YakshaScans: Fix 403 Error (#6832)

add js challenge interceptor

src/en/yakshascans/build.gradle

@@ -3,7 +3,7 @@ ext {
     extClass = '.YakshaScans'
     themePkg = 'madara'
     baseUrl = 'https://yakshascans.com'
-    overrideVersionCode = 0
+    overrideVersionCode = 1
     isNsfw = true
 }
 

src/en/yakshascans/src/eu/kanade/tachiyomi/extension/en/yakshascans/YakshaScans.kt

@@ -1,8 +1,15 @@
 package eu.kanade.tachiyomi.extension.en.yakshascans
 
 import eu.kanade.tachiyomi.multisrc.madara.Madara
+import eu.kanade.tachiyomi.network.GET
+import eu.kanade.tachiyomi.network.POST
 import eu.kanade.tachiyomi.network.interceptor.rateLimit
+import okhttp3.FormBody
+import okhttp3.Interceptor
 import okhttp3.OkHttpClient
+import okhttp3.Response
+import java.io.IOException
+import java.security.MessageDigest
 
 class YakshaScans : Madara(
     "YakshaScans",
@@ -12,8 +19,45 @@ class YakshaScans : Madara(
 
     override val client: OkHttpClient = super.client.newBuilder()
         .rateLimit(1)
+        .addInterceptor(::jsChallengeInterceptor)
         .build()
 
+    private fun jsChallengeInterceptor(chain: Interceptor.Chain): Response {
+        val request = chain.request()
+        val origRes = chain.proceed(request)
+        if (origRes.code != 403) return origRes
+        origRes.close()
+
+        // Same delay as the source
+        Thread.sleep(3000L)
+        val token = fetchToken(chain).sha256()
+
+        val body = FormBody.Builder().add("challenge", token).build()
+        val challengeReq = POST("$baseUrl/hcdn-cgi/jschallenge-validate", headers, body = body)
+
+        val challengeResponse = chain.proceed(challengeReq)
+        challengeResponse.close()
+        if (challengeResponse.code != 200) throw IOException("Failed to bypass js challenge!")
+
+        return chain.proceed(request)
+    }
+
+    private tailrec fun fetchToken(chain: Interceptor.Chain, attempt: Int = 0): String {
+        if (attempt > 5) throw IOException("Failed to fetch challenge token!")
+        val request = GET("$baseUrl/hcdn-cgi/jschallenge", headers)
+        val res = chain.proceed(request).body.string()
+
+        return res.substringAfter("cjs = '").substringBefore("'")
+            .takeUnless { it == "nil" } ?: fetchToken(chain, attempt + 1)
+    }
+
+    private fun String.sha256(): String {
+        return MessageDigest
+            .getInstance("SHA-256")
+            .digest(toByteArray())
+            .fold("", { str, it -> str + "%02x".format(it) })
+    }
+
     override val useNewChapterEndpoint = true
 
     override val mangaDetailsSelectorDescription: String =