I tried to connect to my POP3 school server as part of my assignment. Now, I can connect to the server but the real problem is when I try to log in using the "USER" command.
c:/>nc server.pop3.com 110
+OK Microsoft Exchange Server 2003 POP3 server version 6.5.7638.1 (server.pop3.com) ready.
USER myuserid
-ERR Protocol error
Now I'm wondering whether there's an issue on my side or on the server? Thank you for the time and answers.
Exchange expects a CRLF as line termination.
Use
netcat -C servername pop3
Use CAPA command just after connection.
You'll see what login mechanisms are supported.
Exchange usually does not allow clear text mechanisms. Most likely you'll be forced to use SSL+plain text, or APOP login mechanism.
Related
I understand that the server will send its SSH version and the client will do the same. What I am wonder is if the order matters.
Additionally, I'm wondering if I could make an SSH server receive an SSH version from a client before sending its own version?
The order of the SSH protocol version exchange is unspecified; it says:
When the connection has been established, both sides MUST send an
identification string. This identification string MUST be
SSH-protoversion-softwareversion SP comments CR LF
The RFC is likely silent on the protocol version exchange order because, practically speaking, it's a race and the order should not matter. When the client's TCP connect is accepted by the server, the client and server send their version information...who gets to the other first is just a matter of speed, traffic, etc.
As a client, you cannot (or should not be able to...) "make" the server wait; it's certainly possible that a particular server implementation waits for client before sending its own information but that's a server implementation detail.
You can Wireshark the SSH connection and see the communication at the TCP level. The SSH client will send its Protocol version first before the server.
I don't think you have the flexibility to change the order of communication. With my SSH client (OpenSSH_8.1p1, LibreSSL 2.7.3) I could see that once SYN-ACK is done, the server is waiting for the SSH client to send it's supported protocol version.
You cannot change the order of the protocol in this case; it's fixed in the RFC, and the order does indeed matter. The server sends its version as part of the opening request, and then the client sends its version. Afterward, the two sides exchange a list of algorithms supported by both sides, and the selected algorithm is generally the first one the client supports that's also supported by the server.
While you cannot change the protocol version number announcement, you can, based on the version that the client has sent, choose to offer different algorithms. For example, some versions of OpenSSH incorrectly implemented curve25519-sha256#libssh.org, so a server which knows about this may choose not to offer that algorithm to a broken version of OpenSSH. Similarly, the client can announce different algorithms to the server based on the server's version announcement.
I am using Telnet on an Ubuntu 18.04 Server being accessed via SSH. I log into the email server being set up that uses PostFix and DoveCot, to test if the "phil#xxxxxxx.com" mail account is working.
This is the exchange:
root#xxxxxxx:/var/log# telnet xxxxxxx.com 110
Trying 2600:3c01::f03c:92ff:fe93:5fa0... Connected to xxxxxxx.com.
Escape character is '^]'. +OK Dovecot (Ubuntu) ready.
USER phil +OK
PASS fakepassword
-ERR [AUTH] Authentication failed.
I'm not trying to solve the entire mystery here, but just wanted to check on whether this is a valid use of Telnet. A website about using Telnet states the following:
However, you should note that Telnet is not encrypted. Most public
internet services, such as Google or Yahoo, require an encrypted
connection—which isn't supported by Telnet.
Is this a situation were the lack of encryption might contribute to the authentication failure? I'm guessing not, since I'm not going through a browser. I just wanted to verify that if everything was set up right, this would be a valid way to test the email account.
Yes, you can use telnet for protocol exploration. POP3 in this case is text based and not wrapped in TLS, so it works out without any other advanced tools (eg openssl).
That said you will want to familiarize yourself with the POP3 AUTH exchange, which is probably not going to accept credentials in cleartext these days. (If this were 1999, different story.)
https://ietf.org/rfc/rfc1939.txt
You might consider using an actual email program (MUA in the parlance) to negotiate the connection, in tandem with a protocol sniffer like wireshark to see how the exchange works.
Running the command redis-server it returns:
The server is now ready to accept connections on port 6379
Trying to connect in my browser localhost:6379 I get this message:
Possible SECURITY ATTACK detected. It looks like somebody is sending POST or Host: commands to Redis. This is likely due to an attacker attempting to use Cross Protocol Scripting to compromise your Redis instance. Connection aborted.
Can anyone help me fix this error please?
You'll need to use a Redis client to connect to Redis, not your browser. Look at this page for a few https://redis.io/clients, or use redis-cli, or even just plain Telnet.
I am trying to connect to SFTP server using notepad++ plugin NppFTP. However, while connecting to the remote server I always get below error:
Connecting
[SFTP] Connection failed : Timeout connecting to <IP address>
Unable to connect
Disconnected
Here are the important configuration details set in NppFTP window for your reference:
Port: 22
Connection Type: SFTP
Authentication: Try password authentication
I tried to go through some of the solutions stated in few the questions in Stack Overflow but to no avail.
Would really appreciate your suggestions/pointers to resolve this. If it is related to SSH private key, would appreciate if you can provide the steps as well.
Edit: I am able to access the server using another FTP tool FileZilla which eliminates any mess with the access front.
You need to find out more about where the issue is:
Can you ping the server you are trying to connect to?
ping 166.178.233.70
Did you try connecting with another ftp tool, like FileZilla, that gives more detailed log information?
The possible issues are numerous:
The ftp server config: set up to exclude connections from certain ip addresses or domains, requires public/private keys...
Your local connection/VPN is not passing the connection.
It may require a
I got the same issue. The problem was solved after I updated NppFTP.
in my case, I changed the wifi connection then, it works.
I can send an email using Thunderbird. I use the same smtp server address when installing blat. But, blat does not send the email. I get the following error:
Error: Server refused connection.
Any ideas on how to fix this?
Sounds like you may trying to use a regular connect rather than an http*s* connection. Or you may be useing the regular 80 port rather than the SSL port 443 (or something like that).