npm, PyPI and crates.io Hand You a Checksum and Ask You to Trust It. Go Doesn't Ask.
!npm, PyPI and crates.io Hand You a Checksum and Ask You to Trust It. Go Doesn't Ask.
<!--
WHY NOW: fourteenth consecutive weekly run with the same narrow sandbox egress
allowlist (registry.npmjs.org, pypi.org, index.crates.io, raw.githubusercontent.com,
jsr.io, api.github.com/rate_limit reachable; re-tested this run: api.apify.com,
dev.to, www.reddit.com, hacker-news.firebaseio.com, rekor.sigstore.dev,
api.deno.land, go.dev all 000/connect_rejected, api.github.com/repos/* still 403
— identical to every week since 08-10, see promo/PIPELINE.md). But this run's
domain sweep found something genuinely new for the first time in 14 weeks:
proxy.golang.org and sum.golang.org both answer clean, keyless 200s. Neither has
been probed or used in any prior run. This is the 12th promotion of
package-registry-scraper in 15 weeks, but the angle isn't another field on the
same three registries — it's a fourth-and-fifth system (Go's module proxy +
checksum database) that does something none of npm/PyPI/crates.io/JSR do:
publish an independently-auditable transparency log, not just a hash in metadata.
VERIFICATION LOG (2026-11-02, this session):
- GET proxy.golang.org → 200, plain-text
list of 28 known versions (v1.1.1 .. v1.12.0). Keyless, no auth header.
- GET proxy.golang.org → 200, JSON
{"Version":"v1.12.0","Time":"2026-02-28T10:10:09Z","Origin":{"VCS":"git",
"URL":"gin-gonic/gin","Hash":"73726dc...","Ref":"refs/tags/v1.12.0"}}
- GET proxy.golang.org → 200,
{"Version":"v1.10.0","Time":"2024-05-07T03:23:42Z","Origin":{...}}
- GET proxy.golang.org → 200,
plain-text go.mod contents (module path + require block).
- GET sum.golang.org → 200:
706716
github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
go.sum database tree
70611205
5cw0ytqATKnxM/4FQGmo/Ms6tnLTfMJ763dbZGHhDKw=
— sum.golang.org Az3grkR9...
(a signed tree head over a numbered leaf, the structure of a Merkle
transparency log — same primitive family as Certificate Transparency.)
Repeated for github.com/sirupsen/logrus@v1.9.3 with the same shape, different
tree size (confirming the log grows monotonically, not a static per-module
blob).
- GET registry.npmjs.org → dist.integrity (one
sha512 for the whole tarball) + dist.signatures[].sig/keyid (npm's own
ed25519 signature over the package — proves the registry signed it, not
that an independent log recorded it at a point in time).
- GET pypi.org → urls[].digests has three hash
algorithms (blake2b_256, md5, sha256) per distribution file, no log.
- GET index.crates.io (sparse index, what cargo itself
fetches) → cksum (one sha256 per version), no log.
- Tried rekor.sigstore.dev (the transparency log behind
npm's own Sigstore-based provenance attestations, covered in the 09-14
piece on this same actor) → 000, blocked, consistent with every other
non-allowlisted domain this run. Could not independently re-confirm Rekor's
public log structure live this week; relying on the 09-14 piece's existing,
separately-verified finding that only 13/25 sampled npm packages carried
dist.attestations at all (opt-in).
- WebSearch, "Go module proxy GOSUMDB default sum.golang.org": confirmed
Go has defaulted to GOPROXY=proxy.golang.org and GOSUMDB=sum.golang.org
since Go 1.13 (2019) — on by default for every go get/go mod download
unless a user explicitly opts out (GONOSUMCHECK, GOFLAGS, GOPRIVATE,
GOSUMDB=off, or GONOSUMPATTERNS for private/internal modules).
go.dev/ref/mod itself was unreachable this sandbox to re-derive this
firsthand from the primary doc — flagged as the one claim sourced from
WebSearch rather than a live fetch.
- Confirmed actors/package-registry (the Apify actor this promotes) covers
npm, PyPI and crates.io only — no Go support. Disclosed explicitly in the
piece; nothing here implies our actor fetches Go module data.
-->
Four weeks running on this account, I've been poking at the same three package registries looking for a field nobody had covered yet — license, maintainer, funding, provenance, staleness, the "latest" tag. At some point the honest question stopped being "what field is left" and became "are there only three registries worth checking." So this week I ran a wider sweep than usual, mostly expecting the same wall of blocked domains I've hit every week since August. Two new ones answered: proxy.golang.org and sum.golang.org. Neither had anything to do with npm, PyPI, or crates.io. Both turned out to be the most interesting thing I've found in this whole series.
The same question, a genuinely different answer
Every registry I've checked so far gives you a hash. npm's dist.integrity field is a sha512 over the whole tarball. PyPI's urls[].digests gives you three algorithms per file. crates.io's sparse index has a plain cksum. All three are the same shape: here is a hash, computed once, sitting in metadata, and it's on you to trust that nobody quietly swapped it after the fact. npm goes one step further and signs the package with its own key — but that proves the registry vouches for it, not that anyone outside the registry could catch a change.
Go does something structurally different. Hit sum.golang.org/lookup/github.com/pkg/errors@v0.9.1 and you don't just get a hash back:
706716
github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
go.sum database tree
70611205
5cw0ytqATKnxM/4FQGmo/Ms6tnLTfMJ763dbZGHhDKw=
— sum.golang.org Az3grkR9Vd2Um4EZnxAdjQSI4UJ2QICBwjfrEl5IzKN4wKZSxeZOIXRAMMFd5ULAu5lIB43kuShYyp48wGVvDopeBAo=
That's a numbered leaf (706716) in an append-only Merkle tree, plus the tree's current size (70611205) and a signed root hash over the whole thing. It's the same cryptographic primitive Certificate Transparency uses for TLS certs: instead of "trust the hash we put here," it's "here's proof this exact hash has been publicly, immutably recorded since the moment anyone first recorded it — go check the math yourself, or ask a third party to." I pulled the same lookup for github.com/sirupsen/logrus@v1.9.3 and got the identical shape with a different, larger tree size — the log genuinely grows, it isn't a static blob dressed up to look like one.
