Retry on transient failures during AWS IAM auth login attempts (#8727)

* use retryer for failed aws auth attempts

* fixes from testing

builtin/credential/aws/path_login.go

@@ -16,11 +16,13 @@ import (
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
+	awsClient "github.com/aws/aws-sdk-go/aws/client"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/aws/aws-sdk-go/service/iam"
 	"github.com/fullsailor/pkcs7"
 	"github.com/hashicorp/errwrap"
 	cleanhttp "github.com/hashicorp/go-cleanhttp"
+	"github.com/hashicorp/go-retryablehttp"
 	uuid "github.com/hashicorp/go-uuid"
 	"github.com/hashicorp/vault/sdk/framework"
 	"github.com/hashicorp/vault/sdk/helper/awsutil"
@@ -35,6 +37,10 @@ const (
 	iamAuthType                   = "iam"
 	ec2AuthType                   = "ec2"
 	ec2EntityType                 = "ec2_instance"
+
+	// Retry configuration
+	retryWaitMin = 500 * time.Millisecond
+	retryWaitMax = 30 * time.Second
 )
 
 func (b *backend) pathLogin() *framework.Path {
@@ -1198,6 +1204,7 @@ func (b *backend) pathLoginUpdateIam(ctx context.Context, req *logical.Request,
 
 	endpoint := "https://sts.amazonaws.com"
 
+	maxRetries := awsClient.DefaultRetryerMaxNumRetries
 	if config != nil {
 		if config.IAMServerIdHeaderValue != "" {
 			err = validateVaultHeaderValue(headers, parsedUrl, config.IAMServerIdHeaderValue)
@@ -1208,9 +1215,12 @@ func (b *backend) pathLoginUpdateIam(ctx context.Context, req *logical.Request,
 		if config.STSEndpoint != "" {
 			endpoint = config.STSEndpoint
 		}
+		if config.MaxRetries >= 0 {
+			maxRetries = config.MaxRetries
+		}
 	}
 
-	callerID, err := submitCallerIdentityRequest(method, endpoint, parsedUrl, body, headers)
+	callerID, err := submitCallerIdentityRequest(ctx, maxRetries, method, endpoint, parsedUrl, body, headers)
 	if err != nil {
 		return logical.ErrorResponse(fmt.Sprintf("error making upstream request: %v", err)), nil
 	}
@@ -1555,18 +1565,31 @@ func parseGetCallerIdentityResponse(response string) (GetCallerIdentityResponse,
 	return result, err
 }
 
-func submitCallerIdentityRequest(method, endpoint string, parsedUrl *url.URL, body string, headers http.Header) (*GetCallerIdentityResult, error) {
+func submitCallerIdentityRequest(ctx context.Context, maxRetries int, method, endpoint string, parsedUrl *url.URL, body string, headers http.Header) (*GetCallerIdentityResult, error) {
 	// NOTE: We need to ensure we're calling STS, instead of acting as an unintended network proxy
 	// The protection against this is that this method will only call the endpoint specified in the
 	// client config (defaulting to sts.amazonaws.com), so it would require a Vault admin to override
 	// the endpoint to talk to alternate web addresses
 	request := buildHttpRequest(method, endpoint, parsedUrl, body, headers)
+	retryableReq, err := retryablehttp.FromRequest(request)
+	if err != nil {
+		return nil, err
+	}
+	retryableReq = retryableReq.WithContext(ctx)
 	client := cleanhttp.DefaultClient()
 	client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
 		return http.ErrUseLastResponse
 	}
+	retryingClient := &retryablehttp.Client{
+		HTTPClient:   client,
+		RetryWaitMin: retryWaitMin,
+		RetryWaitMax: retryWaitMax,
+		RetryMax:     maxRetries,
+		CheckRetry:   retryablehttp.DefaultRetryPolicy,
+		Backoff:      retryablehttp.DefaultBackoff,
+	}
 
-	response, err := client.Do(request)
+	response, err := retryingClient.Do(retryableReq)
 	if err != nil {
 		return nil, errwrap.Wrapf("error making request: {{err}}", err)
 	}