Workload Identity in a Multi System Environment (WIMSE) Architecture
draft-ietf-wimse-arch-03
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| Authors | Joseph A. Salowey , Yaroslav Rosomakho , Hannes Tschofenig | ||
| Last updated | 2025-01-07 (Latest revision 2024-10-21) | ||
| Replaces | draft-salowey-wimse-arch | ||
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draft-ietf-wimse-arch-03
Workload Identity in Multi System Environments J. Salowey
Internet-Draft Venafi
Intended status: Informational Y. Rosomakho
Expires: 5 July 2025 Zscaler
H. Tschofenig
1 January 2025
Workload Identity in a Multi System Environment (WIMSE) Architecture
draft-ietf-wimse-arch-03
Abstract
The increasing prevalence of cloud computing and micro service
architectures has led to the rise of complex software functions being
built and deployed as workloads, where a workload is defined as a
running instance of software executing for a specific purpose. This
document discusses an architecture for designing and standardizing
protocols and payloads for conveying workload identity and security
context information.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the Workload Identity in
Multi System Environments Working Group mailing list
(wimse@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/wimse/.
Source for this draft and an issue tracker can be found at
https://github.com/jsalowey/wimse-arch.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on 5 July 2025.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Workload Identity . . . . . . . . . . . . . . . . . . . . 5
3.1.1. Trust Domain . . . . . . . . . . . . . . . . . . . . 5
3.1.2. Workload Identifier . . . . . . . . . . . . . . . . . 5
3.1.3. Workload Identity Credentials . . . . . . . . . . . . 6
3.2. Workload Identity System Scenarios . . . . . . . . . . . 7
3.2.1. Basic Workload Identity Scenario . . . . . . . . . . 7
3.2.2. Context and workload Identity . . . . . . . . . . . . 9
3.2.3. Cross-Domain Communication . . . . . . . . . . . . . 11
3.3. Workload Identity Use Cases . . . . . . . . . . . . . . . 14
3.3.1. Bootstrapping Workload Identity . . . . . . . . . . . 14
3.3.2. Service Authentication . . . . . . . . . . . . . . . 16
3.3.3. Security Context Establishment and Propagation . . . 17
3.3.4. Service Authorization . . . . . . . . . . . . . . . . 18
3.3.5. Delegation and Impersonation . . . . . . . . . . . . 18
3.3.6. Asynchronous and Batch Requests . . . . . . . . . . . 18
3.3.7. Cross-boundary Workload Identity . . . . . . . . . . 19
4. Security Considerations . . . . . . . . . . . . . . . . . . . 19
4.1. Traffic Interception . . . . . . . . . . . . . . . . . . 19
4.2. Information Disclosure . . . . . . . . . . . . . . . . . 20
4.3. Workload Compromise . . . . . . . . . . . . . . . . . . . 20
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1. Normative References . . . . . . . . . . . . . . . . . . 20
6.2. Informative References . . . . . . . . . . . . . . . . . 21
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
The increasing prevalence of cloud computing and micro service
architectures has led to the rise of complex software functions being
built and deployed as systems composed of workloads, where a workload
is defined as a running instance of software executing for a specific
purpose.
Workloads need to be provisioned with an identity when they are
started. Often, additional information needs to be provided, such as
trust anchors and security context details. Workload identity
credential is used to authenticate communications between workloads.
Workloads make use of identity information and additional context
information to perform authentication and authorization.
This architecture considers two ways to express identity information:
X.509 certificates often used in the TLS layer and JSON Web Tokens
(JWTs) used at the application layer. Collectively, these are
referred to as WIMSE tokens. The applicability of given token format
depends on application and security context and will be explored in
later sections.
Once the workload is started and has obtained identity information,
it can start performing its functions. Once the workload is invoked
it may require interaction with other workloads. An example of such
interaction is shown in [I-D.ietf-oauth-transaction-tokens] where an
externally-facing endpoint is invoked using conventional
authorization mechanism, such as an OAuth 2.0 access token. The
interaction with other workload may require the security context
associated with the authorization to be passed along the call chain.
In the rest of the document we describe terminology and use cases,
discuss details of the architecture, and discuss threats.
