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p2p/discover: fix out-of-bounds slicing for chunked neighbors packets

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The code assumed that Table.closest always returns at least 13 nodes.
This is not true for small tables (e.g. during bootstrap).
This commit is contained in:
Felix Lange 2015-05-13 21:29:32 +02:00
parent b2119d8931
commit 251846d65a
2 changed files with 49 additions and 32 deletions
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50
p2p/discover/udp.go
View File

@ -363,7 +363,31 @@ const (
headSize = macSize + sigSize // space of packet frame data
)
var headSpace = make([]byte, headSize)
var (
headSpace = make([]byte, headSize)
// Neighbors responses are sent across multiple packets to
// stay below the 1280 byte limit. We compute the maximum number
// of entries by stuffing a packet until it grows too large.
maxNeighbors int
)
func init() {
p := neighbors{Expiration: ^uint64(0)}
maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
for n := 0; ; n++ {
p.Nodes = append(p.Nodes, maxSizeNode)
size, _, err := rlp.EncodeToReader(p)
if err != nil {
// If this ever happens, it will be caught by the unit tests.
panic("cannot encode: " + err.Error())
}
if headSize+size+1 >= 1280 {
maxNeighbors = n
break
}
}
}
func (t *udp) send(toaddr *net.UDPAddr, ptype byte, req interface{}) error {
packet, err := encodePacket(t.priv, ptype, req)
@ -402,6 +426,9 @@ func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) ([]byte,
// readLoop runs in its own goroutine. it handles incoming UDP packets.
func (t *udp) readLoop() {
defer t.conn.Close()
// Discovery packets are defined to be no larger than 1280 bytes.
// Packets larger than this size will be cut at the end and treated
// as invalid because their hash won't match.
buf := make([]byte, 1280)
for {
nbytes, from, err := t.conn.ReadFromUDP(buf)
@ -504,20 +531,15 @@ func (req *findnode) handle(t *udp, from *net.UDPAddr, fromID NodeID, mac []byte
closest := t.closest(target, bucketSize).entries
t.mutex.Unlock()
// TODO: this conversion could use a cached version of the slice
closestrpc := make([]rpcNode, len(closest))
p := neighbors{Expiration: uint64(time.Now().Add(expiration).Unix())}
// Send neighbors in chunks with at most maxNeighbors per packet
// to stay below the 1280 byte limit.
for i, n := range closest {
closestrpc[i] = nodeToRPC(n)
}
t.send(from, neighborsPacket, neighbors{
Nodes: closestrpc[:13],
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
if len(closestrpc) > 13 {
t.send(from, neighborsPacket, neighbors{
Nodes: closestrpc[13:],
Expiration: uint64(time.Now().Add(expiration).Unix()),
})
p.Nodes = append(p.Nodes, nodeToRPC(n))
if len(p.Nodes) == maxNeighbors || i == len(closest)-1 {
t.send(from, neighborsPacket, p)
p.Nodes = p.Nodes[:0]
}
}
return nil
}

31
p2p/discover/udp_test.go
View File

@ -164,26 +164,21 @@ func TestUDP_findnode(t *testing.T) {
// check that closest neighbors are returned.
test.packetIn(nil, findnodePacket, &findnode{Target: testTarget, Expiration: futureExp})
expected := test.table.closest(targetHash, bucketSize)
test.waitPacketOut(func(p *neighbors) {
if len(p.Nodes) != 13 {
t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
}
for i := range p.Nodes {
if p.Nodes[i].ID != expected.entries[i].ID {
t.Errorf("result mismatch at %d:\n got: %v\n want: %v", i, p.Nodes[i], expected.entries[i])
waitNeighbors := func(want []*Node) {
test.waitPacketOut(func(p *neighbors) {
if len(p.Nodes) != len(want) {
t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
}
}
})
test.waitPacketOut(func(p *neighbors) {
if len(p.Nodes) != 3 {
t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
}
for i := range p.Nodes {
if p.Nodes[i].ID != expected.entries[i + 13].ID {
t.Errorf("result mismatch at %d:\n got: %v\n want: %v", i, p.Nodes[i], expected.entries[i])
for i := range p.Nodes {
if p.Nodes[i].ID != want[i].ID {
t.Errorf("result mismatch at %d:\n got: %v\n want: %v", i, p.Nodes[i], expected.entries[i])
}
}
}
})
})
}
waitNeighbors(expected.entries[:maxNeighbors])
waitNeighbors(expected.entries[maxNeighbors:])
}
func TestUDP_findnodeMultiReply(t *testing.T) {