mirror of
https://github.com/octoleo/restic.git
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308 lines
9.8 KiB
Go
308 lines
9.8 KiB
Go
/*
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* Minio Go Library for Amazon S3 Compatible Cloud Storage (C) 2017 Minio, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package s3signer
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import (
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"bytes"
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"encoding/hex"
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"fmt"
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"io"
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"io/ioutil"
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"net/http"
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"strconv"
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"strings"
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"time"
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)
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// Reference for constants used below -
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// http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-streaming.html#example-signature-calculations-streaming
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const (
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streamingSignAlgorithm = "STREAMING-AWS4-HMAC-SHA256-PAYLOAD"
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streamingEncoding = "aws-chunked"
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streamingPayloadHdr = "AWS4-HMAC-SHA256-PAYLOAD"
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emptySHA256 = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
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payloadChunkSize = 64 * 1024
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chunkSigConstLen = 17 // ";chunk-signature="
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signatureStrLen = 64 // e.g. "f2ca1bb6c7e907d06dafe4687e579fce76b37e4e93b7605022da52e6ccc26fd2"
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crlfLen = 2 // CRLF
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)
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// Request headers to be ignored while calculating seed signature for
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// a request.
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var ignoredStreamingHeaders = map[string]bool{
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"Authorization": true,
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"User-Agent": true,
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"Content-Type": true,
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}
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// getSignedChunkLength - calculates the length of chunk metadata
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func getSignedChunkLength(chunkDataSize int64) int64 {
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return int64(len(fmt.Sprintf("%x", chunkDataSize))) +
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chunkSigConstLen +
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signatureStrLen +
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crlfLen +
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chunkDataSize +
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crlfLen
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}
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// getStreamLength - calculates the length of the overall stream (data + metadata)
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func getStreamLength(dataLen, chunkSize int64) int64 {
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if dataLen <= 0 {
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return 0
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}
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chunksCount := int64(dataLen / chunkSize)
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remainingBytes := int64(dataLen % chunkSize)
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streamLen := int64(0)
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streamLen += chunksCount * getSignedChunkLength(chunkSize)
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if remainingBytes > 0 {
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streamLen += getSignedChunkLength(remainingBytes)
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}
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streamLen += getSignedChunkLength(0)
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return streamLen
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}
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// buildChunkStringToSign - returns the string to sign given chunk data
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// and previous signature.
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func buildChunkStringToSign(t time.Time, region, previousSig string, chunkData []byte) string {
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stringToSignParts := []string{
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streamingPayloadHdr,
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t.Format(iso8601DateFormat),
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getScope(region, t),
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previousSig,
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emptySHA256,
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hex.EncodeToString(sum256(chunkData)),
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}
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return strings.Join(stringToSignParts, "\n")
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}
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// prepareStreamingRequest - prepares a request with appropriate
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// headers before computing the seed signature.
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func prepareStreamingRequest(req *http.Request, sessionToken string, dataLen int64, timestamp time.Time) {
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// Set x-amz-content-sha256 header.
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req.Header.Set("X-Amz-Content-Sha256", streamingSignAlgorithm)
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if sessionToken != "" {
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req.Header.Set("X-Amz-Security-Token", sessionToken)
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}
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req.Header.Set("Content-Encoding", streamingEncoding)
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req.Header.Set("X-Amz-Date", timestamp.Format(iso8601DateFormat))
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// Set content length with streaming signature for each chunk included.
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req.ContentLength = getStreamLength(dataLen, int64(payloadChunkSize))
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req.Header.Set("x-amz-decoded-content-length", strconv.FormatInt(dataLen, 10))
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}
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// buildChunkHeader - returns the chunk header.
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// e.g string(IntHexBase(chunk-size)) + ";chunk-signature=" + signature + \r\n + chunk-data + \r\n
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func buildChunkHeader(chunkLen int64, signature string) []byte {
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return []byte(strconv.FormatInt(chunkLen, 16) + ";chunk-signature=" + signature + "\r\n")
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}
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// buildChunkSignature - returns chunk signature for a given chunk and previous signature.
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func buildChunkSignature(chunkData []byte, reqTime time.Time, region,
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previousSignature, secretAccessKey string) string {
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chunkStringToSign := buildChunkStringToSign(reqTime, region,
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previousSignature, chunkData)
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signingKey := getSigningKey(secretAccessKey, region, reqTime)
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return getSignature(signingKey, chunkStringToSign)
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}
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// getSeedSignature - returns the seed signature for a given request.
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func (s *StreamingReader) setSeedSignature(req *http.Request) {
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// Get canonical request
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canonicalRequest := getCanonicalRequest(*req, ignoredStreamingHeaders)
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// Get string to sign from canonical request.
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stringToSign := getStringToSignV4(s.reqTime, s.region, canonicalRequest)
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signingKey := getSigningKey(s.secretAccessKey, s.region, s.reqTime)
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// Calculate signature.
