anytls 0.2.0

A proxy protocol that attempts to mitigate the TLS in TLS fingerprinting problem
Documentation 
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use crate::core::action::ProtocolAction;
use crate::core::padding::PaddingFactory;
use crate::core::state::State;
use crate::core::string_map::{StringMap, StringMapExt};
use crate::core::{Command, Frame};
use bytes::Bytes;
use std::sync::Arc;
use std::time::Duration;

pub struct Engine;

impl Engine {
    pub fn on_session_start(state: &Arc<State>, is_client: bool, client_name: &str) -> std::io::Result<Vec<ProtocolAction>> {
        if !is_client {
            return Ok(Vec::new());
        }

        let mut settings = StringMap::new();
        settings.insert("v".to_string(), "2".to_string());
        settings.insert("client".to_string(), client_name.to_string());
        settings.insert("padding-md5".to_string(), state.padding().md5().to_string());

        Ok(vec![ProtocolAction::SendFrame(Frame::with_data(
            Command::Settings,
            0,
            settings.to_bytes().into(),
        ))])
    }

    pub fn on_frame(state: &Arc<State>, is_client: bool, frame: &Frame) -> std::io::Result<Vec<ProtocolAction>> {
        let mut actions = Vec::new();

        match frame.cmd {
            Command::Waste | Command::HeartResponse => {}
            Command::Psh if !frame.data.is_empty() => {
                actions.push(ProtocolAction::PushStreamData {
                    sid: frame.sid,
                    data: frame.data.clone(),
                });
            }
            Command::Syn if !is_client => {
                if !state.received_settings_from_client() {
                    actions.push(ProtocolAction::AlertAndFail {
                        message: "client did not send its settings".to_string(),
                    });
                } else {
                    actions.push(ProtocolAction::EnsureIncomingStream { sid: frame.sid });
                }
            }
            Command::Fin => {
                actions.push(ProtocolAction::CloseLocalStream { sid: frame.sid });
            }
            Command::Settings if !is_client && !frame.data.is_empty() => {
                let settings = StringMap::from_bytes(frame.data.as_ref());
                state.mark_received_settings_from_client();

                let padding = state.padding();
                if settings.get("padding-md5").map(String::as_str) != Some(padding.md5()) {
                    actions.push(ProtocolAction::SendFrameSync(Frame::with_data(
                        Command::UpdatePaddingScheme,
                        0,
                        Bytes::copy_from_slice(padding.raw_scheme()),
                    )));
                }

                if let Some(version) = settings.get("v").and_then(|value| value.parse::<u8>().ok())
                    && version >= 2
                {
                    state.set_peer_version(version);
                    let mut server_settings = StringMap::new();
                    server_settings.insert("v".to_string(), "2".to_string());
                    actions.push(ProtocolAction::SendFrameSync(Frame::with_data(
                        Command::ServerSettings,
                        0,
                        server_settings.to_bytes().into(),
                    )));
                }
            }
            Command::UpdatePaddingScheme if !frame.data.is_empty() && is_client => {
                if let Some(factory) = PaddingFactory::new(frame.data.as_ref()) {
                    state.set_padding(factory);
                }
            }
            Command::HeartRequest => {
                actions.push(ProtocolAction::SendFrame(Frame::new(Command::HeartResponse, frame.sid)));
            }
            Command::ServerSettings if !frame.data.is_empty() && is_client => {
                let settings = StringMap::from_bytes(frame.data.as_ref());
                if let Some(version) = settings.get("v").and_then(|value| value.parse::<u8>().ok()) {
                    state.set_peer_version(version);
                }
            }
            Command::SynAck => {
                actions.push(ProtocolAction::CancelSynAckTimeout { sid: frame.sid });
                if !frame.data.is_empty() {
                    actions.push(ProtocolAction::CloseRemoteStream {
                        sid: frame.sid,
                        message: String::from_utf8_lossy(frame.data.as_ref()).to_string(),
                    });
                }
            }
            _ => log::warn!(
                "Received unexpected frame: cmd={}, sid={}, data_len={}",
                frame.cmd,
                frame.sid,
                frame.data.len()
            ),
        }

        Ok(actions)
    }

    pub fn on_open_stream(state: &Arc<State>, sid: u32) -> Vec<ProtocolAction> {
        let mut actions = Vec::new();

        if sid >= 2 && state.peer_version() >= 2 {
            actions.push(ProtocolAction::ArmSynAckTimeout {
                sid,
                timeout: Duration::from_secs(3),
            });
        }

        actions.push(ProtocolAction::SendFrameSync(Frame::new(Command::Syn, sid)));
        actions.push(ProtocolAction::ReleaseWriteBuffering);

        actions
    }
}