the ^s in
// "http://auth/path?^k=v#frag^".
urlPartQueryOrFrag
// urlPartUnknown occurs due to joining of contexts both before and
// after the query separator.
urlPartUnknown
)
var urlPartNames = [...]string{
urlPartNone: "urlPartNone",
urlPartPreQuery: "urlPartPreQuery",
urlPartQueryOrFrag: "urlPartQueryOrFrag",
urlPartUnknown: "urlPartUnknown",
}
func (u urlPart) String() string {
if int(u) < len(urlPartNames) {
return urlPartNames[u]
}
return fmt.Sprintf("illegal urlPart %d", int(u))
}
// jsCtx determines whether a '/' starts a regular expression literal or a
// division operator.
type jsCtx uint8
const (
// jsCtxRegexp occurs where a '/' would start a regexp literal.
jsCtxRegexp jsCtx = iota
// jsCtxDivOp occurs where a '/' would start a division operator.
jsCtxDivOp
// jsCtxUnknown occurs where a '/' is ambiguous due to context joining.
jsCtxUnknown
)
func (c jsCtx) String() string {
switch c {
case jsCtxRegexp:
return "jsCtxRegexp"
case jsCtxDivOp:
return "jsCtxDivOp"
case jsCtxUnknown:
return "jsCtxUnknown"
}
return fmt.Sprintf("illegal jsCtx %d", int(c))
}
// element identifies the HTML element when inside a start tag or special body.
// Certain HTML element (for example <script> and <style>) have bodies that are
// treated differently from stateText so the element type is necessary to
// transition into the correct context at the end of a tag and to identify the
// end delimiter for the body.
type element uint8
const (
// elementNone occurs outside a special tag or special element body.
elementNone element = iota
// elementScript corresponds to the raw text <script> element.
elementScript
// elementStyle corresponds to the raw text <style> element.
elementStyle
// elementTextarea corresponds to the RCDATA <textarea> element.
elementTextarea
// elementTitle corresponds to the RCDATA <title> element.
elementTitle
)
var elementNames = [...]string{
elementNone: "elementNone",
elementScript: "elementScript",
elementStyle: "elementStyle",
elementTextarea: "elementTextarea",
elementTitle: "elementTitle",
}
func (e element) String() string {
if int(e) < len(elementNames) {
return elementNames[e]
}
return fmt.Sprintf("illegal element %d", int(e))
}
// attr identifies the most recent HTML attribute when inside a start tag.
type attr uint8
const (
// attrNone corresponds to a normal attribute or no attribute.
attrNone attr = iota
// attrScript corresponds to an event handler attribute.
attrScript
// attrStyle corresponds to the style attribute whose value is CSS.
attrStyle
// attrURL corresponds to an attribute whose value is a URL.
attrURL
)
var attrNames = [...]string{
attrNone: "attrNone",
attrScript: "attrScript",
attrStyle: "attrStyle",
attrURL: "attrURL",
}
func (a attr) String() string {
if int(a) < len(attrNames) {
return attrNames[a]
}
return fmt.Sprintf("illegal attr %d", int(a))
}
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// escapeTemplates rewrites the named templates, which must be
// associated with t, to guarantee that the output of any of the named
// templates is properly escaped. Names should include the names of
// all templates that might be Executed but need not include helper
// templates. If no error is returned, then the named templates have
// been modified. Otherwise the named templates have been rendered
// unusable.
func escapeTemplates(tmpl *Template, names ...string) error {
e := newEscaper(tmpl)
for _, name := range names {
c, _ := e.escapeTree(context{}, name, 0)
var err error
if c.err != nil {
err, c.err.Name = c.err, name
} else if c.state != stateText {
err = &Error{ErrEndContext, name, 0, fmt.Sprintf("ends in a non-text context: %v", c)}
}
if err != nil {
// Prevent execution of unsafe templates.
for _, name := range names {
if t := tmpl.set[name]; t != nil {
t.text.Tree = nil
t.Tree = nil
}
}
return err
}
}
e.commit()
for _, name := range names {
if t := tmpl.set[name]; t != nil {
t.escaped = true
t.Tree = t.text.Tree
}
}
return nil
}
// funcMap maps command names to functions that render their inputs safe.
var funcMap = template.FuncMap{
"html_template_attrescaper": attrEscaper,
"html_template_commentescaper": commentEscaper,
"html_template_cssescaper": cssEscaper,
"html_template_cssvaluefilter": cssValueFilter,
"html_template_htmlnamefilter": htmlNameFilter,
"html_template_htmlescaper": htmlEscaper,
"html_template_jsregexpescaper": jsRegexpEscaper,
"html_template_jsstrescaper": jsStrEscaper,
"html_template_jsvalescaper": jsValEscaper,
"html_template_nospaceescaper": htmlNospaceEscaper,
"html_template_rcdataescaper": rcdataEscaper,
"html_template_urlescaper": urlEscaper,
"html_template_urlfilter": urlFilter,
"html_template_urlnormalizer": urlNormalizer,
}
// equivEscapers matches contextual escapers to equivalent template builtins.
