commit 84e1775961de1c9d2ab32159fc03f758591f5238
Author: Steffan Karger <steffan.karger@fox-it.com>
Date:   Mon Jun 19 11:28:38 2017 +0200

    Fix remote-triggerable memory leaks (CVE-2017-7521)
    
    Several of our OpenSSL-specific certificate-parsing code paths did not
    always clear all allocated memory.  Since a client can cause a few bytes
    of memory to be leaked for each connection attempt, a client can cause a
    server to run out of memory and thereby kill the server.  That makes this
    a (quite inefficient) DoS attack.
    
    When using the --x509-alt-username option on openssl builds with an
    extension (argument prefixed with "ext:", e.g. "ext:subjectAltName"), the
    code would not free all allocated memory.  Fix this by using the proper
    free function.
    
    If ASN1_STRING_to_UTF8() returns 0, it didn't fail and *did* allocate
    memory.  So also free the returned buffer if it returns 0.
    
    These issues were found, analysed and reported to the OpenVPN team by Guido
    Vranken.
    
    CVE: 2017-7521
    Signed-off-by: Steffan Karger <steffan.karger@fox-it.com>
    Acked-by: Gert Doering <gert@greenie.muc.de>
    Acked-by: David Sommerseth <davids@openvpn.net>
    Acked-by: Guido Vranken <guidovranken@gmail.com>
    Message-Id: <1497864520-12219-4-git-send-email-steffan.karger@fox-it.com>
    URL: https://www.mail-archive.com/search?l=mid&q=1497864520-12219-4-git-send-email-steffan.karger@fox-it.com
    Signed-off-by: Gert Doering <gert@greenie.muc.de>
    (cherry picked from commit 2d032c7fcdfd692c851ea2fa858b4c2d9ea7d52d)

Index: openvpn-2.3.4/src/openvpn/ssl_verify_openssl.c
===================================================================
--- openvpn-2.3.4.orig/src/openvpn/ssl_verify_openssl.c
+++ openvpn-2.3.4/src/openvpn/ssl_verify_openssl.c
@@ -144,7 +144,7 @@ bool extract_x509_extension(X509 *cert,
                 break;
             }
           }
-        sk_GENERAL_NAME_free (extensions);
+        GENERAL_NAMES_free(extensions);
     }
   return retval;
 }
@@ -191,8 +191,7 @@ extract_x509_field_ssl (X509_NAME *x509,
   asn1 = X509_NAME_ENTRY_get_data(x509ne);
   if (!asn1)
     return FAILURE;
-  tmp = ASN1_STRING_to_UTF8(&buf, asn1);
-  if (tmp <= 0)
+  if (ASN1_STRING_to_UTF8(&buf, asn1) < 0)
     return FAILURE;
 
   strncpynt(out, (char *)buf, size);
@@ -364,7 +363,7 @@ x509_setenv_track (const struct x509_tra
 		  ASN1_STRING *val = X509_NAME_ENTRY_get_data (ent);
 		  unsigned char *buf;
 		  buf = (unsigned char *)1; /* bug in OpenSSL 0.9.6b ASN1_STRING_to_UTF8 requires this workaround */
-		  if (ASN1_STRING_to_UTF8 (&buf, val) > 0)
+		  if (ASN1_STRING_to_UTF8 (&buf, val) >= 0)
 		    {
 		      do_setenv_x509(es, xt->name, (char *)buf, depth);
 		      OPENSSL_free (buf);
@@ -440,7 +439,7 @@ x509_setenv (struct env_set *es, int cer
       if (!objbuf)
 	continue;
       buf = (unsigned char *)1; /* bug in OpenSSL 0.9.6b ASN1_STRING_to_UTF8 requires this workaround */
-      if (ASN1_STRING_to_UTF8 (&buf, val) <= 0)
+      if (ASN1_STRING_to_UTF8 (&buf, val) < 0)
 	continue;
       name_expand_size = 64 + strlen (objbuf);
       name_expand = (char *) malloc (name_expand_size);