The Scala library that adds a little security to applications.
This project is archived and read-only. See Ergo for active fork.
To get started, add little-security to your library dependencies.
libraryDependencies += "com.github.losizm" %% "little-security" % "1.1.0"NOTE: Starting with version 1, little-security is written for Scala 3 exclusively. See previous releases for compatibility with Scala 2.12 and Scala 2.13.
little-security is powered by a pair of traits: Permission and
SecurityContext.
A Permission is defined with a given name, and one or more permissions can be
applied to a restricted operation.
A SecurityContext establishes a pattern in which a restricted operation is
performed only if its required permissions are granted; otherwise, a
SecurityViolation is raised.
The following script demonstrates how read/write access to an in-memory cache could be implemented.
import little.security.{ Permission, SecurityContext, UserContext }
import scala.collection.concurrent.TrieMap
object SecureCache:
// Define permissions for reading and writing cache entries
private val getPermission = Permission("cache:get")
private val putPermission = Permission("cache:put")
private val cache = TrieMap[String, String](
"gang starr" -> "step in the arena",
"digable planets" -> "blowout comb"
)
def get(key: String)(using security: SecurityContext): String =
// Test for read permission before getting cache entry
security(getPermission) { cache(key) }
def put(key: String, value: String)(using security: SecurityContext): Unit =
// Test for write permission before putting cache entry
security(putPermission) { cache += key -> value }
// Set security context for user with read permission to cache
given SecurityContext = UserContext("losizm", "staff", Permission("cache:get"))
// Get cache entry
val classic = SecureCache.get("gang starr")
// Throw SecurityViolation because user lacks write permission
SecureCache.put("sucker mc", classic)A Permission is identified by its name, and you're free to implement any
convention for the names.
The following defines 3 permissions, any of which could be used as a permission for read access to an archive module.
val perm1 = Permission("archive:read")
val perm2 = Permission("module=archive; access=read")
val perm3 = Permission("[[GET]] /api/modules/archive")A user permission is created with UserPermission. There's no implementing
class: It's just a factory. It constructs a permission with a specially
formatted name using a user identifier.
import little.security.UserPermission
val userPermission = UserPermission("losizm")
// Destructure permission to its user identifier
userPermission match
case UserPermission(userId) => println(s"uid=$userId")
case perm => throw Exception(s"Unexpected permission: ${perm.name}")And GroupPermission constructs a permission with a specially formatted name
using a group identifier.
import little.security.GroupPermission
val groupPermission = GroupPermission("staff")
// Destructure permission to its group identifier
groupPermission match
case GroupPermission(groupId) => println(s"gid=$groupId")
case perm => throw Exception(s"Unexpected permission: ${perm.name}")See also Automatic User and Group Permissions.
A SecurityContext is consulted for authorization to apply a restricted
operation. If authorized, the operation is applied; otherwise, the security
context raises a SecurityViolation.
UserContext is an implementation of a security context. It is constructed
with supplied user and group identifiers along with a set of granted
permissions.
import little.security.{ Permission, SecurityContext, UserContext }
object BuildManager:
private val buildPermission = Permission("action=build")
private val deployDevPermission = Permission("action=deploy; env=dev")
private val deployProdPermission = Permission("action=deploy; env=prod")
def build(project: String)(using security: SecurityContext): Unit =
// Test permission before building project
security(buildPermission) {
println(s"Build $project.")
}
def deployToDev(project: String)(using security: SecurityContext): Unit =
// Test permission before deploying project
security(deployDevPermission) {
println(s"Deploy $project to dev environment.")
}
def deployToProd(project: String)(using security: SecurityContext): Unit =
// Test permission before deploying project
security(deployProdPermission) {
println(s"Deploy $project to prod environment.")
}
// Set security context for user with two permissions
given SecurityContext = UserContext("ishmael", "developer",
Permission("action=build"),
Permission("action=deploy; env=dev")
)
// Permission granted to build
BuildManager.build("my-favorite-app")
// Permission granted to deploy to dev
BuildManager.deployToDev("my-favorite-app")
// Permission not granted to deploy to prod -- throw SecurityViolation
BuildManager.deployToProd("my-favorite-app")SecurityContext.any(Permission*) is used to ensure that at least one of
supplied permissions is granted before an operation is applied.
SecurityContext.all(Permission*) is used to ensure that all supplied
permissions are granted before an operation is applied.
import little.security.{ Permission, SecurityContext, UserContext }
object FileManager:
private val readOnlyPermission = Permission("file:read-only")
private val readWritePermission = Permission("file:read-write")
private val encryptPermission = Permission("file:encrypt")
def read(fileName: String)(using security: SecurityContext): Unit =
// Get either read-only or read-write permission before performing operation
security.any(readOnlyPermission, readWritePermission) {
println(s"Read $fileName.")
