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fp.rs
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fp.rs
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use hex_literal::hex;
use itertools::Itertools;
use ja3_rustls::{grease_u16_be, is_grease_u16_be, try_regrease_u16_be, Ja3};
use rustls::internal::msgs::base::Payload;
use rustls::internal::msgs::codec::Codec;
use rustls::internal::msgs::enums::{ExtensionType, NamedCurve};
use rustls::internal::msgs::handshake::{
ClientExtension, ConvertProtocolNameList, HandshakeMessagePayload, HandshakePayload,
KeyShareEntry, ProtocolName, UnknownExtension,
};
use rustls::internal::msgs::message::{Message, MessagePayload};
use rustls::{ProtocolVersion, SignatureScheme};
use tracing::{debug, trace, warn};
use std::collections::HashMap;
use std::fmt::{self, Debug, Formatter};
use std::sync::Arc;
use crate::utils::try_assign;
const RFC7685_PADDING_TARGET: usize = 512;
/// Spec of fingerprints instructing how TLS ClientHello messages are mutated
#[derive(Clone, Default)]
pub struct FingerprintSpec {
pub ja3: Option<Ja3>,
pub alpn: Option<Vec<Vec<u8>>>,
pub signature_algos: Option<Vec<u16>>,
pub supported_versions: Option<Vec<u16>>,
pub keyshare_curves: Option<Vec<u16>>,
}
impl FingerprintSpec {
pub fn new() -> Self {
Default::default()
}
// pub fn with_ja3(self, ja3: Ja3) -> Self {
// self.ja3 = Some(ja3);
// self
// }
pub fn is_empty(&self) -> bool {
self.ja3.is_none()
&& self.alpn.is_none()
&& self.signature_algos.is_none()
&& self.supported_versions.is_none()
&& self.keyshare_curves.is_none()
}
pub fn overwrite_client_hello(
&self,
msg: &mut Message,
add_empty_if_extension_not_in_message: bool,
drop_extensions_not_in_ja3: bool,
) -> Option<Vec<ExtensionType>> {
overwrite_client_hello_with_fingerprint_spec(
msg,
self,
add_empty_if_extension_not_in_message,
drop_extensions_not_in_ja3,
)
}
pub fn get_client_hello_overwriter(
self: &Arc<Self>,
add_empty_if_extension_not_in_message: bool,
drop_extensions_not_in_ja3: bool,
) -> Option<impl FnOnce(&mut Message) -> Option<Vec<ExtensionType>>> {
if self.is_empty() {
return None;
}
let fp = self.clone();
Some(move |msg: &mut Message| {
fp.overwrite_client_hello(
msg,
add_empty_if_extension_not_in_message,
drop_extensions_not_in_ja3,
)
})
}
}
impl Debug for FingerprintSpec {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
let mut d = f.debug_struct("FingerprintSpec");
if let Some(ref ja3) = self.ja3 {
d.field("version", &ja3.version_to_typed())
.field("ciphers", &ja3.ciphers_as_typed().format(" "))
.field("extensions", &ja3.extensions_as_typed().format(" "))
.field("curves", &ja3.curves_as_typed().format(" "))
.field("point_formats", &ja3.point_formats_as_typed().format(" "));
}
if let Some(ref alpn) = self.alpn {
d.field(
"alpn",
&alpn.iter().map(|p| String::from_utf8_lossy(p)).format(" "),
);
}
if let Some(ref vers) = self.supported_versions {
d.field(
"supported_versions",
&vers
.iter()
.map(|&ver| ProtocolVersion::from(ver))
.format(" "),
);
}
if let Some(ref algos) = self.signature_algos {
d.field(
"signature_algos",
&algos
.iter()
.map(|&algo| SignatureScheme::from(algo))
.format(" "),
);
}
if let Some(ref curves) = self.keyshare_curves {
d.field(
"keyshare_curves",
&curves
.iter()
.map(|&curve| NamedCurve::from(curve))
.format(" "),
);
}
d.finish()
}
}
/// Apply a JA3 fingerprint to a ClientHello [`Message`].
///
/// Cipher suites, curvres, and EC point formats are simply overwritten with the those specified by
/// a JA3. For TLS extensions, the function manages to match the sort order, **optionally** add
/// empty or hardcoded dummy records for those not in message yet but listed in JA3, and
/// **optionally** drop existing ones from client hello payload if they are not present in JA3.