2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document uses the following terms:
* Workload
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A workload is a running instance of software executing for a specific
purpose. Workload typically interacts with other parts of a larger
system. A workload may exist for a very short durations of time
(fraction of a second) and run for a specific purpose such as to
provide a response to an API request. Other kinds of workloads may
execute for a very long duration, such as months or years. Examples
include database services and machine learning training jobs.
* Security Context
A security context provides information needed for a workload to
perform its function. This information is often used for
authorization, accounting and auditing purposes and often contains
information about the request being made. Some examples include user
information, software and hardware information or information about
what processing has already happened for the request. Different
pieces of context information may originate from different sources.
* Identity Proxy
Identity proxy is an intermediary that can inspect, replace or
augment workload identity and security context information. Identity
proxy can be a capability of a transparent network service, such as a
security gateway, or it can be implemented in a service performing
explicit connection processing, such as an ingress gateway or a
Content Delivery Network (CDN) service.
* Attestation
Attestation is the function through which a task verifies the
identity of a separate Workload. (TBD: sync definition with
reference RaTS architecture)
* Workload Identity Token
A token that contains a workload identifier used for service to
service authentication. The token is bound to a cryptographic key
and requires that the presenter provide proof of possession of the
secret key material. This token is further defined in
[I-D.ietf-wimse-s2s-protocol]
3. Architecture
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3.1. Workload Identity
Workload identity construct consists of three basic building blocks:
trust domain, workload identifier and workflow identity credentials.
These components are sufficient for establishing authentication,
authorization and accounting processes. More complex identity
constructs can be created from these basic building blocks.
3.1.1. Trust Domain
A trust domain is a logical grouping of systems that share a common
set of security controls and policies. Workload certificates and
tokens are issued under the authority of a trust domain. Trust
domains SHOULD be identified by a fully qualified domain name
associated with the organization defining the trust domain. THe FQDN
format of trust domain helps to ensure uniqueness of the trust domain
identifier. A trust domain maps to one or more trust anchors for
validating X.509 certificates and a mechanism to securely obtain a
JWK Set [RFC7517] for validating WIMSE WIT tokens. This mapping MUST
be obtained through a secure mechanism that ensures the authenticity
and integrity of the mapping is fresh and not compromised. This
secure mechanism is out of scope for this document.
A single organization may define multiple trust domains for different
purpose such as different departments or environments. Each trust
domain must have a unique identifier. Workload identifiers are
scoped within a trust domain. If two identifiers differ only by
trust domain they still refer to two different entities.
3.1.2. Workload Identifier
The WIMSE architecture defines a workload identifier as a URI
[RFC3986]. This URI is used in the subject fields in the
certificates and tokens defined later in this document. The URI MUST
meet the criteria for the URI type of Subject Alternative Name
defined in Section 4.2.1.6 of [RFC5280].
The name MUST NOT be a relative URI, and it MUST follow the URI
syntax and encoding rules specified in [RFC3986]. The name MUST
include both a scheme and a scheme-specific-part.
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In addition the URI MUST include an authority that identifies the
trust domain within which the identifier is scoped. The trust domain
SHOULD be a fully qualified domain name belonging to the organization
defining the trust domain to help provide uniqueness for the trust
domain identifier. The scheme and scheme specific part are not
defined by this specification. An example of an identifier format
that conforms to this definition is SPIFFE ID
(https://github.com/spiffe/spiffe/blob/main/standards/SPIFFE-ID.md).
While the URI encoding rules allow host names to be specified as IP
addresses, IP addresses MUT NOT be used to represent trust domains
except in the case where they are needed for compatibility with
existing naming schemes.
A workload identity only has meaning within the scope of a specific
issuer. Two identities of the same value issued by different issuers
may or may not refer to the same workload. In order to avoid
collisions identity URIs SHOULD specify, in the URI's "authority"
field, the trust domain associated with an issuer that is selected
from a global name space such as host domains. However, the
validator of an identity credential MUST make sure that they are
using the correct issuer credential to verify the identity credential
and that the issuer is trusted to issue tokens for the defined trust
domain.
3.1.3. Workload Identity Credentials
The Agent provisions the identity credentials to the workload. These
credentials are represented in form of JWT tokens and/or X.509
certificates.
