sms: Added result buffer size parameter to 7bit conv funs

The 7bit<->8bit encoding/decoding functions didn't check whether
there is still enough space in the destination buffer. Therefore a
buffer size parameter has been added to each of the functions which
is used to truncate the output if the buffer is too small.

In addition, the return value of the decoding functions has been
changed to number of characters written (excluding \0), so this
value is always equal to strlen(decoded).

The old functions are still available as wrapper functions.

2 files changed, 54 insertions, 7 deletions

diff --git a/tests/ussd/ussd_test.c b/tests/ussd/ussd_test.c
index e3e8e08a..b04f8e8a 100644
--- a/tests/ussd/ussd_test.c
+++ b/tests/ussd/ussd_test.c
@@ -73,20 +73,42 @@ static void test_7bit_ussd(const char *text, const char *encoded_hex, const char
 {
 	uint8_t coded[256];
 	char decoded[256];
-	int y;
+	int octets_written;
+	int buffer_size;
+	int nchars;
 
 	printf("original = %s\n", osmo_hexdump((uint8_t *)text, strlen(text)));
-	gsm_7bit_encode_ussd(coded, text, &y);
-	printf("encoded = %s\n", osmo_hexdump(coded, y));
+	gsm_7bit_encode_n_ussd(coded, sizeof(coded), text, &octets_written);
+	printf("encoded = %s\n", osmo_hexdump(coded, octets_written));
 
-	OSMO_ASSERT(strcmp(encoded_hex, osmo_hexdump_nospc(coded, y)) == 0);
+	OSMO_ASSERT(strcmp(encoded_hex, osmo_hexdump_nospc(coded, octets_written)) == 0);
 
-	gsm_7bit_decode_ussd(decoded, coded, y * 8 / 7);
-	y = strlen(decoded);
-	printf("decoded = %s\n\n", osmo_hexdump((uint8_t *)decoded, y));
+	gsm_7bit_decode_n_ussd(decoded, sizeof(decoded), coded, octets_written * 8 / 7);
+	octets_written = strlen(decoded);
+	printf("decoded = %s\n\n", osmo_hexdump((uint8_t *)decoded, octets_written));
 
 	OSMO_ASSERT(strncmp(text, decoded, strlen(text)) == 0);
 	OSMO_ASSERT(strcmp(appended_after_decode, decoded + strlen(text)) == 0);
+
+	/* check buffer limiting */
+	memset(decoded, 0xaa, sizeof(decoded));
+
+	for (buffer_size = 1; buffer_size < sizeof(decoded) - 1; ++buffer_size)
+	{
+		nchars = gsm_7bit_decode_n_ussd(decoded, buffer_size, coded, octets_written * 8 / 7);
+		OSMO_ASSERT(nchars <= buffer_size);
+		OSMO_ASSERT(decoded[buffer_size] == (char)0xaa);
+		OSMO_ASSERT(decoded[nchars] == '\0');
+	}
+
+	memset(coded, 0xaa, sizeof(coded));
+
+	for (buffer_size = 0; buffer_size < sizeof(coded) - 1; ++buffer_size)
+	{
+		gsm_7bit_encode_n_ussd(coded, buffer_size, text, &octets_written);
+		OSMO_ASSERT(octets_written <= buffer_size);
+		OSMO_ASSERT(coded[buffer_size] == 0xaa);
+	}
 }
 
 int main(int argc, char **argv)
@@ -94,6 +116,7 @@ int main(int argc, char **argv)
 	struct ussd_request req;
 	const int size = sizeof(ussd_request);
 	int i;
+	struct msgb *msg;
 
 	osmo_init_logging(&info);
 
@@ -122,5 +145,18 @@ int main(int argc, char **argv)
 	test_7bit_ussd("0123456\r",  "b0986c46abd91a0d", "\r");
 	test_7bit_ussd("012345\r",   "b0986c46ab351a",   "");
 
+	printf("Checking GSM 04.80 USSD message generation.\n");
+
+	test_7bit_ussd("", "", "");
+	msg = gsm0480_create_unstructuredSS_Notify (0x00, "");
+	printf ("Created unstructuredSS_Notify (0x00): %s\n",
+			osmo_hexdump(msgb_data(msg), msgb_length(msg)));
+	msgb_free (msg);
+
+	test_7bit_ussd("forty-two", "e6b79c9e6fd1ef6f", "");
+	msg = gsm0480_create_unstructuredSS_Notify (0x42, "forty-two");
+	printf ("Created unstructuredSS_Notify (0x42): %s\n",
+			osmo_hexdump(msgb_data(msg), msgb_length(msg)));
+	msgb_free (msg);
 	return 0;
 }
diff --git a/tests/ussd/ussd_test.ok b/tests/ussd/ussd_test.ok
index 91f2a315..54d59eef 100644
--- a/tests/ussd/ussd_test.ok
+++ b/tests/ussd/ussd_test.ok
@@ -72,3 +72,14 @@ original = 30 31 32 33 34 35 0d
 encoded = b0 98 6c 46 ab 35 1a 
 decoded = 30 31 32 33 34 35 0d 
 
+Checking GSM 04.80 USSD message generation.
+original = 
+encoded = 
+decoded = 
+
+Created unstructuredSS_Notify (0x00): 30 08 04 01 0f 04 00 04 01 00 
+original = 66 6f 72 74 79 2d 74 77 6f 
+encoded = e6 b7 9c 9e 6f d1 ef 6f 
+decoded = 66 6f 72 74 79 2d 74 77 6f 
+
+Created unstructuredSS_Notify (0x42): 30 10 04 01 0f 04 08 e6 b7 9c 9e 6f d1 ef 6f 04 01 42