Authentication Reverse Proxy

Sits between the TLS termination proxy and the application, authenticating all requests. Session management is via cookies.

Supports the following identity providers:

• GitHub, via OAuth2
• TLS client certificates

Upstream, the following headers are set:

X-Auth-Name
X-Auth-Email
X-Auth-User
X-Auth-Groups

Downstream, the above information is available at /auth/userinfo as JSON.

Build and Run

To build:

$ go get
$ go build

To run, you need the Oauth settings from GitHub, which are passed via environment variables. You'll also need to specify the port to listen on and upstream URLs:

GITHUB_ORG=example \
GITHUB_OAUTH2_CLIENT_ID=xxx \
GITHUB_OAUTH2_CLIENT_SECRET=xxx \
GITHUB_OAUTH2_CALLBACK_URL=https://example.com/oauth2/callback \
PORT=9000 \
UPSTREAMS="/=http://localhost:9001,/api=http://other.host:9002" \
./authn-proxy

You can pass the secrets as bare values, or as paths to files containing the value, e.g.:

GITLAB_OAUTH2_CLIENT_ID=file:/run/secrets/gitlab-client-id
GITLAB_OAUTH2_CLIENT_SECRET=file:/run/secrets/gitlab-client-secret

Client Certificates

If the X-Tls-Client-Subject header is present, authn-proxy assumes the user presented a valid client certificate, and that this header contains the value of the certificate's subject name field.

Subject	User info
CN	Name
emailAddress	Email
UID	User
OU	Groups

Generating the CA certificate

This generates a self-signed X.509 certificate authority:

openssl req -x509 -newkey rsa:4096 -sha256 -keyout client-ca.key.pem -out client-ca.cert.pem -nodes -days 1000 -subj "/CN=authn-proxy/O=FYST"

Configuring the downstream TLS termination proxy

For nginx, you need the following configuration:

ssl_client_certificate /path/to/client-ca.cert.pem;
ssl_verify_client optional;
location / {
    proxy_pass http://127.0.0.1:9000;
    proxy_set_header X-Tls-Client-Subject $ssl_client_s_dn;
}

Generate and sign the client certificate

$ openssl req -newkey rsa:2048 -sha256 -keyout client.key.pem -out client.csr.pem -nodes -subj "/CN=My Name/[email protected]/UID=me/OU=gid1/OU=gid2"
$ openssl x509 -req -sha256 -CA client-ca.cert.pem -CAkey client-ca.key.pem -in client.csr.pem -out client.cert.pem -set_serial 001 -days 390

Connect

$ curl --cert client.cert.pem --key client.key.pem https://example.com/auth/userinfo
{"name":"My Name","email":"[email protected]","user":"me","groups":["gid2","gid1"]}