[openssl-users] [openssl-dev] verify depth behavior change from 1.0.2 to 1.1.0?

Short, Todd tshort at akamai.com
Tue Apr 4 14:41:16 UTC 2017

Ben Kaduk:

Do we know the values that are being passed to SSL_CTX_set_Verify_depth() match the -verify_depth argument, or do they differ?
If they differ, do identical arguments to the function behave the same in 1.1.0 and 1.0.2?


What we’re getting at here, is that this appears to be a potentially significant behavioral change. We want to understand it better.
-Todd Short
// tshort at akamai.com<mailto:tshort at akamai.com>
// "One if by land, two if by sea, three if by the Internet."

On Apr 3, 2017, at 4:43 PM, Viktor Dukhovni <openssl-users at dukhovni.org<mailto:openssl-users at dukhovni.org>> wrote:

On Apr 3, 2017, at 4:26 PM, Benjamin Kaduk <bkaduk at akamai.com<mailto:bkaduk at akamai.com>> wrote:

There was a fair amount of churn in x509_vfy.c with the inclusion
of the DANE stuff and whatnot, so it's not immediately clear to me
when this change actually happened.  I think there are good
arguments for the current 1.1.0 behavior and it doesn't really make
sense to try to change back to the historical behavior, but it would
be good to know when the change actually happened and that it is/was
a known change.  Ideally we could also document the different
behavior between 1.0.x and 1.1.0 better; any thoughts about where to
do so?


  -verify_depth num

Limit the certificate chain to num intermediate CA certificates.
A maximal depth chain can have up to num+2 certificates, since
neither the end-entity certificate nor the trust-anchor
certificate count against the -verify_depth limit.


SSL_CTX_set_verify_depth() sets the maximum depth for the
certificate chain verification that shall be allowed for ctx.
(See the BUGS section.)

The certificate verification depth set with SSL[_CTX]_verify_depth()
stops the verification at a certain depth. The error message
produced will be that of an incomplete certificate chain and
not X509_V_ERR_CERT_CHAIN_TOO_LONG as may be expected.

The 1.0.2 behaviour was under-documented and somewhat broken.  This
was fixed in 1.1.0.

Unfortunately, the SSL_CTX_set_verify_depth(3) was not brought up to date,
contributes welcome:



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