K2GO-554 feat(download): app-side rootfs signature verify

.github/workflows/bake-rootfs.yml

@@ -265,8 +265,20 @@ jobs:
             if printf '%s\n' "$members" | grep -Eq '^/|(^|/)\.\.(/|$)'; then
               echo "FATAL: $tb has an unsafe member (absolute or ..); refusing to sign" >&2; exit 1
             fi
-            echo ">> sign $tb"
-            minisign -S -H -s "$KEY" -m "$tb" -t "k2go rootfs ${tb%.tar.gz}" </dev/null
+            # ADR Amendment 1 (A1): the trusted comment is a manifest that the app authenticates with
+            # the global signature alone, so the phone never hashes the tarball for identity. The
+            # sha-256 is recomputed here: a stale .sha256 or .meta4 fails the bake instead of shipping
+            # a manifest that the app rejects.
+            sha="$(sha256sum "$tb" | awk '{print $1}')"
+            [ "$sha" = "$(awk '{print $1}' "${tb}.sha256")" ] \
+              || { echo "FATAL: ${tb}.sha256 does not match $tb" >&2; exit 1; }
+            { [ -f "${tb}.meta4" ] && grep -q "$sha" "${tb}.meta4"; } \
+              || { echo "FATAL: ${tb}.meta4 is missing or does not carry the sha-256 of $tb" >&2; exit 1; }
+            manifest="k2go-rootfs v1 file=$tb size=$(stat -c%s "$tb") sha256=$sha meta4=$(sha256sum "${tb}.meta4" | awk '{print $1}')"
+            echo ">> sign $tb: $manifest"
+            minisign -S -H -s "$KEY" -m "$tb" -t "$manifest" </dev/null
+            [ "$(sed -n 3p "${tb}.minisig")" = "trusted comment: $manifest" ] \
+              || { echo "FATAL: ${tb}.minisig does not carry the manifest" >&2; exit 1; }
             # The app verifier accepts ONLY the prehashed form (algorithm tag "ED"); assert it here.
             tag="$(sed -n 2p "${tb}.minisig" | base64 -d 2>/dev/null | head -c2 || true)"
             [ "$tag" = "ED" ] || { echo "FATAL: ${tb}.minisig is not prehashed (tag '$tag', want ED)" >&2; exit 1; }

CLAUDE.md

@@ -301,6 +301,18 @@ Enforces the ABI-separation policy + rootfs sanity at the two untrusted gates.
   `tools/rootfs-builder/iiab_tree_hash.py`), the in-app backup-writer emitting both members, and
   the arbitrary-file attack-vector analysis.
 
+**Slice (PR #760): signed rootfs trust (`org.appdevforall.k2go.download`)**
+K2GO-554: an official signed download skips the archive listing pass.
+
+- `domain/RootfsManifest` (pure JVM): strict parse of the manifest in the minisign
+  trusted comment, and `judge` = integrity (bytes passed the SHA-256 check) + identity
+  (authentic manifest names this file, size, sha-256) + the requested tier/ABI.
+  `deploy/domain/ExtractProgress.trustedStreamTotal` lifts the gzip ISIZE past 4 GiB.
+- `data/MinisignVerifier` checks only the global signature (no read of the tarball);
+  `data/TrustedSigningKeys` pins the public key.
+- **Legacy seam:** `Aria2Manager.signedManifestVouchesFor` (after DownloadVerifier) ->
+  `InstallService` -> `TarExtractor` trusted single pass. ADR-K2GO-554 (Amendment 1).
+
 **Legacy (NOT yet layered)**: the redesign retired the original god classes
 `MainActivity` and `DeployFragment` (they no longer exist; DONE-slice seams above
 that still name them are pre-redesign records). The current god-tier classes,

