技术

SecureFX连接失败

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连接linux主机A失败，返回

i Available Remote Kex Methods = curve25519-sha256,curve25519-sha256@libssh.org,...
i Selected Kex Method =

连接linux主机B成功，返回

i Available Remote Kex Methods = curve25519-sha256@libssh.org,ecdh-sha2-nistp256,...
i Selected Kex Method = diffie-hellman-group14-sha1

原因是主机A中的OpenSSH升级了，可用以下命令确认

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ssh -V

解决办法为，在/etc/ssh/sshd_config文件尾部加入

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#Ciphers aes128-cbc
#MACs hmac-md5,hmac-sha1
KexAlgorithms diffie-hellman-group14-sha1

重启sshd

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service sshd restart

refer to:
https://blog.csdn.net/lk_db/article/details/50964912

验证IPSec抗重放攻击

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linux内核xfrm参数replay-window用于设定抗重放攻击效果。

replay-window为0表示不启用抗重放攻击，大于0时表示当前esp/ah包活动序列窗口大小，序号太旧的包因赶不上活动窗口而被丢弃或回复失败包。

在基于
StrongSwan PSK RSA
连通的环境下。

在C机器中编辑/etc/strongswan.d/charon.conf，更改replay-window值。
重启strongswan并启动连接后，可能通过命令

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ip xfrm state

查看strongswan有没有将参数值设定到内核中。

在B机器中

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apt install tcpreplay

在B机器中启动两个wireshark进程，分别抓包vmnet2和vmnet3。

当B和C中的strongswan都启动并连通后，在A中ping D的ip。

此时在B中抓vmnet3上的esp包，抓了几个后，点击对应wireshark窗口菜单

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File/Export Specified Packet

将这些esp包保存为文件

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/tmp/esp-b2c.pcapng

在A中停止ping D的ip。

在B的bash中执行

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tcpreplay -i enp2s6 /tmp/esp-b2c.pcapng

其中enp2s6是网卡vmnet3对应的识别名。

可以看到，
当C中的replay-window参数设为0时，B中的vmnet2上会抓到模拟重放的icmp ping包，并且方向是10.2.0.10至10.1.0.10。
当C中的replay-window参数不为0时，B中的vmnet2上抓不到模拟重放的icmp ping包。
一旦重启B或C中的strongswan，使用旧的esp-b2c.pcapng文件重放时，不管C中的replay-window取何值，B中的vmnet2上都不会出现模拟重放包。

Strongswan中验证NATT

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在基于
StrongSwan PSK RSA
连通的环境下。

四台虚拟机ABCD，三段Host Only虚拟网络vmnet2、vmnet3、vmnet4，DHCP都禁掉。

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A
vmnet2: 10.1.0.10/24 gw 10.1.0.2
B
vmnet2: 10.1.0.2/24
vmnet3: 192.168.0.12/24  <--这里变了
C
vmnet3: 192.168.0.3/24
vmnet4: 10.2.0.2/24
D
vmnet4: 10.2.0.10/24 gw 10.2.0.2

在B的bash中执行

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iptables -t nat -A POSTROUTING -s 192.168.0.12 -j SNAT --to-source 192.168.0.2
iptables -t nat -A PREROUTING -d 192.168.0.2 -j DNAT --to-destination 192.168.0.12

在B中用ifconfig命令查看vmnet3的hwaddr，比如为00:0c:29:5a:fc:8e。
在C的bash中执行

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arp -s 192.168.0.2 00:0c:29:5a:fc:8e

修改B的ipsec.conf中指定conn下的left为192.168.0.12。
而仍将C的ipsec.conf中指定conn下的right设为192.168.0.2。

之后再重启BC中的strongswan并连接会看到第5条ISAKMP消息开始端口都走4500了。

gdb调试有管道的命令行

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以pcre2调试为例

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#!/bin/sh
 
cd `pwd`/installed/bin
 
mkfifo /tmp/pcre
echo "<h1>hello</h1>" > /tmp/pcre &
 
gdb ./pcre2grep -ex 'b main' -ex 'r -o "<.*>" < /tmp/pcre'
rm /tmp/pcre

refer to:
http://www.voidcn.com/article/p-migwptlv-bsq.html

apt testing source

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/etc/apt/sources.list

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deb http://http.us.debian.org/debian/ testing non-free contrib main
#deb http://http.us.debian.org/debian/ stable non-free contrib main
#deb http://http.us.debian.org/debian/ unstable non-free contrib main
#deb http://http.us.debian.org/debian/ wheezy non-free contrib main
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#apt edit-sources
apt update

