fix: validate returnTo parameter to prevent open redirect #46
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Add URL validation for the returnTo parameter in OIDC authentication flow to prevent open redirect vulnerabilities. - Add isValidReturnToUrl() helper function to validate URLs - Validate returnTo at input point (when storing in session) - Validate returnTo at output points (before redirects) - Reject external URLs with BadRequestError - Use safe fallback for invalid URLs at redirect points Fixes jetkvm#7
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IDisposable
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Jan 28, 2026
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This is an extremely good idea. :)
adamshiervani
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Feb 2, 2026
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| // Validate returnTo before redirecting (defense in depth) | ||
| if (!isValidReturnToUrl(returnTo, APP_HOSTNAME)) { | ||
| console.warn("Invalid returnTo URL detected at redirect point:", returnTo); | ||
| // Fall back to safe default | ||
| const safeUrl = new URL(`${APP_HOSTNAME}/devices`); | ||
| safeUrl.searchParams.append("tempToken", tempToken); | ||
| safeUrl.searchParams.append("deviceId", deviceId); | ||
| safeUrl.searchParams.append("oidcGoogle", tokenSet.id_token.toString()); | ||
| safeUrl.searchParams.append("clientId", process.env.GOOGLE_CLIENT_ID); | ||
| return res.redirect(safeUrl.toString()); | ||
| } | ||
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| const url = new URL(returnTo); | ||
| url.searchParams.append("tempToken", tempToken); | ||
| url.searchParams.append("deviceId", deviceId); | ||
| url.searchParams.append("oidcGoogle", tokenSet.id_token.toString()); | ||
| url.searchParams.append("clientId", process.env.GOOGLE_CLIENT_ID); | ||
| return res.redirect(url.toString()); | ||
| } | ||
| // Validate returnTo before redirecting (defense in depth) | ||
| if (!isValidReturnToUrl(returnTo, APP_HOSTNAME)) { | ||
| console.warn("Invalid returnTo URL detected at redirect point:", returnTo); | ||
| // Fall back to safe default | ||
| return res.redirect(`${APP_HOSTNAME}/devices`); | ||
| } |
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This is not needed, as we are the one setting the session cookie, and we sign them with our COOKIE_SECRET.
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Add URL validation for the returnTo parameter in OIDC authentication flow to prevent open redirect vulnerabilities.
Fixes #7