1 files changed, 76 insertions, 0 deletions
diff --git a/src/Agent.Windows/Security/TaskAclManager.cs b/src/Agent.Windows/Security/TaskAclManager.cs
new file mode 100644
index 0000000..f01e859
--- /dev/null
+++ b/src/Agent.Windows/Security/TaskAclManager.cs
@@ -0,0 +1,76 @@
+using System.Security.AccessControl;
+using System.Security.Principal;
+using Agent.Windows.Recovery;
+
+namespace Agent.Windows.Security;
+
+public sealed record AclSnapshot(string Path, byte[] SecurityDescriptor, Guid? JournalEntryId = null);
+
+public sealed class TaskAclManager(SecurityIdentifier appContainerSid, ISecurityAuditSink audit, TaskResourceJournal? journal = null)
+{
+    public AclSnapshot Grant(Guid taskId, string path, FileCapability capabilities)
+    {
+        string canonical = CanonicalPath.Resolve(path);
+        FileSystemSecurity security = ReadSecurity(canonical);
+        byte[] original = security.GetSecurityDescriptorBinaryForm();
+        Guid? journalEntry = journal?.Prepare("acl", canonical, new Dictionary<string, string>
+        {
+            ["security_descriptor"] = Convert.ToBase64String(original)
+        });
+        FileSystemRights rights = ToRights(capabilities);
+        if (rights == 0) throw new ArgumentOutOfRangeException(nameof(capabilities));
+        bool directory = Directory.Exists(canonical);
+        var rule = new FileSystemAccessRule(appContainerSid, rights,
+            directory ? InheritanceFlags.ContainerInherit | InheritanceFlags.ObjectInherit : InheritanceFlags.None,
+            PropagationFlags.None, AccessControlType.Allow);
+        security.AddAccessRule(rule);
+        WriteSecurity(canonical, security);
+        if (journalEntry is not null) journal!.MarkApplied(journalEntry.Value);
+        audit.Write(new(DateTimeOffset.UtcNow, taskId, "acl.apply", "applied", new Dictionary<string, string> { ["path"] = canonical, ["sid"] = appContainerSid.Value, ["rights"] = rights.ToString() }));
+        return new(canonical, original, journalEntry);
+    }
+
+    public void Restore(Guid taskId, AclSnapshot snapshot)
+    {
+        FileSystemSecurity security = Directory.Exists(snapshot.Path) ? new DirectorySecurity() : new FileSecurity();
+        security.SetSecurityDescriptorBinaryForm(snapshot.SecurityDescriptor, AccessControlSections.Access);
+        WriteSecurity(snapshot.Path, security);
+        if (snapshot.JournalEntryId is not null) journal!.MarkCleaned(snapshot.JournalEntryId.Value);
+        audit.Write(new(DateTimeOffset.UtcNow, taskId, "acl.restore", "restored", new Dictionary<string, string> { ["path"] = snapshot.Path }));
+    }
+
+    public void NormalizeNewEntry(Guid taskId, string path)
+    {
+        string canonical = CanonicalPath.Resolve(path);
+        FileSystemSecurity security = ReadSecurity(canonical);
+        security.SetAccessRuleProtection(isProtected: true, preserveInheritance: false);
+        foreach (FileSystemAccessRule rule in security.GetAccessRules(includeExplicit: true, includeInherited: false, typeof(SecurityIdentifier))
+            .OfType<FileSystemAccessRule>()
+            .Where(rule => rule.IdentityReference == appContainerSid)
+            .ToArray())
+            security.RemoveAccessRuleSpecific(rule);
+        security.SetAccessRuleProtection(isProtected: false, preserveInheritance: false);
+        WriteSecurity(canonical, security);
+        audit.Write(new(DateTimeOffset.UtcNow, taskId, "acl.normalize", "normalized", new Dictionary<string, string> { ["path"] = canonical }));
+    }
+
+    private static FileSystemSecurity ReadSecurity(string path) => Directory.Exists(path)
+        ? FileSystemAclExtensions.GetAccessControl(new DirectoryInfo(path), AccessControlSections.Access)
+        : FileSystemAclExtensions.GetAccessControl(new FileInfo(path), AccessControlSections.Access);
+
+    private static void WriteSecurity(string path, FileSystemSecurity security)
+    {
+        if (security is DirectorySecurity directorySecurity) FileSystemAclExtensions.SetAccessControl(new DirectoryInfo(path), directorySecurity);
+        else FileSystemAclExtensions.SetAccessControl(new FileInfo(path), (FileSecurity)security);
+    }
+
+    private static FileSystemRights ToRights(FileCapability capabilities)
+    {
+        FileSystemRights rights = 0;
+        if ((capabilities & FileCapability.Read) != 0) rights |= FileSystemRights.ReadAndExecute | FileSystemRights.ListDirectory;
+        if ((capabilities & FileCapability.Write) != 0) rights |= FileSystemRights.Write;
+        if ((capabilities & FileCapability.Execute) != 0) rights |= FileSystemRights.ReadAndExecute;
+        if ((capabilities & FileCapability.Delete) != 0) rights |= FileSystemRights.Delete | FileSystemRights.DeleteSubdirectoriesAndFiles;
+        return rights;
+    }
+}