fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bsc/+/27509 )
Change subject: struct gsm_encr: store alg_id in human-readable format ......................................................................
struct gsm_encr: store alg_id in human-readable format
I find it weird that we store the A5 algorithm ID in a format that is used on the wire: N + 1 (valid for both A-bis and A interfaces). What confused me even more is that in some functions we print it as if it was in a normal, human-readable format. And this is also why one can see weird constructions like:
if (lchan->encr.alg_id > ALG_A5_NR_TO_RSL(0)) ciph_mod_set = (lchan->encr.alg_id-2)<<1 | 1;
Let's ensure that our internal structures use the A5/N format:
alg_id=0: A5/0 (0x01 on the A-bis/A interface) alg_id=1: A5/1 (0x02 on the A-bis/A interface) alg_id=2: A5/2 (0x03 on the A-bis/A interface) ... alg_id=7: A5/7 (0x08 on the A-bis/A interface)
so that we can print and compare the value alg_id without using additional arithmetics. This is how the above snippet changes:
if (lchan->encr.alg_id > 0) ciph_mod_set = (lchan->encr.alg_id << 1) | 1;
Change-Id: Ieb50c9a352cfa5481aebac2379e0a461663543ec --- M include/osmocom/bsc/gsm_data.h M src/osmo-bsc/abis_rsl.c M src/osmo-bsc/assignment_fsm.c M src/osmo-bsc/gsm_04_08_rr.c M src/osmo-bsc/gsm_08_08.c M src/osmo-bsc/handover_fsm.c M src/osmo-bsc/lchan_fsm.c M src/osmo-bsc/osmo_bsc_bssap.c 8 files changed, 19 insertions(+), 18 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/09/27509/1
diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h index 4fe97a2..434af5f 100644 --- a/include/osmocom/bsc/gsm_data.h +++ b/include/osmocom/bsc/gsm_data.h @@ -546,6 +546,7 @@ * These macros convert from n to the other representations: */ #define ALG_A5_NR_TO_RSL(A5_N) ((A5_N) >= 0 ? (A5_N)+1 : 0) +#define ALG_A5_NR_TO_BSSAP(A5_N) ALG_A5_NR_TO_RSL(A5_N) #define ALG_A5_NR_TO_PERM_ALG_BITS(A5_N) ((A5_N) >= 0 ? 1<<(A5_N) : 0)
/* Up to 16 SI2quater are multiplexed; each fits 3 EARFCNS, so the practical maximum is 3*16. @@ -608,6 +609,7 @@ #define MAX_A5_KEY_LEN (128/8)
struct gsm_encr { + /* Human readable: 0 (A5/0), 1 (A5/1), ... 7 (A5/7) */ uint8_t alg_id; uint8_t key_len; uint8_t key[MAX_A5_KEY_LEN]; diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c index a49cc65..b367149 100644 --- a/src/osmo-bsc/abis_rsl.c +++ b/src/osmo-bsc/abis_rsl.c @@ -159,8 +159,8 @@ * 'out' must provide room for 17 bytes. */ static int build_encr_info(uint8_t *out, struct gsm_lchan *lchan) { - *out++ = lchan->encr.alg_id & 0xff; - switch (lchan->encr.alg_id) { + *out = ALG_A5_NR_TO_RSL(lchan->encr.alg_id); + switch (*out++) { case GSM0808_ALG_ID_A5_1: case GSM0808_ALG_ID_A5_2: case GSM0808_ALG_ID_A5_3: @@ -660,7 +660,7 @@ msg->l3h = len + 1; *len = msgb_l3len(msg);
- if (lchan->encr.alg_id > ALG_A5_NR_TO_RSL(0)) { + if (lchan->encr.alg_id > 0) { uint8_t encr_info[MAX_A5_KEY_LEN+2]; rc = build_encr_info(encr_info, lchan); if (rc > 0) @@ -764,7 +764,7 @@ msgb_tlv_put(msg, RSL_IE_CHAN_MODE, sizeof(cm), (uint8_t *) &cm);
- if (lchan->encr.alg_id > ALG_A5_NR_TO_RSL(0)) { + if (lchan->encr.alg_id > 0) { uint8_t encr_info[MAX_A5_KEY_LEN+2]; rc = build_encr_info(encr_info, lchan); if (rc > 0) diff --git a/src/osmo-bsc/assignment_fsm.c b/src/osmo-bsc/assignment_fsm.c index 0243058..2b8b8b0 100644 --- a/src/osmo-bsc/assignment_fsm.c +++ b/src/osmo-bsc/assignment_fsm.c @@ -226,7 +226,7 @@
resp = gsm0808_create_ass_compl2(lchan->abis_ip.ass_compl.rr_cause, chosen_channel, - lchan->encr.alg_id, perm_spch, + ALG_A5_NR_TO_BSSAP(lchan->encr.alg_id), perm_spch, addr_local_p, sc_ptr, NULL, lcls_get_status(conn));
if (!resp) { diff --git a/src/osmo-bsc/gsm_04_08_rr.c b/src/osmo-bsc/gsm_04_08_rr.c index 560eb16..2232762 100644 --- a/src/osmo-bsc/gsm_04_08_rr.c +++ b/src/osmo-bsc/gsm_04_08_rr.c @@ -374,10 +374,10 @@
DEBUGP(DRR, "TX CIPHERING MODE CMD\n");
