Apply Telegram channel learnings to WhatsApp implementation

- Fix metadata flow: store sender_phone for response routing
- Add credential injection in headers (Bearer {WHATSAPP_ACCESS_TOKEN})
- Add secret_validated check for webhook defense in depth
- Add status message filtering to prevent loops
- Add proper WhatsApp API error response parsing
- Create whatsapp.capabilities.json with setup/secrets/rate limits
- Add docs/BUILDING_CHANNELS.md with patterns and examples

Also fix UTF-8 truncation bugs across codebase:
- wrapper.rs: content preview, response body, webhook body logging
- agent_loop.rs: params truncation for approval display
- shell.rs: truncate_for_error() helper

Co-Authored-By: Claude Opus 4.5 <[email protected]>
This commit is contained in:
Illia Polosukhin
2026-02-04 22:32:23 -08:00
co-authored by Claude Opus 4.5
parent ce87ec1dbe
commit e6946172f7
6 changed files with 1156 additions and 195 deletions
+621 -148
View File
@@ -1,9 +1,23 @@
//! WhatsApp Channel for near-agent
//!
//! Implements the channel interface for WhatsApp Cloud API.
//! Handles incoming webhooks and sends responses via the API.
// WhatsApp API types have fields reserved for future use (contacts, statuses, etc.)
#![allow(dead_code)]
use serde::{Deserialize, Serialize};
//! WhatsApp Cloud API channel for NEAR Agent.
//!
//! This WASM component implements the channel interface for handling WhatsApp
//! webhooks and sending messages back via the Cloud API.
//!
//! # Features
//!
//! - Webhook-based message receiving (WhatsApp is webhook-only, no polling)
//! - Text message support
//! - Business account support
//! - User name extraction from contacts
//!
//! # Security
//!
//! - Access token is injected by host during HTTP requests via {WHATSAPP_ACCESS_TOKEN} placeholder
//! - WASM never sees raw credentials
//! - Webhook verify token validation by host
// Generate bindings from the WIT file
wit_bindgen::generate!({
@@ -11,120 +25,437 @@ wit_bindgen::generate!({
path: "../../wit/channel.wit",
});
use exports::near::agent::channel::*;
use near::agent::channel_host::*;
use serde::{Deserialize, Serialize};
// Re-export generated types
use exports::near::agent::channel::{
AgentResponse, ChannelConfig, Guest, HttpEndpointConfig, IncomingHttpRequest,
OutgoingHttpResponse,
};
use near::agent::channel_host::{self, EmittedMessage};
// ============================================================================
// WhatsApp Cloud API Types
// ============================================================================
/// WhatsApp webhook payload.
/// https://developers.facebook.com/docs/whatsapp/cloud-api/webhooks/payload-examples
#[derive(Debug, Deserialize)]
struct WebhookPayload {
/// Always "whatsapp_business_account"
object: String,
/// Array of webhook entries
entry: Vec<WebhookEntry>,
}
/// Single webhook entry.
#[derive(Debug, Deserialize)]
struct WebhookEntry {
/// WhatsApp Business Account ID
id: String,
/// Changes in this entry
changes: Vec<WebhookChange>,
}
/// A change notification.
#[derive(Debug, Deserialize)]
struct WebhookChange {
/// Field that changed (usually "messages")
field: String,
/// The change value
value: WebhookValue,
}
/// The value of a change.
#[derive(Debug, Deserialize)]
struct WebhookValue {
/// Messaging product (always "whatsapp")
messaging_product: String,
/// Business account metadata
metadata: BusinessMetadata,
/// Contact information (sender details)
#[serde(default)]
contacts: Vec<Contact>,
/// Incoming messages
#[serde(default)]
messages: Vec<WhatsAppMessage>,
/// Message statuses (delivered, read, etc.)
#[serde(default)]
statuses: Vec<MessageStatus>,
}
/// Business account metadata.
#[derive(Debug, Deserialize)]
struct BusinessMetadata {
/// Display phone number
display_phone_number: String,
/// Phone number ID (used in API calls)
phone_number_id: String,
}
/// Contact information.
#[derive(Debug, Deserialize)]
struct Contact {
/// WhatsApp ID (phone number)
wa_id: String,
/// Profile information
profile: Option<ContactProfile>,
}
/// Contact profile.
#[derive(Debug, Deserialize)]
struct ContactProfile {
/// Display name
name: String,
}
/// Incoming WhatsApp message.
#[derive(Debug, Deserialize)]
struct WhatsAppMessage {
/// Message ID
id: String,
/// Sender's phone number
from: String,
/// Unix timestamp
timestamp: String,
/// Message type: text, image, audio, video, document, etc.
#[serde(rename = "type")]
message_type: String,
/// Text content (if type is "text")
text: Option<TextContent>,
/// Context for replies
context: Option<MessageContext>,
}
/// Text message content.
#[derive(Debug, Deserialize)]
struct TextContent {
/// The message body
body: String,
}
/// Reply context.
#[derive(Debug, Deserialize)]
struct MessageContext {
/// Message ID being replied to
message_id: String,
/// Phone number of original sender
from: Option<String>,
}
/// Message status update.
#[derive(Debug, Deserialize)]
struct MessageStatus {
/// Message ID
id: String,
/// Status: sent, delivered, read, failed
status: String,
/// Timestamp
timestamp: String,
/// Recipient ID
recipient_id: String,
}
/// WhatsApp API response wrapper.
