Add first test cases for EAB and make provisioner unique per EAB

Before this commit, EAB keys could be used CA-wide, meaning that
an EAB credential could be used at any ACME provisioner. This
commit changes that behavior, so that EAB credentials are now
intended to be used with a specific ACME provisioner. I think
that makes sense, because from the perspective of an ACME client
the provisioner is like a distinct CA.

Besides that this commit also includes the first tests for EAB.
The logic for creating the EAB JWS as a client has been taken
from github.com/mholt/acmez. This logic may be moved or otherwise
sourced (i.e. from a vendor) as soon as the step client also
(needs to) support(s) EAB with ACME.

acme/account.go

@@ -45,6 +45,7 @@ func KeyToID(jwk *jose.JSONWebKey) (string, error) {
 
 type ExternalAccountKey struct {
 	ID              string    `json:"id"`
+	ProvisionerName string    `json:"provisioner_name"`
 	Name            string    `json:"name"`
 	AccountID       string    `json:"-"`
 	KeyBytes        []byte    `json:"-"`

acme/api/account.go

@@ -93,6 +93,12 @@ func (h *Handler) NewAccount(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	prov, err := acmeProvisionerFromContext(ctx)
+	if err != nil {
+		api.WriteError(w, err)
+		return
+	}
+
 	httpStatus := http.StatusCreated
 	acc, err := accountFromContext(r.Context())
 	if err != nil {
@@ -126,7 +132,7 @@ func (h *Handler) NewAccount(w http.ResponseWriter, r *http.Request) {
 		}
 		if eak != nil { // means that we have a (valid) External Account Binding key that should be bound, updated and sent in the response
 			eak.BindTo(acc)
-			if err := h.db.UpdateExternalAccountKey(ctx, eak); err != nil {
+			if err := h.db.UpdateExternalAccountKey(ctx, prov.Name, eak); err != nil {
 				api.WriteError(w, acme.WrapErrorISE(err, "error updating external account binding key"))
 				return
 			}
@@ -224,7 +230,7 @@ func (h *Handler) GetOrdersByAccountID(w http.ResponseWriter, r *http.Request) {
 	logOrdersByAccount(w, orders)
 }
 
-// validateExternalAccountBinding validates the externalAccountBinding property in a call to new-account
+// validateExternalAccountBinding validates the externalAccountBinding property in a call to new-account.
 func (h *Handler) validateExternalAccountBinding(ctx context.Context, nar *NewAccountRequest) (*acme.ExternalAccountKey, error) {
 	acmeProv, err := acmeProvisionerFromContext(ctx)
 	if err != nil {
@@ -253,8 +259,11 @@ func (h *Handler) validateExternalAccountBinding(ctx context.Context, nar *NewAc
 	// TODO: implement strategy pattern to allow for different ways of verification (i.e. webhook call) based on configuration
 
 	keyID := eabJWS.Signatures[0].Protected.KeyID
-	externalAccountKey, err := h.db.GetExternalAccountKey(ctx, keyID)
+	externalAccountKey, err := h.db.GetExternalAccountKey(ctx, acmeProv.Name, keyID)
 	if err != nil {
+		if _, ok := err.(*acme.Error); ok {
+			return nil, err
+		}
 		return nil, acme.WrapErrorISE(err, "error retrieving external account key")
 	}
 
@@ -285,6 +294,8 @@ func (h *Handler) validateExternalAccountBinding(ctx context.Context, nar *NewAc
 	return externalAccountKey, nil
 }
 
+// keysAreEqual performs an equality check on two JWKs by comparing
+// the (base64 encoding) of the Key IDs.
 func keysAreEqual(x, y *squarejose.JSONWebKey) bool {
 	if x == nil || y == nil {
 		return false

acme/api/account_test.go

@@ -3,11 +3,19 @@ package api
 import (
 	"bytes"
 	"context"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/hmac"
+	"crypto/rsa"
+	"crypto/sha256"
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
+	"math/big"
 	"net/http/httptest"
 	"net/url"
+	"reflect"
 	"testing"
 	"time"
 
