AT-TLS Operates at the transport layer of the OSI model.
SFTP (open SSH,...) operates at the session layer of the OSI model.

BTW, TLS has been supported "forever" by FTP, etc. The problem is, with TLS, 
the application needs to be modified to make TLS calls in the session layer. 
With AT-TLS, session layer TLS calls are moved to the transport layer and 
eliminated from the session layer. 
No application changes are needed.

HTH,

-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of Tom 
Brennan
Sent: Tuesday, June 30, 2020 4:22 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: [EXTERNAL] Re: AT-TLS ? Very Basic Questions

[CAUTION: This Email is from outside the Organization. Unless you trust the 
sender, Don’t click links or open attachments as it may be a Phishing email, 
which can steal your Information and compromise your Computer.]

Thanks Allan.  In TCP/IP programs I've written in C (both mainframe and 
non-mainframe), I've used connect(), send(), recv() and similar C functions for 
clear-text communication.  So I think that would be called the "logical layer".

And I'm assuming the "physical layer" would be at the point where software is 
talking to an OSA card.  In this case that would be the TCPIP address space, 
since my program doesn't talk directly to hardware.

That would mean AT-TLS comes into play via the TCPIP task, doing the encryption 
at that point, while my clear-text program has no idea and doesn't care.  
Certificates and other encryption parameters would be handled by AT-TLS at that 
point.

That's the picture I have so far.

Now in my own program if I called OpenSSL functions like SSL_connect() or 
SSL_read(), then encryption would be done at the logical layer, and my own 
program would then be responsible for certificates.  AT-TLS would not be 
needed, well, unless an auditor doesn't trust my SSL code.  That actually could 
be a consideration even for things like SFTP I guess - there's your first flame 
:)

