feat: adds integration tests for STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER requests

s3api/utils/signed-chunk-reader.go

@@ -402,7 +402,7 @@ func (cr *ChunkReader) parseChunkHeaderBytes(header []byte) (int64, string, int,
 	}
 	sig, err := readBytes(rdr, 64)
 	if err != nil {
-		debuglogger.Logf("failed to read '\\r', after chunk signature: %v", err)
+		debuglogger.Logf("failed to read the chunk signature: %v", err)
 		return cr.handleRdrErr(err, header)
 	}
 
@@ -484,6 +484,10 @@ func (cr *ChunkReader) parseChunkHeaderBytes(header []byte) (int64, string, int,
 		return 0, sig, 0, nil
 	}
 
+	// add the chunk size at the end of header parsing
+	// to avoid duplication because of header stashing
+	cr.addChunkSize(chunkSize)
+
 	// find the index of chunk ending: '\r\n'
 	// skip the first 2 bytes as it is the starting '\r\n'
 	// the first chunk doesn't contain the starting '\r\n', but
@@ -511,7 +515,7 @@ func (cr *ChunkReader) stashAndSkipHeader(header []byte) (int64, string, int, er
 // calls "cr.stashAndSkipHeader" if the passed err is "io.EOF" and cr.isEOF is false
 // Returns the error otherwise
 func (cr *ChunkReader) handleRdrErr(err error, header []byte) (int64, string, int, error) {
-	if err == io.EOF {
+	if err == io.EOF || err == io.ErrUnexpectedEOF {
 		if cr.isEOF {
 			debuglogger.Logf("incomplete chunk encoding, EOF reached")
 			return 0, "", 0, s3err.GetAPIError(s3err.ErrIncompleteBody)
@@ -540,11 +544,14 @@ func (cr *ChunkReader) parseChunkSize(rdr *bufio.Reader, header []byte) (int64,
 		return 0, s3err.GetAPIError(s3err.ErrInvalidChunkSize)
 	}
 
-	cr.chunkSizes = append(cr.chunkSizes, chunkSize)
-
 	return chunkSize, nil
 }
 
+// addChunkSize adds the input chunk size to chunkSizes slice
+func (cr *ChunkReader) addChunkSize(size int64) {
+	cr.chunkSizes = append(cr.chunkSizes, size)
+}
+
 // isValidChunkSize checks if the parsed chunk size is valid
 // they follow one rule: all chunk sizes except for the last one
 // should be greater than 8192

tests/integration/group-tests.go

@@ -808,6 +808,8 @@ func TestFullFlow(ts *TestState) {
 	TestAccessControl(ts)
 	TestRouter(ts)
 	TestUnsignedStreaminPayloadTrailer(ts)
+	TestSignedStreaminPayload(ts)
+	TestSignedStreaminPayloadTrailer(ts)
 	// FIXME: The tests should pass for azure as well
 	// but this issue should be fixed with https://github.com/versity/versitygw/issues/1336
 	if !ts.conf.azureTests {
@@ -1122,6 +1124,17 @@ func TestSignedStreaminPayload(ts *TestState) {
 	}
 }
 
+func TestSignedStreaminPayloadTrailer(ts *TestState) {
+	if !ts.conf.azureTests {
+		ts.Run(SignedStreamingPayloadTrailer_malformed_trailer)
+		ts.Run(SignedStreamingPayloadTrailer_incomplete_body)
+		ts.Run(SignedStreamingPayloadTrailer_missing_x_amz_trailer_header)
+		ts.Run(SignedStreamingPayloadTrailer_invalid_checksum)
+		ts.Run(SignedStreamingPayloadTrailer_bad_digest)
+		ts.Run(SignedStreamingPayloadTrailer_success)
+	}
+}
+
 type IntTest func(s3 *S3Conf) error
 
