RADIUS
Sunil Vallamkonda
Oct. 25, 2006
RADIUS presentation by Sunil
Vallamkonda
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What is AAA ?
• Authentication
• Authorization
• Accounting
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Authentication
• Verify a person’s or machine’s declared
identity.
• Mechanisms: passwords, PKI.
• Key aspect is Trust relationships between
servers.
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Authorization
• Rules or templates on what a
authenticated user can do on a system.
• Dial up user requests can be one link or
multiple.
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Accounting
• Measures and tracks resources a user
accesses.
• Include time, amount of data, session
statistics, resource utilization etc.
• Logs sent and analyzed for billing, security
servers.
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Properties
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Client/server model
UDP based
Hop by hop security
Stateless
Uses MD5 for password hiding.
A-V pairs
PAP/CHAP via PPP
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Packet format
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ACCESS-REQUEST (1)
ACCESS-RESPONSE (2)
ACCESS-REJECT (3)
ACCESS-CHALLENGE (11)
ACCOUNTING-REQUEST (4)
ACCOUNTING-RESPONSE (5)
STATUS-SERVER (12)
STATUS-CLIENT (13)
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RADIUS Packet
• Header : Code (1), Identifier (1), length
(2), Authenticator (16), payload
• Code: as above
• Identifier: used to perform auto linking of
initial requests and subsequent replies.
• Length: valid range: 20 – 4096.
• Authenticator: used to conceal passwords
using one way MD5. Request (random
number) / Response authenticators.
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Packet formats
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Packet formats
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Access-Request/Accept Packet
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Access-Reject
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Authentication methods
• PAP: Password Authentication Protocol
(MD5/XOR).
• CHAP: Challenge Access protocol:
password is never sent on wire.
• PAP is preferred sometimes in cases
where authorization must travel outside
the realm of control
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The CHAP 3-way handshake
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CHAP Security
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Using RADIUS and CHAP
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Realm
• Identifiers placed before or after values
normally contained in User-Name attribute
for server to identify which server to
contact.
• Examples: prefix realm such as @, \,/ as
CSI\john.
• Suffix realms as: james@itmm
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Hints
• RADIUS can be setup to handle service
authorizations based on hints.
• To controls resources needed to provision
service for client
• Example: specific IP address, IP pool.
• If NAS cannot allocate, service is
disconnected.
• Can be temporary, optional or extra
characteristics.
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Attributes
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Describe a property of type of service.
RADIUS attributes vs VSA.
RADIUS attribute types (RFC):
INT (4, 32 bit unsigned), ENUM(4, 32 bit unsigned), IPADDR (4, 32bit) , STRING (1-253, variable), DATE (4, 32-bit unsigned), BINARY
(1,1 bit).
Examples:
INT: 6, 256
ENUM: 3 = callback-login, 4 = callback-Framed.
STRING: “Charlotte”, “San Jose”
IPADDR: 0x1954ff8e
DATE: 0x00000a
BINARY: 1
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Attributes - example
Standard: Example – call back-number
Number: 19
Length: 3 or more octets
Value: String
Allowed in: Access-Request, Access-Accept
Prohibited in: Access-Reject, Access-Challenge
Maximum Iterations: 1
Presence in packet: not required
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Dictionary
• Server machines has a way of relating
which attribute corresponds to which
attribute number and expected type.
• Example:
• Attribute-Name: User-Name, Type: String
• Attribute-Name: NAS-IP-ADDR, Type:
IPADDR
• Attribute-Name: Service-Type, Type:
ENUM
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AVP pattern
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Accounting
• Client/Server model.
• Extensible: proxy, defined and qualified by
AVPs.
• Packet: Accounting-Request Start/Stop.
• Accounting- Response.
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Ports
• Authentication: udp/1812
• Accounting: udp/1813
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Implementations
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Livingston
GNU
FreeRADIUS
Cistron
Radiator
Alepo
Juniper: Steel Belt.
