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Attack of the Week: Airdrop Tracing
- JimDabell 3y ago> While AirDrop’s device-to-device communications channel is typically protected from third-party snooping by its own layer of security, that wouldn’t shield someone who may have been tricked into connecting with a stranger, perhaps by tapping on a deceptively named device in a list of contacts or by thoughtlessly accepting an unsolicited connection request. This step is required for the sender to be identified, according to security experts. Apple already acted on this, didn’t they? AirDrop now defaults to off and you can only switch it on for ten minutes at a time – you can’t forget to switch it off again. When Apple implemented this change, I remember that they were criticised because people said they were doing what China wanted by cracking down on P2P communication. Now it’s the opposite situation but the same criticism.
- zaltekk 3y agoI believe what they changed is the ability for "everyone" to discover you to a 10 minute toggle. It defaults to always being discoverable to your contacts. I assume that it still broadcasts your hashes even in the contacts-only mode, so you'd need to turn receiving off to stop that. Or go a step further and disable Bluetooth entirely* when you don't need it. * If you disable Bluetooth in the Control Center pulldown it won't actually disable Bluetooth or beacons. It just won't connect to devices. You need to go into Settings to actually disable Bluetooth.
- varenc 3y agoYour phone isn't passively broadcasting hashes if it's just an AirDrop receiver no matter what mode it's in. This vuln only poses a privacy risk for those sending AirDrops.
- jorvi 3y agoI understand why they put it on a 10 minute time-out, but it still makes me slightly sad. Sending (or receiving!) goofy cat pics on the subway had its own kind of charm.
- deleted 3y ago[deleted]
- fragmede 3y agoPSI is an interesting bit of cryptography. If I were random Apple engineer, how would I have found it or found a cryptographer to talk to to find it?
- fma 3y agoAs far as I know, dissidents would hang around major population area (i.e, subway station) and allow for anonymous users to connect to them to transfer files. This security issue would allow the Chinese government to track them. However, also as far as I know...although VPNs are banned in China, there are ways to get them. I'd wonder how much do dissidents use Airdrop in this manner if they can access the global Internet anonymously. Given mass surveillance in China, I'm sure the Chinese government can track "oh this airdrop sender appears every time this person is in this station". I also hope that Apple adopts an open source protocol for AirDrop not just for cross platform compatibility, but auditable security. Android has its own "Nearby Share". If Apple doesn't want to get in trouble for "fixing" this, they can easily adopt a cross platform compatible protocol that just happens to also fix this.
- vyrotek 3y agoIs this sort of sharing big enough to warrant dedicated and open-source devices just to do this? A sort-of glorified USB Drive with a sharing protocol and nothing else. You walk around and it just syncs up with things around you. Something that looks like an original iPod with a screen and folders of files. I don't know anything about the AirDrop or NearbyShare protocols, but I wonder if they can be implemented in such a device? All the recently announced dedicated AI devices make me think people might be into it.
- samstave 3y agoThis would be a really cool way to secretly do intel "dead-drops" where you just need to walk by a certain place at a certain time to receive your dead-drop/
- notso411 3y agoWhy doesn’t it store a shared secret based on some information from both parties once a contact has been mutually agreed to be shared… then you can quickly do a verification without any interception from outside sources or any information leaking
- lxgr 3y agoHow do you Airdrop to new contacts then? And how do you sync shared secrets securely across multiple devices of a single user?
- notso411 3y agoYou must have been in person to share contact details Same way it does with password manager
- lxgr 3y agoThat would unfortunately make for behavior inconsistent with the way AirDrop works today. You might have to become “visible to everyone” randomly on a new device, for example. Not insurmountable, but it would probably be quite un-Apple-like.
- error503 3y agoIt can't be mutual because the receivers don't broadcast, so the sender doesn't know which contacts are in range. I was also thinking you might be able to use asymmetric crypto for this, and encrypt the hash + a nonce using your private key, and anyone with your public key can decrypt it and check the hash against the contact list. But this means the potential receiver needs to decrypt with every public key it knows, which for large contact lists might be prohibitively expensive. Someone has probably devised a more clever way, though.
- notso411 3y agoThis is what I was thinking. Apple guys are smart they will sort it out
- deafpolygon 3y agoIs it an unfixed exploit when Apple knowingly left it as is for whatever reason?
- Pixie_Dust 3y ago> Is it an unfixed exploit when Apple knowingly left it as is for whatever reason? Danger Will Robinson ö “AirDrop uses iCloud services to help users authenticate. When a user signs in to iCloud, a 2048-bit RSA identity is stored on the device, and when the user turns on AirDrop, an AirDrop short identity hash is created based on the email addresses and phone numbers associated with the user’s Apple ID.” https://support.apple.com/en-gb/guide/security/sec2261183f4/web https://support.apple.com/en-gb/guide/security/sec2261183f4/...
- kornhole 3y agoIf a company creates a back door for a government in a way that it looks like an oopsie vulnerability, it gives them plausible deniability. If someone reports the vuln and they don't fix it, this somewhat shatters the plausible deniability. Operation triangulation https://securelist.com/operation-triangulation-the-last-hardware-mystery/111669/ https://securelist.com/operation-triangulation-the-last-hard... revealed the use of four different vulnerabilities, hidden code and undocumented features to take over Iphones. Its sophistication points to an APT. Apple did not deny helping the attacker TMK.
