feat: pin keychain item ACLs to the app's code signature (macOS) (#21)

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

@@ -1,3 +1,4 @@
+use crate::keychain_acl;
 use tauri_plugin_keyring_store::KeyringExt;
 
 /// Store a connection password in the OS keychain.
@@ -11,7 +12,10 @@ pub fn save_connection_password(
     app.keyring()
         .store
         .set_password(&connection_id, &password)
-        .map_err(|e| e.to_string())
+        .map_err(|e| e.to_string())?;
+    // Best-effort: pin the item's ACL to this app so re-signed builds never prompt.
+    keychain_acl::after_store(&app, &connection_id);
+    Ok(())
 }
 
 /// Retrieve a connection password from the OS keychain.
@@ -55,7 +59,9 @@ pub fn save_connection_ssh_password(
     app.keyring()
         .store
         .set_password(&ssh_account("password", &connection_id), &password)
-        .map_err(|e| e.to_string())
+        .map_err(|e| e.to_string())?;
+    keychain_acl::after_store(&app, &ssh_account("password", &connection_id));
+    Ok(())
 }
 
 /// Retrieve an SSH tunnel password from the OS keychain.
@@ -93,7 +99,9 @@ pub fn save_connection_ssh_passphrase(
     app.keyring()
         .store
         .set_password(&ssh_account("passphrase", &connection_id), &passphrase)
-        .map_err(|e| e.to_string())
+        .map_err(|e| e.to_string())?;
+    keychain_acl::after_store(&app, &ssh_account("passphrase", &connection_id));
+    Ok(())
 }
 
 /// Retrieve an SSH private-key passphrase from the OS keychain.

