#4588

Committed 07 Mar 2024 09:50AM UTC coverage: 44.999% (-0.02%) from 45.016%

Build # #4588

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Commit Message

Merge pull request #5587 from oasisprotocol/ptrus/stable/23.0.x/go-1.21.8

[stable/23.0.x] go: update to 1.21.8

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/keymanager/src/runtime/methods.rs

//! Methods exported to remote clients via EnclaveRPC.
use std::{
    collections::{HashMap, HashSet},
    convert::TryInto,
    sync::Arc,
};

use anyhow::Result;

use oasis_core_runtime::{
    common::{
        crypto::{
            mrae::{
                deoxysii::{self, Opener},
                nonce::Nonce,
            },
            signature::{self, Signer},
            x25519,
        },
        namespace::Namespace,
        sgx::EnclaveIdentity,
    },
    consensus::{
        beacon::EpochTime,
        keymanager::{
            EncryptedEphemeralSecret, EncryptedMasterSecret, EncryptedSecret,
            SignedEncryptedEphemeralSecret, SignedEncryptedMasterSecret,
        },
        state::{
            beacon::ImmutableState as BeaconState,
            keymanager::{ImmutableState as KeyManagerState, Status},
            registry::ImmutableState as RegistryState,
        },
    },
    enclave_rpc::Context as RpcContext,
    future::block_on,
    policy::PolicyVerifier,
    runtime_context, BUILD_INFO,
};

use crate::{
    api::{
        EphemeralKeyRequest, GenerateEphemeralSecretRequest, GenerateEphemeralSecretResponse,
        GenerateMasterSecretRequest, GenerateMasterSecretResponse, InitRequest, InitResponse,
        KeyManagerError, LoadEphemeralSecretRequest, LoadMasterSecretRequest, LongTermKeyRequest,
        ReplicateEphemeralSecretRequest, ReplicateEphemeralSecretResponse,
        ReplicateMasterSecretRequest, ReplicateMasterSecretResponse, SignedInitResponse,
    },
    client::RemoteClient,
    crypto::{
        kdf::{Kdf, State},
        pack_runtime_id_epoch, pack_runtime_id_generation_epoch, unpack_encrypted_secret_nonce,
        KeyPair, Secret, SignedPublicKey, SECRET_SIZE,
    },
    policy::Policy,
    runtime::context::Context as KmContext,
    secrets::{KeyManagerSecretProvider, SecretProvider},
};

/// Maximum age of an ephemeral key in the number of epochs.
const MAX_EPHEMERAL_KEY_AGE: EpochTime = 10;
/// Maximum age of a fresh height in the number of blocks.
///
/// A height is considered fresh if it is not more than specified amount
/// of blocks lower than the height of the latest trust root.
const MAX_FRESH_HEIGHT_AGE: u64 = 50;

/// Initialize the Kdf.
pub fn init_kdf(ctx: &mut RpcContext, req: &InitRequest) -> Result<SignedInitResponse> {
    let rctx = runtime_context!(ctx, KmContext);
    let runtime_id = rctx.runtime_id;
    let storage = ctx.untrusted_local_storage;

    // Note that the first validation of the status will probably fail,
    // as the verifier is one block behind the consensus.
    let status = req.status.clone();
    let status = validate_key_manager_status(ctx, runtime_id, status)?;

    // Empty policies are allowed only in unsafe builds.
    let policy = Policy::global();
    let policy_checksum = policy.init(storage, status.policy)?;

    // Initialize or update the KDF.
    let generation = status.generation;
    let checksum = status.checksum;
    let nodes = status.nodes;
    let epoch = consensus_epoch(ctx)?;
    let client = key_manager_client_for_replication(ctx);
    let provider = KeyManagerSecretProvider::new(client, nodes);

    let kdf = Kdf::global();
    let state = kdf.init(storage, runtime_id, generation, checksum, epoch, &provider)?;

    // State is up-to-date, build the response and sign it with the RAK.
    sign_init_response(ctx, state, policy_checksum)
}

