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package ntp
import (
"encoding/binary"
"errors"
"fmt"
"net"
"time"
"github.com/authelia/authelia/v4/internal/configuration/schema"
"github.com/authelia/authelia/v4/internal/logging"
)
// NewProvider instantiate a ntp provider given a configuration.
func NewProvider(config *schema.NTP) *Provider {
return &Provider{
config: config,
log: logging.Logger(),
}
}
// StartupCheck implements the startup check provider interface.
func (p *Provider) StartupCheck() (err error) {
var offset time.Duration
if offset, err = p.GetOffset(); err != nil {
p.log.WithError(err).Warnf("Could not determine the clock offset due to an error")
return nil
}
if offset > p.config.MaximumDesync {
return errors.New("the system clock is not synchronized accurately enough with the configured NTP server")
}
return nil
}
// GetOffset returns the current offset for this provider.
func (p *Provider) GetOffset() (offset time.Duration, err error) {
var conn net.Conn
if conn, err = net.Dial(p.config.Address.Network(), p.config.Address.NetworkAddress()); err != nil {
return offset, fmt.Errorf("error occurred during dial: %w", err)
}
defer func() {
if closeErr := conn.Close(); closeErr != nil {
p.log.WithError(err).Error("Error occurred closing connection with NTP sever")
}
}()
if err = conn.SetDeadline(time.Now().Add(5 * time.Second)); err != nil {
return offset, fmt.Errorf("error occurred setting connection deadline: %w", err)
}
version := ntpV4
if p.config.Version == 3 {
version = ntpV3
}
req := &ntpPacket{LeapVersionMode: ntpLeapVersionClientMode(version)}
if err = binary.Write(conn, binary.BigEndian, req); err != nil {
return offset, fmt.Errorf("error occurred writing ntp packet request to the connection: %w", err)
}
now := time.Now()
resp := &ntpPacket{}
if err = binary.Read(conn, binary.BigEndian, resp); err != nil {
return offset, fmt.Errorf("error occurred reading ntp packet response to the connection: %w", err)
}
ntpTime := ntpPacketToTime(resp)
return calcOffset(now, ntpTime), nil
}
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