105 lines
3.3 KiB
Go
105 lines
3.3 KiB
Go
// Copyright 2020-2021 Buf Technologies, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package netextended
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import (
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"errors"
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"fmt"
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"net"
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)
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const (
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domainNameMinLength = 2
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domainNameMaxLength = 254
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maxSegmentLength = 63
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)
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// ValidateHostname verifies the given hostname is a well-formed IP address
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// or domain name.
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func ValidateHostname(hostname string) (string, error) {
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if len(hostname) == 0 {
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return "", errors.New("must not be empty")
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}
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if len(hostname) < domainNameMinLength || len(hostname) > domainNameMaxLength {
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return "", fmt.Errorf("must be at least %d and at most %d characters", domainNameMinLength, domainNameMaxLength)
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}
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parsedHost := hostname
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if host, _, err := net.SplitHostPort(hostname); err == nil {
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parsedHost = host
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}
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if net.ParseIP(parsedHost) != nil {
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// hostname is a valid IP address
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return hostname, nil
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}
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if err := isValidDomainName(parsedHost); err != nil {
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return "", fmt.Errorf("must either be a valid IP address or domain name: invalid domain name %q, %w", hostname, err)
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}
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return hostname, nil
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}
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// isValidDomainName validates a hostname according to the requirements set for
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// domain names internally in the Go standard library's net package, see
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// golang.org/issue/12421.
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//
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// Adapted from https://github.com/golang/go/blob/f4e7a6b905ce60448e506a3f6578d01b60602cdd/src/net/dnsclient.go#L73-L128
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// See https://github.com/golang/go/blob/f4e7a6b905ce60448e506a3f6578d01b60602cdd/LICENSE for the license.
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func isValidDomainName(hostname string) error {
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previous := rune('.')
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nonNumeric := false
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segmentLen := 0
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for _, char := range hostname {
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switch {
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case '0' <= char && char <= '9':
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segmentLen++
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case 'a' <= char && char <= 'z' || 'A' <= char && char <= 'Z' || char == '_':
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nonNumeric = true
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segmentLen++
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case char == '-':
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if previous == '.' {
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return fmt.Errorf("cannot begin a segment after a period (.) with a hyphen (-)")
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}
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nonNumeric = true
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segmentLen++
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case char == '.':
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if previous == '.' {
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return fmt.Errorf("cannot contain two periods (.) in a row")
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}
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if previous == '-' {
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return fmt.Errorf("cannot have a hyphen (-) immediately before a period (.)")
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}
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if segmentLen > maxSegmentLength {
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return fmt.Errorf("cannot have segments greater than %v characters between periods (.)", maxSegmentLength)
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}
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segmentLen = 0
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default:
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return fmt.Errorf("included invalid character %q, must only contain letters, digits, periods (.), hyphens (-), or underscores (_)", char)
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}
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previous = char
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}
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if previous == '-' {
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return fmt.Errorf("cannot have a hyphen (-) as the final character")
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}
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if segmentLen > maxSegmentLength {
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return fmt.Errorf("cannot have segments greater than %v characters between periods (.)", maxSegmentLength)
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}
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if !nonNumeric {
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return errors.New("must have at least one non-numeric character")
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}
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return nil
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}
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