Certificate Authority Certificates

The Public Key Inrastructure is used for many security issues in a Linux system. In order for a certificate to be trusted, it must be signed by a trusted agent called a Certificate Authority (CA). The certificates loaded by this section are from the list on the Mozilla version control system and formats it into a form used by OpenSSL-1.0.1h. The certificates can also be used by other applications either directly of indirectly through openssl.

This package is known to build and work properly using an LFS-7.5 platform.

Introduction to Certificate Authorities

Package Information

[Note]

Note

The certfile.txt file above is actually retrieved from https://hg.mozilla.org/releases/mozilla-release/file/default/security/nss/lib/ckfw/builtins/certdata.txt. It is really an HTML file, but the text file can be retrieved indirectly from the HTML file. The Download URL above automates that process and also adds a line where the date can be extracted as a revision number by the scripts below.

Certificate Authority Certificates Dependencies

Required

OpenSSL-1.0.1h

Recommended

User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/cacerts

Installation of Certificate Authority Certificates

First create a script to reformat a certificate into a form needed by openssl. As the root user:

cat > /bin/make-cert.pl << "EOF"
#!/usr/bin/perl -w

# Used to generate PEM encoded files from Mozilla certdata.txt.
# Run as ./mkcrt.pl > certificate.crt
#
# Parts of this script courtesy of RedHat (mkcabundle.pl)
#
# This script modified for use with single file data (tempfile.cer) extracted
# from certdata.txt, taken from the latest version in the Mozilla NSS source.
# mozilla/security/nss/lib/ckfw/builtins/certdata.txt
#
# Authors: DJ Lucas
#          Bruce Dubbs
#
# Version 20120211

my $certdata = './tempfile.cer';

open( IN, "cat $certdata|" )
    || die "could not open $certdata";

my $incert = 0;

while ( <IN> )
{
    if ( /^CKA_VALUE MULTILINE_OCTAL/ )
    {
        $incert = 1;
        open( OUT, "|openssl x509 -text -inform DER -fingerprint" )
            || die "could not pipe to openssl x509";
    }

    elsif ( /^END/ && $incert )
    {
        close( OUT );
        $incert = 0;
        print "\n\n";
    }

    elsif ($incert)
    {
        my @bs = split( /\\/ );
        foreach my $b (@bs)
        {
            chomp $b;
            printf( OUT "%c", oct($b) ) unless $b eq '';
        }
    }
}
EOF

chmod +x /bin/make-cert.pl

The following script creates the certificates and a bundle of all the certificates. It creates a ./certs directory and ./BLFS-ca-bundle-${VERSION}.crt. Again create this script as the root user:

cat > /bin/make-ca.sh << "EOF"
#!/bin/bash
# Begin make-ca.sh
# Script to populate OpenSSL's CApath from a bundle of PEM formatted CAs
#
# The file certdata.txt must exist in the local directory
# Version number is obtained from the version of the data.
#
# Authors: DJ Lucas
#          Bruce Dubbs
#
# Version 20120211

certdata="certdata.txt"

if [ ! -r $certdata ]; then
  echo "$certdata must be in the local directory"
  exit 1
fi

REVISION=$(grep CVS_ID $certdata | cut -f4 -d'$')

if [ -z "${REVISION}" ]; then
  echo "$certfile has no 'Revision' in CVS_ID"
  exit 1
fi

VERSION=$(echo $REVISION | cut -f2 -d" ")

TEMPDIR=$(mktemp -d)
TRUSTATTRIBUTES="CKA_TRUST_SERVER_AUTH"
BUNDLE="BLFS-ca-bundle-${VERSION}.crt"
CONVERTSCRIPT="/bin/make-cert.pl"
SSLDIR="/etc/ssl"

mkdir "${TEMPDIR}/certs"

# Get a list of staring lines for each cert
CERTBEGINLIST=$(grep -n "^# Certificate" "${certdata}" | cut -d ":" -f1)

# Get a list of ending lines for each cert
CERTENDLIST=`grep -n "^CKA_TRUST_STEP_UP_APPROVED" "${certdata}" | cut -d ":" -f 1`

# Start a loop
for certbegin in ${CERTBEGINLIST}; do
  for certend in ${CERTENDLIST}; do
    if test "${certend}" -gt "${certbegin}"; then
      break
    fi
  done

  # Dump to a temp file with the name of the file as the beginning line number
  sed -n "${certbegin},${certend}p" "${certdata}" > "${TEMPDIR}/certs/${certbegin}.tmp"
done

unset CERTBEGINLIST CERTDATA CERTENDLIST certebegin certend

mkdir -p certs
rm -f certs/*      # Make sure the directory is clean

for tempfile in ${TEMPDIR}/certs/*.tmp; do
  # Make sure that the cert is trusted...
  grep "CKA_TRUST_SERVER_AUTH" "${tempfile}" | \
    egrep "TRUST_UNKNOWN|NOT_TRUSTED" > /dev/null

  if test "${?}" = "0"; then
    # Throw a meaningful error and remove the file
    cp "${tempfile}" tempfile.cer
    perl ${CONVERTSCRIPT} > tempfile.crt
    keyhash=$(openssl x509 -noout -in tempfile.crt -hash)
    echo "Certificate ${keyhash} is not trusted!  Removing..."
    rm -f tempfile.cer tempfile.crt "${tempfile}"
    continue
  fi