JWT bearer tokens are presented to another party as a proof of
identity. They are signed to prevent forgery, however since these
credentials are often not bound to other information it is possible
that they could be stolen and reused elsewhere. To mitigate these
risks and make the token more generally useful the WIMSE architecture
defines a workload identity token that binds a JWT to a cryptographic
key.
Both X.509 certificate and workload identity token credentials
consist of two parts:
* a certificate or WIT is a signed data structure that contains a
public key and identity information
* a corresponding private key
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The certificate or WIT is presented during authentication, however
the private key is kept secret and only used in cryptographic
computation to prove that the presenter has access to the private key
corresponding to the public key.
3.2. Workload Identity System Scenarios
3.2.1. Basic Workload Identity Scenario
+-------------------------------Trust Boundary---------------+
| |
| |
+-----+ +--------------+ |
| | | | (3) |
| | +---> Workload 1 +-------------------+ |
| G | | | | | |
| a | | +-------^------+ | |
| t | | | | |
+------------+ | e | | | (1) | |
| | (2) | w | (3) | | | |
| App Client +----->| a +-----+ +-------+-------+ | |
| | | y | | | +-------+------+ |
+------------+ | +-----+ | CA/Credential | (1) | | |
| S | (4) | | Service +----------> Workload 3 | |
| e | | | | | | |
| r | | +-------+-------+ +-------+------+ |
| v | | | | |
| i | | | (1) | |
| c | | | | |
| e | | +-------v------+ | |
| | | | | (4) | |
| | +---> Workload 2 +-------------------+ |
| | | | |
+-----+ +--------------+ |
| |
| |
| |
+------------------------------------------------------------+
Figure 1: Basic example workload application system.
The above diagram presents a basic workload application system. The
large box represents a trust domain within which the workload
application is hosted. Within this example there are three
workloads, a gateway, that accepts external clients and a CA/
credential service that issues workload identity credentials for the
trust domain. External to the workload application system there is
an application client that calls APIs on workloads.
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Here is a brief summary of each component
* Trust Domain
The large box represents a trust domain of the application that is
composed of several workloads. A trust domain may have a more
complex internal structure with more workloads, multiple gateways,
internal infrastructure, and other services.
* Workload
Three workloads are shown. Each workload is an instance of running
software executing for a specific purpose. Workloads obtain their
identity credentials from a Credentials Service (1) and use them to
authenticate to other workloads and systems in the process of sending
and receiving requests to and from external systems or other internal
workloads.
* Gateway Service
A gateway service typically acts as an intermediary between the
internal application trust domain and external systems. The gateway
is responsible for ensuring appropriate isolation between external
and internal domains. It also routes incoming requests to the
correct workload. The gateway may also handle authentication, token
exchange, and token transformation.
* CA/Credential Service
In this diagram the token/Credential service is a service responsible
for issuing workload identities to workloads in the same trust
domain. The credentials are often X.509 based or JWT based.
High level flows within the diagram
* (1) Workload Identity Credential Distribution
Workloads typically retrieve their workload identity credentials
early in their lifecycle from a credentials service associated with
their trust domain. The protocol interaction for obtaining
credentials varies with deployment and is not detailed here.
* (2) Application client Requests
Clients send API requests to the application. In the example above,
the gateway routes the request to the correct workload. In addition,
the gateway may assist in authenticating the incoming request and
provide information resulting from the authentication to the target
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workload. The authentication exchange is not covered in detail in
this example. The client request is typically made over HTTPS, but
other protocols may be used in some systems. The gateway usually
terminates the TLS session so it has visibility into the request in
order to route it correctly.
* (3) API request to workload 1
The gateway is configured to forward requests to the correct
workload. The gateway often modifies the request to include specific
authentication information about the application client and to remove
any information that should not be forwarded internally. The gateway
authenticates the workload before forwarding the request. This
authentication usually uses TLS. The target workload may
authenticate the gateway using TLS or some other means. As part of
servicing the request the workload must make a request to another
workload in the system. In this scenario the workload is making a
request to workload 3 over HTTPS. Workload 1 may be able to
authenticate the identity of workload 3 through the TLS protocol to
ensure it is making a request of the right party. Workload 3 will
authenticate workload 1 using its workload identity credentials. If
the workload identity credentials are X.509 certificates then this
can happen through TLS client authentication (mutual TLS).
