/
matchpattern.go
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/
matchpattern.go
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// Copyright 2018 Authors of Cilium
//
// 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 matchpattern
import (
"errors"
"regexp"
"strings"
"github.com/miekg/dns"
)
const allowedDNSCharsREGroup = "[-a-zA-Z0-9_]"
// Validate ensures that pattern is a parseable matchPattern. It returns the
// regexp generated when validating.
func Validate(pattern string) (matcher *regexp.Regexp, err error) {
pattern = strings.TrimSpace(pattern)
pattern = strings.ToLower(pattern)
// error check
if strings.ContainsAny(pattern, "[]+{},") {
return nil, errors.New(`Only alphanumeric ASCII characters, the hyphen "-", underscore "_", "." and "*" are allowed in a matchPattern`)
}
return regexp.Compile(ToRegexp(pattern))
}
// Sanitize canonicalized the pattern for use by ToRegexp
func Sanitize(pattern string) string {
if pattern == "*" {
return pattern
}
return strings.ToLower(dns.Fqdn(pattern))
}
// ToRegexp converts a MatchPattern field into a regexp string. It does not
// validate the pattern.
// It supports:
// * to select 0 or more DNS valid characters
func ToRegexp(pattern string) string {
pattern = strings.TrimSpace(pattern)
pattern = strings.ToLower(pattern)
// handle the * match-all case. This will filter down to the end.
if pattern == "*" {
return "(^(" + allowedDNSCharsREGroup + "+[.])+$)|(^[.]$)"
}
// base case. * becomes .*, but only for DNS valid characters
// NOTE: this only works because the case above does not leave the *
pattern = strings.Replace(pattern, "*", allowedDNSCharsREGroup+"*", -1)
// base case. "." becomes a literal .
pattern = strings.Replace(pattern, ".", "[.]", -1)
// Anchor the match to require the whole string to match this expression
return "^" + pattern + "$"
}