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sslhttpsopensslx509pki

Openssl Certificate Chain

Executed the command:

openssl s_client  -connect (redacted):443

and I get the output

depth=1 C = US, O = Let's Encrypt, CN = R3
verify error:num=20:unable to get local issuer certificate
verify return:1
depth=0 CN = *.(redacted)
verify return:1
---
Certificate chain
 0 s:CN = *.(redacted)
   i:C = US, O = Let's Encrypt, CN = R3
 1 s:C = US, O = Let's Encrypt, CN = R3
   i:O = Digital Signature Trust Co., CN = DST Root CA X3
---

What does the error "unable to get local issuer certificate" mean? From the above I can see that the full chain is there, and that the root CA "DST Root CA X3" signed the "R3" cert. So surely that R3 cert does not need to be explicitly trusted? Is this good enough? Is this cause for concern?

Solution

  • verify error:num=20:unable to get local issuer certificate

    The trust chain from the leaf (server certificate) via the intermediate chain certificates (R3) must end in a locally trusted root CA (DST Root CA X3). Obviously this root CA is not locally trusted in the CA store used by your openssl setup (or maybe you have explicitly used -CApath or -CAfile).