From 6cd206d33133da15a0cbd7b64abbcf8af274f74b Mon Sep 17 00:00:00 2001
From: Luke Dashjr <luke-jr+git@utopios.org>
Date: Sat, 11 May 2024 15:54:24 +0000
Subject: [PATCH] RPC: Delete cookie file before replacing it

Unclear if this is the best thing to do, but due to v26.1.knots20240325 creating it read-only, it is somewhat necessary for now
---
 src/rpc/request.cpp          |  5 +++++
 test/functional/rpc_users.py | 12 ++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/src/rpc/request.cpp b/src/rpc/request.cpp
index bf2a156bdc..1f3397f633 100644
--- a/src/rpc/request.cpp
+++ b/src/rpc/request.cpp
@@ -106,6 +106,11 @@ bool GenerateAuthCookie(std::string* cookie_out, const std::pair<std::optional<f
     file.close();
 
     fs::path filepath = GetAuthCookieFile(false);
+    try {
+        fs::remove(filepath);
+    } catch (const fs::filesystem_error& e) {
+        // ignore
+    }
     if (!RenameOver(filepath_tmp, filepath)) {
         LogInfo("Unable to rename cookie authentication file %s to %s\n", fs::PathToString(filepath_tmp), fs::PathToString(filepath));
         return false;
diff --git a/test/functional/rpc_users.py b/test/functional/rpc_users.py
index 4e09b19806..8003225447 100755
--- a/test/functional/rpc_users.py
+++ b/test/functional/rpc_users.py
@@ -257,6 +257,18 @@ class HTTPBasicsTest(BitcoinTestFramework):
         (self.nodes[0].chain_path / ".cookie.tmp").mkdir()
         (self.nodes[0].chain_path / ".cookie.tmp/subdir").mkdir()
         self.nodes[0].assert_start_raises_init_error(expected_msg=init_error)
+        (self.nodes[0].chain_path / ".cookie.tmp/subdir").rmdir()
+        (self.nodes[0].chain_path / ".cookie.tmp").rmdir()
+
+        (self.nodes[0].chain_path / ".cookie").mkdir()
+        (self.nodes[0].chain_path / ".cookie/subdir").mkdir()
+        self.nodes[0].assert_start_raises_init_error(expected_msg=init_error)
+        (self.nodes[0].chain_path / ".cookie/subdir").rmdir()
+        (self.nodes[0].chain_path / ".cookie").rmdir()
+
+        self.log.info('Check that a non-writable cookie file will get replaced gracefully')
+        (self.nodes[0].chain_path / ".cookie").mkdir(mode=1)
+        self.restart_node(0)
 
         self.test_rpccookieperms()