Trust the OS certificate store for engine HTTPS requests (#757) (#759)

The engine verified TLS against the Mozilla roots bundled through
webpki-roots only, so behind a TLS-inspecting proxy (Aikido, Zscaler,
Netskope) whose root lives in the OS trust store, `impeccable update`
and `install` failed with `invalid peer certificate: UnknownIssuer`
while curl and npm on the same machine succeeded.

crates/context/src/http.rs builds one rustls ClientConfig per process:
the OS trust store (rustls-native-certs: Keychain, Windows store, the
OpenSSL paths on Linux) merged with the bundled roots. A union, not a
replacement, so a container without ca-certificates or a store that
fails to load still verifies exactly as before. SSL_CERT_FILE and
SSL_CERT_DIR replace the OS store the way they do for OpenSSL and curl.
Every HTTPS call site (bundle and signature downloads, /api/version,
/api/commands, the roll API, image generation) builds its agent from
this module; the plain-HTTP live-server calls on localhost are
untouched.

Verified against a local HTTPS server signed by a throwaway CA: trusted
through SSL_CERT_FILE the update check reaches it; without it the same
server is rejected as UnknownIssuer; with SSL_CERT_FILE pointing at that
CA or at a missing file, impeccable.style still verifies through the
bundled roots. cargo test --workspace and the oracle corpus (832) pass.

Written with AI assistance (Claude Code).

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

crates/context/src/concept_seed.rs

@@ -47,7 +47,7 @@ fn card_base(env: &Env) -> String {
 }
 
 fn agent(timeout: Duration) -> ureq::Agent {
-    ureq::AgentBuilder::new().timeout_connect(timeout).timeout(timeout).build()
+    crate::http::agent_builder().timeout_connect(timeout).timeout(timeout).build()
 }
 
 /// URLSearchParams serialization (application/x-www-form-urlencoded).

crates/context/src/context_cli.rs

@@ -468,7 +468,7 @@ fn fetch_latest_skill_version(env: &Env) -> Option<String> {
         .cloned()
         .unwrap_or_else(|| "https://impeccable.style".to_string());
     let host = host.strip_suffix('/').unwrap_or(&host).to_string();
-    let agent = ureq::AgentBuilder::new()
+    let agent = crate::http::agent_builder()
         .timeout(std::time::Duration::from_millis(FETCH_TIMEOUT_MS))
         .build();
     let res = agent.get(&format!("{}/api/version", host)).call().ok()?;

crates/context/src/generate_image.rs

@@ -294,7 +294,7 @@ pub fn run(args: &[String], io: &mut Io) -> i32 {
             }
         }
     }
-    let agent = ureq::AgentBuilder::new().build();
+    let agent = crate::http::agent_builder().build();
     let response = if !refs.is_empty() {
         let boundary = format!("----impeccable{:x}", crate::util::now_ms() as u64);
         let mut body: Vec<u8> = Vec::new();

