use apkdiff from amber repo

Dockerfile

@@ -84,9 +84,7 @@ RUN mkdir -p /tmp/signed /tmp/release && \
     cd /tmp/signed && zip -qr /app/signed-stripped.apk . && \
     cd /tmp/release && zip -qr /release_apk/official-stripped.apk .
 
-# Download apkdiff.py from Signal's reproducible builds branch
-RUN wget -q https://raw.githubusercontent.com/signalapp/Signal-Android/refs/heads/main/reproducible-builds/apkdiff/apkdiff.py \
-    -O /usr/local/bin/apkdiff.py && chmod +x /usr/local/bin/apkdiff.py
+RUN chmod +x apkdiff.py && cp apkdiff.py /usr/local/bin/apkdiff.py
 
 # Compare the stripped APKs
 CMD sh -c "python3 /usr/local/bin/apkdiff.py /release_apk/official-stripped.apk /app/signed-stripped.apk"

apkdiff.py

@@ -0,0 +1,84 @@
+#! /usr/bin/env python3
+
+import sys
+from zipfile import ZipFile
+
+
+class ApkDiff:
+    IGNORE_FILES = [
+        # Related to app signing. Not expected to be present in unsigned builds. Doesn't affect app code.
+        "META-INF/MANIFEST.MF",
+        "META-INF/CERTIFIC.SF",
+        "META-INF/CERTIFIC.RSA",
+        "META-INF/TEXTSECU.SF",
+        "META-INF/TEXTSECU.RSA",
+        "META-INF/BNDLTOOL.SF",
+        "META-INF/BNDLTOOL.RSA",
+        "META-INF/code_transparency_signed.jwt",
+        "stamp-cert-sha256"
+    ]
+
+    def compare(self, firstApk, secondApk):
+        firstZip = ZipFile(firstApk, 'r')
+        secondZip = ZipFile(secondApk, 'r')
+
+        return self.compareEntryNames(firstZip, secondZip) and self.compareEntryContents(firstZip, secondZip) == True
+
+    def compareEntryNames(self, firstZip, secondZip):
+        firstNameListSorted = sorted(firstZip.namelist())
+        secondNameListSorted = sorted(secondZip.namelist())
+
+        for ignoreFile in self.IGNORE_FILES:
+            while ignoreFile in firstNameListSorted:
+                firstNameListSorted.remove(ignoreFile)
+            while ignoreFile in secondNameListSorted:
+                secondNameListSorted.remove(ignoreFile)
+
+        if len(firstNameListSorted) != len(secondNameListSorted):
+            print("Manifest lengths differ!")
+
+        for (firstEntryName, secondEntryName) in zip(firstNameListSorted, secondNameListSorted):
+            if firstEntryName != secondEntryName:
+                print("Sorted manifests don't match, %s vs %s" % (firstEntryName, secondEntryName))
+                return False
+
+        return True
+
+    def compareEntryContents(self, firstZip, secondZip):
+        firstInfoList = list(filter(lambda info: info.filename not in self.IGNORE_FILES, firstZip.infolist()))
+        secondInfoList = list(filter(lambda info: info.filename not in self.IGNORE_FILES, secondZip.infolist()))
+
+        if len(firstInfoList) != len(secondInfoList):
+            print("APK info lists of different length!")
+            return False
+
+        success = True
+        for firstEntryInfo in firstInfoList:
+            for secondEntryInfo in list(secondInfoList):
+                if firstEntryInfo.filename == secondEntryInfo.filename:
+                    firstEntryBytes = firstZip.read(firstEntryInfo.filename)
+                    secondEntryBytes = secondZip.read(secondEntryInfo.filename)
+
+                    if firstEntryBytes != secondEntryBytes:
+                        firstZip.extract(firstEntryInfo, "mismatches/first")
+                        secondZip.extract(secondEntryInfo, "mismatches/second")
+                        print("APKs differ on file %s! Files extracted to the mismatches/ directory." % (firstEntryInfo.filename))
+                        success = False
+
+                    secondInfoList.remove(secondEntryInfo)
+                    break
+
+        return success
+
+
+if __name__ == '__main__':
+    if len(sys.argv) != 3:
+        print("Usage: apkdiff <pathToFirstApk> <pathToSecondApk>")
+        sys.exit(1)
+
+    if ApkDiff().compare(sys.argv[1], sys.argv[2]):
+        print("APKs match!")
+        sys.exit(0)
+    else:
+        print("APKs don't match!")
+        sys.exit(1)