On incident 0, its unclear whether a cert was actually mis-issued. Although 
they used a higher level port, did the researcher successfully bypass WoSign's 
domain validation process? Is the only concern that WoSign permitted higher 
level ports?

On incident 1, I agree this was a bad practice and should have been reported. 
I'd love an incident report from WoSign on it. Perhaps it was a language 
barrier in interpreting requirements? 

On incident 2, it sounds like they are both using the same auto-generation 
script. This doesn't sound much different from what ACME is hoping to do. 
Backdating the cert seems sketchy but, as you pointed out, isn't expressly 
against the Mozilla policy or the Baseline Requirements.  Giving WoSign the 
benefit of the doubt, it sounds like maybe it was a bug in their software that 
permitted SHA1 certs not an intentional back-dating issue. Is there any clarity 
around how this worked?


-----Original Message-----
From: dev-security-policy 
 On Behalf Of Gervase Markham
Sent: Wednesday, August 24, 2016 7:08 AM
Cc: Richard Wang <>
Subject: Incidents involving the CA WoSign

Dear m.d.s.policy,

Several incidents have come to our attention involving the CA "WoSign".
Mozilla is considering what action it should take in response to these 
incidents. This email sets out our understanding of the situation.

Before we begin, we note that Section 1 of the Mozilla CA Certificate 
Enforcement Policy[0] says: "When a serious security concern is noticed, such 
as a major root compromise, it should be treated as a security-sensitive bug, 
and the Mozilla Policy for Handling Security Bugs should be followed." It is 
clear to us, and appears to be clear to other CAs based on their actions, that 
misissuances where domain control checks have failed fall into the category of 
"serious security concern".

Incident 0

On or around April 23rd, 2015, WoSign's certificate issuance system for their 
free certificates allowed the applicant to choose any port for validation. Once 
validation had been completed, WoSign would issue certificates for that domain. 
A researcher was able to obtain a certificate for a university by opening a 
high-numbered port (>50,000) and getting WoSign to use that port for validation 
of control.

This problem was reported to Google, and thence to WoSign and resolved.
Mozilla only became aware of it recently.

* Before the recent passage of Ballot 169 in the CAB Forum, which limits the 
ports and paths which can be used, the Baseline Requirements said that one 
acceptable method of domain validation was "Having the Applicant demonstrate 
practical control over the FQDN by making an agreed‐upon change to information 
found on an online Web page identified by a uniform resource identifier 
containing the FQDN". This method therefore did not violate the letter of the 
BRs. However, Mozilla considers the basic security knowledge that ports over 
1024 are unprivileged should have led all CAs not to accept validations of 
domain control on such ports, even when not documented in the BRs.

* The misissuance incident was not reported to Mozilla by WoSign as it should 
have been (see above).

* This misissuance incident did not turn up on WoSign's subsequent BR audit[1].

Incident 1

In June 2015, an applicant found a problem with WoSign's free certificate 
service, which allowed them to get a certificate for the base domain if they 
were able to prove control of a subdomain.

The reporter proved the problem in two ways. They accidentally discovered it 
when trying to get a certificate for and mistakenly also applied 
for, which was approved. They then confirmed the problem by using 
their control of to get a cert 
for,, and

They reported this to WoSign, giving only the Github certificate as an example. 
That cert was revoked and the vulnerability was fixed. However recently, they 
got in touch with Google to note that the cert still had not been 
revoked almost a year later.

* The lack of revocation of the certificate (still unrevoked at time of 
writing, although it may have been by time of posting) strongly suggests that 
WoSign either did not or could not search their issuance databases for other 
occurrences of the same problem. Mozilla considers such a search a basic part 
of the response to disclosure of a vulnerability which causes misissuance, and 
expects CAs to keep records detailed enough to make it possible.

* This misissuance incident was not reported to Mozilla by WoSign as it should 
have been (see above).

* This misissuance incident did not turn up on WoSign's subsequent BR audit[1].

Incident 2

In July 2016, it became clear that there was some problems with the 
StartEncrypt automatic issuance service recently deployed by the CA StartCom. 
As well as other problems it had, which are outside the scope of this 
discussion, changing a simple API parameter in the POST request on the 
submission page changed the root certificate to which the resulting certificate 
chained up. The value "2" made a certificate signed by "StartCom Class 1 DV 
Server CA", "1" selected "WoSign CA Free SSL Certificate G2" and "0" selected 
"CA 沃通根证书", another root certificate owned by WoSign and trusted by Firefox.

Using the value "1" led to a certificate which had a notBefore date (usage 
start date) of 20th December 2015, and which was signed using the
SHA-1 checksum algorithm.

* The issuance of certificates using SHA-1 has been banned by the Baseline 
Requirements since January 1st, 2016. Browsers, including Firefox, planned to 
enforce this[2] by not trusting certs with a notBefore date after that date, 
but in the case of Firefox the fix had to be backed out due to web 
compatibility issues. However, we are considering how/when to reintroduce it, 
and CAs presumably know this.

* The issuance of backdated certificates is not forbidden, but is listed in 
Mozilla's list of Problematic Practices[3]. It says "Minor tweaking for 
technical compatibility reasons is accepted, but backdating certificates in 
order to avoid some deadline or code-enforced restriction is not."

* WoSign deny that their code backdated the certificates in order to avoid 
browser-based restrictions - they say "this date is the day we stop to use this 
code"[4]. If that is true, it is not clear to us how StartCom came to deploy 
WoSign code that WoSign itself had abandoned.

* It seems clear from publicly available information that StartCom's issuance 
systems are linked to WoSign's issuance systems in some way.
Nevertheless, it should not have been possible for an application for a cert 
from StartCom to produce a cert signed by WoSign.

* This misissuance incident was not reported to Mozilla by WoSign as it should 
have been.

Taking into account all these incidents and the actions of this CA, Mozilla is 
considering what action to take. Your input is welcomed.

Gerv, Kathleen and Richard

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