fix: require Feishu webhook authentication (#1638)

* fix: require Feishu webhook authentication

* fix: handle Feishu v2 webhook token auth

* fix: skip empty verification token write, consistent with app_id/app_secret

Address zmanian review nit #4: only write verification_token to workspace
when present, matching the if-let pattern used for app_id and app_secret.
Functionally identical (the auth check filters empty strings), but
consistent.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>

channels-src/feishu/Cargo.lock

@@ -44,6 +44,7 @@ version = "0.1.0"
 dependencies = [
  "serde",
  "serde_json",
+ "subtle",
  "wit-bindgen",
 ]
 
@@ -208,6 +209,12 @@ dependencies = [
  "smallvec",
 ]
 
+[[package]]
+name = "subtle"
+version = "2.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
+
 [[package]]
 name = "syn"
 version = "2.0.117"

channels-src/feishu/Cargo.toml

@@ -15,6 +15,7 @@ wit-bindgen = "0.36"
 # Serialization
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
+subtle = "2.6"
 
 # Exclude from parent workspace (this is a standalone WASM component)
 

channels-src/feishu/feishu.capabilities.json

@@ -27,7 +27,7 @@
       {
         "name": "feishu_verification_token",
         "prompt": "Enter your Feishu/Lark Verification Token (from Event Subscription webhook settings)",
-        "optional": true
+        "optional": false
       }
     ],
     "setup_url": "https://open.feishu.cn/app"
@@ -63,13 +63,15 @@
       },
       "webhook": {
         "secret_header": "X-Feishu-Verification-Token",
-        "secret_name": "feishu_verification_token"
+        "secret_name": "feishu_verification_token",
+        "managed_by_host": false
       }
     }
   },
   "config": {
     "app_id": null,
     "app_secret": null,
+    "verification_token": null,
     "api_base": "https://open.feishu.cn",
     "owner_id": null,
     "dm_policy": "pairing",

channels-src/feishu/src/lib.rs

@@ -23,7 +23,8 @@
 //! - App credentials (app_id, app_secret) are injected by the host into
 //!   the config JSON during startup for token exchange
 //! - Bearer token for API calls is obtained via token exchange and cached
-//! - Verification token validated by host for webhook requests
+//! - Webhook requests must be authenticated by the host or by a matching
+//!   Feishu verification token in the request body
 
 // Generate bindings from the WIT file
 wit_bindgen::generate!({
@@ -32,6 +33,7 @@ wit_bindgen::generate!({
 });
 
 use serde::{Deserialize, Serialize};
+use subtle::ConstantTimeEq;
 
 // Re-export generated types
 use exports::near::agent::channel::{
@@ -50,6 +52,7 @@ const ALLOW_FROM_PATH: &str = "allow_from";
 const API_BASE_PATH: &str = "api_base";
 const APP_ID_PATH: &str = "app_id";
 const APP_SECRET_PATH: &str = "app_secret";
+const VERIFICATION_TOKEN_PATH: &str = "verification_token";
 const TOKEN_PATH: &str = "tenant_access_token";
 const TOKEN_EXPIRY_PATH: &str = "token_expiry";
 
@@ -102,6 +105,10 @@ struct FeishuEventHeader {
     /// Tenant key.
     #[serde(default)]
     tenant_key: Option<String>,
+
+    /// Verification token for v2 event payloads.
+    #[serde(default)]
+    token: Option<String>,
 }
 
 /// Message receive event payload (im.message.receive_v1).
@@ -251,6 +258,9 @@ struct FeishuConfig {
     /// Feishu App Secret (for token exchange).
     app_secret: Option<String>,
 
+    /// Feishu Event Subscription verification token.
+    verification_token: Option<String>,
+
     /// API base URL. Defaults to "https://open.feishu.cn" (use
     /// "https://open.larksuite.com" for Lark international).
     #[serde(default = "default_api_base")]
@@ -300,6 +310,9 @@ impl Guest for FeishuChannel {
         if let Some(ref app_secret) = config.app_secret {
             let _ = channel_host::workspace_write(APP_SECRET_PATH, app_secret);
         }
+        if let Some(ref verification_token) = config.verification_token {
+            let _ = channel_host::workspace_write(VERIFICATION_TOKEN_PATH, verification_token);
+        }
 
         if let Some(owner_id) = &config.owner_id {
             let _ = channel_host::workspace_write(OWNER_ID_PATH, owner_id);
@@ -376,6 +389,23 @@ impl Guest for FeishuChannel {
             }
         };
 
