Split out verifier parts of tendermint-light-client to `tendermint-…

…light-client-verifier` (#1071) * Split out verifier parts of tendermint-light-client to tendermint-light-client-verifier * Add Time::now() method behind clock feature * light-client refactor: Re-export new verifier crate from `tendermint-light-client` (#1074) * Re-export tendermint_light_client_verifier as verifier from tendermint_light_client Signed-off-by: Thane Thomson <[email protected]> * Remove unnecessary tendermint-light-client import Signed-off-by: Thane Thomson <[email protected]> * Fix crate docs to reflect verifier extraction Signed-off-by: Thane Thomson <[email protected]> * Add changelog entry Signed-off-by: Thane Thomson <[email protected]> * Re-export the original exports in light-client crate Co-authored-by: Thane Thomson <[email protected]>
informalsystems · Jan 12, 2022 · b52a5af · b52a5af
1 parent 8d77986
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diff --git a/.changelog/unreleased/breaking-changes/1027-light-client-verifier.md b/.changelog/unreleased/breaking-changes/1027-light-client-verifier.md
@@ -0,0 +1,5 @@
+- `[tendermint-light-client]` Split out the verification functionality from the
+  `tendermint-light-client` crate into its own `no_std`-compatible crate:
+  `tendermint-light-client-verifier`. This helps move us closer to `no_std`
+  compliance in both tendermint-rs and ibc-rs
+  ([#1027](https://github.com/informalsystems/tendermint-rs/issues/1027))
diff --git a/Cargo.toml b/Cargo.toml
@@ -5,6 +5,7 @@ members = [
     "config",
     "light-client",
     "light-client-js",
+    "light-client-verifier",
     "p2p",
     "pbt-gen",
     "proto",

diff --git a/light-client-js/Cargo.toml b/light-client-js/Cargo.toml
@@ -25,7 +25,7 @@ serde_json = { version = "1.0", default-features = false }
 # TODO(thane): Remove once https://github.com/rustwasm/wasm-bindgen/issues/2508 is resolved
 syn = { version = "=1.0.65", default-features = false }
 tendermint = { version = "0.23.0", default-features = false, path = "../tendermint" }
-tendermint-light-client = { version = "0.23.0", default-features = false, path = "../light-client" }
+tendermint-light-client-verifier = { version = "0.23.0", default-features = false, path = "../light-client-verifier" }
 wasm-bindgen = { version = "0.2.63", default-features = false, features = [ "serde-serialize" ] }
 
 # The `console_error_panic_hook` crate provides better debugging of panics by

diff --git a/light-client-js/src/lib.rs b/light-client-js/src/lib.rs
@@ -1,22 +1,22 @@
 //! Tendermint Light Client JavaScript/WASM interface.
 //!
-//! This crate exposes some of the [`tendermint-light-client`] crate's
+//! This crate exposes some of the [`tendermint-light-client-verifier`] crate's
 //! functionality to be used from the JavaScript ecosystem.
 //!
 //! For a detailed example, please see the [`verifier-web` example] in the
 //! repository.
 //!
-//! [`tendermint-light-client`]: https://github.com/informalsystems/tendermint-rs/tree/master/light-client
+//! [`tendermint-light-client-verifier`]: https://github.com/informalsystems/tendermint-rs/tree/master/light-client-verifier
 //! [`verifier-web` example]: https://github.com/informalsystems/tendermint-rs/tree/master/light-client-js/examples/verifier-web
 
 mod utils;
 
 use serde::{Deserialize, Serialize};
 use std::time::Duration;
 use tendermint::Time;
-use tendermint_light_client::components::verifier::{ProdVerifier, Verifier};
-use tendermint_light_client::light_client::Options;
-use tendermint_light_client::types::{LightBlock, TrustThreshold};
+use tendermint_light_client_verifier::options::Options;
+use tendermint_light_client_verifier::types::{LightBlock, TrustThreshold};
+use tendermint_light_client_verifier::{ProdVerifier, Verifier};
 use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsValue;
 

diff --git a/light-client-js/tests/web.rs b/light-client-js/tests/web.rs
@@ -4,9 +4,9 @@
 
 extern crate wasm_bindgen_test;
 use tendermint::Time;
-use tendermint_light_client::components::verifier::Verdict;
-use tendermint_light_client::types::LightBlock;
 use tendermint_light_client_js::{verify, Error, JsOptions};
+use tendermint_light_client_verifier::types::LightBlock;
+use tendermint_light_client_verifier::Verdict;
 use wasm_bindgen::JsValue;
 use wasm_bindgen_test::*;
 

