API#

This document describes version 3 of the API provided by eduVPN and Let’s Connect! servers.

The API is intended to be used by the eduVPN and Let’s Connect! applications. If you are creating your own application, look here how to register your own client in the server.

Using this document you should be able to implement the API in your VPN client, or provide the same API for your VPN server to leverage the existing VPN clients.

This API is fully supported by all eduVPN / Let’s Connect! 3.x servers and 2.x servers with version >= 2.4.1.

The API design was finalized and is considered stable from 2022-01-27.

Standards#

We use a simple HTTP API protected by OAuth 2, following all recommendations of the OAuth 2.1 draft specification.

For some further implementation notes and recommendations for the client, please read this document.

Server Discovery#

As there are many servers running eduVPN / Let’s Connect! you need to know which server you need to connect to. This can be either hard-coded in the application, the user can be asked to provide a server address or a “discovery” can be implemented.

For eduVPN specific we implement “server discovery” as documented here.

Server Endpoint Discovery#

A “well-known” URL is provided to figure out the OAuth and API endpoint one has to use. The document can be retrieved from /.well-known/vpn-user-portal, e.g.:

{
    "api": {
        "http://eduvpn.org/api#3": {
            "api_endpoint": "https://vpn.example.org/vpn-user-portal/api/v3",
            "authorization_endpoint": "https://vpn.example.org/vpn-user-portal/oauth/authorize",
            "token_endpoint": "https://vpn.example.org/vpn-user-portal/oauth/token"
        }
    },
    "v": "3.0.0-1.fc34"
}

Servers that provide the http://eduvpn.org/api#3 key under api, support this API.

The application MUST retrieve this document at least once per application run, i.e. if the user restarts the application this document MUST be retrieved fresh for each server the client interacts with. An application MAY opt to refresh the document more frequently.

Rationale: if a server gets upgraded from e.g. 2.x to 3.x, we MUST make sure that the app does not get stuck trying to access old endpoints and the user can at the very least fix it themselves by restarting the application (once).

Endpoint Location#

When fetching this document, redirects, e.g. 301, 302, 303, MUST be followed, but MUST NOT allow redirect to anything else than other https:// URLs, e.g. redirects to http:// MUST be rejected.

Authorization Endpoint#

The authorization_endpoint is used to obtain an authorization code through an “Authorization Request”. All query parameters as defined by the OAuth specification are required, even optional ones:

• client_id;
• redirect_uri;
• response_type: MUST be code;
• scope: MUST be config;
• state;
• code_challenge_method: MUST be S256;
• code_challenge.

The authorization_endpoint with its parameters set MUST be opened in the platform’s default browser or follow the platform’s best practice dealing with application authorization(s). The redirect_uri parameter MUST point back to a location the application can intercept.

All error conditions, both during the authorization phase AND when talking to the API endpoint MUST be handled according to the OAuth specification(s).

Token Endpoint#

The token_endpoint is used to exchange the authorization code, as obtained through the redirect_uri as part of the authorization, for an access and refresh token. It is also used to retrieve new access tokens when the current access token expires.

All error conditions, both during the authorization phase AND when talking to the API endpoint MUST be handled according to the OAuth specification(s).

Using the API#

Every API call below will include a cURL example, and an example response that can be expected.

All POST requests MUST be sent encoded as application/x-www-form-urlencoded.

The API can be used with the access token obtained using the OAuth flow as documented above. The following API calls are available:

• Get “Info” from the VPN server, including a list of available profiles (/info);
• “Connect” to a VPN profile (/connect);
• “Disconnect” from a VPN profile (/disconnect)

API Calls#

Info#

This call will show the available VPN profiles for this instance. This will allow the application to show the user which profiles are available.

This GET call has no parameters.

Request#

Request all available VPN profiles:

$ curl \
    -H "Authorization: Bearer abcdefgh" \
    https://vpn.example.org/vpn-user-portal/api/v3/info

Response#

HTTP/1.1 200 OK
Content-Type: application/json

{
    "info": {
        "profile_list": [
            {
                "default_gateway": true,
                "display_name": {
                    "en": "Employees",
                    "nl": "Medewerkers"
                },
                "profile_id": "employees",
                "vpn_proto_list": [
                    "openvpn",
                    "wireguard"
                ]
            },
            {
                "default_gateway": false,
                "display_name": "Administrators",
                "profile_id": "admins",
                "vpn_proto_list": [
                    "wireguard"
                ]
            }
        ]
    }
}

The fields are described in the table below, look under the table for additional information.

The display_name field can be either of type string or object. When the field is an object, the keys are BCP-47 language codes and the values the human readable string with the name of the profile.

