refactor(tvix/castore): factor out node checks

Implement `validate()` on `node::Node`, and call it from PathInfo's
validate() too. Node-related errors are moved to a ValidateNodeError
error type.

This additionally adds some more validations for symlink targets (they
must not be empty, and not contain null bytes).

Change-Id: Ib9b89f1c9c795e868a1533281239bc8a36d97c5d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9715
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: edef <edef@edef.eu>

tvix/store/src/proto/mod.rs

@@ -3,10 +3,7 @@ use data_encoding::BASE64;
 // https://github.com/hyperium/tonic/issues/1056
 use nix_compat::store_path::{self, StorePath};
 use thiserror::Error;
-use tvix_castore::{
-    proto::{self as castorepb, NamedNode},
-    B3Digest, B3_LEN,
-};
+use tvix_castore::proto::{self as castorepb, NamedNode, ValidateNodeError};
 
 mod grpc_pathinfoservice_wrapper;
 
@@ -34,14 +31,14 @@ pub enum ValidatePathInfoError {
     #[error("No node present")]
     NoNodePresent(),
 
-    /// Invalid node name encountered.
+    /// Node fails validation
+    #[error("Invalid root node: {:?}", .0.to_string())]
+    InvalidRootNode(ValidateNodeError),
+
+    /// Invalid node name encountered. Root nodes in PathInfos have more strict name requirements
     #[error("Failed to parse {0:?} as StorePath: {1}")]
     InvalidNodeName(Vec<u8>, store_path::Error),
 
-    /// The digest the (root) node refers to has invalid length.
-    #[error("Invalid Digest length: expected {}, got {}", B3_LEN, .0)]
-    InvalidNodeDigestLen(usize),
-
     /// The digest in narinfo.nar_sha256 has an invalid len.
     #[error("Invalid narinfo.nar_sha256 length: expected {}, got {}", 32, .0)]
     InvalidNarSha256DigestLen(usize),
@@ -146,27 +143,8 @@ impl PathInfo {
                 Err(ValidatePathInfoError::NoNodePresent())?
             }
             Some(castorepb::Node { node: Some(node) }) => {
-                match node {
-                    // for a directory root node, ensure the digest has the appropriate size.
-                    castorepb::node::Node::Directory(directory_node) => {
-                        if TryInto::<B3Digest>::try_into(directory_node.digest.clone()).is_err() {
-                            return Err(ValidatePathInfoError::InvalidNodeDigestLen(
-                                directory_node.digest.len(),
-                            ));
-                        }
-                    }
-                    // for a file root node, ensure the digest has the appropriate size.
-                    castorepb::node::Node::File(file_node) => {
-                        // ensure the digest has the appropriate size.
-                        if TryInto::<B3Digest>::try_into(file_node.digest.clone()).is_err() {
-                            return Err(ValidatePathInfoError::InvalidNodeDigestLen(
-                                file_node.digest.len(),
-                            ));
-                        }
-                    }
-                    // nothing to do specifically for symlinks
-                    castorepb::node::Node::Symlink(_) => {}
-                }
+                node.validate()
+                    .map_err(|e| ValidatePathInfoError::InvalidRootNode(e))?;
                 // parse the name of the node itself and return
                 parse_node_name_root(node.get_name(), ValidatePathInfoError::InvalidNodeName)?
             }

tvix/store/src/proto/tests/pathinfo.rs

@@ -43,7 +43,7 @@ fn validate_no_node(
         digest: Bytes::new(),
         size: 0,
     },
-    Err(ValidatePathInfoError::InvalidNodeDigestLen(0));
+    Err(ValidatePathInfoError::InvalidRootNode(castorepb::ValidateNodeError::InvalidDigestLen(0)));
     "invalid digest length"
 )]
 #[test_case(
@@ -88,7 +88,7 @@ fn validate_directory(
         digest: Bytes::new(),
         ..Default::default()
     },
-    Err(ValidatePathInfoError::InvalidNodeDigestLen(0));
+    Err(ValidatePathInfoError::InvalidRootNode(castorepb::ValidateNodeError::InvalidDigestLen(0)));
     "invalid digest length"
 )]
 #[test_case(
@@ -120,7 +120,7 @@ fn validate_file(
 #[test_case(
     castorepb::SymlinkNode {
         name: DUMMY_NAME.into(),
-        ..Default::default()
+        target: "foo".into(),
     },
     Ok(StorePath::from_str(DUMMY_NAME).expect("must succeed"));
     "ok"
@@ -128,7 +128,7 @@ fn validate_file(
 #[test_case(
     castorepb::SymlinkNode {
         name: "invalid".into(),
-        ..Default::default()
+        target: "foo".into(),
     },
     Err(ValidatePathInfoError::InvalidNodeName(
         "invalid".into(),
@@ -239,3 +239,26 @@ fn validate_inconsistent_narinfo_reference_name_digest() {
         e => panic!("unexpected error: {:?}", e),
     }
 }
+
+/// Create a node with an empty symlink target, and ensure it fails validation.
+#[test]
+fn validate_symlink_empty_target_invalid() {
+    let node = castorepb::node::Node::Symlink(castorepb::SymlinkNode {
+        name: "foo".into(),
+        target: "".into(),
+    });
+
+    node.validate().expect_err("must fail validation");
+}
+
+/// Create a node with a symlink target including null bytes, and ensure it
+/// fails validation.
+#[test]
+fn validate_symlink_target_null_byte_invalid() {
+    let node = castorepb::node::Node::Symlink(castorepb::SymlinkNode {
+        name: "foo".into(),
+        target: "foo\0".into(),
+    });
+
+    node.validate().expect_err("must fail validation");
+}