resolve user identifier to stable ID

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/app.go

@@ -1026,14 +1026,18 @@ func (h *Headscale) loadACLPolicy() error {
 		if err != nil {
 			return fmt.Errorf("loading nodes from database to validate policy: %w", err)
 		}
+		users, err := h.db.ListUsers()
+		if err != nil {
+			return fmt.Errorf("loading users from database to validate policy: %w", err)
+		}
 
-		_, err = pol.CompileFilterRules(nodes)
+		_, err = pol.CompileFilterRules(users, nodes)
 		if err != nil {
 			return fmt.Errorf("verifying policy rules: %w", err)
 		}
 
 		if len(nodes) > 0 {
-			_, err = pol.CompileSSHPolicy(nodes[0], nodes)
+			_, err = pol.CompileSSHPolicy(nodes[0], users, nodes)
 			if err != nil {
 				return fmt.Errorf("verifying SSH rules: %w", err)
 			}

hscontrol/db/node_test.go

@@ -255,10 +255,10 @@ func (s *Suite) TestGetACLFilteredPeers(c *check.C) {
 	c.Assert(err, check.IsNil)
 	c.Assert(len(testPeers), check.Equals, 9)
 
-	adminRules, _, err := policy.GenerateFilterAndSSHRulesForTests(aclPolicy, adminNode, adminPeers)
+	adminRules, _, err := policy.GenerateFilterAndSSHRulesForTests(aclPolicy, adminNode, adminPeers, []types.User{*stor[0].user, *stor[1].user})
 	c.Assert(err, check.IsNil)
 
-	testRules, _, err := policy.GenerateFilterAndSSHRulesForTests(aclPolicy, testNode, testPeers)
+	testRules, _, err := policy.GenerateFilterAndSSHRulesForTests(aclPolicy, testNode, testPeers, []types.User{*stor[0].user, *stor[1].user})
 	c.Assert(err, check.IsNil)
 
 	peersOfAdminNode := policy.FilterNodesByACL(adminNode, adminPeers, adminRules)

hscontrol/db/routes.go

@@ -648,8 +648,13 @@ func EnableAutoApprovedRoutes(
 			if approvedAlias == node.User.Username() {
 				approvedRoutes = append(approvedRoutes, advertisedRoute)
 			} else {
+				users, err := ListUsers(tx)
+				if err != nil {
+					return fmt.Errorf("looking up users to expand route alias: %w", err)
+				}
+
 				// TODO(kradalby): figure out how to get this to depend on less stuff
-				approvedIps, err := aclPolicy.ExpandAlias(types.Nodes{node}, approvedAlias)
+				approvedIps, err := aclPolicy.ExpandAlias(types.Nodes{node}, users, approvedAlias)
 				if err != nil {
 					return fmt.Errorf("expanding alias %q for autoApprovers: %w", approvedAlias, err)
 				}

hscontrol/grpcv1.go

@@ -737,14 +737,18 @@ func (api headscaleV1APIServer) SetPolicy(
 	if err != nil {
 		return nil, fmt.Errorf("loading nodes from database to validate policy: %w", err)
 	}
+	users, err := api.h.db.ListUsers()
+	if err != nil {
+		return nil, fmt.Errorf("loading users from database to validate policy: %w", err)
+	}
 
-	_, err = pol.CompileFilterRules(nodes)
+	_, err = pol.CompileFilterRules(users, nodes)
 	if err != nil {
 		return nil, fmt.Errorf("verifying policy rules: %w", err)
 	}
 
 	if len(nodes) > 0 {
-		_, err = pol.CompileSSHPolicy(nodes[0], nodes)
+		_, err = pol.CompileSSHPolicy(nodes[0], users, nodes)
 		if err != nil {
 			return nil, fmt.Errorf("verifying SSH rules: %w", err)
 		}

hscontrol/mapper/mapper.go

@@ -153,6 +153,7 @@ func addNextDNSMetadata(resolvers []*dnstype.Resolver, node *types.Node) {
 func (m *Mapper) fullMapResponse(
 	node *types.Node,
 	peers types.Nodes,
+	users []types.User,
 	pol *policy.ACLPolicy,
 	capVer tailcfg.CapabilityVersion,
 ) (*tailcfg.MapResponse, error) {
@@ -167,6 +168,7 @@ func (m *Mapper) fullMapResponse(
 		pol,
 		node,
 		capVer,
+		users,
 		peers,
 		peers,
 		m.cfg,
@@ -189,8 +191,12 @@ func (m *Mapper) FullMapResponse(
 	if err != nil {
 		return nil, err
 	}
+	users, err := m.db.ListUsers()
+	if err != nil {
+		return nil, err
+	}
 
-	resp, err := m.fullMapResponse(node, peers, pol, mapRequest.Version)
+	resp, err := m.fullMapResponse(node, peers, users, pol, mapRequest.Version)
 	if err != nil {
 		return nil, err
 	}
@@ -253,6 +259,11 @@ func (m *Mapper) PeerChangedResponse(
 		return nil, err
 	}
 
+	users, err := m.db.ListUsers()
+	if err != nil {
+		return nil, fmt.Errorf("listing users for map response: %w", err)
+	}
+
 	var removedIDs []tailcfg.NodeID
 	var changedIDs []types.NodeID
 	for nodeID, nodeChanged := range changed {
@@ -276,6 +287,7 @@ func (m *Mapper) PeerChangedResponse(
 		pol,
 		node,
 		mapRequest.Version,
+		users,
 		peers,
 		changedNodes,
 		m.cfg,
@@ -508,16 +520,17 @@ func appendPeerChanges(
 	pol *policy.ACLPolicy,
 	node *types.Node,
 	capVer tailcfg.CapabilityVersion,
+	users []types.User,
 	peers types.Nodes,
 	changed types.Nodes,
 	cfg *types.Config,
 ) error {
-	packetFilter, err := pol.CompileFilterRules(append(peers, node))
+	packetFilter, err := pol.CompileFilterRules(users, append(peers, node))
 	if err != nil {
 		return err
 	}
 
