[Auth] Add keyring support for Codex CLI (#5591)

Follow-up PR to #5569. Add Keyring Support for Auth Storage in Codex CLI
as well as a hybrid mode (default to persisting in keychain but fall
back to file when unavailable.)

It also refactors out the keyringstore implementation from rmcp-client
[here](https://github.com/openai/codex/blob/main/codex-rs/rmcp-client/src/oauth.rs)
to a new keyring-store crate.

There will be a follow-up that picks the right credential mode depending
on the config, instead of hardcoding `AuthCredentialsStoreMode::File`.

codex-rs/core/src/auth/storage.rs

@@ -2,6 +2,8 @@ use chrono::DateTime;
 use chrono::Utc;
 use serde::Deserialize;
 use serde::Serialize;
+use sha2::Digest;
+use sha2::Sha256;
 use std::fmt::Debug;
 use std::fs::File;
 use std::fs::OpenOptions;
@@ -12,8 +14,11 @@ use std::os::unix::fs::OpenOptionsExt;
 use std::path::Path;
 use std::path::PathBuf;
 use std::sync::Arc;
+use tracing::warn;
 
 use crate::token_data::TokenData;
+use codex_keyring_store::DefaultKeyringStore;
+use codex_keyring_store::KeyringStore;
 
 /// Determine where Codex should store CLI auth credentials.
 #[derive(Debug, Default, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
@@ -22,7 +27,10 @@ pub enum AuthCredentialsStoreMode {
     #[default]
     /// Persist credentials in CODEX_HOME/auth.json.
     File,
-    // TODO: Implement keyring support.
+    /// Persist credentials in the keyring. Fail if unavailable.
+    Keyring,
+    /// Use keyring when available; otherwise, fall back to a file in CODEX_HOME.
+    Auto,
 }
 
 /// Expected structure for $CODEX_HOME/auth.json.
@@ -114,25 +122,177 @@ impl AuthStorageBackend for FileAuthStorage {
     }
 }
 