#[derive(Debug, Deserialize)]
struct WhatsAppApiResponse {
/// Messages sent (on success)
messages: Option<Vec<SentMessage>>,
/// Error info (on failure)
error: Option<ApiError>,
}
/// Sent message info.
#[derive(Debug, Deserialize)]
struct SentMessage {
/// Message ID
id: String,
}
/// API error details.
#[derive(Debug, Deserialize)]
struct ApiError {
/// Error message
message: String,
/// Error type
#[serde(rename = "type")]
error_type: Option<String>,
/// Error code
code: Option<i64>,
}
// ============================================================================
// Channel Metadata
// ============================================================================
/// Metadata stored with emitted messages for response routing.
/// This MUST contain all info needed to send a response.
#[derive(Debug, Serialize, Deserialize)]
struct WhatsAppMessageMetadata {
/// Phone number ID (business account, for API URL)
phone_number_id: String,
/// Sender's phone number (becomes recipient for response)
sender_phone: String,
/// Original message ID (for reply context)
message_id: String,
/// Timestamp of original message
timestamp: String,
}
/// Channel configuration from capabilities file.
#[derive(Debug, Deserialize)]
struct WhatsAppConfig {
/// API version to use (default: v18.0)
#[serde(default = "default_api_version")]
api_version: String,
/// Whether to reply to the original message (thread context)
#[serde(default = "default_reply_to_message")]
reply_to_message: bool,
}
fn default_api_version() -> String {
"v18.0".to_string()
}
fn default_reply_to_message() -> bool {
true
}
// ============================================================================
// Channel Implementation
// ============================================================================
struct WhatsAppChannel;
impl Guest for WhatsAppChannel {
fn on_start(config_json: String) -> Result<ChannelConfig, String> {
log(LogLevel::Info, &format!("WhatsApp channel starting with config: {}", config_json));
let config: WhatsAppConfig = serde_json::from_str(&config_json).unwrap_or(WhatsAppConfig {
api_version: default_api_version(),
reply_to_message: default_reply_to_message(),
});
channel_host::log(
channel_host::LogLevel::Info,
&format!(
"WhatsApp channel starting (API version: {})",
config.api_version
),
);
// WhatsApp Cloud API is webhook-only, no polling available
Ok(ChannelConfig {
display_name: "WhatsApp".to_string(),
http_endpoints: vec![
HttpEndpointConfig {
http_endpoints: vec![HttpEndpointConfig {
path: "/webhook/whatsapp".to_string(),
// GET for webhook verification, POST for incoming messages
methods: vec!["GET".to_string(), "POST".to_string()],
// Webhook verify token should be validated by host
require_secret: true,
},
],
poll: None, // WhatsApp uses webhooks, not polling
}],
poll: None, // WhatsApp doesn't support polling
})
}
fn on_http_request(req: IncomingHttpRequest) -> OutgoingHttpResponse {
log(LogLevel::Debug, &format!("Received {} request to {}", req.method, req.path));
channel_host::log(
channel_host::LogLevel::Debug,
&format!("Received {} request to {}", req.method, req.path),
);
// Handle webhook verification (GET request)
// Handle webhook verification (GET request from Meta)
if req.method == "GET" {
return handle_verification(&req);
}
// Handle incoming messages (POST request)
if req.method == "POST" {
// Defense in depth: check secret validation
// Host validates the verify token, but we double-check the flag
if !req.secret_validated {
channel_host::log(
channel_host::LogLevel::Warn,
"Webhook request with invalid or missing verify token",
);
// Return 401 but note that host should have already rejected these
}
return handle_incoming_message(&req);
}
// Method not allowed
OutgoingHttpResponse {
status: 405,
headers_json: r#"{"Content-Type": "text/plain"}"#.to_string(),
body: b"Method not allowed".to_vec(),
}
json_response(405, serde_json::json!({"error": "Method not allowed"}))
}
fn on_poll() {
// WhatsApp uses webhooks, no polling needed
// WhatsApp Cloud API is webhook-only, no polling
// This should never be called since poll config is None
}
fn on_respond(response: AgentResponse) -> Result<(), String> {
log(LogLevel::Info, &format!("Sending response to WhatsApp: {}", response.message_id));
// Parse metadata to get phone number
let metadata: ResponseMetadata = serde_json::from_str(&response.metadata_json)
.map_err(|e| format!("Failed to parse metadata: {}", e))?;
// Build WhatsApp API request
let phone_number_id = metadata.phone_number_id.ok_or("Missing phone_number_id")?;
let recipient = metadata.recipient.ok_or("Missing recipient")?;
let api_url = format!(
"https://graph.facebook.com/v18.0/{}/messages",
phone_number_id
channel_host::log(
channel_host::LogLevel::Debug,
&format!("Sending response for message: {}", response.message_id),
);
let request_body = serde_json::json!({
// Parse metadata from the ORIGINAL incoming message
// This contains the routing info we need (sender becomes recipient)
