keyusage digitalSignature in CA certs

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keyusage digitalSignature in CA certs

Robert Moskowitz
Should digitalSignature be included in keyusage in CA certs?


https://jamielinux.com/docs/openssl-certificate-authority/create-the-root-pair.html

Includes it.

https://stackoverflow.com/questions/21297139/how-do-you-sign-certificate-signing-request-with-your-certification-authority/21340898#21340898

Does not include it.

It seems to make a root or intermediate CA be able to have more purposes
than it should?  e.g.

SSL client : Yes
SSL server : Yes
S/MIME signing : Yes

So which is the right for a CA's key usage?

thanks

Bob

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Re: keyusage digitalSignature in CA certs

Blumenthal, Uri - 0553 - MITLL
AFAIK it must.

Regards,
Uri

Sent from my iPhone

> On Aug 17, 2017, at 09:21, Robert Moskowitz <[hidden email]> wrote:
>
> Should digitalSignature be included in keyusage in CA certs?
>
>
> https://jamielinux.com/docs/openssl-certificate-authority/create-the-root-pair.html
>
> Includes it.
>
> https://stackoverflow.com/questions/21297139/how-do-you-sign-certificate-signing-request-with-your-certification-authority/21340898#21340898
>
> Does not include it.
>
> It seems to make a root or intermediate CA be able to have more purposes than it should?  e.g.
>
> SSL client : Yes
> SSL server : Yes
> S/MIME signing : Yes
>
> So which is the right for a CA's key usage?
>
> thanks
>
> Bob
>
> --
> openssl-users mailing list
> To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users

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Re: keyusage digitalSignature in CA certs

OpenSSL - User mailing list
In reply to this post by Robert Moskowitz
Bonjour,

> Le 17 août 2017 à 15:20, Robert Moskowitz <[hidden email]> a écrit :
>
> Should digitalSignature be included in keyusage in CA certs?

It depends on what you plan to do with the corresponding private key.
If you want this private key to sign messages other than certificates and CRLs (such as OCSP responses), then yes.

>
> https://jamielinux.com/docs/openssl-certificate-authority/create-the-root-pair.html
>
> Includes it.
>
> https://stackoverflow.com/questions/21297139/how-do-you-sign-certificate-signing-request-with-your-certification-authority/21340898#21340898
>
> Does not include it.
>
> It seems to make a root or intermediate CA be able to have more purposes than it should?  e.g.
>
> SSL client : Yes
> SSL server : Yes
> S/MIME signing : Yes

This is the result of an analysis of the keyUsage *and* the extendedKeyUsage extensions (and maybe obsolete Netscape proprietary ones).

> So which is the right for a CA's key usage?

That really depends on what you want it to be valid for.

keyUsage=keyCertSign is fine for certificate signing
keyUsage=cRLSign is fine for CRL signing
keyUsage=digitalSignature is fine for OCSP signing

The other bits are not that common for a CA.

You can achieve the capabilities with different certificates.

For example, a keyCertSign-only CA cert can self-issue a cRLSign certificate in order to produce CRLs and a digitalSignature certificate to sign OCSP responses, or an issuing CA can issue different certificates for the same CA (they all have the same Subject, which is different from the issuing’s Subject) but for different purposes (and thus different keyUsage bits).

Cordialement,
Erwann Abalea

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Re: keyusage digitalSignature in CA certs

Robert Moskowitz
Thank you for your response.

I am basically skipping 20 years of PKI development and trying to get to
current best practices...

On 08/17/2017 09:50 AM, Erwann Abalea via openssl-users wrote:
> Bonjour,
>
>> Le 17 août 2017 à 15:20, Robert Moskowitz <[hidden email]> a écrit :
>>
>> Should digitalSignature be included in keyusage in CA certs?
> It depends on what you plan to do with the corresponding private key.
> If you want this private key to sign messages other than certificates and CRLs (such as OCSP responses), then yes.

Got it and your follow-on points.

Again, thank you.

>
>> https://jamielinux.com/docs/openssl-certificate-authority/create-the-root-pair.html
>>
>> Includes it.
>>
>> https://stackoverflow.com/questions/21297139/how-do-you-sign-certificate-signing-request-with-your-certification-authority/21340898#21340898
>>
>> Does not include it.
>>
>> It seems to make a root or intermediate CA be able to have more purposes than it should?  e.g.
>>
>> SSL client : Yes
>> SSL server : Yes
>> S/MIME signing : Yes
> This is the result of an analysis of the keyUsage *and* the extendedKeyUsage extensions (and maybe obsolete Netscape proprietary ones).
>
>> So which is the right for a CA's key usage?
> That really depends on what you want it to be valid for.
>
> keyUsage=keyCertSign is fine for certificate signing
> keyUsage=cRLSign is fine for CRL signing
> keyUsage=digitalSignature is fine for OCSP signing
>
> The other bits are not that common for a CA.
>
> You can achieve the capabilities with different certificates.
>
> For example, a keyCertSign-only CA cert can self-issue a cRLSign certificate in order to produce CRLs and a digitalSignature certificate to sign OCSP responses, or an issuing CA can issue different certificates for the same CA (they all have the same Subject, which is different from the issuing’s Subject) but for different purposes (and thus different keyUsage bits).
>
> Cordialement,
> Erwann Abalea
>

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