[#607] Support sigV4a streaming with trailers

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

api/handler/s3v4aReader.go

@@ -7,6 +7,8 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"slices"
+	"strings"
 	"time"
 
 	v4a "git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/auth/signer/v4asdk2"
@@ -20,10 +22,12 @@ type (
 		reader       *bufio.Reader
 		streamSigner *v4a.StreamSigner
 
-		requestTime time.Time
-		buffer      []byte
-		offset      int
-		err         error
+		trailerHeaders []string
+		trailers       map[string]string
+		requestTime    time.Time
+		buffer         []byte
+		offset         int
+		err            error
 	}
 )
 
@@ -87,21 +91,9 @@ func (c *s3v4aChunkReader) Read(buf []byte) (num int, err error) {
 		c.err = errMalformedChunkedEncoding
 		return num, c.err
 	}
-	b, err := c.reader.ReadByte()
-	if err != nil {
-		return c.handleErr(num, err)
-	}
-	if b != '\r' {
-		c.err = errMalformedChunkedEncoding
-		return num, c.err
-	}
-	b, err = c.reader.ReadByte()
-	if err != nil {
-		return c.handleErr(num, err)
-	}
-	if b != '\n' {
-		c.err = errMalformedChunkedEncoding
-		return num, c.err
+
+	if err = c.readCRLF(); err != nil {
+		return num, err
 	}
 
 	if cap(c.buffer) < size {
@@ -119,19 +111,6 @@ func (c *s3v4aChunkReader) Read(buf []byte) (num int, err error) {
 		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 != nil {
-		return c.handleErr(num, 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 is valid.
@@ -150,10 +129,23 @@ func (c *s3v4aChunkReader) Read(buf []byte) (num int, err error) {
 	// If the chunk size is zero we return io.EOF. As specified by AWS,
 	// only the last chunk is zero-sized.
 	if size == 0 {
+		if len(c.trailerHeaders) != 0 {
+			if err = c.readTrailers(); err != nil {
+				c.err = err
+				return num, c.err
+			}
+		} else if err = c.readCRLF(); err != nil {
+			return num, err
+		}
+
 		c.err = io.EOF
 		return num, c.err
 	}
 
+	if err = c.readCRLF(); err != nil {
+		return num, err
+	}
+
 	c.offset = copy(buf, c.buffer)
 	num += c.offset
 	return num, err
@@ -168,10 +160,77 @@ func (c *s3v4aChunkReader) handleErr(num int, err error) (int, error) {
 	return num, c.err
 }
 
-func (c *s3v4aChunkReader) TrailerHeaders() map[string]string {
+func (c *s3v4aChunkReader) readCRLF() error {
+	for _, ch := range [2]byte{'\r', '\n'} {
+		b, err := c.reader.ReadByte()
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+
+		if err != nil {
+			c.err = err
+			return c.err
+		}
+		if b != ch {
+			c.err = errMalformedChunkedEncoding
+			return c.err
+		}
+	}
+
 	return nil
 }
 
+func (c *s3v4aChunkReader) readTrailers() error {
+	var k, v []byte
+	var err error
+	for err == nil {
+		k, err = c.reader.ReadBytes(':')
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			c.err = errMalformedTrailerHeaders
+			return c.err
+		}
+		v, err = c.reader.ReadBytes('\n')
+		if err != nil && err != io.EOF {
+			c.err = errMalformedTrailerHeaders
+			return c.err
+		}
+		if len(v) >= 2 && v[len(v)-2] == '\r' {
+			v[len(v)-2] = '\n'
+			v = v[:len(v)-1]
+		}
+
+		switch {
+		case slices.Contains(c.trailerHeaders, string(k[:len(k)-1])):
+			c.buffer = append(append(c.buffer, k...), v...) // todo use copy
+		case string(k) == "x-amz-trailer-signature:":
+			n, err := hex.Decode(v[:], bytes.TrimRight(v[:], "*\n"))
+			if err != nil {
+				c.err = errMalformedChunkedEncoding
+				return c.err
+			}
+
+			if err = c.streamSigner.VerifyTrailerSignature(c.buffer, c.requestTime, v[:n]); err != nil {
+				c.err = fmt.Errorf("%w: %s", errs.GetAPIError(errs.ErrSignatureDoesNotMatch), err.Error())
+				return c.err
+			}
+		default:
+			c.err = errMalformedTrailerHeaders
+			return c.err
+		}
+
+		c.trailers[string(k[:len(k)-1])] = string(v[:len(v)-1])
+	}
+
+	return nil
+}
+
+func (c *s3v4aChunkReader) TrailerHeaders() map[string]string {
+	return c.trailers
+}
+
 func newSignV4aChunkedReader(req *http.Request) (*s3v4aChunkReader, error) {
 	box, err := middleware.GetBoxData(req.Context())
 	if err != nil {
@@ -204,10 +263,18 @@ func newSignV4aChunkedReader(req *http.Request) (*s3v4aChunkReader, error) {
 
 	newStreamSigner := v4a.NewStreamSigner(creds, "s3", seed)
 
+	var trailerHeaders []string
+	trailer := req.Header.Get("x-amz-trailer")
+	if trailer != "" {
+		trailerHeaders = strings.Split(trailer, ";")
+	}
+
 	return &s3v4aChunkReader{
-		reader:       bufio.NewReader(req.Body),
-		streamSigner: newStreamSigner,
-		requestTime:  reqTime,
-		buffer:       make([]byte, 64*1024),
+		reader:         bufio.NewReader(req.Body),
+		streamSigner:   newStreamSigner,
+		requestTime:    reqTime,
+		buffer:         make([]byte, 64*1024),
+		trailerHeaders: trailerHeaders,
+		trailers:       make(map[string]string, len(trailerHeaders)),
 	}, nil
 }