controller/app/build.gradle

@@ -323,6 +323,10 @@ dependencies {
     implementation 'com.journeyapps:zxing-android-embedded:4.3.0'
     implementation 'com.github.MuntashirAkon:libadb-android:3.1.1'
     implementation 'org.conscrypt:conscrypt-android:2.5.3'
+    // K2GO-554: Ed25519 check of the minisign signature on the rootfs manifest (lightweight API only,
+    // R8 strips the rest). Already a transitive dependency; declared because the app uses it directly.
+    // jdk15to18 variant for Android (no multi-release jar).
+    implementation 'org.bouncycastle:bcprov-jdk15to18:1.78.1'
     implementation 'com.github.PhilJay:MPAndroidChart:v3.1.0'
     implementation 'org.nanohttpd:nanohttpd:2.3.1'
 

controller/app/src/androidTest/assets/minisign/spike.pub

@@ -0,0 +1,2 @@
+untrusted comment: minisign public key D64948BB183F9048
+RWRIkD8Yu0hJ1rxv2Z+ZRMmTM63cAhHeJ1JyneNfhD1cqoGA6ONj0OXj

controller/app/src/androidTest/assets/minisign/test.bin.minisig

@@ -0,0 +1,4 @@
+untrusted comment: signature from minisign secret key
+RURIkD8Yu0hJ1iQrOUgUjV9jpdRLo9OcM0jKEeXSCRss2ifGEKo6DYQE6z3tBCFu8bZKaFbodZwo3UX6A1f0CXkf8PW7WncypA8=
+trusted comment: spike demo trusted comment
+9NYHyKiZwga7qie0aR1cB34HCM7ez9/zDSkDnGs8EiQ5gcqTIQzCQDPdRddbAv3bJpOEguV+AxeQrTYUVT1jBw==

controller/app/src/androidTest/java/org/appdevforall/k2go/download/data/MinisignVerifierInstrumentedTest.java

@@ -0,0 +1,58 @@
+package org.appdevforall.k2go.download.data;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+
+import android.content.Context;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import androidx.test.platform.app.InstrumentationRegistry;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/**
+ * K2GO-554: run the trusted-comment check on-device, inside K2Go, on the real Android runtime
+ * (ART, the app's dependency graph, BouncyCastle on device). The vector is produced by minisign
+ * on the host and bundled as an androidTest asset.
+ */
+@RunWith(AndroidJUnit4.class)
+public class MinisignVerifierInstrumentedTest {
+
+    private Context testCtx() {
+        return InstrumentationRegistry.getInstrumentation().getContext();
+    }
+
+    private String readAsset(String name) throws IOException {
+        try (InputStream in = testCtx().getAssets().open(name);
+             ByteArrayOutputStream bos = new ByteArrayOutputStream()) {
+            byte[] b = new byte[4096];
+            int n;
+            while ((n = in.read(b)) > 0) {
+                bos.write(b, 0, n);
+            }
+            return new String(bos.toByteArray(), StandardCharsets.UTF_8);
+        }
+    }
+
+    @Test
+    public void authenticatesOnDevice() throws Exception {
+        TrustedSigningKeys keys = TrustedSigningKeys.of(readAsset("minisign/spike.pub"));
+        assertNotNull("a minisign signature from a pinned key must authenticate on device",
+                MinisignVerifier.authenticatedComment(readAsset("minisign/test.bin.minisig"), keys));
+    }
+
+    @Test
+    public void rejectsEditedCommentOnDevice() throws Exception {
+        TrustedSigningKeys keys = TrustedSigningKeys.of(readAsset("minisign/spike.pub"));
+        String[] lines = readAsset("minisign/test.bin.minisig").replace("\r\n", "\n").split("\n");
+        lines[2] = lines[2] + "x";
+        assertNull("an edited trusted comment must not authenticate on device",
+                MinisignVerifier.authenticatedComment(String.join("\n", lines) + "\n", keys));
+    }
+}

