[SOLVED] Unable to exchange encryption keys

Issue

I'm facing a hard problem at the moment and I didn't find anything online that can help me.

I want to connect from my server to another one through SSH in order to send instructions (the second server manage Wi-Fi authorizations).

As much as I can say, I think the problem occurred because we updated one server. (I'm not really sure if the problem has appeared because of it).

I'm from a Windows Server and I want to call a Linux one.

Here is the script :

function executeCommand($command) {
    $infoConnection = getInfoConnection();

    $out = '';
    //The Warning occurs here, impossible to go further
    $connection = ssh2_connect($infoConnection["hostname"], 22);

    if ($connection === false) {
        $error = error_get_last();
        throw new Exception("
        Error Type : ".$error["type"]."<br/>
        Message : ".$error["message"]."<br/>
        File : ".$error["file"]."<br/>
        Line : ".$error["line"]."<br/>");
    }

    ssh2_auth_password($connection, $infoConnection["username"], $infoConnection["password"]);

    $stdio_stream = ssh2_shell($connection);
    sleep(2);
    fwrite($stdio_stream,$infoConnection["username"]."\n");
    sleep(1);
    fwrite($stdio_stream,$infoConnection["password"]."\n");
    sleep(1);

    fwrite($stdio_stream, $command."\n");
    sleep(1);
    while($buffer = fgets($stdio_stream)) {

        $out .= $buffer;
    }
    fwrite($stdio_stream, 'exit');
    unset($connection);

    return $out;
}

Here is the warning :

Warning: ssh2_connect() [function.ssh2-connect]: Error starting up SSH connection(-5): Unable to exchange encryption keys in ../aff_wifi.php on line 203

The line 203 is this one :

$connection = ssh2_connect($infoConnection["hostname"], 22);

When I "catch" the warning, I have this :

Error type : 2 Message : ssh2_connect() [function.ssh2-connect]: Unable to connect to ipAdress File: ..\aff_wifi.php Line: 203

Do you have any idea why this occurs? When I try to connect from my server to the other with PuTTY, everything works fine

Have a good day!

Solution

I had this problem when trying to access a focal ubuntu server from a little old xenial through ssh2_connect. The solution was to update libssh2-1. Even with php showing the old version, it worked normally.

In the xenial, I added the focal repository, then installed the latest version of libssh2-1, restarted PHP to apply and removed focal repository.

sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse"
sudo apt-get update
sudo apt -y install libssh2-1
sudo add-apt-repository -r "deb http://archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse"
sudo apt-get update

Answered By - pdropi