|
|
@@ -0,0 +1,186 @@
|
|
|
+/**
|
|
|
+ * @file
|
|
|
+ *
|
|
|
+ * Reference implementation of the TCP ISN algorithm standardized in RFC 6528.
|
|
|
+ * Produce TCP Initial Sequence Numbers by combining an MD5-generated hash
|
|
|
+ * based on the new TCP connection's identity and a stable secret, with the
|
|
|
+ * current time at 4-microsecond granularity.
|
|
|
+ *
|
|
|
+ * Specifically, the implementation uses MD5 to compute a hash of the input
|
|
|
+ * buffer, which contains both the four-tuple of the new TCP connection (local
|
|
|
+ * and remote IP address and port), as well as a 16-byte secret to make the
|
|
|
+ * results unpredictable to external parties. The secret must be given at
|
|
|
+ * initialization time and should ideally remain the same across system
|
|
|
+ * reboots. To be sure: the spoofing-resistance of the resulting ISN depends
|
|
|
+ * mainly on the strength of the supplied secret!
|
|
|
+ *
|
|
|
+ * The implementation takes 32 bits from the computed hash, and adds to it the
|
|
|
+ * current time, in 4-microsecond units. The current time is computed from a
|
|
|
+ * boot time given at initialization, and the current uptime as provided by
|
|
|
+ * sys_now(). Thus, it assumes that sys_now() returns a time value that is
|
|
|
+ * relative to the boot time, i.e., that it starts at 0 at system boot, and
|
|
|
+ * only ever increases monotonically.
|
|
|
+ *
|
|
|
+ * For efficiency reasons, a single MD5 input buffer is used, and partially
|
|
|
+ * filled in at initialization time. Specifically, of this 64-byte buffer, the
|
|
|
+ * first 36 bytes are used for the four-way TCP tuple data, followed by the
|
|
|
+ * 16-byte secret, followed by 12-byte zero padding. The 64-byte size of the
|
|
|
+ * buffer should achieve the best performance for the actual MD5 computation.
|
|
|
+ *
|
|
|
+ * Basic usage:
|
|
|
+ *
|
|
|
+ * 1. in your lwipopts.h, add the following lines:
|
|
|
+ *
|
|
|
+ * #include <lwip/arch.h>
|
|
|
+ * struct ip_addr;
|
|
|
+ * u32_t lwip_hook_tcp_isn(const struct ip_addr *local_ip, u16_t local_port,
|
|
|
+ * const struct ip_addr *remote_ip, u16_t remote_port);
|
|
|
+ * "#define LWIP_HOOK_TCP_ISN lwip_hook_tcp_isn";
|
|
|
+ *
|
|
|
+ * 2. from your own code, call lwip_init_tcp_isn() at initialization time, with
|
|
|
+ * appropriate parameters.
|
|
|
+ */
|
|
|
+
|
|
|
+/*
|
|
|
+ * Copyright (c) 2016 The MINIX 3 Project.
|
|
|
+ * All rights reserved.
|
|
|
+ *
|
|
|
+ * Redistribution and use in source and binary forms, with or without modification,
|
|
|
+ * are permitted provided that the following conditions are met:
|
|
|
+ *
|
|
|
+ * 1. Redistributions of source code must retain the above copyright notice,
|
|
|
+ * this list of conditions and the following disclaimer.
|
|
|
+ * 2. 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.
|
|
|
+ * 3. The name of the author may not be used to endorse or promote products
|
|
|
+ * derived from this software without specific prior written permission.
|
|
|
+ *
|
|
|
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
|
|
|
+ *
|
|
|
+ * Author: David van Moolenbroek <david@minix3.org>
|
|
|
+ */
|
|
|
+
|
|
|
+#include "tcp_isn.h"
|
|
|
+#include "lwip/ip_addr.h"
|
|
|
+#include "lwip/sys.h"
|
|
|
+#include <string.h>
|
|
|
+#include "esp32/rom/md5_hash.h"
|
|
|
+#include "soc/soc_memory_layout.h"
|
|
|
+
|
|
|
+#ifdef LWIP_HOOK_TCP_ISN
|
|
|
+
|
|
|
+static u8_t input[64];
|
|
|
+static u32_t base_time;
|
|
|
+
|
|
|
+/**
|
|
|
+ * Initialize the TCP ISN module, with the boot time and a secret.
|
|
|
+ *
|
|
|
+ * @param boot_time Wall clock boot time of the system, in seconds.
|
|
|
+ * @param secret_16_bytes A 16-byte secret used to randomize the TCP ISNs.
|
|
|
+ */
|
|
|
+void
|
|
|
+lwip_init_tcp_isn(u32_t boot_time, const u8_t *secret_16_bytes)
|
|
|
+{
|
|
|
+ /* Initialize the input buffer with the secret and trailing zeroes. */
|
|
|
+ memset(input, 0, sizeof(input));
|
|
|
+
|
|
|
+ MEMCPY(&input[36], secret_16_bytes, 16);
|
|
|
+
|
|
|
+ /* Save the boot time in 4-us units. Overflow is no problem here. */
|
|
|
+ base_time = boot_time * 250000;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * Hook to generate an Initial Sequence Number (ISN) for a new TCP connection.
