feat: support self-signed chatmail relays (#855)

feat: support self-signed TLS via underscore domain convention
Domains starting with "_" (e.g. _chat.example.org) automatically use
self-signed TLS certificates instead of ACME/Let's Encrypt. The TLS
mode is derived from the domain name — no separate config option needed.

Internally, when config.tls_cert_mode is "self" (underscore domain):
- Generate self-signed certificates via openssl
- Set Postfix smtp_tls_security_level to "encrypt" (opportunistic TLS)
- Add smtp_tls_policy_map entry for underscore domains
- Skip ACME, MTA-STS and www CNAME checks in `cmdeploy dns`
- Serve /new via GET (not redirect to dcaccount:) with rate-limiting
  (nginx limit_req, 2r/s burst=5)
- Return dclogin: URLs with ic=3 (AcceptInvalidCertificates) from /new
- Render QR codes client-side via JavaScript and qrcode-svg
- Use config.tls_cert_path/tls_key_path in Postfix, Dovecot and nginx
  templates instead of hardcoded ACME paths

.github/workflows/test-and-deploy-ipv4only.yaml

@@ -75,8 +75,7 @@ jobs:
           cmdeploy init staging-ipv4.testrun.org
           sed -i 's#disable_ipv6 = False#disable_ipv6 = True#' chatmail.ini
           sed -i 's/#\s*mtail_address/mtail_address/' chatmail.ini
-
+          cmdeploy run --verbose --skip-dns-check
-      - run: cmdeploy run --verbose --skip-dns-check
 
       - name: set DNS entries
         run: |

chatmaild/src/chatmaild/config.py

@@ -60,6 +60,18 @@ class Config:
         self.privacy_pdo = params.get("privacy_pdo")
         self.privacy_supervisor = params.get("privacy_supervisor")
 
+        # TLS certificate management: derived from the domain name.
+        # Domains starting with "_" use self-signed certificates
+        # All other domains use ACME.
+        if self.mail_domain.startswith("_"):
+            self.tls_cert_mode = "self"
+            self.tls_cert_path = "/etc/ssl/certs/mailserver.pem"
+            self.tls_key_path = "/etc/ssl/private/mailserver.key"
+        else:
+            self.tls_cert_mode = "acme"
+            self.tls_cert_path = f"/var/lib/acme/live/{self.mail_domain}/fullchain"
+            self.tls_key_path = f"/var/lib/acme/live/{self.mail_domain}/privkey"
+
         # deprecated option
         mbdir = params.get("mailboxes_dir", f"/home/vmail/mail/{self.mail_domain}")
         self.mailboxes_dir = Path(mbdir.strip())

chatmaild/src/chatmaild/newemail.py

@@ -6,6 +6,7 @@ import json
 import random
 import secrets
 import string
+from urllib.parse import quote
 
 from chatmaild.config import Config, read_config
 
@@ -23,13 +24,26 @@ def create_newemail_dict(config: Config):
     return dict(email=f"{user}@{config.mail_domain}", password=f"{password}")
 
 
+def create_dclogin_url(email, password):
+    """Build a dclogin: URL with credentials and self-signed cert acceptance.
+
+    Uses ic=3 (AcceptInvalidCertificates) so chatmail clients
+    can connect to servers with self-signed TLS certificates.
+    """
+    return f"dclogin:{quote(email, safe='@')}?p={quote(password, safe='')}&v=1&ic=3"
+
+
 def print_new_account():
     config = read_config(CONFIG_PATH)
     creds = create_newemail_dict(config)
 
+    result = dict(email=creds["email"], password=creds["password"])
+    if config.tls_cert_mode == "self":
+        result["dclogin_url"] = create_dclogin_url(creds["email"], creds["password"])
+
     print("Content-Type: application/json")
     print("")
-    print(json.dumps(creds))
+    print(json.dumps(result))
 
 
 if __name__ == "__main__":

chatmaild/src/chatmaild/tests/test_config.py

@@ -73,3 +73,17 @@ def test_config_userstate_paths(make_config, tmp_path):
 def test_config_max_message_size(make_config, tmp_path):
     config = make_config("something.testrun.org", dict(max_message_size="10000"))
     assert config.max_message_size == 10000
+
+
+def test_config_tls_default_acme(make_config):
+    config = make_config("chat.example.org")
+    assert config.tls_cert_mode == "acme"
+    assert config.tls_cert_path == "/var/lib/acme/live/chat.example.org/fullchain"
+    assert config.tls_key_path == "/var/lib/acme/live/chat.example.org/privkey"
+
+
+def test_config_tls_self(make_config):
+    config = make_config("_test.example.org")
+    assert config.tls_cert_mode == "self"
+    assert config.tls_cert_path == "/etc/ssl/certs/mailserver.pem"
+    assert config.tls_key_path == "/etc/ssl/private/mailserver.key"

chatmaild/src/chatmaild/tests/test_filtermail_blackbox.py

@@ -1,9 +1,15 @@
+import shutil
 import smtplib
 import subprocess
 import sys
 
 import pytest
 
+pytestmark = pytest.mark.skipif(
+    shutil.which("filtermail") is None,
+    reason="filtermail binary not found",
+)
+
 
