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Changing the Management WebUI Port, Agent Options, Setting Up IP Rules, Forcing Users to a Login

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8.2.6. HTTP Authentication Chapter 8. User Authentication Changing the Management WebUI Port HTTP authentication will collide with the WebUI's remote management service which also uses TCP port 80. To avoid this, the WebUI port number should be changed before configuring authentication. Do this by going to Remote Management > Advanced Settings in the WebUI and changing the setting WebUI HTTP Port. Port number 81 could instead, be used for this setting. Agent Options For HTTP and HTTPS authentication there is a set of options in Authentication Rules called Agent Options. These are: • Login Type - This can be one of: • FORM - The user is presented with an HTML page for authentication which is filled in and the data sent back to NetDefendOS with a POST. An HTML pre-defined in NetDefendOS will be used but this can be customized as described below. • BASICAUTH - This sends a 401 - Authentication Required message back to the browser which will cause it to use its own inbuilt dialog to ask the user for a username/password combination. A Realm String can optionally be specified which will appear in the browser's dialog. FORM is recommended over BASICAUTH because the in some cases the browser might hold the login data in its cache • If the Agent is set to HTTPS then the Host Certificate and Root Certificate have to be chosen from a list of certificates already loaded into NetDefendOS. Setting Up IP Rules HTTP authentication can't operate unless a rule is added to the IP rule set to explicitly allow authentication to take place. If we consider the example of a number of clients on the local network lannet who would like access to the public Internet on the wan interface then the IP rule set would contain the following rules. Action Src Interface Src Network Dest Interface Dest Network Service 1 Allow lan lannet core lan_ip http-all 2 NAT lan trusted_users wan all-nets http-all 3 NAT lan lannet wan all-nets dns-all The first rule allows the authentication process to take place and assumes the client is trying to access the lan_ip IP address, which is the IP address of the interface on the D-Link Firewall where the local network connects. The second rule allows normal surfing activity but we cannot just use lannet as the source network since the rule would trigger for any unauthenticated client from that network. Instead, the source network is an administrator defined IP object called trusted_users which is the same network as lannet but has additionally either the Authentication option No Defined Credentials enabled or has an Authentication Group assigned to it (which is the same group as that assigned to the users). The third rule allows DNS lookup of URLs. Forcing Users to a Login Page With this setup, when users that aren't authenticated try to surf to any IP except lan_ip they will fall through the rules and their packets will be dropped. To always have these users come to the authentication page we must add a SAT rule and its associated Allow rule. The rule set will now look like this: 224

