Offer parsing from bech32 strings

[rust-lightning] / lightning / src / offers / parse.rs

diff --git a/lightning/src/offers/parse.rs b/lightning/src/offers/parse.rs
new file mode 100644 (file)
index 0000000..c9d568a
--- /dev/null
+++ b/lightning/src/offers/parse.rs
@@ -0,0 +1,125 @@
+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! Parsing and formatting for bech32 message encoding.
+
+use bitcoin::bech32;
+use bitcoin::bech32::{FromBase32, ToBase32};
+use core::convert::TryFrom;
+use core::fmt;
+use crate::ln::msgs::DecodeError;
+
+use crate::prelude::*;
+
+/// Indicates a message can be encoded using bech32.
+pub(crate) trait Bech32Encode: AsRef<[u8]> + TryFrom<Vec<u8>, Error=ParseError> {
+       /// Human readable part of the message's bech32 encoding.
+       const BECH32_HRP: &'static str;
+
+       /// Parses a bech32-encoded message into a TLV stream.
+       fn from_bech32_str(s: &str) -> Result<Self, ParseError> {
+               // Offer encoding may be split by '+' followed by optional whitespace.
+               let encoded = match s.split('+').skip(1).next() {
+                       Some(_) => {
+                               for chunk in s.split('+') {
+                                       let chunk = chunk.trim_start();
+                                       if chunk.is_empty() || chunk.contains(char::is_whitespace) {
+                                               return Err(ParseError::InvalidContinuation);
+                                       }
+                               }
+
+                               let s = s.chars().filter(|c| *c != '+' && !c.is_whitespace()).collect::<String>();
+                               Bech32String::Owned(s)
+                       },
+                       None => Bech32String::Borrowed(s),
+               };
+
+               let (hrp, data) = bech32::decode_without_checksum(encoded.as_ref())?;
+
+               if hrp != Self::BECH32_HRP {
+                       return Err(ParseError::InvalidBech32Hrp);
+               }
+
+               let data = Vec::<u8>::from_base32(&data)?;
+               Self::try_from(data)
+       }
+
+       /// Formats the message using bech32-encoding.
+       fn fmt_bech32_str(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+               bech32::encode_without_checksum_to_fmt(f, Self::BECH32_HRP, self.as_ref().to_base32())
+                       .expect("HRP is invalid").unwrap();
+
+               Ok(())
+       }
+}
+
+// Used to avoid copying a bech32 string not containing the continuation character (+).
+enum Bech32String<'a> {
+       Borrowed(&'a str),
+       Owned(String),
+}
+
+impl<'a> AsRef<str> for Bech32String<'a> {
+       fn as_ref(&self) -> &str {
+               match self {
+                       Bech32String::Borrowed(s) => s,
+                       Bech32String::Owned(s) => s,
+               }
+       }
+}
+
+/// Error when parsing a bech32 encoded message using [`str::parse`].
+#[derive(Debug, PartialEq)]
+pub enum ParseError {
+       /// The bech32 encoding does not conform to the BOLT 12 requirements for continuing messages
+       /// across multiple parts (i.e., '+' followed by whitespace).
+       InvalidContinuation,
+       /// The bech32 encoding's human-readable part does not match what was expected for the message
+       /// being parsed.
+       InvalidBech32Hrp,
+       /// The string could not be bech32 decoded.
+       Bech32(bech32::Error),
+       /// The bech32 decoded string could not be decoded as the expected message type.
+       Decode(DecodeError),
+       /// The parsed message has invalid semantics.
+       InvalidSemantics(SemanticError),
+}
+
+/// Error when interpreting a TLV stream as a specific type.
+#[derive(Debug, PartialEq)]
+pub enum SemanticError {
+       /// An amount was expected but was missing.
+       MissingAmount,
+       /// The amount exceeded the total bitcoin supply.
+       InvalidAmount,
+       /// A required description was not provided.
+       MissingDescription,
+       /// A signing pubkey was not provided.
+       MissingSigningPubkey,
+       /// An unsupported quantity was provided.
+       InvalidQuantity,
+}
+
+impl From<bech32::Error> for ParseError {
+       fn from(error: bech32::Error) -> Self {
+               Self::Bech32(error)
+       }
+}
+
+impl From<DecodeError> for ParseError {
+       fn from(error: DecodeError) -> Self {
+               Self::Decode(error)
+       }
+}
+
+impl From<SemanticError> for ParseError {
+       fn from(error: SemanticError) -> Self {
+               Self::InvalidSemantics(error)
+       }
+}