Adds DNS hostname to NetAddress

Supports Bolt 7 DNS hostnames specified by lightning/bolts#911.

Author: wvanlint

lightning/src/ln/channelmanager.rs

@@ -2859,15 +2859,15 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
 	#[allow(dead_code)]
 	// Messages of up to 64KB should never end up more than half full with addresses, as that would
-	// be absurd. We ensure this by checking that at least 500 (our stated public contract on when
+	// be absurd. We ensure this by checking that at least 100 (our stated public contract on when
 	// broadcast_node_announcement panics) of the maximum-length addresses would fit in a 64KB
 	// message...
 	const HALF_MESSAGE_IS_ADDRS: u32 = ::core::u16::MAX as u32 / (NetAddress::MAX_LEN as u32 + 1) / 2;
 	#[deny(const_err)]
 	#[allow(dead_code)]
 	// ...by failing to compile if the number of addresses that would be half of a message is
-	// smaller than 500:
-	const STATIC_ASSERT: u32 = Self::HALF_MESSAGE_IS_ADDRS - 500;
+	// smaller than 100:
+	const STATIC_ASSERT: u32 = Self::HALF_MESSAGE_IS_ADDRS - 100;
 
 	/// Regenerates channel_announcements and generates a signed node_announcement from the given
 	/// arguments, providing them in corresponding events via
@@ -2884,13 +2884,13 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 	/// tying these addresses together and to this node. If you wish to preserve user privacy,
 	/// addresses should likely contain only Tor Onion addresses.
 	///
-	/// Panics if `addresses` is absurdly large (more than 500).
+	/// Panics if `addresses` is absurdly large (more than 100).
 	///
 	/// [`get_and_clear_pending_msg_events`]: MessageSendEventsProvider::get_and_clear_pending_msg_events
 	pub fn broadcast_node_announcement(&self, rgb: [u8; 3], alias: [u8; 32], mut addresses: Vec<NetAddress>) {
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(&self.total_consistency_lock, &self.persistence_notifier);
 
-		if addresses.len() > 500 {
+		if addresses.len() > 100 {
 			panic!("More than half the message size was taken up by public addresses!");
 		}
 

lightning/src/ln/msgs.rs

@@ -40,7 +40,7 @@ use io_extras::read_to_end;
 
 use util::events::MessageSendEventsProvider;
 use util::logger;
-use util::ser::{Readable, Writeable, Writer, FixedLengthReader, HighZeroBytesDroppedVarInt};
+use util::ser::{Readable, Writeable, Writer, FixedLengthReader, HighZeroBytesDroppedVarInt, ShortAsciiString};
 
 use ln::{PaymentPreimage, PaymentHash, PaymentSecret};
 
@@ -442,6 +442,14 @@ pub enum NetAddress {
 		/// The port on which the node is listening
 		port: u16,
 	},
+	/// A DNS hostname/port on which the peer is listening.
+	DNSHostname {
+		/// The hostname as an ASCII string with a variable length below or equal to 255.
+		/// Can be a Punycode encoding.
+		hostname: ShortAsciiString,
+		/// The port on which the node is listening.
+		port: u16,
+	},
 }
 impl NetAddress {
 	/// Gets the ID of this address type. Addresses in node_announcement messages should be sorted
@@ -452,6 +460,7 @@ impl NetAddress {
 			&NetAddress::IPv6 {..} => { 2 },
 			&NetAddress::OnionV2(_) => { 3 },
 			&NetAddress::OnionV3 {..} => { 4 },
+			&NetAddress::DNSHostname {..} => { 5 },
 		}
 	}
 
@@ -462,11 +471,12 @@ impl NetAddress {
 			&NetAddress::IPv6 { .. } => { 18 },
 			&NetAddress::OnionV2(_) => { 12 },
 			&NetAddress::OnionV3 { .. } => { 37 },
+			&NetAddress::DNSHostname { ref hostname, .. } => { u16::from(hostname.len()) + 3 },
 		}
 	}
 
 	/// The maximum length of any address descriptor, not including the 1-byte type
-	pub(crate) const MAX_LEN: u16 = 37;
+	pub(crate) const MAX_LEN: u16 = u8::MAX as u16 + 3;
 }
 
