fix(ipfs-metadata): bind document_type to a MIME allow-list per type

[1Psalm]

Summary

Binds DocumentType to a MIME allow-list in the IPFS metadata registry, so the registry's provenance claim means something. Also corrects documentation that claims content verification the contract cannot perform.

Addresses #1189 (primary). Partially addresses #1188, and removes the stale snapshot from #1187. #1190 is not addressed — see the per-issue notes.

What the issue got wrong, and what the actual hole was

The issue says file_size, mime_type and document_type are "stored unverified" and that "the Error enum offers FileTypeNotAllowed and SizeLimitExceeded but nothing enforces them". Half of that is not accurate, and the accurate half matters:

• file_size was already enforced. register_ipfs_document compares it against validation_rules.max_file_size and returns SizeLimitExceeded. That error was already reachable. A test is added to pin that down.
• mime_type had a check, but it never fired. The guard is if !allowed_mime_types.is_empty() && !contains(&mime_type), and the constructor seeds allowed_mime_types: Vec::new() with the comment "Initialize empty, populate via update". An empty list means "no restriction", so on any freshly deployed registry the MIME branch is skipped entirely. The defect is a fail-open default, not a missing check — which is why the fix below adds an always-on check rather than trying to make the existing one stricter.
• is_pinned cannot be asserted at registration. register_ipfs_document has no is_pinned parameter; it hardcodes is_pinned: false and pinning happens through a separate pin_document message. There is no assertion channel to reject, so that part of the proposal has nothing to act on.

The fix

New pure function document_type_permits_mime(&DocumentType, &str) -> bool, enforced unconditionally on every registration, before the admin list:

DocumentType	Accepted MIME
Deed, Title, Legal, TaxRecords, Insurance	application/pdf, application/x-pdf, application/octet-stream
Images	image/jpeg, image/png, image/webp, image/tiff
Appraisal, Survey, FloorPlans, Inspection	document or raster
Other	defers to the admin list

Three deliberate choices:

1. Fail-closed by construction. The policy does not consult allowed_mime_types, so it holds regardless of admin configuration. The admin list now narrows policy further instead of being the only defense — which is what makes the empty default harmless.
2. Not admin-overridable. The value of document_type is that a consumer can trust it. An add_allowed_mime_type path that re-opened image/png for a deed would put the guarantee straight back, so the per-type policy is closed. There is a test asserting an admin cannot widen it.
3. The policy is symmetric. It is not just "no images for deeds": Images rejects application/pdf too, so a document cannot be filed as a photograph either.

Inspection accepts raster because the existing test media_registration_and_duplicate_cid_rejected registers an inspection report as image/jpeg, and inspection evidence is legitimately photographic. The other existing registration tests use application/pdf, which the policy permits, so no existing test changes meaning.

#1188: the docs correction, and what is deliberately not here

verify_content_hash(document_id, provided_hash) compares the caller's provided_hash against the uploader's stored content_hash and returns true on a match. Both sides come from callers, so it only proves the supplied hash equals the one on record — a uploader registers whatever hash they like and then trivially "verifies" it. Downstream consumers reading ContentHashVerified are being told content was attested when nothing was.

Corrected in this PR: the verify_content_hash doc now states plainly that the contract cannot reach IPFS and that true means "this hash is the one on record", not "these bytes are attested"; the content_hash field docs on both PropertyMetadata and IpfsDocument no longer say "for verification"; the ContentHashVerified event doc no longer says "when content hash is verified"; and the local is_valid is renamed echoes_registered_hash so the code stops implying otherwise.

Not implemented, because it needs dependencies this crate does not have (ipfs-metadata depends only on ink, scale, scale-info, propchain-traits):

• Hashing the encoded metadata struct. Needs an on-chain hash implementation.
• The uploader signature check. Needs a curve implementation.

Both are security-critical additions that should land with a build and a test suite behind them, not blind. The public message name verify_content_hash is also left alone despite overclaiming, since renaming changes the ink! selector and breaks callers; it should be renamed together with the real fix.