- if (lchan->encr.alg_id <= ALG_A5_NR_TO_RSL(0)) - ciph_mod_set = 0; + if (lchan->encr.alg_id > 0) + ciph_mod_set = (lchan->encr.alg_id << 1) | 0x01; else - ciph_mod_set = (lchan->encr.alg_id-2)<<1 | 1; + ciph_mod_set = 0x00;
gh = (struct gsm48_hdr *) msgb_put(msg, sizeof(*gh) + 1); gh->proto_discr = GSM48_PDISC_RR; @@ -592,9 +592,8 @@ * Shall be included in the case of inter-RAT handover. */ if (ho_scope & HO_INTER_BSC_IN) { uint8_t cms = 0x00; - /* This formula copied from gsm48_send_rr_ciph_mode() */ - if (new_lchan->encr.alg_id > ALG_A5_NR_TO_RSL(0)) - cms = (new_lchan->encr.alg_id - 2) << 1 | 1; + if (new_lchan->encr.alg_id > 0) + cms = (new_lchan->encr.alg_id << 1) | 1; /* T (4 bit) + V (4 bit), see 3GPP TS 44.018, 10.5.2.9 */ msgb_v_put(msg, GSM48_IE_CIP_MODE_SET | (cms & 0x0f)); } diff --git a/src/osmo-bsc/gsm_08_08.c b/src/osmo-bsc/gsm_08_08.c index a99db43..ad64a9c 100644 --- a/src/osmo-bsc/gsm_08_08.c +++ b/src/osmo-bsc/gsm_08_08.c @@ -94,7 +94,7 @@ return;
LOGP(DMSC, LOGL_DEBUG, "CIPHER MODE COMPLETE from MS, forwarding to MSC\n"); - resp = gsm0808_create_cipher_complete(msg, chosen_encr); + resp = gsm0808_create_cipher_complete(msg, ALG_A5_NR_TO_BSSAP(chosen_encr)); rate_ctr_inc(rate_ctr_group_get_ctr(conn->sccp.msc->msc_ctrs, MSC_CTR_BSSMAP_TX_DT1_CIPHER_COMPLETE)); rc = osmo_fsm_inst_dispatch(conn->fi, GSCON_EV_TX_SCCP, resp); if (rc != 0) diff --git a/src/osmo-bsc/handover_fsm.c b/src/osmo-bsc/handover_fsm.c index 5ae3787..6a12d04 100644 --- a/src/osmo-bsc/handover_fsm.c +++ b/src/osmo-bsc/handover_fsm.c @@ -756,7 +756,7 @@ }
/* Put encryption info in the chan activation info */ - info.encr.alg_id = ALG_A5_NR_TO_RSL(chosen_a5_n); + info.encr.alg_id = chosen_a5_n; if (chosen_a5_n > 0) { if (req->ei.key_len > sizeof(info.encr.key)) { ho_fail(HO_RESULT_ERROR, "Encryption Information IE key length is too large: %u", @@ -933,7 +933,7 @@ ho_perf_params.chosen_channel_present = true;
/* Chosen Encryption Algorithm 3.2.2.44 */ - ho_perf_params.chosen_encr_alg = lchan->encr.alg_id; + ho_perf_params.chosen_encr_alg = ALG_A5_NR_TO_BSSAP(lchan->encr.alg_id); ho_perf_params.chosen_encr_alg_present = true;
if (ho->new_lchan->activate.info.requires_voice_stream) { diff --git a/src/osmo-bsc/lchan_fsm.c b/src/osmo-bsc/lchan_fsm.c index 84f8dc5..3a87d42 100644 --- a/src/osmo-bsc/lchan_fsm.c +++ b/src/osmo-bsc/lchan_fsm.c @@ -750,7 +750,7 @@ : "none", gsm_lchant_name(lchan->type), gsm48_chan_mode_name(lchan->activate.ch_mode_rate.chan_mode), - (lchan->activate.info.encr.alg_id ? : 1)-1, + lchan->activate.info.encr.alg_id, lchan->activate.info.encr.key_len ? osmo_hexdump_nospc(lchan->activate.info.encr.key, lchan->activate.info.encr.key_len) : "none");
diff --git a/src/osmo-bsc/osmo_bsc_bssap.c b/src/osmo-bsc/osmo_bsc_bssap.c index df22a09..ed0b7b8 100644 --- a/src/osmo-bsc/osmo_bsc_bssap.c +++ b/src/osmo-bsc/osmo_bsc_bssap.c @@ -532,7 +532,7 @@ goto reject; }
- conn->lchan->encr.alg_id = ALG_A5_NR_TO_RSL(chosen_cipher); + conn->lchan->encr.alg_id = chosen_cipher; if (enc_key_len) { conn->lchan->encr.key_len = enc_key_len; memcpy(conn->lchan->encr.key, enc_key, enc_key_len); @@ -1436,7 +1436,7 @@ .l3_info_len = rr_ho_command->len, .chosen_channel_present = true, .chosen_channel = gsm0808_chosen_channel(new_lchan->type, new_lchan->current_ch_mode_rate.chan_mode), - .chosen_encr_alg = new_lchan->encr.alg_id, + .chosen_encr_alg = ALG_A5_NR_TO_BSSAP(new_lchan->encr.alg_id), .chosen_speech_version = gsm0808_permitted_speech(new_lchan->type, new_lchan->current_ch_mode_rate.chan_mode), }; @@ -1506,7 +1506,7 @@
struct gsm0808_handover_complete params = { .chosen_encr_alg_present = true, - .chosen_encr_alg = lchan->encr.alg_id, + .chosen_encr_alg = ALG_A5_NR_TO_BSSAP(lchan->encr.alg_id),
.chosen_channel_present = true, .chosen_channel = gsm0808_chosen_channel(lchan->type, lchan->current_ch_mode_rate.chan_mode),
-
fixeria