google/externalaccount: moves externalaccount package out of internal and exports it

go/programmable-auth-design for context. Adds support for user defined supplier methods to return subject tokens and AWS security credentials. Change-Id: I7bc41f8c5202ae933fce516632f5049bbeb3d378 GitHub-Last-Rev: ac519b242f8315df572f1b205b0670f139bfc6c3 GitHub-Pull-Request: golang/oauth2#690 Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/550835 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Leo Siracusa <leosiracusa@google.com> Reviewed-by: Chris Smith <chrisdsmith@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cody Oss <codyoss@google.com>
2024-02-26 18:02:12 +00:00
parent ebe81ad837
commit 95bec95381
23 changed files with 1191 additions and 647 deletions
--- a/google/externalaccount/aws.go
+++ b/google/externalaccount/aws.go
@@ -0,0 +1,578 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package externalaccount
+
+import (
+	"bytes"
+	"context"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+	"sort"
+	"strings"
+	"time"
+
+	"golang.org/x/oauth2"
+)
+
+// AwsSecurityCredentials models AWS security credentials.
+type AwsSecurityCredentials struct {
+	// AccessKeyId is the AWS Access Key ID - Required.
+	AccessKeyID string `json:"AccessKeyID"`
+	// SecretAccessKey is the AWS Secret Access Key - Required.
+	SecretAccessKey string `json:"SecretAccessKey"`
+	// SessionToken is the AWS Session token. This should be provided for temporary AWS security credentials - Optional.
+	SessionToken string `json:"Token"`
+}
+
+// awsRequestSigner is a utility class to sign http requests using a AWS V4 signature.
+type awsRequestSigner struct {
+	RegionName             string
+	AwsSecurityCredentials *AwsSecurityCredentials
+}
+
+// getenv aliases os.Getenv for testing
+var getenv = os.Getenv
+
+const (
+	defaultRegionalCredentialVerificationUrl = "https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15"
+
+	// AWS Signature Version 4 signing algorithm identifier.
+	awsAlgorithm = "AWS4-HMAC-SHA256"
+
+	// The termination string for the AWS credential scope value as defined in
+	// https://docs.aws.amazon.com/general/latest/gr/sigv4-create-string-to-sign.html
+	awsRequestType = "aws4_request"
+
+	// The AWS authorization header name for the security session token if available.
+	awsSecurityTokenHeader = "x-amz-security-token"
+
+	// The name of the header containing the session token for metadata endpoint calls
+	awsIMDSv2SessionTokenHeader = "X-aws-ec2-metadata-token"
+
+	awsIMDSv2SessionTtlHeader = "X-aws-ec2-metadata-token-ttl-seconds"
+
+	awsIMDSv2SessionTtl = "300"
+
+	// The AWS authorization header name for the auto-generated date.
+	awsDateHeader = "x-amz-date"
+
+	// Supported AWS configuration environment variables.
+	awsAccessKeyId     = "AWS_ACCESS_KEY_ID"
+	awsDefaultRegion   = "AWS_DEFAULT_REGION"
+	awsRegion          = "AWS_REGION"
+	awsSecretAccessKey = "AWS_SECRET_ACCESS_KEY"
+	awsSessionToken    = "AWS_SESSION_TOKEN"
+
+	awsTimeFormatLong  = "20060102T150405Z"
+	awsTimeFormatShort = "20060102"
+)
+
+func getSha256(input []byte) (string, error) {
+	hash := sha256.New()
+	if _, err := hash.Write(input); err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(hash.Sum(nil)), nil
+}
+
+func getHmacSha256(key, input []byte) ([]byte, error) {
+	hash := hmac.New(sha256.New, key)
+	if _, err := hash.Write(input); err != nil {
+		return nil, err
+	}
+	return hash.Sum(nil), nil
+}
+
+func cloneRequest(r *http.Request) *http.Request {
+	r2 := new(http.Request)
+	*r2 = *r
+	if r.Header != nil {
+		r2.Header = make(http.Header, len(r.Header))
+
+		// Find total number of values.
