fix(core,transports): validate mcp client targets at connect time (#7849) - #7873
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📝 SummarySummary by CodeRabbit
WalkthroughMCP client configuration now stores a public-target requirement. Registration sets and preserves this value under specified authentication conditions. MCP connection transports apply destination checks and route direct and proxied requests according to the client configuration. ChangesMCP public-target enforcement
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~45 minutes Sequence Diagram(s)sequenceDiagram
participant RegistrationClient
participant MCPHandler
participant ConfigStore
participant MCPClientManager
participant Resolver
participant MCPServer
RegistrationClient->>MCPHandler: Submit MCP client registration
MCPHandler->>Resolver: Resolve target when authentication is bypassed
Resolver-->>MCPHandler: Return target addresses or lookup error
MCPHandler->>ConfigStore: Save client and public-target setting
MCPClientManager->>Resolver: Check proxied destination when selected
Resolver-->>MCPClientManager: Return resolved addresses or lookup error
MCPClientManager->>MCPServer: Route request through proxy or direct transport
Suggested reviewers: Merge Risk: 🔵 Low · up to The new public-target setting only applies to HTTP and SSE MCP clients, but the docs describe it as covering every connection. Clarify that scope before merge so operators do not assume STDIO clients are covered. 🚥 Pre-merge checks | ✅ 3 | ❌ 2❌ Failed checks (2 warnings)
✅ Passed checks (3 passed)
Full details: Description checkResolution Replace the template text with a completed description. Summarize the purpose and changes, select the applicable change type and affected areas, provide test steps and results, state whether the change is breaking, add related issues if applicable, describe security implications, and complete the checklist. Full details: Out of Scope Changes checkExplanation The PR targets MCP client destination validation and registration handling. The migration change also reformats local struct fields for the standalone VK budget migration. This change has no connection to the MCP objective and does not affect migration behavior. ✨ Finishing Touches📝 Generate docstrings
🧪 Generate unit tests (beta)
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This was referenced Oct 3, 2026
fix(core,transports): bound request decompression and harden realtime request handling (#7856)
#7880
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akshaydeo
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October 3, 2026 04:28
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Review comments at @core/schemas/mcp.go:
- Line 537: Clarify that RequirePublicTarget applies only to HTTP/SSE clients:
update its field comment in core/schemas/mcp.go:537 to limit the public-address
guarantee to network dials, and update the require_public_target documentation
in docs/deployment-guides/config-json/schema-reference.mdx:398 to specify
HTTP/SSE and exclude STDIO and in-process clients.
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📒 Files selected for processing (17)
core/mcp/clientmanager.gocore/mcp/clientmanager_test.gocore/network/ssrf.gocore/network/ssrf_test.gocore/schemas/mcp.godocs/deployment-guides/config-json/schema-reference.mdxdocs/openapi/openapi.jsondocs/openapi/schemas/management/mcp.yamlframework/configstore/migrations.goframework/configstore/rdb.goframework/configstore/tables/mcp.gotests/e2e/api/collections/provider-harness.jsontransports/bifrost-http/handlers/mcp.gotransports/bifrost-http/handlers/mcpregistrationguard_test.gotransports/bifrost-http/lib/config.gotransports/config.schema.jsonui/lib/types/mcp.ts
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) MCP clients registered over the management API when no admin credential check is in place (dashboard auth unconfigured) can currently target private or loopback addresses on every reconnect and per-call dial, even if the registration-time DNS check passed. This PR introduces a `require_public_target` flag that is set server-side at registration for auth-bypassed callers and enforced on every subsequent dial for the lifetime of the client — not just at registration time. Additionally, the registration gate previously failed open when a target hostname could not be resolved (returning `false` and letting the request through), and an unknown `connection_type` value would skip both registration gates entirely and reach the connect path unchecked. Both are fixed here. - **`RequirePublicTarget` flag on `MCPClientConfig`**: A new boolean field, server-set only, that records whether a client was registered without an admin credential check. It is written at `POST /api/mcp/client` time by reading the `BifrostContextKeyAuthBypassed` context