Articles and news

SFTPPlus Release 3.33.0

Mon 23 April 2018 | general release Written by SFTPPlus

We are pleased to announce the latest release of SFTPPlus version 3.33.0.

This is a significant release in that it supports the Internet's next generation protocol, IPv6, for all server-side functionalities.

As we begin to hit the upper limit of IPv4 addresses, the current standard, what matters to us is to enable our customers and their businesses to set up their services on IPv6 with SFTPPlus.

In addition to IPv6 support, the following are new features and defect fixes associated with this release.

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.

• • •

Data Loss Prevention - Systems, Software and Strategies

Thu 19 April 2018 | article infrastructure Written by Hannah Suarez

What is Data Loss Prevention (DLP)?

Data Loss Prevention (or DLP for short) is the application of technology and policies in order to detect and prevent potential data breaches and data ex-filtration. Data that is of particular interest include sensitive emails, documents and other information leaving the organizational boundary. Data Loss Prevention is one out of many options used in today's arsenal of defense against threats and attacks, and also a layer to harden overall data security.

While SANS may write that DLP is primarily concerned with identifying sensitive data, we have taken on board a more holistic look beyond identification.

Data loss prevention can be in the form of the following:

  • Network-based DLP.
  • Endpoint DLP which monitors on the application level such as email client used.
  • Network policies enforced for information leaving the network.
  • UI, for example in the form of pop up tips, that will help reinforce data protection awareness training.
  • Common dictionaries and regular expressions syntax used to create content protections rules.
  • Staff awareness training.
  • Using file tagging to secure data that can contain intellectual property or trade secrets.

The above is not an exhaustive list.

Data loss prevention tend to be interchanged with data leak prevention when the situation involves the lost data being acquired by an unauthorized third party. However for this article, we will also include both data loss and data leak scenarios under the overall DLP umbrella term.

Upon application of DLP, you can ensure compliance with regulations governing use of data and ensure obligations for best practices are being met. These compliance and regulations include Health Insurance Portability and Accountability Act (HIPAA), (Payment Card Industry) PCI compliance, and General Data Protection Regulation (GDPR) to name a few.

Data loss prevention in file transfers

Within the territory of file transfer, data loss happens via information being inadvertently or intentionally sent to an unauthorized individual through the use of either file transfer software or file transfer protocols. It can also happen due to human ignorance or negligence - for example, uploading sensitive documents using an unapproved cloud provider.

Imagine a scenario where an employee in a large company has just transferred a series of files containing confidential data. Or another scenario where a small business owner has data residing on USB (unencrypted) and has since been lost.

It is with these two scenarios where we see data loss prevention not being applied for both data in transit (the transfer of files containing confidential information) and data at rest (the files residing within the USB).

Types of data in file transfers

As an introduction, the following paragraphs (from Wikipedia) summarizes the differences between data at-rest, data in-use and date in-motion.

Data at-rest

"Data at rest" specifically refers to old archived information. This information is of great concern to businesses and government institutions simply because the longer data is left unused in storage, the more likely it might be retrieved by unauthorized individuals. Protecting such data involves methods such as access control, data encryption and data retention policies.

Data in-use

"Data in use" refers to data that the user is currently interacting with. DLP systems that protect data in-use may monitor and flag unauthorized activities. These activities include screen-capture, copy/paste, print and fax operations involving sensitive data. It can be intentional or unintentional attempts to transmit sensitive data over communication channels.

Data in-motion

"Data in motion" is data that is traversing through a network to an endpoint destination. Networks can be internal or external. DLP systems that protect data in-motion monitor sensitive data traveling across a network through various communication channels.

Data Loss Prevention and SFTPPlus MFT

DLP monitoring network activity

The DLP software is integrated into the network using a network TAP (terminal access point) port to perform real-time scanning and analysis of network traffic.

In addition to DLP inspection for data in-transit, DLP inspection can also be applied for data at-rest, such as within an FTPS or SFTP file server.

DLP and SFTPPlus MFT configuration options

For managed file transfer, data in-motion is of priority concern and is within the realm of control for file transfer software. Data at-rest is also another concern, but controls can also be distributed to controls permissioned by the OS file system.

