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Use the X-Forwarded-For address in response logs if set. #881

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Use the X-Forwarded-For address in response logs if set. #881

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10 changes: 8 additions & 2 deletions server/http.go
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Original file line number Diff line number Diff line change
Expand Up @@ -200,12 +200,18 @@ func (h *httpCache) handleGetValidAC(w http.ResponseWriter, r *http.Request, has

// Helper function for logging responses
func (h *httpCache) logResponse(code int, r *http.Request) {
remoteAddr := r.RemoteAddr
if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
// XFF format: client, proxy1, proxy2
parts := strings.Split(xff, ",")
remoteAddr = strings.TrimSpace(parts[0])
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@mostynb mostynb Jan 16, 2026

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Since this is untrustworthy data, I wonder if we should log it differently?

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@rolandjitsu rolandjitsu Feb 5, 2026

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Let me know what you recommend. The input could be sanitized before logging.

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@mostynb mostynb Feb 24, 2026

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How about if the X-Forwarded-For header is set, instead of logging r.RemoteAddr by itself we log r.RemoteAddr (X-Forwarded-For?) with a question mark to indicate that the value is uncertain?

}
// Parse the client ip:port
var clientAddress string
var err error
clientAddress, _, err = net.SplitHostPort(r.RemoteAddr)
clientAddress, _, err = net.SplitHostPort(remoteAddr)
if err != nil {
clientAddress = r.RemoteAddr
clientAddress = remoteAddr
}
h.accessLogger.Printf("%4s %d %15s %s", r.Method, code, clientAddress, r.URL.Path)
}
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36 changes: 35 additions & 1 deletion server/http_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,17 +8,19 @@ import (
"encoding/json"
"fmt"
"io"
"log"
"math"
"net/http"
"net/http/httptest"
"net/url"
"os"
"strings"
"sync"
"testing"

"github.com/buchgr/bazel-remote/v2/cache"
"github.com/buchgr/bazel-remote/v2/cache/disk"
"github.com/buchgr/bazel-remote/v2/utils"
testutils "github.com/buchgr/bazel-remote/v2/utils"

pb "github.com/buchgr/bazel-remote/v2/genproto/build/bazel/remote/execution/v2"
"google.golang.org/protobuf/proto"
Expand Down Expand Up @@ -564,3 +566,35 @@ func TestManglingACKeys(t *testing.T) {
t.Errorf("Wrong status code, expected %d, got %d", http.StatusNotFound, statusCode)
}
}

func TestResponseLog(t *testing.T) {
cacheDir := testutils.TempDir(t)
defer func() { _ = os.RemoveAll(cacheDir) }()

blobSize := int64(1024)

data, hash := testutils.RandomDataAndHash(blobSize)

// Add some overhead for likely CAS blob storage expansion.
cacheSize := blobSize*2 + disk.BlockSize

c, err := disk.New(cacheDir, cacheSize, disk.WithAccessLogger(testutils.NewSilentLogger()))
if err != nil {
t.Fatal(err)
}
var w bytes.Buffer
logger := log.New(&w, "bz-remote", 0)
h := NewHTTPCache(c, logger, testutils.NewSilentLogger(), true, false, false, false, "", "", math.MaxInt64)

rr := httptest.NewRecorder()
handler := http.HandlerFunc(h.CacheHandler)

pr := httptest.NewRequest("PUT", "/cas/"+hash, bytes.NewReader(data))
pr.Header.Add("X-Forwarded-For", "10.11.12.13")
handler.ServeHTTP(rr, pr)

logLine := w.String()
if !strings.Contains(logLine, "10.11.12.13") {
t.Errorf("expected logged IP to use X-Forwarded-For header but saw `%s`", logLine)
}
}