Implement option_upfront_shutdown_script user-side

We use user config to decide to commit to closing script
in open_channel/accept_channel messages. We don't check
that other peer supporting the option as including
script without other peer public support is borne by
the protocol. If user opt-out, following protocol and
due to the fact we always signal, we provide a zero-length
script

diff --git a/src/ln/channel.rs b/src/ln/channel.rs
index bf5d357645ff21a90e9ed9c0565ac0ed239053d3..4d790cfc91e422433d1cc213f9dcc17292e62180 100644 (file)
--- a/src/ln/channel.rs
+++ b/src/ln/channel.rs
@@ -3081,7 +3081,7 @@ impl Channel {
                        htlc_basepoint: PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.htlc_base_key),
                        first_per_commitment_point: PublicKey::from_secret_key(&self.secp_ctx, &local_commitment_secret),
                        channel_flags: if self.config.announced_channel {1} else {0},
-                       shutdown_scriptpubkey: OptionalField::Absent
+                       shutdown_scriptpubkey: OptionalField::Present(if self.config.commit_upfront_shutdown_pubkey { self.get_closing_scriptpubkey() } else { Builder::new().into_script() })
                }
        }
 
@@ -3113,7 +3113,7 @@ impl Channel {
                        delayed_payment_basepoint: PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.delayed_payment_base_key),
                        htlc_basepoint: PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.htlc_base_key),
                        first_per_commitment_point: PublicKey::from_secret_key(&self.secp_ctx, &local_commitment_secret),
-                       shutdown_scriptpubkey: OptionalField::Absent
+                       shutdown_scriptpubkey: OptionalField::Present(if self.config.commit_upfront_shutdown_pubkey { self.get_closing_scriptpubkey() } else { Builder::new().into_script() })
                }
        }
 

diff --git a/src/util/config.rs b/src/util/config.rs
index f3b574b93fba6c40389761994cb92cddb1b3480a..e1a7e59727cc14d0f6cb9c1ca545b91ead628bae 100644 (file)
--- a/src/util/config.rs
+++ b/src/util/config.rs
@@ -129,6 +129,14 @@ pub struct ChannelConfig {
        ///
        /// This cannot be changed after the initial channel handshake.
        pub announced_channel: bool,
+       /// Set to commit to an upfront shutdown_pubkey at channel opening. In case of mutual
+       /// closing, the other peer will check that our closing transction output is encumbered
+       /// by the provided script.
+       ///
+       /// We set it by default as this ensure greater security to the user funds.
+       ///
+       /// This cannot be changed after channel opening.
+       pub commit_upfront_shutdown_pubkey: bool
 }
 
 impl ChannelConfig {
@@ -137,12 +145,14 @@ impl ChannelConfig {
                ChannelConfig {
                        fee_proportional_millionths: 0,
                        announced_channel: false,
+                       commit_upfront_shutdown_pubkey: true,
                }
        }
 }
 
 //Add write and readable traits to channelconfig
-impl_writeable!(ChannelConfig, 8+1, {
+impl_writeable!(ChannelConfig, 8+1+1, {
        fee_proportional_millionths,
-       announced_channel
+       announced_channel,
+       commit_upfront_shutdown_pubkey
 });