iOS 18 breaks IMAPS self-signed certs • Hacker News Board

Re: iOS 18 breaks IMAPS self-signed certs

#121

Post by mmd45 » Thu, Sep 19, 2024, 10:56 AM UTC

nerdile wrote: post #90

mmd45 wrote: post #36

Earlier quoted context omitted.

bad summary. it prompted you to accept the certificate upon first use and then pinned it which is far different than what you are describing in terms of security implications.

TOFU for invalid/untrusted certificates is the equivalent of "go there anyway" in a browser Very different than explicitly trusting a Private CA. It means that skilled attackers can rely on unskilled users clicking the "trust me, it's fine" button. All so that someone skilled enough to set up their own email server and certificates doesn't have to configure their system securely? This is about making bad things harde…

you are assuming i have users and this is a mail server not a website which has a very different access pattern more analogous to ssh where TOFU works beautifully.

Re: iOS 18 breaks IMAPS self-signed certs

#122

Post by mschuster91 » Thu, Sep 19, 2024, 10:58 AM UTC

0x457 wrote: post #20

mmd45 wrote: post #10

Earlier quoted context omitted.

unfortunately none of that applies to my setup. my imap server lives in a dmz and doesn't have all that other jazz.

Only thing required for this setup to work: client needs to be able to resolve domain to internal ip. I have wireguard mesh with a bunch of services that use LE for TLS that have no access to interwebs and not accessible from interwebs.

> Only thing required for this setup to work: client needs to be able to resolve domain to internal ip.

It does not. Use DNS validation, that way you can issue LE certs for individual domains as well as wildcard certificates without needing to expose anything anywhere other than a CNAME record for the validation.

Re: iOS 18 breaks IMAPS self-signed certs

#123

Post by AlphaCharlie » Thu, Sep 19, 2024, 11:17 AM UTC

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.

How does a self signed cert protect you from MITm if the iPhone will accept any signed certificate thereafter? There’s no cert pinning AFAIK in imaps.

Re: iOS 18 breaks IMAPS self-signed certs

#124

Post by apparentorder » Thu, Sep 19, 2024, 11:28 AM UTC

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?

Re: iOS 18 breaks IMAPS self-signed certs

#125

Post by cpach » Thu, Sep 19, 2024, 11:38 AM UTC

shakow wrote: post #19

stephenmac98 wrote: post #14

It's 2024, PKI best practices are well known and well documented, anybody still using a self-signed certs on their mail server (or anywhere) is either lazy or stupid. Plenty of existing applications will refuse to connect to a self-signed certificate on the belief that allowing the end-user to confirm a certificate offers basically 0 protection against malicious actors.

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.

Please keep in mind that a self-signed certificate is quite different from a certificate that is signed using a private CA.

The self-signed certificate has no link to a trust anchor. So it’s easy for Mallory to replace it with her own malicious certificate. It’s much harder for Mallory to replace a certificate that is tied to a CA.

Re: iOS 18 breaks IMAPS self-signed certs

#126

Post by cpach » Thu, Sep 19, 2024, 11:41 AM UTC

digitalPhonix wrote: post #116

User11110 wrote: post #50

Earlier quoted context omitted.

Internal CAs and self signed certificates are different. You can still generate a CA, sign your certificates, import your own CA into your phone and have that verify your certificates. You don't need Letsencrypt. But you'll learn in time.

How? An internal CA is just a self-signed certificate that you’ve told your device to trust; and to trust other certificates signed by it. Somewhere you still need to trust a self-signed certificate.

You can guard the root certificate better than the leaf certificate. For example, you can keep it offline in an air-gapped environment.

Re: iOS 18 breaks IMAPS self-signed certs

#127

Post by xg15 » Thu, Sep 19, 2024, 11:42 AM UTC

actionfromafar wrote: post #108

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…

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.

Re: iOS 18 breaks IMAPS self-signed certs

#128

Post by xg15 » Thu, Sep 19, 2024, 11:45 AM UTC

AlphaCharlie wrote: post #123

hedora wrote: post #74

Earlier quoted context omitted.

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.

How does a self signed cert protect you from MITm if the iPhone will accept any signed certificate thereafter? There’s no cert pinning AFAIK in imaps.

You'd have to manually trust the MITM cert again? Which you certainly would not do as you know you didn't create a new self-signed cert in that moment.

Re: iOS 18 breaks IMAPS self-signed certs

#129

Post by xg15 » Thu, Sep 19, 2024, 11:49 AM UTC

And the Apple fanboys are loose again...

Regardless how your opinion on PKI and self-signed certificates is, shouldn't we at least be bothered by the fact that Apple just switched off this feature without any communication whatsoever? The community was literally in the dark about whether this is an official policy change or a bug.

Google, in situations like this, at least made some corpospeak press release officially "sunsetting" the feature and provided an official deprecation timeline so users have time to adapt.

Apple is apparently just leaving their users stranded and unable to access their email.

Re: iOS 18 breaks IMAPS self-signed certs

#130

Post by actionfromafar » Thu, Sep 19, 2024, 11:55 AM UTC

outofpaper wrote: post #117

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".

Just because many people using self-signed certs are at the "don't know" stage isn't a reason to invalidate them.

For IMAP, I'm one of them! :-D