diff --git a/light-client-verifier/Cargo.toml b/light-client-verifier/Cargo.toml
@@ -0,0 +1,38 @@
+[package]
+name       = "tendermint-light-client-verifier"
+version    = "0.23.0"
+edition    = "2021"
+license    = "Apache-2.0"
+readme     = "README.md"
+keywords   = ["blockchain", "bft", "consensus", "cosmos", "tendermint"]
+categories = ["cryptography::cryptocurrencies", "network-programming"]
+repository = "https://github.com/informalsystems/tendermint-rs"
+authors    = [
+  "Informal Systems <[email protected]>",
+]
+
+description = """
+    Implementation of the Tendermint Light Client Verification Algorithm.
+"""
+
+# docs.rs-specific configuration
+[package.metadata.docs.rs]
+# document all features
+all-features = true
+# defines the configuration attribute `docsrs`
+rustdoc-args = ["--cfg", "docsrs"]
+
+[features]
+default = ["flex-error/std", "flex-error/eyre_tracer"]
+
+[dependencies]
+tendermint = { version = "0.23.0", path = "../tendermint", default-features = false }
+tendermint-rpc = { version = "0.23.0", path = "../rpc", default-features = false }
+
+derive_more = { version = "0.99.5", default-features = false, features = ["display"] }
+serde = { version = "1.0.106", default-features = false }
+time = { version = "0.3.5", default-features = false }
+flex-error = { version = "0.4.4", default-features = false }
+
+[dev-dependencies]
+tendermint-testgen = { path = "../testgen", default-features = false }
diff --git a/light-client/src/predicates/errors.rs → light-client-verifier/src/errors.rs b/light-client/src/predicates/errors.rs → light-client-verifier/src/errors.rs
@@ -1,14 +1,14 @@
 //! Errors which may be raised when verifying a `LightBlock`
 
+use core::time::Duration;
 use flex_error::define_error;
 use serde::{Deserialize, Serialize};
-use std::time::Duration;
+use tendermint::account::Id;
+use tendermint::Error as TendermintError;
 
-use crate::errors::ErrorExt;
 use crate::operations::voting_power::VotingPowerTally;
+use crate::prelude::*;
 use crate::types::{Hash, Height, Time, Validator, ValidatorAddress};
-use tendermint::account::Id;
-use tendermint::Error as TendermintError;
 
 define_error! {
     #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
@@ -27,15 +27,6 @@ define_error! {
                     e.header_time, e.now)
             },
 
-        ImplementationSpecific
-            {
-                detail: String,
-            }
-            | e | {
-                format_args!("implementation specific: {0}",
-                    e.detail)
-            },
-
         NotEnoughTrust
             {
                 tally: VotingPowerTally,
@@ -171,6 +162,21 @@ define_error! {
     }
 }
 
+/// Extension methods for `ErrorKind`
+pub trait ErrorExt {
+    /// Whether this error means that the light block
+    /// cannot be trusted w.r.t. the latest trusted state.
+    fn not_enough_trust(&self) -> Option<VotingPowerTally>;
+
+    /// Whether this error means that the light block has expired,
+    /// ie. it's outside of the trusting period.
+    fn has_expired(&self) -> bool;
+
+    /// Whether this error means that a timeout occured when
+    /// querying a node.
+    fn is_timeout(&self) -> Option<Duration>;
+}
+
 impl ErrorExt for VerificationErrorDetail {
     fn not_enough_trust(&self) -> Option<VotingPowerTally> {
         match &self {

diff --git a/light-client-verifier/src/lib.rs b/light-client-verifier/src/lib.rs
@@ -0,0 +1,14 @@
+#![no_std]
+
+extern crate alloc;
+
+mod prelude;
+
+pub mod errors;
+pub mod operations;
+pub mod options;
+pub mod predicates;
+pub mod types;
+mod verifier;
+
+pub use verifier::{PredicateVerifier, ProdVerifier, Verdict, Verifier};
diff --git a/light-client/src/operations.rs → light-client-verifier/src/operations.rs b/light-client/src/operations.rs → light-client-verifier/src/operations.rs
diff --git a/...client/src/operations/commit_validator.rs → ...rifier/src/operations/commit_validator.rs b/...client/src/operations/commit_validator.rs → ...rifier/src/operations/commit_validator.rs
@@ -1,8 +1,8 @@
 //! Provides an interface and default implementation for the `CommitValidator` operation
 
 use crate::{
+    errors::VerificationError,
     operations::{Hasher, ProdHasher},
-    predicates::errors::VerificationError,
     types::{SignedHeader, ValidatorSet},
 };
 

diff --git a/light-client/src/operations/hasher.rs → ...-client-verifier/src/operations/hasher.rs b/light-client/src/operations/hasher.rs → ...-client-verifier/src/operations/hasher.rs
diff --git a/light-client/src/operations/voting_power.rs → ...t-verifier/src/operations/voting_power.rs b/light-client/src/operations/voting_power.rs → ...t-verifier/src/operations/voting_power.rs
@@ -1,15 +1,16 @@
 //! Provides an interface and default implementation for the `VotingPower` operation
 
