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Feature #2461

Improve "encryption" VTY parameter

Added by pespin 5 months ago. Updated 26 days ago.

Status:
In Progress
Priority:
High
Assignee:
Category:
-
Target version:
-
Start date:
08/24/2017
Due date:
% Done:

70%

Spec Reference:

Description

Currently the "encryption" parameter lets define which cipher is allowed by BSC, but only one can be allowed at a given time: "encryption a5 (0|1|2|3)". Tests in osmo-gsm-tester showed that currently if "encryption a5 X" is set in osmo-msc, then same config (with X) must also be applied to osmo-bsc, otherwise the set of ciphers coming from MSC will be rejected. The osmo-bsc encryption settings need improvement.

The cipher should be negotiated between MSC, BSC and MS:

  • the MSC allows a set of a5/x by VTY configuration (the MSC sends a "Cipher Mode Command" to the BSC with a bitmask stating the allowed ciphers).
  • the BSC should know which a5/x the connected BTS hardware supports, which the user tells us by VTY configuration.
  • The list of ciphers supported by MS is received as explained in 3GPP TS 24.008: classmark 1 says whether a5/1 is supported, classmark 2 has a5/3 and a5/2 and classmark 3 has the rest of them.

We need to intersect these three capabilites/requirements and pick the highest possible a5/x (except never allow a5/2), or send back a "Reject" if intersection is void.

projected osmo-bsc behavior:

  • By default, accept all A5/x (except 2) in osmo-bsc.
  • Allow the user to pick a subset of allowed a5/x via VTY command, globally.
  • And/or we could allow setting an A5/x bitmask on per-BTS VTY config.

e.g.

encryption a5 <0..7> [<0..7>] [<0..7>] [<0..7>] [<0..7>] [<0..7>] [<0..7>]

allowing

encryption a5 0 1 3

Related issues

Related to OsmoGSMTester - Feature #2457: osmo-gsm-tester: add test case: validate "encryption" & "authentication" vty parameter Closed 08/22/2017
Related to OsmoMSC - Feature #2460: Change "encryption" VTY parameter to allow more than one cipher In Progress 08/24/2017
Related to OsmoBSC - Feature #2462: clarify lchan->encr.alg_id New 08/24/2017
Related to OsmoBSC - Bug #75: A5/2 + A5/3 support in osmo-bsc Closed

History

#1 Updated by pespin 5 months ago

  • Related to Feature #2457: osmo-gsm-tester: add test case: validate "encryption" & "authentication" vty parameter added

#2 Updated by pespin 5 months ago

  • Related to Feature #2460: Change "encryption" VTY parameter to allow more than one cipher added

#3 Updated by pespin 5 months ago

  • Description updated (diff)

#4 Updated by neels 5 months ago

  • Description updated (diff)

#5 Updated by neels 5 months ago

#6 Updated by neels 4 months ago

  • Priority changed from Normal to High

would help a little on the osmo-gsm-tester

#7 Updated by laforge 2 months ago

  • Assignee set to sysmocom

#8 Updated by laforge 27 days ago

  • Assignee changed from sysmocom to laforge

#9 Updated by laforge 27 days ago

  • Related to Bug #75: A5/2 + A5/3 support in osmo-bsc added

#10 Updated by laforge 26 days ago

  • Status changed from New to In Progress
  • % Done changed from 0 to 70

Implemeted in Change-Id "I1d1c8131855bcab2392b4f27f6216bdb2fae10e0" part of my "laforge/fsm" branch.

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