If it doesn't receive it, it returns an HTTP 401 "Unauthorized" error.

And returns a header `WWW-Authenticate` with a value of `Basic`, and an optional `realm` parameter.

That tells the browser to show the integrated prompt for a username and password.

Then, when you type that username and password, the browser sends them in the header automatically.

class OAuth2PasswordRequestForm:
    """
    This is a dependency class to collect the `username` and `password` as form data
    for an OAuth2 password flow.

    The OAuth2 specification dictates that for a password flow the data should be
    collected using form data (instead of JSON) and that it should have the specific
    fields `username` and `password`.

    All the initialization parameters are extracted from the request.

* The **input model** needs to be able to have a password.
* The **output model** should not have a password.
* The **database model** would probably need to have a hashed password.

/// danger

Never store user's plaintext passwords. Always store a "secure hash" that you can then verify.

If you don't know, you will learn what a "password hash" is in the [security chapters](security/simple-oauth2.md#password-hashing).

///

            } else {
                // plain text
                password = new byte[(session.auth.password.length() + 1) * 2];
                passwordLength = writeString(session.auth.password, password, 0);
            }
        } else {
            // no password in tree connect
            passwordLength = 1;
        }

        dst[dstIndex] = disconnectTid ? (byte) 0x01 : (byte) 0x00;

        }
        return redirect(getClass());
    }

    /**
     * Handles password change for the current user.
     *
     * @param form the password form containing new password and confirmation
     * @return the HTML response after password change attempt
     */
    @Execute
    public HtmlResponse changePassword(final PasswordForm form) {

        TermQueryBuilder builder = regTermQ("password", password);
        if (opLambda != null) {
            opLambda.callback(builder);
        }
    }

    public void setPassword_NotEqual(String password) {
        setPassword_NotTerm(password, null);
    }

    public void setPassword_NotTerm(String password) {
        setPassword_NotTerm(password, null);

        assertTrue(testLdapManager.changePasswordCalled);
    }

    @Test
    public void test_changePassword_withNullPassword() {
        // Test password change with null password
        testLdapManager.changePasswordResult = false;
        testFessConfig.ldapAdminSyncPassword = false;

        boolean result = ldapChain.changePassword("testuser", null);

     * @param domain the domain for authentication
     * @param username the username for authentication
     * @param password the password for authentication
     */
    public JAASAuthenticator(String serviceName, String domain, String username, String password) {
        super(null, domain, username, password);
        this.serviceName = serviceName;
    }

    /**
     * Create an authenticator using the given credentials

            throw new IllegalArgumentException("Master password cannot be null or empty");
        }

        // Generate salt for key derivation
        this.salt = new byte[SALT_SIZE];
        secureRandom.nextBytes(this.salt);

        // Derive master key from password
        this.masterKey = deriveKey(masterPassword, salt);

        // Clear the master password after use
        Arrays.fill(masterPassword, '\0');
    }

# 簡易 OAuth2：Password 與 Bearer { #simple-oauth2-with-password-and-bearer }

現在從上一章延伸，補上缺少的部分，完成整個安全流程。

## 取得 `username` 與 `password` { #get-the-username-and-password }

我們要使用 **FastAPI** 提供的安全性工具來取得 `username` 與 `password`。

OAuth2 規範中，當使用「password flow」（我們現在使用的）時，用戶端／使用者必須以表單資料送出 `username` 與 `password` 欄位。

而且規範要求欄位名稱必須就是這兩個，所以像是 `user-name` 或 `email` 都不行。

但別擔心，你在前端要怎麼呈現給最終使用者都可以。

而你的資料庫模型也可以使用任何你想要的欄位名稱。