Support redirects for libgit2 managed transport

For backwards compatibility, support for HTTP redirection is enabled when targeting
the same host, and no TLS downgrade took place.

Signed-off-by: Paulo Gomes <paulo.gomes@weave.works>

pkg/git/libgit2/managed/http.go

@@ -44,6 +44,7 @@ THE SOFTWARE.
 package managed
 
 import (
+ "bytes"
  "crypto/tls"
  "crypto/x509"
  "errors"
@@ -133,6 +134,25 @@ func (t *httpSmartSubtransport) Action(targetUrl string, action git2go.SmartServ
  stream.sendRequestBackground()
  }
 
+ client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
+ if len(via) >= 3 {
+ return fmt.Errorf("too many redirects")
+ }
+
+ // golang will change POST to GET in case of redirects.
+ if len(via) >= 0 && req.Method != via[0].Method {
+ if via[0].URL.Scheme == "https" && req.URL.Scheme == "http" {
+ return fmt.Errorf("downgrade from https to http is not allowed: from %q to %q", via[0].URL.String(), req.URL.String())
+ }
+ if via[0].URL.Host != req.URL.Host {
+ return fmt.Errorf("cross hosts redirects are not allowed: from %s to %s", via[0].URL.Host, req.URL.Host)
+ }
+
+ return http.ErrUseLastResponse
+ }
+ return nil
+ }
+
  return stream, nil
 }
 
@@ -165,7 +185,10 @@ func createClientRequest(targetUrl string, action git2go.SmartServiceAction, t *
  }
  }
 
- client := &http.Client{Transport: t, Timeout: fullHttpClientTimeOut}
+ client := &http.Client{
+ Transport: t,
+ Timeout: fullHttpClientTimeOut,
+ }
 
  switch action {
  case git2go.SmartServiceActionUploadpackLs:
@@ -218,6 +241,7 @@ type httpSmartSubtransportStream struct {
  recvReply sync.WaitGroup
  httpError error
  m sync.RWMutex
+ targetURL string
 }
 
 func newManagedHttpStream(owner *httpSmartSubtransport, req *http.Request, client *http.Client) *httpSmartSubtransportStream {
@@ -246,18 +270,21 @@ func (self *httpSmartSubtransportStream) Read(buf []byte) (int, error) {
  self.recvReply.Wait()
 
  self.m.RLock()
- defer self.m.RUnlock()
- if self.httpError != nil {
+ err := self.httpError
+ self.m.RUnlock()
+
+ if err != nil {
  return 0, self.httpError
  }
-
  return self.resp.Body.Read(buf)
 }
 
 func (self *httpSmartSubtransportStream) Write(buf []byte) (int, error) {
  self.m.RLock()
- defer self.m.RUnlock()
- if self.httpError != nil {
+ err := self.httpError
+ self.m.RUnlock()
+
+ if err != nil {
  return 0, self.httpError
  }
  return self.writer.Write(buf)
@@ -308,29 +335,53 @@ func (self *httpSmartSubtransportStream) sendRequest() error {
  }
  }
 
- req := &http.Request{
- Method: self.req.Method,
- URL: self.req.URL,
- Header: self.req.Header,
- }
- if req.Method == "POST" {
- req.Body = self.reader
- req.ContentLength = -1
- }
+ var content []byte
+ for {
+ req := &http.Request{
+ Method: self.req.Method,
+ URL: self.req.URL,
+ Header: self.req.Header,
+ }
+ if req.Method == "POST" {
+ if len(content) == 0 {
+ // a copy of the request body needs to be saved so
+ // it can be reused in case of redirects.
+ if content, err = io.ReadAll(self.reader); err != nil {
+ return err
+ }
+ }
+ req.Body = ioutil.NopCloser(bytes.NewReader(content))
+ req.ContentLength = -1
+ }
 
- req.SetBasicAuth(userName, password)
- resp, err = self.client.Do(req)
- if err != nil {
- return err
- }
+  req.SetBasicAuth(userName, password)
+  resp, err = self.client.Do(req)
+  if err != nil {
+  return err
+  }
 
- if resp.StatusCode == http.StatusOK {
- self.resp = resp
- self.sentRequest = true
- return nil
+ // GET requests will be automatically redirected.
+ // POST require the new destination, and also the body content.
+ if req.Method == "POST" && resp.StatusCode >= 301 && resp.StatusCode <= 308 {
+ // The next try will go against the new destination
+ self.req.URL, err = resp.Location()
+ if err != nil {
+ return err
+ }
+
+ continue
+ }
+
+ if resp.StatusCode == http.StatusOK {
+ break
+ }
+
+ io.Copy(ioutil.Discard, resp.Body)
+ defer resp.Body.Close()
+ return fmt.Errorf("Unhandled HTTP error %s", resp.Status)
  }
 
- io.Copy(ioutil.Discard, resp.Body)
- defer resp.Body.Close()
- return fmt.Errorf("Unhandled HTTP error %s", resp.Status)
+ self.resp = resp
+ self.sentRequest = true
+ return nil
 }

pkg/git/libgit2/managed/managed_test.go

@@ -304,3 +304,24 @@ func TestManagedTransport_E2E(t *testing.T) {
  g.Expect(err).ToNot(HaveOccurred())
  repo.Free()
 }
+
+func TestManagedTransport_HandleRedirect(t *testing.T) {
+ g := NewWithT(t)
+
+ tmpDir, _ := os.MkdirTemp("", "test")
+ defer os.RemoveAll(tmpDir)
+
+ // Force managed transport to be enabled
+ InitManagedTransport()
+
+ // GitHub will cause a 301 and redirect to https
+ repo, err := git2go.Clone("http://github.com/stefanprodan/podinfo", tmpDir, &git2go.CloneOptions{
+ FetchOptions: git2go.FetchOptions{},
+ CheckoutOptions: git2go.CheckoutOptions{
+ Strategy: git2go.CheckoutForce,
+ },
+ })
+
+ g.Expect(err).ToNot(HaveOccurred())
+ repo.Free()
+}