From 14daeb968049b71296a80b91abd3883afd02b4d1 Mon Sep 17 00:00:00 2001
From: Martti T <desinformatsioon@gmail.com>
Date: Tue, 7 Nov 2023 14:10:06 +0200
Subject: [PATCH] Security: c.Attachment and c.Inline should escape name in
 `Content-Disposition` header to avoid 'Reflect File Download' vulnerability.
 (#2541)

This is same as Go std does it https://github.com/golang/go/blob/9d836d41d0d9df3acabf7f9607d3b09188a9bfc6/src/mime/multipart/writer.go#L132
---
 context.go      |  4 ++-
 context_test.go | 82 +++++++++++++++++++++++++++++++++++++------------
 2 files changed, 65 insertions(+), 21 deletions(-)

diff --git a/context.go b/context.go
index 27da28a9c..6a1811685 100644
--- a/context.go
+++ b/context.go
@@ -584,8 +584,10 @@ func (c *context) Inline(file, name string) error {
 	return c.contentDisposition(file, name, "inline")
 }
 
+var quoteEscaper = strings.NewReplacer("\\", "\\\\", `"`, "\\\"")
+
 func (c *context) contentDisposition(file, name, dispositionType string) error {
-	c.response.Header().Set(HeaderContentDisposition, fmt.Sprintf("%s; filename=%q", dispositionType, name))
+	c.response.Header().Set(HeaderContentDisposition, fmt.Sprintf(`%s; filename="%s"`, dispositionType, quoteEscaper.Replace(name)))
 	return c.File(file)
 }
 
diff --git a/context_test.go b/context_test.go
index 85b221446..01a8784b8 100644
--- a/context_test.go
+++ b/context_test.go
@@ -414,30 +414,72 @@ func TestContextStream(t *testing.T) {
 }
 
 func TestContextAttachment(t *testing.T) {
-	e := New()
-	rec := httptest.NewRecorder()
-	req := httptest.NewRequest(http.MethodGet, "/?pretty", nil)
-	c := e.NewContext(req, rec).(*context)
-
-	err := c.Attachment("_fixture/images/walle.png", "walle.png")
-	if assert.NoError(t, err) {
-		assert.Equal(t, http.StatusOK, rec.Code)
-		assert.Equal(t, "attachment; filename=\"walle.png\"", rec.Header().Get(HeaderContentDisposition))
-		assert.Equal(t, 219885, rec.Body.Len())
+	var testCases = []struct {
+		name         string
+		whenName     string
+		expectHeader string
+	}{
+		{
+			name:         "ok",
+			whenName:     "walle.png",
+			expectHeader: `attachment; filename="walle.png"`,
+		},
+		{
+			name:         "ok, escape quotes in malicious filename",
+			whenName:     `malicious.sh"; \"; dummy=.txt`,
+			expectHeader: `attachment; filename="malicious.sh\"; \\\"; dummy=.txt"`,
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			e := New()
+			rec := httptest.NewRecorder()
+			req := httptest.NewRequest(http.MethodGet, "/", nil)
+			c := e.NewContext(req, rec).(*context)
+
+			err := c.Attachment("_fixture/images/walle.png", tc.whenName)
+			if assert.NoError(t, err) {
+				assert.Equal(t, tc.expectHeader, rec.Header().Get(HeaderContentDisposition))
+
+				assert.Equal(t, http.StatusOK, rec.Code)
+				assert.Equal(t, 219885, rec.Body.Len())
+			}
+		})
 	}
 }
 
 func TestContextInline(t *testing.T) {
-	e := New()
-	rec := httptest.NewRecorder()
-	req := httptest.NewRequest(http.MethodGet, "/?pretty", nil)
-	c := e.NewContext(req, rec).(*context)
-
-	err := c.Inline("_fixture/images/walle.png", "walle.png")
-	if assert.NoError(t, err) {
-		assert.Equal(t, http.StatusOK, rec.Code)
-		assert.Equal(t, "inline; filename=\"walle.png\"", rec.Header().Get(HeaderContentDisposition))
-		assert.Equal(t, 219885, rec.Body.Len())
+	var testCases = []struct {
+		name         string
+		whenName     string
+		expectHeader string
+	}{
+		{
+			name:         "ok",
+			whenName:     "walle.png",
+			expectHeader: `inline; filename="walle.png"`,
+		},
+		{
+			name:         "ok, escape quotes in malicious filename",
+			whenName:     `malicious.sh"; \"; dummy=.txt`,
+			expectHeader: `inline; filename="malicious.sh\"; \\\"; dummy=.txt"`,
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			e := New()
+			rec := httptest.NewRecorder()
+			req := httptest.NewRequest(http.MethodGet, "/", nil)
+			c := e.NewContext(req, rec).(*context)
+
+			err := c.Inline("_fixture/images/walle.png", tc.whenName)
+			if assert.NoError(t, err) {
+				assert.Equal(t, tc.expectHeader, rec.Header().Get(HeaderContentDisposition))
+
+				assert.Equal(t, http.StatusOK, rec.Code)
+				assert.Equal(t, 219885, rec.Body.Len())
+			}
+		})
 	}
 }