canton_core/

config.rs

//! Shared client connection configuration (the Option-B connection kernel).
//!
//! Endpoint, authentication, TLS, and retry live here so every gRPC client in
//! the SDK (`canton-ledger`, `canton-admin`) builds its channel the same way.
//! Authentication is decoupled from any concrete provider via the
//! [`TokenSource`] trait — `canton-auth`'s token provider implements it, which
//! keeps `canton-core` free of a `canton-auth` dependency (that would be a
//! cycle) while letting [`Config`] carry any token source.

use std::fmt;
use std::future::Future;
use std::pin::Pin;
use std::sync::Arc;
use std::time::Duration;

use tonic::transport::{Certificate, Channel, ClientTlsConfig, Endpoint, Identity};

use crate::retry::RetryConfig;
use crate::{Error, Result};

/// A source of bearer tokens for request authentication.
///
/// Implemented by `canton_auth::TokenProvider` (OIDC client-credentials with
/// caching + refresh). Object-safe by design: [`Auth::Dynamic`] stores it as an
/// `Arc<dyn TokenSource>`.
pub trait TokenSource: Send + Sync + fmt::Debug {
    /// Resolve the current bearer token (fetching/refreshing as needed), or
    /// `None` for an unauthenticated call.
    fn fetch_bearer(&self) -> Pin<Box<dyn Future<Output = Result<Option<String>>> + Send + '_>>;
}

/// How the client authenticates each request.
///
/// `#[non_exhaustive]` so new auth modes can be added without a breaking change;
/// construct via [`Config::with_token`] / [`Config::with_oidc`] (or match with a
/// wildcard arm).
#[derive(Clone)]
#[non_exhaustive]
pub enum Auth {
    /// No authentication (unauthenticated endpoints, or shared-secret off).
    None,
    /// A fixed bearer token supplied by the caller.
    Static(String),
    /// A dynamic token source (e.g. OIDC client-credentials with auto-refresh).
    Dynamic(Arc<dyn TokenSource>),
}

impl Auth {
    /// Resolve the current bearer token, if any.
    ///
    /// # Errors
    /// Propagates any error from the underlying [`TokenSource`].
    pub async fn bearer(&self) -> Result<Option<String>> {
        match self {
            Auth::None => Ok(None),
            Auth::Static(token) => Ok(Some(token.clone())),
            Auth::Dynamic(source) => source.fetch_bearer().await,
        }
    }
}

impl fmt::Debug for Auth {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Auth::None => f.write_str("None"),
            Auth::Static(_) => f.write_str("Static(<redacted>)"),
            Auth::Dynamic(source) => write!(f, "Dynamic({source:?})"),
        }
    }
}

/// TLS settings for the gRPC channel.
///
/// An empty `TlsConfig` (from [`TlsConfig::new`]) enables server-side TLS using
/// the platform's native root certificates. Add a custom CA for private/self-
/// signed servers, a domain-name override for SNI/verification, and a client
/// identity for mutual TLS. `#[non_exhaustive]`.
#[derive(Clone, Default)]
#[non_exhaustive]
pub struct TlsConfig {
    /// Custom CA certificate chain (PEM). When set, replaces the native roots
    /// (use for self-signed / private CAs).
    pub ca_certificate_pem: Option<Vec<u8>>,
    /// Domain name to verify the server certificate against (SNI). Defaults to
    /// the endpoint host.
    pub domain_name: Option<String>,
    /// Client identity `(certificate_pem, private_key_pem)` for mutual TLS.
    pub client_identity_pem: Option<(Vec<u8>, Vec<u8>)>,
}

/// Hand-written so PEM bytes never reach a log. The derived `Debug` printed
/// `client_identity_pem` in full, which is the mutual-TLS **private key** — one
/// `tracing` field capturing a `Config` was enough to put it in a log
/// aggregator. Presence and length are what a reader debugging a handshake
/// actually needs.
impl std::fmt::Debug for TlsConfig {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        fn pem(bytes: Option<&Vec<u8>>) -> String {
            bytes.map_or_else(|| "None".to_string(), |b| format!("<{} bytes>", b.len()))
        }
        f.debug_struct("TlsConfig")
            .field("ca_certificate_pem", &pem(self.ca_certificate_pem.as_ref()))
            .field("domain_name", &self.domain_name)
            .field(
                "client_identity_pem",
                &self.client_identity_pem.as_ref().map_or_else(
                    || "None".to_string(),
                    |(cert, key)| {
                        format!(
                            "Some((<{} bytes>, <{} bytes, redacted>))",
                            cert.len(),
                            key.len()
                        )
                    },
                ),
            )
            .finish()
    }
}

impl TlsConfig {
    /// Server-side TLS using the platform's native root certificates.
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Trust this PEM CA certificate (chain) instead of the native roots.
    #[must_use]
    pub fn with_ca_certificate(mut self, ca_pem: impl Into<Vec<u8>>) -> Self {
        self.ca_certificate_pem = Some(ca_pem.into());
        self
    }

