Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

fix lack of escaping of filename in Content-Disposition #3556

Merged
merged 3 commits into from
May 29, 2023
+21 −1
Merged

fix lack of escaping of filename in Content-Disposition #3556

Show file tree
Hide file tree
Changes from 2 commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
ded02a8
fix lack of escaping of filename in Content-Disposition
motoyasu-saburi Apr 1, 2023
96c3c55
add test for Content-Disposition filename escaping process
motoyasu-saburi Apr 1, 2023
ee5b2c9
fix filename escape bypass problem
motoyasu-saburi May 13, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
2 changes: 1 addition & 1 deletion context.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1056,7 +1056,7 @@ func (c *Context) FileFromFS(filepath string, fs http.FileSystem) {
// On the client side, the file will typically be downloaded with the given filename
func (c *Context) FileAttachment(filepath, filename string) {
if isASCII(filename) {
c.Writer.Header().Set("Content-Disposition", `attachment; filename="`+filename+`"`)
c.Writer.Header().Set("Content-Disposition", `attachment; filename="`+strings.Replace(filename, "\"", "\\\"", -1)+`"`)
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This can fix this specific situation (that enables RFD attack) but what about using filePath#Clean?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I tried using that method,
but the " was not escaped (or URL Encoded), so The vulnerability was not fixed.

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

But since it's for file reading those quotes will be needed? File params would be readable with or without it, isn't?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@fabricioereche

Perhaps you are confusing the file name with the file path.
There may be some misunderstandings, so I will add to this.

The first thing to escape is the filename. Not filepath.

The second thing, The Filename escape requirements are then as follows

  • " --> %2F, \"
  • \r --> %0D, \\r
  • \n --> %0A, \\n

The third thing,
This line is the process of "escaping the 'file name at download time' on the HTTP Response Header.
In other words, filepath is irrelevant.

(The part that actually reads the file is the following line (filepath) )
https://github.com/gin-gonic/gin/pull/3556/files#diff-552f47512a00afe5fc6850cc9ddc830a6daeca162750e50aab4ed549685e0253R1063

But since it's for file reading those quotes will be needed? File params would be readable with or without it, isn't?

This is answered by the third matter mentioned above.
This tells the Request side to "download the file with this kind of file name".
It is not the file path to be read by the Server side.

Does this answer your question?

} else {
c.Writer.Header().Set("Content-Disposition", `attachment; filename*=UTF-8''`+url.QueryEscape(filename))
}
Expand Down
14 changes: 14 additions & 0 deletions context_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1032,6 +1032,20 @@ func TestContextRenderAttachment(t *testing.T) {
assert.Equal(t, fmt.Sprintf("attachment; filename=\"%s\"", newFilename), w.Header().Get("Content-Disposition"))
}

func TestContextRenderAndEscapeAttachment(t *testing.T) {
w := httptest.NewRecorder()
c, _ := CreateTestContext(w)
maliciousFilename := "tampering_field.sh\";dummy=.go"
actualEscapedResponseFilename := "tampering_field.sh\\\";dummy=.go"

c.Request, _ = http.NewRequest("GET", "/", nil)
c.FileAttachment("./gin.go", maliciousFilename)

assert.Equal(t, 200, w.Code)
assert.Contains(t, w.Body.String(), "func New() *Engine {")
assert.Equal(t, fmt.Sprintf("attachment; filename=\"%s\"", actualEscapedResponseFilename), w.Header().Get("Content-Disposition"))
}

func TestContextRenderUTF8Attachment(t *testing.T) {
w := httptest.NewRecorder()
c, _ := CreateTestContext(w)
Expand Down