feat: Check delegation in DelegatedIdentity

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 * Added `AgentBuilder::with_max_polling_time` to config the maximum time to wait for a response from the replica.
+* `DelegatedIdentity::new` now checks the delegation chain. The old behavior is available under `new_unchecked`.
 
 ## [0.38.2] - 2024-09-30
 

Cargo.toml

@@ -32,7 +32,9 @@ candid_parser = "0.1.1"
 clap = "4.4.3"
 futures-util = "0.3.21"
 hex = "0.4.3"
+k256 = "0.13.4"
 leb128 = "0.2.5"
+p256 = "0.13.2"
 reqwest = { version = "0.12", default-features = false }
 ring = "0.17.7"
 serde = "1.0.162"

ic-agent/Cargo.toml

@@ -23,16 +23,18 @@ async-watch = { version = "0.3", optional = true }
 backoff = "0.4.0"
 cached = { version = "0.52", features = ["ahash"], default-features = false }
 candid = { workspace = true }
+ecdsa = "0.16"
 ed25519-consensus = { version = "2" }
+elliptic-curve = "0.13"
 futures-util = { workspace = true }
 hex = { workspace = true }
 http = "1.0.0"
 http-body = "1.0.0"
 ic-certification = { workspace = true }
 ic-transport-types = { workspace = true }
 ic-verify-bls-signature = "0.5"
-k256 = { version = "0.13.1", features = ["pem"] }
-p256 = { version = "0.13.2", features = ["pem"] }
+k256 = { workspace = true, features = ["pem"] }
+p256 = { workspace = true, features = ["pem"] }
 leb128 = { workspace = true }
 pkcs8 = { version = "0.10.2", features = ["std"] }
 sec1 = { version = "0.7.2", features = ["pem"] }

ic-agent/src/identity/delegated.rs

@@ -1,8 +1,16 @@
 use candid::Principal;
+use ecdsa::signature::Verifier;
+use k256::Secp256k1;
+use p256::NistP256;
+use pkcs8::{spki::SubjectPublicKeyInfoRef, AssociatedOid, ObjectIdentifier};
+use sec1::{
+    der::{Decode, SliceReader},
+    EcParameters, EncodedPoint,
+};
 
 use crate::{agent::EnvelopeContent, Signature};
 
-use super::{Delegation, Identity, SignedDelegation};
+use super::{error::DelegationError, Delegation, Identity, SignedDelegation};
 
