OpenVPN certificate problem

Ordinary87 · January 26, 2025, 1:31am

Hello everyone, this is the third time this app has a problem and now I can’t find a solution for it… I’m so close to giving up on it forever.
I’ve been using VPN through my Synology NAS and it’s been working for a few days. Ports are open on router, firewall is configured. Now I’m getting this error message about certificate. What is this and how to fix it … ? Thanks
OpenVPN 3.5.1
DS116 7.1.1-42962 Update 7

This is OpenVPN config file

dev tun
tls-client

remote 192.168.1.102 2012

# The "float" tells OpenVPN to accept authenticated packets from any address,
# not only the address which was specified in the --remote option.
# This is useful when you are connecting to a peer which holds a dynamic address
# such as a dial-in user or DHCP client.
# (Please refer to the manual of OpenVPN for more information.)

#float

# If redirect-gateway is enabled, the client will redirect it's
# default network gateway through the VPN.
# It means the VPN connection will firstly connect to the VPN Server
# and then to the internet.
# (Please refer to the manual of OpenVPN for more information.)

#redirect-gateway def1

# dhcp-option DNS: To set primary domain name server address.
# Repeat this option to set secondary DNS server addresses.

#dhcp-option DNS DNS_IP_ADDRESS

pull

# If you want to connect by Server's IPv6 address, you should use
# "proto udp6" in UDP mode or "proto tcp6-client" in TCP mode
proto udp

script-security 2


comp-lzo

reneg-sec 0

cipher AES-256-CBC

auth SHA512

auth-user-pass
<ca>
-----BEGIN CERTIFICATE-----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   CENSURED   XXXXXXXXXXXX
1QnlE4SEN4LOECj8dsIGJXpGUk3aU3KkJz9icKy+aUgA+2cP21uh6NcDIS3XyfaZ
QjmDQ993ChII8SXWupQZVBiIpcWO4RqZk3lr7Bz5MUCwzDIA359e57SSq5CCkY0N
4B6Vulk7LktfwrdGNVI5BsC9qqxSwSKgRJeZ9wygIaehbHFHFhcBaMDKpiZlBHyz
rsnnlFXCb5s8HKn5LsUgGvB24L7sGNZP2CX7dhHov+YhD+jozLW2p9W4959Bz2Ei
RmqDtmiXLnzqTpXbI+suyCsohKRg6Un0RC47+cpiVwHiXZAW+cn8eiNIjqbVgXLx
KPpdzvvtTnOPlC7SQZSYmdunr3Bf9b77AiC/ZidstK36dRILKz7OA54=
-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----
MIIFazCCA1OgAwIBAgIRAIIQz7DSQONZRGPgu2OCiwAwDQYJKoZIhvcNAQELBQAw
TzELMAkGA1UEBhMCVVMxKTAnBgNVBAoTIEludGVybmV0IFNlY3VyaXR5IFJlc2Vh
cmNoIEdyb3VwMRUwEwYDVQQDEwxJU1JHIFJvb3QgWDEwHhcNMTUwNjA0MTEwNDM4
WhcNMzUwNjA0MTEwNDM4WjBPMQswCQYDVQQGEwJVUzEpMCcGA1UEChMgSW50ZXJu
ZXQgU2VjdXJpdHkgUmVzZWFyY2ggR3JvdXAxFTATBgNVBAMTDElTUkcgUm9vdCBY
MTCCAiIwDQYJKoZIhvcNAQEBBQADggIPADCCAgoCggIBAK3oJHP0FDfzm54rVygc
h77ct984kIxuPOZXoHj3dcKi/vVqbvYATyjb3miGbESTtrFj/RQSa78f0uoxmyF+
0TM8ukj13Xnfs7j/EvEhmkvBioZxaUpmZmyPfjxwv60pIgbz5MDmgK7iS4+3mX6U
A5/TR5d8mUgjU+g4rk8Kb4Mu0UlXjIB0ttov0DiNewNwIRt18jA8+o+u3dpjq+sW
T8KOEUt+zwvo/7V3LvSye0rgTBIlDHCNAymg4VMk7BPZ7hm/ELNKjD+Jo2FR3qyH
B5T0Y3HsLuJvW5iB4YlcNHlsdu87kGJ55tukmi8mxdAQ4Q7e2RCOFvu396j3x+UC
B5iPNgiV5+I3lg02dZ77DnKxHZu8A/lJBdiB3QW0KtZB6awBdpUKD9jf1b0SHzUv
KBds0pjBqAlkd25HN7rOrFleaJ1/ctaJxQZBKT5ZPt0m9STJEadao0xAH0ahmbWn
OlFuhjuefXKnEgV4We0+UXgVCwOPjdAvBbI+e0ocS3MFEvzG6uBQE3xDk3SzynTn
jXXXXXXXX   CENSURED    XXXXXXXXXXXX
oyi3B43njTOQ5yOf+1CceWxG1bQVs5ZufpsMljq4Ui0/1lvh+wjChP4kqKOJ2qxq
4RgqsahDYVvTH9w7jXbyLeiNdd8XM2w9U/t7y0Ff/9yi0GE44Za4rF2LN9d11TPA
mRGunUHBcnWEvgJBQl9nJEiU0Zsnvgc/ubhPgXRR4Xq37Z0j4r7g1SgEEzwxA57d
emyPxgcYxn/eR44/KJ4EBs+lVDR3veyJm+kXQ99b21/+jh5Xos1AnX5iItreGCc=
-----END CERTIFICATE-----

