[#106] Add chunk uploading

Signed-off-by: Artem Tataurov <a.tataurov@yadro.com>

CHANGELOG.md

@@ -13,6 +13,7 @@ This document outlines major changes between releases.
 - Use `DisableURIPathEscaping` to presign urls (#125)
 
 ### Added
+- Implement chunk uploading (#106)
 - Reload default and custom copies numbers on SIGHUP (#104)
 - Add `copies_numbers` section to `placement_policy` in config file and support vectors of copies numbers (#70)
 - Return `X-Owner-Id` in `head-bucket` response (#79)

api/auth/center.go

@@ -40,6 +40,7 @@ type (
 	Box struct {
 		AccessBox   *accessbox.Box
 		ClientTime  time.Time
+		AuthHeaders *AuthHeader
 	}
 
 	center struct {
@@ -51,7 +52,8 @@ type (
 
 	prs int
 
-	authHeader struct {
+	//nolint:revive
+	AuthHeader struct {
 		AccessKeyID  string
 		Service      string
 		Region       string
@@ -101,7 +103,7 @@ func New(frostFS tokens.FrostFS, key *keys.PrivateKey, prefixes []string, config
 	}
 }
 
-func (c *center) parseAuthHeader(header string) (*authHeader, error) {
+func (c *center) parseAuthHeader(header string) (*AuthHeader, error) {
 	submatches := c.reg.GetSubmatches(header)
 	if len(submatches) != authHeaderPartsNum {
 		return nil, apiErrors.GetAPIError(apiErrors.ErrAuthorizationHeaderMalformed)
@@ -114,7 +116,7 @@ func (c *center) parseAuthHeader(header string) (*authHeader, error) {
 
 	signedFields := strings.Split(submatches["signed_header_fields"], ";")
 
-	return &authHeader{
+	return &AuthHeader{
 		AccessKeyID:  submatches["access_key_id"],
 		Service:      submatches["service"],
 		Region:       submatches["region"],
@@ -124,7 +126,7 @@ func (c *center) parseAuthHeader(header string) (*authHeader, error) {
 	}, nil
 }
 
-func (a *authHeader) getAddress() (oid.Address, error) {
+func (a *AuthHeader) getAddress() (oid.Address, error) {
 	var addr oid.Address
 	if err := addr.DecodeString(strings.ReplaceAll(a.AccessKeyID, "0", "/")); err != nil {
 		return addr, apiErrors.GetAPIError(apiErrors.ErrInvalidAccessKeyID)
@@ -135,7 +137,7 @@ func (a *authHeader) getAddress() (oid.Address, error) {
 func (c *center) Authenticate(r *http.Request) (*Box, error) {
 	var (
 		err                  error
-		authHdr              *authHeader
+		authHdr              *AuthHeader
 		signatureDateTimeStr string
 		needClientTime       bool
 	)
@@ -146,7 +148,7 @@ func (c *center) Authenticate(r *http.Request) (*Box, error) {
 		if len(creds) != 5 || creds[4] != "aws4_request" {
 			return nil, fmt.Errorf("bad X-Amz-Credential")
 		}
-		authHdr = &authHeader{
+		authHdr = &AuthHeader{
 			AccessKeyID:  creds[0],
 			Service:      creds[3],
 			Region:       creds[2],
@@ -200,7 +202,10 @@ func (c *center) Authenticate(r *http.Request) (*Box, error) {
 		return nil, err
 	}
 
-	result := &Box{AccessBox: box}
+	result := &Box{
+		AccessBox:   box,
+		AuthHeaders: authHdr,
+	}
 	if needClientTime {
 		result.ClientTime = signatureDateTime
 	}
@@ -267,7 +272,7 @@ func (c *center) checkFormData(r *http.Request) (*Box, error) {
 	return &Box{AccessBox: box}, nil
 }
 
-func cloneRequest(r *http.Request, authHeader *authHeader) *http.Request {
+func cloneRequest(r *http.Request, authHeader *AuthHeader) *http.Request {
 	otherRequest := r.Clone(context.TODO())
 	otherRequest.Header = make(http.Header)
 
