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123 lines
16 KiB
Markdown
123 lines
16 KiB
Markdown
ACERTMGR
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========
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This is an automated certificate manager using ACME/letsencrypt with minimal dependencies.
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Running ACERTMGR
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----------------
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The main file acertmgr.py is intended to be run regularly (e.g. as daily cron job / systemd timer) as root or user with enough privileges.
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Requirements
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------------
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* Python (2.7+ and 3.5+ should work)
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* cryptography>=0.6 (usually includes the optional idna module)
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Optional requirements (to use specified features)
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------------------------------------------------------
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* PyYAML: to parse YAML-formatted configuration files
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* dnspython: used by dns.* challenge handlers
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* idna: to allow automatic conversion of unicode domain names to their IDNA2008 counterparts
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* cryptography>=2.1: for creating certificates with the OCSP must-staple flag (cert_must_staple)
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* cryptography>=2.6: for usage of Ed25519/Ed448 keys
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Setup
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-----
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You should decide which challenge mode you want to use with acertmgr:
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* webdir: In this mode, responses to challenges are put into a directory, to be served by an existing webserver
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* standalone: In this mode, challenges are completed by acertmgr directly. This starts a webserver to solve the challenges, which can be used standalone or together with an existing webserver that forwards request to a specified local port/address.
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* dns.*: This mode puts the challenge into a TXT record for the domain (usually _acme-challenge.<domain>) where it will be parsed from by the authority
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* dns.* (Alias mode): Can be used similar to the above but allows redirection of _acme-challenge.<domain> to any other (updatable domain) defined in dns_updatedomain via CNAME (e.g. _acme-challenge.example.net IN CNAME bla.foo.bar with dns_updatedomain="bla.foo.bar" in domainconfig)
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* dns.nsupdate: Updates the TXT record using RFC2136
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You can optionally provide the private key files to be used with the ACME protocol (if you do not they will be automatically created):
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* The account private key is (by default) expected at `/etc/acertmgr/account.key` (used to register an account with the authorities server)
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* The domain private keys are (by default) expected at `/etc/acertmgr/{cert_id}.key`
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* If you are missing these keys, they will be created for you (using RSA with the configured key_length) or you can create them using e.g. `openssl genrsa 4096 > /etc/acertmgr/account.key`
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* Do not forget to set proper permissions of the keys using `chmod 0400 /etc/acertmgr/*.key` if you created those manually
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Finally, you need to setup the configuration files, as shown in the next section.
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While testing, you can use the acme-staging authority instead, in order to avoid issuing too many certificates.
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Authorities (e.g. our default Let's Encrypt) will require you to accept their Terms of Service. This can be done either in the optional global config file and/or via a commandline parameter (see acertmgr.py --help).
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Configuration
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-------------
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Configuration examples are included in the `docs/` directory. All configuration files can use yaml (requires PyYAML) or json syntax. (Note: The JSON examples may be incomplete due to inability to express comments in JSON)
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Unless specified with a commandline parameter (see acertmgr.py --help) the optional global configuration is read from `/etc/acertmgr/acertmgr.conf`.
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Domains for which certificates should be obtained/renewed are be configured in `/etc/acertmgr/*.conf` (the global configuration is always excluded if it is in the same directory).
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By default the directory (work_dir) containing the working data (csr,certificate,key and ca files) is located at `/etc/acertmgr/`.
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4 configuration contexts are known (*domainconfig (d) > globalconfig (g) > commandline (c) > built-in defaults*) with the following directives (subject to change, usual usage context written bold):
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| Directive | Context | Description | Built-in Default |
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| --- | --- | --- | --- |
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| -c/--config-file | **c** | global configuration file (optional) | /etc/acertmgr/acertmgr.conf |
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| -d/--config-dir | **c** | directory containing domain configuration files (ending with .conf, globalconfig will be excluded automatically if in same directory) | /etc/acertmgr/*.conf |
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| -w/--work-dir | **c** | working directory containing csr/certificates/keys/ca files | /etc/acertmgr |
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| --force-renew | **c** | (or --renew-now) Immediately renew all certificates containing the given domain(s) | |
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| --revoke | **c** | Revoke the certificate at the given path | |
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| --revoke-reason | **c** | Provide a reason code for the revocation (see https://tools.ietf.org/html/rfc5280#section-5.3.1 for valid values) | |
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| domain (san-domain...): | **d** | (domainconfig section start) Domains to use in the cert request. This value will be MD5-hashed as cert_id. | |
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| api | d,**g** | Determines the API version used | v2 |
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| authority | d,**g** | URL to the certificate authorities API | https://acme-v02.api.letsencrypt.org |
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| authority_tos_agreement | d,**g**,c | Indicates agreement to the ToS of the certificate authority (--authority-tos-agreement on command line) | |
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| authority_contact_email | d,**g** | (v2 API only) Contact e-mail to be registered with your account key | |