 @pytest.fixture
 def smtpserver():

chatmaild/src/chatmaild/tests/test_newmail.py

@@ -1,7 +1,11 @@
 import json
 
 import chatmaild
-from chatmaild.newemail import create_newemail_dict, print_new_account
+from chatmaild.newemail import (
+    create_dclogin_url,
+    create_newemail_dict,
+    print_new_account,
+)
 
 
 def test_create_newemail_dict(example_config):
@@ -15,6 +19,18 @@ def test_create_newemail_dict(example_config):
     assert ac1["password"] != ac2["password"]
 
 
+def test_create_dclogin_url():
+    url = create_dclogin_url("user@example.org", "p@ss w+rd")
+    assert url.startswith("dclogin:")
+    assert "v=1" in url
+    assert "ic=3" in url
+
+    assert "user@example.org" in url
+    # password special chars must be encoded
+    assert "p%40ss" in url
+    assert "w%2Brd" in url
+
+
 def test_print_new_account(capsys, monkeypatch, maildomain, tmpdir, example_config):
     monkeypatch.setattr(chatmaild.newemail, "CONFIG_PATH", str(example_config._inipath))
     print_new_account()
@@ -25,3 +41,20 @@ def test_print_new_account(capsys, monkeypatch, maildomain, tmpdir, example_conf
     dic = json.loads(lines[2])
     assert dic["email"].endswith(f"@{example_config.mail_domain}")
     assert len(dic["password"]) >= 10
+    # default tls_cert=acme should not include dclogin_url
+    assert "dclogin_url" not in dic
+
+
+def test_print_new_account_self_signed(capsys, monkeypatch, make_config):
+    config = make_config("_test.example.org")
+    monkeypatch.setattr(chatmaild.newemail, "CONFIG_PATH", str(config._inipath))
+    print_new_account()
+    out, err = capsys.readouterr()
+    lines = out.split("\n")
+    dic = json.loads(lines[2])
+    assert "dclogin_url" in dic
+    url = dic["dclogin_url"]
+    assert url.startswith("dclogin:")
+    assert "ic=3" in url
+
+    assert dic["email"].split("@")[0] in url

cmdeploy/src/cmdeploy/chatmail.zone.j2

@@ -8,8 +8,10 @@
 {{ mail_domain }}.                   AAAA  {{ AAAA }}
 {% endif %}
 {{ mail_domain }}.                   MX 10 {{ mail_domain }}.
+{% if strict_tls %}
 _mta-sts.{{ mail_domain }}.          TXT "v=STSv1; id={{ sts_id }}"
 mta-sts.{{ mail_domain }}.           CNAME {{ mail_domain }}.
+{% endif %}
 www.{{ mail_domain }}.               CNAME {{ mail_domain }}.
 {{ dkim_entry }}
 

cmdeploy/src/cmdeploy/cmdeploy.py

@@ -91,9 +91,10 @@ def run_cmd(args, out):
     ssh_host = args.ssh_host if args.ssh_host else args.config.mail_domain
     sshexec = get_sshexec(ssh_host)
     require_iroh = args.config.enable_iroh_relay
+    strict_tls = args.config.tls_cert_mode == "acme"
     if not args.dns_check_disabled:
         remote_data = dns.get_initial_remote_data(sshexec, args.config.mail_domain)
-        if not dns.check_initial_remote_data(remote_data, print=out.red):
+        if not dns.check_initial_remote_data(remote_data, strict_tls=strict_tls, print=out.red):
             return 1
 
     env = os.environ.copy()
@@ -124,7 +125,7 @@ def run_cmd(args, out):
                 out.red("Website deployment failed.")
         elif retcode == 0:
             out.green("Deploy completed, call `cmdeploy dns` next.")
-        elif not args.dns_check_disabled and not remote_data["acme_account_url"]:
+        elif not args.dns_check_disabled and strict_tls and not remote_data["acme_account_url"]:
             out.red("Deploy completed but letsencrypt not configured")
             out.red("Run 'cmdeploy run' again")
             retcode = 0
@@ -151,11 +152,13 @@ def dns_cmd(args, out):
     """Check DNS entries and optionally generate dns zone file."""
     ssh_host = args.ssh_host if args.ssh_host else args.config.mail_domain
     sshexec = get_sshexec(ssh_host, verbose=args.verbose)
+    tls_cert_mode = args.config.tls_cert_mode
+    strict_tls = tls_cert_mode == "acme"
     remote_data = dns.get_initial_remote_data(sshexec, args.config.mail_domain)
-    if not remote_data:
+    if not dns.check_initial_remote_data(remote_data, strict_tls=strict_tls):
         return 1
 
-    if not remote_data["acme_account_url"]:
+    if strict_tls and not remote_data["acme_account_url"]:
         out.red("could not get letsencrypt account url, please run 'cmdeploy run'")
         return 1
 
