sms: Fix alphanumeric TP-OA handling

TP-OA max length comparisons were incorrect because TP-OA's 7-bit
coded octets transport eleven 8-bit chars.  The current code assumed
only 10 chars were possible.

The patch
- increases the array size to 23, (maximum of 22 bytes for UTF8
  encoding + null terminator)
- Updates the sanity check to account for the correct maximum
- For encoding, checks the maximum length in UTF8 characters instead of
  bytes

src/smsutil.c

@@ -524,7 +524,8 @@ static gboolean encode_validity_period(const struct sms_validity_period *vp,
 gboolean sms_encode_address_field(const struct sms_address *in, gboolean sc,
 					unsigned char *pdu, int *offset)
 {
-	size_t len = strlen(in->address);
+	const char *addr = (const char *)&in->address;
+	size_t len = strlen(addr);
 	unsigned char addr_len = 0;
 	unsigned char p[10];
 
@@ -546,7 +547,8 @@ gboolean sms_encode_address_field(const struct sms_address *in, gboolean sc,
 		unsigned char *gsm;
 		unsigned char *r;
 
-		if (len > 11)
+		/* TP-OA's 10 octets transport 11 8-bit chars */
+		if (g_utf8_strlen(addr, strlen(addr)) > 11)
 			return FALSE;
 
 		gsm = convert_utf8_to_gsm(in->address, len, NULL, &written, 0);
@@ -675,7 +677,11 @@ gboolean sms_decode_address_field(const unsigned char *pdu, int len,
 		if (utf8 == NULL)
 			return FALSE;
 
-		if (strlen(utf8) > 20) {
+		/*
+		 * TP-OA's 10 octets transport 11 8-bit chars,
+		 * 22 bytes+terminator in UTF-8.
+		 */
+		if (strlen(utf8) > 22) {
 			g_free(utf8);
 			return FALSE;
 		}

src/smsutil.h

@@ -220,7 +220,11 @@ enum cbs_geo_scope {
 struct sms_address {
 	enum sms_number_type number_type;
 	enum sms_numbering_plan numbering_plan;
-	char address[21]; /* Max 20 in semi-octet, 11 in alnum */
+	/*
+	 * An alphanum TP-OA is 10 7-bit coded octets, which can carry
+	 * 11 8-bit characters. 22 bytes + terminator in UTF-8.
+	 */
+	char address[23];
 };
 
 struct sms_scts {