From 7b09802967706711663492cbedec3da8cd237d81 Mon Sep 17 00:00:00 2001
From: clawbot <35+clawbot@noreply.example.org>
Date: Tue, 29 Sep 2026 08:43:59 +0000
Subject: [PATCH] State what the default blocklist covers (closes #244)

The default blocklist covers private and reserved space, plus public
addresses that serve cloud credentials. A provider's other services on
public addresses, such as IBM Cloud's 161.26.0.0/16 and 166.8.0.0/14,
are deliberately not on it: they serve no credentials, reaching them
can be legitimate, and every cloud has some, so a partial list would
promise coverage it does not give.

The README's egress section and the comment above blockedNetworks now
state this rule, so nobody infers wider coverage and a future candidate
can be accepted or refused against it. No list change.

Model: opus-5-5
---
 README.md                 | 8 ++++++++
 internal/delivery/ssrf.go | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/README.md b/README.md
index 5729606..90b3614 100644
--- a/README.md
+++ b/README.md
@@ -162,6 +162,14 @@ public cloud metadata addresses: currently only `168.63.129.16`, Azure's
 WireServer, which serves an Azure VM its credentials. Because it is a
 public address, listing it in `ALLOWED_EGRESS_CIDRS` reopens it.
 
+That is all the default blocklist covers: private and reserved space,
+plus public addresses that serve cloud credentials. A cloud provider's
+other services on public addresses are not refused — IBM Cloud's
+`161.26.0.0/16` and `166.8.0.0/14`, for example, which carry its DNS
+resolvers, time servers and package mirrors. They serve no credentials,
+reaching them can be a legitimate delivery, and every cloud has some, so
+a partial list would promise coverage it does not give.
+
 That default is also inconvenient for the thing webhooker is mostly
 for: taking a public webhook and forwarding it to something on your own
 network. A container on the same Docker network, a box on `10.x`, a
diff --git a/internal/delivery/ssrf.go b/internal/delivery/ssrf.go
index 0fa73b3..9970dd7 100644
--- a/internal/delivery/ssrf.go
+++ b/internal/delivery/ssrf.go
@@ -43,6 +43,12 @@ var (
 // permit specific blocks out of this set with
 // ALLOWED_EGRESS_CIDRS; see Guard.
 //
+// A public address belongs here only if it serves cloud
+// credentials; a provider's other services on public addresses,
+// such as its DNS resolvers or package mirrors, stay out, since
+// reaching them can be legitimate and no list of them could be
+// complete.
+//
 //nolint:gochecknoglobals // package-level network list is appropriate here
 var blockedNetworks []*net.IPNet