fix(security): harden unauthenticated tool-exec paths (#1360)

* fix(security): harden unauthenticated tool-exec paths (GHSA-pv8c-p6jf-3fpp)

- Exec tool: channel-based access control (default deny remote)
- Cron tool: command scheduling restricted to internal channels
- Web fetch: SSRF defense-in-depth (pre-flight + dial-time + redirect checks)
- File permissions: session/state dirs 0700, files 0600
- Registry: inject __channel/__chat_id into tool args (replaces racy SetContext)

28 new security regression tests.

(cherry picked from commit 191446ae19021604d3d5b0d9376b9655ab749105)

* fix(exec): revalidate working_dir before command start

* test(web): allow local oversized payload fixture

---------

Co-authored-by: xj <gh-xj@users.noreply.github.com>

pkg/channels/wecom/app_test.go

@@ -209,7 +209,7 @@ func TestWeComAppVerifySignature(t *testing.T) {
 		}
 	})
 
-	t.Run("empty token skips verification", func(t *testing.T) {
+	t.Run("empty token rejects verification (fail-closed)", func(t *testing.T) {
 		cfgEmpty := config.WeComAppConfig{
 			CorpID:     "test_corp_id",
 			CorpSecret: "test_secret",
@@ -218,8 +218,8 @@ func TestWeComAppVerifySignature(t *testing.T) {
 		}
 		chEmpty, _ := NewWeComAppChannel(cfgEmpty, msgBus)
 
-		if !verifySignature(chEmpty.config.Token, "any_sig", "any_ts", "any_nonce", "any_msg") {
-			t.Error("empty token should skip verification and return true")
+		if verifySignature(chEmpty.config.Token, "any_sig", "any_ts", "any_nonce", "any_msg") {
+			t.Error("empty token should reject verification (fail-closed)")
 		}
 	})
 }

pkg/channels/wecom/bot_test.go

@@ -189,8 +189,7 @@ func TestWeComBotVerifySignature(t *testing.T) {
 		}
 	})
 
-	t.Run("empty token skips verification", func(t *testing.T) {
-		// Create a channel manually with empty token to test the behavior
+	t.Run("empty token rejects verification (fail-closed)", func(t *testing.T) {
 		cfgEmpty := config.WeComConfig{
 			Token:      "",
 			WebhookURL: "https://qyapi.weixin.qq.com/cgi-bin/webhook/send?key=test",
@@ -199,8 +198,8 @@ func TestWeComBotVerifySignature(t *testing.T) {
 			config: cfgEmpty,
 		}
 
-		if !verifySignature(chEmpty.config.Token, "any_sig", "any_ts", "any_nonce", "any_msg") {
-			t.Error("empty token should skip verification and return true")
+		if verifySignature(chEmpty.config.Token, "any_sig", "any_ts", "any_nonce", "any_msg") {
+			t.Error("empty token should reject verification (fail-closed)")
 		}
 	})
 }

pkg/channels/wecom/common.go

@@ -31,7 +31,7 @@ func computeSignature(token, timestamp, nonce, encrypt string) string {
 // This is a common function used by both WeCom Bot and WeCom App
 func verifySignature(token, msgSignature, timestamp, nonce, msgEncrypt string) bool {
 	if token == "" {
-		return true // Skip verification if token is not set
+		return false
 	}
 	return computeSignature(token, timestamp, nonce, msgEncrypt) == msgSignature
 }