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I need to add a .pem cert file to my default CA cert bundle but I don't know where the default CA Cert bundle is kept.

I need to append my new .pem file to this default bundle. I'd rather do that than specify my own location using --capath

cURL clearly knows where to look but I don't see any cURL commands that reveal the location. Is there a command that will reveal this location? How can I find it?

According to cURL:
Add the CA cert for your server to the existing default CA cert bundle. The default path of the CA bundle used can be changed by running configure with the --with-ca-bundle option pointing out the path of your choice.

Thanks

Running curl with strace might give you a clue.

strace curl https://www.google.com |& grep open

Lots of output, but right near the end I see:

open("/etc/ssl/certs/578d5c04.0", O_RDONLY) = 4

which /etc/ssl/certs/ is where my certificates are stored.

strace not available on macOS, apparently. The "equivalent" dtruss told me "dtrace: failed to initialize dtrace: DTrace requires additional privileges". So I used sudo with it. To which it replied "dtrace: failed to execute curl: dtrace cannot control executables signed with restricted entitlements". Not very helpful. – Mr. Lance E Sloan Dec 1, 2017 at 17:23 curl with level one verbose will do the same, you dont need strace. "curl -v example.com |& grep "CAfile"" – MerlinTheMagic Jun 22, 2020 at 9:56 For followers |& is syntactic sugar for 2>&1 | . @MerlinTheMagic it needs an https://example.com then it somewhat works, see Philip Rego's answer comments. Using dtruss in OS X is possible stackoverflow.com/questions/31045575/… but may not be acurrate superuser.com/questions/247686/wheres-the-ca-cert-bundle-on-osx/… . It outputs CAfile: /etc/ssl/cert.pem and dtruss agrees but for the built-in curl may also be using CA root keys from the System KeyChain in addition (i.e. not using that file at all) – rogerdpack Dec 15, 2020 at 17:59 The |& syntax doesn't seem to work on older versions of bash, e.g., the one included on macOS Mojave. – Quinn Comendant Oct 2, 2021 at 3:25

There should be a program 'curl-config' in curl's 'bin/', i.e. where the 'curl' binary resides.

./curl-config --ca

gives the ca bundle install path.

I just did a whatis curl-config: "Get information about a libcurl installation" so I guess it will only be available if libcurl was installed, which I presume is standard though.

I had to install a package on Ubuntu to run this (you will be shown a list of available options if it's not installed), but using this command led me to the right place! – Robert Dundon Nov 28, 2017 at 20:34 The curl-config program isn't available with all versions of the program or installations. For example, some admins may not understand the purpose of the program and not install it because they think it's only a build configuration tool. Further, if the user that needs the program isn't the admin of a system they can't install it. I have access to two systems, one doesn't have this program, the other gives no output for curl-config --ca . – Mr. Lance E Sloan Dec 1, 2017 at 17:13 I prefer this answer to the accepted one - using strace to find config information shouldn't be necessary. – Ken Williams Dec 28, 2017 at 18:35

I found an easy way: use the --cacert with a wrong file name, the output will show the path.

Example:

~$ curl --cacert non_existing_file https://www.google.com
curl: (77) error setting certificate verify locations:
  CAfile: non_existing_file
  CApath: /etc/ssl/certs
                I thought this looked like a good solution.  However, curl gave me the "77" error, but not the additional information.
– Mr. Lance E Sloan
                Dec 1, 2017 at 17:26
                Some distros don't use the path, only the single file, which will be absent from this output...
– rogerdpack
                Dec 15, 2020 at 18:03
$ curl -v https://google.com
* Rebuilt URL to: https://google.com/
* timeout on name lookup is not supported
*   Trying 172.217.9.174...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0* Connected to google.com (172.217.9.174) port 443 (#0)
* ALPN, offering http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* successfully set certificate verify locations:
*   *CAfile: C:/Program Files/Git/mingw64/ssl/certs/ca-bundle.crt*
                Nope.  It didn't show anything like that for me.  In fact, I compared the output of that with another run adding the -k option to see whether there's a difference.  There was no difference.
– Mr. Lance E Sloan
                Dec 1, 2017 at 17:31
                Unfortunately for me on some boxes all it says is CAfile: none (even when working well) but it does show the right file on some other OS's, and may show the right path. Weird. I guess some have all the cert's in one file while other "split them up" and the latter doesn't show which one it uses. The strace trick seemed to work almost everywhere (see its comments).
– rogerdpack
                Dec 15, 2020 at 18:06
Copy your CA to dir /usr/local/share/ca-certificates/
sudo cp foo.crt /usr/local/share/ca-certificates/foo.crt
Update the CA store
sudo update-ca-certificates
Remove your CA and update the CA store:
sudo update-ca-certificates --fresh
Linux (CentOs 6)
Install the ca-certificates package:
yum install ca-certificates
Enable the dynamic CA configuration feature: update-ca-trust force-enable
Add it as a new file to /etc/pki/ca-trust/source/anchors/:
cp foo.crt /etc/pki/ca-trust/source/anchors/
update-ca-trust extract
Linux (CentOs 5)
Append your trusted certificate to file /etc/pki/tls/certs/ca-bundle.crt
cat foo.crt >>/etc/pki/tls/certs/ca-bundle.crt
https://manuals.gfi.com/en/kerio/connect/content/server-configuration/ssl-certificates/adding-trusted-root-certificates-to-the-server-1605.html very nice link,
which explains, how to add it to several popular OS.
                Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference.
– Gerald Schneider
                Aug 13, 2019 at 12:20
                Another idea:      # strings /usr/lib64/libcurl.so.3 | egrep '^/'      /etc/pki/tls/certs/ca-bundle.crt
– offby1
                Aug 30, 2013 at 18:57