Attention is currently required from: flichtenheld.

Hello flichtenheld, 

I'd like you to reexamine a change. Please visit

to look at the new patch set (#2).

Change subject: Extend the error message when TLS 1.0 PRF fails

Extend the error message when TLS 1.0 PRF fails

This error will probably become more and more common in the future when
more and more system will drop TLS 1.0 PRF support. We are already seeing
people stumbling upon this (see GitHub issue #460)

The current error messages

  TLS Error: PRF calcuation failed
  TLS Error: generate_key_expansion failed

are not very helpful for people that do not have deep understanding of TLS or
the OpenVPN protocol. Improve a on this message to give a normal user a chance
to understand that the peer needs to be OpenVPN 2.6.x or newer.

Change-Id: Ib3b64b52beed69dc7740f191b0e9a9dc9af5b7f3
Signed-off-by: Arne Schwabe <>
M src/openvpn/ssl.c
1 file changed, 6 insertions(+), 1 deletion(-)

  git pull ssh:// refs/changes/56/456/2

diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index 400230c..9817b2e 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -1641,7 +1641,12 @@
         if (!generate_key_expansion_openvpn_prf(session, &key2))
-            msg(D_TLS_ERRORS, "TLS Error: PRF calcuation failed");
+            msg(D_TLS_ERRORS, "TLS Error: PRF calculation failed. Your system "
+                "might not support the old TLS 1.0 PRF calculation anymore or "
+                "the policy does not allow TLS1 PRF calculation anymore "
+                "(e.g. running in FIPS mode). The peer did not announce 
support "
+                "for the modern TLS Export feature that replaces the TLS 1.0"
+                "RPF (requires OpenVPN 2.6.x or higher)");
             goto exit;

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Gerrit-Project: openvpn
Gerrit-Branch: master
Gerrit-Change-Id: Ib3b64b52beed69dc7740f191b0e9a9dc9af5b7f3
Gerrit-Change-Number: 456
Gerrit-PatchSet: 2
Gerrit-Owner: plaisthos <>
Gerrit-Reviewer: flichtenheld <>
Gerrit-CC: openvpn-devel <>
Gerrit-Attention: flichtenheld <>
Gerrit-MessageType: newpatchset
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