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Text of the page (random words):
ut it s nice research to make one think about threat models to address some common misconceptions the adversary doesn t need to know the pre shared secret the ssid confusion attack can cause a victim to connect to a different ssid as long as that ssid uses the same credentials as another ssid however the adversary doesn t need to know these credentials after all if the adversary for instance already has access to the password of a home network they could simply perform a generic man in the middle attack by spoofing the real ssid the adversary doesn t need access to the radius server to execute this attack against an enterprise network the adversary doesn t require any access to the radius server the attack doesn t require any enterprise network credentials no usernames passwords certificates or radius access the adversary is always an outsider having some kind of additional access can increase the impact of the attack though for example in section 4 3 the adversary is also assumed to have the capability to obtain the wi fi decryption keys from a hotspot however even in this scenario direct access to the radius server is not required only access to the pairwise master key pmk is needed the attack applies to most if not all eap methods the attack isn t limited to ms chapv2 it applies to all eap methods in the paper we mentioned ms chapv2 and eap pwd because they are often used by eduroam networks note that based on scraped public configuration profiles ms chapv2 is still the most common eap method for eduroam networks the 2 4 ghz band can support management frame protection previous surveys i e wardrives of over 250 000 networks have found that on average 2 4 ghz networks are less likely to use management frame protection so 2 4 ghz networks can certainly support management frame protection but it s less common in practice compared to 5 ghz networks especially on networks that only broadcast on the 2 4 ghz band typically the same equipment advertises 2 4 and 5 ghz ssids usually the same router or access point advertises both the 2 4 and 5 ghz ssids as we ll further discuss below it s therefore less common for the 2 4 and 5 ghz ssids to have different security settings however previous research has found that this does occasionally occur in particular a separate ssid for the 2 4 ghz band can be created for backwards compatibility in which case management frame protection is then also disabled to further enhance backwards compatibility security of 2 4 vs 5 ghz networks the attack can make a client connect to the 2 4 ghz ssid of a network even if the client is configured to connect only to the 5 ghz ssid this might not seem useful but real world measurements have shown that the 2 4 ghz ssid is often less secure and more vulnerable to older attacks that being said due to the point discussed above this difference in security is lower for networks that support both the 2 4 and 5 ghz band nevertheless even for networks that support both 2 4 and 5 ghz it does occasionally occur that the 2 4 ghz band is less secure as mentioned above what s the real lesson the most interesting part of the paper is not its practical impact given the specific threat model i don t expect many real world attacks however it highlights the importance of considering threat models in particular it shows that only verifying credentials without checking the ssid can impact security additionally it highlights that some enterprise networks with different purposes and different ssids may actually share the same radius server and security configuration these scenarios may not be typical but they represent how some use wi fi in practice we should consider these use cases or at least warn about their potential insecurity geplaatst door mathy op 00 44 email this blogthis share to x share to facebook share to pinterest thursday 10 august 2023 making the cloudflare warp vpn leak dns requests cloudflare offers a free vpn client called cloudflare warp i found that its windows client can be tricked into leaking all dns requests the adversary can then spoof dns responses and intercept nearly all traffic to exploit the vulnerability the adversary needs to create a rogue wi fi or ethernet network that supports ipv6 when the local network supports ipv6 all dns requests are leaked why are dns requests leaked when you enable the vpn tunnel the cloudflare warp client will configure a local dns server this can be seen when executing ipconfig ethernet adapter ethernet connection specific dns suffix cs kuleuven be dns servers fd01 db8 1111 2 fd01 db8 1111 3 127 0 2 2 127 0 2 3 netbios over tcpip enabled the idea is that the cloudflare warp client will act as a local dns server this local dns server will perform the actual dns requests in a secure manner for ipv4 the special ip addresses 127 0 2 2 and 127 0 0 3 are configured as the dns server these ip addresses refer to the windows computer itself they re called loopback addresses so when the network only supports ipv4 these loopback ip addresses are used for the dns server and all dns requests are handled by the cloudflare warp client the warp client will then securely handle the dns requests so everything works as expected when using ipv4 the cloudflare warp client also configures the ipv6 addresses fd01 db8 1111 2 and fd01 db8 1111 3 as dns servers when the local network supports ipv6 these addresses will be used but these are not loopback addresses referring to the windows machine itself these special are unique local addresses ulas this means they behave the same as private ipv4 address of the form 192 168 x y in other words these two ipv6 addresses represent random computers in the local network they don t represent the windows computer itself all combined the cloudflare warp client is configuring two random ipv6 computers in the local network as dns servers namely the computers fd01 db8 1111 2 and fd01 db8 1111 3 are configured as dns servers so a rogue wi fi network simply needs to advertise support for ipv6 assign itself the ipv6 address fd01 db8 1111 2 and then it will receive all dns requests the leakage of dns requests has a direct impact on the user s privacy you can now see which websites the victim is visiting which apps are being used and so on but there s more once the adversary can intercept dns requests they can also spoof dns responses and by doing so the adversary can easily intercept nearly all ip based traffic of the victim for instance if the victim is looking up the ip address of website com the adversary can return the ip address of their own server when the victim now visits this website all traffic will be sent to the adversary s server and the adversary can forward it to the real server and back if the website uses https then traffic is still protected but the vpn itself is now completely bypassed and all unprotected protocols can be subsequently attacked the severity was rated as high this matches the cvss score of 7 4 it doesn t require user interaction and has a high attack complexity intuitively i would actually say it has a low attack complexity but cvss has the following example for high attack complexity the attacker must inject themselves into the logical network path e g a man in the middle attack and exploiting the vulnerability essentially requires a mitm position another harder to exploit flaw a second issue was that the clouldflare warp client only updated the dns servers of the first two network interfaces if