Receive payjoin

Author: DanGould

mutiny-core/Cargo.toml

@@ -41,6 +41,7 @@ aes = { version = "0.8" }
 jwt-compact = { version = "0.8.0-beta.1", features = ["es256k"] }
 argon2 = { version = "0.5.0", features = ["password-hash", "alloc"] }
 hashbrown = { version = "0.8" }
+payjoin = { git = "https://github.com/DanGould/rust-payjoin.git", branch = "serverless-payjoin", features = ["v2", "send", "receive", "base64"] }
 
 base64 = "0.13.0"
 pbkdf2 = "0.11"

mutiny-core/src/nodemanager.rs

@@ -162,6 +162,7 @@ pub struct MutinyBip21RawMaterials {
     pub invoice: Option<Bolt11Invoice>,
     pub btc_amount: Option<String>,
     pub labels: Vec<String>,
+    pub pj: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize, Clone, Eq, PartialEq)]
@@ -1009,7 +1010,7 @@ impl<S: MutinyStorage> NodeManager<S> {
         Err(MutinyError::WalletOperationFailed)
     }
 
-    /// Creates a BIP 21 invoice. This creates a new address and a lightning invoice.
+    /// Creates a BIP 21 invoice. This creates a new address, a lightning invoice, and payjoin session.
     /// The lightning invoice may return errors related to the LSP. Check the error and
     /// fallback to `get_new_address` and warn the user that Lightning is not available.
     ///
@@ -1052,14 +1053,126 @@ impl<S: MutinyStorage> NodeManager<S> {
             return Err(MutinyError::WalletOperationFailed);
         };
 
+        // If we are in safe mode, we don't create payjoin sessions
+        let pj = {
+            // TODO get from &self config
+            const PJ_RELAY_URL: &str = "http://localhost:8080";
+            const OH_RELAY_URL: &str = "http://localhost:8080";
+            const OHTTP_CONFIG_BASE64: &str = "AQAg7YjKSn1zBziW3LvPCQ8X18hH0dU67G-vOcMHu0-m81AABAABAAM";
+            let mut enroller = payjoin::receive::Enroller::from_relay_config(
+                PJ_RELAY_URL,
+                OHTTP_CONFIG_BASE64,
+                OH_RELAY_URL,
+                //Some("c53989e590b0f02edeec42a9c43fd1e4e960aec243bb1e6064324bd2c08ec498")
+            );
+            let http_client = reqwest::Client::builder()
+                //.danger_accept_invalid_certs(true) ? is tls unchecked :O
+                .build()
+                .unwrap();
+            // enroll client
+            let (req, context) = enroller.extract_req().unwrap();
+            let ohttp_response = http_client
+                .post(req.url)
+                .body(req.body)
+                .send()
+                .await
+                .unwrap();
+            let ohttp_response = ohttp_response.bytes().await.unwrap();
+            let enrolled = enroller
+                .process_res(ohttp_response.as_ref(), context)
+                .map_err(|e| anyhow!("parse error {}", e))
+                .unwrap();
+            let pj_uri = enrolled.fallback_target();
+            log_debug!(self.logger, "{pj_uri}");
+            let wallet = self.wallet.clone();
+            // run await payjoin task in the background as it'll keep polling the relay
+            wasm_bindgen_futures::spawn_local(async move {
+                let wallet = wallet.clone();
+                let pj_txid = Self::receive_payjoin(wallet, enrolled).await.unwrap();
+                log::info!("Received payjoin txid: {}", pj_txid);
+            });
+            Some(pj_uri)
+        };
+
         Ok(MutinyBip21RawMaterials {
             address,
             invoice,
             btc_amount: amount.map(|amount| bitcoin::Amount::from_sat(amount).to_btc().to_string()),
             labels,
+            pj,
         })
     }
 
