all: [experiment] add means to set device posture attributes from node

Updates tailscale/corp#24690
Updates #4077

Change-Id: I05fe799beb1d2a71d1ec3ae08744cc68bcadae2a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/direct.go

@@ -1643,6 +1643,43 @@ func (c *Direct) ReportHealthChange(w *health.Warnable, us *health.UnhealthyStat
 	res.Body.Close()
 }
 
+func (c *Auto) SetDeviceAttrs(ctx context.Context, attrs map[string]any) error {
+	return c.direct.SetDeviceAttrs(ctx, attrs)
+}
+
+func (c *Direct) SetDeviceAttrs(ctx context.Context, attrs map[string]any) error {
+	np, err := c.getNoiseClient()
+	if err != nil {
+		return err
+	}
+	nodeKey, ok := c.GetPersist().PublicNodeKeyOK()
+	if !ok {
+		return errors.New("no node key")
+	}
+	if c.panicOnUse {
+		panic("tainted client")
+	}
+	// TODO(angott): at some point, update `Subsys` in the request to be `Warnable`
+	req := &tailcfg.SetDeviceAttributesRequest{
+		NodeKey: nodeKey,
+		Version: tailcfg.CurrentCapabilityVersion,
+		Update:  attrs,
+	}
+
+	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
+	defer cancel()
+	res, err := np.doWithBody(ctx, "PATCH", "/machine/set-device-attr", nodeKey, req)
+	if err != nil {
+		return err
+	}
+	defer res.Body.Close()
+	all, _ := io.ReadAll(res.Body)
+	if res.StatusCode != 200 {
+		return fmt.Errorf("HTTP error from control plane: %v: %s", res.Status, all)
+	}
+	return nil
+}
+
 func addLBHeader(req *http.Request, nodeKey key.NodePublic) {
 	if !nodeKey.IsZero() {
 		req.Header.Add(tailcfg.LBHeader, nodeKey.String())

control/controlclient/noise.go

@@ -9,6 +9,7 @@
 	"context"
 	"encoding/json"
 	"errors"
+	"log"
 	"math"
 	"net/http"
 	"net/url"
@@ -380,17 +381,21 @@ func (nc *NoiseClient) dial(ctx context.Context) (*noiseconn.Conn, error) {
 // post does a POST to the control server at the given path, JSON-encoding body.
 // The provided nodeKey is an optional load balancing hint.
 func (nc *NoiseClient) post(ctx context.Context, path string, nodeKey key.NodePublic, body any) (*http.Response, error) {
+	return nc.doWithBody(ctx, "POST", path, nodeKey, body)
+}
+
+func (nc *NoiseClient) doWithBody(ctx context.Context, method, path string, nodeKey key.NodePublic, body any) (*http.Response, error) {
 	jbody, err := json.Marshal(body)
 	if err != nil {
 		return nil, err
 	}
-	req, err := http.NewRequestWithContext(ctx, "POST", "https://"+nc.host+path, bytes.NewReader(jbody))
+	req, err := http.NewRequestWithContext(ctx, method, "https://"+nc.host+path, bytes.NewReader(jbody))
 	if err != nil {
 		return nil, err
 	}
 	addLBHeader(req, nodeKey)
 	req.Header.Set("Content-Type", "application/json")
-
+	log.Printf("XXXX doing %+v", req)
 	conn, err := nc.getConn(ctx)
 	if err != nil {
 		return nil, err

ipn/ipnlocal/local.go

@@ -6325,6 +6325,16 @@ func (b *LocalBackend) SetExpirySooner(ctx context.Context, expiry time.Time) er
 	return cc.SetExpirySooner(ctx, expiry)
 }
 
+func (b *LocalBackend) SetDeviceAttrs(ctx context.Context, attrs map[string]any) error {
+	b.mu.Lock()
+	cc := b.ccAuto
+	b.mu.Unlock()
+	if cc == nil {
+		return errors.New("not running")
+	}
+	return cc.SetDeviceAttrs(ctx, attrs)
+}
+
 // exitNodeCanProxyDNS reports the DoH base URL ("http://foo/dns-query") without query parameters
 // to exitNodeID's DoH service, if available.
 //

ipn/localapi/localapi.go

@@ -14,6 +14,7 @@
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"maps"
 	"mime"
 	"mime/multipart"
@@ -149,6 +150,7 @@
 	"usermetrics":                 (*Handler).serveUserMetrics,
 	"watch-ipn-bus":               (*Handler).serveWatchIPNBus,
 	"whois":                       (*Handler).serveWhoIs,
+	"alpha-set-device-attrs":      (*Handler).serveSetDeviceAttrs,
 }
 
 var (
@@ -226,6 +228,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	if fn, ok := handlerForPath(r.URL.Path); ok {
 		fn(h, w, r)
 	} else {
+		log.Printf("XXX nothing found for %q", r.URL.Path)
 		http.NotFound(w, r)
 	}
 }
@@ -446,6 +449,29 @@ func (h *Handler) serveWhoIs(w http.ResponseWriter, r *http.Request) {
 	h.serveWhoIsWithBackend(w, r, h.b)
 }
 
+func (h *Handler) serveSetDeviceAttrs(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	if !h.PermitWrite {
+		http.Error(w, "set-device-attrs access denied", http.StatusForbidden)
+		return
+	}
+	if r.Method != "PATCH" {
+		http.Error(w, "only PATCH allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	var req map[string]any
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+	if err := h.b.SetDeviceAttrs(ctx, req); err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	w.Header().Set("Content-Type", "application/json")
+	io.WriteString(w, "{}\n")
+}
+
 // localBackendWhoIsMethods is the subset of ipn.LocalBackend as needed
 // by the localapi WhoIs method.
 type localBackendWhoIsMethods interface {

tailcfg/tailcfg.go

@@ -2450,6 +2450,13 @@ type HealthChangeRequest struct {
 	NodeKey key.NodePublic
 }
 
+type SetDeviceAttributesRequest struct {
+	Version CapabilityVersion
+	NodeKey key.NodePublic
+
+	Update map[string]any // attribute name => {string, float64, int64, bool, nil to delete}
+}
+
 // SSHPolicy is the policy for how to handle incoming SSH connections
 // over Tailscale.
 type SSHPolicy struct {