fix: reject newlines in names and values when writing profile files

If the profile file writing was enabled, we emitted newlines into the
file verbatim, permitting injecting arbitrary profiles into the file.
Writing now fails instead.

src/profileManager.ts

@@ -53,8 +53,15 @@ export function parseIni(iniData: string): Record<string, Record<string, string>
 export function stringifyIni(data: Record<string, Record<string, string>>): string {
   const sections: string[] = [];
   for (const [sectionName, sectionData] of Object.entries(data)) {
+    if (/[\r\n]/.test(sectionName)) {
+      throw new Error('INI section names must not contain newline characters');
+    }
     const lines: string[] = [`[${sectionName}]`];
     for (const [key, value] of Object.entries(sectionData)) {
+      // A newline in a key or value would inject arbitrary INI lines (e.g. credential_process).
+      if (/[\r\n]/.test(key) || /[\r\n]/.test(value)) {
+        throw new Error('INI keys and values must not contain newline characters');
+      }
       lines.push(`${key} = ${value}`);
     }
     sections.push(lines.join('\n'));

test/profileManager.test.ts

@@ -114,6 +114,22 @@ describe('Profile Manager', {}, () => {
       const result = stringifyIni({ dev: {} });
       expect(result).toBe('[dev]\n');
     });
+
+    it('rejects values containing newlines', {}, () => {
+      expect(() =>
+        stringifyIni({ dev: { aws_session_token: 'token\n[injected]\ncredential_process = evil' } }),
+      ).toThrow('must not contain newline characters');
+    });
+
+    it('rejects keys containing newlines', {}, () => {
+      expect(() => stringifyIni({ dev: { 'key\ninjected': 'val' } })).toThrow('must not contain newline characters');
+    });
+
+    it('rejects section names containing newlines', {}, () => {
+      expect(() => stringifyIni({ 'dev\r\n[injected]': { key: 'val' } })).toThrow(
+        'must not contain newline characters',
+      );
+    });
   });
 
   describe('validateProfileName', {}, () => {
@@ -423,6 +439,24 @@ describe('Profile Manager', {}, () => {
       expect(configParsed['profile dev'].region).toBe('us-east-1');
     });
 
+    it('refuses to write credentials containing newlines instead of injecting profiles', {}, () => {
+      expect(() =>
+        writeProfileFiles(
+          'dev',
+          {
+            AccessKeyId: 'AKIAIOSFODNN7EXAMPLE',
+            SecretAccessKey: 'wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY',
+            SessionToken: 'token\n[injected]\ncredential_process = evil-command',
+          },
+          'us-east-1',
+          false,
+        ),
+      ).toThrow('must not contain newline characters');
+
+      const credsPath = getProfileFilePaths().credentials;
+      expect(fs.existsSync(credsPath)).toBe(false);
+    });
+
     it('uses correct section naming for default profile', {}, () => {
       writeProfileFiles(
         'default',