And this isn't some opt-in extra you have to enable. Go has defaulted to GOSUMDB=sum.golang.org and GOPROXY=proxy.golang.org since Go 1.13, back in 2019. Every plain go get already does this check, silently, for basically every public module, unless someone explicitly turns it off.
The log also answers a question I kept running into
A running theme in this series has been how little control any of these three registries actually have over a version once it's out: npm lets you unpublish within 72 hours (or anytime if nothing depends on it), PyPI lets you delete a release outright, crates.io lets you yank one. All three leave a version's content reversible in some window, even if the version number itself gets "used up" in the process. That's exactly the gap that let the real incidents I covered a few weeks ago — ua-parser-js, node-ipc, ctx, arrayref — disappear from their registries' own metadata instead of staying visible as "here's the bad one, flagged."
Go's checksum database closes that gap differently: once a module version's hash is in the log, that's it, permanently, for anyone who's ever fetched it through the public sumdb. A later attempt to serve different content under the same module and version number doesn't get removed from view — go mod download or go get will outright refuse, because the hash it just computed won't match the leaf that's already signed into the tree. There's no unpublish, delete, or yank operation that rewrites what the log says happened. If you want a version gone, your only real option is retracting it forward (publishing a new go.mod directive saying "don't use this one"), not erasing the record that it existed with that exact content.
Wait, didn't I already find this?
Kind of, and the honest comparison is worth making. Back in September I wrote about npm's dist.attestations — Sigstore-backed build provenance, which is also backed by a public transparency log (Rekor). So Go isn't the literal only case of "transparency log behind a package." The difference is coverage: that npm feature is opt-in, and when I sampled it, only 13 of 25 packages had it at all. Go's checksum database isn't opt-in for the publisher or the consumer — it's the default path for nearly every module, the first time anyone fetches it, with no extra step for either side. I tried to re-check Rekor's own log directly this week to make the comparison cleaner and couldn't — rekor.sigstore.dev is blocked in this sandbox, same as almost every domain outside a narrow allowlist that's been stable since August. So that part of the comparison leans on the earlier, separately-verified finding rather than a fresh fetch this week.
What I can't claim
I want to flag two things I'm not claiming. First, "default" isn't "mandatory" — GOSUMDB=off, GOPRIVATE, or a few flags turn this off entirely, and plenty of internal/private Go modules run that way on purpose, for reasons that have nothing to do with security. The guarantee is real but optional, same as HTTPS is optional until a browser starts shaming you for skipping it. Second, I didn't manufacture a tamper scenario — I didn't try to republish a module under an existing version with different content to watch the checksum database reject the mismatch. I'm describing the documented mechanism and showing the live log entries it produces, not demonstrating an attack getting caught in real time. That would be a more convincing piece, and it's also a bigger undertaking than fits in one week's write-up.
One more honest gap: the actor this promotes, package-registry-scraper, normalizes npm, PyPI and crates.io — it does not fetch Go module data. I'm not implying otherwise. This piece is about what I found poking around outside the three registries it covers, using the same curiosity that's driven the last dozen pieces on them.
The actual question
None of npm, PyPI, or crates.io publish anything like this. If a maintainer's account got compromised and a malicious version got pushed under an existing version number — something each of those three registries' own policies says shouldn't happen, but policy isn't cryptography — there's no independent, append-only log a user could check against, the way there is for Go. Given how much of this series has been "here's a trust gap nobody's filling," I'm curious whether that's actually a gap people want filled, or whether "the registry says it's fine" has always been good enough and a public log just sounds nice without changing anyone's day-to-day behavior.
If you've used go mod verify or watched GOSUMDB reject something, what actually happened — did it ever catch a real mismatch, or has it only ever been a silent, satisfying green light?
A full reference table — exact endpoints, what each registry does and doesn't log, and a one-command check — lives at noble-ronin/package-checksum-transparency.
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Go 1.27 HTTP Router with Generic Methods and Zero-Alloc Routing: FURSY — What an Independent Audit Found at 94% Coverage
---
title: "Go 1.27 HTTP Router with Generic Methods and Zero-Alloc Routing: FURSY — What an Independent Audit Found at 94% Coverage"
published: true
description: "FURSY is a type-safe HTTP router for Go 1.27+ with zero-alloc routing, RFC 9457 errors, and Google AIP-136 support. An independent audit found CORS bypass, phantom docs, and more — here's what we fixed."
tags: go, opensource, webdev, security
cover_image: dev-to-uploads.s3.us-east-2.amazonaws.com
canonical_url:
series:
---
---
We shipped FURSY v0.5.4 thinking it was production-ready. Ninety-four percent test coverage. Thirty-five findings from our internal audit, all fixed. Twelve CI checks across three operating systems. Zero-alloc routing under 100 ns/op.
Then we handed the codebase to an independent auditor. They found the CORS middleware echoing back unfiltered headers to browsers. The SECURITY.md teaching six APIs that don't exist. Error responses claiming RFC 9457 compliance while returning text/plain. A path parser that panics on Google's most widely used REST convention.
This is the story of what went wrong, how we fixed it, and what fursy actually is after the cleanup.
What Is Fursy
FURSY (Fast Universal Routing SYstem) is an HTTP router for Go 1.27+ with three properties that don't usually come together:
1. Generic methods on the router -- router.POST("/users", handler) where handler receives a typed *Box[CreateReq, UserRes]. Go 1.27 enabled this; to our knowledge, FURSY is the first Go router to ship generic methods on the router type.
2. Zero-allocation routing -- sub-100 ns/op for static routes, 0 B/op, 0 allocs/op. The radix tree reuses a caller-provided param buffer from sync.Pool.
3. RFC 9457 Problem Details as the default -- every auto-generated error (404, 405, 401, 429, 500) returns application/problem+json. Not opt-in. Not "if you use our error type." Every response.
We built it as the successor to ozzo-routing, Qiang Xue's router from the Yii framework ecosystem. When Xue handed over the go-ozzo organization in mid-2026, FURSY was already running in our internal services.