desktop/src-tauri/src/keychain_acl.rs

@@ -0,0 +1,198 @@
+//! Keychain ACL normalization for stored secrets (macOS).
+//!
+//! # Why this exists
+//!
+//! Generic-password items stored via the legacy keychain API get a default ACL
+//! that grants access to "the application that created the item". When a Tauri
+//! app is rebuilt, its code signature changes (dev builds are ad-hoc signed, so
+//! the identity differs on every build), and the new binary no longer matches
+//! the item's ACL — macOS then shows the "Gridline wants to access your
+//! keychain" prompt.
+//!
+//! The fix: after storing a secret, replace the item's ACL with an explicit
+//! `SecAccess` whose trusted-application list contains exactly *this app*,
+//! resolved by `SecTrustedApplicationCreateFromPath(NULL)` — the current
+//! process's code-signature requirement. For a Developer ID-signed release
+//! build that requirement is stable across versions (anchored to the signing
+//! certificate), so items stay accessible without prompts through upgrades.
+//!
+//! # Prompt behavior
+//!
+//! - Item created by this build → the ACL set is silent.
+//! - Item created by an older/differently-signed build → macOS shows the
+//!   standard one-time authorization dialog; "Always Allow" replaces the ACL
+//!   and the prompt never reappears (the same dialog the app would show on the
+//!   first read anyway — this just makes the result permanent and clean).
+//!
+//! All operations are best-effort: `after_store` swallows errors so keychain
+//! writes never fail because of ACL normalization.
+
+/// Best-effort ACL normalization after a successful keychain write.
+///
+/// Resolves the service name the same way `tauri-plugin-keyring-store` does
+/// (the Tauri bundle identifier) and never fails the caller's operation.
+pub fn after_store(app: &tauri::AppHandle, account: &str) {
+    let service = app.config().identifier.clone();
+    if let Err(e) = ensure_item_acl(&service, account) {
+        eprintln!("[keychain_acl] skipped for {account}: {e}");
+    }
+}
+
+/// Grant this app (by its code-signature requirement) access to a keychain item.
+#[cfg(target_os = "macos")]
+pub fn ensure_item_acl(service: &str, account: &str) -> Result<(), String> {
+    use core_foundation::array::CFArray;
+    use core_foundation::base::{CFTypeRef, TCFType};
+    use core_foundation::string::CFString;
+    use security_framework::item::{ItemClass, ItemSearchOptions, Reference, SearchResult};
+    use security_framework::os::macos::access::SecAccess;
+    use security_framework_sys::base::SecAccessRef;
+
+    // Locate the item WITHOUT reading its secret: a ref-only lookup
+    // (`kSecReturnRef`, no data/attributes) never triggers an authorization
+    // prompt, so merely probing an item we can't yet access is safe.
+    let found = ItemSearchOptions::new()
+        .class(ItemClass::generic_password())
+        .service(service)
+        .account(account)
+        .load_refs(true)
+        .load_data(false)
+        .load_attributes(false)
+        .search()
+        .map_err(|e| format!("keychain item lookup failed: {e}"))?;
+
+    let item = match found.first() {
+        Some(SearchResult::Ref(Reference::KeychainItem(item))) => item,
+        // No item (yet) or an unexpected result shape — nothing to normalize.
+        _ => return Ok(()),
+    };
+
+    fn cvt(status: i32) -> Result<(), String> {
+        if status == 0 {
+            Ok(())
+        } else {
+            Err(format!("security framework error {status}"))
+        }
+    }
+
+    // Build an access object whose trusted list is exactly this app. A NULL
+    // path resolves the trusted application to the current process's code
+    // signature requirement.
+    unsafe {
+        let mut trusted_app_ref: *mut OpaqueSecTrustedApplication = std::ptr::null_mut();
+        cvt(SecTrustedApplicationCreateFromPath(std::ptr::null(), &mut trusted_app_ref))?;
+        let trusted_app = SecTrustedApplication::wrap_under_create_rule(trusted_app_ref);
+        let trusted_list = CFArray::from_CFTypes(&[trusted_app]);
+
+        let descriptor = CFString::new("Gridline");
+        let mut access_ref: SecAccessRef = std::ptr::null_mut();
+        cvt(SecAccessCreate(
+            descriptor.as_concrete_TypeRef() as CFTypeRef,
+            trusted_list.as_concrete_TypeRef() as CFTypeRef,
+            &mut access_ref,
+        ))?;
+        let access = SecAccess::wrap_under_create_rule(access_ref);
+
+        // Replace the item's ACL. Silent when we already own the item;
+        // one-time authorization dialog when the item was created by a
+        // differently-signed build.
+        cvt(SecKeychainItemSetAccess(
+            item.as_concrete_TypeRef(),
+            access.as_concrete_TypeRef(),
+        ))
+    }
+}
+
+/// Non-macOS platforms have no keychain ACL concept — nothing to do.
+#[cfg(not(target_os = "macos"))]
+pub fn ensure_item_acl(_service: &str, _account: &str) -> Result<(), String> {
+    Ok(())
+}
+
+#[cfg(target_os = "macos")]
+mod macos_ffi {
+    use core_foundation::base::{CFTypeRef, CFTypeID};
+
+    /// Minimal `TCFType` wrapper for `SecTrustedApplication` — the
+    /// security-framework crate exposes no high-level API for it.
+    #[repr(C)]
+    pub struct OpaqueSecTrustedApplication {
+        _priv: [u8; 0],
+    }
+    pub type SecTrustedApplicationRef = *mut OpaqueSecTrustedApplication;
+
+    use core_foundation::{declare_TCFType, impl_TCFType};
+    declare_TCFType!(SecTrustedApplication, SecTrustedApplicationRef);
+    impl_TCFType!(
+        SecTrustedApplication,
+        SecTrustedApplicationRef,
+        SecTrustedApplicationGetTypeID
+    );
+    unsafe impl Send for SecTrustedApplication {}
+    unsafe impl Sync for SecTrustedApplication {}
+
+    extern "C" {
+        // SecAccess/SecTrustedApplication APIs are deprecated in the macOS SDK
+        // but remain fully functional (the legacy keychain store this app uses
+        // via tauri-plugin-keyring-store relies on the same API family).
+        pub fn SecTrustedApplicationGetTypeID() -> CFTypeID;
+        pub fn SecTrustedApplicationCreateFromPath(
+            path: CFTypeRef,
+            app: *mut SecTrustedApplicationRef,
+        ) -> i32;
+        pub fn SecAccessCreate(
+            descriptor: CFTypeRef,
+            trustedlist: CFTypeRef,
+            access: *mut security_framework_sys::base::SecAccessRef,
+        ) -> i32;
+        pub fn SecKeychainItemSetAccess(
+            item: security_framework_sys::base::SecKeychainItemRef,
+            access: security_framework_sys::base::SecAccessRef,
+        ) -> i32;
+    }
+}
+
+#[cfg(target_os = "macos")]
+use macos_ffi::{
+    OpaqueSecTrustedApplication, SecAccessCreate, SecKeychainItemSetAccess, SecTrustedApplication,
+    SecTrustedApplicationCreateFromPath,
+};
+
+#[cfg(all(test, target_os = "macos"))]
+mod tests {
+    use super::*;
+    use security_framework::os::macos::keychain::SecKeychain;
+    use security_framework::os::macos::passwords::find_generic_password;
+
+    /// Real-keychain integration test: creates a generic-password item the
+    /// same way the keyring store does, normalizes its ACL, verifies the
+    /// secret is still readable, and cleans up.
+    ///
+    /// Ignored by default (`cargo test`) so CI/dev runs never touch the login
+    /// keychain. Run explicitly with:
+    /// `cargo test -- --ignored keychain_acl`
+    #[test]
+    #[ignore = "touches the real login keychain"]
+    fn keychain_acl_normalizes_item() {
+        let keychain = SecKeychain::default().expect("default keychain");
+        let service = "com.adrianbonpin.gridline.acl-test";
+        let account = format!("acl-test-{}", std::process::id());
+
+        // Create the item exactly like apple-native-keyring-store does
+        // (legacy SecKeychain generic-password API).
+        keychain
+            .set_generic_password(service, &account, b"test-secret")
+            .expect("create test item");
+
+        // ACL normalization must succeed on an item we just created.
+        ensure_item_acl(service, &account).expect("normalize ACL");
+
+        // The item must remain readable with the correct secret.
+        let (password, item) =
+            find_generic_password(Some(&[keychain]), service, &account).expect("read back");
+        assert_eq!(password.as_ref(), b"test-secret");
+
+        // Cleanup: delete the test item.
+        item.delete();
+    }
+}

desktop/src-tauri/src/lib.rs

@@ -5,6 +5,7 @@
 mod cancel;
 mod commands;
 mod db;
+mod keychain_acl;
 mod models;
 mod store;