-	sshPolicy, err := pol.CompileSSHPolicy(node, peers)
+	sshPolicy, err := pol.CompileSSHPolicy(node, users, peers)
 	if err != nil {
 		return err
 	}

hscontrol/mapper/mapper_test.go

@@ -159,6 +159,9 @@ func Test_fullMapResponse(t *testing.T) {
 	lastSeen := time.Date(2009, time.November, 10, 23, 9, 0, 0, time.UTC)
 	expire := time.Date(2500, time.November, 11, 23, 0, 0, 0, time.UTC)
 
+	user1 := types.User{Model: gorm.Model{ID: 0}, Name: "mini"}
+	user2 := types.User{Model: gorm.Model{ID: 1}, Name: "peer2"}
+
 	mini := &types.Node{
 		ID: 0,
 		MachineKey: mustMK(
@@ -173,8 +176,8 @@ func Test_fullMapResponse(t *testing.T) {
 		IPv4:       iap("100.64.0.1"),
 		Hostname:   "mini",
 		GivenName:  "mini",
-		UserID:     0,
+		UserID:     user1.ID,
-		User:       types.User{Name: "mini"},
+		User:       user1,
 		ForcedTags: []string{},
 		AuthKey:    &types.PreAuthKey{},
 		LastSeen:   &lastSeen,
@@ -253,8 +256,8 @@ func Test_fullMapResponse(t *testing.T) {
 		IPv4:       iap("100.64.0.2"),
 		Hostname:   "peer1",
 		GivenName:  "peer1",
-		UserID:     0,
+		UserID:     user1.ID,
-		User:       types.User{Name: "mini"},
+		User:       user1,
 		ForcedTags: []string{},
 		LastSeen:   &lastSeen,
 		Expiry:     &expire,
@@ -308,8 +311,8 @@ func Test_fullMapResponse(t *testing.T) {
 		IPv4:       iap("100.64.0.3"),
 		Hostname:   "peer2",
 		GivenName:  "peer2",
-		UserID:     1,
+		UserID:     user2.ID,
-		User:       types.User{Name: "peer2"},
+		User:       user2,
 		ForcedTags: []string{},
 		LastSeen:   &lastSeen,
 		Expiry:     &expire,
@@ -468,6 +471,7 @@ func Test_fullMapResponse(t *testing.T) {
 			got, err := mappy.fullMapResponse(
 				tt.node,
 				tt.peers,
+				[]types.User{user1, user2},
 				tt.pol,
 				0,
 			)

hscontrol/policy/acls.go

@@ -137,20 +137,21 @@ func GenerateFilterAndSSHRulesForTests(
 	policy *ACLPolicy,
 	node *types.Node,
 	peers types.Nodes,
+	users []types.User,
 ) ([]tailcfg.FilterRule, *tailcfg.SSHPolicy, error) {
 	// If there is no policy defined, we default to allow all
 	if policy == nil {
 		return tailcfg.FilterAllowAll, &tailcfg.SSHPolicy{}, nil
 	}
 
-	rules, err := policy.CompileFilterRules(append(peers, node))
+	rules, err := policy.CompileFilterRules(users, append(peers, node))
 	if err != nil {
 		return []tailcfg.FilterRule{}, &tailcfg.SSHPolicy{}, err
 	}
 
 	log.Trace().Interface("ACL", rules).Str("node", node.GivenName).Msg("ACL rules")
 
-	sshPolicy, err := policy.CompileSSHPolicy(node, peers)
+	sshPolicy, err := policy.CompileSSHPolicy(node, users, peers)
 	if err != nil {
 		return []tailcfg.FilterRule{}, &tailcfg.SSHPolicy{}, err
 	}
@@ -161,6 +162,7 @@ func GenerateFilterAndSSHRulesForTests(
 // CompileFilterRules takes a set of nodes and an ACLPolicy and generates a
 // set of Tailscale compatible FilterRules used to allow traffic on clients.
 func (pol *ACLPolicy) CompileFilterRules(
+	users []types.User,
 	nodes types.Nodes,
 ) ([]tailcfg.FilterRule, error) {
 	if pol == nil {
@@ -176,7 +178,7 @@ func (pol *ACLPolicy) CompileFilterRules(
 
 		var srcIPs []string
 		for srcIndex, src := range acl.Sources {
-			srcs, err := pol.expandSource(src, nodes)
+			srcs, err := pol.expandSource(src, users, nodes)
 			if err != nil {
 				return nil, fmt.Errorf("parsing policy, acl index: %d->%d: %w", index, srcIndex, err)
 			}
@@ -197,6 +199,7 @@ func (pol *ACLPolicy) CompileFilterRules(
 
 			expanded, err := pol.ExpandAlias(
 				nodes,
+				users,
 				alias,
 			)
 			if err != nil {
@@ -281,6 +284,7 @@ func ReduceFilterRules(node *types.Node, rules []tailcfg.FilterRule) []tailcfg.F
 