The use of secure file transfer protocols as well as other processes for secure file transfer should form part of the stock for data loss prevention - transmission security. These services and configuration options can be configured using SFTPPlus.

An SFTPPlus feature, Digital signature validation can be configured to check if files have a valid signature:


The signature validation process is based on the RSA Digital Signature Algorithm PKCS#1 v2.1 also known as RSASSA-PSS and documented in RFC 3447.

Post process actions may also be added as part of the automated, client transfer rule in order to contain policy rules. A file dispatcher can then be set so that a transfer is quarantined via a separate folder if it has failed a policy rule.

A UUID prefix can also be appended to a file name in order to create unique names so that for each data uploaded, even if duplicate, there is a unique filename.

For authorization control, SFTPPlus administrators can apply permissions to specific groups or users. These permissions will help determine the access to which resources within the file transfer home directory of that user, and other the specific access rights. Permissions can also be set depending on regular expressions (regex), such as disallowing certain file formats. Through the options covered above, administrators can secure data or set permissions to ensure certain resources are not being inappropriately accessed or changed.

For more details about the above configuration options, please consult our documentation or talk to the Support team.

Audit trails for DLP

While operating, SFTPPlus will emit a set of events. Each event has a unique ID and defines a specific operation carried out by the server.

An example of an audit trail upon first connection to an FTP service is below:

| 20076 2018-03-07 19:44:05 ftp-only-1 Process Service “ftp”
  started on “” using “ftp” protocol.
| 10033 2018-03-07 19:44:10 ftp-only-1 Unknown
  New FTP/FTPS client connection made.

Administrators can gather a comprehensive picture of data-handling activities performed by users through the detailed, server-side audit trail. For example, see below audit trail for an attempt to access an authorized resource:

| 40007 2018-03-28 11:10:25 Process alice HTTP/HTTPS file access
  successfully started in "/ftps-folders/alice_files" as "/".

Through this online record of server events, organizations can be made aware for the purposes of any legal framework or compliance obligations.

Please see our Users Guides for specific examples pertaining to audit trails for HIPAA/HITECH, and GPG/PMO obligations. More articles are being written for other compliance and regulations.

Evaluating SFTPPlus MFT

The features listed in this article are just a select few out of many integration and configuration options that is available to teams today to ensure data loss prevention. Feel free to talk to the Support team with your DLP requirements with file transfer software.

SFTPPlus MFT Server supports FTP, Explicit FTPS, Implicit FTPS, SFTP, SCP, HTTP and HTTPS.

SFTPPlus MFT is available as an on-premise solution supported on Windows, Linux, AIX, MacOS, Solaris, HP-UX, and FreeBSD. Please add your email below to sign up for an evaluation trial.

• • •

SFTPPlus and its relevance with the OIAC Privacy Act and ASD ISM

Mon 16 April 2018 | australia compliance privacy Written by Hannah Suarez

In this post, we outline two main compliance obligations relevant to Australia - the OIAC Privacy Act and the ASD ISM. For those familiar with other international compliance obligations, such as the GPG13 (Good Practice Guide) provided by the UK or HIPAA (Health Insurance Portability and Accountability Act) provided by the US, they will find the following information useful, especially when handling data and subsequent file transfers with Australian customers.

The following is just an introductory overview focusing on how SFTPPlus can help organizations with these obligations.

About the Privacy Act 1988

The Office of the Australian Information Commissioner (OIAC) administers the Privacy Act 1988. This Act is an Australian law which regulates the handling of personal information about individuals.

According to the OIAC, the Privacy Act includes thirteen Australian Privacy Principles (APPs). These APPs set out standards, rights and obligations for the handling, holding, use, access and correction of personal information including sensitive information. For more details, please refer to the OIAC website.

By ensuring that there is data in-motion encryption, such as the use of SFTP and FTPS in file transfers, organizations and businesses can ensure further security for their file transfers in order to help meet certain obligations indicated within the Privacy Act 1988.

