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lightsail.go
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lightsail.go
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// Package lightsail implements a DNS provider for solving the DNS-01 challenge using AWS Lightsail DNS.
package lightsail
import (
"context"
"errors"
"fmt"
"math/rand"
"strconv"
"time"
"github.com/aws/aws-sdk-go-v2/aws"
"github.com/aws/aws-sdk-go-v2/aws/retry"
awsconfig "github.com/aws/aws-sdk-go-v2/config"
"github.com/aws/aws-sdk-go-v2/service/lightsail"
awstypes "github.com/aws/aws-sdk-go-v2/service/lightsail/types"
"github.com/go-acme/lego/v4/challenge/dns01"
"github.com/go-acme/lego/v4/platform/config/env"
)
const (
maxRetries = 5
)
// Environment variables names.
const (
envNamespace = "LIGHTSAIL_"
EnvRegion = envNamespace + "REGION"
EnvDNSZone = "DNS_ZONE"
EnvPropagationTimeout = envNamespace + "PROPAGATION_TIMEOUT"
EnvPollingInterval = envNamespace + "POLLING_INTERVAL"
)
// Config is used to configure the creation of the DNSProvider.
type Config struct {
DNSZone string
Region string
PropagationTimeout time.Duration
PollingInterval time.Duration
}
// NewDefaultConfig returns a default configuration for the DNSProvider.
func NewDefaultConfig() *Config {
return &Config{
PropagationTimeout: env.GetOrDefaultSecond(EnvPropagationTimeout, dns01.DefaultPropagationTimeout),
PollingInterval: env.GetOrDefaultSecond(EnvPollingInterval, dns01.DefaultPollingInterval),
}
}
// DNSProvider implements the challenge.Provider interface.
type DNSProvider struct {
client *lightsail.Client
config *Config
}
// NewDNSProvider returns a DNSProvider instance configured for the AWS Lightsail service.
//
// AWS Credentials are automatically detected in the following locations
// and prioritized in the following order:
// 1. Environment variables: AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY,
// [AWS_SESSION_TOKEN], [DNS_ZONE], [LIGHTSAIL_REGION]
// 2. Shared credentials file (defaults to ~/.aws/credentials)
// 3. Amazon EC2 IAM role
//
// public hosted zone via the FQDN.
//
// See also: https://github.com/aws/aws-sdk-go/wiki/configuring-sdk
func NewDNSProvider() (*DNSProvider, error) {
config := NewDefaultConfig()
config.DNSZone = env.GetOrFile(EnvDNSZone)
config.Region = env.GetOrDefaultString(EnvRegion, "us-east-1")
return NewDNSProviderConfig(config)
}
// NewDNSProviderConfig return a DNSProvider instance configured for AWS Lightsail.
func NewDNSProviderConfig(config *Config) (*DNSProvider, error) {
if config == nil {
return nil, errors.New("lightsail: the configuration of the DNS provider is nil")
}
ctx := context.Background()
cfg, err := awsconfig.LoadDefaultConfig(ctx,
awsconfig.WithRegion(config.Region),
awsconfig.WithRetryer(func() aws.Retryer {
return retry.NewStandard(func(options *retry.StandardOptions) {
options.MaxAttempts = maxRetries
// It uses a basic exponential backoff algorithm that returns an initial
// delay of ~400ms with an upper limit of ~30 seconds which should prevent
// causing a high number of consecutive throttling errors.
// For reference: Route 53 enforces an account-wide(!) 5req/s query limit.
options.Backoff = retry.BackoffDelayerFunc(func(attempt int, err error) (time.Duration, error) {
retryCount := attempt
if retryCount > 7 {
retryCount = 7
}
delay := (1 << uint(retryCount)) * (rand.Intn(50) + 200)
return time.Duration(delay) * time.Millisecond, nil
})
})
}),
)
if err != nil {
return nil, err
}
return &DNSProvider{
config: config,
client: lightsail.NewFromConfig(cfg),
}, nil
}
// Present creates a TXT record using the specified parameters.
func (d *DNSProvider) Present(domain, _, keyAuth string) error {
ctx := context.Background()
info := dns01.GetChallengeInfo(domain, keyAuth)
params := &lightsail.CreateDomainEntryInput{
DomainName: aws.String(d.config.DNSZone),
DomainEntry: &awstypes.DomainEntry{
Name: aws.String(info.EffectiveFQDN),
Target: aws.String(strconv.Quote(info.Value)),
Type: aws.String("TXT"),
},
}
_, err := d.client.CreateDomainEntry(ctx, params)
if err != nil {
return fmt.Errorf("lightsail: %w", err)
}
return nil
}
// CleanUp removes the TXT record matching the specified parameters.
func (d *DNSProvider) CleanUp(domain, _, keyAuth string) error {
ctx := context.Background()
info := dns01.GetChallengeInfo(domain, keyAuth)
params := &lightsail.DeleteDomainEntryInput{
DomainName: aws.String(d.config.DNSZone),
DomainEntry: &awstypes.DomainEntry{
Name: aws.String(info.EffectiveFQDN),
Type: aws.String("TXT"),
Target: aws.String(strconv.Quote(info.Value)),
},
}
_, err := d.client.DeleteDomainEntry(ctx, params)
if err != nil {
return fmt.Errorf("lightsail: %w", err)
}
return nil
}
// Timeout returns the timeout and interval to use when checking for DNS propagation.
// Adjusting here to cope with spikes in propagation times.
func (d *DNSProvider) Timeout() (timeout, interval time.Duration) {
return d.config.PropagationTimeout, d.config.PollingInterval
}