caddy-auth-portal

Authentication Plugin for Caddy v2 implementing Form-Based, Basic, Local, LDAP, OpenID Connect, OAuth 2.0, SAML Authentication.

Please see other relevant plugins:

• caddy-auth-jwt
• caddy-trace

Download Caddy with the plugins enabled:

• linux/amd64
• windows/amd64

Please show your appreciation for this work and ⭐️ ⭐️ ⭐️

Please ask questions either here or via LinkedIn. I am happy to help you! @greenpau

Table of Contents

• Overview
• Authentication Portal
  • User Identity
  • User Settings
  • Multi-Factor Authentication MFA
    • Enabling MFA
    • Add MFA Authenticator Application
  • Theming
• Authorization Cookie
  • Intra-Domain Cookies
  • JWT Tokens
    • JWT Signing Method
• Usage Examples
  • Secure Prometheus
  • Secure Kibana
• Authentication Methods
  • Basic Authentication
  • Form-Based Authentication
• User Interface Features
  • Auto-Redirect URL
  • User Registration
  • Custom CSS Styles
  • Custom Javascript
  • Portal Links
  • Custom Header
  • Static Assets of Any Type
• Local Authentication Backend
  • Configuration Primer
  • Identity Store
  • Password Management
• LDAP Authentication Backend
  • Configuration Primer
  • LDAP Authentication Process
• SAML Authentication Backend
  • Time Synchronization
  • Configuration
  • Azure Active Directory (Office 365) Applications
    • Azure AD SAML Configuration
    • Set Up Azure AD Application
    • Configure SAML Authentication
    • Azure AD IdP Metadata and Certificate
    • User Interface Options
    • Development Notes
• OAuth 2.0 and OpenID Connect (OIDC) Authentication Backend
  • OAuth 2.0 Flow
  • Adding Role Claims
  • OAuth 2.0 Authorization Servers and Identity Providers
    • Okta
    • Google Identity Platform
    • LinkedIn
    • Auth0
    • OneLogin
    • Microsoft
    • Github
    • Facebook
• X.509 Certificate-based Authentication Backend
• Miscellaneous
  • Binding to Privileged Ports
  • Recording Source IP Address in JWT Token
  • Session ID Cache
  • Caddyfile Shortcuts

Overview

The purpose of this plugin is providing authentication only. The plugin issue JWT tokens upon successful authentication. In turn, the authorization of the tokens is being handled by caddy-auth-jwt.

The plugin supports the following authentication backends:

• Local (local) - JSON flat file database
• LDAP (ldap) - remote Microsoft AD database
• SAML
• OAuth 2.0 and OpenID Connect (OIDC)

The plugin accepts user credentials for authentication with:

• Form-based Authentication: POST with application/x-www-form-urlencoded
• Basic Authentication: GET with Authorization: Basic header

The following digram is visual representation of the configuration of caddy-auth-portal and caddy-auth-jwt.

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Authentication Portal

User Identity

The following screenshot is from /auth/whoami endpoint:

User Settings

The following screenshot is from /auth/settings/ endpoint:

Multi-Factor Authentication MFA

Enabling MFA

MFA can be enabled globally and on per-backend basis via require mfa directive.

        local_backend {
          method local
          path /etc/gatekeeper/auth/local/users_db.json
          realm local
          require mfa
        }

Currently, the MFA requirement can be applied only to local backend type.

Importantly, a user may choose to enable MFA via the user's settings page.

Add MFA Authenticator Application

The following screenshot is from /auth/settings/mfa/add/app endpoint:

The QR Code displayed on the page complies Key Uri Format.

In your MFA application, e.g. Microsoft Authenticator, follow these steps to onboard your web account.

Theming

The theming of the portal works as follows.

It starts with a concept of theme. By default, the portal uses basic theme. There is no need to defind it in Caddyfile.

localhost {
  route /auth* {
    auth_portal {
      ui {
        theme basic
      }

Each theme must have a set of default pages:

• generic
• login
• portal
• register
• whoami
• settings
• sandbox

The plain text templates are being stored in assets/templates/<THEME>/<PAGE>.template.

assets/templates/basic/generic.template
assets/templates/basic/login.template
assets/templates/basic/portal.template
assets/templates/basic/register.template
assets/templates/basic/whoami.template
assets/templates/basic/settings.template
assets/templates/basic/sandbox.template

These templates are the parts of pkg/ui/pages.go. They are compiled in the portal's binary. That is, there is no need to store them on the disk.

Next, if a user wants to use a different template, then it could be passed via Caddyfile directives. Specifically, use <PAGE>_template directive to point to a file on disk.

localhost {
  route /auth* {
    auth_portal {
      ui {
        theme basic
        login_template "/etc/gatekeeper/ui/login.template"
      }

TODO: Review Refactoring UI Feed and Refactoring UI Website.

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Authorization Cookie

Intra-Domain Cookies

The following Caddyfile settings define the scope of the cookies issued by the plugin. Specifically, what URLs the cookies should be sent to. See MDN - Using HTTP cookies - Define where cookies are sent for more information.

• cookie_domain: adds the Domain attribute to a cookie. It determines which hosts are allowed to receive the cookie.
• cookie_path: adds the Path attribute to a cookie. It determines the URL path that must exist in the requested URL in order to send the Cookie header.
• cookie_lifetime: sets the number of seconds until the cookie expires. The directive sets "Max-Age" cookie attribute.

JWT Tokens

The plugin sends JWT token via the cookie.

