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Diffstat (limited to 'src/html/template/escape.go')
| -rw-r--r-- | src/html/template/escape.go | 892 |
1 files changed, 892 insertions, 0 deletions
diff --git a/src/html/template/escape.go b/src/html/template/escape.go new file mode 100644 index 0000000..8739735 --- /dev/null +++ b/src/html/template/escape.go @@ -0,0 +1,892 @@ +// 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. + +package template + +import ( + "bytes" + "fmt" + "html" + "io" + "text/template" + "text/template/parse" +) + +// escapeTemplate rewrites the named template, which must be +// associated with t, to guarantee that the output of any of the named +// templates is properly escaped. If no error is returned, then the named templates have +// been modified. Otherwise the named templates have been rendered +// unusable. +func escapeTemplate(tmpl *Template, node parse.Node, name string) error { + c, _ := tmpl.esc.escapeTree(context{}, node, name, 0) + var err error + if c.err != nil { + err, c.err.Name = c.err, name + } else if c.state != stateText { + err = &Error{ErrEndContext, nil, name, 0, fmt.Sprintf("ends in a non-text context: %v", c)} + } + if err != nil { + // Prevent execution of unsafe templates. + if t := tmpl.set[name]; t != nil { + t.escapeErr = err + t.text.Tree = nil + t.Tree = nil + } + return err + } + tmpl.esc.commit() + if t := tmpl.set[name]; t != nil { + t.escapeErr = escapeOK + t.Tree = t.text.Tree + } + return nil +} + +// evalArgs formats the list of arguments into a string. It is equivalent to +// fmt.Sprint(args...), except that it deferences all pointers. +func evalArgs(args ...interface{}) string { + // Optimization for simple common case of a single string argument. + if len(args) == 1 { + if s, ok := args[0].(string); ok { + return s + } + } + for i, arg := range args { + args[i] = indirectToStringerOrError(arg) + } + return fmt.Sprint(args...) +} + +// 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_srcsetescaper": srcsetFilterAndEscaper, + "_html_template_urlescaper": urlEscaper, + "_html_template_urlfilter": urlFilter, + "_html_template_urlnormalizer": urlNormalizer, + "_eval_args_": evalArgs, +} + +// escaper collects type inferences about templates and changes needed to make +// templates injection safe. +type escaper struct { + // ns is the nameSpace that this escaper is associated with. + ns *nameSpace + // 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 +} + +// makeEscaper creates a blank escaper for the given set. +func makeEscaper(n *nameSpace) escaper { + return escaper{ + n, + 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.CommentNode: + return c + 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) + // Check for disallowed use of predefined escapers in the pipeline. + for pos, idNode := range n.Pipe.Cmds { + node, ok := idNode.Args[0].(*parse.IdentifierNode) + if !ok { + // A predefined escaper "esc" will never be found as an identifier in a + // Chain or Field node, since: + // - "esc.x ..." is invalid, since predefined escapers return strings, and + // strings do not have methods, keys or fields. + // - "... .esc" is invalid, since predefined escapers are global functions, + // not methods or fields of any types. + // Therefore, it is safe to ignore these two node types. + continue + } + ident := node.Ident + if _, ok := predefinedEscapers[ident]; ok { + if pos < len(n.Pipe.Cmds)-1 || + c.state == stateAttr && c.delim == delimSpaceOrTagEnd && ident == "html" { + return context{ + state: stateError, + err: errorf(ErrPredefinedEscaper, n, n.Line, "predefined escaper %q disallowed in template", ident), + } + } + } + } + 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, n.Line, "%s appears in an ambiguous context within a URL", 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") + case stateSrcset: + s = append(s, "_html_template_srcsetescaper") + 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 +} + +// ensurePipelineContains ensures that the pipeline ends with the commands with +// the identifiers in s in order. If the pipeline ends with a predefined escaper +// (i.e. "html" or "urlquery"), merge it with the identifiers in s. +func ensurePipelineContains(p *parse.PipeNode, s []string) { + if len(s) == 0 { + // Do not rewrite pipeline if we have no escapers to insert. + return + } + // Precondition: p.Cmds contains at most one predefined escaper and the + // escaper will be present at p.Cmds[len(p.Cmds)-1]. This precondition is + // always true because of the checks in escapeAction. + pipelineLen := len(p.Cmds) + if pipelineLen > 0 { + lastCmd := p.Cmds[pipelineLen-1] + if idNode, ok := lastCmd.Args[0].(*parse.IdentifierNode); ok { + if esc := idNode.Ident; predefinedEscapers[esc] { + // Pipeline ends with a predefined escaper. + if len(p.Cmds) == 1 && len(lastCmd.Args) > 1 { + // Special case: pipeline is of the form {{ esc arg1 arg2 ... argN }}, + // where esc is the predefined escaper, and arg1...argN are its arguments. + // Convert this into the equivalent form + // {{ _eval_args_ arg1 arg2 ... argN | esc }}, so that esc can be easily + // merged with the escapers in s. + lastCmd.Args[0] = parse.NewIdentifier("_eval_args_").SetTree(nil).SetPos(lastCmd.Args[0].Position()) + p.Cmds = appendCmd(p.Cmds, newIdentCmd(esc, p.Position())) + pipelineLen++ + } + // If any of the commands in s that we are about to insert is equivalent + // to the predefined escaper, use the predefined escaper instead. + dup := false + for i, escaper := range s { + if escFnsEq(esc, escaper) { + s[i] = idNode.Ident + dup = true + } + } + if dup { + // The predefined escaper will already be inserted along with the + // escapers in s, so do not copy it to the rewritten pipeline. + pipelineLen-- + } + } + } + } + // Rewrite the pipeline, creating the escapers in s at the end of the pipeline. + newCmds := make([]*parse.CommandNode, pipelineLen, pipelineLen+len(s)) + insertedIdents := make(map[string]bool) + for i := 0; i < pipelineLen; i++ { + cmd := p.Cmds[i] + newCmds[i] = cmd + if idNode, ok := cmd.Args[0].(*parse.IdentifierNode); ok { + insertedIdents[normalizeEscFn(idNode.Ident)] = true + } + } + for _, name := range s { + if !insertedIdents[normalizeEscFn(name)] { + // When two templates share an underlying parse tree via the use of + // AddParseTree and one template is executed after the other, this check + // ensures that escapers that were already inserted into the pipeline on + // the first escaping pass do not get inserted again. + newCmds = appendCmd(newCmds, newIdentCmd(name, p.Position())) + } + } + p.Cmds = newCmds +} + +// predefinedEscapers contains template predefined escapers that are equivalent +// to some contextual escapers. Keep in sync with equivEscapers. +var predefinedEscapers = map[string]bool{ + "html": true, + "urlquery": true, +} + +// equivEscapers matches contextual escapers to equivalent predefined +// template escapers. +var equivEscapers = map[string]string{ + // The following pairs of HTML escapers provide equivalent security + // guarantees, since they all escape '\000', '\'', '"', '&', '<', and '>'. + "_html_template_attrescaper": "html", + "_html_template_htmlescaper": "html", + "_html_template_rcdataescaper": "html", + // These two URL escapers produce URLs safe for embedding in a URL query by + // percent-encoding all the reserved characters specified in RFC 3986 Section + // 2.2 + "_html_template_urlescaper": "urlquery", + // These two functions are not actually equivalent; urlquery is stricter as it + // escapes reserved characters (e.g. '#'), while _html_template_urlnormalizer + // does not. It is therefore only safe to replace _html_template_urlnormalizer + // with urlquery (this happens in ensurePipelineContains), but not the otherI've + // way around. We keep this entry around to preserve the behavior of templates + // written before Go 1.9, which might depend on this substitution taking place. + "_html_template_urlnormalizer": "urlquery", +} + +// escFnsEq reports whether the two escaping functions are equivalent. +func escFnsEq(a, b string) bool { + return normalizeEscFn(a) == normalizeEscFn(b) +} + +// normalizeEscFn(a) is equal to normalizeEscFn(b) for any pair of names of +// escaper functions a and b that are equivalent. +func normalizeEscFn(e string) string { + if norm := equivEscapers[e]; norm != "" { + return norm + } + return e +} + +// 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, okLast := cmds[n-1].Args[0].