Fix cloud login: decode JWT payload with matlab.net.base64decode

src/ndi/+ndi/+cloud/+internal/decodeJwt.m

@@ -40,7 +40,7 @@
     if padding > 0
         payloadBase64 = [payloadBase64, repmat('=', 1, 4 - padding)];
     end
-    payloadBytes = javax.xml.bind.DatatypeConverter.parseBase64Binary(payloadBase64);
+    payloadBytes = matlab.net.base64decode(payloadBase64);
     payloadJSON = native2unicode(payloadBytes, 'UTF-8');
 
     % Ensure json payload is a row vector

tests/+ndi/+unittest/+cloud/DecodeJwtTest.m

@@ -0,0 +1,104 @@
+classdef DecodeJwtTest < matlab.unittest.TestCase
+    % DECODEJWTTEST - offline tests for ndi.cloud.internal.decodeJwt
+    %
+    % decodeJwt used javax.xml.bind.DatatypeConverter to Base64-decode the JWT
+    % payload. That class is gone from the Java shipped with recent MATLAB
+    % releases, so every cloud login failed in getTokenExpiration. It now uses
+    % matlab.net.base64decode. These tests build a JWT locally from a known
+    % JSON payload, so they need no network or credentials.
+    %
+    % Authored without a local MATLAB runtime; needs MATLAB to validate/run.
+
+    methods (Test)
+
+        function testPayloadWithoutPadding(testCase)
+            % Payload byte count is a multiple of 3: no '=' to restore.
+            payload = ndi.unittest.cloud.DecodeJwtTest.examplePayload();
+            [token, payloadSegment] = ...
+                ndi.unittest.cloud.DecodeJwtTest.makeJwt(payload, 0);
+            testCase.verifyEqual(mod(numel(payloadSegment), 4), 0);
+
+            decoded = ndi.cloud.internal.decodeJwt(token);
+            ndi.unittest.cloud.DecodeJwtTest.verifyPayload(testCase, decoded, payload);
+        end
+
+        function testPayloadNeedingOnePadCharacter(testCase)
+            % Payload byte count mod 3 == 2: one '=' was stripped.
+            payload = ndi.unittest.cloud.DecodeJwtTest.examplePayload();
+            [token, payloadSegment] = ...
+                ndi.unittest.cloud.DecodeJwtTest.makeJwt(payload, 2);
+            testCase.verifyEqual(mod(numel(payloadSegment), 4), 3);
+
+            decoded = ndi.cloud.internal.decodeJwt(token);
+            ndi.unittest.cloud.DecodeJwtTest.verifyPayload(testCase, decoded, payload);
+        end
+
+        function testPayloadNeedingTwoPadCharacters(testCase)
+            % Payload byte count mod 3 == 1: two '=' were stripped.
+            payload = ndi.unittest.cloud.DecodeJwtTest.examplePayload();
+            [token, payloadSegment] = ...
+                ndi.unittest.cloud.DecodeJwtTest.makeJwt(payload, 1);
+            testCase.verifyEqual(mod(numel(payloadSegment), 4), 2);
+
+            decoded = ndi.cloud.internal.decodeJwt(token);
+            ndi.unittest.cloud.DecodeJwtTest.verifyPayload(testCase, decoded, payload);
+        end
+
+        function testReturnsTokenExpiration(testCase)
+            % The real caller: getTokenExpiration reads the 'exp' claim.
+            payload = ndi.unittest.cloud.DecodeJwtTest.examplePayload();
+            token = ndi.unittest.cloud.DecodeJwtTest.makeJwt(payload, 0);
+
+            decoded = ndi.cloud.internal.decodeJwt(token);
+            testCase.verifyTrue(isfield(decoded, 'exp'));
+            testCase.verifyEqual(decoded.exp, 1893456000);
+        end
+
+    end
+
+    methods (Static, Access = private)
+
+        function payload = examplePayload()
+            % A JWT-like payload. The name includes non-ASCII characters
+            % (e-acute and the euro sign) to exercise the UTF-8 decode.
+            payload = struct( ...
+                'exp', 1893456000, ...
+                'email', 'test.user@example.com', ...
+                'name', ['Ren', char(233), ' ', char(8364)], ...
+                'nonce', '');
+        end
+
+        function [token, payloadSegment] = makeJwt(payload, targetMod3)
+            % Build HEADER.PAYLOAD.SIGNATURE with Base64Url segments. The
+            % 'nonce' field is lengthened until the UTF-8 payload byte count
+            % mod 3 equals targetMod3, which fixes how much padding the
+            % decoder has to restore.
+            payloadBytes = unicode2native(jsonencode(payload), 'UTF-8');
+            while mod(numel(payloadBytes), 3) ~= targetMod3
+                payload.nonce = [payload.nonce, 'x'];
+                payloadBytes = unicode2native(jsonencode(payload), 'UTF-8');
+            end
+
+            headerBytes = unicode2native('{"alg":"HS256","typ":"JWT"}', 'UTF-8');
+            headerSegment = ndi.unittest.cloud.DecodeJwtTest.base64UrlEncode(headerBytes);
+            payloadSegment = ndi.unittest.cloud.DecodeJwtTest.base64UrlEncode(payloadBytes);
+            token = [headerSegment, '.', payloadSegment, '.', 'dummySignature'];
+        end
+
+        function encoded = base64UrlEncode(bytes)
+            encoded = char(matlab.net.base64encode(uint8(bytes)));
+            encoded = strrep(encoded, '+', '-');
+            encoded = strrep(encoded, '/', '_');
+            encoded = strrep(encoded, '=', '');
+        end
+
+        function verifyPayload(testCase, decoded, payload)
+            testCase.verifyClass(decoded, 'struct');
+            testCase.verifyEqual(decoded.exp, payload.exp);
+            testCase.verifyEqual(decoded.email, payload.email);
+            testCase.verifyEqual(decoded.name, payload.name);
+        end
+
+    end
+
+end