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| ▲ | tptacek a day ago | parent | next [-] | | It really probably is the worst security specification ever written. | | |
| ▲ | stouset a day ago | parent | next [-] | | It’s also enormous, I assume from the attempt to have nominally composable parts that could be reused for other flows. It’s three entire specs bundled as one. One for the XML components, another for the documents you build from them, and another for the authentication flows built on top. | | |
| ▲ | cryptonector a day ago | parent [-] | | It is truly surprising how large the specs for each of these ecosystems are: PKI, Kerberos, TLS, OAuth, SAML, etc. They are gargantuan, especially when you include essential dependencies like DER codecs and ASN.1 compilers (PKI, Kerberos) or XML (SAML). | | |
| ▲ | arethuza 20 hours ago | parent | next [-] | | “There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies. The first method is far more difficult.” C. A. R. Hoare | | |
| ▲ | cryptonector 9 hours ago | parent [-] | | The problem with this is the assumption that there's a simpler way to do all of this, and if only we could stop looking for large and complex solutions we could just land on the simple ones. I listed a number of solutions, all built by different people, at different times, in different orgs, and some of those solutions (OAuth, SASL) being much more organic in how they evolved, and yet all are ultimately large and complex. I think that hints at the problem space being... large and complex and requiring large and complex solutions. What we _can_ do is avoid adding complexity unnecessarily, but what looks like a simplification today (e.g., picking the best current encoding system) might look like a terrible mistake in twenty years. |
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| ▲ | pseudohadamard 13 hours ago | parent | prev [-] | | The thing is that they don't have to be that big at all, you could probably specify enough of PKI and TLS and SSH to cover most uses cases in, I dunno, 30-40 pages. However the standards bodies that produced them, termed "working groups", are more like standing committees that will (a) standardize any random idea that any member brings along and (b) are worse than the energizer bunny, they just keep going and going and going and going. Even ones that have been forcibly shut down like PKIX just keep going in other forms (LAMPS). You can't stop these standards mills, they'll just keep grinding out more stuff that no-one ever asked for, for all of eternity. | | |
| ▲ | cryptonector 9 hours ago | parent | next [-] | | It sure sounds like it should be like this, but when you actually try you end up with not this. TLS is huge! Yes, but SSL 2.0 was smaller, and buggy as hell, so it had to evolve, and after 30+ years it became the monster that it is today. Of course, SSL 2.0 did reference x.509, so hey, SSL 2.0 should have invented its own PKI. Except that Netscape might have come up with something terrible that worked in 1993 in labs but didn't scale to the web, or just full of security problems, or... What you say sounds nice and right right up until you actually look at the details of what actually happened in real life, and how things actually evolve when they have little standards involvement. | |
| ▲ | cryptonector 9 hours ago | parent | prev [-] | | > Even ones that have been forcibly shut down like PKIX just keep going in other forms (LAMPS). Was the IETF PKIX WG "forcibly" shut down, or it merely concluded, with new WGs popping up to do similar things when needs arose? |
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| ▲ | koolba a day ago | parent | prev | next [-] | | The root problem with SAML is there’s a million and one permutations to do the same thing. Signed assertions. Signed messages. Encrypted messages. Encrypted assertions. Sign after normalization. Sign before normalization. Encrypt then sign. Sign then encrypt. There’s too many ways to do too many things. | | |
| ▲ | pseudohadamard 19 hours ago | parent [-] | | That's because its built in part on XMLDSig, a genius idea to sign active content that can redefine its own semantics as it's being signed/verified. It's a triumph of ideology over common sense. | | |
| ▲ | arethuza 19 hours ago | parent | next [-] | | I think I got to the canonicalization part of the relevant spec and decided that life was too short... NB I can absolutely see why canonicalization is required... just that it was the bit where I lost interest | | |
| ▲ | pseudohadamard 15 hours ago | parent [-] | | The first book that came out on XMLDSig, "Secure XML: The New Syntax for Signatures and Encryption", written by the chair of the working group, spent over half of its 500 pages wrestling with canonicalization, and even then it read more as a 250-page problem statement than a solution. And that was before you got into deliberately malicious content that actively subverts the signature process. |
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| ▲ | 19 hours ago | parent | prev [-] | | [deleted] |