controller/app/src/main/java/org/appdevforall/k2go/Aria2Manager.java

@@ -27,13 +27,18 @@
 import org.appdevforall.k2go.download.domain.MetalinkSplit;
 import org.appdevforall.k2go.download.domain.MetalinkFile;
 import org.appdevforall.k2go.download.domain.DownloadVerifier;
+import org.appdevforall.k2go.download.domain.RootfsManifest;
+import org.appdevforall.k2go.download.data.MinisignVerifier;
+import org.appdevforall.k2go.download.data.TrustedSigningKeys;
 import org.appdevforall.k2go.download.domain.ByteToken;
 import org.appdevforall.k2go.download.domain.DownloadEta;
 import org.appdevforall.k2go.download.domain.Aria2ProgressLine;
 
 public class Aria2Manager {
 
     private static final String TAG = "IIAB-Aria2-Native";
+    /** K2GO-554: upper bound for a signature sidecar read; a minisig is about 300 bytes. */
+    private static final int SIDECAR_MAX_BYTES = 16 * 1024;
     /**
      * ADFA-4895: volatile for the same reason as the flag below, and it is the more important of
      * the two. It is assigned on the download thread and read by {@code stopDownload()} on the
@@ -108,6 +113,15 @@ default void onProgress(int percentage, String speed, String eta,
             onProgress(percentage, speed, eta);
         }
         void onComplete(String downloadPath);
+        /**
+         * K2GO-554 D6: the download completed AND {@code trusted} = it was verified against the .meta4
+         * and carries a signature from a pinned key. A default forwards to the single-arg form, so callers
+         * that do not care about trust are untouched; the install path overrides this to skip the listing
+         * pass on a trusted artifact.
+         */
+        default void onComplete(String downloadPath, boolean trusted) {
+            onComplete(downloadPath);
+        }
         void onError(String error);
 
         /**
@@ -146,6 +160,17 @@ default void onPaused() { }
     }
 
     public void startDownload(Context context, String url, DownloadListener listener) {
+        startDownload(context, url, null, listener);
+    }
+
+    /**
+     * K2GO-554: {@code signedTarget} non-null = after the integrity gate passes, also look for an
+     * official signed manifest for this tier and ABI next to the artifact, and report trust via
+     * {@link DownloadListener#onComplete(String, boolean)}. Only the rootfs install opts in; other
+     * downloads pass null, so they pay no sidecar lookups.
+     */
+    public void startDownload(Context context, String url, RootfsManifest.Target signedTarget,
+                              DownloadListener listener) {
         stopRequest = Stop.NONE;
         Handler mainHandler = new Handler(Looper.getMainLooper());
 
@@ -213,7 +238,10 @@ public void startDownload(Context context, String url, DownloadListener listener
                             // Fully downloaded and verified (no control file) -> skip download.
                             pruneStaleSiblings(downloadDir, mf.fileName());
                             Log.d(TAG, "Reusing already-verified artifact: " + mf.fileName() + " (skipping download)");
-                            mainHandler.post(() -> listener.onComplete(downloadDir.getAbsolutePath()));
+                            // This branch runs only after DownloadVerifier returned OK above.
+                            final boolean trusted = signedTarget != null
+                                    && signedManifestVouchesFor(mf, true, signedTarget);
+                            mainHandler.post(() -> listener.onComplete(downloadDir.getAbsolutePath(), trusted));
                             return;
                         } else if (len > mf.sizeBytes()) {
                             // Larger than the declared size: no piece map can match it. Discard.
@@ -502,6 +530,7 @@ public void startDownload(Context context, String url, DownloadListener listener
                 // verify the artifact against the .meta4 <size> + file-level SHA-256
                 // before reporting success, so an incomplete/corrupt/stale file cannot
                 // reach extraction.
+                boolean bytesVerified = false;
                 if (mf != null && mf.canVerify()) {
                     File artifact = new File(downloadDir, mf.fileName());
                     DownloadVerifier.Result vr = DownloadVerifier.verify(artifact, mf.sizeBytes(), mf.sha256());
@@ -517,8 +546,11 @@ public void startDownload(Context context, String url, DownloadListener listener
                     }
                     pruneStaleSiblings(downloadDir, mf.fileName());
                     Log.d(TAG, "Integrity verified: " + mf.fileName() + " (" + mf.sizeBytes() + " bytes, sha-256 OK)");
+                    bytesVerified = true;
                 }
-                mainHandler.post(() -> listener.onComplete(downloadDir.getAbsolutePath()));
+                final boolean trusted = signedTarget != null
+                        && signedManifestVouchesFor(mf, bytesVerified, signedTarget);
+                mainHandler.post(() -> listener.onComplete(downloadDir.getAbsolutePath(), trusted));
 
