Update signer v1 example for AOSS

- Updated SDK v1 signer
- Updated user guide
- Update changelog

Signed-off-by: Harrison Jones <harrison@hhj.me>

CHANGELOG.md

@@ -18,7 +18,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Added
 - Github workflow for changelog verification ([#172](https://github.com/opensearch-project/opensearch-go/pull/172))
 - Add Go Documentation link for the client ([#182](https://github.com/opensearch-project/opensearch-go/pull/182))
-- Support for Amazon OpenSearch Serverless ([#216](https://github.com/opensearch-project/opensearch-go/pull/216))
+- Support for Amazon OpenSearch Serverless ([#216](https://github.com/opensearch-project/opensearch-go/pull/216), [#252](https://github.com/opensearch-project/opensearch-go/pull/252))
 
 ### Dependencies
 - Bumps `github.com/stretchr/testify` from 1.8.0 to 1.8.1

USER_GUIDE.md

@@ -184,37 +184,40 @@ func main() {
 
 	// Create an AWS request Signer and load AWS configuration using default config folder or env vars.
 	// See https://docs.aws.amazon.com/opensearch-service/latest/developerguide/request-signing.html#request-signing-go
-	signer, err := requestsigner.NewSigner(session.Options{SharedConfigState: session.SharedConfigEnable})
+	signer, err := requestsigner.NewSignerWithService(
+		session.Options{SharedConfigState: session.SharedConfigEnable},
+		requestsigner.OpenSearchService, // Use requestsigner.OpenSearchServerless for Amazon OpenSearch Serverless.
+	)
 	if err != nil {
-		log.Fatal(err) // Do not log.fatal in a production ready app.
+		log.Fatalf("failed to create signer: %v", err) // Do not log.fatal in a production ready app.
 	}
 
-	// Create an opensearch client and use the request-signer
+	// Create an opensearch client and use the request-signer.
 	client, err := opensearch.NewClient(opensearch.Config{
 		Addresses: []string{endpoint},
 		Signer:    signer,
 	})
 	if err != nil {
-		log.Fatal("client creation err", err)
+		log.Fatalf("failed to create new opensearch client: %v", err)
 	}
 
 	ping := opensearchapi.PingRequest{}
 
 	resp, err := ping.Do(ctx, client)
 	if err != nil {
-		log.Fatal(err)
+		log.Fatalf("failed to ping: %v", err)
 	}
 	defer resp.Body.Close()
 
 	if resp.IsError() {
-		log.Println("ping response status ", resp.Status())
+		log.Printf("ping response status: %q", resp.Status())
 
 		respBody, err := io.ReadAll(resp.Body)
 		if err != nil {
-			log.Fatal("response body read err", err)
+			log.Fatalf("failed to read response body body: %v", err)
 		}
 
-		log.Fatal("ping resp body", respBody)
+		log.Fatalf("ping resp body: %s", respBody)
 	}
 
 	log.Println("PING OK")
@@ -231,6 +234,7 @@ package main
 import (
 	"context"
 	"log"
+	"strings"
 
 	"github.com/aws/aws-sdk-go-v2/aws"
 	"github.com/aws/aws-sdk-go-v2/config"
@@ -251,25 +255,25 @@ func main() {
 		),
 	)
 	if err != nil {
-		log.Fatal(err) // Do not log.fatal in a production ready app.
+		log.Fatalf("failed to load aws configuraiton: %v", err) // Do not log.fatal in a production ready app.
 	}
 
 	// Create an AWS request Signer and load AWS configuration using default config folder or env vars.
-	signer, err := requestsigner.NewSignerWithService(awsCfg, "es") // "aoss" for Amazon OpenSearch Serverless
+	signer, err := requestsigner.NewSignerWithService(awsCfg, "es") // Use "aoss" for Amazon OpenSearch Serverless
 	if err != nil {
-		log.Fatal(err) // Do not log.fatal in a production ready app.
+		log.Fatalf("failed to create signer: %v", err)
 	}
 
-	// Create an opensearch client and use the request-signer
+	// Create an opensearch client and use the request-signer.
 	client, err := opensearch.NewClient(opensearch.Config{
 		Addresses: []string{endpoint},
 		Signer:    signer,
 	})
 	if err != nil {
-		log.Fatal("client creation err", err)
+		log.Fatalf("failed to create new opensearch client: %v", err)
 	}
 
-	indexName = "go-test-index"
+	indexName := "go-test-index"
 
 	// Define index mapping.
 	mapping := strings.NewReader(`{
@@ -287,11 +291,9 @@ func main() {
 	}
 	createIndexResponse, err := createIndex.Do(context.Background(), client)
 	if err != nil {
-		log.Println("Error ", err.Error())
-		log.Println("failed to create index ", err)
-		log.Fatal("create response body read err", err)
+		log.Fatalf("failed to create index: %v", err)
 	}
-	log.Println(createIndexResponse)
+	log.Printf("created index: %#v", createIndexResponse)
 
