[feature] S3 support (#674)

* feat: vendor minio client

* feat: introduce storage package with s3 support

* feat: serve s3 files directly

this saves a lot of bandwith as the files are fetched from the object
store directly

* fix: use explicit local storage in tests

* feat: integrate s3 storage with the main server

* fix: add s3 config to cli tests

* docs: explicitly set values in example config

also adds license header to the storage package

* fix: use better http status code on s3 redirect

HTTP 302 Found is the best fit, as it signifies that the resource
requested was found but not under its presumed URL

307/TemporaryRedirect would mean that this resource is usually located
here, not in this case

303/SeeOther indicates that the redirection does not link to the
requested resource but to another page

* refactor: use context in storage driver interface

vendor/github.com/minio/minio-go/v7/pkg/signer/request-signature-streaming.go

@@ -0,0 +1,306 @@
+/*
+ * MinIO Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2017 MinIO, Inc.
+ *
+ * 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 signer
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Reference for constants used below -
+// http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-streaming.html#example-signature-calculations-streaming
+const (
+	streamingSignAlgorithm = "STREAMING-AWS4-HMAC-SHA256-PAYLOAD"
+	streamingPayloadHdr    = "AWS4-HMAC-SHA256-PAYLOAD"
+	emptySHA256            = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+	payloadChunkSize       = 64 * 1024
+	chunkSigConstLen       = 17 // ";chunk-signature="
+	signatureStrLen        = 64 // e.g. "f2ca1bb6c7e907d06dafe4687e579fce76b37e4e93b7605022da52e6ccc26fd2"
+	crlfLen                = 2  // CRLF
+)
+
+// Request headers to be ignored while calculating seed signature for
+// a request.
+var ignoredStreamingHeaders = map[string]bool{
+	"Authorization": true,
+	"User-Agent":    true,
+	"Content-Type":  true,
+}
+
+// getSignedChunkLength - calculates the length of chunk metadata
+func getSignedChunkLength(chunkDataSize int64) int64 {
+	return int64(len(fmt.Sprintf("%x", chunkDataSize))) +
+		chunkSigConstLen +
+		signatureStrLen +
+		crlfLen +
+		chunkDataSize +
+		crlfLen
+}
+
+// getStreamLength - calculates the length of the overall stream (data + metadata)
+func getStreamLength(dataLen, chunkSize int64) int64 {
+	if dataLen <= 0 {
+		return 0
+	}
+
+	chunksCount := int64(dataLen / chunkSize)
+	remainingBytes := int64(dataLen % chunkSize)
+	streamLen := int64(0)
+	streamLen += chunksCount * getSignedChunkLength(chunkSize)
+	if remainingBytes > 0 {
+		streamLen += getSignedChunkLength(remainingBytes)
+	}
+	streamLen += getSignedChunkLength(0)
+	return streamLen
+}
+
+// buildChunkStringToSign - returns the string to sign given chunk data
+// and previous signature.
+func buildChunkStringToSign(t time.Time, region, previousSig string, chunkData []byte) string {
+	stringToSignParts := []string{
+		streamingPayloadHdr,
+		t.Format(iso8601DateFormat),
+		getScope(region, t, ServiceTypeS3),
+		previousSig,
+		emptySHA256,
+		hex.EncodeToString(sum256(chunkData)),
+	}
+
+	return strings.Join(stringToSignParts, "\n")
+}
+
+// prepareStreamingRequest - prepares a request with appropriate
+// headers before computing the seed signature.
+func prepareStreamingRequest(req *http.Request, sessionToken string, dataLen int64, timestamp time.Time) {
+	// Set x-amz-content-sha256 header.
+	req.Header.Set("X-Amz-Content-Sha256", streamingSignAlgorithm)
+	if sessionToken != "" {
