Change in osmo-msc[master]: libmsc/db.c: properly get / set TP-UD length (octets vs septets)

Vadim Yanitskiy gerrit-no-reply at lists.osmocom.org
Tue Apr 2 12:05:46 UTC 2019


Vadim Yanitskiy has uploaded this change for review. ( https://gerrit.osmocom.org/13490


Change subject: libmsc/db.c: properly get / set TP-UD length (octets vs septets)
......................................................................

libmsc/db.c: properly get / set TP-UD length (octets vs septets)

According to 3GPP TS 03.40, section 9.2.3.16, the TP-UDL field
indicates the length of TP-UD (User-Data, including TP-UDH)
either in septets, or in octets, depending on DSC in use.

When retrieving the TP-UD from the database, we get the length
in octets (bytes), regardless of the DCS value. Before this
patch, it was merely copied to struct 'gsm_sms', without
any conversion from octets to septets.

The same problem was in db_sms_store(), which could run into
a buffer overflow, using the amount of septets (e.g. 160) to
store some 8-bit or UCS-2 encoded data (up to 140 octets).

Change-Id: I84f973bc6561a9822b4b26975a781abd2b6e026a
---
M src/libmsc/db.c
1 file changed, 25 insertions(+), 3 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-msc refs/changes/90/13490/1

diff --git a/src/libmsc/db.c b/src/libmsc/db.c
index 6cd8493..f48384e 100644
--- a/src/libmsc/db.c
+++ b/src/libmsc/db.c
@@ -38,6 +38,7 @@
 #include <osmocom/msc/vlr.h>
 
 #include <osmocom/gsm/protocol/gsm_23_003.h>
+#include <osmocom/gsm/gsm0411_utils.h>
 #include <osmocom/core/talloc.h>
 #include <osmocom/core/statistics.h>
 #include <osmocom/core/rate_ctr.h>
@@ -227,6 +228,7 @@
 
 static void parse_tp_ud_from_result(struct gsm_sms *sms, dbi_result result)
 {
+	enum sms_alphabet dcs_alphabet;
 	const unsigned char *user_data;
 	unsigned int user_data_len;
 	unsigned int text_len;
@@ -240,12 +242,20 @@
 		     user_data_len, sizeof(sms->user_data));
 		user_data_len = (uint8_t) sizeof(sms->user_data);
 	}
-	sms->user_data_len = user_data_len;
 
 	/* Retrieve the TP-UD (User-Data) itself */
 	user_data = dbi_result_get_binary(result, "user_data");
 	memcpy(sms->user_data, user_data, user_data_len);
 
+	/* We may need to convert the length in octets to a value in septets,
+	 * if 7-bit default alphabet is used (see 3GPP TS 03.40,
+	 * section 9.2.3.16 for details). */
+	dcs_alphabet = gsm338_get_sms_alphabet(sms->data_coding_scheme);
+	if (dcs_alphabet == DCS_7BIT_DEFAULT)
+		sms->user_data_len = user_data_len * 8 / 7;
+	else
+		sms->user_data_len = user_data_len;
+
 	/* Retrieve the text length (excluding '\0') */
 	text_len = dbi_result_get_field_length(result, "text");
 	if (text_len >= sizeof(sms->text)) {
@@ -716,12 +726,24 @@
 	char *q_text, *q_daddr, *q_saddr;
 	unsigned char *q_udata;
 	time_t now, validity_timestamp;
+	enum sms_alphabet dcs_alphabet;
+	unsigned int user_data_len;
+
+	/* We may need to convert the length in septets to a value in octets,
+	 * if 7-bit default alphabet is used (see 3GPP TS 03.40,
+	 * section 9.2.3.16 for details). */
+	dcs_alphabet = gsm338_get_sms_alphabet(sms->data_coding_scheme);
+	if (dcs_alphabet == DCS_7BIT_DEFAULT) {
+		user_data_len = sms->user_data_len * 7 / 8;
+		if (sms->user_data_len * 7 % 8 != 0)
+			user_data_len++;
+	} else
+		user_data_len = sms->user_data_len;
 
 	dbi_conn_quote_string_copy(conn, (char *)sms->text, &q_text);
 	dbi_conn_quote_string_copy(conn, (char *)sms->dst.addr, &q_daddr);
 	dbi_conn_quote_string_copy(conn, (char *)sms->src.addr, &q_saddr);
-	dbi_conn_quote_binary_copy(conn, sms->user_data, sms->user_data_len,
-				   &q_udata);
+	dbi_conn_quote_binary_copy(conn, sms->user_data, user_data_len, &q_udata);
 
 	now = time(NULL);
 	validity_timestamp = now + sms->validity_minutes * 60;

-- 
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Gerrit-Project: osmo-msc
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I84f973bc6561a9822b4b26975a781abd2b6e026a
Gerrit-Change-Number: 13490
Gerrit-PatchSet: 1
Gerrit-Owner: Vadim Yanitskiy <axilirator at gmail.com>
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