add osmo_auth_c3() (separate from gsm_milenage())
To send a Ciphering Mode Command, we may need to derive a Kc from UMTS AKA
tokens. gsm_milenage() derives Kc from 3G tokens, but also derives an SRES.
For SRES, it requires an OPC, which may need to be derived from OP first. All
we need is a Kc, so we could feed a zero OPC ... but to simplify the function
call for cases where just a Kc is required, separate the c3 function out from
gsm_milenage(), as osmo_auth_c3(). Obviously call osmo_auth_c3() from
gsm_milenage() (meaning that osmo-hlr's 55.205 derived auc tests still cover
exactly that implementation).
Prepares: If04e405426c55a81341747a9b450a69188525d5c (osmo-msc)
Related: OS#2745
Change-Id: I85a1d6ae95ad9e5ce9524ef7fc06414848afc2aa
diff --git a/src/gsm/milenage/milenage.c b/src/gsm/milenage/milenage.c
index 7cf3312..3c14ab9 100644
--- a/src/gsm/milenage/milenage.c
+++ b/src/gsm/milenage/milenage.c
@@ -29,7 +29,7 @@
#include "common.h"
#include "aes_wrap.h"
#include "milenage.h"
-
+#include <osmocom/crypt/auth.h>
/**
* milenage_f1 - Milenage f1 and f1* algorithms
@@ -249,8 +249,7 @@
if (milenage_f2345(opc, k, _rand, res, ck, ik, NULL, NULL))
return -1;
- for (i = 0; i < 8; i++)
- kc[i] = ck[i] ^ ck[i + 8] ^ ik[i] ^ ik[i + 8];
+ osmo_auth_c3(kc, ck, ik);
#ifdef GSM_MILENAGE_ALT_SRES
os_memcpy(sres, res, 4);