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Meeting Today’s Security Needs With IPsec VPN and IPFilter

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Defense Against The Dark Arts

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Presentation Overview

IPFilter (firewall/NAT) IPsec (VPN)

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What is IPFilter?

Very popular open-source package, written by Darren Reed Runs on many UNIX/Linux versions, including all SCO

platforms Version 4.1.3 ships with OSr600 and UW714mp2 Version 3.4.24 ships with OSr507

Provides: Packet filtering (firewall) Network address translation (NAT)

Usage notes Filtering and NAT take place inside kernel ("ipf" driver). There is

no daemon. To configure, create configuration files, then run command-line

utilities ("ipf", "ipnat", etc) to load them into the kernel System is normally configured and boot time, but can be

reconfigured on the fly

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Configuring a firewall

What is a "firewall"? A means of preventing packets from traversing a

network if they violate the network's security policy

Creating a filter configuration file Run mkdev ipfilter on OSr5, OSr6 Or, edit file /etc/ipf.conf Run ipf -v -Fa -f /etc/ipf.conf

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Sample firewall configurations

To block spoofing: pass in on net0 all block in quick on net0 from 192.168.0.0/16 to any block in quick on net0 from 10.0.0.0/8 to any block in log quick on net0 from <mynetwork> to any

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Sample firewall configurations

To block spoofing: pass in on net0 all block in quick on net0 from 192.168.0.0/16 to any block in quick on net0 from 10.0.0.0/8 to any block in log quick on net0 from <mynetwork> to any

To block smurf attacks: block in quick on net0 from any to 20.20.20.0/32 to any block in quick on net0 from any to 20.20.20.255/32 to

any

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Sample firewall configurations

To block spoofing: pass in on net0 all block in quick on net0 from 192.168.0.0/16 to any block in quick on net0 from 10.0.0.0/8 to any block in log quick on net0 from <mynetwork> to any

To block smurf attacks: block in quick on net0 from any to 20.20.20.0/32 to any block in quick on net0 from any to 20.20.20.255/32 to

any

To allow a single port: pass in quick on net0 proto tcp from any to <myaddr>/32 port 80 block in all

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Sample firewall configurations

"keep state" and established connections: block in quick on net0 all

pass out quick on net0 proto tcp from <myaddr>/32 to any keep state

pass out quick on net0 proto udp from <myaddr>/32 to any keep state

pass out quick on net0 proto icmp from <myaddr>/32 to any keep state

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Sample firewall configurations

"keep state" and established connections: block in quick on net0 all

pass out quick on net0 proto tcp from <myaddr>/32 to any keep state

pass out quick on net0 proto udp from <myaddr>/32 to any keep state

pass out quick on net0 proto icmp from <myaddr>/32 to any keep state

To log certain packets: block in log quick on net0 from 20.20.20.0/24 to any

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Monitoring the system

ipfstat shows filter status, keeps statistics on network

traffic on all interfaces, in and out

ipmon shows logged packets in real time (can even

include contents)

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Configuring NAT

What is NAT? Modification of source and/or destination

addresses of packets

Enables: Connecting a network of "unregistered" IP

addresses to the internet Mapping a large address space to a smaller one LAN-wide change of IP addresses Temporary re-routing of a LAN Redirection of incoming connections

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Enabling NAT

Run mkdev ipfilter on OSr5, OSr6 Or, edit /etc/ipnat.conf Run ipnat -v -f /etc/ipnat.conf

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Sample NAT configurations

To map non-routable network to internet: map net0 192.168.100.0/24 -> <myaddr>/32

To do the same but with a dynamic address map net0 192.168.100.0/24 -> 0/32

(run ipf -y each time dynamic address is changed)

To redirect inbound traffic to a particular "natted" machine:

rdr net0 <myaddr>/32 port 80 -> 192.168.100.15 port 80 tcp

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What is IPsec?

Comprehensive data security architecture for IP and upper-level protocols

Designed for (and obligatory on) IPv6. Optional on IPv4.

Supported on OSR6, UW714 SCO IPsec based on KAME, an open source

implementation for *BSD

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Why IPsec?

Code economy and flexibility: Applications need not be aware of security architecture

Lower costs: Can establish secure links (e.g. between home and brance offices) using public networks rather than private, dedicated circuits

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What is IPsec?