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Performance
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Logons per second
Logoffs per second
Rejects per second
Reject cause threshold
Total packets per second per interface
Load average
Memory, disk usage
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EAP
• Extensible Authentication Protocol
• Used over links running on PPP
• Authentication schemes such as public
key, smart cards, OTP, Kerberos etc. are
supported over PPP when EAP is used.
• RADIUS includes 2 new attributes: EAPMessage and Message-Authenticator.
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EAP architecture
User EAP Authentication Protocol (PAP, CHAP, MS-CHAP, etc.)
Inner Application Extension to TLS
TLS
EAP - TTLS
EAP
Carrier Protocol (PPP, EAPOL, RADIUS, etc)
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User protocol : EAP layering
User EAP Authentication Protocol (MD-Challenge, etc.)
EAP
Inner Application extension to TLS
TLS
EAP - TTLS
EAP
RADIUS
by Sunil
Carrier Protocol
(PPP,presentation
EAPOL, RADIUS,
Diameter, etc)
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802.1x
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Port based authentication
• Why is it called "port"-based
authentication? The Authenticator deals
with controlled and uncontrolled ports.
Both the controlled and the uncontrolled
port are logical entities (virtual ports), but
use the same physical connection to the
LAN (same point of attachment).
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Port based Auth
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contd
• Figure port: The authorization state of the
controlled port.
• Before authentication, only the uncontrolled port
is "open". The only traffic allowed is EAPOL; see
Authenticator System 1 on figure port. After the
Supplicant has been authenticated, the
controlled port is opened, and access to other
LAN resources are granted; see Authenticator
System 2 on figure port.
• 802.1X plays a major role in the new IEEE
wireless standard 802.11i.
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WEP
• Wired Equivalent Privacy (WEP), which is part of the
original 802.11 standard, should provide confidentiality.
Unfortunately WEP is poorly designed and easily
cracked. There is no authentication mechanism, only a
weak form of access control (must have the shared key
to communicate).
• As a response to WEP broken security, IEEE has come
up with a new wireless security standard named 802.11i.
802.1X plays a major role in this new standard.
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802.11
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The new security standard, 802.11i, which was ratified in June 2004, fixes all
WEP weaknesses. It is divided into three main categories:
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Temporary Key Integrity Protocol (TKIP) is a short-term solution that fixes all
WEP weaknesses. TKIP can be used with old 802.11 equipment (after a
driver/firmware upgrade) and provides integrity and confidentiality.
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Counter Mode with CBC-MAC Protocol (CCMP) [RFC2610] is a new protocol,
designed from ground up. It uses AES [FIPS 197] as its cryptographic
algorithm, and, since this is more CPU intensive than RC4 (used in WEP and
TKIP), new 802.11 hardware may be required. Some drivers can implement
CCMP in software. CCMP provides integrity and confidentiality.
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802.1X Port-Based Network Access Control: Either when using TKIP or CCMP,
802.1X is used for authentication.
In addition, an optional encryption method called "Wireless Robust
Authentication Protocol" (WRAP) may be used instead of CCMP. WRAP was the
original AES-based proposal for 802.11i, but was replaced by CCMP since it
became plagued by property encumbrances. Support for WRAP is optional, but
CCMP support is mandatory in 802.11i.
802.11i also has an extended key derivation/management.
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802.1x
• 802.1X takes advantage of an existing authentication
protocol known as the Extensible Authentication Protocol
(EAP [RFC 2284]). 802.1X takes EAP, which is written
around PPP, and ties it to the physical medium, be it
Ethernet, Token Ring or wireless LAN. EAP messages
are encapsulated in 802.1X messages and referred to as
EAPOL, or EAP over LAN.
• 802.1X authentication for wireless LANs has three main
components: The supplicant (usually the client software);
the authenticator (usually the access point); and the
authentication server (usually a Remote Authentication
Dial-In User Service server, although RADIUS is not
specifically required by 802.1X).
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8021.X and RADIUS
• Remote Authentication Dial-In User Service (RADIUS) is
defined in [RFC2865] (with friends), and was primarily
used by ISPs who authenticated username and
password before the user got authorized to use the ISP's
network.
