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Comments in reqtls and session, and the README Quick Start and deployment checklist, still spoke as if an unset WEBHOOKER_ENVIRONMENT meant dev. The checklist now asks only that the environment is not dev (unset or prod); the Quick Start describes running from the clone. Model: opus-5-5
60 lines
2.6 KiB
Go
60 lines
2.6 KiB
Go
// Package reqtls answers one question, in one place, for the whole
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// application: did this request reach the service over TLS?
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//
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// It exists because that question used to be answered independently in
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// several packages, by hand, and the answers disagreed. The session
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// cookie's Secure attribute was decided at startup from the configured
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// environment while the CSRF cookie's was decided per-request, so a
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// deployment behind a TLS proxy in the dev environment emitted one
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// Secure cookie and one non-Secure cookie on the same response.
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// Everything kept working, which is exactly why nobody noticed.
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//
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// Any code that needs a scheme or a Secure flag must call IsTLS rather
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// than reading the request itself.
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package reqtls
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import (
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"net/http"
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"strings"
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)
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// forwardedProtoHeader is the de-facto standard header by which a
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// TLS-terminating reverse proxy reports the protocol the CLIENT used.
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const forwardedProtoHeader = "X-Forwarded-Proto"
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// IsTLS reports whether the client-facing connection uses TLS: either
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// the request arrived over TLS directly, or a reverse proxy terminated
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// TLS and said so in X-Forwarded-Proto.
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//
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// The header is only as trustworthy as whatever sits in front of the
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// listener. A proxy that overwrites it -- which is what the deployment
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// documentation requires -- makes it authoritative; a listener exposed
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// directly to clients lets any client assert it. That is the same
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// exposure every X-Forwarded-* consumer carries.
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func IsTLS(r *http.Request) bool {
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return r.TLS != nil || forwardedProto(r) == "https"
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}
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// forwardedProto reduces X-Forwarded-Proto to a bare, comparable
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// protocol token, or "" when the header is absent or blank.
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//
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// Two shapes that real infrastructure emits do not survive an exact
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// comparison against "https", and both name a TLS client connection:
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//
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// - "HTTPS", because the header value is a case-insensitive token and
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// nothing obliges a proxy to emit it lowercased.
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// - "https, http", because a proxy chained behind another proxy
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// APPENDS its own hop instead of replacing the value. As with
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// X-Forwarded-For, the leftmost element is the one nearest the
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// client, so it is the element that describes the browser's
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// connection -- the only hop a cookie's Secure attribute is about.
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//
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// Landing on the plaintext path for either of those spellings is not a
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// cosmetic error: it stops gorilla/csrf enforcing the strict Referer
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// check on a site that genuinely is HTTPS.
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func forwardedProto(r *http.Request) string {
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first, _, _ := strings.Cut(r.Header.Get(forwardedProtoHeader), ",")
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return strings.ToLower(strings.TrimSpace(first))
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}
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