JAAS Security Overview¶
This document provides an overview of JAAS security measures, focusing on areas related to sensitive data storage, transmission, and cryptographic technologies.
Cloud Credentials¶
Cloud credentials are API keys used by Juju/JAAS to provision cloud infrastructure. These credentials are securely uploaded to and stored by JAAS. When a model is created, the key is passed to the Juju controller to manage cloud resources.
User-provided cloud credentials are stored securely in a Vault, a tool for managing secrets. Ensuring the secure handling of these credentials is essential to prevent unauthorised access or data breaches.
Vault encrypts credentials at rest and provides mechanisms to prevent unauthorised access.
JAAS - Juju Communication¶
JAAS acts as an authentication gateway between users and Juju controllers.
Juju controllers trust JAAS by setting the login-token-refresh-url during bootstrap.
More information on setting up a Juju controller for JAAS can be found in our how-to guide.
Trust between Juju controllers and JAAS is established through asymmetric cryptography and JSON Web Tokens (JWTs).
Hint
While JWTs are also used for user sessions, the tokens exchanged between JAAS and Juju controllers are separate from user tokens.
The login-token-refresh-url points to a
JSON Web Key Set (JWKS)
endpoint, containing public keys used to verify tokens issued by JAAS.
The JWKS public and private key pair are generated at startup and placed in Vault. The keys are then periodically rotated.
When JAAS makes requests to a Juju controller, a JWT is issued that encodes user information and permissions, securely delegating authentication and authorisation from the controller to JAAS.
Details:
JWKS Endpoint:
<jimm-url>/.well-known/jwks.jsonKey Type/Size: RSA 4096 bits
Signing Algorithm: RS256
The following Go packages are used:
github.com/lestrrat-go/jwx/v2/jwagithub.com/lestrrat-go/jwx/v2/jwtgithub.com/lestrrat-go/jwx/v2/jwk
User Sessions¶
CLI-Based Sessions¶
When authenticating the Juju CLI to JAAS, users go through an OAuth login flow, (see Device Code Flow) after which the CLI is issued a JWT as an application session token. This token is stored on the filesystem and sent with each request, eliminating the need for repeated logins.
While Juju controller tokens use asymmetric cryptography, session tokens for users are signed using symmetric cryptography (i.e., a shared secret) with a cryptographic hash function. A symmetric-key signature is used here because only JAAS needs to verify the token.
The shared secret is generated by the JIMM charm operator using Juju secrets and passed to the application.
JWTs for CLI sessions contain the user’s email address, so they must be secured to prevent information leakage and malicious account use.
Details:
Key Size: >=512 bits
Signing Algorithm: HS256
The following Go packages are used:
github.com/lestrrat-go/jwx/v2/jwtgithub.com/lestrrat-go/jwx/v2/jwa
OIDC Authentication¶
JAAS uses OAuth 2.0 and OpenID Connect (OIDC) for user authentication. You can learn more from this overview.
The following Go packages are used:
golang.org/x/oauth2golang.org/x/oauth2/clientcredentialsgithub.com/coreos/go-oidc/v3/oidc
Device Code Flow¶
For CLI logins, the device code flow is used, where the Juju CLI prompts the user to log in via a browser with a random code. The backend stores access and refresh tokens, and the CLI receives an application session token.
This process does not rely on browser redirects and is not susceptible to traditional browser vulnerabilities.
Client Credential Flow¶
For machine-to-machine authentication, the client credentials flow is used. However, in JAAS, the client application sends its credentials to JAAS, which proxies them to the identity provider. A good example of this includes the Juju Terraform Provider where the client-credential flow is employed.
This scheme simplifies authentication for client applications but is only possible since JAAS is a trusted application in the system.
Macaroons & Offer Authentication¶
Macaroons are a tool for decentralised authentication similar to JSON Web Tokens. The Go Macaroon package is used by JAAS and has more details on the low-level operations that Macaroons are capable of.
Macaroons are used by Juju for various purposes but in JAAS their primary purpose is for authorising cross-model relations between controllers. When two Juju controllers (that are connected to JAAS) communicate for the purposes of sharing an application offer, JAAS acts as the source of truth for authorisation data. These checks are handled using macaroons.
Macaroons use a combination of HMAC for cryptographic signatures and symmetric encryption to encode the scope (or caveats) of what a macaroon is entitled to.
These operations are performed using HMAC-SHA256 and XSalsa20-Poly1305. The following Go
packages are used by the underlying macaroon package for these operations:
Hint
For those new to Go, the crypto/hmac and crypto/sha256 packages below
are included in the Go standard library.
crypto/hmaccrypto/sha256golang.org/x/crypto/nacl/secretbox
Additionally, the higher-level Macaroon Bakery package is used to interface with macaroons and introduces public key cryptography to perform similar operations as mentioned above. This allows services to trust macaroons generated externally.
These operations are performed using Ed25519 and XSalsa20-Poly1305. The following Go packages are
used by the underlying macaroon bakery package for these operations:
golang.org/x/crypto/nacl/boxgolang.org/x/crypto/curve25519
When a Juju controller is connected to JAAS, the login-token-refresh-url is used to determine where
the JAAS macaroon public key is located. This public key is used when Juju controllers issue macaroons
and enforces that the macaroon can only be discharged by JAAS, who holds the private key. Discharging
a macaroon refers to the process of verifying its claims.
Specific details are below:
Macaroon Public Key endpoint:
<jimm-url>/macaroons/publickeyKey Type: Ed25519 (256-bit key)
Signing algorithm: Ed25519
TLS Communication¶
TLS encryption is enforced between various components in JAAS, using Go’s standard
library (crypto/tls and crypto/x509). The minimum supported version is TLS v1.2.
Client - JAAS¶
The GO Juju client enforces TLS for all connections to JAAS, including the Juju CLI and Juju Terraform Provider.
JAAS - Juju Controllers¶
JAAS enforces TLS when connecting to Juju controllers.
JAAS - OpenFGA¶
TLS is not currently enforced between JAAS and OpenFGA due to a lack of TLS support in the OpenFGA charm operator.
JAAS - Vault¶
JAAS assumes TLS is used to communicate with Vault. The Vault charm uses TLS by default.
JAAS - PostgreSQL¶
JAAS does not enforce TLS when communicating with PostgreSQL, but it can be enabled when using the PostgreSQL charm. TLS is not enabled by default.
CORS¶
CORS or Cross-Origin Resource Sharing is a browser security feature designed to prevent malicious use of your online credentials. Read more about CORS here.
JAAS supports the use of CORS headers specifically for the Juju dashboard. The dashboard requires the ability to send cross-origin requests from the domain where it is hosted to the domain where JAAS is hosted. More information on how to set up CORS to securely handle these requests will be available in a future how-to guide.
The following Go package is used to validate CORS requests:
github.com/rs/cors