+		req.Header.Set("X-Amz-Security-Token", sessionToken)
+	}
+
+	req.Header.Set("X-Amz-Date", timestamp.Format(iso8601DateFormat))
+	// Set content length with streaming signature for each chunk included.
+	req.ContentLength = getStreamLength(dataLen, int64(payloadChunkSize))
+	req.Header.Set("x-amz-decoded-content-length", strconv.FormatInt(dataLen, 10))
+}
+
+// buildChunkHeader - returns the chunk header.
+// e.g string(IntHexBase(chunk-size)) + ";chunk-signature=" + signature + \r\n + chunk-data + \r\n
+func buildChunkHeader(chunkLen int64, signature string) []byte {
+	return []byte(strconv.FormatInt(chunkLen, 16) + ";chunk-signature=" + signature + "\r\n")
+}
+
+// buildChunkSignature - returns chunk signature for a given chunk and previous signature.
+func buildChunkSignature(chunkData []byte, reqTime time.Time, region,
+	previousSignature, secretAccessKey string,
+) string {
+	chunkStringToSign := buildChunkStringToSign(reqTime, region,
+		previousSignature, chunkData)
+	signingKey := getSigningKey(secretAccessKey, region, reqTime, ServiceTypeS3)
+	return getSignature(signingKey, chunkStringToSign)
+}
+
+// getSeedSignature - returns the seed signature for a given request.
+func (s *StreamingReader) setSeedSignature(req *http.Request) {
+	// Get canonical request
+	canonicalRequest := getCanonicalRequest(*req, ignoredStreamingHeaders, getHashedPayload(*req))
+
+	// Get string to sign from canonical request.
+	stringToSign := getStringToSignV4(s.reqTime, s.region, canonicalRequest, ServiceTypeS3)
+
+	signingKey := getSigningKey(s.secretAccessKey, s.region, s.reqTime, ServiceTypeS3)
+
+	// Calculate signature.
+	s.seedSignature = getSignature(signingKey, stringToSign)
+}
+
+// StreamingReader implements chunked upload signature as a reader on
+// top of req.Body's ReaderCloser chunk header;data;... repeat
+type StreamingReader struct {
+	accessKeyID     string
+	secretAccessKey string
+	sessionToken    string
+	region          string
+	prevSignature   string
+	seedSignature   string
+	contentLen      int64         // Content-Length from req header
+	baseReadCloser  io.ReadCloser // underlying io.Reader
+	bytesRead       int64         // bytes read from underlying io.Reader
+	buf             bytes.Buffer  // holds signed chunk
+	chunkBuf        []byte        // holds raw data read from req Body
+	chunkBufLen     int           // no. of bytes read so far into chunkBuf
+	done            bool          // done reading the underlying reader to EOF
+	reqTime         time.Time
+	chunkNum        int
+	totalChunks     int
+	lastChunkSize   int
+}
+
+// signChunk - signs a chunk read from s.baseReader of chunkLen size.
+func (s *StreamingReader) signChunk(chunkLen int) {
+	// Compute chunk signature for next header
+	signature := buildChunkSignature(s.chunkBuf[:chunkLen], s.reqTime,
+		s.region, s.prevSignature, s.secretAccessKey)
+
+	// For next chunk signature computation
+	s.prevSignature = signature
+
+	// Write chunk header into streaming buffer
+	chunkHdr := buildChunkHeader(int64(chunkLen), signature)
+	s.buf.Write(chunkHdr)
+
+	// Write chunk data into streaming buffer
+	s.buf.Write(s.chunkBuf[:chunkLen])
+
+	// Write the chunk trailer.
+	s.buf.Write([]byte("\r\n"))
+
+	// Reset chunkBufLen for next chunk read.
+	s.chunkBufLen = 0
+	s.chunkNum++
+}
+
+// setStreamingAuthHeader - builds and sets authorization header value
+// for streaming signature.
+func (s *StreamingReader) setStreamingAuthHeader(req *http.Request) {
+	credential := GetCredential(s.accessKeyID, s.region, s.reqTime, ServiceTypeS3)
+	authParts := []string{