+		headerCount := 0
+		for _, headerValues := range r.Header {
+			headerCount += len(headerValues)
+		}
+		copiedHeaders := make([]string, headerCount) // shared backing array for headers' values
+
+		for headerKey, headerValues := range r.Header {
+			headerCount = copy(copiedHeaders, headerValues)
+			r2.Header[headerKey] = copiedHeaders[:headerCount:headerCount]
+			copiedHeaders = copiedHeaders[headerCount:]
+		}
+	}
+	return r2
+}
+
+func canonicalPath(req *http.Request) string {
+	result := req.URL.EscapedPath()
+	if result == "" {
+		return "/"
+	}
+	return path.Clean(result)
+}
+
+func canonicalQuery(req *http.Request) string {
+	queryValues := req.URL.Query()
+	for queryKey := range queryValues {
+		sort.Strings(queryValues[queryKey])
+	}
+	return queryValues.Encode()
+}
+
+func canonicalHeaders(req *http.Request) (string, string) {
+	// Header keys need to be sorted alphabetically.
+	var headers []string
+	lowerCaseHeaders := make(http.Header)
+	for k, v := range req.Header {
+		k := strings.ToLower(k)
+		if _, ok := lowerCaseHeaders[k]; ok {
+			// include additional values
+			lowerCaseHeaders[k] = append(lowerCaseHeaders[k], v...)
+		} else {
+			headers = append(headers, k)
+			lowerCaseHeaders[k] = v
+		}
+	}
+	sort.Strings(headers)
+
+	var fullHeaders bytes.Buffer
+	for _, header := range headers {
+		headerValue := strings.Join(lowerCaseHeaders[header], ",")
+		fullHeaders.WriteString(header)
+		fullHeaders.WriteRune(':')
+		fullHeaders.WriteString(headerValue)
+		fullHeaders.WriteRune('\n')
+	}
+
+	return strings.Join(headers, ";"), fullHeaders.String()
+}
+
+func requestDataHash(req *http.Request) (string, error) {
+	var requestData []byte
+	if req.Body != nil {
+		requestBody, err := req.GetBody()
+		if err != nil {
+			return "", err
+		}
+		defer requestBody.Close()
+
+		requestData, err = ioutil.ReadAll(io.LimitReader(requestBody, 1<<20))
+		if err != nil {
+			return "", err
+		}
+	}
+
+	return getSha256(requestData)
+}
+
+func requestHost(req *http.Request) string {
+	if req.Host != "" {
+		return req.Host
+	}
+	return req.URL.Host
+}
+
+func canonicalRequest(req *http.Request, canonicalHeaderColumns, canonicalHeaderData string) (string, error) {
+	dataHash, err := requestDataHash(req)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%s\n%s\n%s\n%s\n%s\n%s", req.Method, canonicalPath(req), canonicalQuery(req), canonicalHeaderData, canonicalHeaderColumns, dataHash), nil
+}
+
+// SignRequest adds the appropriate headers to an http.Request
+// or returns an error if something prevented this.