 type IntTests map[string]IntTest
@@ -1778,5 +1791,11 @@ func GetIntTests() IntTests {
 		"SignedStreamingPayload_invalid_encoding":                                  SignedStreamingPayload_invalid_encoding,
 		"SignedStreamingPayload_invalid_chunk_size":                                SignedStreamingPayload_invalid_chunk_size,
 		"SignedStreamingPayload_decoded_content_length_mismatch":                   SignedStreamingPayload_decoded_content_length_mismatch,
+		"SignedStreamingPayloadTrailer_malformed_trailer":                          SignedStreamingPayloadTrailer_malformed_trailer,
+		"SignedStreamingPayloadTrailer_incomplete_body":                            SignedStreamingPayloadTrailer_incomplete_body,
+		"SignedStreamingPayloadTrailer_missing_x_amz_trailer_header":               SignedStreamingPayloadTrailer_missing_x_amz_trailer_header,
+		"SignedStreamingPayloadTrailer_invalid_checksum":                           SignedStreamingPayloadTrailer_invalid_checksum,
+		"SignedStreamingPayloadTrailer_bad_digest":                                 SignedStreamingPayloadTrailer_bad_digest,
+		"SignedStreamingPayloadTrailer_success":                                    SignedStreamingPayloadTrailer_success,
 	}
 }

tests/integration/signed_streaming_payload.go

@@ -74,9 +74,13 @@ func SignedStreamingPayload_invalid_chunk_size(s *S3Conf) error {
 			{10, bytes.Repeat([]byte{'b'}, 100), true},
 			{1000, bytes.Repeat([]byte{'a'}, 200), false},
 			{8192, bytes.Repeat([]byte{'c'}, 10000), false},
+			{8192, bytes.Repeat([]byte{'c'}, 20000), false},
 			{1000, bytes.Repeat([]byte{'c'}, 1024*64), true},
 		} {
-			_, apiErr, err := testSignedStreamingObjectPut(s, bucket, object, test.payload, withChunkSize(test.chunkSize))
+			_, apiErr, err := testSignedStreamingObjectPut(s, bucket, object, test.payload, withChunkSize(test.chunkSize), withCustomHeaders(map[string]string{
+				"Content-Length":    "-1",
+				"Transfer-Encoding": "chunked",
+			}))
 			if err != nil {
 				return fmt.Errorf("test %v failed: %w", i+1, err)
 			}

