SFTP connection failure with Perl "Net::SFTP" module - perl

Question

I am trying to connect to SFTP server using Perl but I get the following connection error: Permission denied at /app/perl-5.24.3/lib/site_perl/5.24.3/Net/SFTP.pm line 63.
My connection code 'sftp_test2.pl':
use strict;
use warnings;
use Net::SFTP;
my $server = 'downloads-server';
my $user = 'user';
my $port = "10022";
my $password = '';
my %args = (
user => "$user",
port => "$port",
ssh_args => {
user => "$user",
identity_files => [ 'path/sftp_download'],
port => "$port",
protocol=>'2,1',
debug => 1,
}
);
my $sftp=Net::SFTP->new($server, %args) or die "could not open connection to $server\n";
execution:
$>perl sftp_test2.pl
Reading configuration data path/home/.ssh/config
Reading configuration data /etc/ssh_config
Connecting to downloads-server, port 10022.
Remote version string: SSH-2.0-CrushFTPSSHD
Remote protocol version 2.0, remote software version CrushFTPSSHD
Net::SSH::Perl Version 2.14, protocol version 2.0.
No compat match: CrushFTPSSHD.
Connection established.
Sent key-exchange init (KEXINIT), waiting for response.
Using diffie-hellman-group-exchange-sha256 for key exchange
Host key algorithm: ssh-rsa
Algorithms, c->s: aes256-ctr hmac-sha2-512-etm#openssh.com none
Algorithms, s->c: aes256-ctr hmac-sha2-512-etm#openssh.com none
Entering Diffie-Hellman Group Exchange.
SSH2_MSG_KEX_DH_GEX_REQUEST(2048<4096<8192) sent
Sent DH Group Exchange request, waiting for reply.
Received 4096 bit DH Group Exchange reply.
Generating new Diffie-Hellman keys.
Entering Diffie-Hellman key exchange.
Sent DH public key, waiting for reply.
Received host key, type 'ssh-rsa'.
Host 'downloads-server' is known and matches the host key.
Verifying server signature.
Send NEWKEYS.
Waiting for NEWKEYS message.
Enabling encryption/MAC/compression.
Sending request for user-authentication service.
Service accepted: ssh-userauth.
Trying empty user-authentication request.
Authentication methods that can continue: password,publickey,keyboard-interactive.
Next method to try is password.
Trying password authentication.
Will not query passphrase in batch mode.
Authentication methods that can continue: password,publickey,keyboard-interactive.
Next method to try is password.
Trying password authentication.
Will not query passphrase in batch mode.
Authentication methods that can continue: password,publickey,keyboard-interactive.
Next method to try is password.
Trying password authentication.
Will not query passphrase in batch mode.
Authentication methods that can continue: password,publickey,keyboard-interactive.
Next method to try is password.
Next method to try is publickey.
Publickey: testing agent key 'my-server'
Authentication methods that can continue: password,publickey,keyboard-interactive.
Next method to try is password.
Next method to try is publickey.
Publickey: testing agent key 'path/home/.ssh/id_rsa'
Authentication methods that can continue: password,publickey,keyboard-interactive.
Next method to try is password.
Next method to try is publickey.
Trying pubkey authentication with key file 'path/sftp_download'
Authentication methods that can continue: password,publickey,keyboard-interactive.
Next method to try is password.
Next method to try is publickey.
Permission denied at /app/perl-5.24.3/lib/site_perl/5.24.3/Net/SFTP.pm line 63.
I thought that it is related to my private key, but I can connect via unix command:
sftp -oPort=10022 -oIdentityFile=path/sftp_download user#downloads-server
Connecting to downloads-server...
sftp>
I tried to find a solution in many articles and also tried few code variations, but without a success.
Am I doing something wrong?
Is it a known bug? any workaround?
How can I debug it to find the reason (I am not very well familiar with SSH/FTP).
EDIT:
I suspected that it may be related to multiple connection failing attempts with password so I removed the password authentication from "%AUTH_MAP" in the file "app/perl-5.24.3/lib/site_perl/5.24.3/x86_64-linux/Net/SSH/Perl/AuthMgr.pm" and it connected as expected!
Is there a way to force using only/first key authentication?
Thanks in advance!
Mike

Answer 1

The code to disable password authentication (only authentication key) is:
ssh_args => {
user => $user,
options => [ 'PasswordAuthentication no' ],
identity_files => [ 'path/sftp_download'],
port => $port,
protocol =>'2,1',
debug => 1,
}