@@ -163,6 +166,7 @@ def dns_cmd(args, out):
         out.red("could not determine dkim_entry, please run 'cmdeploy run'")
         return 1
 
+    remote_data["strict_tls"] = strict_tls
     zonefile = dns.get_filled_zone_file(remote_data)
 
     if args.zonefile:

cmdeploy/src/cmdeploy/deployers.py

@@ -19,6 +19,7 @@ from pyinfra.operations import apt, files, pip, server, systemd
 from cmdeploy.cmdeploy import Out
 
 from .acmetool import AcmetoolDeployer
+from .selfsigned.deployer import SelfSignedTlsDeployer
 from .basedeploy import (
     Deployer,
     Deployment,
@@ -569,7 +570,10 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
     port_services = [
         (["master", "smtpd"], 25),
         ("unbound", 53),
-        ("acmetool", 80),
+    ]
+    if config.tls_cert_mode == "acme":
+        port_services.append(("acmetool", 80))
+    port_services += [
         (["imap-login", "dovecot"], 143),
         ("nginx", 443),
         (["master", "smtpd"], 465),
@@ -597,6 +601,11 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
 
     tls_domains = [mail_domain, f"mta-sts.{mail_domain}", f"www.{mail_domain}"]
 
+    if config.tls_cert_mode == "acme":
+        tls_deployer = AcmetoolDeployer(config.acme_email, tls_domains)
+    else:
+        tls_deployer = SelfSignedTlsDeployer(mail_domain)
+
     all_deployers = [
         ChatmailDeployer(mail_domain),
         LegacyRemoveDeployer(),
@@ -605,7 +614,7 @@ def deploy_chatmail(config_path: Path, disable_mail: bool, website_only: bool) -
         UnboundDeployer(config),
         TurnDeployer(mail_domain),
         IrohDeployer(config.enable_iroh_relay),
-        AcmetoolDeployer(config.acme_email, tls_domains),
+        tls_deployer,
         WebsiteDeployer(config),
         ChatmailVenvDeployer(config),
         MtastsDeployer(),

cmdeploy/src/cmdeploy/dns.py

@@ -12,14 +12,14 @@ def get_initial_remote_data(sshexec, mail_domain):
     )
 
 
-def check_initial_remote_data(remote_data, *, print=print):
+def check_initial_remote_data(remote_data, *, strict_tls=True, print=print):
     mail_domain = remote_data["mail_domain"]
     if not remote_data["A"] and not remote_data["AAAA"]:
         print(f"Missing A and/or AAAA DNS records for {mail_domain}!")
-    elif remote_data["MTA_STS"] != f"{mail_domain}.":
+    elif strict_tls and remote_data["MTA_STS"] != f"{mail_domain}.":
         print("Missing MTA-STS CNAME record:")
         print(f"mta-sts.{mail_domain}.   CNAME  {mail_domain}.")
-    elif remote_data["WWW"] != f"{mail_domain}.":
+    elif strict_tls and remote_data["WWW"] != f"{mail_domain}.":
         print("Missing www CNAME record:")
         print(f"www.{mail_domain}.   CNAME  {mail_domain}.")
     else:

cmdeploy/src/cmdeploy/dovecot/dovecot.conf.j2

@@ -228,8 +228,8 @@ service anvil {
 }
 
 ssl = required
-ssl_cert = </var/lib/acme/live/{{ config.mail_domain }}/fullchain
+ssl_cert = <{{ config.tls_cert_path }}
-ssl_key = </var/lib/acme/live/{{ config.mail_domain }}/privkey
+ssl_key = <{{ config.tls_key_path }}
 ssl_dh = </usr/share/dovecot/dh.pem
 ssl_min_protocol = TLSv1.3
 ssl_prefer_server_ciphers = yes