 func (pol *ACLPolicy) CompileSSHPolicy(
 	node *types.Node,
+	users []types.User,
 	peers types.Nodes,
 ) (*tailcfg.SSHPolicy, error) {
 	if pol == nil {
@@ -312,7 +316,7 @@ func (pol *ACLPolicy) CompileSSHPolicy(
 	for index, sshACL := range pol.SSHs {
 		var dest netipx.IPSetBuilder
 		for _, src := range sshACL.Destinations {
-			expanded, err := pol.ExpandAlias(append(peers, node), src)
+			expanded, err := pol.ExpandAlias(append(peers, node), users, src)
 			if err != nil {
 				return nil, err
 			}
@@ -363,6 +367,7 @@ func (pol *ACLPolicy) CompileSSHPolicy(
 			} else {
 				expandedSrcs, err := pol.ExpandAlias(
 					peers,
+					users,
 					rawSrc,
 				)
 				if err != nil {
@@ -512,9 +517,10 @@ func parseProtocol(protocol string) ([]int, bool, error) {
 // with the given src alias.
 func (pol *ACLPolicy) expandSource(
 	src string,
+	users []types.User,
 	nodes types.Nodes,
 ) ([]string, error) {
-	ipSet, err := pol.ExpandAlias(nodes, src)
+	ipSet, err := pol.ExpandAlias(nodes, users, src)
 	if err != nil {
 		return []string{}, err
 	}
@@ -538,6 +544,7 @@ func (pol *ACLPolicy) expandSource(
 // and transform these in IPAddresses.
 func (pol *ACLPolicy) ExpandAlias(
 	nodes types.Nodes,
+	users []types.User,
 	alias string,
 ) (*netipx.IPSet, error) {
 	if isWildcard(alias) {
@@ -552,12 +559,12 @@ func (pol *ACLPolicy) ExpandAlias(
 
 	// if alias is a group
 	if isGroup(alias) {
-		return pol.expandIPsFromGroup(alias, nodes)
+		return pol.expandIPsFromGroup(alias, users, nodes)
 	}
 
 	// if alias is a tag
 	if isTag(alias) {
-		return pol.expandIPsFromTag(alias, nodes)
+		return pol.expandIPsFromTag(alias, users, nodes)
 	}
 
 	if isAutoGroup(alias) {
@@ -565,7 +572,7 @@ func (pol *ACLPolicy) ExpandAlias(
 	}
 
 	// if alias is a user
-	if ips, err := pol.expandIPsFromUser(alias, nodes); ips != nil {
+	if ips, err := pol.expandIPsFromUser(alias, users, nodes); ips != nil {
 		return ips, err
 	}
 
@@ -574,7 +581,7 @@ func (pol *ACLPolicy) ExpandAlias(
 	if h, ok := pol.Hosts[alias]; ok {
 		log.Trace().Str("host", h.String()).Msg("ExpandAlias got hosts entry")
 
-		return pol.ExpandAlias(nodes, h.String())
+		return pol.ExpandAlias(nodes, users, h.String())
 	}
 
 	// if alias is an IP
@@ -751,16 +758,17 @@ func (pol *ACLPolicy) expandUsersFromGroup(
 
 func (pol *ACLPolicy) expandIPsFromGroup(
 	group string,
+	users []types.User,
 	nodes types.Nodes,
 ) (*netipx.IPSet, error) {
 	var build netipx.IPSetBuilder
 
-	users, err := pol.expandUsersFromGroup(group)
+	userTokens, err := pol.expandUsersFromGroup(group)
 	if err != nil {
 		return &netipx.IPSet{}, err
 	}
-	for _, user := range users {
+	for _, user := range userTokens {
-		filteredNodes := filterNodesByUser(nodes, user)
+		filteredNodes := filterNodesByUser(nodes, users, user)
 		for _, node := range filteredNodes {
 			node.AppendToIPSet(&build)
 		}
@@ -771,6 +779,7 @@ func (pol *ACLPolicy) expandIPsFromGroup(
 
 func (pol *ACLPolicy) expandIPsFromTag(
 	alias string,
+	users []types.User,
 	nodes types.Nodes,
 ) (*netipx.IPSet, error) {
 	var build netipx.IPSetBuilder
@@ -803,7 +812,7 @@ func (pol *ACLPolicy) expandIPsFromTag(
 
 	// filter out nodes per tag owner
 	for _, user := range owners {
-		nodes := filterNodesByUser(nodes, user)
+		nodes := filterNodesByUser(nodes, users, user)
 		for _, node := range nodes {
 			if node.Hostinfo == nil {
 				continue
@@ -820,11 +829,12 @@ func (pol *ACLPolicy) expandIPsFromTag(
 
 func (pol *ACLPolicy) expandIPsFromUser(
 	user string,
+	users []types.User,
 	nodes types.Nodes,
 ) (*netipx.IPSet, error) {
 	var build netipx.IPSetBuilder
 
-	filteredNodes := filterNodesByUser(nodes, user)
+	filteredNodes := filterNodesByUser(nodes, users, user)
 	filteredNodes = excludeCorrectlyTaggedNodes(pol, filteredNodes, user)
 
 	// shortcurcuit if we have no nodes to get ips from.
@@ -953,10 +963,43 @@ func (pol *ACLPolicy) TagsOfNode(
 	return validTags, invalidTags
 }
 
