diff options
| author | Neels Hofmeyr <neels@hofmeyr.de> | 2017-12-18 03:12:01 +0100 |
|---|---|---|
| committer | Harald Welte <laforge@gnumonks.org> | 2017-12-18 23:05:24 +0000 |
| commit | aa84b71f0fe014156e90dde2f0c44694368dc034 (patch) | |
| tree | e89ecebe87b71d8735b92bb35b7a8d656c6d516c /src/gsm/auth_core.c | |
| parent | d589f1dcfddb672edddc84a06f0443569ac44bcc (diff) | |
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
Diffstat (limited to 'src/gsm/auth_core.c')
| -rw-r--r-- | src/gsm/auth_core.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/src/gsm/auth_core.c b/src/gsm/auth_core.c index 400708f9..f171ed49 100644 --- a/src/gsm/auth_core.c +++ b/src/gsm/auth_core.c @@ -236,4 +236,17 @@ const struct value_string osmo_sub_auth_type_names[] = { { 0, NULL } }; +/* Derive GSM AKA ciphering key Kc from UMTS AKA CK and IK (auth function c3 from 3GPP TS 33.103 ยง + * 4.6.1). + * \param[out] kc GSM AKA Kc, 8 byte target buffer. + * \param[in] ck UMTS AKA CK, 16 byte input buffer. + * \param[in] ik UMTS AKA IK, 16 byte input buffer. + */ +void osmo_auth_c3(uint8_t kc[], const uint8_t ck[], const uint8_t ik[]) +{ + int i; + for (i = 0; i < 8; i++) + kc[i] = ck[i] ^ ck[i + 8] ^ ik[i] ^ ik[i + 8]; +} + /*! @} */ |