• token_name: specifies the names of the cookie with authorization credentials

By default the lifetime of the token is 15 minutes. The token_lifetime can be used to change it to 1 hour (3600 seconds).

      jwt {
        token_name access_token
        token_secret 0e2fdcf8-6868-41a7-884b-7308795fc286
        token_lifetime 3600
      }

The issued JWT token could be of two types:

1. HS512: signed using shared secret key
2. RS512: signed using private PEM key

The HS512 is being configured with token_secret

      jwt {
        ...
        # token_secret <shared_key>
        token_secret 0e2fdcf8-6868-41a7-884b-7308795fc286
        ...
      }

The RS512 is being configured with token_rsa_file directive:

      jwt {
        ...
        token_rsa_file <key_id> <file_path>
        token_rsa_file Hz789bc303f0db /etc/gatekeeper/auth/jwt/sign_key.pem
        ...
      }

If necessary, generate the signing key:

$ openssl genrsa -out /etc/gatekeeper/auth/jwt/sign_key.pem 2048
Generating RSA private key, 2048 bit long modulus (2 primes)
.....................................................................................................................+++++
....+++++
e is 65537 (0x010001)

JWT Signing Method

By default, the plugin uses HS512 (shared secret) and RS512 (public/private keys) for the signing of JWT tokens. User token_sign_method to change the algorithm, e.g.

      jwt {
        ...
        token_secret 0e2fdcf8-6868-41a7-884b-7308795fc286
        token_sign_method HS256
        ...
      }

or:

      jwt {
        ...
        token_rsa_file Hz789bc303f0db /etc/gatekeeper/auth/jwt/sign_key.pem
        token_sign_method RS256
        ...
      }

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Usage Examples

Secure Prometheus

The following Caddyfile secures Prometheus/Alertmanager services:

{
  http_port     8080
  https_port    8443
  debug
}

localhost:8443 {
  route /auth* {
    auth_portal {
      path /auth
      backends {
        local_backend {
          method local
          path /etc/gatekeeper/auth/local/users.json
          realm local
        }
      }
      jwt {
        token_name access_token
        token_secret 0e2fdcf8-6868-41a7-884b-7308795fc286
      }
      ui {
        links {
          "Prometheus" /prometheus
          "Alertmanager" /alertmanager
          "My App" /myapp
        }
      }
    }
  }

  route /prometheus* {
    jwt {
      primary yes
      trusted_tokens {
        static_secret {
          token_name access_token
          token_secret 0e2fdcf8-6868-41a7-884b-7308795fc286
        }
      }
      auth_url /auth
      allow roles anonymous guest admin
      allow roles superadmin
    }
    uri strip_prefix /prometheus
    reverse_proxy http://127.0.0.1:9080
  }

  route /alertmanager* {
    jwt
    uri strip_prefix /alertmanager
    reverse_proxy http://127.0.0.1:9083
  }

  route /myapp* {
    jwt
    respond * "myapp" 200
  }

  route /version* {
    respond * "1.0.0" 200
  }

  route {
    redir https://{hostport}/auth 302
  }
}

If you would like to style the UI differently, then specify your templates and settings:

      ui {
        login_template "/etc/gatekeeper/ui/login.template"
        portal_template "/etc/gatekeeper/ui/portal.template"
        logo_url "https://caddyserver.com/resources/images/caddy-circle-lock.svg"
        logo_description "Caddy"
        links {
          "Prometheus" /prometheus
          "Alertmanager" /alertmanager
          "My App" /myapp
        }
      }

In fact, if you are not going to display any links, then remove the ui section and use an auto-redirect feature.

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Secure Kibana

First, add the following line in /etc/kibana/kibana.yml. It must match the the prefix used when proxying traffic through:

server.basePath: "/elk"

Next, add the following route in you Caddyfile:

  route /elk* {
    jwt
    uri strip_prefix /elk
    reverse_proxy KIBANA_IP:5601
  }

Also, add the link to Kibana in ui section of Caddyfile:

      ui {
        ...
        links {
          ...
          "Kibana" /elk/
          ...
        }
      }

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Authentication Methods

Basic Authentication

The following command demonstrates basic authentication process. The plugin returns JWT token via Set-Cookie: access_token and token field in JSON response.

curl --insecure -H "Accept: application/json" --user webadmin:password123 -v https://127.0.0.1:3443/auth

The expected output is as follows:

* About to connect() to 127.0.0.1 port 3443 (#0)
*   Trying 127.0.0.1...
* Connected to 127.0.0.1 (127.0.0.1) port 3443 (#0)
* Initializing NSS with certpath: sql:/etc/pki/nssdb
* skipping SSL peer certificate verification
* SSL connection using TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
* Server certificate:
*       subject: [email protected],OU=Local Developement,CN=*.caddy.localhost,L=Local Developement,O=Local Developement,ST=NY,C=US
*       start date: Mar 02 08:01:16 2020 GMT
*       expire date: Feb 28 08:01:16 2030 GMT
*       common name: *.caddy.localhost
*       issuer: [email protected],OU=Local Developement,CN=*.caddy.localhost,L=Local Developement,O=Local Developement,ST=NY,C=US
* Server auth using Basic with user 'webadmin'
> GET /auth HTTP/1.1
> Authorization: Basic d2ViYWRtaW46cGFzc3dvcmQxMjM=
> User-Agent: curl/7.29.0
> Host: 127.0.0.1:3443
> Accept: application/json
>
< HTTP/1.1 200 OK
< Authorization: Bearer eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE1OTE3MzE0NzksInN1YiI6IndlYmFkbWluIiwiZW1haWwiOiJ3ZWJhZG1pbkBsb2NhbGRvbWFpbi5sb2NhbCIsInJvbGVzIjpbInN1cGVyYWRtaW4iLCJndWVzdCIsImFub255bW91cyJdLCJvcmlnaW4iOiJsb2NhbGhvc3QifQ.OmFOCu-UJdx16FYLa2ezr7WRmOdUbgrQadhfk1tN4AliIwu69x9TLgzoke_Cr3TqzvMjlQDd22r-3DHBXuzllw
< Cache-Control: no-store
< Content-Type: application/json
< Pragma: no-cache
< Server: Caddy
< Set-Cookie: access_token=eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE1OTE3MzE0NzksInN1YiI6IndlYmFkbWluIiwiZW1haWwiOiJ3ZWJhZG1pbkBsb2NhbGRvbWFpbi5sb2NhbCIsInJvbGVzIjpbInN1cGVyYWRtaW4iLCJndWVzdCIsImFub255bW91cyJdLCJvcmlnaW4iOiJsb2NhbGhvc3QifQ.OmFOCu-UJdx16FYLa2ezr7WRmOdUbgrQadhfk1tN4AliIwu69x9TLgzoke_Cr3TqzvMjlQDd22r-3DHBXuzllw Secure; HttpOnly;
< Date: Tue, 09 Jun 2020 19:22:59 GMT
< Content-Length: 318
<
* Connection #0 to host 127.0.0.1 left intact
{"token":"eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE1OTE3MzE0NzksInN1YiI6IndlYmFkbWluIiwiZW1haWwiOiJ3ZWJhZG1pbkBsb2NhbGRvbWFpbi5sb2NhbCIsInJvbGVzIjpbInN1cGVyYWRtaW4iLCJndWVzdCIsImFub255bW91cyJdLCJvcmlnaW4iOiJsb2NhbGhvc3QifQ.OmFOCu-UJdx16FYLa2ezr7WRmOdUbgrQadhfk1tN4AliIwu69x9TLgzoke_Cr3TqzvMjlQDd22r-3DHBXuzllw"}

Form-Based Authentication

TBD.