-func filterNodesByUser(nodes types.Nodes, user string) types.Nodes {
+// filterNodesByUser returns a list of nodes that match the given userToken from a
+// policy.
+// Matching nodes are determined by first matching the user token to a user by checking:
+// - If it is an ID that mactches the user database ID
+// - It is the Provider Identifier from OIDC
+// - It matches the username or email of a user
+//
+// If the token matches more than one user, zero nodes will returned.
+func filterNodesByUser(nodes types.Nodes, users []types.User, userToken string) types.Nodes {
 	var out types.Nodes
+
+	var potentialUsers []types.User
+	for _, user := range users {
+		if id, err := strconv.ParseUint(userToken, 10, 64); err == nil && user.ID == uint(id) {
+			potentialUsers = append(potentialUsers, user)
+			break
+		}
+		if user.ProviderIdentifier == userToken {
+			potentialUsers = append(potentialUsers, user)
+			break
+		}
+		if user.Email == userToken {
+			potentialUsers = append(potentialUsers, user)
+		}
+		if user.Name == userToken {
+			potentialUsers = append(potentialUsers, user)
+		}
+	}
+
+	if len(potentialUsers) != 1 {
+		return nil
+	}
+
+	user := potentialUsers[0]
+
 	for _, node := range nodes {
-		if node.User.Username() == user {
+		if node.User.ID == user.ID {
 			out = append(out, node)
 		}
 	}

hscontrol/policy/acls_test.go

@@ -14,6 +14,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"go4.org/netipx"
 	"gopkg.in/check.v1"
+	"gorm.io/gorm"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/tailcfg"
 )
@@ -375,18 +376,24 @@ func TestParsing(t *testing.T) {
 				return
 			}
 
-			rules, err := pol.CompileFilterRules(types.Nodes{
+			user := types.User{
-				&types.Node{
+				Model: gorm.Model{ID: 1},
-					IPv4: iap("100.100.100.100"),
+				Name:  "testuser",
+			}
+			rules, err := pol.CompileFilterRules(
+				[]types.User{
+					user,
 				},
-				&types.Node{
+				types.Nodes{
-					IPv4: iap("200.200.200.200"),
+					&types.Node{
-					User: types.User{
+						IPv4: iap("100.100.100.100"),
-						Name: "testuser",
 					},
-					Hostinfo: &tailcfg.Hostinfo{},
+					&types.Node{
-				},
+						IPv4:     iap("200.200.200.200"),
-			})
+						User:     user,
+						Hostinfo: &tailcfg.Hostinfo{},
+					},
+				})
 
 			if (err != nil) != tt.wantErr {
 				t.Errorf("parsing() error = %v, wantErr %v", err, tt.wantErr)
@@ -533,7 +540,7 @@ func (s *Suite) TestRuleInvalidGeneration(c *check.C) {
 	c.Assert(pol.ACLs, check.HasLen, 6)
 	c.Assert(err, check.IsNil)
 
-	rules, err := pol.CompileFilterRules(types.Nodes{})
+	rules, err := pol.CompileFilterRules([]types.User{}, types.Nodes{})
 	c.Assert(err, check.NotNil)
 	c.Assert(rules, check.IsNil)
 }
@@ -549,7 +556,7 @@ func (s *Suite) TestInvalidAction(c *check.C) {
 			},
 		},
 	}
-	_, _, err := GenerateFilterAndSSHRulesForTests(pol, &types.Node{}, types.Nodes{})
+	_, _, err := GenerateFilterAndSSHRulesForTests(pol, &types.Node{}, types.Nodes{}, []types.User{})
 	c.Assert(errors.Is(err, ErrInvalidAction), check.Equals, true)
 }
 
@@ -568,7 +575,7 @@ func (s *Suite) TestInvalidGroupInGroup(c *check.C) {
 			},
 		},
 	}
-	_, _, err := GenerateFilterAndSSHRulesForTests(pol, &types.Node{}, types.Nodes{})
+	_, _, err := GenerateFilterAndSSHRulesForTests(pol, &types.Node{}, types.Nodes{}, []types.User{})
 	c.Assert(errors.Is(err, ErrInvalidGroup), check.Equals, true)
 }
 
@@ -584,7 +591,7 @@ func (s *Suite) TestInvalidTagOwners(c *check.C) {
 		},
 	}
 
-	_, _, err := GenerateFilterAndSSHRulesForTests(pol, &types.Node{}, types.Nodes{})
+	_, _, err := GenerateFilterAndSSHRulesForTests(pol, &types.Node{}, types.Nodes{}, []types.User{})
 	c.Assert(errors.Is(err, ErrInvalidTag), check.Equals, true)
 }
 
