* fix(mcp): constrain stdio launcher args and env at the config API
The API-managed stdio allowlist validated only `command`. Since `npx`/`uvx`
exist to fetch and run code, allowlisting the command name alone named a
binary without constraining what that binary ran, so the restriction did not
match the intent stated in `_validate_mcp_update_request`'s own docstring:
reducing the blast radius of a compromised authenticated browser session.
Screen two more fields on the stdio path, shared by `PUT /api/mcp/config` and
the enable branch of `PATCH`:
- `_ARBITRARY_EXEC_ARGS` rejects the flags that make a launcher evaluate a
string (`-c`, `--call`, `-e`, `--eval`, `--print`, `--shell`, `--node-arg`,
`--node-options`), matching `--flag=value` as well as `--flag value`, for
every allowlisted command rather than just `npx`/`uvx`. `-p` is deliberately
absent: it means `--package` for npx and `--python` for uv.
- `_CODE_INJECTING_ENV_VARS` rejects env names that inject code at process
startup (`NODE_OPTIONS`, `LD_PRELOAD`, `PYTHONSTARTUP`, ...), which would
otherwise sidestep the argument check.
Remote transports skip both -- they spawn nothing. Rejection messages echo
only the normalized flag, never the caller's value.
This is defense in depth, not a trust boundary: `npx`/`uvx` fetch and execute
remote packages by design, so an admin can still point one at a package they
published. Gateway admin remains equivalent to code execution on the host, and
the code, backend/AGENTS.md, and README all say so explicitly to keep the
check from being mistaken for a boundary.
`npx`/`uvx` stay in the default allowlist: nearly every official MCP server is
`npx -y @modelcontextprotocol/server-*`, so dropping them would break the
primary UI flow for adding one.
Tests cover each rejected flag spelling, case-insensitivity, `python -c` under
an extended allowlist, env injection, and the PATCH enable path, plus nine
positive cases pinning that real-world `npx`/`uvx`/`python -m` invocations
still validate.
* fix(mcp): screen PYTHONPATH and interpreter short-flag clusters
Review follow-up on the stdio launcher screen.
`PYTHONPATH` bypassed the env denylist on the *default* allowlist: `site`
imports `sitecustomize.py` from any `sys.path` entry before the tool's
entry point runs, so a caller-controlled directory is code execution
under plain `uvx` (verified against the real launcher). `PYTHONHOME` is
the same class via a repointed stdlib. Both are now rejected.
`PYTHONSTARTUP` is inert for non-interactive launchers and stays only as
belt-and-braces, now documented as such.
`-p` was exempted for every command, but it is node's `--print` --- the
long spelling was blocked while the short one passed once an operator
extended the allowlist. Whole-token matching also missed combined short
options (`node -pe`, `perl -we`, `python -Ic`). Both rules now apply to
commands outside `{npx, uvx}`, which are interpreters rather than package
runners; scoping them that way leaves the default allowlist unchanged,
since npx/uvx do not cluster short options and their trailing arguments
belong to a third-party server's own CLI where `-name` is ordinary.
`LD_LIBRARY_PATH`/`DYLD_LIBRARY_PATH` are recorded as an accepted
residual: conditional on the process loading a shadowable library, and
legitimately set by native-dependency servers.
Still defense in depth, not a trust boundary.
* docs(mcp): record NODE_PATH as an accepted search-path residual
Reviewer asked whether NODE_PATH belongs in _CODE_INJECTING_ENV_VARS for
parity with NODE_OPTIONS/PYTHONPATH. It does not, and the mechanism in the
report does not hold: verified on node v22, NODE_PATH is searched *after* the
local node_modules chain (the resolver unshifts the requiring module's paths
ahead of it), so it cannot shadow an installed dependency, and ESM import
ignores it entirely. It can only supply a CJS module that would otherwise
fail to resolve.
That puts it with LD_LIBRARY_PATH as a conditional search path, not with the
unconditional startup execution every entry in the set provides. Widen the
residual note from native-library shadowing to the general class, name
NODE_PATH in it, and pin the boundary with a test so it reads as a decision.
* fix(mcp): scope the stdio arg screen to the launcher's option region
`_arbitrary_exec_arg` inspected every element of `args`, justified by the claim
that the launchers in scope treat the token after `--` as a package name. That
is inaccurate: only the *first* token after `--` is the package name, and with
or without the separator every token from the package name onward is handed to
the third-party server's own argv, where `-c` is routinely "config" and `-e`
"env". So `npx -y @scope/server -c config.json` was rejected even though npm
never parses that `-c`, and the positive cases stayed green only because they
were picked to dodge the denylist. Over-blocking, not a bypass -- a regression
against the PR's own "the primary UI flow must keep working" goal.
