fix: play song without login

reversed cna function for n and signature function, transpiled into kotlin
Malopieds · Oct 28, 2024 · 9b7f0dc · 9b7f0dc
1 parent afb3268
commit 9b7f0dc
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Showing 6 changed files with 102 additions and 6 deletions.
diff --git a/app/src/main/java/com/zionhuang/music/playback/MusicService.kt b/app/src/main/java/com/zionhuang/music/playback/MusicService.kt
@@ -703,9 +703,8 @@ class MusicService : MediaLibraryService(),
                 )
             }
             scope.launch(Dispatchers.IO) { recoverSong(mediaId, playerResponse) }
-
-            songUrlCache[mediaId] = format.url!! to playerResponse.streamingData!!.expiresInSeconds * 1000L
-            dataSpec.withUri(format.url!!.toUri()).subrange(dataSpec.uriPositionOffset, CHUNK_LENGTH)
+            songUrlCache[mediaId] = format.findUrl() to playerResponse.streamingData!!.expiresInSeconds * 1000L
+            dataSpec.withUri(format.findUrl().toUri()).subrange(dataSpec.uriPositionOffset, CHUNK_LENGTH)
         }
     }
 

diff --git a/innertube/src/main/java/com/zionhuang/innertube/InnerTube.kt b/innertube/src/main/java/com/zionhuang/innertube/InnerTube.kt
@@ -5,8 +5,10 @@ import com.zionhuang.innertube.models.Context
 import com.zionhuang.innertube.models.YouTubeClient
 import com.zionhuang.innertube.models.YouTubeLocale
 import com.zionhuang.innertube.models.body.*
+import com.zionhuang.innertube.utils.nSigDecode
 import com.zionhuang.innertube.utils.parseCookieString
 import com.zionhuang.innertube.utils.sha1
+import com.zionhuang.innertube.utils.sigDecode
 import io.ktor.client.*
 import io.ktor.client.engine.okhttp.*
 import io.ktor.client.plugins.*
@@ -244,4 +246,16 @@ class InnerTube {
         ytClient(client, setLogin = true)
         setBody(AccountMenuBody(client.toContext(locale, visitorData)))
     }
+
+    fun decodeCipher(cipher: String): String? {
+        val params = parseQueryString(cipher)
+        val signature = params["s"] ?: return null
+        val signatureParam = params["sp"] ?: return null
+        val url = params["url"]?.let { URLBuilder(it) } ?: return null
+        val n = url.parameters["n"]
+        url.parameters["n"] = nSigDecode(n.toString())
+        url.parameters[signatureParam] = sigDecode(signature)
+        url.parameters["c"] = "ANDROID_MUSIC"
+        return url.toString()
+    }
 }
diff --git a/innertube/src/main/java/com/zionhuang/innertube/YouTube.kt b/innertube/src/main/java/com/zionhuang/innertube/YouTube.kt
@@ -425,8 +425,9 @@ object YouTube {
                 return@runCatching playerResponse
             }
         }
-        playerResponse = innerTube.player(IOS, videoId, playlistId).body<PlayerResponse>()
-        if (playerResponse.playabilityStatus.status == "OK") {
+        playerResponse = innerTube.player(WEB_REMIX, videoId, playlistId).body<PlayerResponse>()
+        if (playerResponse.playabilityStatus.status == "OK" && playerResponse.streamingData?.adaptiveFormats?.any
+            { it.url != null || it.signatureCipher != null } == true) {
             return@runCatching playerResponse
         }
         val safePlayerResponse = innerTube.player(TVHTML5, videoId, playlistId).body<PlayerResponse>()

