Logjam hotfix for older Conjur servers

logjam-fix.sh

#!/bin/bash -e
#
# Conjur servers older than v4.4.1 might be susceptible to Logjam attack
# (see weakdh.org for details). While the feasibility of such an attack is
# partly mitigated by network architectures Conjur is typically deployed into,
# the following script allows patching older appliances without upgrading to
# the new version.
#
# To apply the hotfix use `logjam-fix.sh apply`:
#   $ wget https://gist.githubusercontent.com/dividedmind/aa32c62508ceefb8186e/raw/logjam-fix.sh
#   $ chmod +x logjam-fix.sh
#   $ sudo ./logjam-fix.sh detect
#   $ sudo ./logjam-fix.sh apply
#
# Note this should be done on every server, whether master, follower or
# standby.
#
# Author: Rafal Rzepecki <[email protected]>
# This script is public domain.

DHPARAM=/etc/ssl/dhparam.pem
NGINXCONF=/etc/nginx/sites-available/conjur
NGINXCONF_BACKUP=$NGINXCONF.logjam.orig

detect() {
  if [ -f $DHPARAM ]; then
    echo $DHPARAM found.
    DHPARAM_PRESENT=true
  fi

  case `grep -q $DHPARAM $NGINXCONF ; echo $?` in
  0)
    echo Nginx configuration looks ok.
    DHPARAM_USED=true
    ;;
  1)
    ;;
  *)
    exit $?
  esac

  if [ -f $NGINXCONF_BACKUP ]; then
    BACKUP_PRESENT=true
  fi
}

case $1 in
  detect)
    detect
    if [ -z "$DHPARAM_PRESENT" ]; then
      echo $DHPARAM not present. Use \`$0 apply\` to generate.
      exit 1
    fi
    if [ -z "$DHPARAM_USED" ]; then
      echo $DHPARAM not used in nginx configuration. Use \`$0 apply\` to fix.
      exit 1
    fi
    echo Your system is safe!
    exit 0
    ;;
  revert)
    detect
    if [ -z "$BACKUP_PRESENT" ]; then
      echo $NGINXCONF_BACKUP not present. Has the hotfix been applied?
      exit 1
    fi
    echo Reverting $NGINXCONF using $NGINXCONF_BACKUP.
    mv -f $NGINXCONF_BACKUP $NGINXCONF
    ;;
  apply)
    detect
    if [ -z "$DHPARAM_PRESENT" ]; then
      echo Generating $DHPARAM. Note this can take a couple of minutes.
      openssl dhparam -out /etc/ssl/dhparam.pem 2048
    fi
    if ! [ -z "$DHPARAM_USED" ]; then
      echo It seems everything is already fine!
      exit 0
    fi
    if ! [ -z "$BACKUP_PRESENT" ]; then
      echo $NGINXCONF_BACKUP present. It seems the hotfix is already applied.
      exit 1
    fi
    echo Updating nginx configuration in $NGINXCONF
    echo Copying existing configuration to $NGINXCONF_BACKUP
    cp $NGINXCONF $NGINXCONF_BACKUP

    cat > $NGINXCONF << \EOF
ssl_certificate /opt/conjur/etc/ssl/conjur.pem;
ssl_certificate_key /opt/conjur/etc/ssl/conjur.key;
ssl on;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;  # don’t use SSLv3 ref: POODLE

server {
  ssl_dhparam /etc/ssl/dhparam.pem;
  ssl_session_cache shared:SSL:10m;

  listen 443;

  proxy_set_header X-Forwarded-Proto $scheme;
  proxy_set_header X-Real_IP $remote_Addr;
  proxy_set_header X-Forwarded_For $proxy_add_x_forwarded_for;

  location /api/authn {
    proxy_pass http://localhost:5000;
  }

  location /api/authz {
    rewrite /api/authz/(.*) /$1 break;
    proxy_pass http://localhost:5100;
  }

  location /api/audit {
    rewrite /api/audit/(.*) /$1 break;
    proxy_pass http://localhost:5300;
    proxy_buffering off;
    # needed to support streaming and chunked encoding
    proxy_http_version 1.1;
  }

  location /api {
    proxy_pass http://localhost:5200;
    proxy_redirect http://localhost:5200/ /api/;
    proxy_redirect https://localhost:5200/ /api/; # for enrollment urls only
  }

  location /api/pubkeys {
    rewrite /api/pubkeys/(.*) /$1 break;
    proxy_pass http://localhost:5400;
  }

  location /api/host_factories {
    proxy_pass http://localhost:5500;
    proxy_redirect http://localhost:5500/ /api/;
  }
}
EOF

    echo Restarting nginx...
    restart nginx
    ;;
  *)
    echo $"Usage: $0 {detect|apply|revert}"
    exit 1
esac