tests/integration/signed_streaming_payload_trailer.go

@@ -0,0 +1,207 @@
+// Copyright 2023 Versity Software
+// This file is licensed under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package integration
+
+import (
+	"fmt"
+
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+	"github.com/aws/aws-sdk-go-v2/service/s3/types"
+	"github.com/versity/versitygw/s3err"
+)
+
+func SignedStreamingPayloadTrailer_malformed_trailer(s *S3Conf) error {
+	testName := "SignedStreamingPayloadTrailer_malformed_trailer"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		object := "my-object"
+		for i, test := range []struct {
+			trailerHdr       string
+			trailingChecksum string
+		}{
+			{"x-amz-checksum-crc64nvme", "x-amz-invalid:invalid"},
+			{"x-amz-checksum-crc64nvme", ""},
+			// x-amz-trailer and trailing checksum mismatch
+			{"x-amz-checksum-sha1", "x-amz-checksum-crc32:QWaN2w=="},
+			{"x-amz-checksum-crc32c", "x-amz-checksum-sha1:YR/1TvTYOJz5gtqVFoBJBtmTibY="},
+		} {
+			_, apiErr, err := testSignedStreamingObjectPut(s, bucket, object, []byte("dummy data"), withTrailingChecksum(test.trailingChecksum), withCustomHeaders(map[string]string{
+				"x-amz-trailer": test.trailerHdr,
+			}))
+			if err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+
+			if err := compareS3ApiError(s3err.GetAPIError(s3err.ErrMalformedTrailer), apiErr); err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+		}
+
+		return nil
+	})
+}
+
+func SignedStreamingPayloadTrailer_incomplete_body(s *S3Conf) error {
+	testName := "SignedStreamingPayloadTrailer_incomplete_body"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		object := "my-object"
+		for i, test := range []struct {
+			modifFrom    int
+			modifTo      int
+			modifPayload []byte
+		}{
+			{175, 176, []byte("k")},
+			{175, 177, []byte("cc")},
+			{215, 216, []byte("bcd")},
+			{220, 223, []byte("invalid")},
+			{230, 235, []byte("abcd")},
+			{241, 245, []byte("abcde")},
+			{306, 308, []byte("pp")},
+			{304, 308, []byte("erty")},
+		} {
+			_, apiErr, err := testSignedStreamingObjectPut(
+				s,
+				bucket,
+				object,
+				[]byte("abcdefg"),
+				withTrailingChecksum("x-amz-checksum-crc64nvme:SmzZ/LTp1CA="),
+				withCustomHeaders(map[string]string{"x-amz-trailer": "x-amz-checksum-crc64nvme"}),
+				withModifyPayload(test.modifFrom, test.modifTo, test.modifPayload),
+			)
+			if err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+
+			if err := compareS3ApiError(s3err.GetAPIError(s3err.ErrIncompleteBody), apiErr); err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+		}
+
+		return nil
+	})
+}
+
+func SignedStreamingPayloadTrailer_missing_x_amz_trailer_header(s *S3Conf) error {
+	testName := "SignedStreamingPayloadTrailer_missing_x_amz_trailer_header"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		_, apiErr, err := testSignedStreamingObjectPut(s, bucket, "my-object", []byte("hello"), withTrailingChecksum("x-amz-checksum-crc32:NhCmhg=="))
+		if err != nil {
+			return err
+		}
+
+		return compareS3ApiError(s3err.GetAPIError(s3err.ErrMalformedTrailer), apiErr)
+	})
+}
+
+func SignedStreamingPayloadTrailer_invalid_checksum(s *S3Conf) error {
+	testName := "SignedStreamingPayloadTrailer_invalid_checksum"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		object := "my-object"
+		for i, test := range []struct {
+			trailerHdr       string
+			trailingChecksum string
+		}{
+			{"x-amz-checksum-crc32", "x-amz-checksum-crc32:invalid"},
+			{"x-amz-checksum-crc32c", "x-amz-checksum-crc32c:invalid"},
+			{"x-amz-checksum-crc64nvme", "x-amz-checksum-crc64nvme:invalid"},
+			{"x-amz-checksum-sha1", "x-amz-checksum-sha1:invalid"},
+			{"x-amz-checksum-sha256", "x-amz-checksum-sha256:invalid"},
+		} {
+			_, apiErr, err := testSignedStreamingObjectPut(s, bucket, object, []byte("dummy data"), withTrailingChecksum(test.trailingChecksum), withCustomHeaders(map[string]string{
+				"x-amz-trailer": test.trailerHdr,
+			}))
+			if err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+
+			if err := compareS3ApiError(s3err.GetInvalidTrailingChecksumHeaderErr(test.trailerHdr), apiErr); err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+		}
+
+		return nil
+	})
+}
+
+func SignedStreamingPayloadTrailer_bad_digest(s *S3Conf) error {
+	testName := "SignedStreamingPayloadTrailer_bad_digest"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		object := "my-object"
+		for i, test := range []struct {
+			algo             types.ChecksumAlgorithm
+			trailerHdr       string
+			trailingChecksum string
+		}{
+			{types.ChecksumAlgorithmCrc32, "x-amz-checksum-crc32", "x-amz-checksum-crc32:NhCmhg=="},
+			{types.ChecksumAlgorithmCrc32c, "x-amz-checksum-crc32c", "x-amz-checksum-crc32c:+Cy97w=="},
+			{types.ChecksumAlgorithmCrc64nvme, "x-amz-checksum-crc64nvme", "x-amz-checksum-crc64nvme:QFRKMGE3tuw="},
+			{types.ChecksumAlgorithmSha1, "x-amz-checksum-sha1", "x-amz-checksum-sha1:qvTGHdzF6KLavt4PO0gs2a6pQ00="},
+			{types.ChecksumAlgorithmSha256, "x-amz-checksum-sha256", "x-amz-checksum-sha256:LPJNul+wow4m6DsqxbninhsWHlwfp0JecwQzYpOLmCQ="},
+		} {
+			_, apiErr, err := testSignedStreamingObjectPut(s, bucket, object, []byte("some random data"), withTrailingChecksum(test.trailingChecksum), withCustomHeaders(map[string]string{
+				"x-amz-trailer": test.trailerHdr,
+			}))
+			if err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+
+			if err := compareS3ApiError(s3err.GetChecksumBadDigestErr(test.algo), apiErr); err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+		}
+
+		return nil
+	})
+}
+
+func SignedStreamingPayloadTrailer_success(s *S3Conf) error {
+	testName := "SignedStreamingPayloadTrailer_success"
+	return actionHandler(s, testName, func(s3client *s3.Client, bucket string) error {
+		object := "my-object"
+		for i, test := range []struct {
+			checksumKey   string
+			checksumValue string
+		}{
+			{"x-amz-checksum-crc32", "z3mWAA=="},
+			{"x-amz-checksum-crc32c", "rxvjPA=="},
+			{"x-amz-checksum-crc64nvme", "dYnI3/Fh0gM="},
+			{"x-amz-checksum-sha1", "8O8FwCfmd5fCbCBvH09mrKMVoHU="},
+			{"x-amz-checksum-sha256", "OoSow5X4zTIPl27MtdFdYT+9O3C367C75+Cb2MFtRBc="},
+		} {
+			headers, apiErr, err := testSignedStreamingObjectPut(
+				s,
+				bucket,
+				object,
+				[]byte("the object data"),
+				withTrailingChecksum(fmt.Sprintf("%s:%s", test.checksumKey, test.checksumValue)),
+				withCustomHeaders(map[string]string{
+					"x-amz-trailer": test.checksumKey,
+				}),
+			)
+
+			if err != nil {
+				return fmt.Errorf("test %v failed: %w", i+1, err)
+			}
+			if apiErr != nil {
+				return fmt.Errorf("test %v failed: (%s) %s", i+1, apiErr.Code, apiErr.Message)
+			}
+
+			if headers[test.checksumKey] != test.checksumValue {
+				return fmt.Errorf("test %v failed: expected %s header value to be %s, instead got %s", i+1, test.checksumKey, test.checksumValue, headers[test.checksumKey])
+			}
+		}
+
+		return nil
+	})
+}