+		signV4Algorithm + " Credential=" + credential,
+		"SignedHeaders=" + getSignedHeaders(*req, ignoredStreamingHeaders),
+		"Signature=" + s.seedSignature,
+	}
+
+	// Set authorization header.
+	auth := strings.Join(authParts, ",")
+	req.Header.Set("Authorization", auth)
+}
+
+// StreamingSignV4 - provides chunked upload signatureV4 support by
+// implementing io.Reader.
+func StreamingSignV4(req *http.Request, accessKeyID, secretAccessKey, sessionToken,
+	region string, dataLen int64, reqTime time.Time,
+) *http.Request {
+	// Set headers needed for streaming signature.
+	prepareStreamingRequest(req, sessionToken, dataLen, reqTime)
+
+	if req.Body == nil {
+		req.Body = ioutil.NopCloser(bytes.NewReader([]byte("")))
+	}
+
+	stReader := &StreamingReader{
+		baseReadCloser:  req.Body,
+		accessKeyID:     accessKeyID,
+		secretAccessKey: secretAccessKey,
+		sessionToken:    sessionToken,
+		region:          region,
+		reqTime:         reqTime,
+		chunkBuf:        make([]byte, payloadChunkSize),
+		contentLen:      dataLen,
+		chunkNum:        1,
+		totalChunks:     int((dataLen+payloadChunkSize-1)/payloadChunkSize) + 1,
+		lastChunkSize:   int(dataLen % payloadChunkSize),
+	}
+
+	// Add the request headers required for chunk upload signing.
+
+	// Compute the seed signature.
+	stReader.setSeedSignature(req)
+
+	// Set the authorization header with the seed signature.
+	stReader.setStreamingAuthHeader(req)
+
+	// Set seed signature as prevSignature for subsequent
+	// streaming signing process.
+	stReader.prevSignature = stReader.seedSignature
+	req.Body = stReader
+
+	return req
+}
+
+// Read - this method performs chunk upload signature providing a
+// io.Reader interface.
+func (s *StreamingReader) Read(buf []byte) (int, error) {
+	switch {
+	// After the last chunk is read from underlying reader, we
+	// never re-fill s.buf.
+	case s.done:
+
+	// s.buf will be (re-)filled with next chunk when has lesser
+	// bytes than asked for.
+	case s.buf.Len() < len(buf):
+		s.chunkBufLen = 0
+		for {
+			n1, err := s.baseReadCloser.Read(s.chunkBuf[s.chunkBufLen:])
+			// Usually we validate `err` first, but in this case
+			// we are validating n > 0 for the following reasons.
+			//
+			// 1. n > 0, err is one of io.EOF, nil (near end of stream)
+			// A Reader returning a non-zero number of bytes at the end
+			// of the input stream may return either err == EOF or err == nil
+			//
+			// 2. n == 0, err is io.EOF (actual end of stream)
+			//
+			// Callers should always process the n > 0 bytes returned
+			// before considering the error err.
+			if n1 > 0 {
+				s.chunkBufLen += n1
+				s.bytesRead += int64(n1)
+
+				if s.chunkBufLen == payloadChunkSize ||
+					(s.chunkNum == s.totalChunks-1 &&
+						s.chunkBufLen == s.lastChunkSize) {
+					// Sign the chunk and write it to s.buf.
+					s.signChunk(s.chunkBufLen)
+					break
+				}
+			}
+			if err != nil {
+				if err == io.EOF {
+					// No more data left in baseReader - last chunk.
+					// Done reading the last chunk from baseReader.
+					s.done = true
+
+					// bytes read from baseReader different than
+					// content length provided.
+					if s.bytesRead != s.contentLen {
+						return 0, fmt.Errorf("http: ContentLength=%d with Body length %d", s.contentLen, s.bytesRead)
+					}
+
+					// Sign the chunk and write it to s.buf.
+					s.signChunk(0)
+					break
+				}
+				return 0, err
+			}
+
+		}
+	}
+	return s.buf.Read(buf)
+}
+
+// Close - this method makes underlying io.ReadCloser's Close method available.
+func (s *StreamingReader) Close() error {
+	return s.baseReadCloser.Close()
+}

