util/syspolicy/policyclient: add Client interface to the syspolicy universebradfitz/syspolicy_key

This removes the dependency on syspolicy/... from LocalBackend and tailscaled
when ts_omit_syspolicy is true.

Updates #12614

Change-Id: I309deb0f50f8e7d6bc11454e4210bb3b358abc77
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

2 files changed, 67 insertions, 50 deletions

diff --git a/ipn/localapi/localapi.go b/ipn/localapi/localapi.go
index 157f72a65..072ad6b4a 100644
--- a/ipn/localapi/localapi.go
+++ b/ipn/localapi/localapi.go
@@ -62,8 +62,6 @@ import (
 	"tailscale.com/util/osdiag"
 	"tailscale.com/util/progresstracking"
 	"tailscale.com/util/rands"
-	"tailscale.com/util/syspolicy/rsop"
-	"tailscale.com/util/syspolicy/setting"
 	"tailscale.com/version"
 	"tailscale.com/wgengine/magicsock"
 )
@@ -78,7 +76,6 @@ var handler = map[string]localAPIHandler{
 	"cert/":     (*Handler).serveCert,
 	"file-put/": (*Handler).serveFilePut,
 	"files/":    (*Handler).serveFiles,
-	"policy/":   (*Handler).servePolicy,
 	"profiles/": (*Handler).serveProfiles,
 
 	// The other /localapi/v0/NAME handlers are exact matches and contain only NAME
@@ -1389,53 +1386,6 @@ func (h *Handler) servePrefs(w http.ResponseWriter, r *http.Request) {
 	e.Encode(prefs)
 }
 
-func (h *Handler) servePolicy(w http.ResponseWriter, r *http.Request) {
-	if !h.PermitRead {
-		http.Error(w, "policy access denied", http.StatusForbidden)
-		return
-	}
-
-	suffix, ok := strings.CutPrefix(r.URL.EscapedPath(), "/localapi/v0/policy/")
-	if !ok {
-		http.Error(w, "misconfigured", http.StatusInternalServerError)
-		return
-	}
-
-	var scope setting.PolicyScope
-	if suffix == "" {
-		scope = setting.DefaultScope()
-	} else if err := scope.UnmarshalText([]byte(suffix)); err != nil {
-		http.Error(w, fmt.Sprintf("%q is not a valid scope", suffix), http.StatusBadRequest)
-		return
-	}
-
-	policy, err := rsop.PolicyFor(scope)
-	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
-		return
-	}
-
-	var effectivePolicy *setting.Snapshot
-	switch r.Method {
-	case "GET":
-		effectivePolicy = policy.Get()
-	case "POST":
-		effectivePolicy, err = policy.Reload()
-		if err != nil {
-			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
-		}
-	default:
-		http.Error(w, "unsupported method", http.StatusMethodNotAllowed)
-		return
-	}
-
-	w.Header().Set("Content-Type", "application/json")
-	e := json.NewEncoder(w)
-	e.SetIndent("", "\t")
-	e.Encode(effectivePolicy)
-}
-
 type resJSON struct {
 	Error string `json:",omitempty"`
 }
diff --git a/ipn/localapi/syspolicy_api.go b/ipn/localapi/syspolicy_api.go
new file mode 100644
index 000000000..366045de3
--- /dev/null
+++ b/ipn/localapi/syspolicy_api.go
@@ -0,0 +1,67 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !ts_omit_syspolicy
+
+package localapi
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"tailscale.com/util/syspolicy/rsop"
+	"tailscale.com/util/syspolicy/setting"
+)
+
+func init() {
+	handler["policy/"] = (*Handler).servePolicy
+}
+
+func (h *Handler) servePolicy(w http.ResponseWriter, r *http.Request) {
+	if !h.PermitRead {
+		http.Error(w, "policy access denied", http.StatusForbidden)
+		return
+	}
+
+	suffix, ok := strings.CutPrefix(r.URL.EscapedPath(), "/localapi/v0/policy/")
+	if !ok {
+		http.Error(w, "misconfigured", http.StatusInternalServerError)
+		return
+	}
+
+	var scope setting.PolicyScope
+	if suffix == "" {
+		scope = setting.DefaultScope()
+	} else if err := scope.UnmarshalText([]byte(suffix)); err != nil {
+		http.Error(w, fmt.Sprintf("%q is not a valid scope", suffix), http.StatusBadRequest)
+		return
+	}
+
+	policy, err := rsop.PolicyFor(scope)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	var effectivePolicy *setting.Snapshot
+	switch r.Method {
+	case "GET":
+		effectivePolicy = policy.Get()
+	case "POST":
+		effectivePolicy, err = policy.Reload()
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	default:
+		http.Error(w, "unsupported method", http.StatusMethodNotAllowed)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	e := json.NewEncoder(w)
+	e.SetIndent("", "\t")
+	e.Encode(effectivePolicy)
+}