About the ASD ISM

The Australian Signals Directorate (ASD), an intelligence agency in the Australian Government Department of Defence, has provisioned the Information Security Manual (ISM). Originally for government agencies to apply in order to protect ICT systems, the manual can also be of use for the private sector.

For the full documentation and details, please go to the ASD website. This page is based on the 2017 ISM Manual that was updated in November 2017.

Standard Operating Procedures (SOPs)

While the manual itself encompasses a wide range of topics from access controls to the use of ICT equipment, we have mapped components (SOPs) that is of direct or indirect relevance to file transfers involving SFTPPlus.

The following are Standard Operating Procedures (SOPs) as listed from page 36 of the ISM.

Access control

Procedure to be included: Authorising access rights to applications and data.

The SFTPPlus features that will help organizations meet this SOP include; ability to authorize access based on an existing authentication method (such as LDAP or operating system), ability to authorize or via an SFTPPlus application account.

Another example of rolling out proper access authorization is via permissions. User permissions can be set in the application based on extension (such as only making .exe files read-only) and directory (such as only allowing full control for certain folders).

Audit logs

Procedures to be included: Reviewing system audit trails and manual logs, particularly for privileged users.

For each server event that is emitted, this is logged within an audit trail that is available for SFTPPlus administrators. The example log below is of a user authenticating:

| 30014 2018-04-02 10:50:42 Process Unknown New SSH
  connection made.
| 20137 2018-04-02 10:50:42 single-server-uuid Account
  "erica" of type "os" authenticated as "erica" by os authentication
  "Operating System Accounts" using ssh-key.

Note that details such as the date, time, type of connection, type of authentication, account name and more are included in this audit log.

Data Transfers

Procedures to be included: Managing the review of media containing information that is to be transferred off-site. Managing the review of incoming media for viruses or unapproved software.

For the thorough review of media containing sensitive information, it is expected that SFTPPlus be integrated with a DLP (data leak prevention) software and other related policies to help prevent data leaks.

For the review of incoming media, SFTPPlus can also be integrated with antivirus checks as part of a file transfer process.

Our own customers are already integrating with a number of software that monitors and protects the boundary as part of their file transfer infrastructure.

System integrity audit

Procedures to be included: Reviewing user accounts, system parameters and access controls to ensure that the system is secure. Checking the integrity of system software. Testing access controls.

The text configuration server.ini file is available to review all configurations - from the authentication methods, configuration parameters and configuration options right through to the services being used.

The SFTPPlus Local Manager also includes the ability to review any changes made, before applying it to the system.

System maintenance

Procedures to be included: Managing the ongoing security and functionality of system software, including; maintaining awareness of current software vulnerabilities, testing and applying software patches /updates / signatures, and applying appropriate hardening techniques

SFTPPlus upgrades are designed to minimize disruption.

Transport Layer Security (TLS) in the ISM

Page 250 of the ISM details these conditions under which TLS can be used, including FTP over TLS (or in other words, FTPS).

The FTPS service can be configured to ensure meeting this conditions - such as using tls v1.2. To meet the requirement of meeting Perfect Forward Secrecy as determined in page 251 of the ISM, SFTPPlus administrators can explicitly state which SSL ciphers to use. These are cipher suites that implement Perfect Forward Secrecy - Diffie–Hellman key exchange (DHE-RSA, DHE-DSA) or elliptic curve Diffie–Hellman (ECDHE-RSA, ECDHE-ECDSA). Administrators can use the secure configuration option to only ensure the SSL Cipher Suite configuration for the FTPS service is updated to only use the secure ciphers as recommended by the OpenSSL library.

Evaluating SFTPPlus MFT

Thank you for reading about SFTPPlus.

We work with customers, as well as outsourcers (including IBM, HP/DXC, Fujitsu, Tata etc) and integrators, in order to deliver secure file transfer systems. SFTPPlus can be installed as a standalone secure file transfer solution and is also designed to integrate with enterprise systems in complex environments. We are happy to talk to local integrators and distributors who are often the most knowledgeable when it comes to local market needs. While our support hours are based in the UK, one of our focuses is to deliver high quality but low maintenance file transfer software that requires minimal support once configured correctly. Our existing customers have operations in many timezones including UK, USA, Australia, India as well as a large number of European countries.

