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Use AWS SDK to retrieve ec2 instance identity doc #1360

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Use AWS SDK to retrieve ec2 instance identity doc #1360

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100 changes: 49 additions & 51 deletions pkg/agent/plugin/nodeattestor/aws/iid.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,27 +3,27 @@ package aws
import (
"context"
"encoding/json"
"errors"
"fmt"
"io/ioutil"
"net/http"
"strings"
"sync"

awsSdk "github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/ec2metadata"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/hashicorp/hcl"
"github.com/spiffe/spire/pkg/agent/plugin/nodeattestor"
"github.com/spiffe/spire/pkg/common/catalog"
"github.com/spiffe/spire/pkg/common/plugin/aws"
"github.com/spiffe/spire/proto/spire/common"
spi "github.com/spiffe/spire/proto/spire/common/plugin"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"

"errors"

spi "github.com/spiffe/spire/proto/spire/common/plugin"
)

const (
defaultIdentityDocumentURL = "http://169.254.169.254/latest/dynamic/instance-identity/document"
defaultIdentitySignatureURL = "http://169.254.169.254/latest/dynamic/instance-identity/signature"
docPath = "instance-identity/document"
sigPath = "instance-identity/signature"
)

func BuiltIn() catalog.Plugin {
Expand All @@ -36,15 +36,15 @@ func builtin(p *IIDAttestorPlugin) catalog.Plugin {

// IIDAttestorConfig configures a IIDAttestorPlugin.
type IIDAttestorConfig struct {
EC2MetadataEndpoint string `hcl:"ec2_metadata_endpoint"`
IdentityDocumentURL string `hcl:"identity_document_url"`
IdentitySignatureURL string `hcl:"identity_signature_url"`
trustDomain string
}

// IIDAttestorPlugin implements aws nodeattestation in the agent.
type IIDAttestorPlugin struct {
config *IIDAttestorConfig
mtx sync.RWMutex
session *session.Session
mtx sync.RWMutex
}

// New creates a new IIDAttestorPlugin.
Expand All @@ -55,24 +55,25 @@ func New() *IIDAttestorPlugin {
// FetchAttestationData fetches attestation data from the aws metadata server and sends an attestation response
// on given stream.
func (p *IIDAttestorPlugin) FetchAttestationData(stream nodeattestor.NodeAttestor_FetchAttestationDataServer) error {
c, err := p.getConfig()
if err != nil {
return err
if p.session == nil {
return errors.New("not configured")
}

docBytes, err := httpGetBytes(c.IdentityDocumentURL)
client := ec2metadata.New(p.session)

doc, err := client.GetDynamicData(docPath)
if err != nil {
return aws.AttestationStepError("retrieving the IID from AWS", err)
}

sigBytes, err := httpGetBytes(c.IdentitySignatureURL)
sig, err := client.GetDynamicData(sigPath)
if err != nil {
return aws.AttestationStepError("retrieving the IID signature from AWS", err)
}

attestationData := aws.IIDAttestationData{
Document: string(docBytes),
Signature: string(sigBytes),
Document: doc,
Signature: sig,
}

respData, err := json.Marshal(attestationData)
Expand All @@ -96,27 +97,30 @@ func (p *IIDAttestorPlugin) Configure(ctx context.Context, req *spi.ConfigureReq
return nil, status.Errorf(codes.InvalidArgument, "unable to decode configuration: %v", err)
}

if req.GlobalConfig == nil {
return nil, status.Error(codes.InvalidArgument, "global configuration is required")
}
if req.GlobalConfig.TrustDomain == "" {
return nil, status.Error(codes.InvalidArgument, "global configuration missing trust domain")
// If the endpoint isn't explicitly configured but the legacy URLs are, extract the endpoint from it
// This code is transitional, here until these deprecated configs are removed
if config.EC2MetadataEndpoint == "" && (config.IdentityDocumentURL != "" || config.IdentitySignatureURL != "") {
endpoint, err := endpointFromLegacyConfig(config.IdentityDocumentURL, config.IdentitySignatureURL)
if err != nil {
return nil, status.Error(codes.InvalidArgument, err.Error())
}
config.EC2MetadataEndpoint = endpoint
}
// Set local vars from config struct
config.trustDomain = req.GlobalConfig.TrustDomain

