Add web identify support

cmd/aws-iam-authenticator/token.go

@@ -38,6 +38,7 @@ var tokenCmd = &cobra.Command{
 		tokenOnly := viper.GetBool("tokenOnly")
 		forwardSessionName := viper.GetBool("forwardSessionName")
 		sessionName := viper.GetString("sessionName")
+		wiToken := viper.GetString("token")
 		cache := viper.GetBool("cache")
 
 		if clusterID == "" {
@@ -52,6 +53,15 @@ var tokenCmd = &cobra.Command{
 			os.Exit(1)
 		}
 
+		if wiToken != "" {
+			_, err := os.Stat(wiToken)
+			if os.IsNotExist(err) {
+				fmt.Fprintf(os.Stderr, "Error: token path is provided, but there is no such file\n")
+				cmd.Usage()
+				os.Exit(1)
+			}
+		}
+
 		var tok token.Token
 		var out string
 		var err error
@@ -67,6 +77,7 @@ var tokenCmd = &cobra.Command{
 			AssumeRoleExternalID: externalID,
 			SessionName:          sessionName,
 			Region:               region,
+			Token:                wiToken,
 		})
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "could not get token: %v\n", err)
@@ -88,6 +99,7 @@ func init() {
 	tokenCmd.Flags().StringP("external-id", "e", "", "External ID to pass when assuming the IAM Role")
 	tokenCmd.Flags().StringP("session-name", "s", "", "Session name to pass when assuming the IAM Role")
 	tokenCmd.Flags().Bool("token-only", false, "Return only the token for use with Bearer token based tools")
+	tokenCmd.Flags().StringP("token", "t", "", "Path to a web identity token file or it's raw value")
 	tokenCmd.Flags().Bool("forward-session-name",
 		false,
 		"Enable mapping a federated sessions caller-specified-role-name attribute onto newly assumed sessions. NOTE: Only applicable when a new role is requested via --role")
@@ -98,6 +110,7 @@ func init() {
 	viper.BindPFlag("tokenOnly", tokenCmd.Flags().Lookup("token-only"))
 	viper.BindPFlag("forwardSessionName", tokenCmd.Flags().Lookup("forward-session-name"))
 	viper.BindPFlag("sessionName", tokenCmd.Flags().Lookup("session-name"))
+	viper.BindPFlag("token", tokenCmd.Flags().Lookup("token"))
 	viper.BindPFlag("cache", tokenCmd.Flags().Lookup("cache"))
 	viper.BindEnv("role", "DEFAULT_ROLE")
 }

pkg/token/token.go

@@ -20,6 +20,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
+	"github.com/pkg/errors"
 	"io/ioutil"
 	"net/http"
 	"net/url"
@@ -109,6 +110,7 @@ type GetTokenOptions struct {
 	ClusterID            string
 	AssumeRoleARN        string
 	AssumeRoleExternalID string
+	Token                string
 	SessionName          string
 	Session              *session.Session
 }
@@ -276,9 +278,31 @@ func (g generator) GetWithOptions(options *GetTokenOptions) (Token, error) {
 	// use an STS client based on the direct credentials
 	stsAPI := sts.New(options.Session)
 
-	// if a roleARN was specified, replace the STS client with one that uses
-	// temporary credentials from that role.
-	if options.AssumeRoleARN != "" {
+	if options.AssumeRoleARN != "" && options.Token != "" {
+		// if a roleARN and Token were specified,
+		// replace the STS client with one that uses web identity temporary credentials from that role.
+
+		webIdentityProvider := stscreds.NewWebIdentityRoleProviderWithOptions(
+			stsAPI,
+			options.AssumeRoleARN,
+			options.SessionName,
+			getTokenFetcher(options.Token),
+		)
+
+		// Check if the webIdentityProvider can successfully retrieve
+		// credentials (via sts:AssumeRole), and warn if there's a problem.
+		if _, err := webIdentityProvider.Retrieve(); err != nil {
+			return Token{}, errors.Wrap(err, "failed to get web identity provider")
+		}
+
+		stsAPI = sts.New(
+			options.Session,
+			&aws.Config{
+				Credentials: credentials.NewCredentials(webIdentityProvider),
+			})
+	} else if options.AssumeRoleARN != "" {
+		// if a roleARN was specified, replace the STS client with one that uses
+		// temporary credentials from that role.
 		var sessionSetters []func(*stscreds.AssumeRoleProvider)
 
 		if options.AssumeRoleExternalID != "" {
@@ -627,3 +651,17 @@ func hasSignedClusterIDHeader(paramsLower *url.Values) bool {
 	}
 	return false
 }
+
+func getTokenFetcher(token string) stscreds.TokenFetcher {
+	if strings.HasPrefix(token, "/") || strings.HasPrefix(token, "./") {
+		return stscreds.FetchTokenPath(token)
+	}
+	return FetchTokenRaw(token)
+}
+
+type FetchTokenRaw string
+
+// FetchToken returns a token by reading from the filesystem
+func (f FetchTokenRaw) FetchToken(_ credentials.Context) ([]byte, error) {
+	return []byte(f), nil
+}