/// See `Kdf::get_or_create_keys`.
pub fn get_or_create_keys(ctx: &mut RpcContext, req: &LongTermKeyRequest) -> Result<KeyPair> {
    authorize_private_key_generation(ctx, &req.runtime_id)?;
    validate_height_freshness(ctx, req.height)?;

    Kdf::global().get_or_create_longterm_keys(
        ctx.untrusted_local_storage,
        req.runtime_id,
        req.key_pair_id,
        req.generation,
    )
}

/// See `Kdf::get_public_key`.
pub fn get_public_key(ctx: &mut RpcContext, req: &LongTermKeyRequest) -> Result<SignedPublicKey> {
    // No authentication or authorization.
    // Absolutely anyone is allowed to query public long-term keys.

    let kdf = Kdf::global();
    let pk = kdf.get_public_longterm_key(
        ctx.untrusted_local_storage,
        req.runtime_id,
        req.key_pair_id,
        req.generation,
    )?;
    let sig = kdf.sign_public_key(pk, req.runtime_id, req.key_pair_id, None)?;
    Ok(sig)
}

/// See `Kdf::get_or_create_ephemeral_keys`.
pub fn get_or_create_ephemeral_keys(
    ctx: &mut RpcContext,
    req: &EphemeralKeyRequest,
) -> Result<KeyPair> {
    authorize_private_key_generation(ctx, &req.runtime_id)?;
    validate_ephemeral_key_epoch(ctx, req.epoch)?;
    validate_height_freshness(ctx, req.height)?;

    Kdf::global().get_or_create_ephemeral_keys(req.runtime_id, req.key_pair_id, req.epoch)
}

/// See `Kdf::get_public_ephemeral_key`.
pub fn get_public_ephemeral_key(
    ctx: &mut RpcContext,
    req: &EphemeralKeyRequest,
) -> Result<SignedPublicKey> {
    // No authentication or authorization.
    // Absolutely anyone is allowed to query public ephemeral keys.
    validate_ephemeral_key_epoch(ctx, req.epoch)?;

    let kdf = Kdf::global();
    let pk = kdf.get_public_ephemeral_key(req.runtime_id, req.key_pair_id, req.epoch)?;
    let mut sig = kdf.sign_public_key(pk, req.runtime_id, req.key_pair_id, Some(req.epoch))?;

    // Outdated key manager clients request public ephemeral keys via secure RPC calls,
    // they never verify their signatures and are not aware that signed ephemeral keys expire.
    // To ensure backwards compatibility we clear the expiration epoch. This should be removed
    // in the future once all clients are upgraded.
    // XXX: Remove this after 23.0.x.
    if ctx.is_secure {
        sig.expiration = None;
    }

    Ok(sig)
}

/// See `Kdf::replicate_master_secret`.
pub fn replicate_master_secret(
    ctx: &mut RpcContext,
    req: &ReplicateMasterSecretRequest,
) -> Result<ReplicateMasterSecretResponse> {
    authorize_secret_replication(ctx)?;
    validate_height_freshness(ctx, req.height)?;

    let master_secret =
        Kdf::global().replicate_master_secret(ctx.untrusted_local_storage, req.generation)?;
    let checksum = Kdf::load_checksum(ctx.untrusted_local_storage, req.generation);

    Ok(ReplicateMasterSecretResponse {
        master_secret,
        checksum,
    })
}

/// See `Kdf::replicate_ephemeral_secret`.
pub fn replicate_ephemeral_secret(
    ctx: &mut RpcContext,
    req: &ReplicateEphemeralSecretRequest,
) -> Result<ReplicateEphemeralSecretResponse> {
    authorize_secret_replication(ctx)?;
    validate_height_freshness(ctx, req.height)?;

    let ephemeral_secret = Kdf::global().replicate_ephemeral_secret(req.epoch)?;
    Ok(ReplicateEphemeralSecretResponse { ephemeral_secret })
}

/// Generate a master secret and encrypt it using the key manager's REK keys.
pub fn generate_master_secret(
    ctx: &mut RpcContext,
    req: &GenerateMasterSecretRequest,
) -> Result<GenerateMasterSecretResponse> {
    let kdf = Kdf::global();
    let runtime_id = kdf.runtime_id()?;