if config.IdentityDocumentURL == "" {
config.IdentityDocumentURL = defaultIdentityDocumentURL
awsCfg := awsSdk.NewConfig()

if config.EC2MetadataEndpoint != "" {
awsCfg.WithEndpoint(config.EC2MetadataEndpoint)
}

if config.IdentitySignatureURL == "" {
config.IdentitySignatureURL = defaultIdentitySignatureURL
newSession, err := session.NewSession(awsCfg)
if err != nil {
return nil, status.Error(codes.InvalidArgument, err.Error())
}

p.mtx.Lock()
defer p.mtx.Unlock()

p.config = config
p.session = newSession

return &spi.ConfigureResponse{}, nil
}
Expand All @@ -126,30 +130,24 @@ func (*IIDAttestorPlugin) GetPluginInfo(context.Context, *spi.GetPluginInfoReque
return &spi.GetPluginInfoResponse{}, nil
}

func (p *IIDAttestorPlugin) getConfig() (*IIDAttestorConfig, error) {
p.mtx.RLock()
defer p.mtx.RUnlock()

if p.config == nil {
return nil, errors.New("not configured")
// endpointFromLegacyConfig extracts the endpoint from legacy configuration values
// This code is transitional, here until these deprecated configs are removed
func endpointFromLegacyConfig(docURL, sigURL string) (string, error) {
docSuffix := "/dynamic/" + docPath
if !strings.HasSuffix(docURL, docSuffix) {
return "", fmt.Errorf("IID URL '%s' doesn't end in expected suffix %s", docURL, docSuffix)
}
return p.config, nil
}
docEndpoint := strings.TrimSuffix(docURL, docSuffix)

func httpGetBytes(url string) ([]byte, error) {
resp, err := http.Get(url) //nolint: gosec // URL is provided via explicit configuration
if err != nil {
return nil, err
sigSuffix := "/dynamic/" + sigPath
if !strings.HasSuffix(sigURL, sigSuffix) {
return "", fmt.Errorf("IID signature URL '%s' doesn't end in expected suffix %s", sigURL, sigSuffix)
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Contributor Author

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This is source #1 of incompatibility: If you don't use the regular path suffix, it's not going to work.

}
defer resp.Body.Close()
sigEndpoint := strings.TrimSuffix(sigURL, sigSuffix)

if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("unexpected status code: %d", resp.StatusCode)
if docEndpoint != sigEndpoint {
return "", fmt.Errorf("IID URL and Signature URL had different endpoints: %s != %s", docEndpoint, sigEndpoint)
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Contributor Author

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This is source #2 of incompatibility: If you use two different endpoints it doesn't work -- the SDK only takes a single one.

}

bytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, err
}
return bytes, nil
return docEndpoint, nil
}
42 changes: 27 additions & 15 deletions pkg/agent/plugin/nodeattestor/aws/iid_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -13,14 +13,17 @@ import (
"testing"

"github.com/aws/aws-sdk-go/aws/ec2metadata"
"github.com/aws/aws-sdk-go/aws/endpoints"
"github.com/spiffe/spire/pkg/agent/plugin/nodeattestor"
"github.com/spiffe/spire/pkg/common/pemutil"
"github.com/spiffe/spire/pkg/common/plugin/aws"
"github.com/spiffe/spire/proto/spire/common/plugin"
"github.com/spiffe/spire/test/spiretest"
"github.com/stretchr/testify/require"
)

const (
apiTokenPath = "/latest/api/token" //nolint: gosec // false positive
defaultIdentityDocumentPath = "/latest/dynamic/instance-identity/document"
defaultIdentitySignaturePath = "/latest/dynamic/instance-identity/signature"
)
Expand Down Expand Up @@ -57,6 +60,10 @@ type Suite struct {
func (s *Suite) SetupTest() {
s.server = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
switch path := req.URL.Path; path {
case apiTokenPath:
// Token requested by AWS SDK for IMDSv2 authentication
w.WriteHeader(http.StatusOK)
_, _ = w.Write([]byte("token"))
case defaultIdentityDocumentPath:
// write doc resp
w.WriteHeader(s.status)
Expand All @@ -67,17 +74,15 @@ func (s *Suite) SetupTest() {
_, _ = w.Write([]byte(s.sigBody))
default:
// unexpected path
fmt.Printf("unexpected path %s", path)
w.WriteHeader(http.StatusForbidden)
}
}))

s.p = s.newPlugin()

