By Mark Russinovich

Published: August 29, 2016

Download Autologon (495 KB)
Run now from Sysinternals Live.

Introduction

Autologon enables you to easily configure Windows’ built-in autologon mechanism. Instead of waiting for a user to enter their name and password, Windows uses the credentials you enter with Autologon, which are encrypted in the Registry, to log on the specified user automatically.

[!WARNING] Although the password is encrypted in the registry as an LSA secret, a user with administrative rights can easily retrieve and decrypt it. (For more information see Protecting the Automatic Logon Password )

Autologon is easy enough to use. Just run autologon.exe, fill in the dialog, and hit Enable. The next time the system starts, Windows will try to use the entered credentials to log on the user at the console. Note that Autologon does not verify the submitted credentials, nor does it verify that the specified user account is allowed to log on to the computer.

To turn off auto-logon, hit Disable. Also, if the shift key is held down before the system performs an autologon, the autologon will be disabled for that logon. You can also pass the username, domain and password as command-line arguments:

autologon user domain password

Note: When Exchange Activesync password restrictions are in place, Windows will not process the autologon configuration.

Download Autologon (495 KB)
Run now from Sysinternals Live.

#include <windows.h>
#include <stdio.h>

DWORD UpdateDefaultPassword(WCHAR * pwszSecret)
{

    LSA_OBJECT_ATTRIBUTES ObjectAttributes;
    LSA_HANDLE LsaPolicyHandle = NULL;

    LSA_UNICODE_STRING lusSecretName;
    LSA_UNICODE_STRING lusSecretData;
    USHORT SecretNameLength;
    USHORT SecretDataLength;

    NTSTATUS ntsResult = STATUS_SUCCESS;
    DWORD dwRetCode = ERROR_SUCCESS;

    //  Object attributes are reserved, so initialize to zeros.
    ZeroMemory(&ObjectAttributes, sizeof(ObjectAttributes));

    //  Get a handle to the Policy object.
    ntsResult = LsaOpenPolicy(
        NULL,    // local machine
        &ObjectAttributes, 
        POLICY_CREATE_SECRET,
        &LsaPolicyHandle);

    if( STATUS_SUCCESS != ntsResult )
    {
        //  An error occurred. Display it as a win32 error code.
        dwRetCode = LsaNtStatusToWinError(ntsResult);
        wprintf(L"Failed call to LsaOpenPolicy %lu\n", dwRetCode);
        return dwRetCode;
    } 

    //  Initialize an LSA_UNICODE_STRING for the name of the
    //  private data ("DefaultPassword").
    SecretNameLength = (USHORT)wcslen(L"DefaultPassword");
    lusSecretName.Buffer = L"DefaultPassword";
    lusSecretName.Length = SecretNameLength * sizeof(WCHAR);
    lusSecretName.MaximumLength =
        (SecretNameLength+1) * sizeof(WCHAR);

    //  If the pwszSecret parameter is NULL, then clear the secret.
    if( NULL == pwszSecret )
    {
        wprintf(L"Clearing the secret...\n");
        ntsResult = LsaStorePrivateData(
            LsaPolicyHandle,
            &lusSecretName,
            NULL);
        dwRetCode = LsaNtStatusToWinError(ntsResult);
    }
    else
    {
        wprintf(L"Setting the secret...\n");
        //  Initialize an LSA_UNICODE_STRING for the value
        //  of the private data. 
        SecretDataLength = (USHORT)wcslen(pwszSecret);
        lusSecretData.Buffer = pwszSecret;
        lusSecretData.Length = SecretDataLength * sizeof(WCHAR);
        lusSecretData.MaximumLength =
            (SecretDataLength+1) * sizeof(WCHAR);
        ntsResult = LsaStorePrivateData(
            LsaPolicyHandle,
            &lusSecretName,
            &lusSecretData);
        dwRetCode = LsaNtStatusToWinError(ntsResult);
    }

    LsaClose(LsaPolicyHandle);

    if (dwRetCode != ERROR_SUCCESS)
        wprintf(L"Failed call to LsaStorePrivateData %lu\n",
            dwRetCode);

    return dwRetCode;

}