This changeset covers a sidebar discussion that @schmichael and I had around the
design for pre-forwarding auth. This includes some changes extracted out of
#15513 to make it easier to review both and leave a clean history.
* Remove fast path for NodeID. Previously-connected clients will have a NodeID
set on the context, and because this is a large portion of the RPCs sent we
fast-pathed it at the top of the `Authenticate` method. But the context is
shared for all yamux streams over the same yamux session (and TCP
connection). This lets an authenticated HTTP request to a client use the
NodeID for authentication, which is a privilege escalation. Remove the fast
path and annotate it so that we don't break it again.
* Add context to decisions around AuthenticatedIdentity. The `Authenticate`
method taken on its own looks like it wants to return an `acl.ACL` that folds
over all the various identity types (creating an ephemeral ACL on the fly if
neccessary). But keeping these fields idependent allows RPC handlers to
differentiate between internal and external origins so we most likely want to
avoid this. Leave some docstrings as a warning as to why this is built the way
it is.
* Mutate the request rather than returning. When reviewing #15513 we decided
that forcing the request handler to call `SetIdentity` was repetitive and
error prone. Instead, the `Authenticate` method mutates the request by setting
its `AuthenticatedIdentity`.
Upcoming work to instrument the rate of RPC requests by consumer (and eventually
rate limit) require that we authenticate a RPC request before forwarding. Add a
new top-level `Authenticate` method to the server and have it return an
`AuthenticatedIdentity` struct. RPC handlers will use the relevant fields of
this identity for performing authorization.
This changeset includes:
* The main implementation of `Authenticate`
* Provide a new RPC `ACL.WhoAmI` for debugging authentication. This endpoint
returns the same `AuthenticatedIdentity` that will be used by RPC handlers. At
some point we might want to give this an equivalent HTTP endpoint but I didn't
want to add that to our public API until some of the other Workload Identity
work is solidified, especially if we don't need it yet.
* A full coverage test of the `Authenticate` method. This sets up two server
nodes with mTLS and ACLs, some tokens, and some allocations with workload
identities.
* Wire up an example of using `Authenticate` in the `Namespace.Upsert` RPC and
see how authorization happens after forwarding.
* A new semgrep rule for `Authenticate`, which we'll need to update once we're
ready to wire up more RPC endpoints with authorization steps.
The List RPC correctly authorized against the prefix argument. But when
filtering results underneath the prefix, it only checked authorization for
standard ACL tokens and not Workload Identity. This results in WI tokens being
able to read List results (metadata only: variable paths and timestamps) for
variables under the `nomad/` prefix that belong to other jobs in the same
namespace.
Fixes the filtering and split the `handleMixedAuthEndpoint` function into
separate authentication and authorization steps so that we don't need to
re-verify the claim token on each filtered object.
Also includes:
* update semgrep rule for mixed auth endpoints
* variables: List returns empty set when all results are filtered
Metrics state is local to the server and needs to use time, which is normally
forbidden in the FSM code. We have a bypass for this rule for
`metrics.MeasureSince` but needed one for `metrics.MeasureSinceWithLabels` as well.
* test: don't use loop vars in goroutines
fixes a data race in the test
* test: copy objects in statestore before mutating
fixes data race in test
* test: @lgfa29's segmgrep rule for loops/goroutines
Found 2 places where we were improperly using loop variables inside
goroutines.
In order to support implicit ACL policies for tasks to get their own
secrets, each task would need to have its own ACL token. This would
add extra raft overhead as well as new garbage collection jobs for
cleaning up task-specific ACL tokens. Instead, Nomad will create a
workload Identity Claim for each task.
An Identity Claim is a JSON Web Token (JWT) signed by the server’s
private key and attached to an Allocation at the time a plan is
applied. The encoded JWT can be submitted as the X-Nomad-Token header
to replace ACL token secret IDs for the RPCs that support identity
claims.
Whenever a key is is added to a server’s keyring, it will use the key
as the seed for a Ed25519 public-private private keypair. That keypair
will be used for signing the JWT and for verifying the JWT.
This implementation is a ruthlessly minimal approach to support the
secure variables feature. When a JWT is verified, the allocation ID
will be checked against the Nomad state store, and non-existent or
terminal allocation IDs will cause the validation to be rejected. This
is sufficient to support the secure variables feature at launch
without requiring implementation of a background process to renew
soon-to-expire tokens.
PR #11956 implemented a new mTLS RPC check to validate the role of the
certificate used in the request, but further testing revealed two flaws:
1. client-only endpoints did not accept server certificates so the
request would fail when forwarded from one server to another.
2. the certificate was being checked after the request was forwarded,
so the check would happen over the server certificate, not the
actual source.
This commit checks for the desired mTLS level, where the client level
accepts both, a server or a client certificate. It also validates the
cercertificate before the request is forwarded.
Tim Gross