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nora 2024-08-11 00:11:49 +02:00
parent 1adf798c5d
commit ed30d5b4dc
8 changed files with 75 additions and 87 deletions
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27
Cargo.lock generated
View file

@ -17,16 +17,6 @@ version = "1.0.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
[[package]]
name = "aead"
version = "0.5.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "d122413f284cf2d62fb1b7db97e02edb8cda96d769b16e443a4f6195e35662b0"
dependencies = [
"crypto-common",
"generic-array",
]
[[package]]
name = "aho-corasick"
version = "1.1.3"
@ -113,19 +103,6 @@ dependencies = [
"cpufeatures",
]
[[package]]
name = "chacha20poly1305"
version = "0.10.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "10cd79432192d1c0f4e1a0fef9527696cc039165d729fb41b3f4f4f354c2dc35"
dependencies = [
"aead",
"chacha20",
"cipher",
"poly1305",
"zeroize",
]
[[package]]
name = "cipher"
version = "0.4.4"
@ -134,7 +111,6 @@ checksum = "773f3b9af64447d2ce9850330c473515014aa235e6a783b02db81ff39e4a3dad"
dependencies = [
"crypto-common",
"inout",
"zeroize",
]
[[package]]
@ -159,7 +135,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "1bfb12502f3fc46cca1bb51ac28df9d618d813cdc3d2f25b9fe775a34af26bb3"
dependencies = [
"generic-array",
"rand_core",
"typenum",
]
@ -693,7 +668,6 @@ name = "ssh-transport"
version = "0.1.0"
dependencies = [
"chacha20",
"chacha20poly1305",
"ed25519-dalek",
"eyre",
"hex-literal",
@ -703,7 +677,6 @@ dependencies = [
"sha2",
"subtle",
"tracing",
"tracing-subscriber",
"x25519-dalek",
]

13
src/main.rs
View file

@ -8,14 +8,19 @@ use tokio::{
use tracing::{error, info};
use ssh_transport::{ServerConnection, SshError, ThreadRngRand};
use tracing_subscriber::EnvFilter;
#[tokio::main]
async fn main() -> eyre::Result<()> {
tracing_subscriber::fmt().init();
tracing_subscriber::fmt()
.with_env_filter(EnvFilter::from_default_env())
.init();
let listener = TcpListener::bind("0.0.0.0:2222")
.await
.wrap_err("binding listener")?;
let addr = "0.0.0.0:2222".parse::<SocketAddr>().unwrap();
info!(?addr, "Starting server");
let listener = TcpListener::bind(addr).await.wrap_err("binding listener")?;
loop {
let next = listener.accept().await?;

2
ssh-transport/Cargo.toml
View file

@ -5,7 +5,6 @@ edition = "2021"
[dependencies]
chacha20 = "0.9.1"
chacha20poly1305 = "0.10.1"
ed25519-dalek = { version = "2.1.1" }
eyre = "0.6.12"
poly1305 = "0.8.0"
@ -14,7 +13,6 @@ rand_core = "0.6.4"
sha2 = "0.10.8"
subtle = "2.6.1"
tracing = "0.1.40"
tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
x25519-dalek = "2.0.1"
[dev-dependencies]

3
ssh-transport/README.md
View file

@ -3,7 +3,8 @@
Transport layer of SSH.
Based on [RFC 4253 The Secure Shell (SSH) Transport Layer Protocol](https://datatracker.ietf.org/doc/html/rfc4253)
and [RFC 4251 The Secure Shell (SSH) Protocol Architecture](https://datatracker.ietf.org/doc/html/rfc4251).
and [RFC 4251 The Secure Shell (SSH) Protocol Architecture](https://datatracker.ietf.org/doc/html/rfc4251)
and [RFC 4250 The Secure Shell (SSH) Protocol Assigned Numbers](https://datatracker.ietf.org/doc/html/rfc4250).
Other relevant RFCs:
- [RFC 5649 AES Galois Counter Mode for the Secure Shell Transport Layer Protocol](https://datatracker.ietf.org/doc/html/rfc5647)

