Drop ahash dependency in favor of core's SipHasher

tkaitchuck/aHash#196 bumped the MSRV of
`ahash` in a patch release, which makes it rather difficult for us
to have it as a dependency.

Further, it seems that `ahash` hasn't been particularly robust in
the past, notably
tkaitchuck/aHash#163 and
tkaitchuck/aHash#166.

Luckily, `core` provides `SipHasher` even on no-std (sadly its
SipHash-2-4 unlike the SipHash-1-3 used by the `DefaultHasher` in
`std`). Thus, we drop the `ahash` dependency entirely here and
simply wrap `SipHasher` for our `no-std` HashMaps.

Author: TheBlueMatt

bench/Cargo.toml

@@ -9,7 +9,7 @@ name = "bench"
 harness = false
 
 [features]
-hashbrown = ["lightning/hashbrown", "lightning/ahash"]
+hashbrown = ["lightning/hashbrown"]
 
 [dependencies]
 lightning = { path = "../lightning", features = ["_test_utils", "criterion"] }

ci/check-cfg-flags.py

@@ -13,7 +13,7 @@ def check_feature(feature):
         pass
     elif feature == "no-std":
         pass
-    elif feature == "ahash":
+    elif feature == "possiblyrandom":
         pass
     elif feature == "getrandom":
         pass

lightning/Cargo.toml

@@ -31,7 +31,7 @@ unsafe_revoked_tx_signing = []
 # Override signing to not include randomness when generating signatures for test vectors.
 _test_vectors = []
 
-no-std = ["hashbrown", "ahash", "bitcoin/no-std", "core2/alloc", "libm"]
+no-std = ["hashbrown", "possiblyrandom", "bitcoin/no-std", "core2/alloc", "libm"]
 std = ["bitcoin/std"]
 
 # Generates low-r bitcoin signatures, which saves 1 byte in 50% of the cases
@@ -43,24 +43,14 @@ default = ["std", "grind_signatures"]
 bitcoin = { version = "0.30.2", default-features = false, features = ["secp-recovery"] }
 
 hashbrown = { version = "0.13", optional = true }
-ahash = { version = "0.8", optional = true, default-features = false }
+possiblyrandom = { version = "0.1", optional = true, default-features = false }
 hex = { package = "hex-conservative", version = "0.1.1", default-features = false }
 regex = { version = "1.5.6", optional = true }
 backtrace = { version = "0.3", optional = true }
 
 core2 = { version = "0.3.0", optional = true, default-features = false }
 libm = { version = "0.2", optional = true, default-features = false }
 
-# Because ahash no longer (kinda poorly) does it for us, (roughly) list out the targets that
-# getrandom supports and turn on ahash's `runtime-rng` feature for them.
-[target.'cfg(not(any(target_os = "unknown", target_os = "none")))'.dependencies]
-ahash = { version = "0.8", optional = true, default-features = false, features = ["runtime-rng"] }
-
-# Not sure what target_os gets set to for sgx, so to be safe always enable runtime-rng for x86_64
-# platforms (assuming LDK isn't being used on embedded x86-64 running directly on metal).
-[target.'cfg(target_arch = "x86_64")'.dependencies]
-ahash = { version = "0.8", optional = true, default-features = false, features = ["runtime-rng"] }
-
 [dev-dependencies]
 regex = "1.5.6"
 

lightning/src/lib.rs

@@ -165,113 +165,12 @@ mod io_extras {
 }
 
 mod prelude {
-	#[cfg(feature = "hashbrown")]
-	extern crate hashbrown;
-	#[cfg(feature = "ahash")]
-	extern crate ahash;
-
 	pub use alloc::{vec, vec::Vec, string::String, collections::VecDeque, boxed::Box};
 
 	pub use alloc::borrow::ToOwned;
 	pub use alloc::string::ToString;
 
