5 files changed, 240 insertions, 0 deletions
diff --git a/src/authorization/authorizer.rs b/src/authorization/authorizer.rs
new file mode 100644
index 00000000..14a7df27
--- /dev/null
+++ b/src/authorization/authorizer.rs
@@ -0,0 +1,5 @@
+use envoy_types::ext_authz::v3::pb::CheckRequest;
+
+pub trait Authorizer: std::fmt::Debug {
+    fn authorize(&self, request: CheckRequest) -> bool;
+}
diff --git a/src/authorization/cedar_authorizer.rs b/src/authorization/cedar_authorizer.rs
new file mode 100644
index 00000000..a877cf87
--- /dev/null
+++ b/src/authorization/cedar_authorizer.rs
@@ -0,0 +1,141 @@
+use super::authorizer::Authorizer;
+use cedar_policy::{
+    Authorizer as CedarAuth, Context, Entities, EntityId, EntityTypeName, EntityUid, PolicySet,
+    Request as CedarRequest, RestrictedExpression,
+};
+use envoy_types::ext_authz::v3::pb::CheckRequest;
+use std::collections::HashMap;
+use std::fs;
+use std::str::FromStr;
+
+#[derive(Debug)]
+pub struct CedarAuthorizer {
+    policies: PolicySet,
+    authorizer: CedarAuth,
+}
+
+impl CedarAuthorizer {
+    pub fn new(policies: cedar_policy::PolicySet) -> CedarAuthorizer {
+        CedarAuthorizer {
+            policies,
+            authorizer: CedarAuth::new(),
+        }
+    }
+
+    pub fn new_from(path: &std::path::Path) -> CedarAuthorizer {
+        Self::new(Self::load_from(path).unwrap_or_else(|_| PolicySet::default()))
+    }
+
+    fn load_from(path: &std::path::Path) -> Result<PolicySet, Box<dyn std::error::Error>> {
+        if !path.exists() || !path.is_dir() {
+            return Ok(PolicySet::default());
+        }
+
+        let mut policies = PolicySet::new();
+
+        for entry in fs::read_dir(path)? {
+            let file_path = entry?.path();
+
+            if let Some(extension) = file_path.extension() {
+                if extension == "cedar" {
+                    let content = fs::read_to_string(&file_path)?;
+                    let file_policies = PolicySet::from_str(&content)?;
+
+                    for policy in file_policies.policies() {
+                        policies.add(policy.clone())?;
+                    }
+                }
+            }
+        }
+
+        Ok(policies)
+    }
+}
+
+impl Default for CedarAuthorizer {
+    fn default() -> Self {
+        Self::new_from(std::path::Path::new("/etc/authzd"))
+    }
+}
+
+impl Authorizer for CedarAuthorizer {
+    fn authorize(&self, request: CheckRequest) -> bool {
+        let headers = match request
+            .attributes
+            .as_ref()
+            .and_then(|attr| attr.request.as_ref())
+            .and_then(|req| req.http.as_ref())
+            .map(|http| &http.headers)
+        {
+            Some(headers) => headers,
+            None => return false,
+        };
+
+        // Extract authorization token
+        let bearer_token = headers
+            .get("authorization")
+            .and_then(|auth| auth.strip_prefix("Bearer "))
+            .unwrap_or("");
+
+        // Extract request path for static asset checking
+        let path = headers
+            .get(":path")
+            .or_else(|| headers.get("path"))
+            .map_or("", |v| v.as_str());
+
+        // Create Cedar entities and request
+        match self.create_cedar_request(bearer_token, path) {
+            Ok(cedar_request) => {
+                let entities = Entities::empty();
+                let response =
+                    self.authorizer
+                        .is_authorized(&cedar_request, &self.policies, &entities);
+                matches!(response.decision(), cedar_policy::Decision::Allow)
+            }
+            Err(_) => false,
+        }
+    }
+}
+
+impl CedarAuthorizer {
+    fn create_cedar_request(
+        &self,
+        bearer_token: &str,
+        path: &str,
+    ) -> Result<CedarRequest, Box<dyn std::error::Error>> {
+        // Create principal entity
+        let principal_id = EntityId::from_str("client")?;
+        let principal_type = EntityTypeName::from_str("User")?;
+        let principal = EntityUid::from_type_name_and_id(principal_type, principal_id);
+
+        // Create action entity
+        let action_id = EntityId::from_str("check")?;
+        let action_type = EntityTypeName::from_str("Action")?;
+        let action = EntityUid::from_type_name_and_id(action_type, action_id);
+
+        // Create resource entity