+func (rs *awsRequestSigner) SignRequest(req *http.Request) error {
+	signedRequest := cloneRequest(req)
+	timestamp := now()
+
+	signedRequest.Header.Add("host", requestHost(req))
+
+	if rs.AwsSecurityCredentials.SessionToken != "" {
+		signedRequest.Header.Add(awsSecurityTokenHeader, rs.AwsSecurityCredentials.SessionToken)
+	}
+
+	if signedRequest.Header.Get("date") == "" {
+		signedRequest.Header.Add(awsDateHeader, timestamp.Format(awsTimeFormatLong))
+	}
+
+	authorizationCode, err := rs.generateAuthentication(signedRequest, timestamp)
+	if err != nil {
+		return err
+	}
+	signedRequest.Header.Set("Authorization", authorizationCode)
+
+	req.Header = signedRequest.Header
+	return nil
+}
+
+func (rs *awsRequestSigner) generateAuthentication(req *http.Request, timestamp time.Time) (string, error) {
+	canonicalHeaderColumns, canonicalHeaderData := canonicalHeaders(req)
+
+	dateStamp := timestamp.Format(awsTimeFormatShort)
+	serviceName := ""
+	if splitHost := strings.Split(requestHost(req), "."); len(splitHost) > 0 {
+		serviceName = splitHost[0]
+	}
+
+	credentialScope := fmt.Sprintf("%s/%s/%s/%s", dateStamp, rs.RegionName, serviceName, awsRequestType)
+
+	requestString, err := canonicalRequest(req, canonicalHeaderColumns, canonicalHeaderData)
+	if err != nil {
+		return "", err
+	}
+	requestHash, err := getSha256([]byte(requestString))
+	if err != nil {
+		return "", err
+	}
+
+	stringToSign := fmt.Sprintf("%s\n%s\n%s\n%s", awsAlgorithm, timestamp.Format(awsTimeFormatLong), credentialScope, requestHash)
+
+	signingKey := []byte("AWS4" + rs.AwsSecurityCredentials.SecretAccessKey)
+	for _, signingInput := range []string{
+		dateStamp, rs.RegionName, serviceName, awsRequestType, stringToSign,
+	} {
+		signingKey, err = getHmacSha256(signingKey, []byte(signingInput))
+		if err != nil {
+			return "", err
+		}
+	}
+
+	return fmt.Sprintf("%s Credential=%s/%s, SignedHeaders=%s, Signature=%s", awsAlgorithm, rs.AwsSecurityCredentials.AccessKeyID, credentialScope, canonicalHeaderColumns, hex.EncodeToString(signingKey)), nil
+}
+
+type awsCredentialSource struct {
+	environmentID                  string
+	regionURL                      string
+	regionalCredVerificationURL    string
+	credVerificationURL            string
+	imdsv2SessionTokenURL          string
+	targetResource                 string
+	requestSigner                  *awsRequestSigner
+	region                         string
+	ctx                            context.Context
+	client                         *http.Client
+	awsSecurityCredentialsSupplier AwsSecurityCredentialsSupplier
+	supplierOptions                SupplierOptions
+}
+
+type awsRequestHeader struct {
+	Key   string `json:"key"`
+	Value string `json:"value"`
+}
+
+type awsRequest struct {
+	URL     string             `json:"url"`
+	Method  string             `json:"method"`
+	Headers []awsRequestHeader `json:"headers"`
+}
+
+func (cs awsCredentialSource) doRequest(req *http.Request) (*http.Response, error) {
+	if cs.client == nil {
+		cs.client = oauth2.NewClient(cs.ctx, nil)
+	}
+	return cs.client.Do(req.WithContext(cs.ctx))
+}
+
+func canRetrieveRegionFromEnvironment() bool {
+	// The AWS region can be provided through AWS_REGION or AWS_DEFAULT_REGION. Only one is
+	// required.
+	return getenv(awsRegion) != "" || getenv(awsDefaultRegion) != ""
+}
+
+func canRetrieveSecurityCredentialFromEnvironment() bool {
+	// Check if both AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are available.
