Date: Wed, 10 Jan 2018 00:56:27 +0100 From: "oststrom \(public\)" <pub@...strom.com> To: <oss-security@...ts.openwall.com> Subject: CVE-2017-18016 - Paritytech Parity Ethereum built-in Dapp Browser <= v1.6.10 webproxy token reuse same-origin policy bypass VuNote ====== Author: <github.com/tintinweb> Ref: https://github.com/tintinweb/pub/tree/master/pocs/cve-2017-18016  Version: 0.3 Date: Jun 16th, 2017 Tag: parity same origin policy bypass webproxy token reuse Overview -------- Name: parity Vendor: paritytech References: * https://parity.io/  Version: 1.6.8 Latest Version: 1.7.12 (stable) - fixed 1.8.5 (beta) - fixed Other Versions: <= 1.6.10 (stable) - vulnerable Platform(s): cross Technology: rust js Vuln Classes: CWE-346 Origin: local (remote website, malicious dapp) Min. Privs.: --- CVE: CVE-2017-18016 Description --------- quote website  >Parity Technologies is proud to present our powerful new Parity Browser. Integrated directly into your Web browser, Parity is the fastest and most secure way of interacting with the Ethereum network. Summary ------- PoC: https://tintinweb.github.io/pub/pocs/cve-2017-18016/  > Parity Browser <=1.6.8 allows remote attackers to bypass the Same Origin Policy and obtain sensitive information by requesting other websites via the Parity web proxy engine (reusing the current website's token, which is not bound to an origin). ![parity cookie](sop_cookie.gif) **(A)** Ethereum Parity's built-in dapp/web-browsing functionality is rendering browser same-origin policy (SOP) ineffective by proxying requests with the parity main process. As a result, any website navigated to ends up being origin http://localhost:8080. This also means that all websites navigated to share the same origin and thus are not protected by the browser SOP allowing any proxied website/dapp to access another proxied website/dapp's resources (Cookies, ...). //see attached PoC - index.html / PoC ![parity frame](sop_frame.gif) **(B)** Worse, due to the structure of proxy cache urls and the fact that they contain a reusable non-secret non-url specific cache-token it is possible for one proxied website/dapp to navigate to any other proxied website/dapp gaining full script/XHR control due to **(A)** the SOP being applied without any restrictions. This could allow a malicious website/dapp to take control of another website/dapp, performing user interactions, XHR or injecting scripts/DOM elements to mislead the user or to cause other unspecified damage. When navigating to a website with the built-in parity webbrowser a webproxy request token is requested and sent along an encoded request for an url. For example, navigating parity to http://oststrom.com the url gets turned into a proxy url like http://127.0.0.1:8080/web/8X4Q4EBJ71SM2CK6E5AQ6YBNB4NPGX3ME0X2YBVFEDT76X3JDX PJWRVFDM of the form http://127.0.0.1:8080/web/[base32_encode(token+url)]. A malicious dapp can use this information to decode its own url, extract the token and reuse it for any other url as the token is not locked to the url. The PoC exploits this in order to load any other website into a same-origin iframe by reusing the proxy token. Code see  //see attached PoC - index.html / PoC //see github  for details Proof of Concept ---------------- Prerequisites: * (if hosted locally) modify /etc/hosts to resolve your testdomain to your webserver * make `index.html` accessible on a webserver (e.g. `cd /path/to/index.html; python -m SimpleHTTPServer 80`) 1. launch parity, navigate to the built-in webbrowser (http://127.0.0.1:8180/#/web) 2. navigate the built-in parity webbrowser to where the PoC `index.html` is hosted (e.g. ) 3. follow the instructions. 4. Issue 1: navigate to some websites to have them set cookies, reload the PoC page and click "Display Cookies". Note that while the main request is proxied by parity, subsequent calls might not be (e.g. xhr, resources). That means you'll only see cookies set by the main site as only the initial call shares the origin `localhost:8080`. 5. Issue 2: enter an url into the textbox and hit `Spawn SOP Iframe`. A new iframe will appear on the bottom of the page containing the proxied website. Note that the calling website has full script/dom/xhr access to the proxied target. You can also use the "Display Cookies" button from Issue 1 to show cookies that have been merged into the origin by loading the proxied iframe. 6. Demo 2: Just a PoC to find local-lan web interfaces (e.g. your gateways web interface) and potentially mess with its configuration (e.g. router with default password on your lan being reconfigured by malicious dapp that excploits the token reuse issue 2) Fix ----- * Commit  (first in 1.7.0) * Does not fix Issue #1 - sites are generally put into same origin due to proxy * Fixes Issue #2 - Token Reuse * Parity now added a note that browsing websites with their browser is insecure ![parity fixed](v1712.png) * Issue #1 is not yet fixed as the cookie of instagram.com is still shown. * Parity v1.7.12 added a note. References ----------  https://parity.io/  https://github.com/paritytech/parity/blame/e8b418ca03866fd952d456830b30e9225 c81035a/dapps/src/web.rs  https://github.com/paritytech/parity/commit/53609f703e2f1af76441344ac3b72811 c726a215  https://tintinweb.github.io/pub/pocs/cve-2017-18016/  https://github.com/tintinweb/pub/tree/master/pocs/cve-2017-18016 Contact ------- https://github.com/tintinweb
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