feat: Provide external shell command to retrieve AWS credentials (#37)

* feat: Provide external shell command to retrieve AWS credentials

* resolve bkneis' comment(s)

cmd/init.go

@@ -3,7 +3,6 @@ package cmd
 import (
 	"context"
 
-	AwsConfig "github.com/aws/aws-sdk-go-v2/config"
 	"github.com/loft-sh/devpod-provider-aws/pkg/aws"
 	"github.com/loft-sh/devpod-provider-aws/pkg/options"
 	"github.com/loft-sh/devpod/pkg/log"
@@ -43,7 +42,7 @@ func (cmd *InitCmd) Run(
 		return err
 	}
 
-	cfg, err := AwsConfig.LoadDefaultConfig(ctx)
+	cfg, err := aws.NewAWSConfig(ctx, logs, config)
 	if err != nil {
 		return err
 	}

hack/provider/provider.yaml

@@ -34,6 +34,10 @@ optionGroups:
       - INJECT_GIT_CREDENTIALS
     name: "Agent options"
     defaultVisible: false
+  - options:
+      - CUSTOM_AWS_CREDENTIAL_COMMAND
+    name: "Credential handling options"
+    defaultVisible: true
 options:
   AWS_REGION:
     suggestions:
@@ -272,6 +276,9 @@ options:
   AGENT_PATH:
     description: The path where to inject the DevPod agent to.
     default: /var/lib/toolbox/devpod
+  CUSTOM_AWS_CREDENTIAL_COMMAND:
+    description: "Shell command which is executed to get the AWS credentials. The command must return a json containing the keys `AccessKeyID` (required), `SecretAccessKey` (required) and `SessionToken` (optional)."
+    default: ""
 agent:
   path: ${AGENT_PATH}
   inactivityTimeout: ${INACTIVITY_TIMEOUT}

pkg/aws/aws.go

@@ -1,10 +1,15 @@
 package aws
 
 import (
+	"bytes"
 	"context"
 	"encoding/base64"
+	"encoding/json"
 	"fmt"
+	"github.com/aws/aws-sdk-go-v2/credentials"
+	"github.com/sirupsen/logrus"
 	"net/http"
+	"os/exec"
 	"regexp"
 	"sort"
 	"strings"
@@ -46,7 +51,7 @@ func NewProvider(ctx context.Context, logs log.Logger) (*AwsProvider, error) {
 		return nil, err
 	}
 
-	cfg, err := awsConfig.LoadDefaultConfig(ctx)
+	cfg, err := NewAWSConfig(ctx, logs, config)
 	if err != nil {
 		return nil, err
 	}
@@ -80,6 +85,38 @@ func NewProvider(ctx context.Context, logs log.Logger) (*AwsProvider, error) {
 	return provider, nil
 }
 
+func NewAWSConfig(ctx context.Context, logs log.Logger, options *options.Options) (aws.Config, error) {
+	var opts []func(*awsConfig.LoadOptions) error
+	if options.CustomCredentialCommand != "" {
+		var output bytes.Buffer
+		cmd := exec.Command("sh", "-c", options.CustomCredentialCommand)
+		cmd.Stdout = &output
+		cmd.Stderr = logs.Writer(logrus.ErrorLevel, true)
+		if err := cmd.Run(); err != nil {
+			return aws.Config{}, fmt.Errorf("run command %q: %w", options.CustomCredentialCommand, err)
+		}
+
+		// parse the JSON output to an aws.Credentials object
+		var creds aws.Credentials
+		if err := json.Unmarshal(output.Bytes(), &creds); err != nil {
+			return aws.Config{}, fmt.Errorf("parse AWS credential JSON output %q: %w", output.Bytes(), err)
+		}
+
+		if creds.AccessKeyID == "" || creds.SecretAccessKey == "" {
+			return aws.Config{}, fmt.Errorf("missing access key id or secret access key in JSON output %q", output.Bytes())
+		}
+
+		// we managed to parse credentials from the external source. Let's use them through a credentials provider
+		opts = append(opts, awsConfig.WithCredentialsProvider(credentials.StaticCredentialsProvider{Value: creds}))
+	}
+
+	cfg, err := awsConfig.LoadDefaultConfig(ctx, opts...)
+	if err != nil {
+		return aws.Config{}, err
+	}
+	return cfg, nil
+}
+
 type AwsProvider struct {
 	Config           *options.Options
 	AwsConfig        aws.Config

pkg/options/options.go

@@ -24,6 +24,7 @@ var (
 	AWS_KMS_KEY_ARN_FOR_SESSION_MANAGER = "AWS_KMS_KEY_ARN_FOR_SESSION_MANAGER"
 	AWS_USE_ROUTE53                     = "AWS_USE_ROUTE53"
 	AWS_ROUTE53_ZONE_NAME               = "AWS_ROUTE53_ZONE_NAME"
+	CUSTOM_AWS_CREDENTIAL_COMMAND       = "CUSTOM_AWS_CREDENTIAL_COMMAND"
 )
 
 type Options struct {
@@ -46,12 +47,14 @@ type Options struct {
 	KmsKeyARNForSessionManager string
 	UseRoute53Hostnames        bool
 	Route53ZoneName            string
+	CustomCredentialCommand    string
 }
 
 func FromEnv(init bool) (*Options, error) {
 	retOptions := &Options{}
 
 	var err error
+	retOptions.CustomCredentialCommand = os.Getenv(CUSTOM_AWS_CREDENTIAL_COMMAND)
 
 	retOptions.MachineType, err = fromEnvOrError(AWS_INSTANCE_TYPE)
 	if err != nil {
@@ -84,7 +87,7 @@ func FromEnv(init bool) (*Options, error) {
 	retOptions.UseRoute53Hostnames = os.Getenv(AWS_USE_ROUTE53) == "true"
 	retOptions.Route53ZoneName = os.Getenv(AWS_ROUTE53_ZONE_NAME)
 
-	// Return eraly if we're just doing init
+	// Return early if we're just doing init
 	if init {
 		return retOptions, nil
 	}