Yeah, I agree I don’t think it was intended.  But now that I am aware of the 
issue, I think the crossing workaround per EKU is actually a good thing for 
people to be doing.  Unless someone can point out why it's bad ...

Might want to give people a little more time to plan and adapt to that change 
though since I doubt anyone thought of it and people need planning runway to 
change their procedures if it is going to be interpreted this way.

-Tim

> -----Original Message-----
> From: dev-security-policy [mailto:dev-security-policy-
> bounces+tim.hollebeek=digicert....@lists.mozilla.org] On Behalf Of Bruce via
> dev-security-policy
> Sent: Friday, July 13, 2018 10:17 AM
> To: mozilla-dev-security-pol...@lists.mozilla.org
> Subject: Re: Do We Now Require Separate Cross-certificates for SSL and
> S/MIME?
> 
> Agreed that old cross-certificates will not be impacted, but this does impact
> new cross-certificates. I assume the work around would be to just issue more
> than one cross-certificate with different EKUs, but I don't assume that was
> intended by this policy change.
> 
> Bruce.
> 
> On Friday, July 13, 2018 at 8:02:00 AM UTC-4, Tim Hollebeek wrote:
> > Doesn't the "created after January 1, 2019" mean that there is no problem
> with old crosses?  It would just be a new policy for new crosses as of next 
> year?
> >
> > -Tim
> >
> > > -----Original Message-----
> > > From: dev-security-policy [mailto:dev-security-policy-
> > > bounces+tim.hollebeek=digicert....@lists.mozilla.org] On Behalf Of
> > > bounces+Bruce via
> > > dev-security-policy
> > > Sent: Thursday, July 12, 2018 10:28 AM
> > > To: mozilla-dev-security-pol...@lists.mozilla.org
> > > Subject: Re: Do We Now Require Separate Cross-certificates for SSL
> > > and S/MIME?
> > >
> > > Note the BRs define Cross Certificate as "a certificate that is used
> > > to establish a trust relationship between two Root CAs."
> > >
> > > I think the intent was to technically restrict subordinate CAs or
> > > rather CAs which are online and issue end entity certificates. My
> > > assumption is that we want to 1) not allow a subordinate CA to issue
> > > a certificate which it was no intended to issue and 2) mitigate the
> > > risk if an online subordinate CA has been compromised.
> > >
> > > Typically, if an old root cross-certifies a new root, the purpose is
> > > to give the new root browser/OS ubiquity. The new root may be used
> > > to support end entity certificates of many types (e.g., Server Auth,
> > > S/MIME, Client Auth, Code Signing, Document Signing, Time-stamping
> > > ...). If we restrict the cross- certificate, then this will limit
> > > the use of a new root. Also note that the new root is 1) not an
> > > issuing CA and 2) is offline, so the mitigation of technical restriction 
> > > may
> already be satisfied.
> > >
> > > Thanks, Bruce.
> > >
> > > On Tuesday, July 10, 2018 at 7:21:26 PM UTC-4, Wayne Thayer wrote:
> > > > During a 2.6 policy discussion [1], we agreed to add the following
> > > > language to section 5.3 "Intermediate Certificates":
> > > >
> > > > > Intermediate certificates created after January 1, 2019:
> > > > >
> > > > >
> > > > > * MUST contain an EKU extension; and,
> > > > > * MUST NOT include the anyExtendedKeyUsage KeyPurposeId; and,
> > > > > * MUST NOT include both the id-kp-serverAuth and
> > > > > id-kp-emailProtection KeyPurposeIds in the same certificate.
> > > > >
> > > >
> > > > It has been pointed out to me that the very next paragraph of
> > > > section
> > > > 5.3
> > > > states:
> > > >
> > > > These requirements include all cross-certified certificates which
> > > > chain to
> > > > > a certificate that is included in Mozilla’s CA Certificate Program.
> > > > >
> > > >
> > > > The term "cross-certified certificates" could refer to the actual
> > > > cross-certificate, or it could refer to intermediate certificates
> > > > that chain up to the cross certificate. In the case of a root that
> > > > is being cross-certified, the former interpretation effectively
> > > > means that distinct cross-certificates would be required for
> > > > serverAuth and emailProtection, as
> > > > follows:
> > > >
> > > > 1 - Root <-- Cross-certificate (EKU=emailProtection) <--
> > > > Intermediate certificate (EKU=emailProtection) <-- leaf
> > > > certificate (S/MIME)
> > > > 2 - Root <-- Cross-certificate (EKU=serverAuth) <-- Intermediate
> > > > certificate (EKU=serverAuth) <-- leaf certificate (SSL/TLS)
> > > >
> > > > Should our policy require cross-certificates to be constrained to
> > > > either serverAuth or emailProtection via EKU, or should this
> > > > requirement only apply to [all other] intermediate certificates?
> > > >
> > > > What is the correct interpretation of section 5.3 of the policy as
> > > > currently written?
> > > >
> > > > I would appreciate everyone's input on these questions.
> > > >
> > > > - Wayne
> > > >
> > > > [1]
> > > >
> > >
> https://clicktime.symantec.com/a/1/82jRdde1a_TDsUNagUMK3MwXRBX4JdeH
> > > iAL
> > > > jfsD2zgM=?d=5n7PC5UMMMf8ow60aA_zACOHRkVy-
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> > > >
> > >
> rU6JcvMPF1WEp4WBRfAgKXpN15C1244hstaDLxsVmE8bwd8UMj0MNvk5w_Q
> > > C8ibEWzPC_L
> > > > UljJwJbyQ12v-
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> > > > Lo77olEchKsy8cAbTYPtzG0lkCI1j4UDxcZ-FUsyVeArS-
> > > GdV0BnikfsrccHi35Z67abn6
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> > > > Oru-
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> > > Y6H_
> > > >
> > >
> W_xOw3VB6Mp7gtxMSK0v72SLI%3D&u=https%3A%2F%2Fgroups.google.com
> > > %2Fd%2Fm
> > > > sg%2Fmozilla.dev.security.policy%2FQIweY3cHRyA%2FvbtnfJ4zCAAJ
> > >
> > > _______________________________________________
> > > dev-security-policy mailing list
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> https://clicktime.symantec.com/a/1/UqWB6X0ty8ImZMghiLXK4dj9WfPgHxf31
> > > p
> > > FYXlE5W5k=?d=5n7PC5UMMMf8ow60aA_zACOHRkVy-
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> > > hstaDLxsVmE8bwd8UMj0MNvk5w_QC8ibEWzPC_LUljJwJbyQ12v-
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> eTKN6FpHJwudbiXqkteAL6SsQfa0QGrVhJI2REzKkz7jXD0KovgoCzWARmueHAH
> > > Vd9wo-
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> Zf8cGao91RrkdklVah1kaEBTyUKOPMlGbnavPLTjmV4ZRDrnrDCFX4rkD1Lo77olE
> > > chKsy8cAbTYPtzG0lkCI1j4UDxcZ-FUsyVeArS-GdV0BnikfsrccHi35Z67abn6-
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> > >
> Y6H_W_xOw3VB6Mp7gtxMSK0v72SLI%3D&u=https%3A%2F%2Flists.mozilla.or
> > > g%2Flistinfo%2Fdev-security-policy
> 
> _______________________________________________
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> https://clicktime.symantec.com/a/1/wNze3hZcZDNkGJs2uz-
> SeEqGu_7QRemtNV2zTN4w6eA=?d=UWO2h2txAwcfMe5bqfj4PnyJC-fPf-
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> 2EfeLpWB2b7&u=https%3A%2F%2Flists.mozilla.org%2Flistinfo%2Fdev-
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