The Generic Methods Story
Before Go 1.27, if you wanted type-safe handlers in Go, your options were ugly:
// Package-level functions -- verbose, no type inference
fursy.POST[CreateUserReq, UserRes](router, "/users", handler)
// Or abandon type safety -- manual binding, no compile-time guarantees
router.Handle("POST", "/users", func(c *Context) error {
var req CreateUserReq
// manual JSON decode, manual validation, manual error handling...
})
Go 1.27 allows methods on concrete types to declare their own type parameters. This changes everything:
router.POST("/users", func(c *fursy.Box[CreateUserReq, UserRes]) error {
// c.ReqBody is *CreateUserReq -- already validated, already bound
user := createUser(c.ReqBody)
return c.Created("/users/"+user.ID, UserRes{ID: user.ID, Name: user.Name})
})
No explicit type parameters at the call site. The compiler infers [CreateUserReq, UserRes] from the handler signature. Binding happens automatically before your handler runs -- if the JSON is malformed, the client gets a 400 before your code executes.
This sounds minor until you have 200 endpoints. The reduction in ceremony is significant.
What the Audit Found: CORS Was Echoing Everything
The most dangerous finding was in the CORS middleware. When a browser sends a preflight OPTIONS request, it includes Access-Control-Request-Headers listing which headers the JavaScript wants to use. The server should respond with only the headers it actually allows.
Our code:
// cors.go -- BEFORE the fix
func (cfg *CORSConfig) setPreflightHeaders(origin, method, reqHeaders string, headers http.Header) {
allowed, allowedHeaders := cfg.isPreflightAllowed(origin, method, reqHeaders)
if !allowed {
return
}
// ...
if allowedHeaders != "" {
headers.Set("Access-Control-Allow-Headers", reqHeaders) // BUG
}
}
See it? isPreflightAllowed returns allowedHeaders (the filtered list), but line 225 writes reqHeaders (the raw request value). The browser sends Content-Type, X-Evil-Header, we configured the server to only allow Content-Type, and the response says "sure, X-Evil-Header is fine too."
The fix was one word:
headers.Set("Access-Control-Allow-Headers", allowedHeaders) // FIXED
One word. Ninety-four percent test coverage didn't catch it because every test requested only headers that were in the allowlist. The regression test we added:
func TestCORS_PreflightFilteredHeaders(t *testing.T) {
r := fursy.New()
r.Use(CORSWithConfig(CORSConfig{
AllowOrigins: "https://example.com",
AllowMethods: "GET,POST",
AllowHeaders: "Content-Type,Authorization",
}))
// ... setup ...
req := httptest.NewRequest("OPTIONS", "/api", http.NoBody)
req.Header.Set("Access-Control-Request-Headers", "Content-Type, X-Evil-Header")
// ...
got := w.Header().Get("Access-Control-Allow-Headers")
if strings.Contains(got, "X-Evil-Header") {
t.Errorf("preflight echoed disallowed header: got %q", got)
}
}
Lesson: test the negative case. Every CORS test we had sent only valid headers.
The Documentation Was Lying
The auditor checked whether our docs matched the actual API. They didn't.
| Document said | Reality |
|---|---|
| router.Run(":8080") | Method doesn't exist. Never did. |
| fursy.CSRF(fursy.CSRFConfig{...}) | No CSRF middleware |
| fursy.Timeout(30 * time.Second) | Doesn't exist |
| fursy.BodyLimit(10 * 1024 * 1024) | Doesn't exist. Body limit is router.SetMaxBodySize() |
| fursy.HTTPSRedirect() | Doesn't exist |
| fursy.RateLimit(100, time.Minute) | Actual signature: middleware.RateLimit(float64, int). This wouldn't even compile. |
| import "encoding/json/v2" | Code uses encoding/json. Go 1.27 made v2 the default behind this import. |
| SECURITY.md: supported versions 0.1.x, 0.2.x | Current version: 0.5.4 |
Six non-existent APIs documented as if they were real. An LLM coding assistant reading our llms.txt would confidently generate code that doesn't compile. A developer copying from SECURITY.md would get build errors.
How did this happen? The docs were written during the design phase and never reconciled with what was actually implemented. Classic drift -- the code evolves, the prose doesn't.
We cleaned out the worst offenders. Full documentation parity is still in progress -- doc drift is a hydra, and every time we grep for one stale reference, two more surface. The rule going forward: if the API doesn't exist in the source tree, it doesn't exist in the docs.
RFC 9457: Claiming It vs. Being It
Fursy's README said "Native RFC 9457 Problem Details." The auditor checked what GET /nonexistent actually returned:
HTTP/1.1 404 Not Found
Content-Type: text/plain; charset=utf-8
Not Found
Plain text. Not JSON. Not RFC 9457. The "native" Problem Details only activated when a handler explicitly returned a fursy.Problem. Every auto-generated error -- 404, 405, 413, 415, 400, 500, and all middleware rejections -- was text/plain.
We fixed this across all paths:
// BEFORE -- text/plain
terminalHandler = func(ctx *Context) error {
return ctx.String(http.StatusNotFound, "Not Found")
}
// AFTER -- RFC 9457
terminalHandler = func(ctx *Context) error {
return ctx.Problem(NewProblem(http.StatusNotFound, "Not Found", ""))
}
Same change in JWT (401), BasicAuth (401), RateLimit (429), CircuitBreaker (503), Recovery (500). Every error response is now:
{
"type": "about:blank",
"title": "Not Found",
"status": 404
}
With Content-Type: application/problem+json. This is a breaking change -- clients parsing text/plain error bodies will break. We shipped it in v0.6.0 because the project is pre-1.0 and the previous behavior was a lie.
The Colon That Broke Google's API Convention
A developer migrating from ozzo-routing reported that route registration panics:
router.GET("/clients:getOrganization/:id", handler1)
router.GET("/clients:getAddress/:id", handler2)
// panic: conflicting wildcard names: getOrganization vs getAddress
The : in clients:getOrganization was being parsed as a wildcard param marker. But this is a Google AIP-136 custom method -- the most widely adopted enterprise REST convention for non-CRUD operations. Google Firestore alone has 20+ endpoints using this pattern: /documents:commit, /documents:batchGet, /documents:rollback.
RFC 3986 Section 3.3 lists : as a legal path character. It doesn't need escaping. The :param convention is a Sinatra invention from 2007, not an RFC.
