docs: record tested paid-download PRs for next release

docs/TODO.md

@@ -14,6 +14,17 @@ doc. See [`ROADMAP.md`](ROADMAP.md) for the curated, public-facing direction.
 
 ## Next release after 1.8.21 — reported 2026-09-30
 
+- [x] Review and repair open paid-download PRs #161 and #162, refresh both
+  branches from main, run independent and combined isolated suites, and verify
+  rootless file permissions in disposable scratch storage. Combined result:
+  1,585 passed, zero failed, four existing tests ignored. See the
+  [review evidence and remaining acceptance work](pr-review-20260930.md).
+- [ ] Integrate the reviewed PR branches into the next release and run funded
+  candidate acceptance, including Tor-only transport and payments with change.
+  PRs remain open; the reviewed code has not been deployed to live wallets.
+- [ ] Design durable recovery for an accepted payment whose response is lost.
+  Preserve the truthful unconfirmed-refund warning and prevent automatic
+  duplicate payment while that recovery work is outstanding.
 - [ ] **ThinkPad X250 kiosk: Bitcoin installation version selector is unreadable
   and appears underneath the pruning information.** Operator reports white
   styling with invisible text on the actual kiosk; the same flow works in remote

docs/pr-review-20260930.md

@@ -0,0 +1,113 @@
+# Paid-download PR review — 2026-09-30
+
+## Scope and result
+
+Reviewed both open PRs from the repository pull-request list: [#161](https://source.archipelago-foundation.org/lfg2025/archy/pulls/161)
+and [#162](https://source.archipelago-foundation.org/lfg2025/archy/pulls/162).
+Both branches were updated from main, repaired and tested independently and
+together. Their existing remote branches were advanced without rewriting the
+contributors' history. They remain open for integration into the release after
+1.8.21; no reviewed code was merged into main or deployed to a live wallet.
+The signed 1.8.21 artifacts are unchanged.
+
+| Candidate | Tested commit | Isolated backend result |
+| --- | --- | --- |
+| PR #161 | `971d4777` | 1,576 passed, 0 failed, 4 existing tests ignored |
+| PR #162 | `0677924a` | 1,568 passed, 0 failed, 4 existing tests ignored |
+| Both together | `4bf4bf1a` | 1,585 passed, 0 failed, 4 existing tests ignored |
+
+Both individual branches also passed production `cargo check`, with the
+repository's existing 16 warnings. The combined merge required no conflict
+resolution. Backend tests ran through `scripts/test-backend-isolated.sh` so they
+could not access host wallets, native services or production container storage.
+
+## Findings and repairs
+
+### #161 — payment delivery and file readability
+
+- The branch conflicted with newer mint-fee, keyset-ID and truthful refund
+  reporting fixes. Preserve those implementations from main; do not reintroduce
+  its older unconditional “refunded” messages or duplicate keyset resolution.
+- Opening a file before charging, then reopening/reading it afterward, still
+  permits a read failure after payment. Prepare the complete requested bytes
+  before redemption, including ranged reads. Tests delete or alter the backing
+  file during payment verification and still receive the prepared original data.
+- Empty/out-of-bounds/reversed ranges could fail after redemption, and empty
+  files could underflow the range calculation. Validate ranges before charging
+  and return HTTP 416 when unsatisfiable.
+- `chmod a+r` unnecessarily changed the permissions of shared paid/private
+  files. Read restricted FileBrowser files through the rootless namespace while
+  retaining their mode. Scope the fallback to regular files canonically inside
+  FileBrowser storage, and reject unauthorized peers before reading.
+- A single-delivery flag must also prevent redirects and ambiguous transport
+  retries. Payment-bearing GET and POST requests now retain the first HTTP
+  response and do not retry after timeouts or disconnects that might follow
+  delivery. Refused connections and normal nonpayment browsing retain the
+  appropriate retry behavior.
+- Interrupted response bodies now report the outcome using the actual local
+  refund result. Seller explanations are bounded, stripped of control
+  characters and explicitly identified as peer text.
+- Original permission tests silently returned when run as root. Replacement
+  tests inject read/payment boundary failures, exercise them under the isolated
+  runner, and assert that read failures never invoke redemption.
+
+### #162 — saving purchases in Files
+
+- Its host-permission repair overlapped 1.8.21's authenticated Files API path.
+  Review of [FileBrowser v2.63.23's resource handler](https://github.com/filebrowser/filebrowser/blob/v2.63.23/http/resource.go)
+  showed that `override=false` checks for existence separately from opening
+  with truncation. It does not guarantee no overwrites under concurrent saves.
+- The proposed direct path exposed the final filename before the write
+  completed. Both direct and namespace paths now finish a private temporary
+  file and publish it through a no-clobber hard link, retrying numbered names.
+- Plain `ln` could place a temporary file inside an existing directory instead
+  of treating the destination as a collision. Use `ln -T`; existing directories
+  and dangling symlinks are conflicts, never replacement targets.
+- Add filename and destination checks, unique temporary names, bounded name
+  retries, synchronization before publication, and exact input-length checks.
+  Truncated pipe input cannot become a completed purchased file.
+- Files storage remains optional. An unavailable copy destination does not
+  undo the purchase or create a fake FileBrowser installation; the durable
+  purchased-content cache remains primary.
+
+## Additional verification on the development node
+
+Used disposable scratch directories only, then removed them:
+
+- Reproduced a FileBrowser-style rootless-owned 0640 upload. The host backend
+  UID could not read it. `podman unshare cat` returned identical bytes without
+  changing its 0640 mode.
+- Ran the exact namespace writer script with four concurrent writers against
+  a directory owned by the container UID range. Every file had unique naming,
+  exact bytes, the expected owner and mode, and no remaining temporary file.
+- Sent truncated input to the namespace writer and verified refusal, no final
+  file and temporary-file cleanup.
+
+The isolated tests additionally exercised 24 simultaneous direct writes,
+existing-file preservation, symlink/directory conflicts, collision exhaustion,
+root-independent permission failures, read-before-redemption ordering,
+authorization, redirects and peer disconnects.
+
+Logs on the development box:
+`/tmp/archy-pr161-tests.log`, `/tmp/archy-pr162-tests.log`,
+`/tmp/archy-pr-integration-tests.log`, `/tmp/archy-pr161-check.log`,
+`/tmp/archy-pr162-check.log`, `/tmp/archy-pr-userns-scratch-test.log`.
+
+## Next-release acceptance and limits
+
+- Integrate the reviewed branches and repeat the release gates against the
+  final release commit if additional code changes land.
+- Perform funded peer-to-peer acceptance on the candidate build, including a
+  Tor-only purchase and a purchase requiring change, before the next release.
+  The new review branches were not deployed to funded live wallets here.
+- These PRs do not implement durable payment receipts. If a seller redeems a
+  payment and the connection subsequently loses the response, the buyer may
+  receive an unconfirmed-refund warning. Do not represent that warning as proof
+  of a refund or automatically charge the buyer again. Receipt-based recovery
+  remains separate follow-up work.
+- Abrupt process termination can leave a hidden namespace temporary file;
+  ordinary write failures and truncated input are tested to clean up. The final
+  filename is published only after complete input, and existing files remain
+  protected.
+- The separately reported X250 kiosk version-selector rendering issue remains
+  open in `TODO.md` and requires validation on the actual kiosk.