Provide keyutils with persistence-after-reboot using secret-service

.github/workflows/ci.yaml

@@ -56,6 +56,12 @@ jobs:
           - "async-secret-service,async-io,crypto-rust"
           - "async-secret-service,tokio,crypto-openssl"
           - "async-secret-service,async-io,crypto-openssl"
+          - "linux-native-sync-persistent,crypto-rust"
+          - "linux-native-sync-persistent,crypto-openssl"
+          - "linux-native-async-persistent,tokio,crypto-rust"
+          - "linux-native-async-persistent,async-io,crypto-rust"
+          - "linux-native-async-persistent,tokio,crypto-openssl"
+          - "linux-native-async-persistent,async-io,crypto-openssl"
 
     steps:
       - name: Install CI dependencies

Cargo.toml

@@ -17,6 +17,8 @@ linux-native = ["dep:linux-keyutils"]
 apple-native = ["dep:security-framework"]
 windows-native = ["dep:windows-sys", "dep:byteorder"]
 
+linux-native-sync-persistent = ["linux-native", "sync-secret-service"]
+linux-native-async-persistent = ["linux-native", "async-secret-service"]
 sync-secret-service = ["dep:dbus-secret-service"]
 async-secret-service = ["dep:secret-service", "dep:zbus"]
 crypto-rust = ["dbus-secret-service?/crypto-rust", "secret-service?/crypto-rust"]

README.md

@@ -56,14 +56,14 @@ This crate allows clients to "bring their own credential store" by providing tra
 
 This crate provides built-in implementations of the following platform-specific credential stores:
 
-* _Linux_: The DBus-based Secret Service and the kernel keyutils.
+* _Linux_: The DBus-based Secret Service, the kernel keyutils, and a combo of the two.
 * _FreeBSD_, _OpenBSD_: The DBus-based Secret Service.
 * _macOS_, _iOS_: The local keychain.
 * _Windows_: The Windows Credential Manager.
 
 To enable the stores you want, you use features: there is one feature for each possibly-included credential store. If you specify a feature (e.g., `dbus-secret-service`) _and_ your target platform (e.g., `freebsd`) supports that credential store, it will be included as the default credential store in that build. That way you can have a build command that specifies a single credential store for each of your target platforms, and use that same build command for all targets.
 
-If you don't enable any credential stores that are supported on a given platform, or you enable multiple credential stores for some platform, the _mock_ keystore will be the default on that platform. See the [developer docs](https://docs.rs/keyring/) for details of which features control the inclusion of which credential stores (and which platforms each credential store targets).
+If you don't enable any credential stores that are supported on a given platform, the _mock_ keystore will be the default on that platform. See the [developer docs](https://docs.rs/keyring/) for details of which features control the inclusion of which credential stores.
 
 ### Platform-specific issues
 

build-xplat-docs.sh

@@ -1,5 +1,11 @@
 #!/bin/bash
-cargo doc --no-deps --features=linux-native --target aarch64-unknown-linux-musl $OPEN_DOCS
-cargo doc --no-deps --features=windows-native --target aarch64-pc-windows-msvc $OPEN_DOCS
-cargo doc --no-deps --features=apple-native --target aarch64-apple-darwin $OPEN_DOCS
-cargo doc --no-deps --features=apple-native --target aarch64-apple-ios $OPEN_DOCS
+if [[ "$OSTYPE" == "linux"* ]]; then
+  cargo doc --no-deps --features=linux-native-sync-persistent $OPEN_DOCS
+  cargo doc --no-deps --features=sync-secret-service $OPEN_DOCS
+  cargo doc --no-deps --features=linux-native $OPEN_DOCS
+elif [[ "$OSTYPE" == "darwin"* ]]; then
+  cargo doc --no-deps --features=linux-native --target aarch64-unknown-linux-musl $OPEN_DOCS
+  cargo doc --no-deps --features=windows-native --target aarch64-pc-windows-msvc $OPEN_DOCS
+  cargo doc --no-deps --features=apple-native --target aarch64-apple-darwin $OPEN_DOCS
+  cargo doc --no-deps --features=apple-native --target aarch64-apple-ios $OPEN_DOCS
+fi

