Configuring pREST

The prestd configuration is via an environment variable or toml file. Starting from version v1.2.0 it will be possible to use prestd without any environment variable or the toml file, but the configurations used will be the described in the default column bellow.

Environment variables

var	default	description
PREST_VERSION	1	version used for environment variables, v2 introduces better naming for SSL pg connection
PREST_CONF	./prest.conf
PREST_MIGRATIONS	./migrations
PREST_QUERIES_LOCATION	./queries
PREST_HTTP_HOST	0.0.0.0
PREST_HTTP_PORT or PORT	3000	PORT is for cloud factor, when declared this variable overwrittes PREST_HTTP_PORT
PREST_PG_HOST	127.0.0.1	host used to connect
PREST_PG_USER	postgres	user used to connect
PREST_PG_PASS	postgres	password used to connect
PREST_PG_DATABASE	prest	database name used to connect
PREST_PG_PORT	5432
PREST_PG_URL or DATABASE_URL		cloud factor, when declaring this variable all the previous connection fields are overwritten
PREST_PG_SSL_MODE	require	v2 of configuration envs, is the postgres connection SSL mode
PREST_PG_SSL_CERT		v2 of configuration envs, is the postgres connection SSL certificate
PREST_PG_SSL_KEY		v2 of configuration envs, is the postgres connection SSL key
PREST_PG_SSL_ROOTCERT		v2 of configuration envs, is the postgres connection SSL root certificate
PREST_PG_SINGLE	true	Serving multiple databases over the same API with prestd is doable
PREST_CACHE_ENABLED	false	embedded cache system
PREST_CACHE_TIME	10	TTL in minute (time to live)
PREST_CACHE_STORAGEPATH	./	path where the cache file will be created
PREST_CACHE_SUFIXFILE	.cache.prestd.db	suffix of the name of the file that is created
PREST_JWT_KEY
PREST_JWT_ALGO	HS256	(Deprecrated) Not used
PREST_JWT_WELLKNOWNURL		URL of .wellknown config of IDP used to fetch the JWKS used to verify token signature. Ignored if PREST_JWT_JWKS is set
PREST_JWT_JWKS		JWKS used to verify token signature. If set, PREST_JWT_WELLKNOWNURL is ignored
PREST_JWT_WHITELIST	[/auth]
PREST_AUTH_ENABLED	false
PREST_AUTH_ENCRYPT	MD5
PREST_AUTH_TYPE	body
PREST_AUTH_SCHEMA	public
PREST_AUTH_TABLE	prest_users
PREST_AUTH_USERNAME	username
PREST_AUTH_PASSWORD	password
PREST_SSL_MODE	require	SSL mode used to connect to postgres, not related to server SSL
PREST_SSL_CERT		SSL certificate used to connect to postgres, not related to server SSL
PREST_SSL_KEY		SSL key used to connect to postgres, not related to server SSL
PREST_SSL_ROOTCERT		SSL root certificate used to connect to postgres, not related to server SSL
PREST_PLUGINPATH	./lib	path to plugin storage .so
PREST_EXPOSE_ENABLED	false	expose data setting enables you to configure if you want users to be able to reach listing endpoints, read more here
PREST_EXPOSE_TABLES	true	expose the tables listing, read more here
PREST_EXPOSE_SCHEMAS	true	expose the schemas listing, read more here
PREST_EXPOSE_DATABASES	true	expose the databases listing, read more here
PREST_JSON_AGG_TYPE	jsonb_agg	changes how pREST encodes data from the database, can be set also to json_agg

TOML

Optionally the prestd can be configured by TOML file.

You can follow this sample and create your own prest.toml file and put this on the same folder that you run prestd command.

migrations = "./migrations"

# debug = true
# enabling debug mode will disable JWT authorization

[http]
port = 3000

[jwt]
key = "secret"
algo = "HS256"

[auth]
enabled = true
type = "body"
encrypt = "MD5"
table = "prest_users"
username = "username"
password = "password"

[pg]
host = "127.0.0.1"
user = "postgres"
pass = "mypass"
port = 5432
database = "prest"
single = true
## or used cloud factor
# URL = "postgresql://user:pass@localhost/mydatabase/?sslmode=disable"

[ssl]
mode = "disable"
sslcert = "./PATH"
sslkey = "./PATH"
sslrootcert = "./PATH"

[expose]
enabled = true
databases = true
schemas = true
tables = true

Authorization

JWT

JWT middleware is enabled by default. To disable JWT need to set default to false. Enabling debug mode will also disable it.

[jwt]
default = false

The algorithm used is the one contained in the header of the token. The token is then validated with the provided key or JWKS.