Alternatively, the workloads can use a JWT based authentication
mechanism to authenticate on another. Workload three can use the
authenticated identity of workload 1 to determine which APIs workload
1 is authorized 2 and to associated the authenticated identity with
logs and other audit information.
* (4) API request to workload 2
Similarly to the previous flow, the gateway may determine that for
another API call, the application client's request needs to be
handled by workload 2. The case behaves the same as the previous
flow except that the gateway may need to authenticate workload 2
before forwarding traffic to it. Workload 3 will then authorize and
audit the request based on the authenticated identity of workload 2.
Workload 2 and workload 1 may be authorized to use different APIs on
workload 3. If workload 1 or 2 makes an API request that it is not
authorized for, then workload 3 will reject the request.
3.2.2. Context and workload Identity
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+-----------------------Trust Boundary---------+
| |
| +----------------+ |
+--+--+ | | |
| +------------------>| Context | |
| | (3) | | |
| |<------------------+ Service | |
| | (c) | | |
| G | +----------------+ |
| a | |
(1) | t | |
+-------+ | e | +------------+ +-------------+ |
| App | (2) | w | (4) | | (5) | | |
| Client+---->| a +----->| workload 1 +----->| workload 2 | |
+-------+ (a) | y | (c) | | (c) | | |
| | +------------+ +-------------+ |
| S | |
| e | |
| r | |
| v | |
| i | |
| c | |
| e | |
| | |
+--+--+ |
| |
| |
| |
+----------------------------------------------+
Figure 2: Context example workload application system.
In many cases the application system uses other security context
information about the request during authorization and auditing. The
following is a basic scenario that illustrates the propagation of
security context in the workload system. Some of the components and
interactions have been removed from the previous scenario for
simplicity.
* Context Service This scenario adds a context service component
which is responsible for creating security context based on
authentication and other calculations. Context can be represented
in many ways; it can be a plaintext data structure, a signed data
structure such as a jwt or a pointer used to lookup the context as
a data structure stored somewhere else. In one common example,
creating the context may involve a token exchange converting an
OAuth 2.0 access token into a different token format, such as a
transaction token, that is understood by internal services.
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* (1) Initial Authentication In the initial authentication the
gateway service obtains credentials it can use with the gateway
service. This authentication may involve several steps and may be
performed by an external entity such as an identity provider. The
authentication process will result in a credential that the
gateway service can evaluate. For example, the credential could
be an OAuth Access token. If the client already has an access
token that it can use to authenticate to the gateway, such as an
X.509 certificate, then it may skip this step.
* (2) Application Client Request The application client makes a
request to the gateway over HTTPS. The client may be
authenticated to the gateway through TLS client authentication
(mutual TLS) or through a credential such as an access token
obtained in step 1.
* (3) Establishing the request context The gateway service requests
a security context token (c) from a token service. This process
may entail sending an access token (a) along with other
information to a token exchange endpoint to obtain the context
token, which contains information about the entity accessing the
system. This context is typically only relevant to the internal
system and is not returned to the client. The gateway may use
alternative mechanisms to get the internal security context
information (c).
* (4) Forwarding Request to Workload The gateway forwards the
request along with the context information (c) to the appropriate
workload. A bearer token, such as an access token (a), is not
usually forwarded as it is only meant for external access. The
workload uses information in the context token in applying
authorization policy to the application client's request. If the
workload does not receive a context token, then it will deny
requests that rely on information from the token.
* (5) Making Additional Workload Originated Requests The workload
may need to make requests of other workloads. When making these
requests, the workload includes the context information so
Workload 2 can authorize and audit the request. Workload 2 may
have a policy requiring Workload 1 to authenticate its service
identity and provide valid context information (c) to access
certain APIs.
