IEEE 802.1X is anIEEE Standard for port-basednetwork access control (PNAC). It is part of theIEEE 802.1 group of networking protocols. It provides anauthentication mechanism to devices wishing to attach to aLAN orWLAN.
The standard directly addresses an attack technique called Hardware Addition[1] where an attacker posing as a guest, customer or staff smuggles a hacking device into the building that they then plug into the network giving them full access. A notable example of the issue occurred in 2005 when a machine attached toWalmart's network hacked thousands of their servers.[2]
IEEE 802.1X defines the encapsulation of theExtensible Authentication Protocol (EAP) over wiredIEEE 802 networks[3]: §3.3 and over 802.11 wireless networks,[3]: §7.12 which is known as "EAP over LAN" or EAPOL.[4] EAPOL was originally specified forIEEE 802.3 Ethernet,IEEE 802.5 Token Ring, andFDDI (ANSI X3T9.5/X3T12 and ISO 9314) in 802.1X-2001,[5] but was extended to suit other IEEE 802 LAN technologies such asIEEE 802.11 wireless in 802.1X-2004.[6] The EAPOL was also modified for use withIEEE 802.1AE ("MACsec") andIEEE 802.1AR (Secure Device Identity, DevID) in 802.1X-2010[7][8] to support service identification and optional point to point encryption over the internal LAN segment. 802.1X is part of thelogical link control (LLC) sublayer of the 802 reference model.[9]
802.1X authentication involves three parties: a supplicant, an authenticator, and an authentication server. Thesupplicant is aclient device (such as a laptop) that wishes to attach to the LAN/WLAN. The term 'supplicant' is also used interchangeably to refer to the software running on the client that provides credentials to the authenticator. Theauthenticator is a network device that provides a data link between the client and the network and can allow or block network traffic between the two, such as anEthernet switch orwireless access point; and theauthentication server is typically a trusted server that can receive and respond to requests for network access, and can tell the authenticator if the connection is to be allowed, and various settings that should apply to that client's connection or setting. Authentication servers typically run software supporting theRADIUS andEAP protocols. In some cases, the authentication server software may be running on the authenticator hardware.
The authenticator acts like a security guard to a protected network. The supplicant (i.e., client device) is not allowed access through the authenticator to the protected side of the network until the supplicant's identity has been validated and authorized. With 802.1X port-based authentication, the supplicant must initially provide the required credentials to the authenticator - these will have been specified in advance by the network administrator and could include a user name/password or a permitteddigital certificate. The authenticator forwards these credentials to the authentication server to decide whether access is to be granted. If the authentication server determines the credentials are valid, it informs the authenticator, which in turn allows the supplicant (client device) to access resources located on the protected side of the network.[10]
EAPOL operates over thedata link layer, and inEthernet II framing protocol has anEtherType value of 0x888E.
802.1X-2001 defines two logical port entities for an authenticated port—the "controlled port" and the "uncontrolled port". The controlled port is manipulated by the 802.1X PAE (Port Access Entity) to allow (in the authorized state) or prevent (in the unauthorized state) network traffic ingress and egress to/from the controlled port. The uncontrolled port is used by the 802.1X PAE to transmit and receive EAPOL frames.
802.1X-2004 defines the equivalent port entities for the supplicant; so a supplicant implementing 802.1X-2004 may prevent higher-level protocols from being used if it is not content that authentication has successfully completed. This is particularly useful when an EAP method providingmutual authentication is used, as the supplicant can prevent data leakage when connected to an unauthorized network.
The typical authentication procedure consists of:
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An open-source project namedOpen1X produces a client,Xsupplicant. This client is currently available for both Linux and Windows. The main drawbacks of the Open1X client are that it does not provide comprehensible and extensive user documentation and that most Linux vendors do not provide a package for it. The more generalwpa_supplicant can be used for802.11 wireless networks and wired networks. Both support a very wide range of EAP types.[11]
TheiPhone andiPod Touch support 802.1X since the release ofiOS 2.0.Android has support for 802.1X since the release of 1.6 Donut.ChromeOS has supported 802.1X since mid-2011.[12]
macOS has offered native support sinceMac OS X Panther.[13]
Avenda Systems provides a supplicant forWindows,Linux andmacOS. They also have a plugin for the MicrosoftNAP framework.[14] Avenda also offers health checking agents.
Windows defaults to not responding to 802.1X authentication requests for 20 minutes after a failed authentication. This can cause significant disruption to clients.
The block period can be configured using the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\dot3svc\BlockTime[15] DWORD value (HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\wlansvc\BlockTime for wireless networks) in the registry (entered in minutes). Ahotfix is required for Windows XP SP3 and Windows Vista SP2 to make the period configurable.[16]
Wildcard server certificates are not supported by EAPHost, the Windows component that provides EAP support in the operating system.[17] The implication of this is that when using a commercial certification authority, individual certificates must be purchased.