 /// An identity that has been delegated the authority to authenticate as a different principal.
 pub struct DelegatedIdentity {
@@ -14,8 +22,93 @@ pub struct DelegatedIdentity {
 impl DelegatedIdentity {
     /// Creates a delegated identity that signs using `to`, for the principal corresponding to the public key `from_key`.
     ///
-    /// `chain` must be a list of delegations connecting `from_key` to `to.public_key()`, and in that order.
-    pub fn new(from_key: Vec<u8>, to: Box<dyn Identity>, chain: Vec<SignedDelegation>) -> Self {
+    /// `chain` must be a list of delegations connecting `from_key` to `to.public_key()`, and in that order;
+    /// otherwise, this function will return an error.
+    pub fn new(
+        from_key: Vec<u8>,
+        to: Box<dyn Identity>,
+        chain: Vec<SignedDelegation>,
+    ) -> Result<Self, DelegationError> {
+        let mut last_verified = &from_key;
+        for delegation in &chain {
+            let spki = SubjectPublicKeyInfoRef::decode(
+                &mut SliceReader::new(&last_verified[..]).map_err(|_| DelegationError::Parse)?,
+            )
+            .map_err(|_| DelegationError::Parse)?;
+            if spki.algorithm.oid == elliptic_curve::ALGORITHM_OID {
+                let Some(params) = spki.algorithm.parameters else {
+                    return Err(DelegationError::UnknownAlgorithm);
+                };
+                let params = params
+                    .decode_as::<EcParameters>()
+                    .map_err(|_| DelegationError::Parse)?;
+                let curve = params
+                    .named_curve()
+                    .ok_or(DelegationError::UnknownAlgorithm)?;
+                if curve == Secp256k1::OID {
+                    let pt = EncodedPoint::from_bytes(spki.subject_public_key.raw_bytes())
+                        .map_err(|_| DelegationError::Parse)?;
+                    let vk = k256::ecdsa::VerifyingKey::from_encoded_point(&pt)
+                        .map_err(|_| DelegationError::Parse)?;
+                    let sig = k256::ecdsa::Signature::try_from(&delegation.signature[..])
+                        .map_err(|_| DelegationError::Parse)?;
+                    vk.verify(&delegation.delegation.signable(), &sig)
+                        .map_err(|_| DelegationError::BrokenChain {
+                            from: last_verified.clone(),
+                            to: Some(delegation.delegation.clone()),
+                        })?;
+                } else if curve == NistP256::OID {
+                    let pt = EncodedPoint::from_bytes(spki.subject_public_key.raw_bytes())
+                        .map_err(|_| DelegationError::Parse)?;
+                    let vk = p256::ecdsa::VerifyingKey::from_encoded_point(&pt)
+                        .map_err(|_| DelegationError::Parse)?;
+                    let sig = p256::ecdsa::Signature::try_from(&delegation.signature[..])
+                        .map_err(|_| DelegationError::Parse)?;
+                    vk.verify(&delegation.delegation.signable(), &sig)
+                        .map_err(|_| DelegationError::BrokenChain {
+                            from: last_verified.clone(),
+                            to: Some(delegation.delegation.clone()),
+                        })?;
+                } else {
+                    return Err(DelegationError::UnknownAlgorithm);
+                }
+            } else if spki.algorithm.oid == ObjectIdentifier::new_unwrap("1.3.101.112") {
+                let vk = ed25519_consensus::VerificationKey::try_from(
+                    spki.subject_public_key.raw_bytes(),
+                )
+                .map_err(|_| DelegationError::Parse)?;
+                let sig = ed25519_consensus::Signature::try_from(&delegation.signature[..])
+                    .map_err(|_| DelegationError::Parse)?;
+                vk.verify(&sig, &delegation.delegation.signable())
+                    .map_err(|_| DelegationError::BrokenChain {
+                        from: last_verified.clone(),
+                        to: Some(delegation.delegation.clone()),
+                    })?
+            } else {
+                return Err(DelegationError::UnknownAlgorithm);
+            }
+            last_verified = &delegation.delegation.pubkey;
+        }
+        let delegated_principal = Principal::self_authenticating(last_verified);
+        if delegated_principal != to.sender().map_err(DelegationError::IdentityError)? {
+            return Err(DelegationError::BrokenChain {
+                from: last_verified.clone(),
+                to: None,
+            });
+        }
+
+        Ok(Self::new_unchecked(from_key, to, chain))
+    }
+
+    /// Creates a delegated identity that signs using `to`, for the principal corresponding to the public key `from_key`.
+    ///
+    /// `chain` must be a list of delegations connecting `from_key` to `to.public_key()`, and in that order;
+    /// otherwise, the replica will reject this delegation when used as an identity.
+    pub fn new_unchecked(
+        from_key: Vec<u8>,
+        to: Box<dyn Identity>,
+        chain: Vec<SignedDelegation>,
+    ) -> Self {
         Self {
             to,
             from_key,

ic-agent/src/identity/error.rs

@@ -1,6 +1,8 @@
+use ic_transport_types::Delegation;
 use thiserror::Error;
 
 /// An error happened while reading a PEM file.
+#[cfg(feature = "pem")]
 #[derive(Error, Debug)]
 pub enum PemError {
     /// An error occurred with disk I/O.
@@ -24,3 +26,25 @@ pub enum PemError {
     #[error("A key was rejected by k256: {0}")]
     ErrorStack(#[from] k256::pkcs8::Error),
 }
+
+/// An error occurred constructing a [`DelegatedIdentity`](super::delegated::DelegatedIdentity).
+#[derive(Error, Debug)]
+pub enum DelegationError {
+    /// Parsing error in delegation bytes.
+    #[error("A delegation could not be parsed")]
+    Parse,
+    /// A key in the chain did not match the signature of the next chain link.
+    #[error("A link was missing in the delegation chain")]
+    BrokenChain {
+        /// The key that should have matched the next delegation
+        from: Vec<u8>,
+        /// The delegation that didn't match, or `None` if the `Identity` didn't match
+        to: Option<Delegation>,
+    },
+    /// A key with an unknown algorithm was used. The IC supports Ed25519, secp256k1, and prime256v1, and in ECDSA the curve must be specified.
+    #[error("The delegation chain contained a key with an unknown algorithm")]
+    UnknownAlgorithm,
+    /// One of `Identity`'s functions returned an error.
+    #[error("A delegated-to identity encountered an error: {0}")]
+    IdentityError(String),
+}

ic-agent/src/identity/mod.rs

@@ -6,26 +6,27 @@ use crate::{agent::EnvelopeContent, export::Principal};
 pub(crate) mod anonymous;
 pub(crate) mod basic;
 pub(crate) mod delegated;
+pub(crate) mod error;
 pub(crate) mod prime256v1;
 pub(crate) mod secp256k1;
 