NO_PUBKEY 04EE7237B7D453EC NO_PUBKEY 648ACFD622F3D138

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apt-key adv --keyserver keyserver.ubuntu.com --recv 04EE7237B7D453EC
apt-key adv --keyserver keyserver.ubuntu.com --recv 648ACFD622F3D138

ubuntu repo names

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wheezy: debian 7.0
xenial: Ubuntu 16.04
focal: Ubuntu 20.04

refer to:
https://serverfault.com/questions/550855/how-to-add-debian-testing-repository-to-apt-get
https://yunwei365.blog.csdn.net/article/details/114930145

in gdb tui mode scroll the command window

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Use cgdb instead.

Let GDBW denote the command window,
let SRCW denote the source window
let TTYW denote the input window.

Cgdb basic usage

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ESC key in GDBW: switch to SRCW
i key in SRCW: switch to GDBW
T key in SRCW: switch on/off TTYW
PgUp/PgDn key in GDBW: scroll GDBW
PgUp/PgDn key in SRCW: scroll SRCW
-/= in SRCW: decrease/increase SRCW size

Patch: GDBW output is truncated.
cgdb/scroller.cpp:146
https://github.com/cgdb/cgdb/pull/269

refer to:
https://github.com/cgdb/cgdb/blob/master/doc/cgdb.texi

webrtc备忘录

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名词

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I帧: Intra-coded picture
P帧: Predictive-coded Picture
B帧: Bidirectionally predicted picture
GOP: Group of Pictures
IDR: Instantaneous Decoding Refresh
DTS: Decoding Time Stamp
PTS: Presentation Time Stamp

WebRTC 之视频捕获
https://hyjk2000.github.io/2015/04/21/webrtc-video-capture/
https://github.com/uxctx/DesktopLiveStreaming

so动态库只导出指定函数

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retain_sym.txt

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func1
func2

ver_script.txt

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LIBA_1.1 {
	global:
		foo1;
		foo2;
	local:
		*;
};
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ld -shared --retain-symbols-file=retain_sym.txt --version-script=ver_script.txt tst.o -o tst.so

refer to:
https://blog.csdn.net/chdhust/article/details/79356717
http://blog.sina.com.cn/s/blog_493667730100csde.html
http://www.gnu.org/software/gnulib/manual/html_node/LD-Version-Scripts.html

linux命令备忘录

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名词

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pie: position-independent executable
pic: position-independent code
aslr: address space layout randomization
got: global offset table
vdso: virtual dynamic shared object

Basic command

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grep [OPTION]... PATTERNS [FILE]...
find [-H] [-L] [-P] [-Olevel] [-D debugopts] [path...] [expression]
find . -size +2G -exec du -sh {} \;
ps axl | grep VirtualBoxVM | grep -v grep | awk '{print $3};'
cat /etc/passwd | sort -k5,5 -t: | column -t -s:
while true; do echo sleep 1 sec; sleep 1; cat /home/work/aa.txt 2>/dev/null && echo ok && break; done
echo first | xargs -i echo {} second
 
cat /etc/shadow
sudo !!
 
cd other_dir
cd - # return back

swap文件

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dd if=/dev/zero of=./swap_file bs=1G count=8
mkswap ./swap_file
swapon ./swap_file
swapoff ./swap_file

objcopy

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objcopy -I binary -O elf32-i386 -B i386 test.jpg test.o
objdump -s -b binary test.o
readelf -s test.o

静态链编stdc++

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-Bstatic -lstdc++ -Bdynamic

工具

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systemtap
inotify-tools
windres
reptyr
nmcli
nmtui

自启动

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#/lib/systemd/system/mytask.service
#ln -s /lib/systemd/system/mytask.service /etc/systemd/system/multi-user.target.wants/mytask.service
[Unit]
Description=mytask
After=network.target
 
