Add support to assume an AWS role and renew expired credentials

Co-authored-by: Christoph Burmeister <christoph.burmeister@idealo.de>

README.md

@@ -49,7 +49,7 @@ elasticsearch_exporter --help
 ```
 
 | Argument                | Introduced in Version | Description | Default     |
-| --------                | --------------------- | ----------- | ----------- |
+| ----------------------- | --------------------- | ----------- | ----------- |
 | es.uri                  | 1.0.2                 | Address (host and port) of the Elasticsearch node we should connect to. This could be a local node (`localhost:9200`, for instance), or the address of a remote Elasticsearch server. When basic auth is needed, specify as: `<proto>://<user>:<password>@<host>:<port>`. E.G., `http://admin:pass@localhost:9200`. Special characters in the user credentials need to be URL-encoded. | <http://localhost:9200> |
 | es.all                  | 1.0.2                 | If true, query stats for all nodes in the cluster, rather than just the node we connect to.                             | false |
 | es.cluster_settings     | 1.1.0rc1              | If true, query stats for cluster settings. | false |
@@ -69,7 +69,8 @@ elasticsearch_exporter --help
 | es.ssl-skip-verify      | 1.0.4rc1              | Skip SSL verification when connecting to Elasticsearch. | false |
 | web.listen-address      | 1.0.2                 | Address to listen on for web interface and telemetry. | :9114 |
 | web.telemetry-path      | 1.0.2                 | Path under which to expose metrics. | /metrics |
-| aws.region              | 1.5.0                 | Region for AWS elasticsearch | |
+| aws.region              | 1.5.0                 | AWS region to send STS requests to. | |
+| aws.role-arn            | 1.6.0                 | AWS role ARN of an IAM role to assume. | |
 | version                 | 1.0.2                 | Show version info on stdout and exit. | |
 
 Commandline parameters start with a single `-` for versions less than `1.1.0rc1`.

go.mod

@@ -5,6 +5,8 @@ go 1.19
 require (
 	github.com/aws/aws-sdk-go-v2 v1.16.16
 	github.com/aws/aws-sdk-go-v2/config v1.17.8
+	github.com/aws/aws-sdk-go-v2/credentials v1.12.21
+	github.com/aws/aws-sdk-go-v2/service/sts v1.16.19
 	github.com/blang/semver/v4 v4.0.0
 	github.com/go-kit/log v0.2.1
 	github.com/imdario/mergo v0.3.13
@@ -17,15 +19,13 @@ require (
 require (
 	github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 // indirect
 	github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d // indirect
-	github.com/aws/aws-sdk-go-v2/credentials v1.12.21 // indirect
 	github.com/aws/aws-sdk-go-v2/feature/ec2/imds v1.12.17 // indirect
 	github.com/aws/aws-sdk-go-v2/internal/configsources v1.1.23 // indirect
 	github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.4.17 // indirect
 	github.com/aws/aws-sdk-go-v2/internal/ini v1.3.24 // indirect
 	github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.9.17 // indirect
 	github.com/aws/aws-sdk-go-v2/service/sso v1.11.23 // indirect
 	github.com/aws/aws-sdk-go-v2/service/ssooidc v1.13.6 // indirect
-	github.com/aws/aws-sdk-go-v2/service/sts v1.16.19 // indirect
 	github.com/aws/smithy-go v1.13.3 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect

main.go

@@ -120,7 +120,10 @@ func main() {
 			"Sets the log output. Valid outputs are stdout and stderr").
 			Default("stdout").String()
 		awsRegion = kingpin.Flag("aws.region",
-			"Region for AWS elasticsearch").
+			"AWS region to send STS requests to.").
+			Default("").String()
+		awsRoleArn = kingpin.Flag("aws.role-arn",
+			"AWS role ARN of an IAM role to assume.").
 			Default("").String()
 	)
 
@@ -171,7 +174,7 @@ func main() {
 	}
 
 	if *awsRegion != "" {
-		httpClient.Transport, err = roundtripper.NewAWSSigningTransport(httpTransport, *awsRegion, logger)
+		httpClient.Transport, err = roundtripper.NewAWSSigningTransport(httpTransport, *awsRegion, *awsRoleArn, logger)
 		if err != nil {
 			_ = level.Error(logger).Log("msg", "failed to create AWS transport", "err", err)
 			os.Exit(1)

pkg/roundtripper/roundtripper.go

@@ -26,6 +26,8 @@ import (
 	"github.com/aws/aws-sdk-go-v2/aws"
 	v4 "github.com/aws/aws-sdk-go-v2/aws/signer/v4"
 	"github.com/aws/aws-sdk-go-v2/config"
+	"github.com/aws/aws-sdk-go-v2/credentials/stscreds"
+	"github.com/aws/aws-sdk-go-v2/service/sts"
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
 )
@@ -36,24 +38,24 @@ const (
 
 type AWSSigningTransport struct {
 	t      http.RoundTripper
-	creds  aws.Credentials
+	creds  aws.CredentialsProvider
 	region string
 	log    log.Logger
 }
 
-func NewAWSSigningTransport(transport http.RoundTripper, region string, log log.Logger) (*AWSSigningTransport, error) {
+func NewAWSSigningTransport(transport http.RoundTripper, region string, roleArn string, log log.Logger) (*AWSSigningTransport, error) {
 	cfg, err := config.LoadDefaultConfig(context.Background(), config.WithRegion(region))
 	if err != nil {
-		_ = level.Error(log).Log("msg", "fail to load aws default config", "err", err)
+		_ = level.Error(log).Log("msg", "failed to load aws default config", "err", err)
 		return nil, err
 	}
 
-	creds, err := cfg.Credentials.Retrieve(context.Background())
-	if err != nil {
-		_ = level.Error(log).Log("msg", "fail to retrive aws credentials", "err", err)
-		return nil, err
+	if roleArn != "" {
+		cfg.Credentials = stscreds.NewAssumeRoleProvider(sts.NewFromConfig(cfg), roleArn)
 	}
 
+	creds := aws.NewCredentialsCache(cfg.Credentials)
+
 	return &AWSSigningTransport{
 		t:      transport,
 		region: region,
@@ -66,13 +68,20 @@ func (a *AWSSigningTransport) RoundTrip(req *http.Request) (*http.Response, erro
 	signer := v4.NewSigner()
 	payloadHash, newReader, err := hashPayload(req.Body)
 	if err != nil {
-		_ = level.Error(a.log).Log("msg", "fail to hash request body", "err", err)
+		_ = level.Error(a.log).Log("msg", "failed to hash request body", "err", err)
 		return nil, err
 	}
 	req.Body = newReader
-	err = signer.SignHTTP(context.Background(), a.creds, req, payloadHash, service, a.region, time.Now())
+
+	creds, err := a.creds.Retrieve(context.Background())
+	if err != nil {
+		_ = level.Error(a.log).Log("msg", "failed to retrieve aws credentials", "err", err)
+		return nil, err
+	}
+
+	err = signer.SignHTTP(context.Background(), creds, req, payloadHash, service, a.region, time.Now())
 	if err != nil {
-		_ = level.Error(a.log).Log("msg", "fail to sign request body", "err", err)
+		_ = level.Error(a.log).Log("msg", "failed to sign request body", "err", err)
 		return nil, err
 	}
 	return a.t.RoundTrip(req)