[Openvpn-devel,v3,04/21,OSSL,3.0] Remove DES check with OpenSSL 3.0

Message ID 20211019183127.614175-5-arne@rfc2549.org
State Accepted
Headers show
Series
  • OpenSSL 3.0 improvements for OpenVPN
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Commit Message

Arne Schwabe Oct. 19, 2021, 6:31 p.m.
DES is very deprecated and accidently getting on the of the 16 insecure
keys that OpenSSL checks is extremely unlikely so we no longer use the
deprecated functions without replacement in OpenSSL 3.0.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
---
 src/openvpn/crypto_openssl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Maximilian Fillinger Oct. 21, 2021, 9:23 a.m. | #1
On 19/10/2021 20:31, Arne Schwabe wrote:
> DES is very deprecated and accidently getting on the of the 16 insecure
> keys that OpenSSL checks is extremely unlikely so we no longer use the
> deprecated functions without replacement in OpenSSL 3.0.
> 
> Signed-off-by: Arne Schwabe <arne@rfc2549.org>
> ---
>   src/openvpn/crypto_openssl.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c
> index 021698f12..8db2ddd09 100644
> --- a/src/openvpn/crypto_openssl.c
> +++ b/src/openvpn/crypto_openssl.c
> @@ -521,6 +521,11 @@ key_des_num_cblocks(const EVP_CIPHER *kt)
>   bool
>   key_des_check(uint8_t *key, int key_len, int ndc)
>   {
> +#if OPENSSL_VERSION_NUMBER < 0x30000000L
> +    /* DES is deprecated and the method to even check the keys is deprecated
> +     * in OpenSSL 3.0. Instead of checking for the 16 weak/semi-weak keys
> +     * we just accept them in OpenSSL 3.0 since the risk of randomly getting
> +     * these is pretty weak */
>       int i;
>       struct buffer b;
>   
> @@ -553,6 +558,9 @@ key_des_check(uint8_t *key, int key_len, int ndc)
>   err:
>       ERR_clear_error();
>       return false;
> +#else
> +    return true;
> +#endif
>   }
>   
>   void
> 

The code change looks good to me. Dropping the check is no loss because 
*all* DES keys are weak keys.

The comment probably makes more sense in the #else branch, or before the 
version check. Since I'm already nitpicking, it should be "the risk is 
low", not "weak".
Gert Doering Oct. 21, 2021, 2:11 p.m. | #2
Acked-by: Gert Doering <gert@greenie.muc.de>

Taking MaxF review into account, moving the comment as suggested, and
changing "risk ... is ... weak" to "low".

Your patch has been applied to the master branch.

commit d67658feeab4742b9b6f57806ba8e93c8eec75b8
Author: Arne Schwabe
Date:   Tue Oct 19 20:31:10 2021 +0200

     Remove DES check with OpenSSL 3.0

     Signed-off-by: Arne Schwabe <arne@rfc2549.org>
     Acked-by: Gert Doering <gert@greenie.muc.de>
     Message-Id: <20211019183127.614175-5-arne@rfc2549.org>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg23004.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering

Patch

diff --git a/src/openvpn/crypto_openssl.c b/src/openvpn/crypto_openssl.c
index 021698f12..8db2ddd09 100644
--- a/src/openvpn/crypto_openssl.c
+++ b/src/openvpn/crypto_openssl.c
@@ -521,6 +521,11 @@  key_des_num_cblocks(const EVP_CIPHER *kt)
 bool
 key_des_check(uint8_t *key, int key_len, int ndc)
 {
+#if OPENSSL_VERSION_NUMBER < 0x30000000L
+    /* DES is deprecated and the method to even check the keys is deprecated
+     * in OpenSSL 3.0. Instead of checking for the 16 weak/semi-weak keys
+     * we just accept them in OpenSSL 3.0 since the risk of randomly getting
+     * these is pretty weak */
     int i;
     struct buffer b;
 
@@ -553,6 +558,9 @@  key_des_check(uint8_t *key, int key_len, int ndc)
 err:
     ERR_clear_error();
     return false;
+#else
+    return true;
+#endif
 }
 
 void