Section	Page
User Manual	3
Table of Contents	4
Preface	12
Chapter 1. Product Overview	14
1.1. About D-Link NetDefendOS	14
1.2. NetDefendOS Architecture	16
1.2.1. State-based Architecture	16
1.2.2. NetDefendOS Building Blocks	16
1.2.3. Basic Packet Flow	17
1.3. NetDefendOS State Engine Packet Flow	19
Chapter 2. Management and Maintenance	23
2.1. Managing NetDefendOS	23
2.1.1. Overview	23
2.1.2. Default Administrator Accounts	23
2.1.3. The CLI	24
2.1.4. The WebUI	26
2.1.5. Working with Configurations	29
2.2. Events and Logging	35
2.2.1. Overview	35
2.2.2. Event Messages	35
2.2.3. Event Message Distribution	35
2.2.3.1. Logging to Syslog Hosts	36
2.2.3.2. SNMP Traps	37
2.3. RADIUS Accounting	39
2.3.1. Overview	39
2.3.2. RADIUS Accounting Messages	39
2.3.3. Interim Accounting Messages	41
2.3.4. Activating RADIUS Accounting	41
2.3.5. RADIUS Accounting Security	41
2.3.6. RADIUS Accounting and High Availability	41
2.3.7. Handling Unresponsive Servers	42
2.3.8. Accounting and System Shutdowns	42
2.3.9. Limitations with NAT	42
2.4. Monitoring	43
2.4.1. SNMP Monitoring	43
2.5. Maintenance	45
2.5.1. Auto-Update Mechanism	45
2.5.2. Configuration Backup and Restore	45
2.5.3. Resetting to Factory Defaults	45
Chapter 3. Fundamentals	48
3.1. The Address Book	48
3.1.1. Overview	48
3.1.2. IP Addresses	48
3.1.3. Ethernet Addresses	50
3.1.4. Address Groups	51
3.1.5. Auto-Generated Address Objects	51
3.2. Services	52
3.2.1. Overview	52
3.2.2. TCP and UDP Based Services	53
3.2.3. ICMP Services	55
3.2.4. Custom IP Protocol Services	55
3.3. Interfaces	57
3.3.1. Overview	57
3.3.2. Ethernet	58
3.3.3. VLAN	60
3.3.4. PPPoE	61
3.3.4.1. Overview of PPP	61
3.3.4.2. PPPoE Client Configuration	62
3.3.5. GRE Tunnels	63
3.3.6. Interface Groups	66
3.4. ARP	68
3.4.1. Overview	68
3.4.2. ARP in NetDefendOS	68
3.4.3. ARP Cache	68
3.4.4. Static and Published ARP Entries	69
3.4.5. Advanced ARP Settings	71
3.5. The IP Rule Set	73
3.5.1. Security Policies	73
3.5.2. IP Rule Evaluation	74
3.5.3. IP Rule Actions	75
3.5.4. Editing IP rule set Entries	76
3.6. Schedules	77
3.7. X.509 Certificates	79
3.7.1. Overview	79
3.7.2. X.509 Certificates in NetDefendOS	80
3.8. Setting Date and Time	82
3.8.1. General Date and Time Settings	82
3.8.2. Time Servers	83
3.9. DNS Lookup	87
Chapter 4. Routing	89
4.1. Overview	89
4.2. Static Routing	90
4.2.1. Basic Principles of Routing	90
4.2.2. Static Routing	91
4.2.3. Route Failover	94
4.2.4. Proxy ARP	96
4.3. Policy-based Routing	98
4.3.1. Overview	98
4.3.2. Policy-based Routing Tables	98
4.3.3. Policy-based Routing Rules	98
4.3.4. Policy-based Routing Table Selection	99
4.3.5. The Ordering parameter	99
4.4. Dynamic Routing	103
4.4.1. Dynamic Routing overview	103
4.4.2. OSPF	104
4.4.3. Dynamic Routing Policy	107
4.5. Multicast Routing	110
4.5.1. Overview	110
4.5.2. Multicast Forwarding using the SAT Multiplex Rule	110
4.5.2.1. Multicast Forwarding - No Address Translation	111
4.5.2.2. Multicast Forwarding - Address Translation Scenario	112
4.5.3. IGMP Configuration	114
4.5.3.1. IGMP Rules Configuration - No Address Translation	115
4.5.3.2. IGMP Rules Configuration - Address Translation	116
4.6. Transparent Mode	119
4.6.1. Overview of Transparent Mode	119
4.6.2. Comparison with Routing mode	119
4.6.3. Transparent Mode Implementation	119
4.6.4. Enabling Transparent Mode	120
4.6.5. High Availability with Transparent Mode	120
4.6.6. Transparent Mode Scenarios	120
Chapter 5. DHCP Services	127
5.1. Overview	127
5.2. DHCP Servers	128
5.3. Static DHCP Assignment	130
5.4. DHCP Relaying	131
5.5. IP Pools	132
Chapter 6. Security Mechanisms	135
6.1. Access Rules	135
6.1.1. Introduction	135
6.1.2. IP spoofing	135
6.1.3. Access Rule Settings	136
6.2. Application Layer Gateways	138
6.2.1. Overview	138
6.2.2. HTTP	139
6.2.3. FTP	140
6.2.4. TFTP	145
6.2.5. SMTP	146
6.2.5.1. DNSBL SPAM Filtering	147
6.2.6. POP3	151
6.2.7. SIP	152
6.2.8. H.323	155
6.3. Web Content Filtering	169
6.3.1. Overview	169
6.3.2. Active Content Handling	169
6.3.3. Static Content Filtering	170
6.3.4. Dynamic Web Content Filtering	172
6.3.4.1. Content Filtering Categories	176
6.4. Anti-Virus Scanning	183
6.4.1. Overview	183
6.4.2. Implementation	183
6.4.3. Activating Anti-Virus Scanning	184
6.4.4. The Signature Database	184
6.4.5. Subscribing to the D-Link Anti-Virus Service	184
6.4.6. Anti-Virus Options	184
6.5. Intrusion Detection and Prevention	188
6.5.1. Overview	188
6.5.2. IDP Availability in D-Link Models	188
6.5.3. IDP Rules	190
6.5.4. Insertion/Evasion Attack Prevention	191
6.5.5. IDP Pattern Matching	192
6.5.6. IDP Signature Groups	192
6.5.7. IDP Actions	194
6.5.8. SMTP Log Receiver for IDP Events	194
