DYNR/netbird
2
0
Fork 0
mirror of https://github.com/netbirdio/netbird.git synced 2026-08-05 00:15:26 -04:00
Code Issues 23.5k Packages Projects Releases 10 Wiki Activity

[PR #7059] [client] Do not misroute WireGuard packets to the STUN handler #29505

New Issue
Open
opened 2026-08-05 08:08:11 -04:00 by saavagebueno · 0 comments
saavagebueno commented 2026-08-05 08:08:11 -04:00
Owner
Copy Link

📋 Pull Request Information

Original PR: https://github.com/netbirdio/netbird/pull/7059
Author: @lixmal
Created: 8/4/2026
Status: 🔄 Open

Base: main ← Head: ice-stun-wg-demux

📝 Commits (3)

  • 7099f59 Do not misroute WireGuard packets to the STUN handler
  • e950a94 Clear the size of a packet consumed by the STUN handler
  • d8fc0fd Require a minimum length before classifying a packet as WireGuard

📊 Changes

2 files changed (+267 additions, -14 deletions)

View changed files

📝 client/iface/bind/ice_bind.go (+52 -14)
➕ client/iface/bind/stun_filter_test.go (+215 -0)

📄 Description

Describe your changes

Packets are classified as STUN by looking only at the magic cookie, which sits at the same offset as the WireGuard receiver index. That index is a random uint32 drawn fresh on every handshake, so a session can draw the cookie value, and while that keypair lives every inbound packet of the session is handed to the STUN handler instead of to WireGuard.

The odds are 1 in 2^32 per session. Since an active session rekeys every 120 seconds, a peer with 50 active sessions draws roughly 25 indices per minute, which puts the expected interval for any single client in the range of centuries. It scales linearly with the number of sessions in existence, however, so it is worth fixing rather than dismissing. The consequence is asymmetric and self-healing, which makes it hard to attribute: outbound traffic keeps flowing because it carries the remote index, while inbound traffic is dropped for up to one rekey interval, and then the next handshake draws a new index and the peer recovers on its own. The handshake watcher does not cover it: only messages carrying our own index in that field are affected, which is transport data and cookie replies, while a handshake response carries the responder's index there and ours further in. Handshakes therefore keep succeeding on schedule and the peer reports itself connected with a recent handshake while nothing inbound arrives. A handshake initiation whose sender index collides is dropped the same way, but WireGuard retries every 5 seconds with a fresh index, so that case clears on the next attempt.

  • Reject WireGuard-shaped packets before the STUN cookie check, which is exact rather than heuristic because the low byte of a STUN message type is non-zero for every method in use
  • Classify on the received length instead of the buffer capacity, so leftover bytes from an earlier packet cannot decide the outcome
  • Clear the reported size of a packet consumed by the STUN handler, so WireGuard no longer processes that buffer again under the previous packet's length and endpoint
  • Skip counting a packet too short to hold a WireGuard header as peer activity

Only the userspace path is affected. In kernel mode the equivalent check lives in a BPF filter on a raw socket, which receives a copy rather than consuming the packet, so a collision there costs a log line instead of the traffic.

Issue ticket number and link

Trivial fix, no behavior or API change.

Stack

Checklist

  • Is it a bug fix
  • Is a typo/documentation fix
  • Is a feature enhancement
  • It is a refactor
  • Created tests that fail without the change (if possible)
  • I ran and tested this change locally — I did not rely on CI to find out whether it works
  • This PR has a single purpose (not a fix + refactor + feature in one)
  • This change is a trivial fix, OR it links an issue the NetBird team agreed on beforehand. Changes to the public API, gRPC protocols, functionality behavior, CLI / service flags, or new features always need that agreement first. See CONTRIBUTING.md.

By submitting this pull request, you confirm that you have read and agree to the terms of the Contributor License Agreement.

Documentation

Select exactly one:

  • I added/updated documentation for this change
  • Documentation is not needed for this change (internal packet classification, no user-visible surface)

Docs PR URL (required if "docs added" is checked)

Paste the PR link from https://github.com/netbirdio/docs here:

https://github.com/netbirdio/docs/pull/__

Summary by CodeRabbit

  • Bug Fixes
    • Improved network packet handling by safely validating short, malformed, and partially received packets.
    • Improved distinction between WireGuard traffic and STUN messages, including packets with overlapping header patterns.
    • Prevented stale data from previously processed packets from affecting subsequent network activity detection.
    • Improved handling and reporting of invalid STUN messages.

🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.

## 📋 Pull Request Information **Original PR:** https://github.com/netbirdio/netbird/pull/7059 **Author:** [@lixmal](https://github.com/lixmal) **Created:** 8/4/2026 **Status:** 🔄 Open **Base:** `main` ← **Head:** `ice-stun-wg-demux` --- ### 📝 Commits (3) - [`7099f59`](https://github.com/netbirdio/netbird/commit/7099f5907b9d632fb3fd1419128af6839e26c651) Do not misroute WireGuard packets to the STUN handler - [`e950a94`](https://github.com/netbirdio/netbird/commit/e950a9487fbc3e0402e4863dd7b85e9f1a7f2a29) Clear the size of a packet consumed by the STUN handler - [`d8fc0fd`](https://github.com/netbirdio/netbird/commit/d8fc0fdbe45ea5ad4dcff12d044d814c7dfe82fe) Require a minimum length before classifying a packet as WireGuard ### 📊 Changes **2 files changed** (+267 additions, -14 deletions) <details> <summary>View changed files</summary> 📝 `client/iface/bind/ice_bind.go` (+52 -14) ➕ `client/iface/bind/stun_filter_test.go` (+215 -0) </details> ### 📄 Description ## Describe your changes Packets are classified as STUN by looking only at the magic cookie, which sits at the same offset as the WireGuard receiver index. That index is a random uint32 drawn fresh on every handshake, so a session can draw the cookie value, and while that keypair lives every inbound packet of the session is handed to the STUN handler instead of to WireGuard. The odds are 1 in 2^32 per session. Since an active session rekeys every 120 seconds, a peer with 50 active sessions draws roughly 25 indices per minute, which puts the expected interval for any single client in the range of centuries. It scales linearly with the number of sessions in existence, however, so it is worth fixing rather than dismissing. The consequence is asymmetric and self-healing, which makes it hard to attribute: outbound traffic keeps flowing because it carries the remote index, while inbound traffic is dropped for up to one rekey interval, and then the next handshake draws a new index and the peer recovers on its own. The handshake watcher does not cover it: only messages carrying our own index in that field are affected, which is transport data and cookie replies, while a handshake response carries the responder's index there and ours further in. Handshakes therefore keep succeeding on schedule and the peer reports itself connected with a recent handshake while nothing inbound arrives. A handshake initiation whose sender index collides is dropped the same way, but WireGuard retries every 5 seconds with a fresh index, so that case clears on the next attempt. - Reject WireGuard-shaped packets before the STUN cookie check, which is exact rather than heuristic because the low byte of a STUN message type is non-zero for every method in use - Classify on the received length instead of the buffer capacity, so leftover bytes from an earlier packet cannot decide the outcome - Clear the reported size of a packet consumed by the STUN handler, so WireGuard no longer processes that buffer again under the previous packet's length and endpoint - Skip counting a packet too short to hold a WireGuard header as peer activity Only the userspace path is affected. In kernel mode the equivalent check lives in a BPF filter on a raw socket, which receives a copy rather than consuming the packet, so a collision there costs a log line instead of the traffic. ## Issue ticket number and link Trivial fix, no behavior or API change. ## Stack <!-- branch-stack --> ### Checklist - [x] Is it a bug fix - [ ] Is a typo/documentation fix - [ ] Is a feature enhancement - [ ] It is a refactor - [x] Created tests that fail without the change (if possible) - [x] I ran and tested this change locally — I did not rely on CI to find out whether it works - [x] This PR has a single purpose (not a fix + refactor + feature in one) - [x] This change is a trivial fix, **OR** it links an issue the NetBird team agreed on beforehand. Changes to the public API, gRPC protocols, functionality behavior, CLI / service flags, or new features always need that agreement first. See [CONTRIBUTING.md](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTING.md#ticket-first-pr-second). > By submitting this pull request, you confirm that you have read and agree to the terms of the [Contributor License Agreement](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTOR_LICENSE_AGREEMENT.md). ## Documentation Select exactly one: - [ ] I added/updated documentation for this change - [x] Documentation is **not needed** for this change (internal packet classification, no user-visible surface) ### Docs PR URL (required if "docs added" is checked) Paste the PR link from https://github.com/netbirdio/docs here: https://github.com/netbirdio/docs/pull/__ <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit - **Bug Fixes** - Improved network packet handling by safely validating short, malformed, and partially received packets. - Improved distinction between WireGuard traffic and STUN messages, including packets with overlapping header patterns. - Prevented stale data from previously processed packets from affecting subsequent network activity detection. - Improved handling and reporting of invalid STUN messages. <!-- end of auto-generated comment: release notes by coderabbit.ai --> --- <sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>
saavagebueno added the pull-request label 2026-08-05 08:08:11 -04:00
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels
2021 Q4
2021 Q4
2021 Q4
2022 Q1
2022 Q1
2022 Q1
2022 Q1
2022 Q1
2022 Q1
accessibility
accessibility
accessibility
acl
acl
acl
agent
agent
agent
agent
agent
agent
Android
Android
Android
Android
Android
Android
api
api
api
authentik
authentik
authentik
automation
automation
automation
azure
azure
azure
battery-usage
battery-usage
battery-usage
bug
cache
cache
cache
client
client
client
client-ui
client-ui
client-ui
cloud
cloud
cloud
cloud-only
cloud-only
cloud-only
cloudflare
cloudflare
cloudflare
community
community
community
compatibility
compatibility
compatibility
config-idp
config-idp
config-idp
config-issue
config-issue
config-issue
connection
connection
connection
contribution
contribution
contribution
coturn
coturn
coturn
cross-vpn
cross-vpn
cross-vpn
dashboard
dashboard
dashboard
data-usage
data-usage
data-usage
distribution
distribution
distribution
dns
dns
dns
docker
docker
docker
documentation
documentation
documentation
duplicate
duplicate
duplicate
enhancement
enhancement
event-stream
event-stream
event-stream
feature-request
feature-request
feature-request
freebsd
freebsd
freebsd
getting-started
getting-started
getting-started
go
go
go
good first issue
good first issue
good first issue
gui
gui
gui
help wanted
help wanted
help wanted
home-assistant
home-assistant
home-assistant
idp
idp
idp
inconsistency
inconsistency
inconsistency
integration
integration
integration
integrations
integrations
integrations
ios
ios
ios
ipv6
ipv6
ipv6
jwt
jwt
jwt
k8s
k8s
k8s
keycloak
keycloak
keycloak
linux
linux
linux
login
login
login
macos
macos
macos
management-service
management-service
management-service
Medium
Medium
Medium
missing-docs
missing-docs
missing-docs
mobile
mobile
mobile
moved-internal
moved-internal
moved-internal
needs-review
needs-review
needs-review
netbird-ui
netbird-ui
netbird-ui
networking
networking
networking
new-platform
new-platform
new-platform
nginx
nginx
nginx
notification
notification
notification
okta
okta
okta
openwrt
openwrt
openwrt
P2
P2
P2
packaging
packaging
packaging
peer-management
peer-management
peer-management
peer-management
peer-management
peer-management
peer-management
peer-management
peer-management
performance
performance
performance
postgres
postgres
postgres
posture-checks
posture-checks
posture-checks
psk
psk
psk
pull-request
Mirrored from GitHub Pull Request
 question
question
question
refactor
refactor
refactor
relay
relay
relay
release
release
release
rfc
rfc
rfc
routes
routes
routes
security
security
security
security-improvement
security-improvement
security-improvement
security-related
security-related
security-related
self-hosting
self-hosting
self-hosting
server
server
server
signal
signal
signal
sleep-issue
sleep-issue
sleep-issue
ssh
ssh
ssh
ssl
ssl
ssl
status
status
status
store
store
store
synology
synology
synology
system-compatibility-issue
system-compatibility-issue
system-compatibility-issue
test-suite
test-suite
test-suite
third-party-integration
third-party-integration
third-party-integration
triage
triage
triage
triage
triage
triage
triage-needed
triage-needed
triage-needed
troubleshooting
troubleshooting
troubleshooting
UX
UX
UX
waiting-feedback
waiting-feedback
waiting-feedback
windows
windows
windows
wontfix
wontfix
wontfix
zitadel
zitadel
zitadel
No Label pull-request
Milestone
No items
No Milestone
Projects
Clear projects
No project
Assignees
Clear assignees
dynr-servers saavagebueno
No Assignees
1 Participants
Notifications
Due Date
No due date set.
Dependencies

No dependencies set.

Reference: DYNR/netbird#29505
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?