Screen the launcher's own option region instead. Finding that region needs each
launcher's option *arity*, because a value is not a positional:
`npx -p <pkg> -c '<command>'` runs the command -- `-p` is `npm exec`'s
`--package` (it overrides the global `--parseable` shorthand), so `<pkg>` is
its value and npm keeps parsing its own flags. Ending the region at the first
non-flag token, the obvious rule, walks straight past that and turns an
over-block into a real eval bypass. The tables are therefore generated, not
guessed: `_NPX_BOOLEAN_ARGS` from `@npmcli/config` (npm 10.9.4) with the `-p`
override applied, `_UVX_VALUE_ARGS` from `uvx --help` (uv 0.11.1).
The unknown-option default is deliberately opposite per launcher, following the
exec set rather than symmetry. npx owns real exec flags, so an unknown option
consumes a value and keeps the region open; npm errors on options it does not
define, so that direction cannot reject an invocation that would otherwise
work. uvx owns no string-eval flag at all, so its screen is a tripwire rather
than a control, and an unknown option consumes nothing -- which keeps uv's
large and growing boolean surface from over-blocking. uvx also drops the short
spellings from its exec set, since `-c` is uv's `--constraints <file>`: an
ordinary documented option the old screen rejected outright.
Short options are matched case-sensitively now, because their case selects a
different option -- npm reads `-C` as `--prefix`, and folding it onto `-c`
rejected it. Long spellings stay case-insensitive: npm accepts `--CALL` and
runs it. Commands outside the package-launcher table are interpreters rather
than package runners and keep the unchanged whole-args screen, including the
`-p` rule and cluster decomposition.
Verified against the real launchers rather than by reading their docs. For
every argument vector in the new tests the validator's verdict matches whether
`npx` actually executes the string or passes it through to the server, and the
bypass-guard cases were confirmed to fail under the naive first-non-flag-token
boundary before being pinned.
Reported by @willem-bd on #4617. Two further false positives found while
confirming it are covered here: `uvx -c constraints.txt <tool>` above, and
`docker run -i --rm -e KEY <image>` -- the canonical GitHub MCP server
invocation -- which an operator who extends the allowlist with `docker` still
hits, since the conservative non-package-launcher path is unchanged.
---------
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
* fix(channels): harden runtime credential management APIs
* fix(channels): address review feedback on credential hardening
Follow-up to the runtime credential-hardening pass, resolving five review
findings:
- WeChat auth persistence now writes through a 0o600 NamedTemporaryFile +
Path.replace instead of write_text-then-chmod, so the iLink bot_token is
never briefly readable at umask defaults (mirrors ChannelRuntimeConfigStore).
- The post-write chmod is split into its own try/except: a chmod failure on a
filesystem without POSIX perms now logs at debug instead of masquerading as
a "failed to persist" warning.
- Extracted the three near-identical _require_admin_user helpers (mcp,
channel_connections, channels) into a single require_admin_user(request, *,
detail) in app/gateway/deps.py; each router supplies its own detail string.
- Strengthened the runtime-config-store chmod coverage: a new test injects a
temp-file chmod failure and asserts it is logged at debug while the
destination is still owner-only (mutation-verified to fail if the chmod is
dropped), plus a loose-pre-existing-file case.
- Removed the unused _FakeRepo from the blocking-io test: its isinstance gate
routes through the repo-less 503 path, so neither stub was ever invoked.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
* fix(security): mask sensitive values in MCP config API responses
GET /api/mcp/config previously returned plaintext secrets including
env dict values (API keys), headers (auth tokens), and OAuth
client_secret/refresh_token. Any authenticated user could read all
MCP service credentials.
This commit masks sensitive fields in GET/PUT responses while
preserving the key structure so the frontend round-trip (GET masked
→ toggle enabled → PUT) correctly preserves existing secrets.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
* fix(security): address Copilot review on MCP config masking
- Load raw JSON (un-resolved $VAR placeholders) as merge source instead
of resolved config, preventing plaintext secrets from replacing
$VAR placeholders on disk (Comment 2)
- Preserve all top-level keys (e.g. mcpInterceptors) in PUT, not just
mcpServers/skills (Comment 1)
- Reject masked value '***' for new keys that don't exist in existing
config, returning 400 with actionable error (Comment 3)
- Allow empty string '' to explicitly clear OAuth secrets, while None
means 'preserve existing' for safe round-trip (Comment 4)
- Add 3 new tests for rejection, clearing, and edge cases (18 total)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
