[release-branch.go1.20] html/template: disallow actions in JS template literals
ECMAScript 6 introduced template literals[0][1] which are delimited with
backticks. These need to be escaped in a similar fashion to the
delimiters for other string literals. Additionally template literals can
contain special syntax for string interpolation.
There is no clear way to allow safe insertion of actions within JS
template literals, as handling (JS) string interpolation inside of these
literals is rather complex. As such we've chosen to simply disallow
template actions within these template literals.
A new error code is added for this parsing failure case, errJsTmplLit,
but it is unexported as it is not backwards compatible with other minor
release versions to introduce an API change in a minor release. We will
export this code in the next major release.
The previous behavior (with the cavet that backticks are now escaped
properly) can be re-enabled with GODEBUG=jstmpllitinterp=1.
This change subsumes CL471455.
Thanks to Sohom Datta, Manipal Institute of Technology, for reporting
this issue.
Fixes CVE-2023-24538
For #59234
Fixes #59272
[0] https://tc39.es/ecma262/multipage/ecmascript-language-expressions.html#sec-template-literals
[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals
Change-Id: Idff74ec386e9b73d6e9a3c9f71990eabc0ce7506
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1802457
Reviewed-by: Damien Neil <dneil@google.com>
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-by: Julie Qiu <julieqiu@google.com>
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1802688
Run-TryBot: Roland Shoemaker <bracewell@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/481993
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
TryBot-Bypass: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
diff --git a/src/html/template/context.go b/src/html/template/context.go
index a97c8be..c28fb0c 100644
--- a/src/html/template/context.go
+++ b/src/html/template/context.go
@@ -120,6 +120,8 @@
stateJSDqStr
// stateJSSqStr occurs inside a JavaScript single quoted string.
stateJSSqStr
+ // stateJSBqStr occurs inside a JavaScript back quoted string.
+ stateJSBqStr
// stateJSRegexp occurs inside a JavaScript regexp literal.
stateJSRegexp
// stateJSBlockCmt occurs inside a JavaScript /* block comment */.
diff --git a/src/html/template/error.go b/src/html/template/error.go
index 5c51f77..d7d6f5b 100644
--- a/src/html/template/error.go
+++ b/src/html/template/error.go
@@ -214,6 +214,19 @@
// pipeline occurs in an unquoted attribute value context, "html" is
// disallowed. Avoid using "html" and "urlquery" entirely in new templates.
ErrPredefinedEscaper
+
+ // errJSTmplLit: "... appears in a JS template literal"
+ // Example:
+ // <script>var tmpl = `{{.Interp}`</script>
+ // Discussion:
+ // Package html/template does not support actions inside of JS template
+ // literals.
+ //
+ // TODO(rolandshoemaker): we cannot add this as an exported error in a minor
+ // release, since it is backwards incompatible with the other minor
+ // releases. As such we need to leave it unexported, and then we'll add it
+ // in the next major release.
+ errJSTmplLit
)
func (e *Error) Error() string {
diff --git a/src/html/template/escape.go b/src/html/template/escape.go
index 54fbcdc..23ece7a 100644
--- a/src/html/template/escape.go
+++ b/src/html/template/escape.go
@@ -8,6 +8,7 @@
"bytes"
"fmt"
"html"
+ "internal/godebug"
"io"
"text/template"
"text/template/parse"
@@ -160,6 +161,8 @@
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 {
@@ -223,6 +226,15 @@
c.jsCtx = jsCtxDivOp
case stateJSDqStr, stateJSSqStr:
s = append(s, "_html_template_jsstrescaper")
+ case stateJSBqStr:
+ if debugAllowActionJSTmpl.Value() == "1" {
+ s = append(s, "_html_template_jsstrescaper")
+ } else {
+ return context{
+ state: stateError,
+ err: errorf(errJSTmplLit, n, n.Line, "%s appears in a JS template literal", n),
+ }
+ }
case stateJSRegexp:
s = append(s, "_html_template_jsregexpescaper")
case stateCSS:
diff --git a/src/html/template/escape_test.go b/src/html/template/escape_test.go
index 12add07..3dd212b 100644
--- a/src/html/template/escape_test.go
+++ b/src/html/template/escape_test.go
@@ -681,35 +681,31 @@
}
for _, test := range tests {
- tmpl := New(test.name)
- tmpl = Must(tmpl.Parse(test.input))
- // Check for bug 6459: Tree field was not set in Parse.