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User Interface Features

Auto-Redirect URL

Consider the following configuration snippet. When the JWT plugin detects unauthenticated user, it forwards the user to https://auth.example.com. The redirect_url in URL query creates AUTH_PORTAL_REDIRECT_URL cookie in the users session. Upon successful authentication, the portal clears the cookie and redirects the user to the path specified in AUTH_PORTAL_REDIRECT_URL cookie.

https://chat.example.com {
  jwt {
    auth_url https://auth.example.com/auth?redirect_url=https://chat.example.com
  }
}

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User Registration

The following Caddy configuration enables user registration.

registration {
  dropbox /etc/gatekeeper/auth/local/registrations_db.json
  title "User Registration"
  code "NY2020"
  require accept_terms
  require domain_mx
}

The parameters are:

• dropbox: The file path pointing to registration database.
• code: The registration code. A user must know what that code is to successfully submit a registration request.
• require accept_terms: A user must accept terms and conditions, as well as privacy policy to proceed
• disabled on: disables user registration
• title: changes the title of the registration page
• require domain_mx: forces the check of domain MX record

This screenshot is the registration screen with default options:

The following is the registration screen with mandatory registration code and the acceptable of terms and conditions:

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Custom CSS Styles

The following Caddyfile directive adds a custom CSS stylesheet to the plugin's pages. The stylesheet is available under auth/assets/css/custom.css

      ui {
        ...
        custom_css_path path/to/styles.css
        ...
      }

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Custom Javascript

The following Caddyfile directive adds a custom javascript file to the plugin's pages. The script is available under auth/assets/js/custom.js

      ui {
        ...
        custom_js_path path/to/script.js
        ...
      }

This directive is usefule for adding Google Analytics or other minor javascript code.

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Portal Links

The following Caddyfile directive sets links that a user would see upon a successful login:

      ui {
        ...
        links {
          "Prometheus" /prometheus
          "Alertmanager" /alertmanager
          "My App" /myapp
        }
        ...
      }

The link can be opened in a new tab or window via target_blank argument:

          "My App" /myapp target_blank

The link can be disabled with disabled argument:

          "My App" /myapp disabled

The link can have an icon associated with it via icon argument:

          "My App" /myapp icon "las la-cog"

The icon is the reference to Line Awesome by Icon8.

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Custom Header

The following Caddyfile directive injects the code found in path/to/head.html to <head> section of the portal's pages:

      ui {
        ...
        custom_html_header_path path/to/head.html
        ...
      }

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Static Assets of Any Type

The following Caddyfile directive is capable of loading and serving any type of static asset, e.g. js, css, etc.

      ui {
        ...
        static_asset "assets/css/app.css" "text/css" /path/to/app/styles.css
        ...
      }

The above configuration would cause the plugin to read /path/to/app/styles.css and begin serving it with content type of text/css at AUTH_PORTAL/assets/css/app.css, e.g. https://localhost:8443/auth/assets/css/app.css.

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Local Authentication Backend

Configuration Primer

Please refer to the assets/conf/local/config.json configuration file when configurin the plugin backend. In the example, the route refers to local backend in the file assets/backends/local/users.json. Specify the path to the file where you want your database to reside. Do not create a file, but rather create leading directories.

For example, create /etc/caddy/auth/local directory and specify the path value as:

"path": "/etc/caddy/auth/local/users.json",

Next, start the server, and find the following following log entries:

{"level":"info","ts":1588704471.5784082,"logger":"http.authentication.providers.portal","msg":"created new user","user_id":"cd5f647a-cc04-4ae2-9d0a-2d5e9b95cf98","user_name":"webadmin","user_email":"[email protected]","user_claims":{"roles":"superadmin"}}
{"level":"info","ts":1588704471.5784378,"logger":"http.authentication.providers.portal","msg":"created default superadmin user for the database","user_name":"webadmin","user_secret":"d87e7749-0dd8-482b-91a2-ada370263293"}

Identity Store

The user_name and user_secret are password for the superuser in the database.

The plugin creates the following a file having the following structure.

{
  "revision": 1,
  "users": [
    {
      "id": "cd5f647a-cc04-4ae2-9d0a-2d5e9b95cf98",
      "username": "webadmin",
      "email_addresses": [
        {
          "address": "[email protected]",
          "domain": "localdomain.local"
        }
      ],
      "passwords": [
        {
          "purpose": "generic",
          "type": "bcrypt",
          "hash": "$2a$10$B67nHY0PEdxLYdyoLk1YLOomvs.T/dSIyzPuoX9vWULrsD3PRf/sq",
          "cost": 10,
          "expired_at": "0001-01-01T00:00:00Z",
          "created_at": "2020-05-05T18:47:51.513552501Z",
          "disabled_at": "0001-01-01T00:00:00Z"
        }
      ],
      "created": "2020-05-05T18:47:51.513552066Z",
      "last_modified": "2020-05-05T18:47:51.513552175Z",
      "roles": [
        {
          "name": "superadmin"
        }
      ]
    }
  ]
}

Finally, browse to /auth and login with the username and password:

Password Management

An administrator may change the password directly in /etc/caddy/auth/local/users.json file.

First, download bcrypt-cli:

go get -u github.com/bitnami/bcrypt-cli

Then, use it to generate a new password:

$ echo -n "password123" | bcrypt-cli -c 10
$2a$10$OVnOaHDkcOXfbUZPFh5qt.yJqUt6pl9uJaqEMxxM.vS5fY/cZNmsq

Finally, replace the newly generated password is user database file.

