** Description changed: + [Impact] + + * backport upstream fix to avoid issues with newer kernels handling of + getrandom calls + + * The Bionic kernel itself doesn't have the changes yet that made this + much more common to show up in cloud environments, but when the cosmic + kernel will be available as HWE it will also affect Bionic. + + [Test Case] + + * The actual testcase is just "start the service". + To simplify you can ignore the service and directly start it in a + console in "no detach" mode + $ chronyd -d + + * The more complex part on the test is the condition under which this + becomes an issue, which is in low entropy environments. + The real cases are due to changes in the upstream kernel at ~4.17 + and examples can be found on the linked discussions as well as the + Debian bug. + + [Regression Potential] + + * The change itself only adds "one more" case to the conditions that + let it fall back to urandom. Never the less this can be considered a + security risk as discussed in the linked mail threads. + To be sure on that I added security as an extra reviewer on the first + MP for this before pushing it into any release. + See [4] for the ack by Seth. + Other than that + + [Other Info] + + * n/a + + ---- + Started in a discussion at [1] And eventually finalized in [2] and a commit at [3] We need to avoid systems hanging due to the long delay on start especially with kernel >=4.17 IIRC. Since this will soon be released with Cosmic and HWE Kernels for Bionic we don't want cloud instances to suddenly initialize much slower. TL;DR: The fallback always was to urandom, it just got a new case to do so, which is not being able to deliver enough entropy. Since this has a rather low but potential security drawback [2] I also will ping the security people to check and [n]ack this. [1]: https://listengine.tuxfamily.org/chrony.tuxfamily.org/chrony-users/2018/04/msg00036.html - [2]: https://listengine.tuxfamily.org/chrony.tuxfamily.org/chrony-users/2018/05/msg00060.html + [2]: https://listengine.tuxfamily.org/chrony.tuxfamily.org/chrony-users/2018/05/msg00060.html [3]: https://git.tuxfamily.org/chrony/chrony.git/commit/?id=7c5bd948bb7e21fa0ee22f29e97748b2d0360319 + [4]: https://code.launchpad.net/~paelzer/ubuntu/+source/chrony/+git/chrony/+merge/353232/comments/919347
** Bug watch added: Debian Bug tracker #906276 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=906276 ** Also affects: chrony (Debian) via https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=906276 Importance: Unknown Status: Unknown -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1787366 Title: avoid service start hang due to random changes To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/chrony/+bug/1787366/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
