acme_certificate: allow 'no challenge' (#615)

* Allow 'no challenge'.

* Fix undefined variable.

changelogs/fragments/615-no-challenge.yml

@@ -0,0 +1,4 @@
+minor_changes:
+  - "acme_certificate - allow to use no challenge by providing ``no challenge`` for the ``challenge`` option.
+     This is needed for ACME servers where validation is done without challenges
+     (https://github.com/ansible-collections/community.crypto/issues/613, https://github.com/ansible-collections/community.crypto/pull/615)."

plugins/modules/acme_certificate.py

@@ -124,10 +124,19 @@
     type: bool
     default: true
   challenge:
-    description: The challenge to be performed.
+    description:
+      - The challenge to be performed.
+      - If set to C(no challenge), no challenge will be used. This is necessary for some private
+        CAs which use External Account Binding and other means of validating certificate assurance.
+        For example, an account could be allowed to issue certificates for C(foo.example.com)
+        without any further validation for a certain period of time.
     type: str
     default: 'http-01'
-    choices: [ 'http-01', 'dns-01', 'tls-alpn-01' ]
+    choices:
+      - 'http-01'
+      - 'dns-01'
+      - 'tls-alpn-01'
+      - 'no challenge'
   csr:
     description:
       - "File containing the CSR for the new certificate."
@@ -578,6 +587,9 @@
 )
 
 
+NO_CHALLENGE = 'no challenge'
+
+
 class ACMECertificateClient(object):
     '''
     ACME client class. Uses an ACME account object and a CSR to
@@ -589,6 +601,9 @@ def __init__(self, module, backend):
         self.module = module
         self.version = module.params['acme_version']
         self.challenge = module.params['challenge']
+        # We use None instead of a magic string for 'no challenge'
+        if self.challenge == NO_CHALLENGE:
+            self.challenge = None
         self.csr = module.params['csr']
         self.csr_content = module.params['csr_content']
         self.dest = module.params.get('dest')
@@ -696,7 +711,7 @@ def get_challenges_data(self, first_step):
                 continue
             # We drop the type from the key to preserve backwards compatibility
             data[identifier] = authz.get_challenge_data(self.client)
-            if first_step and self.challenge not in data[identifier]:
+            if first_step and self.challenge is not None and self.challenge not in data[identifier]:
                 raise ModuleFailException("Found no challenge of type '{0}' for identifier {1}!".format(
                     self.challenge, type_identifier))
         # Get DNS challenge data
@@ -735,7 +750,14 @@ def finish_challenges(self):
         for type_identifier, authz in self.authorizations.items():
             if authz.status == 'pending':
                 identifier_type, identifier = split_identifier(type_identifier)
-                authz.call_validate(self.client, self.challenge)
+                if self.challenge is not None:
+                    authz.call_validate(self.client, self.challenge)
+                # If there is no challenge, we must check whether the authz is valid
+                elif authz.status != 'valid':
+                    authz.raise_error(
+                        'Status is not "valid", even though no challenge should be necessary',
+                        module=self.client.module,
+                    )
                 self.changed = True
 
     def download_alternate_chains(self, cert):
@@ -832,7 +854,7 @@ def main():
         account_email=dict(type='str'),
         agreement=dict(type='str'),
         terms_agreed=dict(type='bool', default=False),
-        challenge=dict(type='str', default='http-01', choices=['http-01', 'dns-01', 'tls-alpn-01']),
+        challenge=dict(type='str', default='http-01', choices=['http-01', 'dns-01', 'tls-alpn-01', NO_CHALLENGE]),
         csr=dict(type='path', aliases=['src']),
         csr_content=dict(type='str'),
         data=dict(type='dict'),