The vpn_proto_transport_list field enhances the vpn_proto_list field by also listing the supported transports, whereas vpn_proto_list only listed the protocols, e.g.:

{
    "vpn_proto_transport_list": [
        "openvpn+udp",
        "openvpn+tcp",
        "wireguard+udp"
    ]
}

Possible values for vpn_proto_transport_list:

The VPN client SHOULD ignore vpn_proto_list when vpn_proto_transport_list is set.

The dns_search_domain_list field contains the DNS search domains of the VPN server if they are set for a profile. This can be used by VPN clients to configure the DNS search domains of the connection “out of band” if needed.

Connect#

Get the profile configuration for the profile you want to connect to.

Request#

Connect to the “Employees” profile (employees) and specify a WireGuard public key for when WireGuard will be used:

$ curl \
    -d "profile_id=employees" \
    --data-urlencode "public_key=nmZ5ExqRpLgJV9yWKlaC7KQ7EAN7eRJ4XBz9eHJPmUU=" \
    -H "Authorization: Bearer abcdefgh" \
    "https://vpn.example.org/vpn-user-portal/api/v3/connect"

NOTE: a call to /connect immediately invalidates any previously obtained VPN configuration files that belong to the same OAuth authorization.

The POST request has (optional) parameters:

The HTTP Accept request header can be used to persuade the VPN server to only return VPN configurations of a particular protocol and/or transport. This request header is OPTIONAL.

See VPN Protocol Selection for more info on how it is determined which VPN configuration file is returned.

Profile ID#

The value of profile_id MUST be of one of the identifiers for the profiles returned in the /info response.

Public Key#

When the WireGuard protocol is expected to be used, the public_key parameter MUST be set. The value of public_key MUST be a valid WireGuard public key. It has this format:

$ wg genkey | wg pubkey
e4C2dNBB7k/U8KjS+xZdbicbZsqR1BqWIr1l924P3R4=

Prefer TCP#

The prefer_tcp parameter is a hint for the VPN server, currently only for the OpenVPN protocol.

If set to yes, the client indicates that a connection over TCP is preferred. The server MAY accept this and return an OpenVPN configuration with the TCP “remotes” first and thus have the client try to connect over TCP first.

The server MAY ignore the option, for example when the profile only supports WireGuard, or the OpenVPN server configuration does not use TCP.

Response#

If the profile is an OpenVPN profile you’ll get the complete OpenVPN client configuration with Content-Type: application/x-openvpn-profile, e.g.:

HTTP/1.1 201 Created
Expires: Fri, 06 Aug 2021 03:59:59 GMT
Content-Type: application/x-openvpn-profile

dev tun
client
nobind
remote-cert-tls server
verb 3
server-poll-timeout 10
tls-version-min 1.3
data-ciphers AES-256-GCM:CHACHA20-POLY1305
reneg-sec 0
<ca>
-----BEGIN CERTIFICATE-----
MIIBQzCB9qADAgECAhBiISHrvtMXVOiLSaTsLKTKMAUGAytlcDARMQ8wDQYDVQQD
EwZWUE4gQ0EwHhcNMjExMDExMTk1MDE0WhcNMzExMDExMTk1NTE0WjARMQ8wDQYD
VQQDEwZWUE4gQ0EwKjAFBgMrZXADIQBysHsh1pkJpLj6wJVQLGQW1C6cfW74tSZu
cCUP/wXF86NkMGIwDgYDVR0PAQH/BAQDAgKEMB0GA1UdJQQWMBQGCCsGAQUFBwMB
BggrBgEFBQcDAjASBgNVHRMBAf8ECDAGAQH/AgEAMB0GA1UdDgQWBBQmdLockXn6
YJFZ/a1X9PvhH2eD+jAFBgMrZXADQQCI2MtG+k3CtCHDM8+4lZG7LXpVLFG4EACJ
JJlplLlFlLr5qMsNFkf2oTjWccsn9qXmBkfvIcda4BLJF0xRZ08L
-----END CERTIFICATE-----
</ca>
<cert>
-----BEGIN CERTIFICATE-----
MIIBbjCCASCgAwIBAgIQTXCf2KpYiGLLFMl3roW7BTAFBgMrZXAwETEPMA0GA1UE
AxMGVlBOIENBMB4XDTIxMTEwMjA4MjM0MloXDTIyMDEzMTAzNTk1OVowSTEQMA4G
A1UECxMHZGVmYXVsdDE1MDMGA1UEAxMsanlkUkprdUd1Vk9uL1QzNnR6dEE3aVNq
KzFTUThtZXZKQlYxZ1hvZ3l0VT0wKjAFBgMrZXADIQADR7x0pbS6C8YxHOW4wXUE
0wXlez1go0xrhnEXaKjSBqNWMFQwDgYDVR0PAQH/BAQDAgeAMBMGA1UdJQQMMAoG
CCsGAQUFBwMCMAwGA1UdEwEB/wQCMAAwHwYDVR0jBBgwFoAUJnS6HJF5+mCRWf2t
V/T74R9ng/owBQYDK2VwA0EAY1pNvtE2N11hkyGEFXyTJzYvp/FRnR4AOM1mtxCu
1cLEt2mZW+lGB/0JOLDyyrYJ/1A+DvYeJhbto30FY50yDA==
-----END CERTIFICATE-----
</cert>
<key>
-----BEGIN PRIVATE KEY-----
MC4CAQAwBQYDK2VwBCIEIDtCkdkMVO5IV1HWsGqDSX0sIE0FENW6estLvfDSr4bp
-----END PRIVATE KEY-----
</key>
<tls-crypt>
#
# 2048 bit OpenVPN static key
#
-----BEGIN OpenVPN Static key V1-----
7a086674dc25cf16c609a6cf6b206046
0592cf3e98dc58262d4c780d9d37ad30
e726d4d4b4da651ccaa232e84e0eea14
13870e2cd391057ca402fac3eb3ced8e
e88c848a785a6878f01ea9f9c8e947d9
2cede35d0a51a34f6c2e06a6c118e5c2
267a81a8c69b67d110c264d03bd7e2e9
a529a7d37828050f1031cc405369903a
d092231c573794e07333c72b832cddde
a4f071a90063edf1561b32ab28884a4b
786abe2438c5e6e312811e3eacf90196
648a17cc193295e684a475ad5bb6510f
d4cf0f1061ddb7d69dc4fd355774cf7f
d904456b668e128a861151ed12da788c
c34b9a63c3f74fa96a26a61d203a0e85
fe9edd1611499201429a2f6e91d1e307
-----END OpenVPN Static key V1-----
</tls-crypt>
remote vpn.example 1194 udp
remote vpn.example 1194 tcp