-#[cfg(feature = "pem")]
-pub(crate) mod error;
-
 #[doc(inline)]
 pub use anonymous::AnonymousIdentity;
 #[doc(inline)]
 pub use basic::BasicIdentity;
 #[doc(inline)]
 pub use delegated::DelegatedIdentity;
 #[doc(inline)]
+pub use error::DelegationError;
+#[doc(inline)]
 pub use ic_transport_types::{Delegation, SignedDelegation};
 #[doc(inline)]
 pub use prime256v1::Prime256v1Identity;
 #[doc(inline)]
 pub use secp256k1::Secp256k1Identity;
 
 #[cfg(feature = "pem")]
+#[doc(inline)]
 pub use error::PemError;
 
 /// A cryptographic signature, signed by an [Identity].

ref-tests/Cargo.toml

@@ -11,6 +11,8 @@ candid = { workspace = true }
 ic-agent = { path = "../ic-agent" }
 ic-identity-hsm = { path = "../ic-identity-hsm" }
 ic-utils = { path = "../ic-utils", features = ["raw"] }
+k256 = { workspace = true }
+p256 = { workspace = true }
 ring = { workspace = true }
 serde = { workspace = true, features = ["derive"] }
 sha2 = { workspace = true }

ref-tests/tests/integration.rs

@@ -674,7 +674,10 @@ mod sign_send {
 mod identity {
     use candid::Principal;
     use ic_agent::{
-        identity::{BasicIdentity, DelegatedIdentity, Delegation, SignedDelegation},
+        identity::{
+            BasicIdentity, DelegatedIdentity, Delegation, Prime256v1Identity, Secp256k1Identity,
+            SignedDelegation,
+        },
         Identity,
     };
     use ref_tests::{universal_canister::payload, with_universal_canister_as};
@@ -685,7 +688,7 @@ mod identity {
 
     #[ignore]
     #[test]
-    fn delegated_identity() {
+    fn delegated_eddsa_identity() {
         let random = SystemRandom::new();
         let mut seed = [0; 32];
         random.fill(&mut seed).unwrap();
@@ -707,7 +710,49 @@ mod identity {
                 delegation,
                 signature: signature.signature.unwrap(),
             }],
+        )
+        .unwrap();
+        with_universal_canister_as(delegated_identity, |agent, canister| async move {
+            let payload = payload().caller().append_and_reply().build();
+            let caller_resp = agent
+                .query(&canister, "query")
+                .with_arg(payload)
+                .call()
+                .await
+                .unwrap();
+            let caller = Principal::from_slice(&caller_resp);
+            assert_eq!(caller, sending_identity.sender().unwrap());
+            Ok(())
+        })
+    }
+
+    #[ignore]
+    #[test]
+    fn delegated_ecdsa_identity() {
+        let random = SystemRandom::new();
+        let mut seed = [0; 32];
+        random.fill(&mut seed).unwrap();
+        let sending_identity =
+            Secp256k1Identity::from_private_key(k256::SecretKey::from_bytes(&seed.into()).unwrap());
+        random.fill(&mut seed).unwrap();
+        let signing_identity = Prime256v1Identity::from_private_key(
+            p256::SecretKey::from_bytes(&seed.into()).unwrap(),
         );
+        let delegation = Delegation {
+            expiration: i64::MAX as u64,
+            pubkey: signing_identity.public_key().unwrap(),
+            targets: None,
+        };
+        let signature = sending_identity.sign_delegation(&delegation).unwrap();
+        let delegated_identity = DelegatedIdentity::new(
+            signature.public_key.unwrap(),
+            Box::new(signing_identity),
+            vec![SignedDelegation {
+                delegation,
+                signature: signature.signature.unwrap(),
+            }],
+        )
+        .unwrap();
         with_universal_canister_as(delegated_identity, |agent, canister| async move {
             let payload = payload().caller().append_and_reply().build();
             let caller_resp = agent