IPsec provides: Confidentiality (encryption) Integrity (tampering detection) Access control Replay protection Source address authentication Virtual private network (VPN)

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IPsec Modes

Transport (host to host) Only the original packet's payload is protected Traffic analysis can see IP protocol types and port

numbers

Tunnel (network to network) All traffic protected IP packets fully encrypted and encapsulated

within new IP packets Traffic analysis can only see encrypted data

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IPsec Protocols

Four protocols: AH: Authentication Header ESP: Encapsulating Security Payload IPcomp: Compression IKE: Internet Key Exchange

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AH: Authentication Header

Provides data source authentication, replay protection, and integrity Does *not* provide encryption A new header, inserted between IP header and packet data,

containing a cryptographically-secure checksum on the whole packet

Before: --------------------------- | IP | TCP | DATA ... ---------------------------

After: ---------------------------------- | IP | AH | TCP | DATA ... ----------------------------------

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ESP: Encapsulating Security Payload

Provides payload encryption Can be used together with AH, but isn't

ordinarily Provides most of the services of AH (doesn't

account for IP header)

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ESP: Encapsulating Security Payload

A new header, similar to AH

Before: --------------------------- | IP | TCP | DATA ... ---------------------------

After (transport mode): ----------------------------------------------------------- | IP | ESP Hdr | TCP | DATA | ESP Trailer | ESP Auth | ----------------------------------------------------------- |<-------- encrypted --------->| |<----------- authenticated ------------>|

Or (tunnel mode): ----------------------------------------------------------------- | New | | Orig | | | | | | IP | ESP Hdr | IP | TCP | DATA | ESP Trailer | ESP Auth | | Hdr | | Hdr | | | | | ----------------------------------------------------------------- |<----------- encrypted ------------>| |<-------------- authenticated --------------->|

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IPcomp: IP Compression

Compresses data prior to encryption Needed because encryption makes data

hard to compress

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IPsec encryption algorithms

Data integrity: MD5, SHA1, SHA2 Confidentiality: AES, DES, 3DES, blowfish,

cast128, RC4 Modular design; can acquire new algorithms

as they are developed

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IKE: Internet Key Exchange

Implemented by user daemon racoon Runs as a UDP service, port 500 Uses Diffie-Hellman key exchange to

establish shared secrets on two systems Updates shared secrets as needed according

to Security Policy (e.g., every N hours, or every M bytes)

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Security Associations (SA's) and theSecurity Association Database

An SA represents a single active unidirectional "connection" between two endpoints

Contains parameters controlling security and encryption - algorithm, key, etc

Stored in the SAD, which is controlled by ipseckey

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Security Policies (SP's) and theSecurity Policy Database

An SP defines the actions to take on packets that meet a given set of criteria (e.g., source or destination address/port, protocol, etc).

Like SA's, SP's are unidirectional: There must be separate IN and OUT SP's for each full-duplex connection

Stored in the SPD, which is controlled by ipseckey

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Configuring IPsec

Activating IPsec edit /etc/conf/pack.d/inet/space.c set “ipsec_enable” to 1 /etc/conf/bin/idbuild -M inet reboot the system

IPsec support utilities ipseckey (aka setkey) to configure SAD, SPD racoon for IKE

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Manually setting keys (transport mode)

Create ipseckey files (e.g., /etc/inet/ipsec.cf) on two hosts:

# associate ESP with the two systems; add SAD entries add 10.10.1.100 10.10.2.100 esp 0x10001 -m transport -E 3des-cbc "scoforum2005scoforum2005" ; add 10.10.2.100 10.10.1.100 esp 0x10002 -m transport -E 3des-cbc "scoforum2005scoforum2005" ; # OPTIONAL: associate AH with the two systems add 10.10.1.100 10.10.2.100 ah 0x10003 -m transport -A hmac-md5 "scoforumscoforum" ; add 10.10.2.100 10.10.1.100 ah 0x10003 -m transport -A hmac-md5 "scoforumscoforum" ;

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Manually setting keys (transport mode)

ipseckey files (continued): # set the security policy for the two systems -- add SPD entries # on the peer host, these lines must have "out" and "in" reversed spdadd 10.10.1.100 10.10.2.100 any -P out ipsec esp/transport/10.10.1.100-10.10.2.100/require ah/transport/10.10.1.100-10.10.2.100/require ; spdadd 10.10.2.100 10.10.1.100 any -P in ipsec esp/transport/10.10.2.100-10.10.1.100/require ah/transport/10.10.2.100-10.10.1.100/require ;

Clear ipsec configuration if necessary: # ipseckey -FP; ipseckey -F Load ipsec configuration: # ipseckey -f /etc/inet/ipsec.cf Test configuration: # tcpdump host <peer> # netstat -nsp ipsec

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Manually setting keys (tunnel mode)

