One of the main disadvantages of FTP for file transfer is the lack of protection and encryption means for the transferred data. When connecting to an FTP server username and password are also sent in clear text. To transfer data (especially using public communication channels), it is recommended to use more secure protocols, like FTPS or SFTP. Let’s see how to configure an FTPS server on Windows Server 2012 R2.
FTPS protocol (FTP over SSL/TLS, FTP+SSL) is an extension of the standard FTP protocol, but the connection between a client and a server is protected (encrypted) using SSL /TLS. As a rule, the same 21 port is used for connection.
- The first FTP port is the 'command port' which utilizes the communication between the FTP server and the FTP client. The second port is the 'data transfer' port where the real file transfer runs. Typically, the command port is set to port 21 and the data transfer port is port 20, but actually, depending on the connection mode, the data transfer.
- FTP may run in active or passive mode, which determines how the data connection is established. ( Note, somewhat confusingly, this sense of 'mode' is different from that of the MODE command in the FTP protocol, and actually corresponds to the PORT/PASV/EPSV/etc commands instead.) In both cases, the client creates a TCP control connection from a random, usually an unprivileged, port.
Implicit FTPS was the first method created to encrypt data sent “via FTP”; although a different port is used. When using implicit FTPS, an SSL connection is immediately established via port 990 before login or file transfer can begin. If the recipient fails to comply with the security request, the server immediately drops the connection. By default, the open command uses the TCP port 21 to make the FTP connection. If a different TCP port is needed to connect, enter the port number after the domain name or IP address in the open command.
Note. You should not mix FTPS and SFTP (Secure FTP or SSH FTP). The latter is the extension of the SSH protocol having nothing in common with FTP.
FTP over SSL support appeared in IIS 7.0 (Windows Server 2008). To make an FTPS server work, you will have to install an SSL certificate on your IIS server.
Installation of the FTP Server Role
The installation of the FTP server role in Windows Server 2012 doesn’t cause any problems and has been already described.
How to Generate and Install an SSL Certificate in IIS
Then open the IIS Manager console, select a server and go to the Server Certificates section.
In this section you can import a certificate, create certificate request, update a certificate or create a self-signed certificate. For demonstrative purposes, let’s create a self-signed certificate. (It can also be created using New-SelfSifgnedCertificate cmdlet.) When addressing a service, a warning that the certificate is issued by an untrusted CA will appear. To disable this warning for this certificate, add it to the list of trusted certificates using GPO.
Select Create Self-Signed Certificate.
In the Create Certificate wizard, specify its name and select Web Hosting type of the certificate.
A new self-signed certificate will appear in the list of available certificates. This certificate will expire in 1 year.
How to Create an FTP Site with SSL Support
Then you have to create an FTP site. In the IIS Manager console, right-click Sites and create a new FTP site (Add FTP).
Specify its name and the path to the root directory of the FTP site (in our case, it is default path C:inetpubftproot ).
In the next window of the wizard, select the certificate you have created in the SSL certificates section.
Now you only have to select the type of authentication and user access permissions.
Tip. If each user must have their own FTP root folder, you can use the manual How to create an FTP server with user isolation.
Click Finish in the wizard window. By default, SSL protection is mandatory and used to encrypt both management commands and transferred data.
FTPS and Firewalls
When using FTP protocol, 2 different TCP connections are used, one is for command transfer and another is for data transfer. For each data transfer channel, an individual TCP port is opened, which number is selected by a client or a server. Most firewalls allow to inspect FTP traffic, and after analyzing it, automatically open the necessary ports. When using protected FTPS connection, the transferred data are encrypted and not subject to analysis. As the result, a firewall cannot determine, which port has to be opened for data transfer.
In order not to open the whole range of TCP ports 1024-65535 to an FTPS server from outside, you can specify the range of used addresses for the FTP server. The range is specified in the IIS site settings in FTP Firewall Support section.
After the range of ports has been changed, restart the service (iisreset).
The following rules are responsible for the incoming traffic in the Windows Firewall:
How to Test FTP over SSL ConnectionTo test an FTPS connection, let’s use Filezilla.
Ftps Port 21
- Start FileZilla (or any other client supporting FTPS).
- Click File > Site Manager, and create a new connection (New Site).
