Security
Security is an important topic between clients and the Avatica server. Most JDBC drivers and databases implement some level of authentication and authorization for limit what actions clients are allowed to perform.
Similarly, Avatica must limit what users are allowed to connect and interact with the server. Avatica must primarily deal with authentication while authorization is deferred to the underlying database. By default, Avatica provides no authentication. Avatica does have the ability to perform client authentication using Kerberos, HTTP Basic, and HTTP Digest.
The authentication and authorization provided by Avatica are designed for use
instead of the authentication and authorization provided by the underlying database.
The typical user
and password
JDBC properties are always passed through to
the Avatica server which will cause the server to enforce those credentials. As such,
Avatica’s authentication types mentioned here only have relevance when the underlying database’s authentication
and authorization features are not used. (The Kerberos/SPNEGO integration is one difference as the impersonation feature
is specifically designed to allow the Kerberos identity to be passed to the database -
new advanced implementations could also follow this same approach if desired).
Table of Contents
HTTP Basic Authentication
Avatica supports authentication over HTTP Basic. This is simple username-password based authentication which is ultimately insecure when operating over an untrusted network. Basic authentication is only secure when the transport is encrypted (e.g. TLS) as the credentials are passed in the clear. This authentication is supplementary to the provided JDBC authentication. If credentials are passed to the database already, this authentication is unnecessary.
Enabling Basic Authentication
The properties file must be in a form consumable by Jetty. Each line in this
file is of the form: username: password[,rolename ...]
For example:
Passwords can also be obfuscated as MD5 hashes or oneway cryptography (“CRYPT”). For more information, see the official Jetty documentation.
HTTP Digest Authentication
Avatica also supports HTTP Digest. This is desirable for Avatica as it does not require the use of TLS to secure communication between the Avatica client and server. It is configured very similarly to HTTP Basic authentication. This authentication is supplementary to the provided JDBC authentication. If credentials are passed to the database already, this authentication is unnecessary.
Enabling Digest Authentication
The properties file must be in a form consumable by Jetty. Each line in this
file is of the form: username: password[,rolename ...]
For example:
Passwords can also be obfuscated as MD5 hashes or oneway cryptography (“CRYPT”). For more information, see the official Jetty documentation.
Kerberos with SPNEGO Authentication
Because Avatica operates over an HTTP interface, the simple and protected GSSAPI negotiation mechanism (SPNEGO) is a logical choice. This mechanism makes use of the “HTTP Negotiate” authentication extension to communicate with the Kerberos Key Distribution Center (KDC) to authenticate a client.
Enabling SPNEGO/Kerberos Authentication in servers
The Avatica server can operate either by performing the login using a JAAS configuration file or login programmatically. By default, authenticated clients will have queries executed as the Avatica server’s kerberos user. Impersonation is the feature which enables actions to be run in the server as the actual end-user.
As a note, it is required that the Kerberos principal in use by the Avatica server
must have an primary of HTTP
(where Kerberos principals are of the form
primary[/instance]@REALM
). This is specified by RFC-4559.
Programmatic Login
This approach requires no external file configurations and only requires a keytab file for the principal.
JAAS Configuration File Login
A JAAS configuration file can be set via the system property java.security.auth.login.config
.
The user must set this property when launching their Java application invoking the Avatica server.
The presence of this file will automatically perform login as necessary in the first use
of the Avatica server. The invocation is nearly the same as the programmatic login.
The contents of the JAAS configuration file are very specific:
Ensure the keyTab
and principal
attributes are set correctly for your system.
Impersonation
Impersonation is a feature of the Avatica server which allows the Avatica clients to execute the server-side calls (e.g. the underlying JDBC calls). Because the details on what it means to execute such an operation are dependent on the actual system, a callback is exposed for downstream integrators to implement.
For example, the following is an example for creating an Apache Hadoop UserGroupInformation
“proxy user”. This example takes a UserGroupInformation
object representing the Avatica server’s
identity, creates a “proxy user” with the client’s username, and performs the action as that
client but using the server’s identity.
Remote user extraction
In some cases, it may be desirable to execute some queries on behalf of another user. For example, Apache Knox has a gateway service which can act as a proxy for all requests to the backend Avatica server. In this case, we don’t want to run the queries as the Knox user, instead the real user communicating with Knox.
There are presently two options to extract the “real” user from HTTP requests:
- The authenticated user from the HTTP request,
org.apache.calcite.avatica.server.HttpRequestRemoteUserExtractor
(default) - The value of a parameter in the HTTP query string,
org.apache.calcite.avatica.server.HttpQueryStringParameterRemoteUserExtractor
(e.g “doAs”)
Implementations of Avatica can configure this using the AvaticaServerConfiguration
and providing
an implementation of RemoteUserExtractor
. There are two implementations provided as listed above.
Custom Authentication
Avatica server allows users to plugin their Custom Authentication
mechanism through the HTTPServer Builder. This is useful if users
want to combine features of various authentication types. Examples
include combining basic authentication with impersonation or adding
mutual authentication with impersonation. More Examples are available
in CustomAuthHttpServerTest
class.
Note: Users need to configure their own ServerConnectors
and
Handlers
with the help of ServerCustomizers
.
Client implementation
Many HTTP client libraries, such as Apache Commons HttpComponents, already have support for performing Basic, Digest, and SPNEGO authentication. When in doubt, refer to one of these implementations as it is likely correct.
SPNEGO
For information on building SPNEGO support by hand, consult RFC-4559 which describes how the authentication handshake, through use of the “WWW-authenticate=Negotiate” HTTP header, is used to authenticate a client.
Password-based
For both HTTP Basic and Digest authentication, the avatica_user and avatica_password properties are used to identify the client with the server. If the underlying database (the JDBC driver inside the Avatica server) require their own user and password combination, these are set via the traditional “user” and “password” properties in the Avatica JDBC driver. This also implies that adding HTTP-level authentication in Avatica is likely superfluous.