feat: add runner authentication middleware and identity context

internal/api/middleware.go

@@ -2,6 +2,8 @@
 package api
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
 	"net/http"
 	"strings"
 	"time"
@@ -148,6 +150,39 @@ func (s *Server) RequireWritable(next http.Handler) http.Handler {
 	})
 }
 
+// RequireRunnerAuth extracts and validates a runner token from the
+// Authorization header. On success, injects RunnerIdentity into context
+// and updates the runner's heartbeat.
+func (s *Server) RequireRunnerAuth(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		token := extractBearerToken(r)
+		if token == "" || !strings.HasPrefix(token, "silo_runner_") {
+			writeError(w, http.StatusUnauthorized, "unauthorized", "Runner token required")
+			return
+		}
+
+		hash := sha256.Sum256([]byte(token))
+		tokenHash := hex.EncodeToString(hash[:])
+
+		runner, err := s.jobs.GetRunnerByToken(r.Context(), tokenHash)
+		if err != nil || runner == nil {
+			writeError(w, http.StatusUnauthorized, "unauthorized", "Invalid runner token")
+			return
+		}
+
+		// Update heartbeat on every authenticated request
+		_ = s.jobs.Heartbeat(r.Context(), runner.ID)
+
+		identity := &auth.RunnerIdentity{
+			ID:   runner.ID,
+			Name: runner.Name,
+			Tags: runner.Tags,
+		}
+		ctx := auth.ContextWithRunner(r.Context(), identity)
+		next.ServeHTTP(w, r.WithContext(ctx))
+	})
+}
+
 func extractBearerToken(r *http.Request) string {
 	h := r.Header.Get("Authorization")
 	if strings.HasPrefix(h, "Bearer ") {

internal/auth/runner.go

@@ -0,0 +1,24 @@
+package auth
+
+import "context"
+
+const runnerContextKey contextKey = iota + 1
+
+// RunnerIdentity represents an authenticated runner in the request context.
+type RunnerIdentity struct {
+	ID   string
+	Name string
+	Tags []string
+}
+
+// RunnerFromContext extracts the authenticated runner from the request context.
+// Returns nil if no runner is present.
+func RunnerFromContext(ctx context.Context) *RunnerIdentity {
+	r, _ := ctx.Value(runnerContextKey).(*RunnerIdentity)
+	return r
+}
+
+// ContextWithRunner returns a new context carrying the given runner identity.
+func ContextWithRunner(ctx context.Context, r *RunnerIdentity) context.Context {
+	return context.WithValue(ctx, runnerContextKey, r)
+}