From a1660bc016cfe9f0b5fa15ee4192876ee9e82da4 Mon Sep 17 00:00:00 2001
From: RRFZ <247457381+Plastic-time@users.noreply.github.com>
Date: Wed, 4 Nov 2026 12:18:40 -0500
Subject: [PATCH] fix(pe): reject certificates whose signature algorithms
 disagree (#8922)

* fix(pe): reject certificates whose signature algorithms disagree

* test(pe): keep the signature algorithm case apart from the version case
---
 src/native/pe/PeCertificateAsn1.ts        |  9 ++++++++
 src/native/pe/PeCertificateParser.test.ts | 25 +++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/native/pe/PeCertificateAsn1.ts b/src/native/pe/PeCertificateAsn1.ts
index f4f1c20e8b..0b8f760798 100644
--- a/src/native/pe/PeCertificateAsn1.ts
+++ b/src/native/pe/PeCertificateAsn1.ts
@@ -484,6 +484,15 @@ export const parseCertificate = (
       "TBSCertificate is missing serial, signature, issuer, validity, subject, or subjectPublicKeyInfo.",
     );
   algorithmOid(tbsSignature);
+  // RFC 5280 4.1.1.2: signatureAlgorithm MUST equal the TBSCertificate
+  // signature field. Compare encodings, parameters included.
+  if (
+    signatureAlgorithm.tag !== tbsSignature.tag ||
+    !signatureAlgorithm.content.equals(tbsSignature.content)
+  )
+    return fail(
+      "Certificate signatureAlgorithm differs from the TBSCertificate signature.",
+    );
   requireSubjectPublicKeyInfo(subjectPublicKeyInfo);
   finishTbsCertificate(tbsChildren, index + 6);
   const validityChildren = sequence(validity, "Validity");
diff --git a/src/native/pe/PeCertificateParser.test.ts b/src/native/pe/PeCertificateParser.test.ts
index 3befe7b42b..66bb62bb26 100644
--- a/src/native/pe/PeCertificateParser.test.ts
+++ b/src/native/pe/PeCertificateParser.test.ts
@@ -1035,3 +1035,28 @@ it.each([
     expect(certificate.subject.attributes[0]?.value).toBe(value);
   },
 );
+
+it("rejects a certificate whose signatureAlgorithm differs from its TBS signature", () => {
+  const name = directoryName(der(0x0c, Buffer.from("Fixture")));
+  const certificate = (outer: Buffer) =>
+    readAsn1(
+      derSeq(
+        derSeq(derInt(1), SHA256_ALG, name, validity, name, spki),
+        outer,
+        der(0x03, Buffer.from([0])),
+      ),
+    );
+  const sha1 = derSeq(der(0x06, Buffer.from([0x2b, 0x0e, 0x03, 0x02, 0x1a])));
+  // The same OID with explicit NULL parameters is still a different identifier.
+  const sha256WithNull = der(
+    0x30,
+    Buffer.concat([SHA256_ALG.subarray(2), der(0x05, Buffer.alloc(0))]),
+  );
+  for (const outer of [sha1, sha256WithNull])
+    expect(() => parseCertificate(certificate(outer))).toThrow(
+      /signatureAlgorithm differs from the TBSCertificate signature/u,
+    );
+  expect(
+    parseCertificate(certificate(SHA256_ALG)).signature_algorithm_oid,
+  ).toBe("2.16.840.1.101.3.4.2.1");
+});