Question

CoreFTP SSL Connection Problem

From behind a firewall I am getting the message in the code block below.  At item 234 what is happening is a certificate is trying to be delivered to set up the SSL session, but is not successful and therefore the process is timing-out. From another location (not behind my firewall) the certificate is received and the SSL connection is built very quickly.  Being that this only happens when behind my firewall I  believe the problem lies with my PIX and not on the server (or its firewall), which is outside of my domain/network.  I am not the SSL (or its related processes) expert.

Connect socket #712 to xxx.xxx.xxx.xxx, port 21...
220-FTPSECRE IBM FTP CS V1R9 at server.domain.xxx, 19:57:56 on 2009-01-29.  
220-FTPSECRE IBM FTP CS V1R9 at server.domain.xxx, 19:57:56 on 2009-01-29.  
AUTH TLS  
234 Security environment established - ready for negotiation  
SSL/TLS error - 0, SSL error - 1, error:00000001:lib(0):func(0):reason(1)   
SSL Connection not established

                                  
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Asked On
2009-01-30 at 08:55:46ID24099012
Topics

FTP Software

,

Cisco PIX Firewall

,

FTP Servers

Participating Experts
1
Points
100
Comments
9

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Answers

 

by: bignewfPosted on 2009-01-31 at 10:37:08ID: 23518004

can U please send your config (and block out public ip's)

also, did you check your inbound access-lists to allow SSL?


thanks

 

by: bignewfPosted on 2009-01-31 at 10:47:19ID: 23518045

also, try opening these ports to test:

PIX Firewall allows the configuration to allow/deny secure FTP traffic through it. There are no fixup commands for this. However you can use access lists to open ports 989 and 990 for FTPS traffic to pass through. Port 989 is for FTPS data (FTP protocol and data over TLS/SSL) and port 990 is for FTP (FTP protocol and control over TLS/SSL).

 

by: Wizard_MicrosystemsPosted on 2009-02-09 at 14:45:22ID: 23595473

Sorry for the delay.  I was ill most of last week.  Here is the SLL portion of my running configuration:

ssh xxx.xxx.xxx.xxx 255.255.255.224 outside
ssh xxx.xxx.xxx.xxx 255.255.255.255 outside
ssh 192.xxx.xxx.xxx 255.255.255.255 inside
ssh 192.xxx.xxx.xxx 255.255.255.255 inside
ssh timeout 60
ssh version 2
console timeout 20

Does this cover the "PIX Firewall allows the configuration to allow/deny secure FTP traffic through it" part?

If there are any other lines you are looking for, please specify what you believe the beginning of those lines should look like.  And how would an access list that is not specific to the outside host look if I am to open specific ports on my firewall?  The entity that I need to connect to also maintains tight security and so they may be redirecting behind their firewall as well.  Back on access lists, I am a beginner at PIX stuff and am only used to seeing those types of specifics when configuring NAT.

Thanks in advance for your assistance.

 

by: Wizard_MicrosystemsPosted on 2009-02-13 at 11:26:43ID: 23636266

Here is a Wireshark depiction of the attempt.  It is seen that the initial SSL/TLS session is established, but the certificate transaction is getting blocked.  I just can't figure out where the block is coming from.  This works great outside of our business fiewall (like my house), but not from work (where it's supposed to and needs to work from).  I have looked at our PIX and asked our IPS provider, and I'm not saying that I have covered all the bases there, but I'm getting a zero; I just need to figure out where the breakdown/block is coming from.  Can anyone decode the lingo in this capture?  Thanks in advance.