+const KEYRING_SERVICE: &str = "Codex Auth";
+
+// turns codex_home path into a stable, short key string
+fn compute_store_key(codex_home: &Path) -> std::io::Result<String> {
+    let canonical = codex_home
+        .canonicalize()
+        .unwrap_or_else(|_| codex_home.to_path_buf());
+    let path_str = canonical.to_string_lossy();
+    let mut hasher = Sha256::new();
+    hasher.update(path_str.as_bytes());
+    let digest = hasher.finalize();
+    let hex = format!("{digest:x}");
+    let truncated = hex.get(..16).unwrap_or(&hex);
+    Ok(format!("cli|{truncated}"))
+}
+
+#[derive(Clone, Debug)]
+struct KeyringAuthStorage {
+    codex_home: PathBuf,
+    keyring_store: Arc<dyn KeyringStore>,
+}
+
+impl KeyringAuthStorage {
+    fn new(codex_home: PathBuf, keyring_store: Arc<dyn KeyringStore>) -> Self {
+        Self {
+            codex_home,
+            keyring_store,
+        }
+    }
+
+    fn load_from_keyring(&self, key: &str) -> std::io::Result<Option<AuthDotJson>> {
+        match self.keyring_store.load(KEYRING_SERVICE, key) {
+            Ok(Some(serialized)) => serde_json::from_str(&serialized).map(Some).map_err(|err| {
+                std::io::Error::other(format!(
+                    "failed to deserialize CLI auth from keyring: {err}"
+                ))
+            }),
+            Ok(None) => Ok(None),
+            Err(error) => Err(std::io::Error::other(format!(
+                "failed to load CLI auth from keyring: {}",
+                error.message()
+            ))),
+        }
+    }
+
+    fn save_to_keyring(&self, key: &str, value: &str) -> std::io::Result<()> {
+        match self.keyring_store.save(KEYRING_SERVICE, key, value) {
+            Ok(()) => Ok(()),
+            Err(error) => {
+                let message = format!(
+                    "failed to write OAuth tokens to keyring: {}",
+                    error.message()
+                );
+                warn!("{message}");
+                Err(std::io::Error::other(message))
+            }
+        }
+    }
+}
+
+impl AuthStorageBackend for KeyringAuthStorage {
+    fn load(&self) -> std::io::Result<Option<AuthDotJson>> {
+        let key = compute_store_key(&self.codex_home)?;
+        self.load_from_keyring(&key)
+    }
+
+    fn save(&self, auth: &AuthDotJson) -> std::io::Result<()> {
+        let key = compute_store_key(&self.codex_home)?;
+        // Simpler error mapping per style: prefer method reference over closure
+        let serialized = serde_json::to_string(auth).map_err(std::io::Error::other)?;
+        self.save_to_keyring(&key, &serialized)?;
+        if let Err(err) = delete_file_if_exists(&self.codex_home) {
+            warn!("failed to remove CLI auth fallback file: {err}");
+        }
+        Ok(())
+    }
+
+    fn delete(&self) -> std::io::Result<bool> {
+        let key = compute_store_key(&self.codex_home)?;
+        let keyring_removed = self
+            .keyring_store
+            .delete(KEYRING_SERVICE, &key)
+            .map_err(|err| {
+                std::io::Error::other(format!("failed to delete auth from keyring: {err}"))
+            })?;
+        let file_removed = delete_file_if_exists(&self.codex_home)?;
+        Ok(keyring_removed || file_removed)
+    }
+}
+
+#[derive(Clone, Debug)]
+struct AutoAuthStorage {
+    keyring_storage: Arc<KeyringAuthStorage>,
+    file_storage: Arc<FileAuthStorage>,
+}
+
+impl AutoAuthStorage {
+    fn new(codex_home: PathBuf, keyring_store: Arc<dyn KeyringStore>) -> Self {
+        Self {
+            keyring_storage: Arc::new(KeyringAuthStorage::new(codex_home.clone(), keyring_store)),
+            file_storage: Arc::new(FileAuthStorage::new(codex_home)),
+        }
+    }
+}
+
+impl AuthStorageBackend for AutoAuthStorage {
+    fn load(&self) -> std::io::Result<Option<AuthDotJson>> {
+        match self.keyring_storage.load() {
+            Ok(Some(auth)) => Ok(Some(auth)),
+            Ok(None) => self.file_storage.load(),
+            Err(err) => {
+                warn!("failed to load CLI auth from keyring, falling back to file storage: {err}");
+                self.file_storage.load()
+            }
+        }
+    }
+
+    fn save(&self, auth: &AuthDotJson) -> std::io::Result<()> {
+        match self.keyring_storage.save(auth) {
+            Ok(()) => Ok(()),
+            Err(err) => {
+                warn!("failed to save auth to keyring, falling back to file storage: {err}");
+                self.file_storage.save(auth)
+            }
+        }
+    }
+
+    fn delete(&self) -> std::io::Result<bool> {
+        // Keyring storage will delete from disk as well
+        self.keyring_storage.delete()
+    }
+}
+
 pub(super) fn create_auth_storage(
     codex_home: PathBuf,
     mode: AuthCredentialsStoreMode,
+) -> Arc<dyn AuthStorageBackend> {
+    let keyring_store: Arc<dyn KeyringStore> = Arc::new(DefaultKeyringStore);
+    create_auth_storage_with_keyring_store(codex_home, mode, keyring_store)
+}
+
+fn create_auth_storage_with_keyring_store(
+    codex_home: PathBuf,
+    mode: AuthCredentialsStoreMode,
+    keyring_store: Arc<dyn KeyringStore>,
 ) -> Arc<dyn AuthStorageBackend> {
     match mode {
         AuthCredentialsStoreMode::File => Arc::new(FileAuthStorage::new(codex_home)),
+        AuthCredentialsStoreMode::Keyring => {
+            Arc::new(KeyringAuthStorage::new(codex_home, keyring_store))
+        }
+        AuthCredentialsStoreMode::Auto => Arc::new(AutoAuthStorage::new(codex_home, keyring_store)),
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::token_data::IdTokenInfo;
     use anyhow::Context;
+    use base64::Engine;
     use pretty_assertions::assert_eq;
+    use serde_json::json;
     use tempfile::tempdir;
 
