feat: port payjoin core to no_std

.github/workflows/rust.yml

@@ -145,3 +145,18 @@ jobs:
         uses: Swatinem/rust-cache@v2
       - name: "Build fuzz targets"
         run: cd fuzz && cargo build
+
+  Embedded:
+    name: Embedded build
+    runs-on: ubuntu-latest
+    steps:
+      - name: "Checkout repo"
+        uses: actions/checkout@v4
+      - name: "Use cache"
+        uses: Swatinem/rust-cache@v2
+      - name: "Install nix"
+        uses: DeterminateSystems/determinate-nix-action@main
+      - name: "Use nix cache"
+        uses: DeterminateSystems/magic-nix-cache-action@main
+      - name: "Build embedded target"
+        run: nix develop .#embedded -c cargo build -p payjoin --no-default-features --features "alloc,v2" --target thumbv7em-none-eabihf -Zbuild-std=core,alloc

flake.nix

@@ -340,6 +340,24 @@
           AR_wasm32_unknown_unknown = "${pkgs.llvmPackages.bintools-unwrapped}/bin/llvm-ar";
         };
 
+        embeddedRustToolchain = (pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml).override {
+          extensions = [
+            "rust-src"
+            "rustfmt"
+            "llvm-tools-preview"
+          ];
+          targets = [ "thumbv7em-none-eabihf" ];
+        };
+
+        embeddedDevShell = pkgs.mkShell {
+          name = "embedded-dev";
+          packages = with pkgs; [
+            embeddedRustToolchain
+            gcc-arm-embedded
+          ];
+          CC_thumbv7em_none_eabihf = "arm-none-eabi-gcc";
+        };
+
         dartDevShell = pkgs.mkShell {
           name = "dart-dev";
           packages =
@@ -461,6 +479,7 @@
           javascript = javascriptDevShell;
           csharp = csharpDevShell;
           dart = dartDevShell;
+          embedded = embeddedDevShell;
         };
         formatter = treefmtEval.config.build.wrapper;
         checks =

payjoin/Cargo.toml

@@ -19,28 +19,36 @@ exclude = ["tests"]
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [features]
-default = ["v2"]
-#[doc = "Core features for payjoin state machines"]
-_core = [
+default = ["std", "v2", "v2-ohttp"]
+
+alloc = []
+
+std = [
+  "alloc",
+  "bitcoin/rand",
   "bitcoin/rand-std",
-  "dep:http",
+  "bitcoin/base64",
   "serde_json",
   "dep:percent-encoding-rfc3986",
   "bitcoin_uri",
-  "serde",
-  "bitcoin/serde",
 ]
-directory = []
-v1 = ["_core"]
-v2 = ["_core", "hpke", "hkdf", "bhttp", "ohttp", "directory"]
+#[doc = "Core features for payjoin state machines"]
+_core = ["alloc", "serde", "bitcoin/serde"]
+
+directory = ["alloc", "_core"]
+v1 = ["_core", "std"]
+
+v2 = ["_core", "directory", "hkdf"]
+
+v2-ohttp = ["v2", "std", "dep:hpke", "dep:bhttp", "dep:ohttp", "dep:http"]
 #[doc = "Functions to fetch OHTTP keys via CONNECT proxy using reqwest. Enables `v2` since only `v2` uses OHTTP."]
-io = ["v2", "reqwest/rustls-tls"]
-_manual-tls = ["rustls"]
+io = ["v2-ohttp", "reqwest/rustls-tls", "dep:reqwest"]
+_manual-tls = ["reqwest/rustls-tls", "rustls"]
 