    // Allow generating a secret for the next epoch only.
    let epoch = consensus_epoch(ctx)? + 1;
    if epoch != req.epoch {
        return Err(KeyManagerError::InvalidEpoch(epoch, req.epoch).into());
    }

    // Generate a secret and encrypt it.
    // Note that the checksum can be computed for the next generation only.
    let generation = req.generation;
    let secret = Secret::generate();
    let checksum = kdf.checksum_master_secret_proposal(runtime_id, &secret, generation)?;
    let additional_data = pack_runtime_id_generation_epoch(&runtime_id, generation, epoch);
    let secret = encrypt_secret(ctx, secret, checksum, additional_data, runtime_id)?;

    // Sign the secret.
    let signer: Arc<dyn Signer> = ctx.identity.clone();
    let secret = EncryptedMasterSecret {
        runtime_id,
        generation,
        epoch,
        secret,
    };
    let signed_secret = SignedEncryptedMasterSecret::new(secret, &signer)?;

    Ok(GenerateMasterSecretResponse { signed_secret })
}

/// Generate an ephemeral secret and encrypt it using the key manager's REK keys.
pub fn generate_ephemeral_secret(
    ctx: &mut RpcContext,
    req: &GenerateEphemeralSecretRequest,
) -> Result<GenerateEphemeralSecretResponse> {
    let kdf = Kdf::global();
    let runtime_id = kdf.runtime_id()?;

    // Allow generating a secret for the next epoch only.
    let epoch = consensus_epoch(ctx)? + 1;
    if epoch != req.epoch {
        return Err(KeyManagerError::InvalidEpoch(epoch, req.epoch).into());
    }

    // Generate a secret and encrypt it.
    let secret = Secret::generate();
    let checksum = Kdf::checksum_ephemeral_secret(&runtime_id, &secret, epoch);
    let additional_data = pack_runtime_id_epoch(&runtime_id, epoch);
    let secret = encrypt_secret(ctx, secret, checksum, additional_data, runtime_id)?;

    // Sign the secret.
    let signer: Arc<dyn Signer> = ctx.identity.clone();
    let secret = EncryptedEphemeralSecret {
        runtime_id,
        epoch,
        secret,
    };
    let signed_secret = SignedEncryptedEphemeralSecret::new(secret, &signer)?;

    Ok(GenerateEphemeralSecretResponse { signed_secret })
}

/// Encrypt a secret using the Deoxys-II MRAE algorithm and the key manager's REK keys.
fn encrypt_secret(
    ctx: &mut RpcContext,
    secret: Secret,
    checksum: Vec<u8>,
    additional_data: Vec<u8>,
    runtime_id: Namespace,
) -> Result<EncryptedSecret> {
    // Fetch REK keys of the key manager committee members.
    let rek_keys = key_manager_rek_keys(ctx, runtime_id)?;
    let rek_keys: HashSet<_> = rek_keys.values().collect();
    // Abort if our REK hasn't been published.
    if rek_keys.get(&ctx.identity.public_rek()).is_none() {
        return Err(KeyManagerError::REKNotPublished.into());
    }
    // Encrypt the secret.
    let priv_key = x25519::PrivateKey::generate();
    let pub_key = x25519::PublicKey::from(&priv_key);
    let mut nonce = Nonce::generate();
    let plaintext = secret.0.to_vec();
    let mut ciphertexts = HashMap::new();
    for &rek in rek_keys.iter() {
        nonce.increment()?;

        let mut ciphertext = deoxysii::box_seal(
            &nonce,
            plaintext.clone(),
            additional_data.clone(),
            &rek.0,
            &priv_key.0,
        )?;
        ciphertext.extend_from_slice(&nonce.to_vec());

        ciphertexts.insert(*rek, ciphertext);
    }

    Ok(EncryptedSecret {
        checksum,
        pub_key,
        ciphertexts,
    })
}

/// Decrypt and store a proposal for the next master secret.
pub fn load_master_secret(ctx: &mut RpcContext, req: &LoadMasterSecretRequest) -> Result<()> {
    let signed_secret = validate_signed_master_secret(ctx, &req.signed_secret)?;

    let secret = match decrypt_master_secret(ctx, &signed_secret)? {
        Some(secret) => secret,
        None => return Ok(()),
    };