- if tmpl.Tree != tmpl.text.Tree {
- t.Errorf("%s: tree not set properly", test.name)
- continue
- }
- b := new(strings.Builder)
- if err := tmpl.Execute(b, data); err != nil {
- t.Errorf("%s: template execution failed: %s", test.name, err)
- continue
- }
- if w, g := test.output, b.String(); w != g {
- t.Errorf("%s: escaped output: want\n\t%q\ngot\n\t%q", test.name, w, g)
- continue
- }
- b.Reset()
- if err := tmpl.Execute(b, pdata); err != nil {
- t.Errorf("%s: template execution failed for pointer: %s", test.name, err)
- continue
- }
- if w, g := test.output, b.String(); w != g {
- t.Errorf("%s: escaped output for pointer: want\n\t%q\ngot\n\t%q", test.name, w, g)
- continue
- }
- if tmpl.Tree != tmpl.text.Tree {
- t.Errorf("%s: tree mismatch", test.name)
- continue
- }
+ t.Run(test.name, func(t *testing.T) {
+ tmpl := New(test.name)
+ tmpl = Must(tmpl.Parse(test.input))
+ // Check for bug 6459: Tree field was not set in Parse.
+ if tmpl.Tree != tmpl.text.Tree {
+ t.Fatalf("%s: tree not set properly", test.name)
+ }
+ b := new(strings.Builder)
+ if err := tmpl.Execute(b, data); err != nil {
+ t.Fatalf("%s: template execution failed: %s", test.name, err)
+ }
+ if w, g := test.output, b.String(); w != g {
+ t.Fatalf("%s: escaped output: want\n\t%q\ngot\n\t%q", test.name, w, g)
+ }
+ b.Reset()
+ if err := tmpl.Execute(b, pdata); err != nil {
+ t.Fatalf("%s: template execution failed for pointer: %s", test.name, err)
+ }
+ if w, g := test.output, b.String(); w != g {
+ t.Fatalf("%s: escaped output for pointer: want\n\t%q\ngot\n\t%q", test.name, w, g)
+ }
+ if tmpl.Tree != tmpl.text.Tree {
+ t.Fatalf("%s: tree mismatch", test.name)
+ }
+ })
}
}
@@ -936,6 +932,10 @@
"{{range .Items}}<a{{if .X}}{{end}}>{{if .X}}{{break}}{{end}}{{end}}",
"",
},
+ {
+ "<script>var a = `${a+b}`</script>`",
+ "",
+ },
// Error cases.
{
"{{if .Cond}}<a{{end}}",
@@ -1082,6 +1082,10 @@
// html is allowed since it is the last command in the pipeline, but urlquery is not.
`predefined escaper "urlquery" disallowed in template`,
},
+ {
+ "<script>var tmpl = `asd {{.}}`;</script>",
+ `{{.}} appears in a JS template literal`,
+ },
}
for _, test := range tests {
buf := new(bytes.Buffer)
@@ -1304,6 +1308,10 @@
context{state: stateJSSqStr, delim: delimDoubleQuote, attr: attrScript},
},
{
+ "<a onclick=\"`foo",
+ context{state: stateJSBqStr, delim: delimDoubleQuote, attr: attrScript},
+ },
+ {
`<A ONCLICK="'`,
context{state: stateJSSqStr, delim: delimDoubleQuote, attr: attrScript},
},
diff --git a/src/html/template/js.go b/src/html/template/js.go
index 50523d0..fe7054e 100644
--- a/src/html/template/js.go
+++ b/src/html/template/js.go
@@ -308,6 +308,7 @@
// Encode HTML specials as hex so the output can be embedded
// in HTML attributes without further encoding.
'"': `\u0022`,
+ '`': `\u0060`,
'&': `\u0026`,
'\'': `\u0027`,
'+': `\u002b`,
@@ -331,6 +332,7 @@
'"': `\u0022`,
'&': `\u0026`,
'\'': `\u0027`,
+ '`': `\u0060`,
'+': `\u002b`,
'/': `\/`,
'<': `\u003c`,
diff --git a/src/html/template/js_test.go b/src/html/template/js_test.go
index 580cb0a..eee7eb2 100644
--- a/src/html/template/js_test.go
+++ b/src/html/template/js_test.go
@@ -291,7 +291,7 @@
`0123456789:;\u003c=\u003e?` +
`@ABCDEFGHIJKLMNO` +
`PQRSTUVWXYZ[\\]^_` +
- "`abcdefghijklmno" +
+ "\\u0060abcdefghijklmno" +
"pqrstuvwxyz{|}~\u007f" +
"\u00A0\u0100\\u2028\\u2029\ufeff\U0001D11E",
},
diff --git a/src/html/template/jsctx_string.go b/src/html/template/jsctx_string.go
index dd1d87ee..2394893 100644
--- a/src/html/template/jsctx_string.go
+++ b/src/html/template/jsctx_string.go
@@ -4,6 +4,15 @@
import "strconv"
+func _() {
+ // An "invalid array index" compiler error signifies that the constant values have changed.
+ // Re-run the stringer command to generate them again.
