[Original at: https://wwws.nightwatchcybersecurity.com/2016/07/29/advisory-intel-crosswalk-ssl-prompt-issue/]

Summary

The Intel Crosswalk Project library for cross-platform mobile
development did not properly handle SSL errors. This behaviour could
subject applications developed using this library to SSL MITM attacks.

Vulnerability Details

The Crosswalk Project, created by Intels Open Source Technology
Center, allows mobile developers to use HTML, CSS and Javascript to
develop and deploy mobile apps across multiple platforms from the same
codebase. The library packages the HTML assets provided by the
developer and runs them inside a WebView on the device. The library
also bridges some of the common APIs and services from the Javascript
code in the WebView to the underlying platform. The project supports
deployment to iOS, Windows Phone and Android. It is implemented in
multiple apps, some of which can be found here.

For the Android implementation of CrossWalk  when an invalid or
self-signed SSL certificate is used during communication with the
server, the underlying library displays a prompt to the user asking
them to grant permission or deny permission to this certificate. If
the user allows the certificate, that choice is remembered going
forward and from that point in, all subsequent requests with invalid
SSL certificates are accepted by the application, and are not
rechecked. This applies even to connections over different WiFi
hotspots and different certificates. This may allow a network-level
attacker to mount MITM attack using invalid SSL certificate and
capture sensitive data.

Example of error dialog

The fix changes the behaviour to generate a programmatic error message
not visible to the user  about an invalid SSL certificate. This issue
has been fixed in the following versions of Crosswalk and all users of
the library are encouraged to upgrade:

- 19.49.514.5 (stable)
- 20.50.533.11 (beta)
- 21.51.546.0 (beta)
- 22.51.549.0 (canary)

This issue was originally discovered while testing a third-party
Android app using this library.

References

CERT/CC vulnerability note:
https://www.kb.cert.org/vuls/id/217871

Crosswalk security advisory:
https://lists.crosswalk-project.org/pipermail/crosswalk-help/2016-July/002167.html

CVE - CVE-2016-5672:
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-5672

Intel blog post:
https://blogs.intel.com/evangelists/2016/07/28/crosswalk-security-vulnerability/

Credits

Thank you to CERT/CC for coordination on this issue, and to the Intel
Open Source Technology Center for the fix.

Timeline

2016-05-25: Reported issue to the Intel PSIRT, got an automated reply
2016-05-30: Reached out to CERT/CC for help reaching Intel
2016-06-01: Request from CERT/CC for more details, provided details
via secure form
2016-06-15: Response from CERT/CC that Intel is planning a fix within 45 days
2016-06-23: Direct contact from Intel
2016-07-01: Asking CERT/CC to reserve a CVE, CERT/CC assigns a CVE
2016-07-22: Intel fix is finished and ready for testing
2016-07-25: We confirm the fix and coordinate disclosure dates
2016-07-29: Coordinated public disclosure