Migrate the REST router off go-chi/chi onto go-pkgz/routegroup (backed by the
stdlib http.ServeMux), removing the last use of go-chi from the backend:
- rest.go routes() builds the tree with routegroup (Mount/Group/Route/With) and
net/http method+path patterns instead of chi's Get/Post/Route/Mount helpers
- chi.URLParam(...) -> r.PathValue(...) in the admin, public and private handlers
- rest_public_test.go loadPictureCtrl test uses routegroup + http.ServeMux
- rest_test.go: add TestRest_FileServerStaticAssets (bare /web -> /web/ redirect,
cache headers, 404, directory-listing block) and update the path-traversal test
for ServeMux normalising a literal ".." (encoded traversal is still rejected
by the handler)
- drop go-chi/chi from go.mod, go.sum and vendor; update the CLAUDE.md reference
* fix(security): reject non-image content-types in image proxy and /picture/ to prevent stored XSS
The /api/v1/img proxy and /api/v1/picture/{user}/{id} endpoints emitted
http.DetectContentType on the served bytes as the response Content-Type. A
controlled upstream serving Content-Type: image/png with an HTML body passed
the upstream check (only the response header was inspected, not the body),
and the body bytes then sniffed back to text/html — so the proxy served the
attacker's HTML from the remark42 origin. Browsers honoured the declared
text/html and executed the response as a document with access to cookies and
CSRF tokens. Affected from v1.6.0 (April 2020) through v1.15.0; verified live
via published docker images.
Layered defense applied to both handlers:
- rest.SafeImgContentType (in backend/app/rest/) validates sniffed content
against a strict allowlist: image/png, image/jpeg, image/gif, image/webp,
image/bmp, image/x-icon. Anything else (HTML, XML, SVG, plain text,
octet-stream, or any future image type the stdlib sniffer may learn) is
rejected with no body echo. SVG is implicitly excluded — it sniffs as
text/xml or text/plain, never image/svg+xml, and SVG can execute scripts
when navigated to top-level. The previous octet-stream → image/* fallback
is gone.
- Per-endpoint Content-Security-Policy override sets
"default-src 'none'; sandbox; frame-ancestors 'none'" on every response
(success, 304, or error). Sandbox neuters scripts even if Content-Type
ever regresses. The same policy is also applied to all /api/v1/* via
apiCSPMiddleware as defense-in-depth.
- Content-Disposition: inline; filename="image" frames the response as a
file rather than a renderable document.
- /picture/ rejection paths set Cache-Control: no-store so 4xx responses
are never cached.
The defense headers and the strict ETag matcher are extracted as
rest.SetImageDefenseHeaders and rest.EtagMatches in the shared rest package
(consumed by both proxy/image and api/rest_public — no package cycle).
The /api/v1/img path additionally bumps the ETag to a versioned `"v2:..."`
so revalidating clients (top-level navigation, Ctrl+R, intermediaries) get
a fresh 200 instead of a 304 against poisoned pre-fix cached HTML.
DELIBERATE TRADEOFF: Cache-Control on /api/v1/img success responses remains
max-age=2592000 (30 days), unchanged from before. An aggressive "force
revalidate on every reuse" policy was prototyped during review but reverted
because the perf cost (a server round-trip on every image view, even with
304 saving the body bytes) outweighed the corner-case mitigation. The
realistic exposure of cache carryover is narrow: cache carryover only
affects users who navigated top-level to an attacker URL pre-fix and still
have it in their local cache — the normal <img> embed path cached text/html
but never executed it. Local browser caches that hold pre-fix bytes
continue to serve them until their 30-day TTL expires or are evicted under
memory pressure. The ETag bump reaches all clients that DO revalidate
during the cached lifetime (Ctrl+R, intermediaries, post-expiry use); for
the rest, exposure self-limits via cache expiry. Operators running a
CDN/edge cache in front of remark42 should purge /api/v1/img after deploy.
The /api/v1/img handler short-circuits on a matching current-version
If-None-Match before any store Load or upstream fetch, returning a bodyless
304 with the defense headers set. Safe because the 304 carries no body and
the client's cached bytes came from a prior validated 200; an attacker
fabricating an etag value can only short-circuit fetches for URLs they
themselves crafted. This avoids upstream DoS amplification when clients
revalidate on hot comment pages.
