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authorRoberto Clapis <roberto@golang.org>2020-08-26 08:53:03 +0200
committerFilippo Valsorda <filippo@golang.org>2020-09-14 15:42:03 +0000
commit4f5cd0c0331943c7ec72df3b827d972584f77833 (patch)
tree9aba6fa0d87f10f1cf442a95a6c9e6f1200d28fb /src/net/http/cgi
parent66e66e71132034aa620ffbae9008f951da0f9f27 (diff)
downloadgo-4f5cd0c0331943c7ec72df3b827d972584f77833.tar.xz
net/http/cgi,net/http/fcgi: add Content-Type detection
This CL ensures that responses served via CGI and FastCGI have a Content-Type header based on the content of the response if not explicitly set by handlers. If the implementers of the handler did not explicitly specify a Content-Type both CGI implementations would default to "text/html", potentially causing cross-site scripting. Thanks to RedTeam Pentesting GmbH for reporting this. Fixes #40928 Fixes CVE-2020-24553 Change-Id: I82cfc396309b5ab2e8d6e9a87eda8ea7e3799473 Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/823217 Reviewed-by: Russ Cox <rsc@google.com> Reviewed-on: https://go-review.googlesource.com/c/go/+/252179 Run-TryBot: Filippo Valsorda <filippo@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Katie Hockman <katie@golang.org>
Diffstat (limited to 'src/net/http/cgi')
-rw-r--r--src/net/http/cgi/child.go36
-rw-r--r--src/net/http/cgi/child_test.go58
-rw-r--r--src/net/http/cgi/integration_test.go53
3 files changed, 135 insertions, 12 deletions
diff --git a/src/net/http/cgi/child.go b/src/net/http/cgi/child.go
index d7d813e68a..690986335c 100644
--- a/src/net/http/cgi/child.go
+++ b/src/net/http/cgi/child.go
@@ -166,10 +166,12 @@ func Serve(handler http.Handler) error {
}
type response struct {
- req *http.Request
- header http.Header
- bufw *bufio.Writer
- headerSent bool
+ req *http.Request
+ header http.Header
+ code int
+ wroteHeader bool
+ wroteCGIHeader bool
+ bufw *bufio.Writer
}
func (r *response) Flush() {
@@ -181,26 +183,38 @@ func (r *response) Header() http.Header {
}
func (r *response) Write(p []byte) (n int, err error) {
- if !r.headerSent {
+ if !r.wroteHeader {
r.WriteHeader(http.StatusOK)
}
+ if !r.wroteCGIHeader {
+ r.writeCGIHeader(p)
+ }
return r.bufw.Write(p)
}
func (r *response) WriteHeader(code int) {
- if r.headerSent {
+ if r.wroteHeader {
// Note: explicitly using Stderr, as Stdout is our HTTP output.
fmt.Fprintf(os.Stderr, "CGI attempted to write header twice on request for %s", r.req.URL)
return
}
- r.headerSent = true
- fmt.Fprintf(r.bufw, "Status: %d %s\r\n", code, http.StatusText(code))
+ r.wroteHeader = true
+ r.code = code
+}
- // Set a default Content-Type
+// writeCGIHeader finalizes the header sent to the client and writes it to the output.
+// p is not written by writeHeader, but is the first chunk of the body
+// that will be written. It is sniffed for a Content-Type if none is
+// set explicitly.
+func (r *response) writeCGIHeader(p []byte) {
+ if r.wroteCGIHeader {
+ return
+ }
+ r.wroteCGIHeader = true
+ fmt.Fprintf(r.bufw, "Status: %d %s\r\n", r.code, http.StatusText(r.code))
if _, hasType := r.header["Content-Type"]; !hasType {
- r.header.Add("Content-Type", "text/html; charset=utf-8")
+ r.header.Set("Content-Type", http.DetectContentType(p))
}
-
r.header.Write(r.bufw)
r.bufw.WriteString("\r\n")
r.bufw.Flush()
diff --git a/src/net/http/cgi/child_test.go b/src/net/http/cgi/child_test.go
index 14e0af475f..18cf789bd5 100644
--- a/src/net/http/cgi/child_test.go
+++ b/src/net/http/cgi/child_test.go
@@ -7,6 +7,11 @@
package cgi
import (
+ "bufio"
+ "bytes"
+ "net/http"
+ "net/http/httptest"
+ "strings"
"testing"
)
@@ -148,3 +153,56 @@ func TestRequestWithoutRemotePort(t *testing.T) {
t.Errorf("RemoteAddr: got %q; want %q", g, e)
}
}
+
+func TestResponse(t *testing.T) {
+ var tests = []struct {
+ name string
+ body string
