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feat: add TLS 1.3 support, replace ecdh-curve with tls-groups (#1421)

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## Summary

- Add TLS 1.3 support with `--tls-version-min` and `--tls-ciphersuites`
- Replace deprecated `ecdh-curve` with `tls-groups`
- Remove traditional DH support (OpenVPN 2.7 defaults to ECDH)

## New options

| Option | Default |
|--------|---------|
| `--tls-version-min` | `1.2` |
| `--tls-ciphersuites` |
`TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256`
|
| `--tls-groups` | `X25519:prime256v1:secp384r1:secp521r1` |

## Removed

- `--dh-type`, `--dh-bits`, `--dh-curve`
- DH parameter generation

Closes https://github.com/angristan/openvpn-install/issues/1231
Closes https://github.com/angristan/openvpn-install/issues/637
Closes https://github.com/angristan/openvpn-install/issues/1362
This commit is contained in:
Stanislas
2025-12-15 12:13:03 +01:00
committed by GitHub
parent 2e0605e2eb
commit 04f7178c80
3 changed files with 180 additions and 101 deletions
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README.md
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@@ -289,9 +289,9 @@ The `install` command supports many options for customization:
- `--rsa-bits <2048|3072|4096>` - RSA key size (default: `2048`)
- `--hmac <alg>` - HMAC algorithm (default: `SHA256`). Options: `SHA256`, `SHA384`, `SHA512`
- `--tls-sig <mode>` - TLS mode (default: `crypt-v2`). Options: `crypt-v2`, `crypt`, `auth`
- `--dh-type <ecdh|dh>` - DH key exchange type (default: `ecdh`)
- `--dh-curve <curve>` - ECDH curve (default: `prime256v1`). Options: `prime256v1`, `secp384r1`, `secp521r1`
- `--dh-bits <2048|3072|4096>` - DH key size when using `--dh-type dh` (default: `2048`)
- `--tls-version-min <1.2|1.3>` - Minimum TLS version (default: `1.2`)
- `--tls-ciphersuites <list>` - TLS 1.3 cipher suites, colon-separated (default: `TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256`)
- `--tls-groups <list>` - Key exchange groups, colon-separated (default: `X25519:prime256v1:secp384r1:secp521r1`)
- `--server-cert-days <n>` - Server cert validity in days (default: `3650`)
**Client Options:**
@@ -415,9 +415,17 @@ OpenVPN 2.6+ defaults `--allow-compression` to `no`, blocking even server-pushed
OpenVPN 2.5 and earlier accepted TLS 1.0 by default, which is nearly [20 years old](https://en.wikipedia.org/wiki/Transport_Layer_Security#TLS_1.0).
With `tls-version-min 1.2` we enforce TLS 1.2, which the best protocol available currently for OpenVPN.
This script defaults to `tls-version-min 1.2` for compatibility with all OpenVPN 2.4+ clients. You can optionally set `tls-version-min 1.3` for environments where all clients support TLS 1.3.
TLS 1.2 is supported since OpenVPN 2.3.3.
**TLS 1.3 support** was added in OpenVPN 2.5 and requires OpenSSL 1.1.1+. TLS 1.3 offers improved security and performance with a simplified handshake.
The script configures TLS 1.3 cipher suites via `--tls-ciphersuites` (separate from the TLS 1.2 `--tls-cipher` option). The default TLS 1.3 cipher suites are:
- `TLS_AES_256_GCM_SHA384`
- `TLS_AES_128_GCM_SHA256`
- `TLS_CHACHA20_POLY1305_SHA256`
TLS 1.2 is supported since OpenVPN 2.3.3. TLS 1.3 is supported since OpenVPN 2.5.
### Certificate
@@ -476,6 +484,8 @@ OpenVPN 2.4 added a feature called "NCP": _Negotiable Crypto Parameters_. It mea
OpenVPN 2.4 will negotiate the best cipher available by default (e.g ECDHE+AES-256-GCM)
#### TLS 1.2 ciphers (`--tls-cipher`)
The script proposes the following options, depending on the certificate:
- ECDSA:
@@ -489,20 +499,34 @@ The script proposes the following options, depending on the certificate:
It defaults to `TLS-ECDHE-*-WITH-AES-128-GCM-SHA256`.
### Diffie-Hellman key exchange
#### TLS 1.3 ciphers (`--tls-ciphersuites`)
OpenVPN uses a 2048 bits DH key by default.
When TLS 1.3 is negotiated, a separate set of cipher suites is used. These are configured via `--tls-ciphersuites` and use OpenSSL naming conventions:
OpenVPN 2.4 added support for ECDH keys. Elliptic curve cryptography is faster, lighter and more secure.
- `TLS_AES_256_GCM_SHA384`
- `TLS_AES_128_GCM_SHA256`
- `TLS_CHACHA20_POLY1305_SHA256`
Also, generating a classic DH keys can take a long, looong time. ECDH keys are ephemeral: they are generated on-the-fly.
By default, all three cipher suites are enabled. TLS 1.3 cipher suites are simpler because they don't include the key exchange algorithm (which is negotiated separately via key shares).
The script provides the following options:
### Key exchange
- ECDH: `prime256v1`/`secp384r1`/`secp521r1` curves
- DH: `2048`/`3072`/`4096` bits keys
OpenVPN historically defaulted to 2048-bit DH parameters for key exchange. This script used to offer both DH (with configurable key sizes) and ECDH as alternatives.
It defaults to `prime256v1`.
OpenVPN 2.4 added ECDH support, and OpenVPN 2.7 made `dh none` (ECDH) the default, as finite-field DH is being deprecated. Since ECDH is now universally supported and preferred, this script no longer offers traditional DH.
The script configures `tls-groups` with the following preference list:
```
X25519:prime256v1:secp384r1:secp521r1
```
- **X25519**: Fast, modern curve (Curve25519), widely supported
- **prime256v1**: NIST P-256, most compatible
- **secp384r1**: NIST P-384, higher security
- **secp521r1**: NIST P-521, highest security
You can customize this with `--tls-groups`.
### HMAC digest algorithm