Same as transport mode, but with "transport" changed to "tunnel" in ipsec.cf

Shows different behavior in tcpdump

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Automated key management

Create psk.txt files on both hosts, such as:

10.10.1.100 scoforum2005scoforum2005

Create ipsec.conf files:

spdadd 10.10.2.100/32 10.10.1.100/32 all -P out ipsec

esp/tunnel/10.10.2.100-10.10.1.100/require ;

spdadd 10.10.1.100/32 10.10.2.100/32 all -P in ipsec

esp/tunnel/10.10.1.100-10.10.2.100/require ;

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Automated key management

Create racoon.conf files: path pre_shared_key "/etc/inet/psk.txt" ; log debug; remote anonymous { exchange_mode aggressive ; my_identifier address 10.10.2.100 ; lifetime time 1 hour ; # sec,min,hour # phase 1 proposal (for ISAKMP SA) proposal { encryption_algorithm 3des; hash_algorithm sha1; authentication_method pre_shared_key ; dh_group 2 ; } # the following makes racoon (as a # responder) obey the initiator's # lifetime and PFS group proposal. # this makes testing easier. proposal_check obey; }

sainfo anonymous { pfs_group 2; lifetime time 10 hour ; encryption_algorithm 3des, blowfish; authentication_algorithm hmac_sha1, hmac_md5 ; compression_algorithm deflate ; }

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Road Warrior mode

Create ipsec.conf file on server: spdadd <myaddr> 0.0.0.0 any -P out ipsec

esp/tunnel/<myaddr>-0.0.0.0/require;

spdadd 0.0.0.0 <myaddr> any -P in ipsec

esp/tunnel/0.0.0.0-<myaddr>/require;

Create psk.txt on server: <domain name> scoforum2005scoforum2005

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Road Warrior mode

Create racoon.conf files: path pre_shared_key "/etc/inet/psk.txt" ; timer { phase1 60 seconds ; phase2 60 seconds ; }

remote anonymous { exchange_mode main, aggressive, base ; doi ipsec_doi ; situation identity_only ; lifetime time 1 hour ; generate_policy on; passive on; my_identifier address <myaddr> ; peers_identifier fqdn "<domain name>" ; proposal { encryption_algorithm 3des; hash_algorithm sha1; authentication_method pre_shared_key; dh_group modp1024; } proposal_check obey ; }

sainfo anonymous { pfs_group modp1024; lifetime time 1 hour ; encryption_algorithm 3des, blowfish; authentication_algorithm hmac_sha1, hmac_md5; compression_algorithm deflate; }

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Creating an IP tunnel for connecting two networks through a VPN

Generic tunnel interfaces (ipencap) not supported; planned for Fusion

However, Morning Star PPP can create a tunnel between two OSr6 systems, or with a bit more hassle, between OSr6 and any UNIX system with PPP and an open telnet port

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IPsec and IPFilter together

To allow VPN through a firewall, add IPFilter rules:

pass out on net0 from any to any keep state pass in quick on net0 proto esp from any to any pass in quick on net0 proto udp from any port = 500

to any port = 500 block in on net0 all

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IPsec limitations

Arcane Long development cycle (e.g. IKE) Interoperability problems Difficult to traverse NAT

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SSL VPN

Limited access control Poorer performance than IPsec

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Future

New IKEv2 protocol (racoon2) NAT traversal support (RFC3948, RFC3715) Generic IP-over-IP tunneling interfaces

(ipencap)

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Online resources - IPFilter

SCO IP Filter documentation: http://osr600doc.sco.com/en/NET_tcp/ipfintro.html

IP Filter website (with source):http://coombs.anu.edu.au/~avalon/

IP Filter FAQ:http://www.phildev.net/ipf

IP Filter HOWTO:http://www.obfuscation.org/ipf/

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Online resources - IPsec

SCO IPsec documentation:http://osr600doc.sco.com/en/NET_ipsec/ipsec_top.html

KAME site (with source):http://www.kame.org

IPsec related RFCs, 2401 - 2412:http://www.ietf.org/rfc2401.txt - Security Architecture for IP

http://www.ietf.org/rfc2402.txt - Authentication Header http://www.ietf.org/rfc2406.txt - Encapsulating Security Payload http://www.ietf.org/rfc2407.txt - IPsec DoI for ISAKMP http://www.ietf.org/rfc2408.txt - ISAKMP http://www.ietf.org/rfc2409.txt - Internet Key Exchange http://www.ietf.org/rfc2410.txt - NULL encryption algorithm http://www.ietf.org/rfc2411.txt - IP Security Document Roadmap http://www.ietf.org/rfc2412.txt - OAKLEY Key Determination Protocol