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Remove support for key-method 1 from master/2.4

Openvpn-devel Superseded Steffan Karger 3 participants 7 messages Mar 8, 2015 – Nov 14, 2016

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Steffan Karger

author
#0 lore raw

Hi,

To create keys for the data channel, OpenVPN currently supports two mechanisms, 'Key method 1' and the newer 'Key method 2'. Key method 2 is supported since OpenVPN 1.5, and has been the default from OpenVPN 2.0. See the manpage and/or http://openvpn.net/index.php/open-source/documentation/security-overview.html for a short recap of both methods.

I think the time has come to remove support for key method 1 from OpenVPN. This will allow us to remove quite some legacy code, and will probably allow us to simplify some of the surrounding code.

However, before investing time in preparing a patch for this, I would like to hear if there are objections to this proposal. So, if you have a setup that uses key method 1, and you want to use that setup with OpenVPN 2.4, or have other reasons to believe we should keep supporting key method 1 in OpenVPN 2.4, please speak up.

-Steffan

author
#1 lore raw

PATCH 1/1 Deprecate key-method 1

Key method 2 has been the default since OpenVPN 2.0, and is both more functional and secure. Also, key method 1 was only ever supported for peer-to-peer connections (i.e. not for client-server).

Let's get rid of some legacy and phase out key method 1.

Signed-off-by Steffan Karger <[email protected]...>
---
 src/openvpn/options.c | 6 ++++++
 1 file changed, 6 insertions(+)
src/openvpn/options.c +6 -0
index 1eb3a41..f39c4fa 100644
@@ -2245,6 +2245,12 @@ options_postprocess_verify_ce (const struct options *options, const struct conne
 	  "may accept clients which do not present a certificate");
     }
 
+  if (options->key_method == 1)
+    {
+      msg (M_WARN, "WARNING: --key-method 1 is deprecated and will be removed"
+	  "in OpenVPN 2.5.  Migrate to --key-method 2 as soon as possible.");
+    }
+
   if (options->tls_server || options->tls_client)
     {
 #ifdef ENABLE_PKCS11
Signature · 1 line
2.7.4
author
#2 lore raw

PATCH v2 1/1 Deprecate key-method 1

Key method 2 has been the default since OpenVPN 2.0, and is both more functional and secure. Also, key method 1 was only ever supported for peer-to-peer connections (i.e. not for client-server).

Let's get rid of some legacy and phase out key method 1.

v2: add Changes.rst entry, and update man page

Signed-off-by Steffan Karger <[email protected]...>
---
 Changes.rst           | 7 +++++++
 doc/openvpn.8         | 5 ++++-
 src/openvpn/options.c | 6 ++++++
 3 files changed, 17 insertions(+), 1 deletion(-)
Changes.rst +7 -0
index c1b49c7..17d8edb 100644
@@ -112,6 +112,13 @@ AIX platform support
     devices since AIX does not provide tun interface.
 
 
+Deprecated features
+-------------------
+- ``--key-method 1`` is deprecated in 2.4 and will be removed in 2.5.  Migrate
+  to ``--key-method 2`` as soon as possible.  Note that this requires changing
+  the option in both the client and server side configs.
+
+
 User-visible Changes
 --------------------
 - For certificate DNs with duplicate fields, e.g. "OU=one,OU=two", both fields
doc/openvpn.8 +4 -1
index 863dcf9..7227d22 100644
@@ -4782,7 +4782,10 @@ exchanged over the TLS session.
 
 In method 1 (the default for OpenVPN 1.x), both sides generate
 random encrypt and HMAC-send keys which are forwarded to
-the other host over the TLS channel.
+the other host over the TLS channel. Method 1 is
+.B deprecated in OpenVPN 2.4
+, and
+.B will be removed in OpenVPN 2.5\fR.
 
 In method 2, (the default for OpenVPN 2.0)
 the client generates a random key.  Both client
src/openvpn/options.c +6 -0
index 1eb3a41..f39c4fa 100644
@@ -2245,6 +2245,12 @@ options_postprocess_verify_ce (const struct options *options, const struct conne
 	  "may accept clients which do not present a certificate");
     }
 
+  if (options->key_method == 1)
+    {
+      msg (M_WARN, "WARNING: --key-method 1 is deprecated and will be removed"
+	  "in OpenVPN 2.5.  Migrate to --key-method 2 as soon as possible.");
+    }
+
   if (options->tls_server || options->tls_client)
     {
 #ifdef ENABLE_PKCS11
Signature · 1 line
2.7.4
#3 lore raw

Re: [Openvpn-devel] [PATCH v2] Deprecate key-method 1

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Hash: SHA1

Quoted 5 lines · Steffan Karger

Key method 2 has been the default since OpenVPN 2.0, and is both more functional and secure. Also, key method 1 was only ever supported for peer-to-peer connections (i.e. not for client-server).

Quoted 7 lines

Let's get rid of some legacy and phase out key method 1.

v2: add Changes.rst entry, and update man page

Signed-off-by Steffan Karger <[email protected]...> --- Changes.rst

| 7 +++++++ doc/openvpn.8 | 5 ++++- src/openvpn/options.c |
6 ++++++ 3 files changed, 17 insertions(+), 1 deletion(-)

I wanted to give this an ACK ... but I think we should just remove it all together as we seem to be in a broken state already.

/usr/sbin/openvpn --dev tun --local 192.168.122.1 --lport 1194 \
         --remote 192.168.122.100 --rport 194 \
         --secret ../../sample/sample-keys/ta.key 0 \
         --ifconfig 10.8.0.10 10.8.0.20 --verb 3 \
         --key-method 1

Options error: Parameter key_method can only be specified in TLS-mode, i.e. where --tls-server or --tls-client is also specified. Use --help for more information.

