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Regression #16421

closed

OpenVPN servers will not start with DH parameters < 2048

Added by Jim Pingle 2 months ago. Updated about 18 hours ago.

Status:
Resolved
Priority:
High
Assignee:
Marcos M
Category:
OpenVPN
Target version:
2.9.0
Start date:
Due date:
% Done:

100%

Estimated time:
Plus Target Version:
25.11
Release Notes:
Default
Affected Version:
Affected Architecture:

Description

On current Plus 25.11 and CE 2.9.0 snapshots, OpenVPN servers will not start if they have a DH parameter size of 1024 in the configuration:

<dh_length>1024</dh_length>

A recent upstream change in OpenSSL appears to have enacted a new lower limit for security:

Sep 9 14:23:39     openvpn     86194     OpenSSL: error:0A00018A:SSL routines::dh key too small:
Sep 9 14:23:39     openvpn     86194     SSL_CTX_set0_tmp_dh_pkey
Sep 9 14:23:39     openvpn     86194     Exiting due to fatal error

We need some upgrade code to bump those to 2048 (or higher) on all server instances.

We also need to remove the 1024 choice from the drop-down and remove the file with the 1024 DH material and so on.

In the meantime those testing snapshots can edit the server and choose a DH value >= 2048.

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 #1

Updated by Jim Pingle 2 months ago

  • Description updated (diff)
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 #2

Updated by aleksei prokofiev 13 days ago

Tested on
25.11-BETA (amd64)
built on Tue Oct 28 18:38:00 UTC 2025
FreeBSD 16.0-CURRENT

I can confirm this behavior.
ct 31 10:22:07 openvpn 26250 OpenSSL: error:0A00018A:SSL routines::dh key too small:
Oct 31 10:22:07 openvpn 26250 SSL_CTX_set0_tmp_dh_pkey
Oct 31 10:22:07 openvpn 26250 Exiting due to fatal error

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 #3

Updated by Marcos M 3 days ago

  • Assignee set to Marcos M
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 #4

Updated by Marcos M 3 days ago

  • Status changed from New to Feedback
  • % Done changed from 0 to 100
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 #5

Updated by Jim Pingle about 18 hours ago

  • Status changed from Feedback to Resolved

Looks good here now:

  • GUI option for 1024 is gone
  • The file with 1024 DH parameter data is no longer present
  • The configuration is changed on upgrade if needed
  • When the configuration is changed, a notice is filed letting the user know about the change
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