Mask each line of multi-line secrets

src/action.js

@@ -77,8 +77,12 @@ async function exportSecrets() {
         const { value, request, cachedResponse } = result;
         if (cachedResponse) {
             core.debug('ℹ using cached response');
-        }        
-        command.issue('add-mask', value);
+        }
+        for (const line of value.split('\n')) {
+            if (line.length > 0) {
+                command.issue('add-mask', line);
+            }
+        }
         if (exportEnv) {
             core.exportVariable(request.envVarName, `${value}`);
         }

src/action.test.js

@@ -2,6 +2,7 @@ jest.mock('got');
 jest.mock('@actions/core');
 jest.mock('@actions/core/lib/command');
 
+const command = require('@actions/core/lib/command');
 const core = require('@actions/core');
 const got = require('got');
 const {
@@ -294,4 +295,40 @@ describe('exportSecrets', () => {
         expect(core.exportVariable).toBeCalledWith('KEY', '1');
         expect(core.setOutput).toBeCalledWith('key', '1');
     });
+
+    it('single-line secret gets masked', async () => {
+        mockInput('test key');
+        mockVaultData({
+            key: 'secret'
+        });
+        mockExportToken("false")
+
+        await exportSecrets();
+
+        expect(command.issue).toBeCalledTimes(1);
+
+        expect(command.issue).toBeCalledWith('add-mask', 'secret');
+        expect(core.setOutput).toBeCalledWith('key', 'secret');
+    })
+
+    it('multi-line secret gets masked for each line', async () => {
+        const multiLineString = `a multi-line string
+
+with blank lines
+
+`
+        mockInput('test key');
+        mockVaultData({
+            key: multiLineString
+        });
+        mockExportToken("false")
+
+        await exportSecrets();
+
+        expect(command.issue).toBeCalledTimes(2); // 1 for each non-empty line.
+
+        expect(command.issue).toBeCalledWith('add-mask', 'a multi-line string');
+        expect(command.issue).toBeCalledWith('add-mask', 'with blank lines');
+        expect(core.setOutput).toBeCalledWith('key', multiLineString);
+    })
 });