Refactor key derivation logic to properly handle Next Hop (NH) chain
synchronization according to 3GPP TS 33.501 specifications for both RRC
Reestablishment and Master Key Update procedures.
Changes in rrc_gNB.c:
- Clarify key derivation in rrc_gNB_generate_RRCReestablishment by explicitly
selecting base key (NH or KgNB) based on nh_ncc value
- Add comment explaining vertical vs horizontal derivation logic
Changes in rrc_UE.c:
Refactored the NH chain synchronization and key derivation code to match
TS 33.501 terminology:
- nr_sync_nh_chain(): Common helper to synchronize NH parameter chain per
TS 33.501 Annex A.10, supporting both Master Key Update and RRC Reestablishment
procedures
- nr_derive_kgnb_horizontal(): Derive KNG-RAN* from current KgNB when NCC values
match (horizontal derivation per TS 33.501 A.11/A.12)
- nr_derive_kgnb_vertical(): Derive KNG-RAN* from synchronized NH after NH chain
sync (vertical derivation per TS 33.501 A.11/A.12)
- nr_update_kgnb_from_ncc(): Unified function implementing TS 33.501 6.9.2.3.4
logic for updating KgNB based on received nextHopChainingCount
- Refactor as_security_key_update(): Use new nr_update_kgnb_from_ncc() helper
function for cleaner, more maintainable code
- Fix nr_rrc_ue_process_rrcReestablishment(): Properly handle received
nextHopChainingCount and update KgNB using unified helper function
- Replaced the previous nr_rrc_nh_update() helper with these functions to
improve clarity and alignment with the specification.
- Add debug logging for key derivation process
Key NAS deriver utils:
- update derive_kgnb documentation and protect input keys with const attribute
Closes#857
Jaroslava Fiedlerova
82bccfb9fe