Articles from security category

New Features

• You can now set up an UNC path or a symbolic link to Windows Shares as home folder for an account. [#4635]
• The HTTP/HTTPS file transfer service and the Local Manager service now provide the option to configure a set of headers which are sent for all responses. You can use this to set the Strict-Transport-Security header or the use a custom Server header in an attempt to conceal the identity of the server. [security] [#4784]
• The LDAP authentication method can now connect to LDAP servers using IPv6 address literals. [server-side] [#4824-1]
• It is now possible to dynamically associate LDAP accounts to SFTPPlus groups based on arbitrary LDAP entry attributes. This is designed to augment the LDAP configuration without requiring any updates to the LDAP database. [server-side] [#4824]
• We now provide limited support for running SFTPPlus on legacy Windows 2003 Servers. For more details, check the known issues section in our documentation. [#4896]
• Ubuntu 18.04 LTS on X86_64 is now a supported platform. [#4912]
• A new permission, allow-traverse, was added to allow viewing only the folder structure without any files. In this way, accounts can traverse the folder hierarchy without seeing what files are already there. [#4931]
• A new permission allow-list was added to allow configuration of only the folder/directory listing operations. This has no effect for the SCP protocol, as the protocol itself does not support the folder listing operation. [#4932]
• A new permission allow-rename was added to allow configuration of only the rename operations available in the SFTP and FTP/FTPS file transfer servers. [#4933]
• The Ban IP for a time interval authentication method is now enabled by default in new installations. [#4934]

Defect Fixes

• The HTTP/HTTPS file transfer service and the Local Manager service now advertise a set of HTTP headers to mitigate CSRF and XSS attacks. [security] [#4930]
• The low-level JSON-RPC used by the Local Manager service now explicitly informs the web browser not to cache its POST responses. In the previous version, only GET requests were instructing the web browser not to cache the response. [security] [#4937]
• The LDAP authentication method no longer accepts credentials with empty passwords. [server-side][security] [#4939-1]
• When receiving a request which is authenticated via SSH key or SSL/X.509 certificates, the LDAP authentication method now emits a message informing that only password credentials are supported. [server-side] [#4939]

Deprecations and Removals

• The allow-read permission will no longer allow listing the content of a folder. If you want to allow folder listing, you will need to update the configuration and add the new explicit allow-list permission. [#4932-1]
• The error message returned when denying a folder listing operation was changed to include allow-list instead of the previous allow-read details. [#4932]
• The error message returned when denying a rename operation was changed to include allow-rename instead of the previous allow-full-control details. [#4933]

You can check the full release notes here.

Default SSL cipher suites

With the release of SFTPPlus 3.32.0, we have changed the default set of SSL cipher suites for the Local Manager and the HTTPS service. As with any product that runs in many environments, SFTPPlus uses a default set of SSL-related parameters that are a compromise between security and compatibility. Up to SFTPPlus version 3.31.0, we were using this highly compatible, but still reasonably secure, default set:

ssl_cipher_list = 'ALL:!RC4:!DES:!3DES:!MD5:!EXP'

Starting with SFTPPlus version 3.32.0, we strongly emphasize our focus on security. The default setting for OpenSSL cipher suites in SFTPPlus is now:

ssl_cipher_list = 'HIGH:!PSK:!RSP:!eNULL:!aNULL:!RC4:!MD5:!DES:!3DES:!aDH:!kDH:!DSS'

Notice that we now derive our default set from the HIGH set of cipher suites in OpenSSL. As improved cipher suites are added in OpenSSL, and new vulnerabilities are discovered and patched for, this specific set of cipher suites will be continuously improved upon by the OpenSSL developers. By keeping OpenSSL libraries updated through OS-specific procedures, our customers' SFTPPlus installations will benefit from these upstream improvements.

This new default set of safe cipher suites is also encapsulated within the secure configuration option, so you may simply use the following:

ssl_cipher_list = secure

Testing your HTTPS server

In ensuring that the secure configuration option for ssl_cipher_list in SFTPPlus is actually secure enough for your needs, you should try auditing your HTTPS setup using the Qualys SSL Labs' SSL Server Test.

This is a free online service that performs an analysis of the configuration of any public HTTPS server listening on the standard 443 port. When results are submitted, a grade from A to F is provided. You can read more about Qualys' SSL Server Rating Guide in their GitHub wiki here.

Assuming you are using a modern version of OpenSSL, such as version 1.0.2, a default installation of SFTPPlus version 3.32.0 will currently yield a score of B. This is because we still care about compatibility with older clients in the default setup.

However, you might want to go beyond that and try to obtain a Qualys SSL Server Rating of A for your SFTPPlus installation. A set of ciphers suites that sacrifices a bit of compatibility to reach the Grade A rating would be:

| ECDHE-RSA-AES128-SHA:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES128-GCM-SHA256:
| ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES256-GCM-SHA384

Keep in mind that clients such as Internet Explorer on Windows XP, Java 6.x clients and Android 2.x users will not be able to access your server any more. For guiding you in picking the best cipher suites for your OpenSSL version, we recommend Mozilla's SSL Configuration Generator.