@@ -288,7 +293,7 @@ func cloneRequest(r *http.Request, authHeader *authHeader) *http.Request {
 	return otherRequest
 }
 
-func (c *center) checkSign(authHeader *authHeader, box *accessbox.Box, request *http.Request, signatureDateTime time.Time) error {
+func (c *center) checkSign(authHeader *AuthHeader, box *accessbox.Box, request *http.Request, signatureDateTime time.Time) error {
 	awsCreds := credentials.NewStaticCredentials(authHeader.AccessKeyID, box.Gate.AccessKey, "")
 	signer := v4.NewSigner(awsCreds)
 	signer.DisableURIPathEscaping = true

api/auth/center_test.go

@@ -19,12 +19,12 @@ func TestAuthHeaderParse(t *testing.T) {
 	for _, tc := range []struct {
 		header   string
 		err      error
-		expected *authHeader
+		expected *AuthHeader
 	}{
 		{
 			header: defaultHeader,
 			err:    nil,
-			expected: &authHeader{
+			expected: &AuthHeader{
 				AccessKeyID:  "oid0cid",
 				Service:      "s3",
 				Region:       "us-east-1",
@@ -54,29 +54,29 @@ func TestAuthHeaderGetAddress(t *testing.T) {
 	defaulErr := errors.GetAPIError(errors.ErrInvalidAccessKeyID)
 
 	for _, tc := range []struct {
-		authHeader *authHeader
+		authHeader *AuthHeader
 		err        error
 	}{
 		{
-			authHeader: &authHeader{
+			authHeader: &AuthHeader{
 				AccessKeyID: "vWqF8cMDRbJcvnPLALoQGnABPPhw8NyYMcGsfDPfZJM0HrgjonN8CgFvCZ3kh9BUXw4W2tJ5E7EAGhueSF122HB",
 			},
 			err: nil,
 		},
 		{
-			authHeader: &authHeader{
+			authHeader: &AuthHeader{
 				AccessKeyID: "vWqF8cMDRbJcvnPLALoQGnABPPhw8NyYMcGsfDPfZJMHrgjonN8CgFvCZ3kh9BUXw4W2tJ5E7EAGhueSF122HB",
 			},
 			err: defaulErr,
 		},
 		{
-			authHeader: &authHeader{
+			authHeader: &AuthHeader{
 				AccessKeyID: "oid0cid",
 			},
 			err: defaulErr,
 		},
 		{
-			authHeader: &authHeader{
+			authHeader: &AuthHeader{
 				AccessKeyID: "oidcid",
 			},
 			err: defaulErr,

api/handler/multipart_upload.go

@@ -232,6 +232,27 @@ func (h *handler) UploadPartHandler(w http.ResponseWriter, r *http.Request) {
 		Reader:     r.Body,
 	}
 
+	if api.IsSignedStreamingV4(r) {
+		if decodeContentSize := r.Header.Get(api.AmzDecodedContentLength); len(decodeContentSize) > 0 {
+			_, err := strconv.Atoi(decodeContentSize)
+			if err != nil {
+				h.logAndSendError(w, "cannot parse decode content length information", reqInfo,
+					errors.GetAPIError(errors.ErrMissingContentLength))
+				return
+			}
+		} else {
+			h.logAndSendError(w, "expecting decode content length information", reqInfo,
+				errors.GetAPIError(errors.ErrMissingContentLength))
+			return
+		}
+		chunkReader, err := newSignV4ChunkedReader(r)
+		if err != nil {
+			h.logAndSendError(w, "cannot initialize chunk reader", reqInfo, err)
+			return
+		}
+		p.Reader = chunkReader
+	}
+
 	p.Info.Encryption, err = formEncryptionParams(r)
 	if err != nil {
 		h.logAndSendError(w, "invalid sse headers", reqInfo, err)

api/handler/put.go

@@ -233,6 +233,27 @@ func (h *handler) PutObjectHandler(w http.ResponseWriter, r *http.Request) {
 		Encryption: encryptionParams,
 	}
 
