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commit 2341f716198fa90193e040b3fdb16959a47c6c27
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-2.4.0/src/openvpn/ssl_verify_openssl.c
===================================================================
--- openvpn-2.4.0.orig/src/openvpn/ssl_verify_openssl.c
+++ openvpn-2.4.0/src/openvpn/ssl_verify_openssl.c
@@ -165,7 +165,7 @@ extract_x509_extension(X509 *cert, char
break;
}
}
- sk_GENERAL_NAME_free(extensions);
+ GENERAL_NAMES_free(extensions);
}
return retval;
}
@@ -218,8 +218,7 @@ extract_x509_field_ssl(X509_NAME *x509,
{
return FAILURE;
}
- tmp = ASN1_STRING_to_UTF8(&buf, asn1);
- if (tmp <= 0)
+ if (ASN1_STRING_to_UTF8(&buf, asn1) < 0)
{
return FAILURE;
}
@@ -460,7 +459,7 @@ x509_setenv_track(const struct x509_trac
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);
@@ -548,7 +547,7 @@ x509_setenv(struct env_set *es, int cert
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;
}
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