Another way to increase the security of your HTTPS setup is to disable support for older SSL methods such as TLS v1.0 and v1.1. While as of April 2018 there are no known vulnerabilities specific to TLS v1.0 or v1.1, supporting only the newest standard will ensure better security through the use of more modern cipher suites.

In seeking the perfect balance between security and compatibility, you may wish to consider configuring only some services to have stricter cipher suites and/or TLS policy. These could be administration facing services such as the SFTPPlus Local Manager. For other services, you may need to adopt a policy that allows a compatible set as the default value for services such as HTTPS.

For example, here's the difference between secure and compatible SSL methods. Note that the secure method does not provide backward compatibility:

Secure methods:
ssl_allowed_methods = tlsv1.2

This indicates that the server will only support TLS v1.2, and will not communicate with a client that supports only TLS v1.0 and/or TLS v1.1.

A more lenient set of SSL methods would be:

Compatible methods:
ssl_allowed_methods = tlsv1.0 tlsv1.1 tlsv1.2

This indicates that the server will support clients using TLS version v1.2 and can communicate with clients that only support TLS v1.0 and/or TLS v1.1.

Beware that not supporting TLS v1.0 would mean dropping support for clients from older operating systems such as RHEL 5, SLES 11 and Solaris 10, as well as obsolete platforms like Android 4.0-4.3, Internet Explorer on Windows Vista and Win Phone 8.0, Java 7 clients. Anything using the old OpenSSL 0.9.8 version is also included.

Therefore, you may need to reach a compromise in choosing the ssl_allowed_methods too, and only restrict the SSL methods for the more sensitive services such as Local Manager.

Other resources to use

• Mozilla documentation from the OpSec team on Security and Server Side TLS
• SSL and TLS Deployment Best Practices

The details in this resource is for guidance only. Influences such as own security policies, requirements, and threat models should be considered when adopting this type of guidance.

This resource is written as of SFTPPlus version 3.33.0.

Customers using HTTP/HTTPS services should upgrade to 3.33.0

The SFTPPlus version 3.33.0 release is a major security update for the HTTP/HTTPS file transfer service and the SFTPPlus Local Manager service.

This update addresses the vulnerabilities concerning Cross-Site Request Forgery Attacks and Cross-Site Scripting Attacks on the aforementioned services.

Customers that are not accessing SFTPPlus services from a web browser are not exposed to these vulnerabilities.

In addition, customers utilizing FTP, FTPS, SFTP, and SCP protocols are not affected.

We recommend that all affected customers should upgrade to the SFTPPlus 3.33.0 release, since it includes fixes for Cross-Site Request Forgery and Cross-Site Scripting vulnerabilities.

To mitigate the risk in older SFTPPlus versions, we recommend the following actions:

• Do not have other tabs or windows open in the same browser while being authenticated to a SFTPPlus service, or
• Use a private window or a separate profile / container.
• Log out from the SFTPPlus service as soon as your have completed your tasks.

The aforementioned security issues were due to ProAtria not performing a security audit of SFTPPlus, when used from an interactive browser.

Taking into consideration the current challenges of HTTP security, we have now updated our security practices and implemented automated tests. These tests will cover the HTTP-specific attacks against SFTPPlus when accessed from a web browser.

SFTPPlus continues to be focused on automated, non-interactive file transfers in a secure fashion. Our security practices have been designed to make this a reality for our clients.

You can check the rest of the 3.33.0 release notes here.

New Features

• A new authentication method was added which allows the server to read application accounts from a separate file. [server-side] [#1056]
• It is now possible to configure the supported ciphers for an SFTP location using the ssh_cipher_list configuration option. [#4619]
• The FTP and FTPS file transfer services now support IPv6 as specified in RFC 2428. [server-side][ftp][ftps] [#4823-1]
• The HTTP and HTTPS file transfer services now support IPv6. [server-side][http][https] [#4823]
• The event with ID 30011 now contains details about the encryption used by the SFTP and SCP connections. [server-side][sftp][scp] [#4850]

Defect fixes

• A defect was fixed in the SFTP service for the chmod operation. In previous versions, the chmod was ignored and always returned a success result. [server-side][sftp] [#4338]
• The HTTP PUT method of the file transfer service now returns a correct code when the HTTP request contains Expect: 100-continue and the request fails to be authenticated. [server-side][http][https] [#4856]
• When uploading files into an empty folder using a web browser which has Javascript enabled, you will now see the uploaded file in the folder listing. This issue was introduced in 3.31.0. This was not an issue for web browsers with Javascript disabled. [server-side][http][https] [#4865]
• The HTTP file transfer service will now force any file to be downloaded by the browser. Previously, it was displaying HTML or images inside the browser without forcing a download. [server-side][http][https][security] [#4877-1]
• The HTTP file transfer service and the Local Manager service were updated to prevent cross-site request forgery (CSRF / XSRF) attacks by validating the Origin and Referer headers against the Host header. [server-side][http][https][security] [#4877]
• The HTTP file transfer service will now set the session cookie using the httpOnly and 'sameSite' options. [server-side][http][https][security] [#4881]
• The error messages in the HTTP service were updated to prevent cross site scripting attacks (XSS). [server-side][http][https] [#4884]

You can check the full release notes here.