1 files changed, 231 insertions, 0 deletions
diff --git a/src/binddynport.c b/src/binddynport.c
new file mode 100644
index 0000000..c2e9a20
--- /dev/null
+++ b/src/binddynport.c
@@ -0,0 +1,231 @@
+/*
+ * Copyright (c) 2018, Oracle America, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ * - Neither the name of "Oracle America, Inc." nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+
+#include <netdb.h>
+#include <netinet/in.h>
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <syslog.h>
+
+#include <rpc/rpc.h>
+
+#include "reentrant.h"
+#include "rpc_com.h"
+
+extern pthread_mutex_t port_lock;
+
+/*
+ * Dynamic port range as defined in RFC 6335 Section 6.
+ * This range avoids all IANA-assigned service port
+ * numbers.
+ */
+enum {
+	LOWPORT		= 49152,
+	ENDPORT		= 65534,
+	NPORTS		= ENDPORT - LOWPORT + 1,
+};
+
+/*
+ * This function decodes information about given port from provided array and
+ * return if port is reserved or not.
+ *
+ * @reserved_ports an array of size at least "NPORTS / (8*sizeof(char)) + 1".
+ * @port port number within range LOWPORT and ENDPORT
+ *
+ * Returns 0 if port is not reserved, non-negative if port is reserved.
+ */
+static int is_reserved(char *reserved_ports, int port) {
+	port -= LOWPORT;
+	if (port < 0 || port >= NPORTS)
+		return 0;
+	return reserved_ports[port/(8*sizeof(char))] & 1<<(port%(8*sizeof(char)));
+}
+
+/*
+ * This function encodes information about given *reserved* port into provided
+ * array. Don't call this function for ports which are not reserved.
+ *
+ * @reserved_ports an array of size at least "NPORTS / (8*sizeof(char)) + 1".
+ * @port port number within range LOWPORT and ENDPORT
+ *
+ */
+static void set_reserved(char *reserved_ports, int port) {
+	port -= LOWPORT;
+	if (port < 0 || port >= NPORTS)
+		return;
+	reserved_ports[port/(8*sizeof(char))] |= 1<<(port%(8*sizeof(char)));
+}
+
+/*
+ * Parse local reserved ports obtained from
+ * /proc/sys/net/ipv4/ip_local_reserved_ports into bit array.
+ *
+ * @reserved_ports a zeroed array of size at least
+ * "NPORTS / (8*sizeof(char)) + 1". Will be used for bit-wise encoding of
+ * reserved ports.
+ *
+ * On each call, reserved ports are read from /proc and bit-wise stored into
+ * provided array
+ *
+ * Returns 0 on success, -1 on failure.
+ */
+
+static int parse_reserved_ports(char *reserved_ports) {
+	int from=0, to;
+	char delimiter = ',';
+	int res;
+	FILE * file_ptr = fopen("/proc/sys/net/ipv4/ip_local_reserved_ports","r");
+	if (file_ptr == NULL) {
+		(void) syslog(LOG_ERR,
+			"Unable to open open /proc/sys/net/ipv4/ip_local_reserved_ports.");
+		return -1;
+	}
+	do {
+		if ((res = fscanf(file_ptr, "%d", &to)) != 1) {
+			if (res == EOF) break;
+			goto err;
+		}
+		if (delimiter != '-') {
+			from = to;
+		}
+		for (int i = from; i <= to; ++i) {
+			set_reserved(reserved_ports, i);
+		}
+	} while ((res = fscanf(file_ptr, "%c", &delimiter)) == 1);
+	if (res != EOF)
+		goto err;
+	fclose(file_ptr);
+	return 0;
+err:
+	(void) syslog(LOG_ERR,
+		"An error occurred while parsing ip_local_reserved_ports.");
+	fclose(file_ptr);
+	return -1;
+}
+
+/*
+ * Bind a socket to a dynamically-assigned IP port.
+ *
+ * @fd is an open but unbound socket.
+ *
+ * On each call, a port number is chosen at random from
+ * within the dynamic/private port range, even if the
+ * caller has CAP_NET_ADMIN_BIND.
+ *
+ * Returns 0 on success, -1 on failure. errno may be
+ * set to a non-determinant value.
+ *
+ * This function is re-entrant.
+ */
+int __binddynport(int fd)
+{
+	struct sockaddr_storage ss;
+#ifdef INET6
+	struct sockaddr_in6 *sin6;
+#endif
+	struct sockaddr_in *sin;
+	static unsigned int seed;
+	in_port_t port, *portp;
+	struct sockaddr *sap;
+	socklen_t salen;
+	int i, res, array_size;
+	char *reserved_ports = NULL;
+
+	if (__rpc_sockisbound(fd))
+		return 0;
+
+	res = -1;
+	sap = (struct sockaddr *)(void *)&ss;
+	salen = sizeof(ss);
+	memset(sap, 0, salen);
+
+	mutex_lock(&port_lock);
+
+	if (getsockname(fd, sap, &salen) == -1)
+		goto out;
+
+	switch (ss.ss_family) {
+	case AF_INET:
+		sin = (struct sockaddr_in *)(void *)&ss;
+		portp = &sin->sin_port;
+		salen = sizeof(struct sockaddr_in);
+		break;
+#ifdef INET6
+	case AF_INET6:
+		sin6 = (struct sockaddr_in6 *)(void *)&ss;
+		portp = &sin6->sin6_port;
+		salen = sizeof(struct sockaddr_in6);
+		break;
+#endif
+	default:
+		goto out;
+	}
+
+	if (!seed) {
+		struct timeval tv;
+
+		gettimeofday(&tv, NULL);
+		seed = tv.tv_usec * getpid();
+	}
+	array_size = NPORTS / (8*sizeof(char)) + 1;
+	reserved_ports = malloc(array_size);
+	if (!reserved_ports) {
+		goto out;
+	}
+	memset(reserved_ports, 0, array_size);
+	if (parse_reserved_ports(reserved_ports) < 0)
+		goto out;
+
+	port = (rand_r(&seed) % NPORTS) + LOWPORT;
+	for (i = 0; i < NPORTS; ++i) {
+		*portp = htons(port);
+		if (!is_reserved(reserved_ports, port++)) {
+			res = bind(fd, sap, salen);
+			if (res >= 0) {
+				res = 0;
+				break;
+			}
+			if (errno != EADDRINUSE)
+				break;
+		}
+		if (port > ENDPORT)
+			port = LOWPORT;
+	}
+
+out:
+	free(reserved_ports);
+	mutex_unlock(&port_lock);
+	return res;
+}