You can add your email below to sign up for an evaluation trial or get in touch with our Sales team to discuss your options.

• • •

SFTPPlus Release 3.32.0

Thu 05 April 2018 | general release Written by SFTPPlus

We are pleased to announce the latest release of SFTPPlus version 3.32.0.

New Features

  • SFTP and SCP file transfer services can now listen on IPv6 addresses and accept connections from IPv6 clients. [server-side][sftp][scp] [#1924]
  • The HTTP and HTTPS service now accepts creating new folders with the HTTP PUT and WebDAV MKCOL methods. [server-side][http][https] [#4828-1]
  • The HTTP and HTTPS service now accepts deleting folders and files with the HTTP DELETE method. [server-side][http][https] [#4828-2]
  • The HTTP and HTTPS service now accepts file uploads using the HTTP PUT method. [server-side][http][https] [#4828]

Defect fixes

  • FTP and FTPS client side transfer can now transfer files larger than a few bytes from a remote FTP/FTPS server and to the local filesystem. This issue was introduced in SFTPPlus version 3.20.0. This defect was not affecting uploading / pushing files to a remote FTP/FTPS server. [client-side][ftp][ftps] [#4754]
  • The Developer Documentation for the HTTP authentication method was updated to make it clear the expected repose codes for the authentication server. [server-side] [#4758]
  • The JavaScript UI for the HTTP and HTTPS file transfer services no longer limit the file size to 256MB. This defect was introduced in 3.31.0. [server-side][http][https] [#4815]

Deprecations and Removals

  • The default secure ssl_cipher_list configuration was updated to HIGH:!PSK:!RSP:!eNULL:!aNULL:!RC4:!MD5:!DES:!3DES:!aDH:!kDH:!DSS. The previous value was ALL:!RC4:!DES:!3DES:!MD5:!EXP. In this way, when updating the OpenSSL library you will automatically get an update in the list of secure ciphers, without the need to update SFTPPlus. [security][ftps][https][client-side][server-side] [#4748]
  • The event (ID 40025) that was emitted when an unknown error was generated by the HTTP service during a JSON API request was removed. It has been replaced with event ID 40003. [server-side][http][https] [#4828]

You can check the full release notes here.

• • •

Understanding the exchange between SFTP Client and SFTP Server

Thu 08 March 2018 | article Written by Hannah Suarez

Why read this?

As part of meeting the Accounting component of the AAA (Authorization, Authentication and Accounting) framework, each event and action on the server and/or the client-side are recorded by SFTPPlus. These events have an associated Event ID which is also publicly searchable both on our website and on the internal documentation included in the software package that you have downloaded.

System and network administrators touching on logs - be it in the most verbose format or not - may find this article describing the breakdown of such logs helpful.

For this example, we will be touching on SFTPPlus SFTP transfers from both the client-side and server-side only. Please do not hesitate to get in touch with us if you are interested in learning more about other file transfer protocols.

SFTPPlus SFTP Server-side Perspective

Initial configuration notes

If you are currently evaluating SFTPPlus, please follow our documentation to learn more about how you can configure your database and event handlers to suit your specifications.

Read more about configuring databases with SFTPPlus.

Read more about configuring event handlers. These provide further ways to configure SFTPPlus to create logging actions based on the events recorded.

Even if you are an existing customer, you can follow our documentation links above in order to refresh your knowledge on configuring SFTPPlus version 3. For those on legacy versions, please consult the documentation relevant to your version.

Example logs from SFTPPlus

The following are snippets when logging in for the first time from a GUI client to an SFTPPlus 3.30.0 SFTP server.

A new connection has been made to the service sftp-1. Knowing the service name is useful in case there are multiple other SFTP services running:

| 30014 2018-02-27 17:28:53 sftp-1 Unknown
  New SSH connection made.
| 2018-02-27 17:28:53 30014 New SSH connection made.

