Tenable Nessus can't verify OCSP Signature

My domain is:

agences-cegee.fr

I ran this command:

openssl ocsp -noverify -no_nonce -respout ~/ocsp.resp -issuer /etc/letsencrypt/live/agences-cegee.fr/chain.pem -cert /etc/letsencrypt/live/agences-cegee.fr/cert.pem -url http://ocsp.int-x3.letsencrypt.org

It produced this output:
/etc/letsencrypt/live/agences-cegee.fr/cert.pem: good
This Update: Oct 11 15:00:00 2019 GMT
Next Update: Oct 18 15:00:00 2019 GMT

I can login to a root shell on my machine (yes or no, or I don’t know):
Yes

So When checking OCSP via a shel command, I have a good OCSP verification. Nonetheless when I run Nessus on my server to detect vulnerabilities it produces this :

The following certificate was part of the certificate chain
sent by the remote host, but it has an invalid OCSPResponse
signature :

|-Subject             : C=US/O=Let's Encrypt/CN=Let's Encrypt Authority X3
|-OCSP Signature      :  

As this is part of securing the server and I expect my client will run security audits on it in the future, I’m trying to plug any vulnerability or perceived vulnerability, and I’m pretty sure I’m gonna get heat for this on account of the title of this one ’ SSL Certificate Cannot Be Trusted’ :slight_smile:

Any idea of what’s happening for the OCSP not being properly verified nny Nessus ?

Thanks in advance

Hi @ericb2038

checking your domain manual with OpenSsl, there is no error visible:

openssl s_client -connect agences-cegee.fr:443 -servername agences-cegee.fr -status
CONNECTED(000001C8)
depth=1 C = US, O = Let’s Encrypt, CN = Let’s Encrypt Authority X3
verify error:num=20:unable to get local issuer certificate
OCSP response:
======================================
OCSP Response Data:
OCSP Response Status: successful (0x0)
Response Type: Basic OCSP Response
Version: 1 (0x0)
Responder Id: C = US, O = Let’s Encrypt, CN = Let’s Encrypt Authority X3
Produced At: Oct 14 15:05:00 2019 GMT
Responses:
Certificate ID:
Hash Algorithm: sha1
Issuer Name Hash: 7EE66AE7729AB3FCF8A220646C16A12D6071085D
Issuer Key Hash: A84A6A63047DDDBAE6D139B7A64565EFF3A8ECA1
Serial Number: 0393560465F50F1D0141690AD004743FCF98
Cert Status: good
This Update: Oct 14 15:00:00 2019 GMT
Next Update: Oct 21 15:00:00 2019 GMT

Signature Algorithm: sha256WithRSAEncryption
     84:2d:78:39:7d:26:de:6d:49:4c:73:78:28:f4:41:7a:97:41:
     96:ba:ac:84:9d:8b:b3:7d:4d:93:08:b1:00:ea:1d:6c:c6:87:
     46:20:b9:28:70:3f:ac:1a:bb:9a:85:ee:b0:5f:32:da:34:82:
     91:6b:c6:c4:41:cb:74:d1:76:ea:d0:4a:ce:8a:7f:d3:08:00:
     50:68:17:f3:a2:af:b7:29:cb:59:d1:9c:37:7d:f5:a2:cd:b1:
     04:c1:f1:ac:fa:9b:1d:4c:c4:40:bc:c3:d1:c3:12:62:a3:b0:
     7a:21:8f:cd:77:42:c6:55:57:01:92:c8:6a:07:03:f3:50:5a:
     83:f7:70:85:8b:e5:f4:cb:5f:1b:c7:e9:50:a5:d5:e7:7f:7a:
     06:e4:ee:85:f3:5d:3e:61:ab:ad:a5:ad:a1:94:91:3e:8e:14:
     ac:75:ba:ea:a8:8a:03:3f:17:94:fa:ac:08:b8:c9:74:4d:30:
     50:10:d1:ac:f6:8d:57:ad:be:e6:6e:7b:ac:5f:90:27:1c:6a:
     b5:a6:c4:3d:63:83:1a:7c:d8:69:99:59:04:2d:0b:c2:90:c4:
     da:32:32:bf:af:a0:02:9a:8c:b8:ff:a8:7a:dd:ad:80:9e:91:
     05:91:30:71:bf:73:6a:5a:d7:da:d2:5e:d6:bf:24:1d:a3:55:
     3d:50:3c:5f

======================================

Certificate chain
0 s:CN = agences-cegee.fr
i:C = US, O = Let’s Encrypt, CN = Let’s Encrypt Authority X3
1 s:C = US, O = Let’s Encrypt, CN = Let’s Encrypt Authority X3
i:O = Digital Signature Trust Co., CN = DST Root CA X3

Your domain has a critical error - https://check-your-website.server-daten.de/?q=agences-cegee.fr#url-checks

Redirects http -> https to https://%agences-cegee.fr/ - the % isn’t allowed.