3.2.3. Cross-Domain Communication
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+--------------------------Trust Boundary------+
| |
+--+--+ |
| | |
| G | |
| a | |
| t | |
+-------+ | e | +------------+ +-------------+ |
| App | (1) | w | (2) | | (4) | | |
| Client+---->| a +----->| workload 1 +----->| workload 2 | |
+-------+ (a) | y | (c) | | (c) | | |
| | +-+---------++ ++--------+---+ |
| S | | | | |
| e | (3)| (5)|(c) | |
| r | | | | |
| v | | +-+--------++ | |
| i | | | Token | | |
| c | | | | (6)|(t) |
| e | | | Service | | |
| | | +-----------+ | |
+--+--+ | | |
| | | |
| | | |
| | | |
+-----------+---------------------------+------+
| |
| |
| |
| |
| |
+-------v--------+ +------------v--+
| Infrastructure | | External |
| | | |
| Service | | Service |
+----------------+ +---------------+
Figure 3: External request workload application system.
In many applications workloads must make requests of infrastructure
that operates as a different trust domain or external services that
are in a separate trust domain. Figure Figure 3 shows this scenario.
The scenario shows some new components described below. Components
and interactions from previous scenarios are still relevant to this
example, but are omitted for simplicity.
* Token Service - the token service is responsible for exchanging
information that is internal to the system such as service
identity and/or security context information for a token that can
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be presented to an external service to gain access to
infrastructure or an external service. Note that in some cases
the token service may reside in a different trust domain or there
may be token services in multiple trust domains. In some cases
the workload will need to contact token services in various
domains in order to gain access to infrastructure or external
service.
* Infrastructure Service - this service is often part of the
application, but it is managed by an infrastructure provider and
may require different information to access it.
* External Service - this service is distinct from the application
and hosted in a separate trust domain. This trust domain often
has different access requirements that workloads in the internal
trust domain.
Some example interactions in this scenario:
* (1) The application client is making requests with authentication
information as in the other scenarios
* (2) The gateway forwards the request to the appropriate workload
with the security context information
* (3) The workload needs to access an infrastructure service and,
because it is managed by the same organization, it authenticates
to the service directly using its workload credentials.
* (4) Workload 1 contacts Workload 2 to perform an operation. This
request is accompanied by a security context as in the other
scenarios.
* (5) Workload 2 determines it needs to communicate with an external
service. In order to gain access to this service it must first
obtain a token/credential (t) that it can use externally. It
authenticates to the token service using its workload identity and
provides security context information. The token service
determines what type of externally usable token to issue to the
workload.
* (6) Workload 2 uses this new token/credential (t) to access the
external service.
* Note that in (3) and (6) the workload may need to authenticate to
an external token service to obtain an access token to access the
system in the foreign trust domain.
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3.3. Workload Identity Use Cases
3.3.1. Bootstrapping Workload Identity
[TODO: this section will need to be updated to discuss workload
identifier as a concept as well]
A workload needs to obtain its identity early in its lifecycle. This
identity is the base identity upon which further identity and
security context are built.
Identity bootstrapping often utilizes identity information
provisioned through mechanisms specific to hosting platforms and
orchestration services. This initial bootstrapping information is
used to obtain specific identity credentials for a workload. This
process may use attestation to ensure the workload receives the
correct identity credentials. An example of a bootstrapping process
follows.
Figure 4 provides an example of software layering at a host running
workloads. During startup, workloads bootstrap their identity with
the help of an agent. The agent may be associated with one or more
workloads to help ensure that workloads are provisioned with the
correct identity. The agent provides attestation evidence and other
relevant information to a server. The server validates this
information and provides the agent with identity credentials for the
workloads it is associated with. The server can use a variety of
internal and external means to validate the request against policy.
After obtaining identity credentials from the Server, the agent
passes them to the workload.
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+-----------------+
| Server |
| |
| +-------------+ |
| | Attestation | |
| +-------------+ |
+---------+-------+
^ | . .
| | Identity | | Workload
| | Credentials | | to
| | | | Workload
| | | | Communication
+-------+-+------------------------------+-+-----------+
| | | v V |
| | v +----------------+ |
| +----+----------+ +-+--------------+ | |
| | Agent | | Workloads | | |
| | <+--------------+> | | |
| | ^ | Identity | ^ +-+ |
| +------------+--+ Credentials +--+-------------+ |
| | | |
| | | Identity |
| Attestation | | Credentials |
| v v |
+------------------------------------------------------+
| Host Operating System and Hardware |
+------------------------------------------------------+
Figure 4: Host Software Layering in a Workload Identity Architecture.