+use crate::prelude::*;
 use crate::{
-    predicates::errors::VerificationError,
+    errors::VerificationError,
     types::{Commit, SignedHeader, TrustThreshold, ValidatorSet},
 };
 
+use alloc::collections::BTreeSet as HashSet;
+use core::fmt;
 use serde::{Deserialize, Serialize};
-use std::collections::HashSet;
-use std::fmt;
 
-use std::convert::TryFrom;
+use core::convert::TryFrom;
 use tendermint::block::CommitSig;
 use tendermint::trust_threshold::TrustThreshold as _;
 use tendermint::vote::{SignedVote, ValidatorIndex, Vote};
@@ -220,7 +221,7 @@ fn non_absent_vote(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::predicates::errors::VerificationErrorDetail;
+    use crate::errors::VerificationErrorDetail;
     use crate::types::LightBlock;
     use tendermint::trust_threshold::TrustThresholdFraction;
     use tendermint_testgen::light_block::generate_signed_header;

diff --git a/light-client-verifier/src/options.rs b/light-client-verifier/src/options.rs
@@ -0,0 +1,30 @@
+//! Light client implementation as per the [Core Verification specification][1].
+//!
+//! [1]: https://github.com/informalsystems/tendermint-rs/blob/master/docs/spec/lightclient/verification/verification.md
+
+use core::time::Duration;
+
+use derive_more::Display;
+use serde::{Deserialize, Serialize};
+
+use crate::types::TrustThreshold;
+
+/// Verification parameters
+#[derive(Copy, Clone, Debug, PartialEq, Display, Serialize, Deserialize)]
+#[display(fmt = "{:?}", self)]
+pub struct Options {
+    /// Defines what fraction of the total voting power of a known
+    /// and trusted validator set is sufficient for a commit to be
+    /// accepted going forward.
+    pub trust_threshold: TrustThreshold,
+
+    /// How long a validator set is trusted for (must be shorter than the chain's
+    /// unbonding period)
+    pub trusting_period: Duration,
+
+    /// Correction parameter dealing with only approximately synchronized clocks.
+    /// The local clock should always be ahead of timestamps from the blockchain; this
+    /// is the maximum amount that the local clock may drift behind a timestamp from the
+    /// blockchain.
+    pub clock_drift: Duration,
+}
diff --git a/light-client/src/predicates.rs → light-client-verifier/src/predicates.rs b/light-client/src/predicates.rs → light-client-verifier/src/predicates.rs
@@ -1,16 +1,15 @@
 //! Predicates for light block validation and verification.
 
+use crate::errors::VerificationError;
+use crate::prelude::*;
 use crate::{
     operations::{CommitValidator, Hasher, VotingPowerCalculator},
     types::{Header, SignedHeader, Time, TrustThreshold, ValidatorSet},
 };
 
-use errors::VerificationError;
-use std::time::Duration;
+use core::time::Duration;
 use tendermint::{block::Height, hash::Hash};
 
-pub mod errors;
-
 /// Production predicates, using the default implementation
 /// of the `VerificationPredicates` trait.
 #[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
@@ -205,8 +204,8 @@ pub trait VerificationPredicates: Send + Sync {
 
 #[cfg(test)]
 mod tests {
-    use std::convert::TryInto;
-    use std::time::Duration;
+    use core::convert::TryInto;
+    use core::time::Duration;
     use tendermint::block::CommitSig;
     use tendermint::validator::Set;
     use time::OffsetDateTime;
@@ -216,9 +215,10 @@ mod tests {
         Commit, Generator, Header, Validator, ValidatorSet,
     };
 
-    use crate::predicates::{
+    use crate::prelude::*;
+    use crate::{
         errors::{VerificationError, VerificationErrorDetail},
-        ProdPredicates, VerificationPredicates,
+        predicates::{ProdPredicates, VerificationPredicates},
     };
 
     use crate::operations::{

diff --git a/light-client-verifier/src/prelude.rs b/light-client-verifier/src/prelude.rs
@@ -0,0 +1,14 @@
+pub use core::prelude::v1::*;
+
+// Re-export according to alloc::prelude::v1 because it is not yet stabilized
+// https://doc.rust-lang.org/src/alloc/prelude/v1.rs.html
+pub use alloc::borrow::ToOwned;
+pub use alloc::boxed::Box;
+pub use alloc::string::{String, ToString};
+pub use alloc::vec::Vec;
+
+pub use alloc::format;
+pub use alloc::vec;
+
+// will be included in 2021 edition.
+pub use core::convert::{TryFrom, TryInto};
diff --git a/light-client/src/types.rs → light-client-verifier/src/types.rs b/light-client/src/types.rs → light-client-verifier/src/types.rs
@@ -1,5 +1,7 @@
 //! Defines or just re-exports the main datatypes used by the light client.
 