+ wantCT string
+ }{
+ {
+ name: "no body",
+ wantCT: "text/plain; charset=utf-8",
+ },
+ {
+ name: "html",
+ body: "<html><head><title>test page</title></head><body>This is a body</body></html>",
+ wantCT: "text/html; charset=utf-8",
+ },
+ {
+ name: "text",
+ body: strings.Repeat("gopher", 86),
+ wantCT: "text/plain; charset=utf-8",
+ },
+ {
+ name: "jpg",
+ body: "\xFF\xD8\xFF" + strings.Repeat("B", 1024),
+ wantCT: "image/jpeg",
+ },
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ var buf bytes.Buffer
+ resp := response{
+ req: httptest.NewRequest("GET", "/", nil),
+ header: http.Header{},
+ bufw: bufio.NewWriter(&buf),
+ }
+ n, err := resp.Write([]byte(tt.body))
+ if err != nil {
+ t.Errorf("Write: unexpected %v", err)
+ }
+ if want := len(tt.body); n != want {
+ t.Errorf("reported short Write: got %v want %v", n, want)
+ }
+ resp.writeCGIHeader(nil)
+ resp.Flush()
+ if got := resp.Header().Get("Content-Type"); got != tt.wantCT {
+ t.Errorf("wrong content-type: got %q, want %q", got, tt.wantCT)
+ }
+ if !bytes.HasSuffix(buf.Bytes(), []byte(tt.body)) {
+ t.Errorf("body was not correctly written")
+ }
+ })
+ }
+}
diff --git a/src/net/http/cgi/integration_test.go b/src/net/http/cgi/integration_test.go
index eaa090f6fe..76cbca8e60 100644
--- a/src/net/http/cgi/integration_test.go
+++ b/src/net/http/cgi/integration_test.go
@@ -16,7 +16,9 @@ import (
"io"
"net/http"
"net/http/httptest"
+ "net/url"
"os"
+ "strings"
"testing"
"time"
)
@@ -52,7 +54,7 @@ func TestHostingOurselves(t *testing.T) {
}
replay := runCgiTest(t, h, "GET /test.go?foo=bar&a=b HTTP/1.0\nHost: example.com\n\n", expectedMap)
- if expected, got := "text/html; charset=utf-8", replay.Header().Get("Content-Type"); got != expected {
+ if expected, got := "text/plain; charset=utf-8", replay.Header().Get("Content-Type"); got != expected {
t.Errorf("got a Content-Type of %q; expected %q", got, expected)
}
if expected, got := "X-Test-Value", replay.Header().Get("X-Test-Header"); got != expected {
@@ -169,6 +171,51 @@ func TestNilRequestBody(t *testing.T) {
_ = runCgiTest(t, h, "POST /test.go?nil-request-body=1 HTTP/1.0\nHost: example.com\nContent-Length: 0\n\n", expectedMap)
}
+func TestChildContentType(t *testing.T) {
+ testenv.MustHaveExec(t)
+
+ h := &Handler{
+ Path: os.Args[0],
+ Root: "/test.go",
+ Args: []string{"-test.run=TestBeChildCGIProcess"},
+ }
+ var tests = []struct {
+ name string
+ body string
+ wantCT string
+ }{
+ {
+ name: "no body",
+ wantCT: "text/plain; charset=utf-8",
+ },
+ {
+ name: "html",
+ body: "<html><head><title>test page</title></head><body>This is a body</body></html>",
+ wantCT: "text/html; charset=utf-8",
+ },
+ {
+ name: "text",
+ body: strings.Repeat("gopher", 86),
+ wantCT: "text/plain; charset=utf-8",
+ },
+ {
+ name: "jpg",
+ body: "\xFF\xD8\xFF" + strings.Repeat("B", 1024),
+ wantCT: "image/jpeg",
+ },
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ expectedMap := map[string]string{"_body": tt.body}
+ req := fmt.Sprintf("GET /test.go?exact-body=%s HTTP/1.0\nHost: example.com\n\n", url.QueryEscape(tt.body))
+ replay := runCgiTest(t, h, req, expectedMap)
+ if got := replay.Header().Get("Content-Type"); got != tt.wantCT {
+ t.Errorf("got a Content-Type of %q; expected it to start with %q", got, tt.wantCT)
+ }
+ })
+ }
+}
+
// golang.org/issue/7198
func Test500WithNoHeaders(t *testing.T) { want500Test(t, "/immediate-disconnect") }
func Test500WithNoContentType(t *testing.T) { want500Test(t, "/no-content-type") }
@@ -224,6 +271,10 @@ func TestBeChildCGIProcess(t *testing.T) {
if req.FormValue("no-body") == "1" {
return
}
+ if eb, ok := req.Form["exact-body"]; ok {
+ io.WriteString(rw, eb[0])
+ return
+ }
if req.FormValue("write-forever") == "1" {
io.Copy(rw, neverEnding('a'))
for {
generated by cgit v1.3 (git 2.53.0) at 2026-04-15 17:35:37 +0000