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LDAP Authentication Backend

It is recommended reading the documentation for Local backend, because it outlines important principles of operation of all backends.

Additionally, the LDAP backend works in conjunction with Local backend. As you will see later, the two can be used together by introducing a dropdown in UI interface to choose local versus LDAP domain authentication.

The reference configuration for the backend is assets/conf/ldap/config.json.

The following Caddy endpoint at /auth authentications users from contoso.com domain.

There is a single LDAP server associated with the domain: ldaps://ldaps.contoso.com.

The plugin DOES NOT ignore certificate errors when connecting to the servers. However, one may ignore the errors by setting ignore_cert_errors to true.

As a better alternative to ignoring certificate errors, the plugin allows adding trusted certificate authorities via trusted_authority Caddyfile directive:

          servers {
            ldaps://ldaps.contoso.com
          }
          trusted_authority /etc/gatekeeper/tls/trusted_authority/contoso_com_root1_ca_cert.pem
          trusted_authority /etc/gatekeeper/tls/trusted_authority/contoso_com_root2_ca_cert.pem
          trusted_authority /etc/gatekeeper/tls/trusted_authority/contoso_com_root3_ca_cert.pem

The LDAP attribute mapping to JWT fields is as follows.

JWT Token Field	LDAP Attribute
name	givenName
surname	sn
username	sAMAccountName
member_of	memberOf
email	mail

The plugin uses authzsvc domain user to perform LDAP bind.

The base search DN is DC=CONTOSO,DC=COM.

The plugin accepts username (sAMAccountName) or email address (mail) and uses the following search filter: (&(|(sAMAccountName=%s)(mail=%s))(objectclass=user)).

For example:

      {
        "Name": "sAMAccountName",
        "Values": [
          "jsmith"
        ]
      },
      {
        "Name": "mail",
        "Values": [
          "[email protected]"
        ]
      }

Upon successful authentication, the plugin assign the following rules to a user, provided the user is a member of a group:

JWT Role	LDAP Group Membership
admin	CN=Admins,OU=Security,OU=Groups,DC=CONTOSO,DC=COM
editor	CN=Editors,OU=Security,OU=Groups,DC=CONTOSO,DC=COM
viewer	CN=Viewers,OU=Security,OU=Groups,DC=CONTOSO,DC=COM

The security of the password could be improved by the following techniques:

• pass the password via environment variable LDAP_USER_SECRET
• store the password in a file and pass the file inside the password field with file: prefix, e.g. file:/path/to/password.

Configuration Primer

The following Caddyfile secures Prometheus/Alertmanager services. Users may access using local and LDAP credentials.

{
  http_port     8080
  https_port    8443
  debug
}

127.0.0.1:8443 {
  route /auth* {
    auth_portal {
      path /auth
      backends {
        local_backend {
          method local
          path assets/conf/local/auth/user_db.json
          realm local
        }
        ldap_backend {
          method ldap
          realm contoso.com
          servers {
            ldaps://ldaps.contoso.com
          }
          trusted_authority /etc/gatekeeper/tls/trusted_authority/contoso_com_root1_ca_cert.pem
          trusted_authority /etc/gatekeeper/tls/trusted_authority/contoso_com_root2_ca_cert.pem
          trusted_authority /etc/gatekeeper/tls/trusted_authority/contoso_com_root3_ca_cert.pem
          attributes {
            name givenName
            surname sn
            username sAMAccountName
            member_of memberOf
            email mail
          }
          username "CN=authzsvc,OU=Service Accounts,OU=Administrative Accounts,DC=CONTOSO,DC=COM"
          # password "[email protected]"
          password "file:/etc/gatekeeper/auth/ldap.secret"
          search_base_dn "DC=CONTOSO,DC=COM"
          search_filter "(&(|(sAMAccountName=%s)(mail=%s))(objectclass=user))"
          groups {
            "CN=Admins,OU=Security,OU=Groups,DC=CONTOSO,DC=COM" admin
            "CN=Editors,OU=Security,OU=Groups,DC=CONTOSO,DC=COM" editor
            "CN=Viewers,OU=Security,OU=Groups,DC=CONTOSO,DC=COM" viewer
          }
        }
      }
      jwt {
        token_name access_token
        token_secret 0e2fdcf8-6868-41a7-884b-7308795fc286
      }
      ui {
        logo_url "https://caddyserver.com/resources/images/caddy-circle-lock.svg"
        logo_description "Caddy"
        links {
          "Prometheus" /prometheus
          "Alertmanager" /alertmanager
          "My App" /myapp
        }
      }
    }
  }

  route /prometheus* {
    jwt {
      primary yes
      trusted_tokens {
        static_secret {
          token_name access_token
          token_secret 0e2fdcf8-6868-41a7-884b-7308795fc286
        }
      }
      auth_url /auth
      allow roles anonymous guest admin
      allow roles superadmin
      allow roles admin editor viewer
      allow roles AzureAD_Administrator AzureAD_Editor AzureAD_Viewer
    }
    uri strip_prefix /prometheus
    reverse_proxy http://127.0.0.1:9080
  }

  route /alertmanager* {
    jwt
    uri strip_prefix /alertmanager
    reverse_proxy http://127.0.0.1:9083
  }

  route /myapp* {
    jwt
    respond * "myapp" 200
  }

  route /version* {
    respond * "1.0.0" 200
  }

  route {
    redir https://{hostport}/auth 302
  }
}

LDAP Authentication Process

The plugin does not keep connections open to LDAP servers. The plugin tears a connection down each time it finishes authenticating a request associated with the connection.

First, the plugin uses username and password to bind to an LDAP server. The purpose of the connection is searching for user objects in the server's directory.

The plugin takes the username provided in a request. Next, the plugin substitutes %s with the username in its search filter, i.e. (&(|(sAMAccountName=%s)(mail=%s))(objectclass=user)).

The plugin initiates a search for a user object in the scope provided via search_base_dn, e.g. DC=CONTOSO,DC=COM.

If the number of objects in the result of the search is not 1, then authentication fails.