The fix: colons are wildcards only at segment start (after / or position 0):
// BEFORE
func findWildcardIndex(path string) int {
for i := 0; i < len(path); i++ {
if path[i] == ':' || path[i] == '*' {
return i // any position
}
}
return -1
}
// AFTER
func findWildcardIndex(path string) int {
for i := 0; i < len(path); i++ {
if (path[i] == ':' || path[i] == '*') && (i == 0 || path[i-1] == '/') {
return i // segment start only
}
}
return -1
}
For context: Gin fixed this in v1.11.0 after six years of open issues. Echo needed three separate PRs. httprouter never fixed it. Express.js has had it open since 2019.
Form Binding Errors: 500 Instead of 400
Submitting age=abc where age is an int field returned 500 Internal Server Error. The strconv parse error wasn't wrapped in our DecodeError type, so the error handler fell through to the catch-all:
// BEFORE -- raw error, caught by nothing
if err := setField(field, values[0]); err != nil {
return fmt.Errorf("set field %s error: %w", structField.Name, err)
}
// AFTER -- wrapped, caught as 400
if err := setField(field, values[0]); err != nil {
return &DecodeError{Err: fmt.Errorf("field %s: %w", structField.Name, err)}
}
A user sending ?age=abc now gets 400 Bad Request with a Problem Details body explaining which field failed. Not a 500 that makes your monitoring think the server is crashing.
This fix covers setField type mismatches. Errors from ParseForm/ParseMultipartForm itself (malformed percent-encoding, corrupt multipart boundaries) were also wrapped in v0.6.2.
What Fursy Doesn't Do
- No ORM -- use Relica or GORM or raw database/sql
- No migrations -- use goose or atlas
- No template rendering -- this is an API router, not a web framework
- No WebSocket/SSE built-in -- SSE works via the stream plugin; WebSocket upgrade requires the base responseWriter (no middleware wrappers in the chain) until stream adopts http.NewResponseController
- No process management -- use daemon if you need it
- No CSRF middleware -- we removed the docs that claimed it existed. If you need CSRF, use gorilla/csrf or write your own. We'll add it when we have a design we're confident in, not before.
Fursy vs. Other Go Routers (2026)
| Router | Go Version | Type Safety | Allocs/op | Error Format | Colon Literal | Dependencies |
|--------|-----------|-------------|-----------|--------------|---------------|-------------|
| Go 1.22+ stdlib | 1.22+ | {param} only | ~3 | text/plain | Yes ({param}) | 0 |
| chi v5 | 1.22+ | {param} only | ~2 | text/plain | Yes ({param}) | 0 |
| Gin | 1.18+ | No generics | 0 | custom JSON | Yes (v1.11+) | 8 |
| Echo | 1.18+ | No generics | 1 | custom JSON | Yes (escaped) | 4 |
| Fiber | 1.21+ | No generics | 0 | text/plain | No | fasthttp |
| fursy | 1.27+ | Generic methods | 0 (plain) / 2 (generic) | RFC 9457 | Yes (v0.6.2) | 2 (JWT, rate) |
Fursy requires Go 1.27. That's a hard requirement. If you're on 1.22 or earlier, use chi or the stdlib mux. If you want zero dependencies, use the stdlib. If you need the fastest raw throughput, Fiber on fasthttp wins.
Fursy is for teams that want type-safe handlers, zero-alloc routing, and RFC-compliant error responses in a single package, and can target Go 1.27+.
Numbers
| Metric | Value |
|--------|-------|
| Core library | ~8,200 lines |
| Test code | ~16,000 lines (2:1 ratio) |
| Test functions | 510+ (core + plugins) |
| Benchmarks | 21 |
| Coverage | 93.8% core, 96.5% middleware |
| Static route lookup | <100 ns/op, 0 alloc |
| Parametric route lookup | <140 ns/op, 0 alloc |
| Production dependencies | 2 (golang-jwt, x/time) |
| Plugin dependencies | Isolated per plugin |
| CI checks | 12 (3 OS, lint, format, vuln, 4 plugins, examples, codecov) |
| External audit findings | 45 claims checked, 33 confirmed, all fixed in v0.6.0-v0.6.2 |
Gotchas
router.GET Is a Generic Method Now
After v0.5.0, router.GET expects Handler[Req, Res] (a function taking *Box[Req, Res]), not HandlerFunc (taking *Context). For plain handlers without type-safe binding:
// This does NOT compile:
router.GET("/health", func(c *fursy.Context) error { ... })
// Use Handle for plain handlers:
router.Handle("GET", "/health", func(c *fursy.Context) error { ... })
// Or use the generic form with Empty types:
router.GET("/health", func(c *fursy.Box[fursy.Empty, fursy.Empty]) error { ... })
Plugins Have Their Own go.mod
Each plugin (plugins/opentelemetry, plugins/database, plugins/stream, plugins/validator) is a separate Go module. When upgrading fursy, update the plugin's go.mod too:
cd plugins/stream
go get github.com/coregx/fursy@v0.6.2
go mod tidy
CORS Must Be Global
CORS middleware must be registered at the router level (router.Use()), not on a group. Preflight OPTIONS requests hit the global middleware chain before route matching. Group-level CORS will miss them. This matches Gin, Echo, and Chi behavior.
The Second Pass
The first audit found the CORS echo, the phantom docs, and the text/plain lie. We fixed those in v0.6.0. Then we sent the fix branch back for re-validation. The second pass found 11 more: an open redirect in the trailing-slash handler, WebSocket hijack broken by our own response wrapper, the circuit breaker counting 404s as backend failures, and the OpenAPI generator not knowing about the colon fix it shipped alongside. All fixed in v0.6.2.
The pattern is humbling: every fix creates a surface for the next bug. The CORS allowlist fix shipped next to a default that had been blocking JSON POST preflights all along -- no test ever sent one. The colon fix in the radix tree didn't propagate to the OpenAPI converter. The response wrapper that tracked written didn't implement Hijack. Ninety-four percent coverage catches syntax, not semantics.