The following are authentication methods associated with the server and confirmation of which methods are not active. There may be more methods, depending on how many of these are set up and enabled. To simplify the login process, please make sure to disable all unused authentication methods.:

| 20138 2018-02-27 17:28:55 some-http-auth-uuid Unknown
  Ignoring http authentication "auth-over-remote-http" for "user" since it
  is not active.
| 2018-02-27 17:28:55 20138 Ignoring http authentication "auth-over-remote-http"
  for "user" since it is not active.
| 20138 2018-02-27 17:28:55 ldap-uuid Unknown Ignoring
  ldap authentication "LDAP against local test server" for "user" since it
  is not active.

The following logs list out a successful authentication of user using the ssh-key:

| 20137 2018-02-27 17:28:55 test-server-uuid Unknown
  Account "user" of type "application" authenticated as "user" by
  application authentication "Application Accounts" using ssh-key.
| 2018-02-27 17:28:55 20137 Account "user" of type "application"
  authenticated as "user" by application authentication "Application
  Accounts" using ssh-key.

The following log message confirms the type of permissions allowed for the account and an active transfer that is already running:

| 20182 2018-02-27 17:28:55 Process user Account "user"
  logged in with permissions [[u'allow-full-control'], [u'/main_folder/*', u'allow-full-control'],
  [u'*.PDF', u'allow-read']]. Files uploaded as: test.txt

The following confirms that the user has logged into and now has access to the folder as the root ("/") folder:

| 30011 2018-02-27 17:28:55 Process user Subsystem SFTP
  successfully started in "/root/home/node/user/" as "/".
| 2018-02-27 17:28:55 30011 Subsystem SFTP successfully started in
  "/root/home/node/user/" as "/".
| 30060 2018-02-27 17:28:55 Process user Canonical file
  name requested for ".".
| 2018-02-27 17:28:55 30060 Canonical file name requested for ".".
| 30060 2018-02-27 17:28:55 Process user Canonical file
  name requested for "/.".
| 2018-02-27 17:28:55 30060 Canonical file name requested for "/.".
| 30019 2018-02-27 17:28:55 Process user Listing folder "/".
| 2018-02-27 17:28:55 30019 Listing folder "/".
| 30020 2018-02-27 17:28:55 Process user Successfully
  listed folder "/".
| 2018-02-27 17:28:55 30020 Successfully listed folder "/".

SFTPPlus SFTP Client-side Perspective

Initial configuration notes

If you are currently evaluating SFTPPlus, please follow our client side documentation.

The SFTPPlus Client software utilizes the command-line client-shell to access remote file servers using the interactive shell.

Even if you are an existing customer, you can follow our documentation links above in order to refresh your knowledge on configuring SFTPPlus version 3. For those on legacy versions, please consult the documentation relevant to your version.

Example logs from SFTPPlus

Let's connect with SFTPPlus Client using the SFTP protocol on port 10022. The following log details the UUID of the sftp service and confirms the connections:

| $ ./bin/ sftp://user@localhost:10022 -p pass
  --ssh-server-fingerprint 06:cb:46:2b:9a:9a:c4:10:54:f0:ea:2f:b6:05:cb:a0
| SFTPPlus (3.31.0) file transfer client shell
| > connect
| 20140 2018-03-05 16:40:59 51e1db00-8214-4b68-96fe-58470b8b2fc5 Process Connecting resource "sftp".
| 30072 2018-03-05 16:40:59 Process user localhost:10022 Location sftp
  connected to the SSH server.
| 30076 2018-03-05 16:40:59 Process user localhost:10022 Client SFTP
  subsystem initialized for location sftp.
| 20141 2018-03-05 16:40:59 51e1db00-8214-4b68-96fe-58470b8b2fc5 Process Resource "sftp" successfully connected.
| 20156 2018-03-05 16:40:59 51e1db00-8214-4b68-96fe-58470b8b2fc5 Process Successfully started location "sftp" of type sftp.

