Hi all, I have a path validation/hierarchy question - specifically wondering about the path validation problems incurred on various clients. (I realize there's no definite answer besides "test it on all the clients you care about".)
Imagine a four-cert hierarchy R -> A -> B -> L (Root, Leaf, and two Intermediates A & B). R's Issuer and Subject will match, A's Issuer will be R; B's Issuer will be A; and L's Issuer will be B. R is a root because of the dual combination of i) being installed in the trust store and ii) matching the Subject/Issuer. I send a chain of A->B->L and clients are happy. Now what happens when I decide that I want to trust A, but not everything else off of R? I tested it out, and installing A into the trust store on Firefox and on my MacBook doesn't cause any problems with Firefox/Chrome/Safari/curl. It seems the issuer/subject mismatch was not an issue. IS this technique recommended/not recommended/documented or otherwise known to work or not work under any circumstances? ---- The reverse question I have is in the event of Cross Certification. Imagine a simpler hierarchy R -> A -> L. However in this model, R is cross-signed by other CA, C - and some clients only have C in their trust store (while others have C and R). In order for this to actually work, there would need to be two R's: R (self-signed, where Issuer=Subject for a proper root) and R' (signed by C, with Issuer=C). Which works fine if you know under what circumstances to send R and R', but poor L doesn't know when to send which - right? I'm also confused by all the extensions: - AKI and SKI: Both R and R' would have the same SKI. R's AKI points to it's own SKI; R''s AKI would point to C's SKI. - What will A's AIA point to? Presumably R and not R'; correct? Won't this cause problems? Is there an elegant solution to this Cross Certification problem? It seems like Let's Encrypt is going to deal with this (albeit one level removed), so what's the plan there? -tom -- dev-tech-crypto mailing list dev-tech-crypto@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-tech-crypto
