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HTTP nos brinda un framework general para control de acceso y de autenticación. El esquema de autenticación HTTP más común es la autenticación "Basic". Esta página presenta el framework general de autenticación HTTP y muestra cómo restringir el acceso a tu servidor con la autenticación HTTP Basic.

El framework general de autenticación HTTP

RFC 7235 define el framework de autenticación HTTP que puede ser usado por un servidor para revisar la solicitud de un cliente y por un cliente para proveer información de autenticación. El flujo de la revisión y la respuesta funciona de la siguiente manera: El servidor responde al cliente con un estado de respuesta 401 (Unauthorized) y devuelve al cliente información sobre cómo autorizarse con un encabezado de respuesta WWW-Authenticate que contiene al menos una revisión. Un cliente que quiera autenticarse con un servidor puede hacerlo incluyendo un encabezado de solicitud Authorization  con sus credenciales. Normalmente un cliente hará una solicitud de contraseña al usuario y luego enviará la solicitud incluyendo el encabezado Authorization correcto al servidor.

En el caso de una autenticación "Basic" como la mostrada en la figura, el intercambio debe realizarse sobre una conexión HTTPS (TLS) para que sea seguro.

Proxy authentication

The same challenge and response mechanism can be used for proxy authentication. In this case, it is an intermediate proxy that requires authentication. As both resource authentication and proxy authentication can coexist, a different set of headers and status codes is needed. In the case of proxies, the challenging status code is 407 (Proxy Authentication Required), the Proxy-Authenticate response header contains at least one challenge applicable to the proxy, and the Proxy-Authorization request header is used for providing the credentials to the proxy server.

Access forbidden

If a (proxy) server receives valid credentials that are not adequate to gain access for a given resource, the server should respond with the 403 Forbidden status code. Unlike 401 Unauthorized or 407 Proxy Authentication Required, authentication is impossible for this user.

WWW-Authenticate and Proxy-Authenticate headers

The WWW-Authenticate and Proxy-Authenticate response headers define the authentication method that should be used to gain access to a resource. They need to specify which authentication scheme is used, so that the client that wishes to authorize knows how to provide the credentials. The syntax for these headers is the following:

WWW-Authenticate: <type> realm=<realm>
Proxy-Authenticate: <type> realm=<realm>

Here, <type> is the authentication scheme ("Basic" is the most common scheme and introduced below). The realm is used to describe the protected area or to indicate the scope of protection. This could be a message like "Access to the staging site" or similar, so that the user knows to which space they are trying to get access to.

Authorization and Proxy-Authorization headers

The Authorization and Proxy-Authorization request headers contain the credentials to authenticate a user agent with a (proxy) server. Here, the type is needed again followed by the credentials, which can be encoded or encrypted depending on which authentication scheme is used.

Authorization: <type> <credentials>
Proxy-Authorization: <type> <credentials>

Authentication schemes

The general HTTP authentication framework is used by several authentication schemes. Schemes can differ in security strength and in their availability in client or server software.

The most common authentication scheme is the "Basic" authentication scheme which is introduced in more details below. IANA maintains a list of authentication schemes, but there are other schemes offered by host services, such as Amazon AWS. Common authentication schemes include:

  • Basic (see RFC 7617, base64-encoded credentials. See below for more information.),
  • Bearer (see RFC 6750, bearer tokens to access OAuth 2.0-protected resources),
  • Digest (see RFC 7616, only md5 hashing is supported in Firefox, see error 472823 for SHA encryption support),
  • HOBA (see RFC 7486 (draft), HTTP Origin-Bound Authentication, digital-signature-based),
  • Mutual (see draft-ietf-httpauth-mutual),
  • AWS4-HMAC-SHA256 (see AWS docs).

Basic authentication scheme

The "Basic" HTTP authentication scheme is defined in RFC 7617, which transmits credentials as user ID/password pairs, encoded using base64.

Security of basic authentication

As the user ID and password are passed over the network as clear text (it is base64 encoded, but base64 is a reversible encoding), the basic authentication scheme is not secure. HTTPS / TLS should be used in conjunction with basic authentication. Without these additional security enhancements, basic authentication should not be used to protect sensitive or valuable information.

Restricting access with Apache and basic authentication

To password-protect a directory on an Apache server, you will need a .htaccess and a .htpasswd file.

The .htaccess file typically looks like this:

AuthType Basic
AuthName "Access to the staging site"
AuthUserFile /path/to/.htpasswd
Require valid-user

The .htaccess file references a .htpasswd file in which each line contains of a username and a password separated by a colon (":"). You can not see the actual passwords as they are encrypted (md5 in this case). Note that you can name your .htpasswd file differently if you like, but keep in mind this file shouldn't be accessible to anyone. (Apache is usually configured to prevent access to .ht* files).


Restricting access with nginx and basic authentication

For nginx, you will need to specify a location that you are going to protect and the auth_basic directive that provides the name to the password-protected area. The auth_basic_user_file directive then points to a .htpasswd file containing the encrypted user credentials, just like in the Apache example above.

location /status {                                       
    auth_basic           "Access to the staging site";
    auth_basic_user_file /etc/apache2/.htpasswd;

Access using credentials in the URL

Many clients also let you avoid the login prompt by using an encoded URL containing the username and the password like this:


The use of these URLs is deprecated. In Chrome, the username:password@ part in URLs is even stripped out for security reasons. In Firefox, it is checked if the site actually requires authentication and if not, Firefox will warn the user with a prompt "You are about to log in to the site “www.example.com” with the username “username”, but the website does not require authentication. This may be an attempt to trick you.".

See also

Etiquetas y colaboradores del documento

Colaboradores en esta página: JuanMacias, deiberdev, DavidPeniafiel
Última actualización por: JuanMacias,