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Separate hpke and ohttp v2 modules
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@DanGould
DanGould committed Oct 15, 2024
1 parent 2cec51f commit b307fa2
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Showing 8 changed files with 299 additions and 299 deletions.
254 changes: 1 addition & 253 deletions payjoin/src/v2.rs → payjoin/src/hpke.rs
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Original file line number Diff line number Diff line change
@@ -1,8 +1,6 @@
use std::ops::{Deref, DerefMut};
use std::ops::Deref;
use std::{error, fmt};

use bitcoin::base64::prelude::BASE64_URL_SAFE_NO_PAD;
use bitcoin::base64::Engine;
use bitcoin::key::constants::UNCOMPRESSED_PUBLIC_KEY_SIZE;
use hpke::aead::ChaCha20Poly1305;
use hpke::kdf::HkdfSha256;
Expand Down Expand Up @@ -272,253 +270,3 @@ impl error::Error for HpkeError {
}
}
}

pub fn ohttp_encapsulate(
ohttp_keys: &mut ohttp::KeyConfig,
method: &str,
target_resource: &str,
body: Option<&[u8]>,
) -> Result<(Vec<u8>, ohttp::ClientResponse), OhttpEncapsulationError> {
use std::fmt::Write;

let ctx = ohttp::ClientRequest::from_config(ohttp_keys)?;
let url = url::Url::parse(target_resource)?;
let authority_bytes = url.host().map_or_else(Vec::new, |host| {
let mut authority = host.to_string();
if let Some(port) = url.port() {
write!(authority, ":{}", port).unwrap();
}
authority.into_bytes()
});
let mut bhttp_message = bhttp::Message::request(
method.as_bytes().to_vec(),
url.scheme().as_bytes().to_vec(),
authority_bytes,
url.path().as_bytes().to_vec(),
);
// None of our messages include headers, so we don't add them
if let Some(body) = body {
bhttp_message.write_content(body);
}
let mut bhttp_req = Vec::new();
let _ = bhttp_message.write_bhttp(bhttp::Mode::KnownLength, &mut bhttp_req);
let encapsulated = ctx.encapsulate(&bhttp_req)?;
Ok(encapsulated)
}

/// decapsulate ohttp, bhttp response and return http response body and status code
pub fn ohttp_decapsulate(
res_ctx: ohttp::ClientResponse,
ohttp_body: &[u8],
) -> Result<http::Response<Vec<u8>>, OhttpEncapsulationError> {
let bhttp_body = res_ctx.decapsulate(ohttp_body)?;
let mut r = std::io::Cursor::new(bhttp_body);
let m: bhttp::Message = bhttp::Message::read_bhttp(&mut r)?;
let mut builder = http::Response::builder();
for field in m.header().iter() {
builder = builder.header(field.name(), field.value());
}
builder
.status(m.control().status().unwrap_or(http::StatusCode::INTERNAL_SERVER_ERROR.into()))
.body(m.content().to_vec())
.map_err(OhttpEncapsulationError::Http)
}

/// Error from de/encapsulating an Oblivious HTTP request or response.
#[derive(Debug)]
pub enum OhttpEncapsulationError {
Http(http::Error),
Ohttp(ohttp::Error),
Bhttp(bhttp::Error),
ParseUrl(url::ParseError),
}

impl From<http::Error> for OhttpEncapsulationError {
fn from(value: http::Error) -> Self { Self::Http(value) }
}

impl From<ohttp::Error> for OhttpEncapsulationError {
fn from(value: ohttp::Error) -> Self { Self::Ohttp(value) }
}

impl From<bhttp::Error> for OhttpEncapsulationError {
fn from(value: bhttp::Error) -> Self { Self::Bhttp(value) }
}

impl From<url::ParseError> for OhttpEncapsulationError {
fn from(value: url::ParseError) -> Self { Self::ParseUrl(value) }
}

impl fmt::Display for OhttpEncapsulationError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
use OhttpEncapsulationError::*;

match &self {
Http(e) => e.fmt(f),
Ohttp(e) => e.fmt(f),
Bhttp(e) => e.fmt(f),
ParseUrl(e) => e.fmt(f),
}
}
}

impl error::Error for OhttpEncapsulationError {
fn source(&self) -> Option<&(dyn error::Error + 'static)> {
use OhttpEncapsulationError::*;

match &self {
Http(e) => Some(e),
Ohttp(e) => Some(e),
Bhttp(e) => Some(e),
ParseUrl(e) => Some(e),
}
}
}

#[derive(Debug, Clone)]
pub struct OhttpKeys(pub ohttp::KeyConfig);

impl OhttpKeys {
/// Decode an OHTTP KeyConfig
pub fn decode(bytes: &[u8]) -> Result<Self, ohttp::Error> {
ohttp::KeyConfig::decode(bytes).map(Self)
}
}

const KEM_ID: &[u8] = b"\x00\x16"; // DHKEM(secp256k1, HKDF-SHA256)
const SYMMETRIC_LEN: &[u8] = b"\x00\x04"; // 4 bytes
const SYMMETRIC_KDF_AEAD: &[u8] = b"\x00\x01\x00\x03"; // KDF(HKDF-SHA256), AEAD(ChaCha20Poly1305)

impl fmt::Display for OhttpKeys {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let bytes = self.encode().map_err(|_| fmt::Error)?;
let key_id = bytes[0];
let pubkey = &bytes[3..68];

let compressed_pubkey =
bitcoin::secp256k1::PublicKey::from_slice(pubkey).map_err(|_| fmt::Error)?.serialize();

let mut buf = vec![key_id];
buf.extend_from_slice(&compressed_pubkey);

let encoded = BASE64_URL_SAFE_NO_PAD.encode(buf);
write!(f, "{}", encoded)
}
}

impl std::str::FromStr for OhttpKeys {
type Err = ParseOhttpKeysError;

