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Add a fallback ContentProtection implementation for known DRM schemes (#161)
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‎readium/streamer/CHANGELOG.md‎

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@@ -9,6 +9,8 @@ All notable changes to this project will be documented in this file.
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### Added
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* EPUB publications implement a `SearchService` to search through the content.
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* Known DRM schemes (LCP and Adobe ADEPT) are now sniffed by the `Streamer`, when no registered `ContentProtection` supports them.
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* This is helpful to present an error message when the user attempts to open a protected publication not supported by the app.
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### Changed
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‎readium/streamer/r2-streamer/src/main/java/org/readium/r2/streamer/Streamer.kt‎

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@@ -22,14 +22,14 @@ import org.readium.r2.shared.util.http.DefaultHttpClient
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import org.readium.r2.shared.util.logging.WarningLogger
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import org.readium.r2.shared.util.mediatype.MediaType
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import org.readium.r2.shared.util.pdf.PdfDocumentFactory
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import org.readium.r2.streamer.parser.FallbackContentProtection
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import org.readium.r2.streamer.parser.audio.AudioParser
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import org.readium.r2.streamer.parser.epub.EpubParser
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import org.readium.r2.streamer.parser.epub.setLayoutStyle
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import org.readium.r2.streamer.parser.image.ImageParser
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import org.readium.r2.streamer.parser.pdf.PdfParser
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import org.readium.r2.streamer.parser.pdf.PdfiumPdfDocumentFactory
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import org.readium.r2.streamer.parser.readium.ReadiumWebPubParser
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import kotlin.Exception
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internal typealias PublicationTry<SuccessT> = Try<SuccessT, Publication.OpeningException>
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@@ -55,13 +55,16 @@ class Streamer constructor(
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context: Context,
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parsers: List<PublicationParser> = emptyList(),
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ignoreDefaultParsers: Boolean = false,
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private val contentProtections: List<ContentProtection> = emptyList(),
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contentProtections: List<ContentProtection> = emptyList(),
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private val archiveFactory: ArchiveFactory = DefaultArchiveFactory(),
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private val pdfFactory: PdfDocumentFactory = DefaultPdfDocumentFactory(context),
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private val httpClient: DefaultHttpClient = DefaultHttpClient(),
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private val onCreatePublication: Publication.Builder.() -> Unit = {}
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) {
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private val contentProtections: List<ContentProtection> =
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contentProtections + listOf(FallbackContentProtection())
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/**
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* Parses a [Publication] from the given asset.
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*

‎readium/streamer/r2-streamer/src/main/java/org/readium/r2/streamer/parser/FallbackContentProtection.kt‎

