Grcov report - socks.rs

1

//! SOCKS-specific proxy support.

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use futures::io::{AsyncRead, AsyncReadExt, AsyncWrite, BufReader};

4

use safelog::sensitive;

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use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};

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use tracing::{debug, instrument, warn};

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8

#[allow(unused)]

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use arti_client::HasKind;

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use arti_client::{ErrorKind, IntoTorAddr as _, StreamPrefs};

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#[cfg(feature = "rpc")]

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use tor_rpcbase::{self as rpc};

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use tor_rtcompat::Runtime;

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use tor_socksproto::{Handshake as _, SocksAddr, SocksAuth, SocksCmd, SocksRequest};

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use anyhow::{Context, Result, anyhow};

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use super::{

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    ListenerIsolation, ProvidedIsolation, ProxyContext, StreamIsolationKey, write_all_and_close,

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    write_all_and_flush,

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};

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cfg_if::cfg_if! {

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    if #[cfg(feature="rpc")] {

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        use crate::rpc::conntarget::ConnTarget;

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    } else {

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        use arti_client::TorClient;

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28

        /// A type returned by get_prefs_and_session,

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        /// and used to launch data streams or resolve attempts.

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///

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        /// TODO RPC: This is quite ugly; we should do something better.

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        /// At least, we should never expose this outside the socks module.

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        type ConnTarget<R> = TorClient<R>;

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/// Payload to return when an HTTP connection arrive on a Socks port

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/// without HTTP support.

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#[cfg(not(feature = "http-connect"))]

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pub(super) const WRONG_PROTOCOL_PAYLOAD: &[u8] = br#"HTTP/1.0 501 Not running as an HTTP Proxy

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Content-Type: text/html; charset=utf-8

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<!DOCTYPE html>

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<html>

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<head>

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<title>This is a SOCKS Proxy, Not An HTTP Proxy</title>

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</head>

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<body>

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<h1>This is a SOCKS proxy, not an HTTP proxy.</h1>

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<p>

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It appears you have configured your web browser to use this Tor port as

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an HTTP proxy.

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</p>

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<p>

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This is not correct: This port is configured as a SOCKS proxy, not

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an HTTP proxy. If you need an HTTP proxy tunnel,

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build Arti with the <code>http-connect</code> feature enabled.

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</p>

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<p>

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See <a href="https://gitlab.torproject.org/tpo/core/arti/#todo-need-to-change-when-arti-get-a-user-documentation">https://gitlab.torproject.org/tpo/core/arti</a> for more information.

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</p>

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</body>

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</html>"#;

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/// Find out which kind of address family we can/should use for a

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/// given `SocksRequest`.

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#[cfg_attr(feature = "experimental-api", visibility::make(pub))]

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fn stream_preference(req: &SocksRequest, addr: &str) -> StreamPrefs {

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    let mut prefs = StreamPrefs::new();

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    if addr.parse::<Ipv4Addr>().is_ok() {

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        // If they asked for an IPv4 address correctly, nothing else will do.

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        prefs.ipv4_only();

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    } else if addr.parse::<Ipv6Addr>().is_ok() {

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        // If they asked for an IPv6 address correctly, nothing else will do.

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        prefs.ipv6_only();

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    } else if req.version() == tor_socksproto::SocksVersion::V4 {

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        // SOCKS4 and SOCKS4a only support IPv4

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        prefs.ipv4_only();

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    } else {

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        // Otherwise, default to saying IPv4 is preferred.

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        prefs.ipv4_preferred();

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    prefs

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/// The meaning of a SOCKS authentication field, according to our conventions.

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struct AuthInterpretation {

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    /// Associate this stream with a DataStream created by using a particular RPC object

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    /// as a Tor client.

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    #[cfg(feature = "rpc")]

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    rpc_object: Option<rpc::ObjectId>,

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    /// Isolate this stream from other streams that do not have the same

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    /// value.

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    isolation: ProvidedIsolation,

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/// Given the authentication object from a socks connection, determine what it's telling

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/// us to do.

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///

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/// (In no case is it actually SOCKS authentication: it can either be a message

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/// to the stream isolation system or the RPC system.)

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fn interpret_socks_auth(auth: &SocksAuth) -> Result<AuthInterpretation> {

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    /// Interpretation of a SOCKS5 username according to

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    /// the [SOCKS extended authentication](https://spec.torproject.org/socks-extensions.html#extended-auth)

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    /// specification.

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    enum Uname<'a> {

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        /// This is a legacy username; it's just part of the

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        /// isolation information.

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//

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        // Note: We're not actually throwing away the username here;

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        // instead we're going to use the whole SocksAuth

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        // in a `ProvidedAuthentication::Legacy``.

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        // TODO RPC: Find a more idiomatic way to express this data flow.