src/keyutils_persistent.rs

@@ -0,0 +1,265 @@
+/*!
+
+# Linux (keyutils) store with Secret Service backing
+
+This store, contributed by [@soywod](https://github.com/soywod),
+uses the [keyutils module](crate::keyutils) as a cache
+available to headless processes, while using the
+[secret-service module](crate::secret_service)
+to provide credential storage beyond reboot.
+The expected usage pattern
+for this module is as follows:
+
+- Processes that run on headless systems are built with `keyutils` support via the
+  `linux-native` feature of this crate. After each reboot, these processes
+  are either launched after the keyutils cache has been reloaded from the secret service,
+  or (if launched immediately) they wait until the keyutils cache has been reloaded.
+- A headed "configuration" process is built with this module that allows its user
+  to configure the credentials needed by the headless processes. After each reboot,
+  this process unlocks the secret service (see both the keyutils and secret-service
+  module for information about how this can be done headlessly, if desired) and then
+  accesses each of the configured credentials (which loads them into keyutils). At
+  that point the headless clients can be started (or become active, if already started).
+
+This store works by creating a keyutils entry and a secret-service entry for
+each of its entries. Because keyutils entries don't have attributes, entries
+in this store don't expose attributes either. Because keyutils entries can't
+store empty passwords/secrets, this store's entries can't either.
+
+See the documentation for the `keyutils` and `secret-service` modules if you
+want details about how the underlying storage is handled.
+ */
+
+use log::debug;
+
+use super::credential::{
+    Credential, CredentialApi, CredentialBuilder, CredentialBuilderApi, CredentialPersistence,
+};
+use super::error::{Error, Result};
+use super::keyutils::KeyutilsCredential;
+use super::secret_service::{SsCredential, SsCredentialBuilder};
+
+/// Representation of a keyutils-persistent credential.
+///
+/// The credential owns a [KeyutilsCredential] for in-memory usage and
+/// a [SsCredential] for persistence.
+#[derive(Debug, Clone)]
+pub struct KeyutilsPersistentCredential {
+    keyutils: KeyutilsCredential,
+    ss: SsCredential,
+}
+
+impl CredentialApi for KeyutilsPersistentCredential {
+    /// Set a password in the underlying store
+    fn set_password(&self, password: &str) -> Result<()> {
+        self.set_secret(password.as_bytes())
+    }
+
+    /// Set a secret in the underlying store
+    ///
+    /// It sets first the secret in keyutils, then in
+    /// secret-service. If the latter set fails, the former
+    /// is reverted.
+    fn set_secret(&self, secret: &[u8]) -> Result<()> {
+        let prev_secret = self.keyutils.get_secret();
+        self.keyutils.set_secret(secret)?;
+
+        if let Err(err) = self.ss.set_secret(secret) {
+            debug!("Failed set of secret-service: {err}; reverting keyutils");
+            match prev_secret {
+                Ok(ref secret) => self.keyutils.set_secret(secret),
+                Err(Error::NoEntry) => self.keyutils.delete_credential(),
+                Err(err) => Err(err),
+            }?;
+
+            return Err(err);
+        }
+
+        Ok(())
+    }
+
+    /// Retrieve a password from the underlying store
+    ///
+    /// The password is retrieved from keyutils. In case of error, the
+    /// password is retrieved from secret-service instead (and
+    /// keyutils is updated).
+    fn get_password(&self) -> Result<String> {
+        match self.keyutils.get_password() {
+            Ok(password) => {
+                return Ok(password);
+            }
+            Err(err) => {
+                debug!("Failed get from keyutils: {err}; trying secret service")
+            }
+        }
+
+        let password = self.ss.get_password().map_err(ambiguous_to_no_entry)?;
+        self.keyutils.set_password(&password)?;
+
+        Ok(password)
+    }
+
+    /// Retrieve a secret from the underlying store
+    ///
+    /// The secret is retrieved from keyutils. In case of error, the
+    /// secret is retrieved from secret-service instead (and keyutils
+    /// is updated).
+    fn get_secret(&self) -> Result<Vec<u8>> {
+        match self.keyutils.get_secret() {
+            Ok(secret) => {
+                return Ok(secret);
+            }
+            Err(err) => {
+                debug!("Failed get from keyutils: {err}; trying secret service")
