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Fix: Decoding of IPFIX templates with Enterprise Number field #68

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Fix: Decoding of IPFIX templates with Enterprise Number field #68

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39 changes: 36 additions & 3 deletions decoders/netflow/netflow.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import (
"bytes"
"encoding/binary"
"fmt"
"math"
"sync"

"github.com/cloudflare/goflow/v3/decoders/utils"
Expand Down Expand Up @@ -90,7 +91,7 @@ func DecodeIPFIXOptionsTemplateSet(payload *bytes.Buffer) ([]IPFIXOptionsTemplat
return records, nil
}

func DecodeTemplateSet(payload *bytes.Buffer) ([]TemplateRecord, error) {
func DecodeNFv9TemplateSet(payload *bytes.Buffer) ([]TemplateRecord, error) {
records := make([]TemplateRecord, 0)
var err error
for payload.Len() >= 4 {
Expand All @@ -117,6 +118,38 @@ func DecodeTemplateSet(payload *bytes.Buffer) ([]TemplateRecord, error) {
return records, nil
}

func DecodeIPFIXTemplateSet(payload *bytes.Buffer) ([]TemplateRecord, error) {
records := make([]TemplateRecord, 0)
var err error
for payload.Len() >= 4 {
templateRecord := TemplateRecord{}
err = utils.BinaryDecoder(payload, &templateRecord.TemplateId, &templateRecord.FieldCount)
if err != nil {
break
}

if int(templateRecord.FieldCount) < 0 {
return records, NewErrorDecodingNetFlow("Error decoding TemplateSet: zero count.")
}

fields := make([]Field, int(templateRecord.FieldCount))
for i := 0; i < int(templateRecord.FieldCount); i++ {
field := Field{}
err = utils.BinaryDecoder(payload, &field)
if field.Type > math.MaxInt16 {
field.Type = field.Type - math.MaxInt16
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This is off by one, you need

field.Type -= 1 << 15

Because:

1000000000000001

needs to turn into just '1', so you need to subtract

1000000000000000

not

0111111111111111

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Thanks, will update. (could've sworn it was in my fork)

// Skip Enterprise Number field - rfc7011#section-3.2
_ = payload.Next(4)
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Skipping the 4 bytes fixes the parsing, but I think it needs to track that this was a PEN field inside the Field type. In the data that I have the resulting Type will be 1 or 2. The later bits will then just treat those fields as as IPFIX_FIELD_octetDeltaCount or IPFIX_FIELD_packetDeltaCount which would be wrong.

}
fields[i] = field
}
templateRecord.Fields = fields
records = append(records, templateRecord)
}

return records, nil
}

func GetTemplateSize(template []Field) int {
sum := 0
for _, templateField := range template {
Expand Down Expand Up @@ -347,7 +380,7 @@ func DecodeMessage(payload *bytes.Buffer, templates NetFlowTemplateSystem) (inte

if fsheader.Id == 0 && version == 9 {
templateReader := bytes.NewBuffer(payload.Next(nextrelpos))
records, err := DecodeTemplateSet(templateReader)
records, err := DecodeNFv9TemplateSet(templateReader)
if err != nil {
return returnItem, err
}
Expand Down Expand Up @@ -384,7 +417,7 @@ func DecodeMessage(payload *bytes.Buffer, templates NetFlowTemplateSystem) (inte

} else if fsheader.Id == 2 && version == 10 {
templateReader := bytes.NewBuffer(payload.Next(nextrelpos))
records, err := DecodeTemplateSet(templateReader)
records, err := DecodeIPFIXTemplateSet(templateReader)
if err != nil {
return returnItem, err
}
Expand Down