[PATCH v2] OpenSSL: Accept certificates marked for both server and client use

[Anders Kaseorg]

Commit 51e3eafb68e15e78e98ca955704be8a6c3a7b304 was too strict in
forbidding certificates marked for client use.  For example, this
broke the MIT SECURE wireless network.  The extended key usage is a
_list_ of allowed uses, and rather than checking that client use is
not in the list, we should check that server use is in the list.

Signed-off-by: Anders Kaseorg <andersk at mit.edu>
---
(Change from v1: accept XKU_ANYEKU.)

 src/crypto/tls.h         |  2 +-
 src/crypto/tls_openssl.c | 10 ++++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/crypto/tls.h b/src/crypto/tls.h
index 287fd33..3f07600 100644
--- a/src/crypto/tls.h
+++ b/src/crypto/tls.h
@@ -42,7 +42,7 @@ enum tls_fail_reason {
 	TLS_FAIL_BAD_CERTIFICATE = 7,
 	TLS_FAIL_SERVER_CHAIN_PROBE = 8,
 	TLS_FAIL_DOMAIN_SUFFIX_MISMATCH = 9,
-	TLS_FAIL_SERVER_USED_CLIENT_CERT = 10
+	TLS_FAIL_NON_SERVER_KEY_USAGE = 10,
 };
 
 union tls_event_data {
diff --git a/src/crypto/tls_openssl.c b/src/crypto/tls_openssl.c
index d025ae0..a935e4b 100644
--- a/src/crypto/tls_openssl.c
+++ b/src/crypto/tls_openssl.c
@@ -1479,11 +1479,13 @@ static int tls_verify_cb(int preverify_ok, X509_STORE_CTX *x509_ctx)
 
 	if (!conn->server && err_cert && preverify_ok && depth == 0 &&
 	    (err_cert->ex_flags & EXFLAG_XKUSAGE) &&
-	    (err_cert->ex_xkusage & XKU_SSL_CLIENT)) {
-		wpa_printf(MSG_WARNING, "TLS: Server used client certificate");
+	    !(err_cert->ex_xkusage & (XKU_SSL_SERVER | XKU_ANYEKU))) {
+		wpa_printf(MSG_WARNING, "TLS: Server certificate marked for "
+			   "non-server key usage");
 		openssl_tls_fail_event(conn, err_cert, err, depth, buf,
-				       "Server used client certificate",
-				       TLS_FAIL_SERVER_USED_CLIENT_CERT);
+				       "Server certificate marked for "
+				       "non-server key usage",
+				       TLS_FAIL_NON_SERVER_KEY_USAGE);
 		preverify_ok = 0;
 	}
 
-- 
1.9.0