ma1 pushed to branch mullvad-browser-128.7.0esr-14.5-1 at The Tor Project / Applications / Mullvad Browser Commits: 911dbf28 by Henry Wilkes at 2025-02-03T17:56:38+01:00 BB 29745: Limit remote access to content accessible resources - - - - - 1 changed file: - caps/nsScriptSecurityManager.cpp Changes: ===================================== caps/nsScriptSecurityManager.cpp ===================================== @@ -1044,6 +1044,48 @@ nsresult nsScriptSecurityManager::CheckLoadURIFlags( } } + // Only allow some "about:" pages to have access to contentaccessible + // "chrome://branding/" assets. Otherwise web pages could easily and + // consistently detect the differences between channels when their + // branding differs. See tor-browser#43308 and tor-browser#42319. + // NOTE: The same assets under the alternative URI + // "resource:///chrome/browser/content/branding/" should already be + // inaccessible to web content, so we only add a condition for the chrome + // path. + if (targetScheme.EqualsLiteral("chrome")) { + nsAutoCString targetHost; + rv = aTargetBaseURI->GetHost(targetHost); + NS_ENSURE_SUCCESS(rv, rv); + if (targetHost.EqualsLiteral("branding")) { + // Disallow any Principal whose scheme is not "about", or is a + // contentaccessible "about" URI ("about:blank" or "about:srcdoc"). + // NOTE: "about:blank" and "about:srcdoc" would be unexpected here + // since such a document spawned by a web document should inherit the + // same Principal URI. I.e. they would be "http:" or "https:" schemes. + // But we add this condition for extra assurances. + // NOTE: Documents with null Principals, like "about:blank" typed by + // the user, would also be excluded since the Principal URI would be + // "moz-nullprincipal:". + if (!aSourceBaseURI->SchemeIs("about") || + NS_IsContentAccessibleAboutURI(aSourceBaseURI)) { + return NS_ERROR_DOM_BAD_URI; + } + // Also exclude "about:reader" from accessing branding assets. I.e. if + // a web page includes `<img src="chrome://branding/..." />` we do not + // want it to render within "about:reader" either. + // Though it is unknown whether the information within "about:reader" + // would be exploitable by a web page, we also want to exclude + // "about:reader" for consistency: if it does not display in the + // original web page, it should not display in "about:reader" either. + nsAutoCString sourcePath; + rv = aSourceBaseURI->GetFilePath(sourcePath); + NS_ENSURE_SUCCESS(rv, rv); + if (sourcePath.EqualsLiteral("reader")) { + return NS_ERROR_DOM_BAD_URI; + } + } + } + if (targetScheme.EqualsLiteral("resource")) { if (StaticPrefs::security_all_resource_uri_content_accessible()) { return NS_OK; View it on GitLab: https://gitlab.torproject.org/tpo/applications/mullvad-browser/-/commit/911d... -- View it on GitLab: https://gitlab.torproject.org/tpo/applications/mullvad-browser/-/commit/911d... You're receiving this email because of your account on gitlab.torproject.org.