cmdeploy/src/cmdeploy/nginx/autoconfig.xml.j2

@@ -1,47 +1,47 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
 <clientConfig version="1.1">
-  <emailProvider id="{{ config.domain_name }}">
+  <emailProvider id="{{ config.mail_domain }}">
-    <domain>{{ config.domain_name }}</domain>
+    <domain>{{ config.mail_domain }}</domain>
-    <displayName>{{ config.domain_name }} chatmail</displayName>
+    <displayName>{{ config.mail_domain }} chatmail</displayName>
-    <displayShortName>{{ config.domain_name }}</displayShortName>
+    <displayShortName>{{ config.mail_domain }}</displayShortName>
     <incomingServer type="imap">
-      <hostname>{{ config.domain_name }}</hostname>
+      <hostname>{{ config.mail_domain }}</hostname>
       <port>993</port>
       <socketType>SSL</socketType>
       <authentication>password-cleartext</authentication>
       <username>%EMAILADDRESS%</username>
     </incomingServer>
     <incomingServer type="imap">
-      <hostname>{{ config.domain_name }}</hostname>
+      <hostname>{{ config.mail_domain }}</hostname>
       <port>143</port>
       <socketType>STARTTLS</socketType>
       <authentication>password-cleartext</authentication>
       <username>%EMAILADDRESS%</username>
     </incomingServer>
     <incomingServer type="imap">
-      <hostname>{{ config.domain_name }}</hostname>
+      <hostname>{{ config.mail_domain }}</hostname>
       <port>443</port>
       <socketType>SSL</socketType>
       <authentication>password-cleartext</authentication>
       <username>%EMAILADDRESS%</username>
     </incomingServer>
     <outgoingServer type="smtp">
-      <hostname>{{ config.domain_name }}</hostname>
+      <hostname>{{ config.mail_domain }}</hostname>
       <port>465</port>
       <socketType>SSL</socketType>
       <authentication>password-cleartext</authentication>
       <username>%EMAILADDRESS%</username>
     </outgoingServer>
     <outgoingServer type="smtp">
-      <hostname>{{ config.domain_name }}</hostname>
+      <hostname>{{ config.mail_domain }}</hostname>
       <port>587</port>
       <socketType>STARTTLS</socketType>
       <authentication>password-cleartext</authentication>
       <username>%EMAILADDRESS%</username>
     </outgoingServer>
     <outgoingServer type="smtp">
-      <hostname>{{ config.domain_name }}</hostname>
+      <hostname>{{ config.mail_domain }}</hostname>
       <port>443</port>
       <socketType>SSL</socketType>
       <authentication>password-cleartext</authentication>

cmdeploy/src/cmdeploy/nginx/deployer.py

@@ -70,7 +70,7 @@ def _configure_nginx(config: Config, debug: bool = False) -> bool:
         user="root",
         group="root",
         mode="644",
-        config={"domain_name": config.mail_domain},
+        config=config,
         disable_ipv6=config.disable_ipv6,
     )
     need_restart |= main_config.changed
@@ -81,7 +81,7 @@ def _configure_nginx(config: Config, debug: bool = False) -> bool:
         user="root",
         group="root",
         mode="644",
-        config={"domain_name": config.mail_domain},
+        config=config,
     )
     need_restart |= autoconfig.changed
 
@@ -91,7 +91,7 @@ def _configure_nginx(config: Config, debug: bool = False) -> bool:
         user="root",
         group="root",
         mode="644",
-        config={"domain_name": config.mail_domain},
+        config=config,
     )
     need_restart |= mta_sts_config.changed
 

cmdeploy/src/cmdeploy/nginx/mta-sts.txt.j2

@@ -1,4 +1,4 @@
 version: STSv1
 mode: enforce
-mx: {{ config.domain_name }}
+mx: {{ config.mail_domain }}
 max_age: 2419200

cmdeploy/src/cmdeploy/nginx/nginx.conf.j2

@@ -42,6 +42,9 @@ stream {
 }
 
 http {
+{% if config.tls_cert_mode == "self" %}
+	limit_req_zone $binary_remote_addr zone=newaccount:10m rate=2r/s;
+{% endif %}
 	sendfile on;
 	tcp_nopush on;
 
@@ -53,8 +56,8 @@ http {
 
 	ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
 	ssl_prefer_server_ciphers on;
-	ssl_certificate /var/lib/acme/live/{{ config.domain_name }}/fullchain;
+	ssl_certificate {{ config.tls_cert_path }};
-	ssl_certificate_key /var/lib/acme/live/{{ config.domain_name }}/privkey;
+	ssl_certificate_key {{ config.tls_key_path }};
 
 	gzip on;
 
@@ -66,7 +69,7 @@ http {
 
 		index index.html index.htm;
 
-		server_name {{ config.domain_name }} www.{{ config.domain_name }} mta-sts.{{ config.domain_name }};
+		server_name {{ config.mail_domain }} www.{{ config.mail_domain }} mta-sts.{{ config.mail_domain }};
 
 		access_log syslog:server=unix:/dev/log,facility=local7;
 
@@ -81,11 +84,15 @@ http {
 		}
 
 		location /new {
+{% if config.tls_cert_mode == "acme" %}
 			if ($request_method = GET) {
 				# Redirect to Delta Chat,
 				# which will in turn do a POST request.
-				return 301 dcaccount:https://{{ config.domain_name }}/new;
+				return 301 dcaccount:https://{{ config.mail_domain }}/new;
 			}
+{% else %}
+			limit_req zone=newaccount burst=5 nodelay;
+{% endif %}
 
 			fastcgi_pass unix:/run/fcgiwrap.socket;
 			include /etc/nginx/fastcgi_params;
@@ -99,9 +106,11 @@ http {
 		#
 		# Redirects are only for browsers.
 		location /cgi-bin/newemail.py {
+{% if config.tls_cert_mode == "acme" %}
 			if ($request_method = GET) {
-				return 301 dcaccount:https://{{ config.domain_name }}/new;
+				return 301 dcaccount:https://{{ config.mail_domain }}/new;
 			}
+{% endif %}
 