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        Legacy,

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        /// This is using the socks extension: contains the extension

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        /// format code and the remaining information from the username.

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        Extended(u8, &'a [u8]),

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    /// Helper: Try to interpret a SOCKS5 username field as indicating the start of a set of

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    /// extended socks authentication information.

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///

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    /// Implements [SOCKS extended authentication](https://spec.torproject.org/socks-extensions.html#extended-auth).

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///

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    /// If it does indicate that extensions are in use,

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    /// return a `Uname::Extended` containing

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    /// the extension format type and the remaining information from the username.

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///

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    /// If it indicates that no extensions are in use,

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    /// return `Uname::Legacy`.

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///

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    /// If it is badly formatted, return an error.

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    fn interpret_socks5_username(username: &[u8]) -> Result<Uname<'_>> {

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        /// 8-byte "magic" sequence from

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        /// [SOCKS extended authentication](https://spec.torproject.org/socks-extensions.html#extended-auth).

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        /// When it appears at the start of a username,

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        /// indicates that the username/password are to be interpreted as

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        /// as encoding SOCKS5 extended parameters,

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        /// but the format might not be one we recognize.

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        const SOCKS_EXT_CONST_ANY: &[u8] = b"<torS0X>";

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        let Some(remainder) = username.strip_prefix(SOCKS_EXT_CONST_ANY) else {

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            return Ok(Uname::Legacy);

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};

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        let (format_code, remainder) = remainder

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            .split_at_checked(1)

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            .ok_or_else(|| anyhow!("Extended SOCKS information without format code."))?;

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        Ok(Uname::Extended(format_code[0], remainder))

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    let isolation = match auth {

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        SocksAuth::Username(user, pass) => match interpret_socks5_username(user)? {

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            Uname::Legacy => ProvidedIsolation::LegacySocks(auth.clone()),

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            Uname::Extended(b'1', b"") => {

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                return Err(anyhow!("Received empty RPC object ID"));

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            Uname::Extended(format_code @ b'1', remainder) => {

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                #[cfg(not(feature = "rpc"))]

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                return Err(anyhow!(

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                    "Received RPC object ID, but not built with support for RPC"

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));

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                #[cfg(feature = "rpc")]

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                return Ok(AuthInterpretation {

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                    rpc_object: Some(rpc::ObjectId::from(

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                        std::str::from_utf8(remainder).context("Rpc object ID was not utf-8")?,

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)),

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                    isolation: ProvidedIsolation::ExtendedSocks {

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                        format_code,

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                        isolation: pass.clone().into(),

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},

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});

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            Uname::Extended(format_code @ b'0', b"") => ProvidedIsolation::ExtendedSocks {

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                format_code,

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                isolation: pass.clone().into(),

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},

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            Uname::Extended(b'0', _) => {

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                return Err(anyhow!("Extraneous information in SOCKS username field."));

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            _ => return Err(anyhow!("Unrecognized SOCKS format code")),

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},

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        _ => ProvidedIsolation::LegacySocks(auth.clone()),

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};

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    Ok(AuthInterpretation {

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        #[cfg(feature = "rpc")]

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        rpc_object: None,

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        isolation,

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})

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impl<R: Runtime> super::ProxyContext<R> {

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    /// Interpret a SOCKS request and our input information to determine which

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    /// TorClient / ClientConnectionTarget object and StreamPrefs we should use.

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///

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    /// TODO RPC: The return type here is a bit ugly.

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    fn get_prefs_and_session(

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        &self,

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        request: &SocksRequest,

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        target_addr: &str,

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        conn_isolation: ListenerIsolation,

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    ) -> Result<(StreamPrefs, ConnTarget<R>)> {

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        // Determine whether we want to ask for IPv4/IPv6 addresses.

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        let mut prefs = stream_preference(request, target_addr);

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        // Interpret socks authentication to see whether we want to connect to an RPC connector.

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        let interp = interpret_socks_auth(request.auth())?;

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        prefs.set_isolation(StreamIsolationKey(conn_isolation, interp.isolation));

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        #[cfg(feature = "rpc")]

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        if let Some(session) = interp.rpc_object {

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            if let Some(mgr) = &self.rpc_mgr {

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                let (context, object) = mgr

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                    .lookup_object(&session)

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                    .context("no such session found")?;

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                let target = ConnTarget::Rpc { context, object };

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                return Ok((prefs, target));

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            } else {

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                return Err(anyhow!("no rpc manager found!?"));

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        let client = self.tor_client.clone();

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        #[cfg(feature = "rpc")]

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        let client = ConnTarget::Client(Box::new(client));

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        Ok((prefs, client))

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/// Given a just-received TCP connection `S` on a SOCKS port, handle the

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/// SOCKS handshake and relay the connection over the Tor network.