If the profile is an WireGuard profile you’ll get a WireGuard client configuration with Content-Type: application/x-wireguard-profile, e.g.:

Expires: Fri, 06 Aug 2021 03:59:59 GMT
Content-Type: application/x-wireguard-profile

[Interface]
Address = 10.43.43.2/24, fd43::2/64
DNS = 9.9.9.9, 2620:fe::fe

[Peer]
PublicKey = iWAHXts9w9fQVEbA5pVriPlAYMwwEPD5XcVCZDZn1AE=
AllowedIPs = 0.0.0.0/0, ::/0
Endpoint = vpn.example:51820

As can be seen in the examples, this API response also contains an Expires header that indicates when the VPN configuration will expire.

Disconnect#

This call is to indicate to the server that the VPN session(s) belonging to this OAuth authorization can be terminated.

The purpose of this call is to clean up, i.e. release the IP address reserved for the client (WireGuard) and delete the certificate from the list of allowed certificates (OpenVPN).

Request#

$ curl -X POST \
    -H "Authorization: Bearer abcdefgh" \
    "https://vpn.example.org/vpn-user-portal/api/v3/disconnect"

This POST call has no parameters.

Response#

HTTP/1.1 204 No Content

Error Responses#

An example:

HTTP/1.1 404 Not Found
Content-Type: application/json

{"error":"no such \"profile_id\""}

In addition to these errors, there can also be an error with the server that we did not anticipate or is an unusual situation. In that case the response code will be 500 and the JSON error key will contain more information about the error.

VPN Protocol Selection#

The VPN server has a preferred protocol for a VPN connection, but the client can influence this decision by using the HTTP request Accept header and the prefer_tcp POST parameter.

A VPN client that supports ALL protocols and transports would have this HTTP Accept request header value:

Accept: application/x-openvpn-profile,application/x-wireguard-profile,application/x-wireguard+tcp-profile

The client can also claim support for a subset of these protocols/transports by only explicitly listing the supported protocols/transports in the Accept header. This makes sure the server never responds with a VPN configuration that is not supported by the VPN client.

NOTE: if the Accept request header is missing, it is assumed that the VPN client supports both OpenVPN and WireGuard, but not WireGuard+TCP.

In addition, the VPN client can indicate if they prefer to connect over TCP using the prefer_tcp HTTP POST field.

Without WireGuard+TCP support#

“Yes” in the “OpenVPN” and “WireGuard” columns means that both the server and client support the protocol, “No” means that only one of them, or neither support the protocol. The value N/A in the “Result” column means that no connection can be established at all.

NOTE: If both WireGuard and OpenVPN are supported by the client, but not WireGuard+TCP, see below, and prefer_tcp is set to true, OpenVPN will be used, even if the server’s preferred protocol is WireGuard!

With WireGuard+TCP support#

“Yes” in the “OpenVPN”, “WireGuard” and “WireGuard+TCP” columns means that both the server and client support the protocol, “No” means that only one of them, or neither support the protocol. The value N/A in the “Result” column means that no connection can be established at all.

History#

The changes made to the API documentation.