glm-5.1
f6e62a37ef
- Replace admin socket section with admin HTTP API section - Update config table (admin_socket_path → admin_key_path) - Update project structure (admin/auth.rs, handler.rs, config/mod.rs) - Update architecture diagram (Admin HTTP API instead of Unix socket) - Update Docker compose volume (admin-key instead of socket dir) - Mark all four task files as status: completed with summaries
103 lines
3.9 KiB
Markdown
103 lines
3.9 KiB
Markdown
---
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id: fix/config-reload-toctou
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name: Add mtime check to config reload to detect mid-write file changes (ADR-029)
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status: completed
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depends_on: []
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scope: narrow
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risk: low
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impact: component
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level: implementation
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review_findings: [W2]
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adr: [029]
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---
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## Description
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Both the SIGHUP reload path (`src/shutdown.rs:handle_sighup_reload`) and the
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admin HTTP reload path (`src/admin/socket.rs:handle_reload`, soon
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`src/admin/handler.rs`) read the config file from disk with
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`tokio::fs::read_to_string()`, then parse and apply it. If another process is
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writing to the config file at the same time, the proxy could read a partially
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written config.
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ADR-029 specifies a simple mitigation: compare file modification timestamps
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before and after reading. If mtime changed, reject the reload and return a
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"please retry" message.
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### Changes Required
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**Shared reload function** — Extract the common file-read-and-validate logic
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from `src/shutdown.rs:handle_sighup_reload()` and
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`src/admin/socket.rs:handle_reload()` into a shared function (e.g.,
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`src/config/dynamic_config.rs` or a new `src/config/reload.rs`):
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```rust
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pub async fn read_and_validate_config(
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config_path: &str,
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cli_allow_wildcard_bind: bool,
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) -> Result<(StaticConfig, DynamicConfig), ReloadError> {
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let metadata_before = tokio::fs::metadata(config_path).await
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.map_err(ReloadError::Io)?;
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let config_content = tokio::fs::read_to_string(config_path).await
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.map_err(ReloadError::Io)?;
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let metadata_after = tokio::fs::metadata(config_path).await
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.map_err(ReloadError::Io)?;
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if metadata_before.modified().ok() != metadata_after.modified().ok() {
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return Err(ReloadError::FileChangedDuringRead);
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}
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let full_config = FullConfig::parse(&config_content)?;
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let (new_static, new_dynamic) = full_config.into_static_and_dynamic();
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validate(&new_static, &new_dynamic, cli_allow_wildcard_bind)?;
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Ok((new_static, new_dynamic))
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}
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```
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**`src/shutdown.rs`** — Replace inline file read + parse + validate with a
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call to `read_and_validate_config()`. On `ReloadError::FileChangedDuringRead`,
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log a warning: "config file changed during read, please retry SIGHUP".
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**`src/admin/handler.rs`** (after admin-http-api task) — Same call. On
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`ReloadError::FileChangedDuringRead`, return
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`{"status": "error", "message": "config file changed during read, please retry"}`.
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**Error type** — Define `ReloadError` enum with variants:
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- `Io(std::io::Error)`
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- `Parse(toml::de::Error)`
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- `Validation(String)`
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- `FileChangedDuringRead`
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## Acceptance Criteria
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- [ ] Both SIGHUP and admin HTTP reload paths use the same file-reading logic
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- [ ] mtime is checked before and after reading the config file
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- [ ] If mtime changed, reload is rejected with a clear error message
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- [ ] Error message in admin HTTP response is generic ("config file changed
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during read, please retry") — no filesystem paths leaked
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- [ ] Full error details are logged server-side (path, mtime values)
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- [ ] SIGHUP path logs the same error at warn level
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- [ ] `cargo test` passes
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- [ ] `cargo clippy` passes with no warnings
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## References
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- docs/architecture/decisions/029-config-reload-toctou.md — ADR-029
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- docs/reviews/005-admin-socket-security-review.md — W2 finding
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- src/shutdown.rs — handle_sighup_reload
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- src/admin/socket.rs — handle_reload (to be replaced by admin/handler.rs)
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## Notes
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> This fix is independent of the admin socket → HTTP migration. It applies to
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> both reload paths (SIGHUP and admin). The implementation should be done
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> after or alongside the admin-http-api task since that task replaces
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> socket.rs with handler.rs.
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## Summary
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Implemented `read_and_validate_config()` in `src/config/mod.rs` with mtime check
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before/after reading. Both SIGHUP and admin HTTP reload paths use this shared
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function. `ReloadError::FileChangedDuringRead` returns HTTP 409 Conflict from
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the admin endpoint and logs a warning on SIGHUP. 7 new unit tests added. |