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# ADR-0036: Uploaded documents are scanned by ClamAV in the Domain Service, fail closed
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- **Status:** Accepted
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- **Date:** 2026-10-02
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- **Deciders:** Respellion engineering
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- **Slice:** proposed in [#190](https://git.labs.respellion.tech/eho/register-referentie/issues/190);
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clamd deployed in [#191](https://git.labs.respellion.tech/eho/register-referentie/issues/191) (S-28),
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scanning wired in [#192](https://git.labs.respellion.tech/eho/register-referentie/issues/192) (S-29).
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## Context
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A zorgprofessional's diploma upload goes portal → BFF → Domain (`ProvideDocuments`) →
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ACL → OpenZaak. Nothing on that path looks at the file. It is not checked for malware,
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and nobody checks that it is a PDF. Behandelaars open these files later, so the
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register stores, and then serves, whatever a citizen sends.
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Scanning needs a signature engine that stays up to date. That means a new peer service,
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and that makes it an ADR (CLAUDE.md §14).
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## Decision
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1. **Engine:** the ClamAV daemon (`clamd`), official image `clamav/clamav`, pinned tag,
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as its own service in compose and in the Helm chart. `freshclam` in the same container
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keeps the signatures current, and they live on a volume.
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2. **Where the check lives:** in the **Domain Service**, behind an `IDocumentScanner` port
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in `Big.Application`. "Only a clean PDF is stored and unblocks beoordeling" is a rule
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of the provide-documents use case. The BFF is a thin proxy (§8.3), and the ACL
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translates ZGW and nothing else (§8.1). A check in the domain also covers every
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entry point, not just the portal.
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3. **Protocol:** the adapter in `Big.Infrastructure` speaks clamd's INSTREAM protocol over
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`TcpClient`: `zINSTREAM\0`, length-prefixed chunks, a zero-length terminator, then a
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`stream: OK` or `stream: <name> FOUND` reply. That is a few lines of code, so we add
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**no NuGet package** for it (nClam and similar).
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4. **Fail closed:** if clamd can't be reached, the upload is refused (503). Nothing is
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stored and the document wait stays open. We never store an unscanned file.
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5. **Type check:** content must start with `%PDF-`. This refuses a renamed executable
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before the scan, and it costs nothing.
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## Consequences
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- One more long-running service. clamd holds its signatures in memory (about 1 GB idle).
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`ConcurrentDatabaseReload no` stops a signature reload from holding a second copy,
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but clamd pauses scans for the few seconds a reload takes. Compose caps it at
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`mem_limit: 2g`, and the chart requests 1200Mi. This counts against the verify-stack
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runner's memory ceiling (#182).
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- The first start downloads about 300 MB of signatures from the ClamAV CDN, so the
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runner and the cluster node need outbound internet (as `seed-zaaktype` already does).
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The CDN rate-limits by IP. A CI runner that starts fresh often can get throttled, and
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then the health check doesn't go green. If that happens, mirror the signatures
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(`cvdupdate`) rather than retrying.
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- Tests use the EICAR test string, built from two halves so the repo itself does not trip
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an on-access scanner. No real malware is ever committed.
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- Infected or non-PDF uploads are refused with 422 and a business message. We don't keep
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a quarantine copy: a refused file is simply not stored.
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