    /// Override the domain name the server certificate is verified against.
    #[must_use]
    pub fn with_domain_name(mut self, domain: impl Into<String>) -> Self {
        self.domain_name = Some(domain.into());
        self
    }

    /// Present a client identity (mutual TLS): `(certificate_pem, key_pem)`.
    #[must_use]
    pub fn with_client_identity(
        mut self,
        certificate_pem: impl Into<Vec<u8>>,
        private_key_pem: impl Into<Vec<u8>>,
    ) -> Self {
        self.client_identity_pem = Some((certificate_pem.into(), private_key_pem.into()));
        self
    }
}

/// Build a `ClientTlsConfig` from a [`TlsConfig`] (or native roots when TLS is
/// implicit for an `https` endpoint).
fn build_tls(tls: Option<&TlsConfig>) -> ClientTlsConfig {
    let mut config = ClientTlsConfig::new();
    match tls.and_then(|t| t.ca_certificate_pem.as_ref()) {
        Some(ca) => config = config.ca_certificate(Certificate::from_pem(ca.clone())),
        None => config = config.with_native_roots(),
    }
    if let Some(domain) = tls.and_then(|t| t.domain_name.as_ref()) {
        config = config.domain_name(domain.clone());
    }
    if let Some((cert, key)) = tls.and_then(|t| t.client_identity_pem.as_ref()) {
        config = config.identity(Identity::from_pem(cert.clone(), key.clone()));
    }
    config
}

/// Replace the userinfo of a URL with `***`, so a connection string can be put
/// in an error message or a log line without carrying credentials with it.
///
/// `https://alice:s3cret@host:3901/x` becomes `https://***@host:3901/x`; a URL
/// without userinfo is returned untouched, and so is anything that does not
/// parse as one. Deliberately not a real URL parse: this is used on the failure
/// path of *invalid* URIs, where a parser would have nothing to work with.
#[must_use]
pub fn redact_url(url: &str) -> std::borrow::Cow<'_, str> {
    let Some(scheme_end) = url.find("://") else {
        return std::borrow::Cow::Borrowed(url);
    };
    let authority_start = scheme_end + 3;
    let authority_end = url[authority_start..]
        .find(['/', '?', '#'])
        .map_or(url.len(), |i| authority_start + i);
    let authority = &url[authority_start..authority_end];
    let Some(at) = authority.rfind('@') else {
        return std::borrow::Cow::Borrowed(url);
    };
    std::borrow::Cow::Owned(format!(
        "{}***{}",
        &url[..authority_start],
        &url[authority_start + at..]
    ))
}

/// Configuration for an SDK gRPC client (shared by `canton-ledger` and
/// `canton-admin`).
#[derive(Clone)]
pub struct Config {
    endpoint: String,
    auth: Auth,
    retry: Option<RetryConfig>,
    tls: Option<TlsConfig>,
    timeout: Option<Duration>,
    max_decoding_message_size: usize,
}

/// The largest gRPC response this SDK will decode, unless configured otherwise.
///
/// `tonic` defaults to 4 MiB, which a Ledger API client meets in ordinary use:
/// one `GetActiveContractsPageResponse` carries a whole page, the participant
/// permits page sizes up to 10 000, and a page of that size on a modest ledger
/// is several times over the limit. It surfaces as a client-side
/// `OUT_OF_RANGE` — "decoded message length too large" — which reads like a
/// server fault and is not retriable, so the caller has nothing useful to do
/// with it.
///
/// 128 MiB is a bound that a real page, transaction or created-event blob
/// stays under while still refusing a response large enough to be a memory
/// problem.
pub const DEFAULT_MAX_DECODING_MESSAGE_SIZE: usize = 128 * 1024 * 1024;