The /api/v1/img route was moved from the "open routes" group (which uses
middleware.NoCache, stripping If-None-Match from incoming requests) to the
"open routes, cached" group alongside /picture/ and /qr/telegram so the
304 revalidation path is no longer broken upstream of the handler.
The /picture/{user}/{id} endpoint does not need the v2 etag prefix. Upload
validates input format via readAndValidateImage and the serve path
re-validates the stored bytes via rest.SafeImgContentType. Bytes within
the resize dimension limits are preserved verbatim, so the browser defense
relies on the response headers (validated Content-Type + nosniff + strict
CSP + Content-Disposition: inline), not on byte normalization.
Global CSP: font-src data: → font-src 'none'. Audit confirmed no @font-face,
no base64 fonts, no icon-font library in the bundle. Drops an unnecessary
attack surface; no behavioural change.
Tests: TestImage_ContentTypeHandling table-tests a real PNG and attack
shapes (HTML claimed as image/png, image/jpeg, image/gif, image/svg+xml,
image/webp; svg with onload; html fragment; polyglot PNG+HTML), proving
the defense holds across arbitrary upstream Content-Type variation.
Polyglot case is intentionally served as image/png — the browser cannot
execute the trailing HTML when the response type is image/png with nosniff.
TestImage_ContentTypeHandling_CacheHit exercises the cache-hit branch with
attacker bytes preloaded into the store. TestImage_PerRequestRevalidation
alternates upstream PNG/HTML across four proxy calls to prove no trust
accumulates between requests. TestImage_RoutesUsingCachedImage asserts
cache-poisoning is caught at serve time. TestImage_EtagVersioned asserts
the v2 prefix invalidates pre-fix etags AND that the revalidation 304
triggers no store Load. TestImage_RevalidationSkipsIO proves the
short-circuit works even with no upstream reachable. TestSafeImgContentType
covers the allowlist directly. TestRest_LoadPictureDefenseHeaders and
TestRest_LoadPictureRejectsNonImage exercise the /picture/ endpoint.
TestRest_apiCSP covers the strict CSP middleware on JSON API + RSS routes;
TestRest_securityHeaders confirms /web/ HTML pages keep the global CSP.
Verified end-to-end against the dev docker image: the original demo URL
(arbitrary HTML claimed as image/png) now returns 415 application/json with
CSP/nosniff/Content-Disposition set, no XSS in the browser.
* fix(security): set Cache-Control: no-store on image-proxy error paths, sync stale route comment
Addresses two review comments on #2067:
1. Cache-Control: max-age=2592000 and Etag were set before the
load/download/validation block, so 404/400/415 error responses inherited
the 30-day cache TTL and the versioned etag — a transient failure (or an
intentionally triggered 415) would be pinned in browser/intermediary
caches for that TTL, keeping users locked out even after the underlying
cause was resolved. Now: etag is computed but not set as a header until
after validation succeeds; error paths route through sendImageProxyError
which sets Cache-Control: no-store and never sets Etag. The 304
short-circuit still sets both because that path serves the same validated
content the client already has cached.
2. The comment at rest.go:282 still described the prototyped
no-cache/must-revalidate Cache-Control policy that was reverted before
the PR landed. Updated to match the actual 30-day max-age behavior.
Tests: TestImage_ContentTypeHandling now asserts reject paths carry
Cache-Control: no-store and have no Etag header, and accept paths carry
the max-age=2592000 + v2: etag.
Commit aca0cff3 silenced the path-traversal, SSRF and XSS taint rules
project-wide as "false positives" while fixing image-proxy SSRF. With
the path-traversal and TitleExtractor SSRF gaps now closed, restore the
rules so future regressions get flagged. The four genuine false positives
that remain (image proxy http.NewRequest, QR png Write, two RSS XML
Writes) get individual //nolint:gosec comments naming the reason.
Address PR #2045 review (umputun):
* The //nolint:gosec on telegramQrCtrl's w.Write(png) was byte-identical
to the same line in #2044 (gosec-rule restoration). Drop it here so
the two PRs do not conflict; #2044 owns it.
* `seg == ".."` in safePictureSegment was already covered by the
strings.Contains(seg, "..") check two lines down — trim and add an
inline comment so the cover-by-superset is explicit.