crates/context/src/http.rs

@@ -0,0 +1,104 @@
+//! One TLS trust configuration for every HTTPS request the engine makes.
+//!
+//! `ureq`'s default rustls config trusts only the Mozilla roots compiled in
+//! through `webpki-roots`. On a machine where an endpoint security agent
+//! inspects TLS (Aikido, Zscaler, Netskope: routine in managed corporate
+//! setups), every connection terminates at a proxy whose root lives in the
+//! OS trust store and nowhere else, so `update` and `install` failed with
+//! `invalid peer certificate: UnknownIssuer` while curl and npm on the same
+//! machine succeeded (#757).
+//!
+//! The store built here is the union of the OS trust store
+//! (`rustls-native-certs`: the macOS Keychain, the Windows store, the
+//! OpenSSL paths on Linux) and the bundled Mozilla roots. A union, not a
+//! replacement: a container without `ca-certificates`, or a store that
+//! fails to load, verifies against the bundled roots exactly as before.
+//! `SSL_CERT_FILE` / `SSL_CERT_DIR` stand in for the OS store, as they do
+//! for OpenSSL and curl; the bundled roots stay either way.
+
+use std::sync::Arc;
+
+use once_cell::sync::Lazy;
+use ureq::rustls::pki_types::CertificateDer;
+use ureq::rustls::{self, ClientConfig, RootCertStore};
+
+/// `ureq::AgentBuilder::new()` with the engine's trust store installed.
+/// Every HTTPS call site builds its agent from this; the plain-HTTP calls
+/// to the live server on localhost do not need it.
+pub fn agent_builder() -> ureq::AgentBuilder {
+    ureq::AgentBuilder::new().tls_config(tls_config())
+}
+
+fn tls_config() -> Arc<ClientConfig> {
+    static CONFIG: Lazy<Arc<ClientConfig>> = Lazy::new(|| {
+        // Mirrors ureq's own default config (provider and protocol versions);
+        // only the root store differs.
+        let config =
+            ClientConfig::builder_with_provider(rustls::crypto::ring::default_provider().into())
+                .with_protocol_versions(&[&rustls::version::TLS12, &rustls::version::TLS13])
+                .expect("the ring provider supports TLS 1.2 and 1.3")
+                .with_root_certificates(root_store(rustls_native_certs::load_native_certs().certs))
+                .with_no_client_auth();
+        Arc::new(config)
+    });
+    CONFIG.clone()
+}
+
+/// The bundled Mozilla roots plus every parsable certificate in `native`.
+/// Unparsable entries are dropped, so one broken certificate in the OS
+/// store cannot take the bundled roots down with it.
+fn root_store(native: Vec<CertificateDer<'static>>) -> RootCertStore {
+    let mut store = RootCertStore {
+        roots: webpki_roots::TLS_SERVER_ROOTS.to_vec(),
+    };
+    store.add_parsable_certificates(native);
+    store
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use ureq::rustls::pki_types::pem::PemObject;
+
+    /// Self-signed CA minted for this test (P-256, v3, CA:TRUE): the shape
+    /// of the root a TLS-inspecting proxy installs into the OS store.
+    const PROXY_ROOT_PEM: &str = "-----BEGIN CERTIFICATE-----
+MIIBdTCCARugAwIBAgIJANhTZvQvv7HJMAoGCCqGSM49BAMCMB0xGzAZBgNVBAMM
+EmltcGVjY2FibGUgdGVzdCBDQTAgFw0yNjA5MDcwNjQxMjdaGA8yMTI2MDgxNDA2
+NDEyN1owHTEbMBkGA1UEAwwSaW1wZWNjYWJsZSB0ZXN0IENBMFkwEwYHKoZIzj0C
+AQYIKoZIzj0DAQcDQgAEYVZtCOXaZsY71/0Roy62iBVcyx8UfMDkPbEbf/IEw5Bm
+yNBfKTFS/8FbRBMWHXOwNE0Ns1BLVOB1oQ1XFC5Bz6NCMEAwDwYDVR0TAQH/BAUw
+AwEB/zAOBgNVHQ8BAf8EBAMCAQYwHQYDVR0OBBYEFFONzBxi7ewOfuP6cBIIqsxu
+3pEiMAoGCCqGSM49BAMCA0gAMEUCIQD98Q0ZRe8ceuopnUwQKYleZd5IzfWhhpmO
+tB0WGTOG3QIgdJa8gBPU9Y6WsrursItsnUeGTYHKDCZZ6MjlekLFuoc=
+-----END CERTIFICATE-----
+";
+
+    fn bundled() -> usize {
+        webpki_roots::TLS_SERVER_ROOTS.len()
+    }
+
+    #[test]
+    fn bundled_roots_alone_when_the_os_store_is_empty() {
+        assert_eq!(root_store(Vec::new()).len(), bundled());
+    }
+
+    #[test]
+    fn os_store_root_joins_the_bundled_roots() {
+        let proxy = CertificateDer::from_pem_slice(PROXY_ROOT_PEM.as_bytes()).unwrap();
+        assert_eq!(root_store(vec![proxy]).len(), bundled() + 1);
+    }
+
+    #[test]
+    fn unparsable_os_store_entry_is_dropped() {
+        let junk = CertificateDer::from(b"not a certificate".to_vec());
+        assert_eq!(root_store(vec![junk]).len(), bundled());
+    }
+
+    #[test]
+    fn agent_builds_from_this_hosts_store() {
+        // Runs the real rustls-native-certs load: it must not panic, and the
+        // shared config must be accepted by a ureq agent.
+        let _agent = agent_builder().build();
+    }
+}

crates/context/src/lib.rs

@@ -5,6 +5,7 @@
 pub mod jsp;
 pub mod util;
 pub mod url;
+pub mod http;
 pub mod provider;
 pub mod hook_markers;
 pub mod target_args;