@@ -861,6 +868,13 @@ func Test_expandPorts(t *testing.T) {
 }
 
 func Test_listNodesInUser(t *testing.T) {
+	users := []types.User{
+		{Model: gorm.Model{ID: 1}, Name: "marc"},
+		{Model: gorm.Model{ID: 2}, Name: "joe", Email: "joe@headscale.net"},
+		{Model: gorm.Model{ID: 3}, Name: "mikael", Email: "mikael@headscale.net", ProviderIdentifier: "http://oidc.org/1234"},
+		{Model: gorm.Model{ID: 4}, Name: "mikael2", Email: "mikael@headscale.net"},
+	}
+
 	type args struct {
 		nodes types.Nodes
 		user  string
@@ -874,47 +888,101 @@ func Test_listNodesInUser(t *testing.T) {
 			name: "1 node in user",
 			args: args{
 				nodes: types.Nodes{
-					&types.Node{User: types.User{Name: "joe"}},
+					&types.Node{User: users[1]},
 				},
 				user: "joe",
 			},
 			want: types.Nodes{
-				&types.Node{User: types.User{Name: "joe"}},
+				&types.Node{User: users[1]},
 			},
 		},
 		{
 			name: "3 nodes, 2 in user",
 			args: args{
 				nodes: types.Nodes{
-					&types.Node{ID: 1, User: types.User{Name: "joe"}},
+					&types.Node{ID: 1, User: users[1]},
-					&types.Node{ID: 2, User: types.User{Name: "marc"}},
+					&types.Node{ID: 2, User: users[0]},
-					&types.Node{ID: 3, User: types.User{Name: "marc"}},
+					&types.Node{ID: 3, User: users[0]},
 				},
 				user: "marc",
 			},
 			want: types.Nodes{
-				&types.Node{ID: 2, User: types.User{Name: "marc"}},
+				&types.Node{ID: 2, User: users[0]},
-				&types.Node{ID: 3, User: types.User{Name: "marc"}},
+				&types.Node{ID: 3, User: users[0]},
 			},
 		},
 		{
 			name: "5 nodes, 0 in user",
 			args: args{
 				nodes: types.Nodes{
-					&types.Node{ID: 1, User: types.User{Name: "joe"}},
+					&types.Node{ID: 1, User: users[1]},
-					&types.Node{ID: 2, User: types.User{Name: "marc"}},
+					&types.Node{ID: 2, User: users[0]},
-					&types.Node{ID: 3, User: types.User{Name: "marc"}},
+					&types.Node{ID: 3, User: users[0]},
-					&types.Node{ID: 4, User: types.User{Name: "marc"}},
+					&types.Node{ID: 4, User: users[0]},
-					&types.Node{ID: 5, User: types.User{Name: "marc"}},
+					&types.Node{ID: 5, User: users[0]},
 				},
 				user: "mickael",
 			},
 			want: nil,
 		},
+		{
+			name: "match-by-userid",
+			args: args{
+				nodes: types.Nodes{
+					&types.Node{ID: 1, User: users[1]},
+					&types.Node{ID: 2, User: users[0]},
+					&types.Node{ID: 3, User: users[0]},
+					&types.Node{ID: 4, User: users[0]},
+					&types.Node{ID: 5, User: users[0]},
+				},
+				user: "2",
+			},
+			want: types.Nodes{
+				&types.Node{ID: 1, User: users[1]},
+			},
+		},
+		{
+			name: "match-by-provider-ident",
+			args: args{
+				nodes: types.Nodes{
+					&types.Node{ID: 1, User: users[1]},
+					&types.Node{ID: 2, User: users[2]},
+				},
+				user: "http://oidc.org/1234",
+			},
+			want: types.Nodes{
+				&types.Node{ID: 2, User: users[2]},
+			},
+		},
+		{
+			name: "match-by-email",
+			args: args{
+				nodes: types.Nodes{
+					&types.Node{ID: 1, User: users[1]},
+					&types.Node{ID: 2, User: users[2]},
+				},
+				user: "joe@headscale.net",
+			},
+			want: types.Nodes{
+				&types.Node{ID: 1, User: users[1]},
+			},
+		},
+		{
+			name: "multi-match-is-zero",
+			args: args{
+				nodes: types.Nodes{
+					&types.Node{ID: 1, User: users[1]},
+					&types.Node{ID: 2, User: users[2]},
+					&types.Node{ID: 3, User: users[3]},
+				},
+				user: "mikael@headscale.net",
+			},
+			want: nil,
+		},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			got := filterNodesByUser(test.args.nodes, test.args.user)
+			got := filterNodesByUser(test.args.nodes, users, test.args.user)
 
 			if diff := cmp.Diff(test.want, got, util.Comparers...); diff != "" {
 				t.Errorf("listNodesInUser() = (-want +got):\n%s", diff)
@@ -940,6 +1008,12 @@ func Test_expandAlias(t *testing.T) {
 		return s
 	}
 
