Sprint 1 unified-master-audit closure. Pre-fix the agent built its
on-disk key path via:
keyPath := filepath.Join(a.config.KeyDir, job.CertificateID+".key")
migrations/000001_initial_schema.up.sql declares managed_certificates.id
as TEXT PRIMARY KEY with no shape constraint, so a compromised control
plane (or a poisoned database row) could deliver a job whose
certificate_id is '../../etc/passwd', '/absolute/path', a NUL-byte
payload, or a Windows-separator-laden string — driving arbitrary
file write or read on the agent host.
Fix (two ends; both load-bearing):
Server side:
- New internal/validation/certificate_id.go: ValidateCertificateID
pins the canonical TEXT-PK shape (^[A-Za-z0-9._-]{1,128}$, plus
explicit '.'/'..' rejection).
- CertificateService.Create now invokes ValidateCertificateID after
the existing required-fields check; malformed IDs are refused
before persistence or downstream job creation.
Agent side:
- cmd/agent/keymem.go: validateAgentCertID mirrors the server-side
shape regex. safeAgentKeyPath additionally asserts the joined
path is contained within KeyDir via filepath.Rel — even if a
future refactor bypasses the shape check, a path that escapes
KeyDir fails closed.
- poll.go + deploy.go: both filepath.Join call sites routed
through safeAgentKeyPath; rejection surfaces via reportJobStatus
so the control plane sees the failure.
Regression coverage:
- internal/validation/certificate_id_test.go: production shapes
accepted; explicit rejection table for empty, overlong, posix
traversal, absolute, Windows traversal, Windows separator, NUL
byte, newline/tab injection, drive prefix, space, unicode dots.
- cmd/agent/keymem_test.go: validateAgentCertID acceptance +
rejection tables; safeAgentKeyPath happy path + the 8 audit
vectors plus empty-keyDir refusal.
Closes SEC-002.
shankar0123