[v2] Harden the dev-mode IPC WebSocket against cross-origin and DNS rebinding - #6036
[v2] Harden the dev-mode IPC WebSocket against cross-origin and DNS rebinding#6036nft wants to merge 2 commits into
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Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review. WalkthroughThe development server now validates hosts and origins, issues a process-wide HttpOnly, SameSite=Strict capability cookie, and requires that cookie for IPC WebSocket upgrades. The macOS window also changes Escape and unhandled key event handling. ChangesDevelopment IPC security
macOS window input handling
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: ⚪ Minimal · up to The PR restricts development IPC WebSocket access to validated hosts, same-origin requests, and a per-launch capability cookie; no actionable merge-blocking risk remains. Sequence Diagram(s)sequenceDiagram
participant Browser
participant DevServer
participant HostGuard
participant ipcauth
participant IPCDispatcher
Browser->>DevServer: Request application resource
DevServer->>HostGuard: Validate Host
HostGuard-->>DevServer: Allow request
DevServer->>ipcauth: Token()
ipcauth-->>DevServer: Capability token
DevServer-->>Browser: Capability cookie
Browser->>DevServer: IPC WebSocket upgrade with Origin and cookie
DevServer->>HostGuard: Validate Host
HostGuard-->>DevServer: Allow upgrade
DevServer->>ipcauth: Valid(cookie)
ipcauth-->>DevServer: Validation result
DevServer->>IPCDispatcher: Forward authorized IPC messages
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🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Description checkExplanation The description explains the security issue, implementation, threat model, testing, configuration, and checklist status. It does not provide an issue number, but it explicitly states that no public issue exists. The unchecked documentation item is minor because the changelog was updated. Full details: Docstring CoverageExplanation Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 20 functions across 7 files. (1 skipped: 1 unsupported.)
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Inline comments:
In `@v2/internal/frontend/devserver/devserver.go`:
- Around line 87-99: The devserver middleware’s ipcauth cookie is bearer
authentication that any local HTTP client can obtain and reuse for the
/wails/ipc WebSocket. Replace this anonymous cookie bootstrap in the
d.server.Use handler with a bootstrap mechanism unavailable to arbitrary local
HTTP clients, or revise the implementation and security claim to provide only
cross-origin browser protection; preserve WebSocket handling and ensure the
method dispatcher cannot be reached under the current cookie flow.
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v2/internal/frontend/devserver/devserver.gov2/internal/frontend/devserver/origin_test.gov2/internal/frontend/ipcauth/ipcauth.gov2/internal/frontend/ipcauth/ipcauth_test.gowebsite/src/pages/changelog.mdx
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Gate the wails dev IPC WebSocket behind a per-launch capability cookie and a strict same-origin check, and validate every request's Host against an allowlist (localhost, IP literals, the configured bind address, and WAILS_DEV_ALLOWED_HOSTS) so a malicious page in the developer's browser cannot reach the bound-method dispatcher.
