feat: assume role provider credentials

This commit updates the awsutil depedency to its latest version, which
supports the capabilty of using dynamic credentials. The storage service
was refactored to make static credentials optional. The credentials pkg
was refactored to support several attribute fields used for the assume
role provider. The host service still enforces the use of static
credentials.

README.md

@@ -5,15 +5,32 @@ Boundary](https://www.boundaryproject.io/).
 
 ## Credential Rotation
 
-Although credentials are stored encrypted within Boundary, by default this
+This is the following priority for the credential chain:
+static, assume role, environment variables.
+
+### Static Credentials
+
+Although static credentials are stored encrypted within Boundary, by default this
 plugin will attempt to rotate credentials when they are supplied through the
 `secrets` object. The given credentials will be used to create a new credential,
 and then the given credential will be revoked. In this way, after rotation,
-only Boundary knows the client secret in use by this plugin.
+only Boundary knows the client secret in use by this plugin. More information
+about AWS static credentials can be found [here](https://docs.aws.amazon.com/sdkref/latest/guide/feature-static-credentials.html).
 
 Credential rotation can be turned off by setting the 
 `disable_credential_rotation` attribute to `true`.
 
+### Assume Role Credentials
+
+This plugin will attempt to assume a role when a `role_arn` is supplied through the
+`attributes` object. More information about assume an AWS role can be found [here](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRole.html). This feature only works when the plugin is running on a self managed Boundary [worker](https://developer.hashicorp.com/boundary/tutorials/hcp-administration/hcp-manage-workers).
+
+### Environment Credentials
+
+This plugin will attempt to retrieve credentials from environment variables. More
+information about environment variables for AWS credentials can be found [here](https://docs.aws.amazon.com/sdkref/latest/guide/feature-static-credentials.html). This feature only works when the plugin is running on
+a self managed Boundary [worker](https://developer.hashicorp.com/boundary/tutorials/hcp-administration/hcp-manage-workers).
+
 ## Dynamic Hosts
 
 This plugin supports dynamically sourcing hosts from Amazon EC2.

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/google/go-cmp v0.5.9
 	github.com/google/uuid v1.3.0
 	github.com/hashicorp/boundary/sdk v0.0.33
-	github.com/hashicorp/go-secure-stdlib/awsutil v0.1.6
+	github.com/hashicorp/go-secure-stdlib/awsutil v0.2.2
 	github.com/hashicorp/terraform-json v0.14.0
 	github.com/mitchellh/mapstructure v1.5.0
 	github.com/stretchr/testify v1.8.2

go.sum

@@ -5,6 +5,7 @@ github.com/apparentlymart/go-textseg v1.0.0/go.mod h1:z96Txxhf3xSFMPmb5X/1W05FF/
 github.com/apparentlymart/go-textseg/v13 v13.0.0/go.mod h1:ZK2fH7c4NqDTLtiYLvIkEghdlcqw7yxLeM89kiTRPUo=
 github.com/armon/go-radix v1.0.0 h1:F4z6KzEeeQIMeLFa97iZU6vupzoecKdU5TX24SNppXI=
 github.com/aws/aws-sdk-go v1.30.27/go.mod h1:5zCpMtNQVjRREroY7sYe8lOMRSxkhG6MZveU8YkpAk0=
+github.com/aws/aws-sdk-go v1.34.0/go.mod h1:5zCpMtNQVjRREroY7sYe8lOMRSxkhG6MZveU8YkpAk0=
 github.com/aws/aws-sdk-go v1.44.80 h1:jEXGecSgPdvM5KnyDsSgFhZSm7WwaTp4h544Im4SfhI=
 github.com/aws/aws-sdk-go v1.44.80/go.mod h1:y4AeaBuwd2Lk+GepC1E9v0qOiTws0MIWAX4oIKwKHZo=
 github.com/aws/aws-sdk-go-v2 v1.17.7 h1:CLSjnhJSTSogvqUGhIC6LqFKATMRexcxLZ0i/Nzk9Eg=
@@ -91,6 +92,8 @@ github.com/hashicorp/go-multierror v1.1.1/go.mod h1:iw975J/qwKPdAO1clOe2L8331t/9
 github.com/hashicorp/go-plugin v1.4.9 h1:ESiK220/qE0aGxWdzKIvRH69iLiuN/PjoLTm69RoWtU=
 github.com/hashicorp/go-secure-stdlib/awsutil v0.1.6 h1:W9WN8p6moV1fjKLkeqEgkAMu5rauy9QeYDAmIaPuuiA=
 github.com/hashicorp/go-secure-stdlib/awsutil v0.1.6/go.mod h1:MpCPSPGLDILGb4JMm94/mMi3YysIqsXzGCzkEZjcjXg=
+github.com/hashicorp/go-secure-stdlib/awsutil v0.2.2 h1:kWg2vyKl7BRXrNxYziqDJ55n+vtOQ1QsGORjzoeB+uM=
+github.com/hashicorp/go-secure-stdlib/awsutil v0.2.2/go.mod h1:oKHSQs4ivIfZ3fbXGQOop1XuDfdSb8RIsWTGaAanSfg=
 github.com/hashicorp/go-secure-stdlib/base62 v0.1.1/go.mod h1:EdWO6czbmthiwZ3/PUsDV+UD1D5IRU4ActiaWGwt0Yw=
 github.com/hashicorp/go-secure-stdlib/base62 v0.1.2 h1:ET4pqyjiGmY09R5y+rSd70J2w45CtbWDNvGqWp/R3Ng=
 github.com/hashicorp/go-secure-stdlib/configutil/v2 v2.0.9 h1:YZ01/aiARPneDUryzjiPGvr3pmjCSC+1WBZKI1P7I7k=

internal/credential/attributes.go

@@ -20,33 +20,47 @@ type CredentialAttributes struct {
 
 	// DisableCredentialRotation disables the rotation of aws secrets associated with the plugin
 	DisableCredentialRotation bool
+
+	// RoleArn is the role arn associated with the aws credentials
+	RoleArn string
+
+	// RoleExternalId is the external id associated with the aws credentials
+	RoleExternalId string
+
+	// RoleSessionName is the session name associated with the aws credentials
+	RoleSessionName string
+
+	// RoleTags is the tags associated with the aws credentials
+	RoleTags map[string]string
 }
 
