Not able to establish VPN connection using SharedSecret

Question

I'm trying to connect to a vpn using Swift. I have created class VpnHandler and I'm using Keychain Swift to keep keychain reference. My code look like this:

    import Foundation
    import NetworkExtension
    import KeychainSwift
    
    
    final class VPNHandler {

    let vpnManager = NEVPNManager.shared()
    
    func initVPNTunnelProviderManager(serverAdress: String, remoteIdentifier : String, sharedSecred:String) {
        let sharedKey = sharedSecred.data(using: .utf8)
        let keychain = KeychainSwift()
        guard let sharedKey = sharedKey else { return }
        keychain.set(sharedKey, forKey: "shared_secret")
        vpnManager.loadFromPreferences { error in
            if let error = error {
                print(error.localizedDescription)
                return
            }
            let IKEv2Protocol = NEVPNProtocolIKEv2()
            IKEv2Protocol.username = nil
            IKEv2Protocol.localIdentifier = nil
            IKEv2Protocol.serverAddress = serverAdress
            IKEv2Protocol.remoteIdentifier = remoteIdentifier
            IKEv2Protocol.authenticationMethod = .sharedSecret
            IKEv2Protocol.disconnectOnSleep = false
            IKEv2Protocol.useExtendedAuthentication = false
            IKEv2Protocol.sharedSecretReference = keychain.getData("shared_secret", asReference: true)
            IKEv2Protocol.passwordReference = nil
            var rules = [NEOnDemandRule]()
            let rule = NEOnDemandRuleConnect()
            rule.interfaceTypeMatch = .any
            rules.append(rule)
            self.vpnManager.localizedDescription = "My VPN"
            self.vpnManager.protocolConfiguration = IKEv2Protocol
            self.vpnManager.onDemandRules = rules
            self.vpnManager.isOnDemandEnabled = true
            self.vpnManager.isEnabled = true
            print("SAVE TO PREFERENCES...")
            self.vpnManager.saveToPreferences { error in
                if (error != nil) {
                    print(error!)
                    return
                }
                print("CALL LOAD TO PREFERENCES AGAIN...")
                self.vpnManager.loadFromPreferences { error in
                    if let error = error {
                        print(error.localizedDescription)
                        return
                    }
                    do {
                        try self.vpnManager.connection.startVPNTunnel()
                        print("Starting VPN...")
                    } catch let error {
                        print("can't connect VPN'")
                        print(error.localizedDescription)
                    }
                }
            }
        }
    } 
}

When I call the function initVPNTunnelProviderManager, the vpn configuration in the phone setting is created. Our app starting connecting to vpn, but then disconnect immediately. When we connect vpn configuration in the phone setting, it's working. I don't know what the problem is.

Any help is appreciated.

Thanks in advance

Answer 1

I just solved the issue. In your server in /etc/ipsec.conf file, replace the following:

ike=aes256-sha1-modp1024,3des-sha1-modp1024!,aes256-sha2_256
    esp=aes256-sha1,3des-sha1!

With 

ike=aes256-sha2_256-modp2048
esp=aes256-sha2_256