var equivEscapers = map[string]string{
"html_template_attrescaper": "html",
"html_template_htmlescaper": "html",
"html_template_nospaceescaper": "html",
"html_template_rcdataescaper": "html",
"html_template_urlescaper": "urlquery",
"html_template_urlnormalizer": "urlquery",
}
// escaper collects type inferences about templates and changes needed to make
// templates injection safe.
type escaper struct {
tmpl *Template
// output[templateName] is the output context for a templateName that
// has been mangled to include its input context.
output map[string]context
// derived[c.mangle(name)] maps to a template derived from the template
// named name templateName for the start context c.
derived map[string]*template.Template
// called[templateName] is a set of called mangled template names.
called map[string]bool
// xxxNodeEdits are the accumulated edits to apply during commit.
// Such edits are not applied immediately in case a template set
// executes a given template in different escaping contexts.
actionNodeEdits map[*parse.ActionNode][]string
templateNodeEdits map[*parse.TemplateNode]string
textNodeEdits map[*parse.TextNode][]byte
}
// newEscaper creates a blank escaper for the given set.
func newEscaper(t *Template) *escaper {
return &escaper{
t,
map[string]context{},
map[string]*template.Template{},
map[string]bool{},
map[*parse.ActionNode][]string{},
map[*parse.TemplateNode]string{},
map[*parse.TextNode][]byte{},
}
}
// filterFailsafe is an innocuous word that is emitted in place of unsafe values
// by sanitizer functions. It is not a keyword in any programming language,
// contains no special characters, is not empty, and when it appears in output
// it is distinct enough that a developer can find the source of the problem
// via a search engine.
const filterFailsafe = "ZgotmplZ"
// escape escapes a template node.
func (e *escaper) escape(c context, n parse.Node) context {
switch n := n.(type) {
case *parse.ActionNode:
return e.escapeAction(c, n)
case *parse.IfNode:
return e.escapeBranch(c, &n.BranchNode, "if")
case *parse.ListNode:
return e.escapeList(c, n)
case *parse.RangeNode:
return e.escapeBranch(c, &n.BranchNode, "range")
case *parse.TemplateNode:
return e.escapeTemplate(c, n)
case *parse.TextNode:
return e.escapeText(c, n)
case *parse.WithNode:
return e.escapeBranch(c, &n.BranchNode, "with")
}
panic("escaping " + n.String() + " is unimplemented")
}
// escapeAction escapes an action template node.
func (e *escaper) escapeAction(c context, n *parse.ActionNode) context {
if len(n.Pipe.Decl) != 0 {
// A local variable assignment, not an interpolation.
return c
}
c = nudge(c)
s := make([]string, 0, 3)
switch c.state {
case stateError:
return c
case stateURL, stateCSSDqStr, stateCSSSqStr, stateCSSDqURL, stateCSSSqURL, stateCSSURL:
switch c.urlPart {
case urlPartNone:
s = append(s, "html_template_urlfilter")
fallthrough
case urlPartPreQuery:
switch c.state {
case stateCSSDqStr, stateCSSSqStr:
s = append(s, "html_template_cssescaper")
default:
s = append(s, "html_template_urlnormalizer")
}
case urlPartQueryOrFrag:
s = append(s, "html_template_urlescaper")
case urlPartUnknown:
return context{
state: stateError,
err: errorf(ErrAmbigContext, n.Line, "%s appears in an ambiguous URL context", n),
}
default:
panic(c.urlPart.String())
}
case stateJS:
s = append(s, "html_template_jsvalescaper")
// A slash after a value starts a div operator.
c.jsCtx = jsCtxDivOp
case stateJSDqStr, stateJSSqStr:
s = append(s, "html_template_jsstrescaper")
case stateJSRegexp:
s = append(s, "html_template_jsregexpescaper")
case stateCSS:
s = append(s, "html_template_cssvaluefilter")
case stateText:
s = append(s, "html_template_htmlescaper")
case stateRCDATA:
s = append(s, "html_template_rcdataescaper")
case stateAttr:
// Handled below in delim check.
case stateAttrName, stateTag:
c.state = stateAttrName
s = append(s, "html_template_htmlnamefilter")
default:
if isComment(c.state) {
s = append(s, "html_template_commentescaper")
} else {
panic("unexpected state " + c.state.String())
}
}
switch c.delim {
case delimNone:
// No extra-escaping needed for raw text content.
case delimSpaceOrTagEnd:
s = append(s, "html_template_nospaceescaper")
default:
s = append(s, "html_template_attrescaper")
}
e.editActionNode(n, s)
return c
}
// allIdents returns the names of the identifiers under the Ident field of the node,
// which might be a singleton (Identifier) or a slice (Field).
func allIdents(node parse.Node) []string {
switch node := node.(type) {
case *parse.IdentifierNode:
return []string{node.Ident}
case *parse.FieldNode:
return node.Ident
}
panic("unidentified node type in allIdents")
}
// ensurePipelineContains ensures that the pipeline has commands with
// the identifiers in s in order.
