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package networkdial
import (
"crypto/tls"
"errors"
"fmt"
"maps"
"net"
"sort"
"strings"
)
var (
ErrNoResolver = errors.New("networkdial: no host resolver was given")
ErrUnknownHost = errors.New("networkdial: the host is not in the network host map")
ErrInvalidHost = errors.New("networkdial: invalid host map entry")
ErrNoCABundle = errors.New("networkdial: no network CA bundle was given")
ErrInvalidCABundle = errors.New("networkdial: the network CA bundle has no certificates")
ErrSystemDNSBlocked = errors.New("networkdial: system DNS is not allowed")
)
type Host struct {
Name string
Address string
}
type Resolver interface {
Address(hostport string) (string, bool)
}
type HostMap struct {
hosts map[string]string
}
func NewHostMap(hosts []Host) (*HostMap, error) {
m := &HostMap{hosts: map[string]string{}}
for _, host := range hosts {
if err := m.add(host.Name, host.Address); err != nil {
return nil, err
}
}
return m, nil
}
func HostMapFromPairs(pairs map[string]string) (*HostMap, error) {
m := &HostMap{hosts: map[string]string{}}
for name, address := range pairs {
if err := m.add(name, address); err != nil {
return nil, err
}
}
return m, nil
}
func ParseHostMap(value string) (*HostMap, error) {
m := &HostMap{hosts: map[string]string{}}
for pair := range strings.SplitSeq(value, ",") {
pair = strings.TrimSpace(pair)
if pair == "" {
continue
}
i := strings.IndexByte(pair, '=')
if i <= 0 {
return nil, fmt.Errorf("%w: %q is not name=address", ErrInvalidHost, pair)
}
if err := m.add(pair[:i], pair[i+1:]); err != nil {
return nil, err
}
}
return m, nil
}
func (m *HostMap) add(name, address string) error {
host := normalizeHost(name)
if host == "" {
return fmt.Errorf("%w: %q has no host name", ErrInvalidHost, name)
}
address = strings.TrimSpace(address)
if address == "" {
return fmt.Errorf("%w: %q has no address", ErrInvalidHost, name)
}
_, port, err := net.SplitHostPort(address)
if err != nil {
return fmt.Errorf("%w: %q address %q is not host:port: %v", ErrInvalidHost, name, address, err)
}
if port == "" {
return fmt.Errorf("%w: %q address %q has no port", ErrInvalidHost, name, address)
}
if _, ok := m.hosts[host]; ok {
return fmt.Errorf("%w: %q appears more than once", ErrInvalidHost, host)
}
m.hosts[host] = address
return nil
}
func (m *HostMap) Lookup(host string) (string, bool) {
if m == nil {
return "", false
}
name := normalizeHost(host)
if address, ok := m.hosts[name]; ok {
return address, true
}
for base, address := range m.hosts {
if strings.HasSuffix(name, "."+base) {
return address, true
}
}
return "", false
}
func (m *HostMap) Address(hostport string) (string, bool) {
return m.Lookup(hostport)
}
func (m *HostMap) Hosts() map[string]string {
if m == nil {
return nil
}
out := make(map[string]string, len(m.hosts))
maps.Copy(out, m.hosts)
return out
}
func (m *HostMap) Names() []string {
if m == nil {
return nil
}
out := make([]string, 0, len(m.hosts))
for name := range m.hosts {
out = append(out, name)
}
sort.Strings(out)
return out
}
func (m *HostMap) Len() int {
if m == nil {
return 0
}
return len(m.hosts)
}
func (m *HostMap) TLSConfig(caBundlePEM []byte, host string) (*tls.Config, error) {
name := normalizeHost(host)
if name == "" {
return nil, fmt.Errorf("%w: %q", ErrInvalidHost, host)
}
if _, ok := m.Lookup(name); !ok {
return nil, fmt.Errorf("%w: %s", ErrUnknownHost, name)
}
return TLSConfigFromCA(caBundlePEM, name)
}
func normalizeHost(value string) string {
host := strings.TrimSpace(value)
if h, _, err := net.SplitHostPort(host); err == nil {
host = h
}
host = strings.Trim(host, "[]")
host = strings.TrimSuffix(host, ".")
host = strings.ToLower(host)
if strings.ContainsAny(host, "/?#@") {
return ""
}
return host
}