/// Hand-written so the endpoint's userinfo is redacted. `auth` and `tls` redact
/// themselves; the endpoint was the remaining way a credential reached a log
/// through a `Config`, and a `Config` is exactly the thing an application
/// attaches to a tracing span while debugging a connection.
impl std::fmt::Debug for Config {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("Config")
            .field("endpoint", &redact_url(&self.endpoint))
            .field("auth", &self.auth)
            .field("retry", &self.retry)
            .field("tls", &self.tls)
            .field("timeout", &self.timeout)
            .field("max_decoding_message_size", &self.max_decoding_message_size)
            .finish()
    }
}

impl Config {
    /// Create a configuration targeting `endpoint`, with no authentication and
    /// no retrying.
    pub fn new(endpoint: impl Into<String>) -> Self {
        Self {
            endpoint: endpoint.into(),
            auth: Auth::None,
            retry: None,
            tls: None,
            timeout: None,
            max_decoding_message_size: DEFAULT_MAX_DECODING_MESSAGE_SIZE,
        }
    }

    /// Authenticate with a fixed bearer token.
    #[must_use]
    pub fn with_token(mut self, token: impl Into<String>) -> Self {
        self.auth = Auth::Static(token.into());
        self
    }

    /// Authenticate with a dynamic token source (e.g. an OIDC provider with
    /// client-credentials and auto-refresh).
    #[must_use]
    pub fn with_oidc<T: TokenSource + 'static>(mut self, provider: T) -> Self {
        self.auth = Auth::Dynamic(Arc::new(provider));
        self
    }

    /// Enable retrying of unary calls on retriable errors, per `retry`.
    #[must_use]
    pub fn with_retry(mut self, retry: RetryConfig) -> Self {
        self.retry = Some(retry);
        self
    }

    /// Use TLS for the gRPC channel (server-side and, if configured, mutual).
    #[must_use]
    pub fn with_tls(mut self, tls: TlsConfig) -> Self {
        self.tls = Some(tls);
        self
    }

    /// Set the per-request timeout on the gRPC channel (default 30s). Long
    /// `submitAndWait` calls under load may need a higher bound.
    #[must_use]
    pub fn with_timeout(mut self, timeout: Duration) -> Self {
        self.timeout = Some(timeout);
        self
    }

    /// The largest gRPC response to decode, in bytes
    /// (default [`DEFAULT_MAX_DECODING_MESSAGE_SIZE`], 128 MiB).
    ///
    /// Raise it for a participant that returns very large ACS pages or
    /// transactions; lower it to bound the memory a single response can claim.
    #[must_use]
    pub fn with_max_decoding_message_size(mut self, bytes: usize) -> Self {
        self.max_decoding_message_size = bytes;
        self
    }

    /// The largest gRPC response this configuration will decode, in bytes.
    #[must_use]
    pub fn max_decoding_message_size(&self) -> usize {
        self.max_decoding_message_size
    }

    /// The gRPC endpoint of the target service, e.g. `http://localhost:3901`.
    #[must_use]
    pub fn endpoint(&self) -> &str {
        &self.endpoint
    }

    /// The configured authentication mode.
    #[must_use]
    pub fn auth(&self) -> &Auth {
        &self.auth
    }

    /// The configured retry policy, if any.
    #[must_use]
    pub fn retry(&self) -> Option<&RetryConfig> {
        self.retry.as_ref()
    }

    /// Build a lazily-connected gRPC [`Channel`] for this configuration.
    ///
    /// Returns immediately; the TCP/TLS handshake happens on the first RPC. TLS
    /// is applied when [`Config::with_tls`] was set or the endpoint is `https`;
    /// a `with_tls` endpoint given as `http://` is normalised to `https://` so
    /// TLS is never silently downgraded (see the private `resolve_endpoint`).
    ///
    /// # Errors
    /// Returns [`Error::InvalidRequest`] if the endpoint URI or the TLS
    /// configuration is invalid.
    pub fn connect_channel(&self) -> Result<Channel> {
        let (uri, want_tls) = resolve_endpoint(&self.endpoint, self.tls.is_some());
        let mut endpoint = Endpoint::from_shared(uri.clone())
            .map_err(|e| {
                Error::InvalidRequest(format!("invalid endpoint uri {}: {e}", redact_url(&uri)))
            })?
            .timeout(self.timeout.unwrap_or(Duration::from_secs(30)))
            .connect_timeout(Duration::from_secs(10))
            .http2_keep_alive_interval(Duration::from_secs(30))
            .keep_alive_timeout(Duration::from_secs(20))
            .keep_alive_while_idle(true)
            .tcp_keepalive(Some(Duration::from_secs(60)))
            .tcp_nodelay(true);

        if want_tls {
            endpoint = endpoint
                .tls_config(build_tls(self.tls.as_ref()))
                .map_err(|e| Error::InvalidRequest(format!("invalid TLS config: {e}")))?;
        }

