Securing Envoy

Envoy provides a number of features to secure traffic in and out of your network, and between proxies and services within your network.

Transport Layer Security (TLS) can be used to secure all types of HTTP traffic, including WebSockets.

Envoy also has support for transmitting and receiving generic TCP traffic with TLS.

Envoy also offers a number of other HTTP-based protocols for authentication and authorization such as JWT, RBAC and OAuth.

Warning

The following guide takes you through individual aspects of securing traffic.

To secure traffic over a network that is untrusted, you are strongly advised to make use of encryption and mutual authentication wherever you control both sides of the connection or where relevant protocols are available.

Here we provide a guide to using mTLS which provides both encryption and mutual authentication.

When using TLS, you are strongly encouraged to validate all certificates wherever possible.

It is your responsibility to ensure the integrity of your certificate chain, and outside the scope of this guide.

Upstream and downstream TLS contexts

Machines connecting to Envoy to proxy traffic are “downstream” in relation to Envoy.

Specifying a TLS context that clients can connect to is achieved by setting the DownstreamTLSContext in the transport_socket of a listener.

You will also need to provide valid certificates.

envoy-demo-tls.yaml
 1static_resources:
 2
 3  listeners:
 4  - name: listener_0
 5    address:
 6      socket_address:
 7        address: 0.0.0.0
 8        port_value: 10000
 9    filter_chains:
10    - filters:
11      - name: envoy.filters.network.http_connection_manager
12        typed_config:
13          "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
14          stat_prefix: ingress_http
15          http_filters:
16          - name: envoy.filters.http.router
17            typed_config:
18              "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
19          route_config:
20            name: local_route
21            virtual_hosts:
22            - name: local_service
23              domains: ["*"]
24              routes:
25              - match:
26                  prefix: "/"
27                route:
28                  host_rewrite_literal: www.envoyproxy.io
29                  cluster: service_envoyproxy_io
30      transport_socket:
31        name: envoy.transport_sockets.tls
32        typed_config:
33          "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.DownstreamTlsContext
34          common_tls_context:
35            tls_certificates:
36            - certificate_chain:
37                filename: certs/servercert.pem
38              private_key:
39                filename: certs/serverkey.pem

Connecting to an “upstream” TLS service is conversely done by adding an UpstreamTLSContext to the transport_socket of a cluster.

envoy-demo-tls.yaml
40  clusters:
41  - name: service_envoyproxy_io
42    type: LOGICAL_DNS
43    # Comment out the following line to test on v6 networks
44    dns_lookup_family: V4_ONLY
45    load_assignment:
46      cluster_name: service_envoyproxy_io
47      endpoints:
48      - lb_endpoints:
49        - endpoint:
50            address:
51              socket_address:
52                address: www.envoyproxy.io
53                port_value: 443
54    transport_socket:
55      name: envoy.transport_sockets.tls
56      typed_config:
57        "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext

Validate an endpoint’s certificates when connecting

When Envoy connects to an upstream TLS service, it does not, by default, validate the certificates that it is presented with.

You can use the validation_context to specify how Envoy should validate these certificates.

Firstly, you can ensure that the certificates are from a mutually trusted certificate authority:

envoy-demo-tls-validation.yaml
42              socket_address:
43                address: www.envoyproxy.io
44                port_value: 443
45    transport_socket:
46      name: envoy.transport_sockets.tls
47      typed_config:
48        "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext
49        common_tls_context:
50          validation_context:
51            trusted_ca:
52              filename: certs/cacert.pem

You should also ensure that the Subject Alternative Names (SANs) for the certificate match.

This is commonly used by web certificates (X.509) to identify the domain or domains that a certificate is valid for.

For the most common case where the certificate should have a SAN matching the SNI which was sent, you can enable auto_sni_san_validation and omit match_typed_subject_alt_names in the validation context.

To validate that a certificate has a SAN matching the downstream request host or :authority header, you can enable auto_san_validation.

When multiple validation options are configured, auto_san_validation has the highest priority, followed by auto_sni_san_validation, followed by match_typed_subject_alt_names.

envoy-demo-tls-validation.yaml
44                port_value: 443
45    transport_socket:
46      name: envoy.transport_sockets.tls
47      typed_config:
48        "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext
49        common_tls_context:
50          validation_context:
51            trusted_ca:
52              filename: certs/cacert.pem
53            match_typed_subject_alt_names:
54            - san_type: DNS

Note

See here to view all of the possible configurations for certificate validation.