+    use codex_keyring_store::tests::MockKeyringStore;
+    use keyring::Error as KeyringError;
+
     #[tokio::test]
     async fn file_storage_load_returns_auth_dot_json() -> anyhow::Result<()> {
-        let codex_home = tempdir().unwrap();
+        let codex_home = tempdir()?;
         let storage = FileAuthStorage::new(codex_home.path().to_path_buf());
         let auth_dot_json = AuthDotJson {
             openai_api_key: Some("test-key".to_string()),
@@ -151,7 +311,7 @@ mod tests {
 
     #[tokio::test]
     async fn file_storage_save_persists_auth_dot_json() -> anyhow::Result<()> {
-        let codex_home = tempdir().unwrap();
+        let codex_home = tempdir()?;
         let storage = FileAuthStorage::new(codex_home.path().to_path_buf());
         let auth_dot_json = AuthDotJson {
             openai_api_key: Some("test-key".to_string()),
@@ -188,4 +348,325 @@ mod tests {
         assert!(!dir.path().join("auth.json").exists());
         Ok(())
     }
+
+    fn seed_keyring_and_fallback_auth_file_for_delete<F>(
+        mock_keyring: &MockKeyringStore,
+        codex_home: &Path,
+        compute_key: F,
+    ) -> anyhow::Result<(String, PathBuf)>
+    where
+        F: FnOnce() -> std::io::Result<String>,
+    {
+        let key = compute_key()?;
+        mock_keyring.save(KEYRING_SERVICE, &key, "{}")?;
+        let auth_file = get_auth_file(codex_home);
+        std::fs::write(&auth_file, "stale")?;
+        Ok((key, auth_file))
+    }
+
+    fn seed_keyring_with_auth<F>(
+        mock_keyring: &MockKeyringStore,
+        compute_key: F,
+        auth: &AuthDotJson,
+    ) -> anyhow::Result<()>
+    where
+        F: FnOnce() -> std::io::Result<String>,
+    {
+        let key = compute_key()?;
+        let serialized = serde_json::to_string(auth)?;
+        mock_keyring.save(KEYRING_SERVICE, &key, &serialized)?;
+        Ok(())
+    }
+
+    fn assert_keyring_saved_auth_and_removed_fallback(
+        mock_keyring: &MockKeyringStore,
+        key: &str,
+        codex_home: &Path,
+        expected: &AuthDotJson,
+    ) {
+        let saved_value = mock_keyring
+            .saved_value(key)
+            .expect("keyring entry should exist");
+        let expected_serialized = serde_json::to_string(expected).expect("serialize expected auth");
+        assert_eq!(saved_value, expected_serialized);
+        let auth_file = get_auth_file(codex_home);
+        assert!(
+            !auth_file.exists(),
+            "fallback auth.json should be removed after keyring save"
+        );
+    }
+
+    fn id_token_with_prefix(prefix: &str) -> IdTokenInfo {
+        #[derive(Serialize)]
+        struct Header {
+            alg: &'static str,
+            typ: &'static str,
+        }
+
+        let header = Header {
+            alg: "none",
+            typ: "JWT",
+        };
+        let payload = json!({
+            "email": format!("{prefix}@example.com"),
+            "https://api.openai.com/auth": {
+                "chatgpt_account_id": format!("{prefix}-account"),
+            },
+        });
+        let encode = |bytes: &[u8]| base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(bytes);
+        let header_b64 = encode(&serde_json::to_vec(&header).expect("serialize header"));
+        let payload_b64 = encode(&serde_json::to_vec(&payload).expect("serialize payload"));
+        let signature_b64 = encode(b"sig");
+        let fake_jwt = format!("{header_b64}.{payload_b64}.{signature_b64}");
+
+        crate::token_data::parse_id_token(&fake_jwt).expect("fake JWT should parse")
+    }
+
+    fn auth_with_prefix(prefix: &str) -> AuthDotJson {
+        AuthDotJson {
+            openai_api_key: Some(format!("{prefix}-api-key")),
+            tokens: Some(TokenData {
