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Merge branch 'feature/lwip_tcp_isn_hook_v4.2' into 'release/v4.2'

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lw-ip: enable TCP ISN hook (v4.2)

See merge request espressif/esp-idf!11062
This commit is contained in:
David Čermák 2020-12-18 00:18:36 +08:00
commit b1b673eaa2
7 changed files with 283 additions and 1 deletions
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16
components/esp_netif/lwip/esp_netif_lwip.c
View File

@ -33,6 +33,10 @@
#include "lwip/dns.h"
#endif
#if CONFIG_LWIP_TCP_ISN_HOOK
#include "tcp_isn.h"
#endif
#include "esp_netif_lwip_ppp.h"
#include "dhcpserver/dhcpserver.h"
#include "dhcpserver/dhcpserver_options.h"
@ -263,6 +267,18 @@ esp_err_t esp_netif_init(void)
{
if (tcpip_initialized == false) {
tcpip_initialized = true;
#if CONFIG_LWIP_TCP_ISN_HOOK
uint8_t rand_buf[16];
/*
* This is early startup code where WiFi/BT is yet to be enabled and hence
* relevant entropy source is not available. However, bootloader enables
* SAR ADC based entropy source at its initialization, and our requirement
* of random bytes is pretty small (16), so we can assume that following
* API will provide sufficiently random data.
*/
esp_fill_random(rand_buf, sizeof(rand_buf));
lwip_init_tcp_isn(esp_log_timestamp(), rand_buf);
#endif
tcpip_init(NULL, NULL);
ESP_LOGD(TAG, "LwIP stack has been initialized");
}

5
components/lwip/CMakeLists.txt
View File

@ -4,6 +4,7 @@ set(include_dirs
lwip/src/include
port/esp32/include
port/esp32/include/arch
port/esp32/tcp_isn
)
set(srcs
@ -135,6 +136,10 @@ else()
list(APPEND srcs "port/esp32/no_vfs_syscalls.c")
endif()
if(CONFIG_LWIP_TCP_ISN_HOOK)
list(APPEND srcs "port/esp32/tcp_isn/tcp_isn.c")
endif()
idf_component_register(SRCS "${srcs}"
INCLUDE_DIRS "${include_dirs}"
LDFRAGMENTS linker.lf

11
components/lwip/Kconfig
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@ -327,6 +327,17 @@ menu "LWIP"
menu "TCP"
config LWIP_TCP_ISN_HOOK
bool "Enable TCP ISN Hook"
default y
help
Enables custom TCP ISN hook to randomize initial sequence
number in TCP connection. This is recommended as default
lwIP implementation (`tcp_next_iss`) is not very strong,
as it does not take into consideration any platform
specific entropy source.
config LWIP_MAX_ACTIVE_TCP
int "Maximum active TCP Connections"
range 1 1024

7
components/lwip/component.mk
View File

@ -8,7 +8,8 @@ COMPONENT_ADD_INCLUDEDIRS := \
include/apps/sntp \
lwip/src/include \
port/esp32/include \
port/esp32/include/arch
port/esp32/include/arch \
port/esp32/tcp_isn
COMPONENT_SRCDIRS := \
apps/dhcpserver \
@ -39,6 +40,10 @@ ifdef CONFIG_LWIP_PPP_SUPPORT
COMPONENT_SRCDIRS += lwip/src/netif/ppp lwip/src/netif/ppp/polarssl
endif
ifdef CONFIG_LWIP_TCP_ISN_HOOK
COMPONENT_SRCDIRS += port/esp32/tcp_isn
endif
CFLAGS += -Wno-address # lots of LWIP source files evaluate macros that check address of stack variables
lwip/src/netif/ppp/ppp.o: CFLAGS += -Wno-uninitialized

11
components/lwip/port/esp32/include/lwipopts.h
View File

@ -420,6 +420,17 @@
*/
#define LWIP_TCP_RTO_TIME CONFIG_LWIP_TCP_RTO_TIME
/**
* Set TCP hook for Initial Sequence Number (ISN)
*/
#ifdef CONFIG_LWIP_TCP_ISN_HOOK
#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
#endif
/*
----------------------------------
---------- Pbuf options ----------

186
components/lwip/port/esp32/tcp_isn/tcp_isn.c Normal file
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@ -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 */

48
components/lwip/port/esp32/tcp_isn/tcp_isn.h Normal file
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@ -0,0 +1,48 @@
/*
* 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>
*/
#ifndef LWIP_TCP_ISN_H
#define LWIP_TCP_ISN_H
#include "lwip/opt.h"
#include "lwip/ip_addr.h"
#ifdef __cplusplus
extern "C" {
#endif
void lwip_init_tcp_isn(u32_t boot_time, const u8_t *secret_16_bytes);
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);
#ifdef __cplusplus
}
#endif
#endif /* LWIP_TCP_ISN_H */