- Specify the FTPS server address (Host), protocol type (RequireexplicitFTPoverTLS), user name (User) and the requirement to enter a password to authenticate (Askforpassword)
- Click Connect and enter your password.
- The warning of the untrusted certificate will appear (in case of using self-signed certificate). Confirm the connection.
- The connection has to be established, and the following entries will appear in the log:
Status: Initializing TLS..
Status: Verifying certificate..
Status: TLS connection established. - It means that the secure connection is established and you can transfer files using FTPS protocol.
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July 24, 2020FTPS (also known FTP-SSL, and FTP Secure) is an extension to the commonly used File Transfer Protocol (FTP) that adds support for the Transport Layer Security (TLS) and, formerly, the Secure Sockets Layer (SSL, which is now prohibited by RFC7568) cryptographic protocols.
FTPS should not be confused with the SSH File Transfer Protocol (SFTP), a secure file transfer subsystem for the Secure Shell (SSH) protocol with which it is not compatible. It is also different from FTP over SSH, which is the practice of tunneling FTP through an SSH connection.
Background[edit]
The File Transfer Protocol was drafted in 1971 for use with the scientific and research network, ARPANET.[1] Access to the ARPANET during this time was limited to a small number of military sites and universities and a narrow community of users who could operate without data security and privacy requirements within the protocol.
As the ARPANET gave way to the NSFnet and then the Internet, a broader population potentially had access to the data as it traversed increasingly longer paths from client to server. Macfamilytree 9 0 10 millimeters. The opportunity for unauthorized third parties to eavesdrop on data transmissions increased proportionally.
In 1994, the Internet browser company Netscape developed and released the application layer wrapper, Secure Sockets Layer.[2] This protocol enabled applications to communicate across a network in a private and secure fashion, discouraging eavesdropping, tampering, and message forgery. While it could add security to any protocol that uses reliable connections, such as TCP, it was most commonly used by Netscape with HTTP to form HTTPS.
The SSL protocol was eventually applied to FTP, with a draft Request for Comments (RFC) published in late 1996.[3] An official IANA port was registered shortly thereafter. However, the RFC was not finalized until 2005.[4]
Methods of invoking security[edit]
Two separate methods were developed to invoke client security for use with FTP clients: Implicit and Explicit. While the implicit method requires that a Transport Layer Security is established from the beginning of the connection, which in turn breaks the compatibility with non-FTPS-aware clients and servers, the explicit method uses standard FTP protocol commands and replies in order to upgrade a plain text connection to an encrypted one, allowing a single control port to be used for serving both FTPS-aware and non-FTPS-aware clients.
Implicit[edit]
Negotiation is not supported with implicit FTPS configurations. A client is immediately expected to challenge the FTPS server with a TLSClientHello message. If such a message is not received by the FTPS server, the server should drop the connection.
In order to maintain compatibility with existing non-FTPS-aware clients, implicit FTPS was expected to listen on the IANA well known port 990/TCP for the FTPS control channel, and port 989/TCP for the FTPS data channel.[5] This allowed administrators to retain legacy-compatible services on the original 21/TCP FTP control channel.
Note that implicit negotiation was not defined in RFC 4217. As such, it is considered an earlier, deprecated method of negotiating TLS/SSL for FTP.[6]
Explicit[edit]
In explicit mode (also known as FTPES), an FTPS client must 'explicitly request' security from an FTPS server and then step up to a mutually agreed encryption method. If a client does not request security, the FTPS server can either allow the client to continue in insecure mode or refuse the connection.
The mechanism for negotiating authentication and security with FTP was added under RFC 2228, which included the new FTP command AUTH. While this RFC does not explicitly define any required security mechanisms, e.g. Amadine vector graphics design 1 0 7. SSL or TLS, it does require the FTPS client to challenge the FTPS server with a mutually known mechanism. If the FTPS client challenges the FTPS server with an unknown security mechanism, the FTPS server will respond to the AUTH command with error code 504 (not supported). Clients may determine which mechanisms are supported by querying the FTPS server with the FEAT command, although servers are not necessarily required to be honest in disclosing what levels of security they support. Common methods of invoking FTPS security included AUTH TLS and AUTH SSL.
The explicit method is defined in RFC 4217. In the later versions of the document, FTPS compliance required that clients always negotiate using the AUTH TLS method.