+use crate::prelude::*;
+
 use derive_more::Display;
 use serde::{Deserialize, Serialize};
 
@@ -73,7 +75,7 @@ impl Status {
     ///
     /// From least to most trusted: `Failed`, `Unverified`, `Verified`, `Trusted`.
     pub fn most_trusted(a: Self, b: Self) -> Self {
-        std::cmp::max(a, b)
+        core::cmp::max(a, b)
     }
 }
 
@@ -201,6 +203,7 @@ impl LatestStatus {
 mod tests {
 
     mod status {
+        use crate::prelude::*;
         use crate::types::Status;
         use Status::*;
 

diff --git a/light-client/src/components/verifier.rs → light-client-verifier/src/verifier.rs b/light-client/src/components/verifier.rs → light-client-verifier/src/verifier.rs
@@ -1,21 +1,18 @@
 //! Provides an interface and default implementation of the `Verifier` component
 
+use crate::errors::{ErrorExt, VerificationError, VerificationErrorDetail};
 use crate::operations::voting_power::VotingPowerTally;
 use crate::predicates as preds;
 use crate::types::{TrustedBlockState, UntrustedBlockState};
 use crate::{
-    errors::ErrorExt,
-    light_client::Options,
     operations::{
         CommitValidator, Hasher, ProdCommitValidator, ProdHasher, ProdVotingPowerCalculator,
         VotingPowerCalculator,
     },
+    options::Options,
     types::Time,
 };
-use preds::{
-    errors::{VerificationError, VerificationErrorDetail},
-    ProdPredicates, VerificationPredicates,
-};
+use preds::{ProdPredicates, VerificationPredicates};
 use serde::{Deserialize, Serialize};
 
 /// Represents the result of the verification performed by the

diff --git a/light-client/Cargo.toml b/light-client/Cargo.toml
@@ -36,6 +36,7 @@ mbt = []
 [dependencies]
 tendermint = { version = "0.23.0", path = "../tendermint", default-features = false }
 tendermint-rpc = { version = "0.23.0", path = "../rpc", default-features = false }
+tendermint-light-client-verifier = { version = "0.23.0", path = "../light-client-verifier", default-features = false }
 
 contracts = { version = "0.4.0", default-features = false }
 crossbeam-channel = { version = "0.4.2", default-features = false }

diff --git a/light-client/examples/light_client.rs b/light-client/examples/light_client.rs
@@ -3,15 +3,14 @@ use std::{path::PathBuf, time::Duration};
 use gumdrop::Options;
 
 use tendermint::Hash;
-use tendermint_rpc as rpc;
-
 use tendermint_light_client::supervisor::{Handle as _, Instance};
+use tendermint_light_client::verifier::options::Options as LightClientOptions;
+use tendermint_light_client::verifier::types::{Height, PeerId, TrustThreshold};
 use tendermint_light_client::{
     builder::{LightClientBuilder, SupervisorBuilder},
-    light_client,
     store::memory::MemoryStore,
-    types::{Height, PeerId, TrustThreshold},
 };
+use tendermint_rpc as rpc;
 
 #[derive(Debug, Options)]
 struct CliOptions {
@@ -82,7 +81,7 @@ fn make_instance(
 ) -> Result<Instance, Box<dyn std::error::Error>> {
     let light_store = MemoryStore::new();
     let rpc_client = rpc::HttpClient::new(addr).unwrap();
-    let options = light_client::Options {
+    let options = LightClientOptions {
         trust_threshold: TrustThreshold::default(),
         trusting_period: Duration::from_secs(36000),
         clock_drift: Duration::from_secs(1),

diff --git a/light-client/src/builder/error.rs b/light-client/src/builder/error.rs
@@ -5,7 +5,7 @@ use tendermint::block::Height;
 use tendermint::Hash;
 
 use crate::components::io::IoError;
-use crate::predicates::errors::VerificationError;
+use crate::verifier::errors::VerificationError;
 
 define_error! {
     Error {