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authorRoberto Clapis <roberto@golang.org>2020-08-26 08:53:03 +0200
committerFilippo Valsorda <valsorda@google.com>2020-09-01 12:31:45 +0000
commiteb07103a083237414145a45f029c873d57037e06 (patch)
tree22816017d9892e7a0ee0382e8db61d4c27525829
parent0fdc3801bfd43d6f55e4ea5bf095e1ea55430339 (diff)
downloadgo-eb07103a083237414145a45f029c873d57037e06.tar.gz
go-eb07103a083237414145a45f029c873d57037e06.zip
[release-branch.go1.15-security] 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 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> (cherry picked from commit 23d675d07fdc56aafd67c0a0b63d5b7e14708ff0) Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/835311 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Diffstat
-rw-r--r--src/net/http/cgi/child.go36
-rw-r--r--src/net/http/cgi/child_test.go69
-rw-r--r--src/net/http/cgi/integration_test.go53
-rw-r--r--src/net/http/fcgi/child.go39
-rw-r--r--src/net/http/fcgi/fcgi_test.go52
5 files changed, 227 insertions, 22 deletions
diff --git a/src/net/http/cgi/child.go b/src/net/http/cgi/child.go
index 9474175f17..61de6165f6 100644
--- a/src/net/http/cgi/child.go
+++ b/src/net/http/cgi/child.go
@@ -163,10 +163,12 @@ 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() {
@@ -178,26 +180,38 @@ 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..f6ecb6eb80 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 +153,67 @@ func TestRequestWithoutRemotePort(t *testing.T) {
t.Errorf("RemoteAddr: got %q; want %q", g, e)
}
}
+
+type countingWriter int
+
+func (c *countingWriter) Write(p []byte) (int, error) {
+ *c += countingWriter(len(p))
+ return len(p), nil
+}
+func (c *countingWriter) WriteString(p string) (int, error) {
+ *c += countingWriter(len(p))
+ return len(p), nil
+}
+
+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 32d59c09a3..295c3b82d4 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 {
@@ -152,6 +154,51 @@ func TestChildOnlyHeaders(t *testing.T) {
}
}
+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") }
@@ -203,6 +250,10 @@ 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 {
diff --git a/src/net/http/fcgi/child.go b/src/net/http/fcgi/child.go
index 30a6b2ce2d..a31273b3ec 100644
--- a/src/net/http/fcgi/child.go
+++ b/src/net/http/fcgi/child.go
@@ -74,10 +74,12 @@ func (r *request) parseParams() {
// response implements http.ResponseWriter.
type response struct {
- req *request
- header http.Header
- w *bufWriter
- wroteHeader bool
+ req *request
+ header http.Header
+ code int
+ wroteHeader bool
+ wroteCGIHeader bool
+ w *bufWriter
}
func newResponse(c *child, req *request) *response {
@@ -92,11 +94,14 @@ func (r *response) Header() http.Header {
return r.header
}
-func (r *response) Write(data []byte) (int, error) {
+func (r *response) Write(p []byte) (n int, err error) {
if !r.wroteHeader {
r.WriteHeader(http.StatusOK)
}
- return r.w.Write(data)
+ if !r.wroteCGIHeader {
+ r.writeCGIHeader(p)
+ }
+ return r.w.Write(p)
}
func (r *response) WriteHeader(code int) {
@@ -104,22 +109,34 @@ func (r *response) WriteHeader(code int) {
return
}
r.wroteHeader = true
+ r.code = code
if code == http.StatusNotModified {
// Must not have body.
r.header.Del("Content-Type")
r.header.Del("Content-Length")
r.header.Del("Transfer-Encoding")
- } else if r.header.Get("Content-Type") == "" {
- r.header.Set("Content-Type", "text/html; charset=utf-8")
}
-
if r.header.Get("Date") == "" {
r.header.Set("Date", time.Now().UTC().Format(http.TimeFormat))
}
+}
- fmt.Fprintf(r.w, "Status: %d %s\r\n", code, http.StatusText(code))
+// 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.w, "Status: %d %s\r\n", r.code, http.StatusText(r.code))
+ if _, hasType := r.header["Content-Type"]; r.code != http.StatusNotModified && !hasType {
+ r.header.Set("Content-Type", http.DetectContentType(p))
+ }
r.header.Write(r.w)
r.w.WriteString("\r\n")
+ r.w.Flush()
}
func (r *response) Flush() {
@@ -290,6 +307,8 @@ func (c *child) serveRequest(req *request, body io.ReadCloser) {
httpReq = httpReq.WithContext(envVarCtx)
c.handler.ServeHTTP(r, httpReq)
}
+ // Make sure we serve something even if nothing was written to r
+ r.Write(nil)
r.Close()
c.mu.Lock()
delete(c.requests, req.reqId)
diff --git a/src/net/http/fcgi/fcgi_test.go b/src/net/http/fcgi/fcgi_test.go
index e9d2b34023..4a27a12c35 100644
--- a/src/net/http/fcgi/fcgi_test.go
+++ b/src/net/http/fcgi/fcgi_test.go
@@ -10,6 +10,7 @@ import (
"io"
"io/ioutil"
"net/http"
+ "strings"
"testing"
)
@@ -344,3 +345,54 @@ func TestChildServeReadsEnvVars(t *testing.T) {
<-done
}
}
+
+func TestResponseWriterSniffsContentType(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) {
+ input := make([]byte, len(streamFullRequestStdin))
+ copy(input, streamFullRequestStdin)
+ rc := nopWriteCloser{bytes.NewBuffer(input)}
+ done := make(chan bool)
+ var resp *response
+ c := newChild(rc, http.HandlerFunc(func(
+ w http.ResponseWriter,
+ r *http.Request,
+ ) {
+ io.WriteString(w, tt.body)
+ resp = w.(*response)
+ done <- true
+ }))
+ defer c.cleanUp()
+ go c.serve()
+ <-done
+ if got := resp.Header().Get("Content-Type"); got != tt.wantCT {
+ t.Errorf("got a Content-Type of %q; expected it to start with %q", got, tt.wantCT)
+ }
+ })
+ }
+}
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