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//! The encrypted portion of an INTRODUCE{1,2} message.
//!
//! (This is as described as the "decrypted plaintext" in section 3.3 of
//! rend-spec-v3.txt. It tells the onion service how to find the rendezvous
//! point, and how to handshake with the client there.)
use super::pow::ProofOfWork;
use crate::relaycell::{extend::CircRequestExt, extlist::ExtList};
use caret::caret_int;
use tor_bytes::{EncodeError, EncodeResult, Error, Readable, Reader, Result, Writeable, Writer};
use tor_hscrypto::RendCookie;
use tor_linkspec::EncodedLinkSpec;
caret_int! {
/// An enumeration value to identify a type of onion key.
///
/// Corresponds to `ONION_KEY_TYPE` in section 3.3 of
/// rend-spec-v3.txt \[PROCESS_INTRO].
//
// TODO this shouldn't live here. It ought to be in some more general crate.
// But it should then also be usable in the netdoc parser. In particular, it ought
// to be able to handle the *textual* values in `hsdesc/inner.rs`, and maybe
// the ad-hocery in the routerdesc parsing too.
struct OnionKeyType(u8) {
NTOR = 0x01,
}
/// An onion key provided in an IntroduceHandshakePayload.
/// Corresponds to `ONION_KEY` in the spec.
// TODO: Is there a logical type somewhere else to coalesce this with?
// Currently there is no wrapper around curve25519::PublicKey when it's used as
// an Ntor key, nor is there (yet) a generic onion key enum. tor-linkspec might be
// the logical place for those. See arti#893.
#[derive(Clone, Debug)]
#[non_exhaustive]
pub enum OnionKey {
/// A key usable with the ntor or ntor-v3 handshake.
NtorOnionKey(tor_llcrypto::pk::curve25519::PublicKey),
// There is no "unknown" variant for this type, since we don't support any
// other key types yet.
impl Readable for OnionKey {
fn take_from(r: &mut Reader<'_>) -> Result<Self> {
let kind: OnionKeyType = r.take_u8()?.into();
r.read_nested_u16len(|r_inner| match kind {
OnionKeyType::NTOR => Ok(OnionKey::NtorOnionKey(r_inner.extract()?)),
_ => Err(Error::InvalidMessage(
format!("Unrecognized onion key type {kind}").into(),
)),
})
impl Writeable for OnionKey {
fn write_onto<B: Writer + ?Sized>(&self, w: &mut B) -> EncodeResult<()> {
match self {
OnionKey::NtorOnionKey(key) => {
w.write_u8(OnionKeyType::NTOR.into());
let mut w_inner = w.write_nested_u16len();
w_inner.write(key)?;
w_inner.finish()?;
Ok(())
/// The plaintext of the encrypted portion of an INTRODUCE{1,2} message.
/// This is not a RelayMsg itself; it is instead used as the payload for an
/// `hs-ntor` handshake, which is passed to the onion service in `Introduce[12]`
/// message.
/// This payload is sent from a client to the onion service to tell it how to reach
/// the client's chosen rendezvous point.
/// This corresponds to the "decrypted payload" in section 3.3 of
/// rend-spec-v3.txt, **excluding the PAD field**.
/// The user of this type is expected to discard, or generate, appropriate
/// padding, as required.
pub struct IntroduceHandshakePayload {
/// The rendezvous cookie to use at the rendezvous point.
/// (`RENDEZVOUS_COOKIE` in the spec.)
cookie: RendCookie,
/// A list of extensions to this payload.
/// (`N_EXTENSIONS`, `EXT_FIELD_TYPE`, `EXT_FIELD_LEN`, and `EXT_FIELD` in
/// the spec.)
extensions: ExtList<CircRequestExt>,
/// The onion key to use when extending a circuit to the rendezvous point.
/// (`ONION_KEY_TYPE`, `ONION_KEY_LEN`, and `ONION_KEY` in the spec. This
/// represents `KP_ntor` for the rendezvous point.)
onion_key: OnionKey,
/// A list of link specifiers to identify the rendezvous point.
/// (`NSPEC`, `LSTYPE`, `LSLEN`, and `LSPEC` in the spec.)
link_specifiers: Vec<EncodedLinkSpec>,
impl Readable for IntroduceHandshakePayload {
let cookie = r.extract()?;
let extensions = r.extract()?;
let onion_key = r.extract()?;
let n_link_specifiers = r.take_u8()?;
let link_specifiers = r.extract_n(n_link_specifiers.into())?;
Ok(Self {
cookie,
extensions,
onion_key,
link_specifiers,
impl Writeable for IntroduceHandshakePayload {
w.write(&self.cookie)?;
w.write(&self.extensions)?;
w.write(&self.onion_key)?;
w.write_u8(
self.link_specifiers
.len()
.try_into()
.map_err(|_| EncodeError::BadLengthValue)?,
);
self.link_specifiers.iter().try_for_each(|ls| w.write(ls))?;
impl IntroduceHandshakePayload {
/// Construct a new [`IntroduceHandshakePayload`]
pub fn new(
proof_of_work: Option<ProofOfWork>,
) -> Self {
let mut extensions = ExtList::default();
if let Some(proof_of_work) = proof_of_work {
extensions.push(proof_of_work.into());
Self {
/// Return the rendezvous cookie specified in this handshake payload.
pub fn cookie(&self) -> &RendCookie {
&self.cookie
/// Return the provided onion key for the specified rendezvous point
pub fn onion_key(&self) -> &OnionKey {
&self.onion_key
/// Return the provided link specifiers for the specified rendezvous point.
pub fn link_specifiers(&self) -> &[EncodedLinkSpec] {
&self.link_specifiers[..]
/// Return the proof-of-work extension for the specified rendezvous point.
pub fn proof_of_work_extension(&self) -> Option<&ProofOfWork> {
// TODO: it would be nice to change ExtList to provide a nicer API for this...
self.extensions.extensions.iter().find_map(|x| match x {
CircRequestExt::ProofOfWork(x) => Some(x),
_ => None,