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/*
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* Copyright 2021 Readium Foundation. All rights reserved.
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* Use of this source code is governed by the BSD-style license
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* available in the top-level LICENSE file of the project.
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*/
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package org.readium.r2.streamer.parser
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import org.readium.r2.shared.UserException
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import org.readium.r2.shared.fetcher.Fetcher
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import org.readium.r2.shared.publication.ContentProtection
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import org.readium.r2.shared.publication.ContentProtection.Scheme
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import org.readium.r2.shared.publication.Publication
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import org.readium.r2.shared.publication.asset.PublicationAsset
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import org.readium.r2.shared.publication.services.ContentProtectionService
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import org.readium.r2.shared.publication.services.contentProtectionServiceFactory
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import org.readium.r2.shared.util.Try
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import org.readium.r2.shared.util.mediatype.MediaType
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import org.readium.r2.streamer.extensions.readAsJsonOrNull
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import org.readium.r2.streamer.extensions.readAsXmlOrNull
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import org.readium.r2.streamer.parser.epub.EncryptionParser
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import org.readium.r2.streamer.parser.epub.Namespaces
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/**
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* [ContentProtection] implementation used as a fallback by the Streamer to detect known DRM
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* schemes (e.g. LCP or ADEPT), if they are not supported by the app.
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*/
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internal class FallbackContentProtection : ContentProtection {
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class Service(override val scheme: Scheme?) : ContentProtectionService {
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override val isRestricted: Boolean = true
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override val credentials: String? = null
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override val rights = ContentProtectionService.UserRights.AllRestricted
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override val error: UserException = ContentProtection.Exception.SchemeNotSupported(scheme)
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companion object {
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fun createFactory(scheme: Scheme?): (Publication.Service.Context) -> Service =
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{ Service(scheme) }
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}
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}
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override suspend fun open(
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asset: PublicationAsset,
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fetcher: Fetcher,
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credentials: String?,
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allowUserInteraction: Boolean,
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sender: Any?
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): Try<ContentProtection.ProtectedAsset, Publication.OpeningException>? {
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val scheme: Scheme = sniffScheme(fetcher, asset.mediaType())
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?: return null
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val protectedFile = ContentProtection.ProtectedAsset(
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asset = asset,
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fetcher = fetcher,
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onCreatePublication = {
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servicesBuilder.contentProtectionServiceFactory = Service.createFactory(scheme)
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}
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)
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return Try.success(protectedFile)
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}
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internal suspend fun sniffScheme(fetcher: Fetcher, mediaType: MediaType): Scheme? =
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when {
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fetcher.readAsJsonOrNull("/license.lcpl") != null ->
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Scheme.Lcp
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mediaType.matches(MediaType.EPUB) -> {
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val rightsXml = fetcher.readAsXmlOrNull("/META-INF/rights.xml")
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val encryptionXml = fetcher.readAsXmlOrNull("/META-INF/encryption.xml")
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val encryption = encryptionXml?.let { EncryptionParser.parse(it) }
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when {
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(
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fetcher.readAsJsonOrNull("/META-INF/license.lcpl") != null ||
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encryption?.any { it.value.scheme == "http://readium.org/2014/01/lcp" } == true
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) -> Scheme.Lcp
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(
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encryptionXml != null && (
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rightsXml?.namespace == "http://ns.adobe.com/adept" ||
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encryptionXml
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.get("EncryptedData", Namespaces.ENC)
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.flatMap { it.get("KeyInfo", Namespaces.SIG) }
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.flatMap { it.get("resource", "http://ns.adobe.com/adept")}
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.isNotEmpty()
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)
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) -> Scheme.Adept
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// A file with only obfuscated fonts might still have an `encryption.xml` file.
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// To make sure that we don't lock a readable publication, we ignore unknown
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// encryption.xml schemes.
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else -> null
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}
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}
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else -> null
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}
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}

‎readium/streamer/r2-streamer/src/test/java/org/readium/r2/streamer/parser/FallbackContentProtectionTest.kt‎