-	// For no-std builds, we need to use hashbrown, however, by default, it doesn't randomize the
-	// hashing and is vulnerable to HashDoS attacks. Thus, when not fuzzing, we use its default
-	// ahash hashing algorithm but randomize, opting to not randomize when fuzzing to avoid false
-	// positive branch coverage.
-
-	#[cfg(not(feature = "hashbrown"))]
-	mod std_hashtables {
-		pub(crate) use std::collections::{HashMap, HashSet, hash_map};
-
-		pub(crate) type OccupiedHashMapEntry<'a, K, V> =
-			std::collections::hash_map::OccupiedEntry<'a, K, V>;
-		pub(crate) type VacantHashMapEntry<'a, K, V> =
-			std::collections::hash_map::VacantEntry<'a, K, V>;
-	}
-	#[cfg(not(feature = "hashbrown"))]
-	pub(crate) use std_hashtables::*;
-
-	#[cfg(feature = "hashbrown")]
-	pub(crate) use self::hashbrown::hash_map;
-
-	#[cfg(all(feature = "hashbrown", fuzzing))]
-	mod nonrandomized_hashbrown {
-		pub(crate) use hashbrown::{HashMap, HashSet};
-
-		pub(crate) type OccupiedHashMapEntry<'a, K, V> =
-			hashbrown::hash_map::OccupiedEntry<'a, K, V, hashbrown::hash_map::DefaultHashBuilder>;
-		pub(crate) type VacantHashMapEntry<'a, K, V> =
-			hashbrown::hash_map::VacantEntry<'a, K, V, hashbrown::hash_map::DefaultHashBuilder>;
-	}
-	#[cfg(all(feature = "hashbrown", fuzzing))]
-	pub(crate) use nonrandomized_hashbrown::*;
-
-
-	#[cfg(all(feature = "hashbrown", not(fuzzing)))]
-	mod randomized_hashtables {
-		use super::*;
-		use ahash::RandomState;
-
-		pub(crate) type HashMap<K, V> = hashbrown::HashMap<K, V, RandomState>;
-		pub(crate) type HashSet<K> = hashbrown::HashSet<K, RandomState>;
-
-		pub(crate) type OccupiedHashMapEntry<'a, K, V> =
-			hashbrown::hash_map::OccupiedEntry<'a, K, V, RandomState>;
-		pub(crate) type VacantHashMapEntry<'a, K, V> =
-			hashbrown::hash_map::VacantEntry<'a, K, V, RandomState>;
-
-		pub(crate) fn new_hash_map<K, V>() -> HashMap<K, V> {
-			HashMap::with_hasher(RandomState::new())
-		}
-		pub(crate) fn hash_map_with_capacity<K, V>(cap: usize) -> HashMap<K, V> {
-			HashMap::with_capacity_and_hasher(cap, RandomState::new())
-		}
-		pub(crate) fn hash_map_from_iter<K: core::hash::Hash + Eq, V, I: IntoIterator<Item=(K, V)>>(iter: I) -> HashMap<K, V> {
-			let iter = iter.into_iter();
-			let min_size = iter.size_hint().0;
-			let mut res = HashMap::with_capacity_and_hasher(min_size, RandomState::new());
-			res.extend(iter);
-			res
-		}
-
-		pub(crate) fn new_hash_set<K>() -> HashSet<K> {
-			HashSet::with_hasher(RandomState::new())
-		}
-		pub(crate) fn hash_set_with_capacity<K>(cap: usize) -> HashSet<K> {
-			HashSet::with_capacity_and_hasher(cap, RandomState::new())
-		}
-		pub(crate) fn hash_set_from_iter<K: core::hash::Hash + Eq, I: IntoIterator<Item=K>>(iter: I) -> HashSet<K> {
-			let iter = iter.into_iter();
-			let min_size = iter.size_hint().0;
-			let mut res = HashSet::with_capacity_and_hasher(min_size, RandomState::new());
-			res.extend(iter);
-			res
-		}
-	}
-
-	#[cfg(any(not(feature = "hashbrown"), fuzzing))]
-	mod randomized_hashtables {
-		use super::*;
-
-		pub(crate) fn new_hash_map<K, V>() -> HashMap<K, V> { HashMap::new() }
-		pub(crate) fn hash_map_with_capacity<K, V>(cap: usize) -> HashMap<K, V> {
-			HashMap::with_capacity(cap)
-		}
-		pub(crate) fn hash_map_from_iter<K: core::hash::Hash + Eq, V, I: IntoIterator<Item=(K, V)>>(iter: I) -> HashMap<K, V> {
-			HashMap::from_iter(iter)
-		}
-
-		pub(crate) fn new_hash_set<K>() -> HashSet<K> { HashSet::new() }
-		pub(crate) fn hash_set_with_capacity<K>(cap: usize) -> HashSet<K> {
-			HashSet::with_capacity(cap)
-		}
-		pub(crate) fn hash_set_from_iter<K: core::hash::Hash + Eq, I: IntoIterator<Item=K>>(iter: I) -> HashSet<K> {
-			HashSet::from_iter(iter)
-		}
-	}
-
-	pub(crate) use randomized_hashtables::*;
+	pub(crate) use crate::util::hash_tables::*;
 }
 