+	if api.IsSignedStreamingV4(r) {
+		if decodeContentSize := r.Header.Get(api.AmzDecodedContentLength); len(decodeContentSize) > 0 {
+			_, err := strconv.Atoi(decodeContentSize)
+			if err != nil {
+				h.logAndSendError(w, "cannot parse decode content length information", reqInfo,
+					errors.GetAPIError(errors.ErrMissingContentLength))
+				return
+			}
+		} else {
+			h.logAndSendError(w, "expecting decode content length information", reqInfo,
+				errors.GetAPIError(errors.ErrMissingContentLength))
+			return
+		}
+		chunkReader, err := newSignV4ChunkedReader(r)
+		if err != nil {
+			h.logAndSendError(w, "cannot initialize chunk reader", reqInfo, err)
+			return
+		}
+		params.Reader = chunkReader
+	}
+
 	params.CopiesNumbers, err = h.pickCopiesNumbers(metadata, bktInfo.LocationConstraint)
 	if err != nil {
 		h.logAndSendError(w, "invalid copies number", reqInfo, err)

api/handler/put_test.go

@@ -2,16 +2,24 @@ package handler
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
+	"io"
 	"mime/multipart"
 	"net/http"
+	"net/http/httptest"
 	"strconv"
 	"strings"
 	"testing"
 	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/auth"
+	v4 "git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/auth/signer/v4"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/errors"
 	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/layer"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/creds/accessbox"
+	"github.com/aws/aws-sdk-go/aws/credentials"
 	"github.com/stretchr/testify/require"
 )
 
@@ -146,3 +154,88 @@ func TestPutObjectWithNegativeContentLength(t *testing.T) {
 	assertStatus(t, w, http.StatusOK)
 	require.Equal(t, strconv.Itoa(len(content)), w.Header().Get(api.ContentLength))
 }
+
+func TestPutObjectWithStreamBodyError(t *testing.T) {
+	tc := prepareHandlerContext(t)
+
+	bktName, objName := "bucket-for-put", "object-for-put"
+	createTestBucket(tc, bktName)
+
+	content := []byte("content")
+	w, r := prepareTestPayloadRequest(tc, bktName, objName, bytes.NewReader(content))
+	r.Header.Set(api.AmzContentSha256, api.StreamingContentSHA256)
+	r.Header.Set(api.ContentEncoding, api.AwsChunked)
+	tc.Handler().PutObjectHandler(w, r)
+	assertS3Error(t, w, errors.GetAPIError(errors.ErrMissingContentLength))
+
+	checkNotFound(t, tc, bktName, objName, emptyVersion)
+}
+
+func TestPutObjectWithStreamBodyAWSExample(t *testing.T) {
+	tc := prepareHandlerContext(t)
+
+	bktName, objName := "examplebucket", "chunkObject.txt"
+	createTestBucket(tc, bktName)
+
+	chunk := make([]byte, 65*1024)
+	for i := range chunk {
+		chunk[i] = 'a'
+	}
+	chunk1 := chunk[:64*1024]
+	chunk2 := chunk[64*1024:]
+
+	AWSAccessKeyID := "AKIAIOSFODNN7EXAMPLE"
+	AWSSecretAccessKey := "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY"
+
+	awsCreds := credentials.NewStaticCredentials(AWSAccessKeyID, AWSSecretAccessKey, "")
+	signer := v4.NewSigner(awsCreds)
+
+	reqBody := bytes.NewBufferString("10000;chunk-signature=ad80c730a21e5b8d04586a2213dd63b9a0e99e0e2307b0ade35a65485a288648\r\n")
+	_, err := reqBody.Write(chunk1)
+	require.NoError(t, err)
+	_, err = reqBody.WriteString("\r\n400;chunk-signature=0055627c9e194cb4542bae2aa5492e3c1575bbb81b612b7d234b86a503ef5497\r\n")
+	require.NoError(t, err)
+	_, err = reqBody.Write(chunk2)
+	require.NoError(t, err)
+	_, err = reqBody.WriteString("\r\n0;chunk-signature=b6c6ea8a5354eaf15b3cb7646744f4275b71ea724fed81ceb9323e279d449df9\r\n\r\n")
+	require.NoError(t, err)
+
+	req, err := http.NewRequest("PUT", "https://s3.amazonaws.com/"+bktName+"/"+objName, nil)
+	require.NoError(t, err)
+	req.Header.Set("content-encoding", "aws-chunked")
+	req.Header.Set("content-length", "66824")
+	req.Header.Set("x-amz-content-sha256", "STREAMING-AWS4-HMAC-SHA256-PAYLOAD")
+	req.Header.Set("x-amz-decoded-content-length", "66560")
+	req.Header.Set("x-amz-storage-class", "REDUCED_REDUNDANCY")
+
+	signTime, err := time.Parse("20060102T150405Z", "20130524T000000Z")
+	require.NoError(t, err)
+
+	_, err = signer.Sign(req, nil, "s3", "us-east-1", signTime)
+	require.NoError(t, err)
+
+	req.Body = io.NopCloser(reqBody)
+
+	w := httptest.NewRecorder()
+	reqInfo := api.NewReqInfo(w, req, api.ObjectRequest{Bucket: bktName, Object: objName})
+	req = req.WithContext(api.SetReqInfo(tc.Context(), reqInfo))
+	req = req.WithContext(context.WithValue(req.Context(), api.ClientTime, signTime))
+	req = req.WithContext(context.WithValue(req.Context(), api.AuthHeaders, &auth.AuthHeader{
+		AccessKeyID: AWSAccessKeyID,
+		SignatureV4: "4f232c4386841ef735655705268965c44a0e4690baa4adea153f7db9fa80a0a9",
+		Service:     "s3",
+		Region:      "us-east-1",
+	}))
+	req = req.WithContext(context.WithValue(req.Context(), api.BoxData, &accessbox.Box{
+		Gate: &accessbox.GateData{
+			AccessKey: AWSSecretAccessKey,
+		},
+	}))
+	tc.Handler().PutObjectHandler(w, req)
+	assertStatus(t, w, http.StatusOK)
+
+	data := getObjectRange(t, tc, bktName, objName, 0, 66824)
+	for i := range chunk {
+		require.Equal(t, chunk[i], data[i])
+	}
+}

