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fqdn.go
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fqdn.go
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// Copyright 2019-2020 Authors of Hubble
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package filters
import (
"context"
"fmt"
"regexp"
"strings"
flowpb "github.com/cilium/cilium/api/v1/flow"
v1 "github.com/cilium/cilium/pkg/hubble/api/v1"
)
func sourceFQDN(ev *v1.Event) []string {
return ev.GetFlow().GetSourceNames()
}
func destinationFQDN(ev *v1.Event) []string {
return ev.GetFlow().GetDestinationNames()
}
var (
fqdnFilterAllowedChars = "[-a-zA-Z0-9_.]*"
fqdnFilterIsValidFilter = regexp.MustCompile("^[-a-zA-Z0-9_.*]+$")
)
func parseFQDNFilter(pattern string) (*regexp.Regexp, error) {
pattern = strings.ToLower(pattern)
pattern = strings.TrimSpace(pattern)
pattern = strings.TrimSuffix(pattern, ".")
if !fqdnFilterIsValidFilter.MatchString(pattern) {
return nil, fmt.Errorf(`only alphanumeric ASCII characters, the hyphen "-", "." and "*" are allowed: %s`,
pattern)
}
// "." becomes a literal .
pattern = strings.Replace(pattern, ".", "[.]", -1)
// "*" becomes a zero or more of the allowed characters
pattern = strings.Replace(pattern, "*", fqdnFilterAllowedChars, -1)
return regexp.Compile("^" + pattern + "$")
}
func filterByFQDNs(fqdnPatterns []string, getFQDNs func(*v1.Event) []string) (FilterFunc, error) {
matchPatterns := make([]*regexp.Regexp, 0, len(fqdnPatterns))
for _, pattern := range fqdnPatterns {
re, err := parseFQDNFilter(pattern)
if err != nil {
return nil, fmt.Errorf("invalid FQDN in filter: %s", err)
}
matchPatterns = append(matchPatterns, re)
}
return func(ev *v1.Event) bool {
names := getFQDNs(ev)
if len(names) == 0 {
return false
}
for _, name := range names {
for _, re := range matchPatterns {
if re.MatchString(name) {
return true
}
}
}
return false
}, nil
}
// filterByDNSQueries returns a FilterFunc that filters a flow by L7.DNS.query field.
// The filter function returns true if and only if the DNS query field matches any of
// the regular expressions.
func filterByDNSQueries(queryPatterns []string) (FilterFunc, error) {
queries := make([]*regexp.Regexp, 0, len(queryPatterns))
for _, pattern := range queryPatterns {
query, err := regexp.Compile(pattern)
if err != nil {
return nil, fmt.Errorf("failed to compile regexp: %v", err)
}
queries = append(queries, query)
}
return func(ev *v1.Event) bool {
dns := ev.GetFlow().GetL7().GetDns()
if dns == nil {
return false
}
for _, query := range queries {
if query.MatchString(dns.Query) {
return true
}
}
return false
}, nil
}
// FQDNFilter implements filtering based on FQDN information
type FQDNFilter struct{}
// OnBuildFilter builds a FQDN filter
func (f *FQDNFilter) OnBuildFilter(ctx context.Context, ff *flowpb.FlowFilter) ([]FilterFunc, error) {
var fs []FilterFunc
if ff.GetSourceFqdn() != nil {
ff, err := filterByFQDNs(ff.GetSourceFqdn(), sourceFQDN)
if err != nil {
return nil, err
}
fs = append(fs, ff)
}
if ff.GetDestinationFqdn() != nil {
ff, err := filterByFQDNs(ff.GetDestinationFqdn(), destinationFQDN)
if err != nil {
return nil, err
}
fs = append(fs, ff)
}
if ff.GetDnsQuery() != nil {
dnsFilters, err := filterByDNSQueries(ff.GetDnsQuery())
if err != nil {
return nil, fmt.Errorf("invalid DNS query filter: %v", err)
}
fs = append(fs, dnsFilters)
}
return fs, nil
}