///
/// It returns a list of allowed unsolicited server extensions matched with the updated message.
///
/// # Note
/// It is caller's responsibility to ensure that the message constitutes a valid ClientHello. Otherwise,
/// only the protocol version in the message header is overwritten.
pub fn overwrite_client_hello_with_fingerprint_spec(
msg: &mut Message,
fp: &FingerprintSpec,
add_empty_if_extension_not_in_message: bool,
drop_extensions_not_in_ja3: bool,
) -> Option<Vec<ExtensionType>> {
use ExtensionType::*;
#[allow(unused_mut)]
let mut allowed_unsolicited_extensions = vec![ExtensionType::RenegotiationInfo];
trace!(
"overwrite client hello of {:?} with fingerprint {:?}",
msg,
fp
);
try_assign!(
msg.version,
fp.ja3.as_ref().map(|ja3| ja3.version_to_typed())
);
if let MessagePayload::Handshake {
ref mut parsed,
ref mut encoded,
} = msg.payload
{
let mut pad_per_rfc7685 = false;
if let HandshakeMessagePayload {
payload: HandshakePayload::ClientHello(ref mut chp),
..
} = parsed
{
try_assign!(
chp.cipher_suites,
fp.ja3.as_ref().map(|ja3| ja3.ciphers_as_typed().collect())
);
match &fp.ja3 {
Some(ja3) => {
// try to match extension order
let mut new_extensions = Vec::with_capacity(if drop_extensions_not_in_ja3 {
ja3.extensions.len()
} else {
chp.extensions.len()
});
let mut oldextmap: HashMap<u16, &ClientExtension> = chp
.extensions
.iter()
.map(|extension| (extension.get_type().get_u16(), extension))
.collect();
for exttyp in ja3
.extensions_regreasing_as_typed()
.map(|extension_type| extension_type.get_u16())
{
match oldextmap.remove(&exttyp) {
Some(extension) => new_extensions.push(extension.clone()),
None => {
if !add_empty_if_extension_not_in_message {
continue;
}
trace!(
"ja3 overwiting: missing extension {:?} in original chp, add an dummy one",
ExtensionType::from(exttyp));
// Some extension expect vectored struct, we cannot just set empty.
let extpld = match ExtensionType::from(exttyp) {
// ALPN: http/1.1 + h2
ALProtocolNegotiation => {
panic!("Expect ALPN present in original message if it is listed in JA3")
// allowed_unsolicited_extensions
// .push(ExtensionType::ALProtocolNegotiation);
// Vec::from(hex!("000c08687474702f312e31026832"))
}
// Renegotiation Info: still empty, but an additional length field
RenegotiationInfo => Vec::from(hex!("00")),
// ALPS: supported ALPN list: h2 (TODO: what is it?)
ExtensionType::Unknown(0x4469) => Vec::from(hex!("0003026832")),
Padding => {
pad_per_rfc7685 = true;
vec![]
}
// Compress Certificate: Rustls does not support it.
// Chrome use 02 00 02 (brotli).
// By setting it non-empty, we risk at TLS negotiation error.