}
def encrypt(fileName: String)(using security: SecurityContext): Unit =
// Get both read-write and encrypt permissions before performing operation
security.all(readWritePermission, encryptPermission) {
println(s"Encrypt $fileName.")
}
// Set security context for read/write permission
given SecurityContext = UserContext("isaac", "ops", Permission("file:read-write"))
// Can read via read-write permission
FileManager.read("/etc/passwd")
// Has read-write but lacks encrypt permission -- throw SecurityViolation
FileManager.encrypt("/etc/passwd")Sometimes, it may be enough to simply test a permission to see whether it is
granted, and not necessarily throw a SecurityViolation if it isn't. That's
precisely what SecurityContext.test(Permission) is for. It returns true or
false based on the permission being granted or not. It's an ideal predicate to
a security filter, as demonstrated in the following script.
import little.security.{ Permission, SecurityContext, UserContext }
object SecureMessages:
// Define class for text message with assigned permission
private case class Message(text: String, permission: Permission)
private val messages = Seq(
Message("This is a public message." , Permission("public")),
Message("This is a protected message.", Permission("protected")),
Message("This is a private message." , Permission("private"))
)
def list(using security: SecurityContext): Seq[String] =
// Filter messages by testing permission
messages.filter(msg => security.test(msg.permission)).map(_.text)
// Set security context for user with "public" and "protected" permissions
given SecurityContext = UserContext("losizm", "staff",
Permission("public"),
Permission("protected")
)
// Print all accessible messages
SecureMessages.list.foreach(println)When an instance of UserContext is created, user and group permissions are
added to the permissions expressly supplied in constructor.
val user = UserContext("losizm", "staff", Permission("read"))
assert(user.test(Permission("read")))
assert(user.test(UserPermission("losizm")))
assert(user.test(GroupPermission("staff")))You may use these permissions in your application. For example, a document store could be implemented giving a single user read/write permissions, while allowing other users in her group read permission only.
import little.security.*
import scala.collection.concurrent.TrieMap
class DocumentStore(userId: String, groupId: String):
private val userPermission = UserPermission(userId)
private val groupPermission = GroupPermission(groupId)
private val storage = TrieMap[String, String]()
def get(name: String)(using security: SecurityContext): String =
// Anyone in group can retrieve document
security(groupPermission) { storage(name) }
def put(name: String, doc: String)(using security: SecurityContext): Unit =
// Only owner can store document
security(userPermission) { storage += name -> doc }
// Create security context with user and group permissions only
val owner = UserContext("lupita", "finance")
val docs = DocumentStore(owner.userId, owner.groupId)
// Set security context to owner
given SecurityContext = owner
// Owner can read and write to document store
docs.put("meeting-agenda.txt", "Increase developers' salaries")
docs.get("meeting-agenda.txt")In the examples so far, we've used UserContext, which is a security context
with a finite set of granted permissions.
The other type of security context is RootContext, which has an infinite set
of granted permissions. Rather, there's no permission it doesn't have. It's the
superuser security context.
RootContext is an object implementation, so there is only one instance of it.
It should be used for the purpose of effectively bypassing security checks.
// Print all messages
SecureMessages.list(using RootContext).foreach(println)
(0 to 999999).foreach { _ =>
// Create permission with randomly generated name
val perm = Permission(scala.util.Random.nextString(8))
// Assert permission is granted
assert(RootContext.test(perm))
}The following script is a more intricate example. It demonstrates how to
simulate sudo functionality. It does this by defining a group permission to
regulate user access to RootContext.
import little.security.*
object sudo:
// Define group permission required for sudo
private val sudoers = GroupPermission("sudoers")
def apply[T](op: SecurityContext => T)(using security: SecurityContext): T =
// Test permission before switching to root
security(sudoers) { op(RootContext) }
object SecureMessages:
private case class Message(text: String, permission: Permission)
private val messages = Seq(
Message("This is a public message." , Permission("public")),
Message("This is a protected message.", Permission("protected")),
Message("This is a private message." , Permission("private"))
)
def list(using security: SecurityContext): Seq[String] =
messages.filter(msg => security.test(msg.permission)).map(_.text)
// Set security context
given SecurityContext = UserContext("losizm", "staff",
Permission("public"),
Permission("protected"),
GroupPermission("sudoers") // Add group permission required for sudo
)
println("Print messages in user context...")
SecureMessages.list.foreach(println)
println("Print messages in sudo context...")
// NOTE: The `implicit security` below "shadows" the previously declared
// security context. The new context is provided by sudo.
sudo { implicit security =>
SecureMessages.list.foreach(println)
}See scaladoc for additional details.
little-security is licensed under the Apache License, Version 2. See LICENSE for more information.
