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nr: add some comments to pdcp nia2 integrity

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This commit is contained in:
Cedric Roux
2021-03-30 16:01:57 +02:00
parent 63b7ff981e
commit fe4a9b005a
1 changed files with 6 additions and 0 deletions
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openair2/LAYER2/nr_pdcp/nr_pdcp_integrity_nia2.c
+6
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@@ -59,12 +59,18 @@ void nr_pdcp_integrity_nia2_integrity(void *integrity_context,
unsigned char mac[16]; unsigned char mac[16];
size_t maclen; size_t maclen;
/* see 33.401 B.2.3 for the input to 128-EIA2
* (which is identical to 128-NIA2, see 33.501 D.3.1.3) */
compute_t(t, count, bearer, direction); compute_t(t, count, bearer, direction);
CMAC_Update(ctx, t, 8); CMAC_Update(ctx, t, 8);
CMAC_Update(ctx, buffer, length); CMAC_Update(ctx, buffer, length);
CMAC_Final(ctx, mac, &maclen); CMAC_Final(ctx, mac, &maclen);
/* AES CMAC (RFC 4493) outputs 128 bits but NR PDCP PDUs have a MAC-I of
* 32 bits (see 38.323 6.2). RFC 4493 2.1 says to truncate most significant
* bit first (so seems to say 33.401 B.2.3)
*/
memcpy(out, mac, 4); memcpy(out, mac, 4);
} }