+	users := []types.User{
+		{Model: gorm.Model{ID: 1}, Name: "joe"},
+		{Model: gorm.Model{ID: 2}, Name: "marc"},
+		{Model: gorm.Model{ID: 3}, Name: "mickael"},
+	}
+
 	type field struct {
 		pol ACLPolicy
 	}
@@ -989,19 +1063,19 @@ func Test_expandAlias(t *testing.T) {
 				nodes: types.Nodes{
 					&types.Node{
 						IPv4: iap("100.64.0.1"),
-						User: types.User{Name: "joe"},
+						User: users[0],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.2"),
-						User: types.User{Name: "joe"},
+						User: users[0],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.3"),
-						User: types.User{Name: "marc"},
+						User: users[1],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.4"),
-						User: types.User{Name: "mickael"},
+						User: users[2],
 					},
 				},
 			},
@@ -1022,19 +1096,19 @@ func Test_expandAlias(t *testing.T) {
 				nodes: types.Nodes{
 					&types.Node{
 						IPv4: iap("100.64.0.1"),
-						User: types.User{Name: "joe"},
+						User: users[0],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.2"),
-						User: types.User{Name: "joe"},
+						User: users[0],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.3"),
-						User: types.User{Name: "marc"},
+						User: users[1],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.4"),
-						User: types.User{Name: "mickael"},
+						User: users[2],
 					},
 				},
 			},
@@ -1185,7 +1259,7 @@ func Test_expandAlias(t *testing.T) {
 				nodes: types.Nodes{
 					&types.Node{
 						IPv4: iap("100.64.0.1"),
-						User: types.User{Name: "joe"},
+						User: users[0],
 						Hostinfo: &tailcfg.Hostinfo{
 							OS:          "centos",
 							Hostname:    "foo",
@@ -1194,7 +1268,7 @@ func Test_expandAlias(t *testing.T) {
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.2"),
-						User: types.User{Name: "joe"},
+						User: users[0],
 						Hostinfo: &tailcfg.Hostinfo{
 							OS:          "centos",
 							Hostname:    "foo",
@@ -1203,11 +1277,11 @@ func Test_expandAlias(t *testing.T) {
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.3"),
-						User: types.User{Name: "marc"},
+						User: users[1],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.4"),
-						User: types.User{Name: "joe"},
+						User: users[0],
 					},
 				},
 			},
@@ -1260,21 +1334,21 @@ func Test_expandAlias(t *testing.T) {
 				nodes: types.Nodes{
 					&types.Node{
 						IPv4:       iap("100.64.0.1"),
-						User:       types.User{Name: "joe"},
+						User:       users[0],
 						ForcedTags: []string{"tag:hr-webserver"},
 					},
 					&types.Node{
 						IPv4:       iap("100.64.0.2"),
-						User:       types.User{Name: "joe"},
+						User:       users[0],
 						ForcedTags: []string{"tag:hr-webserver"},
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.3"),
-						User: types.User{Name: "marc"},
+						User: users[1],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.4"),
-						User: types.User{Name: "mickael"},
+						User: users[2],
 					},
 				},
 			},
@@ -1295,12 +1369,12 @@ func Test_expandAlias(t *testing.T) {
 				nodes: types.Nodes{
 					&types.Node{
 						IPv4:       iap("100.64.0.1"),
-						User:       types.User{Name: "joe"},
+						User:       users[0],
 						ForcedTags: []string{"tag:hr-webserver"},
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.2"),
-						User: types.User{Name: "joe"},
+						User: users[0],
 						Hostinfo: &tailcfg.Hostinfo{
 							OS:          "centos",
 							Hostname:    "foo",
@@ -1309,11 +1383,11 @@ func Test_expandAlias(t *testing.T) {
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.3"),
-						User: types.User{Name: "marc"},
+						User: users[1],
 					},
 					&types.Node{
 						IPv4: iap("100.64.0.4"),
-						User: types.User{Name: "mickael"},
+						User: users[2],
 					},
 				},
 			},
@@ -1350,12 +1424,12 @@ func Test_expandAlias(t *testing.T) {
 					},
 					&types.Node{
 						IPv4:     iap("100.64.0.3"),
-						User:     types.User{Name: "marc"},
+						User:     users[1],
 						Hostinfo: &tailcfg.Hostinfo{},
 					},
 					&types.Node{
 						IPv4:     iap("100.64.0.4"),
-						User:     types.User{Name: "joe"},
+						User:     users[0],
 						Hostinfo: &tailcfg.Hostinfo{},
 					},
 				},
@@ -1368,6 +1442,7 @@ func Test_expandAlias(t *testing.T) {
 		t.Run(test.name, func(t *testing.T) {
 			got, err := test.field.pol.ExpandAlias(
 				test.args.nodes,
+				users,
 				test.args.alias,
 			)
 			if (err != nil) != test.wantErr {
@@ -1715,6 +1790,7 @@ func TestACLPolicy_generateFilterRules(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			got, err := tt.field.pol.CompileFilterRules(
+				[]types.User{},
 				tt.args.nodes,
 			)
 			if (err != nil) != tt.wantErr {
@@ -1834,6 +1910,13 @@ func TestTheInternet(t *testing.T) {
 }
 
