From: Steffan Karger <steffan@karger.me>
Date: Sat, 24 Feb 2018 17:04:49 +0000 (+0100)
Subject: Warn if tls-version-max < tls-version-min
X-Git-Tag: v2.4.5~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2d705accea3e53;p=thirdparty%2Fopenvpn.git

Warn if tls-version-max < tls-version-min

This adds warnings for when a user or our code tries to set a maximum
TLS version that's smaller then the current configured minimum TLS
version.

(And fixes some related whitespace now I touch it anyway.)

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Selva Nair <selva.nair@gmail.com>
Message-Id: <20180224170449.25194-1-steffan@karger.me>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg16545.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit f8a92a4393aae32fc44e03241b5cc891ca6e58a4)
---

diff --git a/src/openvpn/cryptoapi.c b/src/openvpn/cryptoapi.c
index f155123d0..89d253c3d 100644
--- a/src/openvpn/cryptoapi.c
+++ b/src/openvpn/cryptoapi.c
@@ -528,12 +528,18 @@ SSL_CTX_use_CryptoAPI_certificate(SSL_CTX *ssl_ctx, const char *cert_prop)
     if ((!max_version || max_version > TLS1_1_VERSION)
         && cd->key_spec != CERT_NCRYPT_KEY_SPEC)
     {
-        msg(M_WARN,"WARNING: cryptoapicert: private key is in a legacy store."
+        msg(M_WARN, "WARNING: cryptoapicert: private key is in a legacy store."
             " Restricting TLS version to 1.1");
+        if (SSL_CTX_get_min_proto_version(ssl_ctx) > TLS1_1_VERSION)
+        {
+            msg(M_NONFATAL,
+                "ERROR: cryptoapicert: min TLS version larger than 1.1."
+                " Try config option --tls-version-min 1.1");
+            goto err;
+        }
         if (!SSL_CTX_set_max_proto_version(ssl_ctx, TLS1_1_VERSION))
         {
-            msg(M_NONFATAL,"ERROR: cryptoapicert: unable to set max TLS version"
-                " to 1.1. Try config option --tls-version-min 1.1");
+            msg(M_NONFATAL, "ERROR: cryptoapicert: set max TLS version failed");
             goto err;
         }
     }
diff --git a/src/openvpn/openssl_compat.h b/src/openvpn/openssl_compat.h
index a69a70796..c3152d0c1 100644
--- a/src/openvpn/openssl_compat.h
+++ b/src/openvpn/openssl_compat.h
@@ -662,10 +662,24 @@ EC_GROUP_order_bits(const EC_GROUP *group)
 #endif
 
 #ifndef SSL_CTX_get_min_proto_version
-/** Dummy SSL_CTX_get_min_proto_version for OpenSSL < 1.1 (not really needed) */
+/** Return the min SSL protocol version currently enabled in the context.
+ *  If no valid version >= TLS1.0 is found, return 0. */
 static inline int
 SSL_CTX_get_min_proto_version(SSL_CTX *ctx)
 {
+    long sslopt = SSL_CTX_get_options(ctx);
+    if (!(sslopt & SSL_OP_NO_TLSv1))
+    {
+        return TLS1_VERSION;
+    }
+    if (!(sslopt & SSL_OP_NO_TLSv1_1))
+    {
+        return TLS1_1_VERSION;
+    }
+    if (!(sslopt & SSL_OP_NO_TLSv1_2))
+    {
+        return TLS1_2_VERSION;
+    }
     return 0;
 }
 #endif /* SSL_CTX_get_min_proto_version */
@@ -680,18 +694,18 @@ SSL_CTX_get_max_proto_version(SSL_CTX *ctx)
 #ifdef SSL_OP_NO_TLSv1_2
     if (!(sslopt & SSL_OP_NO_TLSv1_2))
     {
-	return TLS1_2_VERSION;
+        return TLS1_2_VERSION;
     }
 #endif
 #ifdef SSL_OP_NO_TLSv1_1
     if (!(sslopt & SSL_OP_NO_TLSv1_1))
     {
-	return TLS1_1_VERSION;
+        return TLS1_1_VERSION;
     }
 #endif
     if (!(sslopt & SSL_OP_NO_TLSv1))
     {
-	return TLS1_VERSION;
+        return TLS1_VERSION;
     }
     return 0;
 }
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index c9f1773af..3f9164c78 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -2556,6 +2556,18 @@ options_postprocess_verify_ce(const struct options *options, const struct connec
             "in the configuration file, which is the recommended approach.");
     }
 
+    const int tls_version_max =
+        (options->ssl_flags >> SSLF_TLS_VERSION_MAX_SHIFT)
+        & SSLF_TLS_VERSION_MAX_MASK;
+    const int tls_version_min =
+        (options->ssl_flags >> SSLF_TLS_VERSION_MIN_SHIFT)
+        & SSLF_TLS_VERSION_MIN_MASK;
+
+    if (tls_version_max > 0 && tls_version_max < tls_version_min)
+    {
+        msg(M_USAGE, "--tls-version-min bigger than --tls-version-max");
+    }
+
     if (options->tls_server || options->tls_client)
     {
 #ifdef ENABLE_PKCS11