tcp listener

The TCP listener configures Vault to listen on a TCP address/port.

listener "tcp" {
  address = "127.0.0.1:8200"
}

The listener stanza may be specified more than once to make Vault listen on multiple interfaces. If you configure multiple listeners you also need to specify api_addr and cluster_addr so Vault will advertise the correct address to other nodes.

Default TLS configuration

By default, Vault TCP listeners only accept TLS 1.2 or 1.3 connections and will drop connection requests from clients using TLS 1.0 or 1.1.

Vault uses the following ciphersuites by default:

• TLS 1.3 - TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384, or TLS_CHACHA20_POLY1305_SHA256.
• TLS 1.2 - depends on whether you configure Vault with a RSA or ECDSA certificate.

You can configure Vault with any cipher supported by the tls and tlsutil Go packages. Vault uses the tlsutil package to parse ciphersuite configurations.

Before overriding Vault defaults, we recommend reviewing the recommended Go team approach to TLS configuration with particular attention to their ciphersuite selections.

Listener's custom response headers

As of version 1.9, Vault supports defining custom HTTP response headers for the root path (/) and also on API endpoints (/v1/*). The headers are defined based on the returned status code. For example, a user can define a list of custom response headers for the 200 status code, and another list of custom response headers for the 307 status code. There is a "/sys/config/ui" API endpoint which allows users to set UI specific custom headers. If a header is configured in a configuration file, it is not allowed to be reconfigured through the "/sys/config/ui" API endpoint. In cases where a custom header value needs to be modified or the custom header needs to be removed, the Vault's configuration file needs to be modified accordingly, and a SIGHUP signal needs to be sent to the Vault process.

If a header is defined in the configuration file and the same header is used by the internal processes of Vault, the configured header is not accepted. For example, a custom header which has the X-Vault- prefix will not be accepted. A message will be logged in the Vault's logs upon start up indicating the header with X-Vault- prefix is not accepted.

Order of precedence

If the same header is configured in both the configuration file and in the "/sys/config/ui" API endpoint, the header in the configuration file takes precedence. For example, the "Content-Security-Policy" header is defined by default in the "/sys/config/ui" API endpoint. If that header is also defined in the configuration file, the value in the configuration file is set in the response headers instead of the default value in the "/sys/config/ui" API endpoint.

tcp listener parameters

• address (string: "127.0.0.1:8200") – Specifies the address to bind to for listening. This can be dynamically defined with a go-sockaddr template that is resolved at runtime.

• cluster_address (string: "127.0.0.1:8201") – Specifies the address to bind to for cluster server-to-server requests. This defaults to one port higher than the value of address. This does not usually need to be set, but can be useful in case Vault servers are isolated from each other in such a way that they need to hop through a TCP load balancer or some other scheme in order to talk. This can be dynamically defined with a go-sockaddr template that is resolved at runtime.

• chroot_namespace (string: "") – Specifies an alternate top-level namespace for the listener. Vault appends namespaces provided in the X-Vault-Namespace header or the -namespace field in a CLI command to the top-level namespace to determine the full namespace path for the request. For example, if chroot_namespace is set to admin and the X-Vault-Namespace header is ns1, the full namespace path is admin/ns1. Calls to the listener will fail with a 4XX error if the top-level namespace provided for chroot_namespace does not exist.

• http_idle_timeout (string: "5m") - Specifies the maximum amount of time to wait for the next request when keep-alives are enabled. If http_idle_timeout is zero, the value of http_read_timeout is used. If both are zero, the value of http_read_header_timeout is used. This is specified using a label suffix like "30s" or "1h".

• http_read_header_timeout (string: "10s") - Specifies the amount of time allowed to read request headers. This is specified using a label suffix like "30s" or "1h".

• http_read_timeout (string: "30s") - Specifies the maximum duration for reading the entire request, including the body. This is specified using a label suffix like "30s" or "1h".

• http_write_timeout string: "0") - Specifies the maximum duration before timing out writes of the response and is reset whenever a new request's header is read. The default value of "0" means infinity. This is specified using a label suffix like "30s" or "1h".

• max_request_size (int: 33554432) – Specifies a hard maximum allowed request size, in bytes. Defaults to 32 MB if not set or set to 0. Specifying a number less than 0 turns off limiting altogether.

• max_request_duration (string: "90s") – Specifies the maximum request duration allowed before Vault cancels the request. This overrides default_max_request_duration for this listener.

• proxy_protocol_behavior (string: "") – When specified, enables a PROXY protocol version 1 behavior for the listener. Accepted Values:

  • use_always - The client's IP address will always be used.
  • allow_authorized - If the source IP address is in the proxy_protocol_authorized_addrs list, the client's IP address will be used. If the source IP is not in the list, the source IP address will be used.
  • deny_unauthorized - The traffic will be rejected if the source IP address is not in the proxy_protocol_authorized_addrs list.

