From e955ccf2cd1cbca8f1b9997c6afd3a7943bbab0d Mon Sep 17 00:00:00 2001
From: Jason Del Ponte <delpontej@gmail.com>
Date: Tue, 16 Mar 2021 18:59:54 -0700
Subject: [PATCH] aws/signer/v4: Add helper for using unsigned payload instead
 of compute hash

Updates the v4 package with a new helper to swap out the compute payload
hash middleware for the unsigned payload middleware. This allows API
operations to be updated to not compute the payload hash, and
use UNSIGNED-PAYLOAD instead.
---
 .../sdk-feature-1615946574682127000.json      |   9 ++
 aws/signer/v4/middleware.go                   |  10 ++
 aws/signer/v4/middleware_test.go              | 101 ++++++++++++++++++
 3 files changed, 120 insertions(+)
 create mode 100644 .changes/next-release/sdk-feature-1615946574682127000.json

diff --git a/.changes/next-release/sdk-feature-1615946574682127000.json b/.changes/next-release/sdk-feature-1615946574682127000.json
new file mode 100644
index 00000000000..1e0ae796a3a
--- /dev/null
+++ b/.changes/next-release/sdk-feature-1615946574682127000.json
@@ -0,0 +1,9 @@
+{
+ "ID": "sdk-feature-1615946574682127000",
+ "SchemaVersion": 1,
+ "Module": "/",
+ "Type": "feature",
+ "Description": "Add helper to V4 signer package to swap compute payload hash middleware with unsigned payload middleware",
+ "MinVersion": "",
+ "AffectedModules": null
+}
\ No newline at end of file
diff --git a/aws/signer/v4/middleware.go b/aws/signer/v4/middleware.go
index ffa297668e1..b6e28b4bd46 100644
--- a/aws/signer/v4/middleware.go
+++ b/aws/signer/v4/middleware.go
@@ -156,6 +156,16 @@ func (m *computePayloadSHA256) HandleBuild(
 	return next.HandleBuild(ctx, in)
 }
 
+// SwapComputePayloadSHA256ForUnsignedPayloadMiddleware replaces the
+// ComputePayloadSHA256 middleware with the UnsignedPayload middleware.
+//
+// Use this to disable computing the Payload SHA256 checksum and instead use
+// UNSIGNED-PAYLOAD for the SHA256 value.
+func SwapComputePayloadSHA256ForUnsignedPayloadMiddleware(stack *middleware.Stack) error {
+	_, err := stack.Build.Swap(computePayloadHashMiddlewareID, &unsignedPayload{})
+	return err
+}
+
 // contentSHA256Header sets the X-Amz-Content-Sha256 header value to
 // the Payload hash stored in the context.
 type contentSHA256Header struct{}
diff --git a/aws/signer/v4/middleware_test.go b/aws/signer/v4/middleware_test.go
index a56058a86c0..acbc3d827b3 100644
--- a/aws/signer/v4/middleware_test.go
+++ b/aws/signer/v4/middleware_test.go
@@ -18,6 +18,7 @@ import (
 	"github.com/aws/smithy-go/logging"
 	"github.com/aws/smithy-go/middleware"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
+	"github.com/google/go-cmp/cmp"
 )
 
 func TestComputePayloadHashMiddleware(t *testing.T) {
@@ -205,6 +206,106 @@ func TestSignHTTPRequestMiddleware(t *testing.T) {
 	}
 }
 
+func TestSwapComputePayloadSHA256ForUnsignedPayloadMiddleware(t *testing.T) {
+	cases := map[string]struct {
+		InitStep  func(*middleware.Stack) error
+		Mutator   func(*middleware.Stack) error
+		ExpectErr string
+		ExpectIDs []string
+	}{
+		"swap in place": {
+			InitStep: func(s *middleware.Stack) (err error) {
+				err = s.Build.Add(middleware.BuildMiddlewareFunc("before", nil), middleware.After)
+				if err != nil {
+					return err
+				}
+				err = AddComputePayloadSHA256Middleware(s)
+				if err != nil {
+					return err
+				}
+				err = s.Build.Add(middleware.BuildMiddlewareFunc("after", nil), middleware.After)
+				if err != nil {
+					return err
+				}
+				return nil
+			},
+			Mutator: SwapComputePayloadSHA256ForUnsignedPayloadMiddleware,
+			ExpectIDs: []string{
+				"before",
+				computePayloadHashMiddlewareID,
+				"after",
+			},
+		},
+
+		"already unsigned payload exists": {
+			InitStep: func(s *middleware.Stack) (err error) {
+				err = s.Build.Add(middleware.BuildMiddlewareFunc("before", nil), middleware.After)
+				if err != nil {
+					return err
+				}
+				err = AddUnsignedPayloadMiddleware(s)
+				if err != nil {
+					return err
+				}
+				err = s.Build.Add(middleware.BuildMiddlewareFunc("after", nil), middleware.After)
+				if err != nil {
+					return err
+				}
+				return nil
+			},
+			Mutator: SwapComputePayloadSHA256ForUnsignedPayloadMiddleware,
+			ExpectIDs: []string{
+				"before",
+				computePayloadHashMiddlewareID,
+				"after",
+			},
+		},
+
+		"no compute payload": {
+			InitStep: func(s *middleware.Stack) (err error) {
+				err = s.Build.Add(middleware.BuildMiddlewareFunc("before", nil), middleware.After)
+				if err != nil {
+					return err
+				}
+				err = s.Build.Add(middleware.BuildMiddlewareFunc("after", nil), middleware.After)
+				if err != nil {
+					return err
+				}
+				return nil
+			},
+			Mutator:   SwapComputePayloadSHA256ForUnsignedPayloadMiddleware,
+			ExpectErr: "not found, " + computePayloadHashMiddlewareID,
+		},
+	}
+
+	for name, c := range cases {
+		t.Run(name, func(t *testing.T) {
+			stack := middleware.NewStack(t.Name(), smithyhttp.NewStackRequest)
+			if err := c.InitStep(stack); err != nil {
+				t.Fatalf("expect no error, got %v", err)
+			}
+
+			err := c.Mutator(stack)
+			if len(c.ExpectErr) != 0 {
+				if err == nil {
+					t.Fatalf("expect error, got none")
+				}
+				if e, a := c.ExpectErr, err.Error(); !strings.Contains(a, e) {
+					t.Fatalf("expect error to contain %v, got %v", e, a)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("expect no error, got %v", err)
+			}
+
+			if diff := cmp.Diff(c.ExpectIDs, stack.Build.List()); len(diff) != 0 {
+				t.Errorf("expect match\n%v", diff)
+			}
+		})
+	}
+}
+
 type nonSeeker struct{}
 
 func (nonSeeker) Read(p []byte) (n int, err error) {