forked from remote/oauth2
google: Create AWS V4 Signing Utility
Change-Id: I59b4a13ed0433de7dfaa064a0f7dc1f3dd724518
GitHub-Last-Rev: 8cdc6a9ad0
GitHub-Pull-Request: golang/oauth2#467
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/284632
Run-TryBot: Cody Oss <codyoss@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Cody Oss <codyoss@google.com>
Trust: Tyler Bui-Palsulich <tbp@google.com>
Reviewed-by: Cody Oss <codyoss@google.com>
This commit is contained in:
Ryan Kohler
230
google/internal/externalaccount/aws.go
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230
google/internal/externalaccount/aws.go
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package externalaccount
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import (
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"crypto/hmac"
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"crypto/sha256"
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"encoding/hex"
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"errors"
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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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"path"
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"sort"
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"strings"
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"time"
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)
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// RequestSigner is a utility class to sign http requests using a AWS V4 signature.
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type awsRequestSigner struct {
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RegionName string
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AwsSecurityCredentials map[string]string
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}
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const (
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// AWS Signature Version 4 signing algorithm identifier.
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awsAlgorithm = "AWS4-HMAC-SHA256"
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// The termination string for the AWS credential scope value as defined in
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// https://docs.aws.amazon.com/general/latest/gr/sigv4-create-string-to-sign.html
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awsRequestType = "aws4_request"
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// The AWS authorization header name for the security session token if available.
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awsSecurityTokenHeader = "x-amz-security-token"
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// The AWS authorization header name for the auto-generated date.
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awsDateHeader = "x-amz-date"
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awsTimeFormatLong = "20060102T150405Z"
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awsTimeFormatShort = "20060102"
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)
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func getSha256(input []byte) (string, error) {
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hash := sha256.New()
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if _, err := hash.Write(input); err != nil {
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return "", err
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}
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return hex.EncodeToString(hash.Sum(nil)), nil
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}
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func getHmacSha256(key, input []byte) ([]byte, error) {
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hash := hmac.New(sha256.New, key)
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if _, err := hash.Write(input); err != nil {
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return nil, err
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}
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return hash.Sum(nil), nil
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}
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func cloneRequest(r *http.Request) *http.Request {
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r2 := new(http.Request)
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*r2 = *r
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if r.Header != nil {
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r2.Header = make(http.Header, len(r.Header))
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// Find total number of values.
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headerCount := 0
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for _, headerValues := range r.Header {
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headerCount += len(headerValues)
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}
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copiedHeaders := make([]string, headerCount) // shared backing array for headers' values
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for headerKey, headerValues := range r.Header {
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headerCount = copy(copiedHeaders, headerValues)
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r2.Header[headerKey] = copiedHeaders[:headerCount:headerCount]
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copiedHeaders = copiedHeaders[headerCount:]
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}
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}
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return r2
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}
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func canonicalPath(req *http.Request) string {
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result := req.URL.EscapedPath()
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if result == "" {
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return "/"
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}
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return path.Clean(result)
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}
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func canonicalQuery(req *http.Request) string {
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queryValues := req.URL.Query()
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for queryKey := range queryValues {
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sort.Strings(queryValues[queryKey])
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}
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return queryValues.Encode()
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}
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func canonicalHeaders(req *http.Request) (string, string) {
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// Header keys need to be sorted alphabetically.
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var headers []string
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lowerCaseHeaders := make(http.Header)
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for k, v := range req.Header {
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k := strings.ToLower(k)
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if _, ok := lowerCaseHeaders[k]; ok {
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// include additional values
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lowerCaseHeaders[k] = append(lowerCaseHeaders[k], v...)