 			fastcgi_pass unix:/run/fcgiwrap.socket;
 			include /etc/nginx/fastcgi_params;
@@ -132,8 +141,8 @@ http {
 	# Redirect www. to non-www
 	server {
 		listen 127.0.0.1:8443 ssl;
-		server_name www.{{ config.domain_name }};
+		server_name www.{{ config.mail_domain }};
-		return 301 $scheme://{{ config.domain_name }}$request_uri;
+		return 301 $scheme://{{ config.mail_domain }}$request_uri;
 		access_log syslog:server=unix:/dev/log,facility=local7;
 	}
 }

cmdeploy/src/cmdeploy/postfix/main.cf.j2

@@ -15,12 +15,12 @@ readme_directory = no
 compatibility_level = 3.6
 
 # TLS parameters
-smtpd_tls_cert_file=/var/lib/acme/live/{{ config.mail_domain }}/fullchain
+smtpd_tls_cert_file={{ config.tls_cert_path }}
-smtpd_tls_key_file=/var/lib/acme/live/{{ config.mail_domain }}/privkey
+smtpd_tls_key_file={{ config.tls_key_path }}
 smtpd_tls_security_level=may
 
 smtp_tls_CApath=/etc/ssl/certs
-smtp_tls_security_level=verify
+smtp_tls_security_level={{ "verify" if config.tls_cert_mode == "acme" else "encrypt" }}
 # Send SNI extension when connecting to other servers.
 # <https://www.postfix.org/postconf.5.html#smtp_tls_servername>
 smtp_tls_servername = hostname

cmdeploy/src/cmdeploy/postfix/smtp_tls_policy_map

@@ -1,2 +1,3 @@
 /^\[[^]]+\]$/ encrypt
+/^_/          encrypt
 /^nauta\.cu$/    may

cmdeploy/src/cmdeploy/selfsigned/deployer.py

@@ -0,0 +1,36 @@
+from pyinfra.operations import apt, files, server
+
+from cmdeploy.basedeploy import Deployer
+
+
+class SelfSignedTlsDeployer(Deployer):
+    """Generates a self-signed TLS certificate for all chatmail endpoints."""
+
+    def __init__(self, mail_domain):
+        self.mail_domain = mail_domain
+        self.cert_path = "/etc/ssl/certs/mailserver.pem"
+        self.key_path = "/etc/ssl/private/mailserver.key"
+
+    def install(self):
+        apt.packages(
+            name="Install openssl",
+            packages=["openssl"],
+        )
+
+    def configure(self):
+        server.shell(
+            name="Generate self-signed TLS certificate if not present",
+            commands=[
+                f"[ -f {self.cert_path} ] || openssl req -x509"
+                f" -newkey ec -pkeyopt ec_paramgen_curve:P-256"
+                f" -noenc -days 36500"
+                f" -keyout {self.key_path}"
+                f" -out {self.cert_path}"
+                f' -subj "/CN={self.mail_domain}"'
+                f' -addext "extendedKeyUsage=serverAuth,clientAuth"'
+                f' -addext "subjectAltName=DNS:{self.mail_domain},DNS:www.{self.mail_domain},DNS:mta-sts.{self.mail_domain}"',
+            ],
+        )
+
+    def activate(self):
+        pass

cmdeploy/src/cmdeploy/tests/online/test_0_qr.py

@@ -1,3 +1,4 @@
+import pytest
 import requests
 
 from cmdeploy.genqr import gen_qr_png_data
@@ -8,18 +9,33 @@ def test_gen_qr_png_data(maildomain):
     assert data
 
 
+@pytest.mark.filterwarnings("ignore::urllib3.exceptions.InsecureRequestWarning")
 def test_fastcgi_working(maildomain, chatmail_config):
     url = f"https://{maildomain}/new"
     print(url)
-    res = requests.post(url)
+    verify = chatmail_config.tls_cert_mode == "acme"
+    res = requests.post(url, verify=verify)
     assert maildomain in res.json().get("email")
     assert len(res.json().get("password")) > chatmail_config.password_min_length
 
 
-def test_newemail_configure(maildomain, rpc):
+@pytest.mark.filterwarnings("ignore::urllib3.exceptions.InsecureRequestWarning")
+def test_newemail_configure(maildomain, rpc, chatmail_config):
     """Test configuring accounts by scanning a QR code works."""
     url = f"DCACCOUNT:https://{maildomain}/new"
     for i in range(3):
         account_id = rpc.add_account()
-        rpc.set_config_from_qr(account_id, url)
+        if chatmail_config.tls_cert_mode == "self":
-        rpc.configure(account_id)
+            # deltachat core's rustls rejects self-signed HTTPS certs during
+            # set_config_from_qr, so fetch credentials via requests instead
+            res = requests.post(f"https://{maildomain}/new", verify=False)
+            data = res.json()
+            rpc.add_or_update_transport(account_id, {
+                "addr": data["email"],
+                "password": data["password"],
+                "imapServer": maildomain,
+                "smtpServer": maildomain,
+                "certificateChecks": "acceptInvalidCertificates",
+            })
+        else:
+            rpc.add_transport_from_qr(account_id, url)

