macos

Root doesn't read from the current user trust settings, but there are both an admin trust settings and root-user-specific trust settings. (These are also distinct from the system trust settings.) Note, also, that certificate trust settings are somewhat distinct from just adding a certificate to a keychain; you can mark a cert as trusted without fully adding it. (The exact situation here is not clear to me, and the docs I've seen are vague.)

You can mark a cert as trusted for your current user as

but that doesn't help with root. The solution, as you might now guess, is either to sudo the above, which then marks it as trusted for the root user specifically:

or to use the -d flag to add it to the admin trust settings:

(OS X will pop up a password dialog to confirm this one.)

Either of the latter two seems to be sufficient for sudo curl.

Reference: https://developer.apple.com/library/mac/Documentation/Darwin/Reference/ManPages/man1/security.1.html