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gsm0808: fix: do not encode invalid encryption algorithm 

According to 3GPP TS 48.008, section 3.2.2.44, the Chosen Encryption
Algorithm IE, which may be included in the following messages:

  - 3.2.1.2   ASSIGNMENT COMPLETE
  - 3.2.1.8   HANDOVER REQUEST
  - 3.2.1.10  HANDOVER REQUEST ACKNOWLEDGE
  - 3.2.1.12  HANDOVER COMPLETE
  - 3.2.1.25  HANDOVER PERFORMED
  - 3.2.1.31  CIPHER MODE COMPLETE

is coded as follows:

  0000 0001   No encryption used
  0000 0010   GSM A5/1
  0000 0011   GSM A5/2
  0000 0100   GSM A5/3
  0000 0101   GSM A5/4
  0000 0110   GSM A5/5
  0000 0111   GSM A5/6
  0000 1000   GSM A5/7

basically A5/X => X + 1.  All other values are Reserved for future
international use.  As can be seen, value 0x00 is RFU.  Passing
this value to some encoding functions would result in a PDU with
this IE omitted.  Although, some functions would still encode
Chosen Encryption Algorithm IE with this RFU value.

Let's ensure that all functions behave consistently.

Change-Id: If10e433a8174eabe6aa6d2c2937bf9cf5d14d7c9
This commit is contained in:
Vadim Yanitskiy 2020-08-31 19:10:39 +07:00 committed by laforge
parent 7da6ace594
commit ecaf5faa79
1 changed files with 9 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
src/gsm/gsm0808.c
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@ -283,8 +283,9 @@ struct msgb *gsm0808_create_cipher_complete(struct msgb *layer3, uint8_t alg_id)
msgb_l3len(layer3), layer3->l3h);
}
/* and the optional BSS message */
msgb_tv_put(msg, GSM0808_IE_CHOSEN_ENCR_ALG, alg_id);
/* Optional Chosen Encryption Algorithm IE */
if (alg_id > 0)
msgb_tv_put(msg, GSM0808_IE_CHOSEN_ENCR_ALG, alg_id);
/* pre-pend the header */
msg->l3h = msgb_tv_push(msg, BSSAP_MSG_BSS_MANAGEMENT, msgb_length(msg));
@ -603,7 +604,8 @@ struct msgb *gsm0808_create_ass_compl2(uint8_t rr_cause, uint8_t chosen_channel,
msgb_tv_put(msg, GSM0808_IE_CHOSEN_CHANNEL, chosen_channel);
/* write chosen encryption algorithm 3.2.2.44 */
msgb_tv_put(msg, GSM0808_IE_CHOSEN_ENCR_ALG, encr_alg_id);
if (encr_alg_id > 0)
msgb_tv_put(msg, GSM0808_IE_CHOSEN_ENCR_ALG, encr_alg_id);
/* write circuit pool 3.2.2.45 */
/* write speech version chosen: 3.2.2.51 when BTS picked it */
@ -964,7 +966,7 @@ struct msgb *gsm0808_create_handover_request(const struct gsm0808_handover_reque
}
/* Chosen Encryption Algorithm (Serving) 3.2.2.44 */
if (params->chosen_encryption_algorithm_serving)
if (params->chosen_encryption_algorithm_serving > 0)
msgb_tv_put(msg, GSM0808_IE_CHOSEN_ENCR_ALG, params->chosen_encryption_algorithm_serving);
/* Old BSS to New BSS Information 3.2.2.58 */
@ -1027,7 +1029,7 @@ struct msgb *gsm0808_create_handover_request_ack2(const struct gsm0808_handover_
if (params->chosen_channel_present)
msgb_tv_put(msg, GSM0808_IE_CHOSEN_CHANNEL, params->chosen_channel);
if (params->chosen_encr_alg)
if (params->chosen_encr_alg > 0)
msgb_tv_put(msg, GSM0808_IE_CHOSEN_ENCR_ALG, params->chosen_encr_alg);
if (params->chosen_speech_version != 0)
@ -1157,7 +1159,7 @@ struct msgb *gsm0808_create_handover_complete(const struct gsm0808_handover_comp
gsm0808_enc_speech_codec_list(msg, &params->codec_list_bss_supported);
/* Chosen Encryption Algorithm 3.2.2.44 */
if (params->chosen_encr_alg_present)
if (params->chosen_encr_alg_present && params->chosen_encr_alg > 0)
msgb_tv_put(msg, GSM0808_IE_CHOSEN_ENCR_ALG, params->chosen_encr_alg);
/* LCLS-BSS-Status 3.2.2.119 */
@ -1225,7 +1227,7 @@ struct msgb *gsm0808_create_handover_performed(const struct gsm0808_handover_per
msgb_tv_put(msg, GSM0808_IE_CHOSEN_CHANNEL, params->chosen_channel);
/* Chosen Encryption Algorithm 3.2.2.44 */
if (params->chosen_encr_alg_present)
if (params->chosen_encr_alg_present && params->chosen_encr_alg > 0)
msgb_tv_put(msg, GSM0808_IE_CHOSEN_ENCR_ALG, params->chosen_encr_alg);
/* Speech Version (chosen) 3.2.2.51 */