Typically, the response would have the following structure:

[
  {
    "DN": "CN=Smith\\, John,OU=Users,DC=CONTOSO,DC=COM",
    "Attributes": [
      {
        "Name": "sn",
        "Values": [
          "Smith"
        ]
      },
      {
        "Name": "givenName",
        "Values": [
          "John"
        ]
      },
      {
        "Name": "memberOf",
        "Values": [
          "CN=Admins,OU=Security,OU=Groups,DC=CONTOSO,DC=COM",
          "CN=Editors,OU=Security,OU=Groups,DC=CONTOSO,DC=COM",
          "CN=Viewers,OU=Security,OU=Groups,DC=CONTOSO,DC=COM"
        ]
      },
      {
        "Name": "sAMAccountName",
        "Values": [
          "jsmith"
        ]
      },
      {
        "Name": "mail",
        "Values": [
          "[email protected]"
        ]
      }
    ]
  }
]

The plugin iterates over memberOf attribute and compares the values to its group mapping:

              "groups": [
                {
                  "dn": "CN=Admins,OU=Security,OU=Groups,DC=CONTOSO,DC=COM",
                  "roles": [
                    "admin"
                  ]
                },
                {
                  "dn": "CN=Editors,OU=Security,OU=Groups,DC=CONTOSO,DC=COM",
                  "roles": [
                    "editor"
                  ]
                },
                {
                  "dn": "CN=Viewers,OU=Security,OU=Groups,DC=CONTOSO,DC=COM",
                  "roles": [
                    "viewer"
                  ]
                }
              ]

If there are no matches, the authentication fails.

Once the plugin determines the user's roles, e.g. admin, editor, viewer, the plugin actually checks whether the user's password is valid.

It does so by doing LDAP re-binding with the user's DN and the password provided in the request. In this example, the user's DN is CN=Smith\\, John,OU=Users,DC=CONTOSO,DC=COM.

If the re-binding is successful, the plugin issues a JWT token.

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SAML Authentication Backend

The plugin supports the following SAML identity providers (IdP):

• Azure Active Directory (Office 365) Applications

If you would like to see the support for the following identity providers, please reach out:

• Salesforce
• Okta
• Ping Identity

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Time Synchronization

Importantly, SAML assertion validation checks timestamps. It is critical that the application validating the assertions maintains accurate clock. The out of sync time WILL result in failed authentications.

Configuration

The following configuration is common across variations of SAML backend:

      backends {
        azure_saml_backend {
          method saml
          realm azure
          provider azure
        }
      }

Parameter Name	Description
method	Must be set to saml
realm	The realm is used to distinguish between various SAML authentication providers
provider	It is either generic or specific, e.g. azure, okta, etc.

The URL for the SAML endpoint is: <AUTH_PORTAL_PATH>/saml/<REALM_NAME>.

If you specify realm as azure and the portal is being served at /auth, then you could access the endpoint via /auth/saml/azure.

The Reply URL could be https://localhost:8443/auth/saml/azure.

Azure Active Directory (Office 365) Applications

Azure AD SAML Configuration

The Azure SAML backend configuration:

      backends {
        azure_saml_backend {
          method saml
          realm azure
          provider azure
          idp_metadata_location /etc/gatekeeper/auth/idp/azure_ad_app_metadata.xml
          idp_sign_cert_location /etc/gatekeeper/auth/idp/azure_ad_app_signing_cert.pem
          tenant_id "1b9e886b-8ff2-4378-b6c8-6771259a5f51"
          application_id "623cae7c-e6b2-43c5-853c-2059c9b2cb58"
          application_name "My Gatekeeper"
          entity_id "urn:caddy:mygatekeeper"
          acs_url https://mygatekeeper/auth/saml/azure
          acs_url https://mygatekeeper.local/auth/saml/azure
          acs_url https://192.168.10.10:3443/auth/saml/azure
          acs_url https://localhost:3443/auth/saml/azure
        }
      }

The plugin supports the following parameters for Azure Active Directory (Office 365) applications:

Parameter Name	Description
idp_metadata_location	The url or path to Azure IdP Metadata
idp_sign_cert_location	The path to Azure IdP Signing Certificate
tenant_id	Azure Tenant ID
application_id	Azure Application ID
application_name	Azure Application Name
entity_id	Azure Application Identifier (Entity ID)
acs_url	Assertion Consumer Service URLs

Use the acs_url directive to list all URLs the users of the application can reach it at. One URL per line:

  acs_url https://mygatekeeper/auth/saml/azure
  acs_url https://mygatekeeper.local/auth/saml/azure
  acs_url https://192.168.10.10:3443/auth/saml/azure
  acs_url https://localhost:3443/auth/saml/azure

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Set Up Azure AD Application

In Azure AD, you will have an application, e.g. "My Gatekeeper".

The application is a Caddy web server running on port 3443 on localhost. This example meant to emphasize that the authorization is asynchronious. That is when a user clicks on "My Gatekeeper" icon in Office 365, the browser takes the user to a sign in page at URL https://localhost:3443/saml.

The Application Identifiers are as follows:

• Application (client) ID: 623cae7c-e6b2-43c5-853c-2059c9b2cb58
• Directory (tenant) ID: 1b9e886b-8ff2-4378-b6c8-6771259a5f51
• Object ID: 515d2e8b-7548-413f-abee-a23ece1ea576

The "Branding" page configures "Home Page URL".

For demostration purposes, we will create the following "Roles" in the application:

Azure Role Name	Role Name in SAML Assertion
Viewer	AzureAD_Viewer
Editor	AzureAD_Editor
Administrator	AzureAD_Administrator

Use "Manifest" tab to add roles in the manifest via appRoles key:

{
  "allowedMemberTypes": [
    "User"
  ],
  "description": "Administrator",
  "displayName": "Administrator",
  "id": "91287df2-7028-4d5f-b5ae-5d489ba217dd",
  "isEnabled": true,
  "lang": null,
  "origin": "Application",
  "value": "AzureAD_Administrator"
},
{
  "allowedMemberTypes": [
    "User"
  ],
  "description": "Editor",
  "displayName": "Editor",
  "id": "d482d827-1757-4f60-9bea-021c10037674",
  "isEnabled": true,
  "lang": null,
  "origin": "Application",
  "value": "AzureAD_Editor"
},
{
  "allowedMemberTypes": [
    "User"
  ],
  "description": "Viewer",
  "displayName": "Viewer",
  "id": "c69f7abd-0a88-401e-b515-92d74b6fff2f",
  "isEnabled": true,
  "lang": null,
  "origin": "Application",
  "value": "AzureAD_Viewer"
}

After, we added the roles, we could assign any of the roles to a user:

The app is now available to the provisioned users in Office 365:

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Configure SAML Authentication

Go to "Enterprise Application" and browse to "My Gatekeeper" application.