 impl Writeable for NetAddress {
@@ -492,7 +502,12 @@ impl Writeable for NetAddress {
 				checksum.write(writer)?;
 				version.write(writer)?;
 				port.write(writer)?;
-			}
+			},
+			&NetAddress::DNSHostname { ref hostname, ref port } => {
+				5u8.write(writer)?;
+				hostname.write(writer)?;
+				port.write(writer)?;
+			},
 		}
 		Ok(())
 	}
@@ -523,6 +538,12 @@ impl Readable for Result<NetAddress, u8> {
 					port: Readable::read(reader)?,
 				}))
 			},
+			5 => {
+				Ok(Ok(NetAddress::DNSHostname {
+					hostname: Readable::read(reader)?,
+					port: Readable::read(reader)?,
+				}))
+			},
 			_ => return Ok(Err(byte)),
 		}
 	}
@@ -1829,7 +1850,7 @@ mod tests {
 	use ln::features::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, NodeFeatures};
 	use ln::msgs;
 	use ln::msgs::{FinalOnionHopData, OptionalField, OnionErrorPacket, OnionHopDataFormat};
-	use util::ser::{Writeable, Readable};
+	use util::ser::{Writeable, Readable, ShortAsciiString};
 
 	use bitcoin::hashes::hex::FromHex;
 	use bitcoin::util::address::Address;
@@ -1843,6 +1864,7 @@ mod tests {
 
 	use io::Cursor;
 	use prelude::*;
+	use std::convert::TryFrom;
 
 	#[test]
 	fn encoding_channel_reestablish_no_secret() {
@@ -1971,7 +1993,7 @@ mod tests {
 		do_encoding_channel_announcement(true, true);
 	}
 
-	fn do_encoding_node_announcement(unknown_features_bits: bool, ipv4: bool, ipv6: bool, onionv2: bool, onionv3: bool, excess_address_data: bool, excess_data: bool) {
+	fn do_encoding_node_announcement(unknown_features_bits: bool, ipv4: bool, ipv6: bool, onionv2: bool, onionv3: bool, dns_hostname: bool, excess_address_data: bool, excess_data: bool) {
 		let secp_ctx = Secp256k1::new();
 		let (privkey_1, pubkey_1) = get_keys_from!("0101010101010101010101010101010101010101010101010101010101010101", secp_ctx);
 		let sig_1 = get_sig_on!(privkey_1, secp_ctx, String::from("01010101010101010101010101010101"));
@@ -2007,6 +2029,12 @@ mod tests {
 				port: 9735
 			});
 		}
+		if dns_hostname {
+			addresses.push(msgs::NetAddress::DNSHostname {
+				hostname: ShortAsciiString::try_from("host").unwrap(),
+				port: 9735,
+			});
+		}
 		let mut addr_len = 0;
 		for addr in &addresses {
 			addr_len += addr.len() + 1;
@@ -2047,6 +2075,9 @@ mod tests {
 		if onionv3 {
 			target_value.append(&mut hex::decode("04fffefdfcfbfaf9f8f7f6f5f4f3f2f1f0efeeedecebeae9e8e7e6e5e4e3e2e1e00020102607").unwrap());
 		}
+		if dns_hostname {
+			target_value.append(&mut hex::decode("0504686f73742607").unwrap());
+		}
 		if excess_address_data {
 			target_value.append(&mut hex::decode("216c280b5395a2546e7e4b2663e04f811622f15a4f92e83aa2e92ba2a573c139142c54ae63072a1ec1ee7dc0c04bde5c847806172aa05c92c22ae8e308d1d269").unwrap());
 		}
@@ -2058,15 +2089,16 @@ mod tests {
 
 	#[test]
 	fn encoding_node_announcement() {
-		do_encoding_node_announcement(true, true, true, true, true, true, true);
-		do_encoding_node_announcement(false, false, false, false, false, false, false);
-		do_encoding_node_announcement(false, true, false, false, false, false, false);
-		do_encoding_node_announcement(false, false, true, false, false, false, false);
-		do_encoding_node_announcement(false, false, false, true, false, false, false);
-		do_encoding_node_announcement(false, false, false, false, true, false, false);
-		do_encoding_node_announcement(false, false, false, false, false, true, false);
-		do_encoding_node_announcement(false, true, false, true, false, true, false);
-		do_encoding_node_announcement(false, false, true, false, true, false, false);
+		do_encoding_node_announcement(true, true, true, true, true, true, true, true);
+		do_encoding_node_announcement(false, false, false, false, false, false, false, false);
+		do_encoding_node_announcement(false, true, false, false, false, false, false, false);
+		do_encoding_node_announcement(false, false, true, false, false, false, false, false);
+		do_encoding_node_announcement(false, false, false, true, false, false, false, false);
+		do_encoding_node_announcement(false, false, false, false, true, false, false, false);
+		do_encoding_node_announcement(false, false, false, false, false, true, false, false);
+		do_encoding_node_announcement(false, false, false, false, false, false, true, false);
+		do_encoding_node_announcement(false, true, false, true, false, false, true, false);
+		do_encoding_node_announcement(false, false, true, false, true, false, false, false);
 	}
 
 	fn do_encoding_channel_update(direction: bool, disable: bool, htlc_maximum_msat: bool, excess_data: bool) {

