Curl Request TLS alert, unknown CA in Windows WSL

Question

Running this command inside wsl 2 windows delivers the below output. Can anyone explain why there are mixed TLSv1.3 and TLSv1.2 IN and OUT and is this a potential reason as to why its unable to get local issuer certificate. The Windows host OS is Enterprise

I have installed ca-certificates and ran update-ca-certificates

curl -v https://google.com:443/
* Trying 172.217.169.78...
* TCP_NODELAY set
* Connected to google.com (172.217.169.78) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
* CAfile: /etc/ssl/certs/ca-certificates.crt
  CApath: /etc/ssl/certs
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (OUT), TLS alert, unknown CA (560):
* SSL certificate problem: unable to get local issuer certificate
* Closing connection 0
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.haxx.se/docs/sslcerts.html

Answer 1

Are you using a network connection subject to monitoring or 'protection' such as antivirus, like one provided by a business, organization or school? If so you are probably getting a fake cert/chain from the interceptor.

Try openssl s_client -connect google.com:443 and look at the s:and i: lines under Certificate chain. (Many hosts today require SNI to respond correctly and if your OpenSSL is below 1.1.1 you need to add -servername x to provide SNI, but google is not one of them, and anyway since your curl is at least trying 1.3 it cannot be OpenSSL below 1.1.1.)

Or, if connecting from Chrome, Edge or IE (but maybe not Firefox) on the host Windows works normally, doubleclick the padlock and look at the cert chain to see if it leads to GlobalSign Root CA (as the real google does) or something else (like e.g. BlueCoat); if the latter the interceptor's root cert is installed in your host Windows store, but not the WSL system. You can export the cert from the host browser and put it in a file, and either use it manually with curl --cacert $file, or import it to the WSL system's truststore, but that depends on what system you are running in WSL which you didn't say.

Added: the mixture of TLS 1.3 and 1.2 in the logging info is probably because 1.3 uses the same record header version as 1.2 as a transition hack, with an extension that indicates it is really 1.3 only in the two Hello messages, and the callback probably doesn't deal with this.

Answer 2

Turns out there were missing certificates that once provided and installed it worked fine