The SSRF blocklist had no escape hatch, so the thing webhooker is
mostly for — taking a public webhook and forwarding it to something
on your own network — could not be configured at all. Every private
address, Docker sibling and loopback service was permanently
unreachable as a delivery destination.
ALLOWED_EGRESS_CIDRS (default empty) names blocks that delivery
targets may reach despite the default blocklist. It is an allowlist
and only ever adds destinations: there is no boolean, and no value
disables SSRF protection wholesale. Empty, the guard behaves exactly
as before.
A fixed set of addresses is refused before the allowlist is
consulted, so no supplied CIDR opens one — not the exact address,
not a supernet, not 0.0.0.0/0 or ::/0. It is the two link-local
blocks (169.254.0.0/16, fe80::/10) plus host routes for the cloud
metadata endpoints that sit outside them: AWS's IPv6 IMDS at
fd00:ec2::254, which lives in ordinary ULA space, and Alibaba's
100.100.100.200, which lives in CGNAT. Allowlisting fd00::/8 or
100.64.0.0/10 (Tailscale's range) is an ordinary thing for an
operator to do and must not reopen instance-credential theft. The
IPv4-compatible (::a9fe:a9fe) and NAT64 (64:ff9b::a9fe:a9fe)
spellings of 169.254.169.254 are listed too, because To4() does not
normalise them into the link-local block the way it does the
IPv4-mapped form. Reaching any of these is credential theft rather
than delivery to an internal service.
The policy now lives in one function, Guard.checkIP, which both
target-creation validation and the delivery dialer call. The two
paths previously decided separately, which is how they came to
disagree about a destination. The guard is built once from config
and injected via fx into both the handlers and the delivery engine,
so there is a single instance and a single answer.
A set-but-unparseable value aborts startup naming the variable,
reusing the existing envPrefixList parser. A non-empty list is
logged at startup with the blocks spelled out, not counted, so the
hole is visible in the log of any deployment that has one.
Tests: an allowlisted loopback CIDR both validates and delivers to a
live server (and the same URL still fails without the allowlist); a
private address outside the listed block stays refused on both
paths; every unconditionally blocked address stays refused on both
paths under an allowlist that covers it, and the set itself is
pinned entry by entry; public addresses are unaffected either way;
and config coverage for parsing, startup abort, and the warning's
contents.
check / check (push) Superseded by a newer commit; never tested
`clientForConfig()` in `internal/delivery/engine.go` built a fresh `http.Client` without a Transport when a per-target timeout was configured, dropping the request-time private-IP guard for that path.
It now reuses the shared client's SSRF-safe transport (`e.client.Transport`, the same `NewSSRFSafeTransport` instance), overriding only the `Timeout`. Behaviour is unchanged when no per-target timeout is set (the shared client is returned as before), so no engine code path makes an outbound target request with a client lacking the SSRF-safe transport.
Adds a delivery-package test proving a client from `clientForConfig()` with a per-target timeout still refuses private/reserved/link-local destinations, that the timeout is applied, that the SSRF-safe transport is reused (not duplicated), and that the no-timeout path returns the shared client unchanged.
Confined to `internal/delivery/` only; handlers and server code untouched.
Closes#69
Co-authored-by: sneak <sneak@sneak.berlin>
Co-authored-by: Jeffrey Paul <sneak@noreply.example.org>
Reviewed-on: #74
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>