+	return getenv(awsAccessKeyId) != "" && getenv(awsSecretAccessKey) != ""
+}
+
+func (cs awsCredentialSource) shouldUseMetadataServer() bool {
+	return cs.awsSecurityCredentialsSupplier == nil && (!canRetrieveRegionFromEnvironment() || !canRetrieveSecurityCredentialFromEnvironment())
+}
+
+func (cs awsCredentialSource) credentialSourceType() string {
+	if cs.awsSecurityCredentialsSupplier != nil {
+		return "programmatic"
+	}
+	return "aws"
+}
+
+func (cs awsCredentialSource) subjectToken() (string, error) {
+	// Set Defaults
+	if cs.regionalCredVerificationURL == "" {
+		cs.regionalCredVerificationURL = defaultRegionalCredentialVerificationUrl
+	}
+	if cs.requestSigner == nil {
+		headers := make(map[string]string)
+		if cs.shouldUseMetadataServer() {
+			awsSessionToken, err := cs.getAWSSessionToken()
+			if err != nil {
+				return "", err
+			}
+
+			if awsSessionToken != "" {
+				headers[awsIMDSv2SessionTokenHeader] = awsSessionToken
+			}
+		}
+
+		awsSecurityCredentials, err := cs.getSecurityCredentials(headers)
+		if err != nil {
+			return "", err
+		}
+		cs.region, err = cs.getRegion(headers)
+		if err != nil {
+			return "", err
+		}
+
+		cs.requestSigner = &awsRequestSigner{
+			RegionName:             cs.region,
+			AwsSecurityCredentials: awsSecurityCredentials,
+		}
+	}
+
+	// Generate the signed request to AWS STS GetCallerIdentity API.
+	// Use the required regional endpoint. Otherwise, the request will fail.
+	req, err := http.NewRequest("POST", strings.Replace(cs.regionalCredVerificationURL, "{region}", cs.region, 1), nil)
+	if err != nil {
+		return "", err
+	}
+	// The full, canonical resource name of the workload identity pool
+	// provider, with or without the HTTPS prefix.
+	// Including this header as part of the signature is recommended to
+	// ensure data integrity.
+	if cs.targetResource != "" {
+		req.Header.Add("x-goog-cloud-target-resource", cs.targetResource)
+	}
+	cs.requestSigner.SignRequest(req)
+
+	/*
+	   The GCP STS endpoint expects the headers to be formatted as:
+	   # [
+	   #   {key: 'x-amz-date', value: '...'},
+	   #   {key: 'Authorization', value: '...'},
+	   #   ...
+	   # ]
+	   # And then serialized as:
+	   # quote(json.dumps({
+	   #   url: '...',
+	   #   method: 'POST',
+	   #   headers: [{key: 'x-amz-date', value: '...'}, ...]
+	   # }))
+	*/
+
+	awsSignedReq := awsRequest{
+		URL:    req.URL.String(),
+		Method: "POST",
+	}
+	for headerKey, headerList := range req.Header {
+		for _, headerValue := range headerList {
+			awsSignedReq.Headers = append(awsSignedReq.Headers, awsRequestHeader{
+				Key:   headerKey,
+				Value: headerValue,
+			})
+		}
+	}
+	sort.Slice(awsSignedReq.Headers, func(i, j int) bool {
+		headerCompare := strings.Compare(awsSignedReq.Headers[i].Key, awsSignedReq.Headers[j].Key)
+		if headerCompare == 0 {
+			return strings.Compare(awsSignedReq.Headers[i].Value, awsSignedReq.Headers[j].Value) < 0
+		}
+		return headerCompare < 0
+	})
+
+	result, err := json.Marshal(awsSignedReq)
+	if err != nil {
+		return "", err
+	}
+	return url.QueryEscape(string(result)), nil
+}
+
+func (cs *awsCredentialSource) getAWSSessionToken() (string, error) {
+	if cs.imdsv2SessionTokenURL == "" {
+		return "", nil
+	}
+
+	req, err := http.NewRequest("PUT", cs.imdsv2SessionTokenURL, nil)
+	if err != nil {
+		return "", err
+	}
+
+	req.Header.Add(awsIMDSv2SessionTtlHeader, awsIMDSv2SessionTtl)
+
+	resp, err := cs.doRequest(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return "", err
+	}
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS session token - %s", string(respBody))
+	}
+
+	return string(respBody), nil
+}
+
+func (cs *awsCredentialSource) getRegion(headers map[string]string) (string, error) {
+	if cs.awsSecurityCredentialsSupplier != nil {
+		return cs.awsSecurityCredentialsSupplier.AwsRegion(cs.ctx, cs.supplierOptions)
+	}
+	if canRetrieveRegionFromEnvironment() {
+		if envAwsRegion := getenv(awsRegion); envAwsRegion != "" {
+			cs.region = envAwsRegion
+			return envAwsRegion, nil
+		}
+		return getenv("AWS_DEFAULT_REGION"), nil
+	}
+
+	if cs.regionURL == "" {
+		return "", errors.New("oauth2/google/externalaccount: unable to determine AWS region")
+	}
+
+	req, err := http.NewRequest("GET", cs.regionURL, nil)
+	if err != nil {
+		return "", err
+	}
+
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+
+	resp, err := cs.doRequest(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return "", err
+	}
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS region - %s", string(respBody))
+	}
+
+	// This endpoint will return the region in format: us-east-2b.
