3 ms·

Ubuntu Cloud PRNG seed

9 points by lelf 12y ago

mjschultz 12y ago
I was curious so I decided to post some of the Google links about this: * man page: http://manpages.ubuntu.com/manpages/trusty/man1/pollinate.1.html http://manpages.ubuntu.com/manpages/trusty/man1/pollinate.1.... * Q&A style blog post: http://blog.dustinkirkland.com/2014/02/random-seeds-in-ubuntu-1404-lts-cloud.html http://blog.dustinkirkland.com/2014/02/random-seeds-in-ubunt... * A "why this is scary" blog post: https://tim.siosm.fr/blog/2014/04/25/why-not-ubuntu-14.04-lts/#pollinate https://tim.siosm.fr/blog/2014/04/25/why-not-ubuntu-14.04-lt...
wtbob 12y ago
I don't know how I feel about this. It's at least stirring the pot a little bit, but—as the Pollinate README indicates—it's not really increasing the entropy in the system at all. Thus one still needs to collect actual entropy, e.g. with CPU jitter[0]—and if one has collected enough entropy that way, then stirring the pot doesn't help (although it doesn't really hurt either). I think that the real answer has to be blocking boot until enough entropy has been gathered, based on CPU or storage timing, or on console input. [0] http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.html http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.html
m1el 12y ago
Quoting this comment by atoponce from /r/netsec: http://www.reddit.com/r/netsec/comments/2xlruv/ubuntu_cloud_prng_seed/cp1996q http://www.reddit.com/r/netsec/comments/2xlruv/ubuntu_cloud_...: >"Starting with Ubuntu 14.04 LTS, Ubuntu cloud images include the Pollinate client, which will try to seed the PRNG with input from https://entropy.ubuntu.com https://entropy.ubuntu.com for up to 3 seconds on first boot." So, let me get this straight. An Ubuntu cloud image doesn't have enough entropy to create strong crypto keys on first boot (SSH, SSL, etc.). So, it connects over the Internet, via HTTPS, which requires strong crypto keys to make the connection, to gather its entropy. Facepalm. The correct answer to generating enough entropy on boot is to either install haveged(8) as part of the imaging process, or to have the cloud image attach to a HWRNG using something similar to VirtIORNG. Enough entropy needs to be created before making an HTTPS connection, not after.

9 points by lelf 12y ago

I was curious so I decided to post some of the Google links about this: * man page: http://manpages.ubuntu.com/manpages/trusty/man1/pollinate.1.html http://manpages.ubuntu.com/manpages/trusty/man1/pollinate.1.... * Q&A style blog post: http://blog.dustinkirkland.com/2014/02/random-seeds-in-ubuntu-1404-lts-cloud.html http://blog.dustinkirkland.com/2014/02/random-seeds-in-ubunt... * A "why this is scary" blog post: https://tim.siosm.fr/blog/2014/04/25/why-not-ubuntu-14.04-lts/#pollinate https://tim.siosm.fr/blog/2014/04/25/why-not-ubuntu-14.04-lt...

wtbob 12y ago

I don't know how I feel about this. It's at least stirring the pot a little bit, but—as the Pollinate README indicates—it's not really increasing the entropy in the system at all. Thus one still needs to collect actual entropy, e.g. with CPU jitter[0]—and if one has collected enough entropy that way, then stirring the pot doesn't help (although it doesn't really hurt either). I think that the real answer has to be blocking boot until enough entropy has been gathered, based on CPU or storage timing, or on console input. [0] http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.html http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.html

m1el 12y ago

Quoting this comment by atoponce from /r/netsec: http://www.reddit.com/r/netsec/comments/2xlruv/ubuntu_cloud_prng_seed/cp1996q http://www.reddit.com/r/netsec/comments/2xlruv/ubuntu_cloud_...: >"Starting with Ubuntu 14.04 LTS, Ubuntu cloud images include the Pollinate client, which will try to seed the PRNG with input from https://entropy.ubuntu.com https://entropy.ubuntu.com for up to 3 seconds on first boot." So, let me get this straight. An Ubuntu cloud image doesn't have enough entropy to create strong crypto keys on first boot (SSH, SSL, etc.). So, it connects over the Internet, via HTTPS, which requires strong crypto keys to make the connection, to gather its entropy. Facepalm. The correct answer to generating enough entropy on boot is to either install haveged(8) as part of the imaging process, or to have the cloud image attach to a HWRNG using something similar to VirtIORNG. Enough entropy needs to be created before making an HTTPS connection, not after.