1452549 - application_data before handshake completes terminates DTLS

Status: RESOLVED FIXED

(NSS :: Libraries, enhancement)

Description

[Martin Thomson [:mt:]]

This manifests as an annoying intermittent error, such as:
https://queue.taskcluster.net/v1/task/fKr3A92TSUq8Tgb-3ATosw/runs/0/artifacts/public/logs/live_backing.log

Why it doesn't cause errors more often is that the length field that is being read is actually ciphertext, and most times that produces a value that exceeds the amount of data available, so we (correctly) identify it as junk and throw it away.  Only when the length is small enough do we see an error.  In the real world, failure rates would increase in proportion to the certificate size, up to the MTU.

What happens here is that if the application data arrives early, then the connection explodes.

Comment 1

[Phabricator Automation]

Attachment: Bug 1452549 - Discard application data that arrives before DTLS handshake completes, r?ekr

Comment 2

[Martin Thomson [:mt:]]

I realize that I wasn't very clear here.  TLS 1.3 handshake messages appear to use the application_data content type, so if those handshake messages arrive too early, then NSS might think that they are valid application_data messages and process them with the NULL cipher, which tends to work.  That then triggers the explosion.

Comment 4

[Tim Taubert [:ttaubert] (inactive)]

Here's another one: https://queue.taskcluster.net/v1/task/4stHngDbQNq-8Ypwq303fQ/runs/0/artifacts/public/logs/live_backing.log

Comment 5

[Intermittent Failures Robot]

1 failures in 792 pushes (0.001 failures/push) were associated with this bug in the last 7 days.    

Repository breakdown:
* nss: 1

Platform breakdown:
* mac: 1

For more details, see:
https://treeherder.mozilla.org/intermittent-failures.html#/bugdetails?bug=1452549&startday=2018-04-09&endday=2018-04-15&tree=trunk

Comment 6

[Intermittent Failures Robot]

2 failures in 551 pushes (0.004 failures/push) were associated with this bug in the last 7 days.    

Repository breakdown:
* nss-try: 1
* nss: 1

Platform breakdown:
* mac: 1
* linux32: 1

For more details, see:
https://treeherder.mozilla.org/intermittent-failures.html#/bugdetails?bug=1452549&startday=2018-04-30&endday=2018-05-06&tree=trunk

Comment 7

[Phabricator Automation]

Comment on attachment 8966118 [details]
Bug 1452549 - Discard application data that arrives before DTLS handshake completes, r?ekr

Eric Rescorla (:ekr) has approved the revision.

https://phabricator.services.mozilla.com/D879

Comment 8

[Martin Thomson [:mt:]]

https://hg.mozilla.org/projects/nss/rev/350b7210e90758de454feb4339379ef7f6b9b470