I want to make sure that the only network traffic on my linux CentOS server is my own.
All my server runs is a Tomcat instance with one servlet. This servlet takes a parameter, which is a URL to download. It will download from that url, and pass the contents back to the calling program through the usual http response.
I want to block all network traffic to this server except
1) Ability to ssh
2) Ability to download from host abc.xyz.com
3) Ability for server with IP 111.222.333.444 to download from me
Can someone please tell me the commands to do this in iptables? I tried finding this out myself but I was a bit out my depth with the lingo.
thanks
Configuring a firewall is simple, first of all select what ports you want to be open.
For example Webserver ports:
iptables -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 443 -j ACCEPT
For example SSH port:
iptables -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
In any way your server is able to download files from other server/hosts.
3) Ability for server with IP 111.222.333.444 to download from me
I suppose that must be port 80, (or any port where the server is downloading from) if your uploading files to your website.
After these steps you need to look if the firewall is configured right:
iptables -L -n
If it's looking good then you're able to save your iptables, and restart the service.
If there is any problem configureren your firewall, please let me know.
Related
I have a system with centOS 7 installed. And on the second system I have windows 10. Both the machines are connected to private network. Now, I want to access the centOS machine remotely over ssh.
I checked the IP address of my windows machine, and then I edited the
/etc/ssh/sshd_config
file on the centOS system, With the following entries
ListenAddress <Ip_address_of_window_machine>
But when I restart the ssh service using the following command
systemctl restart sshd.service
I get the following error
bind to port 22 on <ip-address> failed. cannot assign requested address
But when I configure entries like this
ListenAddress 0.0.0.0
ListenAddress [::]
it works fine. But I want to bound my ssh to just particular iP-address
The ListenAddress configuration options tells sshd process to bind to a specific network interface on the server. If you want restrict access to a CentOS host then you need to use firewall. Though firewalld is the proper way to go (with zones and so on), old good iptables will do the job:
sudo iptables -A INPUT -p tcp -s a.b.c.d --dport ssh -j ACCEPT
sudo iptables -A INPUT -p tcp --dport ssh -j REJECT
Where a.b.c.d is the ip address of windows hosts.
NOTICE: By configuring firewall over the networks you can easily lock yourself out!
I have a webapp running on a Raspberry Pi, which is behind a NAT, and I'm trying to make a tunnel to the company's server so that I can access it from the web. Right now I've been able to establish a tunnel using ssh -fN -R 192.168.0.28:54321:localhost:443 username#192.168.0.28 (both the server and the RPi are in the same LAN at the time), and doing curl -k https://192.168.0.28:54321 returns the contents of the webpage hosted in the RPi, but only if I do it from the server. I have set GatewayPorts yes and AllowTcpForwarding yes (which anyway is the default).
It was the firewall on the server blocking the port. ¬¬
To open said port, the command is sudo iptables -I INPUT -p tcp --dport 54321 -j ACCEPT, which says that any connection comming to the TCP port 54321 must be accepted.
I'm trying to setup a haproxy gateway between server and client for full transparent proxy like below diagram. My main aim is to provide load balancing.
There is a simple application that listens port 25 in the server side. The client tries to connect port 25 on the gateway machine, and haproxy on the gateway chooses an avaliable server then redirects the connection to the server.
Network analysis of this approach produces tcp flow like diagram: The client resets the connection at the end since it doesn't send a syn packet to the server.
Is this haproxy usage true and my problem related configuation? Or should the client connect to the server directly (This doesn't make much sense to me but I'm not sure actually. If this is true then how haproxy will intervene the connection and make load balancing)?
EDIT:
I've started to think this problem is related to routing and NAT on the gateway. All of these three machines are in same subnetwork but I've added routes to the gateway for both client and server. Also rules on the gateway are:
iptables -t mangle -N DIVERT
iptables -t mangle -A DIVERT -j MARK --set-mark 0x01/0x01
iptables -t mangle -A DIVERT -j ACCEPT
iptables -t mangle -A PREROUTING -p tcp -m socket -j DIVERT
iptables -t mangle -A PREROUTING -p tcp --dport 25 -j TPROXY \
--tproxy-mark 0x1/0x1 --on-port 10025
ip route flush table 100
ip rule add fwmark 1 lookup 100
ip route add local 0.0.0.0/0 dev lo table 100
Now the question is what should I do in the gateway to change "syn-ack (src: S, dst: C)" to "syn-ack (src: GW, dst: C)"?
Here is the definition of my situation.
