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azure.go
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azure.go
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// Package azure implements a DNS provider for solving the DNS-01 challenge using azure DNS.
// Azure doesn't like trailing dots on domain names, most of the acme code does.
package azure
import (
"context"
"errors"
"fmt"
"io/ioutil"
"net/http"
"strings"
"time"
"github.com/Azure/azure-sdk-for-go/services/dns/mgmt/2017-09-01/dns"
"github.com/Azure/go-autorest/autorest"
aazure "github.com/Azure/go-autorest/autorest/azure"
"github.com/Azure/go-autorest/autorest/azure/auth"
"github.com/Azure/go-autorest/autorest/to"
"github.com/simonmittag/lego/v4/challenge/dns01"
"github.com/simonmittag/lego/v4/platform/config/env"
)
const defaultMetadataEndpoint = "http://169.254.169.254"
// Environment variables names.
const (
envNamespace = "AZURE_"
EnvEnvironment = envNamespace + "ENVIRONMENT"
EnvMetadataEndpoint = envNamespace + "METADATA_ENDPOINT"
EnvSubscriptionID = envNamespace + "SUBSCRIPTION_ID"
EnvResourceGroup = envNamespace + "RESOURCE_GROUP"
EnvTenantID = envNamespace + "TENANT_ID"
EnvClientID = envNamespace + "CLIENT_ID"
EnvClientSecret = envNamespace + "CLIENT_SECRET"
EnvTTL = envNamespace + "TTL"
EnvPropagationTimeout = envNamespace + "PROPAGATION_TIMEOUT"
EnvPollingInterval = envNamespace + "POLLING_INTERVAL"
)
// Config is used to configure the creation of the DNSProvider.
type Config struct {
// optional if using instance metadata service
ClientID string
ClientSecret string
TenantID string
SubscriptionID string
ResourceGroup string
MetadataEndpoint string
ResourceManagerEndpoint string
ActiveDirectoryEndpoint string
PropagationTimeout time.Duration
PollingInterval time.Duration
TTL int
HTTPClient *http.Client
}
// NewDefaultConfig returns a default configuration for the DNSProvider.
func NewDefaultConfig() *Config {
return &Config{
TTL: env.GetOrDefaultInt(EnvTTL, 60),
PropagationTimeout: env.GetOrDefaultSecond(EnvPropagationTimeout, 2*time.Minute),
PollingInterval: env.GetOrDefaultSecond(EnvPollingInterval, 2*time.Second),
MetadataEndpoint: env.GetOrFile(EnvMetadataEndpoint),
ResourceManagerEndpoint: aazure.PublicCloud.ResourceManagerEndpoint,
ActiveDirectoryEndpoint: aazure.PublicCloud.ActiveDirectoryEndpoint,
}
}
// DNSProvider implements the challenge.Provider interface.
type DNSProvider struct {
config *Config
authorizer autorest.Authorizer
}
// NewDNSProvider returns a DNSProvider instance configured for azure.
// Credentials can be passed in the environment variables:
// AZURE_ENVIRONMENT, AZURE_CLIENT_ID, AZURE_CLIENT_SECRET,
// AZURE_SUBSCRIPTION_ID, AZURE_TENANT_ID, AZURE_RESOURCE_GROUP
// If the credentials are _not_ set via the environment,
// then it will attempt to get a bearer token via the instance metadata service.
// see: https://github.com/Azure/go-autorest/blob/v10.14.0/autorest/azure/auth/auth.go#L38-L42
func NewDNSProvider() (*DNSProvider, error) {
config := NewDefaultConfig()
environmentName := env.GetOrFile(EnvEnvironment)
if environmentName != "" {
var environment aazure.Environment
switch environmentName {
case "china":
environment = aazure.ChinaCloud
case "german":
environment = aazure.GermanCloud
case "public":
environment = aazure.PublicCloud
case "usgovernment":
environment = aazure.USGovernmentCloud
default:
return nil, fmt.Errorf("azure: unknown environment %s", environmentName)
}
config.ResourceManagerEndpoint = environment.ResourceManagerEndpoint
config.ActiveDirectoryEndpoint = environment.ActiveDirectoryEndpoint
}
config.SubscriptionID = env.GetOrFile(EnvSubscriptionID)
config.ResourceGroup = env.GetOrFile(EnvResourceGroup)
config.ClientSecret = env.GetOrFile(EnvClientSecret)
config.ClientID = env.GetOrFile(EnvClientID)
config.TenantID = env.GetOrFile(EnvTenantID)
return NewDNSProviderConfig(config)
}
// NewDNSProviderConfig return a DNSProvider instance configured for Azure.
func NewDNSProviderConfig(config *Config) (*DNSProvider, error) {
if config == nil {
return nil, errors.New("azure: the configuration of the DNS provider is nil")
}
if config.HTTPClient == nil {
config.HTTPClient = http.DefaultClient
}
authorizer, err := getAuthorizer(config)
if err != nil {
return nil, err
}
if config.SubscriptionID == "" {
subsID, err := getMetadata(config, "subscriptionId")
if err != nil {
return nil, fmt.Errorf("azure: %w", err)
}
if subsID == "" {
return nil, errors.New("azure: SubscriptionID is missing")
}
config.SubscriptionID = subsID
}
if config.ResourceGroup == "" {
resGroup, err := getMetadata(config, "resourceGroupName")
if err != nil {
return nil, fmt.Errorf("azure: %w", err)
}
if resGroup == "" {
return nil, errors.New("azure: ResourceGroup is missing")
}
config.ResourceGroup = resGroup
}
return &DNSProvider{config: config, authorizer: authorizer}, 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
}
// Present creates a TXT record to fulfill the dns-01 challenge.
