Trim period at the end of OS user name

Bug: 1113075
Change-Id: If6dd51dc9adf71fbceea1421a650a8f0e906c97c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2337769
Commit-Queue: Rakesh Soma <rakeshsoma@google.com>
Reviewed-by: Rakesh Soma <rakeshsoma@google.com>
Cr-Commit-Position: refs/heads/master@{#794914}

chrome/credential_provider/gaiacp/gaia_credential_base.cc

@@ -565,6 +565,12 @@ HRESULT MakeUsernameForAccount(const base::Value& result,
   if (os_username.size() > kWindowsUsernameBufferLength - 1)
     os_username.resize(kWindowsUsernameBufferLength - 1);
 
+  // After resizing the os user name above, the last char may be a '.' which is
+  // illegal as the last character per Microsoft documentation.
+  // https://docs.microsoft.com/en-us/windows/win32/api/lmaccess/ns-lmaccess-user_info_1#remarks
+  if (os_username.size() > 0 && os_username.back() == '.')
+    os_username.resize(os_username.size() - 1);
+
   // Replace invalid characters.  While @ is not strictly invalid according to
   // MSDN docs, it causes trouble.
   for (auto& c : os_username) {

chrome/credential_provider/gaiacp/gaia_credential_base_unittests.cc

@@ -854,6 +854,31 @@ TEST_F(GcpGaiaCredentialBaseTest, StripEmailTLD) {
   EXPECT_EQ(test->GetFinalEmail(), email);
 }
 
+TEST_F(GcpGaiaCredentialBaseTest, TrimPeriodAtTheEnd) {
+  USES_CONVERSION;
+  // Create provider and start logon.
+  Microsoft::WRL::ComPtr<ICredentialProviderCredential> cred;
+
+  ASSERT_EQ(S_OK, InitializeProviderAndGetCredential(0, &cred));
+
+  Microsoft::WRL::ComPtr<ITestCredential> test;
+  ASSERT_EQ(S_OK, cred.As(&test));
+
+  // The top level domain("info" in this example) is removed and the rest is
+  // truncated to be 20 characters. However, in this example, this will result
+  // with "abcdefghijklmn_abcd." which isn't valid per Microsoft documentation.
+  // The rule says there shouldn't be a '.' at the end. Thus it needs to be
+  // removed.
+  constexpr char email[] = "abcdefghijklmn@abcd.ef.info";
+
+  ASSERT_EQ(S_OK, test->SetGlsEmailAddress(email));
+
+  ASSERT_EQ(S_OK, StartLogonProcessAndWait());
+
+  ASSERT_STREQ(W2COLE(L"abcdefghijklmn_abcd"), test->GetFinalUsername());
+  EXPECT_EQ(test->GetFinalEmail(), email);
+}
+
 TEST_F(GcpGaiaCredentialBaseTest, NewUserDisabledThroughUsageScenario) {
   USES_CONVERSION;
   // Create provider and start logon.