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//! Types related to stream isolation
use downcast_rs::{impl_downcast, Downcast};
use dyn_clone::{clone_trait_object, DynClone};
use std::sync::atomic::{AtomicU64, Ordering};
/// A type that can make isolation decisions about streams it is attached to.
///
/// Types that implement `Isolation` contain properties about a stream that are
/// used to make decisions about whether that stream can share the same circuit
/// as other streams. You may pass in any type implementing `Isolation` when
/// creating a stream via `TorClient::connect_with_prefs`, or constructing a
/// circuit with [`CircMgr::get_or_launch_exit()`](crate::CircMgr::get_or_launch_exit).
///
/// You typically do not want to implement this trait directly. Instead, most
/// users should implement [`IsolationHelper`].
pub trait Isolation:
seal::Sealed + Downcast + DynClone + std::fmt::Debug + Send + Sync + 'static
{
/// Return true if this Isolation is compatible with another.
///
/// Two streams may share a circuit if and only if they have compatible
/// `Isolation`s.
///
/// # Requirements
///
/// For correctness, this relation must be symmetrical and reflexive:
/// `self.compatible(other)` must equal `other.compatible(self)`, and
/// `self.compatible(self)` must be true.
///
/// For correctness, this function must always give the same result as
/// `self.join(other).is_some()`.
///
/// This relationship does **not** have to be transitive: it's possible that
/// stream A can share a circuit with either stream B or stream C, but not
/// with both.
fn compatible(&self, other: &dyn Isolation) -> bool;
/// Join two [`Isolation`] into the intersection of what each allows.
///
/// A circuit's isolation is the `join` of the isolation values of all of
/// the streams that have _ever_ used that circuit. A circuit's isolation
/// can never be `None`: streams that would cause it to be `None` can't be
/// attached to the circuit.
///
/// When a stream is added to a circuit, `join` is used to calculate the
/// circuit's new isolation.
///
/// # Requirements
///
/// For correctness, this function must be commutative: `self.join(other)`
/// must equal `other.join(self)`. Also, it must be idempotent:
/// `self.join(self)` must equal self.
//
// TODO: (This function probably should be associative too, but we haven't done
// all the math.)
fn join(&self, other: &dyn Isolation) -> Option<Box<dyn Isolation>>;
}
/// Seal preventing implementation of Isolation not relying on IsolationHelper
mod seal {
/// Seal preventing implementation of Isolation not relying on IsolationHelper
pub trait Sealed {}
impl<T: super::IsolationHelper> Sealed for T {}
}
impl_downcast!(Isolation);
clone_trait_object!(Isolation);
impl<T: Isolation> From<T> for Box<dyn Isolation> {
fn from(isolation: T) -> Self {
Box::new(isolation)
}
}
impl<T: IsolationHelper + Clone + std::fmt::Debug + Send + Sync + 'static> Isolation for T {
fn compatible(&self, other: &dyn Isolation) -> bool {
if let Some(other) = other.as_any().downcast_ref() {
self.compatible_same_type(other)
} else {
false
}
}
fn join(&self, other: &dyn Isolation) -> Option<Box<dyn Isolation>> {
if let Some(other) = other.as_any().downcast_ref() {
self.join_same_type(other)
.map(|res| Box::new(res) as Box<dyn Isolation>)
} else {
None
}
}
}
/// Trait to help implement [`Isolation`].
///
/// You should generally implement this trait whenever you need to implement a
/// new set of stream isolation rules: it takes care of down-casting and type
/// checking for you.
///
/// When you implement this trait for some type T, isolation objects of that
/// type will be incompatible (unable to share circuits) with objects of _any
/// other type_. (That's usually what you want; if you're defining a new type
/// of Isolation rules, then you probably don't want streams using different
/// rules to share circuits with yours.)
pub trait IsolationHelper: Sized {
/// Returns whether self and other are compatible.
///
/// Two streams may share a circuit if and only if they have compatible
/// `Isolation`s.
///
/// (See [`Isolation::compatible`] for more information and requirements.)
fn compatible_same_type(&self, other: &Self) -> bool;
/// Join self and other into the intersection of what they allows.
///
/// (See [`Isolation::join`] for more information and requirements.)
fn join_same_type(&self, other: &Self) -> Option<Self>;
}
/// A token used to isolate unrelated streams on different circuits.