tests/integration/utils.go

@@ -17,6 +17,7 @@ package integration
 import (
 	"bytes"
 	"context"
+	"crypto/hmac"
 	"crypto/md5"
 	"crypto/rand"
 	"crypto/sha1"
@@ -2120,11 +2121,13 @@ func constructUnsignedPaylod(chunkSizes ...int64) (int64, []byte, error) {
 }
 
 type signedReqCfg struct {
-	headers      map[string]string
-	chunkSize    int64
-	modifFrom    *int
-	modifTo      *int
-	modifPayload []byte
+	headers          map[string]string
+	chunkSize        int64
+	modifFrom        *int
+	modifTo          *int
+	modifPayload     []byte
+	trailingChecksum *string
+	isTrailer        bool
 }
 
 type signedReqOpt func(*signedReqCfg)
@@ -2145,6 +2148,13 @@ func withModifyPayload(from int, to int, p []byte) signedReqOpt {
 	}
 }
 
+func withTrailingChecksum(checksum string) signedReqOpt {
+	return func(src *signedReqCfg) {
+		src.trailingChecksum = &checksum
+		src.isTrailer = true
+	}
+}
+
 func testSignedStreamingObjectPut(s *S3Conf, bucket, object string, payload []byte, opts ...signedReqOpt) (map[string]string, *s3err.APIErrorResponse, error) {
 	cfg := &signedReqCfg{
 		chunkSize: 8192, // minimal valid chunk size
@@ -2162,6 +2172,7 @@ func testSignedStreamingObjectPut(s *S3Conf, bucket, object string, payload []by
 	}
 