6.6. Denial-Of-Service (DoS) Attacks	198
6.6.1. Overview	198
6.6.2. DoS Attack Mechanisms	198
6.6.3. Ping of Death and Jolt Attacks	198
6.6.4. Fragmentation overlap attacks: Teardrop, Bonk, Boink and Nestea	199
6.6.5. The Land and LaTierra attacks	199
6.6.6. The WinNuke attack	199
6.6.7. Amplification attacks: Smurf, Papasmurf, Fraggle	200
6.6.8. TCP SYN Flood Attacks	201
6.6.9. The Jolt2 Attack	201
6.6.10. Distributed DoS Attacks	201
6.7. Blacklisting Hosts and Networks	202
Chapter 7. Address Translation	204
7.1. Dynamic Network Address Translation	204
7.2. NAT Pools	207
7.3. Static Address Translation	210
7.3.1. Translation of a Single IP Address (1:1)	210
7.3.2. Translation of Multiple IP Addresses (M:N)	213
7.3.3. All-to-One Mappings (N:1)	215
7.3.4. Port Translation	216
7.3.5. Protocols handled by SAT	216
7.3.6. Multiple SAT rule matches	217
7.3.7. SAT and FwdFast Rules	217
Chapter 8. User Authentication	220
8.1. Overview	220
8.2. Authentication Setup	221
8.2.1. Setup Summary	221
8.2.2. The Local Database	221
8.2.3. External Authentication Servers	221
8.2.4. Authentication Rules	222
8.2.5. Authentication Processing	223
8.2.6. HTTP Authentication	223
Chapter 9. VPN	229
9.1. Overview	229
9.1.1. The Need for VPNs	229
9.1.2. VPN Encryption	229
9.1.3. VPN Planning	229
9.1.4. Key Distribution	230
9.2. VPN Quickstart Guide	231
9.2.1. IPsec LAN to LAN with Pre-shared Keys	231
9.2.2. IPsec Roaming Clients with Pre-shared Keys	232
9.2.3. IPsec Roaming Clients with Certificates	234
9.2.4. L2TP Roaming Clients with Pre-Shared Keys	234
9.2.5. L2TP Roaming Clients with Certificates	236
9.2.6. PPTP Roaming Clients	236
9.2.7. VPN Troubleshooting	237
9.3. IPsec	240
9.3.1. Overview	240
9.3.2. Internet Key Exchange (IKE)	240
9.3.3. IKE Authentication	245
9.3.4. IPsec Protocols (ESP/AH)	247
9.3.5. NAT Traversal	248
9.3.6. Proposal Lists	249
9.3.7. Pre-shared Keys	250
9.3.8. Identification Lists	251
9.4. IPsec Tunnels	253
9.4.1. Overview	253
9.4.2. LAN to LAN Tunnels with Pre-shared Keys	253
9.4.3. Roaming Clients	253
9.4.3.1. PSK based client tunnels	254
9.4.3.2. Self-signed Certificate based client tunnels	255
9.4.3.3. CA Server issued Certificates based client tunnels	256
9.4.3.4. Using Config Mode	257
9.4.4. Fetching CRLs from an alternate LDAP server	259
9.5. PPTP/L2TP	260
9.5.1. PPTP	260
9.5.2. L2TP	261
Chapter 10. Traffic Management	267
10.1. Traffic Shaping	267
10.1.1. Introduction	267
10.1.2. Traffic Shaping in NetDefendOS	268
10.1.3. Simple Bandwidth Limiting	269
10.1.4. Limiting Bandwidth in Both Directions	270
10.1.5. Creating Differentiated Limits with Chains	271
10.1.6. Precedences	272
10.1.7. Guarantees	274
10.1.8. Differentiated Guarantees	274
10.1.9. Groups	275
10.1.10. Recommendations	276
10.1.11. A Summary of Traffic Shaping	277
10.2. Threshold Rules	279
10.2.1. Overview	279
10.2.2. Connection Rate/Total Connection Limiting	279
10.2.3. Grouping	279
10.2.4. Rule Actions	279
10.2.5. Multiple Triggered Actions	280
10.2.6. Exempted Connections	280
10.2.7. Threshold Rules and ZoneDefense	280
10.2.8. Threshold Rule Blacklisting	280
10.3. Server Load Balancing	281
10.3.1. Overview	281
10.3.2. Identifying the Servers	282
10.3.3. The Load Distribution Mode	282
10.3.4. The Distribution Algorithm	282
10.3.5. Server Health Monitoring	284
10.3.6. SLB_SAT Rules	284
Chapter 11. High Availability	289
11.1. Overview	289
11.2. High Availability Mechanisms	291
11.3. High Availability Setup	293
11.3.1. Hardware Setup	293
11.3.2. NetDefendOS Setup	294
11.3.3. Verifying Cluster Functioning	294
11.4. High Availability Issues	296
Chapter 12. ZoneDefense	298
12.1. Overview	298
12.2. ZoneDefense Switches	299
12.3. ZoneDefense Operation	300
12.3.1. SNMP	300
12.3.2. Threshold Rules	300
12.3.3. Manual Blocking and Exclude Lists	300
12.3.4. Limitations	302
Chapter 13. Advanced Settings	304
13.1. IP Level Settings	304
13.2. TCP Level Settings	307
13.3. ICMP Level Settings	311
13.4. ARP Settings	312
13.5. Stateful Inspection Settings	314
13.6. Connection Timeouts	316
13.7. Size Limits by Protocol	318
13.8. Fragmentation Settings	320
13.9. Local Fragment Reassembly Settings	324
13.10. DHCP Settings	325
13.11. DHCPRelay Settings	326
13.12. DHCPServer Settings	327
13.13. IPsec Settings	328
13.14. Logging Settings	330
13.15. Time Synchronization Settings	331
13.16. PPP Settings	333
13.17. Hardware Monitor Settings	334
13.18. Packet Re-assembly Settings	335
13.19. Miscellaneous Settings	336
Appendix A. Subscribing to Security Updates	338
Appendix B. IDP Signature Groups	340
Appendix C. Checked MIME filetypes	344
Appendix D. The OSI Framework	348
Appendix E. D-Link worldwide offices	349

