Add WIF support for AWS Auth (#26507)

* Add wif support * update cli + add stubs * revert cli changes + add changelog * update with suggestions
hashicorp · May 9, 2024 · bdc16c3 · bdc16c3
1 parent 3150c32
commit bdc16c3
Show file tree

Hide file tree

Showing 4 changed files with 173 additions and 12 deletions.
diff --git a/builtin/credential/aws/client.go b/builtin/credential/aws/client.go
@@ -6,6 +6,8 @@ package awsauth
 import (
 	"context"
 	"fmt"
+	"strconv"
+	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/credentials/stscreds"
@@ -14,7 +16,10 @@ import (
 	"github.com/aws/aws-sdk-go/service/iam"
 	"github.com/aws/aws-sdk-go/service/sts"
 	cleanhttp "github.com/hashicorp/go-cleanhttp"
+	"github.com/hashicorp/go-hclog"
 	"github.com/hashicorp/go-secure-stdlib/awsutil"
+	"github.com/hashicorp/vault/helper/namespace"
+	"github.com/hashicorp/vault/sdk/helper/pluginutil"
 	"github.com/hashicorp/vault/sdk/logical"
 )
 
@@ -58,6 +63,26 @@ func (b *backend) getRawClientConfig(ctx context.Context, s logical.Storage, reg
 		credsConfig.AccessKey = config.AccessKey
 		credsConfig.SecretKey = config.SecretKey
 		maxRetries = config.MaxRetries
+
+		if config.IdentityTokenAudience != "" {
+			ns, err := namespace.FromContext(ctx)
+			if err != nil {
+				return nil, fmt.Errorf("failed to get namespace from context: %w", err)
+			}
+
+			fetcher := &PluginIdentityTokenFetcher{
+				sys:      b.System(),
+				logger:   b.Logger(),
+				ns:       ns,
+				audience: config.IdentityTokenAudience,
+				ttl:      config.IdentityTokenTTL,
+			}
+
+			sessionSuffix := strconv.FormatInt(time.Now().UnixNano(), 10)
+			credsConfig.RoleSessionName = fmt.Sprintf("vault-aws-auth-%s", sessionSuffix)
+			credsConfig.WebIdentityTokenFetcher = fetcher
+			credsConfig.RoleARN = config.RoleARN
+		}
 	}
 
 	credsConfig.HTTPClient = cleanhttp.DefaultClient()
@@ -302,3 +327,36 @@ func (b *backend) clientIAM(ctx context.Context, s logical.Storage, region, acco
 	}
 	return b.IAMClientsMap[region][stsRole], nil
 }
+
+// PluginIdentityTokenFetcher fetches plugin identity tokens from Vault. It is provided
+// to the AWS SDK client to keep assumed role credentials refreshed through expiration.
+// When the client's STS credentials expire, it will use this interface to fetch a new
+// plugin identity token and exchange it for new STS credentials.
+type PluginIdentityTokenFetcher struct {
+	sys      logical.SystemView
+	logger   hclog.Logger
+	audience string
+	ns       *namespace.Namespace
+	ttl      time.Duration
+}
+
+var _ stscreds.TokenFetcher = (*PluginIdentityTokenFetcher)(nil)
+
+func (f PluginIdentityTokenFetcher) FetchToken(ctx aws.Context) ([]byte, error) {
+	nsCtx := namespace.ContextWithNamespace(ctx, f.ns)
+	resp, err := f.sys.GenerateIdentityToken(nsCtx, &pluginutil.IdentityTokenRequest{
+		Audience: f.audience,
+		TTL:      f.ttl,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate plugin identity token: %w", err)
+	}
+	f.logger.Info("fetched new plugin identity token")
+
+	if resp.TTL < f.ttl {
+		f.logger.Debug("generated plugin identity token has shorter TTL than requested",
+			"requested", f.ttl, "actual", resp.TTL)
+	}
+
+	return []byte(resp.Token.Token()), nil
+}
diff --git a/builtin/credential/aws/path_config_client.go b/builtin/credential/aws/path_config_client.go
@@ -14,11 +14,13 @@ import (
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/hashicorp/go-secure-stdlib/strutil"
 	"github.com/hashicorp/vault/sdk/framework"
+	"github.com/hashicorp/vault/sdk/helper/pluginidentityutil"
+	"github.com/hashicorp/vault/sdk/helper/pluginutil"
 	"github.com/hashicorp/vault/sdk/logical"
 )
 
 func (b *backend) pathConfigClient() *framework.Path {
-	return &framework.Path{
+	p := &framework.Path{
 		Pattern: "config/client$",
 
