From 03077d54afc49613db4e38f70c506bc60f5223aa Mon Sep 17 00:00:00 2001
From: morluto <76467478+morluto@users.noreply.github.com>
Date: Sat, 24 Oct 2026 02:29:37 +0800
Subject: [PATCH] fix(pe): separate certificate content from counted alignment

---
 docs/pe-certificates.md                   |  5 +++
 src/native/pe/PeCertificateAsn1.ts        |  4 +--
 src/native/pe/PeCertificateParser.test.ts | 41 +++++++++++++++++++++++
 src/native/pe/PeCertificateParser.ts      | 12 ++++++-
 4 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/docs/pe-certificates.md b/docs/pe-certificates.md
index 9875e19f91..0987cee27d 100644
--- a/docs/pe-certificates.md
+++ b/docs/pe-certificates.md
@@ -28,6 +28,11 @@ The inline Evidence result contains the artifact path, SHA-256, and byte length.
 absent or zero. Each `entries[]` item reports `WIN_CERTIFICATE` length,
 revision, type, and the payload SHA-256.
 
+Type-2 entries may count their zero alignment padding in `dwLength`. The PE
+entry owner accepts only the exact gap to the next eight-byte boundary after
+the parsed ContentInfo; extra data or nonzero counted padding fails. Entry and
+payload ranges and hashes retain all declared bytes, including counted padding.
+
 For `WIN_CERTIFICATE` type 2 (PKCS#7 signedData) `pkcs7` contains digest
 algorithm OIDs, embedded X.509 serial/issuer/subject/validity fields, and
 signer identifier facts. A signer identified by subject key identifier reports
diff --git a/src/native/pe/PeCertificateAsn1.ts b/src/native/pe/PeCertificateAsn1.ts
index b104ccc7b4..4b3125e769 100644
--- a/src/native/pe/PeCertificateAsn1.ts
+++ b/src/native/pe/PeCertificateAsn1.ts
@@ -569,9 +569,7 @@ const parseSignedData = (
 };
 
 /** Decode ContentInfo wrapping SignedData; other content types remain unsupported. */
-export const parsePkcs7SignedData = (bytes: Buffer): ParsedSignedData => {
-  const root = readAsn1(bytes);
-  if (root.end !== bytes.length) return fail("ContentInfo has trailing data.");
+export const parsePkcs7SignedData = (root: Asn1Node): ParsedSignedData => {
   const children = sequence(root, "ContentInfo");
   const type = children[0];
   const content = children[1];
diff --git a/src/native/pe/PeCertificateParser.test.ts b/src/native/pe/PeCertificateParser.test.ts
index 4f95700723..4e94bf88e0 100644
--- a/src/native/pe/PeCertificateParser.test.ts
+++ b/src/native/pe/PeCertificateParser.test.ts
@@ -72,6 +72,47 @@ it("reads PE32 and PE32+ PKCS#7 certificate tables", () => {
   }
 });
 
+it.each([false, true])(
+  "preserves PE certificate bytes when dwLength counts alignment padding (PE32+ = %s)",
+  (plus) => {
+    // Choose a fixture with nonzero alignment padding so the control distinguishes
+    // an ASN.1 terminator from the end of the WIN_CERTIFICATE payload.
+    const payload = ["Padding", "Paddingx"]
+      .map((name) => pkcs7SignedDataFixture(name))
+      .find((value) => (value.length + 8) % 8 !== 0)!;
+    const bytes = peCertificateFixture(plus, payload);
+    const control = parse(bytes);
+    const entry = control.entries[0]!;
+    const aligned = Math.ceil(entry.length / 8) * 8;
+    expect(aligned).toBeGreaterThan(entry.length);
+    bytes.writeUInt32LE(aligned, entry.location.offset);
+    const report = peCertificatesSchema.parse(parse(bytes));
+    expect(report.entries[0]?.pkcs7).toEqual(entry.pkcs7);
+    expect(report.entries[0]?.length).toBe(aligned);
+    expect(report.entries[0]?.payload.sha256).toBe(
+      createHash("sha256")
+        .update(
+          bytes.subarray(
+            entry.payload.location.offset,
+            entry.location.offset + aligned,
+          ),
+        )
+        .digest("hex"),
+    );
+    bytes[entry.location.offset + aligned - 1] = 1;
+    expect(() => parse(bytes)).toThrow(/ContentInfo has trailing data/);
+  },
+);
+
+it("refuses surplus zero bytes beyond the PE entry alignment gap", () => {
+  const payload = pkcs7SignedDataFixture();
+  expect(() =>
+    parse(
+      peCertificateFixture(false, Buffer.concat([payload, Buffer.alloc(8)])),
+    ),
+  ).toThrow(/ContentInfo has trailing data/);
+});
+
 it("reads BER indefinite constructed ContentInfo and preserves certificate bytes", () => {
   const payload = pkcs7SignedDataIndefiniteEnvelopeFixture();
   const root = readAsn1(payload);
diff --git a/src/native/pe/PeCertificateParser.ts b/src/native/pe/PeCertificateParser.ts
index 5f8cbb1e21..9866a9ee76 100644
--- a/src/native/pe/PeCertificateParser.ts
+++ b/src/native/pe/PeCertificateParser.ts
@@ -9,6 +9,7 @@ import {
   oidName,
   parsePkcs7SignedData,
   PeCertificateAsn1Failure,
+  readAsn1,
 } from "./PeCertificateAsn1.js";
 import { readPeHeaders } from "./PeResourceLayout.js";
 
@@ -115,7 +116,16 @@ export const parsePeCertificates = (
     let pkcs7: PeCertificates["entries"][number]["pkcs7"] = null;
     if (peCertificateTypeName(certificateType) === "pkcs7") {
       try {
-        const parsed = parsePkcs7SignedData(payload);
+        const content = readAsn1(payload);
+        // The PE entry owns alignment outside the ASN.1 ContentInfo. Accept
+        // either uncounted padding or the exact counted zero-padding extent.
+        if (
+          content.end !== payload.length &&
+          (payload.length !== align8(8 + content.end) - 8 ||
+            !payload.subarray(content.end).every((byte) => byte === 0))
+        )
+          throw new PeCertificateAsn1Failure("ContentInfo has trailing data.");
+        const parsed = parsePkcs7SignedData(content);
         teletexStringCompatibilityUsed ||=
           parsed.teletexStringCompatibilityUsed;
         pkcs7 = {