The supported signing algorithms are described in the documentation of the JWK package.

They include the following algorithms:

• The HMAC signing method: HS256, HS384, HS512

• The RSA signing method: RS256, RS384, RS512

• The ECDSA signing method: ES256, ES384, ES512

• The RSA signing method: RS256, RS384, RS512

• The ECDSA signing method: ES256, ES384, ES512

• The RSA signing method: RS256, RS384, RS512

• The ECDSA signing method: ES256, ES384, ES512

Instead of the key, you could provide the URL of a .well-known OpenID configuration or the JWKS directly through PREST_JWT_WELLKNOWNURL or PREST_JWT_JWKS as environment variables or by using the TOML configuration file:

[jwt]
wellknownurl = https://accounts.google.com/.well-known/openid-configuration
jwks = {"keys": [{"kty": "RSA", "alg": "RS256", "kid": "93b495162af0c87cc7a51686294097040daf3b43", "n": "3NXwASNf_7-9hOWDKyZ39qgz-yl_npuIsBgxnhNoE7WyQQl-muajPsQRdFqM-HWsAAbS_WtLrmf2aRSmjXBm8wXHIeJjcrZiWeUnSyfZLDr13jxXhN0rDvdiZEsAlaKuh-iCgwC_pXd0TtWpaYlv5FFguuSitKTOiDR6z3eSZUd0XNxr8POCDQ7VlG_4HyzhsO7nOwgivO-PzekDEbcoLI93U8uzKZXYHSRxYWhoSp47PbM9D5WbuwXqbmXRp9TjiJUy6GqEOJ4K2FNvqe-g6C3BnpPVuHZNaVf8QGP806rWrWPdJ0irGBhg-EasC-sdFSrH3kxMxBFfVsuj69U-7Q", "use": "sig", "e": "AQAB" }]}

prestd will parse the JWKS to find the corresponding key from the token and fail if it does not find it.

White list

By default the endpoints /auth do not require JWT, the whitelist option serves to configure which endpoints will not ask for jwt token

[jwt]
default = true
whitelist = ["\/auth", "\/ping", "\/ping\/.*"]

Auth

pREST has support in jwt token generation based on two fields (example user and password), being possible to use an existing table from your database to login configuring some parameters in the configuration file (or environment variable), by default this feature is disabled.

[auth]
enabled = true
type = "body"
encrypt = "MD5"
table = "prest_users"
username = "username"
password = "password"

Name	Description
enabled	Boolean field that activates or deactivates token generation endpoint support
type	Type that will receive the login, support for body and http basic authentication
encrypt	Type of encryption used in password field, support for MD5 and SHA1
table	Table name we will consult (query)
username	User field that will be consulted - if your software uses email just abstract name username (at prestd code level it was necessary to define an internal standard)
password	Password field that will be consulted

to validate all endpoints with generated jwt token must be activated jwt option

Expose Data

The expose data setting enables you to configure if you want users to be able to reach listing endpoints, such as:

• /databases

• /schemas

• /tables

An example of a configuration file disabling all listings:

# previous toml content
[expose]
enabled = true

If you want to disable just the database listing:

# previous toml content
[expose]
databases = true

Name	Description
enabled	Set this as true if you want to disable all listing endpoints available.
databases	Set this as false if you want to disable databases listing endpoints only.
schemas	Set this as false if you want to disable schemas listing endpoints only.
tables	Set this as false if you want to disable tables listing endpoints only.

Default values for Exposure Settings

Name	Default Value
enabled	false
databases	true
schemas	true
tables	true

SSL

There are 4 options to set on ssl mode:

Name	Description	Comment
require	Always SSL, is the default value	skips SSL verification step
disable	SSL off	also used when prestd is started without a toml file
verify-ca	Always SSL	verifies that the certificate presented is signed by a trusted CA
verify-full	Always SSL	verifies that the certificate presented is signed by a trusted CA and the server host name matches the one in the certificate

Debug Mode

Set environment variable PREST_DEBUG or debug=true on top of prest.toml file.

PREST_DEBUG=true

Single mode - multi database (PostgreSQL)

Serving multiple databases over the same API with prestd is doable, but it is not currently supported. Thus it was introduced by default the single configuration, it can be disabled by the following config in the toml file:

[pg]
single = false

Since v1.1.2 it is a lot safer to use multiple databases, but not yet in the ideal state of security that we want, so use it in your own risk.

CORS support

Cross-Origin Resource Sharing

Read the specific topic where we talk about CROS here.

Health check endpoint

If you need to setup a health check on your deployment (ECS/EKS or others), you can use /_health as a provider of this information.

The server will return 503 whenever a pREST is not working properly.