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//
// Socks5EndpointReader.swift
// MullvadTransport
//
// Created by pronebird on 21/10/2023.
//
import Foundation
import MullvadTypes
import Network
/// The object reading the endpoint data from connection.
struct Socks5EndpointReader: Sendable {
/// Connection to the socks proxy.
let connection: NWConnection
/// The expected address type.
let addressType: Socks5AddressType
/// Completion handler called upon success.
let onComplete: @Sendable (Socks5Endpoint) -> Void
/// Failure handler.
let onFailure: @Sendable (Error) -> Void
/// Start reading endpoint from connection.
func perform() {
// The length of IPv4 address in bytes.
let ipv4AddressLength = 4
// The length of IPv6 address in bytes.
let ipv6AddressLength = 16
switch addressType {
case .ipv4:
readBoundAddressAndPortInner(addressLength: ipv4AddressLength)
case .ipv6:
readBoundAddressAndPortInner(addressLength: ipv6AddressLength)
case .domainName:
readBoundDomainNameLength { [self] domainLength in
readBoundAddressAndPortInner(addressLength: domainLength)
}
}
}
private func readBoundAddressAndPortInner(addressLength: Int) {
// The length of port in bytes.
let portLength = MemoryLayout<UInt16>.size
// The entire length of address + port
let byteSize = addressLength + portLength
connection.receive(exactLength: byteSize) { [self] addressData, _, _, error in
if let error {
onFailure(Socks5Error.remoteConnectionFailure(error))
} else if let addressData {
do {
let endpoint = try parseEndpoint(addressData: addressData, addressLength: addressLength)
onComplete(endpoint)
} catch {
onFailure(error)
}
} else {
onFailure(Socks5Error.unexpectedEndOfStream)
}
}
}
private func readBoundDomainNameLength(completion: @escaping @Sendable (Int) -> Void) {
// The length of domain length parameter in bytes.
let domainLengthLength = MemoryLayout<UInt8>.size
connection.receive(exactLength: domainLengthLength) { [self] data, _, _, error in
if let error {
onFailure(Socks5Error.remoteConnectionFailure(error))
} else if let domainNameLength = data?.first {
completion(Int(domainNameLength))
} else {
onFailure(Socks5Error.unexpectedEndOfStream)
}
}
}
private func parseEndpoint(addressData: Data, addressLength: Int) throws -> Socks5Endpoint {
// The length of port in bytes.
let portLength = MemoryLayout<UInt16>.size
guard addressData.count == addressLength + portLength else { throw Socks5Error.unexpectedEndOfStream }
// Read address bytes.
let addressBytes = addressData[0..<addressLength]
// Read port bytes.
let port = addressData[addressLength...].withUnsafeBytes { buffer in
let value = buffer.load(as: UInt16.self)
// Port is passed in network byte order. Convert it to host order.
return UInt16(bigEndian: value)
}
// Parse address into endpoint.
switch addressType {
case .ipv4:
guard let ipAddress = IPv4Address(addressBytes) else { throw Socks5Error.parseIPv4Address }
return .ipv4(IPv4Endpoint(ip: ipAddress, port: port))
case .ipv6:
guard let ipAddress = IPv6Address(addressBytes) else { throw Socks5Error.parseIPv6Address }
return .ipv6(IPv6Endpoint(ip: ipAddress, port: port))
case .domainName:
guard let hostname = String(bytes: addressBytes, encoding: .utf8),
let endpoint = Socks5HostEndpoint(hostname: hostname, port: port)
else {
throw Socks5Error.decodeDomainName
}
return .domain(endpoint)
}
}
}
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