Protect metadata with Oblivious HTTP

Author: DanGould

Cargo.lock

@@ -52,30 +52,50 @@ impl App {
             .danger_accept_invalid_certs(self.config.danger_accept_invalid_certs)
             .build()
             .with_context(|| "Failed to build reqwest http client")?;
-        let _ = client
-            .post(req.url.as_str())
-            .body(req.body)
-            .header("Content-Type", "text/plain")
-            .send()
-            .await
-            .with_context(|| "HTTP request failed")?;
+        let ohttp_config =
+            payjoin::bitcoin::base64::decode_config(&self.config.ohttp_config, base64::URL_SAFE)
+                .unwrap();
+        let (ohttp_req, _) =
+            payjoin::v2::ohttp_encapsulate(ohttp_config, "POST", req.url.as_str(), Some(&req.body));
+        dbg!(&ohttp_req);
+        let _ = client.post(&self.config.ohttp_proxy).body(ohttp_req).send().await?;
 
         log::debug!("Awaiting response");
-        let res = Self::long_poll(&client, req.url.as_str()).await?;
+        let res = self.long_poll(&client, req.url.as_str()).await?;
         let mut res = std::io::Cursor::new(&res);
         self.process_pj_response(ctx, &mut res)?;
         Ok(())
     }
 
     #[cfg(feature = "v2")]
-    async fn long_poll(client: &reqwest::Client, url: &str) -> Result<Vec<u8>, reqwest::Error> {
+    async fn long_poll(
+        &self,
+        client: &reqwest::Client,
+        url: &str,
+    ) -> Result<Vec<u8>, reqwest::Error> {
         loop {
-            let response = client.get(url).send().await?;
-
-            if response.status().is_success() {
-                let body = response.bytes().await?;
+            let req = client.get(url).build()?;
+            let ohttp_config = payjoin::bitcoin::base64::decode_config(
+                &self.config.ohttp_config,
+                payjoin::bitcoin::base64::URL_SAFE,
+            )
+            .unwrap();
+            let body = req.body().and_then(|b| b.as_bytes());
+            let (ohttp_req, ctx) = payjoin::v2::ohttp_encapsulate(
+                ohttp_config,
+                req.method().as_str(),
+                req.url().as_str(),
+                body,
+            );
+
+            let ohttp_response =
+                client.post(&self.config.ohttp_proxy).body(ohttp_req).send().await?;
+            log::debug!("Response: {:?}", ohttp_response);
+            if ohttp_response.status().is_success() {
+                let body = ohttp_response.bytes().await?;
                 if !body.is_empty() {
-                    return Ok(body.to_vec());
+                    let res_body = payjoin::v2::ohttp_decapsulate(ctx, &body);
+                    return Ok(res_body);
                 } else {
                     log::info!("No response yet for payjoin request, retrying in 5 seconds");
                 }
@@ -215,7 +235,7 @@ impl App {
             .with_context(|| "Failed to build reqwest http client")?;
         log::debug!("Awaiting request");
         let receive_endpoint = format!("{}/{}", self.config.pj_endpoint, context.receive_subdir());
-        let mut buffer = Self::long_poll(&client, &receive_endpoint).await?;
+        let mut buffer = self.long_poll(&client, &receive_endpoint).await?;
 
         log::debug!("Received request");
         let proposal = context
@@ -226,9 +246,14 @@ impl App {
             .map_err(|e| anyhow!("Failed to process UncheckedProposal {}", e))?;
 
         let body = payjoin_proposal.serialize_body();
+        let ohttp_config =
+            payjoin::bitcoin::base64::decode_config(&self.config.ohttp_config, base64::URL_SAFE)
+                .unwrap();
+        let (req, _) =
+            payjoin::v2::ohttp_encapsulate(ohttp_config, "POST", &receive_endpoint, Some(&body));
         let _ = client
-            .post(receive_endpoint)
-            .body(body)
+            .post(&self.config.ohttp_proxy)
+            .body(req)
             .send()
             .await
             .with_context(|| "HTTP request failed")?;
@@ -268,14 +293,15 @@ impl App {
         let amount = Amount::from_sat(amount_arg.parse()?);
         //let subdir = self.config.pj_endpoint + pubkey.map_or(&String::from(""), |s| &format!("/{}", s));
         let pj_uri_string = format!(
-            "{}?amount={}&pj={}",
+            "{}?amount={}&pj={}&ohttp={}",
             pj_receiver_address.to_qr_uri(),
             amount.to_btc(),
             format!(
                 "{}{}",
                 self.config.pj_endpoint,
                 pubkey.map_or(String::from(""), |s| format!("/{}", s))
-            )
+            ),
+            self.config.ohttp_config,
         );
 
