(partially tested) add scrape JWT validation

* remove `xorshift` package, add internal function in `varinterval`
* change `bittorrent.QueryParams` getters to search case insensitive keys

middleware/varinterval/varinterval.go

@@ -3,14 +3,15 @@ package varinterval
 
 import (
 	"context"
+	"encoding/binary"
 	"errors"
 	"fmt"
+	"math"
 	"sync"
 	"time"
 
 	"github.com/sot-tech/mochi/bittorrent"
 	"github.com/sot-tech/mochi/middleware"
-	"github.com/sot-tech/mochi/middleware/pkg/random"
 	"github.com/sot-tech/mochi/pkg/conf"
 	"github.com/sot-tech/mochi/storage"
 )
@@ -79,14 +80,12 @@ type hook struct {
 }
 
 func (h *hook) HandleAnnounce(ctx context.Context, req *bittorrent.AnnounceRequest, resp *bittorrent.AnnounceResponse) (context.Context, error) {
-	s0, s1 := random.DeriveEntropyFromRequest(req)
 	// Generate a probability p < 1.0.
-	v, s0, s1 := random.Intn(s0, s1, 1<<24)
-	p := float32(v) / (1 << 24)
-	if h.cfg.ModifyResponseProbability == 1 || p < h.cfg.ModifyResponseProbability {
+	p, s0, s1 := xoroshiro128p(deriveEntropyFromRequest(req))
+	if float32(float64(p)/math.MaxUint64) < h.cfg.ModifyResponseProbability {
 		// Generate the increase delta.
-		v, _, _ = random.Intn(s0, s1, h.cfg.MaxIncreaseDelta)
-		add := time.Duration(v+1) * time.Second
+		v, _, _ := xoroshiro128p(s0, s1)
+		add := time.Duration(v%uint64(h.cfg.MaxIncreaseDelta)+1) * time.Second
 
 		resp.Interval += add
 
@@ -102,3 +101,26 @@ func (h *hook) HandleScrape(ctx context.Context, _ *bittorrent.ScrapeRequest, _
 	// Scrapes are not altered.
 	return ctx, nil
 }
+
+// deriveEntropyFromRequest generates 2*64 bits of pseudo random state from an
+// bittorrent.AnnounceRequest.
+//
+// Calling deriveEntropyFromRequest multiple times yields the same values.
+func deriveEntropyFromRequest(req *bittorrent.AnnounceRequest) (v0 uint64, v1 uint64) {
+	if len(req.InfoHash) >= bittorrent.InfoHashV1Len {
+		v0 = binary.BigEndian.Uint64([]byte(req.InfoHash[:8])) + binary.BigEndian.Uint64([]byte(req.InfoHash[8:16]))
+	}
+	v1 = binary.BigEndian.Uint64(req.ID[:8]) + binary.BigEndian.Uint64(req.ID[8:16])
+	return
+}
+
+// xoroshiro128p calculates predictable pseudorandom number
+// with XOR/rotate/shift/rotate 128+ algorithm.
+// see https://prng.di.unimi.it/xoroshiro128plus.c
+func xoroshiro128p(s0, s1 uint64) (result, ns0, ns1 uint64) {
+	result = s0 + s1
+	s1 ^= s0
+	ns0 = ((s0 << 24) | (s0 >> 40)) ^ s1 ^ (s1 << 16) // rotl(s0, 24) ^ s1 ^ (s1 << 16)
+	ns1 = (s1 << 37) | (s1 >> 27)                     // rotl(s1, 37)
+	return
+}

middleware/varinterval/varinterval_test.go

@@ -3,12 +3,15 @@ package varinterval
 import (
 	"context"
 	"fmt"
+	"math/rand"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	"github.com/sot-tech/mochi/bittorrent"
 	"github.com/sot-tech/mochi/pkg/conf"
+
+	_ "github.com/sot-tech/mochi/pkg/randseed"
 )
 
 var configTests = []struct {
@@ -61,3 +64,13 @@ func TestHandleAnnounce(t *testing.T) {
 	require.True(t, resp.Interval > 0, "interval should have been increased")
 	require.True(t, resp.MinInterval > 0, "min_interval should have been increased")
 }
+
+func BenchmarkXORoShiRo128Plus(b *testing.B) {
+	s0, s1 := rand.Uint64(), rand.Uint64()
+	var v uint64
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		v, s0, s1 = xoroshiro128p(s0, s1)
+	}
+	_, _, _ = v, s0, s1
+}