  # If execution made it to here in the loop, the temp cert is trusted
  # Find the cert data and generate a cert file for it

  cp "${tempfile}" tempfile.cer
  perl ${CONVERTSCRIPT} > tempfile.crt
  keyhash=$(openssl x509 -noout -in tempfile.crt -hash)
  mv tempfile.crt "certs/${keyhash}.pem"
  rm -f tempfile.cer "${tempfile}"
  echo "Created ${keyhash}.pem"
done

# Remove blacklisted files
# MD5 Collision Proof of Concept CA
if test -f certs/8f111d69.pem; then
  echo "Certificate 8f111d69 is not trusted!  Removing..."
  rm -f certs/8f111d69.pem
fi

# Finally, generate the bundle and clean up.
cat certs/*.pem >  ${BUNDLE}
rm -r "${TEMPDIR}"
EOF

chmod +x /bin/make-ca.sh

Add a short script to remove expired certificates from a directory. Again create this script as the root user:

cat > /bin/remove-expired-certs.sh << "EOF"
#!/bin/bash
# Begin /bin/remove-expired-certs.sh
#
# Version 20120211

# Make sure the date is parsed correctly on all systems
function mydate()
{
  local y=$( echo $1 | cut -d" " -f4 )
  local M=$( echo $1 | cut -d" " -f1 )
  local d=$( echo $1 | cut -d" " -f2 )
  local m

  if [ ${d} -lt 10 ]; then d="0${d}"; fi

  case $M in
    Jan) m="01";;
    Feb) m="02";;
    Mar) m="03";;
    Apr) m="04";;
    May) m="05";;
    Jun) m="06";;
    Jul) m="07";;
    Aug) m="08";;
    Sep) m="09";;
    Oct) m="10";;
    Nov) m="11";;
    Dec) m="12";;
  esac

  certdate="${y}${m}${d}"
}

OPENSSL=/usr/bin/openssl
DIR=/etc/ssl/certs

if [ $# -gt 0 ]; then
  DIR="$1"
fi

certs=$( find ${DIR} -type f -name "*.pem" -o -name "*.crt" )
today=$( date +%Y%m%d )

for cert in $certs; do
  notafter=$( $OPENSSL x509 -enddate -in "${cert}" -noout )
  date=$( echo ${notafter} |  sed 's/^notAfter=//' )
  mydate "$date"

  if [ ${certdate} -lt ${today} ]; then
     echo "${cert} expired on ${certdate}! Removing..."
     rm -f "${cert}"
  fi
done
EOF

chmod +x /bin/remove-expired-certs.sh

The following commands will fetch the certificates and convert them to the correct format. If desired, a web browser may be used instead of wget but the file will need to be saved with the name certdata.txt. These commands can be repeated as necessary to update the CA Certificates.

certhost='http://mxr.mozilla.org'                        &&
certdir='/mozilla/source/security/nss/lib/ckfw/builtins' &&
url="$certhost$certdir/certdata.txt?raw=1"               &&

wget --output-document certdata.txt $url &&
unset certhost certdir url               &&
make-ca.sh                               &&
remove-expired-certs.sh certs

Now, as the root user:

SSLDIR=/etc/ssl                                             &&
install -d ${SSLDIR}/certs                                  &&
cp -v certs/*.pem ${SSLDIR}/certs                           &&
c_rehash                                                    &&
install BLFS-ca-bundle*.crt ${SSLDIR}/ca-bundle.crt         &&
ln -sv ../ca-bundle.crt ${SSLDIR}/certs/ca-certificates.crt &&
unset SSLDIR

Finally, clean up the current directory:

rm -r certs BLFS-ca-bundle*

After installing or updating certificates, if OpenJDK is installed, update the certificates for Java using the procedures at the section called “Install or update the JRE Certificate Authority Certificates (cacerts) file”.

Contents

Installed Programs: make-ca.sh, make-cert.pl and remove-expired-certs.sh
Installed Libraries: None
Installed Directories: /etc/ssl/certs

Short Descriptions

make-ca.sh

is a bash script that reformats the certdata.txt file for use by openssl.

make-cert.pl

is a utility perl script that converts a single binary certificate (.der format) into .pem format.

remove-expired-certs.sh

is a utility perl script that removes expired certificates from a directory. The default directory is /etc/ssl/certs.

Last updated on 2014-03-10 04:39:15 +0000