From 55e83d6bfd379a829b81ea6a14b0cec31d199f2d Mon Sep 17 00:00:00 2001
From: Admin <1+admin@noreply.git.dcntrlized.org>
Date: Mon, 19 Oct 2026 02:28:59 +0100
Subject: [PATCH] [feat](alarm): hash client identifiers in stdout request logs
A request log should not name a client directly, and the durable event log deliberately has no network columns. Hash the IP and user agent with internal/loghash for the stdout line; empty values stay empty rather than logging a constant digest. This is record anonymisation, not cryptographic protection, and the package says so.
---
src/internal/loghash/loghash.go | 38 ++++++++++++++++++++++++++++
src/internal/loghash/loghash_test.go | 34 +++++++++++++++++++++++++
src/logger/logger.go | 3 ++-
src/middleware/logger.go | 20 ++++++++++++---
4 files changed, 91 insertions(+), 4 deletions(-)
create mode 100644 src/internal/loghash/loghash.go
create mode 100644 src/internal/loghash/loghash_test.go
diff --git a/src/internal/loghash/loghash.go b/src/internal/loghash/loghash.go
new file mode 100644
index 0000000..3df2a43
--- /dev/null
+++ b/src/internal/loghash/loghash.go
@@ -0,0 +1,38 @@
+// Copyright (C) 2026 Dcntrlized
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see .
+
+// Package loghash anonymises client identifiers for stdout request lines: plain
+// SHA-256 hex, no salt, no key, no work factor (user ruling: keep it simple).
+//
+// Honest limitation, recorded so nobody mistakes it for more than it is: a plain
+// digest of a low-entropy value such as an IPv4 address is enumerable by anyone
+// who can run 2^32 hashes. This anonymises *records* (a log dump does not
+// directly name a client); it is not cryptographic protection.
+package loghash
+
+import (
+ "crypto/sha256"
+ "encoding/hex"
+)
+
+// Hash returns the SHA-256 hex digest of raw, or "" for an empty value so callers
+// can omit the field rather than log a constant digest.
+func Hash(raw string) string {
+ if raw == "" {
+ return ""
+ }
+ sum := sha256.Sum256([]byte(raw))
+ return hex.EncodeToString(sum[:])
+}
diff --git a/src/internal/loghash/loghash_test.go b/src/internal/loghash/loghash_test.go
new file mode 100644
index 0000000..f648909
--- /dev/null
+++ b/src/internal/loghash/loghash_test.go
@@ -0,0 +1,34 @@
+// Copyright (C) 2026 Dcntrlized
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see .
+
+package loghash
+
+import "testing"
+
+func TestHashIsStableSha256(t *testing.T) {
+ got := Hash("192.0.2.10")
+ if len(got) != 64 {
+ t.Fatalf("digest length = %d, want 64 hex chars", len(got))
+ }
+ if got != Hash("192.0.2.10") {
+ t.Fatal("hash is not stable")
+ }
+ if Hash("192.0.2.11") == got {
+ t.Fatal("different addresses collided")
+ }
+ if Hash("") != "" {
+ t.Fatal("empty identifier should map to empty")
+ }
+}
diff --git a/src/logger/logger.go b/src/logger/logger.go
index c728c50..2832dd5 100644
--- a/src/logger/logger.go
+++ b/src/logger/logger.go
@@ -157,7 +157,8 @@ func Warn(format string, v ...any) {
func Error(format string, v ...any) {
once.Do(initLogger)
file, line := callSite()
- errorLogger.Output(0, fmt.Sprintf("%s:%d: %s", filepath.Base(file), line, fmt.Sprintf(format, v...)))
+ msg := fmt.Sprintf(format, v...)
+ errorLogger.Output(0, fmt.Sprintf("%s:%d: %s", filepath.Base(file), line, msg))
}
// Debug accepts a format string and an optional, arbitrary number of arguments.
diff --git a/src/middleware/logger.go b/src/middleware/logger.go
index fce9f7c..ca2b399 100644
--- a/src/middleware/logger.go
+++ b/src/middleware/logger.go
@@ -17,11 +17,13 @@ package middleware
import (
"bufio"
+ "fmt"
"net"
"net/http"
"strings"
"time"
+ "git.dcntrlized.org/Dcntrlized/Alarm/internal/loghash"
"git.dcntrlized.org/Dcntrlized/Alarm/logger"
)
@@ -49,19 +51,31 @@ func LoggingMiddleware(next http.Handler) http.Handler {
rec := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
next.ServeHTTP(rec, r)
- logger.Info("%s request=%s %s path=%s status=%d ua=%q ip=%s duration=%s",
+ // Identifiers are not written in the clear on stdout: IP and user agent
+ // go through plain SHA-256 (internal/loghash). They never reach durable
+ // storage at all — the event_log table has no network columns.
+ ipHash, uaHash := hashClient(ip, r.UserAgent())
+ line := fmt.Sprintf("%s request=%s %s path=%s status=%d ua=%s ip=%s duration=%s",
time.Now().Format(time.RFC3339),
r.Method,
r.Proto,
r.URL.Path,
rec.status,
- r.UserAgent(),
- ip,
+ uaHash,
+ ipHash,
time.Since(start),
)
+ logger.Info("%s", line)
})
}
+// hashClient anonymises request identifiers for stdout. The durable event log
+// never stores network identifiers at all; this is only so a stdout request line
+// does not name a client directly.
+func hashClient(ip, ua string) (ipHash, uaHash string) {
+ return loghash.Hash(ip), loghash.Hash(ua)
+}
+
// statusRecorder captures the response status without altering the response.
// It preserves http.Hijacker so the /ws/alarm upgrade still works when the
// route is mounted behind this middleware.