Require user cooperative close payout scripts to be Segwit

There is little reason for users to be paying out to non-Segwit
scripts when closing channels at this point. Given we will soon, in
rare cases, force-close during shutdown when a counterparty closes
to a non-Segwit script, we should also require it of our own users.

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index f02818b264300974b0dc9dcebb5f229b05558945..57da708baf503ce473807c164bb2a5c21af38206 100644 (file)
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -26,7 +26,7 @@ use ln::{PaymentPreimage, PaymentHash};
 use ln::features::{ChannelFeatures, InitFeatures};
 use ln::msgs;
 use ln::msgs::{DecodeError, OptionalField, DataLossProtect};
-use ln::script::ShutdownScript;
+use ln::script::{self, ShutdownScript};
 use ln::channelmanager::{CounterpartyForwardingInfo, PendingHTLCStatus, HTLCSource, HTLCFailReason, HTLCFailureMsg, PendingHTLCInfo, RAACommitmentOrder, BREAKDOWN_TIMEOUT, MIN_CLTV_EXPIRY_DELTA, MAX_LOCAL_BREAKDOWN_TIMEOUT};
 use ln::chan_utils::{CounterpartyCommitmentSecrets, TxCreationKeys, HTLCOutputInCommitment, HTLC_SUCCESS_TX_WEIGHT, HTLC_TIMEOUT_TX_WEIGHT, make_funding_redeemscript, ChannelPublicKeys, CommitmentTransaction, HolderCommitmentTransaction, ChannelTransactionParameters, CounterpartyChannelTransactionParameters, MAX_HTLCS, get_commitment_transaction_number_obscure_factor, ClosingTransaction};
 use ln::chan_utils;
@@ -44,7 +44,6 @@ use util::scid_utils::scid_from_parts;
 use io;
 use prelude::*;
 use core::{cmp,mem,fmt};
-use core::convert::TryFrom;
 use core::ops::Deref;
 #[cfg(any(test, feature = "fuzztarget", debug_assertions))]
 use sync::Mutex;
@@ -896,10 +895,10 @@ impl<Signer: Sign> Channel<Signer> {
                                        if script.len() == 0 {
                                                None
                                        } else {
-                                               match ShutdownScript::try_from((script.clone(), their_features)) {
-                                                       Ok(shutdown_script) => Some(shutdown_script.into_inner()),
-                                                       Err(_) => return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script))),
+                                               if !script::is_bolt2_compliant(&script, their_features) {
+                                                       return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script)))
                                                }
+                                               Some(script.clone())
                                        }
                                },
                                // Peer is signaling upfront shutdown but don't opt-out with correct mechanism (a.k.a 0-length script). Peer looks buggy, we fail the channel
@@ -1641,10 +1640,10 @@ impl<Signer: Sign> Channel<Signer> {
                                        if script.len() == 0 {
                                                None
                                        } else {
-                                               match ShutdownScript::try_from((script.clone(), their_features)) {
-                                                       Ok(shutdown_script) => Some(shutdown_script.into_inner()),
-                                                       Err(_) => return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script))),
+                                               if !script::is_bolt2_compliant(&script, their_features) {
+                                                       return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script)));
                                                }
+                                               Some(script.clone())
                                        }
                                },
                                // Peer is signaling upfront shutdown but don't opt-out with correct mechanism (a.k.a 0-length script). Peer looks buggy, we fail the channel
@@ -3494,17 +3493,16 @@ impl<Signer: Sign> Channel<Signer> {
                }
                assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
 
-               let shutdown_scriptpubkey = match ShutdownScript::try_from((msg.scriptpubkey.clone(), their_features)) {
-                       Ok(script) => script.into_inner(),
-                       Err(_) => return Err(ChannelError::Close(format!("Got a nonstandard scriptpubkey ({}) from remote peer", msg.scriptpubkey.to_bytes().to_hex()))),
-               };
+               if !script::is_bolt2_compliant(&msg.scriptpubkey, their_features) {
+                       return Err(ChannelError::Close(format!("Got a nonstandard scriptpubkey ({}) from remote peer", msg.scriptpubkey.to_bytes().to_hex())));
+               }
 
                if self.counterparty_shutdown_scriptpubkey.is_some() {
-                       if Some(&shutdown_scriptpubkey) != self.counterparty_shutdown_scriptpubkey.as_ref() {
-                               return Err(ChannelError::Close(format!("Got shutdown request with a scriptpubkey ({}) which did not match their previous scriptpubkey.", shutdown_scriptpubkey.to_bytes().to_hex())));
+                       if Some(&msg.scriptpubkey) != self.counterparty_shutdown_scriptpubkey.as_ref() {
+                               return Err(ChannelError::Close(format!("Got shutdown request with a scriptpubkey ({}) which did not match their previous scriptpubkey.", msg.scriptpubkey.to_bytes().to_hex())));
                        }
                } else {
-                       self.counterparty_shutdown_scriptpubkey = Some(shutdown_scriptpubkey);
+                       self.counterparty_shutdown_scriptpubkey = Some(msg.scriptpubkey.clone());
                }
 