/// Parses a base64URL-encoded string into OhttpKeys.
/// The string format is: key_id || compressed_public_key
fn from_str(s: &str) -> Result<Self, Self::Err> {
let bytes = BASE64_URL_SAFE_NO_PAD.decode(s).map_err(ParseOhttpKeysError::DecodeBase64)?;

let key_id = *bytes.first().ok_or(ParseOhttpKeysError::InvalidFormat)?;
let compressed_pk = bytes.get(1..34).ok_or(ParseOhttpKeysError::InvalidFormat)?;

let pubkey = bitcoin::secp256k1::PublicKey::from_slice(compressed_pk)
.map_err(|_| ParseOhttpKeysError::InvalidPublicKey)?;

let mut buf = vec![key_id];
buf.extend_from_slice(KEM_ID);
buf.extend_from_slice(&pubkey.serialize_uncompressed());
buf.extend_from_slice(SYMMETRIC_LEN);
buf.extend_from_slice(SYMMETRIC_KDF_AEAD);

ohttp::KeyConfig::decode(&buf).map(Self).map_err(ParseOhttpKeysError::DecodeKeyConfig)
}
}

impl PartialEq for OhttpKeys {
fn eq(&self, other: &Self) -> bool {
match (self.encode(), other.encode()) {
(Ok(self_encoded), Ok(other_encoded)) => self_encoded == other_encoded,
// If OhttpKeys::encode(&self) is Err, return false
_ => false,
}
}
}

impl Eq for OhttpKeys {}

impl Deref for OhttpKeys {
type Target = ohttp::KeyConfig;

fn deref(&self) -> &Self::Target { &self.0 }
}

impl DerefMut for OhttpKeys {
fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 }
}

impl<'de> serde::Deserialize<'de> for OhttpKeys {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: serde::Deserializer<'de>,
{
let bytes = Vec::<u8>::deserialize(deserializer)?;
OhttpKeys::decode(&bytes).map_err(serde::de::Error::custom)
}
}

impl serde::Serialize for OhttpKeys {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: serde::Serializer,
{
let bytes = self.encode().map_err(serde::ser::Error::custom)?;
bytes.serialize(serializer)
}
}

#[derive(Debug)]
pub enum ParseOhttpKeysError {
InvalidFormat,
InvalidPublicKey,
DecodeBase64(bitcoin::base64::DecodeError),
DecodeKeyConfig(ohttp::Error),
}

impl std::fmt::Display for ParseOhttpKeysError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
ParseOhttpKeysError::InvalidFormat => write!(f, "Invalid format"),
ParseOhttpKeysError::InvalidPublicKey => write!(f, "Invalid public key"),
ParseOhttpKeysError::DecodeBase64(e) => write!(f, "Failed to decode base64: {}", e),
ParseOhttpKeysError::DecodeKeyConfig(e) =>
write!(f, "Failed to decode KeyConfig: {}", e),
}
}
}

impl std::error::Error for ParseOhttpKeysError {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
match self {
ParseOhttpKeysError::DecodeBase64(e) => Some(e),
ParseOhttpKeysError::DecodeKeyConfig(e) => Some(e),
ParseOhttpKeysError::InvalidFormat | ParseOhttpKeysError::InvalidPublicKey => None,
}
}
}

#[cfg(test)]
mod test {
use super::*;

#[test]
fn test_ohttp_keys_roundtrip() {
use std::str::FromStr;

use ohttp::hpke::{Aead, Kdf, Kem};
use ohttp::{KeyId, SymmetricSuite};
const KEY_ID: KeyId = 1;
const KEM: Kem = Kem::K256Sha256;
const SYMMETRIC: &[SymmetricSuite] =
&[ohttp::SymmetricSuite::new(Kdf::HkdfSha256, Aead::ChaCha20Poly1305)];
let keys = OhttpKeys(ohttp::KeyConfig::new(KEY_ID, KEM, Vec::from(SYMMETRIC)).unwrap());
let serialized = &keys.to_string();
let deserialized = OhttpKeys::from_str(serialized).unwrap();
assert_eq!(keys.encode().unwrap(), deserialized.encode().unwrap());
}
}
6 changes: 4 additions & 2 deletions payjoin/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,9 +28,11 @@ pub use crate::receive::Error;
pub mod send;

#[cfg(feature = "v2")]
pub(crate) mod v2;
pub(crate) mod hpke;
#[cfg(feature = "v2")]
pub use v2::OhttpKeys;
pub(crate) mod ohttp;
#[cfg(feature = "v2")]
pub use ohttp::OhttpKeys;

#[cfg(feature = "io")]
pub mod io;
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