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| ▲ | pseudohadamard 13 hours ago | parent | prev [-] | | Which, given the output of the IPsec and PKIX working groups, is saying something. | | |
| ▲ | tptacek 11 hours ago | parent [-] | | I say this a lot, but: there was a conspiracy theory that NSA had infiltrated the IETF during the original IPSEC standardization effort and injected the "TLS BEAST" CBC IV chaining vulnerability, which is funny because we actually know exactly how that happened (professional academic cryptographers took out a petition to get the bug fixed and were shouted down by standards body gadflies who literally rejected the premise that there was such a thing as a professional academic cryptographer). This is really easy to see once you've done an engagement on DSIG security! Standards bodies are more than capable of fucking things up entirely on their own. If anything, NSA would risk making protocols stronger by intervening in their natural processes. |
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| ▲ | thway15269037 a day ago | parent | prev | next [-] | | Thanks now I can't sleep and I need to send our pentesters who just finished pentesting seventh security patch to our SAML another email. | |
| ▲ | jitbit 11 hours ago | parent | prev [-] | | I maintain a popular Saml library for NET (aspnetsaml). And yep, I made that rookie mistake too |
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| ▲ | unscaled a day ago | parent | next [-] | | JWT has two out of the three issues mentioned above: 1. It has the ill-conceived "alg": "none". But this feature made breaking JWT so easy and low stakes, that many libraries have removed this feature completely, or just disabled it by default. Modern RFCs that mandate JWT use in servers (e.g. RFC 9068) often explicitly forbid this, and the latest BCP for JWT (RFC 8725) recommends that libraries only accept or generate tokens with "none" when the user _explicitly_ requests that. And yet, we're still seeing "alg": "none" vulnerabilities even to this day. I'm not sure if it made sense to support "alg": "none" in the first place, but if we ended up doing that, the RFC should have been much more strict about this. 2. The other issue is mixing up asymmetric and symmetric encryption. You can't embed the HMAC password directly in the user-generated message; but if the library is not built securely, it would just treat the public key itself as the HMAC key when it gets an HMAC alg in the header. This makes forging tokens quite trivial if the library is misconfigured. JWT is not nearly as bad SAML and its designers learned some important lessons (simpler base format, no canonicalization or embedded signatures), but this is still a design-by-committee standard that didn't properly involve. The full JOSE standard (including JWA) is even worse, but fortunately JWA doesn't get used a lot. | | |
| ▲ | jamesfinlayson a day ago | parent | next [-] | | Yeah I wanted to use alg none for some unit tests once (it was easier than setting up the next lowest tier security option) but whichever Java library I was using had completely disabled it. I could see it had been supported at some point but it had been updated so that it couldn't be enabled at all. | | |
| ▲ | talkin 20 hours ago | parent [-] | | Yes, that’s a good thing. That alg:none might be easy in tests is not a good reason for a weak mode in the real code and spec. Been there, done that, wrote the stub/mock and ended up with the better test. :) | | |
| ▲ | unj 10 hours ago | parent [-] | | Wasn’t it like a month ago when Sharepoint still accepted alg:none? I guess that proves they’re not using Java :) |
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| ▲ | huflungdung 17 hours ago | parent | prev [-] | | [dead] |
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| ▲ | bawolff a day ago | parent | prev | next [-] | | Yes. JWT also had a bug where some implementations would use the pubkey as an hmac password if you switched the algorithm which is similarly bad. Specifying the algorithm in the attacker controlled document is a bad design imo. Still i feel like SAML is much worse. JWT has a few rough edges, but SAML its like everything. | | |
| ▲ | patmorgan23 11 hours ago | parent [-] | | Yeah, the standard should have just specified like a sha256 HMAC, when that becomes broken in 20 years we can just do a JWT2 (or invent some new successor standard) | | |
| ▲ | bawolff 10 hours ago | parent [-] | | given that md5-hmac isn't even broken despite md5 being broken, it seems unlikely sha256-hmac will fall in 20 years. that said, algorithm agility isn't the primary issue, its whether you want symmetric (hmac) or asymmetric (digital signature). Both have advantages and disadvantages so there is no per-se right answer, it depends on context. |
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| ▲ | mcpherrinm a day ago | parent | prev | next [-] | | https://www.howmanydayssinceajwtalgnonevuln.com/ | |
| ▲ | dwaite a day ago | parent | prev [-] | | Yes, but you shouldn't be taking instruction on how to verify the security of a JWT from the JWT itself in the first place. Don't follow an attacker's security steps. |
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