From a09088ebffd0d0b537654314d73cfce1f2372411 Mon Sep 17 00:00:00 2001
From: Emil Lerch <emil@lerch.org>
Date: Wed, 22 Jul 2026 06:22:59 -0700
Subject: [PATCH] use response arena rather than db allocator for responses

---
 src/main.zig | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 31c0476..4eb2222 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -130,7 +130,7 @@ pub fn main() !u8 {
     return 0;
 }
 
-fn indexHandler(db: *root.NotmuchDb, _: *httpz.Request, res: *httpz.Response) !void {
+fn indexHandler(_: *root.NotmuchDb, _: *httpz.Request, res: *httpz.Response) !void {
     const file = std.fs.cwd().openFile("static/index.html", .{}) catch {
         res.status = 500;
         res.body = "Error loading index.html";
@@ -138,7 +138,7 @@ fn indexHandler(db: *root.NotmuchDb, _: *httpz.Request, res: *httpz.Response) !v
     };
     defer file.close();
 
-    const content = file.readToEndAlloc(db.allocator, 1024 * 1024) catch {
+    const content = file.readToEndAlloc(res.arena, 1024 * 1024) catch {
         res.status = 500;
         res.body = "Error reading index.html";
         return;
@@ -149,7 +149,7 @@ fn indexHandler(db: *root.NotmuchDb, _: *httpz.Request, res: *httpz.Response) !v
     res.body = content;
 }
 
-fn staticHandler(db: *root.NotmuchDb, req: *httpz.Request, res: *httpz.Response) !void {
+fn staticHandler(_: *root.NotmuchDb, req: *httpz.Request, res: *httpz.Response) !void {
     const path = req.url.path;
 
     const file_path = if (std.mem.eql(u8, path, "/style.css"))
@@ -169,7 +169,7 @@ fn staticHandler(db: *root.NotmuchDb, req: *httpz.Request, res: *httpz.Response)
     };
     defer file.close();
 
-    const content = file.readToEndAlloc(db.allocator, 1024 * 1024) catch {
+    const content = file.readToEndAlloc(res.arena, 1024 * 1024) catch {
         res.status = 500;
         res.body = "Error reading file";
         return;
@@ -345,8 +345,13 @@ fn attachmentHandler(db: *root.NotmuchDb, req: *httpz.Request, res: *httpz.Respo
     }
 
     const att = msg.attachments[num];
-    res.header("Content-Type", att.content_type);
-    res.header("Content-Disposition", try std.fmt.allocPrint(db.allocator, "attachment; filename=\"{s}\"", .{att.filename}));
+    // httpz stores header values by reference and serializes them after this
+    // handler returns -- i.e. after `defer msg.deinit` has freed att.* and
+    // without ever freeing anything allocated here. Copy both values into the
+    // per-request arena (reset by httpz after the response is written) to avoid
+    // a use-after-free on Content-Type and a leak on Content-Disposition.
+    res.header("Content-Type", try res.arena.dupe(u8, att.content_type));
+    res.header("Content-Disposition", try std.fmt.allocPrint(res.arena, "attachment; filename=\"{s}\"", .{att.filename}));
 
     // TODO: Actually retrieve and send attachment content
     // For now, just send metadata