SideStore/AltStore/Operations/VerifyAppOperation.swift

//
//  VerifyAppOperation.swift
//  AltStore
//
//  Created by Riley Testut on 5/2/20.
//  Copyright © 2020 Riley Testut. All rights reserved.
//

import Foundation

import AltStoreCore
import AltSign
import Roxas

extension VerificationError
{
    enum Code: Int, ALTErrorCode, CaseIterable {
        typealias Error = VerificationError

        case privateEntitlements
        case mismatchedBundleIdentifiers
        case iOSVersionNotSupported
    }

    static func privateEntitlements(_ entitlements: [String: Any], app: ALTApplication) -> VerificationError {
        VerificationError(code: .privateEntitlements, app: app, entitlements: entitlements)
    }

    static func mismatchedBundleIdentifiers(sourceBundleID: String, app: ALTApplication) -> VerificationError {
        VerificationError(code: .mismatchedBundleIdentifiers, app: app, sourceBundleID: sourceBundleID)
    }

    static func iOSVersionNotSupported(app: ALTApplication) -> VerificationError {
        VerificationError(code: .iOSVersionNotSupported, app: app)
    }
}

struct VerificationError: ALTLocalizedError {
    let code: Code

    var errorTitle: String?
    var errorFailure: String?

    var app: ALTApplication?
    var entitlements: [String: Any]?
    var sourceBundleID: String?

    var errorFailureReason: String {
        switch self.code
        {
        case .privateEntitlements:
            let appName = (self.app?.name as String?).map { String(format: NSLocalizedString("'%@'", comment: ""), $0) } ??
            	NSLocalizedString("Unknown app", comment: "")
            return String(format: NSLocalizedString("“%@” requires private permissions.", comment: ""), appName)

        case .mismatchedBundleIdentifiers:
            if let app, let sourceBundleID {
                return String(format: NSLocalizedString("The bundle ID '%@' does not match the one specified by the source ('%@').", comment: ""), app.bundleIdentifier, sourceBundleID)
            } else {
                return NSLocalizedString("The bundle ID does not match the one specified by the source.", comment: "")
            }

        case .iOSVersionNotSupported:
            var failureReason: String!
            if let app {
                var version = "iOS \(app.minimumiOSVersion.majorVersion).\(app.minimumiOSVersion.minorVersion)"
                if app.minimumiOSVersion.patchVersion > 0 {
                    version += ".\(app.minimumiOSVersion.patchVersion)"
                }
                failureReason = String(format: NSLocalizedString("%@ requires %@.", comment: ""), app.name, version)
            } else {
                let version = ProcessInfo.processInfo.operatingSystemVersionString
                failureReason = String(format: NSLocalizedString("This app does not support iOS %@.", comment: ""), version)
            }
            return failureReason
        }
    }
}

@objc(VerifyAppOperation)
final class VerifyAppOperation: ResultOperation<Void>
{
    let context: AppOperationContext
    var verificationHandler: ((VerificationError) -> Bool)?
    
    init(context: AppOperationContext)
    {
        self.context = context
        
        super.init()
    }
    
    override func main()
    {
        super.main()
        
        do
        {
            if let error = self.context.error
            {
                throw error
            }
            
            guard let app = self.context.app else { throw OperationError.invalidParameters }
            
            guard app.bundleIdentifier == self.context.bundleIdentifier else {
                throw VerificationError.mismatchedBundleIdentifiers(sourceBundleID: self.context.bundleIdentifier, app: app)
            }
            
            guard ProcessInfo.processInfo.isOperatingSystemAtLeast(app.minimumiOSVersion) else {
                throw VerificationError.iOSVersionNotSupported(app: app)
            }
            
            if #available(iOS 13.5, *)
            {
                // No psychic paper, so we can ignore private entitlements
                app.hasPrivateEntitlements = false
            }
            else
            {
                // Make sure this goes last, since once user responds to alert we don't do any more app verification.
                if let commentStart = app.entitlementsString.range(of: "<!---><!-->"), let commentEnd = app.entitlementsString.range(of: "<!-- -->")
                {
                    // Psychic Paper private entitlements.
                    
                    let entitlementsStart = app.entitlementsString.index(after: commentStart.upperBound)
                    let rawEntitlements = String(app.entitlementsString[entitlementsStart ..< commentEnd.lowerBound])
                    
                    let plistTemplate = """
                        <?xml version="1.0" encoding="UTF-8"?>
                        <!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
                        <plist version="1.0">
                            <dict>
                            %@
                            </dict>
                        </plist>
                        """
                    let entitlementsPlist = String(format: plistTemplate, rawEntitlements)
                    let entitlements = try PropertyListSerialization.propertyList(from: entitlementsPlist.data(using: .utf8)!, options: [], format: nil) as! [String: Any]
                    
                    app.hasPrivateEntitlements = true
                    let error = VerificationError.privateEntitlements(entitlements, app: app)
                    self.process(error) { (result) in
                        self.finish(result.mapError { $0 as Error })
                    }
                    
                    return
                }
                else
                {
                    app.hasPrivateEntitlements = false
                }
            }
            
            self.finish(.success(()))
        }
        catch
        {
            self.finish(.failure(error))
        }
    }
}

private extension VerifyAppOperation
{
    func process(_ error: VerificationError, completion: @escaping (Result<Void, VerificationError>) -> Void)
    {
        guard let presentingViewController = self.context.presentingViewController else { return completion(.failure(error)) }
        
        DispatchQueue.main.async {
            switch error.code
            {
            case .privateEntitlements:
                guard let entitlements = error.entitlements else { return completion(.failure(error)) }
                let permissions = entitlements.keys.sorted().joined(separator: "\n")
                let message = String(format: NSLocalizedString("""
                    You must allow access to these private permissions before continuing:

                    %@

                    Private permissions allow apps to do more than normally allowed by iOS, including potentially accessing sensitive private data. Make sure to only install apps from sources you trust.
                    """, comment: ""), permissions)
                
                let alertController = UIAlertController(title: error.failureReason ?? error.localizedDescription, message: message, preferredStyle: .alert)
                alertController.addAction(UIAlertAction(title: NSLocalizedString("Allow Access", comment: ""), style: .destructive) { (action) in
                    completion(.success(()))
                })
                alertController.addAction(UIAlertAction(title: NSLocalizedString("Deny Access", comment: ""), style: .default, handler: { (action) in
                    completion(.failure(error))
                }))
                presentingViewController.present(alertController, animated: true, completion: nil)
                
            case .mismatchedBundleIdentifiers: return completion(.failure(error))
            case .iOSVersionNotSupported: return completion(.failure(error))
            }
        }
    }
}