There, click "Single Sign-On" and select "SAML" as the authentication method.

Next, in the "Set up Single Sign-On with SAML", provide the following "Basic SAML Configuration":

• Identifier (Entity ID): urn:caddy:mygatekeeper
• Reply URL (Assertion Consumer Service URL): https://localhost:3443/auth/saml/azure

Under "User Attributes & Claims", add the following claims to the list of default claims:

Namespace	Claim name	Value
http://claims.contoso.com/SAML/Attributes	RoleSessionName	user.userprincipalname
http://claims.contoso.com/SAML/Attributes	Role	user.assignedroles
http://claims.contoso.com/SAML/Attributes	MaxSessionDuration	3600

Next, record the following:

• App Federation Metadata Url
• Login URL

Further, download:

• Federation Metadata XML
• Certificate (Base64 and Raw)

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Azure AD IdP Metadata and Certificate

The following command downloads IdP metadata file for Azure AD Tenant with ID 1b9e886b-8ff2-4378-b6c8-6771259a5f51. Please note the xmllint utility is a part of libxml2 library.

mkdir -p /etc/gatekeeper/auth/saml/idp/
curl -s -L -o /tmp/federationmetadata.xml https://login.microsoftonline.com/1b9e886b-8ff2-4378-b6c8-6771259a5f51/federationmetadata/2007-06/federationmetadata.xml
sudo mkdir -p /etc/gatekeeper/auth/saml/idp/
cat /tmp/federationmetadata.xml | xmllint --format - | sudo tee /etc/gatekeeper/auth/saml/idp/azure_ad_app_metadata.xml

The /etc/gatekeeper/auth/saml/idp/azure_ad_app_metadata.xml contains IdP metadata. This file contains the data necessary to verify the SAML claims received by this service and signed by Azure AD. The idp_metadata argument is being used to pass the location of IdP metadata.

Next, download the "Certificate (Base64)" and store it in /etc/gatekeeper/auth/saml/idp/azure_ad_app_signing_cert.pem.

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User Interface Options

First option is a login button on the login server web page. Once Azure AD has been enabled, the /auth/saml/azure page will have "Sign in with Office 365" button

Second option is Office 365 applications. When a user click on the application's icon in Office 365, the user gets redirected to the web server by Office 365.

The URL is https://localhost:3443/auth/saml/azure.

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Development Notes

The below are the headers of the redirected POST request that the user's browser makes upon clicking "My Gatekeeper" application:

Method: POST
URL: /auth/saml/azure
Protocol: HTTP/2.0
Host: localhost:3443
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate, br
Accept-Language: en-US,en;q=0.9,ru;q=0.8
Cache-Control: max-age=0
Content-Length: 7561
Content-Type: application/x-www-form-urlencoded
Origin: https://login.microsoftonline.com
Referer: https://login.microsoftonline.com/
Sec-Fetch-Mode: navigate
Sec-Fetch-Site: cross-site
Upgrade-Insecure-Requests: 1

The above redirect contains login.microsoftonline.com in the request's Referer header. It is the trigger to perform SAML-based authorization.

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OAuth 2.0 and OpenID Connect (OIDC) Authentication Backend

OAuth 2.0 Flow

Generally, a developer must create an "Application" with and identity provider. e.g. Google, Okta, Azure, etc., and obtain OAuth 2.0 "Client ID" and "Client Secret".

The authentication flow begins with obtaining "Authorization Code" from an identity provider.

• What does the portal send to Okta?

  • Client ID
  • Redirect URI
  • Response Type
  • Scope

• What does the portal receive from Okta?

  • Authorization Code

Once, the portal has the "Authorization Code", it could get "Access Token" to access the user's data at the identity provider.

• What does the portal send to Okta?

  • Authorization Code
  • Client ID
  • Client Secret

• What does Okta respond with?

  • Access Token

• What could the portal use "Access Token" for?

  • Make API calls to obtain user information

The OpenID Connect (OIDC) adds login and profile information about the person who is logged in. The differences between standard OAuth2.0 flow are:

1. In the initial request, a specific scope of openid is used
2. In the final exchange the Client receives both an "Access Token" and an "ID Token" (JWT Token).

References:

• Mozilla - OIDC in a nutshell

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Adding Role Claims

The Caddyfile user directive allows adding roles to a user based on the user's email.

A user with email claim of contoso.com would get an additional superuser role.

          user [email protected] add role superuser

A user with the email address beginning with jsmith would get additional roles. Specifically, it would be viewer, editor, and admin.

          user "^greenpau" regex add roles viewer editor admin

All users with contoso.com email address would get "employee" role:

          user "@contoso.com$" regex add role employee

In sum, Caddyfile may look as follows:

myapp.localdomain.local, localhost, 127.0.0.1 {
  route /auth* {
    auth_portal {
      path /auth
      backends {
        google_oauth2_backend {
          method oauth2
          realm google
          provider google
          client_id XXXXXXXXXXXXXX.apps.googleusercontent.com
          client_secret YYYYYYYYYYYYYYYYY
          scopes openid email profile
          user "^greenpau" regex add role superuser
        }

OAuth 2.0 Authorization Servers and Identity Providers

The Caddyfile snippet for generic (non-specific) OAuth 2.0 backend.

Based on the below configuration, OAuth 2.0 endpoint is /auth/oauth2/generic. If a user browses to the endpoint, the user will be redirected to the provider discovered via metadata_url and base_auth_url URLs.

