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#!/bin/sh
# Wrapper around openssl to generate self-signed X.509 server
# certificates or Certificate Signing Requests, or DKIM private keys.
# Inspired from make-ssl-cert(8) and opendkim-genkey(8).
#
# Copyright © 2014 Guilhem Moulin <guilhem@fripost.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
set -ue
PATH=/usr/bin:/bin
# Default values
type=rsa
bits=
hash=
force=0
config=
pubkey=pubkey.pem
privkey=privkey.pem
dns=
ou=
cn=
usage=
chmod=
chown=
usage() {
cat >&2 <<- EOF
Usage: $0 command [OPTIONS]
Command:
x509: generate a self-signed X.509 server certificate
csr: generate a Certificate Signing Request
dkim: generate a private key (to use for DKIM signing)
Options:
-t type: key type (default: rsa)
-b bits: key length or EC curve (default: 2048 for RSA, 1024 for DSA, secp224r1 for ECDSA)
-h digest: digest algorithm
--ou: organizational Unit Name; can be repeated
--cn: common Name (default: \$(hostname --fqdn)
--dns: hostname for AltName; can be repeated
-f: force; can be repeated (0: don't overwrite, default;
1: reuse private key if it exists;
2: overwrite both keys if they exist)
--config: configuration file
--pubkey: public key file (default: pubkey.pem)
--privkey: private key file (default: privkey.pem; created with og-rwx)
--usage: key usage (default: digitalSignature,keyEncipherment)
--chmod: chmod the private key
--chown: chown the private key
Return values:
0 The key pair was successfully generated
1 The public or private key file exists, and -f is not set
2 The key generation failed
EOF
}
dkiminfo() {
echo "Add the following TXT record to your DNS zone:"
echo "${cn:-$(date +%Y%m%d)}._domainkey\tIN\tTXT ( "
# See https://tools.ietf.org/html/rfc4871#section-3.6.1
# t=s: the "i=" domain in signature headers MUST NOT be a subdomain of "d="
# s=email: limit DKIM signing to email
openssl pkey -pubout <"$privkey" | sed '/^--.*--$/d' \
| { echo -n "v=DKIM1; k=$type; t=s; s=email; p="; tr -d '\n'; } \
| fold -w 250 \
| { sed 's/.*/\t"&"/'; echo ' )'; }
}
[ $# -gt 0 ] || { usage; exit 2; }
cmd="$1"; shift
case "$cmd" in
x509|csr|dkim) ;;
*) echo "Unrecognized command: $cmd" >&2; exit 2
esac
nou=1
while [ $# -gt 0 ]; do
case "$1" in
-t) shift; type="$1";;
-t*) type="${1#-t}";;
-b) shift; bits="$1";;
-b*) bits="${1#-b}";;
-h) shift; hash="$1";;
-h*) hash="${1#-h}";;
--dns=?*) dns="${dns:+$dns, }DNS:${1#--dns=}";;
--cn=?*) cn="${1#--cn=}";;
--ou=?*) ou="${ou:+$ou\n}$nou.organizationalUnitName = ${1#--ou=}"
nou=$(( 1 + $nou ));;
-f) force=$(( 1 + $force ));;
--pubkey=?*) pubkey="${1#--pubkey=}";;
--privkey=?*) privkey="${1#--privkey=}";;
--usage=?*) usage="${usage:+$usage,}${1#--usage=}";;
--config=?*) dns="${1#--config=}";;
--chmod=?*) chmod="${1#--chmod=}";;
--chown=?*) chown="${1#--chown=}";;
--help) usage; exit;;
*) echo "Unrecognized argument: $1" >&2; exit 2
esac
shift;
done
rand=/dev/urandom
case "$type" in
# XXX: genrsa and dsaparam have been deprecated in favor of genpkey.
# genpkey can also create explicit EC parameters, but not named.
rsa) genkey=genrsa; genkeyargs="-f4 ${bits:-2048}";;
dsa) genkey=dsaparam; genkeyargs="-noout -genkey ${bits:-1024}";;
# See 'openssl ecparam -list_curves' for the list of supported
# curves. StrongSwan doesn't support explicit curve parameters
# (however explicit parameters might be required to make exotic
# curves work with some clients.)
ecdsa) genkey=ecparam
genkeyargs="-noout -name ${bits:-secp224r1} -param_enc named_curve -genkey";;
*) echo "Unrecognized key type: $type" >&2; exit 2
esac
if [ "$cmd" = x509 -o "$cmd" = csr ]; then
case "$hash" in
md5|rmd160|sha1|sha224|sha256|sha384|sha512|'') ;;
*) echo "Invalid digest algorithm: $hash" >&2; exit 2;
esac
[ "$cn" ] || cn="$(hostname --fqdn)"
[ ${#cn} -le 64 ] || { echo "CommonName too long: $cn" >&2; exit 2; }
fi
if [ -z "$config" -a \( "$cmd" = x509 -o "$cmd" = csr \) ]; then
config=$(mktemp) || exit 2
trap 'rm -f "$config"' EXIT
# see /usr/share/ssl-cert/ssleay.cnf
cat >"$config" <<- EOF
[ req ]
distinguished_name = req_distinguished_name
prompt = no
policy = policy_anything
req_extensions = v3_req
x509_extensions = v3_req
[ req_distinguished_name ]
organizationName = Fripost
organizationalUnitName = SSLcerts
$(echo "$ou")
commonName = $cn
[ v3_req ]
subjectAltName = email:admin@fripost.org${dns:+, $dns}
basicConstraints = critical, CA:FALSE
# https://security.stackexchange.com/questions/24106/which-key-usages-are-required-by-each-key-exchange-method
keyUsage = critical, ${usage:-digitalSignature, keyEncipherment}
EOF
fi
if [ -s "$privkey" -a $force -eq 0 ]; then
echo "Error: private key exists: $privkey" >&2
[ "$cmd" = dkim ] && dkiminfo
exit 1
elif [ ! -s "$privkey" -o $force -ge 2 ]; then
# Ensure "$privkey" is created with umask 0077
mv -f "$(mktemp)" "$privkey" || exit 2
chmod "${chmod:-og-rwx}" "$privkey" || exit 2
[ -z "$chown" ] || chown "$chown" "$privkey" || exit 2
openssl $genkey -rand /dev/urandom $genkeyargs >"$privkey" || exit 2
[ "$cmd" = dkim ] && { dkiminfo; exit; }
fi
if [ "$cmd" = x509 -o "$cmd" = csr ]; then
if [ -s "$pubkey" -a $force -eq 0 ]; then
echo "Error: public key exists: $pubkey" >&2
exit 1
else
[ "$cmd" = x509 ] && x509=-x509 || x509=
openssl req -config "$config" -new $x509 ${hash:+-$hash} -days 3650 -key "$privkey" >"$pubkey" || exit 2
fi
fi
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