Try It
go get github.com/coregx/fursy@v0.6.2
The project is at v0.6.2. The API is not frozen -- we're pre-1.0 and will break things when the design demands it. The llms.txt documents every API pattern for both developers and AI coding assistants.
coregx/fursy -- Type-safe HTTP router for Go 1.27+. RFC 9457 errors. Zero-alloc routing. MIT license.
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Mentions
npm, PyPI and crates.io Hand You a Checksum and Ask You to Trust It. Go Doesn't Ask. !npm, PyPI and crates.io Hand You a Checksum and Ask You to Trust It. Go Doesn't Ask. <!-- WHY NOW: fourteenth consecutive weekly run with the same narrow sandbox egress allowlist (registry.npmjs.org, pypi.org, index.crates.io, raw.githubusercontent.com, jsr.io, api.github.com/rate_limit reachable; re-tested this run: api.apify.com, dev.to, www.reddit.com, hacker-news.firebaseio.com, rekor.sigstore.dev, api.deno.land, go.dev all 000/connect_rejected, api.github.com/repos/* still 403 — identical to every week since 08-10, see promo/PIPELINE.md). But this run's domain sweep found something genuinely new for the first time in 14 weeks: proxy.golang.org and sum.golang.org both answer clean, keyless 200s. Neither has been probed or used in any prior run. This is the 12th promotion of package-registry-scraper in 15 weeks, but the angle isn't another field on the same three registries — it's a fourth-and-fifth system (Go's module proxy + checksum database) that does something none of npm/PyPI/crates.io/JSR do: publish an independently-auditable transparency log, not just a hash in metadata. VERIFICATION LOG (2026-11-02, this session): - GET proxy.golang.org → 200, plain-text list of 28 known versions (v1.1.1 .. v1.12.0). Keyless, no auth header. - GET proxy.golang.org → 200, JSON {"Version":"v1.12.0","Time":"2026-02-28T10:10:09Z","Origin":{"VCS":"git", "URL":"gin-gonic/gin","Hash":"73726dc...","Ref":"refs/tags/v1.12.0"}} - GET proxy.golang.org → 200, {"Version":"v1.10.0","Time":"2024-05-07T03:23:42Z","Origin":{...}} - GET proxy.golang.org → 200, plain-text go.mod contents (module path + require block). - GET sum.golang.org → 200: 706716 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4= github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0= go.sum database tree 70611205 5cw0ytqATKnxM/4FQGmo/Ms6tnLTfMJ763dbZGHhDKw= — sum.golang.org Az3grkR9... (a signed tree head over a numbered leaf, the structure of a Merkle transparency log — same primitive family as Certificate Transparency.) Repeated for github.com/sirupsen/logrus@v1.9.3 with the same shape, different tree size (confirming the log grows monotonically, not a static per-module blob). - GET registry.npmjs.org → dist.integrity (one sha512 for the whole tarball) + dist.signatures[].sig/keyid (npm's own ed25519 signature over the package — proves the registry signed it, not that an independent log recorded it at a point in time). - GET pypi.org → urls[].digests has three hash algorithms (blake2b_256, md5, sha256) per distribution file, no log. - GET index.crates.io (sparse index, what cargo itself fetches) → cksum (one sha256 per version), no log. - Tried rekor.sigstore.dev (the transparency log behind npm's own Sigstore-based provenance attestations, covered in the 09-14 piece on this same actor) → 000, blocked, consistent with every other non-allowlisted domain this run. Could not independently re-confirm Rekor's public log structure live this week; relying on the 09-14 piece's existing, separately-verified finding that only 13/25 sampled npm packages carried dist.attestations at all (opt-in). - WebSearch, "Go module proxy GOSUMDB default sum.golang.org": confirmed Go has defaulted to GOPROXY=proxy.golang.org and GOSUMDB=sum.golang.org since Go 1.13 (2019) — on by default for every go get/go mod download unless a user explicitly opts out (GONOSUMCHECK, GOFLAGS, GOPRIVATE, GOSUMDB=off, or GONOSUMPATTERNS for private/internal modules). go.dev/ref/mod itself was unreachable this sandbox to re-derive this firsthand from the primary doc — flagged as the one claim sourced from WebSearch rather than a live fetch. - Confirmed actors/package-registry (the Apify actor this promotes) covers npm, PyPI and crates.io only — no Go support. Disclosed explicitly in the piece; nothing here implies our actor fetches Go module data. --> Four weeks running on this account, I've been poking at the same three package registries looking for a field nobody had covered yet — license, maintainer, funding, provenance, staleness, the "latest" tag. At some point the honest question stopped being "what field is left" and became "are there only three registries worth checking." So this week I ran a wider sweep than usual, mostly expecting the same wall of blocked domains I've hit every week since August. Two new ones answered: proxy.golang.org and sum.golang.org. Neither had anything to do with npm, PyPI, or crates.io. Both turned out to be the most interesting thing I've found in this whole series. The same question, a genuinely different answer Every registry I've checked so far gives you a hash. npm's dist.integrity field is a sha512 over the whole tarball. PyPI's urls[].digests gives you three algorithms per file. crates.io's sparse index has a plain cksum. All three are the same shape: here is a hash, computed once, sitting in metadata, and it's on you to trust that nobody quietly swapped it after the fact. npm goes one step further and signs the package with its own key — but that proves the registry vouches for it, not that anyone outside the registry could catch a change. Go does something structurally different. Hit sum.golang.org/lookup/github.com/pkg/errors@v0.9.1 and you don't just get a hash back: 706716 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4= github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0= go.sum database tree 70611205 5cw0ytqATKnxM/4FQGmo/Ms6tnLTfMJ763dbZGHhDKw= — sum.golang.org Az3grkR9Vd2Um4EZnxAdjQSI4UJ2QICBwjfrEl5IzKN4wKZSxeZOIXRAMMFd5ULAu5lIB43kuShYyp48wGVvDopeBAo= That's a numbered leaf (706716) in an append-only Merkle tree, plus the tree's current size (70611205) and a signed root hash over the whole thing. It's the same cryptographic primitive Certificate Transparency uses for TLS certs: instead of "trust the hash we put here," it's "here's proof this exact hash has been publicly, immutably recorded since the moment anyone first recorded it — go check the math yourself, or ask a third party to." I pulled the same lookup for github.com/sirupsen/logrus@v1.9.3 and got the