293 lines
16 KiB
Text
293 lines
16 KiB
Text
[[_x509]]
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=== X.509 Client Certificate User Authentication
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{project_name} supports login with a X.509 client certificate if the server is configured for mutual SSL authentication.
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A typical workflow is as follows:
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- A client sends an authentication request over SSL/TLS channel
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- During SSL/TLS handshake, the server and the client exchange their x.509/v3 certificates
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- The container (WildFly) validates the certificate PKIX path and the certificate expiration
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- The x.509 client certificate authenticator validates the client certificate as follows:
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* Optionally checks the certificate revocation status using CRL and/or CRL Distribution Points
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* Optionally checks the Certificate revocation status using OCSP (Online Certificate Status Protocol)
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* Optionally validates whether the key usage in the certificate matches the expected key usage
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* Optionally validates whether the extended key usage in the certificate matches the expected extended key usage
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- If any of the above checks fails, the x.509 authentication fails
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- Otherwise, the authenticator extracts the certificate identity and maps it to an existing user
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- Once the certificate is mapped to an existing user, the behavior diverges depending on the authentication flow:
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* In the Browser Flow, the server prompts the user to confirm identity or to ignore it and instead sign in with username/password
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* In the case of the Direct Grant Flow, the server signs in the user
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==== Features
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Supported Certificate Identity Sources::
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- Match SubjectDN using regular expression
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- X500 Subject's e-mail attribute
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- X500 Subject's Common Name attribute
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- Match IssuerDN using regular expression
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- X500 Issuer's e-mail attribute
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- X500 Issuer's Common Name attribute
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- Certificate Serial Number
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Regular Expressions::
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The certificate identity can be extracted from either Subject DN or Issuer DN using a regular expression as a filter. For example, the regular expression below will match the e-mail attribute:
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```
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emailAddress=(.*?)(?:,|$)
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```
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The regular expression filtering is applicable only if the `Identity Source` is set to either `Match SubjectDN using regular expression` or `Match IssuerDN using regular expression`.
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Mapping certificate identity to an existing user::
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The certificate identity mapping can be configured to map the extracted user identity to an existing user's username or e-mail or to a custom attribute which value matches the certificate identity. For example, setting the `Identity source` to _Subject's e-mail_ and `User mapping method` to _Username or email_ will have the X.509 client certificate authenticator use the e-mail attribute in the certificate's Subject DN as a search criteria to look up an existing user by username or by e-mail.
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IMPORTANT: Please notice that if we disable `Login with email` at realm settings, the same rules will be applied to certificate authentication. In other words, users won't be able to log in using e-mail attribute.
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Other Features: Extended Certificate Validation::
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- Revocation status checking using CRL
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- Revocation status checking using CRL/Distribution Point
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- Revocation status checking using OCSP/Responder URI
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- Certificate KeyUsage validation
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- Certificate ExtendedKeyUsage validation
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==== Enable X.509 Client Certificate User Authentication
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The following sections describe how to configure Wildfly/Undertow and the {project_name} Server to enable X.509 client certificate authentication.
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Enable mutual SSL in WildFly::
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See link:https://docs.jboss.org/author/display/WFLY10/Admin+Guide#AdminGuide-EnableSSL[Enable SSL] and link:https://docs.jboss.org/author/display/WFLY10/Admin+Guide#AdminGuide-%7B%7B%3Cssl%2F%3E%7D%7D[SSL] for the instructions how to enable SSL in Wildfly.
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* Open {project_dirref}/standalone/configuration/standalone.xml and add a new realm:
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```
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<security-realms>
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<security-realm name="ssl-realm">
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<server-identities>
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<ssl>
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<keystore path="servercert.jks"
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relative-to="jboss.server.config.dir"
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keystore-password="servercert password"/>
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</ssl>
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</server-identities>
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<authentication>
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<truststore path="truststore.jks"
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relative-to="jboss.server.config.dir"
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keystore-password="truststore password"/>
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</authentication>
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</security-realm>
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</security-realms>
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```
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`ssl/keystore`::
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The `ssl` element contains the `keystore` element that defines how to load the server public key pair from a JKS keystore
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`ssl/keystore/path`::
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A path to a JKS keystore
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`ssl/keystore/relative-to`::
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Defines a path the keystore path is relative to
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`ssl/keystore/keystore-password`::
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The password to open the keystore
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`ssl/keystore/alias` (optional)::
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The alias of the entry in the keystore. Set it if the keystore contains multiple entries
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`ssl/keystore/key-password` (optional)::
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The private key password, if different from the keystore password.
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`authentication/truststore`::
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Defines how to load a trust store to verify the certificate presented by the remote side of the inbound/outgoing connection. Typically, the truststore contains a collection of trusted CA certificates.
