Merge pull request #1701 from ericrrath/oci-auth-instance-principal

OCI provider: add support for instance principal authentication

docs/tutorials/oracle.md

@@ -6,16 +6,25 @@ Make sure to use the latest version of ExternalDNS for this tutorial.
 
 ## Creating an OCI DNS Zone
 
-Create a DNS zone which will contain the managed DNS records. Let's use `example.com` as an reference here.
+Create a DNS zone which will contain the managed DNS records. Let's use
+`example.com` as a reference here.  Make note of the OCID of the compartment
+in which you created the zone; you'll need to provide that later.
 
 For more information about OCI DNS see the documentation [here][1].
 
 ## Deploy ExternalDNS
 
 Connect your `kubectl` client to the cluster you want to test ExternalDNS with.
+The OCI provider supports two authentication options: key-based and instance
+principals.
+
+### Key-based
+
 We first need to create a config file containing the information needed to connect with the OCI API.
 
-Create a new file (oci.yaml) and modify the contents to match the example below. Be sure to adjust the values to match your own credentials:
+Create a new file (oci.yaml) and modify the contents to match the example
+below. Be sure to adjust the values to match your own credentials, and the OCID
+of the compartment containing the zone:
 
 ```yaml
 auth:
@@ -37,7 +46,29 @@ Create a secret using the config file above:
 $ kubectl create secret generic external-dns-config --from-file=oci.yaml
 ```
 
-### Manifest (for clusters with RBAC enabled)
+### OCI IAM Instance Principal
+
+If you're running ExternalDNS within OCI, you can use OCI IAM instance
+principals to authenticate with OCI.  This obviates the need to create the
+secret with your credentials.  You'll need to ensure an OCI IAM policy exists
+with a statement granting the `manage dns` permission on zones and records in
+the target compartment to the dynamic group covering your instance running
+ExternalDNS.
+E.g.:
+
+```
+Allow dynamic-group <dynamic-group-name> to manage dns in compartment id <target-compartment-OCID>
+```
+
+You'll also need to add the `--oci-instance-principals=true` flag to enable
+this type of authentication. Finally, you'll need to add the
+`--oci-compartment-ocid=ocid1.compartment.oc1...` flag to provide the OCID of
+the compartment containing the zone to be managed.
+
+For more information about OCI IAM instance principals, see the documentation [here][2].
+For more information about OCI IAM policy details for the DNS service, see the documentation [here][3].
+
+## Manifest (for clusters with RBAC enabled)
 
 Apply the following manifest to deploy ExternalDNS.
 