///
/// When two streams are associated with different isolation tokens, they
/// can never share the same circuit.
///
/// Tokens created with [`IsolationToken::new`] are all different from
/// one another, and different from tokens created with
/// [`IsolationToken::no_isolation`]. However, tokens created with
/// [`IsolationToken::no_isolation`] are all equal to one another.
///
/// # Examples
///
/// Creating distinct isolation tokens:
///
/// ```rust
/// # use tor_circmgr::IsolationToken;
/// let token_1 = IsolationToken::new();
/// let token_2 = IsolationToken::new();
///
/// assert_ne!(token_1, token_2);
///
/// // Demonstrating the behaviour of no_isolation() tokens:
/// assert_ne!(token_1, IsolationToken::no_isolation());
/// assert_eq!(IsolationToken::no_isolation(), IsolationToken::no_isolation());
/// ```
///
/// Using an isolation token to route streams differently over the Tor network:
///
/// ```ignore
/// use arti_client::StreamPrefs;
///
/// let token_1 = IsolationToken::new();
/// let token_2 = IsolationToken::new();
///
/// let mut prefs_1 = StreamPrefs::new();
/// prefs_1.set_isolation(token_1);
///
/// let mut prefs_2 = StreamPrefs::new();
/// prefs_2.set_isolation(token_2);
///
/// // These two connections will come from different source IP addresses.
/// tor_client.connect(("example.com", 80), Some(prefs_1)).await?;
/// tor_client.connect(("example.com", 80), Some(prefs_2)).await?;
/// ```
// # Semver note
//
// This type is re-exported by `arti-client`: any changes to it must be
// reflected in `arti-client`'s version.
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct IsolationToken(u64);
#[allow(clippy::new_without_default)]
impl IsolationToken {
/// Create a new IsolationToken, unequal to any other token this function
/// has created.
///
/// # Panics
///
/// Panics if we have already allocated 2^64 isolation tokens: in that
/// case, we have exhausted the space of possible tokens, and it is
/// no longer possible to ensure isolation.
pub fn new() -> Self {
/// Internal counter used to generate different tokens each time
static COUNTER: AtomicU64 = AtomicU64::new(1);
// Ordering::Relaxed is fine because we don't care about causality, we just want a
// different number each time
let token = COUNTER.fetch_add(1, Ordering::Relaxed);
assert!(token < u64::MAX);
IsolationToken(token)
}
/// Create a new IsolationToken equal to every other token created
/// with this function, but different from all tokens created with
/// `new`.
///
/// This can be used when no isolation is wanted for some streams.
pub fn no_isolation() -> Self {
IsolationToken(0)
}
}
impl IsolationHelper for IsolationToken {
fn compatible_same_type(&self, other: &Self) -> bool {
self == other
}
fn join_same_type(&self, other: &Self) -> Option<Self> {
if self.compatible_same_type(other) {
Some(*self)
} else {
None
}
}
}
/// Helper macro to implement IsolationHelper for tuple of IsolationHelper
macro_rules! tuple_impls {
($(
$Tuple:ident {
$(($idx:tt) -> $T:ident)+
}
)+) => {
$(
impl<$($T:IsolationHelper),+> IsolationHelper for ($($T,)+) {
fn compatible_same_type(&self, other: &Self) -> bool {
$(self.$idx.compatible_same_type(&other.$idx))&&+
}
fn join_same_type(&self, other: &Self) -> Option<Self> {
Some((
$(self.$idx.join_same_type(&other.$idx)?,)+
))
}
}
)+
}
}
tuple_impls! {
Tuple1 {
(0) -> A
}
Tuple2 {
(0) -> A
(1) -> B
}
Tuple3 {
(0) -> A
(1) -> B
(2) -> C
}
Tuple4 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
}
Tuple5 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
(4) -> E
}
Tuple6 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
(4) -> E
(5) -> F
}
Tuple7 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
(4) -> E
(5) -> F
(6) -> G
}
Tuple8 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
(4) -> E
(5) -> F
(6) -> G
(7) -> H
}
Tuple9 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
(4) -> E
(5) -> F
(6) -> G
(7) -> H
(8) -> I
}
Tuple10 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
(4) -> E
(5) -> F
(6) -> G
(7) -> H
(8) -> I
(9) -> J
}
Tuple11 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
(4) -> E
(5) -> F
(6) -> G
(7) -> H
(8) -> I
(9) -> J
(10) -> K
}
Tuple12 {
(0) -> A
(1) -> B
(2) -> C
(3) -> D
(4) -> E
(5) -> F
(6) -> G
(7) -> H
(8) -> I
(9) -> J
(10) -> K
(11) -> L
}
}
/// A set of information about how a stream should be isolated.