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`authentication/truststore/path`::
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A path to a JKS keystore that contains the certificates of the trusted CAs (certificate authorities)
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`authentication/truststore/relative-to`::
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Defines a path the truststore path is relative to
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`authentication/truststore/keystore-password`::
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The password to open the truststore
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Enable https listener::
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See link:https://docs.jboss.org/author/display/WFLY10/Admin+Guide#AdminGuide-HTTPSlistener[HTTPS Listener] for the instructions how to enable HTTPS in Wildfly.
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* Add the <https-listener> element as shown below:
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[source,xml,subs="attributes+"]
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----
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<subsystem xmlns="{subsystem_undertow_xml_urn}">
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....
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<server name="default-server">
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<https-listener name="default"
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socket-binding="https"
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security-realm="ssl-realm"
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verify-client="REQUESTED"/>
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</server>
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</subsystem>
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----
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`https-listener/security-realm`::
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The value must match the name of the realm from the previous section
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`https-listener/verify-client`::
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If set to `REQUESTED`, the server will optionally ask for a client certificate. Setting the attribute to `REQUIRED` will have the server to refuse inbound connections if no client certificate has been provided.
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==== Adding X.509 Client Certificate Authentication to a Browser Flow
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* Select a realm, click on Authentication link, select the "Browser" flow
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* Make a copy of the built-in "Browser" flow. You may want to give the new flow a distinctive name, i.e. "X.509 Browser"
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* Using the drop down, select the copied flow, and click on "Add Execution"
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* Select "X509/Validate User Form" using the drop down and click on "Save"
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image:images/x509-execution.png[]
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* Using the up/down arrows, change the order of the "X509/Validate Username Form" by moving it above the "Browser Forms" execution, and set the requirement to "ALTERNATIVE"
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image:images/x509-browser-flow.png[]
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* Select the "Bindings" tab, find the drop down for "Browser Flow". Select the newly created X509 browser flow from the drop down and click on "Save".
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image:images/x509-browser-flow-bindings.png[]
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Configuring X.509 Client Certificate Authentication::
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image:images/x509-configuration.png[]
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`User Identity Source`::
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Defines how to extract the user identity from a client certificate.
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`A regular expression` (optional)::
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Defines a regular expression to use as a filter to extract the certificate identity. The regular expression must contain a single group.
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`User Mapping Method`::
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Defines how to match the certificate identity to an existing user. _Username or e-mail_ will search for an existing user by username or e-mail. _Custom Attribute Mapper_ will search for an existing user with a custom attribute which value matches the certificate identity. The name of the custom attribute is configurable.
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`A name of user attribute` (optional)::
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A custom attribute which value will be matched against the certificate identity.
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`CRL Checking Enabled` (optional)::
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Defines whether to check the revocation status of the certificate using Certificate Revocation List.
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`Enable CRL Distribution Point to check certificate revocation status` (optional)::
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Defines whether to use CDP to check the certificate revocation status. Most PKI authorities include CDP in their certificates.
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`CRL file path` (optional)::
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Defines a path to a file that contains a CRL list. The value must be a path to a valid file if `CRL Checking Enabled` option is turned on.
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`OCSP Checking Enabled`(optional)::
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Defines whether to check the certificate revocation status using Online Certificate Status Protocol.
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`OCSP Responder URI` (optional)::
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Allows to override a value of the OCSP responder URI in the certificate.
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`Validate Key Usage` (optional)::
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Verifies whether the certificate's KeyUsage extension bits are set. For example, "digitalSignature,KeyEncipherment" will verify if bits 0 and 2 in the KeyUsage extension are asserted. Leave the parameter empty to disable the Key Usage validation. See link:https://tools.ietf.org/html/rfc5280#section-4.2.1.3[RFC5280, Section-4.2.1.3]. The server will raise an error only when flagged as critical by the issuing CA and there is a key usage extension mismatch.
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`Validate Extended Key Usage` (optional)::
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Verifies one or more purposes as defined in the Extended Key Usage extension. See link:https://tools.ietf.org/html/rfc5280#section-4.2.1.12[RFC5280, Section-4.2.1.12]. Leave the parameter empty to disable the Extended Key Usage validation. The server will raise an error only when flagged as critical by the issuing CA and there is a key usage extension mismatch.
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`Bypass identity confirmation`::
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If set, X.509 client certificate authentication will not prompt the user to confirm the certificate identity and will automatically sign in the user upon successful authentication.
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==== Adding X.509 Client Certificate Authentication to a Direct Grant Flow
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* Using {project_name} admin console, click on "Authentication" and select the "Direct Grant" flow,
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* Make a copy of the build-in "Direct Grant" flow. You may want to give the new flow a distinctive name, i.e. "X509 Direct Grant",
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* Delete "Validate Username" and "Password" authenticators,
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* Click on "Execution" and add "X509/Validate Username" and click on "Save" to add the execution step to the parent flow.
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image:images/x509-directgrant-execution.png[]
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* Change the `Requirement` to _REQUIRED_.
