From 565a5ed278a86638c0367c2962031f1c832f74a7 Mon Sep 17 00:00:00 2001
From: Gregor Reitzenstein <me@dequbed.space>
Date: Thu, 10 Sep 2020 11:50:19 +0200
Subject: [PATCH] Implements a simple permission check

---
 src/access.rs | 92 +++++++++++++++++++++++++++++++++++++++++++++++----
 src/error.rs  | 20 +++++++++++
 2 files changed, 105 insertions(+), 7 deletions(-)

diff --git a/src/access.rs b/src/access.rs
index 1e721de..9dfec84 100644
--- a/src/access.rs
+++ b/src/access.rs
@@ -1,31 +1,107 @@
 //! Access control logic
 //!
 
+use std::collections::HashSet;
+
+use flexbuffers;
+use serde::{Serialize, Deserialize};
+
 use slog::Logger;
+use lmdb::{Transaction, RoTransaction, RwTransaction};
 
 use crate::config::Config;
+use crate::error::Result;
 
+type UserIdentifier = u64;
+type RoleIdentifier = u64;
+type PermIdentifier = u64;
 
 pub struct PermissionsProvider {
     log: Logger,
+    roledb: lmdb::Database,
+    permdb: lmdb::Database,
+    userdb: lmdb::Database,
 }
 
 impl PermissionsProvider {
-    pub fn new(log: Logger) -> Self {
-        Self { log }
+    pub fn new(log: Logger, roledb: lmdb::Database, permdb: lmdb::Database, userdb: lmdb::Database) -> Self {
+        Self { log, roledb, permdb, userdb }
+    }
+
+    /// Check if a given user has the given permission
+    #[allow(unused)]
+    pub fn check<T: Transaction>(&self, txn: &T, userID: UserIdentifier, permID: PermIdentifier) -> Result<bool> {
+        if let Some(user) = self.get_user(txn, userID)? {
+            // Tally all roles. Makes dependent roles easier
+            let mut roles = HashSet::new();
+            for roleID in user.roles {
+                self.tally_role(txn, &mut roles, roleID)?;
+            }
+
+            // Iter all unique role->permissions we've found and early return on match. 
+            // TODO: Change this for negative permissions?
+            for role in roles.iter() {
+                for perm in role.permissions.iter() {
+                    if permID == *perm {
+                        return Ok(true);
+                    }
+                }
+            }
+        }
+
+        return Ok(false);
+    }
+
+    fn tally_role<T: Transaction>(&self, txn: &T, roles: &mut HashSet<Role>, roleID: RoleIdentifier) -> Result<()> {
+        if let Some(role) = self.get_role(txn, roleID)? {
+            // Only check and tally parents of a role at the role itself if it's the first time we
+            // see it
+            if !roles.contains(&role) {
+                for parent in role.parents.iter() {
+                    self.tally_role(txn, roles, *parent)?;
+                }
+
+                roles.insert(role);
+            }
+        }
+
+        Ok(())
+    }
+
+    fn get_role<'txn, T: Transaction>(&self, txn: &'txn T, roleID: RoleIdentifier) -> Result<Option<Role>> {
+        match txn.get(self.roledb, &roleID.to_ne_bytes()) {
+            Ok(bytes) => {
+                Ok(Some(flexbuffers::from_slice(bytes)?))
+            },
+            Err(lmdb::Error::NotFound) => { Ok(None) },
+            Err(e) => { Err(e.into()) }
+        }
+    }
+
+    fn get_user<T: Transaction>(&self, txn: &T, userID: UserIdentifier) -> Result<Option<User>> {
+        match txn.get(self.userdb, &userID.to_ne_bytes()) {
+            Ok(bytes) => {
+                Ok(Some(flexbuffers::from_slice(bytes)?))
+            },
+            Err(lmdb::Error::NotFound) => { Ok(None) },
+            Err(e) => { Err(e.into()) }
+        }
     }
 }
 
 /// This line documents init
 pub fn init(log: Logger, config: &Config, env: &lmdb::Environment) -> std::result::Result<PermissionsProvider, crate::error::Error> {
-    return Ok(PermissionsProvider::new(log));
+    let mut flags = lmdb::DatabaseFlags::empty();
+    flags.set(lmdb::DatabaseFlags::INTEGER_KEY, true);
+    let roledb = env.create_db(Some("role"), flags)?;
+    let permdb = env.create_db(Some("perm"), flags)?;
+    let userdb = env.create_db(Some("user"), flags)?;
+    return Ok(PermissionsProvider::new(log, roledb, permdb, userdb));
 }
 
-type RoleIdentifier = u64;
-type PermIdentifier = u64;
-
 /// A Person, from the Authorization perspective
-struct Person {
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+struct User {
     name: String,
 
     /// A Person has N ≥ 0 roles.
@@ -45,6 +121,7 @@ struct Person {
 /// of a machine; if later on a similar enough machine is put to use the administrator can just add
 /// the permission for that machine to an already existing role instead of manually having to
 /// assign to all users.
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct Role {
     name: String,
 
@@ -61,6 +138,7 @@ struct Role {
 ///
 /// Permissions are rather simple flags. A person can have or not have a permission, dictated by
 /// its roles and the permissions assigned to those roles.
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
 struct Permission {
     name: String,
 }
diff --git a/src/error.rs b/src/error.rs
index a746d3a..e7c0dcd 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -13,6 +13,8 @@ pub enum Error {
     Boxed(Box<dyn std::error::Error>),
     Capnp(capnp::Error),
     LMDB(lmdb::Error),
+    FlexbuffersDe(flexbuffers::DeserializationError),
+    FlexbuffersSer(flexbuffers::SerializationError),
 }
 
 impl fmt::Display for Error {
@@ -39,6 +41,12 @@ impl fmt::Display for Error {
             Error::LMDB(e) => {
                 write!(f, "LMDB Error: {}", e)
             },
+            Error::FlexbuffersDe(e) => {
+                write!(f, "Flexbuffers decoding error: {}", e)
+            },
+            Error::FlexbuffersSer(e) => {
+                write!(f, "Flexbuffers encoding error: {}", e)
+            },
         }
     }
 }
@@ -85,4 +93,16 @@ impl From<lmdb::Error> for Error {
     }
 }
 
+impl From<flexbuffers::DeserializationError> for Error {
+    fn from(e: flexbuffers::DeserializationError) -> Error {
+        Error::FlexbuffersDe(e)
+    }
+}
+
+impl From<flexbuffers::SerializationError> for Error {
+    fn from(e: flexbuffers::SerializationError) -> Error {
+        Error::FlexbuffersSer(e)
+    }
+}
+
 pub type Result<T> = std::result::Result<T, Error>;