tailcfg: add CapabilityDebug

Updates tailscale/corp#7948

Signed-off-by: Maisem Ali <maisem@tailscale.com>

ipn/ipnlocal/peerapi.go

@@ -778,6 +778,17 @@ func (h *peerAPIHandler) canPutFile() bool {
 // canDebug reports whether h can debug this node (goroutines, metrics,
 // magicsock internal state, etc).
 func (h *peerAPIHandler) canDebug() bool {
+	// Reread the selfNode as it may have changed since the peerAPIServer
+	// was created.
+	// TODO(maisem): handle this in other places too.
+	nm := h.ps.b.NetMap()
+	if nm == nil || nm.SelfNode == nil {
+		return false
+	}
+	if !slices.Contains(nm.SelfNode.Capabilities, tailcfg.CapabilityDebug) {
+		// This node does not expose debug info.
+		return false
+	}
 	return h.isSelf || h.peerHasCap(tailcfg.CapabilityDebugPeer)
 }
 

ipn/ipnlocal/peerapi_test.go

@@ -25,6 +25,7 @@ import (
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstest"
 	"tailscale.com/types/logger"
+	"tailscale.com/types/netmap"
 	"tailscale.com/util/must"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/filter"
@@ -113,6 +114,7 @@ func TestHandlePeerAPI(t *testing.T) {
 		name       string
 		isSelf     bool // the peer sending the request is owned by us
 		capSharing bool // self node has file sharing capability
+		debugCap   bool // self node has debug capability
 		omitRoot   bool // don't configure
 		req        *http.Request
 		checks     []check
@@ -140,14 +142,23 @@ func TestHandlePeerAPI(t *testing.T) {
 			),
 		},
 		{
-			name:   "peer_api_goroutines_deny",
+			name:     "goroutines/deny-self-no-cap",
+			isSelf:   true,
+			debugCap: false,
+			req:      httptest.NewRequest("GET", "/v0/goroutines", nil),
+			checks:   checks(httpStatus(403)),
+		},
+		{
+			name:     "goroutines/deny-nonself",
 			isSelf:   false,
+			debugCap: true,
 			req:      httptest.NewRequest("GET", "/v0/goroutines", nil),
 			checks:   checks(httpStatus(403)),
 		},
 		{
-			name:   "peer_api_goroutines",
+			name:     "goroutines/accept-self",
 			isSelf:   true,
+			debugCap: true,
 			req:      httptest.NewRequest("GET", "/v0/goroutines", nil),
 			checks: checks(
 				httpStatus(200),
@@ -406,6 +417,7 @@ func TestHandlePeerAPI(t *testing.T) {
 		{
 			name:     "host-val/bad-ip",
 			isSelf:   true,
+			debugCap: true,
 			req:      httptest.NewRequest("GET", "http://12.23.45.66:1234/v0/env", nil),
 			checks: checks(
 				httpStatus(403),
@@ -414,6 +426,7 @@ func TestHandlePeerAPI(t *testing.T) {
 		{
 			name:     "host-val/no-port",
 			isSelf:   true,
+			debugCap: true,
 			req:      httptest.NewRequest("GET", "http://100.100.100.101/v0/env", nil),
 			checks: checks(
 				httpStatus(403),
@@ -422,6 +435,7 @@ func TestHandlePeerAPI(t *testing.T) {
 		{
 			name:     "host-val/peer",
 			isSelf:   true,
+			debugCap: true,
 			req:      httptest.NewRequest("GET", "http://peer/v0/env", nil),
 			checks: checks(
 				httpStatus(200),
@@ -430,10 +444,16 @@ func TestHandlePeerAPI(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			selfNode := &tailcfg.Node{
+				Addresses: []netip.Prefix{
+					netip.MustParsePrefix("100.100.100.101/32"),
+				},
+			}
 			var e peerAPITestEnv
 			lb := &LocalBackend{
 				logf:           e.logBuf.Logf,
 				capFileSharing: tt.capSharing,
+				netMap:         &netmap.NetworkMap{SelfNode: selfNode},
 			}
 			e.ph = &peerAPIHandler{
 				isSelf: tt.isSelf,
@@ -442,13 +462,12 @@ func TestHandlePeerAPI(t *testing.T) {
 				},
 				ps: &peerAPIServer{
 					b:        lb,
-					selfNode: &tailcfg.Node{
+					selfNode: selfNode,
-						Addresses: []netip.Prefix{
-							netip.MustParsePrefix("100.100.100.101/32"),
-						},
-					},
 				},
 			}
+			if tt.debugCap {
+				e.ph.ps.selfNode.Capabilities = append(e.ph.ps.selfNode.Capabilities, tailcfg.CapabilityDebug)
+			}
 			var rootDir string
 			if !tt.omitRoot {
 				rootDir = t.TempDir()

tailcfg/tailcfg.go

@@ -1654,12 +1654,16 @@ type Oauth2Token struct {
 const (
 	// These are the capabilities that the self node has as listed in
 	// MapResponse.Node.Capabilities.
+	//
+	// We've since started referring to these as "Node Attributes" ("nodeAttrs"
+	// in the ACL policy file).
 
 	CapabilityFileSharing        = "https://tailscale.com/cap/file-sharing"
 	CapabilityAdmin              = "https://tailscale.com/cap/is-admin"
 	CapabilitySSH                = "https://tailscale.com/cap/ssh"                   // feature enabled/available
 	CapabilitySSHRuleIn          = "https://tailscale.com/cap/ssh-rule-in"           // some SSH rule reach this node
 	CapabilityDataPlaneAuditLogs = "https://tailscale.com/cap/data-plane-audit-logs" // feature enabled
+	CapabilityDebug              = "https://tailscale.com/cap/debug"                 // exposes debug endpoints over the PeerAPI
 
 	// Inter-node capabilities as specified in the MapResponse.PacketFilter[].CapGrants.