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package org.readium.r2.streamer.parser
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import kotlinx.coroutines.runBlocking
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import org.junit.Assert.*
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import org.junit.Test
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import org.junit.runner.RunWith
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import org.readium.r2.shared.fetcher.FailureResource
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import org.readium.r2.shared.fetcher.Fetcher
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import org.readium.r2.shared.fetcher.Resource
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import org.readium.r2.shared.fetcher.StringResource
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import org.readium.r2.shared.publication.ContentProtection.Scheme
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import org.readium.r2.shared.publication.Link
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import org.readium.r2.shared.util.mediatype.MediaType
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import org.robolectric.RobolectricTestRunner
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@RunWith(RobolectricTestRunner::class)
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class FallbackContentProtectionTest {
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@Test
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fun `Sniff no content protection`() {
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assertNull(sniff(mediaType = MediaType.EPUB, resources = emptyMap()))
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}
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@Test
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fun `Sniff EPUB with empty encryption xml`() {
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assertNull(sniff(mediaType = MediaType.EPUB, resources = mapOf(
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"/META-INF/encryption.xml" to """<?xml version='1.0' encoding='utf-8'?><encryption xmlns="urn:oasis:names:tc:opendocument:xmlns:container" xmlns:enc="http://www.w3.org/2001/04/xmlenc#"></encryption>"""
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)))
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}
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@Test
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fun `Sniff LCP protected package`() {
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assertEquals(Scheme.Lcp, sniff(
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mediaType = MediaType.ZIP,
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resources = mapOf(
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"/license.lcpl" to "{}"
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)
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))
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}
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@Test
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fun `Sniff LCP protected EPUB`() {
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assertEquals(Scheme.Lcp, sniff(
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mediaType = MediaType.EPUB,
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resources = mapOf(
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"/META-INF/license.lcpl" to "{}"
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)
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))
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}
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@Test
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fun `Sniff LCP protected EPUB missing the license`() {
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assertEquals(Scheme.Lcp, sniff(
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mediaType = MediaType.EPUB,
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resources = mapOf(
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"/META-INF/encryption.xml" to """<?xml version="1.0" encoding="UTF-8"?>
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<encryption xmlns="urn:oasis:names:tc:opendocument:xmlns:container">
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<EncryptedData xmlns="http://www.w3.org/2001/04/xmlenc#">
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<EncryptionMethod xmlns="http://www.w3.org/2001/04/xmlenc#" Algorithm="http://www.w3.org/2001/04/xmlenc#aes256-cbc"></EncryptionMethod>
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<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
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<RetrievalMethod xmlns="http://www.w3.org/2000/09/xmldsig#" URI="license.lcpl#/encryption/content_key" Type="http://readium.org/2014/01/lcp#EncryptedContentKey"></RetrievalMethod>
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</KeyInfo>
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<CipherData xmlns="http://www.w3.org/2001/04/xmlenc#">
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<CipherReference xmlns="http://www.w3.org/2001/04/xmlenc#" URI="OPS/chapter_001.xhtml"></CipherReference>
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</CipherData>
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<EncryptionProperties xmlns="http://www.w3.org/2001/04/xmlenc#">
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<EncryptionProperty xmlns="http://www.w3.org/2001/04/xmlenc#">
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<Compression xmlns="http://www.idpf.org/2016/encryption#compression" Method="8" OriginalLength="13877"></Compression>
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</EncryptionProperty>
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</EncryptionProperties>
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</EncryptedData>
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</encryption>"""
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)
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))
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}
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@Test
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fun `Sniff Adobe ADEPT`() {
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assertEquals(Scheme.Adept, sniff(
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mediaType = MediaType.EPUB,
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resources = mapOf(
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"/META-INF/encryption.xml" to """<?xml version="1.0"?><encryption xmlns="urn:oasis:names:tc:opendocument:xmlns:container">
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<EncryptedData xmlns="http://www.w3.org/2001/04/xmlenc#">
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<EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes128-cbc"></EncryptionMethod>
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<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
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<resource xmlns="http://ns.adobe.com/adept">urn:uuid:2c43729c-b985-4531-8e86-ae75ce5e5da9</resource>
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</KeyInfo>
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<CipherData>
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<CipherReference URI="OEBPS/stylesheet.css"></CipherReference>
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</CipherData>
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</EncryptedData>
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</encryption>"""
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)
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))
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}
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@Test
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fun `Sniff Adobe ADEPT from rights xml`() {
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assertEquals(Scheme.Adept, sniff(
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mediaType = MediaType.EPUB,
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resources = mapOf(
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"/META-INF/encryption.xml" to """<?xml version='1.0' encoding='utf-8'?><encryption xmlns="urn:oasis:names:tc:opendocument:xmlns:container" xmlns:enc="http://www.w3.org/2001/04/xmlenc#"></encryption>""",
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"/META-INF/rights.xml" to """<?xml version="1.0"?><adept:rights xmlns:adept="http://ns.adobe.com/adept"></adept:rights>"""
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)
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))
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}
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private fun sniff(mediaType: MediaType, resources: Map<String, String>): Scheme? = runBlocking {
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FallbackContentProtection().sniffScheme(
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fetcher = TestFetcher(resources),
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mediaType = mediaType
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)
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}
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}
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class TestFetcher(private val resources: Map<String, String> = emptyMap()) : Fetcher {
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override suspend fun links(): List<Link> = resources.map { Link(href = it.key) }
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override fun get(link: Link): Resource =
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resources[link.href]?.let { StringResource(link, it) }
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?: FailureResource(link, Resource.Exception.NotFound())
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override suspend fun close() {}
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}

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