Install and trust DoD CA certificates on Mac OS X. Tested on Catalina and Mojave. *NOTE*: This should also enable CAC if you didn't override the system drivers.

import_dod_certs_mac.sh

#!/bin/bash 

set -eu -o pipefail

export CERT_URL='https://dl.dod.cyber.mil/wp-content/uploads/pki-pke/zip/unclass-certificates_pkcs7_DoD.zip'

# Download & Extract DoD root certificates
cd ~/Downloads/ || exit 1
/usr/bin/curl -LOJ "${CERT_URL}"

/usr/bin/unzip -o "$(basename "${CERT_URL}")"

cd "$(/usr/bin/zipinfo -1 "$(basename "${CERT_URL}")" | /usr/bin/awk -F/ '{ print $1 }' | head -1)" || exit 1

# Convert .p7b certs to straight pem and import
for item in *.p7b; do
  TOPDIR=$(pwd)
  TMPDIR=$(mktemp -d "/tmp/$(basename "${item}" .p7b).XXXXXX") || exit 1
  PEMNAME=$(basename "${item}" .p7b)
  openssl pkcs7 -print_certs -in "${item}" -inform der -out "${TMPDIR}/${PEMNAME}"
  cd "${TMPDIR}"
  /usr/bin/split -p '^$' "${PEMNAME}"
  rm "$(find . -name "x*" | sort | tail -1)"
  for cert in x??; do
    sudo security add-trusted-cert -d -r trustRoot -k /Library/Keychains/System.keychain "${cert}"
  done
  
  cd "${TOPDIR}"
  rm -rf "${TMPDIR}"
done

Added your updates @dinosaurhead and some linter goodness to make shellcheck happy. Thanks for the input.

When running this a device running on macOS Sonoma 14.5 it was able to successfully import only the Root CA certificates and all other intermediate CA certs show as not trusted. I have resolved this by filtering through the certs by their CN (I know probably not the best way, but it works) and importing the Root CA certs with the resultType of trustRoot (this is what was done for all of the certs previously) and importing the Intermediate CA certs with the resultType of TrustAsRoot. Here is the adjusted script for this:

#!/bin/bash 

set -eu -o pipefail

export CERT_URL='https://dl.dod.cyber.mil/wp-content/uploads/pki-pke/zip/unclass-certificates_pkcs7_DoD.zip'

# Download & Extract DoD root certificates
cd /Users/Shared || exit 1
/usr/bin/curl -LOJ "${CERT_URL}"

/usr/bin/unzip -o "$(basename "${CERT_URL}")"

cd "$(/usr/bin/zipinfo -1 "$(basename "${CERT_URL}")" | /usr/bin/awk -F/ '{ print $1 }' | head -1)" || exit 1

# Convert .p7b certs to straight pem and import
for item in *.p7b; do
  TOPDIR=$(pwd)
  TMPDIR=$(mktemp -d "/tmp/$(basename "${item}" .p7b).XXXXXX") || exit 1
  PEMNAME=$(basename "${item}" .p7b)
  openssl pkcs7 -print_certs -in "${item}" -inform der -out "${TMPDIR}/${PEMNAME}"
  cd "${TMPDIR}"
  /usr/bin/split -p '^$' "${PEMNAME}"
  rm "$(find . -name "x*" | sort | tail -1)"
  for cert in x??; do
    CERTCN="$(openssl x509 -noout -subject -in ${cert} | sed -n '/^subject/s/^.*CN=//p')"
    if [[ "${CERTCN}" == *"DoD Root CA"* ]]; then
      sudo security add-trusted-cert -d -r trustRoot -k /Library/Keychains/System.keychain "${cert}"
      echo "${CERTCN} has been added as a trusted Root CA to the system certificate keychain."
    elif [[ "${CERTCN}" == *"DOD"* ]] && [[ "${CERTCN}" != *"DoD Root CA"* ]]; then
      sudo security add-trusted-cert -d -r trustAsRoot -k /Library/Keychains/System.keychain "${cert}"
      echo "${CERTCN} has been added as a trusted CA to the system certificate keychain."
    else
      echo "The certificate with the common name ${CERTCN} is not a DoD CA cert."
    fi
  done
  
  cd "${TOPDIR}"
  rm -rf "${TMPDIR}"
done

Thanks @Crimsonize and @dcode, it worked great.