api/handler/s3reader.go

@@ -0,0 +1,224 @@
+package handler
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/hex"
+	"errors"
+	"io"
+	"net/http"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/auth"
+	v4 "git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/auth/signer/v4"
+	errs "git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/errors"
+	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/creds/accessbox"
+	"github.com/aws/aws-sdk-go/aws/credentials"
+)
+
+const (
+	chunkSignatureHeader = "chunk-signature="
+	maxChunkSize         = 16 << 20
+)
+
+type (
+	s3ChunkReader struct {
+		reader       *bufio.Reader
+		streamSigner *v4.StreamSigner
+
+		requestTime time.Time
+		buffer      []byte
+		offset      int
+		err         error
+	}
+)
+
+var (
+	errGiantChunk               = errors.New("chunk too big: choose chunk size <= 16MiB")
+	errMalformedChunkedEncoding = errors.New("malformed chunked encoding")
+)
+
+func (c *s3ChunkReader) Close() (err error) {
+	return nil
+}
+
+func (c *s3ChunkReader) Read(buf []byte) (num int, err error) {
+	if c.offset > 0 {
+		num = copy(buf, c.buffer[c.offset:])
+		if num == len(buf) {
+			c.offset += num
+			return num, nil
+		}
+		c.offset = 0
+		buf = buf[num:]
+	}
+
+	var size int
+	for {
+		b, err := c.reader.ReadByte()
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		if err != nil {
+			c.err = err
+			return num, c.err
+		}
+		if b == ';' { // separating character
+			break
+		}
+
+		// Manually deserialize the size since AWS specified
+		// the chunk size to be of variable width. In particular,
+		// a size of 16 is encoded as `10` while a size of 64 KB
+		// is `10000`.
+		switch {
+		case b >= '0' && b <= '9':
+			size = size<<4 | int(b-'0')
+		case b >= 'a' && b <= 'f':
+			size = size<<4 | int(b-('a'-10))
+		case b >= 'A' && b <= 'F':
+			size = size<<4 | int(b-('A'-10))
+		default:
+			c.err = errMalformedChunkedEncoding
+			return num, c.err
+		}
+		if size > maxChunkSize {
+			c.err = errGiantChunk
+			return num, c.err
+		}
+	}
+
+	// Now, we read the signature of the following payload and expect:
+	//   chunk-signature=" + <signature-as-hex> + "\r\n"
+	//
+	// The signature is 64 bytes long (hex-encoded SHA256 hash) and
+	// starts with a 16 byte header: len("chunk-signature=") + 64 == 80.
+	var signature [80]byte
+	_, err = io.ReadFull(c.reader, signature[:])
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	if err != nil {
+		c.err = err
+		return num, c.err
+	}
+	if !bytes.HasPrefix(signature[:], []byte(chunkSignatureHeader)) {
+		c.err = errMalformedChunkedEncoding
+		return num, c.err
+	}
+	b, err := c.reader.ReadByte()
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	if err != nil {
+		c.err = err
+		return num, c.err
+	}
+	if b != '\r' {
+		c.err = errMalformedChunkedEncoding