        Ok(endpoint.connect_lazy())
    }
}

/// Resolve the effective endpoint URI and whether TLS should be attached.
///
/// `tonic` gates the TLS handshake on the URI **scheme**, not on the presence of
/// a `tls_config` — so attaching TLS to an `http://` endpoint is silently ignored
/// and the connection runs in plaintext (no encryption, no server-cert
/// verification, no client cert). When TLS is configured — or the endpoint is
/// already `https` — the scheme is normalised to `https` so TLS is actually
/// applied. Scheme detection is case-insensitive (tonic lowercases the parsed
/// scheme, so `HTTPS://…` must be treated as `https`).
fn resolve_endpoint(endpoint: &str, tls_configured: bool) -> (String, bool) {
    // A bare `host:port` is what a gRPC client dials, so it is what tooling
    // hands out — canton-devkit's `CANTON_GRPC_LEDGER_API_URL` is exactly this
    // shape. `Endpoint::from_shared` needs a scheme, and without one the
    // failure arrives at connect time as an unexplained transport error, so
    // supply the scheme the rest of this function would have chosen anyway.
    if !endpoint.contains("://") {
        let scheme = if tls_configured { "https" } else { "http" };
        return (format!("{scheme}://{endpoint}"), tls_configured);
    }

    let is_https = endpoint
        .get(..8)
        .is_some_and(|s| s.eq_ignore_ascii_case("https://"));
    let is_http = endpoint
        .get(..7)
        .is_some_and(|s| s.eq_ignore_ascii_case("http://"));
    let want_tls = tls_configured || is_https;
    if want_tls && is_http {
        (format!("https://{}", &endpoint[7..]), true)
    } else {
        (endpoint.to_string(), want_tls)
    }
}

#[cfg(test)]
mod decode_limit_tests {
    use super::*;

    #[test]
    fn the_default_is_far_above_what_a_real_page_needs() {
        // tonic's own default is 4 MiB. A `GetActiveContractsPageResponse`
        // carries a whole page in one message and the participant allows page
        // sizes up to 10 000, so the default is reachable in ordinary use —
        // measured against a live 3.5.7 participant, 627 trivial contracts with
        // created-event blobs already fill a quarter of it.
        assert_eq!(DEFAULT_MAX_DECODING_MESSAGE_SIZE, 128 * 1024 * 1024);
        const { assert!(DEFAULT_MAX_DECODING_MESSAGE_SIZE > 4 * 1024 * 1024) };
        assert_eq!(
            Config::new("http://localhost:3901").max_decoding_message_size(),
            DEFAULT_MAX_DECODING_MESSAGE_SIZE
        );
    }

    #[test]
    fn the_limit_is_configurable_in_both_directions() {
        // Raise it for a participant returning very large pages…
        let big = Config::new("http://x").with_max_decoding_message_size(512 * 1024 * 1024);
        assert_eq!(big.max_decoding_message_size(), 512 * 1024 * 1024);
        // …or lower it to bound what one response can claim.
        let small = Config::new("http://x").with_max_decoding_message_size(1024);
        assert_eq!(small.max_decoding_message_size(), 1024);
    }
}

#[cfg(test)]
#[allow(clippy::unwrap_used, clippy::expect_used)]
mod redaction_tests {
    use super::*;

    const KEY: &[u8] = b"-----BEGIN PRIVATE KEY-----SUPERSECRET-----END PRIVATE KEY-----";

    /// The mutual-TLS private key must never reach a log. The derived `Debug`
    /// printed it byte by byte, and a `Config` is exactly what an application
    /// attaches to a span while debugging a handshake.
    #[test]
    fn debug_never_prints_key_material() {
        let tls = TlsConfig::new().with_client_identity(b"certbytes".to_vec(), KEY.to_vec());
        let rendered = format!("{tls:?}");

        // 'S','U','P' as Debug-formatted bytes, which is how the leak looked.
        assert!(
            !rendered.contains("83, 85, 80"),
            "key bytes leaked: {rendered}"
        );
        assert!(!rendered.contains("PRIVATE KEY"), "{rendered}");
        // What a reader debugging a handshake actually needs is still there.
        assert!(rendered.contains("redacted"), "{rendered}");
        assert!(
            rendered.contains(&format!("{} bytes", KEY.len())),
            "{rendered}"
        );

