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LDAP policy backend

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This commit is contained in:
Dominik Chilla 2021-02-21 22:26:16 +01:00
parent 2e6b1a0432
commit 10e7b47b38
5 changed files with 66 additions and 20 deletions
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33
LDAP/README.md
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@ -1 +1,32 @@
# ExOTA-Milter with LDAP backend
# ExOTA-Milter with LDAP policy backend
For small setups, with not so many domains, the JSON-file policy backend (default) may be sufficient. If you´re an email service provider (ESP), maintaining a lot of customer domains in a LDAP server, you may want use the LDAP backend instead.
### Configuration
To enable LDAP backend support you need to set up the following environment variables:
```
export MILTER_POLICY_SOURCE=ldap
export MILTER_LDAP_SERVER_URI=ldaps://your.ldap.server
export MILTER_LDAP_SEARCH_BASE=ou=your-customer-domains,dc=example,dc=org
export MILTER_LDAP_QUERY='(domainNameAttr=%d)'
export MILTER_LDAP_BINDDN=uid=exota-milter,ou=apps,dc=example,dc=org
export MILTER_LDAP_BINDPW='$uPer§ecRet1!'
```
The `MILTER_LDAP_QUERY` variable requires a macro/placeholder **%d**, which identifies the domain name to search for in the LDAP tree.
### Use EXoTA-Milter LDAP schema
If you´re willing to use the ExOTA-Milter LDAP schema, you don´t need further configuration. Just feed your LDAP-server with the [ready to use schema file](exota-milter.schema) (auxiliary objectclass) and extend your customers domain objects with the following objectclass and attributes:
Objectclass: `exotaMilterPolicy`
Attributes:
* exotaMilterTenantId
* exotaMilterDkimEnabled
* exotaMilterDkimAlignmentRequired
### Use your custom LDAP schema
If you want to use an own custom LDAP schema with ExOTA-Milter you will have to set up the following environment variables as well:
```
export MILTER_LDAP_TENANT_ID_ATTR=your_custom_tenant_id_attr
export MILTER_LDAP_DKIM_ENABLED_ATTR=your_custom_dkim_enabled_attr
export MILTER_LDAP_DKIM_ALIGNMENT_REQUIRED_ATTR=your_custom_dkim_alignment_required_attr
```
Please make sure that your custom LDAP attributes are set up accordingly the **ExOTA-Milter** [LDAP schema](exota-milter.schema), otherwise your setup will not work as expected!

7
README.md
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@ -102,7 +102,7 @@ Further each Microsoft Exchange-Online tenant has a unique tenant-ID in form of
X-MS-Exchange-CrossTenant-Id: <UUID-of-tenant>
[...]
```
At last the **ExOTA-Milter** needs an additional policy (JSON file), that provides a mapping of *sender-domain <-> tenant-id* and if DKIM-signatures must be taken under consideration or not. The JSON policy file itself looks like this:
At last the **ExOTA-Milter** needs an additional policy (currently as JSON file or LDAP server), that provides a mapping of *sender-domain <-> tenant-id* and if DKIM-signatures must be taken under consideration or not. The JSON policy file itself looks like this:
```
{
"yad.onmicrosoft.com": {
@ -112,8 +112,6 @@ At last the **ExOTA-Milter** needs an additional policy (JSON file), that provid
}
}
```
Actually I´m also working on a LDAP-based version as policy backend.
# The solution
So, *how can an Exchange-Online user/tenant be identified by a third party smarthost?*
@ -127,6 +125,9 @@ Finally it´s the combination of all of the above discussed aspects which may re
![Activity policy](http://www.plantuml.com/plantuml/png/5SKn3W8W30NGg-W1f8cZcuEZSN4tM8aq5ahAhyhjZMzvM-ciyIZXkgd0c0SYpv_q5DIunopErb4w4biZhg9gWVsBJj_BzRWxYw8ujJp_POQy1UisJ8LN6j7q1m00)
# How about using LDAP as policy backend?
For small setups, with not so many domains, the JSON-file policy backend (default) may be sufficient. If you´re an email service provider (ESP) maintaining a lot of customer domains in a LDAP server, you may want to use the LDAP backend instead. Details regarding the LDAP backend can be found [in the LDAP readme](LDAP/README.md).