@@ -159,3 +190,6 @@ $ kubectl apply -f nginx.yaml
 ```
 
 [1]: https://docs.cloud.oracle.com/iaas/Content/DNS/Concepts/dnszonemanagement.htm
+[2]: https://docs.cloud.oracle.com/iaas/Content/Identity/Reference/dnspolicyreference.htm
+[3]: https://docs.cloud.oracle.com/iaas/Content/Identity/Tasks/callingservicesfrominstances.htm
+

main.go

@@ -18,6 +18,7 @@ package main
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 	"os"
 	"os/signal"
@@ -312,7 +313,19 @@ func main() {
 		)
 	case "oci":
 		var config *oci.OCIConfig
-		config, err = oci.LoadOCIConfig(cfg.OCIConfigFile)
+		// if the instance-principals flag was set, and a compartment OCID was provided, then ignore the
+		// OCI config file, and provide a config that uses instance principal authentication.
+		if cfg.OCIAuthInstancePrincipal {
+			if len(cfg.OCICompartmentOCID) == 0 {
+				err = fmt.Errorf("instance principal authentication requested, but no compartment OCID provided")
+			} else {
+				authConfig := oci.OCIAuthConfig{UseInstancePrincipal: true}
+				config = &oci.OCIConfig{Auth: authConfig, CompartmentID: cfg.OCICompartmentOCID}
+			}
+		} else {
+			config, err = oci.LoadOCIConfig(cfg.OCIConfigFile)
+		}
+
 		if err == nil {
 			p, err = oci.NewOCIProvider(*config, domainFilter, zoneIDFilter, cfg.DryRun)
 		}

pkg/apis/externaldns/types.go

@@ -131,6 +131,8 @@ type Config struct {
 	DynPassword                       string `secure:"yes"`
 	DynMinTTLSeconds                  int
 	OCIConfigFile                     string
+	OCICompartmentOCID                string
+	OCIAuthInstancePrincipal          bool
 	InMemoryZones                     []string
 	OVHEndpoint                       string
 	OVHApiRateLimit                   int
@@ -498,6 +500,8 @@ func (cfg *Config) ParseFlags(args []string) error {
 	app.Flag("dyn-password", "When using the Dyn provider, specify the password").Default("").StringVar(&cfg.DynPassword)
 	app.Flag("dyn-min-ttl", "Minimal TTL (in seconds) for records. This value will be used if the provided TTL for a service/ingress is lower than this.").IntVar(&cfg.DynMinTTLSeconds)
 	app.Flag("oci-config-file", "When using the OCI provider, specify the OCI configuration file (required when --provider=oci").Default(defaultConfig.OCIConfigFile).StringVar(&cfg.OCIConfigFile)
+	app.Flag("oci-compartment-ocid", "When using the OCI provider, specify the OCID of the OCI compartment containing all managed zones and records.  Required when using OCI IAM instance principal authentication.").StringVar(&cfg.OCICompartmentOCID)
+	app.Flag("oci-auth-instance-principal", "When using the OCI provider, specify whether OCI IAM instance principal authentication should be used (instead of key-based auth via the OCI config file).").Default(strconv.FormatBool(defaultConfig.OCIAuthInstancePrincipal)).BoolVar(&cfg.OCIAuthInstancePrincipal)
 	app.Flag("rcodezero-txt-encrypt", "When using the Rcodezero provider with txt registry option, set if TXT rrs are encrypted (default: false)").Default(strconv.FormatBool(defaultConfig.RcodezeroTXTEncrypt)).BoolVar(&cfg.RcodezeroTXTEncrypt)
 	app.Flag("inmemory-zone", "Provide a list of pre-configured zones for the inmemory provider; specify multiple times for multiple zones (optional)").Default("").StringsVar(&cfg.InMemoryZones)
 	app.Flag("ovh-endpoint", "When using the OVH provider, specify the endpoint (default: ovh-eu)").Default(defaultConfig.OVHEndpoint).StringVar(&cfg.OVHEndpoint)

provider/oci/oci.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 
 	"github.com/oracle/oci-go-sdk/common"
+	"github.com/oracle/oci-go-sdk/common/auth"
 	"github.com/oracle/oci-go-sdk/dns"
 	"github.com/pkg/errors"
 	log "github.com/sirupsen/logrus"
@@ -36,12 +37,13 @@ const ociRecordTTL = 300
 
 // OCIAuthConfig holds connection parameters for the OCI API.
 type OCIAuthConfig struct {
-	Region      string `yaml:"region"`
-	TenancyID   string `yaml:"tenancy"`
-	UserID      string `yaml:"user"`
-	PrivateKey  string `yaml:"key"`
-	Fingerprint string `yaml:"fingerprint"`
-	Passphrase  string `yaml:"passphrase"`
+	Region               string `yaml:"region"`
+	TenancyID            string `yaml:"tenancy"`
+	UserID               string `yaml:"user"`
+	PrivateKey           string `yaml:"key"`
+	Fingerprint          string `yaml:"fingerprint"`
+	Passphrase           string `yaml:"passphrase"`
+	UseInstancePrincipal bool   `yaml:"useInstancePrincipal"`
 }
 
 // OCIConfig holds the configuration for the OCI Provider.
@@ -87,14 +89,25 @@ func LoadOCIConfig(path string) (*OCIConfig, error) {
 // NewOCIProvider initializes a new OCI DNS based Provider.
 func NewOCIProvider(cfg OCIConfig, domainFilter endpoint.DomainFilter, zoneIDFilter provider.ZoneIDFilter, dryRun bool) (*OCIProvider, error) {
 	var client ociDNSClient
-	client, err := dns.NewDnsClientWithConfigurationProvider(common.NewRawConfigurationProvider(
-		cfg.Auth.TenancyID,
-		cfg.Auth.UserID,
-		cfg.Auth.Region,
-		cfg.Auth.Fingerprint,
-		cfg.Auth.PrivateKey,
-		&cfg.Auth.Passphrase,
-	))
+	var err error
+	var configProvider common.ConfigurationProvider
+	if cfg.Auth.UseInstancePrincipal {
+		configProvider, err = auth.InstancePrincipalConfigurationProvider()
+		if err != nil {
+			return nil, errors.Wrap(err, "error creating OCI instance principal config provider")
+		}
+	} else {
+		configProvider = common.NewRawConfigurationProvider(
+			cfg.Auth.TenancyID,
+			cfg.Auth.UserID,
+			cfg.Auth.Region,
+			cfg.Auth.Fingerprint,
+			cfg.Auth.PrivateKey,
+			&cfg.Auth.Passphrase,
+		)
+	}
+
+	client, err = dns.NewDnsClientWithConfigurationProvider(configProvider)
 	if err != nil {
 		return nil, errors.Wrap(err, "initializing OCI DNS API client")
 	}

provider/oci/oci_test.go

@@ -19,6 +19,7 @@ package oci
 import (
 	"context"
 	"sort"
+	"strings"
 	"testing"
 
 	"github.com/oracle/oci-go-sdk/common"
@@ -167,6 +168,17 @@ hKRtDhmSdWBo3tJK12RrAe4t7CUe8gMgTvU7ExlcA3xQkseFPx9K
 				},
 			},
 		},
+		"instance-principal": {
+			// testing the InstancePrincipalConfigurationProvider is tricky outside of an OCI context, because it tries
+			// to request a token from the internal OCI systems; this test-case just confirms that the expected error is
+			// observed, confirming that the instance-principal provider was instantiated.
+			config: OCIConfig{
+				Auth: OCIAuthConfig{
+					UseInstancePrincipal: true,
+				},
+			},
+			err: errors.New("error creating OCI instance principal config provider: failed to create a new key provider for instance principal"),
+		},
 		"invalid": {
 			config: OCIConfig{
 				Auth: OCIAuthConfig{
@@ -192,7 +204,8 @@ hKRtDhmSdWBo3tJK12RrAe4t7CUe8gMgTvU7ExlcA3xQkseFPx9K
 			if err == nil {
 				require.NoError(t, err)
 			} else {
-				require.Equal(t, tc.err.Error(), err.Error())
+				// have to use prefix testing because the expected instance-principal error strings vary after a known prefix
+				require.Truef(t, strings.HasPrefix(err.Error(), tc.err.Error()), "observed: %s", err.Error())
 			}
 		})
 	}