             } catch (Exception e) {
                 // The stream was closed by our own stop; a deliberate stop is not a fatal error,
@@ -603,6 +635,70 @@ private MetalinkFile fetchMetalink(String url) {
         }
     }
 
+    /**
+     * K2GO-554 (ADR Amendment 1, A2/A3): is this an OFFICIAL artifact we may fast-extract? True only when
+     * {@code bytesVerified} (DownloadVerifier returned OK against {@code mf}) and the {@code .minisig}
+     * next to the tarball carries a manifest, authenticated by a pinned key, that names this file, size
+     * and sha-256 for the expected tier and ABI. The rule lives in {@link RootfsManifest#judge}. No
+     * second read of the file happens here. Fail closed: unverified bytes, no sidecar, a bad signature,
+     * no manifest, a mismatch, or another tier/ABI returns false, and the caller keeps the full path.
+     */
+    private boolean signedManifestVouchesFor(MetalinkFile mf, boolean bytesVerified,
+                                             RootfsManifest.Target expected) {
+        if (mf == null) return false;
+        if (!bytesVerified) {
+            Log.i(TAG, "Signature check " + mf.fileName() + ": " + RootfsManifest.Verdict.BYTES_NOT_VERIFIED);
+            return false;
+        }
+        for (String mirror : mf.mirrors()) {
+            String sig = fetchText(mirror + ".minisig");
+            if (sig == null) continue;
+            // The sidecar exists on this mirror, so its verdict is final. Do not try other mirrors
+            // hoping for a different answer.
+            RootfsManifest.Verdict v = RootfsManifest.judge(true,
+                    MinisignVerifier.authenticatedComment(sig, TrustedSigningKeys.PRODUCTION),
+                    mf.fileName(), mf.sizeBytes(), mf.sha256(), expected);
+            Log.i(TAG, "Signature check " + mf.fileName() + ": " + v);
+            return v == RootfsManifest.Verdict.TRUSTED;
+        }
+        Log.i(TAG, "Signature check " + mf.fileName() + ": no .minisig");
+        return false;
+    }
+
+    /**
+     * K2GO-554 D6: GET a small text sidecar (the .minisig, about 300 bytes), or null on any non-200,
+     * error, or a body above {@code SIDECAR_MAX_BYTES}. The mirror URL comes from the unsigned meta4,
+     * so the read is capped: a hostile host cannot stream an endless body into memory.
+     */
+    private String fetchText(String url) {
+        HttpURLConnection conn = null;
+        try {
+            conn = (HttpURLConnection) new URL(url).openConnection();
+            conn.setConnectTimeout(10000);
+            conn.setReadTimeout(10000);
+            conn.setRequestProperty("User-Agent", "K2Go");
+            if (conn.getResponseCode() != 200) {
+                return null;
+            }
+            try (InputStream in = conn.getInputStream()) {
+                java.io.ByteArrayOutputStream bos = new java.io.ByteArrayOutputStream();
+                byte[] buf = new byte[4096];
+                int r;
+                while ((r = in.read(buf)) != -1) {
+                    bos.write(buf, 0, r);
+                    if (bos.size() > SIDECAR_MAX_BYTES) {
+                        return null;
+                    }
+                }
+                return new String(bos.toByteArray(), java.nio.charset.StandardCharsets.UTF_8);
+            }
+        } catch (Exception e) {
+            return null;
+        } finally {
+            if (conn != null) conn.disconnect();
+        }
+    }
+
     /**
      * ADFA-5119: is there a partial download here, asked of the disk alone?
      *