private/model/api: Adding support for unsigned trait (#1130)

* Adding support for unsigned trait

* Removing type aliased option

aws/signer/v4/options.go

@@ -0,0 +1,7 @@
+package v4
+
+// WithUnsignedPayload will enable and set the UnsignedPayload field to
+// true of the signer.
+func WithUnsignedPayload(v4 *Signer) {
+	v4.UnsignedPayload = true
+}

aws/signer/v4/v4.go

@@ -194,6 +194,10 @@ type Signer struct {
 	// This value should only be used for testing. If it is nil the default
 	// time.Now will be used.
 	currentTimeFn func() time.Time
+
+	// UnsignedPayload will prevent signing of the payload. This will only
+	// work for services that have support for this.
+	UnsignedPayload bool
 }
 
 // NewSigner returns a Signer pointer configured with the credentials and optional
@@ -227,6 +231,7 @@ type signingCtx struct {
 	isPresign          bool
 	formattedTime      string
 	formattedShortTime string
+	unsignedPayload    bool
 
 	bodyDigest       string
 	signedHeaders    string
@@ -317,6 +322,7 @@ func (v4 Signer) signWithBody(r *http.Request, body io.ReadSeeker, service, regi
 		ServiceName:            service,
 		Region:                 region,
 		DisableURIPathEscaping: v4.DisableURIPathEscaping,
+		unsignedPayload:        v4.UnsignedPayload,
 	}
 
 	for key := range ctx.Query {
@@ -409,7 +415,18 @@ var SignRequestHandler = request.NamedHandler{
 func SignSDKRequest(req *request.Request) {
 	signSDKRequestWithCurrTime(req, time.Now)
 }
-func signSDKRequestWithCurrTime(req *request.Request, curTimeFn func() time.Time) {
+
+// BuildNamedHandler will build a generic handler for signing.
+func BuildNamedHandler(name string, opts ...func(*Signer)) request.NamedHandler {
+	return request.NamedHandler{
+		Name: name,
+		Fn: func(req *request.Request) {
+			signSDKRequestWithCurrTime(req, time.Now, opts...)
+		},
+	}
+}
+
+func signSDKRequestWithCurrTime(req *request.Request, curTimeFn func() time.Time, opts ...func(*Signer)) {
 	// If the request does not need to be signed ignore the signing of the
 	// request if the AnonymousCredentials object is used.
 	if req.Config.Credentials == credentials.AnonymousCredentials {
@@ -441,6 +458,10 @@ func signSDKRequestWithCurrTime(req *request.Request, curTimeFn func() time.Time
 		v4.DisableRequestBodyOverwrite = true
 	})
 
+	for _, opt := range opts {
+		opt(v4)
+	}
+
 	signingTime := req.Time
 	if !req.LastSignedAt.IsZero() {
 		signingTime = req.LastSignedAt
@@ -634,14 +655,14 @@ func (ctx *signingCtx) buildSignature() {
 func (ctx *signingCtx) buildBodyDigest() {
 	hash := ctx.Request.Header.Get("X-Amz-Content-Sha256")
 	if hash == "" {
-		if ctx.isPresign && ctx.ServiceName == "s3" {
+		if ctx.unsignedPayload || (ctx.isPresign && ctx.ServiceName == "s3") {
 			hash = "UNSIGNED-PAYLOAD"
 		} else if ctx.Body == nil {
 			hash = emptyStringSHA256
 		} else {
 			hash = hex.EncodeToString(makeSha256Reader(ctx.Body))
 		}
-		if ctx.ServiceName == "s3" || ctx.ServiceName == "glacier" {
+		if ctx.unsignedPayload || ctx.ServiceName == "s3" || ctx.ServiceName == "glacier" {
 			ctx.Request.Header.Set("X-Amz-Content-Sha256", hash)
 		}
 	}

private/model/api/operation.go

@@ -44,6 +44,26 @@ func (o *Operation) HasOutput() bool {
 	return o.OutputRef.ShapeName != ""
 }
 
+func (o *Operation) GetSigner() string {
+	if o.AuthType == "v4-unsigned-body" {
+		o.API.imports["github.com/aws/aws-sdk-go/aws/signer/v4"] = true
+	}
+
+	buf := bytes.NewBuffer(nil)
+
+	switch o.AuthType {
+	case "none":
+		buf.WriteString("req.Config.Credentials = credentials.AnonymousCredentials")
+	case "v4-unsigned-body":
+		buf.WriteString("req.Handlers.Sign.Remove(v4.SignRequestHandler)\n")
+		buf.WriteString("handler := v4.BuildNamedHandler(\"v4.CustomSignerHandler\", v4.WithUnsignedPayload)\n")
+		buf.WriteString("req.Handlers.Sign.PushFrontNamed(handler)")
+	}
+
+	buf.WriteString("\n")
+	return buf.String()
+}
+
 // tplOperation defines a template for rendering an API Operation
 var tplOperation = template.Must(template.New("operation").Funcs(template.FuncMap{
 	"GetCrosslinkURL": GetCrosslinkURL,
@@ -104,8 +124,7 @@ func (c *{{ .API.StructName }}) {{ .ExportedName }}Request(` +
 	req = c.newRequest(op, input, output){{ if eq .OutputRef.Shape.Placeholder true }}
 	req.Handlers.Unmarshal.Remove({{ .API.ProtocolPackage }}.UnmarshalHandler)
 	req.Handlers.Unmarshal.PushBackNamed(protocol.UnmarshalDiscardBodyHandler){{ end }}
-	{{ if eq .AuthType "none" }}req.Config.Credentials = credentials.AnonymousCredentials
-	{{ end -}}
+	{{ if ne .AuthType "" }}{{ .GetSigner }}{{ end -}}
 	return
 }