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remote: validate snappy decoded length before allocation in write endpoint

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Signed-off-by: Julien Pivotto <291750+roidelapluie@users.noreply.github.com>
This commit is contained in:
Julien Pivotto 2026-04-27 13:10:33 +02:00
parent cb493a437b
commit 6e1eebf5ba
2 changed files with 35 additions and 1 deletions
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20
storage/remote/write_handler.go
View File

@ -24,6 +24,7 @@ import (
"time"
"github.com/gogo/protobuf/proto"
"github.com/golang/snappy"
deltatocumulative "github.com/open-telemetry/opentelemetry-collector-contrib/processor/deltatocumulativeprocessor"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
@ -58,7 +59,11 @@ type writeHandler struct {
ingestCTZeroSample bool
}
const maxAheadTime = 10 * time.Minute
const (
maxAheadTime = 10 * time.Minute
// decodeWriteLimit is the maximum decoded size of a remote write request body in bytes.
decodeWriteLimit = 32 * 1024 * 1024
)
// NewWriteHandler creates a http.Handler that accepts remote write requests with
// the given message in acceptedProtoMsgs and writes them to the provided appendable.
@ -163,6 +168,19 @@ func (h *writeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
return
}
decodedLen, err := snappy.DecodedLen(body)
if err != nil {
h.logger.Error("Error decoding remote write request", "err", err.Error())
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
if decodedLen > decodeWriteLimit {
err := fmt.Errorf("snappy: decoded length %d exceeds limit %d", decodedLen, decodeWriteLimit)
h.logger.Error("Error decoding remote write request", "err", err.Error())
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
decompressed, err := compression.Decode(compression.Snappy, body, nil)
if err != nil {
// TODO(bwplotka): Add more context to responded error?

16
storage/remote/write_handler_test.go
View File

@ -245,6 +245,22 @@ func TestRemoteWriteHandlerHeadersHandling_V2Message(t *testing.T) {
}
}
func TestRemoteWriteHandlerTooLarge(t *testing.T) {
// 5-byte snappy stream whose header claims 256 MiB decoded length,
// well above decodeWriteLimit (32 MiB).
bomb := []byte{0x80, 0x80, 0x80, 0x80, 0x01}
req, err := http.NewRequest(http.MethodPost, "/", bytes.NewReader(bomb))
require.NoError(t, err)
appendable := &mockAppendable{}
handler := NewWriteHandler(promslog.NewNopLogger(), nil, appendable, []config.RemoteWriteProtoMsg{config.RemoteWriteProtoMsgV1}, false)
recorder := httptest.NewRecorder()
handler.ServeHTTP(recorder, req)
require.Equal(t, http.StatusBadRequest, recorder.Code)
require.Contains(t, recorder.Body.String(), "exceeds limit")
}
func TestRemoteWriteHandler_V1Message(t *testing.T) {
payload, _, _, err := buildWriteRequest(nil, writeRequestFixture.Timeseries, nil, nil, nil, nil, "snappy")
require.NoError(t, err)