Merge pull request #966 from fjl/fixup-discover-chunked-neighbors
p2p/discover: fix out-of-bounds slicing for chunked neighbors packets
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commit
f7fdb4dfbe
@ -363,7 +363,31 @@ const (
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headSize = macSize + sigSize // space of packet frame data
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)
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var headSpace = make([]byte, headSize)
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var (
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headSpace = make([]byte, headSize)
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// Neighbors responses are sent across multiple packets to
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// stay below the 1280 byte limit. We compute the maximum number
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// of entries by stuffing a packet until it grows too large.
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maxNeighbors int
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)
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func init() {
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p := neighbors{Expiration: ^uint64(0)}
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maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
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for n := 0; ; n++ {
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p.Nodes = append(p.Nodes, maxSizeNode)
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size, _, err := rlp.EncodeToReader(p)
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if err != nil {
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// If this ever happens, it will be caught by the unit tests.
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panic("cannot encode: " + err.Error())
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}
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if headSize+size+1 >= 1280 {
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maxNeighbors = n
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break
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}
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}
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}
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func (t *udp) send(toaddr *net.UDPAddr, ptype byte, req interface{}) error {
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packet, err := encodePacket(t.priv, ptype, req)
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@ -402,6 +426,9 @@ func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) ([]byte,
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// readLoop runs in its own goroutine. it handles incoming UDP packets.
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func (t *udp) readLoop() {
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defer t.conn.Close()
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// Discovery packets are defined to be no larger than 1280 bytes.
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// Packets larger than this size will be cut at the end and treated
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// as invalid because their hash won't match.
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buf := make([]byte, 1280)
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for {
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nbytes, from, err := t.conn.ReadFromUDP(buf)
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@ -504,20 +531,15 @@ func (req *findnode) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte
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closest := t.closest(target, bucketSize).entries
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t.mutex.Unlock()
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// TODO: this conversion could use a cached version of the slice
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closestrpc := make([]rpcNode, len(closest))
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p := neighbors{Expiration: uint64(time.Now().Add(expiration).Unix())}
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// Send neighbors in chunks with at most maxNeighbors per packet
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// to stay below the 1280 byte limit.
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for i, n := range closest {
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closestrpc[i] = nodeToRPC(n)
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}
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t.send(from, neighborsPacket, neighbors{
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Nodes: closestrpc[:13],
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Expiration: uint64(time.Now().Add(expiration).Unix()),
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})
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if len(closestrpc) > 13 {
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t.send(from, neighborsPacket, neighbors{
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Nodes: closestrpc[13:],
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Expiration: uint64(time.Now().Add(expiration).Unix()),
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})
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p.Nodes = append(p.Nodes, nodeToRPC(n))
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if len(p.Nodes) == maxNeighbors || i == len(closest)-1 {
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t.send(from, neighborsPacket, p)
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p.Nodes = p.Nodes[:0]
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}
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}
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return nil
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}
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@ -164,26 +164,21 @@ func TestUDP_findnode(t *testing.T) {
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// check that closest neighbors are returned.
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test.packetIn(nil, findnodePacket, &findnode{Target: testTarget, Expiration: futureExp})
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expected := test.table.closest(targetHash, bucketSize)
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test.waitPacketOut(func(p *neighbors) {
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if len(p.Nodes) != 13 {
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t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
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}
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for i := range p.Nodes {
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if p.Nodes[i].ID != expected.entries[i].ID {
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t.Errorf("result mismatch at %d:\n got: %v\n want: %v", i, p.Nodes[i], expected.entries[i])
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waitNeighbors := func(want []*Node) {
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test.waitPacketOut(func(p *neighbors) {
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if len(p.Nodes) != len(want) {
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t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
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}
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}
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})
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test.waitPacketOut(func(p *neighbors) {
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if len(p.Nodes) != 3 {
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t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
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}
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for i := range p.Nodes {
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if p.Nodes[i].ID != expected.entries[i + 13].ID {
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t.Errorf("result mismatch at %d:\n got: %v\n want: %v", i, p.Nodes[i], expected.entries[i])
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for i := range p.Nodes {
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if p.Nodes[i].ID != want[i].ID {
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t.Errorf("result mismatch at %d:\n got: %v\n want: %v", i, p.Nodes[i], expected.entries[i])
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}
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}
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}
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})
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})
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}
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waitNeighbors(expected.entries[:maxNeighbors])
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waitNeighbors(expected.entries[maxNeighbors:])
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}
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func TestUDP_findnodeMultiReply(t *testing.T) {
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