 		DisplayAttrs: &framework.DisplayAttributes{
@@ -85,6 +87,12 @@ func (b *backend) pathConfigClient() *framework.Path {
 				Default:     aws.UseServiceDefaultRetries,
 				Description: "Maximum number of retries for recoverable exceptions of AWS APIs",
 			},
+
+			"role_arn": {
+				Type:        framework.TypeString,
+				Default:     "",
+				Description: "Role ARN to assume for plugin identity token federation",
+			},
 		},
 
 		ExistenceCheck: b.pathConfigClientExistenceCheck,
@@ -121,6 +129,9 @@ func (b *backend) pathConfigClient() *framework.Path {
 		HelpSynopsis:    pathConfigClientHelpSyn,
 		HelpDescription: pathConfigClientHelpDesc,
 	}
+	pluginidentityutil.AddPluginIdentityTokenFields(p.Fields)
+
+	return p
 }
 
 // Establishes dichotomy of request operation between CreateOperation and UpdateOperation.
@@ -168,18 +179,22 @@ func (b *backend) pathConfigClientRead(ctx context.Context, req *logical.Request
 		return nil, nil
 	}
 
+	configData := map[string]interface{}{
+		"access_key":                 clientConfig.AccessKey,
+		"endpoint":                   clientConfig.Endpoint,
+		"iam_endpoint":               clientConfig.IAMEndpoint,
+		"sts_endpoint":               clientConfig.STSEndpoint,
+		"sts_region":                 clientConfig.STSRegion,
+		"use_sts_region_from_client": clientConfig.UseSTSRegionFromClient,
+		"iam_server_id_header_value": clientConfig.IAMServerIdHeaderValue,
+		"max_retries":                clientConfig.MaxRetries,
+		"allowed_sts_header_values":  clientConfig.AllowedSTSHeaderValues,
+		"role_arn":                   clientConfig.RoleARN,
+	}
+
+	clientConfig.PopulatePluginIdentityTokenData(configData)
 	return &logical.Response{
-		Data: map[string]interface{}{
-			"access_key":                 clientConfig.AccessKey,
-			"endpoint":                   clientConfig.Endpoint,
-			"iam_endpoint":               clientConfig.IAMEndpoint,
-			"sts_endpoint":               clientConfig.STSEndpoint,
-			"sts_region":                 clientConfig.STSRegion,
-			"use_sts_region_from_client": clientConfig.UseSTSRegionFromClient,
-			"iam_server_id_header_value": clientConfig.IAMServerIdHeaderValue,
-			"max_retries":                clientConfig.MaxRetries,
-			"allowed_sts_header_values":  clientConfig.AllowedSTSHeaderValues,
-		},
+		Data: configData,
 	}, nil
 }
 
@@ -334,6 +349,41 @@ func (b *backend) pathConfigClientCreateUpdate(ctx context.Context, req *logical
 		configEntry.MaxRetries = data.Get("max_retries").(int)
 	}
 
