fix(fit): preserve leading U+FEFF in property strings (#8083)

src/artifacts/fit/FitStructure.test.ts

@@ -62,6 +62,40 @@ const singleImage = (properties: Record<string, Buffer>): Buffer =>
   });
 
 describe("FIT image facts", () => {
+  it("preserves a leading U+FEFF in string facts and configuration references", () => {
+    const structure = read(
+      fitFixture({
+        images: [kernel({ description: dtString("\uFEFFkernel description") })],
+        configurations: {
+          name: "configurations",
+          properties: { default: dtString("\uFEFFconf-1") },
+          children: [
+            {
+              name: "conf-1",
+              properties: {
+                kernel: dtString("\uFEFFkernel"),
+                loadables: dtString("kernel\0\uFEFFkernel"),
+              },
+            },
+          ],
+        },
+      }),
+    );
+    expect(structure.images[0]?.metadata.description).toBe(
+      "\uFEFFkernel description",
+    );
+    expect(structure.metadata.default_configuration).toBe("\uFEFFconf-1");
+    expect(structure.metadata.configurations[0]).toMatchObject({
+      name: "conf-1",
+      kernel: ["\uFEFFkernel"],
+      loadables: ["kernel", "\uFEFFkernel"],
+      unresolved_reference_count: 2,
+    });
+    expect(structure.limitations).toContain(
+      "/configurations: default \uFEFFconf-1 names no configuration",
+    );
+  });
+
   it("decodes embedded root and image facts with property ranges", () => {
     const structure = read(FIT_EMBEDDED);
     expect(structure.metadata).toMatchObject({

src/artifacts/fit/FitStructure.ts

@@ -88,7 +88,8 @@ const propertyOf = (node: FitNode, name: string): FitProperty | undefined =>
 const valueOf = (fdt: Buffer, property: FitProperty): Buffer =>
   fdt.subarray(property.offset, property.offset + property.bytes);
 
-const utf8 = new TextDecoder("utf-8", { fatal: true });
+// A property value is data: a leading U+FEFF is not a file encoding signature.
+const utf8 = new TextDecoder("utf-8", { fatal: true, ignoreBOM: true });
 const nulCount = (raw: Buffer): number => {
   let count = 0;
   for (const byte of raw) if (byte === 0) count += 1;

tests/acceptance/fitImageCli.test.ts

@@ -1,3 +1,4 @@
+import { createHash } from "node:crypto";
 import { readFile, rm, writeFile } from "node:fs/promises";
 import { join } from "node:path";
 import { expect, onTestFinished } from "vitest";
@@ -413,3 +414,54 @@ cliTest.for([
       ?.declared_size,
   ).toBe(item.bytes);
 });
+
+cliTest.for([
+  { algo: "sha256", verified: 1, unverified: 0 },
+  { algo: "Xsha256", verified: 0, unverified: 1 },
+  { algo: "\uFEFFsha256", verified: 0, unverified: 1 },
+])(
+  "preserves the exact FIT hash algorithm $algo through the CLI",
+  async ({ algo, verified, unverified }, { cli }) => {
+    const directory = await createTestTempDirectory("rea-fit-algorithm-cli-");
+    const source = join(directory, "boot.itb");
+    await writeFile(
+      source,
+      fitFixture({
+        images: [
+          {
+            name: "kernel",
+            data: FIT_KERNEL,
+            children: [
+              {
+                name: "hash-1",
+                properties: {
+                  algo: dtString(algo),
+                  value: createHash("sha256").update(FIT_KERNEL).digest(),
+                },
+              },
+            ],
+          },
+        ],
+      }),
+    );
+    const inspected = await cli.run({
+      arguments: ["inspect-artifact", source, "--json"],
+    });
+    expect(inspected.exitCode, inspected.stdout + inspected.stderr).toBe(0);
+    const inspection = artifactInspectionResultSchema.parse(
+      parseEvidence(inspected.json).normalized_result,
+    );
+    const graph = artifactInventoryResultSchema.parse(
+      inspection.substeps[0]?.evidence.normalized_result,
+    );
+    expect(
+      graph.occurrences.find((row) => row.logical_path === "images/kernel.bin")
+        ?.format_metadata,
+    ).toMatchObject({
+      kind: "fit-image",
+      hash_algorithms: [algo],
+      hashes_verified: verified,
+      hashes_unverified: unverified,
+    });
+  },
+);