feat: implement last.fm API signature

angristan · Jul 17, 2021 · c1fa1b6 · c1fa1b6
1 parent 6810bca
commit c1fa1b6
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Showing 4 changed files with 70 additions and 3 deletions.
diff --git a/firstfm.xcodeproj/project.pbxproj b/firstfm.xcodeproj/project.pbxproj
@@ -41,6 +41,8 @@
 		82BBD2462698B13B009B42FC /* Country.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82BBD2452698B13B009B42FC /* Country.swift */; };
 		82BBD2482698B37F009B42FC /* TrendsViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82BBD2472698B37F009B42FC /* TrendsViewModel.swift */; };
 		82BBD24A2698C33D009B42FC /* TopCountryView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82BBD2492698C33D009B42FC /* TopCountryView.swift */; };
+		82C282E026A2E474000E5F41 /* LoginResponse.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82C282DF26A2E474000E5F41 /* LoginResponse.swift */; };
+		82C282E226A31CFD000E5F41 /* StringMD5.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82C282E126A31CFD000E5F41 /* StringMD5.swift */; };
 		82D5B4D02696DB8500716931 /* ScrobblesView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82D5B4CF2696DB8400716931 /* ScrobblesView.swift */; };
 		82D5B4D22696DBD700716931 /* ScrobblesViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82D5B4D12696DBD700716931 /* ScrobblesViewModel.swift */; };
 		82D5B4D42696DC7800716931 /* RecentTracks.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82D5B4D32696DC7800716931 /* RecentTracks.swift */; };
@@ -89,6 +91,8 @@
 		82BBD2452698B13B009B42FC /* Country.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Country.swift; sourceTree = "<group>"; };
 		82BBD2472698B37F009B42FC /* TrendsViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TrendsViewModel.swift; sourceTree = "<group>"; };
 		82BBD2492698C33D009B42FC /* TopCountryView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TopCountryView.swift; sourceTree = "<group>"; };
+		82C282DF26A2E474000E5F41 /* LoginResponse.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LoginResponse.swift; sourceTree = "<group>"; };
+		82C282E126A31CFD000E5F41 /* StringMD5.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StringMD5.swift; sourceTree = "<group>"; };
 		82D5B4CF2696DB8400716931 /* ScrobblesView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ScrobblesView.swift; sourceTree = "<group>"; };
 		82D5B4D12696DBD700716931 /* ScrobblesViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ScrobblesViewModel.swift; sourceTree = "<group>"; };
 		82D5B4D32696DC7800716931 /* RecentTracks.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RecentTracks.swift; sourceTree = "<group>"; };
@@ -119,6 +123,7 @@
 			isa = PBXGroup;
 			children = (
 				4A8C296026983B7300F55ECC /* LastFMAPI.swift */,
+				82C282E126A31CFD000E5F41 /* StringMD5.swift */,
 			);
 			path = Utils;
 			sourceTree = "<group>";
@@ -225,6 +230,7 @@
 				82D5B4D32696DC7800716931 /* RecentTracks.swift */,
 				82F0D54E2697AC66007CEA98 /* ArtistSearch.swift */,
 				8226AB2326998FAB007ECE5F /* TopCountryArtists.swift */,
+				82C282DF26A2E474000E5F41 /* LoginResponse.swift */,
 			);
 			path = API;
 			sourceTree = "<group>";
@@ -348,6 +354,7 @@
 				82505CE02675074E00CCCB58 /* ChartListView.swift in Sources */,
 				82D5B4D42696DC7800716931 /* RecentTracks.swift in Sources */,
 				82A006C1267963BB0009BD71 /* SpotifyImage.swift in Sources */,
+				82C282E026A2E474000E5F41 /* LoginResponse.swift in Sources */,
 				82FBAE472674B8FC000D8E29 /* Artist.swift in Sources */,
 				82D5B4D02696DB8500716931 /* ScrobblesView.swift in Sources */,
 				82505CDF2675074E00CCCB58 /* ArtistRow.swift in Sources */,
@@ -365,6 +372,7 @@
 				82F0D54F2697AC66007CEA98 /* ArtistSearch.swift in Sources */,
 				82A006BE2679636F0009BD71 /* TrackSearchResponse.swift in Sources */,
 				82BBD2462698B13B009B42FC /* Country.swift in Sources */,
+				82C282E226A31CFD000E5F41 /* StringMD5.swift in Sources */,
 				820455E0267ABC930009A418 /* AuthViewModel.swift in Sources */,
 				4A8C296126983B7300F55ECC /* LastFMAPI.swift in Sources */,
 				82BBD24A2698C33D009B42FC /* TopCountryView.swift in Sources */,
@@ -511,6 +519,7 @@
 				INFOPLIST_FILE = firstfm/Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 14.0;
 				LAST_FM_KEY = d404c94c63e190519d70002332f09509;
+				LAST_FM_SHARED_SECRET = e4e1eb5bf14d2418f51ed6ea6ae5d91a;
 				LD_RUNPATH_SEARCH_PATHS = (
 					"$(inherited)",
 					"@executable_path/Frameworks",
@@ -535,6 +544,7 @@
 				INFOPLIST_FILE = firstfm/Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 14.0;
 				LAST_FM_KEY = d404c94c63e190519d70002332f09509;
+				LAST_FM_SHARED_SECRET = e4e1eb5bf14d2418f51ed6ea6ae5d91a;
 				LD_RUNPATH_SEARCH_PATHS = (
 					"$(inherited)",
 					"@executable_path/Frameworks",