        // And through a Config, which is the realistic path.
        let cfg = Config::new("https://host:3901").with_tls(tls);
        let rendered = format!("{cfg:?}");
        assert!(
            !rendered.contains("83, 85, 80"),
            "leaked via Config: {rendered}"
        );
    }

    #[test]
    fn debug_redacts_credentials_in_the_endpoint() {
        let cfg = Config::new("https://alice:s3cr3t@localhost:3901");
        let rendered = format!("{cfg:?}");
        assert!(!rendered.contains("s3cr3t"), "{rendered}");
        assert!(!rendered.contains("alice"), "{rendered}");
        assert!(
            rendered.contains("localhost:3901"),
            "host must survive: {rendered}"
        );
    }

    #[test]
    fn redact_url_keeps_everything_that_is_not_a_credential() {
        // Redacted.
        assert_eq!(redact_url("https://u:p@h:1/x?q=1"), "https://***@h:1/x?q=1");
        assert_eq!(redact_url("ws://tok@h/v2/updates"), "ws://***@h/v2/updates");
        // An '@' later in the path is not userinfo.
        assert_eq!(redact_url("https://h/a@b"), "https://h/a@b");
        // Untouched: no userinfo, no scheme, empty, and the malformed input
        // this is most likely to meet — it runs on the *invalid*-URI path.
        for url in [
            "https://localhost:3901",
            "http://kc:8082/realms/AppProvider/protocol/openid-connect/token",
            "not a url at all",
            "://",
            "",
        ] {
            assert_eq!(redact_url(url), url, "should be untouched: {url}");
        }
    }
}

#[cfg(test)]
#[allow(clippy::bool_assert_comparison)]
mod tests {
    use super::resolve_endpoint;

    #[test]
    fn with_tls_on_http_endpoint_is_upgraded_to_https() {
        // The security bug: `with_tls` on an http:// endpoint would otherwise
        // connect in plaintext. It must become https so TLS is applied.
        let (uri, tls) = resolve_endpoint("http://host:5001", true);
        assert_eq!(uri, "https://host:5001");
        assert_eq!(tls, true);
    }

    #[test]
    fn https_scheme_detection_is_case_insensitive() {
        // `HTTPS://` (no explicit with_tls) must still get TLS — tonic sees the
        // lowercased scheme and would otherwise error on an https URI with no TLS.
        let (uri, tls) = resolve_endpoint("HTTPS://host:443", false);
        assert_eq!(uri, "HTTPS://host:443");
        assert_eq!(tls, true);
    }

    #[test]
    fn plain_http_without_tls_stays_plaintext() {
        let (uri, tls) = resolve_endpoint("http://host:3901", false);
        assert_eq!(uri, "http://host:3901");
        assert_eq!(tls, false);
    }

    #[test]
    fn https_without_explicit_tls_wants_tls() {
        let (uri, tls) = resolve_endpoint("https://host:443", false);
        assert_eq!(uri, "https://host:443");
        assert_eq!(tls, true);
    }

    #[test]
    fn uppercase_http_with_tls_is_upgraded() {
        let (uri, tls) = resolve_endpoint("HTTP://host:5001", true);
        assert_eq!(uri, "https://host:5001");
        assert_eq!(tls, true);
    }

    /// A bare `host:port` is what a gRPC client dials, so it is the form
    /// tooling hands out — `canton-devkit localnet env` exports
    /// `CANTON_GRPC_LEDGER_API_URL` exactly this way. `Endpoint::from_shared`
    /// needs a scheme, and without one nothing complains until the first RPC
    /// fails as an unexplained transport error.
    #[test]
    fn a_scheme_less_host_and_port_gets_the_scheme_it_implies() {
        let (uri, tls) =
            resolve_endpoint("grpc-ledger-api.app-provider.demo.localhost:3901", false);
        assert_eq!(
            uri,
            "http://grpc-ledger-api.app-provider.demo.localhost:3901"
        );
        assert_eq!(tls, false);

        // With TLS configured it is the same choice the rest of this function
        // makes: never plaintext when the caller asked for TLS.
        let (uri, tls) = resolve_endpoint("ledger.example:443", true);
        assert_eq!(uri, "https://ledger.example:443");
        assert_eq!(tls, true);

        // An IPv6 literal has colons of its own and still is not a scheme.
        let (uri, _) = resolve_endpoint("[::1]:3901", false);
        assert_eq!(uri, "http://[::1]:3901");
    }
}