+            }
+        }
+
+        let secret = self.ss.get_secret().map_err(ambiguous_to_no_entry)?;
+        self.keyutils.set_secret(&secret)?;
+
+        Ok(secret)
+    }
+
+    /// Delete a password from the underlying store.
+    ///
+    /// The credential is deleted from both keyutils and
+    /// secret-service.
+    fn delete_credential(&self) -> Result<()> {
+        if let Err(err) = self.keyutils.delete_credential() {
+            debug!("cannot delete keyutils credential: {err}");
+        }
+
+        self.ss.delete_credential()
+    }
+
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+
+    fn debug_fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Debug::fmt(self, f)
+    }
+}
+
+impl KeyutilsPersistentCredential {
+    /// Create the platform credential for a Keyutils entry.
+    ///
+    /// This just passes the arguments to the underlying two stores
+    /// and wraps their results with an entry that holds both.
+    pub fn new_with_target(target: Option<&str>, service: &str, user: &str) -> Result<Self> {
+        let ss = SsCredential::new_with_target(target, service, user)?;
+        let keyutils = KeyutilsCredential::new_with_target(target, service, user)?;
+        Ok(Self { keyutils, ss })
+    }
+}
+
+/// The builder for keyutils-persistent credentials
+#[derive(Debug, Default)]
+pub struct KeyutilsPersistentCredentialBuilder {}
+
+/// Returns an instance of the keyutils-persistent credential builder.
+///
+/// If keyutils-persistent is the default credential store, this is
+/// called once when an entry is first created.
+pub fn default_credential_builder() -> Box<CredentialBuilder> {
+    Box::new(KeyutilsPersistentCredentialBuilder {})
+}
+
+impl CredentialBuilderApi for KeyutilsPersistentCredentialBuilder {
+    /// Build a [KeyutilsPersistentCredential] for the given target, service, and user.
+    fn build(&self, target: Option<&str>, service: &str, user: &str) -> Result<Box<Credential>> {
+        Ok(Box::new(SsCredential::new_with_target(
+            target, service, user,
+        )?))
+    }
+
+    /// Return the underlying builder object with an `Any` type so that it can
+    /// be downgraded to a [KeyutilsPersistentCredentialBuilder] for platform-specific processing.
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+
+    /// Return the persistence of this store.
+    ///
+    /// This store's persistence derives from that of the secret service.
+    fn persistence(&self) -> CredentialPersistence {
+        SsCredentialBuilder {}.persistence()
+    }
+}
+
+/// Replace any Ambiguous error with a NoEntry one
+fn ambiguous_to_no_entry(err: Error) -> Error {
+    if let Error::Ambiguous(_) = err {
+        return Error::NoEntry;
+    };
+
+    err
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{Entry, Error};
+
+    use super::KeyutilsPersistentCredential;
+
+    fn entry_new(service: &str, user: &str) -> Entry {
+        crate::tests::entry_from_constructor(
+            KeyutilsPersistentCredential::new_with_target,
+            service,
+            user,
+        )
+    }
+
+    #[test]
+    fn test_invalid_parameter() {
+        let credential = KeyutilsPersistentCredential::new_with_target(Some(""), "service", "user");
+        assert!(
+            matches!(credential, Err(Error::Invalid(_, _))),
+            "Created entry with empty target"
+        );
+    }
+
+    #[test]
+    fn test_empty_service_and_user() {
+        crate::tests::test_empty_service_and_user(entry_new);
+    }
+
+    #[test]
+    fn test_missing_entry() {
+        crate::tests::test_missing_entry(entry_new);
+    }
+
+    #[test]
+    fn test_empty_password() {
+        let entry = entry_new("empty password service", "empty password user");
+        assert!(
+            matches!(entry.set_password(""), Err(Error::Invalid(_, _))),
+            "Able to set empty password"
+        );
+    }
+
+    #[test]
+    fn test_round_trip_ascii_password() {
+        crate::tests::test_round_trip_ascii_password(entry_new);
+    }
+
+    #[test]
+    fn test_round_trip_non_ascii_password() {
+        crate::tests::test_round_trip_non_ascii_password(entry_new);
+    }
+
+    #[test]
+    fn test_round_trip_random_secret() {
+        crate::tests::test_round_trip_random_secret(entry_new);
+    }
+
+    #[test]
+    fn test_update() {
+        crate::tests::test_update(entry_new);
+    }
+
+    #[test]
+    fn test_noop_get_update_attributes() {
+        crate::tests::test_noop_get_update_attributes(entry_new);
+    }
+}