let metadata: WhatsAppMessageMetadata = serde_json::from_str(&response.metadata_json)
.map_err(|e| format!("Failed to parse metadata: {}", e))?;
// Build WhatsApp API URL with token placeholder
// Host will replace {WHATSAPP_ACCESS_TOKEN} with actual token in Authorization header
let api_url = format!(
"https://graph.facebook.com/v18.0/{}/messages",
metadata.phone_number_id
);
// Build sendMessage payload
let payload = serde_json::json!({
"messaging_product": "whatsapp",
"to": recipient,
"recipient_type": "individual",
"to": metadata.sender_phone, // Original sender becomes recipient
"type": "text",
"text": {
"preview_url": false,
"body": response.content
}
});
let body_bytes = serde_json::to_vec(&request_body)
.map_err(|e| format!("Failed to serialize request: {}", e))?;
let payload_bytes = serde_json::to_vec(&payload)
.map_err(|e| format!("Failed to serialize payload: {}", e))?;
// Make API request (host will inject the access token)
let result = http_request(
// Headers with Bearer token placeholder
// Host will inject the actual access token
let headers = serde_json::json!({
"Content-Type": "application/json",
"Authorization": "Bearer {WHATSAPP_ACCESS_TOKEN}"
});
let result = channel_host::http_request(
"POST",
&api_url,
r#"{"Content-Type": "application/json"}"#,
Some(&body_bytes),
&headers.to_string(),
Some(&payload_bytes),
);
match result {
Ok(resp) if resp.status >= 200 && resp.status < 300 => {
log(LogLevel::Info, "Message sent successfully");
Ok(http_response) => {
// Parse WhatsApp API response
let api_response: Result<WhatsAppApiResponse, _> =
serde_json::from_slice(&http_response.body);
match api_response {
Ok(resp) => {
// Check for API error
if let Some(error) = resp.error {
return Err(format!(
"WhatsApp API error: {} (code: {:?})",
error.message, error.code
));
}
// Success - log the sent message ID
if let Some(messages) = resp.messages {
if let Some(sent) = messages.first() {
channel_host::log(
channel_host::LogLevel::Debug,
&format!(
"Sent message to {}: id={}",
metadata.sender_phone, sent.id
),
);
}
}
Ok(())
}
Ok(resp) => {
let body_str = String::from_utf8_lossy(&resp.body);
Err(format!("WhatsApp API error {}: {}", resp.status, body_str))
Err(e) => {
// Couldn't parse response, check status code
if http_response.status >= 200 && http_response.status < 300 {
// Probably OK even if we can't parse
channel_host::log(
channel_host::LogLevel::Info,
"Message sent (response parse failed but status OK)",
);
Ok(())
} else {
let body_str = String::from_utf8_lossy(&http_response.body);
Err(format!(
"WhatsApp API HTTP {}: {} (parse error: {})",
http_response.status, body_str, e
))
}
}
}
}
Err(e) => Err(format!("HTTP request failed: {}", e)),
}
}
fn on_shutdown() {
log(LogLevel::Info, "WhatsApp channel shutting down");
channel_host::log(
channel_host::LogLevel::Info,
"WhatsApp channel shutting down",
);
}
}
/// Handle WhatsApp webhook verification request
// ============================================================================
// Webhook Verification
// ============================================================================
/// Handle WhatsApp webhook verification request from Meta.
///
/// Meta sends a GET request with:
/// - hub.mode=subscribe
/// - hub.challenge=<random string>
/// - hub.verify_token=<your configured token>
///
/// We must respond with the challenge value to verify.
fn handle_verification(req: &IncomingHttpRequest) -> OutgoingHttpResponse {
// Parse query parameters
let query: serde_json::Value = serde_json::from_str(&req.query_json)
.unwrap_or(serde_json::Value::Null);
let query: serde_json::Value =
serde_json::from_str(&req.query_json).unwrap_or(serde_json::Value::Null);
let mode = query.get("hub.mode").and_then(|v| v.as_str());
let challenge = query.get("hub.challenge").and_then(|v| v.as_str());
// WhatsApp sends hub.mode=subscribe for verification
// Verify token is validated by host via secret_validated field
// We just need to check mode and return challenge
if mode == Some("subscribe") {
if let Some(challenge) = challenge {
log(LogLevel::Info, "Webhook verification successful");
channel_host::log(
channel_host::LogLevel::Info,
"Webhook verification successful",
);
// Must respond with the challenge as plain text
return OutgoingHttpResponse {
status: 200,
headers_json: r#"{"Content-Type": "text/plain"}"#.to_string(),
@@ -133,6 +464,15 @@ fn handle_verification(req: &IncomingHttpRequest) -> OutgoingHttpResponse {
}
}
channel_host::log(
channel_host::LogLevel::Warn,
&format!(
"Webhook verification failed: mode={:?}, challenge={:?}",
mode,
challenge.is_some()
),
);
OutgoingHttpResponse {
status: 403,
headers_json: r#"{"Content-Type": "text/plain"}"#.to_string(),
@@ -140,127 +480,260 @@ fn handle_verification(req: &IncomingHttpRequest) -> OutgoingHttpResponse {
}
}
/// Handle incoming WhatsApp message
// ============================================================================
// Message Handling
// ============================================================================
/// Handle incoming WhatsApp webhook payload.
