libmsc/db.c: fix storing SMS with empty TP-User-Data

Thanks to db_sms_test, it was discovered that storing an SMS with
empty TP-User-Data (TP-UDL=1) causes buffer overruns in libdbi
and it's SQLite3 driver (libdbdsqlite3):

  DDB NOTICE test_db_sms_store('Empty TP-UD'): ==7791== Invalid write of size 2
  ==7791==    at 0x857DC60: dbd_quote_binary (in /usr/lib/x86_64-linux-gnu/dbd/libdbdsqlite3.so)
  ==7791==    by 0x5B2B321: dbi_conn_quote_binary_copy (in /usr/lib/x86_64-linux-gnu/libdbi.so.1.1.0)
  ==7791==    by 0x4073B1: db_sms_store (db.c:701)
  ==7791==    by 0x405BB5: test_db_sms_store (db_sms_test.c:310)
  ==7791==    by 0x405BB5: main (db_sms_test.c:546)
  ==7791==  Address 0x7ed1cf0 is 0 bytes after a block of size 0 alloc'd
  ==7791==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  ==7791==    by 0x857DC4B: dbd_quote_binary (in /usr/lib/x86_64-linux-gnu/dbd/libdbdsqlite3.so)
  ==7791==    by 0x5B2B321: dbi_conn_quote_binary_copy (in /usr/lib/x86_64-linux-gnu/libdbi.so.1.1.0)
  ==7791==    by 0x4073B1: db_sms_store (db.c:701)
  ==7791==    by 0x405BB5: test_db_sms_store (db_sms_test.c:310)
  ==7791==    by 0x405BB5: main (db_sms_test.c:546)

  ...

  DDB NOTICE test_db_sms_get('Empty TP-UD'): ==8051== Invalid read of size 1
  ==8051==    at 0x5B30510: _dbd_decode_binary (in /usr/lib/x86_64-linux-gnu/libdbi.so.1.1.0)
  ==8051==    by 0x857D957: dbd_fetch_row (in /usr/lib/x86_64-linux-gnu/dbd/libdbdsqlite3.so)
  ==8051==    by 0x5B2C86E: dbi_result_seek_row (in /usr/lib/x86_64-linux-gnu/libdbi.so.1.1.0)
  ==8051==    by 0x40828F: next_row (db.c:188)
  ==8051==    by 0x40828F: db_sms_get (db.c:805)
  ==8051==    by 0x406C29: test_db_sms_get (db_sms_test.c:390)
  ==8051==    by 0x405C14: main (db_sms_test.c:547)
  ==8051==  Address 0x8f74641 is 0 bytes after a block of size 1 alloc'd
  ==8051==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  ==8051==    by 0x5DBEB49: strdup (strdup.c:42)
  ==8051==    by 0x857D93C: dbd_fetch_row (in /usr/lib/x86_64-linux-gnu/dbd/libdbdsqlite3.so)
  ==8051==    by 0x5B2C86E: dbi_result_seek_row (in /usr/lib/x86_64-linux-gnu/libdbi.so.1.1.0)
  ==8051==    by 0x40828F: next_row (db.c:188)
  ==8051==    by 0x40828F: db_sms_get (db.c:805)
  ==8051==    by 0x406C29: test_db_sms_get (db_sms_test.c:390)
  ==8051==    by 0x405C14: main (db_sms_test.c:547)
  ==8051==
  success, as expected
  DDB NOTICE verify_sms('Empty TP-UD'): user_data_len mismatch: E0 vs A3

Apparently, dbi_conn_quote_binary_copy() doesn't properly handle
zero-length input. Let's guard against this.

Observed with:

  - libdbi-dev 0.9.0-1
  - libdbd-sqlite3:amd64 0.9.0-2ubuntu2

Change-Id: If0b2bb557118c5f0e520a2e6c2816336f6028661

2 files changed, 5 insertions, 3 deletions

diff --git a/tests/db_sms/db_sms_test.c b/tests/db_sms/db_sms_test.c
index 93aed2b23..a97f7c75a 100644
--- a/tests/db_sms/db_sms_test.c
+++ b/tests/db_sms/db_sms_test.c
@@ -247,8 +247,6 @@ static struct sms_test {
 		},
 		.ud = &sms_tp_ud_set[0],
 	},
-#if 0
-	/* FIXME: there is a bug that causes ASAN / Valgrind to complain */
 	{
 		.name = "Empty TP-UD",
 		.sms = {
@@ -267,7 +265,6 @@ static struct sms_test {
 		},
 		.ud = NULL,
 	},
-#endif
 };
 
 static void prepare_sms_test_set(void)
diff --git a/tests/db_sms/db_sms_test.err b/tests/db_sms/db_sms_test.err
index 73dbd8ef0..e0a329d32 100644
--- a/tests/db_sms/db_sms_test.err
+++ b/tests/db_sms/db_sms_test.err
@@ -11,6 +11,7 @@ DDB NOTICE test_db_sms_store('Truncated TP-UD (255 octets, 8-bit encoding)'): su
 DDB NOTICE test_db_sms_store('Same MSISDN #1'): success, as expected
 DDB NOTICE test_db_sms_store('Same MSISDN #2'): success, as expected
 DDB NOTICE test_db_sms_store('Expired SMS'): success, as expected
+DDB NOTICE test_db_sms_store('Empty TP-UD'): success, as expected
 DDB INFO Testing db_sms_get()...
 DDB NOTICE test_db_sms_get('Regular MO SMS'): success, as expected
 DDB NOTICE verify_sms('Regular MO SMS'): match
@@ -32,6 +33,8 @@ DDB NOTICE test_db_sms_get('Same MSISDN #2'): success, as expected
 DDB NOTICE verify_sms('Same MSISDN #2'): match
 DDB NOTICE test_db_sms_get('Expired SMS'): success, as expected
 DDB NOTICE verify_sms('Expired SMS'): match
+DDB NOTICE test_db_sms_get('Empty TP-UD'): success, as expected
+DDB NOTICE verify_sms('Empty TP-UD'): match
 DDB INFO Testing db_sms_get_next_unsent() and db_sms_mark_delivered()...
 DDB NOTICE db_sms_get_next_unsent(#1): found
 DDB NOTICE verify_sms('Regular MO SMS'): match
@@ -67,4 +70,6 @@ DDB NOTICE test_db_sms_get('Same MSISDN #1'): failure, as expected
 DDB NOTICE test_db_sms_get('Same MSISDN #2'): failure, as expected
 DDB NOTICE test_db_sms_get('Expired SMS'): unexpected result
 DDB NOTICE verify_sms('Expired SMS'): match
+DDB NOTICE test_db_sms_get('Empty TP-UD'): success, as expected
+DDB NOTICE verify_sms('Empty TP-UD'): match
 full talloc report on 'null_context' (total      0 bytes in   1 blocks)