vendor/github.com/minio/minio-go/v7/pkg/signer/request-signature-v2.go

@@ -0,0 +1,316 @@
+/*
+ * MinIO Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2015-2017 MinIO, Inc.
+ *
+ * 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 signer
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"crypto/sha1"
+	"encoding/base64"
+	"fmt"
+	"net/http"
+	"net/url"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/minio/minio-go/v7/pkg/s3utils"
+)
+
+// Signature and API related constants.
+const (
+	signV2Algorithm = "AWS"
+)
+
+// Encode input URL path to URL encoded path.
+func encodeURL2Path(req *http.Request, virtualHost bool) (path string) {
+	if virtualHost {
+		reqHost := getHostAddr(req)
+		dotPos := strings.Index(reqHost, ".")
+		if dotPos > -1 {
+			bucketName := reqHost[:dotPos]
+			path = "/" + bucketName
+			path += req.URL.Path
+			path = s3utils.EncodePath(path)
+			return
+		}
+	}
+	path = s3utils.EncodePath(req.URL.Path)
+	return
+}
+
+// PreSignV2 - presign the request in following style.
+// https://${S3_BUCKET}.s3.amazonaws.com/${S3_OBJECT}?AWSAccessKeyId=${S3_ACCESS_KEY}&Expires=${TIMESTAMP}&Signature=${SIGNATURE}.
+func PreSignV2(req http.Request, accessKeyID, secretAccessKey string, expires int64, virtualHost bool) *http.Request {
+	// Presign is not needed for anonymous credentials.
+	if accessKeyID == "" || secretAccessKey == "" {
+		return &req
+	}
+
+	d := time.Now().UTC()
+	// Find epoch expires when the request will expire.
+	epochExpires := d.Unix() + expires
+
+	// Add expires header if not present.
+	if expiresStr := req.Header.Get("Expires"); expiresStr == "" {
+		req.Header.Set("Expires", strconv.FormatInt(epochExpires, 10))
+	}
+
+	// Get presigned string to sign.
+	stringToSign := preStringToSignV2(req, virtualHost)
+	hm := hmac.New(sha1.New, []byte(secretAccessKey))
+	hm.Write([]byte(stringToSign))
+
+	// Calculate signature.
+	signature := base64.StdEncoding.EncodeToString(hm.Sum(nil))
+
+	query := req.URL.Query()
+	// Handle specially for Google Cloud Storage.
+	if strings.Contains(getHostAddr(&req), ".storage.googleapis.com") {
+		query.Set("GoogleAccessId", accessKeyID)
+	} else {
+		query.Set("AWSAccessKeyId", accessKeyID)
+	}
+
+	// Fill in Expires for presigned query.
+	query.Set("Expires", strconv.FormatInt(epochExpires, 10))
+
+	// Encode query and save.
+	req.URL.RawQuery = s3utils.QueryEncode(query)
+
+	// Save signature finally.
+	req.URL.RawQuery += "&Signature=" + s3utils.EncodePath(signature)
+
+	// Return.
+	return &req
+}
+
+// PostPresignSignatureV2 - presigned signature for PostPolicy
+// request.
+func PostPresignSignatureV2(policyBase64, secretAccessKey string) string {
+	hm := hmac.New(sha1.New, []byte(secretAccessKey))
+	hm.Write([]byte(policyBase64))
+	signature := base64.StdEncoding.EncodeToString(hm.Sum(nil))
+	return signature
+}
+
+// Authorization = "AWS" + " " + AWSAccessKeyId + ":" + Signature;
+// Signature = Base64( HMAC-SHA1( YourSecretAccessKeyID, UTF-8-Encoding-Of( StringToSign ) ) );
+//
+// StringToSign = HTTP-Verb + "\n" +
+//  	Content-Md5 + "\n" +
+//  	Content-Type + "\n" +
+//  	Date + "\n" +
+//  	CanonicalizedProtocolHeaders +
+//  	CanonicalizedResource;
+//
+// CanonicalizedResource = [ "/" + Bucket ] +
+//  	<HTTP-Request-URI, from the protocol name up to the query string> +
+//  	[ subresource, if present. For example "?acl", "?location", "?logging", or "?torrent"];
+//
+// CanonicalizedProtocolHeaders = <described below>
+
+// SignV2 sign the request before Do() (AWS Signature Version 2).
+func SignV2(req http.Request, accessKeyID, secretAccessKey string, virtualHost bool) *http.Request {
+	// Signature calculation is not needed for anonymous credentials.
+	if accessKeyID == "" || secretAccessKey == "" {
+		return &req
+	}
+
+	// Initial time.
+	d := time.Now().UTC()
+
+	// Add date if not present.
+	if date := req.Header.Get("Date"); date == "" {
+		req.Header.Set("Date", d.Format(http.TimeFormat))
+	}
+
+	// Calculate HMAC for secretAccessKey.
+	stringToSign := stringToSignV2(req, virtualHost)
+	hm := hmac.New(sha1.New, []byte(secretAccessKey))
+	hm.Write([]byte(stringToSign))
+
+	// Prepare auth header.
+	authHeader := new(bytes.Buffer)
+	authHeader.WriteString(fmt.Sprintf("%s %s:", signV2Algorithm, accessKeyID))
+	encoder := base64.NewEncoder(base64.StdEncoding, authHeader)
+	encoder.Write(hm.Sum(nil))
+	encoder.Close()
+
+	// Set Authorization header.
+	req.Header.Set("Authorization", authHeader.String())