Here comes the transparent proxy mode: HAProxy can be configured to spoof the client IP address when establishing the TCP connection to the server. That way, the server thinks the connection comes from the client directly (of course, the server must answer back to HAProxy and not to the client, otherwise it can’t work: the client will get an acknowledge from the server IP while it has established the connection on HAProxy‘s IP).
And the answer is to set ip_nonlocal_bind system control.
I have 2 kinds of proxies in my local machine : stunnel and TOR-VPN.
stunnel is listening on port 6666
TOR-VPN is listening on port 9040
I want to get web traffic to go to stunnel first and the output traffic of stunnel go to tor-vpn. This needs double redirecting. is it possible to do it with iptables? I mean by using "table nat chain OUTPUT".
Because as far as I know "table nat chain OUTPUT" cant be called twice.
web traffic = browser listening on 127.0.0.1:6666
these are my rules:
iptables -t nat -A OUTPUT -p tcp -j REDIRECT --to-ports 6666
iptables -t nat -A OUTPUT -p tcp -m owner --uid-owner bob -m tcp -j
REDIRECT --to-ports 9040
iptables -t nat -A OUTPUT -p udp -m owner --uid-owner bob -m udp
--dport 53 -j REDIRECT --to-ports 53
iptables -t filter -A OUTPUT -p tcp --dport 6666 -j ACCEPT
iptables -t filter -A OUTPUT -p tcp -m owner --uid-owner bob -m tcp
--dport 9040 -j ACCEPT
iptables -t filter -A OUTPUT -p udp -m owner --uid-owner bob -m udp
--dport 53 -j ACCEPT
iptables -t filter -A OUTPUT -m owner --uid-owner bob -j DROP
the above rules make stunnel work independently from TOR/VPN.
i mean when browser is set with proxy, no traffic will go through TOR/VPN but if i turn off the proxy in browser, all traffic will go through TOR/VPN.
now i want to let browser have the proxy on and all web traffic go to stunnel first, but outgoing stunnel traffic(outgoing loopback traffic) redirects to TOR/VPN(127.0.0.1:9040)
is it possible ? how can i do that? somehow i mean double redirecting inside system.
Policy of all tables is ACCEPT
Checking that this is what you mean :
You have stunnel bound to port 6666 (localhost:6666) and you have tor bound to 9040 (localhost:9040). You want it so your web traffic will go THROUGH stunnel (so destination is localhost:6666) but the OUTBOUND traffic FROM stunnel (with inbound traffic originally from your client redirected to stunnel) should be DESTINED to tor (localhost:9040) ? Is this correct ?
If so, and I am thinking clearly enough (it is just 7:00 and I've been awake far too many hours for a difficult night), this is indeed possible (the reverse is, too). You need to masquerade the destination address (and indeed port) based on the source (address and port (you don't have to specify both, I might add)). Something like this:
iptables -t nat -I PREROUTING -p tcp --sport 6666 -j DNAT --to-destination 9040
If this is not what you mean (or alternatively I made a typo, am not clear headed or being an idiot in some way (in all cases showing myself to be a user as everyone is!), if any it is probably the latter) then please respond. I'll see about enabling email notification so that I see the response. If I don't, however, I apologise in advance.
As an aside: unless you have a final rule in each CHAIN (not table, just as an fyi: a table is filter, nat (which I specify in the above and indeed it is necessary), etc. and CHAIN is INPUT, OUTPUT, FORWARD and others created by the option -N) you shouldn't have -P ACCEPT ('that which is not explicitly permitted is forbidden' and similar wording - i.e. have DROP). The exception is perhaps OUTPUT (but depends on what you need, in the end). However, when dealing with interface 'lo' you'll want to ACCEPT all traffic always, in any case (i.e. specify -i lo and -o lo, depending on chain, and jump to ACCEPT). Of course, maybe you're behind another device but still best practise to not accept anything and everything! (I should also state that you have different chains per table so yes you can specify different tables but the policy is for the chain IN that table)
Edit: something else: no, you don't have to deal with SNAT when you want DNAT and the reverse is true. Anything to the contrary is a misunderstanding. The reason is you're masquerading the CONNECTION. As the man page shows:
It specifies that the destination address of the
packet should be modified (and all future packets in this connection will also be mangled), and rules should cease being examined.
Edit:
If I understand you (now) you actually have two interfaces involved. Or more specifically you need the following:
You have a service you want encrypted. This is tor. Now, you're using stunnel to do this. To this end you want stunnel to forward traffic to tor. Is this right? If yes, then know that stunnel has the following directives (I actually use similar for something else). Here's a mock setup of a service.
