forked from TrueCloudLab/restic
303 lines
9 KiB
Go
303 lines
9 KiB
Go
/*
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* Minio Go Library for Amazon S3 Compatible Cloud Storage (C) 2015 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 minio
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import (
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"bytes"
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"encoding/hex"
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"net/http"
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"sort"
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"strconv"
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"strings"
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"time"
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)
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// Signature and API related constants.
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const (
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signV4Algorithm = "AWS4-HMAC-SHA256"
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iso8601DateFormat = "20060102T150405Z"
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yyyymmdd = "20060102"
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)
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///
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/// Excerpts from @lsegal -
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/// https://github.com/aws/aws-sdk-js/issues/659#issuecomment-120477258.
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///
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/// User-Agent:
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///
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/// This is ignored from signing because signing this causes
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/// problems with generating pre-signed URLs (that are executed
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/// by other agents) or when customers pass requests through
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/// proxies, which may modify the user-agent.
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///
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/// Content-Length:
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///
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/// This is ignored from signing because generating a pre-signed
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/// URL should not provide a content-length constraint,
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/// specifically when vending a S3 pre-signed PUT URL. The
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/// corollary to this is that when sending regular requests
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/// (non-pre-signed), the signature contains a checksum of the
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/// body, which implicitly validates the payload length (since
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/// changing the number of bytes would change the checksum)
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/// and therefore this header is not valuable in the signature.
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///
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/// Content-Type:
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///
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/// Signing this header causes quite a number of problems in
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/// browser environments, where browsers like to modify and
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/// normalize the content-type header in different ways. There is
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/// more information on this in https://goo.gl/2E9gyy. Avoiding
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/// this field simplifies logic and reduces the possibility of
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/// future bugs.
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///
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/// Authorization:
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///
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/// Is skipped for obvious reasons
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///
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var ignoredHeaders = map[string]bool{
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"Authorization": true,
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"Content-Type": true,
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"Content-Length": true,
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"User-Agent": true,
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}
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// getSigningKey hmac seed to calculate final signature.
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func getSigningKey(secret, loc string, t time.Time) []byte {
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date := sumHMAC([]byte("AWS4"+secret), []byte(t.Format(yyyymmdd)))
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location := sumHMAC(date, []byte(loc))
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service := sumHMAC(location, []byte("s3"))
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signingKey := sumHMAC(service, []byte("aws4_request"))
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return signingKey
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}
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// getSignature final signature in hexadecimal form.
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func getSignature(signingKey []byte, stringToSign string) string {
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return hex.EncodeToString(sumHMAC(signingKey, []byte(stringToSign)))
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}
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// getScope generate a string of a specific date, an AWS region, and a
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// service.
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func getScope(location string, t time.Time) string {
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scope := strings.Join([]string{
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t.Format(yyyymmdd),
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location,
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"s3",
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"aws4_request",
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}, "/")
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return scope
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}
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// getCredential generate a credential string.
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func getCredential(accessKeyID, location string, t time.Time) string {
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scope := getScope(location, t)
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return accessKeyID + "/" + scope
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}
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// getHashedPayload get the hexadecimal value of the SHA256 hash of
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// the request payload.
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func getHashedPayload(req http.Request) string {
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hashedPayload := req.Header.Get("X-Amz-Content-Sha256")
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if hashedPayload == "" {
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// Presign does not have a payload, use S3 recommended value.
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hashedPayload = "UNSIGNED-PAYLOAD"
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}
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return hashedPayload
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}
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// getCanonicalHeaders generate a list of request headers for
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// signature.
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func getCanonicalHeaders(req http.Request) string {
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var headers []string
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vals := make(map[string][]string)
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for k, vv := range req.Header {
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if _, ok := ignoredHeaders[http.CanonicalHeaderKey(k)]; ok {
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continue // ignored header
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}
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headers = append(headers, strings.ToLower(k))
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vals[strings.ToLower(k)] = vv
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}
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headers = append(headers, "host")
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sort.Strings(headers)
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var buf bytes.Buffer
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// Save all the headers in canonical form <header>:<value> newline
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// separated for each header.
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for _, k := range headers {
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buf.WriteString(k)
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buf.WriteByte(':')
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switch {
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case k == "host":
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buf.WriteString(req.URL.Host)
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fallthrough
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default:
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for idx, v := range vals[k] {
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if idx > 0 {
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buf.WriteByte(',')
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}
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buf.WriteString(v)
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}
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buf.WriteByte('\n')
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}
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}
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return buf.String()
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}
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// getSignedHeaders generate all signed request headers.
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// i.e lexically sorted, semicolon-separated list of lowercase
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// request header names.
