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iOS 18 breaks IMAPS self-signed certs

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Re: iOS 18 breaks IMAPS self-signed certs

#141

Post by nucleardog »

xg15 wrote: post #127
actionfromafar wrote: post #108

Earlier quoted context omitted.

There are or were two kinds of people using self-signed certificates. The vast majority used to be "I don't know how or can't afford to get a certificate chain cert." Now, with letsencrypt, what's left of the "can't afford group" is "I can't be arsed to update my config yet".

I love how the entire free PKI ecosystem is now relying on one single company.

It’s not. There’s LetsEncrypt, ZeroSSL, BuyPass, SSL.com, and Google Trust Services[0]. The ACME protocol is standardized and you can point your client at any of these at any time, and other providers can begin providing certificates at any time. Some tooling[1] even uses other providers by default.

[0] https://acmeclients.com/certificate-authorities/ [1] https://github.com/acmesh-official/acme.sh/wiki/Change-defau...

Re: iOS 18 breaks IMAPS self-signed certs

#142

Post by nucleardog »

kortilla wrote: post #92
commandersaki wrote: post #78

Earlier quoted context omitted.

Uh what is a mitm cert? You're the custodian of the private key associated with the certificate, not LetsEncrypt. And any CA can generate a certificate to MITM anything. That's why it's pretty much a requirement to submit all certs issued to Certificate Transparency, and if you're found to be misbehaving expect to receive ire from CA/B.

> Uh what is a mitm cert? You're the custodian of the private key associated with the certificate, not LetsEncrypt. Don’t be obtuse. Letsencrypt and every other trusted CA has the ability to issue new certs for any domain at any time without you knowing. There is absolutely no requirement to submit these to Certificate Transparency. That’s a thing some browsers do, but not most mail clients. If you don’t trust the ro…

Not that it removes you entirely from the PKI ecosystem as you seem to desire, but in case you’re not aware since 2017 CAs are required to check and honour the CAA DNS records you set. These specify which CAs are allowed to issue certificates for your domain.

If any CA issues a certificate anyway, they’re in violation of requirement 3.2.2.8. Don’t know what you’re up to, but I have to imagine it would have to be pretty interesting to someone for one of those companies to face down an existential threat and misissue a certificate for your domain.

Re: iOS 18 breaks IMAPS self-signed certs

#144

Post by lxgr »

stackskipton wrote: post #139
lxgr wrote: post #136

Earlier quoted context omitted.

What? .local is the dedicated TLD for Zeroconf/Bonjour/mDNS! How is that deprecated? And you’re just reconfirming my point: All of these recommendations are great for publicly hosted sites or corporate environments, but largely impracticable for home users that don’t know how to, or don’t want to, have a second job as sysadmins.

Home users also don't have IMAP servers they run themselves. They are in public email service.

I don't think it's crazy for a NAS to provide an IMAP server, e.g. to backup or archive a large mailbox.

One of the selling points of a NAS is that storage is much cheaper than what the large cloud providers charge per GB and month.

Re: iOS 18 breaks IMAPS self-signed certs

#145

Post by stackskipton »

lxgr wrote: post #144
stackskipton wrote: post #139

Earlier quoted context omitted.

Home users also don't have IMAP servers they run themselves. They are in public email service.

I don't think it's crazy for a NAS to provide an IMAP server, e.g. to backup or archive a large mailbox. One of the selling points of a NAS is that storage is much cheaper than what the large cloud providers charge per GB and month.

Cool, you don't but obviously you don't deal with a ton of normal users. They are not running NASes, they will just toss Google some cash for bigger GMail box.

Re: iOS 18 breaks IMAPS self-signed certs

#146

Post by tadfisher »

londons_explore wrote: post #31
tadfisher wrote: post #30

Earlier quoted context omitted.

Apple isn't doing certificate pinning, it's the apps verifying the certificate chain themselves by baking in public keys (or hashes/fingerprints). So there's not really a way for Apple to break this.

Apple could say "If you wanna talk HTTPS, you have to use our HTTPSClient class, and that only supports using the system certificate store and does not support pinning". Or they could say "All apps that don't support custom certificates for https will be denied app store approval".

The only way to "not support pinning" is to prevent apps from inspecting the certificate chain. This will break much more than pinning.

Re: iOS 18 breaks IMAPS self-signed certs

#147

Post by ThePowerOfFuet »

hedora wrote: post #74
Arnt wrote: post #3

I switched to letsencrypt certs for my imap server. Works well, IMO better than the self-signed ones I used before.

That adds a lot of attack surface vs. issuing a self-signed cert and confirming it was securely verified by your imap client. Not only could let’s encrypt issue a mitm cert for your imap connections, so could other CAs, and any cloud providers / dns providers you use.

https://letsencrypt.org/docs/caa/

Not enough? Account binding.

https://community.letsencrypt.org/t/enabling-acme-caa-accoun...

Re: iOS 18 breaks IMAPS self-signed certs

#148

Post by gjadi »

crote wrote: post #132
ho_schi wrote: post #100

Earlier quoted context omitted.

A threat model which people using self-signed certificates especially care about. The idea of certificate authorities, certificate chains and intermediary certificates is common - and based on top down security. That is the reason why it is so dangerous. There is a “lock” and people believe everything is “good” but actually DigiNotar, TurkTrust or the bad government issued a certificate. Google tried more than once t…

But if you distrust the entire PKI ecosystem, how are you intending to use your email server? If someone is trying to send you an email, their admin definitely isn't going to set up an in-person meeting with you to exchange certificate signatures. Their server is either going to accept any certificate (which means MitM is trivial), or they're going to verify it against PKI (which you don't use because you don't trust…

IMAP is for reading your emails not sending, that means you could accept PKI for SMTP to communicate with untrustworthy clients, but want to ensure that your access to your emails are safe(r).

Re: iOS 18 breaks IMAPS self-signed certs

#149

Post by bdavbdav »

anamexis wrote: post #37
shakow wrote: post #19

Earlier quoted context omitted.

There is no security hole if I am singing my own certificate for my own mails on my own server; it would mean that I do not trust... myself? Now if I were to provide this as a commercial service, sure, my customers may be worried.

It's not that you're trusting your own certificate, it's that you're trusting any self-signed certificate, leaving you open to getting MITM'ed.

How? You add your signed cert explicitly to the trust store. You’re not just hitting “trust” every time.

Re: iOS 18 breaks IMAPS self-signed certs

#150

Post by blcknight »

apparentorder wrote: post #124

I run my own CA and install it as a trusted CA via Configuration Profiles. This works fine, including iOS 17. Does this break in iOS 18 or does this affect only self-signed (untrusted) certificates?

I have the same setup and it works fine on iOS 18.
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