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Description
The development IPC WebSocket (
wails dev) forwards straight to the bound-method dispatcher. Before this PR it accepted a connection from any origin, so while the dev server is running, a malicious web page in the developer's browser could openws://localhost:34115/wails/ipcand invoke the application's entire bound Go API (every method exposed viaBind) — reading or mutating app state, touching the filesystem, or running commands, depending on what the app binds.This is dev-mode only: production builds use the native webview message handler, not this WebSocket, so shipped apps are unaffected. The exposure is on the developer's machine while
wails devis running.This PR hardens the dev server's browser attack surface with three layers:
Hostheader is validated before any route or cookie runs:localhost, any IP literal, the configured bind address, and any hosts named in the newWAILS_DEV_ALLOWED_HOSTSenv var (comma-separated; matched on the hostname only, so a reverse proxy on a different public port still works). DNS rebinding needs a resolvable name inHost, and none of the allowed forms can be repointed by a DNS answer — so a reboundattacker.examplepage is refused even though it is same-origin with itself. This mirrors theserver.allowedHostsprotection in Vite and webpack-dev-server./wails/ipcupgrade now requires anOriginheader equal to the (already-validated)Host—http/httpsonly, compared case-insensitively. The dev runtime always builds its socket URL fromwindow.location, so a genuine browser client is always same-origin; there is no legitimate headerless client, so a missing Origin is refused too.internal/frontend/ipcauthpackage mints a capability once per launch (crypto/rand.Text) and compares it in constant time (crypto/subtle). The dev server hands it to the pages it serves as anHttpOnly,SameSite=Strictcookie and requires it on the upgrade, raising the bar for the browser vector behind the two checks above.A same-origin page returns the cookie automatically, so the normal
wails devworkflow is unchanged — including LAN device testing (which reaches the machine by IP) and hostname/proxy setups (viaWAILS_DEV_ALLOWED_HOSTS).Scope / threat model
In scope: browser-vector attacks against a running dev server — a foreign-origin page, and DNS rebinding. A reviewer found the rebinding bypass against the first revision of this PR: with only a same-origin check, a page served on
attacker.example:34115and rebound to loopback presentsOrigin == Hostand passes; the Host allowlist closes it.Out of scope: other processes running as the same OS user as the developer. Such a process can read the capability cookie off a served response, or read the developer's memory and traffic outright; an HTTP-on-loopback dev server cannot defend against it, and this PR does not claim to. The comments and package docs are written to say so plainly, rather than presenting the cookie as local-client authentication.
This brings the dev server in line with the posture already enforced in production, which validates bridge-message origins (
internal/frontend/originvalidator) and webview request hosts (pkg/assetserver,ExpectedWebViewHost).No public issue exists — this was found in a private security review. Because it is dev-mode only I've raised it as an ordinary PR; happy to move it to a private advisory instead if you'd prefer.
Type of change
How Has This Been Tested?
Reproduction (before the fix): with
wails devrunning, a WebSocket client sendingOrigin: https://evil.exampleconnects tows://localhost:34115/wails/ipcand successfully invokes bound methods; and a DNS-rebound page presentingHost: attacker.example:34115with a matching Origin does the same. After the fix, both are refused with403(the rebound Host before the upgrade, the foreign Origin at it).Automated tests (run with
go test -tags dev):internal/frontend/ipcauth/ipcauth_test.go— the token is stable and non-empty;Validaccepts only the exact token and rejects empty, wrong, over-long, and truncated values.internal/frontend/devserver/host_guard_test.go— table tests for the Host allowlist: localhost / IP literal / IPv6 zone-ID / wildcard-bind / LAN-IP accepted; foreign names, wrong ports, shorthand and octal IPs, unbracketed IPv6, and rebinding names rejected;WAILS_DEV_ALLOWED_HOSTSentries honored (and port-exempt).internal/frontend/devserver/origin_test.go— the same-origin check accepts a same-originhttp/httpspage (case-insensitively) and rejects a missing, foreign, non-HTTP (null,file://,chrome-extension://), or unparseable Origin.internal/frontend/devserver/devserver_test.go— an end-to-end test over the real dev server (httptest+ a gorilla WebSocket dialer): no cookie →403; valid cookie + same origin →101and a working IPC round-trip; foreign Origin →403; missing Origin →403; and the DNS-rebinding regression (forgedHost, matchingOrigin, valid cookie) →403, which fails against the first revision's logic and passes now.Manual smoke against a running dev server:
curl -s -o /dev/null -w '%{http_code}' http://localhost:34115/→200curl -s -o /dev/null -w '%{http_code}' -H 'Host: attacker.example:34115' http://127.0.0.1:34115/→403Note: the
devserverpackage has pre-existinggo vet"non-constant format string" findings (logger.Error(err.Error()), present onmaster) that gatego testunder Go ≥ 1.24; they are unrelated to this change, so I ran the devserver tests with-vet=offand left them for a separate PR to keep this one scoped. The logging added here uses constant format strings and adds no new vet findings.Test Configuration
Checklist:
website/src/pages/changelog.mdxwith details of this PRWAILS_DEV_ALLOWED_HOSTSescape hatch is described in the changelog; happy to add a docs page if you point me at the right place)Summary by CodeRabbit