[openssl-users] openssl is flexible when verifying

[Yuting Chen]

Read a little code of openssl, and found that in
the function
X509_check_issued(X509 *issuer, X509 *subject),

The statement
x509v3_cache_extensions(subject);
is called for four times, but one certificate did not
get the subject keyid (as the block of if(subject->akid) is
called for three times). Seems that if the certificate
has two key ids, the verification is performed just on
the basis of their names (supposing that
subject->akid==NULL).

Not so sure about the correctness of my
reasoning. It could be better if we can discard
these certificates, as they will disturb the
verification.


On Sun, Apr 5, 2015 at 2:26 PM, Yuting Chen <chenyt at cs.sjtu.edu.cn> wrote:

> I checked some other certificates, and found that some non self-signed
> certificates having duplicate extension instances can be verified by
> openssl. I guess openssl is quite gentle when validating these malformed
> certificates.
>
> On Sun, Apr 5, 2015 at 1:55 PM, Yuting Chen <chenyt at cs.sjtu.edu.cn> wrote:
>
>> Hi, when I verify an X509 cert against a ca certificate, I found that the
>> cert can pass validation even if it has two instances of X509v3 Basic
>> Constraints, X509v3 Subject Key ids, and authority key ids. Seems that some
>> issues are not important in verification. (I guess one reason is that one
>> subject key id is the same as the authority key id, and thus openssl may
>> regard it as a self-signed certificate? ) Should this be forbidden?
>> command:  openssl verify -x509_strict -verbose -CAfile  myroot.pem
>> mycert.pem
>>
>
>
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