On the event that the SFTP connections fails, the log will state a number of details. The event ID is 30073. The event will communicat the host key algorithm that is in use to identify the server-side, the cipher used to receive data, the HMAC for both sent and received data, key exchange algorithm, cipher used for sent data and the name of the location associated for this event. Below is an example of the event that has been emitted has part of this new SFTP connection.:

| 30073 2018-03-05 16:36:16 Process user localhost:10022 Connection to
  SSH server was lost for location sftp. Protected using host-key:ssh-rsa key-exchange:
  diffie-hellman-group-exchange-sha256 in-hmac:hmac-sha2-256
  in-cipher:aes256-ctr out-hmac:hmac-sha2-256 out-cipher:aes256-ctr

Providing that the SFTP connection succeeds, supported actions are logged as either a success like below:

| > gattrs remote_get
| 60071 2018-03-05 16:41:22 Process Process Successfully got
  attributes for "Reports_2018" on "sftp".
| name: Reports_2018
| path: Reports_2018
| size: 128
| modified: 2018-02-16 16:15:21
| is_file: False
| is_folder: True

Or error details are caught with an explanation message as to why:

| > get unknown_file
| 20145 2018-03-05 16:42:08 Process Process Failed to resolve
  text for event id "60054" with data "{'path': 'unknown_file\xc8\x9bu',
  'location': u'sftp', 'avatar':
  <chevah.server.identity.avatar.ProcessAvatar object at 0x10efc3110>,
  'details': "'ascii' codec can't decode byte 0xc8 in position 9: ordinal
  not in range(128)"}". 'ascii' codec can't decode byte 0xc8 in position
  9: ordinal not in range(128)

SFTPPlus SFTP Exchange - Detailed Verbose OpenSSH Logs

Initial configuration notes

Following from that, you can use the built-in the client-side or server-side software that you are utilizing. SFTPPlus offers logging functionalities both for the client-side and server-side. Network administrators using other software, such as sftp -vvv, for client or server may wish to use additional logging functionalities.

Example with sftp -vvv output

These lines mean that SSH protocol 2.0 is being utilized with the version of OpenSSH:

debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.6

This line indicates which protocol version is in use service-side and which version:

debug1: Remote protocol version 2.0, remote software version SFTPPlus_3.30.0

This indicates which algorithms are preferred. You may opt to only select the strongest availability supported in your system first. In this case the ordering is logical as it moves from the more secure algorithm down to a less secure algorithm.:

| debug3: order_hostkeyalgs: prefer hostkeyalgs:,rsa-sha2-512,rsa-sha2-256,ssh-rsa

These are the key exchange algorithms that are available.:

| debug2: KEX algorithms: curve25519-sha256,,

These are the host key algorithms.:

| debug2: host key algorithms:,rsa-sha2-512,

These are the ciphers used from client to server (ctos) and from server to client (stoc):

| debug2: ciphers ctos:,aes128-ctr,aes192-ctr,

| debug2: ciphers stoc:,aes128-ctr,

These are the ciphers used from client to server (ctos) and from server to client (stoc):

| debug2: MACs ctos:,,,,,,,

| debug2: MACs stoc:,,,,,,,

These are the compression algorithms used from client to server (ctos) and from server to client (stoc):

debug2: compression ctos: none,,zlib
debug2: compression stoc: none,,zlib

This is the key exchange initialized proposal from the host server:

| debug2: peer server KEXINIT proposal
| debug2: KEX algorithms: diffie-hellman-group-exchange-sha256,
| debug2: host key algorithms: ssh-dss,ssh-rsa
| debug2: ciphers ctos:
| debug2: ciphers stoc:
| debug2: MACs ctos: hmac-sha2-256,hmac-sha1
| debug2: MACs stoc: hmac-sha2-256,hmac-sha1
| debug2: compression ctos: none,zlib
| debug2: compression stoc: none,zlib

These are the key exchange algorithms used from server to client and client to server:

| debug1: kex: algorithm: diffie-hellman-group-exchange-sha256
| debug1: kex: host key algorithm: ssh-rsa
| debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha2-256
  compression: none
| debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha2-256
  compression: none