+	roleArnStr, ok := data.GetOk("role_arn")
+	if ok {
+		if configEntry.RoleARN != roleArnStr.(string) {
+			changedCreds = true
+			configEntry.RoleARN = roleArnStr.(string)
+		}
+	} else if req.Operation == logical.CreateOperation {
+		configEntry.RoleARN = data.Get("role_arn").(string)
+	}
+
+	if err := configEntry.ParsePluginIdentityTokenFields(data); err != nil {
+		return logical.ErrorResponse(err.Error()), nil
+	}
+
+	// handle mutual exclusivity
+	if configEntry.IdentityTokenAudience != "" && configEntry.AccessKey != "" {
+		return logical.ErrorResponse("only one of 'access_key' or 'identity_token_audience' can be set"), nil
+	}
+
+	if configEntry.IdentityTokenAudience != "" && configEntry.RoleARN == "" {
+		return logical.ErrorResponse("role_arn must be set when identity_token_audience is set"), nil
+	}
+
+	if configEntry.IdentityTokenAudience != "" {
+		_, err := b.System().GenerateIdentityToken(ctx, &pluginutil.IdentityTokenRequest{
+			Audience: configEntry.IdentityTokenAudience,
+		})
+		if err != nil {
+			if errors.Is(err, pluginidentityutil.ErrPluginWorkloadIdentityUnsupported) {
+				return logical.ErrorResponse(err.Error()), nil
+			}
+			return nil, err
+		}
+	}
+
 	// Since this endpoint supports both create operation and update operation,
 	// the error checks for access_key and secret_key not being set are not present.
 	// This allows calling this endpoint multiple times to provide the values.
@@ -373,6 +423,8 @@ func (b *backend) configClientToEntry(conf *clientConfig) (*logical.StorageEntry
 // Struct to hold 'aws_access_key' and 'aws_secret_key' that are required to
 // interact with the AWS EC2 API.
 type clientConfig struct {
+	pluginidentityutil.PluginIdentityTokenParams
+
 	AccessKey              string   `json:"access_key"`
 	SecretKey              string   `json:"secret_key"`
 	Endpoint               string   `json:"endpoint"`
@@ -383,6 +435,7 @@ type clientConfig struct {
 	IAMServerIdHeaderValue string   `json:"iam_server_id_header_value"`
 	AllowedSTSHeaderValues []string `json:"allowed_sts_header_values"`
 	MaxRetries             int      `json:"max_retries"`
+	RoleARN                string   `json:"role_arn"`
 }
 
 func (c *clientConfig) validateAllowedSTSHeaderValues(headers http.Header) error {

diff --git a/builtin/credential/aws/path_config_client_test.go b/builtin/credential/aws/path_config_client_test.go
@@ -7,7 +7,10 @@ import (
 	"context"
 	"testing"
 
+	"github.com/hashicorp/vault/sdk/helper/pluginidentityutil"
+	"github.com/hashicorp/vault/sdk/helper/pluginutil"
 	"github.com/hashicorp/vault/sdk/logical"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestBackend_pathConfigClient(t *testing.T) {
@@ -129,3 +132,47 @@ func TestBackend_pathConfigClient(t *testing.T) {
 			data["sts_region"], resp.Data["sts_region"])
 	}
 }
+
+// TestBackend_PathConfigClient_PluginIdentityToken tests that configuration
+// of plugin WIF returns an immediate error.
+func TestBackend_PathConfigClient_PluginIdentityToken(t *testing.T) {
+	config := logical.TestBackendConfig()
+	config.StorageView = &logical.InmemStorage{}
+	config.System = &testSystemView{}
+
+	b, err := Backend(config)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = b.Setup(context.Background(), config)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	configData := map[string]interface{}{
+		"identity_token_ttl":      int64(10),
+		"identity_token_audience": "test-aud",
+		"role_arn":                "test-role-arn",
+	}
+
+	configReq := &logical.Request{
+		Operation: logical.UpdateOperation,
+		Storage:   config.StorageView,
+		Path:      "config/client",
+		Data:      configData,
+	}
+
+	resp, err := b.HandleRequest(context.Background(), configReq)
+	assert.NoError(t, err)
+	assert.NotNil(t, resp)
+	assert.ErrorContains(t, resp.Error(), pluginidentityutil.ErrPluginWorkloadIdentityUnsupported.Error())
+}
+
+type testSystemView struct {
+	logical.StaticSystemView
+}
+
+func (d testSystemView) GenerateIdentityToken(_ context.Context, _ *pluginutil.IdentityTokenRequest) (*pluginutil.IdentityTokenResponse, error) {
+	return nil, pluginidentityutil.ErrPluginWorkloadIdentityUnsupported
+}
diff --git a/changelog/26507.txt b/changelog/26507.txt
@@ -0,0 +1,3 @@
+```release-note:feature
+**Plugin Identity Tokens**: Adds secret-less configuration of AWS auth engine using web identity federation.
+```