cmdeploy/src/cmdeploy/tests/online/test_2_deltachat.py

@@ -11,11 +11,12 @@ from cmdeploy.sshexec import SSHExec
 
 
 @pytest.fixture
-def imap_mailbox(cmfactory):
+def imap_mailbox(cmfactory, ssl_context):
     (ac1,) = cmfactory.get_online_accounts(1)
     user = ac1.get_config("addr")
     password = ac1.get_config("mail_pw")
-    mailbox = imap_tools.MailBox(user.split("@")[1])
+    host = user.split("@")[1]
+    mailbox = imap_tools.MailBox(host, ssl_context=ssl_context)
     mailbox.login(user, password)
     mailbox.dc_ac = ac1
     return mailbox
@@ -171,7 +172,7 @@ class TestEndToEndDeltaChat:
             time.sleep(1)
 
 
-def test_hide_senders_ip_address(cmfactory):
+def test_hide_senders_ip_address(cmfactory, ssl_context):
     public_ip = requests.get("http://icanhazip.com").content.decode().strip()
     assert ipaddress.ip_address(public_ip)
 
@@ -180,6 +181,11 @@ def test_hide_senders_ip_address(cmfactory):
 
     chat.send_text("testing submission header cleanup")
     user2._evtracker.wait_next_incoming_message()
-    user2.direct_imap.select_folder("Inbox")
+    addr = user2.get_config("addr")
-    msg = user2.direct_imap.get_all_messages()[0]
+    host = addr.split("@")[1]
-    assert public_ip not in msg.obj.as_string()
+    pw = user2.get_config("mail_pw")
+    mailbox = imap_tools.MailBox(host, ssl_context=ssl_context)
+    mailbox.login(addr, pw)
+    msgs = list(mailbox.fetch(mark_seen=False))
+    assert msgs, "expected at least one message"
+    assert public_ip not in msgs[0].obj.as_string()

cmdeploy/src/cmdeploy/tests/plugin.py

@@ -4,6 +4,7 @@ import itertools
 import os
 import random
 import smtplib
+import ssl
 import subprocess
 import time
 from pathlib import Path
@@ -144,15 +145,25 @@ def pytest_terminal_summary(terminalreporter):
             tr.write_line(line)
 
 
-@pytest.fixture
+@pytest.fixture(scope="session")
-def imap(maildomain):
+def ssl_context(chatmail_config):
-    return ImapConn(maildomain)
+    if chatmail_config.tls_cert_mode == "self":
+        ctx = ssl.create_default_context()
+        ctx.check_hostname = False
+        ctx.verify_mode = ssl.CERT_NONE
+        return ctx
+    return None
 
 
 @pytest.fixture
-def make_imap_connection(maildomain):
+def imap(maildomain, ssl_context):
+    return ImapConn(maildomain, ssl_context=ssl_context)
+
+
+@pytest.fixture
+def make_imap_connection(maildomain, ssl_context):
     def make_imap_connection():
-        conn = ImapConn(maildomain)
+        conn = ImapConn(maildomain, ssl_context=ssl_context)
         conn.connect()
         return conn
 
@@ -164,12 +175,13 @@ class ImapConn:
     logcmd = "journalctl -f -u dovecot"
     name = "dovecot"
 
-    def __init__(self, host):
+    def __init__(self, host, ssl_context=None):
         self.host = host
+        self.ssl_context = ssl_context
 
     def connect(self):
         print(f"imap-connect {self.host}")
-        self.conn = imaplib.IMAP4_SSL(self.host)
+        self.conn = imaplib.IMAP4_SSL(self.host, ssl_context=self.ssl_context)
 
     def login(self, user, password):
         print(f"imap-login {user!r} {password!r}")
@@ -195,14 +207,14 @@ class ImapConn:
 
 
 @pytest.fixture
-def smtp(maildomain):
+def smtp(maildomain, ssl_context):
-    return SmtpConn(maildomain)
+    return SmtpConn(maildomain, ssl_context=ssl_context)
 
 
 @pytest.fixture
-def make_smtp_connection(maildomain):
+def make_smtp_connection(maildomain, ssl_context):
     def make_smtp_connection():
-        conn = SmtpConn(maildomain)
+        conn = SmtpConn(maildomain, ssl_context=ssl_context)
         conn.connect()
         return conn
 
@@ -214,12 +226,14 @@ class SmtpConn:
     logcmd = "journalctl -f -t postfix/smtpd -t postfix/smtp -t postfix/lmtp"
     name = "postfix"
 
-    def __init__(self, host):
+    def __init__(self, host, ssl_context=None):
         self.host = host
+        self.ssl_context = ssl_context
 
     def connect(self):
         print(f"smtp-connect {self.host}")
-        self.conn = smtplib.SMTP_SSL(self.host)
+        context = self.ssl_context or ssl.create_default_context()
+        self.conn = smtplib.SMTP_SSL(self.host, context=context)
 
     def login(self, user, password):
         print(f"smtp-login {user!r} {password!r}")
@@ -270,11 +284,12 @@ def gencreds(chatmail_config):
 class ChatmailTestProcess:
     """Provider for chatmail instance accounts as used by deltachat.testplugin.acfactory"""
 