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///

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/// Uses `isolation_info` to decide which circuits this connection

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/// may use.  Requires that `isolation_info` is a pair listing the listener

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/// id and the source address for the socks request.

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#[instrument(skip_all, level = "trace")]

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pub(super) async fn handle_socks_conn<R, S>(

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    context: ProxyContext<R>,

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    mut socks_stream: BufReader<S>,

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    isolation_info: ListenerIsolation,

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) -> Result<()>

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where

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    R: Runtime,

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    S: AsyncRead + AsyncWrite + Send + Sync + Unpin + 'static,

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    // Part 1: Perform the SOCKS handshake, to learn where we are

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    // being asked to connect, and what we're being asked to do once

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    // we connect there.

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//

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    // The SOCKS handshake can require multiple round trips (SOCKS5

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    // always does) so we we need to run this part of the process in a

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    // loop.

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    let mut handshake = tor_socksproto::SocksProxyHandshake::new();

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    let mut inbuf = tor_socksproto::Buffer::new();

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    let request = loop {

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        use tor_socksproto::NextStep as NS;

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        // Try to perform the next step in the handshake.

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        // (If there is an handshake error, don't reply with a Socks error, remote does not

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        // seems to speak Socks.)

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        let step = handshake.step(&mut inbuf)?;

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        match step {

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            NS::Recv(mut recv) => {

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                let n = socks_stream

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                    .read(recv.buf())

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                    .await

269

                    .context("Error while reading SOCKS handshake")?;

270

                recv.note_received(n)?;

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            NS::Send(data) => write_all_and_flush(&mut socks_stream, &data).await?,

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            NS::Finished(fin) => break fin.into_output_forbid_pipelining()?,

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};

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    // Make sure there is no buffered data!

278

    if !socks_stream.buffer().is_empty() {

279

        let error = tor_socksproto::Error::ForbiddenPipelining;

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        return reply_error(&mut socks_stream, &request, error.kind()).await;

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    // Unpack the socks request and find out where we're connecting to.

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    let addr = request.addr().to_string();

285

    let port = request.port();

286

    debug!(

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        "Got a socks request: {} {}:{}",

288

        request.command(),

289

        sensitive(&addr),

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        port

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);

292

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    let (prefs, tor_client) = context.get_prefs_and_session(&request, &addr, isolation_info)?;

294

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    match request.command() {

296

        SocksCmd::CONNECT => {

297

            // The SOCKS request wants us to connect to a given address.

298

            // So, launch a connection over Tor.

299

            let tor_addr = (addr.clone(), port).into_tor_addr()?;

300

            let tor_stream = tor_client.connect_with_prefs(&tor_addr, &prefs).await;

301

            let tor_stream = match tor_stream {

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                Ok(s) => s,

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                Err(e) => return reply_error(&mut socks_stream, &request, e.kind()).await,

304

};

305

            // Okay, great! We have a connection over the Tor network.

306

            debug!("Got a stream for {}:{}", sensitive(&addr), port);

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308

            // Send back a SOCKS response, telling the client that it

309

            // successfully connected.

310

            let reply = request

311

                .reply(tor_socksproto::SocksStatus::SUCCEEDED, None)

312

                .context("Encoding socks reply")?;

313

            write_all_and_flush(&mut socks_stream, &reply[..]).await?;

314

315

            let tor_stream = BufReader::with_capacity(super::APP_STREAM_BUF_LEN, tor_stream);

316

317

            // Finally, relay traffic between

318

            // the socks stream and the tor stream.

319

            futures_copy::copy_buf_bidirectional(

320

                socks_stream,

321

                tor_stream,

322

                futures_copy::eof::Close,

323

                futures_copy::eof::Close,

324

325

            .await?;

326

327

        SocksCmd::RESOLVE => {

328

            // We've been asked to perform a regular hostname lookup.

329

            // (This is a tor-specific SOCKS extension.)

330

331

            let addr = if let Ok(addr) = addr.parse() {

332

                // if this is a valid ip address, just parse it and reply.

333

                Ok(addr)

334

            } else {

335

                tor_client

336

                    .resolve_with_prefs(&addr, &prefs)

337

                    .await

338

                    .map_err(|e| e.kind())

339

                    .and_then(|addrs| addrs.first().copied().ok_or(ErrorKind::Other))

340

};

341

            match addr {

342

                Ok(addr) => {

343

                    let reply = request

344

                        .reply(

345

                            tor_socksproto::SocksStatus::SUCCEEDED,

346

                            Some(&SocksAddr::Ip(addr)),

347

348

                        .context("Encoding socks reply")?;

349

                    write_all_and_close(&mut socks_stream, &reply[..]).await?;

350

351

                Err(e) => return reply_error(&mut socks_stream, &request, e).await,

352

353

354

        SocksCmd::RESOLVE_PTR => {

355

            // We've been asked to perform a reverse hostname lookup.

