start-proxy: Fix bug when language is not provided

src/start-proxy.test.ts

@@ -80,3 +80,36 @@
   );
   t.is(credentials.length, 3);
 });
+
+test("getCredentials throws an error when non-printable characters are used", async (t) => {
+  const invalidCredentials = [
+    { type: "nuget_feed", host: "1nuget.pkg.github.com", token: "abc\u0000" }, // Non-printable character in token
+    { type: "nuget_feed", host: "2nuget.pkg.github.com\u0001" }, // Non-printable character in host
+    {
+      type: "nuget_feed",
+      host: "3nuget.pkg.github.com",
+      password: "ghi\u0002",
+    }, // Non-printable character in password
+    { type: "nuget_feed", host: "4nuget.pkg.github.com", password: "ghi\x00" }, // Non-printable character in password
+  ];
+
+  for (const invalidCredential of invalidCredentials) {
+    const credentialsInput = Buffer.from(
+      JSON.stringify([invalidCredential]),
+    ).toString("base64");
+
+    t.throws(
+      () =>
+        startProxyExports.getCredentials(
+          getRunnerLogger(true),
+          undefined,
+          credentialsInput,
+          undefined,
+        ),
+      {
+        message:
+          "Invalid credentials - fields must contain only printable characters",
+      },
+    );
+  }
+});

src/start-proxy.ts

@@ -51,10 +51,19 @@ export function getCredentials(
   }
 
   // Parse and validate the credentials
-  const parsed = JSON.parse(credentialsStr) as Credential[];
+  let parsed: Credential[];
+  try {
+    parsed = JSON.parse(credentialsStr) as Credential[];
+  } catch {
+    // Don't log the error since it might contain sensitive information.
+    logger.error("Failed to parse the credentials data.");
+    throw new Error("Invalid credentials format.");
+  }
+
   const out: Credential[] = [];
   for (const e of parsed) {
     if (e.url === undefined && e.host === undefined) {
+      // The proxy needs one of these to work. If both are defined, the url has the precedence.
       throw new Error("Invalid credentials - must specify host or url");
     }
 
@@ -64,6 +73,23 @@ export function getCredentials(
       continue;
     }
 
+    const isPrintable = (str: string | undefined): boolean => {
+      return str ? /^[\x20-\x7E]*$/.test(str) : true;
+    };
+
+    if (
+      !isPrintable(e.type) ||
+      !isPrintable(e.host) ||
+      !isPrintable(e.url) ||
+      !isPrintable(e.username) ||
+      !isPrintable(e.password) ||
+      !isPrintable(e.token)
+    ) {
+      throw new Error(
+        "Invalid credentials - fields must contain only printable characters",
+      );
+    }
+
     out.push({
       type: e.type,
       host: e.host,