lightning/src/util/errors.rs

@@ -78,6 +78,10 @@ impl fmt::Debug for APIError {
 	}
 }
 
+/// Indicates an error on conversions by core::convert traits.
+#[derive(Debug)]
+pub struct ConversionError;
+
 #[inline]
 pub(crate) fn get_onion_debug_field(error_code: u16) -> (&'static str, usize) {
 	match error_code & 0xff {

lightning/src/util/ser.rs

@@ -16,6 +16,8 @@ use io_extras::{copy, sink};
 use core::hash::Hash;
 use sync::Mutex;
 use core::cmp;
+use core::convert::TryFrom;
+use core::ops::Deref;
 
 use bitcoin::secp256k1::{PublicKey, SecretKey};
 use bitcoin::secp256k1::constants::{PUBLIC_KEY_SIZE, SECRET_KEY_SIZE, COMPACT_SIGNATURE_SIZE};
@@ -32,6 +34,7 @@ use ln::msgs::DecodeError;
 use ln::{PaymentPreimage, PaymentHash, PaymentSecret};
 
 use util::byte_utils::{be48_to_array, slice_to_be48};
+use util::errors::ConversionError;
 
 /// serialization buffer size
 pub const MAX_BUF_SIZE: usize = 64 * 1024;
@@ -913,6 +916,67 @@ impl Readable for String {
 	}
 }
 
+/// Wraps a string with additional validation for serialization purposes.
+/// The string is guaranteed to contain only ASCII characters and its length
+/// is guaranteed to be representable by a single byte.
+/// This serialization is used for example by Bolt 7 DNS hostnames.
+#[derive(Clone, Debug, PartialEq)]
+pub struct ShortAsciiString(String);
+impl ShortAsciiString {
+	/// Returns the length of the string with an appropriate return type for the validated length.
+	pub fn len(&self) -> u8 {
+		(&self.0).len() as u8
+	}
+}
+impl Deref for ShortAsciiString {
+	type Target = String;
+
+	fn deref(&self) -> &Self::Target {
+		&self.0
+	}
+}
+impl From<ShortAsciiString> for String {
+	fn from(short_s: ShortAsciiString) -> Self {
+		short_s.0
+	}
+}
+impl TryFrom<String> for ShortAsciiString {
+	type Error = ConversionError;
+
+	fn try_from(s: String) -> Result<Self, Self::Error> {
+		if s.is_ascii() && s.len() <= u8::MAX.into() {
+			Ok(ShortAsciiString(s))
+		} else {
+			Err(ConversionError)
+		}
+	}
+}
+impl TryFrom<&str> for ShortAsciiString {
+	type Error = ConversionError;
+
+	fn try_from(s: &str) -> Result<Self, Self::Error> {
+		ShortAsciiString::try_from(String::from(s))
+	}
+}
+impl Writeable for ShortAsciiString {
+	#[inline]
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		self.len().write(w)?;
+		w.write_all(self.as_bytes())
+	}
+}
+impl Readable for ShortAsciiString {
+	#[inline]
+	fn read<R: Read>(r: &mut R) -> Result<ShortAsciiString, DecodeError> {
+		let len: u8 = Readable::read(r)?;
+		let mut vec = Vec::with_capacity(len as usize);
+		vec.resize(len as usize, 0);
+		r.read_exact(&mut vec)?;
+		let s = String::from_utf8(vec).map_err(|_| DecodeError::InvalidValue)?;
+		ShortAsciiString::try_from(s).map_err(|_| DecodeError::InvalidValue)
+	}
+}
+
 impl Writeable for Duration {
 	#[inline]
 	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
@@ -928,3 +992,35 @@ impl Readable for Duration {
 		Ok(Duration::new(secs, nanos))
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use core::convert::TryFrom;
+	use std::io::Cursor;
+	use util::ser::{Readable, ShortAsciiString, Writeable};
+
+	#[test]
+	fn short_ascii_string_conversion() {
+		let short_s = ShortAsciiString::try_from("test").unwrap();
+		assert_eq!(short_s.as_str(), "test");
+
+		ShortAsciiString::try_from("⚡").expect_err(
+			"Expected non-ASCII string to fail conversion"
+		);
+
+		let mut large_vec = Vec::with_capacity(u8::MAX as usize + 1);
+		large_vec.resize(u8::MAX as usize + 1, u8::try_from('A').unwrap());
+		ShortAsciiString::try_from(String::from_utf8(large_vec).unwrap()).expect_err(
+			"Expected string with exceeding length to fail conversion"
+		);
+	}
+
+	#[test]
+	fn short_ascii_string_serialization() {
+		let short_s = ShortAsciiString::try_from("test").unwrap();
+		let mut buf = Cursor::new(Vec::new());
+		short_s.write(&mut buf).unwrap();
+		buf.set_position(0);
+		assert_eq!(ShortAsciiString::read(&mut buf).unwrap().as_str(), "test");
+	}
+}