         // check validity
@@ -459,6 +485,19 @@ impl App {
     }
 }
 
+fn serialize_request_to_bytes(req: reqwest::Request) -> Vec<u8> {
+    let mut serialized_request =
+        format!("{} {} HTTP/1.1\r\n", req.method(), req.url()).into_bytes();
+
+    for (name, value) in req.headers().iter() {
+        let header_line = format!("{}: {}\r\n", name.as_str(), value.to_str().unwrap());
+        serialized_request.extend(header_line.as_bytes());
+    }
+
+    serialized_request.extend(b"\r\n");
+    serialized_request
+}
+
 struct SeenInputs {
     set: OutPointSet,
     file: std::fs::File,
@@ -498,6 +537,8 @@ pub(crate) struct AppConfig {
     pub bitcoind_cookie: Option<String>,
     pub bitcoind_rpcuser: String,
     pub bitcoind_rpcpass: String,
+    pub ohttp_config: String,
+    pub ohttp_proxy: String,
 
     // send-only
     pub danger_accept_invalid_certs: bool,
@@ -531,6 +572,16 @@ impl AppConfig {
                 "bitcoind_rpcpass",
                 matches.get_one::<String>("rpcpass").map(|s| s.as_str()),
             )?
+            .set_default("ohttp_config", "")?
+            .set_override_option(
+                "ohttp_config",
+                matches.get_one::<String>("ohttp_config").map(|s| s.as_str()),
+            )?
+            .set_default("ohttp_proxy", "")?
+            .set_override_option(
+                "ohttp_proxy",
+                matches.get_one::<String>("ohttp_proxy").map(|s| s.as_str()),
+            )?
             // Subcommand defaults without which file serialization fails.
             .set_default("danger_accept_invalid_certs", false)?
             .set_default("pj_host", "0.0.0.0:3000")?

payjoin-cli/src/app.rs

@@ -73,6 +73,12 @@ fn cli() -> ArgMatches {
             .long("rpcpass")
             .help("The password for the bitcoin node"))
         .subcommand_required(true)
+        .arg(Arg::new("ohttp_config")
+            .long("ohttp-config")
+            .help("The ohttp config file"))
+        .arg(Arg::new("ohttp_proxy")
+            .long("ohttp-proxy")
+            .help("The ohttp proxy url"))
         .subcommand(
             Command::new("send")
                 .arg_required_else_help(true)

payjoin-cli/src/main.rs

@@ -8,8 +8,15 @@ edition = "2021"
 [dependencies]
 axum = "0.6.2"
 anyhow = "1.0.71"
+hyper = "0.14.27"
+http = "0.2.4"
+# ohttp = "0.4.0"
+httparse = "1.8.0"
+ohttp = { path = "../../ohttp/ohttp" }
+bhttp = { version = "0.4.0", features = ["http"] }
 payjoin = { path = "../payjoin", features = ["v2"] }
 sqlx = { version = "0.7.1", features = ["postgres", "runtime-tokio"] }
 tokio = { version = "1.12.0", features = ["full"] }
+tower-service = "0.3.2"
 tracing = "0.1.37"
 tracing-subscriber = { version = "0.3.17", features = ["env-filter"] }

payjoin-relay/Cargo.toml

@@ -1,10 +1,10 @@
 use std::sync::Arc;
 use std::time::Duration;
 
-use anyhow::Result;
+use anyhow::{Context, Result};
 use axum::body::Bytes;
 use axum::extract::Path;
-use axum::http::StatusCode;
+use axum::http::{Request, StatusCode};
 use axum::routing::{get, post};
 use axum::Router;
 use payjoin::v2::{MAX_BUFFER_SIZE, RECEIVE};
@@ -21,8 +21,9 @@ use crate::db::DbPool;
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
     init_logging();
     let pool = DbPool::new(std::time::Duration::from_secs(30)).await?;
-
-    let app = Router::new()
+    let ohttp = Arc::new(init_ohttp()?);
+    let ohttp_config = ohttp_config(&*ohttp)?;
+    let target_resource = Router::new()
         .route(
             "/:id",
             post({
@@ -46,8 +47,13 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             }),
         );
 
+    let ohttp_gateway = Router::new()
+        .route("/", post(move |body| handle_ohttp(body, target_resource, ohttp)))
+        .route("/ohttp-keys", get({ move || get_ohttp_config(ohttp_config) }));
+
     println!("Serverless payjoin relay awaiting HTTP connection on port 8080");
-    axum::Server::bind(&"0.0.0.0:8080".parse()?).serve(app.into_make_service()).await?;
+    axum::Server::bind(&"0.0.0.0:8080".parse()?).serve(ohttp_gateway.into_make_service()).await?;
+    //hyper::Server::bind(&"0.0.0.0:8080").serve()
     Ok(())
 }
 
