From f44d03b0709bc5fb078b6386f8c4fd18a1e23351 Mon Sep 17 00:00:00 2001
From: _ <🐱>
Date: Tue, 1 Dec 2020 01:13:00 -0700
Subject: [PATCH] Detect erroneous song decryption and alert user when it
 happens

---
 SpotifyKeyDumper/Utils.cpp | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/SpotifyKeyDumper/Utils.cpp b/SpotifyKeyDumper/Utils.cpp
index cc24573..ed35d52 100644
--- a/SpotifyKeyDumper/Utils.cpp
+++ b/SpotifyKeyDumper/Utils.cpp
@@ -217,6 +217,13 @@ void Utils::DownloadSong(std::string fileId, std::string uri, std::string key, s
 		AES_init_ctx_iv(&ctx, reinterpret_cast<const uint8_t*>(&key[0]), IV);
 		AES_CTR_xcrypt_buffer(&ctx, reinterpret_cast<uint8_t*>(&downloadStr[0]), downloadStr.size());
 
+		// Check if decrypted song data has valid header
+		if (downloadStr.length() < 4 || downloadStr.compare(0, 4, "OggS") != 0)
+		{
+			std::cout << "Error: Could not properly decrypt song (try downloading again)!" << std::endl;
+			return;
+		}
+
 		// Remove custom Spotify Ogg page from beginning of file
 		downloadStr = downloadStr.substr(downloadStr.find("\xFF\xFF\xFF\xFFOggS") + 4);
 
@@ -262,9 +269,17 @@ void Utils::DownloadSong(std::string fileId, std::string uri, std::string key, s
 			return;
 		}
 
-		// Download encrypted song data from Spotify
+		// Download episode data from Spotify
 		downloadStr = DownloadSpotifyUrl(songHost, songPath, "");
 
+		// TODO: MP3 files appear to have a variety of headers, not sure this is 100% reliable
+		// Check if downloaded episode data has valid header
+		/*if (downloadStr.length() < 3 || downloadStr.compare(0, 3, "ID3") != 0)
+		{
+			std::cout << "Error: Could not properly download podcast episode (try downloading again)!" << std::endl;
+			return;
+		}*/
+
 		// Download episode and show metadata from Spotify API
 		std::string metadata = DownloadSpotifyUrl("api.spotify.com", "/v1/episodes/"
 			+ uri.substr(uri.find("spotify:episode:") + 16), authToken);