Node: 16

ssh2-sftp-client: 9

Connecting using username&password
Sample code

const Client = require('ssh2-sftp-client');
module.exports = class SFTPClient {
  #sftpClient;
  constructor() {
    this.#sftpClient = new Client();
  }
  async connect(options) {
    try {
      return this.#sftpClient.connect(options); // options = {host,port,username,password}
    } catch (err) {
      return null;
    }
  }
}

The connection was initially functioning properly, but it now fails on the lambda function, while the ECS instances continue to work fine.

here are the detailed logs from the Lambda

2024-10-29T21:37:39.289Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO Debug:  CLIENT[sftp]: ssh2-sftp-client Version: 9.0.4  
{
    "node": "16.20.2",
    "v8": "9.4.146.26-node.26",
    "uv": "1.43.0",
    "zlib": "1.2.11",
    "brotli": "1.0.9",
    "ares": "1.19.1",
    "modules": "93",
    "nghttp2": "1.47.0",
    "napi": "8",
    "llhttp": "6.0.11",
    "openssl": "1.1.1v+quic",
    "cldr": "41.0",
    "icu": "71.1",
    "tz": "2022f",
    "unicode": "14.0",
    "ngtcp2": "0.8.1",
    "nghttp3": "0.7.0"
}

2024-10-29T21:37:39.290Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO Debug:  CLIENT[sftp]: connect: Connect attempt 1
2024-10-29T21:37:39.293Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO Debug:  Custom crypto binding not available
2024-10-29T21:37:39.771Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO Debug:  Verifying signature ...
2024-10-29T21:37:39.772Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO Debug:  Verified signature
2024-10-29T21:37:39.773Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO Debug:  Handshake completed
2024-10-29T21:37:39.773Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO    #sftpClient event handshake:  
{
    "kex": "ecdh-sha2-nistp256",
    "serverHostKey": "ssh-ed25519",
    "cs": {
        "cipher": "aes128-gcm@openssh.com",
        "mac": "",
        "compress": "none",
        "lang": ""
    },
    "sc": {
        "cipher": "aes128-gcm@openssh.com",
        "mac": "",
        "compress": "none",
        "lang": ""
    }
}

2024-10-29T21:37:39.898Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO Debug:  Outbound: Sending USERAUTH_REQUEST (none)
2024-10-29T21:37:40.086Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO Debug:  Socket error: read ECONNRESET
2024-10-29T21:37:40.087Z    b2a4f522-527d-4bbe-ae4f-116600d2bd76    INFO    #sftpClient event error:  Error: read ECONNRESET
    at TCP.onStreamRead (node:internal/stream_base_commons:217:20) {
  errno: -104,
  code: 'ECONNRESET',
  syscall: 'read',
  level: 'client-socket'
}

We also tried using Node v20 and ssh2 v1.16.0, but it failed as well.

We have explored numerous options to resolve the problem.

Option - 1: The third-party responsible for maintaining the SFTP system was contacted, but they didn't provide much info to fix it. They just sent an image attached. sftp-server-log

Option - 2: We initiated an AWS premium support ticket to receive their feedback, but the AWS support system confirmed that everything is okay on their end.

Option - 3: We started searching for Google and asking questions to AI, and tried different solutions. One of our engineers found a simple solution that works fine. I'm including it here in case anyone else experiences the same problem and requires assistance.

Before

options = {host,port,username,password}; this.#sftpClient.connect(options);

After

options = {host,port,username,password, algorithms: { cipher: ['aes256-ctr'] }}; this.#sftpClient.connect(options);

So adding algorithms as options in the configuration works for us. You might need a different cipher version to achieve your desired solution. This algorithms: { cipher: ['aes256-ctr'] } works for us