google/internal/externalaccount: Added check for aws region and security credential environment variables before aws metadata call

Adds check for aws values in environment variables before the metadata server is called to prevent unnecessary off box calls. See https://github.com/googleapis/google-auth-library-java/pull/1100 for same change in java library. Change-Id: Ie86a899be88c38d3fcbbe377f9bf30a7a66530c0 GitHub-Last-Rev: bcab69572cb0dca4c7c6426203d4232e6e89d8db GitHub-Pull-Request: golang/oauth2#612 Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/453715 Reviewed-by: Leo Siracusa <leosiracusa@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Run-TryBot: Cody Oss <codyoss@google.com> Auto-Submit: Cody Oss <codyoss@google.com> Reviewed-by: Cody Oss <codyoss@google.com>
2025-07-21 00:00:09 +08:00 · 2022-11-30 16:37:52 +00:00 · 2022-11-30 16:37:52 +00:00 · 510acbce1f
commit 510acbce1f
parent ec4a9b2ff2
2 changed files with 277 additions and 49 deletions
--- a/google/internal/externalaccount/aws.go
+++ b/google/internal/externalaccount/aws.go
@ -62,6 +62,13 @@ const (
 	// 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"
 )
@ -317,17 +324,34 @@ func (cs awsCredentialSource) doRequest(req *http.Request) (*http.Response, erro
 	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 shouldUseMetadataServer() bool {
+	return !canRetrieveRegionFromEnvironment() || !canRetrieveSecurityCredentialFromEnvironment()
+}
+
 func (cs awsCredentialSource) subjectToken() (string, error) {
 	if cs.requestSigner == nil {
+		headers := make(map[string]string)
+		if shouldUseMetadataServer() {
 			awsSessionToken, err := cs.getAWSSessionToken()
 			if err != nil {
 				return "", err
 			}

-		headers := make(map[string]string)
 			if awsSessionToken != "" {
 				headers[awsIMDSv2SessionTokenHeader] = awsSessionToken
 			}
+		}

 		awsSecurityCredentials, err := cs.getSecurityCredentials(headers)
 		if err != nil {
@ -432,11 +456,11 @@ func (cs *awsCredentialSource) getAWSSessionToken() (string, error) {
 }

 func (cs *awsCredentialSource) getRegion(headers map[string]string) (string, error) {
-	if envAwsRegion := getenv("AWS_REGION"); envAwsRegion != "" {
+	if canRetrieveRegionFromEnvironment() {
+		if envAwsRegion := getenv(awsRegion); envAwsRegion != "" {
 			return envAwsRegion, nil
 		}
-	if envAwsRegion := getenv("AWS_DEFAULT_REGION"); envAwsRegion != "" {
-		return envAwsRegion, nil
+		return getenv("AWS_DEFAULT_REGION"), nil
 	}

 	if cs.RegionURL == "" {
@ -477,15 +501,13 @@ func (cs *awsCredentialSource) getRegion(headers map[string]string) (string, err
 }

 func (cs *awsCredentialSource) getSecurityCredentials(headers map[string]string) (result awsSecurityCredentials, err error) {
-	if accessKeyID := getenv("AWS_ACCESS_KEY_ID"); accessKeyID != "" {
-		if secretAccessKey := getenv("AWS_SECRET_ACCESS_KEY"); secretAccessKey != "" {
+	if canRetrieveSecurityCredentialFromEnvironment() {
 		return awsSecurityCredentials{
-				AccessKeyID:     accessKeyID,
-				SecretAccessKey: secretAccessKey,
-				SecurityToken:   getenv("AWS_SESSION_TOKEN"),
+			AccessKeyID:     getenv(awsAccessKeyId),
+			SecretAccessKey: getenv(awsSecretAccessKey),
+			SecurityToken:   getenv(awsSessionToken),
 		}, nil
 	}
-	}

 	roleName, err := cs.getMetadataRoleName(headers)
 	if err != nil {
--- a/google/internal/externalaccount/aws_test.go
+++ b/google/internal/externalaccount/aws_test.go
@ -474,6 +474,38 @@ func createDefaultAwsTestServer() *testAwsServer {
 	)
 }