+
+	return &req
+}
+
+// From the Amazon docs:
+//
+// StringToSign = HTTP-Verb + "\n" +
+// 	 Content-Md5 + "\n" +
+//	 Content-Type + "\n" +
+//	 Expires + "\n" +
+//	 CanonicalizedProtocolHeaders +
+//	 CanonicalizedResource;
+func preStringToSignV2(req http.Request, virtualHost bool) string {
+	buf := new(bytes.Buffer)
+	// Write standard headers.
+	writePreSignV2Headers(buf, req)
+	// Write canonicalized protocol headers if any.
+	writeCanonicalizedHeaders(buf, req)
+	// Write canonicalized Query resources if any.
+	writeCanonicalizedResource(buf, req, virtualHost)
+	return buf.String()
+}
+
+// writePreSignV2Headers - write preSign v2 required headers.
+func writePreSignV2Headers(buf *bytes.Buffer, req http.Request) {
+	buf.WriteString(req.Method + "\n")
+	buf.WriteString(req.Header.Get("Content-Md5") + "\n")
+	buf.WriteString(req.Header.Get("Content-Type") + "\n")
+	buf.WriteString(req.Header.Get("Expires") + "\n")
+}
+
+// From the Amazon docs:
+//
+// StringToSign = HTTP-Verb + "\n" +
+// 	 Content-Md5 + "\n" +
+//	 Content-Type + "\n" +
+//	 Date + "\n" +
+//	 CanonicalizedProtocolHeaders +
+//	 CanonicalizedResource;
+func stringToSignV2(req http.Request, virtualHost bool) string {
+	buf := new(bytes.Buffer)
+	// Write standard headers.
+	writeSignV2Headers(buf, req)
+	// Write canonicalized protocol headers if any.
+	writeCanonicalizedHeaders(buf, req)
+	// Write canonicalized Query resources if any.
+	writeCanonicalizedResource(buf, req, virtualHost)
+	return buf.String()
+}
+
+// writeSignV2Headers - write signV2 required headers.
+func writeSignV2Headers(buf *bytes.Buffer, req http.Request) {
+	buf.WriteString(req.Method + "\n")
+	buf.WriteString(req.Header.Get("Content-Md5") + "\n")
+	buf.WriteString(req.Header.Get("Content-Type") + "\n")
+	buf.WriteString(req.Header.Get("Date") + "\n")
+}
+
+// writeCanonicalizedHeaders - write canonicalized headers.
+func writeCanonicalizedHeaders(buf *bytes.Buffer, req http.Request) {
+	var protoHeaders []string
+	vals := make(map[string][]string)
+	for k, vv := range req.Header {
+		// All the AMZ headers should be lowercase
+		lk := strings.ToLower(k)
+		if strings.HasPrefix(lk, "x-amz") {
+			protoHeaders = append(protoHeaders, lk)
+			vals[lk] = vv
+		}
+	}
+	sort.Strings(protoHeaders)
+	for _, k := range protoHeaders {
+		buf.WriteString(k)
+		buf.WriteByte(':')
+		for idx, v := range vals[k] {
+			if idx > 0 {
+				buf.WriteByte(',')
+			}
+			buf.WriteString(v)
+		}
+		buf.WriteByte('\n')
+	}
+}
+
+// AWS S3 Signature V2 calculation rule is give here:
+// http://docs.aws.amazon.com/AmazonS3/latest/dev/RESTAuthentication.html#RESTAuthenticationStringToSign
+
+// Whitelist resource list that will be used in query string for signature-V2 calculation.
+//
+// This list should be kept alphabetically sorted, do not hastily edit.
+var resourceList = []string{
+	"acl",
+	"cors",
+	"delete",
+	"encryption",
+	"legal-hold",
+	"lifecycle",
+	"location",
+	"logging",
+	"notification",
+	"partNumber",
+	"policy",
+	"replication",
+	"requestPayment",
+	"response-cache-control",
+	"response-content-disposition",
+	"response-content-encoding",
+	"response-content-language",
+	"response-content-type",
+	"response-expires",
+	"retention",
+	"select",
+	"select-type",
+	"tagging",
+	"torrent",
+	"uploadId",
+	"uploads",
+	"versionId",
+	"versioning",
+	"versions",
+	"website",
+}
+
+// From the Amazon docs:
+//
+// CanonicalizedResource = [ "/" + Bucket ] +
+// 	  <HTTP-Request-URI, from the protocol name up to the query string> +
+// 	  [ sub-resource, if present. For example "?acl", "?location", "?logging", or "?torrent"];
+func writeCanonicalizedResource(buf *bytes.Buffer, req http.Request, virtualHost bool) {
+	// Save request URL.
+	requestURL := req.URL
+	// Get encoded URL path.
+	buf.WriteString(encodeURL2Path(&req, virtualHost))
+	if requestURL.RawQuery != "" {
+		var n int
+		vals, _ := url.ParseQuery(requestURL.RawQuery)
+		// Verify if any sub resource queries are present, if yes
+		// canonicallize them.
+		for _, resource := range resourceList {
+			if vv, ok := vals[resource]; ok && len(vv) > 0 {
+				n++
+				// First element
+				switch n {
+				case 1:
+					buf.WriteByte('?')
+				// The rest
+				default:
+					buf.WriteByte('&')
+				}
+				buf.WriteString(resource)
+				// Request parameters
+				if len(vv[0]) > 0 {
+					buf.WriteByte('=')
+					buf.WriteString(vv[0])
+				}
+			}
+		}
+	}
+}

