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Tim Kimber edited this page Feb 18, 2021 · 16 revisions

getssl

Obtain SSL certificates from the letsencrypt.org ACME server. Suitable for automating the process on remote servers.

Features

  • Bash - It runs on virtually all unix machines, including BSD, most Linux distributions, MAC OSX.
  • Get certificates for remote servers - The tokens used to provide validation of domain ownership, and the certificates themselves can be automatically copied to remote servers (via ssh, sftp or ftp for tokens). The script doesn't need to run on the server itself. This can be useful if you don't have access to run such scripts on the server itself, as it's a shared server for example.
  • Runs as a daily cron - so certificates will be automatically renewed when required.
  • Automatic certificate renewals
  • Checks certificates are correctly loaded. After installation of a new certificate it will test the port specified ( see Server-Types for options ) that the certificate is actually being used correctly.
  • Automatically updates - The script can automatically update itself with bug fixes etc if required.
  • Extensively configurable - With a simple configuration file for each certificate it is possible to configure it exactly for your needs, whether a simple single domain or multiple domains across multiple servers on the same certificate.
  • Supports http and dns challenges - Full ACME implementation
  • Simple and easy to use
  • Detailed debug info - Whilst it shouldn't be needed, detailed debug information is available.
  • Reload services - After a new certificate is obtained then the relevant services (e.g. apache/nginx/postfix) can be reloaded.

Installation

Since the script is only one file, you can use the following command for a quick and dirty installation:

curl --silent https://raw.githubusercontent.com/srvrco/getssl/master/getssl > getssl ; chmod 700 getssl

This will copy the getssl Bash script to the current location and change the permissions to make it executable for you.

For a more comprehensive installation (e.g. install also helper scripts) use the provided Makefile with each release tarball. Use the install target.

You'll find the latest version in the git repository:

git clone https://github.com/srvrco/getssl.git

For Arch Linux there are packages in the AUR, see here and there.

If you use puppet, there is a GetSSL Puppet module by dthielking

Overview

GetSSL was written in standard bash ( so it can be run on a server, a desktop computer, or even a virtualbox) and add the checks, and certificates to a remote server ( providing you have a ssh with key, sftp or ftp access to the remote server).

getssl ver. 2.02
Obtain SSL certificates from the letsencrypt.org ACME server

Usage: getssl [-h|--help] [-d|--debug] [-c|--create] [-f|--force] [-a|--all] [-q|--quiet] [-Q|--mute] [-u|--upgrade] [-k|--keep #] [-U|--nocheck] [-r|--revoke cert key] [-w working_dir] domain

Options:
  -a, --all          Check all certificates
  -d, --debug        Outputs debug information
  -c, --create       Create default config files
  -f, --force        Force renewal of cert (overrides expiry checks)
  -h, --help         Display this help message and exit
  -q, --quiet        Quiet mode (only outputs on error, success of new cert, or getssl was upgraded)
  -Q, --mute         Like -q, but mutes notification about successful upgrade
  -r, --revoke   "cert" "key" [CA_server] Revoke a certificate (the cert and key are required)
  -u, --upgrade      Upgrade getssl if a more recent version is available
  -k, --keep     "#" Maximum amount of old getssl versions to keep when upgrading
  -U, --nocheck      Do not check if a more recent version is available
  -w working_dir "Working directory"
  --preferred-chain "chain"   Use an alternate chain for the certificate

Getting started

Once you have obtained the script (see Installation above), the next step is to use

./getssl -c yourdomain.com

where yourdomain.com is the primary domain name that you want to create a certificate for. This will create the following folders and files.

~/.getssl
~/.getssl/getssl.cfg
~/.getssl/yourdomain.com
~/.getssl/yourdomain.com/getssl.cfg

You can then edit ~/.getssl/getssl.cfg to set the values you want as the default for the majority of your certificates.

Then edit ~/.getssl/yourdomain.com/getssl.cfg to have the values you want for this specific domain (make sure to uncomment and specify correct ACL option, since it is required).

