[Openvpn-devel,v3] Cleanup print_details and add signature/ED certificate print

Message ID 20210326175750.4772-1-arne@rfc2549.org
State Accepted
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  • [Openvpn-devel,v3] Cleanup print_details and add signature/ED certificate print
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Commit Message

Arne Schwabe March 26, 2021, 5:57 p.m.
This commit cleans up the logic in the function a bit. It also makes it
more clear the the details printed in the second part of the message are
details about the peer certificate and not the TLS connection as such.
Also print the signature algorithm as this might help to identify
peer certificate that still use SHA1.

The new format with for TLS 1.3 and an EC certificate.

Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, peer certificate: 384 bit EC, curve secp384r1, signature: ecdsa-with-SHA256

Using the more generic OpenSSL functions also allows use to correctly
print details about ED certificates:

Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, peer certificate: 253 bit ED25519, signature: ED25519

Patch v2: Cleanup multiple calls to EVP_PKEY_id, minor code restructuring

Patch v3: Always initialise sig.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
---
 src/openvpn/ssl_openssl.c | 118 +++++++++++++++++++++++++-------------
 1 file changed, 78 insertions(+), 40 deletions(-)

Comments

Antonio Quartulli March 27, 2021, 11:07 p.m. | #1
Hi,

On 26/03/2021 18:57, Arne Schwabe wrote:
> This commit cleans up the logic in the function a bit. It also makes it
> more clear the the details printed in the second part of the message are
> details about the peer certificate and not the TLS connection as such.
> Also print the signature algorithm as this might help to identify
> peer certificate that still use SHA1.
> 
> The new format with for TLS 1.3 and an EC certificate.
> 
> Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, peer certificate: 384 bit EC, curve secp384r1, signature: ecdsa-with-SHA256
> 
> Using the more generic OpenSSL functions also allows use to correctly
> print details about ED certificates:
> 
> Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, peer certificate: 253 bit ED25519, signature: ED25519
> 
> Patch v2: Cleanup multiple calls to EVP_PKEY_id, minor code restructuring
> 
> Patch v3: Always initialise sig.
> 
> Signed-off-by: Arne Schwabe <arne@rfc2549.org>

It looks good now!
Printing of the peer certificate works as expected with both RSA and
ECDSA certificates.


Acked-by: Antonio Quartulli <antonio@openvpn.net>
Gert Doering March 28, 2021, 9:44 a.m. | #2
Lightly tested on OpenSSL 1.0.2 and 1.1.1 clients, talking to 1.0.2 and
1.1.1 servers (= TLS 1.2 and 1.3).

Your patch has been applied to the master and release/2.5 branch.

I think it falls under the "long term compatibility" clause for 2.5,
as 2.5 will be around for a while and being able to print more details
for TLS 1.3 and EC/ED is good.

commit ca57070630a1b2935ee606cc1309005b56eb925f (master)
commit a177388735566c3d7c3120860ceea71b81db5c34 (release/2.5)
Author: Arne Schwabe
Date:   Fri Mar 26 18:57:50 2021 +0100

     Cleanup print_details and add signature/ED certificate print

     Signed-off-by: Arne Schwabe <arne@rfc2549.org>
     Acked-by: Antonio Quartulli <antonio@openvpn.net>
     Message-Id: <20210326175750.4772-1-arne@rfc2549.org>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg21861.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering

Patch

diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c
index d161f48b8..b85f95be1 100644
--- a/src/openvpn/ssl_openssl.c
+++ b/src/openvpn/ssl_openssl.c
@@ -2001,6 +2001,80 @@  key_state_read_plaintext(struct key_state_ssl *ks_ssl, struct buffer *buf,
     return ret;
 }
 