@@ -16,6 +24,7 @@ import (
 	"github.com/smallstep/certificates/acme"
 	"github.com/smallstep/certificates/authority/provisioner"
 	"go.step.sm/crypto/jose"
+	squarejose "gopkg.in/square/go-jose.v2"
 )
 
 var (
@@ -40,6 +49,136 @@ func newProv() acme.Provisioner {
 	return p
 }
 
+func newACMEProv(t *testing.T) *provisioner.ACME {
+	p := newProv()
+	a, ok := p.(*provisioner.ACME)
+	if !ok {
+		t.Fatal("not a valid ACME provisioner")
+	}
+	return a
+}
+
+var errUnsupportedKey = fmt.Errorf("unknown key type; only RSA and ECDSA are supported")
+
+// keyID is the account identity provided by a CA during registration.
+type keyID string
+
+// noKeyID indicates that jwsEncodeJSON should compute and use JWK instead of a KID.
+// See jwsEncodeJSON for details.
+const noKeyID = keyID("")
+
+// jwsEncodeEAB creates a JWS payload for External Account Binding according to RFC 8555 §7.3.4.
+// Implementation taken from github.com/mholt/acmez
+func jwsEncodeEAB(accountKey crypto.PublicKey, hmacKey []byte, kid keyID, url string) ([]byte, error) {
+	// §7.3.4: "The 'alg' field MUST indicate a MAC-based algorithm"
+	alg, sha := "HS256", crypto.SHA256
+
+	// §7.3.4: "The 'nonce' field MUST NOT be present"
+	phead, err := jwsHead(alg, "", url, kid, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	encodedKey, err := jwkEncode(accountKey)
+	if err != nil {
+		return nil, err
+	}
+
+	payload := base64.RawURLEncoding.EncodeToString([]byte(encodedKey))
+
+	payloadToSign := []byte(phead + "." + payload)
+
+	h := hmac.New(sha256.New, hmacKey)
+	h.Write(payloadToSign)
+	sig := h.Sum(nil)
+
+	return jwsFinal(sha, sig, phead, payload)
+}
+
+// jwsHead constructs the protected JWS header for the given fields.
+// Since jwk and kid are mutually-exclusive, the jwk will be encoded
+// only if kid is empty. If nonce is empty, it will not be encoded.
+// Implementation taken from github.com/mholt/acmez
+func jwsHead(alg, nonce, url string, kid keyID, key crypto.Signer) (string, error) {
+	phead := fmt.Sprintf(`{"alg":%q`, alg)
+	if kid == noKeyID {
+		jwk, err := jwkEncode(key.Public())
+		if err != nil {
+			return "", err
+		}
+		phead += fmt.Sprintf(`,"jwk":%s`, jwk)
+	} else {
+		phead += fmt.Sprintf(`,"kid":%q`, kid)
+	}
+	if nonce != "" {
+		phead += fmt.Sprintf(`,"nonce":%q`, nonce)
+	}
+	phead += fmt.Sprintf(`,"url":%q}`, url)
+	phead = base64.RawURLEncoding.EncodeToString([]byte(phead))
+	return phead, nil
+}
+
+// jwkEncode encodes public part of an RSA or ECDSA key into a JWK.
+// The result is also suitable for creating a JWK thumbprint.
+// https://tools.ietf.org/html/rfc7517
+// Implementation taken from github.com/mholt/acmez
+func jwkEncode(pub crypto.PublicKey) (string, error) {
+	switch pub := pub.(type) {
+	case *rsa.PublicKey:
+		// https://tools.ietf.org/html/rfc7518#section-6.3.1
+		n := pub.N
+		e := big.NewInt(int64(pub.E))
+		// Field order is important.
+		// See https://tools.ietf.org/html/rfc7638#section-3.3 for details.
+		return fmt.Sprintf(`{"e":"%s","kty":"RSA","n":"%s"}`,
+			base64.RawURLEncoding.EncodeToString(e.Bytes()),
+			base64.RawURLEncoding.EncodeToString(n.Bytes()),
+		), nil
+	case *ecdsa.PublicKey:
+		// https://tools.ietf.org/html/rfc7518#section-6.2.1
+		p := pub.Curve.Params()
+		n := p.BitSize / 8
+		if p.BitSize%8 != 0 {
+			n++
+		}
+		x := pub.X.Bytes()
+		if n > len(x) {
+			x = append(make([]byte, n-len(x)), x...)
+		}
+		y := pub.Y.Bytes()
+		if n > len(y) {
+			y = append(make([]byte, n-len(y)), y...)
+		}
+		// Field order is important.
+		// See https://tools.ietf.org/html/rfc7638#section-3.3 for details.
+		return fmt.Sprintf(`{"crv":"%s","kty":"EC","x":"%s","y":"%s"}`,
+			p.Name,
+			base64.RawURLEncoding.EncodeToString(x),
+			base64.RawURLEncoding.EncodeToString(y),
+		), nil
+	}
+	return "", errUnsupportedKey
+}
+