+                id_token: id_token_with_prefix(prefix),
+                access_token: format!("{prefix}-access"),
+                refresh_token: format!("{prefix}-refresh"),
+                account_id: Some(format!("{prefix}-account-id")),
+            }),
+            last_refresh: None,
+        }
+    }
+
+    #[test]
+    fn keyring_auth_storage_load_returns_deserialized_auth() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = KeyringAuthStorage::new(
+            codex_home.path().to_path_buf(),
+            Arc::new(mock_keyring.clone()),
+        );
+        let expected = AuthDotJson {
+            openai_api_key: Some("sk-test".to_string()),
+            tokens: None,
+            last_refresh: None,
+        };
+        seed_keyring_with_auth(
+            &mock_keyring,
+            || compute_store_key(codex_home.path()),
+            &expected,
+        )?;
+
+        let loaded = storage.load()?;
+        assert_eq!(Some(expected), loaded);
+        Ok(())
+    }
+
+    #[test]
+    fn keyring_auth_storage_compute_store_key_for_home_directory() -> anyhow::Result<()> {
+        let codex_home = PathBuf::from("~/.codex");
+
+        let key = compute_store_key(codex_home.as_path())?;
+
+        assert_eq!(key, "cli|940db7b1d0e4eb40");
+        Ok(())
+    }
+
+    #[test]
+    fn keyring_auth_storage_save_persists_and_removes_fallback_file() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = KeyringAuthStorage::new(
+            codex_home.path().to_path_buf(),
+            Arc::new(mock_keyring.clone()),
+        );
+        let auth_file = get_auth_file(codex_home.path());
+        std::fs::write(&auth_file, "stale")?;
+        let auth = AuthDotJson {
+            openai_api_key: None,
+            tokens: Some(TokenData {
+                id_token: Default::default(),
+                access_token: "access".to_string(),
+                refresh_token: "refresh".to_string(),
+                account_id: Some("account".to_string()),
+            }),
+            last_refresh: Some(Utc::now()),
+        };
+
+        storage.save(&auth)?;
+
+        let key = compute_store_key(codex_home.path())?;
+        assert_keyring_saved_auth_and_removed_fallback(
+            &mock_keyring,
+            &key,
+            codex_home.path(),
+            &auth,
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn keyring_auth_storage_delete_removes_keyring_and_file() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = KeyringAuthStorage::new(
+            codex_home.path().to_path_buf(),
+            Arc::new(mock_keyring.clone()),
+        );
+        let (key, auth_file) = seed_keyring_and_fallback_auth_file_for_delete(
+            &mock_keyring,
+            codex_home.path(),
+            || compute_store_key(codex_home.path()),
+        )?;
+
+        let removed = storage.delete()?;
+
+        assert!(removed, "delete should report removal");
+        assert!(
+            !mock_keyring.contains(&key),
+            "keyring entry should be removed"
+        );
+        assert!(
+            !auth_file.exists(),
+            "fallback auth.json should be removed after keyring delete"
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn auto_auth_storage_load_prefers_keyring_value() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = AutoAuthStorage::new(
+            codex_home.path().to_path_buf(),
+            Arc::new(mock_keyring.clone()),
+        );
+        let keyring_auth = auth_with_prefix("keyring");
+        seed_keyring_with_auth(
+            &mock_keyring,
+            || compute_store_key(codex_home.path()),
+            &keyring_auth,
+        )?;
+
+        let file_auth = auth_with_prefix("file");
+        storage.file_storage.save(&file_auth)?;
+
+        let loaded = storage.load()?;