@@ -60,6 +66,79 @@ fn init_logging() {
     println!("Logging initialized");
 }
 
+fn init_ohttp() -> Result<ohttp::Server> {
+    use ohttp::hpke::{Aead, Kdf, Kem};
+    use ohttp::{KeyId, SymmetricSuite};
+
+    const KEY_ID: KeyId = 1;
+    const KEM: Kem = Kem::X25519Sha256;
+    const SYMMETRIC: &[SymmetricSuite] =
+        &[SymmetricSuite::new(Kdf::HkdfSha256, Aead::ChaCha20Poly1305)];
+
+    // create or read from file
+    let server_config = ohttp::KeyConfig::new(KEY_ID, KEM, Vec::from(SYMMETRIC)).unwrap();
+    let encoded_config = server_config.encode().unwrap();
+    let b64_config = payjoin::bitcoin::base64::encode_config(
+        &encoded_config,
+        payjoin::bitcoin::base64::Config::new(
+            payjoin::bitcoin::base64::CharacterSet::UrlSafe,
+            false,
+        ),
+    );
+    info!("ohttp server config base64 UrlSafe: {:?}", b64_config);
+    ohttp::Server::new(server_config).with_context(|| "Failed to initialize ohttp server")
+}
+
+async fn handle_ohttp(
+    enc_request: Bytes,
+    mut target: Router,
+    ohttp: Arc<ohttp::Server>,
+) -> (StatusCode, Vec<u8>) {
+    use axum::body::Body;
+    use http::Uri;
+    use tower_service::Service;
+
+    // decapsulate
+    let (bhttp_req, res_ctx) = ohttp.decapsulate(&enc_request).unwrap();
+    let mut cursor = std::io::Cursor::new(bhttp_req);
+    let req = bhttp::Message::read_bhttp(&mut cursor).unwrap();
+    // let parsed_request: httparse::Request = httparse::Request::new(&mut vec![]).parse(cursor).unwrap();
+    // // handle request
+    // Request::new
+    let uri = Uri::builder()
+        .scheme(req.control().scheme().unwrap())
+        .authority(req.control().authority().unwrap())
+        .path_and_query(req.control().path().unwrap())
+        .build()
+        .unwrap();
+    let body = req.content().to_vec();
+    let mut request = Request::builder().uri(uri).method(req.control().method().unwrap());
+    for header in req.header().fields() {
+        request = request.header(header.name(), header.value())
+    }
+    let request = request.body(Body::from(body)).unwrap();
+
+    let response = target.call(request).await.unwrap();
+
+    let (parts, body) = response.into_parts();
+    let mut bhttp_res = bhttp::Message::response(parts.status.as_u16());
+    let full_body = hyper::body::to_bytes(body).await.unwrap();
+    bhttp_res.write_content(&full_body);
+    let mut bhttp_bytes = Vec::new();
+    bhttp_res.write_bhttp(bhttp::Mode::KnownLength, &mut bhttp_bytes).unwrap();
+    let ohttp_res = res_ctx.encapsulate(&bhttp_bytes).unwrap();
+    (StatusCode::OK, ohttp_res)
+}
+
+fn ohttp_config(server: &ohttp::Server) -> Result<String> {
+    use payjoin::bitcoin::base64;
+
+    let b64_config = base64::Config::new(base64::CharacterSet::UrlSafe, false);
+    let encoded_config =
+        server.config().encode().with_context(|| "Failed to encode ohttp config")?;
+    Ok(base64::encode_config(&encoded_config, b64_config))
+}
+
 async fn post_fallback(Path(id): Path<String>, body: Bytes, pool: DbPool) -> (StatusCode, String) {
     let id = shorten_string(&id);
     let body = body.to_vec();
@@ -73,6 +152,8 @@ async fn post_fallback(Path(id): Path<String>, body: Bytes, pool: DbPool) -> (St
     }
 }
 
+async fn get_ohttp_config(config: String) -> (StatusCode, String) { (StatusCode::OK, config) }
+
 async fn get_request(Path(id): Path<String>, pool: DbPool) -> (StatusCode, Vec<u8>) {
     let id = shorten_string(&id);
     match pool.peek_req(&id).await {

payjoin-relay/src/main.rs

@@ -16,13 +16,16 @@ edition = "2018"
 send = []
 receive = ["rand"]
 base64 = ["bitcoin/base64"]
-v2 = ["bitcoin/rand-std", "chacha20poly1305", "serde", "serde_json"]
+v2 = ["bitcoin/rand-std", "chacha20poly1305", "ohttp", "bhttp", "serde", "serde_json"]
 
 [dependencies]
 bitcoin = { version = "0.30.0", features = ["base64"] }
 bip21 = "0.3.1"
 chacha20poly1305 = { version = "0.10.1", optional = true }
 log = { version = "0.4.14"}
+#ohttp = { version = "0.4.0", optional = true }
+bhttp = { path = "../../ohttp/bhttp", optional = true }
+ohttp = { path = "../../ohttp/ohttp", optional = true }
 rand = { version = "0.8.4", optional = true }
 serde = { version = "1.0", optional = true }
 serde_json = { version = "1.0", optional = true }