- lxgr 3y agoDoes it still count as an "oopsie vulnerability" if Apple has publicly documented this behavior for years in their documentation? https://support.apple.com/guide/security/airdrop-security-sec2261183f4/web https://support.apple.com/guide/security/airdrop-security-se... > Apple did not deny helping the attacker TMK. I can imagine many non-malicious alternative explanations for Apple not commenting on that particular vulnerability. For example, doing that here opens the door to a future in which every non-denial is seen as implicit admission of collaboration. It's also possible that Apple themselves was compromised: It's a large company, and other types of leaks do happen. I'd focus much more on the things Apple very publicly does not do, such as in this case not using private set intersection for AirDrop. The best vulnerability is the one you don't even have to defend, because it's just the absence of a more secure (but also more complicated) alternative. There are countless historical examples of that: Unencrypted instant messaging, non-end-to-end encrypted cloud storage etc.
- deleted 3y ago[deleted]
- SheinhardtWigCo 3y agoThe idea that Apple needs to create backdoors for governments seems absurd when you consider that any competent government will have essentially unfettered access to Radar, i.e. a firehose of almost every security bug discovered by Apple or reported to it.
- dylan604 3y agoWhy would any sane person allow accepting connections like this from any device? I don't even want to allow anyone from my contacts blindly just because I have saved their phone number. That isn't an automatic "I trust this person implicitly" flag. Clearly, I'm of "a certain age" where I don't blindly trust anyone for anything. It's amazing how quickly the concept of trust has been tossed aside from tech
- gruez 3y ago> Why would any sane person allow accepting connections like this from any device? I don't even want to allow anyone from my contacts blindly just because I have saved their phone number. That isn't an automatic "I trust this person implicitly" flag. How is this any different than your phone accepting random MMS, imessages, or phone calls from any random phone number?
- freitzkriesler2 3y ago[flagged]
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- dwb 3y ago[flagged]
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- BuildTheRobots 3y agoGood writeup, thank you for sharing. Even before the discovery phase (which is where this issue sits), the two devices apparently create a TLS tunnel with both client and server certificates, signed by Apple and containing UUIDs linked to the device and Apple ID [0]. I have no idea if/where/how these certs are used elsewhere, but this seems like another avenue of identification and tracking even if it doesn't directly expose the phone number or email address. I'm pondering early IMSI catchers didn't expose the MSISDN, but enough listeners in various places seeing the same IMSI sure helped for correlation. Does anyone know of any writeups on Apple's internal (device) CA infrastructure? [0] Section 2.4: https://www.usenix.org/system/files/sec21-heinrich.pdf https://www.usenix.org/system/files/sec21-heinrich.pdf
- gruez 3y ago>Even before the discovery phase (which is where this issue sits), the two devices apparently create a TLS tunnel with both client and server certificates, signed by Apple and containing UUIDs linked to the device and Apple ID [0]. From the abstract >We propose a novel optimized PSI-based protocol called PrivateDrop that addresses the specific challenges of offline resource-constrained operation and integrates seamlessly into the current AirDrop protocol stack Is section 2.4 how it works today, or what they're proposing for the future?
- BuildTheRobots 3y ago2.4 seems to be part of the description of the current specification, where as their PrivateDrop suggestion doesn't come in until part 4. Even if a different PSI is used it's still (I believe) happening over the TLS connection so it wouldn't fully eliminate the fingerprinting.
- pushcx 3y ago[flagged]
- lelandfe 3y agoDon’t the phones practically need to be touching for that feature? I don’t think that reduces AirDrop privacy, you’d know who it was from that distance anyway.
- jrmg 3y agoYou also need to affirmatively press the button obviously titled ‘share’ before it sends the contact info.
- NavinF 3y agoYep. I'm convinced that anyone complaining about this has never used the feature. Context on how this misinformation started on the Facebook pages of police departments: https://www.macrumors.com/2023/11/27/ios-17-namedrop-misinformation/ https://www.macrumors.com/2023/11/27/ios-17-namedrop-misinfo... Some day I'd like to use an LLM to read every user's comments on websites like this and automatically tag the users that fell for similar fake stories. That way I can avoid wasting time researching their claims
- quacksilver 3y agoI wonder if it is possible to do a relay attack to something like: - a malicious wireless charger - a coffee shop table / bar table / desk - a phone holder in a vehicle or use an SDR with a high gain directed / beam formed antenna to pretend to be much closer than you really are I don't know exactly how it works (or have a modern iOS device to test on), so all speculation
- deleted 3y ago[deleted]
- acdha 3y ago> Then AirDrop got a new feature called NameDrop, on by default, where phones near each other play an animation and display a button to send your Contact Card to the other (single press, no confirmation). There’s no documentation of what info is shared this way, and it’s not delineated on the Contact Card in the Contacts app. You really shouldn’t get your information from Facebook posts. The post you linked even correctly describes the process: the phones need to be VERY “near each other” (almost touching) and – contra “no documentation” – you select which fields are shared and can view or change the fields before hitting the button to share them.
- dang 3y agoRecent and related: Apple knew AirDrop users could be identified and tracked as early as 2019 - https://news.ycombinator.com/item?id=38971811 https://news.ycombinator.com/item?id=38971811 - Jan 2024 (13 comments) China Says It Cracked Apple AirDrop to Identify Message Sources - https://news.ycombinator.com/item?id=38925681 https://news.ycombinator.com/item?id=38925681 - Jan 2024 (21 comments)
- Too 3y agoWhy not include a timestamp in the hash? Everybody has synchronized clocks, round it to 5 minutes to add some margin. That should make any attempts of pre-computed rainbow tables very expensive and only usable for a short time window.
- manmal 3y agoA couple billion hashes (emails) is nothing, these days. One could just continuously recompute hashes for all known (or expected) emails and phone numbers. In case of governments, they can just include emails/numbers of personae non grata - a trivially small list.
- proton_dw 3y ago[dead]