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s.seedSignature = getSignature(signingKey, stringToSign)
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}
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// StreamingReader implements chunked upload signature as a reader on
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// top of req.Body's ReaderCloser chunk header;data;... repeat
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type StreamingReader struct {
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accessKeyID string
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secretAccessKey string
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sessionToken string
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region string
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prevSignature string
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seedSignature string
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contentLen int64 // Content-Length from req header
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baseReadCloser io.ReadCloser // underlying io.Reader
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bytesRead int64 // bytes read from underlying io.Reader
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buf bytes.Buffer // holds signed chunk
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chunkBuf []byte // holds raw data read from req Body
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chunkBufLen int // no. of bytes read so far into chunkBuf
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done bool // done reading the underlying reader to EOF
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reqTime time.Time
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chunkNum int
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totalChunks int
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lastChunkSize int
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}
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// signChunk - signs a chunk read from s.baseReader of chunkLen size.
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func (s *StreamingReader) signChunk(chunkLen int) {
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// Compute chunk signature for next header
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signature := buildChunkSignature(s.chunkBuf[:chunkLen], s.reqTime,
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s.region, s.prevSignature, s.secretAccessKey)
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// For next chunk signature computation
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s.prevSignature = signature
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// Write chunk header into streaming buffer
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chunkHdr := buildChunkHeader(int64(chunkLen), signature)
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s.buf.Write(chunkHdr)
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// Write chunk data into streaming buffer
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s.buf.Write(s.chunkBuf[:chunkLen])
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// Write the chunk trailer.
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s.buf.Write([]byte("\r\n"))
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// Reset chunkBufLen for next chunk read.
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s.chunkBufLen = 0
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s.chunkNum++
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}
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// setStreamingAuthHeader - builds and sets authorization header value
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// for streaming signature.
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func (s *StreamingReader) setStreamingAuthHeader(req *http.Request) {
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credential := GetCredential(s.accessKeyID, s.region, s.reqTime)
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authParts := []string{
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signV4Algorithm + " Credential=" + credential,
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"SignedHeaders=" + getSignedHeaders(*req, ignoredStreamingHeaders),
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"Signature=" + s.seedSignature,
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}
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// Set authorization header.
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auth := strings.Join(authParts, ",")
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req.Header.Set("Authorization", auth)
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}
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// StreamingSignV4 - provides chunked upload signatureV4 support by
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// implementing io.Reader.
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func StreamingSignV4(req *http.Request, accessKeyID, secretAccessKey, sessionToken,
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region string, dataLen int64, reqTime time.Time) *http.Request {
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// Set headers needed for streaming signature.
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prepareStreamingRequest(req, sessionToken, dataLen, reqTime)
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if req.Body == nil {
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req.Body = ioutil.NopCloser(bytes.NewReader([]byte("")))
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}
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stReader := &StreamingReader{
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baseReadCloser: req.Body,
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accessKeyID: accessKeyID,
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secretAccessKey: secretAccessKey,
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sessionToken: sessionToken,
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region: region,
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reqTime: reqTime,
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chunkBuf: make([]byte, payloadChunkSize),
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contentLen: dataLen,
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chunkNum: 1,
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totalChunks: int((dataLen+payloadChunkSize-1)/payloadChunkSize) + 1,
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lastChunkSize: int(dataLen % payloadChunkSize),
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}
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// Add the request headers required for chunk upload signing.
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// Compute the seed signature.
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stReader.setSeedSignature(req)
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// Set the authorization header with the seed signature.
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stReader.setStreamingAuthHeader(req)
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// Set seed signature as prevSignature for subsequent
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// streaming signing process.
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stReader.prevSignature = stReader.seedSignature
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req.Body = stReader
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return req
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}
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// Read - this method performs chunk upload signature providing a
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// io.Reader interface.
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func (s *StreamingReader) Read(buf []byte) (int, error) {
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switch {
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// After the last chunk is read from underlying reader, we
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// never re-fill s.buf.
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case s.done:
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// s.buf will be (re-)filled with next chunk when has lesser
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// bytes than asked for.
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case s.buf.Len() < len(buf):
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s.chunkBufLen = 0
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for {
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n1, err := s.baseReadCloser.Read(s.chunkBuf[s.chunkBufLen:])
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// Usually we validate `err` first, but in this case
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// we are validating n > 0 for the following reasons.
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//
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// 1. n > 0, err is one of io.EOF, nil (near end of stream)
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// A Reader returning a non-zero number of bytes at the end
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// of the input stream may return either err == EOF or err == nil
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//
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// 2. n == 0, err is io.EOF (actual end of stream)
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//
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// Callers should always process the n > 0 bytes returned
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// before considering the error err.
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if n1 > 0 {
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s.chunkBufLen += n1
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s.bytesRead += int64(n1)
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if s.chunkBufLen == payloadChunkSize ||
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(s.chunkNum == s.totalChunks-1 &&
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s.chunkBufLen == s.lastChunkSize) {
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// Sign the chunk and write it to s.buf.
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s.signChunk(s.chunkBufLen)
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break
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}
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}
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if err != nil {
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if err == io.EOF {
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// No more data left in baseReader - last chunk.
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// Done reading the last chunk from baseReader.
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s.done = true
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// bytes read from baseReader different than
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// content length provided.
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if s.bytesRead != s.contentLen {
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return 0, io.ErrUnexpectedEOF
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}
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// Sign the chunk and write it to s.buf.
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s.signChunk(0)
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break
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}
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return 0, err
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}
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}
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}
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return s.buf.Read(buf)
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}
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// Close - this method makes underlying io.ReadCloser's Close method available.
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func (s *StreamingReader) Close() error {
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return s.baseReadCloser.Close()
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}
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