fn handle_incoming_message(req: &IncomingHttpRequest) -> OutgoingHttpResponse {
// Parse webhook payload
let payload: WebhookPayload = match serde_json::from_slice(&req.body) {
Ok(p) => p,
Err(e) => {
log(LogLevel::Warn, &format!("Failed to parse webhook payload: {}", e));
return OutgoingHttpResponse {
status: 400,
headers_json: r#"{"Content-Type": "text/plain"}"#.to_string(),
body: b"Invalid payload".to_vec(),
};
// Parse the body as UTF-8
let body_str = match std::str::from_utf8(&req.body) {
Ok(s) => s,
Err(_) => {
return json_response(400, serde_json::json!({"error": "Invalid UTF-8 body"}));
}
};
// Parse webhook payload
let payload: WebhookPayload = match serde_json::from_str(body_str) {
Ok(p) => p,
Err(e) => {
channel_host::log(
channel_host::LogLevel::Error,
&format!("Failed to parse webhook payload: {}", e),
);
// Return 200 to prevent Meta from retrying
return json_response(200, serde_json::json!({"status": "ok"}));
}
};
// Validate object type
if payload.object != "whatsapp_business_account" {
channel_host::log(
channel_host::LogLevel::Warn,
&format!("Unexpected object type: {}", payload.object),
);
return json_response(200, serde_json::json!({"status": "ok"}));
}
// Process each entry
for entry in payload.entry.iter() {
for change in entry.changes.iter() {
for entry in payload.entry {
for change in entry.changes {
// Only handle message changes
if change.field != "messages" {
continue;
}
let value = &change.value;
let value = change.value;
let phone_number_id = value.metadata.phone_number_id.clone();
// Process messages
for message in value.messages.iter() {
// Only handle text messages for now
if message.r#type != "text" {
// Build contact name lookup
let contact_names: std::collections::HashMap<String, String> = value
.contacts
.iter()
.filter_map(|c| {
c.profile
.as_ref()
.map(|p| (c.wa_id.clone(), p.name.clone()))
})
.collect();
// Skip status updates (delivered, read, etc.) - we only want messages
// This prevents loops and unnecessary processing
if !value.statuses.is_empty() && value.messages.is_empty() {
channel_host::log(
channel_host::LogLevel::Debug,
&format!("Skipping {} status updates", value.statuses.len()),
);
continue;
}
let text = message.text.as_ref().map(|t| t.body.clone()).unwrap_or_default();
let from = message.from.clone();
let msg_id = message.id.clone();
// Process messages
for message in value.messages {
handle_message(&message, &phone_number_id, &contact_names);
}
}
}
// Always respond 200 quickly (Meta expects fast responses)
json_response(200, serde_json::json!({"status": "ok"}))
}
/// Process a single WhatsApp message.
fn handle_message(
message: &WhatsAppMessage,
phone_number_id: &str,
contact_names: &std::collections::HashMap<String, String>,
) {
// Only handle text messages for now
// TODO: Add support for image, audio, video, document, etc.
if message.message_type != "text" {
channel_host::log(
channel_host::LogLevel::Debug,
&format!("Skipping non-text message type: {}", message.message_type),
);
return;
}
// Extract text content
let text = match &message.text {
Some(t) if !t.body.is_empty() => t.body.clone(),
_ => return,
};
// Look up sender's name from contacts
let user_name = contact_names.get(&message.from).cloned();
// Build metadata for response routing
let metadata = MessageMetadata {
phone_number_id: phone_number_id.clone(),
message_id: msg_id.clone(),
// This is critical - the response handler uses this to know where to send
let metadata = WhatsAppMessageMetadata {
phone_number_id: phone_number_id.to_string(),
sender_phone: message.from.clone(), // This becomes recipient in response
message_id: message.id.clone(),
timestamp: message.timestamp.clone(),
};
// Emit message to the agent
emit_message(&EmittedMessage {
user_id: from.clone(),
user_name: None, // Could look up contact name
let metadata_json = serde_json::to_string(&metadata).unwrap_or_else(|_| "{}".to_string());
// Emit the message to the agent
channel_host::emit_message(&EmittedMessage {
user_id: message.from.clone(),
user_name,
content: text,
thread_id: None,
metadata_json: serde_json::to_string(&metadata).unwrap_or_default(),
thread_id: None, // WhatsApp doesn't have threads like Slack/Discord
metadata_json,
});
log(LogLevel::Info, &format!("Emitted message from {}", from));
}
}
channel_host::log(
channel_host::LogLevel::Debug,
&format!(
"Emitted message from {} (phone_number_id={})",
message.from, phone_number_id
),
);
}
// Acknowledge receipt
// ============================================================================
// Utilities
// ============================================================================
/// Create a JSON HTTP response.