+        let configured_token =
+            channel_host::workspace_read(VERIFICATION_TOKEN_PATH).filter(|token| !token.is_empty());
+        if !is_authenticated_webhook(
+            req.secret_validated,
+            configured_token.as_deref(),
+            request_verification_token(&event),
+        ) {
+            channel_host::log(
+                channel_host::LogLevel::Warn,
+                "Rejecting unauthenticated Feishu webhook request",
+            );
+            return json_response(
+                401,
+                serde_json::json!({"error": "Webhook authentication failed"}),
+            );
+        }
+
         // Handle URL verification challenge (initial webhook setup).
         if event.event_type.as_deref() == Some("url_verification") {
             if let Some(challenge) = &event.challenge {
@@ -839,6 +869,31 @@ fn json_response(status: u16, body: serde_json::Value) -> OutgoingHttpResponse {
     }
 }
 
+fn is_authenticated_webhook(
+    secret_validated: bool,
+    configured_token: Option<&str>,
+    request_token: Option<&str>,
+) -> bool {
+    if secret_validated {
+        return true;
+    }
+
+    match (configured_token, request_token) {
+        (Some(expected), Some(provided)) => {
+            bool::from(expected.as_bytes().ct_eq(provided.as_bytes()))
+        }
+        _ => false,
+    }
+}
+
+fn request_verification_token(event: &FeishuEvent) -> Option<&str> {
+    event
+        .header
+        .as_ref()
+        .and_then(|header| header.token.as_deref())
+        .or(event.token.as_deref())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -862,7 +917,10 @@ mod tests {
     fn parse_token_response_rejects_missing_token() {
         let json = r#"{"code": 0, "msg": "ok", "expire": 7200}"#;
         let result: Result<TenantAccessTokenResponse, _> = serde_json::from_str(json);
-        assert!(result.is_err(), "should fail when tenant_access_token is missing");
+        assert!(
+            result.is_err(),
+            "should fail when tenant_access_token is missing"
+        );
     }
 
     #[test]
@@ -894,4 +952,64 @@ mod tests {
         assert_eq!(resp.code, 10003);
         assert!(resp.tenant_access_token.is_empty());
     }
+
+    #[test]
+    fn webhook_auth_requires_host_auth_or_matching_verification_token() {
+        assert!(
+            !is_authenticated_webhook(false, None, Some("token")),
+            "requests without any configured verification mechanism must be rejected"
+        );
+        assert!(
+            !is_authenticated_webhook(false, Some("expected"), None),
+            "requests missing the Feishu token must be rejected when host auth did not pass"
+        );
+        assert!(
+            !is_authenticated_webhook(false, Some("expected"), Some("wrong")),
+            "requests with the wrong Feishu token must be rejected"
+        );
+        assert!(
+            is_authenticated_webhook(false, Some("expected"), Some("expected")),
+            "matching Feishu verification token should authenticate the request"
+        );
+        assert!(
+            is_authenticated_webhook(true, None, None),
+            "host-authenticated requests should still be accepted"
+        );
+        assert!(
+            is_authenticated_webhook(true, Some("expected"), Some("wrong")),
+            "host authentication should take precedence over body token checks"
+        );
+    }
+
+    #[test]
+    fn request_verification_token_prefers_v2_header_token() {
+        let event: FeishuEvent = serde_json::from_str(
+            r#"{
+                "schema": "2.0",
+                "header": {
+                    "event_id": "evt_123",
+                    "event_type": "im.message.receive_v1",
+                    "token": "header-token"
+                },
+                "event": {}
+            }"#,
+        )
+        .unwrap();
+
+        assert_eq!(request_verification_token(&event), Some("header-token"));
+    }
+
+    #[test]
+    fn request_verification_token_falls_back_to_top_level_token() {
+        let event: FeishuEvent = serde_json::from_str(
+            r#"{
+                "type": "url_verification",
+                "challenge": "abc",
+                "token": "top-level-token"
+            }"#,
+        )
+        .unwrap();
+
+        assert_eq!(request_verification_token(&event), Some("top-level-token"));
+    }
 }