 [dependencies]
 bhttp = { version = "0.6.1", optional = true }
-bitcoin = { version = "0.32.9", features = ["base64"] }
-bitcoin-units = "0.1.3"
+bitcoin = { version = "0.32.9", default-features = false }
+bitcoin-units = { version = "0.1.3", default-features = false }
 bitcoin_uri = { version = "0.1.0", optional = true }
 hkdf = { version = "0.12.3", optional = true }
 hpke = { package = "bitcoin-hpke", version = "0.13.0", optional = true }
@@ -53,7 +61,9 @@ rustls = { version = "0.23.38", optional = true, default-features = false, featu
 ] }
 serde = { version = "1.0.228", default-features = false, optional = true }
 serde_json = { version = "1.0.149", optional = true }
-tracing = "0.1.41"
+tracing = { version = "0.1.41", default-features = false, features = [
+  "attributes",
+] }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 web-time = "1.1.0"
@@ -66,7 +76,10 @@ ignored = ["bitcoin-units", "hkdf"]
 once_cell = "1.21.3"
 payjoin-test-utils = { path = "../payjoin-test-utils", features = ["v2"] }
 tokio = { version = "1.52.3", features = ["full"] }
-tracing = "0.1.41"
+tracing = { version = "0.1.41", default-features = false, features = [
+  "attributes",
+] }
+
 
 [package.metadata.docs.rs]
 all-features = true

payjoin/src/bech32.rs

@@ -1,3 +1,8 @@
+#[cfg(feature = "alloc")]
+use alloc::string::String;
+#[cfg(not(feature = "std"))]
+use alloc::vec::Vec;
+
 use bitcoin::bech32::primitives::decode::{CheckedHrpstring, CheckedHrpstringError};
 use bitcoin::bech32::{self, EncodeError, Hrp, NoChecksum};
 

payjoin/src/core/error.rs

@@ -1,6 +1,29 @@
-use std::fmt::Debug;
-use std::{error, fmt};
+#[cfg(not(feature = "std"))]
+use alloc::boxed::Box;
+#[cfg(not(feature = "std"))]
+use core::error;
+use core::fmt::{self, Debug};
+#[cfg(feature = "std")]
+use std::error;
 
+#[derive(Debug)]
+pub struct StdRequiredError;
+
+impl fmt::Display for StdRequiredError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "std is required for this operation")
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for StdRequiredError {}
+
+#[cfg(not(feature = "std"))]
+impl core::error::Error for StdRequiredError {}
+
+impl ImplementationError {
+    pub fn std_required() -> Self { ImplementationError(Box::new(StdRequiredError)) }
+}
 #[derive(Debug)]
 pub struct ImplementationError(Box<dyn error::Error + Send + Sync>);
 
@@ -11,7 +34,7 @@ impl ImplementationError {
 }
 
 impl fmt::Display for ImplementationError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { std::fmt::Display::fmt(&self.0, f) }
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::Display::fmt(&self.0, f) }
 }
 
 impl error::Error for ImplementationError {
@@ -34,16 +57,17 @@ impl From<&str> for ImplementationError {
         ImplementationError::from(error)
     }
 }
+
 /// Errors that can occur when replaying a session event log
 #[cfg(feature = "v2")]
 #[derive(Debug)]
 pub struct ReplayError<SessionState, SessionEvent>(InternalReplayError<SessionState, SessionEvent>);
 
 #[cfg(feature = "v2")]
-impl<SessionState: Debug, SessionEvent: Debug> std::fmt::Display
+impl<SessionState: Debug, SessionEvent: Debug> fmt::Display
     for ReplayError<SessionState, SessionEvent>
 {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use InternalReplayError::*;
         match &self.0 {
             NoEvents => write!(f, "No events found in session"),
@@ -56,8 +80,9 @@ impl<SessionState: Debug, SessionEvent: Debug> std::fmt::Display
         }
     }
 }
+
 #[cfg(feature = "v2")]
-impl<SessionState: Debug, SessionEvent: Debug> std::error::Error
+impl<SessionState: Debug, SessionEvent: Debug> error::Error
     for ReplayError<SessionState, SessionEvent>
 {
 }
@@ -78,6 +103,7 @@ impl<SessionState, SessionEvent> ReplayError<SessionState, SessionEvent> {
 