func (d *DNSProvider) Present(domain, token, keyAuth string) error {
ctx := context.Background()
fqdn, value := dns01.GetRecord(domain, keyAuth)
zone, err := d.getHostedZoneID(ctx, fqdn)
if err != nil {
return fmt.Errorf("azure: %w", err)
}
rsc := dns.NewRecordSetsClientWithBaseURI(d.config.ResourceManagerEndpoint, d.config.SubscriptionID)
rsc.Authorizer = d.authorizer
relative := toRelativeRecord(fqdn, dns01.ToFqdn(zone))
// Get existing record set
rset, err := rsc.Get(ctx, d.config.ResourceGroup, zone, relative, dns.TXT)
if err != nil {
var detailed autorest.DetailedError
if !errors.As(err, &detailed) || detailed.StatusCode != http.StatusNotFound {
return fmt.Errorf("azure: %w", err)
}
}
// Construct unique TXT records using map
uniqRecords := map[string]struct{}{value: {}}
if rset.RecordSetProperties != nil && rset.TxtRecords != nil {
for _, txtRecord := range *rset.TxtRecords {
// Assume Value doesn't contain multiple strings
if txtRecord.Value != nil && len(*txtRecord.Value) > 0 {
uniqRecords[(*txtRecord.Value)[0]] = struct{}{}
}
}
}
var txtRecords []dns.TxtRecord
for txt := range uniqRecords {
txtRecords = append(txtRecords, dns.TxtRecord{Value: &[]string{txt}})
}
rec := dns.RecordSet{
Name: &relative,
RecordSetProperties: &dns.RecordSetProperties{
TTL: to.Int64Ptr(int64(d.config.TTL)),
TxtRecords: &txtRecords,
},
}
_, err = rsc.CreateOrUpdate(ctx, d.config.ResourceGroup, zone, relative, dns.TXT, rec, "", "")
if err != nil {
return fmt.Errorf("azure: %w", err)
}
return nil
}
// CleanUp removes the TXT record matching the specified parameters.
func (d *DNSProvider) CleanUp(domain, token, keyAuth string) error {
ctx := context.Background()
fqdn, _ := dns01.GetRecord(domain, keyAuth)
zone, err := d.getHostedZoneID(ctx, fqdn)
if err != nil {
return fmt.Errorf("azure: %w", err)
}
relative := toRelativeRecord(fqdn, dns01.ToFqdn(zone))
rsc := dns.NewRecordSetsClientWithBaseURI(d.config.ResourceManagerEndpoint, d.config.SubscriptionID)
rsc.Authorizer = d.authorizer
_, err = rsc.Delete(ctx, d.config.ResourceGroup, zone, relative, dns.TXT, "")
if err != nil {
return fmt.Errorf("azure: %w", err)
}
return nil
}
// Checks that azure has a zone for this domain name.
func (d *DNSProvider) getHostedZoneID(ctx context.Context, fqdn string) (string, error) {
authZone, err := dns01.FindZoneByFqdn(fqdn)
if err != nil {
return "", err
}
dc := dns.NewZonesClientWithBaseURI(d.config.ResourceManagerEndpoint, d.config.SubscriptionID)
dc.Authorizer = d.authorizer
zone, err := dc.Get(ctx, d.config.ResourceGroup, dns01.UnFqdn(authZone))
if err != nil {
return "", err
}
// zone.Name shouldn't have a trailing dot(.)
return to.String(zone.Name), nil
}
// Returns the relative record to the domain.
func toRelativeRecord(domain, zone string) string {
return dns01.UnFqdn(strings.TrimSuffix(domain, zone))
}
func getAuthorizer(config *Config) (autorest.Authorizer, error) {
if config.ClientID != "" && config.ClientSecret != "" && config.TenantID != "" {
credentialsConfig := auth.ClientCredentialsConfig{
ClientID: config.ClientID,
ClientSecret: config.ClientSecret,
TenantID: config.TenantID,
Resource: config.ResourceManagerEndpoint,
AADEndpoint: config.ActiveDirectoryEndpoint,
}
spToken, err := credentialsConfig.ServicePrincipalToken()
if err != nil {
return nil, fmt.Errorf("failed to get oauth token from client credentials: %w", err)
}
spToken.SetSender(config.HTTPClient)
return autorest.NewBearerAuthorizer(spToken), nil
}
return auth.NewAuthorizerFromEnvironment()
}
// Fetches metadata from environment or he instance metadata service.
// borrowed from https://github.com/Microsoft/azureimds/blob/master/imdssample.go
func getMetadata(config *Config, field string) (string, error) {
metadataEndpoint := config.MetadataEndpoint
if metadataEndpoint == "" {
metadataEndpoint = defaultMetadataEndpoint
}
resource := fmt.Sprintf("%s/metadata/instance/compute/%s", metadataEndpoint, field)
req, err := http.NewRequest(http.MethodGet, resource, nil)
if err != nil {
return "", err
}
req.Header.Set("Metadata", "True")
q := req.URL.Query()
q.Add("format", "text")
q.Add("api-version", "2017-12-01")
req.URL.RawQuery = q.Encode()
resp, err := config.HTTPClient.Do(req)
if err != nil {
return "", err
}
defer resp.Body.Close()
respBody, err := ioutil.ReadAll(resp.Body)
if err != nil {
return "", err
}
return string(respBody), nil
}