///
/// If two streams are isolated from one another, they may not share
/// a circuit.
#[derive(Clone, Debug, derive_builder::Builder)]
pub struct StreamIsolation {
/// Any isolation set on the stream.
#[builder(default = "Box::new(IsolationToken::no_isolation())")]
stream_isolation: Box<dyn Isolation>,
/// Any additional isolation token set on an object that "owns" this
/// stream. This is typically owned by a `TorClient`.
#[builder(default = "IsolationToken::no_isolation()")]
owner_token: IsolationToken,
}
impl StreamIsolation {
/// Construct a new StreamIsolation with no isolation enabled.
pub fn no_isolation() -> Self {
StreamIsolationBuilder::new()
.build()
.expect("Bug constructing StreamIsolation")
}
/// Return a new StreamIsolationBuilder for constructing
/// StreamIsolation objects.
pub fn builder() -> StreamIsolationBuilder {
StreamIsolationBuilder::new()
}
}
impl IsolationHelper for StreamIsolation {
fn compatible_same_type(&self, other: &StreamIsolation) -> bool {
self.owner_token == other.owner_token
&& self
.stream_isolation
.compatible(other.stream_isolation.as_ref())
}
fn join_same_type(&self, other: &StreamIsolation) -> Option<StreamIsolation> {
if self.owner_token != other.owner_token {
return None;
}
self.stream_isolation
.join(other.stream_isolation.as_ref())
.map(|stream_isolation| StreamIsolation {
stream_isolation,
owner_token: self.owner_token,
})
}
}
impl StreamIsolationBuilder {
/// Construct a builder with no items set.
pub fn new() -> Self {
StreamIsolationBuilder::default()
}
}
#[cfg(test)]
pub(crate) mod test {
#![allow(clippy::unwrap_used)]
use super::*;
/// Trait for testing use only. Much like PartialEq, but for type containing an dyn Isolation
/// which is known to be an IsolationToken.
pub(crate) trait IsolationTokenEq {
/// Compare two values, returning true if they are equals and all dyn Isolation they contain
/// are IsolationToken (which are equal too).
fn isol_eq(&self, other: &Self) -> bool;
}
macro_rules! assert_isoleq {
{ $arg1:expr, $arg2:expr } => {
assert!($arg1.isol_eq(&$arg2))
}
}
pub(crate) use assert_isoleq;
impl IsolationTokenEq for IsolationToken {
fn isol_eq(&self, other: &Self) -> bool {
self == other
}
}
impl<T: IsolationTokenEq> IsolationTokenEq for Option<T> {
fn isol_eq(&self, other: &Self) -> bool {
match (self, other) {
(Some(this), Some(other)) => this.isol_eq(other),
(None, None) => true,
_ => false,
}
}
}
impl<T: IsolationTokenEq + std::fmt::Debug> IsolationTokenEq for Vec<T> {
fn isol_eq(&self, other: &Self) -> bool {
if self.len() != other.len() {
return false;
}
self.iter()
.zip(other.iter())
.all(|(this, other)| this.isol_eq(other))
}
}
impl IsolationTokenEq for dyn Isolation {
fn isol_eq(&self, other: &Self) -> bool {
let this = self.as_any().downcast_ref::<IsolationToken>();
let other = other.as_any().downcast_ref::<IsolationToken>();
match (this, other) {
(Some(this), Some(other)) => this == other,
_ => false,
}
}
}
impl IsolationTokenEq for StreamIsolation {
fn isol_eq(&self, other: &Self) -> bool {
self.stream_isolation
.isol_eq(other.stream_isolation.as_ref())
&& self.owner_token == other.owner_token
}
}
#[derive(PartialEq, Clone, Copy, Debug, Eq)]
struct OtherIsolation(usize);
impl IsolationHelper for OtherIsolation {
fn compatible_same_type(&self, other: &Self) -> bool {
self == other
}
fn join_same_type(&self, other: &Self) -> Option<Self> {
