Temporal Server security

Overview

A secured Temporal server has its network communication encrypted and has authentication and authorization protocols set up for API calls made to it. Without these your server could be accessed by unwanted entities. What is documented on this page are the built-in opt-in security measures that come with Temporal. However users may also choose to design their own security architecture with reverse proxies or run unsecured instances inside of a VPC environment.

Encryption of network traffic

Temporal supports Mutual TLS (mTLS) as a way of encrypting network traffic between the services of a cluster and also between application processes and a cluster. Self-signed or properly minted certificates can be used for mTLS. Mutual TLS is set in Temporal's configuration. The configuration includes two sections such that intra-cluster and external traffic can be encrypted with different sets of certificates and settings:

  • internode: Configuration for encrypting communication between nodes in the cluster.
  • frontend: Configuration for encrypting the Frontend's public endpoints.

A customized configuration can be passed using either the WithConfig or WithConfigLoader server options.

Authentication

There are a few authentication protocols available to prevent unwanted access such as authentication of servers, clients, and users.

Servers

To prevent spoofing and MITM attacks you can specify the serverName in the client section of your respective mTLS configuration. This enables established connections to authenticate the endpoint, ensuring that the server certificate presented to any connecting client has the given server name in its CN property. It can be used for both internode and frontend endpoints.

Client connections

To restrict a client's network access to cluster endpoints you can limit it to clients with certificates issued by a specific Certificate Authority (CA). Use the clientCAFiles/ clientCAData and requireClientAuth properties in both the internode and frontend sections of the mTLS configuration.

Users

To restrict access to specific users, authentication and authorization is performed through extensibility points and plugins as described in the Authorization section below.

Authorization

Temporal offers two plugin interfaces for implementing API call authorization:

  • ClaimMapper
  • Authorizer

The authorization and claim mapping logic is customizable, making it available to a variety of use cases and identity schemes. When these are provided the frontend invokes the implementation of these interfaces before executing the requested operation.

Authorizer plugin interface

The Authorizer has a single Authorize method which is invoked for each incoming API call that is received by the Frontend gRPC service. The Authorize method receives information about the API call and the role/permission claims of the caller.

common/authorization/authorizer.go

// Authorizer is an interface for implementing authorization logic
type Authorizer interface {
Authorize(ctx context.Context, caller *Claims, target *CallTarget) (Result, error)
}

Authorizer allows for a wide range of authorization logic, as information such as the call target, a set of role/permission claims, and any other data available to the system can be used in the authorization logic. The following arguments must be passed to the Authorize method for example:

  • context.Context: General context of the call.
  • authorization.Claims: Claims about the roles assigned to the caller. Its intended use is described below.
  • authorization.CallTarget: Target of the API call.

common/authorization/authorizer.go

// CallTarget is contains information for Authorizer to make a decision.
// It can be extended to include resources like WorkflowType and TaskQueue
type CallTarget struct {
// APIName must be the full API function name.
// Example: "/temporal.api.workflowservice.v1.WorkflowService/StartWorkflowExecution".
APIName string
// If a Namespace is not being targeted this be set to an empty string.
Namespace string
}

The Authorize method then returns one of two possible decisions within the Result.Decision field:

  • DecisionDeny: the requested API call is not invoked and an error is returned to the caller.
  • DecisionAllow: the requested API call is invoked.

If you don't want to create your own, you can use the default Authorizer:

a := authorization.NewDefaultAuthorizer()

Configure your Authorizer when you start the server via the temporal.WithAuthorizer server option.

If an Authorizer is not set in the server options, Temporal uses the nopAuthority authorizer that unconditionally allows all API call to pass through.

ClaimMapper plugin interface

ClaimMapper has a single method, GetClaims that is responsible for translating information from the authorization token and/or mutual TLS certificate of the caller into Claims about the callers roles within Temporal. This component is customizable and can be set via the temporal.WithClaimMapper server option, enabling a wide range of options for interpreting a caller's identity.

common/authorization/claimMapper.go

// ClaimMapper converts authorization info of a subject into Temporal claims (permissions) for authorization
type ClaimMapper interface {
GetClaims(authInfo *AuthInfo) (*Claims, error)
}

A typical approach is for ClaimMapper to interpret custom Claims from a caller's JWT access token, such as membership in groups, and map them to Temporal roles for the user. Another approach is to use the subject information from the caller's TLS certificate as a parameter for determining roles. See the default JWT ClaimMapper as an example.