You can then just run;

getssl yourdomain.com

and it should run, providing output like;

Registering account
Verify each domain
Verifing yourdomain.com
Verified yourdomain.com
Verifing www.yourdomain.com
Verified www.yourdomain.com
Verification completed, obtaining certificate.
Certificate saved in /home/user/.getssl/yourdomain.com/yourdomain.com.crt
The intermediate CA cert is in /home/user/.getssl/yourdomain.com/chain.crt
copying domain certificate to ssh:server5:/home/yourdomain/ssl/domain.crt
copying private key to ssh:server5:/home/yourdomain/ssl/domain.key
copying CA certificate to ssh:server5:/home/yourdomain/ssl/chain.crt
reloading SSL services

This will (by default) use the staging server, so should give you a certificate that isn't trusted ( Fake Let's Encrypt). Change the server in your config file to get a fully valid certificate.

Note: Verification is done via port 80(http), port 443(https) or dns. The certificate can be used ( and checked with getssl) on alternate ports.

Automating updates

I use the following cron

23  5 * * * /root/scripts/getssl -u -a -q

or you might need to specify -w (working dir)

23  5 * * * /root/scripts/getssl -w /etc/getssl -u -a -q

or you might need to specify the path

23  5 * * * export PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin && /root/scripts/getssl -w /etc/getssl -u -a -q

The cron will automatically update getssl and renew any certificates, only giving output if there are issues / errors.

  • Change /root/scripts/getssl to where the script is installed on your system, e.g. /usr/local/sbin
  • The -u flag updates getssl if there is a more recent version available.
  • The -a flag automatically renews any certificates that are due for renewal.
  • The -q flag is "quiet" so that it only outputs and emails me if there was an error / issue.
  • The -w flag tells getssl which directory to look in for the getssl.cfg file

Structure

The design aim was to provide flexibility in running the code. The default working directory is ~/.getssl ( which can be modified via the command line)

Within the working directory is a config file, getssl.cfg which is a simple bash file containing variables, an example of which is

# Uncomment and modify any variables you need
# The staging server is best for testing (hence set as default)
CA="https://acme-staging.api.letsencrypt.org"
# This server issues full certificates, however has rate limits
#CA="https://acme-v01.api.letsencrypt.org"

AGREEMENT="https://letsencrypt.org/documents/LE-SA-v1.0.1-July-27-2015.pdf"

# Set an email address associated with your account - generally set at account level rather than domain.
ACCOUNT_EMAIL="me@example.com"
ACCOUNT_KEY_LENGTH=4096
ACCOUNT_KEY="/home/user/.getssl/account.key"
PRIVATE_KEY_ALG="rsa"

# The time period within which you want to allow renewal of a certificate - this prevents hitting some of the rate limits.
RENEW_ALLOW="30"

# openssl config file.  The default should work in most cases.
SSLCONF="/usr/lib/ssl/openssl.cnf"

then, within the working directory there will be a folder for each certificate (based on it's domain name). Within that folder will be a config file (again called getssl.cfg). An example of which is;

# Uncomment and modify any variables you need
# see https://github.com/srvrco/getssl/wiki/Config-variables for details
# see https://github.com/srvrco/getssl/wiki/Example-config-files for example configs
#
# The staging server is best for testing
#CA="https://acme-staging.api.letsencrypt.org"
# This server issues full certificates, however has rate limits
#CA="https://acme-v01.api.letsencrypt.org"

#AGREEMENT="https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf"

PRIVATE_KEY_ALG="rsa"

# Additional domains - this could be multiple domains / subdomains in a comma separated list
SANS="www.example.org"

# Acme Challenge Location. The first line for the domain, the following ones for each additional domain.
# If these start with ssh: then the next variable is assumed to be the hostname and the rest the location.
# An ssh key will be needed to provide you with access to the remote server.
# Optionally, you can specify a different userid for ssh/scp to use on the remote server before the @ sign.
# If left blank, the username on the local server will be used to authenticate against the remote server.
# If these start with ftp: then the next variables are ftpuserid:ftppassword:servername:ACL_location
# These should be of the form "/path/to/your/website/folder/.well-known/acme-challenge"
# where "/path/to/your/website/folder/" is the path, on your web server, to the web root for your domain.
# Multiple locations can be defined for a file by separating the locations with a semi-colon.
#ACL=('/var/www/${DOMAIN}/web/.well-known/acme-challenge'
#     'ssh:server5:/var/www/${DOMAIN}/web/.well-known/acme-challenge'
#     'ssh:sshuserid@server5:/var/www/${DOMAIN}/web/.well-known/acme-challenge'
#     'ftp:ftpuserid:ftppassword:${DOMAIN}:/web/.well-known/acme-challenge')