+        assert_eq!(loaded, Some(keyring_auth));
+        Ok(())
+    }
+
+    #[test]
+    fn auto_auth_storage_load_uses_file_when_keyring_empty() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = AutoAuthStorage::new(codex_home.path().to_path_buf(), Arc::new(mock_keyring));
+
+        let expected = auth_with_prefix("file-only");
+        storage.file_storage.save(&expected)?;
+
+        let loaded = storage.load()?;
+        assert_eq!(loaded, Some(expected));
+        Ok(())
+    }
+
+    #[test]
+    fn auto_auth_storage_load_falls_back_when_keyring_errors() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = AutoAuthStorage::new(
+            codex_home.path().to_path_buf(),
+            Arc::new(mock_keyring.clone()),
+        );
+        let key = compute_store_key(codex_home.path())?;
+        mock_keyring.set_error(&key, KeyringError::Invalid("error".into(), "load".into()));
+
+        let expected = auth_with_prefix("fallback");
+        storage.file_storage.save(&expected)?;
+
+        let loaded = storage.load()?;
+        assert_eq!(loaded, Some(expected));
+        Ok(())
+    }
+
+    #[test]
+    fn auto_auth_storage_save_prefers_keyring() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = AutoAuthStorage::new(
+            codex_home.path().to_path_buf(),
+            Arc::new(mock_keyring.clone()),
+        );
+        let key = compute_store_key(codex_home.path())?;
+
+        let stale = auth_with_prefix("stale");
+        storage.file_storage.save(&stale)?;
+
+        let expected = auth_with_prefix("to-save");
+        storage.save(&expected)?;
+
+        assert_keyring_saved_auth_and_removed_fallback(
+            &mock_keyring,
+            &key,
+            codex_home.path(),
+            &expected,
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn auto_auth_storage_save_falls_back_when_keyring_errors() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = AutoAuthStorage::new(
+            codex_home.path().to_path_buf(),
+            Arc::new(mock_keyring.clone()),
+        );
+        let key = compute_store_key(codex_home.path())?;
+        mock_keyring.set_error(&key, KeyringError::Invalid("error".into(), "save".into()));
+
+        let auth = auth_with_prefix("fallback");
+        storage.save(&auth)?;
+
+        let auth_file = get_auth_file(codex_home.path());
+        assert!(
+            auth_file.exists(),
+            "fallback auth.json should be created when keyring save fails"
+        );
+        let saved = storage
+            .file_storage
+            .load()?
+            .context("fallback auth should exist")?;
+        assert_eq!(saved, auth);
+        assert!(
+            mock_keyring.saved_value(&key).is_none(),
+            "keyring should not contain value when save fails"
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn auto_auth_storage_delete_removes_keyring_and_file() -> anyhow::Result<()> {
+        let codex_home = tempdir()?;
+        let mock_keyring = MockKeyringStore::default();
+        let storage = AutoAuthStorage::new(
+            codex_home.path().to_path_buf(),
+            Arc::new(mock_keyring.clone()),
+        );
+        let (key, auth_file) = seed_keyring_and_fallback_auth_file_for_delete(
+            &mock_keyring,
+            codex_home.path(),
+            || compute_store_key(codex_home.path()),
+        )?;
+
+        let removed = storage.delete()?;
+
+        assert!(removed, "delete should report removal");
+        assert!(
+            !mock_keyring.contains(&key),
+            "keyring entry should be removed"
+        );
+        assert!(
+            !auth_file.exists(),
+            "fallback auth.json should be removed after delete"
+        );
+        Ok(())
+    }
 }