On 6/30/2020 1:42 PM, Allan Staller wrote:
> Hopefully this will provide the clarity needed.
>
> AT-TLS works at the physical layer.
> FTPS and SFTP work at the logical layer
>
> Although not mutually exclusive, If you are doing one, the other is 
> unnecessary.
>
> Start the flame wars! Shields up. Condition Red! AT-TLS vs. SFTP!
>
> -----Original Message-----
> From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On 
> Behalf Of Tom Brennan
> Sent: Tuesday, June 30, 2020 12:19 PM
> To: IBM-MAIN@LISTSERV.UA.EDU
> Subject: Re: [EXTERNAL] Re: AT-TLS ? Very Basic Questions
>
> [CAUTION: This Email is from outside the Organization. Unless you 
> trust the sender, Don’t click links or open attachments as it may be a 
> Phishing email, which can steal your Information and compromise your 
> Computer.]
>
> Do you know if either of those require AT-TLS?  When I installed and 
> configured SSHD last (a couple of years ago) it did its own encryption.
> I never worked with anything called FTPS.
>
> On 6/30/2020 10:12 AM, Marshall Stone wrote:
>> There are 2 types of FTP in use today on most mainframes.
>>
>> SFTP  - which uses Open/SSH (SSHAGNT as client and SSHD as a server) 
>> and the encryption/authentication is generally provided by the use of 
>> RSA/DSA public/private key pairs. The public keys are exchanged and 
>> stored in known_hosts files (if acting as client) or authorized_keys 
>> file (if acting as server) - Uses Server PORT 22 and ephemeral ports
>>
>> FTPS - completely different mechanism the AT/TLS functions are 
>> provided by ICSF and policy agent (PAGENT) - You must configure an 
>> FTPS TLS rule to allow the connection and the partner side also will 
>> require a similar rule. The encryption/authentication come from the 
>> PAGENT rule and the use of x.509 certificates.  These are exchanged 
>> between partners and loaded onto the RACF keyring. The PAGNET rule 
>> points back to the keyring. - Uses Server PORT 990 by an old implicit 
>> default most sites use a different port and connect clients with 
>> ephemeral port ranges. FTPS handles MVS datasets better if possible 
>> use FTPS for MF to MF and use SFTP for MF to Other
>> platforms(MS,UNIX,etc)
>>
>> MS
>>
>> -----Original Message-----
>> From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On 
>> Behalf Of Tom Brennan
>> Sent: Tuesday, June 30, 2020 12:58 PM
>> To: IBM-MAIN@LISTSERV.UA.EDU
>> Subject: [EXTERNAL] Re: AT-TLS ? Very Basic Questions
>>
>> I've tried to skim some of the AT-TLS doc, and even attended an IBM webinar 
>> last week, but I'm still missing what I imagine are important background 
>> points.  Maybe someone here can explain things, but don't worry too much 
>> about it.
>>
>> Client and server programs like SSH/SSHD call programs such as 
>> OpenSSL to handle the encryption handshake and processing.  So when 
>> you set those up, there is no AT-TLS needed for encryption.  Same 
>> with the
>> TN3270 server and client, as long as you set that up with keys and 
>> parameters on the host side, and settings on the client side.
>>
>> I'm thinking because of the name "Application Transparent" that AT-TLS was 
>> made for programs that DON'T have their own logic to call OpenSSL (or 
>> whatever) to do their own encryption.  Let's use clear-text FTP as an 
>> example.  So somehow, AT-TLS hooks into the processing and provides an 
>> encrypted "tunnel", kind of like VPN does, but only for that one 
>> application.  Does that sound correct?
>>
>> If so, then the encryption is "transparent" to the FTP server code and FTP 
>> does not need to be changed, which I think is the whole idea here.
>> Yet we now have an encrypted session.  Does that sound correct?
>>
>> Then if so, what happens on the FTP client side?  I certainly can't use the 
>> Windows FTP command, for example, because it's not setup for any kind of 
>> encryption.  That's kind of my big question here.
>>
>> On 6/30/2020 1:44 AM, Lionel B Dyck wrote:
>>> Sweet - thank you
>>>
>>>
>>> Lionel B. Dyck <sdg><
>>> Website:
>>> https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fww
>>> w
>>> .lbdsoftware.com%2F&amp;data=02%7C01%7Callan.staller%40HCL.COM%7Cd87
>>> 9
>>> db1f36854d47ffc308d81d19bac1%7C189de737c93a4f5a8b686f4ca9941912%7C0%
>>> 7 
>>> C0%7C637291343650296855&amp;sdata=rYCeChKI6R6cKaQRyHKEfhk3QR%2Fya0rH
>>> S
>>> %2FSvJedIZJo%3D&amp;reserved=0
>>>
>>> "Worry more about your character than your reputation.  Character is 
>>> what you are, reputation merely what others think you are." - John 
>>> Wooden
>>>
>>> -----Original Message-----
>>> From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On 
>>> Behalf Of kekronbekron
>>> Sent: Tuesday, June 30, 2020 2:34 AM
>>> To: IBM-MAIN@LISTSERV.UA.EDU
>>> Subject: Re: AT-TLS ?
>>>
>>> Hi LBD!,
>>>
>>> Check these out-
>>>
>>>
>>> https://apc01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww
>>> - 
>>> 03.ibm.com%2Fsupport%2Ftechdocs%2Fatsmastr.nsf%2FWebIndex%2FPRS5416&
>>> a
>>> mp;data=02%7C01%7Callan.staller%40HCL.COM%7Cd879db1f36854d47ffc308d8
>>> 1
>>> d19bac1%7C189de737c93a4f5a8b686f4ca9941912%7C0%7C0%7C637291343650306
>>> 8 
>>> 44&amp;sdata=9%2BluT%2FKH3wj94fpoHyCHX82zaMk0x2tVSqVkDFjlUQk%3D&amp;
>>> r
>>> eserved=0
>>> https://apc01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww
>>> - 
>>> 03.ibm.com%2Fsupport%2Ftechdocs%2Fatsmastr.nsf%2FWebIndex%2FPRS5415&
>>> a
>>> mp;data=02%7C01%7Callan.staller%40HCL.COM%7Cd879db1f36854d47ffc308d8
>>> 1
>>> d19bac1%7C189de737c93a4f5a8b686f4ca9941912%7C0%7C0%7C637291343650306
>>> 8 
>>> 44&amp;sdata=dGiMYPWuNw7u%2BY3WkaphIHoKPI0DXTwXckMig4%2FEcKs%3D&amp;
>>> r
>>> eserved=0
>>> https://apc01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww
>>> - 
>>> 03.ibm.com%2Fsupport%2Ftechdocs%2Fatsmastr.nsf%2FWebIndex%2FPRS5414&
>>> a
>>> mp;data=02%7C01%7Callan.staller%40HCL.COM%7Cd879db1f36854d47ffc308d8
>>> 1
>>> d19bac1%7C189de737c93a4f5a8b686f4ca9941912%7C0%7C0%7C637291343650306
>>> 8 
>>> 44&amp;sdata=IFmR7%2BNJNVnxEe0kIoOdPI4lv9x3JUN9zNOUzQ8Td%2Fw%3D&amp;
>>> r
>>> eserved=0
>>>
>>> - KB
>>>
>>> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
>>> On Monday, June 29, 2020 3:56 AM, Lionel B Dyck <lbd...@gmail.com> wrote:
>>>
>>>> Anyone have any pointers for configuring AT-TLS on z/OS?
>>>>
>>>> Lionel B. Dyck <sdg><
>>>> Website:
>>>> https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fw
>>>> w
>>>> w.lbdsoftware.com%2F&amp;data=02%7C01%7Callan.staller%40HCL.COM%7Cd
>>>> 8 
>>>> 79db1f36854d47ffc308d81d19bac1%7C189de737c93a4f5a8b686f4ca9941912%7
>>>> C 
>>>> 0%7C0%7C637291343650306844&amp;sdata=KPjRhP3xw6%2FSJgf3%2FHDd%2FWZp
>>>> J
>>>> g4qUv1SDTf5r5q%2FljE%3D&amp;reserved=0
>>>> https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fw
>>>> w
>>>> w.lbdsoftware.com%2F&amp;data=02%7C01%7Callan.staller%40HCL.COM%7Cd
>>>> 8 
>>>> 79db1f36854d47ffc308d81d19bac1%7C189de737c93a4f5a8b686f4ca9941912%7
>>>> C 
>>>> 0%7C0%7C637291343650306844&amp;sdata=KPjRhP3xw6%2FSJgf3%2FHDd%2FWZp
>>>> J
>>>> g4qUv1SDTf5r5q%2FljE%3D&amp;reserved=0
>>>>
>>>> "Worry more about your character than your reputation. Character is 
>>>> what you are, reputation merely what others think you are." - John 
>>>> Wooden
>>>>
>>>>
>>>> -------------------------------------------------------------------
>>>> -
>>>> -
>>>> -
>>>> -------------------------------------------------------------------
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