feat(mtail): deploy filtermail.mtail and gate mtail rule copy on mtail_address

Deploy filtermail.mtail program along delivered_mail.mtail, fetched from
upstream; for this, refactor download_executable to accept mode, so we
can use it to upload non-binaries.
refactor: make hashes (for uniformity) and mtail version (for use by
mtail deployer) module constants.

Additionally, gate both mtail programs on mtail_address being set.

cmdeploy/src/cmdeploy/basedeploy.py

@@ -227,7 +227,7 @@ class Deployer:
         res = files.directory(name=name, path=path, present=False, **kwargs)
         return self._update_restart_signals(path, res)
 
-    def download_executable(self, url, dest, sha256sum, extract=None):
+    def download_executable(self, url, dest, sha256sum, extract=None, mode="755"):
         existing = host.get_fact(Sha256File, dest)
         if existing == sha256sum:
             return
@@ -244,7 +244,7 @@ class Deployer:
                 f"({dl_cmd}"
                 f" && echo '{sha256sum}  {tmp}' | sha256sum -c"
                 f" && mv {tmp} {dest})",
-                f"chmod 755 {dest}",
+                f"chmod {mode} {dest}",
             ],
         )
         self.need_restart = True

cmdeploy/src/cmdeploy/filtermail/deployer.py

@@ -4,6 +4,13 @@ from pyinfra import facts, host
 
 from cmdeploy.basedeploy import Deployer
 
+VERSION = "v0.7.4" # also gets used by mtail deployer
+SHA256SUMS = {
+    "x86_64": "484cb8dff083134aefba9fce4a6b7ef4784a0f0e28e5108ecf8bb9e58a44fd2c",
+    "aarch64": "66aa0ca2ca9add7a12d92883d76f8786384092adfde24a3d3a1d0b1f30d23a9e",
+}
+MTAIL_PROGRAM_SHA256 = "948f688bb89ad47e6eb0fc8fa107e201a689f5adc264ff926be487a2a8562b51"
+
 
 class FiltermailDeployer(Deployer):
     services = ["filtermail", "filtermail-incoming", "filtermail-transport"]
@@ -20,12 +27,8 @@ class FiltermailDeployer(Deployer):
             return
 
         arch = host.get_fact(facts.server.Arch)
-        url = f"https://github.com/chatmail/filtermail/releases/download/v0.7.4/filtermail-{arch}"
-        sha256sum = {
-            "x86_64": "484cb8dff083134aefba9fce4a6b7ef4784a0f0e28e5108ecf8bb9e58a44fd2c",
-            "aarch64": "66aa0ca2ca9add7a12d92883d76f8786384092adfde24a3d3a1d0b1f30d23a9e",
-        }[arch]
-        self.download_executable(url, self.bin_path, sha256sum)
+        url = f"https://github.com/chatmail/filtermail/releases/download/{VERSION}/filtermail-{arch}"
+        self.download_executable(url, self.bin_path, SHA256SUMS[arch])
 
     def configure(self):
         for service in self.services:

cmdeploy/src/cmdeploy/mtail/deployer.py

@@ -2,6 +2,10 @@ from pyinfra import facts, host
 from pyinfra.operations import apt
 
 from cmdeploy.basedeploy import Deployer
+from cmdeploy.filtermail.deployer import (
+    MTAIL_PROGRAM_SHA256 as FILTERMAIL_MTAIL_SHA256,
+    VERSION as FILTERMAIL_VERSION,
+)
 
 
 class MtailDeployer(Deployer):
@@ -42,9 +46,16 @@ class MtailDeployer(Deployer):
             bin_path=self.bin_path,
             progs_dir=self.progs_dir,
         )
-        self.put_file(
-            "mtail/delivered_mail.mtail", f"{self.progs_dir}/delivered_mail.mtail"
-        )
+        if self.mtail_address:
+            self.put_file(
+                "mtail/delivered_mail.mtail", f"{self.progs_dir}/delivered_mail.mtail"
+            )
+            self.download_executable(
+                f"https://raw.githubusercontent.com/chatmail/filtermail/{FILTERMAIL_VERSION}/contrib/filtermail.mtail",
+                f"{self.progs_dir}/filtermail.mtail",
+                FILTERMAIL_MTAIL_SHA256,
+                mode="644",
+            )
 
     def activate(self):
         active = bool(self.mtail_address)