\Magento\Framework\Filesystem\Io\Sftp

We currently have a \Magento\Framework\Filesystem\Io\Ftp class. And this does support FTPS connections, but does not appear to support SFTP connections.

Currently, per the coding standards, direct usage of ssh2_* functions is discouraged, with no alternatives offered.

It would be nice if \Magento\Framework\Filesystem\Io\Sftp supported authenticating with public / private key-pairs.

While not applicable to my current project, I have worked in projects in the past where the system admins prohibited authentication with username / password authentication between internal systems, and enforced that authentication be done with public / private key-pairs that were then maintained by the system admins and regularly rotated. If this were a requirement in my current project today, my only option would be to violate Magento coding standards write my own class to implement this feature the native Sftp lacks.

Start by locating the existing Magento\Framework\Filesystem\Io\Ftp implementation and the coding standards around SFTP access. Define the Sftp class interface and verify that public/private key-pair authentication works without username/password authentication; the feature is complete when this use case is supported.