+	// Only the us-east-2 part should be used.
+	respBodyEnd := 0
+	if len(respBody) > 1 {
+		respBodyEnd = len(respBody) - 1
+	}
+	return string(respBody[:respBodyEnd]), nil
+}
+
+func (cs *awsCredentialSource) getSecurityCredentials(headers map[string]string) (result *AwsSecurityCredentials, err error) {
+	if cs.awsSecurityCredentialsSupplier != nil {
+		return cs.awsSecurityCredentialsSupplier.AwsSecurityCredentials(cs.ctx, cs.supplierOptions)
+	}
+	if canRetrieveSecurityCredentialFromEnvironment() {
+		return &AwsSecurityCredentials{
+			AccessKeyID:     getenv(awsAccessKeyId),
+			SecretAccessKey: getenv(awsSecretAccessKey),
+			SessionToken:    getenv(awsSessionToken),
+		}, nil
+	}
+
+	roleName, err := cs.getMetadataRoleName(headers)
+	if err != nil {
+		return
+	}
+
+	credentials, err := cs.getMetadataSecurityCredentials(roleName, headers)
+	if err != nil {
+		return
+	}
+
+	if credentials.AccessKeyID == "" {
+		return result, errors.New("oauth2/google/externalaccount: missing AccessKeyId credential")
+	}
+
+	if credentials.SecretAccessKey == "" {
+		return result, errors.New("oauth2/google/externalaccount: missing SecretAccessKey credential")
+	}
+
+	return &credentials, nil
+}
+
+func (cs *awsCredentialSource) getMetadataSecurityCredentials(roleName string, headers map[string]string) (AwsSecurityCredentials, error) {
+	var result AwsSecurityCredentials
+
+	req, err := http.NewRequest("GET", fmt.Sprintf("%s/%s", cs.credVerificationURL, roleName), nil)
+	if err != nil {
+		return result, err
+	}
+	req.Header.Add("Content-Type", "application/json")
+
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+
+	resp, err := cs.doRequest(req)
+	if err != nil {
+		return result, err
+	}
+	defer resp.Body.Close()
+
+	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return result, err
+	}
+
+	if resp.StatusCode != 200 {
+		return result, fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS security credentials - %s", string(respBody))
+	}
+
+	err = json.Unmarshal(respBody, &result)
+	return result, err
+}
+
+func (cs *awsCredentialSource) getMetadataRoleName(headers map[string]string) (string, error) {
+	if cs.credVerificationURL == "" {
+		return "", errors.New("oauth2/google/externalaccount: unable to determine the AWS metadata server security credentials endpoint")
+	}
+
+	req, err := http.NewRequest("GET", cs.credVerificationURL, nil)
+	if err != nil {
+		return "", err
+	}
+
+	for name, value := range headers {
+		req.Header.Add(name, value)
+	}
+
+	resp, err := cs.doRequest(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return "", err
+	}
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("oauth2/google/externalaccount: unable to retrieve AWS role name - %s", string(respBody))
+	}
+
+	return string(respBody), nil
+}