[tor]
accept = 6666
connect = 9040
In addition, just as a note: connect can also be a remote address (remote address implies an external address (with port) or even a certain interface (by IP and also with port) on the system (I use external in the sense of you specify ip and port rather than just a port). Furthermore, accept can specify address (with same rules: ip before the port (except that it is obviously on the local machine so no external IP)). You could explain it, perhaps, as stunnel is where the service would bind to except that the service is stunnel and the service it is encrypting is elsewhere (shortly: the bind(2) call allows specific IP or all IPs on the system, and you're basically configuring stunnel to do this).
(And yes, you're right: the sport should have been dport.)
IF this is not what you need then I do not understand all variables. In that case, if you can elaborate on which interfaces (this includes ports and which service per interface) are involved as well as clients involved (and where they send). Because it is a lot more helpful if others know EXACTLY what you need than infer certain parts. Makes it much easier to solve a problem if you know what the problem is entirely. Maybe I've been dense and I should put together it all (and I admit sleep problems - which I have for a long, long time - does not help that, but...) I haven't, I think.
I found the answer by myself. in my first post, i said something that was completely wrong and because of that, i could not do double redirecting.
i said:
Because as far as I know "table nat chain OUTPUT" cant be called twice
it is wrong and "table nat chain OUTPUT" can be called twice. i dont know what exactly i did 2 months ago that thought "table nat chain OUTPUT" cant be called twice.
this is the tables and chains order when using some services on loopback interface or not:
Without having any services on loopback:
Generated packets on local machine -> nat(OUTPUT) -> filter(OUTPUT) -> wlan(ethernet) interface
With having some services on loopback:
Generated packets on local machine -> nat(OUTPUT) -> filter(OUTPUT) -> loopback interface -> nat(OUTPUT) -> filter(OUTPUT) -> wlan(ethernet) interface
these are my rules to solve the problem:
iptables -t nat -A OUTPUT -p tcp -m tcp --dport 6666 -j REDIRECT --to-ports 6666
iptables -t nat -A OUTPUT -p tcp -m owner --uid-owner bob -m tcp -j REDIRECT --to-ports 9040
iptables -t nat -A OUTPUT -p udp -m owner --uid-owner bob -m udp --dport 53 -j REDIRECT --to-ports 53
iptables -t nat -A OUTPUT -d "StunnelServerIp" -o wlan0 -p tcp -j REDIRECT --to-ports 9040
iptables -t filter -A OUTPUT -p tcp -m owner --uid-owner bob -m tcp --dport 9040 -j ACCEPT
iptables -t filter -A OUTPUT -p udp -m owner --uid-owner bob -m udp --dport 53 -j ACCEPT
iptables -t filter -A OUTPUT -p tcp -m tcp --dport 6666 -j ACCEPT
iptables -t filter -A OUTPUT -m owner --uid-owner bob -j DROP
i have trouble setting up a JMeter client to connect to a remote JMeter server over an intermediate jumphost.
Especially which ports need to be open and forwarded to which host and how to configure JMeter for that. Apparently there are some blog posts about similar setups but neither describes the ports in detail nor do the connect over an external host (all use localhost?).
The setups is:
JMeter GUI(client) <-> Jumphost <-> JMeter Server
I need to setup one or more SSH Tunnels on the Jumphost and tell the Client and server to connect to this host.
Help will be much appreciated!
http://rolfje.wordpress.com/2012/02/16/distributed-jmeter-through-vpn-and-ssl/
Here I see ports in the article:
-A RH-Firewall-1-INPUT -p udp -m udp --dport 1099 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 1099 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 50000 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 50000 -j ACCEPT
Tried with Java 8
1. Client - modify jmeter.properties file adding:
remote_hosts=127.0.0.1:55511
client.rmi.localport=55512
2. Server - modify jmeter.properties file adding:
server_port=55511
server.rmi.localhostname=127.0.0.1
server.rmi.localport=55511
3. Connect to the server using:
Linux and Mac users
ssh solr#server -L 55511:127.0.0.1:55511 -R 55512:127.0.0.1:55512
Windows users
putty.exe -ssh user#server -L 55511:127.0.0.1:55511 -R 55512:127.0.0.1:55512
4. Server - start jmeter
cd apache-jmeter-2.13/bin/
./jmeter-server -Djava.rmi.server.hostname=127.0.0.1
5. Client - start jmeter
cd apache-jmeter-2.13/bin/
./jmeter.sh -Djava.rmi.server.hostname=127.0.0.1 -t test.jmx