Forticlient VPN does not negotiate DES

[bcieszewski]

Hi, 

I have a problem in phase 2. The only encryption I can choose is either DES or NULL on the server side. In client side on the other hand I have all options, but I choose DES, so the settings on both sides match. 

However I get Negotiate IPsec SA Error as no proposal was chosen. In the debug I see, that the server offers only DES ciphers, as instructed, however my VPN client proposes 3DES, AES, AES-CBC - so it's no surprise there is no match.

I'm running an evaluation license on the fortigate VPN and Forticlient 7.2.3.0822

Any ideas how I could solve that? 

[pminarik]

You can set both client-side proposals to be the same, thus functionally restrict the offer.

With that said, the FortiGate is expected to pick the matching set out of a list of offers. Are you sure it's not failing match on something else than encryption?

If you can, sharing the ike debug from FortiGate could help.

[bcieszewski]

Edit - I also tried rolling back the client to v6 or even 5, but that did not change :(

Hi, So the part I think is relevant is pasted below. From the configuration side it does look like I have matching settings. 

ike V=root:0:forti_vpn_0:49:forti_vpn:171: my proposal:
ike V=root:0:forti_vpn_0:49:forti_vpn:171: proposal id = 1:
ike V=root:0:forti_vpn_0:49:forti_vpn:171:   protocol id = IPSEC_ESP:
ike V=root:0:forti_vpn_0:49:forti_vpn:171:   PFS DH group = 14
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = ENCAPSULATION_MODE_TUNNEL
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=MD5
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = ENCAPSULATION_MODE_TUNNEL
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA1
ike V=root:0:forti_vpn_0:49:forti_vpn:171: proposal id = 2:
ike V=root:0:forti_vpn_0:49:forti_vpn:171:   protocol id = IPSEC_ESP:
ike V=root:0:forti_vpn_0:49:forti_vpn:171:   PFS DH group = 2
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = ENCAPSULATION_MODE_TUNNEL
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=MD5
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = ENCAPSULATION_MODE_TUNNEL
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA1
ike V=root:0:forti_vpn_0:49:forti_vpn:171: proposal id = 3:
ike V=root:0:forti_vpn_0:49:forti_vpn:171:   protocol id = IPSEC_ESP:
ike V=root:0:forti_vpn_0:49:forti_vpn:171:   PFS DH group = 1
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = ENCAPSULATION_MODE_TUNNEL
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=MD5
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = ENCAPSULATION_MODE_TUNNEL
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA1
ike V=root:0:forti_vpn_0:49:forti_vpn:171: incoming proposal:
ike V=root:0:forti_vpn_0:49:forti_vpn:171: proposal id = 1:
ike V=root:0:forti_vpn_0:49:forti_vpn:171:   protocol id = IPSEC_ESP:
ike V=root:0:forti_vpn_0:49:forti_vpn:171:   PFS DH group = 1
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_3DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA1
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_3DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_256
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_3DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_384
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_3DES
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_512
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 128)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA1
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 128)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_256
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 128)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_384
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 128)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_512
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 192)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA1
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 192)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_256
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 192)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_384
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 192)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_512
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 256)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA1
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 256)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_256
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 256)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_384
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      trans_id = ESP_AES_CBC (key_len = 256)
ike V=root:0:forti_vpn_0:49:forti_vpn:171:      encapsulation = UDP_ENCAPSULATION_MODE_TUNNEL_RFC3947
ike V=root:0:forti_vpn_0:49:forti_vpn:171:         type = AUTH_ALG, val=SHA2_512
ike V=root:0:forti_vpn_0:49:forti_vpn:171: negotiation failure
ike V=root:Negotiate IPsec SA Error:
ike V=root:0:forti_vpn_0:49:171: no SA proposal chosen

[pminarik]

The FortiGate is configured to accept DES-MD5 or DES-SHA1, each with DH group 1, 2, or 14.

The (Forti?)Client offers 3DES, or AES-CBC(128/192/256) + SHA1/256/384/512, plus DH group 1. It does not offer DES.

So this is still a mismatch.Not sure if the client is refusing to save or negotiate the DES that is configured per you screenshot.

[bcieszewski]

Yeah - that is exactly what beats me... I do wonder if my operating system has something  to do with it - I'm running MACOS on M1 processor...

The confusing part is that Phase1 accepts DES and it only fail during phase2 

[pminarik]

DES is ancient, so I wouldn't be surprised if some systems simply didn't offer it. With that said, if it's not possible with the underlying OS, then FortiClient should not offer it as an option (=at least a visual bug).

If you have the chance, try with the same nominal client version on a different OS. That may give a hint if this is MACOS-specific.

[pminarik]

Here's a similar discussion from a year ago on reddit: https://www.reddit.com/r/MacOS/comments/111cgne/ikev2_vpn_not_working_on_new_m1_mbp_exact_same/

Interestingly, the poster there reports having issues with M1 Mac but not with a 2019 intel-Mac. (Using windows RAS for VPN)
So your guess is probably right that this is a limitation/hardening in M1 versions.

[bcieszewski]

I'm trying that - but it seems Windows client is trying to establish connection on port 500 and it does not work (MAC is doing it on 4500). 

I wonder if there is a way to enable stronger ciphers on server-side.Or is it a limitation of a trial license?

[pminarik]

Trial FGT VM is severely restricted in terms of crypto, no way around it. That is expected.
UDP/500 is the standard initial port for IKEv1, expected to switch to 4500 once NAT-T is detected. Make sure you're not blocking this port (or anybody else on the path, including mean ISPs).