OpenSSL: Clear default_passwd_cb more thoroughly

Previously, the pointer to strdup passwd was left in OpenSSL library
default_passwd_cb_userdata and even the default_passwd_cb was left set
on an error path. To avoid unexpected behavior if something were to
manage to use there pointers, clear them explicitly once done with
loading of the private key.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/crypto/tls_openssl.c

@@ -2775,6 +2775,19 @@ static int tls_connection_engine_private_key(struct tls_connection *conn)
 }
 
 
+static void tls_clear_default_passwd_cb(SSL_CTX *ssl_ctx, SSL *ssl)
+{
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
+	if (ssl) {
+		SSL_set_default_passwd_cb(ssl, NULL);
+		SSL_set_default_passwd_cb_userdata(ssl, NULL);
+	}
+#endif /* >= 1.1.0f && !LibreSSL */
+	SSL_CTX_set_default_passwd_cb(ssl_ctx, NULL);
+	SSL_CTX_set_default_passwd_cb_userdata(ssl_ctx, NULL);
+}
+
+
 static int tls_connection_private_key(struct tls_data *data,
 				      struct tls_connection *conn,
 				      const char *private_key,
@@ -2891,14 +2904,12 @@ static int tls_connection_private_key(struct tls_data *data,
 	if (!ok) {
 		tls_show_errors(MSG_INFO, __func__,
 				"Failed to load private key");
+		tls_clear_default_passwd_cb(ssl_ctx, conn->ssl);
 		os_free(passwd);
 		return -1;
 	}
 	ERR_clear_error();
-#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
-	SSL_set_default_passwd_cb(conn->ssl, NULL);
-#endif /* >= 1.1.0f && !LibreSSL */
-	SSL_CTX_set_default_passwd_cb(ssl_ctx, NULL);
+	tls_clear_default_passwd_cb(ssl_ctx, conn->ssl);
 	os_free(passwd);
 
 	if (!SSL_check_private_key(conn->ssl)) {
@@ -2941,13 +2952,14 @@ static int tls_global_private_key(struct tls_data *data,
 	    tls_read_pkcs12(data, NULL, private_key, passwd)) {
 		tls_show_errors(MSG_INFO, __func__,
 				"Failed to load private key");
+		tls_clear_default_passwd_cb(ssl_ctx, NULL);
 		os_free(passwd);
 		ERR_clear_error();
 		return -1;
 	}
+	tls_clear_default_passwd_cb(ssl_ctx, NULL);
 	os_free(passwd);
 	ERR_clear_error();
-	SSL_CTX_set_default_passwd_cb(ssl_ctx, NULL);
 
 	if (!SSL_CTX_check_private_key(ssl_ctx)) {
 		tls_show_errors(MSG_INFO, __func__,