    Kdf::global().add_master_secret_proposal(
        ctx.untrusted_local_storage,
        &signed_secret.runtime_id,
        secret,
        signed_secret.generation,
        &signed_secret.secret.checksum,
    )
}

/// Decrypt and store an ephemeral secret. If decryption fails, try to replicate the secret
/// from another key manager enclave.
pub fn load_ephemeral_secret(ctx: &mut RpcContext, req: &LoadEphemeralSecretRequest) -> Result<()> {
    let signed_secret = validate_signed_ephemeral_secret(ctx, &req.signed_secret)?;

    let secret = match decrypt_ephemeral_secret(ctx, &signed_secret)? {
        Some(secret) => secret,
        None => {
            let nodes = nodes_with_ephemeral_secret(ctx, &signed_secret)?;
            let client = key_manager_client_for_replication(ctx);

            KeyManagerSecretProvider::new(client, nodes)
                .ephemeral_secret_iter(signed_secret.epoch)
                .find(|secret| {
                    let checksum = Kdf::checksum_ephemeral_secret(
                        &signed_secret.runtime_id,
                        secret,
                        signed_secret.epoch,
                    );
                    checksum == signed_secret.secret.checksum
                })
                .ok_or(KeyManagerError::EphemeralSecretNotReplicated(
                    signed_secret.epoch,
                ))?
        }
    };

    Kdf::global().add_ephemeral_secret(
        &signed_secret.runtime_id,
        secret,
        signed_secret.epoch,
        &signed_secret.secret.checksum,
    )
}

/// Decrypt master secret with local REK key.
fn decrypt_master_secret(
    ctx: &mut RpcContext,
    secret: &EncryptedMasterSecret,
) -> Result<Option<Secret>> {
    let generation = secret.generation;
    let epoch = secret.epoch;
    let runtime_id = secret.runtime_id;
    let rek = ctx.identity.public_rek();

    let ciphertext = match secret.secret.ciphertexts.get(&rek) {
        Some(ciphertext) => ciphertext,
        None => return Ok(None),
    };

    let (ciphertext, nonce) =
        unpack_encrypted_secret_nonce(ciphertext).ok_or(KeyManagerError::InvalidCiphertext)?;
    let additional_data = pack_runtime_id_generation_epoch(&runtime_id, generation, epoch);
    let plaintext = ctx.identity.box_open(
        &nonce,
        ciphertext,
        additional_data,
        &secret.secret.pub_key.0,
    )?;

    if plaintext.len() != SECRET_SIZE {
        return Err(KeyManagerError::InvalidCiphertext.into());
    }

    let secret = Secret(plaintext.try_into().expect("slice with incorrect length"));

    Ok(Some(secret))
}

/// Decrypt ephemeral secret with local REK key.
fn decrypt_ephemeral_secret(
    ctx: &mut RpcContext,
    secret: &EncryptedEphemeralSecret,
) -> Result<Option<Secret>> {
    let epoch = secret.epoch;
    let runtime_id = secret.runtime_id;
    let rek = ctx.identity.public_rek();

    let ciphertext = match secret.secret.ciphertexts.get(&rek) {
        Some(ciphertext) => ciphertext,
        None => return Ok(None),
    };

    let (ciphertext, nonce) =
        unpack_encrypted_secret_nonce(ciphertext).ok_or(KeyManagerError::InvalidCiphertext)?;
    let additional_data = pack_runtime_id_epoch(&runtime_id, epoch);
    let plaintext = ctx.identity.box_open(
        &nonce,
        ciphertext,
        additional_data,
        &secret.secret.pub_key.0,
    )?;

    if plaintext.len() != SECRET_SIZE {
        return Err(KeyManagerError::InvalidCiphertext.into());
    }

    let secret = Secret(plaintext.try_into().expect("slice with incorrect length"));

    Ok(Some(secret))
}

/// Key manager client for master and ephemeral secret replication.
fn key_manager_client_for_replication(ctx: &mut RpcContext) -> RemoteClient {
    let rctx = runtime_context!(ctx, KmContext);
    let protocol = rctx.protocol.clone();
    let runtime_id = rctx.runtime_id;