This is the SSH version 2 key exchange Diffie-Hellman Group Exchange request. This specifies the size of the SSH prime moduli being calculated by the SFTP server as indicated in the SFTPPlus /configuration/ file. When you first initialize SFTPPlus version 3, the Time Type Tests Tries Size Generator Modulus is generated and saved in ssh-service.moduli. This file contains primes ranging in size from 1023 to 8191 bits. An example of the contents for the .moduli file is below:

| 20060827134212 2 6 100 3071 2

In the following example below, a SSH moduli prime from 2048 to 8192 bits are used. Specifically, a moduli with a range from 4092 to 8192 are sent for the SSH message key exchange Diffie-Hellman group exchange request as indicated on debug1 line below (SSH2_MSG_KEX_DH_GEX_REQUEST(2048<8192<8192)) Once sent, the server uses the moduli file, the same file that was initialized as part of the SFTPPlus installation steps, in order to crack the shared secret. The server provides its host key back to the client along with the algorithm used as indicated by the final line as Server host key: ssh-rsa SHA256:hdSfa7gb2O984malHerkwerj3m20dHb6Yuwl0&hbxFj.

See the rest of the output below:

| debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(2048<8192<8192) sent
| debug3: receive packet: type 31
| debug1: got SSH2_MSG_KEX_DH_GEX_GROUP
| debug2: bits set: 4092/8192
| debug3: send packet: type 32
| debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
| debug3: receive packet: type 33
| debug1: got SSH2_MSG_KEX_DH_GEX_REPLY
| debug1: Server host key: ssh-rsa

The client then checks to see if the host key is located within the known_hosts file:

| debug3: hostkeys_foreach: reading file "/root/home/node/.ssh/known_hosts"
| debug3: record_hostkey: found key type RSA in file
| debug3: load_hostkeys: loaded 1 keys from [12.345.678.90]:10022

A few more steps occur to verify this server host name and port:

ddebug1: Host '12.345.678.90]:10022' is known and matches the RSA host key.
ddebug1: Found key in /root/home/node/.ssh/known_hosts:8

This is the server rekey interval:

debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 4294967296 blocks

The following are SSH keys found:

debug2: key: imported-openssh-key (0x7e403ff95550), agent
debug2: key: /root/home/node/.ssh/id_rsa (0x0)
debug2: key: /root/home/node/.ssh/id_dsa (0x0)
debug2: key: /root/home/node/.ssh/id_ecdsa (0x0)
debug2: key: /root/home/node/.ssh/id_ed25519 (0x0)

The following are authentication methods that can continue, the preferred authentication order, remaining preferred:

| debug3: send packet: type 5
| debug3: receive packet: type 6
| debug2: service_accept: ssh-userauth
| debug1: SSH2_MSG_SERVICE_ACCEPT received
| debug3: send packet: type 50
| debug3: receive packet: type 51
| debug1: Authentications that can continue: password,publickey
| debug3: start over, passed a different list password,publickey
| debug3: preferred publickey,keyboard-interactive,password
| debug3: authmethod_lookup publickey
| debug3: remaining preferred: keyboard-interactive,password
| debug3: authmethod_is_enabled publickey
| debug1: Next authentication method: publickey
| debug1: Offering public key: RSA
| debug3: send_pubkey_test
| debug3: send packet: type 50
| debug2: we sent a publickey packet, wait for reply

The server will go through the exchange to authenticate until the final preferred method is reached - the password method. Upon success, the client enters an interactive session with the server.

There will also be additional verbose logs after entering an interactive session, such as a brief snippet below:

debug2: fd 6 setting TCP_NODELAY
debug3: ssh_packet_set_tos: set IP_TOS 0x08
debug2: client_session2_setup: id 0
debug1: Sending environment.
debug3: Ignored env _system_type
debug1: Sending env LANG = en_CA.UTF-8
debug2: channel 0: request env confirm 0
debug3: send packet: type 98
debug3: Ignored env _system_arch
debug3: Ignored env XPC_FLAGS
debug3: Ignored env _system_version
debug3: Ignored env XPC_SERVICE_NAME
debug3: Ignored env rvm_version
debug3: Ignored env _system_name
debug1: Sending subsystem: sftp

Evaluating SFTPPlus MFT

This article was written as of SFTPPlus version 3.31.0.

SFTPPlus MFT Server supports FTP, Explicit FTPS, Implicit FTPS, SFTP, SCP, HTTP and HTTPS.

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