 	var payloadOffset int64
+	var trailerLength int
 
 	// any planned modification which is going to affect the
 	// Content-Length header value
@@ -2169,10 +2180,17 @@ func testSignedStreamingObjectPut(s *S3Conf, bucket, object string, payload []by
 		diff := len(cfg.modifPayload) - *cfg.modifTo + *cfg.modifFrom
 		payloadOffset = int64(diff)
 	}
+	if cfg.isTrailer {
+		trailerLength = len(*cfg.trailingChecksum)
+	}
 	// precalculated the Content-Length header to correctly sign the request
-	req.ContentLength = calculateSignedReqContentLength(int64(len(payload)), cfg.chunkSize, payloadOffset)
-	req.Header.Set("x-amz-content-sha256", "STREAMING-AWS4-HMAC-SHA256-PAYLOAD")
+	req.ContentLength = calculateSignedReqContentLength(int64(len(payload)), cfg.chunkSize, payloadOffset, cfg.isTrailer, int64(trailerLength))
+	sha256Header := "STREAMING-AWS4-HMAC-SHA256-PAYLOAD"
+	if cfg.isTrailer {
+		sha256Header = "STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER"
+	}
 	req.Header.Set("x-amz-decoded-content-length", fmt.Sprint(len(payload)))
+	req.Header.Set("x-amz-content-sha256", sha256Header)
 
 	// set custom request headers
 	for key, val := range cfg.headers {
@@ -2183,7 +2201,7 @@ func testSignedStreamingObjectPut(s *S3Conf, bucket, object string, payload []by
 	signingTime := time.Now()
 
 	// sign the request
-	err = signer.SignHTTP(ctx, aws.Credentials{AccessKeyID: s.awsID, SecretAccessKey: s.awsSecret}, req, "STREAMING-AWS4-HMAC-SHA256-PAYLOAD", "s3", s.awsRegion, signingTime)
+	err = signer.SignHTTP(ctx, aws.Credentials{AccessKeyID: s.awsID, SecretAccessKey: s.awsSecret}, req, sha256Header, "s3", s.awsRegion, signingTime)
 	if err != nil {
 		return nil, nil, cancelAndError(fmt.Errorf("failed to sign the request: %w", err), cancel)
 	}
@@ -2197,7 +2215,7 @@ func testSignedStreamingObjectPut(s *S3Conf, bucket, object string, payload []by
 	// initialize v4 stream signed
 	streamSigner := v4.NewStreamSigner(aws.Credentials{AccessKeyID: s.awsID, SecretAccessKey: s.awsSecret}, "s3", s.awsRegion, seedSignature)
 	// create the signed payload
-	body, err := constructSignedStreamingPayload(ctx, streamSigner, signingTime, payload, cfg.chunkSize)
+	body, err := constructSignedStreamingPayload(ctx, streamSigner, signingTime, payload, cfg.chunkSize, cfg.trailingChecksum, s.awsRegion, s.awsSecret)
 	if err != nil {
 		return nil, nil, cancelAndError(fmt.Errorf("failed to encode req body: %w", err), cancel)
 	}
@@ -2254,18 +2272,23 @@ func cancelAndError(err error, cancel context.CancelFunc) error {
 
 const (
 	chunkSigHdrLength int64 = 81
+	trailerSigLength  int64 = 88
 )
 
 // calculateSignedReqContentLength calculates the value of `Content-Length` header
 // sizeOffset marks any planned changes on the body, which will affect the size
-func calculateSignedReqContentLength(decPayloadSize int64, chunkSize int64, sizeOffset int64) int64 {
+func calculateSignedReqContentLength(decPayloadSize int64, chunkSize int64, sizeOffset int64, withTrailer bool, trailerLength int64) int64 {
 	payloadSize := decPayloadSize
 	var chunkHeadersLength int64
 
+	if withTrailer {
+		chunkHeadersLength += trailerLength + 4 + trailerSigLength
+	}
+
 	// special case when chunk size is greater or equal than decoded content length
 	if chunkSize >= decPayloadSize {
 		chSizeLgth := len(fmt.Sprintf("%x", decPayloadSize))
-		return decPayloadSize + sizeOffset + int64(chSizeLgth) + 2*chunkSigHdrLength + 9
+		return decPayloadSize + sizeOffset + int64(chSizeLgth) + 2*chunkSigHdrLength + 9 + chunkHeadersLength
 	}
 
 	for {
@@ -2287,7 +2310,7 @@ func calculateSignedReqContentLength(decPayloadSize int64, chunkSize int64, size
 }
 
