config

Where MixOS keeps its files, and how a *.conf.mix file is read.

• config::path(Dir::Etc | Var | Run | Share): one rule for every directory. A MIXOS_ETC / MIXOS_VAR / MIXOS_RUN / MIXOS_SHARE override wins; else $MIXOS/etc, /var, /run when a root is set; else the XDG directory for a user (~/.config/mixos, ~/.local/share/mixos, $XDG_RUNTIME_DIR/mixos) or the system directory for root (/etc/mixos, /var/lib/mixos, /run/mixos). Share is installed read-only data at /opt/mixos/share whatever the root or user. Resolved once per process and cached; Dirs::resolve(&Environment) applies the rule to explicit inputs for tests.
• config::parse / config::parse_file and Value, Map, Error, ErrorKind: the strict crate's strict-data loader, re-exported so a config reader needs one dependency. Typed loading is strict::from_file.

No dependency on the Mix language. Test with cargo test -p config.

Node configuration and TLS

node::NodeConfig reads node.conf.mix, selected by MIXOS_NODE_CONFIG or the native Dir::Etc search paths. The optional maild section contains typed ports, hostname, storage paths, spam settings, the legacy tls_cert / tls_key pair and tls: { identity: [...], strict_sni: false }. Mail state defaults to path(Dir::Var)/maild/{mail.db,blobs,mds}. Unknown service and mail settings survive typed round trips.

Optional jmap_listen, jmap_upstream, smtp_inbound_listen and smtps_listen fields override the corresponding address helpers. Otherwise the helpers use the node IP and mail ports (8443, 25 and 465 by default). jmap_upstream() uses HTTPS. Missing mail settings remain valid.

node::{TlsConfig,TlsIdentityConfig} are always available. Each identity requires server_name, cert and key; its independent default and no_sni_fallback flags default to false. Enable the optional tls feature for load_tls_config(cert_path, key_path) and tls::sni::{SniCertResolver,TlsIdentity,pick_identity}. The resolver loads PEM pairs and matches names case-insensitively. Unknown SNI uses the default; absent SNI prefers the no-SNI identity then the default. If neither flag is set anywhere, the first identity fills both roles. Strict SNI rejects unknown names and clients which omit SNI. default_identity() remains available for pre-TLS greetings, including in strict mode.

from_conf_mix_str and load_conf_mix_path return config::Error (the strict loader error); node search/load functions retain anyhow::Result. Verify TLS with cargo test -p config --features tls.

The source is libs/config.

Application directories

AppDirs shares the existing Ced/Dopus per-application root, config, state and cache rules. First absolute root wins: MIXOS_APP_HOME, then MIXOS_APPS_HOME/<component>, MIXOS_VAR/apps/<component> (or MIXOS/var/apps/<component>), XDG_STATE_HOME/mixos/apps/<component>, then HOME/.local/state/mixos/apps/<component>. An invalid component or absent absolute root returns None. Resolution performs no I/O. App-owned filenames stay in their owners; this promotion preserves existing paths and lets other native settings consumers use the same isolated cache policy. resolve_with injects inputs for tests without mutating process environment.

Atomic directories

atomic::open_directory refuses symlinks in every component. atomic::create_directory uses the same held-descriptor walk and provisions missing components with mode 0700. It validates the entire absolute path before creation, refuses parent traversal and leaves existing permissions unchanged.

Web configuration and ACME policy

node::WebdConfig adds the web listener, vhost, share roots, auxiliary DB and ACME settings to NodeConfig. web_listen() derives the legacy listen address; synthesize_listeners() validates explicit binds and host ownership, retaining the fail-soft disabled-host path. Unknown web settings survive typed node round trips.

resolve_webd_acme() checks per-vhost issuance choices, HTTP-01 readiness and the node-level Let's Encrypt production Subscriber Agreement. Only the policy resolver can mint an AcmeTosAcceptance proof.

Node loading, directory resolution and TLS/SNI use the existing config implementations. Client discovery and connect helpers already live in bus::client_helpers; config remains independent of the Bus client.