 	// Delete previously created index.
 	deleteIndex := opensearchapi.IndicesDeleteRequest{
@@ -300,10 +302,9 @@ func main() {
 
 	deleteIndexResponse, err := deleteIndex.Do(context.Background(), client)
 	if err != nil {
-		log.Println("failed to delete index ", err)
-		log.Fatal("delete index response body read err", err)
+		log.Fatalf("failed to delete index: %v", err)
 	}
-	log.Println("deleting index", deleteIndexResponse)
+	log.Printf("deleted index: %#v", deleteIndexResponse)
 }
 
 func getCredentialProvider(accessKey, secretAccessKey, token string) aws.CredentialsProviderFunc {

signer/aws/aws.go

@@ -11,6 +11,8 @@ package aws
 
 import (
 	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"io"
@@ -22,54 +24,85 @@ import (
 	v4 "github.com/aws/aws-sdk-go/aws/signer/v4"
 )
 
-// OpenSearchService AWS OpenSearchService Name
+// OpenSearchService Amazon OpenSearch Service Name
 const OpenSearchService = "es"
 
-// Signer is a interface that will implement opensearchtransport.Signer
+// OpenSearchServerless Amazon OpenSearch Serverless Name
+const OpenSearchServerless = "aoss"
+
+const emptyBodySHA256 = "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
+
+// Signer is an interface that will implement opensearchtransport.Signer
 type Signer struct {
 	session session.Session
 	service string
 }
 
-// NewSigner returns an instance of Signer for AWS OpenSearchService
+// NewSigner returns an instance of Signer for configured for Amazon OpenSearch Service.
+// Use NewSignerWithService to configure it for another service such as Amazon OpenSearch Serverless.
 func NewSigner(opts session.Options) (*Signer, error) {
 	return NewSignerWithService(opts, OpenSearchService)
 }
 
-// NewSignerWithService returns an instance of Signer for given service
+// NewSignerWithService returns an instance of Signer for a given service.
 func NewSignerWithService(opts session.Options, service string) (*Signer, error) {
 	if len(strings.TrimSpace(service)) < 1 {
 		return nil, errors.New("service cannot be empty")
 	}
 	awsSession, err := session.NewSessionWithOptions(opts)
 	if err != nil {
-		return nil, fmt.Errorf("failed to get session from given option %v due to %s", opts, err)
+		return nil, fmt.Errorf("failed to get session from given options %v: %v", opts, err)
 	}
 	return &Signer{
 		session: *awsSession,
 		service: service,
 	}, nil
 }
 
-// SignRequest signs the request using SigV4
+// SignRequest signs the request using SigV4.
 func (s Signer) SignRequest(req *http.Request) error {
-	signer := v4.NewSigner(s.session.Config.Credentials)
-	return sign(req, s.session.Config.Region, s.service, signer)
-
+	return sign(req, s.session.Config.Region, s.service, v4.NewSigner(s.session.Config.Credentials))
 }
 
-func sign(req *http.Request, region *string, serviceName string, signer *v4.Signer) (err error) {
+func sign(req *http.Request, region *string, serviceName string, signer *v4.Signer) error {
 	if region == nil || len(*region) == 0 {
 		return fmt.Errorf("aws region cannot be empty")
 	}
-	if req.Body == nil {
-		_, err = signer.Sign(req, nil, serviceName, *region, time.Now().UTC())
-		return
+
+	var body io.ReadSeeker
+	var contentSha256Hash = emptyBodySHA256
+
+	if req.Body != nil {
+		b, err := io.ReadAll(req.Body)
+		if err != nil {
+			return fmt.Errorf("failed to read request body: %v", err)
+		}
+		body = bytes.NewReader(b)
+		hash, err := hexEncodedSha256(b)
+		if err != nil {
+			return fmt.Errorf("failed to calculate hash of request body: %v", err)
+		}
+		contentSha256Hash = hash
 	}
-	buf, err := io.ReadAll(req.Body)
-	if err != nil {
+	// Add the "X-Amz-Content-Sha256" header as required by Amazon OpenSearch Serverless.
+	req.Header.Set("X-Amz-Content-Sha256", contentSha256Hash)
+
+	if _, err := signer.Sign(req, body, serviceName, *region, time.Now().UTC()); err != nil {
 		return err
 	}
-	_, err = signer.Sign(req, bytes.NewReader(buf), serviceName, *region, time.Now().UTC())
-	return
+
+	return nil
+}
+
+func hexEncodedSha256(b []byte) (string, error) {
+	hasher := sha256.New()
+
+	_, err := hasher.Write(b)
+	if err != nil {
+		return "", fmt.Errorf("failed to write: %v", err)
+	}
+
+	digest := hasher.Sum(nil)
+
+	return hex.EncodeToString(digest), nil
 }