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util: fix possible OOB in IPv4 flowkey calc, use switch there

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ihl may grow upto 15*4=60 so extract and check it before using it as offset in flowkey calculation.
also replace IFs with switches for protocol matching as it's less redundant and nicer to document.
This commit is contained in:
cathugger 2019-12-11 15:24:43 +02:00
parent a9cfa5bc0d
commit ff5de89762
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1 changed files with 7 additions and 7 deletions
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14
src/util/util.go
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@ -103,11 +103,11 @@ func GetFlowKey(bs []byte) uint64 {
// Get the IP protocol version from the packet
switch bs[0] & 0xf0 {
case 0x40: // IPv4 packet
// Check the packet meets minimum UDP packet length
if len(bs) >= 24 {
// Is the protocol TCP, UDP or SCTP?
if bs[9] == 0x06 || bs[9] == 0x11 || bs[9] == 0x84 {
ihl := bs[0] & 0x0f * 4 // Header length
ihl := (bs[0] & 0x0f) * 4 // whole IPv4 header length (min 20)
// 8 is minimum UDP packet length
if ihl >= 20 && len(bs)-int(ihl) >= 8 {
switch bs[9] /* protocol */ {
case 0x06 /* TCP */, 0x11 /* UDP */, 0x84 /* SCTP */ :
flowkey = uint64(bs[9])<<32 /* proto */ |
uint64(bs[ihl+0])<<24 | uint64(bs[ihl+1])<<16 /* sport */ |
uint64(bs[ihl+2])<<8 | uint64(bs[ihl+3]) /* dport */
@ -119,8 +119,8 @@ func GetFlowKey(bs []byte) uint64 {
// If the flowlabel isn't present, make protokey from proto | sport | dport
// if the packet meets minimum UDP packet length
if flowkey == 0 && len(bs) >= 48 {
// Is the protocol TCP, UDP or SCTP?
if bs[6] == 0x06 || bs[6] == 0x11 || bs[6] == 0x84 {
switch bs[9] /* protocol */ {
case 0x06 /* TCP */, 0x11 /* UDP */, 0x84 /* SCTP */ :
flowkey = uint64(bs[6])<<32 /* proto */ |
uint64(bs[40])<<24 | uint64(bs[41])<<16 /* sport */ |
uint64(bs[42])<<8 | uint64(bs[43]) /* dport */