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-rw-r--r--src/html/template/escape.go1004
1 files changed, 1004 insertions, 0 deletions
diff --git a/src/html/template/escape.go b/src/html/template/escape.go
new file mode 100644
index 0000000..1eace16
--- /dev/null
+++ b/src/html/template/escape.go
@@ -0,0 +1,1004 @@
+// 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"
+ "internal/godebug"
+ "io"
+ "regexp"
+ "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 dereferences all pointers.
+func evalArgs(args ...any) 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_jstmpllitescaper": jsTmplLitEscaper,
+ "_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
+ // rangeContext holds context about the current range loop.
+ rangeContext *rangeContext
+}
+
+// rangeContext holds information about the current range loop.
+type rangeContext struct {
+ outer *rangeContext // outer loop
+ breaks []context // context at each break action
+ continues []context // context at each continue action
+}
+
+// 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{},
+ nil,
+ }
+}
+
+// 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.BreakNode:
+ c.n = n
+ e.rangeContext.breaks = append(e.rangeContext.breaks, c)
+ return context{state: stateDead}
+ case *parse.CommentNode:
+ return c
+ case *parse.ContinueNode:
+ c.n = n
+ e.rangeContext.continues = append(e.rangeContext.breaks, c)
+ return context{state: stateDead}
+ 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")
+}
+
+var debugAllowActionJSTmpl = godebug.New("jstmpllitinterp")
+
+// 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 stateJSTmplLit:
+ s = append(s, "_html_template_jstmpllitescaper")
+ 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_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_jstmpllitescaper": {
+ "_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.state == stateDead {
+ return b
+ }
+ if b.state == stateDead {
+ return a
+ }
+ 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 {
+ if nodeName == "range" {
+ e.rangeContext = &rangeContext{outer: e.rangeContext}
+ }
+ c0 := e.escapeList(c, n.List)
+ if nodeName == "range" {
+ if c0.state != stateError {
+ c0 = joinRange(c0, e.rangeContext)
+ }
+ e.rangeContext = e.rangeContext.outer
+ if c0.state == stateError {
+ return c0
+ }
+
+ // 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.
+ e.rangeContext = &rangeContext{outer: e.rangeContext}
+ c1, _ := e.escapeListConditionally(c0, n.List, nil)
+ c0 = join(c0, c1, n, nodeName)
+ if c0.state == stateError {
+ e.rangeContext = e.rangeContext.outer
+ // 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
+ }
+ c0 = joinRange(c0, e.rangeContext)
+ e.rangeContext = e.rangeContext.outer
+ if c0.state == stateError {
+ return c0
+ }
+ }
+ c1 := e.escapeList(c, n.ElseList)
+ return join(c0, c1, n, nodeName)
+}
+
+func joinRange(c0 context, rc *rangeContext) context {
+ // Merge contexts at break and continue statements into overall body context.
+ // In theory we could treat breaks differently from continues, but for now it is
+ // enough to treat them both as going back to the start of the loop (which may then stop).
+ for _, c := range rc.breaks {
+ c0 = join(c0, c, c.n, "range")
+ if c0.state == stateError {
+ c0.err.Line = c.n.(*parse.BreakNode).Line
+ c0.err.Description = "at range loop break: " + c0.err.Description
+ return c0
+ }
+ }
+ for _, c := range rc.continues {
+ c0 = join(c0, c, c.n, "range")
+ if c0.state == stateError {
+ c0.err.Line = c.n.(*parse.ContinueNode).Line
+ c0.err.Description = "at range loop continue: " + c0.err.Description
+ return c0
+ }
+ }
+ return c0
+}
+
+// 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)
+ if c.state == stateDead {
+ break
+ }
+ }
+ 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)
+ e1.rangeContext = e.rangeContext
+ // 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 recurring.
+ // 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 (
+ // Per WHATWG HTML specification, section 4.12.1.3, there are extremely
+ // complicated rules for how to handle the set of opening tags <!--,
+ // <script, and </script when they appear in JS literals (i.e. strings,
+ // regexs, and comments). The specification suggests a simple solution,
+ // rather than implementing the arcane ABNF, which involves simply escaping
+ // the opening bracket with \x3C. We use the below regex for this, since it
+ // makes doing the case-insensitive find-replace much simpler.
+ specialScriptTagRE = regexp.MustCompile("(?i)<(script|/script|!--)")
+ specialScriptTagReplacement = []byte("\\x3C$1")
+)
+
+func containsSpecialScriptTag(s []byte) bool {
+ return specialScriptTagRE.Match(s)
+}
+
+func escapeSpecialScriptTags(s []byte) []byte {
+ return specialScriptTagRE.ReplaceAll(s, specialScriptTagReplacement)
+}
+
+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("&lt;")
+ written = j + 1
+ }
+ }
+ } else if isComment(c.state) && c.delim == delimNone {
+ switch c.state {
+ case stateJSBlockCmt:
+ // https://es5.github.io/#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 || c1.state == stateJSHTMLOpenCmt {
+ // "<!--" instead of "/*" or "//"
+ cs -= 2
+ } else if c1.state == stateJSHTMLCloseCmt {
+ // "-->" instead of "/*" or "//"
+ cs -= 1
+ }
+ b.Write(s[written:cs])
+ written = i1
+ }
+ if isInScriptLiteral(c.state) && containsSpecialScriptTag(s[i:i1]) {
+ b.Write(s[written:i])
+ b.Write(escapeSpecialScriptTags(s[i:i1]))
+ 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(&quot;Hi!&quot;)">
+ // 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 ...any) 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 ...any) 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 ...any) string {
+ return template.URLQueryEscaper(args...)
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-28 22:15:37 +0000