AuthInfo

The AuthInfo struct that is passed to claim mapper's GetClaims method contains an authorization token extracted from the authorization header of the gRPC request. It also includes a pointer to the pkix.Name struct that contains a X.509 distinguishable name from the caller's mutual TLS certificate.

common/authorization/claimMapper.go

// Authentication information from subject's JWT token or/and mTLS certificate
type AuthInfo struct {
AuthToken string
TLSSubject *pkix.Name
TLSConnection *credentials.TLSInfo
}

Claims

The Claims struct contains information about permission claims granted to the caller. The Authorizer assumes that the caller has been properly authenticated and trusts the Claims that are passed to it for making an authorization decision.

common/authorization/roles.go

// Claims contains the identity of the subject and subject's roles at the system level and for individual namespaces
type Claims struct {
// Identity of the subject
Subject string
// Role within the context of the whole Temporal cluster or a multi-cluster setup
System Role
// Roles within specific namespaces
Namespaces map[string]Role
}

Role is a bit mask that is a combination of one or more the role constants:

common/authorization/roles.go

// User authz within the context of an entity, such as system, namespace or workflow.
// User may have any combination of these authz within each context, except for RoleUndefined, as a bitmask.
const (
RoleWorker = Role(1 << iota)
RoleReader
RoleWriter
RoleAdmin
RoleUndefined = Role(0)
)

For example, a role can be set as

role := authorization.RoleReader | authorization.RoleWriter

Default JWT ClaimMapper

Temporal offers a default JSON Web Token ClaimMapper that extracts claims from JWT access tokens and translates them into Temporal Claims. The default JWT ClaimMapper needs a public key to perform validation of tokens' digital signatures and expects JWT tokens to be in the certain format described below. You can use the default as an example to build your own for translating a caller's authorization information from other formats and conventions into Temporal Claims.

claimMapper := authorization.NewDefaultJWTClaimMapper(provider, cfg)

Note that the default JWT ClaimMapper sets "permissions" as the permissionsClaimName if the config.Config.Global.Authorization.PermissionsClaimName property is not set as an override for the JWT tokens.

TokenKeyProvider

To obtain public keys from issuers of JWT tokens and to refresh them over time, the default JWT ClaimMapper uses another pluggable component, the TokenKeyProvider.

common/authorization/tokenKeyProvider.go

// Provides keys for validating JWT tokens
type TokenKeyProvider interface {
EcdsaKey(alg string, kid string) (*ecdsa.PublicKey, error)
HmacKey(alg string, kid string) ([]byte, error)
RsaKey(alg string, kid string) (*rsa.PublicKey, error)
Close()
}

Temporal provides an implementation of the TokenKeyProvider, rsaTokenKeyProvider, that dynamically obtains public keys from given issuers' URIs that adhere to the JWKS format.

provider := authorization.NewRSAKeyProvider(cfg)

Note that the rsaTokenKeyProvider returned by NewRSAKeyProvider only implements RSAKey and Close methods, and returns an error from EcdsaKey and HmacKey methods. It is configured via config.Config.Global.Authorization.JWTKeyProvider:

common/service/config/config.go

// Contains the config for signing key provider for validating JWT tokens
JWTKeyProvider struct {
KeySourceURIs []string `yaml:"keySourceURIs"`
RefreshInterval time.Duration `yaml:"refreshInterval"`
}

KeySourceURIs are the HTTP endpoints that return public keys of token issuers in the JWKS format. RefreshInterval defines how frequently keys should be refreshed. For example, Auth0 exposes such endpoints as https://YOUR_DOMAIN/.well-known/jwks.json.

Format of JSON Web Tokens

The default JWT ClaimMapper expects authorization tokens to be in the following format:

bearer <token>
  • <token>: Must be the Base64 url-encoded value of the token.

The default JWT claim mapper expects permission claims in the JWT tokens to be named "permissions", unless overridden in configuration.

Each individual claim is expected to be in the following format:

<namespace>:<permission>
  • <namespace>: This can be either a Temporal Namespace name or "system" to represent system-wide permissions.
  • <permission>: This can be one of the four values:
    • read
    • write
    • worker
    • admin

The default JWT claim mapper converts these permissions into Temporal roles for the caller as described above.

Multiple permissions for the same namespace get OR'ed. For example, when accounting:read and accounting:write are found in a token, they are translated into authorization.RoleReader | authorization.RoleWriter.

Single sign-on integration

Temporal can be integrated with a single sign-on (SSO) experience by utilizing the ClaimMapper and Authorizer plugins. The default JWT ClaimMapper implementation can be used as is or as a base for a custom implementation of a similar plugin.

Temporal Web

To enable SSO for the Temporal Web UI edit the web service's configuration per the Temporal Web README.

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