356

            // (This is a tor-specific SOCKS extension.)

357

            let addr: IpAddr = match addr.parse() {

358

                Ok(ip) => ip,

359

                Err(e) => {

360

                    let reply = request

361

                        .reply(tor_socksproto::SocksStatus::ADDRTYPE_NOT_SUPPORTED, None)

362

                        .context("Encoding socks reply")?;

363

                    write_all_and_close(&mut socks_stream, &reply[..]).await?;

364

                    return Err(anyhow!(e));

365

366

};

367

            let hosts = match tor_client.resolve_ptr_with_prefs(addr, &prefs).await {

368

                Ok(hosts) => hosts,

369

                Err(e) => return reply_error(&mut socks_stream, &request, e.kind()).await,

370

};

371

            if let Some(host) = hosts.into_iter().next() {

372

                // this conversion should never fail, legal DNS names len must be <= 253 but Socks

373

                // names can be up to 255 chars.

374

                let hostname = SocksAddr::Hostname(host.try_into()?);

375

                let reply = request

376

                    .reply(tor_socksproto::SocksStatus::SUCCEEDED, Some(&hostname))

377

                    .context("Encoding socks reply")?;

378

                write_all_and_close(&mut socks_stream, &reply[..]).await?;

379

380

381

        _ => {

382

            // We don't support this SOCKS command.

383

            warn!("Dropping request; {:?} is unsupported", request.command());

384

            let reply = request

385

                .reply(tor_socksproto::SocksStatus::COMMAND_NOT_SUPPORTED, None)

386

                .context("Encoding socks reply")?;

387

            write_all_and_close(&mut socks_stream, &reply[..]).await?;

388

389

};

390

391

    // TODO: we should close the TCP stream if either task fails. Do we?

392

    // See #211 and #190.

393

394

    Ok(())

395

396

397

/// Reply a Socks error based on an arti-client Error and close the stream.

398

/// Returns the error provided in parameter

399

async fn reply_error<W>(

400

    writer: &mut W,

401

    request: &SocksRequest,

402

    error: arti_client::ErrorKind,

403

) -> Result<()>

404

where

405

    W: AsyncWrite + Unpin,

406

407

    use {ErrorKind as EK, tor_socksproto::SocksStatus as S};

408

409

    // TODO: Currently we _always_ try to return extended SOCKS return values

410

    // for onion service failures from proposal 304 when they are appropriate.

411

    // But according to prop 304, this is something we should only do when it's

412

    // requested, for compatibility with SOCKS implementations that can't handle

413

    // unexpected REP codes.

414

//

415

    // I suggest we make these extended error codes "always-on" for now, and

416

    // later add a feature to disable them if it's needed. -nickm

417

418

    // TODO: Perhaps we should map the extended SOCKS return values for onion

419

    // service failures unconditionally, even if we haven't compiled in onion

420

    // service client support.  We can make that change after the relevant

421

    // ErrorKinds are no longer `experimental-api` in `tor-error`.

422

423

    // We need to send an error. See what kind it is.

424

//

425

    // TODO: Perhaps move this to tor-error, so it can be an exhaustive match.

426

    let status = match error {

427

        EK::RemoteNetworkFailed => S::TTL_EXPIRED,

428

429

        #[cfg(feature = "onion-service-client")]

430

        EK::OnionServiceNotFound => S::HS_DESC_NOT_FOUND,

431

        #[cfg(feature = "onion-service-client")]

432

        EK::OnionServiceAddressInvalid => S::HS_BAD_ADDRESS,

433

        #[cfg(feature = "onion-service-client")]

434

        EK::OnionServiceMissingClientAuth => S::HS_MISSING_CLIENT_AUTH,

435

        #[cfg(feature = "onion-service-client")]

436

        EK::OnionServiceWrongClientAuth => S::HS_WRONG_CLIENT_AUTH,

437

438

        // NOTE: This is not a perfect correspondence from these ErrorKinds to

439

        // the errors we're returning here. In the longer run, we'll want to

440

        // encourage other ways to indicate failure to clients.  Those ways might

441

        // include encouraging HTTP CONNECT, or the RPC system, both of which

442

        // would give us more robust ways to report different kinds of failure.

443

        #[cfg(feature = "onion-service-client")]

444

        EK::OnionServiceNotRunning

445

        | EK::OnionServiceConnectionFailed

446

        | EK::OnionServiceProtocolViolation => S::HS_INTRO_FAILED,

447

448

        _ => S::GENERAL_FAILURE,

449

};

450

    let reply = request

451

        .reply(status, None)

452

        .context("Encoding socks reply")?;

453

    // if writing back the error fail, still return the original error

454

    let _ = write_all_and_close(writer, &reply[..]).await;

455

456

    Err(anyhow!(error))

457