 #[cfg(feature = "v2")]
 #[derive(Debug)]
+#[allow(dead_code)]
 pub(crate) enum InternalReplayError<SessionState, SessionEvent> {
     /// No events in the event log
     NoEvents,

payjoin/src/core/hpke.rs

@@ -1,6 +1,11 @@
+#![cfg(any(feature = "v2", feature = "v2-ohttp"))]
+use alloc::vec::Vec;
+#[cfg(not(feature = "std"))]
+use core::error;
 use core::fmt;
+use core::ops::Deref;
+#[cfg(feature = "std")]
 use std::error;
-use std::ops::Deref;
 
 use bitcoin::key::constants::{ELLSWIFT_ENCODING_SIZE, PUBLIC_KEY_SIZE};
 use bitcoin::secp256k1;
@@ -195,6 +200,7 @@ pub fn decrypt_message_a(
     message_a: &[u8],
     receiver_sk: &HpkeSecretKey,
 ) -> Result<(Vec<u8>, HpkePublicKey), HpkeError> {
+    #[cfg(feature = "std")]
     use std::io::{Cursor, Read};
 
     let mut cursor = Cursor::new(message_a);
@@ -243,6 +249,7 @@ pub fn encrypt_message_b(
     Ok(message_b)
 }
 
+#[cfg(feature = "std")]
 pub fn decrypt_message_b(
     message_b: &[u8],
     receiver_pk: HpkePublicKey,

payjoin/src/core/into_url.rs

@@ -1,3 +1,6 @@
+use alloc::string::String;
+use core::{error, fmt};
+
 use crate::core::{Url, UrlParseError};
 
 #[derive(Debug, PartialEq, Eq)]
@@ -6,8 +9,8 @@ pub enum Error {
     ParseError(UrlParseError),
 }
 
-impl std::fmt::Display for Error {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use Error::*;
 
         match self {
@@ -17,7 +20,7 @@ impl std::fmt::Display for Error {
     }
 }
 
-impl std::error::Error for Error {}
+impl error::Error for Error {}
 
 impl From<UrlParseError> for Error {
     fn from(err: UrlParseError) -> Error { Error::ParseError(err) }

payjoin/src/core/io.rs

@@ -1,4 +1,5 @@
 //! IO-related types and functions. Specifically, fetching OHTTP keys from a payjoin directory.
+#[cfg(feature = "std")]
 use std::time::Duration;
 
 use http::header::ACCEPT;

payjoin/src/core/mod.rs

@@ -14,30 +14,42 @@ pub mod receive;
 mod request;
 pub mod send;
 pub use request::*;
+#[cfg(any(feature = "v1", feature = "v2-ohttp"))]
 pub(crate) mod into_url;
+#[cfg(any(feature = "v1", feature = "v2-ohttp"))]
 pub use into_url::{Error as IntoUrlError, IntoUrl};
 pub(crate) mod url;
+#[cfg(feature = "v2-ohttp")]
 pub use url::{ParseError as UrlParseError, Url};
+
+#[cfg(not(feature = "v2-ohttp"))]
+pub use crate::core::url::{ParseError as UrlParseError, Url};
 #[cfg(feature = "v2")]
 pub mod time;
 pub mod uri;
-pub use uri::{PjParam, PjParseError, PjUri, Uri, UriExt};
+#[cfg(feature = "std")]
+pub use uri::PjUri;
+pub use uri::{PjParam, PjParseError};
+#[cfg(feature = "std")]
+pub use uri::{Uri, UriExt};
 pub(crate) mod error_codes;
 
 pub(crate) mod output_substitution;
 #[cfg(feature = "v1")]
 pub use output_substitution::OutputSubstitution;
 
-#[cfg(feature = "v2")]
+#[cfg(feature = "v2-ohttp")]
 pub(crate) mod hpke;
 #[cfg(feature = "v2")]
 pub mod persist;
-#[cfg(feature = "v2")]
+#[cfg(feature = "v2-ohttp")]
 pub use crate::hpke::{HpkeKeyPair, HpkePublicKey};
-#[cfg(feature = "v2")]
+#[cfg(feature = "v2-ohttp")]
 pub(crate) mod ohttp;
-#[cfg(feature = "v2")]
+#[cfg(feature = "v2-ohttp")]
 pub use crate::ohttp::OhttpKeys;
+#[cfg(test)]
+mod no_std_tests;
 
 #[cfg(feature = "io")]
 #[cfg_attr(docsrs, doc(cfg(feature = "io")))]