[PATCH 0/2] Resource leaks and Asus routers

[Ed Rose | Tewke <ed@tewke.com>]

Hi all,

This is my first time submitting a patch to a mailing list so I apologise if I've made mistakes with formatting.

This short patch series fixes a couple of bugs that we've discovered in Connman that are triggered by a weird hack some mainstream routers have implemented. I'll attach a link to an article below on the topic, but the TL;DR is that Asus routers intentionally try to crash a buggy windows service that handles Proxy Auto-configuration by adding DHCP option 252 with the contents '\n' (apparently for performance reasons). Connman unfortunately tries to use this value and gets itself into a loop of failing online checks, breaking online detection and triggering the second bug.

The second bug is a memory and file descriptor leak that occurs due to the `wispr_portal_context` not being unreffed under some conditions, notably when it fails to resolve a proxy.

The result of both of these together is that connman eventually exhausts its fd limit and is unable to function.

Here is a link to a blog post explaining the strange DHCP behaviour:
https://nuxx.net/blog/2022/12/23/how-asus-and-a-microsoft-bug-almost-broke-remote-work/

This bug is super easy to replicate if you have a router that allows configuring DHCP. Ensure connman is configured to perform online checks and set option 252 with a payload of '\n' (0x0a). Watch the file descriptor list in `/proc/<pid>/fd` grow.

Ed Rose (2):
  wispr: Ensure memory cleaned up in all cases
  dhcp: Ignore empty DHCP Option 252

 src/dhcp.c  | 7 +++++--
 src/wispr.c | 3 ++-
 2 files changed, 7 insertions(+), 3 deletions(-)

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2.43.0