Use mutual TLS (mTLS) to enforce client certificate authentication

With mutual TLS (mTLS), Envoy also provides a way to authenticate connecting clients.

At a minimum you will need to set require_client_certificate and specify a mutually trusted certificate authority:

envoy-demo-tls-client-auth.yaml
29                  cluster: service_envoyproxy_io
30      transport_socket:
31        name: envoy.transport_sockets.tls
32        typed_config:
33          "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.DownstreamTlsContext
34          require_client_certificate: true
35          common_tls_context:
36            validation_context:
37              trusted_ca:
38                filename: certs/cacert.pem
39              match_typed_subject_alt_names:
40              - san_type: DNS
41                matcher:
42                  exact: proxy-postgres-frontend.example.com
43            tls_certificates:

You can further restrict the authentication of connecting clients by specifying the allowed “Subject Alternative Names” in match_typed_subject_alt_names, similar to validating upstream certificates described above.

envoy-demo-tls-client-auth.yaml
29                  cluster: service_envoyproxy_io
30      transport_socket:
31        name: envoy.transport_sockets.tls
32        typed_config:
33          "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.DownstreamTlsContext
34          require_client_certificate: true
35          common_tls_context:
36            validation_context:
37              trusted_ca:
38                filename: certs/cacert.pem
39              match_typed_subject_alt_names:
40              - san_type: DNS
41                matcher:
42                  exact: proxy-postgres-frontend.example.com
43            tls_certificates:

Note

See here to view all of the possible configurations for certificate validation.

Use mutual TLS (mTLS) to connect with client certificates

When connecting to an upstream with client certificates you can set them as follows:

envoy-demo-tls-client-auth.yaml
46              private_key:
47                filename: certs/serverkey.pem
48
49  clusters:
50  - name: service_envoyproxy_io
51    type: LOGICAL_DNS
52    # Comment out the following line to test on v6 networks
53    dns_lookup_family: V4_ONLY
54    load_assignment:
55      cluster_name: service_envoyproxy_io
56      endpoints:
57      - lb_endpoints:
58        - endpoint:
59            address:
60              socket_address:
61                address: www.envoyproxy.io
62                port_value: 443
63    transport_socket:
64      name: envoy.transport_sockets.tls
65      typed_config:
66        "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext
67        common_tls_context:
68          tls_certificates:
69          - certificate_chain:
70              filename: certs/clientcert.pem

Provide multiple TLS domains at the same IP address with SNI

SNI is an extension to the TLS protocol which allows multiple domains served from the same IP address to be secured with TLS.

To secure specific domains on a listening connection with SNI, you should set the filter_chain_match of the listener:

envoy-demo-tls-sni.yaml
29                  cluster: service_envoyproxy_io
30      filter_chain_match:
31        server_names:
32        - my-service-name.example.com
33      transport_socket:
34        name: envoy.transport_sockets.tls
35        typed_config:
36          "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.DownstreamTlsContext
37          common_tls_context:

See here for more info about creating multiple endpoints with SNI

Connect to an endpoint with SNI

When connecting to a TLS endpoint that uses SNI you should set sni in the configuration of the UpstreamTLSContext.

This will usually be the DNS name of the service you are connecting to.

envoy-demo-tls-sni.yaml
57                port_value: 443
58    transport_socket:
59      name: envoy.transport_sockets.tls
60      typed_config:
61        "@type": type.googleapis.com/envoy.extensions.transport_sockets.tls.v3.UpstreamTlsContext
62        sni: www.envoyproxy.io

When connecting to an Envoy endpoint that is protected by SNI, this must match one of the server_names set in the endpoint’s filter_chain_match, as described above.

To derive SNI from a downstream HTTP header host or :authority, turn on auto_sni to override the fixed SNI in UpstreamTlsContext. A custom header other than the host or :authority can also be supplied using the optional override_auto_sni_header field.

To derive SNI from the host Envoy is connecting to, turn on auto_host_sni, which will use the hostname of the upstream endpoint.

When multiple options are configured, auto_sni has the highest priority, followed by auto_host_sni, followed by the fixed sni.