How the workload obtains its identity credentials and interacts with
the agent is subject to different implementations. Some common
mechanisms for obtaining this initial identity include:
* File System - in this mechanism the identity credential is
provisioned to the workload via the filesystem.
* Local API - the identity credential is provided through an API,
such as a local domain socket (for example SPIFFE or QEMU guest
agent) or network API (for example Cloud Provider Metadata
Server).
* Environment Variables - identity credential may also be injected
into workloads using operating system environment variables.
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3.3.2. Service Authentication
One of the most basic use cases for workload identity is
authentication of one workload to another, such as in the case where
one service is making a request to another service as part of a
larger, more complex application. Following authentication, the
request to the service offered by the workload needs to be
authorized. Even in this simple case the identity of a workload is
often composed of many attributes such as:
* Trigger Information
* Service Name
* Instance Name
* Role
* Environment
* Trust Domain
* Software Attestation
* Hardware Attestation
These attributes are used for various purposes such as:
* ensuring the request is made to the correct service or service
instance
* authorizing access to APIs and resources
* providing an audit trail of requests within a system
* providing context for other decisions made within a service
There are several methods defined to perform this authentication.
Some of the most common include:
* TLS authentication of the server using X.509 certificates and
client bearer token, encoded as JWTs.
* Mutual TLS authentication using X.509 certificate for both client
and server.
* TLS authentication of the server and HTTP request signing using a
secret key.
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Figure 5 illustrates the communication between different workloads.
Two aspects are important to highlight: First, there is a need to
consider the interaction with workloads that are external to the
trust domain (sometimes called cross-domain). Second, the
interaction does not only occur between workloads that directly
interact with each other but instead may also take place across
intermediate workloads (in an end-to-end style).
+-----------------+
| Workload |
| (external) |
| ^ |
+-------+---------+
|
|
+-------+-------------------------Trust Boundary---------------+
| | |
| | |
| +----+------+ Hop-by- +-----------+ Hop-by- +-----------+ |
| | v | Hop | | Hop | | |
| | Workload | Security | Workload | Security | Workload | |
| | <+----------+> <+----------+> | |
| | | | | | | |
| | | | | | | |
| | O<-----+----------+-----------+----------+---->O | |
| +-----------+ E2E +-----------+ E2E +-----------+ |
| |
| |
+--------------------------------------------------------------+
Figure 5: Workload-to-Workload Communication.
3.3.3. Security Context Establishment and Propagation
In a typical system of workloads additional information is needed in
order for the workload to perform its function. For example, it is
common for a workload to require information about a user or other
entity that originated the request. Other types of information may
include information about the hardware or software that the workload
is running or information about what processing and validation has
already been done to the request. This type of information is part
of the security context that the workload uses during authorization,
accounting and auditing. This context is propagated and possibly
augmented from workload to workload using tokens. Workload identity
comes into play to ensure that the information in the context can
only be used by an authorized workload and that the context
information originated from an authorized workload.
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3.3.4. Service Authorization
After authentication of the peer, a workload can perform
authorization by verifying that the authenticated identity has the
appropriate permissions to access the requested resources and perform
required actions. This process involves evaluating the security
context described previously. The workload validates the security
context, and checks the validity of permissions against its security
policies to ensure that only authorized actions are allowed.
3.3.5. Delegation and Impersonation
When source workloads send authenticated requests to destination
workloads, those destination workloads may rely on upstream
dependencies to fulfill such requests. Such access patterns are
increasingly common in a microservices architecture. While X.509
certificates can be used for point-to-point authentication, such
services relying on upstream microservices for answers, may use
delegation and/or impersonation semantics as described in RFC 8693
OAuth 2.0 Access Token Exchange.
WIMSE credentials constrain the subjects and actors identified in
delegation and impersonation tokens to be bound by TrustDomains, and
to follow their issuing authorities' trust configurations. Upstream
workloads should consider the security context of delegation and/or
impersonation tokens within and across Trust Domains, when arriving
at authorization decisions.