That is with /usr/sbin/openvpn --version:
OpenVPN 2.3.11 x86_64-redhat-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on May 10 2016

So unless I messed up my simple and stupid static key p2p mode tunnel, this doesn't work at all with v2.3. And git master haven't "fixed" this issue.

If nobody noticed this by now, then nobody really uses --key-method.

- --
kind regards,

David Sommerseth
OpenVPN Technologies, Inc

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author
#4 lore raw

Re: [Openvpn-devel] [PATCH v2] Deprecate key-method 1

Hi,

On 14 November 2016 at 22:35, David Sommerseth
<[email protected]...> wrote:

Quoted 29 lines · Steffan Karger
Quoted 5 lines

Key method 2 has been the default since OpenVPN 2.0, and is both more functional and secure. Also, key method 1 was only ever supported for peer-to-peer connections (i.e. not for client-server).

Quoted 7 lines

Let's get rid of some legacy and phase out key method 1.

v2: add Changes.rst entry, and update man page

Signed-off-by Steffan Karger <[email protected]...> --- Changes.rst

| 7 +++++++ doc/openvpn.8 | 5 ++++- src/openvpn/options.c |
6 ++++++ 3 files changed, 17 insertions(+), 1 deletion(-)

I wanted to give this an ACK ... but I think we should just remove it all together as we seem to be in a broken state already.

/usr/sbin/openvpn --dev tun --local 192.168.122.1 --lport 1194 \
         --remote 192.168.122.100 --rport 194 \
         --secret ../../sample/sample-keys/ta.key 0 \
         --ifconfig 10.8.0.10 10.8.0.20 --verb 3 \
         --key-method 1

Options error: Parameter key_method can only be specified in TLS-mode, i.e. where --tls-server or --tls-client is also specified. Use --help for more information.

That is with /usr/sbin/openvpn --version:
OpenVPN 2.3.11 x86_64-redhat-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on May 10 2016

Quoted 5 lines

So unless I messed up my simple and stupid static key p2p mode tunnel, this doesn't work at all with v2.3. And git master haven't "fixed" this issue.

If nobody noticed this by now, then nobody really uses --key-method.

Well, the options parser is right: --key-method should be used together with --tls-server and --tls-client. Use e.g. the loopback-server and loopback-client configs from sample/sample-configs to test this.

-Steffan

#5 lore raw

Re: [Openvpn-devel] [PATCH v2] Deprecate key-method 1

In reply to David Sommerseth

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Hash: SHA1

Quoted 29 lines · David Sommerseth
Quoted 5 lines · Steffan Karger

Key method 2 has been the default since OpenVPN 2.0, and is both more functional and secure. Also, key method 1 was only ever supported for peer-to-peer connections (i.e. not for client-server).

Quoted 8 lines

Let's get rid of some legacy and phase out key method 1.

v2: add Changes.rst entry, and update man page

Signed-off-by Steffan Karger <[email protected]...> ---

Changes.rst | 7 +++++++ doc/openvpn.8 | 5 ++++-
src/openvpn/options.c | 6 ++++++ 3 files changed, 17 insertions(+), 1 deletion(-)

I wanted to give this an ACK ... but I think we should just remove it all together as we seem to be in a broken state already.

/usr/sbin/openvpn --dev tun --local 192.168.122.1 --lport 1194 \
--remote 192.168.122.100 --rport 194 \ --secret ../../sample/sample-keys/ta.key 0 \ --ifconfig 10.8.0.10 10.8.0.20 --verb 3 \ --key-method 1 Options error: Parameter key_method can only be specified in TLS-mode, i.e. where --tls-server or --tls-client is also specified. Use --help for more information.

That is with /usr/sbin/openvpn --version: OpenVPN 2.3.11 x86_64-redhat-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on May 10 2016

Quoted 6 lines

So unless I messed up my simple and stupid static key p2p mode tunnel, this doesn't work at all with v2.3. And git master haven't "fixed" this issue.

If nobody noticed this by now, then nobody really uses --key-method.

Okay, so I was mistaken. It is possible to use p2p mode with
- --tls-server/--tls-client without setting --mode server. My prior tests used --server and --client, which does not allow --key-method to be set to anything but 2.

Running a test-case using the sample/sample-config-files/loopback-{client,server} test configs triggered the correct code path, and both --key-method 1 and 2 could be tested properly.

So it's an ACK after all. But I will slightly modify the warning + Changes.rst to recommend not setting --key-method, as that will currently default to --key-method 2.

- --
kind regards,

David Sommerseth
OpenVPN Technologies, Inc

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#6 lore raw

Re: [Openvpn-devel] [PATCH applied] Deprecate key-method 1

In reply to Steffan Karger

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ACK, but with a minor adjustment to the warning + Changes.rst file. The text now tries to encourage not setting --key-method at all, as that will default to --key-method 2.

Your patch has been applied to the master branch

commit 1ce0638627eb35631af9bfaa569468573568ec65

Author: Steffan Karger
Date:   Mon Nov 14 21:06:07 2016 +0100
     Deprecate key-method 1

     Signed-off-by: Steffan Karger <[email protected]...>
     Acked-by: David Sommerseth <[email protected]...>
     Message-Id: <[email protected]...>
     URL: https://www.mail-archive.com/[email protected]/msg13054.html
     Signed-off-by: David Sommerseth <[email protected]...>

- --
kind regards,

David Sommerseth

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