diff --git a/innertube/src/main/java/com/zionhuang/innertube/models/body/PlayerBody.kt b/innertube/src/main/java/com/zionhuang/innertube/models/body/PlayerBody.kt
@@ -9,4 +9,16 @@ data class PlayerBody(
     val videoId: String,
     val playlistId: String?,
     val contentCheckOk: Boolean = true,
-)
+    val cpn: String? = "wzf9Y0nqz6AUe2Vr", // need some random cpn to get same algorithm for sig
+    val playbackContext: PlaybackContext? = PlaybackContext(ContentPlaybackContext(20019L)),
+) {
+    @Serializable
+    data class PlaybackContext(
+        val contentPlaybackContext: ContentPlaybackContext?,
+    )
+
+    @Serializable
+    data class ContentPlaybackContext(
+        val signatureTimestamp: Long?,
+    )
+}
diff --git a/innertube/src/main/java/com/zionhuang/innertube/models/response/PlayerResponse.kt b/innertube/src/main/java/com/zionhuang/innertube/models/response/PlayerResponse.kt
@@ -1,5 +1,6 @@
 package com.zionhuang.innertube.models.response
 
+import com.zionhuang.innertube.InnerTube
 import com.zionhuang.innertube.models.ResponseContext
 import com.zionhuang.innertube.models.Thumbnails
 import kotlinx.serialization.Serializable
@@ -57,9 +58,12 @@ data class PlayerResponse(
             val audioChannels: Int?,
             val loudnessDb: Double?,
             val lastModified: Long?,
+            val signatureCipher: String?,
         ) {
             val isAudio: Boolean
                 get() = width == null
+
+            fun findUrl() = url ?: signatureCipher?.let { InnerTube().decodeCipher(it) }!!
         }
     }
 

diff --git a/innertube/src/main/java/com/zionhuang/innertube/utils/Utils.kt b/innertube/src/main/java/com/zionhuang/innertube/utils/Utils.kt
@@ -47,3 +47,69 @@ fun String.parseTime(): Int? {
     }
     return null
 }
+
+fun nSigDecode(n: String): String {
+    val step1 =
+        buildString {
+            append(n[8])
+            append(n.substring(2, 8))
+            append(n[1])
+            append(n.substring(9))
+        }
+
+    val step2 =
+        buildString {
+            append(step1.substring(7))
+            append((step1[0] + step1.substring(1, 3).reversed() + step1[3]).reversed())
+            append(step1.substring(4, 7))
+        }
+
+    val step3 = step2.substring(7) + step2.substring(0, 7)
+
+    val step4 =
+        buildString {
+            append(step3[step3.length - 4])
+            append(step3.substring(3, 7))
+            append(step3[2])
+            append(step3.substring(8, 11))
+            append(step3[7])
+            append(step3.takeLast(3))
+            append(step3[1])
+        }
+
+    val step5 = (step4.substring(0, 2) + step4.last() + step4.substring(3, step4.length - 1) + step4[2]).reversed()
+
+    val keyString = "cbrrC5"
+    val charset = ('A'..'Z') + ('a'..'z') + ('0'..'9') + listOf('-', '_')
+    val mutableKeyList = keyString.toMutableList()
+
+    val transformedChars = CharArray(step5.length)
+
+    for (index in step5.indices) {
+        val currentChar = step5[index]
+        val indexInCharset =
+            (charset.indexOf(currentChar) - charset.indexOf(mutableKeyList[index % mutableKeyList.size]) + index + charset.size - index) %
+                charset.size
+        transformedChars[index] = charset[indexInCharset]
+        mutableKeyList[index % mutableKeyList.size] = transformedChars[index]
+    }
+
+    val step6 = String(transformedChars)
+    return step6.dropLast(3).reversed() + step6.takeLast(3)
+}
+
+fun sigDecode(input: String): String {
+    val middleSection = input.substring(3, input.length - 3)
+    val rearranged = (middleSection.take(35) + input[0] + middleSection.drop(36)).reversed()
+    val result =
+        buildString {
+            append("A")
+            append(rearranged.substring(0, 15))
+            append(input[input.length - 2])
+            append(rearranged.substring(16, 34))
+            append(input[input.length - 3])
+            append(rearranged.substring(35))
+            append(input[38])
+        }
+    return result
+}