_, err := s.p.Configure(context.Background(), &plugin.ConfigureRequest{
Configuration: fmt.Sprintf(`
identity_document_url = "http://%s%s"
identity_signature_url = "http://%s%s"
`, s.server.Listener.Addr().String(), defaultIdentityDocumentPath, s.server.Listener.Addr().String(), defaultIdentitySignaturePath),
Configuration: fmt.Sprintf(`ec2_metadata_endpoint = "http://%s/latest"`, s.server.Listener.Addr().String()),
GlobalConfig: &plugin.ConfigureRequest_GlobalConfig{
TrustDomain: "example.org",
},
Expand Down Expand Up @@ -107,7 +112,7 @@ func (s *Suite) TestUnexpectedStatus() {
s.status = http.StatusBadGateway
s.docBody = ""
_, err := s.fetchAttestationData()
s.RequireErrorContains(err, "unexpected status code: 502")
s.RequireErrorContains(err, "status code: 502")
}

func (s *Suite) TestSuccessfulIdentityProcessing() {
Expand Down Expand Up @@ -139,16 +144,6 @@ func (s *Suite) TestConfigure() {
require.Error(err)
require.Nil(resp)

// global configuration not provided
resp, err = s.p.Configure(context.Background(), &plugin.ConfigureRequest{})
s.RequireErrorContains(err, "global configuration is required")
require.Nil(resp)

// missing trust domain
resp, err = s.p.Configure(context.Background(), &plugin.ConfigureRequest{GlobalConfig: &plugin.ConfigureRequest_GlobalConfig{}})
s.RequireErrorContains(err, "global configuration missing trust domain")
require.Nil(resp)

// success
resp, err = s.p.Configure(context.Background(), &plugin.ConfigureRequest{
GlobalConfig: &plugin.ConfigureRequest_GlobalConfig{
Expand Down Expand Up @@ -202,3 +197,20 @@ func (s *Suite) buildDefaultIIDDocAndSig() (docBytes []byte, sigBytes []byte) {

return docBytes, sig
}

func TestEndpointFromLegacyConfig(t *testing.T) {
// These are the formerly-hardcoded default URLs
const defaultIdentityDocumentURL = "http://169.254.169.254/latest/dynamic/instance-identity/document"
const defaultIdentitySignatureURL = "http://169.254.169.254/latest/dynamic/instance-identity/signature"
// This is the default endpoint we should get from them
const defaultEndpointURL = "http://169.254.169.254/latest"

endpoint, err := endpointFromLegacyConfig(defaultIdentityDocumentURL, defaultIdentitySignatureURL)
require.NoError(t, err)
require.Equal(t, defaultEndpointURL, endpoint)

// Verify the endpoint is equal to what's in the SDK, too:
sdkDefaultEndpoint, err := endpoints.DefaultResolver().EndpointFor(ec2metadata.ServiceName, endpoints.CaCentral1RegionID)
require.NoError(t, err)
require.Equal(t, sdkDefaultEndpoint.URL, endpoint)
}
3 changes: 1 addition & 2 deletions pkg/server/plugin/nodeattestor/aws/iid.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,12 +18,11 @@ import (
"text/template"
"time"

"github.com/hashicorp/go-hclog"

"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/client"
"github.com/aws/aws-sdk-go/aws/ec2metadata"
"github.com/aws/aws-sdk-go/service/ec2"
"github.com/hashicorp/go-hclog"
"github.com/hashicorp/hcl"
"github.com/spiffe/spire/pkg/common/catalog"
caws "github.com/spiffe/spire/pkg/common/plugin/aws"
Expand Down