From 612e974ace6b6f9e2666d0305b35fb0cd28ea5e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Geoffrey=20=E2=80=9CFrogeye=E2=80=9D=20Preud=27homme?=
 <geoffrey@frogeye.fr>
Date: Mon, 7 Apr 2025 23:14:37 +0200
Subject: [PATCH] assign{Ips,Macs}: Fix integer overflow

Half of SHA256 sums truncated to 16 chars actually go over 2^63,
which is beyond the range for hexToDec.
This fixes the integer overflow error in Lix 2.91+ and Nix 2.25+,
as well as undefined behaviour for versions below
---
 lib/net.nix | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/net.nix b/lib/net.nix
index 3713f09..2432544 100644
--- a/lib/net.nix
+++ b/lib/net.nix
@@ -230,7 +230,7 @@ in {
           # Generates a hash (i.e. offset value) for a given hostname
           hashElem = x:
             builtins.bitAnd (capacity - 1)
-            (hexToDec (builtins.substring 0 16 (builtins.hashString "sha256" x)));
+            (hexToDec (builtins.substring 0 15 (builtins.hashString "sha256" x)));
           # Do linear probing. Returns the first unused value at or after the given value.
           probe = avoid: value:
             if elem value avoid
@@ -317,7 +317,7 @@ in {
           # Generates a hash (i.e. offset value) for a given hostname
           hashElem = x:
             builtins.bitAnd (capacity - 1)
-            (hexToDec (substring 0 16 (builtins.hashString "sha256" x)));
+            (hexToDec (substring 0 15 (builtins.hashString "sha256" x)));
           # Do linear probing. Returns the first unused value at or after the given value.
           probe = avoid: value:
             if elem value avoid