github.com/elfadel/cilium@v1.6.12/pkg/fqdn/matchpattern/matchpattern.go (about)

     1  // Copyright 2018 Authors of Cilium
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package matchpattern
    16  
    17  import (
    18  	"errors"
    19  	"regexp"
    20  	"strings"
    21  
    22  	"github.com/miekg/dns"
    23  )
    24  
    25  const allowedDNSCharsREGroup = "[-a-zA-Z0-9_]"
    26  
    27  // Validate ensures that pattern is a parseable matchPattern. It returns the
    28  // regexp generated when validating.
    29  func Validate(pattern string) (matcher *regexp.Regexp, err error) {
    30  	pattern = strings.TrimSpace(pattern)
    31  	pattern = strings.ToLower(pattern)
    32  
    33  	// error check
    34  	if strings.ContainsAny(pattern, "[]+{},") {
    35  		return nil, errors.New(`Only alphanumeric ASCII characters, the hyphen "-", "." and "*" are allowed in a matchPattern`)
    36  	}
    37  
    38  	return regexp.Compile(ToRegexp(pattern))
    39  }
    40  
    41  // Sanitize canonicalized the pattern for use by ToRegexp
    42  func Sanitize(pattern string) string {
    43  	if pattern == "*" {
    44  		return pattern
    45  	}
    46  
    47  	return strings.ToLower(dns.Fqdn(pattern))
    48  }
    49  
    50  // ToRegexp converts a MatchPattern field into a regexp string. It does not
    51  // validate the pattern.
    52  // It supports:
    53  // * to select 0 or more DNS valid characters
    54  func ToRegexp(pattern string) string {
    55  	pattern = strings.TrimSpace(pattern)
    56  	pattern = strings.ToLower(pattern)
    57  
    58  	// handle the * match-all case. This will filter down to the end.
    59  	if pattern == "*" {
    60  		return "(^(" + allowedDNSCharsREGroup + "+[.])+$)|(^[.]$)"
    61  	}
    62  
    63  	// base case. * becomes .*, but only for DNS valid characters
    64  	// NOTE: this only works because the case above does not leave the *
    65  	pattern = strings.Replace(pattern, "*", allowedDNSCharsREGroup+"*", -1)
    66  
    67  	// base case. "." becomes a literal .
    68  	pattern = strings.Replace(pattern, ".", "[.]", -1)
    69  
    70  	// Anchor the match to require the whole string to match this expression
    71  	return "^" + pattern + "$"
    72  }