+// jwsFinal constructs the final JWS object.
+// Implementation taken from github.com/mholt/acmez
+func jwsFinal(sha crypto.Hash, sig []byte, phead, payload string) ([]byte, error) {
+	enc := struct {
+		Protected string `json:"protected"`
+		Payload   string `json:"payload"`
+		Sig       string `json:"signature"`
+	}{
+		Protected: phead,
+		Payload:   payload,
+		Sig:       base64.RawURLEncoding.EncodeToString(sig),
+	}
+	result, err := json.Marshal(&enc)
+	if err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
 func TestNewAccountRequest_Validate(t *testing.T) {
 	type test struct {
 		nar *NewAccountRequest
@@ -377,6 +516,27 @@ func TestHandler_NewAccount(t *testing.T) {
 				err:        acme.NewErrorISE("jwk expected in request context"),
 			}
 		},
+		"fail/new-account-no-eab-provided": func(t *testing.T) test {
+			nar := &NewAccountRequest{
+				Contact:                []string{"foo", "bar"},
+				ExternalAccountBinding: nil,
+			}
+			b, err := json.Marshal(nar)
+			assert.FatalError(t, err)
+			jwk, err := jose.GenerateJWK("EC", "P-256", "ES256", "sig", "", 0)
+			assert.FatalError(t, err)
+			prov := newACMEProv(t)
+			prov.RequireEAB = true
+			ctx := context.WithValue(context.Background(), payloadContextKey, &payloadInfo{value: b})
+			ctx = context.WithValue(ctx, jwkContextKey, jwk)
+			ctx = context.WithValue(ctx, baseURLContextKey, baseURL)
+			ctx = context.WithValue(ctx, provisionerContextKey, prov)
+			return test{
+				ctx:        ctx,
+				statusCode: 400,
+				err:        acme.NewError(acme.ErrorExternalAccountRequiredType, "no external account binding provided"),
+			}
+		},
 		"fail/db.CreateAccount-error": func(t *testing.T) test {
 			nar := &NewAccountRequest{
 				Contact: []string{"foo", "bar"},
@@ -456,6 +616,94 @@ func TestHandler_NewAccount(t *testing.T) {
 				statusCode: 200,
 			}
 		},
+		"ok/new-account-no-eab-required": func(t *testing.T) test {
+			nar := &NewAccountRequest{
+				Contact:                []string{"foo", "bar"},
+				ExternalAccountBinding: struct{}{},
+			}
+			b, err := json.Marshal(nar)
+			assert.FatalError(t, err)
+			jwk, err := jose.GenerateJWK("EC", "P-256", "ES256", "sig", "", 0)
+			assert.FatalError(t, err)
+			prov := newACMEProv(t)
+			prov.RequireEAB = false
+			ctx := context.WithValue(context.Background(), payloadContextKey, &payloadInfo{value: b})
+			ctx = context.WithValue(ctx, jwkContextKey, jwk)
+			ctx = context.WithValue(ctx, baseURLContextKey, baseURL)
+			ctx = context.WithValue(ctx, provisionerContextKey, prov)
+			return test{
+				db: &acme.MockDB{
+					MockCreateAccount: func(ctx context.Context, acc *acme.Account) error {
+						acc.ID = "accountID"
+						assert.Equals(t, acc.Contact, nar.Contact)
+						assert.Equals(t, acc.Key, jwk)
+						return nil
+					},
+				},
+				acc: &acme.Account{
+					ID:        "accountID",
+					Key:       jwk,
+					Status:    acme.StatusValid,
+					Contact:   []string{"foo", "bar"},
+					OrdersURL: fmt.Sprintf("%s/acme/%s/account/accountID/orders", baseURL.String(), escProvName),
+				},
+				ctx:        ctx,
+				statusCode: 201,
+			}
+		},
+		"ok/new-account-with-eab": func(t *testing.T) test {
+			jwk, err := jose.GenerateJWK("EC", "P-256", "ES256", "sig", "", 0)
+			assert.FatalError(t, err)
+			eabJWS, err := jwsEncodeEAB(jwk.Public().Key, []byte{1, 3, 3, 7}, "eakID", fmt.Sprintf("%s/acme/%s/account/new-account", baseURL.String(), escProvName))
+			assert.FatalError(t, err)
+			mappedEAB := make(map[string]interface{})
+			err = json.Unmarshal(eabJWS, &mappedEAB)
+			assert.FatalError(t, err)
+			nar := &NewAccountRequest{
+				Contact:                []string{"foo", "bar"},
+				ExternalAccountBinding: mappedEAB,
+			}
+			b, err := json.Marshal(nar)
+			assert.FatalError(t, err)
+			prov := newACMEProv(t)
+			prov.RequireEAB = true