• proxy_protocol_authorized_addrs (string: <required-if-enabled> or array: <required-if-enabled> ) – Specifies the list of allowed source IP addresses to be used with the PROXY protocol. Not required if proxy_protocol_behavior is set to use_always. Source IPs should be comma-delimited if provided as a string. At least one source IP must be provided, proxy_protocol_authorized_addrs cannot be an empty array or string.

• tls_disable (string: "false") – Specifies if TLS will be disabled. Vault assumes TLS by default, so you must explicitly disable TLS to opt-in to insecure communication.

• tls_cert_file (string: <required-if-enabled>, reloads-on-SIGHUP) – Specifies the path to the certificate for TLS. It requires a PEM-encoded file. To configure the listener to use a CA certificate, concatenate the primary certificate and the CA certificate together. The primary certificate should appear first in the combined file. On SIGHUP, the path set here at Vault startup will be used for reloading the certificate; modifying this value while Vault is running will have no effect for SIGHUPs.

• tls_key_file (string: <required-if-enabled>, reloads-on-SIGHUP) – Specifies the path to the private key for the certificate. It requires a PEM-encoded file. If the key file is encrypted, you will be prompted to enter the passphrase on server startup. The passphrase must stay the same between key files when reloading your configuration using SIGHUP. On SIGHUP, the path set here at Vault startup will be used for reloading the certificate; modifying this value while Vault is running will have no effect for SIGHUPs.

• tls_min_version (string: "tls12") – Specifies the minimum supported version of TLS. Accepted values are "tls10", "tls11", "tls12" or "tls13".

  Warning: TLS 1.1 and lower (tls10 and tls11 values for the tls_min_version and tls_max_version parameters) are widely considered insecure.

• tls_max_version (string: "tls13") – Specifies the maximum supported version of TLS. Accepted values are "tls10", "tls11", "tls12" or "tls13".

• tls_cipher_suites (string: "") – Specifies the list of supported ciphersuites as a comma-separated-list. The list of all available ciphersuites is available in the Golang TLS documentation.

  Note: Go only consults the tls_cipher_suites list for TLSv1.2 and earlier; the order of ciphers is not important. For this parameter to be effective, the tls_max_version property must be set to tls12 to prevent negotiation of TLSv1.3, which is not recommended. For more information about this and other TLS related changes, see the Go TLS blog post.

• tls_prefer_server_cipher_suites (string: "false") – Specifies to prefer the server's ciphersuite over the client ciphersuites.

  Warning: The tls_prefer_server_cipher_suites parameter is deprecated. Setting it has no effect. See the above Go blog post for more information about this change.

• tls_require_and_verify_client_cert (string: "false") – Turns on client authentication for this listener; the listener will require a presented client cert that successfully validates against system CAs.

• tls_client_ca_file (string: "") – PEM-encoded Certificate Authority file used for checking the authenticity of client.

• tls_disable_client_certs (string: "false") – Turns off client authentication for this listener. The default behavior (when this is false) is for Vault to request client certificates when available.

  Warning: The tls_disable_client_certs and tls_require_and_verify_client_cert fields in the listener stanza of the Vault server configuration are mutually exclusive fields. Please ensure they are not both set to true. TLS client verification remains optional with default settings and is not enforced.

• x_forwarded_for_authorized_addrs (string: <required-to-enable>) – Specifies the list of source IP CIDRs for which an X-Forwarded-For header will be trusted. Comma-separated list or JSON array. This turns on X-Forwarded-For support. If for example Vault receives connections from the load balancer's IP of 1.2.3.4, adding 1.2.3.4 to x_forwarded_for_authorized_addrs will result in the remote_address field in the audit log being populated with the connecting client's IP, for example 3.4.5.6. Note this requires the load balancer to send the connecting client's IP in the X-Forwarded-For header.

• x_forwarded_for_hop_skips (string: "0") – The number of addresses that will be skipped from the rear of the set of hops. For instance, for a header value of 1.2.3.4, 2.3.4.5, 3.4.5.6, 4.5.6.7, if this value is set to "1", the address that will be used as the originating client IP is 3.4.5.6.

• x_forwarded_for_reject_not_authorized (string: "true") – If set false, if there is an X-Forwarded-For header in a connection from an unauthorized address, the header will be ignored and the client connection used as-is, rather than the client connection rejected.

