Eugeny/thrussh - Change XEKZBXNINGU2NELIKOQXWY5SS4MOVEVXX3QWQUSN42X7V46CQDKQC

Fixing a bug with tokio::select

Each time tokio::select polled the cipher, Thrussh attempted to read the length of the packet, consuming 4 bytes each times. For packets that didn't arrive in one TCP packet, this resulted in incorrect packet length, and a stall of the protocol.

Created by pmeunier on November 23, 2020

XEKZBXNINGU2NELIKOQXWY5SS4MOVEVXX3QWQUSN42X7V46CQDKQC

Dependencies

[2] 7FRJYUI62VW257VVFQXND6OKSAILVTHGEJCXFE6CG6FIOIUTDVYAC

In channels

main

Change contents

Insertion in thrussh/src/server/session.rs at line 151 [2.188192]
[2.192873]
[2.192873]
```
                    debug!("starting rekeying");
```

Replacement in thrussh/src/cipher/mod.rs at line 110 [2.409086]

B:BD[2.412048] → [2.412048:412515]

    let mut len = [0; 4];
    stream.read_exact(&mut len).await?;
    debug!("len = {:?}", len);
    {
        let key = pair.remote_to_local.as_opening_key();
        let seqn = buffer.seqn.0;
        buffer.buffer.clear();
        buffer.buffer.extend(&len);
        let len = key.decrypt_packet_length(seqn, len);
        let len = BigEndian::read_u32(&len) as usize + key.tag_len();
        debug!("clear len = {:?}", len);
        buffer.buffer.resize(len + 4);

[2.412048]

[2.412515]

    if buffer.len == 0 {
        let mut len = [0; 4];
        stream.read_exact(&mut len).await?;
        debug!("reading, len = {:?}", len);
        {
            let key = pair.remote_to_local.as_opening_key();
            let seqn = buffer.seqn.0;
            buffer.buffer.clear();
            buffer.buffer.extend(&len);
            debug!("reading, seqn = {:?}", seqn);
            let len = key.decrypt_packet_length(seqn, len);
            buffer.len = BigEndian::read_u32(&len) as usize + key.tag_len();
            debug!("reading, clear len = {:?}", buffer.len);
        }

Insertion in thrussh/src/cipher/mod.rs at line 125 [2.409086]

[2.412521]

    buffer.buffer.resize(buffer.len + 4);
    debug!("read_exact {:?}", buffer.len + 4);

Insertion in thrussh/src/cipher/mod.rs at line 128 [2.409086]
[2.412576]
[2.412576]
```
    debug!("read_exact done");
```
Replacement in thrussh/src/cipher/mod.rs at line 136 [2.409086]
B:BD[2.412896] → [2.412896:412947]
```
    debug!("padding_length {:?}", padding_length);
```
[2.412896]
[2.412947]
```
    debug!("reading, padding_length {:?}", padding_length);
```
Replacement in thrussh/src/cipher/mod.rs at line 159 [2.409086]
B:BD[2.413618] → [2.413618:413619]
[2.413618]
[2.413619]
```
        debug!("writing, seqn = {:?}", buffer.seqn.0);
```

Fixing a bug with tokio::select

Dependencies

In channels

Change contents

Insertion in thrussh/src/server/session.rs at line 151 [2.188192]

Replacement in thrussh/src/cipher/mod.rs at line 110 [2.409086]

Insertion in thrussh/src/cipher/mod.rs at line 125 [2.409086]

Insertion in thrussh/src/cipher/mod.rs at line 128 [2.409086]

Replacement in thrussh/src/cipher/mod.rs at line 136 [2.409086]

Replacement in thrussh/src/cipher/mod.rs at line 159 [2.409086]