+func createDefaultAwsTestServerWithImdsv2(t *testing.T) *testAwsServer {
+	validateSessionTokenHeaders := func(r *http.Request) {
+		if r.URL.Path == "/latest/api/token" {
+			headerValue := r.Header.Get(awsIMDSv2SessionTtlHeader)
+			if headerValue != awsIMDSv2SessionTtl {
+				t.Errorf("%q = \n%q\n want \n%q", awsIMDSv2SessionTtlHeader, headerValue, awsIMDSv2SessionTtl)
+			}
+		} else {
+			headerValue := r.Header.Get(awsIMDSv2SessionTokenHeader)
+			if headerValue != "sessiontoken" {
+				t.Errorf("%q = \n%q\n want \n%q", awsIMDSv2SessionTokenHeader, headerValue, "sessiontoken")
+			}
+		}
+	}
+
+	return createAwsTestServer(
+		"/latest/meta-data/iam/security-credentials",
+		"/latest/meta-data/placement/availability-zone",
+		"https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15",
+		"/latest/api/token",
+		"gcp-aws-role",
+		"us-east-2b",
+		map[string]string{
+			"SecretAccessKey": secretAccessKey,
+			"AccessKeyId":     accessKeyID,
+			"Token":           securityToken,
+		},
+		"sessiontoken",
+		validateSessionTokenHeaders,
+	)
+}
+
 func (server *testAwsServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	switch p := r.URL.Path; p {
 	case server.url:
@ -597,35 +629,7 @@ func TestAWSCredential_BasicRequest(t *testing.T) {
 }

 func TestAWSCredential_IMDSv2(t *testing.T) {
-	validateSessionTokenHeaders := func(r *http.Request) {
-		if r.URL.Path == "/latest/api/token" {
-			headerValue := r.Header.Get(awsIMDSv2SessionTtlHeader)
-			if headerValue != awsIMDSv2SessionTtl {
-				t.Errorf("%q = \n%q\n want \n%q", awsIMDSv2SessionTtlHeader, headerValue, awsIMDSv2SessionTtl)
-			}
-		} else {
-			headerValue := r.Header.Get(awsIMDSv2SessionTokenHeader)
-			if headerValue != "sessiontoken" {
-				t.Errorf("%q = \n%q\n want \n%q", awsIMDSv2SessionTokenHeader, headerValue, "sessiontoken")
-			}
-		}
-	}
-
-	server := createAwsTestServer(
-		"/latest/meta-data/iam/security-credentials",
-		"/latest/meta-data/placement/availability-zone",
-		"https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15",
-		"/latest/api/token",
-		"gcp-aws-role",
-		"us-east-2b",
-		map[string]string{
-			"SecretAccessKey": secretAccessKey,
-			"AccessKeyId":     accessKeyID,
-			"Token":           securityToken,
-		},
-		"sessiontoken",
-		validateSessionTokenHeaders,
-	)
+	server := createDefaultAwsTestServerWithImdsv2(t)
 	ts := httptest.NewServer(server)
 	tsURL, err := neturl.Parse(ts.URL)
 	if err != nil {
@ -1152,6 +1156,208 @@ func TestAWSCredential_RequestWithBadFinalCredentialURL(t *testing.T) {
 	}
 }