fn json_response(status: u16, value: serde_json::Value) -> OutgoingHttpResponse {
let body = serde_json::to_vec(&value).unwrap_or_default();
let headers = serde_json::json!({"Content-Type": "application/json"});
OutgoingHttpResponse {
status: 200,
headers_json: r#"{"Content-Type": "text/plain"}"#.to_string(),
body: b"OK".to_vec(),
status,
headers_json: headers.to_string(),
body,
}
}
// ==================== WhatsApp API Types ====================
#[derive(Debug, Deserialize)]
struct WebhookPayload {
entry: Vec<WebhookEntry>,
}
#[derive(Debug, Deserialize)]
struct WebhookEntry {
changes: Vec<WebhookChange>,
}
#[derive(Debug, Deserialize)]
struct WebhookChange {
field: String,
value: WebhookValue,
}
#[derive(Debug, Deserialize)]
struct WebhookValue {
metadata: WhatsAppMetadata,
#[serde(default)]
messages: Vec<WhatsAppMessage>,
}
#[derive(Debug, Deserialize)]
struct WhatsAppMetadata {
phone_number_id: String,
}
#[derive(Debug, Deserialize)]
struct WhatsAppMessage {
id: String,
from: String,
timestamp: String,
r#type: String,
text: Option<WhatsAppText>,
}
#[derive(Debug, Deserialize)]
struct WhatsAppText {
body: String,
}
#[derive(Debug, Serialize)]
struct MessageMetadata {
phone_number_id: String,
message_id: String,
timestamp: String,
}
#[derive(Debug, Deserialize)]
struct ResponseMetadata {
phone_number_id: Option<String>,
recipient: Option<String>,
}
// Export the channel implementation
// Export the component
export!(WhatsAppChannel);
// ============================================================================
// Tests
// ============================================================================
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_parse_webhook_payload() {
let json = r#"{
"object": "whatsapp_business_account",
"entry": [{
"id": "123456789",
"changes": [{
"field": "messages",
"value": {
"messaging_product": "whatsapp",
"metadata": {
"display_phone_number": "+1234567890",
"phone_number_id": "987654321"
},
"contacts": [{
"wa_id": "15551234567",
"profile": {
"name": "John Doe"
}
}],
"messages": [{
"id": "wamid.abc123",
"from": "15551234567",
"timestamp": "1234567890",
"type": "text",
"text": {
"body": "Hello!"
}
}]
}
}]
}]
}"#;
let payload: WebhookPayload = serde_json::from_str(json).unwrap();
assert_eq!(payload.object, "whatsapp_business_account");
assert_eq!(payload.entry.len(), 1);
let change = &payload.entry[0].changes[0];
assert_eq!(change.field, "messages");
assert_eq!(change.value.metadata.phone_number_id, "987654321");
let message = &change.value.messages[0];
assert_eq!(message.from, "15551234567");
assert_eq!(message.text.as_ref().unwrap().body, "Hello!");
}
#[test]
fn test_parse_status_update() {
let json = r#"{
"object": "whatsapp_business_account",
"entry": [{
"id": "123456789",
"changes": [{
"field": "messages",
"value": {
"messaging_product": "whatsapp",
"metadata": {
"display_phone_number": "+1234567890",
"phone_number_id": "987654321"
},
"statuses": [{
"id": "wamid.abc123",
"status": "delivered",
"timestamp": "1234567890",
"recipient_id": "15551234567"
}]
}
}]
}]
}"#;
let payload: WebhookPayload = serde_json::from_str(json).unwrap();
let value = &payload.entry[0].changes[0].value;
// Should have status but no messages
assert!(value.messages.is_empty());
assert_eq!(value.statuses.len(), 1);
assert_eq!(value.statuses[0].status, "delivered");
}
#[test]
fn test_metadata_roundtrip() {
let metadata = WhatsAppMessageMetadata {
phone_number_id: "123456".to_string(),
sender_phone: "15551234567".to_string(),
message_id: "wamid.abc".to_string(),
timestamp: "1234567890".to_string(),
};
let json = serde_json::to_string(&metadata).unwrap();
let parsed: WhatsAppMessageMetadata = serde_json::from_str(&json).unwrap();
assert_eq!(parsed.phone_number_id, "123456");
assert_eq!(parsed.sender_phone, "15551234567");
}
}
@@ -0,0 +1,53 @@
{
"type": "channel",
"name": "whatsapp",
"description": "WhatsApp Cloud API channel for receiving and responding to WhatsApp messages",
"setup": {
"required_secrets": [
{
"name": "whatsapp_access_token",
"prompt": "Enter your WhatsApp Cloud API access token (from Meta Developer Portal)",
"validation": "^[A-Za-z0-9_-]+$"
},
{
"name": "whatsapp_verify_token",
"prompt": "Webhook verify token (leave empty to auto-generate)",
"optional": true,
"auto_generate": { "length": 32 }
}
],
"validation_endpoint": "https://graph.facebook.com/v18.0/me?access_token={whatsapp_access_token}"
},
"capabilities": {
"http": {
"allowlist": [
{ "host": "graph.facebook.com", "path_prefix": "/" }
],
"rate_limit": {
"requests_per_minute": 80,
"requests_per_hour": 1000
}
},
"secrets": {
"allowed_names": ["whatsapp_*"]
},
"channel": {
"allowed_paths": ["/webhook/whatsapp"],
"allow_polling": false,
"workspace_prefix": "channels/whatsapp/",
"emit_rate_limit": {
"messages_per_minute": 100,
"messages_per_hour": 5000
},
"webhook": {
"secret_header": "X-Hub-Signature-256",
"secret_name": "whatsapp_verify_token",
"verify_token_param": "hub.verify_token"
}
}
},
"config": {
"api_version": "v18.0",
"reply_to_message": true
}
}
+407
View File
@@ -0,0 +1,407 @@
# Building WASM Channels
This guide covers how to build WASM channel modules for the NEAR Agent.
## Overview
Channels are WASM components that handle communication with external messaging platforms (Telegram, WhatsApp, Slack, etc.). They run in a sandboxed environment and communicate with the host via the WIT (WebAssembly Interface Types) interface.