Address PR #2045 review feedback (Copilot #2045-1). The previous
safePictureSegment allowed CR/LF/TAB through, so a request such as
GET /api/v1/picture/dev%0Auser/abc.png would inject literal newlines
into the access log line ("GET - /api/v1/picture/dev\nuser/abc.png ...")
— a log-forgery primitive against any operator parsing those logs.
Reject any unicode.IsControl rune in either segment (NUL was already
caught via strings.ContainsAny). New TestRest_LoadPictureRejectsControlCharsInSegment
covers LF, CR, TAB, NUL across both segments.
The unauthenticated GET /api/v1/picture/{user}/{id} handler concatenated the
two URL params verbatim into a filesystem path via path.Join, so a request
like /api/v1/picture/../remark.db resolved to <base>/../remark.db, escaping
the image directory. With Partitions=0 (a documented option) this is a
direct arbitrary-file read; with the default Partitions=100 the constructed
path lands in a CRC-derived subdirectory but the server still leaks the
internal filesystem path back to the unauthenticated caller via the JSON
error body — confirmed against demo.remark42.com (master-80c12a3) which
returned `stat /var/folders/.../staging/.../remark.db` for `..` requests.
Validate both URL segments via safePictureSegment (no traversal markers,
no path separators, no NULs) at the handler entry, and replace the raw
storage error with a generic "image not found" response. The original
error is logged for operators.
Reproduction test asserts that ../remark.db, foo/..%2Fremark.db and
%2E%2E/remark.db all return 400 with no internal path leaked.
Replace go-chi/render with go-pkgz/rest for JSON responses and custom
helpers for HTML/plain text responses.
Key changes:
- Replace render.JSON/render.Status with rest.RenderJSON and explicit
w.WriteHeader() calls
- Replace render.DecodeJSON with json.NewDecoder().Decode()
- Add SendErrorJSON helper that sets Content-Type header before
WriteHeader (required since rest.RenderJSON can't set headers after
WriteHeader is called)
- Add HTMLResponse and PlainTextResponse helpers
Fix export double-execution in migrator.go:
The original code called Export twice - once to io.Discard to check for
errors, then again to actually write. This was wasteful and had a race
condition risk. Now file mode buffers to memory first for atomic
success/failure, while stream mode writes directly with proper error
handling.
`format=tree` pagination provides top-level comments with all replies
and returns the last top-level comment as `last_comment` to be used
as `offset` for the next page. If comments and replies overflow
the limit, the one stepping out of the limit will not be returned.
If the first comment and its replies after the given offset overflow
the limit, it will be returned with all the replies.
`format=plain` pagination works by providing all comments and returning
the last comment as `last_comment` to be used as `offset`
for the next page.
MakeTree calculated Info locally for historical reasons,
and the results were consistent with the dataService.Info call
but calculated differently.
That change fixes that, ensuring that Info is requested
in the same manner.
I haven't found a linter for these, so I had to catch these manually.
I found #757 to fix one of these, and I thought it would be good
to fix everything at once.
Telegram authentication requires you to open a chat on the phone.
It's convenient to have a QR code for the case when you want to
log in on the computer but have Telegram only on your phone
and would be able to scan the QR instead of copy-pasting the link
from the computer to the phone any other way.
Originally we thought of generating QR on the client but found
backend-generated QR a better alternative because we avoid adding
one more JavaScript dependency to the frontend that way.
That function returns an error in a never
expected condition, and that error would be
logged message on the caller side:
none of the callers handles it.
That change hides that error from the caller
so that function would have a signature that
better fit what it does and how it behaves.
It was supposed to solve #253 but frontend part for it in
#357 was never finished, and backend code produces false
positive test failures since day 0. The cost of just having
this code around is too high, we'll re-add it in case
frontend implementation will be finished.
@paskal
* sort imports, add missing copyright
* regenerate engine mock
* make all image.Store interface functions public
* go mod tidy
* make image.Store.Load return []byte instead of io.ReadCloser
* separate memory_store example RPC server to multiple files by handlers groups
* add /stream/info as a cheap way to subscribe to comment updates #253
* add check for lastTS change to allow proper info streams in no-cache mode
* check write error in info stream and terminate
* flaky info stream test
* add stream info to readme
* separate timeout middleware foe each route's group
* debug info on stream close
* fix test for streams
* stream timeout on inactivity only
* throttle streams to 500
* restore common throttle
Dmitry VerkhoturovandGitHub