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image:images/x509-directgrant-flow.png[]
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* Set up the x509 authentication configuration by following the steps described earlier in the x.509 Browser Flow section.
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* Select the "Bindings" tab, find the drop down for "Direct Grant Flow". Select the newly created X509 direct grant flow from the drop down and click on "Save".
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image:images/x509-directgrant-flow-bindings.png[]
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==== Client certificate lookup
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When an HTTP request is sent directly to {project_name} server, the {appserver_name} undertow subsystem will establish an SSL handshake and extract the client certificate. The client certificate will be then saved to the attribute `javax.servlet.request.X509Certificate` of the HTTP request, as specified in the servlet specification. The {project_name} X509 authenticator will be then able to lookup the certificate from this attribute.
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However, when the {project_name} server listens to HTTP requests behind a load balancer or reverse proxy, it may be the proxy server which extracts the client certificate and establishes the mutual SSL connection. A reverse proxy usually puts the authenticated client certificate in the HTTP header of the underlying request and forwards it to the back end {project_name} server. In this case, {project_name} must be able to look up the X.509 certificate chain from the HTTP headers instead of from the attribute of HTTP request, as is done for Undertow.
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If {project_name} is behind a reverse proxy, you usually need to configure alternative provider of the `x509cert-lookup` SPI in {project_dirref}/standalone/configuration/standalone.xml. Along with the `default` provider, which looks up the certificate from the HTTP header, we also have two additional built-in providers: `haproxy` and `apache`, which are described next.
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===== HAProxy certificate lookup provider
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You can use this provider when your {project_name} server is behind an HAProxy reverse proxy. Configure the server like this:
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[source,xml]
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----
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<spi name="x509cert-lookup">
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<default-provider>haproxy</default-provider>
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<provider name="haproxy" enabled="true">
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<properties>
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<property name="sslClientCert" value="SSL_CLIENT_CERT"/>
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<property name="sslCertChainPrefix" value="CERT_CHAIN"/>
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<property name="certificateChainLength" value="10"/>
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</properties>
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</provider>
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</spi>
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----
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In this example configuration, the client certificate will be looked up from the HTTP header, `SSL_CLIENT_CERT`, and the other certificates from its chain will be looked up from HTTP headers like `CERT_CHAIN_0` , `CERT_CHAIN_1`, ..., `CERT_CHAIN_9` . The attribute `certificateChainLength` is the maximum length of the chain, so the last one tried attribute would be `CERT_CHAIN_9` .
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Consult the HAProxy documentation for the details of how the HTTP Headers for the client certificate and client certificate chain can be configured and their proper names.
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===== Apache certificate lookup provider
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You can use this provider when your {project_name} server is behind an Apache reverse proxy. Configure the server like this:
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[source,xml]
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----
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<spi name="x509cert-lookup">
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<default-provider>apache</default-provider>
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<provider name="apache" enabled="true">
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<properties>
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<property name="sslClientCert" value="SSL_CLIENT_CERT"/>
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<property name="sslCertChainPrefix" value="CERT_CHAIN"/>
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<property name="certificateChainLength" value="10"/>
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</properties>
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</provider>
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</spi>
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----
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The configuration is same as for the `haproxy` provider. Consult the Apache documentation for the details of how the HTTP Headers for the client certificate and client certificate chain can be configured and their proper names.
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===== Other reverse proxy implementations
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We do not have built-in support for other reverse proxy implementations. However, it is possible that other reverse proxies can be made to behave in a similar way to `apache` or `haproxy` and that some of those providers can be used. If none of those works, you may need to create your own implementation of the `org.keycloak.services.x509.X509ClientCertificateLookupFactory` and `org.keycloak.services.x509.X509ClientCertificateLookup` provider. See the link:{developerguide_link}[{developerguide_name}] for the details on how to add your own provider.
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==== Troubleshooting
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Direct Grant authentication with X.509::
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The following template can be used to request a token using the Resource Owner Password Credentials Grant:
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```
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$ curl https://[host][:port]/auth/realms/master/protocol/openid-connect/token \
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--insecure \
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--data "grant_type=password&scope=openid profile&username=&password=&client_id=CLIENT_ID&client_secret=CLIENT_SECRET" \
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-E /path/to/client_cert.crt \
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--key /path/to/client_cert.key
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```
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`[host][:port]`::
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The host and the port number of a remote {project_name} server that has been configured to allow users authenticate with x.509 client certificates using the Direct Grant Flow.
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`CLIENT_ID`::
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A client id.
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`CLIENT_SECRET`::
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For confidential clients, a client secret; otherwise, leave it empty.
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`client_cert.crt`::
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A public key certificate that will be used to verify the identity of the client in mutual SSL authentication. The certificate should be in PEM format.
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`client_cert.key`::
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A private key in the public key pair. Also expected in PEM format.
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