49
ssh-transport/src/keys.rs
View file

@ -16,6 +16,7 @@ pub(crate) struct Session {
pub(crate) trait Decryptor: Send + Sync + 'static {
fn decrypt_len(&mut self, bytes: &mut [u8; 4], packet_number: u64);
fn decrypt_packet(&mut self, raw_packet: RawPacket, packet_number: u64) -> Result<Packet>;
fn additional_mac_len(&self) -> usize;
fn rekey(&mut self, h: [u8; 32], k: [u8; 32]) -> Result<(), ()>;
}
@ -25,6 +26,9 @@ impl Decryptor for Plaintext {
fn decrypt_packet(&mut self, raw: RawPacket, _: u64) -> Result<Packet> {
Packet::from_raw(&raw.rest())
}
fn additional_mac_len(&self) -> usize {
0
}
fn rekey(&mut self, _: [u8; 32], _: [u8; 32]) -> Result<(), ()> {
Err(())
}
@ -65,6 +69,10 @@ impl Decryptor for Session {
.decrypt_packet(bytes, packet_number)
}
fn additional_mac_len(&self) -> usize {
poly1305::BLOCK_SIZE
}
fn rekey(&mut self, h: [u8; 32], k: [u8; 32]) -> Result<(), ()> {
*self = Self::from_keys(self.session_id, h, k);
Ok(())
@ -120,53 +128,33 @@ type SshChaCha20 = chacha20::ChaCha20Legacy;
struct SshChaCha20Poly1305 {
header_key: chacha20::Key,
main_key2: chacha20::Key,
main_key:
chacha20poly1305::ChaChaPoly1305<chacha20::ChaCha20Legacy, chacha20::cipher::typenum::U8>,
main_key: chacha20::Key,
}
impl SshChaCha20Poly1305 {
fn new(key: [u8; 64]) -> Self {
Self {
main_key2: <[u8; 32]>::try_from(&key[..32]).unwrap().into(),
main_key: chacha20poly1305::ChaChaPoly1305::new(
&<[u8; 32]>::try_from(&key[..32]).unwrap().into(),
),
main_key: <[u8; 32]>::try_from(&key[..32]).unwrap().into(),
header_key: <[u8; 32]>::try_from(&key[32..]).unwrap().into(),
}
}
fn decrypt_len(&self, bytes: &mut [u8], packet_number: u64) {
eprintln!("encrypted len: {:x?}", &bytes);
// <https://github.com/openssh/openssh-portable/blob/1ec0a64c5dc57b8a2053a93b5ef0d02ff8598e5c/PROTOCOL.chacha20poly1305>
let mut cipher = SshChaCha20::new(&self.header_key, &packet_number.to_be_bytes().into());
cipher.apply_keystream(bytes);
}
fn decrypt_packet(&mut self, bytes: RawPacket, packet_number: u64) -> Result<Packet> {
fn decrypt_packet(&mut self, mut bytes: RawPacket, packet_number: u64) -> Result<Packet> {
// <https://github.com/openssh/openssh-portable/blob/1ec0a64c5dc57b8a2053a93b5ef0d02ff8598e5c/PROTOCOL.chacha20poly1305>
//let mut aead_payload = bytes.into_full_packet();
//let mut associated_data = [0; 4];
//associated_data.copy_from_slice(&aead_payload[0..4]);
//aead_payload.splice(0..4, []);
//chacha20poly1305::AeadInPlace::decrypt_in_place(
// &self.main_key,
// &packet_number.to_be_bytes().into(),
// &associated_data,
// &mut aead_payload,
//)
//.map_err(|err| crate::client_error!("failed to decrypt invalid poly1305 MAC: {err}"))?;
let mut cipher = <chacha20::ChaCha20Legacy as chacha20::cipher::KeyIvInit>::new(
&self.main_key2,
let mut cipher = <SshChaCha20 as chacha20::cipher::KeyIvInit>::new(
&self.main_key,
&packet_number.to_be_bytes().into(),
);
let tag_offset = bytes.full_packet().len() - 16;
let data_to_mac = &bytes.full_packet()[..tag_offset];
eprintln!("data_to_mac: {:x?}", &data_to_mac);
let mac = {
let mut poly1305_key = [0; poly1305::KEY_SIZE];
@ -176,20 +164,17 @@ impl SshChaCha20Poly1305 {
let read_tag = poly1305::Tag::from_slice(&bytes.full_packet()[tag_offset..]);
eprintln!("expected MAC: {mac:x?}");
eprintln!("found MAC: {read_tag:x?}");
if !bool::from(mac.ct_eq(read_tag)) {
return Err(crate::client_error!(
"failed to decrypt: invalid poly1305 MAC"
));
}
//mac.verify(read_tag)
// .map_err(|err| crate::client_error!("failed to decrypt invalid poly1305 MAC: {err}"))?;
cipher.seek(64);
todo!()
let encrypted_packet_content = bytes.content_mut();
cipher.apply_keystream(encrypted_packet_content);
Packet::from_raw(encrypted_packet_content)
}
}

16
ssh-transport/src/lib.rs
View file

@ -10,9 +10,10 @@ use packet::{
DhKeyExchangeInitPacket, DhKeyExchangeInitReplyPacket, KeyExchangeInitPacket, Packet,
PacketTransport, SshPublicKey, SshSignature,
};
use parse::{MpInt, NameList};
use parse::{MpInt, NameList, Parser};
use rand::RngCore;
use sha2::Digest;
use tracing::{debug, info};
use x25519_dalek::{EphemeralSecret, PublicKey};
#[derive(Debug)]
@ -304,7 +305,18 @@ impl ServerConnection {
self.state = ServerState::ServiceRequest {};
self.packet_transport.set_key(h, k);
}
ServerState::ServiceRequest {} => {}
ServerState::ServiceRequest {} => {
if packet.payload.get(0) != Some(&Packet::SSH_MSG_SERVICE_REQUEST) {
return Err(client_error!("did not send SSH_MSG_SERVICE_REQUEST"));
}
let mut p = Parser::new(&packet.payload[1..]);
let service = p.utf8_string()?;
debug!(?service, "Client requesting service");
if service != "ssh-userauth" {
return Err(client_error!("only supports ssh-userauth"));
}
}
}
}
Ok(())

