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GSUP transmits AUTS for UMTS authentication procedures, and OAP uses the same
procedures to authenticate. osmo-gen-vec is a utility program that passes AUTS
to our osmo_auth_gen_vec_auts() API.
According to 3GPP 33.102 6.3.3, AUTS = SQN^AK || MAC-S, which are 6 || 8 == 14
bytes. This is confirmed by 24.008 9.2.3a where the TLV has 16 bytes, TL = 2
and AUTS being the V = 14.
It is not harmful for milenage_gen_vec_auts() to pass two more AUTS bytes. But
writing 16 bytes to a GSUP struct is a potential problem when passing in a 14
byte long AUTS buffer to the GSUP API, which then reads past the AUTS buffer.
The API implies the length, so far to be 16, so passing in a 14 byte buffer to
GSUP would require copying to a larger buffer first.
Fix this by using a length of 14 for AUTS everywhere instead.
This constitues an ABI breakage, we may handle it as a "fix before an official
release", otherwise we need a version bump.
The OAP protocol document has also been updated, needs an update in the
osmo-gsm-manuals as well.
Change-Id: If25b173d9ec57ea4c504d860954912b7d82af455
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