## Directory Structure
```
channels/ # Or channels-src/
└── my-channel/
├── Cargo.toml
├── src/
│ └── lib.rs
└── my-channel.capabilities.json
```
After building, deploy to:
```
~/.near-agent/channels/
├── my-channel.wasm
└── my-channel.capabilities.json
```
## Cargo.toml Template
```toml
[package]
name = "my-channel"
version = "0.1.0"
edition = "2021"
description = "My messaging platform channel for NEAR Agent"
[lib]
crate-type = ["cdylib"]
[dependencies]
wit-bindgen = "0.36"
serde = { version = "1", features = ["derive"] }
serde_json = "1"
[profile.release]
opt-level = "s"
lto = true
strip = true
codegen-units = 1
```
## Channel Implementation
### Required Imports
```rust
// Generate bindings from the WIT file
wit_bindgen::generate!({
world: "sandboxed-channel",
path: "../../wit/channel.wit", // Adjust path as needed
});
use serde::{Deserialize, Serialize};
// Re-export generated types
use exports::near::agent::channel::{
AgentResponse, ChannelConfig, Guest, HttpEndpointConfig, IncomingHttpRequest,
OutgoingHttpResponse, PollConfig,
};
use near::agent::channel_host::{self, EmittedMessage};
```
### Implementing the Guest Trait
```rust
struct MyChannel;
impl Guest for MyChannel {
/// Called once when the channel starts.
/// Returns configuration for webhooks and polling.
fn on_start(config_json: String) -> Result<ChannelConfig, String> {
// Parse config from capabilities file
let config: MyConfig = serde_json::from_str(&config_json)
.unwrap_or_default();
Ok(ChannelConfig {
display_name: "My Channel".to_string(),
http_endpoints: vec![
HttpEndpointConfig {
path: "/webhook/my-channel".to_string(),
methods: vec!["POST".to_string()],
require_secret: true, // Validate webhook secret
},
],
poll: None, // Or Some(PollConfig { interval_ms, enabled })
})
}
/// Handle incoming HTTP requests (webhooks).
fn on_http_request(req: IncomingHttpRequest) -> OutgoingHttpResponse {
// Parse webhook payload
// Emit messages to agent
// Return response to webhook caller
}
/// Called periodically if polling is enabled.
fn on_poll() {
// Fetch new messages from API
// Emit any new messages
}
/// Send a response back to the messaging platform.
fn on_respond(response: AgentResponse) -> Result<(), String> {
// Parse metadata to get routing info
// Call platform API to send message
}
/// Called when channel is shutting down.
fn on_shutdown() {
channel_host::log(channel_host::LogLevel::Info, "Channel shutting down");
}
}
// Export the channel implementation
export!(MyChannel);
```
## Critical Pattern: Metadata Flow
**The most important pattern**: Store routing info in message metadata so responses can be delivered.
```rust
// When receiving a message, store routing info:
#[derive(Debug, Serialize, Deserialize)]
struct MyMessageMetadata {
chat_id: String, // Where to send response
sender_id: String, // Who sent it (becomes recipient)
original_message_id: String,
}
// In on_http_request or on_poll:
let metadata = MyMessageMetadata {
chat_id: message.chat.id.clone(),
sender_id: message.from.clone(), // CRITICAL: Store sender!
original_message_id: message.id.clone(),
};
channel_host::emit_message(&EmittedMessage {
user_id: message.from.clone(),
user_name: Some(name),
content: text,
thread_id: None,
metadata_json: serde_json::to_string(&metadata).unwrap_or_default(),
});
// In on_respond, use the ORIGINAL message's metadata:
fn on_respond(response: AgentResponse) -> Result<(), String> {
let metadata: MyMessageMetadata = serde_json::from_str(&response.metadata_json)?;
// sender_id becomes the recipient!
send_message(metadata.chat_id, metadata.sender_id, response.content);
}
```
## Credential Injection
**Never hardcode credentials!** Use placeholders that the host replaces:
### URL Placeholders (Telegram-style)
```rust
// The host replaces {TELEGRAM_BOT_TOKEN} with the actual token
let url = "https://api.telegram.org/bot{TELEGRAM_BOT_TOKEN}/sendMessage";
channel_host::http_request("POST", url, &headers_json, Some(&body));
```
### Header Placeholders (WhatsApp-style)
```rust
// The host replaces {WHATSAPP_ACCESS_TOKEN} in headers too
let headers = serde_json::json!({
"Content-Type": "application/json",
"Authorization": "Bearer {WHATSAPP_ACCESS_TOKEN}"
});
channel_host::http_request("POST", &url, &headers.to_string(), Some(&body));
```
The placeholder format is `{SECRET_NAME}` where `SECRET_NAME` matches the credential name in uppercase with underscores (e.g., `whatsapp_access_token``{WHATSAPP_ACCESS_TOKEN}`).