+    /// Poll the payjoin relay to maintain a payjoin session and create a payjoin proposal.
+    pub async fn receive_payjoin(
+        wallet: Arc<OnChainWallet<S>>,
+        mut enrolled: payjoin::receive::Enrolled,
+    ) -> Result<Txid, MutinyError> {
+        let http_client = reqwest::Client::builder()
+            //.danger_accept_invalid_certs(true) ? is tls unchecked :O
+            .build()
+            .unwrap();
+        let proposal: payjoin::receive::UncheckedProposal =
+            Self::poll_for_fallback_psbt(&http_client, &mut enrolled)
+                .await
+                .unwrap();
+        let payjoin_proposal = wallet.process_payjoin_proposal(proposal).unwrap();
+
+        let (req, ohttp_ctx) = payjoin_proposal
+            .extract_v2_req()
+            .unwrap(); // extraction failed
+        let res = http_client
+            .post(req.url)
+            .body(req.body)
+            .send()
+            .await
+            .unwrap();
+        let res = res.bytes().await.unwrap();
+        // enroll must succeed
+        let _res = payjoin_proposal
+            .deserialize_res(res.to_vec(), ohttp_ctx)
+            .unwrap();
+        // convert from bitcoin 29 to 30
+        let txid = payjoin_proposal.psbt().clone().extract_tx().txid();
+        let txid = Txid::from_str(&txid.to_string()).unwrap();
+        Ok(txid)
+    }
+
+    async fn poll_for_fallback_psbt(
+        client: &reqwest::Client,
+        enroller: &mut payjoin::receive::Enrolled,
+    ) -> Result<payjoin::receive::UncheckedProposal, ()> {
+        loop {
+            let (req, context) = enroller.extract_req().unwrap();
+            let ohttp_response = client
+                .post(req.url)
+                .body(req.body)
+                .send()
+                .await
+                .unwrap();
+            let ohttp_response = ohttp_response.bytes().await.unwrap();
+            let proposal = enroller
+                .process_res(ohttp_response.as_ref(), context)
+                .map_err(|e| anyhow!("parse error {}", e))
+                .unwrap();
+            match proposal {
+                Some(proposal) => return Ok(proposal),
+                None => Self::delay(5000).await.unwrap(),
+            }
+        }
+    }
+
+    async fn delay(millis: u32) -> Result<(), wasm_bindgen::JsValue> {
+        let promise = js_sys::Promise::new(&mut |yes, _| {
+            let win = web_sys::window().expect("should have a Window");
+            win.set_timeout_with_callback_and_timeout_and_arguments_0(&yes, millis as i32)
+                .expect("should set a timeout");
+        });
+
+        wasm_bindgen_futures::JsFuture::from(promise).await?;
+        Ok(())
+    }
+
     /// Sends an on-chain transaction to the given address.
     /// The amount is in satoshis and the fee rate is in sat/vbyte.
     ///

mutiny-core/src/onchain.rs

@@ -1,4 +1,5 @@
 use anyhow::anyhow;
+use esplora_client::FromHex;
 use std::collections::{BTreeMap, HashSet};
 use std::str::FromStr;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -285,10 +286,122 @@ impl<S: MutinyStorage> OnChainWallet<S> {
         Ok(())
     }
 
+    fn is_mine(&self, script: &Script) -> Result<bool, MutinyError> {
+        Ok(self.wallet.try_read()?.is_mine(script))
+    }
+
     pub fn list_utxos(&self) -> Result<Vec<LocalUtxo>, MutinyError> {
         Ok(self.wallet.try_read()?.list_unspent().collect())
     }
 
