mirror of
https://github.com/mauriceboe/TREK.git
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jubnl
3a57cec992
Loopback, link-local, and .local/.internal hostnames are now all
overridable with ALLOW_INTERNAL_NETWORK=true (commit 9a08368). Merge
the two-tier "always blocked / conditionally blocked" structure into a
single table, add a warning about cloud metadata exposure.
53 lines
2.9 KiB
Markdown
53 lines
2.9 KiB
Markdown
# Internal Network Access
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TREK makes outbound HTTP requests when you configure integrations such as Immich or Synology Photos. By default, it blocks requests to private and local IP ranges to prevent server-side request forgery (SSRF) attacks. You need to allow internal network access when those services are hosted on your LAN.
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## Default behavior
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All outbound requests go through an SSRF guard (`ssrfGuard.ts`). The guard resolves the hostname to an IP address before allowing the connection and blocks addresses in private ranges.
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## Blocked unless `ALLOW_INTERNAL_NETWORK=true`
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All of the following are blocked by default and can be permitted by setting `ALLOW_INTERNAL_NETWORK=true`:
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| Range / Hostname | Description |
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|---|---|
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| `127.0.0.0/8`, `::1` | Loopback |
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| `0.0.0.0/8` | Unspecified |
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| `169.254.0.0/16`, `fe80::/10` | Link-local / cloud metadata endpoints |
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| `::ffff:127.x.x.x`, `::ffff:169.254.x.x` | IPv4-mapped loopback and link-local |
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| `10.0.0.0/8` | RFC-1918 private |
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| `172.16.0.0/12` | RFC-1918 private |
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| `192.168.0.0/16` | RFC-1918 private |
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| `100.64.0.0/10` | CGNAT / Tailscale shared address space |
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| `fc00::/7` | IPv6 ULA |
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| IPv4-mapped RFC-1918 variants | e.g. `::ffff:10.x`, `::ffff:192.168.x` |
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| `*.local`, `*.internal` hostnames | mDNS / internal DNS suffixes |
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The hostname `localhost` is not blocked at the hostname stage but resolves to `127.0.0.1`, which falls under the loopback rule above.
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> **Warning:** `ALLOW_INTERNAL_NETWORK=true` also permits loopback and link-local addresses, including `169.254.169.254` (cloud instance metadata). Do **not** set this flag on a cloud-hosted TREK instance.
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## When to enable
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Set `ALLOW_INTERNAL_NETWORK=true` when Immich, Synology Photos, or another integrated service is hosted on your local network and you need TREK to reach it.
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See [Environment-Variables](Environment-Variables) for how to set environment variables.
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> **Admin:** Set `ALLOW_INTERNAL_NETWORK=true` in [Environment-Variables](Environment-Variables) before configuring Immich or Synology on a LAN.
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## DNS rebinding protection
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Even with `ALLOW_INTERNAL_NETWORK=true`, TREK pins the DNS resolution to prevent rebinding attacks. When the guard checks a URL, it resolves the hostname once and records the IP. The outbound connection is then made directly to that IP using a pinned dispatcher (via undici), so the hostname cannot re-resolve to a different address between the check and the actual request.
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## Audit log
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When a user saves an Immich URL that resolves to a private IP, TREK records an `immich.private_ip_configured` entry in the [Audit-Log](Audit-Log) including the URL and the resolved IP address. This audit event is specific to Immich; Synology Photos does not emit an equivalent event.
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## See also
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- [Photo-Providers](Photo-Providers)
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- [User-Settings](User-Settings)
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- [Environment-Variables](Environment-Variables)
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- [Security-Hardening](Security-Hardening)
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