|
|
|
+ *
|
|
|
+ * @param local_ip The local IP address.
|
|
|
+ * @param local_port The local port number, in host-byte order.
|
|
|
+ * @param remote_ip The remote IP address.
|
|
|
+ * @param remote_port The remote port number, in host-byte order.
|
|
|
+ * @return The ISN to use for the new TCP connection.
|
|
|
+ */
|
|
|
+u32_t
|
|
|
+lwip_hook_tcp_isn(const ip_addr_t *local_ip, u16_t local_port,
|
|
|
+ const ip_addr_t *remote_ip, u16_t remote_port)
|
|
|
+{
|
|
|
+ u8_t output[16];
|
|
|
+ u32_t isn;
|
|
|
+
|
|
|
+#if LWIP_IPV4 && LWIP_IPV6
|
|
|
+ if (IP_IS_V6(local_ip))
|
|
|
+#endif /* LWIP_IPV4 && LWIP_IPV6 */
|
|
|
+#if LWIP_IPV6
|
|
|
+ {
|
|
|
+ const ip6_addr_t *local_ip6, *remote_ip6;
|
|
|
+
|
|
|
+ local_ip6 = ip_2_ip6(local_ip);
|
|
|
+ remote_ip6 = ip_2_ip6(remote_ip);
|
|
|
+
|
|
|
+ SMEMCPY(&input[0], &local_ip6->addr, 16);
|
|
|
+ SMEMCPY(&input[16], &remote_ip6->addr, 16);
|
|
|
+ }
|
|
|
+#endif /* LWIP_IPV6 */
|
|
|
+#if LWIP_IPV4 && LWIP_IPV6
|
|
|
+ else
|
|
|
+#endif /* LWIP_IPV4 && LWIP_IPV6 */
|
|
|
+#if LWIP_IPV4
|
|
|
+ {
|
|
|
+ const ip4_addr_t *local_ip4, *remote_ip4;
|
|
|
+
|
|
|
+ local_ip4 = ip_2_ip4(local_ip);
|
|
|
+ remote_ip4 = ip_2_ip4(remote_ip);
|
|
|
+
|
|
|
+ /* Represent IPv4 addresses as IPv4-mapped IPv6 addresses, to ensure that
|
|
|
+ * the IPv4 and IPv6 address spaces are completely disjoint. */
|
|
|
+ memset(&input[0], 0, 10);
|
|
|
+ input[10] = 0xff;
|
|
|
+ input[11] = 0xff;
|
|
|
+ SMEMCPY(&input[12], &local_ip4->addr, 4);
|
|
|
+ memset(&input[16], 0, 10);
|
|
|
+ input[26] = 0xff;
|
|
|
+ input[27] = 0xff;
|
|
|
+ SMEMCPY(&input[28], &remote_ip4->addr, 4);
|
|
|
+ }
|
|
|
+#endif /* LWIP_IPV4 */
|
|
|
+
|
|
|
+ input[32] = (u8_t)(local_port >> 8);
|
|
|
+ input[33] = (u8_t)(local_port & 0xff);
|
|
|
+ input[34] = (u8_t)(remote_port >> 8);
|
|
|
+ input[35] = (u8_t)(remote_port & 0xff);
|
|
|
+
|
|
|
+ /* The secret and padding are already filled in. */
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Generate the hash using ROM MD5 APIs
|
|
|
+ * This hook is invoked in the context of TCP/IP (tiT) task and
|
|
|
+ * it is unlikely that its stack would be placed in SPIRAM. Hence
|
|
|
+ * even with SPIRAM enabled case and ESP32 revision < 3, using ROM
|
|
|
+ * APIs should not create any issues.
|
|
|
+ */
|
|
|
+#if CONFIG_SPIRAM_ALLOW_STACK_EXTERNAL_MEMORY
|
|
|
+ assert(!esp_ptr_external_ram(get_sp()));
|
|
|
+#endif
|
|
|
+
|
|
|
+ struct MD5Context ctx;
|
|
|
+ MD5Init(&ctx);
|
|
|
+ MD5Update(&ctx, input, sizeof(input));
|
|
|
+ MD5Final(output, &ctx);
|
|
|
+
|
|
|
+ /* Arbitrarily take the first 32 bits from the generated hash. */
|
|
|
+ MEMCPY(&isn, output, sizeof(isn));
|
|
|
+
|
|
|
+ /* Add the current time in 4-microsecond units. */
|
|
|
+ return isn + base_time + sys_now() * 250;
|
|
|
+}
|
|
|
+
|
|
|
+#endif /* LWIP_HOOK_TCP_ISN */
|
Jiang Jiang Jian