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feat: block CONNECT tunnels to private/reserved IP ranges (#23109)

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## Description

Blocks `CONNECT` tunnels to private and reserved IP ranges in
aibridgeproxyd, preventing the proxy from being used to reach internal
networks.

The Coder access URL is always exempt (hostname+port match) so the proxy
can reach its own deployment. It is possible to exempt additional ranges
via `CODER_AIBRIDGE_PROXY_ALLOWED_PRIVATE_CIDRS`.

DNS rebinding is handled differently per path:
* Direct (no upstream proxy): validate the resolved IP right before the
TCP dial, no window between check and connect.
* Upstream proxy: Resolves and checks before forwarding to the upstream
dialer. A small rebinding window exists since the upstream proxy
re-resolves independently.

## Changes

* Add blocked IP denylist covering private, reserved, and
special-purpose ranges
* Add `AllowedPrivateCIDRs` option with CLI flag and env var
* Wire IP checks into `proxy.ConnectDial` for both upstream and direct
paths
* Add tests for blocked/allowed cases across direct dial, upstream
proxy, CIDR exemptions, and CoderAccessURL exemption

Notes: documentation will be handled in a follow-up PR.
Closes: https://github.com/coder/security/issues/124
This commit is contained in:
Susana Ferreira
2026-03-20 09:49:26 +00:00
committed by GitHub
parent 06c50d13ad
commit 139594a4f4
13 changed files with 563 additions and 59 deletions
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@@ -1961,6 +1961,16 @@ URL of an upstream HTTP proxy to chain tunneled (non-allowlisted) requests throu
Path to a PEM-encoded CA certificate to trust for the upstream proxy's TLS connection. Only needed for HTTPS upstream proxies with certificates not trusted by the system. If not provided, the system certificate pool is used.
### --aibridge-proxy-allowed-private-cidrs
| | |
|-------------|----------------------------------------------------------|
| Type | <code>string-array</code> |
| Environment | <code>$CODER_AIBRIDGE_PROXY_ALLOWED_PRIVATE_CIDRS</code> |
| YAML | <code>aibridgeproxy.allowed_private_cidrs</code> |
Comma-separated list of CIDR ranges that are permitted even though they fall within blocked private/reserved IP ranges. By default all private ranges are blocked to prevent SSRF attacks. Use this to allow access to specific internal networks.
### --audit-logs-retention
| | |