127.0.0.1, localhost {
  route /auth* {
    auth_portal {
      backends {
        generic_oauth2_backend {
          method oauth2
          realm generic
          provider generic
          client_id XXXXXXXXXXXXXXXXXXX
          client_secret YYYYYYYYYYYYYYYYYYYYYY
          scopes openid email profile
        }

Next, protect a route, e.g. /sso/oauth2/generic*. When a user accesses the page, the the user will be redirected to /auth/oauth2/generic and, then, to the provider. Once authenticated, the user will be redirected back to /sso/oauth2/generic..., i.e. back to the path the user came from.

  route /sso/oauth2/generic* {
    jwt {
      auth_url /auth/oauth2/generic
    }
    respond * "generic oauth2 sso" 200
  }

Okta

Create an "Application," by browsing to "Applications" and clicking "Add Application" button.

For a website, the choice is "Web".

Provided your application is running on localhost port 8443, provide the following information:

Base URI entries:

• https://myapp.localdomain.local:8443/
• https://localhost:8443/

Login redirect URIs:

• https://myapp.localdomain.local:8443/auth/oauth2/okta/authorization-code-callback
• https://localhost:8443/auth/oauth2/okta/authorization-code-callback

Logout redirect URIs:

• https://myapp.localdomain.local:8443/auth/logout
• https://localhost:8443/auth/logout

Group Assignments:

• Everyone
• Viewer
• Editor
• Administrator

Grant type allowed:

• Client acting on behalf of itself
  • Client Credentials: No
• Client acting on behalf of a user
  • Authorization Code: Yes
  • Refresh Token: No
  • Implicit (Hybrid): No

Review the newly created application.

Store the credentials securely.

Review default Sign On Policy.

By default, the default Authorization Server has no groups scope.

Therefore, browse to "API", "Authorization Servers" and select "default".

Next, browse to "Scopes" and click "Add Scope".

Fill out the "Add Scope" form:

• Name: groups
• Description: This allows the app to view your group memberships.
• Check "Set as a default scope"
• Check "Include in public metadata"

Next, browse to "Claims" and click "Add Claim".

Fill out the "Add Claim" form:

• Name: groups
• Include in token type: "ID Token", "Always"
• Value type: Groups
• Filter: Matches .* regex
• Include in: The "groups" scope

Next, review Okta OpenID Connect and OAuth 2.0 API - Get Started.

The Caddyfile snipper for Okta OAuth 2.0 backend is as follows.

Based on the below configuration, Okta endpoint is /auth/oauth2/okta. If a user browses to the endpoint, the user will be redirected to Okta.

127.0.0.1, localhost {
  route /auth* {
    auth_portal {
      backends {
        okta_oauth2_backend {
          method oauth2
          realm okta
          provider okta
          domain_name dev-680653.okta.com
          client_id 0oa121qw81PJW0Tj34x7
          client_secret b3aJC5E59hU18YKC7Yca3994F4qFhWiAo_ZojanF
          server_id default
          scopes openid email profile groups
        }

Next, protect a route, e.g. /sso/oauth2/okta*. When a user accesses the page, the the user will be redirected to /auth/oauth2/okta and, then, to Okta. Once authenticated, the user will be redirected back to /sso/oauth2/okta..., i.e. back to the path the user came from.

  route /sso/oauth2/okta* {
    jwt {
      auth_url /auth/oauth2/okta
    }
    respond * "okta oauth2 sso" 200
  }

Provided the Okta domain is dev-680653.okta.com, the authorization server is default, and Client ID is 0oa121qw81PJW0Tj34x7, check OpenID configuration:

curl -X GET "https://dev-680653.okta.com/oauth2/default/.well-known/openid-configuration?client_id=0oa121qw81PJW0Tj34x7" | jq

By default, the plugin logs public keys from keys endpoint.

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Google Identity Platform

References:

• Google Identity Platform - Using OAuth 2.0 for Web Server Applications
• Google Identity Platform - Identity Platform - OpenID Connect

The Caddyfile snippet for Google OAuth 2.0 OpenID backend is as follows.

Based on the below configuration, Google endpoint is /auth/oauth2/google. If a user browses to the endpoint, the user will be redirected to Google.

127.0.0.1, localhost {
  route /auth* {
    auth_portal {
      backends {
        google_oauth2_backend {
          method oauth2
          realm google
          provider google
          client_id XXXXXXXXXXXXXXXXX.apps.googleusercontent.com
          client_secret YYYYYYYYYYYYYYYYYY
          scopes openid email profile
        }

Next, protect a route, e.g. /sso/oauth2/google*. When a user accesses the page, the the user will be redirected to /auth/oauth2/google and, then, to Google. Once authenticated, the user will be redirected back to /sso/oauth2/google..., i.e. back to the path the user came from.

  route /sso/oauth2/google* {
    jwt {
      auth_url /auth/oauth2/google
    }
    respond * "google oauth2 sso" 200
  }

First, create new application, e.g. "My Gatekeeper".

After the creation of the app, you will land on Credentials page.

Click "Configure Consent Screen" and select an appropriate option, e.g. "External".

Next, provide the name for the application, e.g. "My Gatekeeper" and select appropriate support email.

After configuring the consent screen you will see the following.

Next, browse to "Credentials" and click "Create Credentials". Then, choose "OAuth client ID":

First, choose the type of credentials:

Next, provide Redirect URL:

Login redirect URIs:

• https://localhost:8443/auth/oauth2/google/authorization-code-callback

Finally, you will get a confirmation. Store the Client ID and Client Secret securely.

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LinkedIn

First, browse to https://www.linkedin.com/developers/apps/new and create an application.

Next, note the "Client Secret"

After that, add "redirect URLS":

https://localhost:8443/auth/oauth2/linkedin/authorization-code-callback

Next, browse to "Products" tab and enabled "Sign In with LinkedIn":

References:

• LinkedIn - LinkedIn API Documentation - Authentication - Authorization Code Flow
• LinkedIn - Consumer Solutions Platform - Integrations - Sign In with LinkedIn

Auth0

TBD.

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OneLogin

TBD.

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Microsoft

To register an OAuth2 application for login with Microsoft accounts (either personal, i.e. Live or Xbox accounts, or enterprise, i.e. AzureAD accounts), you can follow the documentation at https://docs.microsoft.com/en-us/advertising/guides/authentication-oauth-identity-platform.