    RemoteClient::new_runtime_with_enclaves_and_policy(
        runtime_id,
        Some(runtime_id),
        Policy::global().may_replicate_from(),
        ctx.identity.quote_policy(),
        protocol,
        ctx.consensus_verifier.clone(),
        ctx.identity.clone(),
        1, // Not used, doesn't matter.
        vec![],
    )
}

/// Create init response and sign it with RAK.
fn sign_init_response(
    ctx: &mut RpcContext,
    state: State,
    policy_checksum: Vec<u8>,
) -> Result<SignedInitResponse> {
    let is_secure = BUILD_INFO.is_secure && !Policy::unsafe_skip();
    let init_response = InitResponse {
        is_secure,
        checksum: state.checksum,
        next_checksum: state.next_checksum,
        policy_checksum,
        rsk: state.signing_key,
        next_rsk: state.next_signing_key,
    };
    let signer: Arc<dyn Signer> = ctx.identity.clone();
    SignedInitResponse::new(init_response, &signer)
}

/// Authorize the remote enclave so that the private keys are never released to an incorrect enclave.
fn authorize_private_key_generation(ctx: &RpcContext, runtime_id: &Namespace) -> Result<()> {
    if Policy::unsafe_skip() {
        return Ok(()); // Authorize unsafe builds always.
    }
    let remote_enclave = authenticate(ctx)?;
    Policy::global().may_get_or_create_keys(remote_enclave, runtime_id)
}

/// Authorize the remote enclave so that the master and ephemeral secrets are never replicated
/// to an incorrect enclave.
fn authorize_secret_replication(ctx: &RpcContext) -> Result<()> {
    if Policy::unsafe_skip() {
        return Ok(()); // Authorize unsafe builds always.
    }
    let remote_enclave = authenticate(ctx)?;
    Policy::global().may_replicate_secret(remote_enclave)
}

/// Authenticate the remote enclave based on the MRSIGNER/MRENCLAVE/request.
fn authenticate<'a>(ctx: &'a RpcContext) -> Result<&'a EnclaveIdentity> {
    let si = ctx.session_info.as_ref();
    let si = si.ok_or(KeyManagerError::NotAuthenticated)?;
    Ok(&si.verified_quote.identity)
}

/// Fetch current epoch from the consensus layer.
fn consensus_epoch(ctx: &RpcContext) -> Result<EpochTime> {
    let consensus_state = block_on(ctx.consensus_verifier.latest_state())?;
    let beacon_state = BeaconState::new(&consensus_state);
    let consensus_epoch = beacon_state.epoch()?;

    Ok(consensus_epoch)
}

/// Verify that the key manager status has been published in the consensus layer.
fn validate_key_manager_status(
    ctx: &RpcContext,
    runtime_id: Namespace,
    status: Status,
) -> Result<Status> {
    let consensus_verifier = ctx.consensus_verifier.clone();
    let verifier = PolicyVerifier::new(consensus_verifier);

    verifier.verify_key_manager_status(status, runtime_id)
}

/// Validate that the epoch used for derivation of ephemeral private keys is not
/// in the future or too far back in the past.
fn validate_ephemeral_key_epoch(ctx: &RpcContext, epoch: EpochTime) -> Result<()> {
    let consensus_epoch = consensus_epoch(ctx)?;
    if consensus_epoch < epoch || consensus_epoch > epoch + MAX_EPHEMERAL_KEY_AGE {
        return Err(KeyManagerError::InvalidEpoch(consensus_epoch, epoch).into());
    }
    Ok(())
}

/// Validate that given height is fresh, i.e. the height is not more than
/// predefined number of blocks lower than the height of the latest trust root.
///
/// Key manager should use this validation to detect whether the runtimes
/// querying it have a fresh enough state.
fn validate_height_freshness(ctx: &RpcContext, height: Option<u64>) -> Result<()> {
    // Outdated key manager clients will not send height in their requests.
    // To ensure backwards compatibility we skip check in those cases.
    // This should be removed in the future by making height mandatory.
    if let Some(height) = height {
        let latest_height = block_on(ctx.consensus_verifier.latest_height())?;
        if latest_height > MAX_FRESH_HEIGHT_AGE && height < latest_height - MAX_FRESH_HEIGHT_AGE {
            return Err(KeyManagerError::HeightNotFresh.into());
        }
    }
    Ok(())
}