-    def __init__(self, pytestconfig, maildomain, gencreds):
+    def __init__(self, pytestconfig, maildomain, gencreds, chatmail_config):
         self.pytestconfig = pytestconfig
         self.maildomain = maildomain
         assert "." in self.maildomain, maildomain
         self.gencreds = gencreds
+        self.chatmail_config = chatmail_config
         self._addr2files = {}
 
     def get_liveconfig_producer(self):
@@ -287,6 +302,9 @@ class ChatmailTestProcess:
             # speed up account configuration
             config["mail_server"] = self.maildomain
             config["send_server"] = self.maildomain
+            if self.chatmail_config.tls_cert_mode == "self":
+                # Accept self-signed TLS certificates
+                config["imap_certificate_checks"] = "3"
             yield config
 
     def cache_maybe_retrieve_configured_db_files(self, cache_addr, db_target_path):
@@ -297,12 +315,14 @@ class ChatmailTestProcess:
 
 
 @pytest.fixture
-def cmfactory(request, gencreds, tmpdir, maildomain):
+def cmfactory(request, gencreds, tmpdir, maildomain, chatmail_config):
     # cloned from deltachat.testplugin.amfactory
     pytest.importorskip("deltachat")
     from deltachat.testplugin import ACFactory
 
-    testproc = ChatmailTestProcess(request.config, maildomain, gencreds)
+    testproc = ChatmailTestProcess(
+        request.config, maildomain, gencreds, chatmail_config
+    )
 
     class Data:
         def read_path(self, path):
@@ -310,6 +330,10 @@ def cmfactory(request, gencreds, tmpdir, maildomain):
 
     am = ACFactory(request=request, tmpdir=tmpdir, testprocess=testproc, data=Data())
 
+    # Skip upstream's init_imap to prevent extra imap connections not
+    # needed for relay testing
+    am._acsetup.init_imap = lambda acc: None
+
     # nb. a bit hacky
     # would probably be better if deltachat's test machinery grows native support
     def switch_maildomain(maildomain2):
@@ -363,38 +387,40 @@ def lp(request):
 
 
 @pytest.fixture
-def cmsetup(maildomain, gencreds):
+def cmsetup(maildomain, gencreds, ssl_context):
-    return CMSetup(maildomain, gencreds)
+    return CMSetup(maildomain, gencreds, ssl_context)
 
 
 class CMSetup:
-    def __init__(self, maildomain, gencreds):
+    def __init__(self, maildomain, gencreds, ssl_context):
         self.maildomain = maildomain
         self.gencreds = gencreds
+        self.ssl_context = ssl_context
 
     def gen_users(self, num):
         print(f"Creating {num} online users")
         users = []
         for i in range(num):
             addr, password = self.gencreds()
-            user = CMUser(self.maildomain, addr, password)
+            user = CMUser(self.maildomain, addr, password, self.ssl_context)
             assert user.smtp
             users.append(user)
         return users
 
 
 class CMUser:
-    def __init__(self, maildomain, addr, password):
+    def __init__(self, maildomain, addr, password, ssl_context=None):
         self.maildomain = maildomain
         self.addr = addr
         self.password = password
+        self.ssl_context = ssl_context
         self._smtp = None
         self._imap = None
 
     @property
     def smtp(self):
         if not self._smtp:
-            handle = SmtpConn(self.maildomain)
+            handle = SmtpConn(self.maildomain, ssl_context=self.ssl_context)
             handle.connect()
             handle.login(self.addr, self.password)
             self._smtp = handle
@@ -403,7 +429,7 @@ class CMUser:
     @property
     def imap(self):
         if not self._imap:
-            imap = ImapConn(self.maildomain)
+            imap = ImapConn(self.maildomain, ssl_context=self.ssl_context)
             imap.connect()
             imap.login(self.addr, self.password)
             self._imap = imap

cmdeploy/src/cmdeploy/tests/test_dns.py

@@ -91,6 +91,16 @@ class TestPerformInitialChecks:
         assert not res
         assert len(l) == 2
 
+    def test_perform_initial_checks_no_mta_sts_self_signed(self, mockdns):
+        del mockdns["CNAME"]["mta-sts.some.domain"]
+        remote_data = remote.rdns.perform_initial_checks("some.domain")
+        assert not remote_data["MTA_STS"]
+
+        l = []
+        res = check_initial_remote_data(remote_data, strict_tls=False, print=l.append)
+        assert res
+        assert not l
+
 
 def parse_zonefile_into_dict(zonefile, mockdns_base, only_required=False):
     for zf_line in zonefile.split("\n"):

doc/source/getting_started.rst

@@ -47,6 +47,14 @@ steps. Please substitute it with your own domain.
        www.chat.example.org. 3600 IN CNAME chat.example.org.
        mta-sts.chat.example.org. 3600 IN CNAME chat.example.org.
 