</ca>
key-direction 1
<tls-auth>
#
# 2048 bit OpenVPN static key
#
-----BEGIN OpenVPN Static key V1-----
371b9f84db5d20c9d9a13ad7c19733de
ff33c35c6948a037bb88913a61b7793d
b7040483bbecf25274c0dfe861494ae9
2b47750ed258b1c7b1bdee2de45b4251
88c42a772212f0898100a39d134c55c7
283a13c99c2978f725eaf2c674d90596
XXXXX   CENSURED   XXXXXXXXX
e0eae893c569e0fecf0c47569716c6d0
81a27fdcedfeee319244893fa6b046c9
a161aaaf6125591da1e3e83fe9d79eb0
698ec222d203154f393a15fdc92999b7
-----END OpenVPN Static key V1-----

</tls-auth>

Paul · January 26, 2025, 9:22am

I suggest you start by adding the following statement in your OpenVPN config file:

client-cert-not-required

This tells the OpenVPN client not to look for an external certificate because the certificate is already in the config file.

Another cause of the certificate issue is that the certificate assigned to the VPN server has changed. Export the config file again, add your statements, and open it in the OpenVPN client, replacing the previous configuration.

I am unsure whether you used the VPN connection outside the premises or over the internet. The ‘remote’ statement uses your internal IP address instead of your router’s external IP address. Maybe you did this to share here.

If your external IP address is dynamic, not static, I suggest you enable a DDNS service. You can use DDNS on your NAS.
All this and more is described in this tutorial: Using VPN With Synology NAS

Ordinary87 · January 26, 2025, 10:25am

Thanks for the reply Paul.

While I was writing that I was trying with client-cert-not-required, that I had configured ddns on the NAS, it hit me how stupid I was,thanks to you .
I don’t know when, but apparently when that certificate started to bother me, I edited the configuration file incorrectly, instead external ddns address, i put the internal IP address of the NAS.

Now I get the same certificate error message, but I can continue and it works, , also with the command line client-cert-not-require it works without an error message.

I also renewed certificate on security-certificate menu on dsm, and get new date 26/4/2025, export file, import in openvpn, but still have problem with same message.

Is it VPN connection less secure without that cert or not … ?

Paul · January 30, 2025, 11:41am

You should not get the missing cert error when you included the statement. There is probably a typo in the text. It should read client-cert-not-required with a -d at the end.