diff options
Diffstat (limited to 'src/gsm/auth_core.c')
| -rw-r--r-- | src/gsm/auth_core.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/src/gsm/auth_core.c b/src/gsm/auth_core.c index 3a0866be..b78cdd50 100644 --- a/src/gsm/auth_core.c +++ b/src/gsm/auth_core.c @@ -90,6 +90,47 @@ int osmo_auth_supported(enum osmo_auth_algo algo) return 0; } +/* C5 function to derive UMTS IK from GSM Kc */ +static inline void c5_function(uint8_t *ik, const uint8_t *kc) +{ + unsigned int i; + + for (i = 0; i < 4; i++) + ik[i] = kc[i] ^ kc[i+4]; + memcpy(ik+4, kc, 8); + for (i = 12; i < 16; i++) + ik[i] = ik[i-12]; +} + +/* C4 function to derive UMTS CK from GSM Kc */ +static inline void c4_function(uint8_t *ck, const uint8_t *kc) +{ + memcpy(ck, kc, 8); + memcpy(ck+8, kc, 8); +} + +/*! \brief Generate 3G CK + IK from 2G authentication vector + * \param vec Authentication Vector to be modified + * + * This function performs the C5 and C4 functions to derive the UMTS key + * material from the GSM key material in the supplied vector, _if_ the input + * vector doesn't yet have UMTS authentication capability */ +int osmo_auth_3g_from_2g(struct osmo_auth_vector *vec) +{ + if ((vec->auth_types & OSMO_AUTH_TYPE_GSM) && + !(vec->auth_types & OSMO_AUTH_TYPE_UMTS)) { + c5_function(vec->ik, vec->kc); + c4_function(vec->ck, vec->kc); + /* We cannot actually set OSMO_AUTH_TYPE_UMTS as we have no + * AUTN and no RES, and thus can only perform GSM + * authentication with this tuple. + * */ + return 1; + } + + return 0; +} + /*! \brief Generate authentication vector * \param[out] vec Generated authentication vector * \param[in] aud Subscriber-specific key material |