Cover the guarded address writers, and cut what the code already says

test/pdu.test.ts

@@ -128,7 +128,6 @@ describe('parsing real PDUs', () => {
 		assert.equal(pduObj.tlvs.message_state?.tagValue, 2);
 	});
 
-	// 'ascii' masks bit 7 on the way in, so this address used to come back Kaffei.
 	test('keeps an alphanumeric sender whole through the wire and back', () => {
 		const pdu = encode({
 			cmdName: 'deliver_sm',
@@ -143,12 +142,9 @@ describe('parsing real PDUs', () => {
 
 		assert.ok(pdu.includes(Buffer.from('Kaffeé', 'latin1')));
 		assert.equal(decode(pdu).params.source_addr, 'Kaffeé');
-		assert.ok(objToPdu({ cmdName: 'deliver_sm', params: { source_addr: '一' } }).err instanceof Error);
 	});
 
-	// The peer reads source_addr to the first NULL and every mandatory field behind it shifts, so an
-	// application forwarding a customer's sender id could have a PDU rewritten under it.
-	test('refuses an address carrying its own terminator', () => {
+	test('refuses an address the field cannot carry rather than truncating it', () => {
 		const smuggled = objToPdu({
 			cmdName: 'submit_sm',
 			params: { destination_addr: '46709771337', source_addr: '46701113311\u0000EVIL' },
@@ -156,6 +152,7 @@ describe('parsing real PDUs', () => {
 
 		assert.ok(smuggled.err instanceof Error);
 		assert.equal(smuggled.buffer, undefined);
+		assert.ok(objToPdu({ cmdName: 'deliver_sm', params: { source_addr: '一' } }).err instanceof Error);
 	});
 });
 

test/types.test.ts

@@ -84,7 +84,6 @@ describe('string (Octet String)', () => {
 		assert.ok(types.string.write('一', Buffer.alloc(4), 0).err instanceof Error);
 	});
 
-	// Its length octet is what ends it, so unlike a C-Octet String it carries a NULL like any other.
 	test('carries a NULL octet, which its length octet already bounds', () => {
 		const target = Buffer.alloc(4);
 
@@ -122,8 +121,6 @@ describe('cstring (C-Octet String)', () => {
 		assert.deepEqual(types.cstring.size(123), { size: 4 });
 	});
 
-	// 'ascii' masks bit 7 on the way in and keeps it on the way out, so an address a peer wrote as
-	// Kaffeé came back Kaffei and objToPdu(pduToObj(x)) stopped being idempotent.
 	test('carries every latin1 octet, and refuses a character past it', () => {
 		const address = Buffer.from([0x4B, 0x61, 0x66, 0x66, 0x65, 0xE9, 0x00]);
 		const target = Buffer.alloc(7);
@@ -136,9 +133,6 @@ describe('cstring (C-Octet String)', () => {
 		assert.ok(types.cstring.write('一', Buffer.alloc(4), 0).err instanceof Error);
 	});
 
-	// The field ends at its first NULL, so writing one smuggles a field boundary into the peer's
-	// parse: every mandatory field behind it shifts, under a command_length that counted the whole
-	// string.
 	test('refuses a NULL of its own rather than ending the field early', () => {
 		assert.ok(types.cstring.size('46701113311\u0000EVIL').err instanceof Error);
 		assert.ok(types.cstring.write('46701113311\u0000EVIL', Buffer.alloc(17), 0).err instanceof Error);
@@ -252,8 +246,6 @@ describe('buffer', () => {
 });
 
 describe('paramText()', () => {
-	// The one reader of a receipt body that arrived with no octets of its own, so masking bit 7
-	// here loses the same characters the wire types used to.
 	test('renders a Buffer parameter as the latin1 text its octets spell', () => {
 		assert.equal(paramText(Buffer.from([0x4B, 0x61, 0x66, 0x66, 0x65, 0xE9])), 'Kaffeé');
 	});
@@ -293,6 +285,11 @@ describe('dest_address_array', () => {
 		types.dest_address_array.write(expected, target, 0);
 
 		assert.deepEqual(target, encoded);
+
+		const smuggled: DestAddress[] = [{ dest_addr_npi: 1, dest_addr_ton: 1, destination_addr: '46\u0000EVIL' }];
+
+		assert.ok(types.dest_address_array.write(smuggled, Buffer.alloc(16), 0).err instanceof Error);
+		assert.ok(types.dest_address_array.write([{ dl_name: '一' }], Buffer.alloc(16), 0).err instanceof Error);
 	});
 
 	test('refuses a field value the wire cannot hold instead of throwing', () => {
@@ -332,6 +329,12 @@ describe('unsuccess_sme_array', () => {
 		types.unsuccess_sme_array.write(expected, target, 0);
 
 		assert.deepEqual(target, encoded);
+
+		const smuggled: UnsuccessSme[] = [
+			{ dest_addr_npi: 1, dest_addr_ton: 1, destination_addr: 'a\u0000b', error_status_code: 0 },
+		];
+
+		assert.ok(types.unsuccess_sme_array.write(smuggled, Buffer.alloc(16), 0).err instanceof Error);
 	});
 
 	test('refuses a field value the wire cannot hold instead of throwing', () => {

test/unsendable.test.ts

@@ -345,6 +345,30 @@ describe('a body the PDU\'s own data_coding cannot carry', () => {
 	});
 });
 
+describe('an address the field cannot carry', () => {
+	test('refuses it through sendSms(), with nothing reaching the socket', async t => {
+		const smsc = await dummySmsc(t);
+		const session = await bindToSmsc(t, smsc.port, { reconnect: false });
+
+		const refusals: [string, RegExp][] = [
+			['46701113311\u0000EVIL', /U\+0000 at index 11/],
+			['Kaffe一', /U\+4E00 at index 5/],
+			['😀', /U\+1F600 at index 0/],
+		];
+
+		for (const [sender, names] of refusals) {
+			const sent = await session.sendSms({ from: sender, message: 'Hello world', to });
+
+			assert.ok(sent.err instanceof Error, sender);
+			assert.match(sent.err.message, /source_addr/);
+			assert.match(sent.err.message, names);
+			assert.deepEqual(sent.smsIds, [], sender);
+		}
+
+		assert.deepEqual(smsc.octets, [], 'an address the field cannot carry never reaches the socket');
+	});
+});
+
 describe('a time no peer can read', () => {
 	const invalid = new Date('nope');