value and overwriting whatever the request body carried. Once stored as `true` it is never cleared by the API, config.json reconciliation, or a sparse update struct. - **Dial-time enforcement via `SSRFSafeDialContext`**: `buildTLSHTTPClient` now accepts the full `MCPClientConfig` instead of just `TLSConfig`. When `RequirePublicTarget` is set, `network.SSRFSafeDialContext` is installed instead of `network.PrivateNetworkDialContext`, blocking loopback and RFC1918 destinations on every dial. The proxy selector (`mcpProxySelector`) also gains a `requirePublicTarget` parameter and refuses IP-literal private destinations on the proxied path, where the dialer only sees the proxy address. - **Fail-closed on unresolvable hostnames**: `rejectPrivateMCPTargetIfAuthBypassed` previously returned `false` (allowed) when DNS lookup failed or returned no addresses. It now sends a `403` and returns `true`, since an unresolvable name gives the gate nothing to classify and is also how a caller could make the check inconclusive deliberately. - **`connection_type` enum validation up front**: `addMCPClient` now validates `connection_type` against the known enum (`http`, `sse`, `stdio`) before either registration gate runs. An unknown value previously matched neither gate and reached the connect path unchecked; it now returns a `400` immediately. - **Database migration**: A new migration (`add_mcp_client_require_public_target_column`) adds the `require_public_target` column to the MCP client table, defaulting to `false` so existing rows keep their current dial policy. - **Config.json reconciliation**: `pinMCPClientImmutableFields` preserves `RequirePublicTarget` using an OR — a file entry that omits the field cannot lift a stored `true`, but declaring it `true` in the file is honored. - **Schema and docs**: `MCPClientConfig` schema, OpenAPI spec, config JSON schema, and the schema reference doc are all updated. The field is marked `readOnly` in the OpenAPI schema. The TypeScript UI type is updated with a read-only annotation. - **Tests**: Unit tests for `buildTLSHTTPClient` and `mcpProxySelector` are updated for the new signatures. New tests cover the `RequirePublicTarget` dial-time block, the proxied-path IP-literal block, the fail-closed DNS behavior wired into the handler, and the `connection_type` enum validation end-to-end. Two new E2E Postman cases cover the unknown `connection_type` (400) and unresolvable target (403) paths against the harness profile. - [ ] Bug fix - [x] Feature - [ ] Refactor - [ ] Documentation - [ ] Chore/CI - [x] Core (Go) - [x] Transports (HTTP) - [ ] Providers/Integrations - [ ] Plugins - [x] UI (React) - [x] Docs ```sh go test ./core/mcp/... ./transports/bifrost-http/handlers/... ./framework/configstore/... ``` **Manual registration-gate checks (no admin auth configured):** 1. POST to `/api/mcp/client` with `"connection_type": "streamable"` — expect `400` with `connection_type` in the error body. 2. POST to `/api/mcp/client` with `"connection_type": "http"` and `"connection_string": "http://does-not-resolve.invalid/mcp"` — expect `403` mentioning `public address`. 3. POST to `/api/mcp/client` with a valid public target — expect the client to be created with `require_public_target: true` in the response. 4. Confirm that a client created in step 3 cannot later be dialed to a loopback or RFC1918 address (e.g. by updating DNS to resolve privately), and that an admin-registered client (no auth bypass) can still reach a local MCP server. - [ ] Yes - [x] No The `buildTLSHTTPClient` and `mcpProxySelector` signatures are internal. The `require_public_target` field defaults to `false` for all existing clients, preserving current behavior. The DNS fail-closed change and `connection_type` validation are behavioral fixes to previously incorrect permissive behavior. This PR is a defense-in-depth SSRF mitigation. The registration-time DNS check is a single point-in-time snapshot; `RequirePublicTarget` extends the public-address requirement to every dial for the client's lifetime, including reconnects and per-call connections, so a DNS rebinding attack or a name that later resolves to a private address is blocked at the transport layer. The fail-closed DNS behavior removes a path where an attacker could supply an unresolvable name to bypass the registration gate entirely. - [x] I read `docs/contributing/README.md` and followed the guidelines - [x] I added/updated tests where appropriate - [x] I updated documentation where needed - [x] I verified builds succeed (Go and UI) - [ ] I verified the CI pipeline passes locally if applicable
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Summary
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Changes
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docs/contributing/README.mdand followed the guidelines