Windows XP has major issues with its handling of IP address changes resulting from user-based 802.1X authentication that changes the VLAN and thus subnet of clients.[18] Microsoft has stated that it will not backport theSSO feature from Vista that resolves these issues.[19]
If users are not logging in with roaming profiles, a hotfix must be downloaded and installed if authenticating via PEAP with PEAP-MSCHAPv2.[20]
Windows Vista-based computers that are connected via an IP phone may not authenticate as expected and, as a result, the client can be placed into the wrong VLAN. A hotfix is available to correct this.[21]
Windows 7 based computers that are connected via an IP phone may not authenticate as expected and, consequently, the client can be placed into the wrong VLAN. A hotfix is available to correct this.[21]
Windows 7 does not respond to 802.1X authentication requests after initial 802.1X authentication fails. This can cause significant disruption to clients. A hotfix is available to correct this.[22]
Windows PE does not have native support for 802.1X. However, support can be added to WinPE 2.1[23] and WinPE 3.0[24] through hotfixes that are available from Microsoft. Although full documentation is not yet available, preliminary documentation for the use of these hotfixes is available via a Microsoft blog.[25]
MostLinux distributions support 802.1X viawpa_supplicant and desktop integration likeNetworkManager.
As ofiOS 17 andmacOS 14, Apple devices support connecting to 802.1X networks usingEAP-TLS with TLS 1.3 (EAP-TLS 1.3). Additionally, devices running iOS/iPadOS/tvOS 17 or later support wired 802.1X networks.[26][27]
eduroam (the international roaming service), mandates the use of 802.1X authentication when providing network access to guests visiting from other eduroam-enabled institutions.[28]
BT (British Telecom, PLC) employs Identity Federation for authentication in services delivered to a wide variety of industries and governments.[29]
Not all devices support 802.1X authentication. Examples include network printers, Ethernet-based electronics like environmental sensors, cameras, and wireless phones. For those devices to be used in a protected network environment, alternative mechanisms must be provided to authenticate them.
One option would be to disable 802.1X on that port, but that leaves that port unprotected and open for abuse. Another slightly more reliable option is to use the MAB option. When MAB is configured on a port, that port will first try to check if the connected device is 802.1X compliant, and if no reaction is received from the connected device, it will try to authenticate with the AAA server using the connected device'sMAC address as username and password. The network administrator then must make provisions on theRADIUS server to authenticate those MAC addresses, either by adding them as regular users or implementing additional logic to resolve them in a network inventory database.
Many managed Ethernet switches[30] offer options for this.
In the summer of 2005, Microsoft's Steve Riley posted an article (based on the original research of Microsoft MVP Svyatoslav Pidgorny) detailing a serious vulnerability in the 802.1X protocol, involving aman-in-the-middle attack. In summary, the flaw stems from the fact that 802.1X authenticates only at the beginning of the connection, but after that authentication, it's possible for an attacker to use the authenticated port if they have the ability to physically insert themselves (perhaps using a workgroup hub) between the authenticated computer and the port. Riley suggests that for wired networks the use ofIPsec or a combination of IPsec and 802.1X would be more secure.[31]
EAPOL-Logoff frames transmitted by the 802.1X supplicant are sent in the clear and contain no data derived from the credential exchange that initially authenticated the client.[32] They are therefore trivially easy to spoof on shared media and can be used as part of a targetedDoS on both wired and wireless LANs. In an EAPOL-Logoff attack, a malicious third party with access to the medium the authenticator is attached to repeatedly sends forged EAPOL-Logoff frames from the target device's MAC Address. The authenticator (believing that the targeted device wishes to end its authentication session) closes the target's authentication session, blocking traffic ingressing from the target, denying it access to the network.
The 802.1X-2010 specification, which began as 802.1af, addresses vulnerabilities in previous 802.1X specifications, by using MACsecIEEE 802.1AE to encrypt data between logical ports (running on top of a physical port) andIEEE 802.1AR (Secure Device Identity / DevID) authenticated devices.[7][8][33][34]
As a stopgap, until these enhancements are widely implemented, some vendors have extended the 802.1X-2001 and 802.1X-2004 protocol, allowing multiple concurrent authentication sessions to occur on a single port. While this prevents traffic from devices with unauthenticated MAC addresses ingressing on an 802.1X authenticated port, it will not stop a malicious device snooping on traffic from an authenticated device and provides no protection againstMAC spoofing, or EAPOL-Logoff attacks.
TheIETF-backed alternative is theProtocol for Carrying Authentication for Network Access (PANA), which also carries EAP, although it works at layer 3, using UDP, thus not being tied to the 802 infrastructure.[35]
802.1X forms part of the LLC sublayer and provides a secure, connectionless service immediately above the MAC sublayer.
With Vista, this is not a problem at all with the SSO feature, however, this feature does not exist in XP and unfortunately, we do not have any plans to backport this feature to XP as it is just too complex a change.
