OCSP, client certificate verification with chained CA

Tue Jan 4 14:44:06 UTC 2022

Good idea, i have tried it now but doesn't change anything

From: nginx <nginx-bounces at nginx.org> On Behalf Of Vahan Yerkanian
Sent: Tuesday, January 4, 2022 2:20 PM
To: nginx at nginx.org
Subject: Re: OCSP, client certificate verification with chained CA

Have you tried increasing the depth?

  ssl_verify_depth 3;

On 4 Jan 2022, at 15:10, Marti, Ueli (Marin) <Ueli.Marti at ch.glory-global.com<mailto:Ueli.Marti at ch.glory-global.com>> wrote:

Hi,
i am trying to setup nginx for OCSP client certificate verification and have troubles getting it to work with chained CA's.
My setup is as follows, all referenced files are in the attached archive.
- RootCa (pki/root/RootCa*.*): Self signed root CA certificate
- IntermediateCa (pki/intermediate/IntermediateCa*.*): Intermediate CA certificate signed by RootCa
- ServerCertificate (pki/intermediate/ ServerCertificate *.*): Server certificate, signed by Intermediate CA
- IntermediateClientA (pki/intermediate/IntermediateClientA*.*): Intermediate client certificate A, signed by Intermediate CA (password for p12: umtest)
- IntermediateClientB (pki/intermediate/IntermediateClientB*.*): Intermediate client certificate B, signed by Intermediate CA, REVOKED (password for p12: umtest)
- IntermediateOcspResponder (pki/intermediate/ IntermediateOcspResponder *.*): Intermediate OCSP responder certificate, extendedKeyUsage=OCSPSigning, signed by Intermediate CA

- nginx 1.20.2 runs on a Manjaro virtual machine
- openssl ocsp responder runs on the same Manjaro box, port 8080 (started with pki/startOcspResponder.sh):
 openssl ocsp -index intermediate/index.txt -port 8080 -rsigner intermediate/IntermediateOcspResponderCert.pem -rkey intermediate/IntermediateOcspResponderKey.pem -CA intermediate/IntermediateChainCaCert.pem -text &

nginx mTls configuration is as follows (full nginx.conf attached):
       ssl_ocsp on;
       ssl_verify_client on;
       ssl_client_certificate /etc/nginx/pki/intermediate/IntermediateChainCaCert.pem;
       ssl_ocsp_responder http://127.0.0.1:8080<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2F127.0.0.1%3A8080%2F&data=04%7C01%7Cueli.marti%40ch.glory-global.com%7Ced5d871335f542aec27d08d9cf85028e%7C28825646ef414c9bb69e305d76fc24e5%7C0%7C0%7C637768994197063164%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0&sdata=ztqUJe1CESaa6gDHvq0bxxsjIxOL4eVsRpnIsV54QD8%3D&reserved=0>;
       ssl_verify_depth 2;

I am trying to connect from Chrome, running on the Windows host, using alternatively Client A/B certificates.

With the above configuration, connection with Client A fails, which is NOT expected, Client A should be able to connect.
nginx error.log indicates:
2022/01/04 10:06:29 [error] 2920#2920: *4 OCSP_basic_verify() failed (SSL: error:27069070:OCSP routines:OCSP_basic_verify:root ca not trusted) while requesting certificate status, responder: 127.0.0.1, peer: 127.0.0.1:8080

Connection with Client B fails too, this is expected as Client B certificate is revoked,
nginx error.log indicates:
2022/01/04 10:06:42 [info] 2920#2920: *14 client SSL certificate verify error: certificate revoked while reading client request headers, client: 192.168.1.115, server: localhost, request: "GET / HTTP/1.1", host: "192.168.1.110"

when changing nginx configuration to:
       ssl_ocsp leaf;
everything works as expected, Client A can connect, Client B not.

Trying ocsp verification dircetly using openssl cli, works as expected as well:
openssl ocsp -issuer intermediate/IntermediateCaCert.pem -CAfile intermediate/IntermediateChainCaCert.pem -cert intermediate/IntermediateClientACert.pem -url http://127.0.0.1:8080<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2F127.0.0.1%3A8080%2F&data=04%7C01%7Cueli.marti%40ch.glory-global.com%7Ced5d871335f542aec27d08d9cf85028e%7C28825646ef414c9bb69e305d76fc24e5%7C0%7C0%7C637768994197063164%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0&sdata=ztqUJe1CESaa6gDHvq0bxxsjIxOL4eVsRpnIsV54QD8%3D&reserved=0>
Response verify OK
intermediate/IntermediateClientACert.pem: good
       This Update: Jan  4 09:20:56 2022 GMT

openssl ocsp -issuer intermediate/IntermediateCaCert.pem -CAfile intermediate/IntermediateChainCaCert.pem -cert intermediate/IntermediateClientBCert.pem -url http://127.0.0.1:8080<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2F127.0.0.1%3A8080%2F&data=04%7C01%7Cueli.marti%40ch.glory-global.com%7Ced5d871335f542aec27d08d9cf85028e%7C28825646ef414c9bb69e305d76fc24e5%7C0%7C0%7C637768994197063164%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0&sdata=ztqUJe1CESaa6gDHvq0bxxsjIxOL4eVsRpnIsV54QD8%3D&reserved=0>
Response verify OK
intermediate/IntermediateClientBCert.pem: revoked
       This Update: Jan  4 09:21:37 2022 GMT
       Revocation Time: Dec 23 09:33:07 2021 GMT

How do i need to configure nginx to make OCSP validation working for the certificate chain, not only the leaf ?
Thanks
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