added opensearch serverless support (#92)

* added opensearch serverless support

Signed-off-by: vasyaxparfenov <[email protected]>

* added unit tests

Signed-off-by: vasyaxparfenov <[email protected]>

* applied suggestions

Signed-off-by: vasyaxparfenov <[email protected]>

---------

Signed-off-by: vasyaxparfenov <[email protected]>
Co-authored-by: vasiliyparfenov <[email protected]>

provider/awsv4.go

@@ -0,0 +1,44 @@
+package provider
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"hash"
+	"io"
+	"net/http"
+)
+
+type awsV4SignerWrapper struct {
+	internal http.RoundTripper
+}
+
+func hashPayload(hasher hash.Hash, payload []byte) string {
+	hasher.Write(payload)
+	hashBytes := hasher.Sum(nil)
+	hash := hex.EncodeToString(hashBytes)
+	return hash
+}
+
+func (client *awsV4SignerWrapper) RoundTrip(request *http.Request) (*http.Response, error) {
+	hasher := sha256.New()
+	var hash string
+	if request.Body == nil {
+		hash = hashPayload(hasher, []byte(""))
+	} else {
+		payload, error := io.ReadAll(request.Body)
+		request.Body = io.NopCloser(bytes.NewReader(payload))
+		if error != nil {
+			return nil, error
+		}
+
+		hash = hashPayload(hasher, payload)
+	}
+	request.Header.Set("X-Amz-Content-Sha256", hash)
+
+	return client.internal.RoundTrip(request)
+}
+
+func Wrap(internal http.RoundTripper) http.RoundTripper {
+	return &awsV4SignerWrapper{internal: internal}
+}

provider/awsv4_test.go

@@ -0,0 +1,57 @@
+package provider
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+type MockRoundTripper struct {
+}
+
+func (roundTripper *MockRoundTripper) RoundTrip(request *http.Request) (*http.Response, error) {
+	return new(http.Response), nil
+}
+
+func TestRoundTripWithEmptyBody(t *testing.T) {
+	sut := Wrap(new(MockRoundTripper))
+
+	request := new(http.Request)
+	request.Header = make(http.Header)
+
+	_, err := sut.RoundTrip(request)
+
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if header, contains := request.Header["X-Amz-Content-Sha256"]; !contains || len(header) != 1 || header[0] != "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855" {
+		t.Fatal("Request with empty body doesn't contain X-Amz-Content-Sha256 header with empty string hash value.")
+	}
+}
+
+func TestRoundTripWithBody(t *testing.T) {
+	sut := Wrap(new(MockRoundTripper))
+	request := new(http.Request)
+	request.Header = make(http.Header)
+
+	body := "body"
+	request.Body = io.NopCloser(strings.NewReader(body))
+
+	hasher := sha256.New()
+	hasher.Write([]byte(body))
+	hashBytes := hasher.Sum(nil)
+	expectedHash := hex.EncodeToString(hashBytes)
+
+	_, err := sut.RoundTrip(request)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if header, contains := request.Header["X-Amz-Content-Sha256"]; !contains || len(header) != 1 || header[0] != expectedHash {
+		t.Fatal("Request with body doesn't contain X-Amz-Content-Sha256 header with correct hash value.")
+	}
+}

provider/provider.go

@@ -38,6 +38,8 @@ const (
 )
 
 var awsUrlRegexp = regexp.MustCompile(`([a-z0-9-]+).es.amazonaws.com$`)
+var awsOpensearchServerlessUrlRegexp = regexp.MustCompile(`([a-z0-9-]+).aoss.amazonaws.com$`)
+var minimalOpensearchServerlessVersion = "2.0.0"
 
 type ProviderConf struct {
 	rawUrl                  string
@@ -313,6 +315,25 @@ func getClient(conf *ProviderConf) (*elastic7.Client, error) {
 			return nil, err
 		}
 		opts = append(opts, elastic7.SetHttpClient(client), elastic7.SetSniff(false))
+	} else if m := awsOpensearchServerlessUrlRegexp.FindStringSubmatch(conf.parsedUrl.Hostname()); (m != nil || (conf.awsSig4Service == "aoss" && conf.awsRegion != "")) && conf.signAWSRequests {
+		var region string
+		if m != nil {
+			region = m[1]
+		} else {
+			region = conf.awsRegion
+		}
+		log.Printf("[INFO] Using AWS: %+v", region)
+		conf.awsSig4Service = "aoss"
+		client, err := awsHttpClient(region, conf, map[string]string{})
+		if err != nil {
+			return nil, err
+		}
+		client.Transport = Wrap(client.Transport)
+		opts = append(opts, elastic7.SetHttpClient(client), elastic7.SetSniff(false))
+		conf.flavor = OpenSearch
+		if conf.osVersion == "" {
+			conf.osVersion = minimalOpensearchServerlessVersion
+		}
 	} else if awsRegion := conf.awsRegion; conf.awsRegion != "" && conf.signAWSRequests {
 		log.Printf("[INFO] Using AWS: %+v", awsRegion)
 		client, err := awsHttpClient(awsRegion, conf, map[string]string{})