vendor/github.com/minio/minio-go/v7/pkg/signer/request-signature-v4.go

@@ -0,0 +1,332 @@
+/*
+ * MinIO Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2015-2017 MinIO, Inc.
+ *
+ * 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 signer
+
+import (
+	"bytes"
+	"encoding/hex"
+	"net/http"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/minio/minio-go/v7/pkg/s3utils"
+)
+
+// Signature and API related constants.
+const (
+	signV4Algorithm   = "AWS4-HMAC-SHA256"
+	iso8601DateFormat = "20060102T150405Z"
+	yyyymmdd          = "20060102"
+)
+
+// Different service types
+const (
+	ServiceTypeS3  = "s3"
+	ServiceTypeSTS = "sts"
+)
+
+//
+// Excerpts from @lsegal -
+// https:/github.com/aws/aws-sdk-js/issues/659#issuecomment-120477258.
+//
+// * User-Agent
+// This is ignored from signing because signing this causes problems with generating pre-signed
+// URLs (that are executed by other agents) or when customers pass requests through proxies, which
+// may modify the user-agent.
+//
+// * Authorization
+// Is skipped for obvious reasons.
+//
+// * Accept-Encoding
+// Some S3 servers like Hitachi Content Platform do not honor this header for signature
+// calculation.
+//
+var v4IgnoredHeaders = map[string]bool{
+	"Accept-Encoding": true,
+	"Authorization":   true,
+	"User-Agent":      true,
+}
+
+// getSigningKey hmac seed to calculate final signature.
+func getSigningKey(secret, loc string, t time.Time, serviceType string) []byte {
+	date := sumHMAC([]byte("AWS4"+secret), []byte(t.Format(yyyymmdd)))
+	location := sumHMAC(date, []byte(loc))
+	service := sumHMAC(location, []byte(serviceType))
+	signingKey := sumHMAC(service, []byte("aws4_request"))
+	return signingKey
+}
+
+// getSignature final signature in hexadecimal form.
+func getSignature(signingKey []byte, stringToSign string) string {
+	return hex.EncodeToString(sumHMAC(signingKey, []byte(stringToSign)))
+}
+
+// getScope generate a string of a specific date, an AWS region, and a
+// service.
+func getScope(location string, t time.Time, serviceType string) string {
+	scope := strings.Join([]string{
+		t.Format(yyyymmdd),
+		location,
+		serviceType,
+		"aws4_request",
+	}, "/")
+	return scope
+}
+
+// GetCredential generate a credential string.
+func GetCredential(accessKeyID, location string, t time.Time, serviceType string) string {
+	scope := getScope(location, t, serviceType)
+	return accessKeyID + "/" + scope
+}
+
+// getHashedPayload get the hexadecimal value of the SHA256 hash of
+// the request payload.
+func getHashedPayload(req http.Request) string {
+	hashedPayload := req.Header.Get("X-Amz-Content-Sha256")
+	if hashedPayload == "" {
+		// Presign does not have a payload, use S3 recommended value.
+		hashedPayload = unsignedPayload
+	}
+	return hashedPayload
+}
+
+// getCanonicalHeaders generate a list of request headers for
+// signature.
+func getCanonicalHeaders(req http.Request, ignoredHeaders map[string]bool) string {
+	var headers []string
+	vals := make(map[string][]string)
+	for k, vv := range req.Header {
+		if _, ok := ignoredHeaders[http.CanonicalHeaderKey(k)]; ok {
+			continue // ignored header
+		}
+		headers = append(headers, strings.ToLower(k))
+		vals[strings.ToLower(k)] = vv
+	}
+	if !headerExists("host", headers) {
+		headers = append(headers, "host")
+	}
+	sort.Strings(headers)
+
+	var buf bytes.Buffer
+	// Save all the headers in canonical form <header>:<value> newline
+	// separated for each header.
+	for _, k := range headers {
+		buf.WriteString(k)
+		buf.WriteByte(':')
+		switch {
+		case k == "host":
+			buf.WriteString(getHostAddr(&req))
+			buf.WriteByte('\n')
+		default:
+			for idx, v := range vals[k] {
+				if idx > 0 {
+					buf.WriteByte(',')
+				}
+				buf.WriteString(signV4TrimAll(v))
+			}
+			buf.WriteByte('\n')
+		}
+	}
+	return buf.String()
+}
+
+func headerExists(key string, headers []string) bool {
+	for _, k := range headers {
+		if k == key {
+			return true
+		}
+	}
+	return false
+}
+
+// getSignedHeaders generate all signed request headers.
+// i.e lexically sorted, semicolon-separated list of lowercase
+// request header names.
+func getSignedHeaders(req http.Request, ignoredHeaders map[string]bool) string {
+	var headers []string
+	for k := range req.Header {
+		if _, ok := ignoredHeaders[http.CanonicalHeaderKey(k)]; ok {
+			continue // Ignored header found continue.
+		}
+		headers = append(headers, strings.ToLower(k))
+	}
+	if !headerExists("host", headers) {
+		headers = append(headers, "host")
+	}
+	sort.Strings(headers)
+	return strings.Join(headers, ";")
+}
+
+// getCanonicalRequest generate a canonical request of style.
+//
+// canonicalRequest =
+//  <HTTPMethod>\n
+//  <CanonicalURI>\n
+//  <CanonicalQueryString>\n
+//  <CanonicalHeaders>\n
+//  <SignedHeaders>\n
+//  <HashedPayload>
+func getCanonicalRequest(req http.Request, ignoredHeaders map[string]bool, hashedPayload string) string {
+	req.URL.RawQuery = strings.ReplaceAll(req.URL.Query().Encode(), "+", "%20")
+	canonicalRequest := strings.Join([]string{