 func TestReduceFilterRules(t *testing.T) {
+	users := []types.User{
+		{Model: gorm.Model{ID: 1}, Name: "mickael"},
+		{Model: gorm.Model{ID: 2}, Name: "user1"},
+		{Model: gorm.Model{ID: 3}, Name: "user2"},
+		{Model: gorm.Model{ID: 4}, Name: "user100"},
+	}
+
 	tests := []struct {
 		name  string
 		node  *types.Node
@@ -1855,13 +1938,13 @@ func TestReduceFilterRules(t *testing.T) {
 			node: &types.Node{
 				IPv4: iap("100.64.0.1"),
 				IPv6: iap("fd7a:115c:a1e0:ab12:4843:2222:6273:2221"),
-				User: types.User{Name: "mickael"},
+				User: users[0],
 			},
 			peers: types.Nodes{
 				&types.Node{
 					IPv4: iap("100.64.0.2"),
 					IPv6: iap("fd7a:115c:a1e0:ab12:4843:2222:6273:2222"),
-					User: types.User{Name: "mickael"},
+					User: users[0],
 				},
 			},
 			want: []tailcfg.FilterRule{},
@@ -1888,7 +1971,7 @@ func TestReduceFilterRules(t *testing.T) {
 			node: &types.Node{
 				IPv4: iap("100.64.0.1"),
 				IPv6: iap("fd7a:115c:a1e0::1"),
-				User: types.User{Name: "user1"},
+				User: users[1],
 				Hostinfo: &tailcfg.Hostinfo{
 					RoutableIPs: []netip.Prefix{
 						netip.MustParsePrefix("10.33.0.0/16"),
@@ -1899,7 +1982,7 @@ func TestReduceFilterRules(t *testing.T) {
 				&types.Node{
 					IPv4: iap("100.64.0.2"),
 					IPv6: iap("fd7a:115c:a1e0::2"),
-					User: types.User{Name: "user1"},
+					User: users[1],
 				},
 			},
 			want: []tailcfg.FilterRule{
@@ -1967,19 +2050,19 @@ func TestReduceFilterRules(t *testing.T) {
 			node: &types.Node{
 				IPv4: iap("100.64.0.1"),
 				IPv6: iap("fd7a:115c:a1e0::1"),
-				User: types.User{Name: "user1"},
+				User: users[1],
 			},
 			peers: types.Nodes{
 				&types.Node{
 					IPv4: iap("100.64.0.2"),
 					IPv6: iap("fd7a:115c:a1e0::2"),
-					User: types.User{Name: "user2"},
+					User: users[2],
 				},
 				// "internal" exit node
 				&types.Node{
 					IPv4: iap("100.64.0.100"),
 					IPv6: iap("fd7a:115c:a1e0::100"),
-					User: types.User{Name: "user100"},
+					User: users[3],
 					Hostinfo: &tailcfg.Hostinfo{
 						RoutableIPs: tsaddr.ExitRoutes(),
 					},
@@ -2026,12 +2109,12 @@ func TestReduceFilterRules(t *testing.T) {
 				&types.Node{
 					IPv4: iap("100.64.0.2"),
 					IPv6: iap("fd7a:115c:a1e0::2"),
-					User: types.User{Name: "user2"},
+					User: users[2],
 				},
 				&types.Node{
 					IPv4: iap("100.64.0.1"),
 					IPv6: iap("fd7a:115c:a1e0::1"),
-					User: types.User{Name: "user1"},
+					User: users[1],
 				},
 			},
 			want: []tailcfg.FilterRule{
@@ -2113,7 +2196,7 @@ func TestReduceFilterRules(t *testing.T) {
 			node: &types.Node{
 				IPv4: iap("100.64.0.100"),
 				IPv6: iap("fd7a:115c:a1e0::100"),
-				User: types.User{Name: "user100"},
+				User: users[3],
 				Hostinfo: &tailcfg.Hostinfo{
 					RoutableIPs: tsaddr.ExitRoutes(),
 				},
@@ -2122,12 +2205,12 @@ func TestReduceFilterRules(t *testing.T) {
 				&types.Node{
 					IPv4: iap("100.64.0.2"),
 					IPv6: iap("fd7a:115c:a1e0::2"),
-					User: types.User{Name: "user2"},
+					User: users[2],
 				},
 				&types.Node{
 					IPv4: iap("100.64.0.1"),
 					IPv6: iap("fd7a:115c:a1e0::1"),
-					User: types.User{Name: "user1"},
+					User: users[1],
 				},
 			},
 			want: []tailcfg.FilterRule{
@@ -2215,7 +2298,7 @@ func TestReduceFilterRules(t *testing.T) {
 			node: &types.Node{
 				IPv4: iap("100.64.0.100"),
 				IPv6: iap("fd7a:115c:a1e0::100"),
-				User: types.User{Name: "user100"},
+				User: users[3],
 				Hostinfo: &tailcfg.Hostinfo{
 					RoutableIPs: []netip.Prefix{netip.MustParsePrefix("8.0.0.0/16"), netip.MustParsePrefix("16.0.0.0/16")},
 				},
@@ -2224,12 +2307,12 @@ func TestReduceFilterRules(t *testing.T) {
 				&types.Node{
 					IPv4: iap("100.64.0.2"),
 					IPv6: iap("fd7a:115c:a1e0::2"),
-					User: types.User{Name: "user2"},
+					User: users[2],
 				},
 				&types.Node{
 					IPv4: iap("100.64.0.1"),
 					IPv6: iap("fd7a:115c:a1e0::1"),
-					User: types.User{Name: "user1"},
+					User: users[1],
 				},
 			},
 			want: []tailcfg.FilterRule{
@@ -2292,7 +2375,7 @@ func TestReduceFilterRules(t *testing.T) {
 			node: &types.Node{
 				IPv4: iap("100.64.0.100"),
 				IPv6: iap("fd7a:115c:a1e0::100"),
-				User: types.User{Name: "user100"},
+				User: users[3],
 				Hostinfo: &tailcfg.Hostinfo{
 					RoutableIPs: []netip.Prefix{netip.MustParsePrefix("8.0.0.0/8"), netip.MustParsePrefix("16.0.0.0/8")},
 				},
@@ -2301,12 +2384,12 @@ func TestReduceFilterRules(t *testing.T) {
 				&types.Node{
 					IPv4: iap("100.64.0.2"),
 					IPv6: iap("fd7a:115c:a1e0::2"),
-					User: types.User{Name: "user2"},
+					User: users[2],
 				},
 				&types.Node{
 					IPv4: iap("100.64.0.1"),
 					IPv6: iap("fd7a:115c:a1e0::1"),
-					User: types.User{Name: "user1"},
+					User: users[1],
 				},
 			},
 			want: []tailcfg.FilterRule{
@@ -2362,7 +2445,7 @@ func TestReduceFilterRules(t *testing.T) {
 			node: &types.Node{
 				IPv4: iap("100.64.0.100"),
 				IPv6: iap("fd7a:115c:a1e0::100"),
-				User: types.User{Name: "user100"},
+				User: users[3],
 				Hostinfo: &tailcfg.Hostinfo{
 					RoutableIPs: []netip.Prefix{netip.MustParsePrefix("172.16.0.0/24")},
 				},
@@ -2372,7 +2455,7 @@ func TestReduceFilterRules(t *testing.T) {
 				&types.Node{
 					IPv4: iap("100.64.0.1"),
 					IPv6: iap("fd7a:115c:a1e0::1"),
-					User: types.User{Name: "user1"},
+					User: users[1],
 				},
 			},
 			want: []tailcfg.FilterRule{
@@ -2400,6 +2483,7 @@ func TestReduceFilterRules(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			got, _ := tt.pol.CompileFilterRules(
+				users,
 				append(tt.peers, tt.node),
 			)
 