+func TestAWSCredential_ShouldNotCallMetadataEndpointWhenCredsAreInEnv(t *testing.T) {
+	server := createDefaultAwsTestServer()
+	ts := httptest.NewServer(server)
+	tsURL, err := neturl.Parse(ts.URL)
+	if err != nil {
+		t.Fatalf("couldn't parse httptest servername")
+	}
+
+	metadataTs := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		t.Error("Metadata server should not have been called.")
+	}))
+
+	tfc := testFileConfig
+	tfc.CredentialSource = server.getCredentialSource(ts.URL)
+	tfc.CredentialSource.IMDSv2SessionTokenURL = metadataTs.URL
+
+	oldGetenv := getenv
+	oldNow := now
+	oldValidHostnames := validHostnames
+	defer func() {
+		getenv = oldGetenv
+		now = oldNow
+		validHostnames = oldValidHostnames
+	}()
+	getenv = setEnvironment(map[string]string{
+		"AWS_ACCESS_KEY_ID":     "AKIDEXAMPLE",
+		"AWS_SECRET_ACCESS_KEY": "wJalrXUtnFEMI/K7MDENG+bPxRfiCYEXAMPLEKEY",
+		"AWS_REGION":            "us-west-1",
+	})
+	now = setTime(defaultTime)
+	validHostnames = []string{tsURL.Hostname()}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	out, err := base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+
+	expected := getExpectedSubjectToken(
+		"https://sts.us-west-1.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15",
+		"us-west-1",
+		"AKIDEXAMPLE",
+		"wJalrXUtnFEMI/K7MDENG+bPxRfiCYEXAMPLEKEY",
+		"",
+	)
+
+	if got, want := out, expected; !reflect.DeepEqual(got, want) {
+		t.Errorf("subjectToken = \n%q\n want \n%q", got, want)
+	}
+}
+
+func TestAWSCredential_ShouldCallMetadataEndpointWhenNoRegion(t *testing.T) {
+	server := createDefaultAwsTestServerWithImdsv2(t)
+	ts := httptest.NewServer(server)
+	tsURL, err := neturl.Parse(ts.URL)
+	if err != nil {
+		t.Fatalf("couldn't parse httptest servername")
+	}
+
+	tfc := testFileConfig
+	tfc.CredentialSource = server.getCredentialSource(ts.URL)
+
+	oldGetenv := getenv
+	oldNow := now
+	oldValidHostnames := validHostnames
+	defer func() {
+		getenv = oldGetenv
+		now = oldNow
+		validHostnames = oldValidHostnames
+	}()
+	getenv = setEnvironment(map[string]string{
+		"AWS_ACCESS_KEY_ID":     accessKeyID,
+		"AWS_SECRET_ACCESS_KEY": secretAccessKey,
+	})
+	now = setTime(defaultTime)
+	validHostnames = []string{tsURL.Hostname()}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	out, err := base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+
+	expected := getExpectedSubjectToken(
+		"https://sts.us-east-2.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15",
+		"us-east-2",
+		accessKeyID,
+		secretAccessKey,
+		"",
+	)
+
+	if got, want := out, expected; !reflect.DeepEqual(got, want) {
+		t.Errorf("subjectToken = \n%q\n want \n%q", got, want)
+	}
+}
+
+func TestAWSCredential_ShouldCallMetadataEndpointWhenNoAccessKey(t *testing.T) {
+	server := createDefaultAwsTestServerWithImdsv2(t)
+	ts := httptest.NewServer(server)
+	tsURL, err := neturl.Parse(ts.URL)
+	if err != nil {
+		t.Fatalf("couldn't parse httptest servername")
+	}
+
+	tfc := testFileConfig
+	tfc.CredentialSource = server.getCredentialSource(ts.URL)
+
+	oldGetenv := getenv
+	oldNow := now
+	oldValidHostnames := validHostnames
+	defer func() {
+		getenv = oldGetenv
+		now = oldNow
+		validHostnames = oldValidHostnames
+	}()
+	getenv = setEnvironment(map[string]string{
+		"AWS_SECRET_ACCESS_KEY": "wJalrXUtnFEMI/K7MDENG+bPxRfiCYEXAMPLEKEY",
+		"AWS_REGION":            "us-west-1",
+	})
+	now = setTime(defaultTime)
+	validHostnames = []string{tsURL.Hostname()}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	out, err := base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+
+	expected := getExpectedSubjectToken(
+		"https://sts.us-west-1.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15",
+		"us-west-1",
+		accessKeyID,
+		secretAccessKey,
+		securityToken,
+	)
+
+	if got, want := out, expected; !reflect.DeepEqual(got, want) {
+		t.Errorf("subjectToken = \n%q\n want \n%q", got, want)
+	}
+}
+
+func TestAWSCredential_ShouldCallMetadataEndpointWhenNoSecretAccessKey(t *testing.T) {
+	server := createDefaultAwsTestServerWithImdsv2(t)
+	ts := httptest.NewServer(server)
+	tsURL, err := neturl.Parse(ts.URL)
+	if err != nil {
+		t.Fatalf("couldn't parse httptest servername")
+	}
+
+	tfc := testFileConfig
+	tfc.CredentialSource = server.getCredentialSource(ts.URL)
+
+	oldGetenv := getenv
+	oldNow := now
+	oldValidHostnames := validHostnames
+	defer func() {
+		getenv = oldGetenv
+		now = oldNow
+		validHostnames = oldValidHostnames
+	}()
+	getenv = setEnvironment(map[string]string{
+		"AWS_ACCESS_KEY_ID": "AKIDEXAMPLE",
+		"AWS_REGION":        "us-west-1",
+	})
+	now = setTime(defaultTime)
+	validHostnames = []string{tsURL.Hostname()}
+
+	base, err := tfc.parse(context.Background())
+	if err != nil {
+		t.Fatalf("parse() failed %v", err)
+	}
+
+	out, err := base.subjectToken()
+	if err != nil {
+		t.Fatalf("retrieveSubjectToken() failed: %v", err)
+	}
+
+	expected := getExpectedSubjectToken(
+		"https://sts.us-west-1.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15",
+		"us-west-1",
+		accessKeyID,
+		secretAccessKey,
+		securityToken,
+	)
+
+	if got, want := out, expected; !reflect.DeepEqual(got, want) {
+		t.Errorf("subjectToken = \n%q\n want \n%q", got, want)
+	}
+}
+
 func TestAWSCredential_Validations(t *testing.T) {
 	var metadataServerValidityTests = []struct {
 		name       string