[release-branch.go1.19] html/template: emit filterFailsafe for empty unquoted attr value
An unquoted action used as an attribute value can result in unsafe
behavior if it is empty, as HTML normalization will result in unexpected
attributes, and may allow attribute injection. If executing a template
results in a empty unquoted attribute value, emit filterFailsafe
instead.
Thanks to Juho Nurminen of Mattermost for reporting this issue.
For #59722
Fixes #59815
Fixes CVE-2023-29400
Change-Id: Ia38d1b536ae2b4af5323a6c6d861e3c057c2570a
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1826631
Reviewed-by: Julie Qiu <julieqiu@google.com>
Run-TryBot: Roland Shoemaker <bracewell@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1851498
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/491357
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
diff --git a/src/html/template/escape.go b/src/html/template/escape.go
index 3d4cc19..bcba8db 100644
--- a/src/html/template/escape.go
+++ b/src/html/template/escape.go
@@ -380,9 +380,8 @@
// 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_attrescaper": true,
+ "_html_template_htmlescaper": true,
},
"_html_template_cssescaper": {
"_html_template_attrescaper": true,
diff --git a/src/html/template/escape_test.go b/src/html/template/escape_test.go
index 972b00b..a1a6c1c 100644
--- a/src/html/template/escape_test.go
+++ b/src/html/template/escape_test.go
@@ -678,6 +678,21 @@
`<img srcset={{",,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,"}}>`,
`<img srcset=,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,>`,
},
+ {
+ "unquoted empty attribute value (plaintext)",
+ "<p name={{.U}}>",
+ "<p name=ZgotmplZ>",
+ },
+ {
+ "unquoted empty attribute value (url)",
+ "<p href={{.U}}>",
+ "<p href=ZgotmplZ>",
+ },
+ {
+ "quoted empty attribute value",
+ "<p name=\"{{.U}}\">",
+ "<p name=\"\">",
+ },
}
for _, test := range tests {
diff --git a/src/html/template/html.go b/src/html/template/html.go
index 46e9d93..6fb9237 100644
--- a/src/html/template/html.go
+++ b/src/html/template/html.go
@@ -14,6 +14,9 @@
// htmlNospaceEscaper escapes for inclusion in unquoted attribute values.
func htmlNospaceEscaper(args ...any) string {
s, t := stringify(args...)
+ if s == "" {
+ return filterFailsafe
+ }
if t == contentTypeHTML {
return htmlReplacer(stripTags(s), htmlNospaceNormReplacementTable, false)
}