+		req.Method,
+		s3utils.EncodePath(req.URL.Path),
+		req.URL.RawQuery,
+		getCanonicalHeaders(req, ignoredHeaders),
+		getSignedHeaders(req, ignoredHeaders),
+		hashedPayload,
+	}, "\n")
+	return canonicalRequest
+}
+
+// getStringToSign a string based on selected query values.
+func getStringToSignV4(t time.Time, location, canonicalRequest, serviceType string) string {
+	stringToSign := signV4Algorithm + "\n" + t.Format(iso8601DateFormat) + "\n"
+	stringToSign = stringToSign + getScope(location, t, serviceType) + "\n"
+	stringToSign += hex.EncodeToString(sum256([]byte(canonicalRequest)))
+	return stringToSign
+}
+
+// PreSignV4 presign the request, in accordance with
+// http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html.
+func PreSignV4(req http.Request, accessKeyID, secretAccessKey, sessionToken, location string, expires int64) *http.Request {
+	// Presign is not needed for anonymous credentials.
+	if accessKeyID == "" || secretAccessKey == "" {
+		return &req
+	}
+
+	// Initial time.
+	t := time.Now().UTC()
+
+	// Get credential string.
+	credential := GetCredential(accessKeyID, location, t, ServiceTypeS3)
+
+	// Get all signed headers.
+	signedHeaders := getSignedHeaders(req, v4IgnoredHeaders)
+
+	// Set URL query.
+	query := req.URL.Query()
+	query.Set("X-Amz-Algorithm", signV4Algorithm)
+	query.Set("X-Amz-Date", t.Format(iso8601DateFormat))
+	query.Set("X-Amz-Expires", strconv.FormatInt(expires, 10))
+	query.Set("X-Amz-SignedHeaders", signedHeaders)
+	query.Set("X-Amz-Credential", credential)
+	// Set session token if available.
+	if sessionToken != "" {
+		query.Set("X-Amz-Security-Token", sessionToken)
+	}
+	req.URL.RawQuery = query.Encode()
+
+	// Get canonical request.
+	canonicalRequest := getCanonicalRequest(req, v4IgnoredHeaders, getHashedPayload(req))
+
+	// Get string to sign from canonical request.
+	stringToSign := getStringToSignV4(t, location, canonicalRequest, ServiceTypeS3)
+
+	// Gext hmac signing key.
+	signingKey := getSigningKey(secretAccessKey, location, t, ServiceTypeS3)
+
+	// Calculate signature.
+	signature := getSignature(signingKey, stringToSign)
+
+	// Add signature header to RawQuery.
+	req.URL.RawQuery += "&X-Amz-Signature=" + signature
+
+	return &req
+}
+
+// PostPresignSignatureV4 - presigned signature for PostPolicy
+// requests.
+func PostPresignSignatureV4(policyBase64 string, t time.Time, secretAccessKey, location string) string {
+	// Get signining key.
+	signingkey := getSigningKey(secretAccessKey, location, t, ServiceTypeS3)
+	// Calculate signature.
+	signature := getSignature(signingkey, policyBase64)
+	return signature
+}
+
+// SignV4STS - signature v4 for STS request.
+func SignV4STS(req http.Request, accessKeyID, secretAccessKey, location string) *http.Request {
+	return signV4(req, accessKeyID, secretAccessKey, "", location, ServiceTypeSTS)
+}
+
+// Internal function called for different service types.
+func signV4(req http.Request, accessKeyID, secretAccessKey, sessionToken, location, serviceType string) *http.Request {
+	// Signature calculation is not needed for anonymous credentials.
+	if accessKeyID == "" || secretAccessKey == "" {
+		return &req
+	}
+
+	// Initial time.
+	t := time.Now().UTC()
+
+	// Set x-amz-date.
+	req.Header.Set("X-Amz-Date", t.Format(iso8601DateFormat))
+
+	// Set session token if available.
+	if sessionToken != "" {
+		req.Header.Set("X-Amz-Security-Token", sessionToken)
+	}
+
+	hashedPayload := getHashedPayload(req)
+	if serviceType == ServiceTypeSTS {
+		// Content sha256 header is not sent with the request
+		// but it is expected to have sha256 of payload for signature
+		// in STS service type request.
+		req.Header.Del("X-Amz-Content-Sha256")
+	}
+
+	// Get canonical request.
+	canonicalRequest := getCanonicalRequest(req, v4IgnoredHeaders, hashedPayload)
+
+	// Get string to sign from canonical request.
+	stringToSign := getStringToSignV4(t, location, canonicalRequest, serviceType)
+
+	// Get hmac signing key.
+	signingKey := getSigningKey(secretAccessKey, location, t, serviceType)
+
+	// Get credential string.
+	credential := GetCredential(accessKeyID, location, t, serviceType)
+
+	// Get all signed headers.
+	signedHeaders := getSignedHeaders(req, v4IgnoredHeaders)
+
+	// Calculate signature.
+	signature := getSignature(signingKey, stringToSign)
+
+	// If regular request, construct the final authorization header.
+	parts := []string{
+		signV4Algorithm + " Credential=" + credential,
+		"SignedHeaders=" + signedHeaders,
+		"Signature=" + signature,
+	}
+
+	// Set authorization header.
+	auth := strings.Join(parts, ", ")
+	req.Header.Set("Authorization", auth)
+
+	return &req
+}
+
+// SignV4 sign the request before Do(), in accordance with
+// http://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html.
+func SignV4(req http.Request, accessKeyID, secretAccessKey, sessionToken, location string) *http.Request {
+	return signV4(req, accessKeyID, secretAccessKey, sessionToken, location, ServiceTypeS3)
+}

