[Openvpn-devel,v6,1/2] Make tls_version_max return the actual maximum version

Message ID 20191109120335.1552-1-arne@rfc2549.org
State New
Headers show
Series
  • [Openvpn-devel,v6,1/2] Make tls_version_max return the actual maximum version
Related show

Commit Message

Arne Schwabe Nov. 9, 2019, 12:03 p.m.
Before OpenSSL 1.1.1 there could be no mismatch between
compiled and actual OpenSSL version. With OpenSSL 1.1.1 we need
runtime detection to detect the actual best TLS version supported.

Allowing this runtime detection also allows removing some of the
TLS 1.3/OpenSSL 1.1.1 #ifdefs

Without this patch tls-min-version 1.3 or-highest will actually
downgrade to TLS 1.3 in the "compiled with 1.1.0 and linked against
1.1.1" scenario.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
---
 src/openvpn/ssl.c         | 11 +++++------
 src/openvpn/ssl_openssl.c | 31 ++++++++++++++++++++++++++++---
 2 files changed, 33 insertions(+), 9 deletions(-)

Comments

Steffan Karger Nov. 9, 2019, 4:07 p.m. | #1
Hi,

On 09-11-2019 13:03, Arne Schwabe wrote:
> Before OpenSSL 1.1.1 there could be no mismatch between
> compiled and actual OpenSSL version. With OpenSSL 1.1.1 we need
> runtime detection to detect the actual best TLS version supported.
> 
> Allowing this runtime detection also allows removing some of the
> TLS 1.3/OpenSSL 1.1.1 #ifdefs
> 
> Without this patch tls-min-version 1.3 or-highest will actually
> downgrade to TLS 1.3 in the "compiled with 1.1.0 and linked against
> 1.1.1" scenario.
> 
> Signed-off-by: Arne Schwabe <arne@rfc2549.org>
> ---
>  src/openvpn/ssl.c         | 11 +++++------
>  src/openvpn/ssl_openssl.c | 31 ++++++++++++++++++++++++++++---
>  2 files changed, 33 insertions(+), 9 deletions(-)
> 
> diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
> index 4455ebb8..e708fc93 100644
> --- a/src/openvpn/ssl.c
> +++ b/src/openvpn/ssl.c
> @@ -4194,12 +4194,11 @@ show_available_tls_ciphers(const char *cipher_list,
>  {
>      printf("Available TLS Ciphers, listed in order of preference:\n");
>  
> -#if (ENABLE_CRYPTO_OPENSSL && OPENSSL_VERSION_NUMBER >= 0x1010100fL)
> -    printf("\nFor TLS 1.3 and newer (--tls-ciphersuites):\n\n");
> -    show_available_tls_ciphers_list(cipher_list_tls13, tls_cert_profile, true);
> -#else
> -    (void) cipher_list_tls13;  /* Avoid unused warning */
> -#endif
> +    if (tls_version_max() >= TLS_VER_1_3)
> +    {
> +        printf("\nFor TLS 1.3 and newer (--tls-ciphersuites):\n\n");
> +        show_available_tls_ciphers_list(cipher_list_tls13, tls_cert_profile, true);
> +    }
>  
>      printf("\nFor TLS 1.2 and older (--tls-cipher):\n\n");
>      show_available_tls_ciphers_list(cipher_list, tls_cert_profile, false);
> diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c
> index 07916c3c..e07d6e74 100644
> --- a/src/openvpn/ssl_openssl.c
> +++ b/src/openvpn/ssl_openssl.c
> @@ -215,7 +215,23 @@ int
>  tls_version_max(void)
>  {
>  #if defined(TLS1_3_VERSION)
> +    /* If this is defined we can safely assume TLS 1.3 support */
>      return TLS_VER_1_3;

This clause is no longer needed, right?

> +#elif OPENSSL_VERSION_NUMBER >= 0x10100000L
> +    /*
> +     * The library we are *linked* against is OpenSSL 1.1.1

s/is/might be/ ?

> +     * and therefore supports TLS 1.3. This needs to be checked at runtime
> +     * since we can be compiled against 1.1.0 and then the library can be
> +     * upgraded to 1.1.1
> +     */
> +    if (OpenSSL_version_num() >= 0x1010100fL)
> +    {
> +        return TLS_VER_1_3;
> +    }
> +    else
> +    {
> +        return TLS_VER_1_2;
> +    }
>  #elif defined(TLS1_2_VERSION) || defined(SSL_OP_NO_TLSv1_2)
>      return TLS_VER_1_2;
>  #elif defined(TLS1_1_VERSION) || defined(SSL_OP_NO_TLSv1_1)
> @@ -241,12 +257,20 @@ openssl_tls_version(int ver)
>      {
>          return TLS1_2_VERSION;
>      }
> -#if defined(TLS1_3_VERSION)
>      else if (ver == TLS_VER_1_3)
>      {
> +        /*
> +         * Supporting the library upgraded to TLS1.3 without recompile
> +         * is enough to support here with a simple constant that the same
> +         * as in the TLS 1.3, so spec it is very unlikely that OpenSSL
> +         * will change this constant
> +         */
> +#ifndef TLS1_3_VERSION
> +        return 0x0304;
> +#else

