When sending data between systems, users and businesses should be cautious preserving data confidentiality and integrity, especially if this data is determined as sensitive or personal. The use of tools or protocols that fail to preserve an appropriate level of security may expose this data to eavesdroppers, leading to a violation of privacy and security regulations. Performing data transactions through SCP Protocol (Secure Copy Protocol) is one of the methods which is built for the secure transfer of digital information.
What is SCP protocol?
SCP, or Secure Copy Protocol, is a method based on (Secure Shell) SSH for safely transferring computer files between a local host and a remote host, or between two remote hosts. The protocol is a "secure" implementation of the RCP (Remote Copy Protocol)—a protocol for transferring files across a network.
SCP combines RCP's file transfer capabilities with SSH's authentication and encryption features, creating a hybrid protocol. This ensures the confidentiality of the data in transit, effectively thwarting packet sniffers from gleaning sensitive information from the data packets. Additionally, SCP leverages SSH's advantages by preserving file permissions and timestamps during uploads.
SCP operates over the SSH protocol, offering an authentication mechanism that ensures both the authenticity and confidentiality of files during transfer, similar to how SSH secures the obsolete and less secure Telnet protocol. With SCP's authentication system between hosts and encryption during data transfer, it guarantees the integrity and security of the data being moved
When users employ applications to transfer files between a server and a client, or in the opposite direction, the SCP protocol typically facilitates these transfers unless the SFTP protocol has been set as the default. SCP enables rapid file transfers through command line use, which is often quicker and more straightforward than using a graphical client interface. Additionally, the command line utility of SCP is advantageous for automating the transfer of batch files and scripts.
Since its first release back in 1983, SCP has been used as a standalone app under the same name but has also been embedded inside other apps. For example, SCP is the standard file transfer method for OpenSSH, Putty, and WinSCP. Since the SCP protocol is cross-platform, there are versions and programs for all operating systems—Windows, macOS, Linux, Android, and iOS.
SSH Machine Identity Management for Dummies
How does SCP protocol work?
Secure Copy requires authentication from the participating hosts. Before initiating a transfer via this protocol, an SSH connection must be established between the local host and the designated remote host. This process involves entering the authorized key as part of the public key authentication procedure.
Once the SSH connection is established between the two hosts, the SCP client can initiate the secure copy operation in either source mode or sink mode. To activate source mode, which reads files from the remote host to send to the client, the SCP client typically uses the -f flag. Conversely, to enable sink mode for transferring data to the remote host, the -t flag is used. In source mode, the SCP client requests and retrieves files from the distant host. In sink mode, the client signals the remote host to prepare for receiving and writing incoming data.
Typically, the syntax of an SCP program is like the syntax of cp (copy). If you wish to copy a local file to a remote host, then you should type in the following command:
scp LocalSourceFile user@remotehost:directory/TargetFile
If you would like to copy a file from remote host or copy a folder from remote host (with -r switch), the following commands apply respectively:
scp user@remotehost:directory/SourceFile LocalTargetFile
scp -r user@host:directory/SourceFolder LocalTargetFolder
Security of SCP Protocol
Despite SCP's reputation as a secure file transfer method, in January 2019, security researcher Harry Sintonen from the Finnish cyber-security company F-Secure identified vulnerabilities within the protocol. He revealed that all versions of SCP since 1983 have been susceptible to four security flaws. These vulnerabilities could permit a rogue SCP server to modify files on a client's system without authorization and conceal malicious activities within the terminal. Sintonen noted that when files were being transferred from remote servers to local directories, SCP failed to validate the filenames being received, opening a door for potential exploits.
Subsequent to the discovery of these vulnerabilities, vendors supporting the SCP protocol have rolled out patches. However, OpenSSH took additional measures by introducing OpenSSH 8.0 in April 2019. The developers pointed out the obsolescence and rigidity of the SCP protocol, acknowledging its challenges in terms of updates and security enhancements. They advocated for the adoption of contemporary protocols such as SFTP and RSYNC as more secure alternatives for file transfer.
Besides patching these vulnerabilities, the security of associated SSH keys is also paramount since the SCP protocol relies on SSH. Businesses and individuals should take extra precaution protecting these keys and rotate them on a frequent basis. The Venafi SSH Protect platform helps organizations safeguard host-to-host connections by discovering, protecting and automating the lifecycle of SSH machine identities.
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