ExtensionType::Unknown(0x001b) => Vec::from(hex!("020002")),
_ => vec![],
};
let extension = ClientExtension::Unknown(UnknownExtension {
typ: ExtensionType::from(exttyp),
payload: Payload(extpld),
});
// Codec works fine with UnknownExtension
new_extensions.push(extension);
}
}
}
if !oldextmap.is_empty() && !drop_extensions_not_in_ja3 {
// there might be some extensions in CHP that are not present in ja3
trace!("ja3 overwriting: extension {:?} in original chp not present in ja3, appending to end: {}", oldextmap, !drop_extensions_not_in_ja3);
new_extensions.extend(oldextmap.into_values().map(|ext| ext.to_owned()));
}
chp.extensions = new_extensions;
}
None => {}
}
// rewrite extension values
let mut grease_curves = vec![];
for extension in chp.extensions.iter_mut() {
use ClientExtension::*;
match extension {
// curves used by KeyShare should be a subset of of those specificed here
NamedGroups(groups) => {
if grease_curves.is_empty() {
try_assign!(
*groups,
fp.ja3.as_ref().map(|ja3| ja3
.curves
.iter()
.map(|&curve| match is_grease_u16_be(curve) {
true => {
let g = grease_u16_be();
grease_curves.push(g);
g
}
false => curve,
}
.into())
.collect())
);
} else {
try_assign!(
*groups,
fp.ja3.as_ref().map(|ja3| ja3
.curves
.iter()
.map(|&curve| {
match is_grease_u16_be(curve) {
true => match grease_curves.pop() {
Some(g) => g,
None => grease_u16_be(),
},
false => curve,
}
.into()
})
.collect())
);
}
}
ECPointFormats(formats) => {
try_assign!(
*formats,
fp.ja3
.as_ref()
.map(|ja3| ja3.point_formats_as_typed().collect())
);
}
// ALProtocolN
Protocols(alpn) => {
try_assign!(
*alpn,
fp.alpn.as_ref().map(|alpn| {
Vec::<ProtocolName>::from_slices(
&alpn.iter().map(|proto| &proto[..]).collect::<Vec<_>>(),
)
})
);
}
SupportedVersions(vers) => {
try_assign!(
*vers,
fp.supported_versions.as_ref().map(|vers| vers
.iter()
.map(|&ver| try_regrease_u16_be(ver).into())
.collect())
)
}
SignatureAlgorithms(algos) => {
try_assign!(
*algos,
fp.signature_algos.as_ref().map(|algos| algos
.iter()
.map(|&algo| try_regrease_u16_be(algo).into())
.collect())
);
}
KeyShare(entries) => {
if let Some(fpcurves) = fp.keyshare_curves.as_ref() {
let mut oldentmap: HashMap<_, _> = entries
.iter()
.map(|ent| (ent.group.get_u16(), ent))
.collect();
let mut new_entries = vec![];
if grease_curves.is_empty() {
for &curve in fpcurves {
match oldentmap.remove(&curve) {
Some(entry) => new_entries.push(entry.clone()),
None => {
let curve = match is_grease_u16_be(curve) {
true => {
let g = grease_u16_be();
grease_curves.push(g);
g
}
false => {
warn!("TLS Key Share of curve {} is not present in original ClientHello. A empty payload is used, which makes traffic look distinctive.", curve);
curve
}
};
new_entries
.push(KeyShareEntry::new(curve.into(), &[0x00]));
}
}
}
} else {
for &curve in fpcurves {
match oldentmap.remove(&curve) {
Some(entry) => new_entries.push(entry.clone()),
None => {
let curve = match is_grease_u16_be(curve) {
true => {
match grease_curves.pop() {
Some(curve) => curve,
// TODO: some server might reject GREASE
// values not present in NamedGroups
None => grease_u16_be(),
}
}
false => {
warn!("TLS Key Share of curve {} is not present in original ClientHello. A empty payload is used, which makes traffic look distinctive.", curve);
curve
}
};
new_entries
.push(KeyShareEntry::new(curve.into(), &[0x00]));
}
}
}
}
// ignore remaining entries in oldentmap, if any
*entries = new_entries;
}
}
Unknown(UnknownExtension {
typ: ExtensionType::Padding,
ref mut payload,
}) => {
payload.0.clear();
pad_per_rfc7685 = true;
}
_ => {}
}
}
}
if pad_per_rfc7685 {
// previous steps ensure padding extension is included already
// Padding as defined in RFC7685: pad the payload to at least 512 bytes
// ref: https://datatracker.ietf.org/doc/html/rfc7685#section-4
let pldlen = parsed.get_encoding().len();
let padlen = RFC7685_PADDING_TARGET.saturating_sub(pldlen);
trace!(padlen, "ja3 overwiting: apply rfc7685 padding");
if padlen != 0 {
if let HandshakeMessagePayload {
payload: HandshakePayload::ClientHello(ref mut chp),
..
} = parsed
{
for extension in chp.extensions.iter_mut() {
if let ClientExtension::Unknown(UnknownExtension {
typ: ExtensionType::Padding,
payload,
}) = extension
{
payload.0.resize(padlen, 0);
break;
}
}
}
}
// TODO: strip padding if final length >= 512 + 4?
}
// Payload are stored twice in struct: one typed and one bytes. Both (or at least the
// latter) needs overwriting.
*encoded = Payload::new(parsed.get_encoding());
if pad_per_rfc7685 && encoded.0.len() >= 512 + 4 {
debug!("ja3 overwriting: len of client hello msg >= 512 + 4, while padding is still applied ");
}
}
Some(allowed_unsolicited_extensions)
}