 #[cfg(all(not(ldk_bench), feature = "backtrace", feature = "std", test))]

lightning/src/util/hash_tables.rs

@@ -0,0 +1,167 @@
+//! Generally LDK uses `std`'s `HashMap`s, however when building for no-std, LDK uses `hashbrown`'s
+//! `HashMap`s with the `std` `SipHasher` and uses `getrandom` to opportunistically randomize it,
+//! if randomization is available.
+//!
+//! This module simply re-exports the `HashMap` used in LDK for public consumption.
+
+#[cfg(feature = "hashbrown")]
+extern crate hashbrown;
+#[cfg(feature = "possiblyrandom")]
+extern crate possiblyrandom;
+
+// For no-std builds, we need to use hashbrown, however, by default, it doesn't randomize the
+// hashing and is vulnerable to HashDoS attacks. Thus, we use the core SipHasher when not using
+// std, but use `getrandom` to randomize it if its available.
+
+#[cfg(not(feature = "hashbrown"))]
+mod std_hashtables {
+	pub use std::collections::HashMap;
+	pub use std::collections::hash_map::RandomState;
+
+	pub(crate) use std::collections::{HashSet, hash_map};
+
+	pub(crate) type OccupiedHashMapEntry<'a, K, V> =
+		std::collections::hash_map::OccupiedEntry<'a, K, V>;
+	pub(crate) type VacantHashMapEntry<'a, K, V> =
+		std::collections::hash_map::VacantEntry<'a, K, V>;
+}
+#[cfg(not(feature = "hashbrown"))]
+pub use std_hashtables::*;
+
+#[cfg(feature = "hashbrown")]
+pub(crate) use self::hashbrown::hash_map;
+
+#[cfg(all(feature = "hashbrown", fuzzing))]
+mod nonrandomized_hashbrown {
+	pub use hashbrown::HashMap;
+	pub use std::collections::hash_map::RandomState;
+
+	pub(crate) use hashbrown::HashSet;
+
+	pub(crate) type OccupiedHashMapEntry<'a, K, V> =
+		hashbrown::hash_map::OccupiedEntry<'a, K, V, hashbrown::hash_map::DefaultHashBuilder>;
+	pub(crate) type VacantHashMapEntry<'a, K, V> =
+		hashbrown::hash_map::VacantEntry<'a, K, V, hashbrown::hash_map::DefaultHashBuilder>;
+}
+#[cfg(all(feature = "hashbrown", fuzzing))]
+pub use nonrandomized_hashbrown::*;
+
+#[cfg(all(feature = "hashbrown", not(fuzzing)))]
+mod randomized_hashtables {
+	#[cfg(feature = "std")]
+	mod hasher {
+		pub use std::collections::hash_map::RandomState;
+	}
+	#[cfg(not(feature = "std"))]
+	mod hasher {
+		#![allow(deprecated)] // hash::SipHasher was deprecated in favor of something only in std.
+		use core::hash::{BuildHasher, SipHasher};
+
+		#[derive(Clone, Copy)]
+		/// A simple implementation of [`BuildHasher`] that uses `getrandom` to opportunistically
+		/// randomize, if the platform supports it.
+		pub struct RandomState {
+			k0: u64, k1: u64,
+		}
+
+		impl RandomState {
+			/// Constructs a new [`RandomState`] which may or may not be random, depending on the
+			/// target platform.
+			pub fn new() -> RandomState {
+				let (k0, k1);
+				#[cfg(feature = "possiblyrandom")] {
+					let mut keys = [0; 16];
+					possiblyrandom::getpossiblyrandom(&mut keys);
+
+					let mut k0_bytes = [0; 8];
+					let mut k1_bytes = [0; 8];
+					k0_bytes.copy_from_slice(&keys[..8]);
+					k1_bytes.copy_from_slice(&keys[8..]);
+					k0 = u64::from_le_bytes(k0_bytes);
+					k1 = u64::from_le_bytes(k1_bytes);