3.3.6. Asynchronous and Batch Requests
Source workloads may send authenticated asynchronous and batch
requests to destination workloads. A destination workload may need
to fulfill such requests with requests to authorized upstream
protected resources and workloads, after the source workload
credentials have expired. Credentials identifying the original
source workload as subject may need to be obtained from the
credential issuing authority with appropriately-downscoped context
needed access to upstream workloads. These credentials should
identify the workload as the actor in the actor chain, but may also
identify other principals that the action is taken on behalf. To
mitigate risks associated with long-duration credentials, these
credentials should be bound to the workload identity credential such
as an X.509 certificate or Workload Identity Token (WIT) of the
acting service performing asynchronous computation on the source
workload's behalf.
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3.3.7. Cross-boundary Workload Identity
As workloads often need to communicate across trust boundaries, extra
care needs to be taken when it comes to identity communication to
ensure scalability and privacy. (TODO: align with OAuth cross domain
identity and authorization)
3.3.7.1. Egress Identity Generalization
A workload communicating with a service, or another workload located
outside the trust boundary may need to provide modified identity
information. Detailed identity of internal workload originating the
communication is relevant inside the trust boundary but could be
excessive for the outside world and expose potentially sensitive
internal topology information.
A security gateway at the edge of a trust boundary can be used to
validate identity information of the workload, perform context
specific authorization of the transaction and replace workload
specific identity with a generalized one for a given trust domain.
3.3.7.2. Inbound Gateway Identity Validation
Inbound security gateway is a common design pattern for service
protection. This functionality is often found in CDN services, API
gateways, load balancers, Web Application Firewalls (WAFs) and other
security solutions. Workload identity verification of inbound
requests should be performed as a part of these security services.
After validation of workload identity, the gateway may either leave
it unmodified or replace it with its own identity to be validated by
the destination.
4. Security Considerations
4.1. Traffic Interception
Workloads communicating with applications may face different threats
to traffic interception in different deployments. In many
deployments security controls are deployed for internal
communications at lower layers to reduce the risk of traffic
observation and modification for network communications. When a
security layer, such as TLS, is deployed in these environments. TLS
may be terminated in various places, including the workload itself,
and in various middleware devices, such as load balancers, gateways,
proxies, and firewalls. Therefore, protection is provided only
between each adjacent pair of TLS endpoints. There are no guarantees
of confidentiality, integrity and correct identity passthrough in
those middleware devices and services.
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4.2. Information Disclosure
Observation and interception of network traffic is not the only means
of disclosure in these systems. Other vectors of information leakage
is through disclosure in log files and other observability and
troubleshooting mechanisms. For example, an application may log the
contents of HTTP headers containing JWT bearer tokens. The
information in these logs may be made available to other systems with
less stringent access controls, which may result in this token
falling into an attackers hands who then uses it to compromise a
system. This creates privacy risks and potential surface for
reconnaissance attacks. If observed tokens can be reused, this also
may allow attackers to impersonate workloads.
4.3. Workload Compromise
Even the most well-designed and implemented workloads may contain
security flaws that allow an attacker to gain limited or full
compromise. For example, a server side request forgery may result in
the ability for an attacker to force the workload to make requests of
other parts of a system even though the rest of the workload
functionality may be unaffected. An attacker with this advantage may
be able to utilize privileges of the compromised workload to attack
other parts of the system. Therefore it is important that
communicating workloads apply the principle of least privilege
through security controls such as authorization.
5. IANA Considerations
This document has no IANA actions.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/rfc/rfc3986>.
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[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/rfc/rfc5280>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/rfc/rfc7517>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
6.2. Informative References
[I-D.ietf-oauth-transaction-tokens]
Tulshibagwale, A., Fletcher, G., and P. Kasselman,
"Transaction Tokens", Work in Progress, Internet-Draft,
draft-ietf-oauth-transaction-tokens-04, 30 December 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-oauth-
transaction-tokens-04>.
[I-D.ietf-wimse-s2s-protocol]
Campbell, B., Feldman, D., Salowey, J., Schwenkschuster,
A., and Y. Sheffer, "WIMSE Service to Service
Authentication", Work in Progress, Internet-Draft, draft-
ietf-wimse-s2s-protocol-01, 18 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-wimse-
s2s-protocol-01>.
Acknowledgments
Todo: Add your name here.
Authors' Addresses
Joseph Salowey
Venafi
Email: joe@salowey.net
Yaroslav Rosomakho
Zscaler
Email: yaroslavros@gmail.com
Hannes Tschofenig
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Email: hannes.tschofenig@gmx.net
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