• x_forwarded_for_reject_not_present (string: "true") – If set false, if there is no X-Forwarded-For header or it is empty, the client address will be used as-is, rather than the client connection rejected.

telemetry parameters

• unauthenticated_metrics_access (bool: false) - If set to true, allows unauthenticated access to the /v1/sys/metrics endpoint.

profiling parameters

• unauthenticated_pprof_access (bool: false) - If set to true, allows unauthenticated access to the /v1/sys/pprof endpoint.

inflight_requests_logging parameters

• unauthenticated_in_flight_requests_access (bool: false) - If set to true, allows unauthenticated access to the /v1/sys/in-flight-req endpoint.

custom_response_headers parameters

• default (key-value-map: {}) - A map of string header names to an array of string values. The default headers are set on all endpoints regardless of the status code value. For an example, please refer to the "Configuring custom http response headers" section.

• <specific status code> (key-value-map: {}) - A map of string header names to an array of string values. These headers are set only when the specific status code is returned. For example, "200" = {"Header-A": ["Value1", "Value2"]}, "Header-A" is set when the http response status code is "200".

• <collective status code> (key-value-map: {}) - A map of string header names to an array of string values. These headers are set only when the response status code falls under the collective status code. For example, "2xx" = {"Header-A": ["Value1", "Value2"]}, "Header-A" is set when the http response status code is "200", "204", etc.

tcp listener examples

Configuring TLS

This example shows enabling a TLS listener.

listener "tcp" {
  address = "127.0.0.1:8200"
  tls_cert_file = "/etc/certs/vault.crt"
  tls_key_file  = "/etc/certs/vault.key"
}

Listening on multiple interfaces

This example shows Vault listening on a private interface, as well as localhost.

listener "tcp" {
  address = "127.0.0.1:8200"
}

listener "tcp" {
  address = "10.0.0.5:8200"
}

# Advertise the non-loopback interface
api_addr = "https://10.0.0.5:8200"
cluster_addr = "https://10.0.0.5:8201"

Configuring unauthenticated metrics access

This example shows enabling unauthenticated metrics access.

listener "tcp" {
  telemetry {
    unauthenticated_metrics_access = true
  }
}

Configuring unauthenticated profiling access

This example shows enabling unauthenticated profiling access.

listener "tcp" {
  profiling {
    unauthenticated_pprof_access = true
    unauthenticated_in_flight_request_access = true
  }
}

Configuring custom http response headers

Note: Requires Vault version 1.9 or newer. This example shows configuring custom http response headers. Operators can configure "custom_response_headers" sub-stanza in the listener stanza to set custom http headers appropriate to their applications. Examples of such headers are "Strict-Transport-Security" and "Content-Security-Policy" which are known HTTP headers, and could be configured to harden the security of an application communicating with the Vault endpoints. Note that vulnerability scans often examine such security related HTTP headers. In addition, application specific custom headers can also be configured. For example, "X-Custom-Header" has been configured in the example below.

listener "tcp" {
  custom_response_headers {
    "default" = {
      "Strict-Transport-Security" = ["max-age=31536000","includeSubDomains"],
      "Content-Security-Policy" = ["connect-src https://clusterA.vault.external/"],
      "X-Custom-Header" = ["Custom Header Default Value"],
    },
    "2xx" = {
      "Content-Security-Policy" = ["connect-src https://clusterB.vault.external/"],
      "X-Custom-Header" = ["Custom Header Value 1", "Custom Header Value 2"],
    },
    "301" = {
      "Strict-Transport-Security" = ["max-age=31536000"],
      "Content-Security-Policy" = ["connect-src https://clusterC.vault.external/"],
    },
  }
}

In situations where a header is defined under several status code subsections, the header matching the most specific response code will be returned. For example, with the config example below, a 307 response would return 307 Custom header value, while a 306 would return 3xx Custom header value.

listener "tcp" {
  custom_response_headers {
    "default" = {
       "X-Custom-Header" = ["default Custom header value"]
    },
    "3xx" = {
       "X-Custom-Header" = ["3xx Custom header value"]
    },
    "307" = {
       "X-Custom-Header" = ["307 Custom header value"]
    }
  }
}

Listening on all IPv6 & IPv4 interfaces

This example shows Vault listening on all IPv4 & IPv6 interfaces including localhost.

listener "tcp" {
  address         = "[::]:8200"
  cluster_address = "[::]:8201"
}

Listening to specific IPv6 address

This example shows Vault only using IPv6 and binding to the interface with the IP address: 2001:1c04:90d:1c00:a00:27ff:fefa:58ec

listener "tcp" {
  address         = "[2001:1c04:90d:1c00:a00:27ff:fefa:58ec]:8200"
  cluster_address = "[2001:1c04:90d:1c00:a00:27ff:fefa:58ec]:8201"
}

# Advertise the non-loopback interface
api_addr = "https://[2001:1c04:90d:1c00:a00:27ff:fefa:58ec]:8200"
cluster_addr = "https://[2001:1c04:90d:1c00:a00:27ff:fefa:58ec]:8201"