fixeria has uploaded this change for review.
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),
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