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func getSignedHeaders(req http.Request) string {
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var headers []string
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for k := range req.Header {
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if _, ok := ignoredHeaders[http.CanonicalHeaderKey(k)]; ok {
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continue // Ignored header found continue.
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}
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headers = append(headers, strings.ToLower(k))
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}
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headers = append(headers, "host")
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sort.Strings(headers)
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return strings.Join(headers, ";")
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}
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// getCanonicalRequest generate a canonical request of style.
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//
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// canonicalRequest =
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// <HTTPMethod>\n
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// <CanonicalURI>\n
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// <CanonicalQueryString>\n
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// <CanonicalHeaders>\n
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// <SignedHeaders>\n
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// <HashedPayload>
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func getCanonicalRequest(req http.Request) string {
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req.URL.RawQuery = strings.Replace(req.URL.Query().Encode(), "+", "%20", -1)
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canonicalRequest := strings.Join([]string{
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req.Method,
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urlEncodePath(req.URL.Path),
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req.URL.RawQuery,
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getCanonicalHeaders(req),
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getSignedHeaders(req),
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getHashedPayload(req),
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}, "\n")
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return canonicalRequest
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}
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// getStringToSign a string based on selected query values.
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func getStringToSignV4(t time.Time, location, canonicalRequest string) string {
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stringToSign := signV4Algorithm + "\n" + t.Format(iso8601DateFormat) + "\n"
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stringToSign = stringToSign + getScope(location, t) + "\n"
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stringToSign = stringToSign + hex.EncodeToString(sum256([]byte(canonicalRequest)))
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return stringToSign
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}
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// preSignV4 presign the request, in accordance with
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// http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html.
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func preSignV4(req http.Request, accessKeyID, secretAccessKey, location string, expires int64) *http.Request {
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// Presign is not needed for anonymous credentials.
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if accessKeyID == "" || secretAccessKey == "" {
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return &req
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}
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// Initial time.
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t := time.Now().UTC()
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// Get credential string.
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credential := getCredential(accessKeyID, location, t)
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// Get all signed headers.
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signedHeaders := getSignedHeaders(req)
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// Set URL query.
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query := req.URL.Query()
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query.Set("X-Amz-Algorithm", signV4Algorithm)
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query.Set("X-Amz-Date", t.Format(iso8601DateFormat))
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query.Set("X-Amz-Expires", strconv.FormatInt(expires, 10))
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query.Set("X-Amz-SignedHeaders", signedHeaders)
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query.Set("X-Amz-Credential", credential)
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req.URL.RawQuery = query.Encode()
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// Get canonical request.
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canonicalRequest := getCanonicalRequest(req)
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// Get string to sign from canonical request.
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stringToSign := getStringToSignV4(t, location, canonicalRequest)
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// Gext hmac signing key.
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signingKey := getSigningKey(secretAccessKey, location, t)
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// Calculate signature.
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signature := getSignature(signingKey, stringToSign)
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// Add signature header to RawQuery.
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req.URL.RawQuery += "&X-Amz-Signature=" + signature
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return &req
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}
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// postPresignSignatureV4 - presigned signature for PostPolicy
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// requests.
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func postPresignSignatureV4(policyBase64 string, t time.Time, secretAccessKey, location string) string {
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// Get signining key.
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signingkey := getSigningKey(secretAccessKey, location, t)
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// Calculate signature.
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signature := getSignature(signingkey, policyBase64)
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return signature
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}
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// signV4 sign the request before Do(), in accordance with
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// http://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html.
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func signV4(req http.Request, accessKeyID, secretAccessKey, location string) *http.Request {
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// Signature calculation is not needed for anonymous credentials.
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if accessKeyID == "" || secretAccessKey == "" {
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return &req
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}
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// Initial time.
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t := time.Now().UTC()
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// Set x-amz-date.
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req.Header.Set("X-Amz-Date", t.Format(iso8601DateFormat))
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// Get canonical request.
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canonicalRequest := getCanonicalRequest(req)
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// Get string to sign from canonical request.
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stringToSign := getStringToSignV4(t, location, canonicalRequest)
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// Get hmac signing key.
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signingKey := getSigningKey(secretAccessKey, location, t)
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// Get credential string.
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credential := getCredential(accessKeyID, location, t)
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// Get all signed headers.
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signedHeaders := getSignedHeaders(req)
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// Calculate signature.
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signature := getSignature(signingKey, stringToSign)
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// If regular request, construct the final authorization header.
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parts := []string{
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signV4Algorithm + " Credential=" + credential,
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"SignedHeaders=" + signedHeaders,
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"Signature=" + signature,
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}
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// Set authorization header.
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auth := strings.Join(parts, ", ")
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req.Header.Set("Authorization", auth)
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return &req
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}
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