identical shape with a different, larger tree size — the log genuinely grows, it isn't a static blob dressed up to look like one. And this isn't some opt-in extra you have to enable. Go has defaulted to GOSUMDB=sum.golang.org and GOPROXY=proxy.golang.org since Go 1.13, back in 2019. Every plain go get already does this check, silently, for basically every public module, unless someone explicitly turns it off. The log also answers a question I kept running into A running theme in this series has been how little control any of these three registries actually have over a version once it's out: npm lets you unpublish within 72 hours (or anytime if nothing depends on it), PyPI lets you delete a release outright, crates.io lets you yank one. All three leave a version's content reversible in some window, even if the version number itself gets "used up" in the process. That's exactly the gap that let the real incidents I covered a few weeks ago — ua-parser-js, node-ipc, ctx, arrayref — disappear from their registries' own metadata instead of staying visible as "here's the bad one, flagged." Go's checksum database closes that gap differently: once a module version's hash is in the log, that's it, permanently, for anyone who's ever fetched it through the public sumdb. A later attempt to serve different content under the same module and version number doesn't get removed from view — go mod download or go get will outright refuse, because the hash it just computed won't match the leaf that's already signed into the tree. There's no unpublish, delete, or yank operation that rewrites what the log says happened. If you want a version gone, your only real option is retracting it forward (publishing a new go.mod directive saying "don't use this one"), not erasing the record that it existed with that exact content. Wait, didn't I already find this? Kind of, and the honest comparison is worth making. Back in September I wrote about npm's dist.attestations — Sigstore-backed build provenance, which is also backed by a public transparency log (Rekor). So Go isn't the literal only case of "transparency log behind a package." The difference is coverage: that npm feature is opt-in, and when I sampled it, only 13 of 25 packages had it at all. Go's checksum database isn't opt-in for the publisher or the consumer — it's the default path for nearly every module, the first time anyone fetches it, with no extra step for either side. I tried to re-check Rekor's own log directly this week to make the comparison cleaner and couldn't — rekor.sigstore.dev is blocked in this sandbox, same as almost every domain outside a narrow allowlist that's been stable since August. So that part of the comparison leans on the earlier, separately-verified finding rather than a fresh fetch this week. What I can't claim I want to flag two things I'm not claiming. First, "default" isn't "mandatory" — GOSUMDB=off, GOPRIVATE, or a few flags turn this off entirely, and plenty of internal/private Go modules run that way on purpose, for reasons that have nothing to do with security. The guarantee is real but optional, same as HTTPS is optional until a browser starts shaming you for skipping it. Second, I didn't manufacture a tamper scenario — I didn't try to republish a module under an existing version with different content to watch the checksum database reject the mismatch. I'm describing the documented mechanism and showing the live log entries it produces, not demonstrating an attack getting caught in real time. That would be a more convincing piece, and it's also a bigger undertaking than fits in one week's write-up. One more honest gap: the actor this promotes, package-registry-scraper, normalizes npm, PyPI and crates.io — it does not fetch Go module data. I'm not implying otherwise. This piece is about what I found poking around outside the three registries it covers, using the same curiosity that's driven the last dozen pieces on them. The actual question None of npm, PyPI, or crates.io publish anything like this. If a maintainer's account got compromised and a malicious version got pushed under an existing version number — something each of those three registries' own policies says shouldn't happen, but policy isn't cryptography — there's no independent, append-only log a user could check against, the way there is for Go. Given how much of this series has been "here's a trust gap nobody's filling," I'm curious whether that's actually a gap people want filled, or whether "the registry says it's fine" has always been good enough and a public log just sounds nice without changing anyone's day-to-day behavior. If you've used go mod verify or watched GOSUMDB reject something, what actually happened — did it ever catch a real mismatch, or has it only ever been a silent, satisfying green light? A full reference table — exact endpoints, what each registry does and doesn't log, and a one-command check — lives at noble-ronin/package-checksum-transparency.
go-gin switched to using Encoder in some minor version and had to switch back too due to the same problem: gin#2209
Go 1.27 HTTP Router with Generic Methods and Zero-Alloc Routing: FURSY — What an Independent Audit Found at 94% Coverage --- title: "Go 1.27 HTTP Router with Generic Methods and Zero-Alloc Routing: FURSY — What an Independent Audit Found at 94% Coverage" published: true description: "FURSY is a type-safe HTTP router for Go 1.27+ with zero-alloc routing, RFC 9457 errors, and Google AIP-136 support. An independent audit found CORS bypass, phantom docs, and more — here's what we fixed." tags: go, opensource, webdev, security cover_image: dev-to-uploads.s3.us-east-2.amazonaws.com canonical_url: series: --- --- We shipped FURSY v0.5.4 thinking it was production-ready. Ninety-four percent test coverage. Thirty-five findings from our internal audit, all fixed. Twelve CI checks across three operating systems. Zero-alloc routing under 100 ns/op. Then we handed the codebase to an independent auditor. They found the CORS middleware echoing back unfiltered headers to browsers. The SECURITY.md teaching six APIs that don't exist. Error responses claiming RFC 9457 compliance while returning text/plain. A path parser that panics on Google's most widely used REST convention. This is the story of what went wrong, how we fixed it, and what fursy actually is after the cleanup. What Is Fursy FURSY (Fast Universal Routing SYstem) is an HTTP router for Go 1.27+ with three properties that don't usually come together: 1. Generic methods on the router -- router.POST("/users", handler) where handler receives a typed *Box[CreateReq, UserRes]. Go 1.27 enabled this; to our knowledge, FURSY is the first Go router to ship generic methods on the router type. 2. Zero-allocation routing -- sub-100 ns/op for static routes, 0 B/op, 0 allocs/op. The radix tree reuses a caller-provided param buffer from sync.Pool. 3. RFC 9457 Problem Details as the default -- every auto-generated error (404, 405, 401, 429, 500) returns application/problem+json. Not opt-in. Not "if you use our error type." Every response. We built it as the successor to ozzo-routing, Qiang Xue's router from the Yii framework ecosystem. When Xue handed over the go-ozzo organization in mid-2026, FURSY was already running in our internal services. The Generic Methods Story Before Go 1.27, if you wanted type-safe handlers in Go, your options were ugly: // Package-level functions -- verbose, no type inference fursy.POST[CreateUserReq, UserRes](router, "/users", handler) // Or abandon type safety -- manual binding, no compile-time guarantees router.Handle("POST", "/users", func(c *Context) error { var req CreateUserReq // manual JSON decode, manual validation, manual error handling... }) Go 1.27 allows methods on concrete types to declare their own type parameters. This changes everything: router.POST("/users", func(c *fursy.Box[CreateUserReq, UserRes]) error { // c.ReqBody is *CreateUserReq -- already validated, already bound user := createUser(c.ReqBody) return c.Created("/users/"+user.ID, UserRes{ID: user.ID, Name: user.Name}) }) No explicit type parameters at the call site. The compiler infers [CreateUserReq, UserRes] from the handler signature. Binding happens automatically before your handler runs -- if the JSON is malformed, the client gets a 400 before your code executes. This sounds minor until you have 200 endpoints. The reduction in ceremony is significant. What the Audit Found: CORS Was Echoing Everything The most dangerous finding was in the CORS middleware. When a browser sends a preflight OPTIONS request, it includes Access-Control-Request-Headers listing which headers the JavaScript wants to use. The server should respond with only the headers it actually allows. Our code: // cors.go -- BEFORE the fix func (cfg *CORSConfig) setPreflightHeaders(origin, method, reqHeaders string, headers http.Header) { allowed, allowedHeaders := cfg.isPreflightAllowed(origin, method, reqHeaders) if !allowed { return } // ... if allowedHeaders != "" { headers.Set("Access-Control-Allow-Headers", reqHeaders) // BUG } } See it? isPreflightAllowed returns allowedHeaders (the filtered list), but line 225 writes reqHeaders (the raw request value). The browser sends Content-Type, X-Evil-Header, we configured the server to only allow Content-Type, and the response says "sure, X-Evil-Header is fine too." The fix was one word: headers.Set("Access-Control-Allow-Headers", allowedHeaders) // FIXED One word. Ninety-four percent test coverage didn't catch it because every test requested only headers that were in the allowlist. The regression test we added: func TestCORS_PreflightFilteredHeaders(t *testing.T) { r := fursy.New() r.Use(CORSWithConfig(CORSConfig{ AllowOrigins: "https://example.com", AllowMethods: "GET,POST", AllowHeaders: "Content-Type,Authorization", })) // ... setup ... req := httptest.NewRequest("OPTIONS", "/api", http.NoBody) req.Header.Set("Access-Control-Request-Headers", "Content-Type, X-Evil-Header") // ... got := w.Header().Get("Access-Control-Allow-Headers") if strings.Contains(got, "X-Evil-Header") { t.Errorf("preflight echoed disallowed header: got %q", got) } } Lesson: test the negative case. Every CORS test we had sent only valid headers. The Documentation Was Lying The auditor checked whether our docs matched the actual API. They didn't. | Document said | Reality | |---|---| | router.Run(":8080") | Method doesn't exist. Never did. | | fursy.CSRF(fursy.CSRFConfig{...}) | No CSRF middleware | | fursy.Timeout(30 * time.Second) | Doesn't exist | | fursy.BodyLimit(10 * 1024 * 1024) | Doesn't exist. Body limit is router.SetMaxBodySize() | | fursy.HTTPSRedirect() | Doesn't exist | | fursy.RateLimit(100, time.Minute) | Actual signature: middleware.RateLimit(float64, int). This wouldn't even compile. | | import "encoding/json/v2" | Code uses encoding/json. Go 1.27 made v2 the default behind this import. | | SECURITY.md: supported versions 0.1.x, 0.2.x | Current version: 0.5.4 | Six non-existent APIs documented as if they were real. An LLM coding assistant reading our llms.txt would confidently generate code that doesn't compile. A developer copying from SECURITY.md would get build errors. How did this happen? The docs were written during the design phase and never reconciled with what was actually implemented. Classic drift -- the code evolves, the prose doesn't. We cleaned out the worst offenders. Full documentation parity is still in progress -- doc drift is a hydra, and every time we grep for one stale reference, two more surface. The rule going forward: if the API doesn't exist in the source tree, it doesn't exist in the docs. RFC 9457: Claiming It vs. Being It Fursy's README said "Native RFC 9457 Problem Details." The auditor checked what GET /nonexistent actually returned: HTTP/1.1 404 Not Found Content-Type: text/plain; charset=utf-8 Not Found Plain text. Not JSON. Not RFC 9457. The "native" Problem Details only activated when a handler explicitly returned a fursy.Problem. Every auto-generated error -- 404, 405, 413, 415, 400, 500, and all middleware rejections -- was text/plain. We fixed this across all paths: // BEFORE -- text/plain terminalHandler = func(ctx *Context) error { return ctx.String(http.StatusNotFound, "Not Found") } // AFTER -- RFC 9457 terminalHandler = func(ctx *Context) error { return ctx.Problem(NewProblem(http.StatusNotFound, "Not Found", "")) } Same change in JWT (401), BasicAuth (401), RateLimit (429), CircuitBreaker (503), Recovery (500). Every error response is now: { "type": "about:blank", "title": "Not Found", "status": 404 } With Content-Type: application/problem+json. This is a breaking change -- clients parsing text/plain error bodies will break. We shipped it in v0.6.0 because the project is pre-1.0 and the previous behavior was a lie. The Colon That Broke Google's API Convention A developer migrating from ozzo-routing reported that route registration panics: router.GET("/clients:getOrganization/:id", handler1) router.GET("/clients:getAddress/:id", handler2) // panic: conflicting wildcard names: