A VM name flows into five places that all have narrower grammars
than "arbitrary string":
- the guest's /etc/hostname (vm_disk.patchRootOverlay)
- the guest's /etc/hosts (same)
- the <name>.vm DNS record (vmdns.RecordName)
- the kernel command line (system.BuildBootArgs*)
- VM-dir file-path fragments (layout.VMsDir/<id>, etc.)
Nothing in the chain was validating the input. A name with
whitespace, newline, dot, slash, colon, or = would produce broken
hostnames, weird DNS labels, smuggled kernel cmdline tokens, or
(in the worst case) surprising traversal through the on-disk
layout. Not host shell injection — we already avoid shelling out
with the raw name — but a real correctness and supportability bug.
New: model.ValidateVMName. Rules:
- 1..63 chars (DNS label max per RFC 1123; also a comfortable
/etc/hostname cap)
- lowercase ASCII letters, digits, '-' only
- no leading or trailing '-'
- no normalization — the name is the user-visible identifier
(store key, `ssh <name>.vm`, `vm show`); silently rewriting
"MyVM" → "myvm" would hand the user back something different
than they typed
Called from two places:
- internal/cli/commands_vm.go vmCreateParamsFromFlags — rejects
bad `--name` values before any RPC. Empty name still passes
through so the daemon can generate one.
- internal/daemon/vm_create.go reserveVM — defense in depth for
any non-CLI RPC caller (SDK, direct JSON over the socket).
Tests:
- internal/model/vm_name_test.go — exhaustive character-class
matrix (space, newline, tab, dot, slash, colon, equals, quote,
control chars, unicode letters, uppercase, leading/trailing
hyphen, over-length, max-length-exact, digits-only).
- internal/cli TestVMCreateParamsFromFlagsRejectsInvalidName —
CLI wire-through + empty-name passthrough.
- internal/daemon TestReserveVMRejectsInvalidName — daemon
defense-in-depth (including `box/../evil` path-traversal).
- scripts/smoke.sh — end-to-end rejection + no-leaked-row
assertion.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