(*parse.IdentifierNode) + next, okNext := cmd.Args[0].(*parse.IdentifierNode) + if okLast && okNext && redundantFuncs[last.Ident][next.Ident] { + return cmds + } + } + return append(cmds, cmd) +} + +// 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).SetTree(nil).SetPos(pos)}, // TODO: SetTree. + } +} + +// 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 +// input contexts differ. +func join(a, b context, node parse.Node, nodeName string) context { + if a.state == stateError { + return a + } + if b.state == stateError { + return b + } + if a.eq(b) { + return a + } + + c := a + c.urlPart = b.urlPart + if c.eq(b) { + // The contexts differ only by urlPart. + c.urlPart = urlPartUnknown + return c + } + + c = a + c.jsCtx = b.jsCtx + if c.eq(b) { + // The contexts differ only by jsCtx. + c.jsCtx = jsCtxUnknown + return c + } + + // Allow a nudged context to join with an unnudged one. + // This means that + // <p title={{if .C}}{{.}}{{end}} + // ends in an unquoted value state even though the else branch + // ends in stateBeforeValue. + if c, d := nudge(a), nudge(b); !(c.eq(a) && d.eq(b)) { + if e := join(c, d, node, nodeName); e.state != stateError { + return e + } + } + + return context{ + state: stateError, + err: errorf(ErrBranchEnd, node, 0, "{{%s}} branches end in different contexts: %v, %v", nodeName, a, b), + } +} + +// escapeBranch escapes a branch template node: "if", "range" and "with". +func (e *escaper) escapeBranch(c context, n *parse.BranchNode, nodeName string) context { + c0 := e.escapeList(c, n.List) + if nodeName == "range" && c0.state != stateError { + // The "true" branch of a "range" node can execute multiple times. + // We check that executing n.List once results in the same context + // as executing n.List twice. + c1, _ := e.escapeListConditionally(c0, n.List, nil) + c0 = join(c0, c1, n, nodeName) + if c0.state == stateError { + // Make clear that this is a problem on loop re-entry + // since developers tend to overlook that branch when + // debugging templates. + c0.err.Line = n.Line + c0.err.Description = "on range loop re-entry: " + c0.err.Description + return c0 + } + } + c1 := e.escapeList(c, n.ElseList) + return join(c0, c1, n, nodeName) +} + +// escapeList escapes a list template node. +func (e *escaper) escapeList(c context, n *parse.ListNode) context { + if n == nil { + return c + } + for _, m := range n.Nodes { + c = e.escape(c, m) + } + return c +} + +// escapeListConditionally escapes a list node but only preserves edits and +// inferences in e if the inferences and output context satisfy filter. +// It returns the best guess at an output context, and the result of the filter +// which is the same as whether e was updated. +func (e *escaper) escapeListConditionally(c context, n *parse.ListNode, filter func(*escaper, context) bool) (context, bool) { + e1 := makeEscaper(e.ns) + // Make type inferences available to f. + for k, v := range e.output { + e1.output[k] = v + } + c = e1.escapeList(c, n) + ok := filter != nil && filter(&e1, c) + if ok { + // Copy inferences and edits from e1 back into e. + for k, v := range e1.output { + e.output[k] = v + } + for k, v := range e1.derived { + e.derived[k] = v + } + for k, v := range e1.called { + e.called[k] = v + } + for k, v := range e1.actionNodeEdits { + e.editActionNode(k, v) + } + for k, v := range e1.templateNodeEdits { + e.editTemplateNode(k, v) + } + for k, v := range e1.textNodeEdits { + e.editTextNode(k, v) + } + } + return c, ok +} + +// escapeTemplate escapes a {{template}} call node. +func (e *escaper) escapeTemplate(c context, n *parse.TemplateNode) context { + c, name := e.escapeTree(c, n, n.Name, n.Line) + if name != n.Name { + e.editTemplateNode(n, name) + } + return c +} + +// escapeTree escapes the named template starting in the given context as +// necessary and returns its output context. +func (e *escaper) escapeTree(c context, node parse.Node, name string, line int) (context, string) { + // Mangle the template name with the input context to produce a reliable + // identifier. + dname := c.mangle(name) + e.called[dname] = true + if out, ok := e.output[dname]; ok { + // Already escaped. + return out, dname + } + t := e.template(name) + if t == nil { + // Two cases: The template exists but is empty, or has never been mentioned at + // all. Distinguish the cases in the error messages. + if e.ns.set[name] != nil { + return context{ + state: stateError, + err: errorf(ErrNoSuchTemplate, node, line, "%q is an incomplete or empty template", name), + }, dname + } + return context{ + state: stateError, + err: errorf(ErrNoSuchTemplate, node, line, "no such template %q", name), + }, dname + } + if dname != name { + // Use any template derived during an earlier call to escapeTemplate + // with different top level templates, or clone if necessary. + dt := e.template(dname) + if dt == nil { + dt = template.New(dname) + dt.Tree = &parse.Tree{Name: dname, Root: t.Root.CopyList()} + e.derived[dname] = dt + } + t = dt + } + return e.computeOutCtx(c, t), dname +} + +// computeOutCtx takes a template and its start context and computes the output +// context while storing any inferences in e. +func (e *escaper) computeOutCtx(c context, t *template.Template) context { + // Propagate context over the body. + c1, ok := e.escapeTemplateBody(c, t) + if !ok { + // Look for a fixed point by assuming c1 as the output context. + if c2, ok2 := e.escapeTemplateBody(c1, t); ok2 { + c1, ok = c2, true + } + // Use c1 as the error context if neither assumption worked. + } + if !ok && c1.state != stateError { + return context{ + state: stateError, + err: errorf(ErrOutputContext, t.Tree.Root, 0, "cannot compute output context for template %s", t.Name()), + } + } + return c1 +} + +// escapeTemplateBody escapes the given template assuming the given output +// context, and returns the best guess at the output context and whether the +// assumption was correct. +func (e *escaper) escapeTemplateBody(c context, t *template.Template) (context, bool) { + filter := func(e1 *escaper, c1 context) bool { + if c1.state == stateError { + // Do not update the input escaper, e. + return false + } + if !e1.called[t.Name()] { + // If t is not recursively called, then c1 is an + // accurate output context. + return true + } + // c1 is accurate if it matches our assumed output context. + return c.eq(c1) + } + // We need to assume an output context so that recursive template calls + // take the fast path out of escapeTree instead of infinitely recursing. + // Naively assuming that the input context is the same as the output + // works >90% of the time. + e.output[t.Name()] = c + return e.escapeListConditionally(c, t.Tree.Root, filter) +} + +// delimEnds maps each delim to a string of characters that terminate it. +var delimEnds = [...]string{ + delimDoubleQuote: `"`, + delimSingleQuote: "'", + // Determined empirically by running the below in various browsers. + // var div = document.createElement("DIV"); + // for (var i = 0; i < 0x10000; ++i) { + // div.innerHTML = "<span title=x" + String.fromCharCode(i) + "-bar>"; + // if (div.getElementsByTagName("SPAN")[0].title.indexOf("bar") < 0) + // document.write("<p>U+" + i.toString(16)); + // } + delimSpaceOrTagEnd: " \t\n\f\r>", +} + +var doctypeBytes = []byte("<!DOCTYPE") + +// escapeText escapes a text template node. +func (e *escaper) escapeText(c context, n *parse.TextNode) context { + s, written, i, b := n.Text, 0, 0, new(bytes.Buffer) + for i != len(s) { + c1, nread := contextAfterText(c, s[i:]) + i1 := i + nread + if c.state == stateText || c.state == stateRCDATA { + end := i1 + if c1.state != c.state { + for j := end - 1; j >= i; j-- { + if s[j] == '<' { + end = j + break + } + } + } + for j := i; j < end; j++ { + if s[j] == '<' && !bytes.HasPrefix(bytes.ToUpper(s[j:]), doctypeBytes) { + b.Write(s[written:j]) + b.WriteString("<") + written = j + 1 + } + } + } else if isComment(c.state) && c.delim == delimNone { + switch c.state { + case stateJSBlockCmt: + // https://es5.github.com/#x7.4: + // "Comments behave like white space and are + // discarded except that, if a MultiLineComment + // contains a line terminator character, then + // the entire comment is considered to be a + // LineTerminator for purposes of parsing by + // the syntactic grammar." + if bytes.ContainsAny(s[written:i1], "\n\r\u2028\u2029") { + b.WriteByte('\n') + } else { + b.WriteByte(' ') + } + case stateCSSBlockCmt: + b.WriteByte(' ') + } + written = i1 + } + if c.state != c1.state && isComment(c1.state) && c1.delim == delimNone { + // Preserve the portion between written and the comment start. + cs := i1 - 2 + if c1.state == stateHTMLCmt { + // "<!--" instead of "/*" or "//" + cs -= 2 + } + b.Write(s[written:cs]) + written = i1 + } + if i == i1 && c.state == c1.state { + panic(fmt.Sprintf("infinite loop from %v to %v on %q..%q", c, c1, s[:i], s[i:])) + } + c, i = c1, i1 + } + + if written != 0 && c.state != stateError { + if !isComment(c.state) || c.delim != delimNone { + b.Write(n.Text[written:]) + } + e.editTextNode(n, b.Bytes()) + } + return c +} + +// contextAfterText starts in context c, consumes some tokens from the front of +// s, then returns the context after those tokens and the unprocessed suffix. +func contextAfterText(c context, s []byte) (context, int) { + if c.delim == delimNone { + c1, i := tSpecialTagEnd(c, s) + if i == 0 { + // A special end tag (`</script>`) has been seen and + // all content preceding it has been consumed. + return c1, 0 + } + // Consider all content up to any end tag. + return transitionFunc[c.state](c, s[:i]) + } + + // We are at the beginning of an attribute value. + + i := bytes.IndexAny(s, delimEnds[c.delim]) + if i == -1 { + i = len(s) + } + if c.delim == delimSpaceOrTagEnd { + // https://www.w3.org/TR/html5/syntax.html#attribute-value-(unquoted)-state + // lists the runes below as error characters. + // Error out because HTML parsers may differ on whether + // "<a id= onclick=f(" ends inside id's or onclick's value, + // "<a class=`foo " ends inside a value, + // "<a style=font:'Arial'" needs open-quote fixup. + // IE treats '`' as a quotation character. + if j := bytes.IndexAny(s[:i], "\"'<=`"); j >= 0 { + return context{ + state: stateError, + err: errorf(ErrBadHTML, nil, 0, "%q in unquoted attr: %q", s[j:j+1], s[:i]), + }, len(s) + } + } + if i == len(s) { + // Remain inside the attribute. + // Decode the value so non-HTML rules can easily handle + // <button onclick="alert("Hi!")"> + // without having to entity decode token boundaries. + for u := []byte(html.UnescapeString(string(s))); len(u) != 0; { + c1, i1 := transitionFunc[c.state](c, u) + c, u = c1, u[i1:] + } + return c, len(s) + } + + element := c.element + + // If this is a non-JS "type" attribute inside "script" tag, do not treat the contents as JS. + if c.state == stateAttr && c.element == elementScript && c.attr == attrScriptType && !isJSType(string(s[:i])) { + element = elementNone + } + + if c.delim != delimSpaceOrTagEnd { + // Consume any quote. + i++ + } + // On exiting an attribute, we discard all state information + // except the state and element. + return context{state: stateTag, element: element}, i +} + +// editActionNode records a change to an action pipeline for later commit. +func (e *escaper) editActionNode(n *parse.ActionNode, cmds []string) { + if _, ok := e.actionNodeEdits[n]; ok { + panic(fmt.Sprintf("node %s shared between templates", n)) + } + e.actionNodeEdits[n] = cmds +} + +// editTemplateNode records a change to a {{template}} callee for later commit. +func (e *escaper) editTemplateNode(n *parse.TemplateNode, callee string) { + if _, ok := e.templateNodeEdits[n]; ok { + panic(fmt.Sprintf("node %s shared between templates", n)) + } + e.templateNodeEdits[n] = callee +} + +// editTextNode records a change to a text node for later commit. +func (e *escaper) editTextNode(n *parse.TextNode, text []byte) { + if _, ok := e.textNodeEdits[n]; ok { + panic(fmt.Sprintf("node %s shared between templates", n)) + } + e.textNodeEdits[n] = text +} + +// commit applies changes to actions and template calls needed to contextually +// autoescape content and adds any derived templates to the set. +func (e *escaper) commit() { + for name := range e.output { + e.template(name).Funcs(funcMap) + } + // Any template from the name space associated with this escaper can be used + // to add derived templates to the underlying text/template name space. + tmpl := e.arbitraryTemplate() + for _, t := range e.derived { + if _, err := tmpl.text.AddParseTree(t.Name(), t.Tree); err != nil { + panic("error adding derived template") + } + } + for n, s := range e.actionNodeEdits { + ensurePipelineContains(n.Pipe, s) + } + for n, name := range e.templateNodeEdits { + n.Name = name + } + for n, s := range e.textNodeEdits { + n.Text = s + } + // Reset state that is specific to this commit so that the same changes are + // not re-applied to the template on subsequent calls to commit. + e.called = make(map[string]bool) + e.actionNodeEdits = make(map[*parse.ActionNode][]string) + e.templateNodeEdits = make(map[*parse.TemplateNode]string) + e.textNodeEdits = make(map[*parse.TextNode][]byte) +} + +// template returns the named template given a mangled template name. +func (e *escaper) template(name string) *template.Template { + // Any template from the name space associated with this escaper can be used + // to look up templates in the underlying text/template name space. + t := e.arbitraryTemplate().text.Lookup(name) + if t == nil { + t = e.derived[name] + } + return t +} + +// arbitraryTemplate returns an arbitrary template from the name space +// associated with e and panics if no templates are found. +func (e *escaper) arbitraryTemplate() *Template { + for _, t := range e.ns.set { + return t + } + panic("no templates in name space") +} + +// Forwarding functions so that clients need only import this package +// to reach the general escaping functions of text/template. + +// HTMLEscape writes to w the escaped HTML equivalent of the plain text data b. +func HTMLEscape(w io.Writer, b []byte) { + template.HTMLEscape(w, b) +} + +// HTMLEscapeString returns the escaped HTML equivalent of the plain text data s. +func HTMLEscapeString(s string) string { + return template.HTMLEscapeString(s) +} + +// HTMLEscaper returns the escaped HTML equivalent of the textual +// representation of its arguments. +func HTMLEscaper(args ...interface{}) string { + return template.HTMLEscaper(args...) +} + +// JSEscape writes to w the escaped JavaScript equivalent of the plain text data b. +func JSEscape(w io.Writer, b []byte) { + template.JSEscape(w, b) +} + +// JSEscapeString returns the escaped JavaScript equivalent of the plain text data s. +func JSEscapeString(s string) string { + return template.JSEscapeString(s) +} + +// JSEscaper returns the escaped JavaScript equivalent of the textual +// representation of its arguments. +func JSEscaper(args ...interface{}) string { + return template.JSEscaper(args...) +} + +// URLQueryEscaper returns the escaped value of the textual representation of +// its arguments in a form suitable for embedding in a URL query. +func URLQueryEscaper(args ...interface{}) string { + return template.URLQueryEscaper(args...) +} |