fix(node): bound REST blob reads - #407
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Resolve REST blob paths to immutable object IDs, enforce size and output ceilings, and retain admission through response delivery. Refs Gitlawb#204
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Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review. 📝 WalkthroughWalkthroughThe REST blob endpoint now uses bounded Git reads, concurrency permits, chunked response streaming, path validation, authorization-denial tests, and explicit oversized-payload handling. Configuration documentation describes the new limits. ChangesREST blob reads
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to Blob reads now return bounded, admission-controlled responses, but the new size, admission, and deadline status contracts lack handler-level coverage. This creates a bounded risk that future changes could alter those client-visible responses without detection. Sequence Diagram(s)sequenceDiagram
participant Client
participant get_blob
participant AppState
participant read_file_bounded
participant BlobResponseStream
Client->>get_blob: Request repository blob
get_blob->>AppState: Acquire read, blob, and caller permits
get_blob->>read_file_bounded: Read blob with size cap and deadline
read_file_bounded-->>get_blob: Return BoundedFileRead
get_blob->>BlobResponseStream: Create chunked response stream
BlobResponseStream-->>Client: Emit 64 KiB response chunks
BlobResponseStream->>AppState: Release permits on EOF or disconnect
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✨ Finishing Touches🧪 Generate unit tests (beta)
Comment |
Greptile SummaryThe PR bounds REST blob reads by resolving paths to immutable blob IDs, checking a 32 MiB ceiling before capture, and enforcing bounded Git execution.
Confidence Score: 5/5The PR appears safe to merge; no concrete changed-code defect remains after accounting for its documented size, deadline, and admission behavior. The new blob path consistently bounds captured output and concurrent retained bodies, releases admission through RAII on errors, EOF, or disconnect, and preserves existing uncapped Git-runner behavior.
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| Filename | Overview |
|---|---|
| crates/gitlawb-node/src/api/repos.rs | Integrates bounded blob reads, layered admission, stable error mapping, and permit-owning chunked response delivery. |
| crates/gitlawb-node/src/git/store.rs | Replaces unbounded git show reads with deadline-bound ref resolution, immutable blob lookup, size preflight, and capped content capture. |
| crates/gitlawb-node/src/git/visibility_pack.rs | Adds optional stdout retention limits while preserving complete pipe draining and existing child-process timeout semantics. |
| crates/gitlawb-node/src/state.rs | Adds the dedicated four-permit REST blob pool and documents its lifecycle. |
| crates/gitlawb-node/src/error.rs | Adds stable HTTP 413 mapping for oversized blob responses. |
| crates/gitlawb-node/src/main.rs | Initializes the dedicated blob semaphore in production application state. |
Flowchart
%%{init: {'theme': 'neutral'}}%%
flowchart TD
A[REST blob request] --> B[Validate path and authorize read]
B --> C[Acquire per-caller, blob, and global permits]
C --> D[Acquire repository under timeout]
D --> E[Resolve branch and path to immutable blob OID]
E --> F{Declared size above 32 MiB?}
F -- Yes --> G[Return 413]
F -- No --> H[Read blob with capped stdout and shared deadline]
H --> I[Stream 64 KiB response chunks]
I --> J[EOF or disconnect]
J --> K[Release admission permits]
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Inline comments:
In `@crates/gitlawb-node/src/api/repos.rs`:
- Around line 531-536: Add authorization-denial tests for the get_blob handler,
covering unauthorized authenticated callers and applicable anonymous callers.
Assert the exact denial status and verify that the response body does not leak
protected resource details; do not add handler-level tests for 413, 503, or 504
responses.
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📒 Files selected for processing (11)
.env.exampleREADME.mdcrates/gitlawb-node/src/api/repos.rscrates/gitlawb-node/src/auth/mod.rscrates/gitlawb-node/src/config.rscrates/gitlawb-node/src/error.rscrates/gitlawb-node/src/git/store.rscrates/gitlawb-node/src/git/visibility_pack.rscrates/gitlawb-node/src/main.rscrates/gitlawb-node/src/state.rscrates/gitlawb-node/src/test_support.rs
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This is a solid DoS bound on a previously unbounded REST blob endpoint. The old git show path is replaced with a two-phase cat-file --batch-check (size probe) then cat-file blob (content read), with a 32 MiB served-size ceiling, a 4-permit dedicated blob pool, process-group deadline teardown (SIGTERM, grace, SIGKILL), and permit retention through response body delivery. Authorization gates on the specific path before any subprocess. Denials are opaque 404s. The 413/504/503 status mapping is correct.
Two items to address before merge:
1. git stderr reaches the 500 response body (blocking)
The bail! sites in read_file_bounded include raw git stderr in the error message:
bail!("git cat-file --batch-check failed: {}", String::from_utf8_lossy(&stderr))This flows through git_service_app_error to AppError::Git(msg), which maps to (500, "git_error", msg.clone()) at error.rs:191. The stderr string becomes the "message" field in the JSON response body, exposing filesystem paths, object names, and internal git state to the client.
The old read_file had the same pattern (bail!("git show failed: {stderr}")), so this is not a regression, but the PR touches these error paths and should map them to the opaque AppError::Internal variant (which emits INTERNAL_ERROR_MESSAGE) or log stderr with tracing::error! and bail with an opaque message. A test asserting the 500 body for a forced cat-file failure contains no stderr or filesystem path would close the gap.
2. .env.example comments for two knobs don't mention REST blob reads
The PR updated the GITLAWB_MAX_CONCURRENT_GIT_OPS comment to mention blob reads and the four-response sub-pool, but two other knobs that now affect blob reads were not updated:
GITLAWB_GIT_SERVICE_TIMEOUT_SECS(line 120-130): still describes upload-pack, info/refs, withheld-blob pack build, and push-side candidate discovery.read_file_boundeduses this deadline for itscat-filecalls, so an operator lowering it to tighten clone behavior would not expect blob downloads to start 504ing.GITLAWB_MAX_CONCURRENT_READS_PER_CALLER(line 180-187): describes the per-source read cap but doesn't mention blob reads.get_blobacquires from this limiter, so a low cap now affects blob downloads too.
A one-line addition to each comment would close the gap.
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Summary
GET /api/v1/repos/:owner/:repo/blob/*pathpreviously ran Git synchronously and materialized the complete child output before responding. Resolve the requested path to an immutable blob object, reject objects above the served-size ceiling before content capture, and enforce a hard stdout limit under the configured Git deadline.REST blob reads now share the existing global and per-source read admission and use a dedicated four-response pool whose permits remain held through chunked body delivery. This bounds retained source buffers while keeping slow clients from recycling admission before their response ends.
Partially addresses #204.
Changes
Test plan
cargo fmt --all -- --checkcargo clippy -p gitlawb-node --bin gitlawb-node -- -D warningscargo test -p gitlawb-node bounded_file_readcargo test -p gitlawb-node stdout_drain_discards_bytes_past_the_retention_limitcargo test -p gitlawb-node blob_response_holds_admission_until_the_body_is_droppedcargo test -p gitlawb-node payload_too_large_maps_to_413The full workspace test command was also attempted; database-backed tests require
DATABASE_URL, which is not available in this environment.Summary by CodeRabbit