+		return num, c.err
+	}
+	b, err = c.reader.ReadByte()
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	if err != nil {
+		c.err = err
+		return num, c.err
+	}
+	if b != '\n' {
+		c.err = errMalformedChunkedEncoding
+		return num, c.err
+	}
+
+	if cap(c.buffer) < size {
+		c.buffer = make([]byte, size)
+	} else {
+		c.buffer = c.buffer[:size]
+	}
+
+	// Now, we read the payload and compute its SHA-256 hash.
+	_, err = io.ReadFull(c.reader, c.buffer)
+	if err == io.EOF && size != 0 {
+		err = io.ErrUnexpectedEOF
+	}
+	if err != nil && err != io.EOF {
+		c.err = err
+		return num, c.err
+	}
+	b, err = c.reader.ReadByte()
+	if b != '\r' || err != nil {
+		c.err = errMalformedChunkedEncoding
+		return num, c.err
+	}
+	b, err = c.reader.ReadByte()
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	if err != nil {
+		c.err = err
+		return num, c.err
+	}
+	if b != '\n' {
+		c.err = errMalformedChunkedEncoding
+		return num, c.err
+	}
+
+	// Once we have read the entire chunk successfully, we verify
+	// that the received signature matches our computed signature.
+
+	calculatedSignature, err := c.streamSigner.GetSignature(nil, c.buffer, c.requestTime)
+	if err != nil {
+		c.err = err
+		return num, c.err
+	}
+	if string(signature[16:]) != hex.EncodeToString(calculatedSignature) {
+		c.err = errs.GetAPIError(errs.ErrSignatureDoesNotMatch)
+		return num, c.err
+	}
+
+	// If the chunk size is zero we return io.EOF. As specified by AWS,
+	// only the last chunk is zero-sized.
+	if size == 0 {
+		c.err = io.EOF
+		return num, c.err
+	}
+
+	c.offset = copy(buf, c.buffer)
+	num += c.offset
+	return num, err
+}
+
+func newSignV4ChunkedReader(req *http.Request) (io.ReadCloser, error) {
+	// Expecting to refactor this in future:
+	// https://git.frostfs.info/TrueCloudLab/frostfs-s3-gw/issues/137
+	box, ok := req.Context().Value(api.BoxData).(*accessbox.Box)
+	if !ok {
+		return nil, errs.GetAPIError(errs.ErrAuthorizationHeaderMalformed)
+	}
+
+	authHeaders, ok := req.Context().Value(api.AuthHeaders).(*auth.AuthHeader)
+	if !ok {
+		return nil, errs.GetAPIError(errs.ErrAuthorizationHeaderMalformed)
+	}
+
+	currentCredentials := credentials.NewStaticCredentials(authHeaders.AccessKeyID, box.Gate.AccessKey, "")
+	seed, err := hex.DecodeString(authHeaders.SignatureV4)
+	if err != nil {
+		return nil, errs.GetAPIError(errs.ErrSignatureDoesNotMatch)
+	}
+
+	reqTime, ok := req.Context().Value(api.ClientTime).(time.Time)
+	if !ok {
+		return nil, errs.GetAPIError(errs.ErrMalformedDate)
+	}
+	newStreamSigner := v4.NewStreamSigner(authHeaders.Region, "s3", seed, currentCredentials)
+
+	return &s3ChunkReader{
+		reader:       bufio.NewReader(req.Body),
+		streamSigner: newStreamSigner,
+		requestTime:  reqTime,
+		buffer:       make([]byte, 64*1024),
+	}, nil
+}