#1190: not addressed

Two problems with the issue as written, and one reason not to attempt it here:

• get_properties_by_owner does not exist in contracts/metadata/src/lib.rs. The real unbounded listings are get_property_version_history (line 587), get_legal_documents (line 643) and get_properties_by_type (line 655), all returning Vec<_> with no bound.
• Fixing it means changing three public message signatures, which changes their ink! selectors and breaks every caller.
• Its acceptance criteria asks for a 10k-property test returning bounded pages, which cannot be written honestly without running it.

Paginating those blind, in a different contract, on top of an unrelated change, is how you ship a broken registry. Left for a dedicated PR against contracts/metadata.

Tests

Ten added, none executed (see below):

• deed_rejects_image_mime, title_rejects_image_mime, legal_instruments_reject_video_mime — the rejections the issue is about.
• deed_accepts_pdf, images_and_inspection_accept_photos — the policy does not over-reject.
• images_type_rejects_pdf — the policy is symmetric.
• other_type_defers_to_admin_list — Other follows the admin list when one is set, and is unrestricted when it is not.
• admin_cannot_widen_the_deed_policy — add_allowed_mime_type("image/png") does not make a PNG deed registrable.
• oversized_document_rejected — reads max_file_size from the contract rather than hardcoding it, so it does not silently drift from the constructor.
• rejected_upload_writes_no_state — after a rejection the counter is unchanged, the property has no documents, and the same CID is still free.

No validation was performed

No cargo command was run — no build, no test, no clippy, no fmt. The tests above have not been executed and are not demonstrated to compile or pass.

Specific risks a reviewer should check first:

• Associated consts inside the ink!-generated impl block. TITLE_DOCUMENT_MIMES and friends are declared in the contract's inherent impl. Valid Rust, but worth confirming against the ink! macro expansion.
• &'static str under no_std. String literals are fine, and the crate already uses ink::prelude::string::String, but the const arrays are a new shape here.
• Test CID helper. cid_for(seed) builds b-prefixed CIDs of 13 characters, satisfying validate_ipfs_cid's b + len >= 10 rule, and varying one trailing character so the registry's duplicate-CID check does not fire within a test.

DocumentType derives Debug, Clone, PartialEq, Eq, which the tests rely on for .clone() and for {document_type:?} assertion messages.

Per-issue notes

• IPFS metadata file_size, mime_type and document type are stored unverified - any uploader can claim a doc is a deed #1189 — the document_type/mime_type pairing is now enforced and no longer depends on admin configuration. FileTypeNotAllowed and SizeLimitExceeded are both reachable and covered. Acceptance criteria met.
• test_output_lib.txt is a stale single-test snapshot committed to the repo - remove or regenerate via CI artifacts #1187 — contracts/lib/test_output_lib.txt deleted (a committed CI snapshot showing running 1 test, captured from /workspaces/PropChain-contract). File removed from git. The issue also asks to re-run cargo test to confirm the surface is green, which the no-validation constraint forbids; that belongs to CI.
• IPFS metadata verify_content_hash computes/rechecks a hash provided by the uploader - verification is trivially spoofable #1188 — docs corrected as described. The hashing and signature requirements are not implemented, so this issue is only partially addressed.
• Metadata registry exposes unbounded listing queries (get_properties_by_type, get_properties_by_owner) with no pagination #1190 — not addressed. No code from this issue is in the diff.

#1188 and #1190 are closed per the assignment convention. Read #1189 and #1187 as delivered; do not read #1188 or #1190 as delivered.

Closes #1190	Metadata registry exposes unbounded listing queries (get_properties_by_type, get_properties_by_owner) with no pagination	Link to this issue
Closes #1187	test_output_lib.txt is a stale single-test snapshot committed to the repo - remove or regenerate via CI artifacts	Link to this issue
Closes #1189	IPFS metadata file_size, mime_type and document type are stored unverified - any uploader can claim a doc is a deed	Link to this issue
Closes #1188

#1190 Metadata registry exposes unbounded listing queries (get_properties_by_type, get_properties_by_owner) with no pagination Link to this issue
#1187 test_output_lib.txt is a stale single-test snapshot committed to the repo - remove or regenerate via CI artifacts Link to this issue
#1189 IPFS metadata file_size, mime_type and document type are stored unverified - any uploader can claim a doc is a deed Link to this issue
#1188

[nanaf6203-bit]

LGTM

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