81 lines
2.0 KiB
Go
81 lines
2.0 KiB
Go
|
package netsafe
|
||
|
|
|
||
|
|
import (
|
||
|
|
"context"
|
||
|
|
"fmt"
|
||
|
|
"net"
|
||
|
|
"regexp"
|
||
|
|
"strings"
|
||
|
|
"time"
|
||
|
|
)
|
||
|
|
|
||
|
|
func IsBlockedIP(ip net.IP) bool {
|
||
|
|
return ip.IsLoopback() || ip.IsPrivate() || ip.IsLinkLocalUnicast() ||
|
||
|
|
ip.IsLinkLocalMulticast() || ip.IsUnspecified()
|
||
|
|
}
|
||
|
|
|
||
|
|
type allowPrivateCtxKey struct{}
|
||
|
|
|
||
|
|
func ContextWithAllowPrivate(ctx context.Context, allow bool) context.Context {
|
||
|
|
return context.WithValue(ctx, allowPrivateCtxKey{}, allow)
|
||
|
|
}
|
||
|
|
|
||
|
|
func AllowPrivateFromContext(ctx context.Context) bool {
|
||
|
|
v, _ := ctx.Value(allowPrivateCtxKey{}).(bool)
|
||
|
|
return v
|
||
|
|
}
|
||
|
|
|
||
|
|
var defaultDialer = &net.Dialer{Timeout: 10 * time.Second}
|
||
|
|
|
||
|
|
func SSRFGuardedDialContext(ctx context.Context, network, addr string) (net.Conn, error) {
|
||
|
|
host, port, err := net.SplitHostPort(addr)
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
allowPrivate := AllowPrivateFromContext(ctx)
|
||
|
|
var ips []net.IPAddr
|
||
|
|
if ip := net.ParseIP(host); ip != nil {
|
||
|
|
ips = []net.IPAddr{{IP: ip}}
|
||
|
|
} else {
|
||
|
|
ips, err = net.DefaultResolver.LookupIPAddr(ctx, host)
|
||
|
|
if err != nil {
|
||
|
|
return nil, err
|
||
|
|
}
|
||
|
|
}
|
||
|
|
var lastErr error
|
||
|
|
for _, ipAddr := range ips {
|
||
|
|
if !allowPrivate && IsBlockedIP(ipAddr.IP) {
|
||
|
|
lastErr = fmt.Errorf("blocked private/internal address %s", ipAddr.IP)
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
conn, derr := defaultDialer.DialContext(ctx, network, net.JoinHostPort(ipAddr.IP.String(), port))
|
||
|
|
if derr == nil {
|
||
|
|
return conn, nil
|
||
|
|
}
|
||
|
|
lastErr = derr
|
||
|
|
}
|
||
|
|
if lastErr == nil {
|
||
|
|
lastErr = fmt.Errorf("no usable address for %s", host)
|
||
|
|
}
|
||
|
|
return nil, lastErr
|
||
|
|
}
|
||
|
|
|
||
|
|
var hostnamePattern = regexp.MustCompile(`^[A-Za-z0-9]([A-Za-z0-9-]*[A-Za-z0-9])?(\.[A-Za-z0-9]([A-Za-z0-9-]*[A-Za-z0-9])?)*$`)
|
||
|
|
|
||
|
|
func NormalizeHost(addr string) (string, error) {
|
||
|
|
addr = strings.TrimSpace(addr)
|
||
|
|
if addr == "" {
|
||
|
|
return "", fmt.Errorf("address is required")
|
||
|
|
}
|
||
|
|
if strings.HasPrefix(addr, "[") && strings.HasSuffix(addr, "]") {
|
||
|
|
addr = addr[1 : len(addr)-1]
|
||
|
|
}
|
||
|
|
if ip := net.ParseIP(addr); ip != nil {
|
||
|
|
return ip.String(), nil
|
||
|
|
}
|
||
|
|
if len(addr) > 253 || !hostnamePattern.MatchString(addr) {
|
||
|
|
return "", fmt.Errorf("invalid host %q", addr)
|
||
|
|
}
|
||
|
|
return addr, nil
|
||
|
|
}
|