In summary, you open the Azure Active Directory section on https://portal.azure.com and navigate to App registrations.

There you select New registration and enter your application's name, your choice of supported account types and the the redirect URI

https://localhost:8443/auth/oauth2/azure/authorization-code-callback

As soon as the application registration was successfully created, you can note down its Application (client) ID listed in the Essentials section at the top.

Finally, you need to generate a client secret to authenticate caddy-auth-portal. In the sidebar, navigate to Certificates and secrets and click on New client secret.

After the secret was successfully created, copy its value (you won't be able to retrieve it again!).

You now have all the necessary information to use the backend in your Caddyfile:

        azure_oauth2_backend {
          method oauth2
          realm azure
          provider azure
          client_id 840e455a-69af-47bb-b033-b3a316f1aff0
          client_secret MnE~D8G5Dh_gWRq_jc3uJ8Q8wjBqBv.N3r
          scopes openid email profile
        }

If you chose Accounts in this organizational directory only as the account type, you additionally need to add the line

          tenant_id <your tenant ID>

where the tenant ID can either be the actual Directory ID, or its friendly name <something>.onmicrosoft.com.

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Github

Follow the instructions at https://github.com/settings/apps/new.

GitHub App name: "My Gatekeeper"

Description: "Caddy v2 Authentication Portal"

Homepage URL: https://localhost:8443/

User authorization callback URL: https://localhost:8443/auth/oauth2/github/authorization-code-callback

Check "Expire user authorization tokens".

Check "Request user authorization (OAuth) during installation"

Upon successful completion of the instructions, you will get:

Additionally, click "generate a private key" to sign access token requests.

Caddyfile configuration:

        github_oauth2_backend {
          method oauth2
          realm github
          provider github
          client_id CLIENT_ID
          client_secret CLIENT_SECRET
          scopes user
        }

The github provider does not have mail claim, i.e. email address. Therefore, if there is a need to assign a role to a user, one could user user directive to match on sub, i.e. subject claim. The sub claim is in the format of github.com/<GITHUB_HANDLE>.

        github_oauth2_backend {
          ...
          user github.com/greenpau add role superuser
        }

The users authenticating via Github would have to accept the terms:

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Facebook

Browse to https://developers.facebook.com/apps/ and click "Create App".

When asked about "What do you need your app to do?", choose "Build Connected Experiences".

Next, choose the name for the application:

Once your app (in this case App ID is 38409328409) is available, click "Set Up" next to "Facebook Login" product:

When at Quickstart screen, select "Other".

Next, click "Settings - Advanced" on the left navigation bar and browse to "Security" section.

Set "Require App Secret" to "Yes". The Client Token is not being used because client_secret is being used to calculate appsecret_proof.

Next, click "Settings - Basic" on the left navigation bar and extract "App Secret". The App Secret is used in client_secret Caddyfile directive.

Next, click "Settings" under "Facebook Login" on the left navigation bar and browse to "Client OAuth Settings" section:

Set "Valid OAuth Redirect URIs" to:

• https://localhost:8443/auth/oauth2/facebook/authorization-code-callback

Additionally, add the URL in "Redirect URI Validator":

• https://localhost:8443/auth/oauth2/facebook/authorization-code-callback

The Caddyfile config is as follows:

127.0.0.1, localhost {
  route /auth* {
    auth_portal {
      backends {
        facebook_oauth2_backend {
          method oauth2
          realm facebook
          provider facebook
          client_id 38409328409
          client_secret 11899bfcd5745a8ed20235c65638f311
        }

When a user get redirected to Facebook Login, the screen looks as follows:

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X.509 Certificate-based Authentication Backend

TBD.

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Miscellaneous

Binding to Privileged Ports

It may be necessary to bind Caddy to privileged port, e.g. 80 or 443. Grant the cap_net_bind_service capability to the Caddy binary, e.g.:

sudo systemctl stop gatekeeper
sudo rm -rf /usr/local/bin/gatekeeper
sudo cp bin/caddy /usr/local/bin/gatekeeper
sudo setcap cap_net_bind_service=+ep /usr/local/bin/gatekeeper
sudo systemctl start gatekeeper

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Recording Source IP Address in JWT Token

The enable source ip tracking Caddyfile directive instructs the plugin to record the source IP address when issuing claims.

localhost {
  route /auth* {
    auth_portal {
      ...
      enable source ip tracking
      ...

This could be useful to force re-authentication when the client IP address changes.

Session ID Cache

When the plugin issues JWT tokens, it either passes jti values from upstream providers or generates its own jti values.

The plugin stores the mappings between jti value and associated data in a cache. The associated data contains claims and the metadata from the backend which authenticated a particular session.

This cache is used to assess whether a claim holder is able using certain portal's capabilities, e.g. add public SSH/GPG key, configure MFA tokens, change password, etc.

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Caddyfile Shortcuts

The following snippet with either jwt_token_file or jwt_token_rsa_file Caddyfile directive:

    auth_portal {
      jwt_token_file 1 /etc/caddy/auth/jwt/jwt_privatekey.pem
      jwt_token_rsa_file 2 /etc/caddy/auth/jwt/jwt_privatekey.pem
      ...
    }

Replaces:

    auth_portal {
      jwt {
        token_rsa_file 1 /etc/caddy/auth/jwt/jwt_privatekey.pem
      }
      ...
    }

The following snippet with jwt_token_name Caddyfile directive:

    auth_portal {
      jwt_token_name access_token
      ...
    }

Replaces:

    auth_portal {
      jwt {
        token_name access_token
      }
      ...
    }

The following snippet with jwt_token_secret Caddyfile directive:

    auth_portal {
      jwt_token_secret bcc8fd6e-8e45-493e-a146-f178ac676841
      ...
    }

Replaces:

    auth_portal {
      jwt {
        token_secret bcc8fd6e-8e45-493e-a146-f178ac676841
      }
      ...
    }

The following snippet with jwt_token_lifetime Caddyfile directive:

    auth_portal {
      jwt_token_lifetime 3600
      ...
    }

Replaces:

    auth_portal {
      jwt {
        token_lifetime 3600
      }
      ...
    }