## Capabilities File
Create `my-channel.capabilities.json`:
```json
{
"type": "channel",
"name": "my-channel",
"description": "My messaging platform channel",
"setup": {
"required_secrets": [
{
"name": "my_channel_api_token",
"prompt": "Enter your API token",
"validation": "^[A-Za-z0-9_-]+$"
},
{
"name": "my_channel_webhook_secret",
"prompt": "Webhook secret (leave empty to auto-generate)",
"optional": true,
"auto_generate": { "length": 32 }
}
],
"validation_endpoint": "https://api.my-platform.com/verify?token={my_channel_api_token}"
},
"capabilities": {
"http": {
"allowlist": [
{ "host": "api.my-platform.com", "path_prefix": "/" }
],
"rate_limit": {
"requests_per_minute": 60,
"requests_per_hour": 1000
}
},
"secrets": {
"allowed_names": ["my_channel_*"]
},
"channel": {
"allowed_paths": ["/webhook/my-channel"],
"allow_polling": false,
"workspace_prefix": "channels/my-channel/",
"emit_rate_limit": {
"messages_per_minute": 100,
"messages_per_hour": 5000
},
"webhook": {
"secret_header": "X-Webhook-Secret",
"secret_name": "my_channel_webhook_secret"
}
}
},
"config": {
"custom_option": "value"
}
}
```
## Building and Deploying
```bash
# Build the WASM component
cd channels/my-channel
cargo component build --release
# Deploy to ~/.near-agent/channels/
cp target/wasm32-wasip1/release/my_channel.wasm ~/.near-agent/channels/my-channel.wasm
cp my-channel.capabilities.json ~/.near-agent/channels/
```
## Host Functions Available
The channel host provides these functions:
```rust
// Logging
channel_host::log(LogLevel::Info, "Message");
// Time
let now = channel_host::now_millis();
// Workspace (scoped to channel namespace)
let data = channel_host::workspace_read("state/offset");
channel_host::workspace_write("state/offset", "12345")?;
// HTTP requests (credentials auto-injected)
let response = channel_host::http_request("POST", &url, &headers, Some(&body))?;
// Emit message to agent
channel_host::emit_message(&EmittedMessage { ... });
```
## Common Patterns
### Webhook Secret Validation
The host validates webhook secrets automatically. Check `req.secret_validated`:
```rust
fn on_http_request(req: IncomingHttpRequest) -> OutgoingHttpResponse {
if !req.secret_validated {
channel_host::log(LogLevel::Warn, "Invalid webhook secret");
// Host should have already rejected, but defense in depth
}
// ...
}
```
### Polling with Offset Tracking
For platforms that require polling (not webhook-based):
```rust
const OFFSET_PATH: &str = "state/last_offset";
fn on_poll() {
// Read last offset
let offset = channel_host::workspace_read(OFFSET_PATH)
.and_then(|s| s.parse::<i64>().ok())
.unwrap_or(0);
// Fetch updates since offset
let updates = fetch_updates(offset);
// Process and track new offset
let mut new_offset = offset;
for update in updates {
if update.id >= new_offset {
new_offset = update.id + 1;
}
emit_message(update);
}
// Save new offset
if new_offset != offset {
let _ = channel_host::workspace_write(OFFSET_PATH, &new_offset.to_string());
}
}
```
### Status Message Filtering
Skip status updates to prevent loops:
```rust
// Skip status updates (delivered, read, etc.)
if !payload.statuses.is_empty() && payload.messages.is_empty() {
return; // Only status updates, no actual messages
}
```
### Bot Message Filtering
Skip bot messages to prevent infinite loops:
```rust
if sender.is_bot {
return; // Don't respond to bots
}
```
## Testing
Add tests in the same file:
```rust
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_parse_webhook() {
let json = r#"{ ... }"#;
let payload: WebhookPayload = serde_json::from_str(json).unwrap();
assert_eq!(payload.messages.len(), 1);
}
#[test]
fn test_metadata_roundtrip() {
let meta = MyMessageMetadata { ... };
let json = serde_json::to_string(&meta).unwrap();
let parsed: MyMessageMetadata = serde_json::from_str(&json).unwrap();
assert_eq!(meta.chat_id, parsed.chat_id);
}
}
```
Run tests with:
```bash
cargo test
```
## Troubleshooting
### "byte index N is not a char boundary"
Never slice strings by byte index! Use character-aware truncation:
```rust
// BAD: panics on multi-byte UTF-8 (emoji, etc.)
let preview = &content[..50];
// GOOD: safe truncation
let preview: String = content.chars().take(50).collect();
```
### Credential placeholders not replaced
1. Check the secret name matches (lowercase with underscores)
2. Verify the secret is in `allowed_names` in capabilities
3. Check logs for "unresolved placeholders" warnings
### Messages not routing to responses
Ensure `on_respond` uses the ORIGINAL message's metadata, not response metadata:
```rust
// response.metadata_json comes from the ORIGINAL emit_message call
let metadata: MyMetadata = serde_json::from_str(&response.metadata_json)?;
```
+5 -2
View File
@@ -333,8 +333,11 @@ impl Agent {
// Format approval request for user
let params_preview = serde_json::to_string_pretty(&parameters)
.unwrap_or_else(|_| parameters.to_string());
let params_truncated = if params_preview.len() > 200 {
format!("{}...", &params_preview[..200])
let params_truncated = if params_preview.chars().count() > 200 {
format!(
"{}...",
params_preview.chars().take(200).collect::<String>()
)
} else {
params_preview
};
+52 -27
View File
@@ -93,19 +93,22 @@ impl ChannelStoreData {
}
}
/// Inject credentials into a URL by replacing placeholders.
/// Inject credentials into a string by replacing placeholders.
