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/include/osmocom/crypt/auth.h b/include/osmocom/crypt/auth.h
index 4dbc6a4..e544126 100644
--- a/include/osmocom/crypt/auth.h
+++ b/include/osmocom/crypt/auth.h
@@ -105,4 +105,6 @@
const char *osmo_auth_alg_name(enum osmo_auth_algo alg);
enum osmo_auth_algo osmo_auth_alg_parse(const char *name);
+void osmo_auth_c3(uint8_t kc[], const uint8_t ck[], const uint8_t ik[]);
+
/* @} */