+/**
+ * Print human readable information about the certifcate into buf
+ * @param cert      the certificate being used
+ * @param buf       output buffer
+ * @param buflen    output buffer length
+ */
+static void
+print_cert_details(X509 *cert, char *buf, size_t buflen)
+{
+    const char *curve = "";
+    const char *type = "(error getting type)";
+    EVP_PKEY *pkey = X509_get_pubkey(cert);
+
+    if (pkey == NULL)
+    {
+        buf[0] = 0;
+        return;
+    }
+
+    int typeid = EVP_PKEY_id(pkey);
+
+#ifndef OPENSSL_NO_EC
+    if (typeid == EVP_PKEY_EC && EVP_PKEY_get0_EC_KEY(pkey) != NULL)
+    {
+        EC_KEY *ec = EVP_PKEY_get0_EC_KEY(pkey);
+        const EC_GROUP *group = EC_KEY_get0_group(ec);
+
+        int nid = EC_GROUP_get_curve_name(group);
+        if (nid == 0 || (curve = OBJ_nid2sn(nid)) == NULL)
+        {
+            curve = "(error getting curve name)";
+        }
+    }
+#endif
+    if (EVP_PKEY_id(pkey) != 0)
+    {
+        int typeid = EVP_PKEY_id(pkey);
+        type = OBJ_nid2sn(typeid);
+
+        /* OpenSSL reports rsaEncryption, dsaEncryption and
+        * id-ecPublicKey, map these values to nicer ones */
+        if (typeid == EVP_PKEY_RSA)
+        {
+            type = "RSA";
+        }
+        else if (typeid == EVP_PKEY_DSA)
+        {
+            type = "DSA";
+        }
+        else if (typeid == EVP_PKEY_EC)
+        {
+            /* EC gets the curve appended after the type */
+            type = "EC, curve ";
+        }
+        else if (type == NULL)
+        {
+            type = "unknown type";
+        }
+    }
+
+    char sig[128] = { 0 };
+    int signature_nid = X509_get_signature_nid(cert);
+    if (signature_nid != 0)
+    {
+        openvpn_snprintf(sig, sizeof(sig), ", signature: %s",
+                         OBJ_nid2sn(signature_nid));
+    }
+
+    openvpn_snprintf(buf, buflen, ", peer certificate: %d bit %s%s%s",
+                     EVP_PKEY_bits(pkey), type, curve, sig);
+
+    EVP_PKEY_free(pkey);
+}
+
 /* **************************************
  *
  * Information functions
@@ -2012,7 +2086,6 @@  void
 print_details(struct key_state_ssl *ks_ssl, const char *prefix)
 {
     const SSL_CIPHER *ciph;
-    X509 *cert;
     char s1[256];
     char s2[256];
 
@@ -2023,48 +2096,13 @@  print_details(struct key_state_ssl *ks_ssl, const char *prefix)
                      SSL_get_version(ks_ssl->ssl),
                      SSL_CIPHER_get_version(ciph),
                      SSL_CIPHER_get_name(ciph));
-    cert = SSL_get_peer_certificate(ks_ssl->ssl);
-    if (cert != NULL)
-    {
-        EVP_PKEY *pkey = X509_get_pubkey(cert);
-        if (pkey != NULL)
-        {
-            if ((EVP_PKEY_id(pkey) == EVP_PKEY_RSA) && (EVP_PKEY_get0_RSA(pkey) != NULL))
-            {
-                RSA *rsa = EVP_PKEY_get0_RSA(pkey);
-                openvpn_snprintf(s2, sizeof(s2), ", %d bit RSA",
-                                 RSA_bits(rsa));
-            }
-            else if ((EVP_PKEY_id(pkey) == EVP_PKEY_DSA) && (EVP_PKEY_get0_DSA(pkey) != NULL))
-            {
-                DSA *dsa = EVP_PKEY_get0_DSA(pkey);
-                openvpn_snprintf(s2, sizeof(s2), ", %d bit DSA",
-                                 DSA_bits(dsa));
-            }
-#ifndef OPENSSL_NO_EC
-            else if ((EVP_PKEY_id(pkey) == EVP_PKEY_EC) && (EVP_PKEY_get0_EC_KEY(pkey) != NULL))
-            {
-                EC_KEY *ec = EVP_PKEY_get0_EC_KEY(pkey);
-                const EC_GROUP *group = EC_KEY_get0_group(ec);
-                const char *curve;
+    X509 *cert = SSL_get_peer_certificate(ks_ssl->ssl);
 
-                int nid = EC_GROUP_get_curve_name(group);
-                if (nid == 0 || (curve = OBJ_nid2sn(nid)) == NULL)
-                {
-                    curve = "Error getting curve name";
-                }
-
-                openvpn_snprintf(s2, sizeof(s2), ", %d bit EC, curve: %s",
-                                 EC_GROUP_order_bits(group), curve);
-
-            }
-#endif
-            EVP_PKEY_free(pkey);
-        }
+    if (cert)
+    {
+        print_cert_details(cert, s2, sizeof(s2));
         X509_free(cert);
     }
-    /* The SSL API does not allow us to look at temporary RSA/DH keys,
-     * otherwise we should print their lengths too */
     msg(D_HANDSHAKE, "%s%s", s1, s2);
 }