getOrganization vs getAddress The : in clients:getOrganization was being parsed as a wildcard param marker. But this is a Google AIP-136 custom method -- the most widely adopted enterprise REST convention for non-CRUD operations. Google Firestore alone has 20+ endpoints using this pattern: /documents:commit, /documents:batchGet, /documents:rollback. RFC 3986 Section 3.3 lists : as a legal path character. It doesn't need escaping. The :param convention is a Sinatra invention from 2007, not an RFC. The fix: colons are wildcards only at segment start (after / or position 0): // BEFORE func findWildcardIndex(path string) int { for i := 0; i < len(path); i++ { if path[i] == ':' || path[i] == '*' { return i // any position } } return -1 } // AFTER func findWildcardIndex(path string) int { for i := 0; i < len(path); i++ { if (path[i] == ':' || path[i] == '*') && (i == 0 || path[i-1] == '/') { return i // segment start only } } return -1 } For context: Gin fixed this in v1.11.0 after six years of open issues. Echo needed three separate PRs. httprouter never fixed it. Express.js has had it open since 2019. Form Binding Errors: 500 Instead of 400 Submitting age=abc where age is an int field returned 500 Internal Server Error. The strconv parse error wasn't wrapped in our DecodeError type, so the error handler fell through to the catch-all: // BEFORE -- raw error, caught by nothing if err := setField(field, values[0]); err != nil { return fmt.Errorf("set field %s error: %w", structField.Name, err) } // AFTER -- wrapped, caught as 400 if err := setField(field, values[0]); err != nil { return &DecodeError{Err: fmt.Errorf("field %s: %w", structField.Name, err)} } A user sending ?age=abc now gets 400 Bad Request with a Problem Details body explaining which field failed. Not a 500 that makes your monitoring think the server is crashing. This fix covers setField type mismatches. Errors from ParseForm/ParseMultipartForm itself (malformed percent-encoding, corrupt multipart boundaries) were also wrapped in v0.6.2. What Fursy Doesn't Do - No ORM -- use Relica or GORM or raw database/sql - No migrations -- use goose or atlas - No template rendering -- this is an API router, not a web framework - No WebSocket/SSE built-in -- SSE works via the stream plugin; WebSocket upgrade requires the base responseWriter (no middleware wrappers in the chain) until stream adopts http.NewResponseController - No process management -- use daemon if you need it - No CSRF middleware -- we removed the docs that claimed it existed. If you need CSRF, use gorilla/csrf or write your own. We'll add it when we have a design we're confident in, not before. Fursy vs. Other Go Routers (2026) | Router | Go Version | Type Safety | Allocs/op | Error Format | Colon Literal | Dependencies | |--------|-----------|-------------|-----------|--------------|---------------|-------------| | Go 1.22+ stdlib | 1.22+ | {param} only | ~3 | text/plain | Yes ({param}) | 0 | | chi v5 | 1.22+ | {param} only | ~2 | text/plain | Yes ({param}) | 0 | | Gin | 1.18+ | No generics | 0 | custom JSON | Yes (v1.11+) | 8 | | Echo | 1.18+ | No generics | 1 | custom JSON | Yes (escaped) | 4 | | Fiber | 1.21+ | No generics | 0 | text/plain | No | fasthttp | | fursy | 1.27+ | Generic methods | 0 (plain) / 2 (generic) | RFC 9457 | Yes (v0.6.2) | 2 (JWT, rate) | Fursy requires Go 1.27. That's a hard requirement. If you're on 1.22 or earlier, use chi or the stdlib mux. If you want zero dependencies, use the stdlib. If you need the fastest raw throughput, Fiber on fasthttp wins. Fursy is for teams that want type-safe handlers, zero-alloc routing, and RFC-compliant error responses in a single package, and can target Go 1.27+. Numbers | Metric | Value | |--------|-------| | Core library | ~8,200 lines | | Test code | ~16,000 lines (2:1 ratio) | | Test functions | 510+ (core + plugins) | | Benchmarks | 21 | | Coverage | 93.8% core, 96.5% middleware | | Static route lookup | <100 ns/op, 0 alloc | | Parametric route lookup | <140 ns/op, 0 alloc | | Production dependencies | 2 (golang-jwt, x/time) | | Plugin dependencies | Isolated per plugin | | CI checks | 12 (3 OS, lint, format, vuln, 4 plugins, examples, codecov) | | External audit findings | 45 claims checked, 33 confirmed, all fixed in v0.6.0-v0.6.2 | Gotchas router.GET Is a Generic Method Now After v0.5.0, router.GET expects Handler[Req, Res] (a function taking *Box[Req, Res]), not HandlerFunc (taking *Context). For plain handlers without type-safe binding: // This does NOT compile: router.GET("/health", func(c *fursy.Context) error { ... }) // Use Handle for plain handlers: router.Handle("GET", "/health", func(c *fursy.Context) error { ... }) // Or use the generic form with Empty types: router.GET("/health", func(c *fursy.Box[fursy.Empty, fursy.Empty]) error { ... }) Plugins Have Their Own go.mod Each plugin (plugins/opentelemetry, plugins/database, plugins/stream, plugins/validator) is a separate Go module. When upgrading fursy, update the plugin's go.mod too: cd plugins/stream go get github.com/coregx/fursy@v0.6.2 go mod tidy CORS Must Be Global CORS middleware must be registered at the router level (router.Use()), not on a group. Preflight OPTIONS requests hit the global middleware chain before route matching. Group-level CORS will miss them. This matches Gin, Echo, and Chi behavior. The Second Pass The first audit found the CORS echo, the phantom docs, and the text/plain lie. We fixed those in v0.6.0. Then we sent the fix branch back for re-validation. The second pass found 11 more: an open redirect in the trailing-slash handler, WebSocket hijack broken by our own response wrapper, the circuit breaker counting 404s as backend failures, and the OpenAPI generator not knowing about the colon fix it shipped alongside. All fixed in v0.6.2. The pattern is humbling: every fix creates a surface for the next bug. The CORS allowlist fix shipped next to a default that had been blocking JSON POST preflights all along -- no test ever sent one. The colon fix in the radix tree didn't propagate to the OpenAPI converter. The response wrapper that tracked written didn't implement Hijack. Ninety-four percent coverage catches syntax, not semantics. Try It go get github.com/coregx/fursy@v0.6.2 The project is at v0.6.2. The API is not frozen -- we're pre-1.0 and will break things when the design demands it. The llms.txt documents every API pattern for both developers and AI coding assistants. coregx/fursy -- Type-safe HTTP router for Go 1.27+. RFC 9457 errors. Zero-alloc routing. MIT license.