feat(tvix/store): Add a signing pathinfoservice

Add a new path-info-service that wraps transparently around another
except that it signs all the incoming path infos with the provided
signer.

Change-Id: I845ddfdf01d14c503c796b2b80c720dab98be091

tvix/Cargo.lock

@@ -4995,6 +4995,7 @@ dependencies = [
  "clap",
  "count-write",
  "data-encoding",
+ "ed25519",
  "futures",
  "hyper-util",
  "lazy_static",

tvix/store/Cargo.toml

@@ -13,6 +13,7 @@ bytes = "1.4.0"
 clap = { version = "4.0", features = ["derive", "env"] }
 count-write = "0.1.0"
 data-encoding = "2.6.0"
+ed25519 = "2.2.3"
 futures = "0.3.30"
 lazy_static = "1.4.0"
 nix-compat = { path = "../nix-compat", features = ["async"] }

tvix/store/src/pathinfoservice/mod.rs

@@ -5,6 +5,7 @@ mod lru;
 mod memory;
 mod nix_http;
 mod redb;
+mod signing_wrapper;
 mod sled;
 
 #[cfg(any(feature = "fuse", feature = "virtiofs"))]
@@ -30,6 +31,7 @@ pub use self::lru::{LruPathInfoService, LruPathInfoServiceConfig};
 pub use self::memory::{MemoryPathInfoService, MemoryPathInfoServiceConfig};
 pub use self::nix_http::{NixHTTPPathInfoService, NixHTTPPathInfoServiceConfig};
 pub use self::redb::{RedbPathInfoService, RedbPathInfoServiceConfig};
+pub use self::signing_wrapper::{KeyFileSigningPathInfoServiceConfig, SigningPathInfoService};
 pub use self::sled::{SledPathInfoService, SledPathInfoServiceConfig};
 
 #[cfg(feature = "cloud")]
@@ -91,6 +93,7 @@ pub(crate) fn register_pathinfo_services(reg: &mut Registry) {
     reg.register::<Box<dyn ServiceBuilder<Output = dyn PathInfoService>>, NixHTTPPathInfoServiceConfig>("nix");
     reg.register::<Box<dyn ServiceBuilder<Output = dyn PathInfoService>>, SledPathInfoServiceConfig>("sled");
     reg.register::<Box<dyn ServiceBuilder<Output = dyn PathInfoService>>, RedbPathInfoServiceConfig>("redb");
+    reg.register::<Box<dyn ServiceBuilder<Output = dyn PathInfoService>>, KeyFileSigningPathInfoServiceConfig>("keyfile-signing");
     #[cfg(feature = "cloud")]
     {
         reg.register::<Box<dyn ServiceBuilder<Output = dyn PathInfoService>>, BigtableParameters>(

tvix/store/src/pathinfoservice/signing_wrapper.rs

@@ -0,0 +1,84 @@
+use super::PathInfoService;
+use crate::proto::PathInfo;
+use futures::stream::BoxStream;
+use std::path::Path;
+use std::sync::Arc;
+use tonic::async_trait;
+
+use tvix_castore::composition::{CompositionContext, ServiceBuilder};
+
+use tvix_castore::Error;
+
+use nix_compat::narinfo::{parse_keypair, SigningKey};
+use nix_compat::nixbase32;
+use tracing::{instrument, warn};
+
+pub struct SigningPathInfoService<T, S> {
+    inner: T,
+    signing_key: Arc<SigningKey<S>>,
+}
+
+#[async_trait]
+impl<T, S> PathInfoService for SigningPathInfoService<T, S>
+where
+    T: PathInfoService,
+    S: ed25519::signature::Signer<ed25519::Signature> + Sync + Send,
+{
+    #[instrument(level = "trace", skip_all, fields(path_info.digest = nixbase32::encode(&digest)))]
+    async fn get(&self, digest: [u8; 20]) -> Result<Option<PathInfo>, Error> {
+        self.inner.get(digest).await
+    }
+
+    async fn put(&self, path_info: PathInfo) -> Result<PathInfo, Error> {
+        let store_path = path_info.validate().map_err(|e| {
+            warn!(err=%e, "invalid PathInfo");
+            Error::StorageError(e.to_string())
+        })?;
+        let root_node = path_info.node.clone();
+        let mut nar_info = path_info
+            .to_narinfo(store_path)
+            .ok_or(Error::StorageError("".to_string()))?;
+        nar_info.add_signature(self.signing_key.as_ref());
+        let mut signed_path_info = PathInfo::from(&nar_info);
+        signed_path_info.node = root_node;
+        self.inner.put(signed_path_info).await
+    }
+
+    fn list(&self) -> BoxStream<'static, Result<PathInfo, Error>> {
+        self.inner.list()
+    }
+}
+
+#[derive(serde::Deserialize)]
+pub struct KeyFileSigningPathInfoServiceConfig {
+    pub inner: String,
+    pub keyfile: Box<Path>,
+}
+
+impl TryFrom<url::Url> for KeyFileSigningPathInfoServiceConfig {
+    type Error = Box<dyn std::error::Error + Send + Sync>;
+    fn try_from(_url: url::Url) -> Result<Self, Self::Error> {
+        Err(Error::StorageError(
+            "Instantiating a SigningPathInfoService from a url is not supported".into(),
+        )
+        .into())
+    }
+}
+
+#[async_trait]
+impl ServiceBuilder for KeyFileSigningPathInfoServiceConfig {
+    type Output = dyn PathInfoService;
+    async fn build<'a>(
+        &'a self,
+        _instance_name: &str,
+        context: &CompositionContext,
+    ) -> Result<Arc<dyn PathInfoService>, Box<dyn std::error::Error + Send + Sync + 'static>> {
+        let inner = context.resolve(self.inner.clone()).await?;
+        let signing_key = Arc::new(
+            parse_keypair(tokio::fs::read_to_string(&self.keyfile).await?.trim())
+                .map_err(|e| Error::StorageError(e.to_string()))?
+                .0,
+        );
+        Ok(Arc::new(SigningPathInfoService { inner, signing_key }))
+    }
+}