add lua app password script

README.md

@@ -29,8 +29,8 @@ Which authentication mechanism to use for the smtp relay.
 
 Whether to use starttls for the smtp relay.
 
-## LDAP_URI
-Complete uri for the authentication ldap host.
+## LDAP_HOST
+Ldap hostname (can include the port).
 
 ## LDAP_SIEVE_HOST
 Has to be the same as `LDAP_URI` but in a different format (like `ldap:389`).
@@ -73,6 +73,12 @@ The ldap attribute which contains the sieve rules.
 
 Whether to use tls when connecting to the ldap host.
 
+## LDAP_APP_PASSWORDS_BASE_DN
+Base DN to look for app passwords for a user.
+
+## LDAP_APP_PASSWORDS_FILTER
+Specifies the filter on what counts as an app password.
+
 ## LDAP_DEFAULT_PASSSCHEME
 - default: SSHA
 

rootfs/etc/confd/templates/auth-ldap.conf.ext.tmpl

@@ -3,6 +3,11 @@ passdb {
   args = /etc/dovecot/dovecot-ldap.conf.ext
 }
 
+passdb {
+   driver = lua
+   args = file=/etc/dovecot/app-password-lookup.lua
+}
+
 userdb {
   driver = static
   args = uid=vmail gid=vmail home=/var/lib/vmail/mail/%d/%n

rootfs/etc/confd/templates/dovecot-ldap.conf.ext.tmpl

@@ -1,4 +1,4 @@
-uris = {{getenv "LDAP_URI"}}
+uris = ldap://{{getenv "LDAP_URI"}}
 dn = {{getenv "LDAP_BIND_DN"}}
 dnpass = {{getenv "LDAP_BIND_PASSWORD"}}
 tls = {{getenv "LDAP_USE_TLS" "yes"}}

rootfs/etc/dovecot/app-password-lookup.lua

@@ -0,0 +1,50 @@
+require "lualdap"
+
+function auth_passdb_lookup(req)
+    ldap_use_tls_env = os.getenv("LDAP_USE_TLS")
+    ldap_use_tls = ldap_use_tls_env == "true" and true or false
+
+    ld = assert (lualdap.open_simple(
+        os.getenv("LDAP_HOST"),
+        os.getenv("LDAP_BIND_DN"),
+        os.getenv("LDAP_BIND_PASSWORD"),
+        ldap_use_tls))
+
+    local username = req.username
+    local ldap_pass_filter = os.getenv("LDAP_PASS_FILTER"):gsub("%%u", username)
+
+    local user_count = 0
+    for dn, attribs in ld:search { base = os.getenv("LDAP_BASE_DN"), scope = "subtree", filter = ldap_pass_filter } do
+        user_count = user_count + 1
+    end
+
+    local user_exists = user_count == 1
+    if user_exists then
+        local app_base_dn = os.getenv("LDAP_APP_PASSWORDS_BASE_DN")
+        local app_pass_filter = os.getenv("LDAP_APP_PASSWORDS_FILTER")
+
+        local user_password = reg.password
+
+        for dn, attribs in ld:search { base = app_base_dn:gsub("%%u", username), scope = "subtree", filter = app_pass_filter } do
+            lualdap.open_simple(
+                os.getenv("LDAP_HOST"),
+                dn,
+                user_password,
+                ldap_use_tls)
+            if test_conn ~= nil then
+                return dovecot.auth.PASSDB_RESULT_OK, string.format("%s=user", os.getenv("LDAP_USER_ATTRIBUTE"))
+            end
+        end
+    else
+        return dovecot.auth.PASSDB_RESULT_USER_UNKNOWN, "no such user"
+    end
+
+    return dovecot.auth.PASSDB_RESULT_NEXT, "no app password matches"
+end
+
+function script_init()
+    return 0
+end
+
+function script_deinit()
+end