# How about a docker/OCI image?
## Using prebuilt images from [dockerhub](https://hub.docker.com/)
* AMD64: https://hub.docker.com/r/chillout2k/exota-milter-amd64

24
app/exota-milter.py
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@ -52,6 +52,8 @@ g_milter_add_header = False
g_milter_authservid = None
# ENV[MILTER_LDAP_SERVER_URI]
g_milter_ldap_server_uri = ''
# ENV[MILTER_LDAP_RECEIVE_TIMEOUT]
g_milter_ldap_receive_timeout = 5
# ENV[MILTER_LDAP_BINDDN]
g_milter_ldap_binddn = ''
# ENV[MILTER_LDAP_BINDPW]
@ -594,6 +596,15 @@ if __name__ == "__main__":
logging.error("ENV[MILTER_LDAP_SERVER_URI] is mandatory!")
sys.exit(1)
g_milter_ldap_server_uri = os.environ['MILTER_LDAP_SERVER_URI']
if 'MILTER_LDAP_RECEIVE_TIMEOUT' in os.environ:
try:
g_milter_ldap_receive_timeout = int(os.environ['MILTER_LDAP_RECEIVE_TIMEOUT'])
except ValueError:
logging.error("ENV[MILTER_LDAP_RECEIVE_TIMEOUT] must be an integer!")
sys.exit(1)
logging.info("ENV[MILTER_LDAP_RECEIVE_TIMEOUT]: {0}".format(
g_milter_ldap_receive_timeout
))
if 'MILTER_LDAP_BINDDN' not in os.environ:
logging.info("ENV[MILTER_LDAP_BINDDN] not set! Continue...")
else:
@ -617,17 +628,18 @@ if __name__ == "__main__":
if 'MILTER_LDAP_DKIM_ALIGNMENT_REQUIRED_ATTR' in os.environ:
g_milter_ldap_dkim_alignment_required_attr = os.environ['MILTER_LDAP_DKIM_ALIGNMENT_REQUIRED_ATTR']
try:
set_config_parameter("RESTARTABLE_SLEEPTIME", 2)
set_config_parameter("RESTARTABLE_TRIES", True)
set_config_parameter("RESTARTABLE_SLEEPTIME", 1)
set_config_parameter("RESTARTABLE_TRIES", 2)
set_config_parameter('DEFAULT_SERVER_ENCODING', 'utf-8')
set_config_parameter('DEFAULT_CLIENT_ENCODING', 'utf-8')
server = Server(g_milter_ldap_server_uri, get_info=NONE)
g_milter_ldap_conn = Connection(server,
g_milter_ldap_binddn,
g_milter_ldap_bindpw,
auto_bind=True,
raise_exceptions=True,
client_strategy='RESTARTABLE'
auto_bind = True,
raise_exceptions = True,
client_strategy = 'RESTARTABLE',
receive_timeout = g_milter_ldap_receive_timeout
)
logging.info("LDAP-Connection established")
try:
@ -644,7 +656,7 @@ if __name__ == "__main__":
logging.error("Policy backend error: {0}".format(e.message))
sys.exit(1)
except LDAPException as e:
print("LDAP-Exception: " + traceback.format_exc())
print("LDAP-Exception: {0}".format(e))
sys.exit(1)
else:
logging.debug("Unsupported backend: {0}!".format(g_milter_policy_source))

18
app/policy.py
View File

@ -46,6 +46,10 @@ class ExOTAPolicy():
raise ExOTAPolicyInvalidException(
"Policy must have a 'tenant_id' key!"