Why not do this outside the function as

  #ifndef TLS1_3_VERSION
  #define TLS1_3_VERSION 0x0304
  #endif

>          return TLS1_3_VERSION;
> -    }
>  #endif
> +    }
>      return 0;
>  }
>  
> @@ -2015,7 +2039,8 @@ show_available_tls_ciphers_list(const char *cipher_list,
>  #if defined(TLS1_3_VERSION)
>      if (tls13)
>      {
> -        SSL_CTX_set_min_proto_version(tls_ctx.ctx, TLS1_3_VERSION);
> +        SSL_CTX_set_min_proto_version(tls_ctx.ctx,
> +                                      openssl_tls_version(TLS_VER_1_3));
>          tls_ctx_restrict_ciphers_tls13(&tls_ctx, cipher_list);
>      }
>      else
> 

Otherwise looks good.

-Steffan

Patch

diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index 4455ebb8..e708fc93 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -4194,12 +4194,11 @@  show_available_tls_ciphers(const char *cipher_list,
 {
     printf("Available TLS Ciphers, listed in order of preference:\n");
 
-#if (ENABLE_CRYPTO_OPENSSL && OPENSSL_VERSION_NUMBER >= 0x1010100fL)
-    printf("\nFor TLS 1.3 and newer (--tls-ciphersuites):\n\n");
-    show_available_tls_ciphers_list(cipher_list_tls13, tls_cert_profile, true);
-#else
-    (void) cipher_list_tls13;  /* Avoid unused warning */
-#endif
+    if (tls_version_max() >= TLS_VER_1_3)
+    {
+        printf("\nFor TLS 1.3 and newer (--tls-ciphersuites):\n\n");
+        show_available_tls_ciphers_list(cipher_list_tls13, tls_cert_profile, true);
+    }
 
     printf("\nFor TLS 1.2 and older (--tls-cipher):\n\n");
     show_available_tls_ciphers_list(cipher_list, tls_cert_profile, false);
diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c
index 07916c3c..e07d6e74 100644
--- a/src/openvpn/ssl_openssl.c
+++ b/src/openvpn/ssl_openssl.c
@@ -215,7 +215,23 @@  int
 tls_version_max(void)
 {
 #if defined(TLS1_3_VERSION)
+    /* If this is defined we can safely assume TLS 1.3 support */
     return TLS_VER_1_3;
+#elif OPENSSL_VERSION_NUMBER >= 0x10100000L
+    /*
+     * The library we are *linked* against is OpenSSL 1.1.1
+     * and therefore supports TLS 1.3. This needs to be checked at runtime
+     * since we can be compiled against 1.1.0 and then the library can be
+     * upgraded to 1.1.1
+     */
+    if (OpenSSL_version_num() >= 0x1010100fL)
+    {
+        return TLS_VER_1_3;
+    }
+    else
+    {
+        return TLS_VER_1_2;
+    }
 #elif defined(TLS1_2_VERSION) || defined(SSL_OP_NO_TLSv1_2)
     return TLS_VER_1_2;
 #elif defined(TLS1_1_VERSION) || defined(SSL_OP_NO_TLSv1_1)
@@ -241,12 +257,20 @@  openssl_tls_version(int ver)
     {
         return TLS1_2_VERSION;
     }
-#if defined(TLS1_3_VERSION)
     else if (ver == TLS_VER_1_3)
     {
+        /*
+         * Supporting the library upgraded to TLS1.3 without recompile
+         * is enough to support here with a simple constant that the same
+         * as in the TLS 1.3, so spec it is very unlikely that OpenSSL
+         * will change this constant
+         */
+#ifndef TLS1_3_VERSION
+        return 0x0304;
+#else
         return TLS1_3_VERSION;
-    }
 #endif
+    }
     return 0;
 }
 
@@ -2015,7 +2039,8 @@  show_available_tls_ciphers_list(const char *cipher_list,
 #if defined(TLS1_3_VERSION)
     if (tls13)
     {
-        SSL_CTX_set_min_proto_version(tls_ctx.ctx, TLS1_3_VERSION);
+        SSL_CTX_set_min_proto_version(tls_ctx.ctx,
+                                      openssl_tls_version(TLS_VER_1_3));
         tls_ctx_restrict_ciphers_tls13(&tls_ctx, cipher_list);
     }
     else