vendor/github.com/minio/minio-go/v7/pkg/signer/utils.go

@@ -0,0 +1,63 @@
+/*
+ * MinIO Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2015-2017 MinIO, Inc.
+ *
+ * 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 signer
+
+import (
+	"crypto/hmac"
+	"net/http"
+	"strings"
+
+	"github.com/minio/sha256-simd"
+)
+
+// unsignedPayload - value to be set to X-Amz-Content-Sha256 header when
+const unsignedPayload = "UNSIGNED-PAYLOAD"
+
+// sum256 calculate sha256 sum for an input byte array.
+func sum256(data []byte) []byte {
+	hash := sha256.New()
+	hash.Write(data)
+	return hash.Sum(nil)
+}
+
+// sumHMAC calculate hmac between two input byte array.
+func sumHMAC(key []byte, data []byte) []byte {
+	hash := hmac.New(sha256.New, key)
+	hash.Write(data)
+	return hash.Sum(nil)
+}
+
+// getHostAddr returns host header if available, otherwise returns host from URL
+func getHostAddr(req *http.Request) string {
+	host := req.Header.Get("host")
+	if host != "" && req.Host != host {
+		return host
+	}
+	if req.Host != "" {
+		return req.Host
+	}
+	return req.URL.Host
+}
+
+// Trim leading and trailing spaces and replace sequential spaces with one space, following Trimall()
+// in http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
+func signV4TrimAll(input string) string {
+	// Compress adjacent spaces (a space is determined by
+	// unicode.IsSpace() internally here) to one space and return
+	return strings.Join(strings.Fields(input), " ")
+}