you have more than two network interfaces the dns servers associated to these extra network interfaces didn t get changed this means a rogue wi fi network could assign itself as the dns server and if the victim has more than two network interfaces windows would use the adversary s wi fi router as the dns server this happened even when the local network only supported ipv4 having multiple network interfaces can occur more often than you think for instance if the victim installed virtualbox then a virtual network interface is created and the attack becomes possible to patch this initial vulnerability the windows client was updated to assign the dns servers 127 0 2 2 and 127 0 0 3 to all network interfaces interestingly it was no longer assigning ipv6 addresses for the dns server so that patch without us really realizing it yet also prevented the above ipv6 based attack all combined these two vulnerabilities were fixed in beta build 2023 5 170 1 which was made available on may 12 2023 the first official release that included the fix was version 2023 7 7 0 which was released on july 7 2023 discussion i first noticed the multiple interfaces dns leakage flaw and immediately reported that while doing so i already saw some weird ipv6 behavior but i didn t have time to investigate it afterwards i also checked the ipv6 issue and also discovered this more impactful attack finally i d like to thank cloudflare for the smooth handling of this vulnerability and disclosure geplaatst door mathy op 18 26 email this blogthis share to x share to facebook share to pinterest tuesday 18 may 2021 fragattacks clarifying some aspects if you haven t yet read about this research then watch my usenix security presentation in this blog post i ll discuss some aspects in more detail than i could in the paper addressing general misconceptions none of the flaws are in the cryptographic primitives used by wi fi in other words we re not attacking rc4 or sha1 the design flaws are instead at the intersection of crypto and protocol design which people colloquially refer to as the encryption used in wi fi in other words the encryption of wi fi is still being broken and in some cases bypassed the aggregation design flaw cve 2020 24588 can be abused to make receivers process a normal frame as if it were an aggregated frame it cannot be abused to force a device to aggregate frames both clients and access points aps are affected some flaws are more common in clients while others are more common in aps being within range just like practically all wi fi vulnerabilities you need to be in proximity of the victim to exploit the discovered flaws put differently as the second line of the fragattack website states an adversary that is within range of a victim s wi fi network can abuse these vulnerabilities this doesn t mean the adversary has to be right next to the target network a simple external antenna can be used to receive a wi fi signal up to one kilometer in leaked documents the nsa even claims that a range of more than 12 kilometers is possible though that extreme range is only possible in perfect conditions antenna made by matt parkinson easy or hard to abuse why not both the design flaws are on their own hard to exploit to quote the fragattacks website the design flaws are hard to abuse because doing so requires user interaction or is only possible when using uncommon network settings as a result in practice the biggest concern are the programming mistakes in wi fi products this echoes the conclusion in the paper our implementation specific vulnerabilities are the most devastating so it s the implementation flaws we have to worry about why because exploiting some of them is absolutely trivial an adversary that is within proximity of the target network can then simply inject plaintext frames it cannot get any easier than that in fact one can argue that this is even easier than exploiting the horribly broken and ancient wep protocol it gets more complicated when design flaws are combined with implementation flaws the biggest example is when the aggregation design flaw cve 2020 24588 in clients is combined with implementation flaw cve 2020 26139 in access points in this scenario the aggregation design flaw can be exploited without user interaction i e without social engineering that means the adversary merely has to be within range of the target network section 6 6 in the paper discusses this in further detail and the presentation also briefly covers this as further context i ve also created a short overview with attacks and their preconditions a quick way to determine whether it s important to immediately patch a device is to see whether it s affected by any of the cves that allow plaintext injection applicability to the old wep and tkip protocols the paper describes the impact of the vulnerabilities on the latest standards such as wpa2 and wpa3 for completeness it also briefly discusses wep and tkip to confirm that some of these vulnerabilities have existed for a long time it s hopefully clear though as also indicated in the paper that wep and tkip should no longer be used they re both insecure old and deprecated by the wi fi alliance image from musheera mirani do attackers need to know the password of the network some have asked me whether any of the attacks require knowing the pairwise transient keys ptk or group key gtk of the victim that s not the case if an attacker knows the ptk it means wi fi security has already been broken the adversary can use the ptk to passively decrypt all data all the attacks work without knowing the password of the network the cache attack cve 2020 24586 does have a more exotic threat model when an ap is vulnerable this flaw can be exploited in hotspot 2 0 or enterprise networks as long as the adversary also has credentials that are needed to connect to this network but even in this threat model the adversary does not know the ptk of the victim and the adversary also does not know the credentials of the victim finally when a client is vulnerable to the fragment cache attack it can only be exploited when the client first connects to the adversary s network and subsequently connects to the target network this threat model to exploit cve 2020 24586 in a client is currently a theoretic threat model and you can ignore it in practice two types of hotspots the less secure and more secure ones the fragment cache design flaw can only be abused against hotspots it s important to note that there are two kinds of hotspots the traditional coffee shop hotspot and the new hotspot 2 0 this difference is touched upon in section 5 1 of the paper the coffee shop hotspots are normal home networks where the password of the network is shared publicly among customers and you can think of hotspot 2 0 networks as special enterprise networks where users are automatically provided unique credentials for more details see section 2 4 in the paper the coffee shop hotspots are less secure because an adversary can set up a rogue clone of the hotspot and intercept traffic the hotspot 2 0 networks are more secure because the authenticity of the network is verified meaning a rogue clone cannot be created by an adversary to exploit aps that are vulnerable to the fragment cache vulnerability we target hotspot 2 0 networks to exploit clients that are vulnerable to the fragment cache vulnerability the attack makes use of traditional coffee shop hotspots in other words these two types of hotspots are abused under different...
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