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} else {
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headers = append(headers, k)
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lowerCaseHeaders[k] = v
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}
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}
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sort.Strings(headers)
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var fullHeaders strings.Builder
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for _, header := range headers {
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headerValue := strings.Join(lowerCaseHeaders[header], ",")
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fullHeaders.WriteString(header)
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fullHeaders.WriteRune(':')
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fullHeaders.WriteString(headerValue)
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fullHeaders.WriteRune('\n')
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}
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return strings.Join(headers, ";"), fullHeaders.String()
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}
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func requestDataHash(req *http.Request) (string, error) {
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var requestData []byte
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if req.Body != nil {
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requestBody, err := req.GetBody()
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if err != nil {
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return "", err
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}
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defer requestBody.Close()
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requestData, err = ioutil.ReadAll(io.LimitReader(requestBody, 1<<20))
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if err != nil {
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return "", err
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}
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}
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return getSha256(requestData)
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}
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func requestHost(req *http.Request) string {
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if req.Host != "" {
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return req.Host
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}
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return req.URL.Host
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}
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func canonicalRequest(req *http.Request, canonicalHeaderColumns, canonicalHeaderData string) (string, error) {
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dataHash, err := requestDataHash(req)
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if err != nil {
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return "", err
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}
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return fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s", req.Method, canonicalPath(req), canonicalQuery(req), canonicalHeaderData, canonicalHeaderColumns, dataHash), nil
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}
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// SignRequest adds the appropriate headers to an http.Request
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// or returns an error if something prevented this.
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func (rs *awsRequestSigner) SignRequest(req *http.Request) error {
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signedRequest := cloneRequest(req)
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timestamp := now()
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signedRequest.Header.Add("host", requestHost(req))
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if securityToken, ok := rs.AwsSecurityCredentials["security_token"]; ok {
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signedRequest.Header.Add(awsSecurityTokenHeader, securityToken)
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}
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if signedRequest.Header.Get("date") == "" {
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signedRequest.Header.Add(awsDateHeader, timestamp.Format(awsTimeFormatLong))
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}
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authorizationCode, err := rs.generateAuthentication(signedRequest, timestamp)
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if err != nil {
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return err
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}
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signedRequest.Header.Set("Authorization", authorizationCode)
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req.Header = signedRequest.Header
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return nil
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}
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func (rs *awsRequestSigner) generateAuthentication(req *http.Request, timestamp time.Time) (string, error) {
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secretAccessKey, ok := rs.AwsSecurityCredentials["secret_access_key"]
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if !ok {
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return "", errors.New("oauth2/google: missing secret_access_key header")
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}
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accessKeyId, ok := rs.AwsSecurityCredentials["access_key_id"]
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if !ok {
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return "", errors.New("oauth2/google: missing access_key_id header")
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}
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canonicalHeaderColumns, canonicalHeaderData := canonicalHeaders(req)
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dateStamp := timestamp.Format(awsTimeFormatShort)
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serviceName := ""
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if splitHost := strings.Split(requestHost(req), "."); len(splitHost) > 0 {
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serviceName = splitHost[0]
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}
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credentialScope := fmt.Sprintf("%s/%s/%s/%s",dateStamp, rs.RegionName, serviceName, awsRequestType)
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requestString, err := canonicalRequest(req, canonicalHeaderColumns, canonicalHeaderData)
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if err != nil {
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return "", err
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}
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requestHash, err := getSha256([]byte(requestString))
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if err != nil{
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return "", err
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}
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stringToSign := fmt.Sprintf("%s\n%s\n%s\n%s", awsAlgorithm, timestamp.Format(awsTimeFormatLong), credentialScope, requestHash)
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signingKey := []byte("AWS4" + secretAccessKey)
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for _, signingInput := range []string{
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dateStamp, rs.RegionName, serviceName, awsRequestType, stringToSign,
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} {
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signingKey, err = getHmacSha256(signingKey, []byte(signingInput))
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if err != nil{
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return "", err
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}
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}
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return fmt.Sprintf("%s Credential=%s/%s, SignedHeaders=%s, Signature=%s", awsAlgorithm, accessKeyId, credentialScope, canonicalHeaderColumns, hex.EncodeToString(signingKey)), nil
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}
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