• 802.1X does not specify what kind of back-end
authentication server must be present, but RADIUS is
the "de-facto" back-end authentication server used in
802.1X.
• There are not many AAA protocols available, but both
RADIUS and DIAMETER [RFC3588] (including their
extensions) conform to full AAA support. AAA stands for
Authentication, Authorization, and Accounting (IETF's
AAA Working Group
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EAP methods
• EAP-MD5: MD5-Challenge requires
username/password, and is equivalent to the PPP CHAP
protocol [RFC1994]. This method does not provide
dictionary attack resistance, mutual authentication, or
key derivation, and has therefore little use in a wireless
authentication enviroment.
• Lightweight EAP (LEAP): A username/password
combination is sent to a Authentication Server (RADIUS)
for authentication. Leap is a proprietary protocol
developed by Cisco, and is not considered secure. Cisco
is phasing out LEAP in favor of PEAP. Ref:
http://lists.cistron.nl/pipermail/cistron-radius/2001September/002042.html
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EAP- methods (contd)
• EAP-TLS: Creates a TLS session within EAP,
between the Supplicant and the Authentication
Server. Both the server and the client(s) need a
valid (x509) certificate, and therefore a PKI. This
method provides authentication both ways. EAPTLS is described in [RFC2716].
• EAP-TTLS: Sets up a encrypted TLS-tunnel for
safe transport of authentication data. Within the
TLS tunnel, (any) other authentication methods
may be used. Developed by Funk Software and
Meetinghouse, and is currently an IETF draft.
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Methods (contd)
• Protected EAP (PEAP): Uses, as EAP-TTLS, an
encrypted TLS-tunnel. Supplicant certificates for
both EAP-TTLS and EAP-PEAP are optional,
but server (AS) certificates are required.
Developed by Microsoft, Cisco, and RSA
Security, and is currently an IETF draft.
• EAP-MSCHAPv2: Requires
username/password, and is basically an EAP
encapsulation of MS-CHAP-v2 [RFC2759].
Usually used inside of a PEAP-encrypted tunnel.
Developed by Microsoft, and is currently an IETF
draft.
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Authentication methods
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Authentication methods
The following authentication types are some of the methods which are
supported by the server
Clear-text password in local configuration file (PAP)
Encrypted password in local configuration file
CHAP
MS-CHAP
MS-CHAPv2
authentication to a Windows Domain Controller (via ntlm_auth and winbindd)
Proxy to another RADIUS server
System authentication. (usually through /etc/passwd )
PAM (Pluggable Authentication Modules)
LDAP (PAP only)
PAM (PAP only)
CRAM
Perl program
Python program
SIP Digest (Cisco VOIP boxes)
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Contd (methods)
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A locally executed program. (like a CGI program.)
Netscape-MTA-MD5 encrypted passwords
Kerberos authentication
X9.9 authentication token (e.g. CRYPTOCard)
EAP, with embedded authentication methods
– EAP-MD5,
– Cisco LEAP,
– EAP-MSCHAP-V2 (as implemented by Microsoft),
– EAP-GTC,
– EAP-SIM,
– EAP-TLS,
– EAP-TTLS, with any authentication protocol inside of the TLS
tunnel,
– EAP-PEAP, with tunneled EAP
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server attributes
• Append attributes to the request
• Re-write any attribute of the request
• Proxy or replicate the request to another RADIUS server,
based on any criteria, not just '@realm'.
• Choose an authentication method to use for this user.
• Administer users by groups
• Implement time of day access restrictions
• Execute a local program
• Limit the number of simultaneous logins by the user
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Typical server configuration
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Attributes which have a given value
Attributes which do not have a given value
Attributes which are in the request (independent of their value)
Attributes which are not in the request
String attributes which match a regular expression
Integer attributes which match a range (e.g. <, >, <=, >=)
Source IP address of the request. This can be different than the
NAS-IP-Address attribute
Group of NAS boxes. (These may be grouped based on Source IP
address, NAS-IP-Address, or any other configuration)
User-Name
a DEFAULT configuration
multiple DEFAULT configurations
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Databases
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Oracle
Informix
Sybase
mSQL
MySQL
Microsoft SQL including versions 6.5, 7 and 2000
ODBC
Interbase
SAP
PostgreSQL
SQLite
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Authorization methods
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Local files
Local DB/DBM database
LDAP
A locally executed program. (like a CGI program.)
