aws/request: Fix for Go 1.8 request incorrectly sent with body

Go 1.8 tightened and clarified the rules code needs to use when building
requests with the http package. Go 1.8 removed the automatic detection
of if the Request.Body was empty, or actually had bytes in it. The SDK
always sets the Request.Body even if it is empty and should not actually
be sent. This is incorrect.

Go 1.8 did add a http.NoBody value that the SDK can use to tell the http
client that the request really should be sent without a body. The
Request.Body cannot be set to nil, which is preferable, because the
field is exported and could introduce nil pointer dereferences for users
of the SDK if they used that field.

Related golang/go#18257

Fix aws#984

aws/request/request.go

@@ -244,8 +244,11 @@ func (r *Request) ResetBody() {
 		r.safeBody.Close()
 	}
 
-	r.safeBody = newOffsetReader(r.Body, r.BodyStart)
-	r.HTTPRequest.Body = r.safeBody
+	// Resets the body with the offset reader. For Go +1.8 the
+	// body is only wrapped if it is no empty. Otherwise the
+	// http.NoBody value will be written to the http.Request.Body
+	// field.
+	resetBody(r)
 }
 
 // GetBody will return an io.ReadSeeker of the Request's underlying

aws/request/request_resetbody.go

@@ -0,0 +1,22 @@
+// +build go1.8
+
+package request
+
+import (
+	"io"
+	"net/http"
+)
+
+func resetBody(r *Request) {
+	curOffset, _ := r.Body.Seek(0, io.SeekCurrent)
+	endOffset, _ := r.Body.Seek(0, io.SeekEnd)
+	r.Body.Seek(r.BodyStart, io.SeekStart)
+
+	r.safeBody = newOffsetReader(r.Body, r.BodyStart)
+
+	if endOffset-curOffset == 0 {
+		r.HTTPRequest.Body = http.NoBody
+	} else {
+		r.HTTPRequest.Body = r.safeBody
+	}
+}

aws/request/request_resetbody_1.7.go

@@ -0,0 +1,8 @@
+// +build !go1.8
+
+package request
+
+func resetBody(r *Request) {
+	r.safeBody = newOffsetReader(r.Body, r.BodyStart)
+	r.HTTPRequest.Body = r.safeBody
+}

aws/request/request_resetbody_1.7_test.go

@@ -0,0 +1,41 @@
+// +build !go1.8
+
+package request
+
+import (
+	"net/http"
+	"strings"
+	"testing"
+)
+
+func TestResetBody_WithBodyContents(t *testing.T) {
+	r := Request{
+		HTTPRequest: &http.Request{},
+	}
+
+	reader := strings.NewReader("abc")
+	r.Body = reader
+
+	r.ResetBody()
+
+	if v, ok := r.HTTPRequest.Body.(*offsetReader); !ok || v == nil {
+		t.Errorf("expected request body to be set to reader, got %#v",
+			r.HTTPRequest.Body)
+	}
+}
+
+func TestResetBody_WithEmptyBody(t *testing.T) {
+	r := Request{
+		HTTPRequest: &http.Request{},
+	}
+
+	reader := strings.NewReader("")
+	r.Body = reader
+
+	r.ResetBody()
+
+	if v, ok := r.HTTPRequest.Body.(*offsetReader); !ok || v == nil {
+		t.Errorf("expected request body to be set to reader, got %#v",
+			r.HTTPRequest.Body)
+	}
+}

aws/request/request_resetbody_test.go

@@ -0,0 +1,41 @@
+// +build go1.8
+
+package request
+
+import (
+	"net/http"
+	"strings"
+	"testing"
+)
+
+func TestResetBody_WithBodyContents(t *testing.T) {
+	r := Request{
+		HTTPRequest: &http.Request{},
+	}
+
+	reader := strings.NewReader("abc")
+	r.Body = reader
+
+	r.ResetBody()
+
+	if v, ok := r.HTTPRequest.Body.(*offsetReader); !ok || v == nil {
+		t.Errorf("expected request body to be set to reader, got %#v",
+			r.HTTPRequest.Body)
+	}
+}
+
+func TestResetBody_WithEmptyBody(t *testing.T) {
+	r := Request{
+		HTTPRequest: &http.Request{},
+	}
+
+	reader := strings.NewReader("")
+	r.Body = reader
+
+	r.ResetBody()
+
+	if a, e := r.HTTPRequest.Body, http.NoBody; a != e {
+		t.Errorf("expected request body to be set to reader, got %#v",
+			r.HTTPRequest.Body)
+	}
+}