api/headers.go

@@ -1,5 +1,7 @@
 package api
 
+import "net/http"
+
 // Standard S3 HTTP request/response constants.
 const (
 	MetadataPrefix              = "X-Amz-Meta-"
@@ -39,11 +41,13 @@ const (
 	IfMatch            = "If-Match"
 	IfNoneMatch        = "If-None-Match"
 
+	AmzContentSha256             = "X-Amz-Content-Sha256"
 	AmzCopyIfModifiedSince       = "X-Amz-Copy-Source-If-Modified-Since"
 	AmzCopyIfUnmodifiedSince     = "X-Amz-Copy-Source-If-Unmodified-Since"
 	AmzCopyIfMatch               = "X-Amz-Copy-Source-If-Match"
 	AmzCopyIfNoneMatch           = "X-Amz-Copy-Source-If-None-Match"
 	AmzACL                       = "X-Amz-Acl"
+	AmzDecodedContentLength      = "X-Amz-Decoded-Content-Length"
 	AmzGrantFullControl          = "X-Amz-Grant-Full-Control"
 	AmzGrantRead                 = "X-Amz-Grant-Read"
 	AmzGrantWrite                = "X-Amz-Grant-Write"
@@ -78,9 +82,13 @@ const (
 	AccessControlRequestMethod  = "Access-Control-Request-Method"
 	AccessControlRequestHeaders = "Access-Control-Request-Headers"
 
+	AwsChunked = "aws-chunked"
+
 	Vary = "Vary"
 
 	DefaultLocationConstraint = "default"
+
+	StreamingContentSHA256 = "STREAMING-AWS4-HMAC-SHA256-PAYLOAD"
 )
 
 // S3 request query params.
@@ -107,3 +115,12 @@ var SystemMetadata = map[string]struct{}{
 	LastModified:       {},
 	ETag:               {},
 }
+
+func IsSignedStreamingV4(r *http.Request) bool {
+	// The Content-Encoding must have "aws-chunked" as part of its value.
+	// https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-streaming.html
+	// Minio does not set this value, thus for compatibility reasons
+	// we do not check it.
+	return r.Header.Get(AmzContentSha256) == StreamingContentSHA256 &&
+		r.Method == http.MethodPut
+}

api/user_auth.go

@@ -13,6 +13,9 @@ import (
 // KeyWrapper is wrapper for context keys.
 type KeyWrapper string
 
+// AuthHeaders is a wrapper for authentication headers of a request.
+var AuthHeaders = KeyWrapper("__context_auth_headers_key")
+
 // BoxData is an ID used to store accessbox.Box in a context.
 var BoxData = KeyWrapper("__context_box_key")
 
@@ -42,6 +45,7 @@ func AuthMiddleware(log *zap.Logger, center auth.Center) mux.MiddlewareFunc {
 				if !box.ClientTime.IsZero() {
 					ctx = context.WithValue(ctx, ClientTime, box.ClientTime)
 				}
+				ctx = context.WithValue(ctx, AuthHeaders, box.AuthHeaders)
 			}
 
 			h.ServeHTTP(w, r.WithContext(ctx))