+   .. note::
+
+      For experimental deployments using self-signed certificates,
+      use a domain name starting with ``_``
+      (e.g. ``_chat.example.org``).
+      The ``mta-sts`` CNAME and ``_mta-sts`` TXT records
+      are not needed for such domains.
+
 2. On your local PC, clone the repository and bootstrap the Python
    virtualenv.
 
@@ -63,6 +71,16 @@ steps. Please substitute it with your own domain.
 
        scripts/cmdeploy init chat.example.org  # <-- use your domain
 
+   To use self-signed TLS certificates
+   instead of Let's Encrypt,
+   use a domain name starting with ``_``
+   (e.g. ``scripts/cmdeploy init _chat.example.org``).
+   Domains starting with ``_`` cannot obtain WebPKI certificates,
+   so self-signed mode is derived automatically.
+   This is useful for private or test deployments.
+   See the :doc:`overview`
+   for details on certificate provisioning.
+
 4. Verify that SSH root login to the deployment server server works:
 
    ::
@@ -169,6 +187,17 @@ creating addresses, login with ssh to the deployment machine and run:
 Chatmail address creation will be denied while this file is present.
 
 
+Running a relay with self-signed certificates
+----------------------------------------------
+
+Use a domain name starting with ``_`` (e.g. ``_chat.example.org``)
+to run a relay with self-signed certificates.
+Domains starting with ``_`` cannot obtain WebPKI certificates
+so the relay automatically uses self-signed certificates
+and all other relays will accept connections from it
+without requiring certificate verification.
+This is useful for experimental setups and testing.
+
 Migrating to a new build machine
 ----------------------------------
 

doc/source/overview.rst

@@ -297,8 +297,7 @@ TLS requirements
 
 Postfix is configured to require valid TLS by setting
 `smtp_tls_security_level <https://www.postfix.org/postconf.5.html#smtp_tls_security_level>`_
-to ``verify``. If emails don’t arrive at your chatmail relay server, the
+to ``verify``.
-problem is likely that your relay does not have a valid TLS certificate.
 
 You can test it by resolving ``MX`` records of your relay domain and
 then connecting to MX relays (e.g ``mx.example.org``) with
@@ -317,6 +316,14 @@ default Exim does not log sessions that are closed before sending the
 by Postfix, so you might think that connection is not established while
 actually it is a problem with your TLS certificate.
 
+If emails don’t arrive at your chatmail relay server, the
+problem is likely that your relay does not have a valid TLS certificate.
+
+Note that connections to relays with underscore-prefixed test domains
+(e.g. ``_chat.example.org``) use ``encrypt`` tls security level,
+because such domains cannot obtain valid Let's Encrypt certificates
+and run with self-signed certificates.
+
 
 .. _dovecot: https://dovecot.org
 .. _postfix: https://www.postfix.org

www/src/dclogin.js

@@ -0,0 +1,21 @@
+/* dclogin profile generator for self-signed chatmail relays.
+ * Fetches credentials from /new and generates a dclogin: QR code.
+ * Requires qrcode-svg.min.js to be loaded first.
+ */
+(function () {
+    function generateProfile() {
+        fetch('/new')
+            .then(function (r) { return r.json(); })
+            .then(function (data) {
+                var url = data.dclogin_url;
+                var link = document.getElementById('dclogin-link');
+                link.href = url;
+                var qrLink = document.getElementById('qr-link');
+                qrLink.href = url;
+                var qrCode = document.getElementById('qr-code');
+                var qr = new QRCode({ content: url, width: 300, height: 300, padding: 1, join: true });
+                qrCode.innerHTML = qr.svg();
+            });
+    }
+    generateProfile();
+})();

www/src/index.md

@@ -11,6 +11,18 @@ for Delta Chat users.  For details how it avoids storing personal information
 please see our [privacy policy](privacy.html). 
 {% endif %}
 
+{% if config.tls_cert_mode == "self" %}
+<a class="cta-button" id="dclogin-link" href="#">Get a {{config.mail_domain}} chat profile</a>
+
+If you are viewing this page on a different device
+without a Delta Chat app,
+you can also **scan this QR code** with Delta Chat:
+
+<a id="qr-link" href="#"><div id="qr-code"></div></a>
+
+<script src="qrcode-svg.min.js"></script>
+<script src="dclogin.js"></script>
+{% else %}
 <a class="cta-button" href="DCACCOUNT:https://{{ config.mail_domain }}/new">Get a {{config.mail_domain}} chat profile</a>
 
 If you are viewing this page on a different device
@@ -19,6 +31,7 @@ you can also **scan this QR code** with Delta Chat:
 
 <a href="DCACCOUNT:https://{{ config.mail_domain }}/new">
     <img width=300 style="float: none;" src="qr-chatmail-invite-{{config.mail_domain}}.png" /></a>
+{% endif %}
 
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