/// Verify that the master secret has been published in the consensus layer.
fn validate_signed_master_secret(
    ctx: &RpcContext,
    signed_secret: &SignedEncryptedMasterSecret,
) -> Result<EncryptedMasterSecret> {
    let consensus_state = block_on(ctx.consensus_verifier.latest_state())?;
    let km_state = KeyManagerState::new(&consensus_state);
    let published_signed_secret = km_state
        .master_secret(signed_secret.secret.runtime_id)?
        .filter(|published_signed_secret| published_signed_secret == signed_secret)
        .ok_or(KeyManagerError::MasterSecretNotPublished)?;

    Ok(published_signed_secret.secret)
}

/// Validate that the ephemeral secret has been published in the consensus layer.
fn validate_signed_ephemeral_secret(
    ctx: &RpcContext,
    signed_secret: &SignedEncryptedEphemeralSecret,
) -> Result<EncryptedEphemeralSecret> {
    let consensus_state = block_on(ctx.consensus_verifier.latest_state())?;
    let km_state = KeyManagerState::new(&consensus_state);
    let published_signed_secret = km_state
        .ephemeral_secret(signed_secret.secret.runtime_id)?
        .filter(|published_signed_secret| published_signed_secret == signed_secret)
        .ok_or(KeyManagerError::EphemeralSecretNotPublished)?;

    Ok(published_signed_secret.secret)
}

/// Fetch the identities of the key manager nodes.
fn key_manager_nodes(ctx: &RpcContext, id: Namespace) -> Result<Vec<signature::PublicKey>> {
    let consensus_state = block_on(ctx.consensus_verifier.latest_state())?;
    let km_state = KeyManagerState::new(&consensus_state);
    let status = km_state
        .status(id)?
        .ok_or(KeyManagerError::StatusNotFound)?;

    Ok(status.nodes)
}

/// Fetch REK keys of the key manager enclaves from the consensus layer.
fn key_manager_rek_keys(
    ctx: &RpcContext,
    id: Namespace,
) -> Result<HashMap<signature::PublicKey, x25519::PublicKey>> {
    let nodes = key_manager_nodes(ctx, id)?;

    let consensus_state = block_on(ctx.consensus_verifier.latest_state())?;
    let registry_state = RegistryState::new(&consensus_state);

    let mut rek_map = HashMap::new();
    for pk in nodes.iter() {
        let node = registry_state.node(pk)?;
        let runtimes = node
            .map(|n| n.runtimes)
            .unwrap_or_default()
            .unwrap_or_default();
        // Skipping version check as key managers are running exactly one version of the runtime.
        let runtime = runtimes.iter().find(|nr| nr.id == id);

        // In an SGX environment we use REK key from the consensus layer.
        #[cfg(target_env = "sgx")]
        let rek = runtime
            .map(|nr| nr.capabilities.tee.as_ref())
            .unwrap_or_default()
            .map(|c| c.rek)
            .unwrap_or_default();

        // Otherwise we use the same insecure REK key for all enclaves.
        #[cfg(not(target_env = "sgx"))]
        let rek = runtime.map(|_| ctx.identity.public_rek());

        if let Some(rek) = rek {
            rek_map.insert(*pk, rek);
        }
    }

    Ok(rek_map)
}

/// Fetch the identities of the key manager nodes that can decrypt the given ephemeral secret.
fn nodes_with_ephemeral_secret(
    ctx: &RpcContext,
    secret: &EncryptedEphemeralSecret,
) -> Result<Vec<signature::PublicKey>> {
    let rek_keys = key_manager_rek_keys(ctx, secret.runtime_id)?;
    let nodes = rek_keys
        .iter()
        .filter(|(_, rek)| secret.secret.ciphertexts.contains_key(rek))
        .map(|(&node, _)| node)
        .collect();

    Ok(nodes)
}

oasisprotocol / oasis-core / #4588

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