Perl program
Python program
MySQL DB
PostgreSQL DB
Oracle SQL DB
any IODBC SQL DB
IBM's DB2
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Accounting methods
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Local 'detail' files
Local 'wtmp' and 'utmp' files
Proxy to another RADIUS server
Replicate to one or more RADIUS servers
SQL (Oracle, MySQL, PostgreSQL,
Sybase, IODBC, etc)
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Tools
• Users in LDAP database
• Users and Groups in SQL database (MySQL or
PostgreSQL)
• Create, test, delete, change personal information, check
accounting and change dialup settings for a user
• Accounting Report Generator
• Bad Users facility to keep a record of users creating
problems
• Online finger facility , Test radius server
• Online Usage Statistics
• Perl, Python
• Configufration GUI
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Other features
• Can optionally act as a TACACS+ server,
converting TACACS+ requests into
RADIUS requests
• Optional tunnelling of Radius requests
using SOAP over HTTP or HTTPS for
improved security.
• SNMP support for the IETF Radius Server
MIB: gather server stats with SNMP
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Features (contd)
• Web reports for usage analysis users
sessions details. Allows your
administrators and customers to see
usage information on a web page and drill
down to connection details.
• Block authentication according to time of
day and day of week, and force
disconnection at the end of valid time
blocks.
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Token based
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Encotone telID
RSA SecurID
Safeword
VASCO Digipass
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Platforms
• Solaris
• Unix including Linux (Red Hat, Debian, Mandrake,
SuSE, Lindows, Slackware, Ubuntu etc on Intel, Sparc,
PPC, HP-PA etc), Solaris (Intel and Sparc), FreeBSD,
NetBSD, SunOS, AIX, IRIX, SCO Open Server, Digital,
HP-UX, etc
• Windows 95, 98, NT, 2000, ME, XP, 2003, etc.
• Mac OS9, Mac OS X.
• Novell Open Enterprise Server (NetWare) 6.5
• VMS
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Third-party
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Billing packages: Platypus, Emerald, Billmax, interbiller, Jet-ISP billing,
Optigold ISP.
NAS: Alcatel DANA
Altiga
Apple AirPort
Ascend (all models)
Assured Access X1000
Bay including RAC8000 and Annex Server 5399
Breezecom
Cisco routers and NAS's
Cisco Aironet AP340 and AP350 wireless Access Points
Cisco SSG and SESM
Computone
Enterasys SS2200, SSR8000 SSR8600
Ericsson ACC
Ericsson GSN
GRIC AimTraveler
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VSA
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USR/3COM
Cisco (including VOIP)
Nortel CVX 4-byte Vendor Specific Attributes, including the Vendor Specific boolean data type.
Ascend
Breezecom with broken VSA's
Bay
Shiva
ACC
Microsoft
Shasta
Springtide
Altiga
Redcreek
Unisphere
Extreme
KarlNet
Colubris
Level3
3GPP2
DTag (Deutsche Telekom)
Nomadix
Redback 64bit integers
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References
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2139/2866 (accounting)
2138/2865 (RADIUS)
2548 (MS-VSA)
2882(NAS)
2869 (Extensions)
3162 (v6)
3579 (EAP)
3580 (802.1x)
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References (contd)
• http://tools.ietf.org/wg/eap/draft-funk-eapttls-v1-01.txt
• http://www.microsoft.com/technet/commun
ity/columns/cableguy/cg0702.mspx
• http://www.oreillynet.com/pub/a/wireless/2
002/10/17/peap.html
• http://www.wifiplanet.com/tutorials/article.php/3073201
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Future
• Diameter: RFC3588
• IPv6 and RADIUS: RFC3162
Contact: sunil_vall@yahoo.com
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