-// GetCredentialsConfig parses values out of a protobuf struct input and returns a
+// GetCredentialsConfig parses values out of a protobuf struct secrets and returns a
 // CredentialsConfig used for configuring an AWS session. An error is returned if
-// any of the following fields are missing from the protobuf struct input or have
-// invalid value types: access_key_id, secret_access_key. An error is returned if
 // any unrecognized fields are found in the protobuf struct input.
-func GetCredentialsConfig(in *structpb.Struct, region string) (*awsutil.CredentialsConfig, error) {
-	unknownFields := values.StructFields(in)
+func GetCredentialsConfig(secrets *structpb.Struct, attrs *CredentialAttributes, required bool) (*awsutil.CredentialsConfig, error) {
+	// initialize secrets if it is nil
+	// secrets can be nil because static credentials are optional
+	if secrets == nil {
+		secrets = &structpb.Struct{
+			Fields: make(map[string]*structpb.Value),
+		}
+	}
+
+	unknownFields := values.StructFields(secrets)
 	badFields := make(map[string]string)
 
-	accessKey, err := values.GetStringValue(in, ConstAccessKeyId, true)
+	accessKey, err := values.GetStringValue(secrets, ConstAccessKeyId, required)
 	if err != nil {
 		badFields[fmt.Sprintf("secrets.%s", ConstAccessKeyId)] = err.Error()
 	}
 	delete(unknownFields, ConstAccessKeyId)
 
-	secretKey, err := values.GetStringValue(in, ConstSecretAccessKey, true)
+	secretKey, err := values.GetStringValue(secrets, ConstSecretAccessKey, required)
 	if err != nil {
 		badFields[fmt.Sprintf("secrets.%s", ConstSecretAccessKey)] = err.Error()
 	}
 	delete(unknownFields, ConstSecretAccessKey)
 
-	if region == "" {
-		badFields[fmt.Sprintf("attributes.%s", ConstRegion)] = err.Error()
-	}
-
 	// the creds_last_rotated_time field will be found in the input struct for
 	// persisted secrets, this value is not needed for creating the CredentialsConfig
 	delete(unknownFields, ConstCredsLastRotatedTime)
@@ -58,11 +72,32 @@ func GetCredentialsConfig(in *structpb.Struct, region string) (*awsutil.Credenti
 		return nil, errors.InvalidArgumentError("Error in the secrets provided", badFields)
 	}
 
-	return awsutil.NewCredentialsConfig(
-		awsutil.WithAccessKey(accessKey),
-		awsutil.WithSecretKey(secretKey),
-		awsutil.WithRegion(region),
-	)
+	opts := []awsutil.Option{
+		awsutil.WithEnvironmentCredentials(true),
+	}
+	if accessKey != "" && secretKey != "" {
+		opts = append(opts,
+			awsutil.WithAccessKey(accessKey),
+			awsutil.WithSecretKey(secretKey),
+		)
+	}
+	if attrs.Region != "" {
+		opts = append(opts, awsutil.WithRegion(attrs.Region))
+	}
+	if attrs.RoleArn != "" {
+		opts = append(opts, awsutil.WithRoleArn(attrs.RoleArn))
+	}
+	if attrs.RoleExternalId != "" {
+		opts = append(opts, awsutil.WithRoleExternalId(attrs.RoleExternalId))
+	}
+	if attrs.RoleSessionName != "" {
+		opts = append(opts, awsutil.WithRoleSessionName(attrs.RoleSessionName))
+	}
+	if len(attrs.RoleTags) != 0 {
+		opts = append(opts, awsutil.WithRoleTags(attrs.RoleTags))
+	}
+
+	return awsutil.NewCredentialsConfig(opts...)
 }
 
 // GetCredentialAttributes parses values out of a protobuf struct input and returns a
@@ -88,12 +123,36 @@ func GetCredentialAttributes(in *structpb.Struct) (*CredentialAttributes, error)
 		badFields[fmt.Sprintf("attributes.%s", ConstDisableCredentialRotation)] = err.Error()
 	}
 
+	roleArn, err := values.GetStringValue(in, ConstRoleArn, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstRoleArn)] = err.Error()
+	}
+
+	roleExternalId, err := values.GetStringValue(in, ConstRoleExternalId, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstRoleExternalId)] = err.Error()
+	}
+
+	roleSessionName, err := values.GetStringValue(in, ConstRoleSessionName, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstRoleSessionName)] = err.Error()
+	}
+
+	roleTags, err := values.GetMapString(in, ConstRoleTags, false)
+	if err != nil {
+		badFields[fmt.Sprintf("attributes.%s", ConstRoleTags)] = err.Error()
+	}
+
 	if len(badFields) > 0 {
 		return nil, errors.InvalidArgumentError("Error in the attributes provided", badFields)
 	}
 
 	return &CredentialAttributes{
 		Region:                    region,
 		DisableCredentialRotation: disableCredentialRotation,
+		RoleArn:                   roleArn,
+		RoleExternalId:            roleExternalId,
+		RoleSessionName:           roleSessionName,
+		RoleTags:                  roleTags,
 	}, nil
 }