SSL 64-bit Block Size Cipher Suites Supported (SWEET32)

Nessus reports a vulnerability because of 64-bit cipher suites and SSL Medium Strength Cipher Suites Supported (even though it shows up as strong). Windows requires the cipher TLS_RSA_WITH_3DES_EDE_CBC_SHA being disabled.

I found that adding the cipher suite to the registry didn’t work as expected. Then I found a reference that says it’s a different key based on the version of Windows. So I added both to our registry file to handle disabling it regardless.

Registry file:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\DES 56/56]
"Enabled"=dword:00000000
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC2 40/128]
"Enabled"=dword:00000000
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 40/128]
"Enabled"=dword:00000000
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 56/128]
"Enabled"=dword:00000000
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 128/128]
"Enabled"=dword:00000000
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\Triple DES 168/168]
"Enabled"=dword:00000000
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\Triple DES 168]
"Enabled"=dword:00000000

Before:

$ nmap --script +ssl-enum-ciphers -p 3389 iprintsrvr -Pn

Starting Nmap 6.47 ( http://nmap.org ) at 2017-01-20 12:28 GMT
Nmap scan report for iprintsrvr (192.168.0.181)
Host is up (0.00051s latency).
rDNS record for 192.168.0.181: iprintsrvr.domain.local
PORT STATE SERVICE
3389/tcp open ms-wbt-server
| ssl-enum-ciphers: 
| TLSv1.0: 
| ciphers: 
| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - strong
| TLS_RSA_WITH_3DES_EDE_CBC_SHA - strong
| TLS_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_RSA_WITH_AES_256_CBC_SHA - strong
| compressors: 
| NULL
|_ least strength: strong

Nmap done: 1 IP address (1 host up) scanned in 6.30 seconds

After:

$ nmap --script +ssl-enum-ciphers -p 3389 iprintsrvr -Pn

Starting Nmap 6.47 ( http://nmap.org ) at 2017-01-20 12:29 GMT
Nmap scan report for iprintsrvr (192.168.0.181)
Host is up (0.00028s latency).
rDNS record for 192.168.0.181: iprintsrvr.domain.local
PORT STATE SERVICE
3389/tcp open ms-wbt-server
| ssl-enum-ciphers: 
| TLSv1.0: 
| ciphers: 
| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - strong
| TLS_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_RSA_WITH_AES_256_CBC_SHA - strong
| compressors: 
| NULL
|_ least strength: strong

Nmap done: 1 IP address (1 host up) scanned in 0.15 seconds

References

See Note For the versions of Windows that releases before Windows Vista, the key should be Triple DES 168/168.

https://support.microsoft.com/en-us/help/245030/how-to-restrict-the-use-of-certain-cryptographic-algorithms-and-protocols-in-schannel.dll

7 Comments

BinTek

April 10, 2017 — 17:51

Hi, thank you for the info, did you make this registry modification on a Windows 2012 server or other versions?

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Warlord (Post author)
April 11, 2017 — 15:37

Reply

We do this for all Windows 2008, 2012 including R2.

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Seth

May 3, 2017 — 13:03

For windows 2008 r2, when you removed 3DES, did it also break Remote Desktop connections?

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Warlord (Post author)
May 3, 2017 — 13:12

Reply

Only from clients that don’t support higher encryption. We don’t allow any client less than Windows 7 these days.

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- Seth
  May 3, 2017 — 13:26
  
  That’s weird that it broke it for Win 7
  I have a Windows 2012 server that I disabled 3DES on (SWEET32), but my win 7 boxes still connect fine to the server using Remote Desktop
  When I did the change up on my Win 2k8 R2 box though, it does not allow connections from any server, windows 7 or windows 2012
  The other weird thing is that when I do Nmap against the Win 2k8 R2 box, it does not show all of the cipher suites you have enabled.
  
  Starting Nmap 6.49BETA4 ( https://nmap.org ) at 2017-05-03 08:35 Eastern Daylight Time
  
  Nmap scan report for cx-web65.webd2ms.com (10.76.65.1)
  
  Host is up (0.00s latency).
  
  PORT STATE SERVICE VERSION
  
  3389/tcp open ms-wbt-server?
  
  | ssl-enum-ciphers:
  
  | TLSv1.0:
  
  | ciphers:
  
  | TLS_RSA_WITH_3DES_EDE_CBC_SHA (rsa 2048) – C
  
  | compressors:
  
  | NULL
  
  | cipher preference: indeterminate
  
  | cipher preference error: Too few ciphers supported
  
  | warnings:
  
  | Weak certificate signature: SHA1
  
  |_ least strength: C
  
  MAC Address: 3C:D9:2B:F9:BC:98 (Hewlett-Packard Company)
  
  Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
  
  Nmap done: 1 IP address (1 host up) scanned in 63.86 seconds
  
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- Warlord (Post author)
  May 4, 2017 — 10:00
  
  I’m not entirely certain what you have locked down there. But for a Win2k8 server this is my ssl cipher result. I did notice your scan shows a weak SHA1 signature and wondered if you can’t support the ciphers because of this?
  
  Starting Nmap 6.47 ( http://nmap.org ) at 2017-05-04 10:55 BST Nmap scan report for monsrvr (192.168.0.165) Host is up (0.00061s latency). rDNS record for 192.169.0.165: monsrvr.domain.local PORT STATE SERVICE 3389/tcp open ms-wbt-server | ssl-enum-ciphers: | TLSv1.0: | ciphers: | TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - strong | TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - strong | TLS_RSA_WITH_AES_128_CBC_SHA - strong | TLS_RSA_WITH_AES_256_CBC_SHA - strong | compressors: | NULL |_ least strength: strong
  Nmap done: 1 IP address (1 host up) scanned in 3.36 seconds
  
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Seth

May 3, 2017 — 13:27

This is the nmap results when ran against the Windows 2012 server:

Starting Nmap 6.49BETA4 ( https://nmap.org ) at 2017-05-03 08:38 Eastern Daylight Time

Nmap scan report for cx-web55.webd2ms.com (10.75.55.1)

Host is up (0.0010s latency).

PORT STATE SERVICE VERSION

3389/tcp open ms-wbt-server?

| ssl-enum-ciphers:

| TLSv1.0:

| ciphers:

| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (dh 521) – A

| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (dh 521) – A

| TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) – A

| TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) – A

| compressors:

| NULL

| cipher preference: server

| TLSv1.1:

| ciphers:

| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (dh 521) – A

| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (dh 521) – A

| TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) – A

| TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) – A

| compressors:

| NULL

| cipher preference: server

| TLSv1.2:

| ciphers:

| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (dh 521) – A

| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA (dh 521) – A

| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (dh 521) – A

| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA (dh 521) – A

| TLS_RSA_WITH_AES_256_GCM_SHA384 (rsa 2048) – A

| TLS_RSA_WITH_AES_128_GCM_SHA256 (rsa 2048) – A

| TLS_RSA_WITH_AES_256_CBC_SHA256 (rsa 2048) – A

| TLS_RSA_WITH_AES_256_CBC_SHA (rsa 2048) – A

| TLS_RSA_WITH_AES_128_CBC_SHA256 (rsa 2048) – A

| TLS_RSA_WITH_AES_128_CBC_SHA (rsa 2048) – A

| TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (dh 128) – B

| TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (dh 128) – C

| compressors:

| NULL

| cipher preference: server

| warnings:

| Key exchange parameters of lower strength than certificate key

|_ least strength: C

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .

Nmap done: 1 IP address (1 host up) scanned in 64.41 seconds

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