Invalid URI: The hostname could not be parsed.

But that’s not your OCSP question.

What’s Nessus? Perhaps that tool has an error. Check other domains.

HI Juergen,

Your domain has a critical error - https://check-your-website.server-daten.de/?q=agences-cegee.fr#url-checks
Redirects http -> https to https://%agences-cegee.fr/ - the % isn’t allowed.
Invalid URI: The hostname could not be parsed.

oops thanks for spotting that one that was a typo in the vhost :slight_smile:

Nessus is a pen test application, comes in handy when checking and plugging security holes. I use it on a regular basis (https://www.tenable.com/products/nessus)

I could be that there’s an error with it, and you’re right, i’d better check in their forums, but i wanted first to check here to see if the problem could be related to my cert install/signature

Thanks, good to know.

Test the check-your-website.server-daten.de one time. There is a Letsencrypt EC certificate.

If you see the same error -> it’s a problem of that tool.

If you see another error -> may be a problem of your configuration.

What version of Nessus?

The OCSP response that Nessus is complaining about is the one for the Let’s Encrypt intermediate (Let’s Encrypt Authority X3) - not your server’s certificate.

$ openssl ocsp -no_nonce -url "http://isrg.trustid.ocsp.identrust.com" -header Host="isrg.trustid.ocsp.identrust.com" -issuer 8395.crt -cert 15706126.crt  -text
OCSP Request Data:
    Version: 1 (0x0)
    Requestor List:
        Certificate ID:
          Hash Algorithm: sha1
          Issuer Name Hash: 6FF4684D4312D24862819CC02B3D472C1D8A2FA6
          Issuer Key Hash: C4A7B1A47B2C71FADBE14B9075FFC41560858910
          Serial Number: 0A0141420000015385736A0B85ECA708
OCSP Response Data:
    OCSP Response Status: successful (0x0)
    Response Type: Basic OCSP Response
    Version: 1 (0x0)
    Responder Id: EFCA20D6D47A4AF521F34994181B752891ABE6C9
    Produced At: Oct 14 10:34:01 2019 GMT
    Responses:
    Certificate ID:
      Hash Algorithm: sha1
      Issuer Name Hash: 6FF4684D4312D24862819CC02B3D472C1D8A2FA6
      Issuer Key Hash: C4A7B1A47B2C71FADBE14B9075FFC41560858910
      Serial Number: 0A0141420000015385736A0B85ECA708
    Cert Status: good
    This Update: Oct 14 10:34:01 2019 GMT
    Next Update: Oct 21 10:34:01 2019 GMT

    Signature Algorithm: sha1WithRSAEncryption
        ac:41:7b:8a:ac:fc:72:c8:b0:8d:96:f6:e0:47:85:cf:fd:35:
        ce:8d:5b:c9:eb:05:25:2c:33:f3:19:5c:89:f6:8b:2c:5a:15:
        ed:79:a8:9a:9e:63:bf:8c:a0:e4:b0:47:96:db:41:b2:9e:23:
        78:9b:62:9f:dc:a4:cc:cd:f4:89:a5:1a:0b:63:ef:15:07:68:
        81:08:a2:12:28:40:fe:9f:30:8f:57:a5:28:25:be:48:34:8a:
        65:3e:ea:2c:1b:fc:b5:e7:3a:5a:0f:fd:79:23:f7:fb:7f:17:
        fa:6a:69:63:6f:35:f0:70:62:db:6b:f4:e3:0f:99:2c:a5:7b:
        cb:b7:f4:a4:89:8c:d1:13:e1:8c:85:c0:1c:c1:e7:aa:73:65:
        da:c3:e6:7e:83:bd:c1:ea:2c:ea:2d:7a:33:ee:0b:a6:53:20:
        d2:9e:4e:1e:49:93:2a:79:70:64:f1:25:e1:05:74:f4:bb:03:
        29:0a:ed:a9:65:38:d8:98:76:ab:b3:9f:76:4b:e8:be:ac:ad:
        47:7d:3b:08:8e:fc:8a:a2:da:9a:a7:1f:e7:e7:0b:52:91:54:
        28:84:76:37:ba:74:3e:e8:ea:67:b6:4f:cd:c7:12:98:56:54:
        f4:2b:73:3d:16:d2:ad:55:64:43:87:8c:2a:28:67:1f:9b:3d:
        19:ff:e4:57
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            40:01:6a:50:e4:37:48:e9:cc:4c:98:0f:43:11:08:52
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: O=Digital Signature Trust Co., CN=DST Root CA X3
        Validity
            Not Before: Sep 18 19:00:00 2019 GMT
            Not After : Oct 18 19:00:00 2019 GMT
        Subject: C=US, O=Digital Signature Trust, OU=DST, CN=DST CA X3 OCSP Signer/emailAddress=pki-ops@IdenTrust.com
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                RSA Public-Key: (2048 bit)
                Modulus:
                    00:b2:43:23:ad:90:aa:1b:e1:85:7d:fc:3e:8a:d0:
                    f8:ed:ed:72:c3:86:1d:de:50:af:82:25:62:95:62:
                    cf:b9:f7:99:6d:68:be:d0:a9:4f:af:14:a1:83:63:
                    9b:3f:d3:e6:31:5f:f2:f2:19:4f:ff:da:d8:d1:39:
                    ea:4b:c0:36:49:f1:23:4f:bd:d2:36:5c:00:e2:60:
                    cb:c3:60:7e:f3:35:cf:9b:26:d9:21:79:90:da:c2:
                    a1:3b:de:e7:59:fe:46:63:6f:62:bc:7d:98:8d:ca:
                    9f:6e:7a:b4:b9:56:bd:ce:ea:88:c6:db:00:46:e4:
                    96:e4:7b:e3:32:85:34:a0:a1:cd:94:41:49:74:84:
                    e6:fb:16:ed:12:15:8d:73:8e:01:6c:67:51:13:a4:
                    76:e9:ef:92:50:37:af:dc:ed:0a:29:64:6b:99:1d:
                    60:91:c2:c8:89:8d:2f:7b:df:09:5e:4e:ec:13:0c:
                    25:2d:98:ca:2f:2d:10:7a:b9:7c:77:16:39:c5:b2:
                    54:46:77:af:28:b6:2e:be:67:e1:ab:fc:16:4b:3d:
                    36:fb:a1:78:72:c5:42:39:cf:0c:64:7b:98:88:4c:
                    66:d8:b5:92:c9:f3:9c:54:8e:b3:b8:06:74:b4:f5:
                    ed:e2:80:a3:ae:b7:b8:31:6e:65:ac:37:b6:74:c8:
                    10:d1
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Basic Constraints: critical
                CA:FALSE
            X509v3 Key Usage: critical
                Digital Signature
            OCSP No Check:

            X509v3 Extended Key Usage:
                OCSP Signing
    Signature Algorithm: sha256WithRSAEncryption
        bf:6e:77:22:d2:6d:2f:8e:4a:de:6d:1a:45:81:0c:a8:9a:ba:
        ac:8d:16:10:30:65:43:44:e7:31:c9:90:35:d3:c9:51:34:a1:
        47:ec:75:c9:42:e4:c9:c5:94:66:1a:2a:6b:c8:b6:e8:ba:15:
        c6:66:89:31:14:9a:6f:01:6e:40:47:75:d1:03:1e:62:cd:ce:
        6e:3f:ac:47:64:6a:ad:f0:1b:65:62:bb:3e:a7:42:84:55:19:
        4c:fe:1a:e2:f4:66:b7:74:f8:83:78:fe:c6:94:29:fe:8e:4f:
        88:7c:01:c2:89:da:f1:b3:dd:08:b2:30:f9:a9:1a:d1:4b:97:
        32:d8:d5:b4:e5:1d:45:bc:5c:fb:a2:99:8c:e9:92:c4:7d:9d:
        0b:c1:aa:4d:85:a8:d0:86:17:8f:0b:e6:2b:87:2d:9c:8a:2f:
        0b:8c:0e:26:f6:bc:f2:08:d5:16:09:80:89:11:82:8a:8d:c4:
        f2:00:fd:c3:ba:8a:70:a7:85:b5:be:a5:33:1e:19:cb:97:df:
        48:99:77:6d:fa:84:31:a5:46:45:45:7c:60:f6:c7:48:f7:68:
        6b:85:0f:68:43:2f:41:37:66:4e:b1:87:68:d9:11:da:6e:2b:
        a2:aa:8f:dd:1e:00:c0:dc:dc:6d:35:29:55:a5:7f:a4:ba:d0:
        13:8b:b7:45
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
Response verify OK
15706126.crt: good
        This Update: Oct 14 10:34:01 2019 GMT
        Next Update: Oct 21 10:34:01 2019 GMT

Tracing the error message back, it seems like Nessus is expecting the signature to come from a different key.

What’s special about the OCSP response from the DST CA is that it uses a dedicated OCSP signing certificate, rather than signing the response from the issuer, like Let’s Encrypt does. It includes this additional certificate in the OCSP response itself.

The version of Nessus I have (8.7.2) handles that properly in its SSL Chain Analysis plugin (57571) and is happy with the OCSP response.

Perhaps an older version might not handle it so gracefully?

As @JuergenAuer suggested, if this issue also affects other sites that also use the DST-signed Let’s Encrypt X3 indermediate, the problem is probably with the Nessus plugin.

3 Likes

Now that becomes clear :slight_smile:

thank @_az you pinpointed it, my version is a bit older (7.0.2) and that probably it. I'l update and rerun a scan just tio be sure. :slight_smile:

3 Likes

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