+				}
+				#[cfg(not(feature = "possiblyrandom"))] {
+					k0 = 0;
+					k1 = 0;
+				}
+				RandomState { k0, k1 }
+			}
+		}
+
+		impl Default for RandomState {
+			fn default() -> RandomState { RandomState::new() }
+		}
+
+		impl BuildHasher for RandomState {
+			type Hasher = SipHasher;
+			fn build_hasher(&self) -> SipHasher {
+				SipHasher::new_with_keys(self.k0, self.k1)
+			}
+		}
+	}
+
+	pub use hasher::*;
+	use super::*;
+
+	/// The HashMap type used in LDK.
+	pub type HashMap<K, V> = hashbrown::HashMap<K, V, RandomState>;
+	pub(crate) type HashSet<K> = hashbrown::HashSet<K, RandomState>;
+
+	pub(crate) type OccupiedHashMapEntry<'a, K, V> =
+		hashbrown::hash_map::OccupiedEntry<'a, K, V, RandomState>;
+	pub(crate) type VacantHashMapEntry<'a, K, V> =
+		hashbrown::hash_map::VacantEntry<'a, K, V, RandomState>;
+
+	pub(crate) fn new_hash_map<K, V>() -> HashMap<K, V> {
+		HashMap::with_hasher(RandomState::new())
+	}
+	pub(crate) fn hash_map_with_capacity<K, V>(cap: usize) -> HashMap<K, V> {
+		HashMap::with_capacity_and_hasher(cap, RandomState::new())
+	}
+	pub(crate) fn hash_map_from_iter<K: core::hash::Hash + Eq, V, I: IntoIterator<Item=(K, V)>>(iter: I) -> HashMap<K, V> {
+		let iter = iter.into_iter();
+		let min_size = iter.size_hint().0;
+		let mut res = HashMap::with_capacity_and_hasher(min_size, RandomState::new());
+		res.extend(iter);
+		res
+	}
+
+	pub(crate) fn new_hash_set<K>() -> HashSet<K> {
+		HashSet::with_hasher(RandomState::new())
+	}
+	pub(crate) fn hash_set_with_capacity<K>(cap: usize) -> HashSet<K> {
+		HashSet::with_capacity_and_hasher(cap, RandomState::new())
+	}
+	pub(crate) fn hash_set_from_iter<K: core::hash::Hash + Eq, I: IntoIterator<Item=K>>(iter: I) -> HashSet<K> {
+		let iter = iter.into_iter();
+		let min_size = iter.size_hint().0;
+		let mut res = HashSet::with_capacity_and_hasher(min_size, RandomState::new());
+		res.extend(iter);
+		res
+	}
+}
+#[cfg(all(feature = "hashbrown", not(fuzzing)))]
+pub use randomized_hashtables::*;
+
+#[cfg(any(not(feature = "hashbrown"), fuzzing))]
+mod hashtable_constructors {
+	use super::*;
+
+	pub(crate) fn new_hash_map<K, V>() -> HashMap<K, V> { HashMap::new() }
+	pub(crate) fn hash_map_with_capacity<K, V>(cap: usize) -> HashMap<K, V> {
+		HashMap::with_capacity(cap)
+	}
+	pub(crate) fn hash_map_from_iter<K: core::hash::Hash + Eq, V, I: IntoIterator<Item=(K, V)>>(iter: I) -> HashMap<K, V> {
+		HashMap::from_iter(iter)
+	}
+
+	pub(crate) fn new_hash_set<K>() -> HashSet<K> { HashSet::new() }
+	pub(crate) fn hash_set_with_capacity<K>(cap: usize) -> HashSet<K> {
+		HashSet::with_capacity(cap)
+	}
+	pub(crate) fn hash_set_from_iter<K: core::hash::Hash + Eq, I: IntoIterator<Item=K>>(iter: I) -> HashSet<K> {
+		HashSet::from_iter(iter)
+	}
+}
+#[cfg(any(not(feature = "hashbrown"), fuzzing))]
+pub(crate) use hashtable_constructors::*;

lightning/src/util/mod.rs

@@ -32,6 +32,7 @@ pub(crate) mod atomic_counter;
 pub(crate) mod byte_utils;
 pub(crate) mod transaction_utils;
 pub(crate) mod time;
+pub mod hash_tables;
 
 pub mod indexed_map;