@@ -3391,7 +3475,7 @@ func TestSSHRules(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got, err := tt.pol.CompileSSHPolicy(&tt.node, tt.peers)
+			got, err := tt.pol.CompileSSHPolicy(&tt.node, []types.User{}, tt.peers)
 			assert.NoError(t, err)
 
 			if diff := cmp.Diff(tt.want, got); diff != "" {
@@ -3474,14 +3558,17 @@ func TestValidExpandTagOwnersInSources(t *testing.T) {
 		RequestTags: []string{"tag:test"},
 	}
 
+	user := types.User{
+		Model: gorm.Model{ID: 1},
+		Name:  "user1",
+	}
+
 	node := &types.Node{
-		ID:       0,
+		ID:             0,
-		Hostname: "testnodes",
+		Hostname:       "testnodes",
-		IPv4:     iap("100.64.0.1"),
+		IPv4:           iap("100.64.0.1"),
-		UserID:   0,
+		UserID:         0,
-		User: types.User{
+		User:           user,
-			Name: "user1",
-		},
 		RegisterMethod: util.RegisterMethodAuthKey,
 		Hostinfo:       &hostInfo,
 	}
@@ -3498,7 +3585,7 @@ func TestValidExpandTagOwnersInSources(t *testing.T) {
 		},
 	}
 
-	got, _, err := GenerateFilterAndSSHRulesForTests(pol, node, types.Nodes{})
+	got, _, err := GenerateFilterAndSSHRulesForTests(pol, node, types.Nodes{}, []types.User{user})
 	assert.NoError(t, err)
 
 	want := []tailcfg.FilterRule{
@@ -3532,7 +3619,8 @@ func TestInvalidTagValidUser(t *testing.T) {
 		IPv4:     iap("100.64.0.1"),
 		UserID:   1,
 		User: types.User{
-			Name: "user1",
+			Model: gorm.Model{ID: 1},
+			Name:  "user1",
 		},
 		RegisterMethod: util.RegisterMethodAuthKey,
 		Hostinfo:       &hostInfo,
@@ -3549,7 +3637,7 @@ func TestInvalidTagValidUser(t *testing.T) {
 		},
 	}
 
-	got, _, err := GenerateFilterAndSSHRulesForTests(pol, node, types.Nodes{})
+	got, _, err := GenerateFilterAndSSHRulesForTests(pol, node, types.Nodes{}, []types.User{node.User})
 	assert.NoError(t, err)
 
 	want := []tailcfg.FilterRule{
@@ -3583,7 +3671,8 @@ func TestValidExpandTagOwnersInDestinations(t *testing.T) {
 		IPv4:     iap("100.64.0.1"),
 		UserID:   1,
 		User: types.User{
-			Name: "user1",
+			Model: gorm.Model{ID: 1},
+			Name:  "user1",
 		},
 		RegisterMethod: util.RegisterMethodAuthKey,
 		Hostinfo:       &hostInfo,
@@ -3608,7 +3697,7 @@ func TestValidExpandTagOwnersInDestinations(t *testing.T) {
 	// c.Assert(rules[0].DstPorts, check.HasLen, 1)
 	// c.Assert(rules[0].DstPorts[0].IP, check.Equals, "100.64.0.1/32")
 
-	got, _, err := GenerateFilterAndSSHRulesForTests(pol, node, types.Nodes{})
+	got, _, err := GenerateFilterAndSSHRulesForTests(pol, node, types.Nodes{}, []types.User{node.User})
 	assert.NoError(t, err)
 
 	want := []tailcfg.FilterRule{
@@ -3637,15 +3726,17 @@ func TestValidTagInvalidUser(t *testing.T) {
 		Hostname:    "webserver",
 		RequestTags: []string{"tag:webapp"},
 	}
+	user := types.User{
+		Model: gorm.Model{ID: 1},
+		Name:  "user1",
+	}
 
 	node := &types.Node{
-		ID:       1,
+		ID:             1,
-		Hostname: "webserver",
+		Hostname:       "webserver",
-		IPv4:     iap("100.64.0.1"),
+		IPv4:           iap("100.64.0.1"),
-		UserID:   1,
+		UserID:         1,
-		User: types.User{
+		User:           user,
-			Name: "user1",
-		},
 		RegisterMethod: util.RegisterMethodAuthKey,
 		Hostinfo:       &hostInfo,
 	}
@@ -3656,13 +3747,11 @@ func TestValidTagInvalidUser(t *testing.T) {
 	}
 
 	nodes2 := &types.Node{
-		ID:       2,
+		ID:             2,
-		Hostname: "user",
+		Hostname:       "user",
-		IPv4:     iap("100.64.0.2"),
+		IPv4:           iap("100.64.0.2"),
-		UserID:   1,
+		UserID:         1,
-		User: types.User{
+		User:           user,
-			Name: "user1",
-		},
 		RegisterMethod: util.RegisterMethodAuthKey,
 		Hostinfo:       &hostInfo2,
 	}
@@ -3678,7 +3767,7 @@ func TestValidTagInvalidUser(t *testing.T) {
 		},
 	}
 
-	got, _, err := GenerateFilterAndSSHRulesForTests(pol, node, types.Nodes{nodes2})
+	got, _, err := GenerateFilterAndSSHRulesForTests(pol, node, types.Nodes{nodes2}, []types.User{user})
 	assert.NoError(t, err)
 
 	want := []tailcfg.FilterRule{