 // constructSignedStreamingPayload creates chunk encoded payload with signatures.
-func constructSignedStreamingPayload(ctx context.Context, signer *v4.StreamSigner, signingTime time.Time, payload []byte, chunkSize int64) ([]byte, error) {
+func constructSignedStreamingPayload(ctx context.Context, signer *v4.StreamSigner, signingTime time.Time, payload []byte, chunkSize int64, trailer *string, region, secret string) ([]byte, error) {
 	buf := bytes.NewBuffer(nil)
 	payloadLen := int64(len(payload))
 
@@ -2326,6 +2349,26 @@ func constructSignedStreamingPayload(ctx context.Context, signer *v4.StreamSigne
 		return nil, err
 	}
 
+	if trailer != nil {
+		_, err = buf.WriteString(fmt.Sprintf("0;chunk-signature=%x\r\n", sig))
+		if err != nil {
+			return nil, err
+		}
+
+		sigKey := getSigningKey(secret, signingTime.Format("20060102"), region)
+		trailerSig, err := getAWS4StreamingTrailer(sigKey, sig, signingTime, region, *trailer)
+		if err != nil {
+			return nil, err
+		}
+
+		_, err = buf.WriteString(fmt.Sprintf("%s\r\nx-amz-trailer-signature:%s\r\n\r\n", *trailer, trailerSig))
+		if err != nil {
+			return nil, err
+		}
+
+		return buf.Bytes(), nil
+	}
+
 	_, err = buf.WriteString(fmt.Sprintf("0;chunk-signature=%x\r\n\r\n", sig))
 	if err != nil {
 		return nil, err
@@ -2379,3 +2422,68 @@ func replaceRange(dst, src []byte, start, end int) ([]byte, error) {
 	copy(out[start+len(src):], dst[end:])
 	return out, nil
 }
+
+func getAWS4StreamingTrailer(
+	signingKey,
+	lastSignature []byte,
+	signingTime time.Time,
+	awsRegion,
+	trailer string,
+) (string, error) {
+
+	// yyyyMMdd
+	yearMonthDay := signingTime.Format("20060102")
+
+	// ISO8601 basic format: yyyyMMdd'T'HHmmss'Z'
+	currentDateTime := signingTime.UTC().Format("20060102T150405Z")
+
+	// <date>/<region>/<service>/aws4_request
+	serviceString := fmt.Sprintf(
+		"%s/%s/s3/aws4_request",
+		yearMonthDay,
+		awsRegion,
+	)
+
+	// Trailer must be newline-terminated for hashing/signing
+	trailerWithNL := trailer + "\n"
+
+	// Hash of trailer
+	trailerHash := sha256.Sum256([]byte(trailerWithNL))
+	trailerHashHex := hex.EncodeToString(trailerHash[:])
+
+	// String-to-sign prefix
+	stringToSignPrefix := fmt.Sprintf(
+		"%s\n%s\n%s",
+		"AWS4-HMAC-SHA256-TRAILER",
+		currentDateTime,
+		serviceString,
+	)
+
+	// Full string-to-sign
+	stringToSign := fmt.Sprintf(
+		"%s\n%x\n%s",
+		stringToSignPrefix,
+		lastSignature,
+		trailerHashHex,
+	)
+
+	// Final trailer signature
+	finalSignature := hex.EncodeToString(
+		hmacSHA256(signingKey, stringToSign),
+	)
+
+	return finalSignature, nil
+}
+
+func hmacSHA256(key []byte, data string) []byte {
+	h := hmac.New(sha256.New, key)
+	h.Write([]byte(data))
+	return h.Sum(nil)
+}
+
+func getSigningKey(secret, yearMonthDay, region string) []byte {
+	dateKey := hmacSHA256([]byte("AWS4"+secret), yearMonthDay)
+	dateRegionKey := hmacSHA256(dateKey, region)
+	dateRegionServiceKey := hmacSHA256(dateRegionKey, "s3")
+	return hmacSHA256(dateRegionServiceKey, "aws4_request")
+}