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webhooker/internal/handlers/entrypoint_view.go
sneak c0f8427259
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Add optional inbound webhook signature verification (closes #67)
A receiver URL was a bare v4 UUID and nothing else: anyone who learned
it could store events and, because inbound headers are forwarded to
targets almost verbatim, choose what the downstream service received.

Entrypoints gain an optional scheme/secret pair. GitHub's
X-Hub-Signature-256 (HMAC-SHA256 hex over the raw body) and GitLab's
X-Gitlab-Token (plain shared token) are supported; both compare with
hmac.Equal. With nothing configured an entrypoint behaves exactly as
before, which is also where every pre-existing row lands after
AutoMigrate adds the columns.

Verification runs after the capped body read and before the first
write, so a rejected request leaves no event row, no delivery row and
no delivery task. A configuration the receiver cannot apply — unknown
scheme, or one half of the pair missing — is refused with a 500 rather
than falling back to unverified.

The secret is credential-bearing and is stored in the clear because
HMAC needs the key itself. It is excluded from JSON, kept out of
templates by a new handlers.EntrypointView projection, and absent from
every log line including the rejection path. The UI sets and rotates
it through one form that never renders the stored value.
2026-08-20 05:02:03 +00:00

81 lines
2.2 KiB
Go

package handlers
import (
"sneak.berlin/go/webhooker/internal/database"
"sneak.berlin/go/webhooker/internal/signature"
)
// signatureUnavailable is what an entrypoint's scheme renders as when
// the stored value is not one this build supports. The stored string
// is never echoed as a fallback: it is operator-supplied and the row
// is already in a state the receiver refuses, so the UI says so
// rather than inventing a description for it.
const signatureUnavailable = "(unavailable)"
// signatureNotVerified is the label for an entrypoint that performs
// no inbound verification.
const signatureNotVerified = "not verified"
// EntrypointView is the display-safe projection of an entrypoint for
// the UI. It deliberately has no secret field, so no template —
// present or future — can render the shared secret, in the same way
// delivery.TargetView keeps a target's stored credential away from
// one.
type EntrypointView struct {
ID string
Path string
Description string
Active bool
// Configured reports whether inbound requests to this entrypoint
// are verified.
Configured bool
// Scheme is the stored scheme, carried so the form can preselect
// it. It names an algorithm, not a secret.
Scheme database.SignatureScheme
// SchemeLabel and SchemeHeader describe the configured scheme for
// display: the sender's name, and the header its signature
// arrives in.
SchemeLabel string
SchemeHeader string
}
// NewEntrypointViews projects entrypoints for rendering, dropping the
// shared secret on the way.
func NewEntrypointViews(
entrypoints []database.Entrypoint,
) []EntrypointView {
views := make([]EntrypointView, 0, len(entrypoints))
for i := range entrypoints {
e := &entrypoints[i]
view := EntrypointView{
ID: e.ID,
Path: e.Path,
Description: e.Description,
Active: e.Active,
Configured: e.SignatureConfigured(),
Scheme: e.SignatureScheme,
SchemeLabel: signatureNotVerified,
SchemeHeader: "",
}
if view.Configured {
view.SchemeLabel = signatureUnavailable
info, ok := signature.Info(e.SignatureScheme)
if ok {
view.SchemeLabel = info.Label
view.SchemeHeader = info.Header
}
}
views = append(views, view)
}
return views
}