+    pub fn process_payjoin_proposal(
+        &self,
+        proposal: payjoin::receive::UncheckedProposal,
+    ) -> Result<payjoin::receive::PayjoinProposal, payjoin::Error> {
+        use payjoin::Error;
+
+        // Receive Check 1 bypass: We're not an automated payment processor.
+        let proposal = proposal.assume_interactive_receiver();
+        log::trace!("check1");
+
+        // Receive Check 2: receiver can't sign for proposal inputs
+        let proposal = proposal.check_inputs_not_owned(|input| {
+            // convert from payjoin::bitcoin 30 to 29
+            let input = bitcoin::Script::from_hex(&input.to_hex()).unwrap();
+            self.is_mine(&input).map_err(|e| Error::Server(e.into()))
+        })?;
+        log::trace!("check2");
+
+        // Receive Check 3: receiver can't sign for proposal inputs
+        let proposal = proposal.check_no_mixed_input_scripts()?;
+        log::trace!("check3");
+
+        // Receive Check 4: have we seen this input before?
+        let payjoin = proposal.check_no_inputs_seen_before(|_input| {
+            // This check ensures an automated sender does not get phished. It is not necessary for interactive payjoin **where the sender cannot generate bip21s from us**
+            // assume false since Mutiny is not an automatic payment processor
+            Ok(false)
+        })?;
+        log::trace!("check4");
+
+        let mut provisional_payjoin =
+            payjoin.identify_receiver_outputs(|output: &payjoin::bitcoin::Script| {
+                // convert from payjoin::bitcoin 30 to 29
+                let output = bitcoin::Script::from_hex(&output.to_hex()).unwrap();
+                self.is_mine(&output).map_err(|e| Error::Server(e.into()))
+            })?;
+        self.try_contributing_inputs(&mut provisional_payjoin)
+            .expect("input contribution failed");
+
+        // Outputs may be substituted for e.g. batching at this stage
+        // We're not doing this yet.
+
+        let payjoin_proposal = provisional_payjoin.finalize_proposal(
+            |psbt: &payjoin::bitcoin::psbt::Psbt| {
+                // convert from payjoin::bitcoin 30.0
+                let mut psbt = PartiallySignedTransaction::from_str(&psbt.to_string()).unwrap();
+                let wallet = self
+                    .wallet
+                    .try_read()
+                    .map_err(|_| Error::Server(MutinyError::WalletSigningFailed.into()))?;
+                wallet
+                    .sign(&mut psbt, SignOptions::default())
+                    .map_err(|_| Error::Server(MutinyError::WalletSigningFailed.into()))?;
+                // convert back to payjoin::bitcoin
+                let psbt = payjoin::bitcoin::psbt::Psbt::from_str(&psbt.to_string()).unwrap();
+                Ok(psbt)
+            },
+            // TODO: check Mutiny's minfeerate is present here
+            Some(payjoin::bitcoin::FeeRate::MIN),
+        )?;
+        let payjoin_proposal_psbt = payjoin_proposal.psbt();
+        log::debug!(
+            "Receiver's Payjoin proposal PSBT Rsponse: {:#?}",
+            payjoin_proposal_psbt
+        );
+        Ok(payjoin_proposal)
+    }
+
+    fn try_contributing_inputs(
+        &self,
+        payjoin: &mut payjoin::receive::ProvisionalProposal,
+    ) -> Result<(), MutinyError> {
+        use payjoin::bitcoin::{Amount, OutPoint};
+
+        let available_inputs = self
+            .list_utxos()
+            .expect("Failed to list unspent from bitcoind");
+        let candidate_inputs: std::collections::HashMap<Amount, OutPoint> = available_inputs
+            .iter()
+            .map(|i| {
+                (
+                    Amount::from_sat(i.txout.value),
+                    OutPoint::from_str(&i.outpoint.to_string()).unwrap(),
+                )
+            })
+            .collect();
+
+        let selected_outpoint = payjoin
+            .try_preserving_privacy(candidate_inputs)
+            .expect("no privacy-preserving selection available");
+        let selected_utxo = available_inputs
+            .iter()
+            .find(|i| OutPoint::from_str(&i.outpoint.to_string()).unwrap() == selected_outpoint)
+            .expect("This shouldn't happen. Failed to retrieve the privacy preserving utxo from those we provided to the seclector.");
+        log::debug!("selected utxo: {:#?}", selected_utxo);
+
+        // calculate receiver payjoin outputs given receiver payjoin inputs and original_psbt,
+        let txo_to_contribute = payjoin::bitcoin::TxOut {
+            value: selected_utxo.txout.value,
+            script_pubkey: payjoin::bitcoin::Script::from_bytes(
+                &selected_utxo.txout.script_pubkey.clone().into_bytes(),
+            )
+            .into(),
+        };
+        payjoin.contribute_witness_input(txo_to_contribute, selected_outpoint);
+        Ok(())
+    }
+
     pub fn list_transactions(
         &self,
         include_raw: bool,

mutiny-wasm/src/lib.rs

@@ -268,6 +268,7 @@ impl MutinyWallet {
             invoice: None,
             btc_amount: None,
             labels,
+            pj: None,
         })
     }
 

mutiny-wasm/src/models.rs

@@ -461,6 +461,7 @@ pub struct MutinyBip21RawMaterials {
     pub(crate) invoice: Option<String>,
     pub(crate) btc_amount: Option<String>,
     pub(crate) labels: Vec<String>,
+    pub(crate) pj: Option<String>,
 }
 
 #[wasm_bindgen]
@@ -489,6 +490,11 @@ impl MutinyBip21RawMaterials {
     pub fn labels(&self) -> JsValue /* Vec<String> */ {
         JsValue::from_serde(&self.labels).unwrap()
     }
+
+    #[wasm_bindgen(getter)]
+    pub fn pj(&self) -> Option<String> {
+        self.pj.clone()
+    }
 }
 
 impl From<nodemanager::MutinyBip21RawMaterials> for MutinyBip21RawMaterials {
@@ -498,6 +504,7 @@ impl From<nodemanager::MutinyBip21RawMaterials> for MutinyBip21RawMaterials {
             invoice: m.invoice.map(|i| i.to_string()),
             btc_amount: m.btc_amount,
             labels: m.labels,
+            pj: m.pj,
         }
     }
 }