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| account_key | d,**g** | Path to the account key | {work_dir}/account.key |
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| account_key_algorithm | d,**g** | Key-algorithm for newly generated account keys (RSA, EC, ED25519, ED448) | RSA |
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| account_key_length | d,**g** | Key-length for newly generated RSA account keys (in bits) or EC curve (256=P-256, 384=P-384, 521=P-521) | depends on account_key_algorithm |
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| ttl_days | d,**g** | Renew certificate if it has less than this value validity left | 30 |
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| cert_dir | d,**g** | Directory containing all certificate related data (crt,key,csr) | {work_dir} |
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| key_algorithm | d,**g** | Key-algorithm for newly generated private keys (RSA, EC, ED25519, ED448) | RSA |
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| key_length | d,**g** | Key-length for newly generated RSA private keys (in bits) or EC curve (256=P-256, 384=P-384, 521=P-521) | depends on key_algorithm |
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| csr_static | **d**,g | Whether to re-use a static CSR or generate a new dynamic CSR | false |
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| csr_file | **d**,g | Path to store (and load) the certificate CSR file | {cert_dir}/{cert_id}.csr |
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| ca_static | **d**,g | Whether to re-use a static CA or download a CA file | false |
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| ca_file | **d**,g | Path to store (and load) the certificate authority file | {cert_dir}/{cert_id}.ca |
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| cert_file | **d** | Path to store (and load) the certificate file | {cert_dir}/{cert_id}.crt |
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| cert_revoke_superseded | **d**,g | Revoke the previous certificate with reason "superseded" after successful deployment | false |
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| cert_must_staple | **d**,g | Generate a certificate (request) with the OCSP must-staple flag (will be honoured on the next newly generated CSR if using csr_static=true) | false |
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| key_file | **d**,g | Path to store (and load) the private key file | {cert_dir}/{cert_id}.key |
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| mode | **d**,g | Mode of challenge handling used | standalone |
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| webdir | **d**,g | [webdir] Put acme challenges into this path | /var/www/acme-challenge/ |
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| http_verify | **d**,g | [webdir/standalone] Verify challenge before attempting authorization | true |
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| bind_address | **d**,g | [standalone] Serve the challenge using a HTTP server on given IP | |
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| port | **d**,g | [standalone] Serve the challenge using a HTTP server on this port | 80 |
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| dns_ttl | **d**,g | [dns.*] Write TXT records with this TTL (also determines the update wait time at twice this value | 60 |
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| dns_updatedomain | **d**,g | [dns.*] Write the TXT records to this domain (you have to create the necessary CNAME on the real challenge domain manually) | |
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| dns_verify_interval | **d**,g | [dns.*] Do verification checks when starting the challenge every {dns_verify_interval} seconds | 10 |
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| dns_verify_failtime | **d**,g | [dns.*] Fail challenge TXT record verification after {dns_verify_failtime} seconds | {dns_waittime} + 1 |
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| dns_verify_waittime | **d**,g | [dns.*] Assume DNS challenges are valid after {dns_verify_waittime} | 2 * {dns_ttl} |
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| dns_verify_all_ns | **d**,g | [dns.*] Verify DNS challenges by querying all known zone NS servers (resolved by zone master from SOA or dns_verify_server) | false |
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| dns_verify_server | **d**,g | [dns.*] Verify DNS challenges by querying this DNS server unless 'dns_verify_all_ns' is enabled, then use to determine zone NS | |
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| nsupdate_server | **d**,g | [dns.nsupdate] DNS Server to delegate the update to | {determine from zone SOA} |
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| nsupdate_verify | **d**,g | [dns.nsupdate] Verify TXT record on the update server upon creation | true |
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| nsupdate_keyfile | **d**,g | [dns.nsupdate] Bind-formatted TSIG key file to use for updates (may be used instead of nsupdate_key*) | |
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| nsupdate_keyname | **d**,g | [dns.nsupdate] TSIG key name to use for updates | |
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| nsupdate_keyvalue | **d**,g | [dns.nsupdate] TSIG key value to use for updates | |
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| nsupdate_keyalgorithm | **d**,g | [dns.nsupdate] TSIG key algorithm to use for updates | HMAC-MD5.SIG-ALG.REG.INT |
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| defaults: | **g** | Default deployment action settings used by all domains | |
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| path | **d** | (deployment) deploy certificate data to the given file | |
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| format | **d**,g(defaults) | (deployment) deploy one or more of the following data to the file at path: key,crt,ca | |
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| user | **d**,g(defaults) | (deployment) change the user of the file deployed at path to this value (optional, defaults to acertmgr current effective user) | |
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| group | **d**,g(defaults) | (deployment) change the group of the file deployed at path to this value (optional,defaults to acertmgr current effective group) | |
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| perm | **d**,g(defaults) | (deployment) change the permissions of the file deployed at path to this value (optional, CAUTION: uses system defaults for new files) | |
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| action | **d**,g(defaults) | (deployment) run the following action after deployment is finished. This command will be run in a shell and supports it's syntax. (optional) | |
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Security
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--------
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Please keep the following in mind when using this software:
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* DO read the source code, since it (usually) will be run as root
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* Make sure that your configuration files are NOT writable by other users - arbitrary commands can be executed after updating certificates
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* Try to run this program non-privileged if possible. This requires you to:
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* Create a dedicated user for acertmgr (e.g. acertmgr)
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* Run a acertmgr as that user (add acertmgr to that users cron!)
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* Access rights to read/write all files configured with the created user
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* Run any programs/scripts defined on cert update as the created user (might need work-arounds with sudo or wrapper scripts) |