# Location for all your certs, these can either be on the server (so full path name) or using ssh as for the ACL
DOMAIN_CERT_LOCATION="ssh:server5:/etc/ssl/domain.crt"
DOMAIN_KEY_LOCATION="ssh:server5:/etc/ssl/domain.key"
#CA_CERT_LOCATION="/etc/ssl/chain.crt"
#DOMAIN_CHAIN_LOCATION="" this is the domain cert and CA cert
#DOMAIN_PEM_LOCATION="" this is the domain_key. domain cert and CA cert


# The command needed to reload apache / nginx or whatever you use
RELOAD_CMD="service apache2 reload"

# Define the server type. This can be https, ftp, ftpi, imap, imaps, pop3, pop3s, smtp,
# smtps_deprecated, smtps, smtp_submission, xmpp, xmpps, ldaps or a port number which
# will be checked for certificate expiry and also will be checked after
# an update to confirm correct certificate is running (if CHECK_REMOTE) is set to true
#SERVER_TYPE="https"
#CHECK_REMOTE="true"

If a location for a file starts with ssh: it is assumed the next part of the file is the hostname, followed by a colon, and then the path. Files will be securely copied using scp, and it assumes that you have a key on the server ( for passwordless access). You can set the user, port etc for the server in your .ssh/config file

If an ACL starts with ftp: or sftp: it as assumed that the line is in the format "ftp:UserID:Password:servername:/path/to/acme-challenge". sftp requires sshpass. Note: FTP can be used for copying tokens only and can not be used for uploading private key or certificates as it's not a secure method of transfer.

You can also user WebDAV over HTTPS as transport mechanism. To do so, start with davs: followed by username, password, host, port (explicitly needed even if using default port 443) and path on the server. "davs:davsuserid:davspassword:{DOMAIN}:443:/path/to/acme-challenge"

ssh can also be used for the reload command if using on remote servers.

Multiple locations can be defined for a file by separating the locations with a semi-colon.

A typical config file for example.com and www.example.com on the same server would be

# uncomment and modify any variables you need
# The staging server is best for testing
CA="https://acme-staging.api.letsencrypt.org"
# This server issues full certificates, however has rate limits
#CA="https://acme-v01.api.letsencrypt.org"

# additional domains - this could be multiple domains / subdomains in a comma separated list
SANS="www.example.com"

#Acme Challenge Location.   The first line for the domain, the following ones for each additional domain
# Multiple locations can be defined for a file by separating the locations with a semi-colon.
ACL=('/var/www/example.com/web/.well-known/acme-challenge')

USE_SINGLE_ACL="true"

DOMAIN_CERT_LOCATION="/etc/ssl/example.com.crt"
DOMAIN_KEY_LOCATION="/etc/ssl/example.com.key"
CA_CERT_LOCATION="/etc/ssl/example.com.bundle"

RELOAD_CMD="service apache2 reload"

Server-Types

OpenSSL has built-in support for getting the certificate from a number of SSL services these are available in getssl to check if the certificate is installed correctly

Server-Type Port Extra
https 443
ftp 21 FTP Explicit
ftpi 990 FTP Implicit
imap 143 StartTLS
imaps 993
pop3 110 StartTLS
pop3s 995
smtp 25 StartTLS
smtps_deprecated 465
smtps 587 StartTLS
smtp_submission 587 StartTLS
xmpp 5222 StartTLS
xmpps 5269
ldaps 636
port number

##Revoke a certificate

In general revoking a certificate is not required.

usage: getssl -r path/to/cert path/to/key [CA_server]

You need to specify both the certificate you want to revoke, and the account or private domain key which was used to sign / obtain the original certificate. The CA_server is an optional parameter and defaults to Let's Encrypt ( "https://acme-v01.api.letsencrypt.org" ) as that is currently the only Certificate Authority using the ACME protocol.

##Elliptic curve keys You can use Elliptic curve keys for both the account key and the domain key (different of course, don't use the same key for both). prime256v1 (NIST P-256) and secp384r1 (NIST P-384) are both fully supported. secp521r1 (NIST P-521) is included in the code, but not currently supported by Let's Encrypt).

Issues / problems / help

If you have any issues, please log them at https://github.com/srvrco/getssl/issues

There are additional help pages on the wiki

If you have any suggestions for improvements then pull requests are welcomed, or raise an issue.

Clone this wiki locally