 

by: bignewfPosted on 2009-02-14 at 07:58:43ID: 23641117

your wireshark capture indicates it is opening ftp connection over port 21  -ftp, not secure ftp

you are confusing ssh (secure shell) with secure ftp. ssh is an encryption protocol used with certain secure ftp servers, but the above commmands you have are not associating traffic with the ftp server

 Secure FTP initiates a connection on TCP port 990 then expects return data on a TCP high port, usually  port 10021 or 10121. If port 990 isn't open or if the server isn't listening on the correct return port, it will fail
verify  which type of secure FTP  you are y using - Secure FTP is often confused with "FTP over SSL".

first, coreFTP operates with ssh on port 22 :
http://www.coreftp.com/server/


second, make sure you are using static NAT if you have a seperate public ip for this server:

static(inside, outside) [public address of ftp server] [inside lan address of server] netmask 255.255.255.255 0 0

the have the appropriate inbound access-lists for allowing ssh traffic for this server:

access-list outside_inside permit tcp any host [public ip of server] eq 22
apply the access list to the outside interface:

access-group outside_in   in interface outside

If you still have traffic getting blocked, then open up access lists for ports 989 and 990 using the access-list syntax above

then test the connection, and take wireshark capture and you will see the encrypted traffic

 

by: bignewfPosted on 2009-02-14 at 08:13:38ID: 23641184

also, forgot to add that unless you are using ssh to run the CLI from the internet, it creates more of a security risk for the firewall. You really should only run ssh from a vpn connection, rather than just open the ports to the outside world.

to enable ssh for CLI sessions:

crypto key generate rsa modula 2048
sh xxx.xxx.xxx.xxx 255.255.255.224 outside
ssh version 2

again, this is for management of the asa - this is not for enabling ssh inbound for the core ftp  so use my commands for that

 

by: Wizard_MicrosystemsPosted on 2009-02-24 at 15:44:01ID: 23728187

Thanks for the correction.  However, there is absolutely NO outside access to the routers or firewall, and all inside access is via SSH; no telnet or http whatsoever.  Sorry for pasting SSH information that is not relevant to my question at all.  

Here is an updated screenshot.  It shows the whole of the SSL connection attempt from a PC on my private network (192.x.x.x) to the server on the remote network (134.x.x.x).  I cannot identify anything in the configuration that would be blocking the establishment of a certificated session.  

Again, here's what I believe is happening.  A secure TLS session is established for the purposes of authentication, or in this instance, the issuing of a certificate.  However, the seond half of this process is breaking down.  I cannot figure out what is blocking it.

Reading back over your last post, I am not totally clear on what the provider is doing insofar as SecureFTP versus FTP over SSL, but it appears to me that they are setting-up a TLS session for the purposes of FTP, so that looks like FTP over SSL (the "new" SSL).  I am not sure on how to allow access to the network through the firewall for port 989-990 when it apprears to me that it's already allowed.  Can you clarify?

Enough for now.  And thanks so much again!

 

by: Wizard_MicrosystemsPosted on 2009-02-25 at 09:16:20ID: 23735954

I have obtained more information from the host service.  

"FTP/SSL -- This method is sometimes referred to as FTP over SSL or FTPS.  Conventional port number used for this protocol is 990.  However, 'host' has a proxy server as a front-end to its mainframe, allowing clients to connect to it.  Clients are expected to use port 21 and ephemeral ports 1xxxx through 1x1xx as transitory data ports."

I am not clear on what I may be overlooking insofar as the higher-numbered port range.  I really don't know how to open those ports as it appears as if I can only assign those to a NATted address/device.  I mean, I can't just "open them up" for all to use.  Although there is only one outside host address to be concerned with, we have several people internally that will be using this service, so I cannot create a NAT entry for 'them'; or more correctly, several NAT entries, one for each of them.

Thanks again for all of your assistance!

 

by: Wizard_MicrosystemsPosted on 2009-03-05 at 08:13:23ID: 23807005

The PIX cannot inspect FTP packets once they have been secured in SSL, so they are dropped.  Hence, end of communications.  It may be possible to use an FTP client that can send connection/control information over an open channel, while sending data over an encrypted channel, but that's outside of the scope of this question.

20120131-EE-VQP-002

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