[Service]
Type=simple
ExecStart=mytask.sh
 
[Install]
WantedBy=multi-user.target

ubuntu

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#网络配置文件路径，默认DHCP的连接不会生成文件
/etc/NetworkManager/system-connections/
#run arm64 binary on x86
dpkg --add-architecture armhf && apt-get update && apt-get install libc6:armhf
cat /proc/sys/fs/binfmt_misc/
qemu-user -L /home/bamanzi/i386-libs ./prog
#disable background process
systemctl disable unattended-upgrades
ss -tap
pv -d <pid>

centos

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#网络配置文件路径
/etc/sysconfig/network-scripts/ifcfg-
#compiz
https://spins.fedoraproject.org/mate-compiz/download/index.html

refer to:
http://blog.chinaunix.net/uid-28461677-id-5766451.html
https://blog.csdn.net/weixin_33842304/article/details/91443399
https://unix.stackexchange.com/questions/4034/how-can-i-disown-a-running-process-and-associate-it-to-a-new-screen-shell
https://blog.csdn.net/wuzhong8809/article/details/117450302
https://stackoverflow.com/questions/18312935/find-file-in-linux-then-report-the-size-of-file-searched
https://www.toutiao.com/a7073448755428688399/
https://www.likecs.com/show-695436.html

Optimizing the kernel for VMware

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[*] 64-bit kernel (leave blank for x86)
 
General Setup --->
  [*] Optimize very unlikely/likely branches
 
Power management and ACPI options --->
  [*] ACPI (Advanced Configuration and Power Interface) Support --->
 
Processor type and features --->
  Processor Family (usually Core2/Newer Xeon)
 
Bus Options --->
  < > PCCard (PCMCIA/Cardbus) support
 
Networking support --->
  [ ] Amateur Radio support
  [ ] Wireless (only if you plan on using nat EXCLUSIVELY)
 
Device Drivers --->
  Generic Driver Options
    [*] Maintain a devtmpfs filesystem to mount at /dev
 
  Misc Devices --->
    [*] VMware Balloon Driver (manages memory between VM and host)
    [*] VMware VMCI Driver (Virtual Machine Communication Interface - low-latency access to host memory bus)
 
  SCSI device support --->
    [*] SCSI low-level drivers --->
      <*> VMware PVSCSI driver support (high throughput storage adapter)
 
  [*] Fusion MPT device support --->
    <*> Fusion MPT ScsiHost drivers for SPI
 
  [*] Network device support --->
    [*] Ethernet driver support --->
      (disable every driver but this)
      [*] AMD Devices
        <*> AMD PCNet32 PCI support
    [ ] Wireless LAN (ONLY if you disabled Wireless networking support above)
    < > VMware VMXNET3 ethernet driver (PCNet32 is more than enough for most use cases - enable this only if you have spare cpu cycles to burn)
 
  Graphics support --->
    <*> Direct Rendering Manager
    < > Intel 8xx/9xx/G3x/G4x/HD Graphics
    <*> DRM driver for VMware Virtual GPU
      [*] Enable framebuffer console support under vmwgfx by default
    <*> Support for frame buffer devices
 
    Console display driver support --->
      <*> Framebuffer Console support
 
  Sound card support --->
    <*> Advanced Linux Sound Architecture --->
      [*] PCI sound devices
        <*> (Creative) Ensoniq AudioPCI 1371/1373
        < > Intel HD Audio
 
  File systems --->
    (enable only those you anticipate using)
    <*> Second extended fs support
    <*> The Extended 4 (ext4) filesystem
    <*> XFS filesystem support
    <*> Btrfs filesystem Unstable disk format
 
    Pseudo filesystems --->
      [*] Tmpfs virtual memory file system support (former shm fs)
        [*] Tmpfs POSIX Access Control Lists

efi boot (uncertain, maybe need to ask pc maker for signing the kernel.)

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Processor type and features --->
  [*] EFI runtime service support 
  [*]   EFI stub support
Firmware Drivers  --->
   EFI (Extensible Firmware Interface) Support  --->
       <*> EFI Variable Support via sysfs

device mapper

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Device Drivers
	Multiple devices driver support (RAID and LVM)
		<M>   Device mapper support

refer to:
https://forums.gentoo.org/viewtopic-p-7332884.html
https://stackoverflow.com/questions/40344484/cant-load-self-compiled-linux-kernel