)
if policy_dict['tenant_id'] is None:
raise ExOTAPolicyInvalidException(
"'tenant_id' needs a value!"
)
for policy_key in policy_dict:
if policy_key == 'tenant_id':
try:
@ -100,11 +104,11 @@ class ExOTAPolicyBackendJSON(ExOTAPolicyBackend):
"Policy {0} is invalid: {1}".format(policy, e.message)
) from e
except json.decoder.JSONDecodeError as e:
raise ExOTAPolicyException(
raise ExOTAPolicyBackendException(
"JSON-error in policy file: " + str(e)
) from e
except Exception as e:
raise ExOTAPolicyException(
raise ExOTAPolicyBackendException(
"Error reading policy file: " + traceback.format_exc()
) from e
@ -123,7 +127,7 @@ class ExOTAPolicyBackendJSON(ExOTAPolicyBackend):
) from e
########## LDAP
class ExOTAPolicyBackendLDAP(ExOTAPolicyBackendJSON):
class ExOTAPolicyBackendLDAP(ExOTAPolicyBackend):
type = 'ldap'
def __init__(self, ldap_config):
try:
@ -134,7 +138,7 @@ class ExOTAPolicyBackendLDAP(ExOTAPolicyBackendJSON):
self.dkim_enabled_attr = ldap_config['ldap_dkim_enabled_attr']
self.dkim_alignment_required_attr = ldap_config['ldap_dkim_alignment_required_attr']
except Exception as e:
raise ExOTAPolicyException(
raise ExOTAPolicyBackendException(
"An error occured while initializing LDAP backend: " + traceback.format_exc()
) from e
@ -167,7 +171,7 @@ class ExOTAPolicyBackendLDAP(ExOTAPolicyBackendJSON):
policy_dict['dkim_alignment_required'] = False
ExOTAPolicy.check_policy(policy_dict)
return ExOTAPolicy(policy_dict)
if len(self.conn.entries) > 1:
elif len(self.conn.entries) > 1:
raise ExOTAPolicyInvalidException(
"Multiple policies found for domain={0}!".format(from_domain)
)
@ -176,6 +180,4 @@ class ExOTAPolicyBackendLDAP(ExOTAPolicyBackendJSON):
"Policy for domain={0} not found".format(from_domain)
)
except LDAPException as e:
raise ExOTAPolicyBackendException(
"asdf"
) from e
raise ExOTAPolicyBackendException(e) from e

4
tests/miltertest.lua
View File

@ -10,7 +10,7 @@ if mt.conninfo(conn, "localhost", "::1") ~= nil then
error "mt.conninfo() failed"
end
mt.set_timeout(3)
mt.set_timeout(60)
-- 5321.FROM
if mt.mailfrom(conn, "envelope.sender@example.org") ~= nil then
@ -57,7 +57,7 @@ end
if mt.header(conn, "Authentication-RESULTS", "my-auth-serv-id;\n dkim=pass header.d=yad.onmicrosoft.comx header.s=selector1-yad-onmicrosoft-com header.b=mmmjFpv8") ~= nil then
error "mt.header(Subject) failed"
end
if mt.header(conn, "Authentication-RESULTS", "my-auth-serv-id;\n dkim=pass header.d=chillout2k.dex header.s=selector1-yad-onmicrosoft-com header.b=mmmjFpv8") ~= nil then
if mt.header(conn, "Authentication-RESULTS", "my-auth-serv-id;\n dkim=pass header.d=chillout2k.de header.s=selector1-yad-onmicrosoft-com header.b=mmmjFpv8") ~= nil then
error "mt.header(Subject) failed"
end
if mt.header(conn, "Authentication-Results", "my-auth-serv-id;\n dkim=fail header.d=yad.onmicrosoft.com header.s=selector2-asdf header.b=mmmjFpv8") ~= nil then