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Changing the Management WebUI Port

HTTP authentication will collide with the WebUI's remote management service which also uses

TCP port 80. To avoid this, the WebUI port number should be changed before configuring

authentication. Do this by going to

Remote Management > Advanced Settings

in the WebUI and

changing the setting

WebUI HTTP Port

. Port number 81 could instead, be used for this setting.

Agent Options

For HTTP and HTTPS authentication there is a set of options in Authentication Rules called

Agent

Options

. These are:

•

- This can be one of:

•

FORM

- The user is presented with an HTML page for authentication which is filled in and

the data sent back to NetDefendOS with a POST. An HTML pre-defined in NetDefendOS

will be used but this can be customized as described below.

•

BASICAUTH

- This sends a

401 - Authentication Required

message back to the browser

which will cause it to use its own inbuilt dialog to ask the user for a username/password

combination. A

Realm String

can optionally be specified which will appear in the browser's

dialog.

FORM

is recommended over

BASICAUTH

because the in some cases the browser might hold

the login data in its cache

•

If the

Agent

is set to

HTTPS

then the

Host Certificate

and

Root Certificate

have to be chosen

from a list of certificates already loaded into NetDefendOS.

Setting Up IP Rules

HTTP authentication can't operate unless a rule is added to the IP rule set to explicitly allow

authentication to take place. If we consider the example of a number of clients on the local network

lannet

who would like access to the public Internet on the

wan

interface then the IP rule set would

contain the following rules.

Action

Src Interface

Src Network

Dest Interface

Dest Network

Service

Allow

lan

lannet

core

lan_ip

http-all

NAT

lan

trusted_users

wan

all-nets

http-all

NAT

lan

lannet

wan

all-nets

dns-all

The first rule allows the authentication process to take place and assumes the client is trying to

access the

lan_ip

IP address, which is the IP address of the interface on the D-Link Firewall where

the local network connects.

The second rule allows normal surfing activity but we cannot just use

lannet

as the source network

since the rule would trigger for any unauthenticated client from that network. Instead, the source

network is an administrator defined IP object called

trusted_users

which is the same network as

lannet

but has additionally either the Authentication option

No Defined Credentials

enabled

has

an Authentication Group assigned to it (which is the same group as that assigned to the users).

The third rule allows DNS lookup of URLs.

Forcing Users to a Login Page

With this setup, when users that aren't authenticated try to surf to any IP except

lan_ip

they will fall

through the rules and their packets will be dropped. To always have these users come to the

authentication page we must add a

SAT

rule and its associated

Allow

rule. The rule set will now

look like this:

8.2.6. HTTP Authentication

Chapter 8. User Authentication

224