+ var x [1]struct{}
+ _ = x[jsCtxRegexp-0]
+ _ = x[jsCtxDivOp-1]
+ _ = x[jsCtxUnknown-2]
+}
+
const _jsCtx_name = "jsCtxRegexpjsCtxDivOpjsCtxUnknown"
var _jsCtx_index = [...]uint8{0, 11, 21, 33}
diff --git a/src/html/template/state_string.go b/src/html/template/state_string.go
index 05104be..6fb1a6e 100644
--- a/src/html/template/state_string.go
+++ b/src/html/template/state_string.go
@@ -4,9 +4,42 @@
import "strconv"
-const _state_name = "stateTextstateTagstateAttrNamestateAfterNamestateBeforeValuestateHTMLCmtstateRCDATAstateAttrstateURLstateSrcsetstateJSstateJSDqStrstateJSSqStrstateJSRegexpstateJSBlockCmtstateJSLineCmtstateCSSstateCSSDqStrstateCSSSqStrstateCSSDqURLstateCSSSqURLstateCSSURLstateCSSBlockCmtstateCSSLineCmtstateError"
+func _() {
+ // An "invalid array index" compiler error signifies that the constant values have changed.
+ // Re-run the stringer command to generate them again.
+ var x [1]struct{}
+ _ = x[stateText-0]
+ _ = x[stateTag-1]
+ _ = x[stateAttrName-2]
+ _ = x[stateAfterName-3]
+ _ = x[stateBeforeValue-4]
+ _ = x[stateHTMLCmt-5]
+ _ = x[stateRCDATA-6]
+ _ = x[stateAttr-7]
+ _ = x[stateURL-8]
+ _ = x[stateSrcset-9]
+ _ = x[stateJS-10]
+ _ = x[stateJSDqStr-11]
+ _ = x[stateJSSqStr-12]
+ _ = x[stateJSBqStr-13]
+ _ = x[stateJSRegexp-14]
+ _ = x[stateJSBlockCmt-15]
+ _ = x[stateJSLineCmt-16]
+ _ = x[stateCSS-17]
+ _ = x[stateCSSDqStr-18]
+ _ = x[stateCSSSqStr-19]
+ _ = x[stateCSSDqURL-20]
+ _ = x[stateCSSSqURL-21]
+ _ = x[stateCSSURL-22]
+ _ = x[stateCSSBlockCmt-23]
+ _ = x[stateCSSLineCmt-24]
+ _ = x[stateError-25]
+ _ = x[stateDead-26]
+}
-var _state_index = [...]uint16{0, 9, 17, 30, 44, 60, 72, 83, 92, 100, 111, 118, 130, 142, 155, 170, 184, 192, 205, 218, 231, 244, 255, 271, 286, 296}
+const _state_name = "stateTextstateTagstateAttrNamestateAfterNamestateBeforeValuestateHTMLCmtstateRCDATAstateAttrstateURLstateSrcsetstateJSstateJSDqStrstateJSSqStrstateJSBqStrstateJSRegexpstateJSBlockCmtstateJSLineCmtstateCSSstateCSSDqStrstateCSSSqStrstateCSSDqURLstateCSSSqURLstateCSSURLstateCSSBlockCmtstateCSSLineCmtstateErrorstateDead"
+
+var _state_index = [...]uint16{0, 9, 17, 30, 44, 60, 72, 83, 92, 100, 111, 118, 130, 142, 154, 167, 182, 196, 204, 217, 230, 243, 256, 267, 283, 298, 308, 317}
func (i state) String() string {
if i >= state(len(_state_index)-1) {
diff --git a/src/html/template/transition.go b/src/html/template/transition.go
index 06df679..92eb351 100644
--- a/src/html/template/transition.go
+++ b/src/html/template/transition.go
@@ -27,6 +27,7 @@
stateJS: tJS,
stateJSDqStr: tJSDelimited,
stateJSSqStr: tJSDelimited,
+ stateJSBqStr: tJSDelimited,
stateJSRegexp: tJSDelimited,
stateJSBlockCmt: tBlockCmt,
stateJSLineCmt: tLineCmt,
@@ -262,7 +263,7 @@
// tJS is the context transition function for the JS state.
func tJS(c context, s []byte) (context, int) {
- i := bytes.IndexAny(s, `"'/`)
+ i := bytes.IndexAny(s, "\"`'/")
if i == -1 {
// Entire input is non string, comment, regexp tokens.
c.jsCtx = nextJSCtx(s, c.jsCtx)
@@ -274,6 +275,8 @@
c.state, c.jsCtx = stateJSDqStr, jsCtxRegexp
case '\'':
c.state, c.jsCtx = stateJSSqStr, jsCtxRegexp
+ case '`':
+ c.state, c.jsCtx = stateJSBqStr, jsCtxRegexp
case '/':
switch {
case i+1 < len(s) && s[i+1] == '/':
@@ -303,6 +306,8 @@
switch c.state {
case stateJSSqStr:
specials = `\'`
+ case stateJSBqStr:
+ specials = "`\\"
case stateJSRegexp:
specials = `\/[]`
}