// If the pipeline already has some of the sanitizers, do not interfere.
// For example, if p is (.X | html) and s is ["escapeJSVal", "html"] then it
// has one matching, "html", and one to insert, "escapeJSVal", to produce
// (.X | escapeJSVal | html).
func ensurePipelineContains(p *parse.PipeNode, s []string) {
if len(s) == 0 {
return
}
n := len(p.Cmds)
// Find the identifiers at the end of the command chain.
idents := p.Cmds
for i := n - 1; i >= 0; i-- {
if cmd := p.Cmds[i]; len(cmd.Args) != 0 {
if _, ok := cmd.Args[0].(*parse.IdentifierNode); ok {
continue
}
}
idents = p.Cmds[i+1:]
}
dups := 0
for _, idNode := range idents {
for _, ident := range allIdents(idNode.Args[0]) {
if escFnsEq(s[dups], ident) {
dups++
if dups == len(s) {
return
}
}
}
}
newCmds := make([]*parse.CommandNode, n-len(idents), n+len(s)-dups)
copy(newCmds, p.Cmds)
// Merge existing identifier commands with the sanitizers needed.
for _, idNode := range idents {
pos := idNode.Args[0].Position()
for _, ident := range allIdents(idNode.Args[0]) {
i := indexOfStr(ident, s, escFnsEq)
if i != -1 {
for _, name := range s[:i] {
newCmds = appendCmd(newCmds, newIdentCmd(name, pos))
}
s = s[i+1:]
}
}
newCmds = appendCmd(newCmds, idNode)
}
// Create any remaining sanitizers.
for _, name := range s {
newCmds = appendCmd(newCmds, newIdentCmd(name, p.Position()))
}
p.Cmds = newCmds
}
// redundantFuncs[a][b] implies that funcMap[b](funcMap[a](x)) == funcMap[a](x)
// for all x.
var redundantFuncs = map[string]map[string]bool{
"html_template_commentescaper": {
"html_template_attrescaper": true,
"html_template_nospaceescaper": true,
"html_template_htmlescaper": true,
},
"html_template_cssescaper": {
"html_template_attrescaper": true,
},
"html_template_jsregexpescaper": {
"html_template_attrescaper": true,
},
"html_template_jsstrescaper": {
"html_template_attrescaper": true,
},
"html_template_urlescaper": {
"html_template_urlnormalizer": true,
},
}
// appendCmd appends the given command to the end of the command pipeline
// unless it is redundant with the last command.
func appendCmd(cmds []*parse.CommandNode, cmd *parse.CommandNode) []*parse.CommandNode {
if n := len(cmds); n != 0 {
last, ok := cmds[n-1].Args[0].(*parse.IdentifierNode)
next, _ := cmd.Args[0].(*parse.IdentifierNode)
if ok && redundantFuncs[last.Ident][next.Ident] {
return cmds
}
}
return append(cmds, cmd)
}
// indexOfStr is the first i such that eq(s, strs[i]) or -1 if s was not found.
func indexOfStr(s string, strs []string, eq func(a, b string) bool) int {
for i, t := range strs {
if eq(s, t) {
return i
}
}
return -1
}
// escFnsEq reports whether the two escaping functions are equivalent.
func escFnsEq(a, b string) bool {
if e := equivEscapers[a]; e != "" {
a = e
}
if e := equivEscapers[b]; e != "" {
b = e
}
return a == b
}
// newIdentCmd produces a command containing a single identifier node.
func newIdentCmd(identifier string, pos parse.Pos) *parse.CommandNode {
return &parse.CommandNode{
NodeType: parse.NodeCommand,
Args: []parse.Node{parse.NewIdentifier(identifier).SetPos(pos)},
}
}
// nudge returns the context that would result from following empty string
// transitions from the input context.
// For example, parsing:
// `<a href=`
// will end in context{stateBeforeValue, attrURL}, but parsing one extra rune:
// `<a href=x`
// will end in context{stateURL, delimSpaceOrTagEnd, ...}.
// There are two transitions that happen when the 'x' is seen:
// (1) Transition from a before-value state to a start-of-value state without
// consuming any character.
// (2) Consume 'x' and transition past the first value character.
// In this case, nudging produces the context after (1) happens.
func nudge(c context) context {
switch c.state {
case stateTag:
// In `<foo {{.}}`, the action should emit an attribute.
c.state = stateAttrName
case stateBeforeValue:
// In `<foo bar={{.}}`, the action is an undelimited value.
c.state, c.delim, c.attr = attrStartStates[c.attr], delimSpaceOrTagEnd, attrNone
case stateAfterName:
// In `<foo bar {{.}}`, the action is an attribute name.
c.state, c.attr = stateAttrName, attrNone
}
return c
}
// join joins the two contexts of a branch template node. The result is an
// error context if either of the input contexts are error contexts, or if the
// the input contexts differ.
func join(a, b context, line int, nodeName string) context {
if a.state == stateError {
return a
}
if b.state == stateError {