1491583 - Can we remove the SRTP_AES128_CM_HMAC_SHA1_32 cipher

Status: NEW

(Core :: WebRTC: Networking, enhancement, P3)

Description

[Nils Ohlmeier [:drno]]

We want to figure out when we can remove the SRTP_AES128_CM_HMAC_SHA1_32 from Firefox SRTP inside WebRTC.

Comment 1

[Nils Ohlmeier [:drno]]

Preliminary data after 13 days https://telemetry.mozilla.org/new-pipeline/dist.html#!cumulative=0&end_date=2018-10-02&include_spill=0&keys=__none__!__none__!__none__&max_channel_version=nightly%252F64&measure=WEBRTC_SRTP_CIPHER&min_channel_version=nightly%252F57&processType=*&product=Firefox&sanitize=0&sort_keys=submissions&start_date=2018-09-20&table=0&trim=1&use_submission_date=0

Surprising 3% use of SRTP_AES128_CM_HMAC_SHA1_32 in the Nightly channel. Lets wait how this evolves in the Beta channel, but so far it doesn't look like we can remove this without causing interop issues.

Comment 2

[Eric Rescorla (:ekr)]

Well, maybe. The problem is the other side might support 80 bit MACs but prefer 32. Not sure how to measure that, though

Comment 3

[Martin Thomson [:mt:]]

We could record new telemetry that splits by role: as a server, we won't pick 32.

Comment 4

[Eric Rescorla (:ekr)]

We could, but that just tells us who prefers 32, not who would fail if we did not offer it.

Comment 5

[Nils Ohlmeier [:drno]]

(In reply to Eric Rescorla (:ekr) from comment #2)

Well, maybe. The problem is the other side might support 80 bit MACs but
prefer 32. Not sure how to measure that, though

I found that Facebook Messenger does exactly that, but only in one direction.

Comment 6

[Nils Ohlmeier [:drno]]

Still around 3% for a full Beta cycle: https://telemetry.mozilla.org/new-pipeline/dist.html#!cumulative=0&end_date=2019-02-05&include_spill=0&keys=__none__!__none__!__none__&max_channel_version=beta%252F66&measure=WEBRTC_SRTP_CIPHER&min_channel_version=nightly%252F57&processType=*&product=Firefox&sanitize=0&sort_by_value=0&sort_keys=submissions&start_date=2018-12-11&table=1&trim=1&use_submission_date=0

Wondering how much of that is from FB Messenger.

Comment 8

[Nils Ohlmeier [:drno]]

With SHA1_32 being well below 1% for quite some time now https://mzl.la/3MnDehl it might be time to finally remove this.