diff --git a/firstfm/Data/Utils/LastFMAPI.swift b/firstfm/Data/Utils/LastFMAPI.swift
@@ -10,17 +10,41 @@ import Foundation
 class LastFMAPI {
     // swiftlint:disable force_cast
     static let lastFMAPIKey = Bundle.main.object(forInfoDictionaryKey: "LastFMAPIKey") as! String
+    // swiftlint:disable force_cast
+    static let lastFMSharedSecret = Bundle.main.object(forInfoDictionaryKey: "LastFMSharedSecret") as! String
 
     static func request<T: Decodable>(method: String = "POST", lastFMMethod: String, args: [String : String] = [:], callback: @escaping (_ Data: T?, Error?) -> Void) -> Void {
         var request = URLRequest(url: URL(string: "https://ws.audioscrobbler.com/2.0/?format=json")!)
 
+        // We need to add these into the dict to compute the signature
+        var fullArgs = args
+        fullArgs["method"] = lastFMMethod
+        fullArgs["api_key"] = lastFMAPIKey
+
         var argsString = ""
 
-        for (key, value) in args {
-            argsString += "&\(key)=\(value)"
+        // Final format will be md5([param1][value1]..[paramN][valueN][shared_secret])
+        // https://www.last.fm/api/mobileauth
+        var toSign = ""
+
+        for key in Array(fullArgs.keys).sorted(by:<) {
+            if argsString != "" {
+                // Not first param
+                argsString += "&"
+            }
+            argsString += "\(key)=\(fullArgs[key] ?? "")"
+
+            toSign += key
+            toSign += fullArgs[key] ?? ""
         }
 
-        let data : Data = "api_key=\(lastFMAPIKey)&method=\(lastFMMethod)\(argsString)".data(using: .utf8)!
+        toSign += lastFMSharedSecret
+
+        let data : Data = "\(argsString)&api_sig=\(toSign.md5Value)".data(using: .utf8)!
+
+        print("argsString: \(argsString)")
+        print("toSign: \(toSign)")
+        print("api_sig: \(toSign.md5Value)")
 
         request.httpMethod = method
         request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField:"Content-Type");

diff --git a/firstfm/Data/Utils/StringMD5.swift b/firstfm/Data/Utils/StringMD5.swift
@@ -0,0 +1,31 @@
+//
+//  StringMD5.swift
+//  firstfm
+//
+//  Created by Stanislas Lange on 17/07/2021.
+//
+
+import Foundation
+import CommonCrypto
+
+// Needed to compute LastFM api Signature
+// https://www.last.fm/api/mobileauth
+
+extension String {
+    var md5Value: String {
+        let length = Int(CC_MD5_DIGEST_LENGTH)
+        var digest = [UInt8](repeating: 0, count: length)
+
+        if let d = self.data(using: .utf8) {
+            _ = d.withUnsafeBytes { body -> String in
+                CC_MD5(body.baseAddress, CC_LONG(d.count), &digest)
+
+                return ""
+            }
+        }
+
+        return (0 ..< length).reduce("") {
+            $0 + String(format: "%02x", digest[$1])
+        }
+    }
+}
diff --git a/firstfm/Info.plist b/firstfm/Info.plist
@@ -50,5 +50,7 @@
 	<string>$(LAST_FM_KEY)</string>
 	<key>SpotifyAPIToken</key>
 	<string>$(SPOTIFY_API_TOKEN)</string>
+	<key>LastFMSharedSecret</key>
+	<string>$(LAST_FM_SHARED_SECRET)</string>
 </dict>
 </plist>