21
ssh-transport/src/packet.rs
View file

@ -63,6 +63,7 @@ pub(crate) struct Packet {
pub(crate) payload: Vec<u8>,
}
impl Packet {
pub(crate) const SSH_MSG_SERVICE_REQUEST: u8 = 5;
pub(crate) const SSH_MSG_KEXINIT: u8 = 20;
pub(crate) const SSH_MSG_NEWKEYS: u8 = 21;
pub(crate) const SSH_MSG_KEXDH_INIT: u8 = 30;
@ -78,9 +79,10 @@ impl Packet {
};
let payload = &bytes[1..][..payload_len];
if (bytes.len() + 4) % 8 != 0 {
return Err(client_error!("full packet length must be multiple of 8"));
}
// TODO: this fails with OpenSSH client... why?
//if (bytes.len() + 4) % 8 != 0 {
// return Err(client_error!("full packet length must be multiple of 8: {}", bytes.len()));
//}
Ok(Self {
payload: payload.to_vec(),
@ -138,7 +140,7 @@ impl<'a> KeyExchangeInitPacket<'a> {
"expected SSH_MSG_KEXINIT packet, found {kind}"
));
}
let cookie = c.read_array::<16>()?;
let cookie = c.array::<16>()?;
let kex_algorithms = c.name_list()?;
let server_host_key_algorithms = c.name_list()?;
let encryption_algorithms_client_to_server = c.name_list()?;
@ -258,6 +260,7 @@ impl<'a> DhKeyExchangeInitReplyPacket<'a> {
pub(crate) struct RawPacket {
len: usize,
mac_len: usize,
raw: Vec<u8>,
}
impl RawPacket {
@ -267,8 +270,9 @@ impl RawPacket {
pub(crate) fn full_packet(&self) -> &[u8] {
&self.raw
}
pub(crate) fn into_full_packet(self) -> Vec<u8> {
self.raw
pub(crate) fn content_mut(&mut self) -> &mut [u8] {
let mac_start = self.raw.len() - self.mac_len;
&mut self.raw[4..mac_start]
}
}
@ -323,9 +327,9 @@ impl PacketParser {
decrytor.decrypt_len(&mut len_to_decrypt, next_seq_nr);
let packet_length = u32::from_be_bytes(len_to_decrypt);
let packet_length = packet_length.try_into().unwrap();
let packet_length: usize = packet_length.try_into().unwrap();
dbg!(packet_length);
let packet_length = packet_length + decrytor.additional_mac_len();
self.packet_length = Some(packet_length);
@ -347,6 +351,7 @@ impl PacketParser {
consumed,
RawPacket {
raw: std::mem::take(&mut self.raw_data),
mac_len: decrytor.additional_mac_len(),
len: packet_length,
},
)))

31
ssh-transport/src/parse.rs
View file

@ -12,16 +12,16 @@ impl<'a> Parser<'a> {
}
pub(crate) fn u8(&mut self) -> Result<u8> {
let arr = self.read_array::<1>()?;
let arr = self.array::<1>()?;
Ok(arr[0])
}
pub(crate) fn u32(&mut self) -> Result<u32> {
let arr = self.read_array()?;
let arr = self.array()?;
Ok(u32::from_be_bytes(arr))
}
pub(crate) fn read_array<const N: usize>(&mut self) -> Result<[u8; N]> {
pub(crate) fn array<const N: usize>(&mut self) -> Result<[u8; N]> {
if self.0.len() < N {
return Err(crate::client_error!("packet too short"));
}
@ -30,7 +30,7 @@ impl<'a> Parser<'a> {
Ok(result)
}
pub(crate) fn read_slice(&mut self, len: usize) -> Result<&'a [u8]> {
pub(crate) fn slice(&mut self, len: usize) -> Result<&'a [u8]> {
if self.0.len() < len {
return Err(crate::client_error!("packet too short"));
}
@ -49,19 +49,28 @@ impl<'a> Parser<'a> {
}
pub(crate) fn name_list(&mut self) -> Result<NameList<'a>> {
let len = self.u32()?;
let list = self.read_slice(len.try_into().unwrap())?;
let Ok(list) = str::from_utf8(list) else {
return Err(crate::client_error!("name-list is invalid UTF-8"));
};
let list = self.utf8_string()?;
Ok(NameList(list))
}
pub(crate) fn mpint(&mut self) -> Result<MpInt<'a>> {
let len = self.u32()?;
let data = self.read_slice(len as usize)?;
let data = self.string()?;
Ok(MpInt(data))
}
pub(crate) fn string(&mut self) -> Result<&'a [u8]> {
let len = self.u32()?;
let data = self.slice(len.try_into().unwrap())?;
Ok(data)
}
pub(crate) fn utf8_string(&mut self) -> Result<&'a str> {
let s = self.string()?;
let Ok(s) = str::from_utf8(s) else {
return Err(crate::client_error!("name-list is invalid UTF-8"));
};
Ok(s)
}
}
/// A simplified `byteorder` clone that emits client errors when the data is too short.