[Tips] Dia

雖然用Linux好一段時間了,可是在文書處理上有時候會切到M$做,因為OpenOffice用起來就是不太順手
最近在畫流程圖,Dia應該是首選吧,紀錄一下相關的資源:
* Dia project
* 流程圖繪製 Dia
* Dia 0.92.2-1影音教學

[阿宅專區] 電腦圖學的應用

最近逛到對岸的一個網站,深入淺出的介紹一些有趣的東西,比如說google的新服務,相似圖片搜索,雖然現在我還不清楚背後的運作原理是什麼,但是這篇提供了一個方向讓我有興趣的繼續瞭解下去...

不過話說回來,搜尋結果跟想像的還有一些差距阿 @@a

reference:
* 相似圖片搜索的原理
* 神奇的圖像處理算法

[資訊安全] Reversing SSH Tunneling

最近需要連到防火牆後的某台電腦找東西,發現透過reverse ssh就可以做反向連線,輕鬆達陣

情境是這樣,要從123.45.67.89(public)連線到192.168.0.100(private):

Destination(192.168.0.100) <-- |NAT| <-- Source(123.45.67.89)

in destination host

dst$ ssh -R 1234:localhost:22 username@123.45.67.89

in source host

src$ ssh localhost -p 1234

目前是用ssh做,我想nc應該也有類似的功能,找到再補上吧

reference: Reverse SSH Tunneling

[阿宅專區] The Architecture of Open Source Applications

The Architecture of Open Source Applications

剛剛逛到這本書,裡面有許多有名的專案,其中唐鳳所做的SocialCalc看起來相當有趣阿,話說我應該會買個PDF的版本支持一下

[Network] Configuring multiple default routes and name resolving with 1 network interface card

繼上篇的多重routing與name resolving,再稍做改良就可以用一張網卡同時使用PPPoE撥號連線並支援多重路由,直接看script吧

#!/bin/bash

# pppoe dial up
RETRY=5
PPP=`ifconfig|grep -in ppp`
until [ $RETRY -le 0 ] || [ -n "$PPP" ]
do pon dsl-provider
  sleep 30
  PPP=`ifconfig|grep -in ppp`
  ((RETRY=RETRY-1))
done

# eth0 setting
IF2=eth0
IP2=10.157.132.104
NM2=255.255.240.0
NT2=10.157.128.0/20
GW2=10.157.143.254

IP3=172.17.125.5
NM3=255.255.255.0
NT3=172.17.125.0/24

# some network for my own purpose
NM4=224.0.0.0

# default gateway
DGW=${GW2}

# set ip/netmask
ifconfig ${IF2} ${IP2} netmask ${NM2}

# create a new policy routing table entry
T2=`cat /etc/iproute2/rt_tables|awk '{print $2}'|grep -in T2|cut -d : -f 2`
if [ -z "$T2" ]; then
  echo "1 T2" >> /etc/iproute2/rt_tables
fi

# add new entry within this policy table
ip route add ${NT2} dev ${IF2} src ${IP2} table T2
ip route add default via ${GW2} dev ${IF2} table T2

ip rule add from ${NT2} table T2
ip rule add to ${NT2} table T2

ip rule add from ${NT3} table T2
ip rule add to ${NT3} table T2

# add some routing for my own purpose
route add -net ${NM4} netmask ${NM4} dev ${IF2}

# options timeout:1 rotate attempts:1
echo "options rotate"          >  /etc/resolv.conf
echo "nameserver 168.95.192.1" >> /etc/resolv.conf
echo "nameserver 172.17.125.5" >> /etc/resolv.conf

# disable reverse packet filter for my own purpose
echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter
echo 0 > /proc/sys/net/ipv4/conf/default/rp_filter
echo 0 > /proc/sys/net/ipv4/conf/eth0/rp_filter
echo 0 > /proc/sys/net/ipv4/conf/lo/rp_filter

[Tips] Ubuntu下PPPoE安裝設定

速記一下Ubuntu的PPPoE設定...

查詢有關PPPoE的package

$ sudo apt-cache search pppoe

pppoeconf - configures PPPoE/ADSL connections
pppoe - PPP over Ethernet driver
pppstatus - console-based PPP status monitor

安裝

$ sudo apt-get install pppoeconf pppoe pppstatus

設定

$ sudo pppoeconf

根據問題回答yes/no,並且設定帳號密碼,設定完成後將自動連線

中斷

$ sudo poff

若超過一個連線

$ sudo poff -a

重新建立連線

$ sudo pon dsl-provider

查詢log

$ sudo plog

預設撥接設定儲存位置,會override /etc/ppp/options

$ sudo vim /etc/ppp/peers/dsl-provider

lcp-echo-interval 30      # interval of sending request to adsl server
lcp-echo-failure 10       # times of retry if sending request fail
# Override any connect script that may have been set in /etc/ppp/options.
persist                   # auto dial-up if lost connection 
user "user@isp.net"       # dial-up user account

若是使用PAP驗證,則帳號密碼會儲存於

$ sudo vim /etc/ppp/pap-secrets

"user@isp.net" * "passowrd"

PPPoE斷線問題檢測先從查詢plog開始,若出現以下訊息表示超出嘗試次數還未能連接上

pppd[1624]: Timeout waiting for PADO packets

解決方法就是定時檢查連線狀態,若沒有連線則持續撥號,常用的檢查方法有ifconfig或是running process,簡單寫一下重新撥號的script

#!/bin/bash
# auto dial-up 

# check ifconfig or check running process
RETRY=5
PPP=`ifconfig|grep -in ppp`
until [ $RETRY -le 0 ] || [ -n "$PPP" ] || [ -e /var/run/ppp0.pid ]
do pon dsl-provider
  sleep 30
  PPP=`ifconfig|grep -in ppp`
  ((RETRY=RETRY-1))
done

reference:
* 使用 PPPoEConf 連接 Internet
* Linux PPP HOWTO

[資訊安全] Reversing for Newbies

今天逛到一個不錯的教學網站,希望練習練習,下次wargame能拿第一