Add support for instance age check in AWS.

Fixes smallstep/step#164

authority/provisioner/aws.go

@@ -121,6 +121,7 @@ type AWS struct {
 	Accounts               []string `json:"accounts"`
 	DisableCustomSANs      bool     `json:"disableCustomSANs"`
 	DisableTrustOnFirstUse bool     `json:"disableTrustOnFirstUse"`
+	InstanceAge            Duration `json:"instanceAge,omitempty"`
 	Claims                 *Claims  `json:"claims,omitempty"`
 	claimer                *Claimer
 	config                 *awsConfig
@@ -236,6 +237,8 @@ func (p *AWS) Init(config Config) (err error) {
 		return errors.New("provisioner type cannot be empty")
 	case p.Name == "":
 		return errors.New("provisioner name cannot be empty")
+	case p.InstanceAge.Value() < 0:
+		return errors.New("provisioner instanceAge cannot be negative")
 	}
 	// Update claims with global ones
 	if p.claimer, err = NewClaimer(p.Claims, config.Claims); err != nil {
@@ -370,11 +373,12 @@ func (p *AWS) authorizeToken(token string) (*awsPayload, error) {
 
 	// According to "rfc7519 JSON Web Token" acceptable skew should be no
 	// more than a few minutes.
+	now := time.Now().UTC()
 	if err = payload.ValidateWithLeeway(jose.Expected{
 		Issuer:   awsIssuer,
 		Subject:  doc.InstanceID,
 		Audience: []string{p.GetID()},
-		Time:     time.Now().UTC(),
+		Time:     now,
 	}, time.Minute); err != nil {
 		return nil, errors.Wrapf(err, "invalid token")
 	}
@@ -392,6 +396,14 @@ func (p *AWS) authorizeToken(token string) (*awsPayload, error) {
 			return nil, errors.New("invalid identity document: accountId is not valid")
 		}
 	}
+
+	// validate instance age
+	if d := p.InstanceAge.Value(); d > 0 {
+		if now.Sub(doc.PendingTime) > d {
+			return nil, errors.New("identity document pendingTime is too old")
+		}
+	}
+
 	payload.document = doc
 	return &payload, nil
 }

authority/provisioner/aws_test.go

@@ -150,6 +150,7 @@ func TestAWS_Init(t *testing.T) {
 	badClaims := &Claims{
 		DefaultTLSDur: &Duration{0},
 	}
+	zero := Duration{Duration: 0}
 
 	type fields struct {
 		Type                   string
@@ -157,6 +158,7 @@ func TestAWS_Init(t *testing.T) {
 		Accounts               []string
 		DisableCustomSANs      bool
 		DisableTrustOnFirstUse bool
+		InstanceAge            Duration
 		Claims                 *Claims
 	}
 	type args struct {
@@ -168,10 +170,12 @@ func TestAWS_Init(t *testing.T) {
 		args    args
 		wantErr bool
 	}{
-		{"ok", fields{"AWS", "name", []string{"account"}, false, false, nil}, args{config}, false},
+		{"ok", fields{"AWS", "name", []string{"account"}, false, false, zero, nil}, args{config}, false},
-		{"fail type ", fields{"", "name", []string{"account"}, false, false, nil}, args{config}, true},
+		{"ok", fields{"AWS", "name", []string{"account"}, true, true, Duration{Duration: 1 * time.Minute}, nil}, args{config}, false},
-		{"fail name", fields{"AWS", "", []string{"account"}, false, false, nil}, args{config}, true},
+		{"fail type ", fields{"", "name", []string{"account"}, false, false, zero, nil}, args{config}, true},
-		{"fail claims", fields{"AWS", "name", []string{"account"}, false, false, badClaims}, args{config}, true},
+		{"fail name", fields{"AWS", "", []string{"account"}, false, false, zero, nil}, args{config}, true},
+		{"bad instance age", fields{"AWS", "name", []string{"account"}, false, false, Duration{Duration: -1 * time.Minute}, nil}, args{config}, true},
+		{"fail claims", fields{"AWS", "name", []string{"account"}, false, false, zero, badClaims}, args{config}, true},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -181,6 +185,7 @@ func TestAWS_Init(t *testing.T) {
 				Accounts:               tt.fields.Accounts,
 				DisableCustomSANs:      tt.fields.DisableCustomSANs,
 				DisableTrustOnFirstUse: tt.fields.DisableTrustOnFirstUse,
+				InstanceAge:            tt.fields.InstanceAge,
 				Claims:                 tt.fields.Claims,
 			}
 			if err := p.Init(tt.args.config); (err != nil) != tt.wantErr {
@@ -200,6 +205,7 @@ func TestAWS_AuthorizeSign(t *testing.T) {
 	p2.Accounts = p1.Accounts
 	p2.config = p1.config
 	p2.DisableCustomSANs = true
+	p2.InstanceAge = Duration{1 * time.Minute}
 
 	p3, err := generateAWS()
 	assert.FatalError(t, err)
@@ -266,6 +272,10 @@ func TestAWS_AuthorizeSign(t *testing.T) {
 		"instance-id", awsIssuer, p1.GetID(), p1.Accounts[0], "instance-id",
 		"127.0.0.1", "us-west-1", time.Now(), badKey)
 	assert.FatalError(t, err)
+	failInstanceAge, err := generateAWSToken(
+		"instance-id", awsIssuer, p2.GetID(), p2.Accounts[0], "instance-id",
+		"127.0.0.1", "us-west-1", time.Now().Add(-1*time.Minute), key)
+	assert.FatalError(t, err)
 
 	type args struct {
 		token string
@@ -292,6 +302,7 @@ func TestAWS_AuthorizeSign(t *testing.T) {
 		{"fail exp", p1, args{failExp}, 0, true},
 		{"fail nbf", p1, args{failNbf}, 0, true},
 		{"fail key", p1, args{failKey}, 0, true},
+		{"fail instance age", p2, args{failInstanceAge}, 0, true},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

authority/provisioner/utils_test.go

@@ -531,7 +531,7 @@ func generateAWSToken(sub, iss, aud, accountID, instanceID, privateIP, region st
 		ImageID:          "ami-123123",
 		InstanceID:       instanceID,
 		InstanceType:     "t2.micro",
-		PendingTime:      time.Now(),
+		PendingTime:      iat,
 		PrivateIP:        privateIP,
 		Region:           region,
 		Version:          "2017-09-30",