Hi,
I would like to have my understanding of the following issue confirmed:
Given a two-level CA where the different generations of Root cross-sign each other, the verification of an end-entity certificate fails with OpenSSL 1.1.1 – “path length constraint exceeded”. With OpenSSL 1.0.2 the same verify succeeds.
All Root CA certificates have Basic Constraints CA:TRUE, pathlen:1. The Sub CA certificate has pathlen:0.
A) Issuer: CN=Root CA, serialNumber=1
Subject: CN=Root CA, serialNumber=1
B) Issuer: CN=Root CA, serialNumber=2
Subject: CN=Root CA, serialNumber=2
C) Issuer: CN=Root CA, serialNumber=1
Subject: CN=Root CA, serialNumber=2
D) Issuer: CN=Root CA, serialNumber=2
Subject: CN=Sub CA, serialNumber=2
E) Issuer: CN=Sub CA, serialNumber=2
Subject: Some end entity
With a CAfile containing D, C, B, A in that order the verify of E fails. If I remove the cross certificate C then the verify succeeds.
I believe OpenSSL 1.1.1 is building a chain of depth 3 (D – C – A) and so pathlen:1 of A is violated. Without the cross certificate the chain is only depth 2 (D – B).
Is my understanding of the reason for this failure correct?
Why is OpenSSL 1.0.2 verifying successfully? Does it not check the path length constraint or is it actually picking the depth 2 chain instead of the depth 3?
Regards,
Andrew.
Assuming that all self-signed certificates are trusted (here, A and B), then providing a CAfile with D+C+B+A to validate E, the different possible paths are:
- E <- D <- B: this path is valid
- E <- D <- C <- A: this path is valid
In the validation algorithm described in RFC5280 and X.509, the pathlenConstraints contained in the certificate of the Trust Anchor (here, A or B) is not taken into account. Therefore, the only ones that matter are the values set in C and D, and these values are coherent with both chains.
On Thu, Sep 15, 2022 at 7:34 PM Andrew Lynch via openssl-users <openssl-users@xxxxxxxxxxx> wrote:
Cordialement,
Erwann Abalea.