+        let resource_id = EntityId::from_str("resource")?;
+        let resource_type = EntityTypeName::from_str("Resource")?;
+        let resource = EntityUid::from_type_name_and_id(resource_type, resource_id);
+
+        // Create context with bearer token and path
+        let mut context_map = HashMap::new();
+        if !bearer_token.is_empty() {
+            context_map.insert(
+                "bearer_token".to_string(),
+                RestrictedExpression::from_str(&format!("\"{}\"", bearer_token))?,
+            );
+        }
+        if !path.is_empty() {
+            context_map.insert(
+                "path".to_string(),
+                RestrictedExpression::from_str(&format!("\"{}\"", path))?,
+            );
+        }
+
+        let context = Context::from_pairs(context_map.into_iter().collect::<Vec<_>>())?;
+
+        CedarRequest::new(principal, action, resource, context, None)
+            .map_err(|e| Box::new(e) as Box<dyn std::error::Error>)
+    }
+}
diff --git a/src/authorization/check_service.rs b/src/authorization/check_service.rs
new file mode 100644
index 00000000..57f7b5d5
--- /dev/null
+++ b/src/authorization/check_service.rs
@@ -0,0 +1,35 @@
+use envoy_types::ext_authz::v3::CheckResponseExt;
+use envoy_types::ext_authz::v3::pb::{CheckRequest, CheckResponse};
+use std::sync::Arc;
+use tonic::{Request, Response, Status};
+
+use super::authorizer::Authorizer;
+
+#[derive(Debug)]
+pub struct CheckService {
+    authorizer: Arc<dyn Authorizer + Send + Sync>,
+}
+
+impl CheckService {
+    pub fn new(authorizer: Arc<dyn Authorizer + Send + Sync>) -> Self {
+        Self { authorizer }
+    }
+}
+
+#[tonic::async_trait]
+impl envoy_types::ext_authz::v3::pb::Authorization for CheckService {
+    async fn check(
+        &self,
+        request: Request<CheckRequest>,
+    ) -> Result<Response<CheckResponse>, Status> {
+        if self.authorizer.authorize(request.into_inner()) {
+            log::info!("OK");
+            Ok(Response::new(CheckResponse::with_status(Status::ok("OK"))))
+        } else {
+            log::info!("Unauthorized");
+            Ok(Response::new(CheckResponse::with_status(
+                Status::unauthenticated("Unauthorized"),
+            )))
+        }
+    }
+}
diff --git a/src/authorization/mod.rs b/src/authorization/mod.rs
new file mode 100644
index 00000000..d664815b
--- /dev/null
+++ b/src/authorization/mod.rs
@@ -0,0 +1,9 @@
+pub mod authorizer;
+pub mod cedar_authorizer;
+pub mod check_service;
+pub mod server;
+
+pub use authorizer::Authorizer;
+pub use cedar_authorizer::CedarAuthorizer;
+pub use check_service::CheckService;
+pub use server::Server;
diff --git a/src/authorization/server.rs b/src/authorization/server.rs
new file mode 100644
index 00000000..2ad270df
--- /dev/null
+++ b/src/authorization/server.rs
@@ -0,0 +1,50 @@
+use super::cedar_authorizer::CedarAuthorizer;
+use super::check_service::CheckService;
+use envoy_types::ext_authz::v3::pb::AuthorizationServer;
+use std::sync::Arc;
+
+pub struct Server {
+    router: tonic::transport::server::Router,
+}
+
+impl Server {
+    pub fn new() -> Result<Server, Box<dyn std::error::Error>> {
+        let (_health_reporter, health_service) = tonic_health::server::health_reporter();
+        let authorization_service =
+            AuthorizationServer::new(CheckService::new(Arc::new(CedarAuthorizer::default())));
+
+        Ok(Self::new_with(|mut builder| {
+            builder
+                .add_service(authorization_service)
+                .add_service(health_service)
+        }))
+    }
+
+    pub fn new_with<F>(f: F) -> Server
+    where
+        F: FnOnce(tonic::transport::Server) -> tonic::transport::server::Router,
+    {
+        let builder = tonic::transport::Server::builder()
+            .trace_fn(|req| {
+                tracing::info_span!(
+                    "request",
+                    method = %req.method(),
+                    path = %req.uri().path(),
+                    headers = ?req.headers(),
+                )
+            })
+            .timeout(std::time::Duration::from_secs(30));
+        let router = f(builder);
+        Server { router }
+    }
+
+    pub async fn serve(self, addr: std::net::SocketAddr) -> Result<(), tonic::transport::Error> {
+        self.router.serve(addr).await
+    }
+}
+
+impl Default for Server {
+    fn default() -> Self {
+        Self::new().unwrap()
+    }
+}