Transport Layer Security (TLS)/Secure Socket Layer (SSL)[edit]
General support[edit]
FTPS includes full support for the TLS and SSL cryptographic protocols, including the use of server-side public key authentication certificates and client-side authorization certificates. It also supports compatible ciphers, including AES, RC4, RC2, Triple DES, and DES. It further supports hash functions SHA, MD5, MD4, and MD2.
Scope of use[edit]
In implicit mode, the entire FTPS session is encrypted. Explicit mode differs in that the client has full control over what areas of the connection are to be encrypted. Enabling and disabling of encryption for the FTPS control channel and FTPS data channel can occur at any time. The only restriction comes from the FTPS server, which has the ability to deny commands based on server encryption policy.
Secure command channel[edit]
The secure command channel mode can be entered through the issue of either the AUTH TLS or AUTH SSL commands. After such time, all command control between the FTPS client and server are assumed to be encrypted. It is generally advised to enter such a state prior to user authentication and authorization in order to avoid the eavesdropping of user name and password data by third parties.
Secure data channel[edit]
The secure data channel can be entered through the issue of the PROT command. It is not enabled by default when the AUTH TLS command is issued. After such time, all data channel communication between the FTPS client and server is assumed to be encrypted.
The FTPS client may exit the secure data channel mode at any time by issuing a CDC (clear data channel) command.
Reasons to disable encryption[edit]
It may not be advantageous to use data channel encryption when performing transfers under the following scenarios:
- Files being transferred are of a non-sensitive nature, making encryption unnecessary,
- Files being transferred are already encrypted at the file level or are passing over an encrypted VPN, making encryption redundant,
- Available TLS or SSL encryption modes do not meet desired level of encryption. This is common with older FTPS clients or servers that may have been limited to 40-bit SSL due to previous United States high-encryption export laws.
It may not be advantageous to use control channel encryption under the following scenarios:
- Use of FTPS when the client or server reside behind a network firewall or network address translation (NAT) device. (See Firewall Incompatibilities below.)
- Repeated use of AUTH and CCC/CDC commands by anonymous FTP clients within the same session. Such behavior can be used as a resource-based denial of service attack as the TLS/SSL session must be regenerated each time, using server processor time.
SSL certificates[edit]
Much like HTTPS, FTPS servers must provide a public key certificate. These certificates can be requested and created using tools such as OpenSSL.
When these certificates are signed by a trusted certificate authority, this provides assurance that the client is connected to the requested server, avoiding a man-in-the-middle attack. If the certificate is not signed by a trusted CA (a self-signed certificate), the FTPS client may generate a warning stating that the certificate is not valid. The client can choose to accept the certificate or reject the connection.
This is in contrast to the SSH File Transfer Protocol (SFTP), which does not present signed certificates, but instead relies on Out-of-band authentication of public keys.
Firewall incompatibilities[edit]
Because FTP uses a dynamic secondary port (for data channels), many firewalls were designed to snoop FTP protocol control messages in order to determine which secondary data connections they need to allow. However, if the FTP control connection is encrypted using TLS/SSL, the firewall cannot determine the TCP port number of a data connection negotiated between the client and FTP server. Therefore, in many firewalled networks, an FTPS deployment will fail when an unencrypted FTP deployment will work. This problem can be solved with the use of a limited range of ports for data and configuring the firewall to open these ports.
See also[edit]
- Secure copy (SCP), a protocol for transferring files using the Secure Shell (SSH) protocol
- SSH File Transfer Protocol (SFTP)
- Files transferred over shell protocol (FISH)
Ftps Port 22
Notes[edit]
Ftps Port 989
- ^RFC-265: File Transfer Protocol (FTP)
- ^The SSL Protocol, Feb. 9th, 1995
- ^RFC draft, Secure FTP Over SSL, revision 1996-11-26
- ^RFC-4217: Securing FTP with TLS
- ^'Service Name and Transport Protocol Port Number Registry'. Retrieved 9 October 2015.
- ^'Deprecated SSL negotiation mechanisms'. Retrieved 9 October 2015.
Ftps Port 22
External links[edit]
- Curl-loader - an open-source FTPS loading/testing tool
Ftps Ports
Ftps Port Numbers
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