                // If we have any LocalAnnounced updates we'll probably just get back an update_fail_htlc

diff --git a/lightning/src/ln/script.rs b/lightning/src/ln/script.rs
index 4e81d76ad670d18b2c8b172d4acd94ea62c64607..00ad48bb1e31c07cf695f52282ea2b746cf05455 100644 (file)
--- a/lightning/src/ln/script.rs
+++ b/lightning/src/ln/script.rs
@@ -3,7 +3,7 @@
 use bitcoin::blockdata::opcodes::all::OP_PUSHBYTES_0 as SEGWIT_V0;
 use bitcoin::blockdata::script::{Builder, Script};
 use bitcoin::hashes::Hash;
-use bitcoin::hash_types::{PubkeyHash, ScriptHash, WPubkeyHash, WScriptHash};
+use bitcoin::hash_types::{WPubkeyHash, WScriptHash};
 use bitcoin::secp256k1::key::PublicKey;
 
 use ln::features::InitFeatures;
@@ -66,16 +66,6 @@ impl ShutdownScript {
                Self(ShutdownScriptImpl::Legacy(pubkey))
        }
 
-       /// Generates a P2PKH script pubkey from the given [`PubkeyHash`].
-       pub fn new_p2pkh(pubkey_hash: &PubkeyHash) -> Self {
-               Self(ShutdownScriptImpl::Bolt2(Script::new_p2pkh(pubkey_hash)))
-       }
-
-       /// Generates a P2SH script pubkey from the given [`ScriptHash`].
-       pub fn new_p2sh(script_hash: &ScriptHash) -> Self {
-               Self(ShutdownScriptImpl::Bolt2(Script::new_p2sh(script_hash)))
-       }
-
        /// Generates a P2WPKH script pubkey from the given [`WPubkeyHash`].
        pub fn new_p2wpkh(pubkey_hash: &WPubkeyHash) -> Self {
                Self(ShutdownScriptImpl::Bolt2(Script::new_v0_wpkh(pubkey_hash)))
@@ -126,7 +116,9 @@ impl ShutdownScript {
        }
 }
 
-fn is_bolt2_compliant(script: &Script, features: &InitFeatures) -> bool {
+/// Check if a given script is compliant with BOLT 2's shutdown script requirements for the given
+/// counterparty features.
+pub(crate) fn is_bolt2_compliant(script: &Script, features: &InitFeatures) -> bool {
        if script.is_p2pkh() || script.is_p2sh() || script.is_v0_p2wpkh() || script.is_v0_p2wsh() {
                true
        } else if features.supports_shutdown_anysegwit() {
@@ -136,6 +128,8 @@ fn is_bolt2_compliant(script: &Script, features: &InitFeatures) -> bool {
        }
 }
 
+// Note that this is only for our own shutdown scripts. Counterparties are still allowed to send us
+// non-witness shutdown scripts which this rejects.
 impl TryFrom<Script> for ShutdownScript {
        type Error = InvalidShutdownScript;
 
@@ -144,11 +138,13 @@ impl TryFrom<Script> for ShutdownScript {
        }
 }
 
+// Note that this is only for our own shutdown scripts. Counterparties are still allowed to send us
+// non-witness shutdown scripts which this rejects.
 impl TryFrom<(Script, &InitFeatures)> for ShutdownScript {
        type Error = InvalidShutdownScript;
 
        fn try_from((script, features): (Script, &InitFeatures)) -> Result<Self, Self::Error> {
-               if is_bolt2_compliant(&script, features) {
+               if is_bolt2_compliant(&script, features) && script.is_witness_program() {
                        Ok(Self(ShutdownScriptImpl::Bolt2(script)))
                } else {
                        Err(InvalidShutdownScript { script })
@@ -216,30 +212,6 @@ mod shutdown_script_tests {
                assert_eq!(shutdown_script.into_inner(), p2wpkh_script);
        }
 
-       #[test]
-       fn generates_p2pkh_from_pubkey_hash() {
-               let pubkey_hash = pubkey().pubkey_hash();
-               let p2pkh_script = Script::new_p2pkh(&pubkey_hash);
-
-               let shutdown_script = ShutdownScript::new_p2pkh(&pubkey_hash);
-               assert!(shutdown_script.is_compatible(&InitFeatures::known()));
-               assert!(shutdown_script.is_compatible(&InitFeatures::known().clear_shutdown_anysegwit()));
-               assert_eq!(shutdown_script.into_inner(), p2pkh_script);
-               assert!(ShutdownScript::try_from(p2pkh_script).is_ok());
-       }
-
-       #[test]
-       fn generates_p2sh_from_script_hash() {
-               let script_hash = redeem_script().script_hash();
-               let p2sh_script = Script::new_p2sh(&script_hash);
-
-               let shutdown_script = ShutdownScript::new_p2sh(&script_hash);
-               assert!(shutdown_script.is_compatible(&InitFeatures::known()));
-               assert!(shutdown_script.is_compatible(&InitFeatures::known().clear_shutdown_anysegwit()));
-               assert_eq!(shutdown_script.into_inner(), p2sh_script);
-               assert!(ShutdownScript::try_from(p2sh_script).is_ok());
-       }
-
        #[test]
        fn generates_p2wpkh_from_pubkey_hash() {
                let pubkey_hash = pubkey().wpubkey_hash().unwrap();