diff options
Diffstat (limited to 'src/sgsn/gprs_gmm.c')
| -rw-r--r-- | src/sgsn/gprs_gmm.c | 48 |
1 files changed, 43 insertions, 5 deletions
diff --git a/src/sgsn/gprs_gmm.c b/src/sgsn/gprs_gmm.c index c5e927a87..1f68558ef 100644 --- a/src/sgsn/gprs_gmm.c +++ b/src/sgsn/gprs_gmm.c @@ -445,6 +445,17 @@ static bool mmctx_is_r99(const struct sgsn_mm_ctx *mm) return false; } +static enum gprs_ciph_algo gprs_ms_net_select_best_gea(uint8_t net_mask, uint8_t ms_mask) { + uint8_t common_mask = net_mask & ms_mask; + uint8_t r = 0; + + while (common_mask >>= 1) { + r++; + } + + return r; +} + /* 3GPP TS 24.008 § 9.4.9: Authentication and Ciphering Request */ int gsm48_tx_gmm_auth_ciph_req(struct sgsn_mm_ctx *mm, const struct osmo_auth_vector *vec, @@ -1147,6 +1158,21 @@ static void mmctx_handle_rat_change(struct sgsn_mm_ctx *mmctx, struct msgb *msg, } +static uint8_t gprs_ms_net_cap_gea_mask(const uint8_t *ms_net_cap, uint8_t cap_len) +{ + uint8_t mask = (1 << GPRS_ALGO_GEA0); + mask |= (0x80 & ms_net_cap[0]) ? (1 << GPRS_ALGO_GEA1) : 0; + + if (cap_len < 2) + return mask; + + /* extended GEA bits start from 2nd bit of the next byte */ + mask |= (0x40 & ms_net_cap[1]) ? (1 << GPRS_ALGO_GEA2) : 0; + mask |= (0x20 & ms_net_cap[1]) ? (1 << GPRS_ALGO_GEA3) : 0; + mask |= (0x10 & ms_net_cap[1]) ? (1 << GPRS_ALGO_GEA4) : 0; + return mask; +} + /* 3GPP TS 24.008 § 9.4.1 Attach request */ static int gsm48_rx_gmm_att_req(struct sgsn_mm_ctx *ctx, struct msgb *msg, struct gprs_llc_llme *llme) @@ -1290,15 +1316,27 @@ static int gsm48_rx_gmm_att_req(struct sgsn_mm_ctx *ctx, struct msgb *msg, ctx->ms_radio_access_capa.len); ctx->ms_network_capa.len = msnc_len; memcpy(ctx->ms_network_capa.buf, msnc, msnc_len); - if (!gprs_ms_net_cap_gea_supported(ctx->ms_network_capa.buf, msnc_len, - ctx->ciph_algo)) { + + ctx->ue_cipher_mask = gprs_ms_net_cap_gea_mask(ctx->ms_network_capa.buf, msnc_len); + + if (!(ctx->ue_cipher_mask & sgsn->cfg.cipher_support_mask)) { reject_cause = GMM_CAUSE_PROTO_ERR_UNSPEC; LOGMMCTXP(LOGL_NOTICE, ctx, "Rejecting ATTACH REQUEST with MI " - "%s because MS do not support required %s " - "encryption\n", mi_log_string, - get_value_string(gprs_cipher_names,ctx->ciph_algo)); + "%s because MS do not support required encryption, mask UE:0x%02x NW:0x%02x \n", + mi_log_string, ctx->ue_cipher_mask, sgsn->cfg.cipher_support_mask); goto rejected; } + + /* just assume that everythig is fine if the phone offers a5/4: + * it requires a valid umts security context which we can only have after + * 1) IDENTITY REQUEST to know what to ask the HLR for + * 2) and AUTHENTICATION AND CIPHERING REQUEST + * ... but 2) already requires selecting a cipher mode. + * So let's just assume we will have the auth data required to make it work. + */ + + ctx->ciph_algo = gprs_ms_net_select_best_gea(ctx->ue_cipher_mask, sgsn->cfg.cipher_support_mask); + #ifdef PTMSI_ALLOC /* Allocate a new P-TMSI (+ P-TMSI signature) and update TLLI */ ptmsi_update(ctx); |