Generate random server secret if not provided from config

modules/restserver/src/main/resources/reference.conf

@@ -47,8 +47,9 @@ docspell.server {
     # The secret for this server that is used to sign the authenicator
     # tokens. If multiple servers are running, all must share the same
     # secret. You can use base64 or hex strings (prefix with b64: and
-    # hex:, respectively).
-    server-secret = "hex:caffee"
+    # hex:, respectively). If empty, a random secret is generated.
+    # Example: b64:YRx77QujCGkHSvll0TVEmtTaw3Z5eXr+nWMsEJowgKg=
+    server-secret = ""
 
     # How long an authentication token is valid. The web application
     # will get a new one periodically.

modules/restserver/src/main/scala/docspell/restserver/ConfigFile.scala

@@ -6,6 +6,8 @@
 
 package docspell.restserver
 
+import java.security.SecureRandom
+
 import cats.Semigroup
 import cats.data.{Validated, ValidatedNec}
 import cats.effect.Async
@@ -20,12 +22,14 @@ import docspell.restserver.auth.OpenId
 
 import pureconfig._
 import pureconfig.generic.auto._
+import scodec.bits.ByteVector
 
 object ConfigFile {
+  private[this] val unsafeLogger = org.log4s.getLogger
   import Implicits._
 
   def loadConfig[F[_]: Async](args: List[String]): F[Config] = {
-    val logger = Logger.log4s(org.log4s.getLogger)
+    val logger = Logger.log4s(unsafeLogger)
     ConfigFactory
       .default[F, Config](logger, "docspell.server")(args)
       .map(cfg => Validate(cfg))
@@ -57,12 +61,25 @@ object ConfigFile {
 
     def all(cfg: Config) = List(
       duplicateOpenIdProvider(cfg),
-      signKeyVsUserUrl(cfg)
+      signKeyVsUserUrl(cfg),
+      generateSecretIfEmpty(cfg)
     )
 
     private def valid(cfg: Config): ValidatedNec[String, Config] =
       Validated.validNec(cfg)
 
+    def generateSecretIfEmpty(cfg: Config): ValidatedNec[String, Config] =
+      if (cfg.auth.serverSecret.isEmpty) {
+        unsafeLogger.warn(
+          "No serverSecret specified. Generating a random one. It is recommended to add a server-secret in the config file."
+        )
+        val random = new SecureRandom()
+        val buffer = new Array[Byte](32)
+        random.nextBytes(buffer)
+        val secret = ByteVector.view(buffer)
+        valid(cfg.copy(auth = cfg.auth.copy(serverSecret = secret)))
+      } else valid(cfg)
+
     def duplicateOpenIdProvider(cfg: Config): ValidatedNec[String, Config] = {
       val dupes =
         cfg.openid