Merge 50165ce9e1 into e2d5ee0927

currently, the policy approach node to user matching
with a quite naive approach looking at the username
provided in the policy and matched it with the username
on the nodes. This worked ok as long as usernames were
unique and did not change.

As usernames are no longer guarenteed to be unique in
an OIDC environment we cant rely on this.

This changes the mechanism that matches the user string
(now user token) with nodes:

- first find all potential users by looking up:
  - database ID
  - provider ID (OIDC)
  - username/email

If more than one user is matching, then the query is
rejected, and zero matching nodes are returned.

When a single user is found, the node is matched against
the User database ID, which are also present on the actual
node.

This means that from this commit, users can use the following
to identify users in the policy:
- provider identity (iss + sub)
- username
- email
- database id

There are more changes coming to this, so it is not recommended
to start using any of these new abilities, with the exception
of email, which will not change since it includes an @.

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

hscontrol/policy/acls.go

@@ -180,7 +180,12 @@ func (pol *ACLPolicy) CompileFilterRules(
 		for srcIndex, src := range acl.Sources {
 			srcs, err := pol.expandSource(src, users, nodes)
 			if err != nil {
-				return nil, fmt.Errorf("parsing policy, acl index: %d->%d: %w", index, srcIndex, err)
+				return nil, fmt.Errorf(
+					"parsing policy, acl index: %d->%d: %w",
+					index,
+					srcIndex,
+					err,
+				)
 			}
 			srcIPs = append(srcIPs, srcs...)
 		}
@@ -339,12 +344,21 @@ func (pol *ACLPolicy) CompileSSHPolicy(
 		case "check":
 			checkAction, err := sshCheckAction(sshACL.CheckPeriod)
 			if err != nil {
-				return nil, fmt.Errorf("parsing SSH policy, parsing check duration, index: %d: %w", index, err)
+				return nil, fmt.Errorf(
+					"parsing SSH policy, parsing check duration, index: %d: %w",
+					index,
+					err,
+				)
 			} else {
 				action = *checkAction
 			}
 		default:
-			return nil, fmt.Errorf("parsing SSH policy, unknown action %q, index: %d: %w", sshACL.Action, index, err)
+			return nil, fmt.Errorf(
+				"parsing SSH policy, unknown action %q, index: %d: %w",
+				sshACL.Action,
+				index,
+				err,
+			)
 		}
 
 		principals := make([]*tailcfg.SSHPrincipal, 0, len(sshACL.Sources))
@@ -978,6 +992,7 @@ func filterNodesByUser(nodes types.Nodes, users []types.User, userToken string)
 	for _, user := range users {
 		if user.ProviderIdentifier == userToken {
 			potentialUsers = append(potentialUsers, user)
+
 			break
 		}
 		if user.Email == userToken {