fix(desktop): reject baked agent credentials (BUZZ-SEC-051)

desktop/src-tauri/build.rs

@@ -2,6 +2,10 @@
 // so the build-time validation below and the runtime parse cannot drift.
 include!("src/commands/reconnect_hook_config.rs");
 
+mod build_agent_env_policy {
+    include!("src/managed_agents/build_agent_env_policy.rs");
+}
+
 use base64::Engine as _;
 
 fn main() {
@@ -33,9 +37,8 @@ fn main() {
         println!("cargo:rustc-env=BUZZ_DESKTOP_BUILD_BUZZ_AGENT_MODEL={model}");
     }
 
-    // Generic KEY=VALUE pairs to inject into every spawned agent process.
-    // Newline-delimited; each line must be non-empty and contain exactly one
-    // `=` separator with a non-empty key.  OSS builds leave this unset.
+    // Explicitly allowlisted, non-secret KEY=VALUE settings to inject into
+    // every spawned agent process. OSS builds leave this unset.
     // The validated value is base64-encoded before emitting so the single-line
     // Cargo build-script output carries all pairs (Cargo output is line-oriented;
     // a raw multiline value would be silently truncated to the first line).
@@ -60,6 +63,14 @@ fn main() {
                     line
                 );
             }
+            if !build_agent_env_policy::is_allowed_build_agent_env_key(key) {
+                panic!(
+                    "BUZZ_BUILD_AGENT_ENV line {}: key {:?} is not approved non-secret build configuration; allowed keys: {:?}",
+                    line_no + 1,
+                    key,
+                    build_agent_env_policy::ALLOWED_BUILD_AGENT_ENV_KEYS
+                );
+            }
         }
         let encoded = base64::engine::general_purpose::STANDARD.encode(raw.as_bytes());
         println!("cargo:rustc-env=BUZZ_DESKTOP_BUILD_AGENT_ENV={encoded}");

desktop/src-tauri/src/commands/agent_config.rs

@@ -234,8 +234,8 @@ pub async fn get_runtime_file_config(
 
 /// Return the key names of all non-empty baked build env vars.
 ///
-/// Internal (Block) builds bake provider credentials and other env pairs into
-/// the binary at compile time via `BUZZ_BUILD_AGENT_ENV`. The backend readiness
+/// Internal (Block) builds bake provider/model defaults and a small allowlist
+/// of non-secret settings into the binary at compile time. The backend readiness
 /// gate already treats these keys as satisfying their requirements (Layer 1 of
 /// `resolve_effective_agent_env`). This command exposes the *key names only* —
 /// never the values — so the frontend dialogs can apply the same logic and avoid

desktop/src-tauri/src/managed_agents/agent_env.rs

@@ -1,17 +1,20 @@
 //! Build-time agent env passthrough.
 //!
-//! Internal builds (buzz-releases) bake arbitrary `KEY=VALUE` pairs into the
-//! binary via `BUZZ_BUILD_AGENT_ENV` (base64-encoded, newline-delimited).
+//! Internal builds (buzz-releases) bake a small allowlist of non-secret
+//! `KEY=VALUE` settings into the binary via `BUZZ_BUILD_AGENT_ENV`
+//! (base64-encoded, newline-delimited).
 //! OSS builds leave the compile-time var unset — nothing is injected.
 
 use std::collections::BTreeMap;
 
 use base64::Engine as _;
 
+use super::build_agent_env_policy::is_allowed_build_agent_env_key;
+
 /// Return the baked-in build-time env pairs as a map.
 ///
-/// Internal builds (buzz-releases) bake provider/model defaults and arbitrary
-/// `KEY=VALUE` pairs into the binary at compile time. This function returns
+/// Internal builds (buzz-releases) bake provider/model defaults and allowlisted
+/// non-secret settings into the binary at compile time. This function returns
 /// those pairs as an owned map so callers can fold them into an in-process env
 /// at the **lowest** precedence layer — user/persona values layered on top
 /// override these baked defaults (last-write-wins, matching the existing
@@ -53,7 +56,9 @@ fn build_env_map(
         if let Ok(decoded) = base64::engine::general_purpose::STANDARD.decode(raw.as_bytes()) {
             if let Ok(text) = std::str::from_utf8(&decoded) {
                 for (key, value) in parse_agent_env_lines(text) {
-                    map.insert(key.to_string(), value.to_string());
+                    if is_allowed_build_agent_env_key(key) {
+                        map.insert(key.to_string(), value.to_string());
+                    }
                 }
             }
         }
@@ -111,6 +116,7 @@ mod tests {
         baked_build_env, build_buzz_agent_provider_defaults, build_env_map,
         discovery_env_with_baked_floor, parse_agent_env_lines,
     };
+    use crate::managed_agents::build_agent_env_policy::is_allowed_build_agent_env_key;
 
     #[test]
     fn buzz_agent_provider_defaults_empty_in_oss_build() {
@@ -301,6 +307,25 @@ mod tests {
         );
     }
 
+    #[test]
+    fn build_agent_env_policy_rejects_credentials_at_build_and_runtime_boundaries() {
+        use base64::Engine as _;
+
+        assert!(is_allowed_build_agent_env_key("DATABRICKS_MODEL"));
+        for key in ["GITHUB_TOKEN", "ANTHROPIC_API_KEY", "DB_PASSWORD"] {
+            assert!(!is_allowed_build_agent_env_key(key), "{key}");
+        }
+
+        let raw = "DATABRICKS_MODEL=reviewed-model\nGITHUB_TOKEN=must-not-be-embedded";
+        let blob = base64::engine::general_purpose::STANDARD.encode(raw.as_bytes());
+        let map = build_env_map(None, None, Some(&blob));
+        assert_eq!(
+            map.get("DATABRICKS_MODEL").map(String::as_str),
+            Some("reviewed-model")
+        );
+        assert!(!map.contains_key("GITHUB_TOKEN"));
+    }
+
     #[test]
     fn build_env_map_user_env_overrides_baked_via_btreemap_extend() {
         // Validates the precedence fold used in agent_models.rs:

desktop/src-tauri/src/managed_agents/build_agent_env_policy.rs

@@ -0,0 +1,12 @@
+/// Non-secret settings that internal release builds may embed through
+/// `BUZZ_BUILD_AGENT_ENV`.
+pub(crate) const ALLOWED_BUILD_AGENT_ENV_KEYS: &[&str] = &[
+    "BUZZ_AGENT_THINKING_EFFORT",
+    "DATABRICKS_HOST",
+    "DATABRICKS_MODEL",
+];
+
+/// Return whether `key` is approved non-secret build configuration.
+pub(crate) fn is_allowed_build_agent_env_key(key: &str) -> bool {
+    ALLOWED_BUILD_AGENT_ENV_KEYS.contains(&key)
+}

desktop/src-tauri/src/managed_agents/mod.rs

@@ -1,6 +1,7 @@
 mod agent_env;
 pub(crate) mod agent_events;
 pub(crate) mod agent_snapshot;
+mod build_agent_env_policy;
 pub(crate) mod team_snapshot;
 pub(crate) use agent_env::{
     baked_build_env, build_buzz_agent_provider_defaults, discovery_env_with_baked_floor,