if self.compatible_same_type(other) {
Some(*self)
} else {
None
}
}
}
#[test]
fn isolation_token() {
let token_1 = IsolationToken::new();
let token_2 = IsolationToken::new();
assert!(token_1.compatible_same_type(&token_1));
assert!(token_2.compatible_same_type(&token_2));
assert!(!token_1.compatible_same_type(&token_2));
assert_eq!(token_1.join_same_type(&token_1), Some(token_1));
assert_eq!(token_2.join_same_type(&token_2), Some(token_2));
assert_eq!(token_1.join_same_type(&token_2), None);
}
#[test]
fn isolation_trait() {
let token_1: Box<dyn Isolation> = Box::new(IsolationToken::new());
let token_2: Box<dyn Isolation> = Box::new(IsolationToken::new());
let other_1: Box<dyn Isolation> = Box::new(OtherIsolation(0));
let other_2: Box<dyn Isolation> = Box::new(OtherIsolation(1));
assert!(token_1.compatible(token_1.as_ref()));
assert!(token_2.compatible(token_2.as_ref()));
assert!(!token_1.compatible(token_2.as_ref()));
assert!(other_1.compatible(other_1.as_ref()));
assert!(other_2.compatible(other_2.as_ref()));
assert!(!other_1.compatible(other_2.as_ref()));
assert!(!token_1.compatible(other_1.as_ref()));
assert!(!other_1.compatible(token_1.as_ref()));
assert!(token_1.join(token_1.as_ref()).is_some());
assert!(token_1.join(token_2.as_ref()).is_none());
assert!(other_1.join(other_1.as_ref()).is_some());
assert!(other_1.join(other_2.as_ref()).is_none());
assert!(token_1.join(other_1.as_ref()).is_none());
assert!(other_1.join(token_1.as_ref()).is_none());
}
#[test]
fn isolation_tuple() {
let token_1 = IsolationToken::new();
let token_2 = IsolationToken::new();
let other_1 = OtherIsolation(0);
let other_2 = OtherIsolation(1);
let token_12: Box<dyn Isolation> = Box::new((token_1, token_2));
let token_21: Box<dyn Isolation> = Box::new((token_2, token_1));
let mix_11: Box<dyn Isolation> = Box::new((token_1, other_1));
let mix_12: Box<dyn Isolation> = Box::new((token_1, other_2));
let revmix_11: Box<dyn Isolation> = Box::new((other_1, token_1));
let join_token = token_12.join(token_12.as_ref()).unwrap();
assert!(join_token.compatible(token_12.as_ref()));
let join_mix = mix_12.join(mix_12.as_ref()).unwrap();
assert!(join_mix.compatible(mix_12.as_ref()));
let isol_list = [token_12, token_21, mix_11, mix_12, revmix_11];
for (i, isol1) in isol_list.iter().enumerate() {
for (j, isol2) in isol_list.iter().enumerate() {
assert_eq!(isol1.compatible(isol2.as_ref()), i == j);
}
}
}
#[test]
fn build_isolation() {
let no_isolation = StreamIsolation::no_isolation();
let no_isolation2 = StreamIsolation::builder()
.owner_token(IsolationToken::no_isolation())
.stream_isolation(Box::new(IsolationToken::no_isolation()))
.build()
.unwrap();
assert_eq!(no_isolation.owner_token, no_isolation2.owner_token);
assert_eq!(
no_isolation
.stream_isolation
.as_ref()
.as_any()
.downcast_ref::<IsolationToken>(),
no_isolation2
.stream_isolation
.as_ref()
.as_any()
.downcast_ref::<IsolationToken>()
);
assert!(no_isolation.compatible(&no_isolation2));
let tok = IsolationToken::new();
let some_isolation = StreamIsolation::builder().owner_token(tok).build().unwrap();
let some_isolation2 = StreamIsolation::builder()
.stream_isolation(Box::new(tok))
.build()
.unwrap();
assert!(!no_isolation.compatible(&some_isolation));
assert!(!no_isolation.compatible(&some_isolation2));
assert!(!some_isolation.compatible(&some_isolation2));
assert!(some_isolation.compatible(&some_isolation));
}
}