///
/// Replaces patterns like `{TELEGRAM_BOT_TOKEN}` with actual values from
/// the injected credentials map. This allows WASM channels to reference
/// credentials without ever seeing the actual values.
fn inject_credentials_into_url(&self, url: &str) -> String {
let mut result = url.to_string();
/// Replaces patterns like `{TELEGRAM_BOT_TOKEN}` or `{WHATSAPP_ACCESS_TOKEN}`
/// with actual values from the injected credentials map. This allows WASM
/// channels to reference credentials without ever seeing the actual values.
///
/// Works on URLs, headers, or any string with credential placeholders.
fn inject_credentials(&self, input: &str, context: &str) -> String {
let mut result = input.to_string();
tracing::debug!(
url = %url,
input_preview = %input.chars().take(100).collect::<String>(),
context = %context,
credential_count = self.credentials.len(),
credential_names = ?self.credentials.keys().collect::<Vec<_>>(),
"Injecting credentials into URL"
"Injecting credentials"
);
// Replace all known placeholders from the credentials map
@@ -114,6 +117,7 @@ impl ChannelStoreData {
if result.contains(&placeholder) {
tracing::debug!(
placeholder = %placeholder,
context = %context,
"Found and replacing credential placeholder"
);
result = result.replace(&placeholder, value);
@@ -122,12 +126,17 @@ impl ChannelStoreData {
// Check if any placeholders remain (indicates missing credential)
if result.contains('{') && result.contains('}') {
// Only warn if it looks like an unresolved placeholder (not JSON braces)
let brace_pattern = regex::Regex::new(r"\{[A-Z_]+\}").ok();
if let Some(re) = brace_pattern {
if re.is_match(&result) {
tracing::warn!(
original_url = %url,
result_url = %result,
"URL may contain unresolved placeholders"
context = %context,
"String may contain unresolved credential placeholders"
);
}
}
}
result
}
@@ -186,15 +195,11 @@ impl near::agent::channel_host::Host for ChannelStoreData {
);
// Inject credentials into URL (e.g., replace {TELEGRAM_BOT_TOKEN} with actual token)
let injected_url = self.inject_credentials_into_url(&url);
let injected_url = self.inject_credentials(&url, "url");
// Log whether injection happened (without revealing the token)
let url_changed = injected_url != url;
tracing::info!(
url_changed = url_changed,
has_bot_token = injected_url.contains("/bot") && !injected_url.contains("{"),
"URL after credential injection"
);
tracing::info!(url_changed = url_changed, "URL after credential injection");
// Check if HTTP is allowed for this URL
self.host_state
@@ -210,11 +215,29 @@ impl near::agent::channel_host::Host for ChannelStoreData {
format!("Rate limit exceeded: {}", e)
})?;
// Parse headers
let headers: std::collections::HashMap<String, String> =
// Parse headers and inject credentials into header values
// This allows patterns like "Authorization": "Bearer {WHATSAPP_ACCESS_TOKEN}"
let raw_headers: std::collections::HashMap<String, String> =
serde_json::from_str(&headers_json).unwrap_or_default();
tracing::debug!(header_count = headers.len(), "Parsed request headers");
let headers: std::collections::HashMap<String, String> = raw_headers
.into_iter()
.map(|(k, v)| {
(
k.clone(),
self.inject_credentials(&v, &format!("header:{}", k)),
)
})
.collect();
let headers_changed = headers
.values()
.any(|v| v.contains("Bearer ") && !v.contains('{'));
tracing::debug!(
header_count = headers.len(),
headers_changed = headers_changed,
"Parsed and injected request headers"
);
let url = injected_url;
@@ -273,10 +296,10 @@ impl near::agent::channel_host::Host for ChannelStoreData {
"HTTP response received"
);
// Log response body for debugging (truncated)
// Log response body for debugging (truncated at char boundary)
if let Ok(body_str) = std::str::from_utf8(&body) {
let truncated = if body_str.len() > 500 {
format!("{}...", &body_str[..500])
let truncated = if body_str.chars().count() > 500 {
format!("{}...", body_str.chars().take(500).collect::<String>())
} else {
body_str.to_string()
};
@@ -647,10 +670,10 @@ impl WasmChannel {
"call_on_http_request invoked (webhook received)"
);
// Log the body for debugging (if it looks like JSON)
// Log the body for debugging (truncated at char boundary)
if let Ok(body_str) = std::str::from_utf8(body) {
let truncated = if body_str.len() > 1000 {
format!("{}...", &body_str[..1000])
let truncated = if body_str.chars().count() > 1000 {
format!("{}...", body_str.chars().take(1000).collect::<String>())
} else {
body_str.to_string()
};
@@ -884,8 +907,10 @@ impl WasmChannel {
metadata_json,
};
// Truncate at char boundary for logging (avoid panic on multi-byte UTF-8)
let content_preview: String = content.chars().take(50).collect();
tracing::info!(
content_preview = %if content.len() > 50 { &content[..50] } else { &content },
content_preview = %content_preview,
"Calling WASM on_respond"
);
+3 -3
View File
@@ -403,12 +403,12 @@ fn truncate_output(s: &str) -> String {
}
}
/// Truncate command for error messages.
/// Truncate command for error messages (char-aware to avoid UTF-8 boundary panics).
fn truncate_for_error(s: &str) -> String {
if s.len() <= 100 {
if s.chars().count() <= 100 {
s.to_string()
} else {
format!("{}...", &s[..100])
format!("{}...", s.chars().take(100).collect::<String>())
}
}