+			ctx := context.WithValue(context.Background(), payloadContextKey, &payloadInfo{value: b})
+			ctx = context.WithValue(ctx, jwkContextKey, jwk)
+			ctx = context.WithValue(ctx, baseURLContextKey, baseURL)
+			ctx = context.WithValue(ctx, provisionerContextKey, prov)
+			return test{
+				db: &acme.MockDB{
+					MockCreateAccount: func(ctx context.Context, acc *acme.Account) error {
+						acc.ID = "accountID"
+						assert.Equals(t, acc.Contact, nar.Contact)
+						assert.Equals(t, acc.Key, jwk)
+						return nil
+					},
+					MockGetExternalAccountKey: func(ctx context.Context, provisionerName string, keyID string) (*acme.ExternalAccountKey, error) {
+						return &acme.ExternalAccountKey{
+							ID:              "eakID",
+							ProvisionerName: escProvName,
+							Name:            "testeak",
+							KeyBytes:        []byte{1, 3, 3, 7},
+							CreatedAt:       time.Now(),
+						}, nil
+					},
+					MockUpdateExternalAccountKey: func(ctx context.Context, provisionerName string, eak *acme.ExternalAccountKey) error {
+						return nil
+					},
+				},
+				acc: &acme.Account{
+					ID:                     "accountID",
+					Key:                    jwk,
+					Status:                 acme.StatusValid,
+					Contact:                []string{"foo", "bar"},
+					OrdersURL:              fmt.Sprintf("%s/acme/%s/account/accountID/orders", baseURL.String(), escProvName),
+					ExternalAccountBinding: mappedEAB,
+				},
+				ctx:        ctx,
+				statusCode: 201,
+			}
+		},
 	}
 	for name, run := range tests {
 		tc := run(t)
@@ -694,3 +942,93 @@ func TestHandler_GetOrUpdateAccount(t *testing.T) {
 		})
 	}
 }
+
+func Test_keysAreEqual(t *testing.T) {
+	jwkX, err := jose.GenerateJWK("EC", "P-256", "ES256", "sig", "", 0)
+	assert.FatalError(t, err)
+	jwkY, err := jose.GenerateJWK("EC", "P-256", "ES256", "sig", "", 0)
+	assert.FatalError(t, err)
+	type args struct {
+		x *squarejose.JSONWebKey
+		y *squarejose.JSONWebKey
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			name: "ok/nil",
+			args: args{
+				x: jwkX,
+				y: nil,
+			},
+			want: false,
+		},
+		{
+			name: "ok/equal",
+			args: args{
+				x: jwkX,
+				y: jwkX,
+			},
+			want: true,
+		},
+		{
+			name: "ok/not-equal",
+			args: args{
+				x: jwkX,
+				y: jwkY,
+			},
+			want: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := keysAreEqual(tt.args.x, tt.args.y); got != tt.want {
+				t.Errorf("keysAreEqual() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestHandler_validateExternalAccountBinding(t *testing.T) {
+	type fields struct {
+		db                       acme.DB
+		backdate                 provisioner.Duration
+		ca                       acme.CertificateAuthority
+		linker                   Linker
+		validateChallengeOptions *acme.ValidateChallengeOptions
+	}
+	type args struct {
+		ctx context.Context
+		nar *NewAccountRequest
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		want    *acme.ExternalAccountKey
+		wantErr bool
+	}{
+		// TODO: Add test cases.
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			h := &Handler{
+				db:                       tt.fields.db,
+				backdate:                 tt.fields.backdate,
+				ca:                       tt.fields.ca,
+				linker:                   tt.fields.linker,
+				validateChallengeOptions: tt.fields.validateChallengeOptions,
+			}
+			got, err := h.validateExternalAccountBinding(tt.args.ctx, tt.args.nar)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Handler.validateExternalAccountBinding() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Handler.validateExternalAccountBinding() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

acme/db.go

@@ -19,9 +19,9 @@ type DB interface {
 	GetAccountByKeyID(ctx context.Context, kid string) (*Account, error)
 	UpdateAccount(ctx context.Context, acc *Account) error
 
-	CreateExternalAccountKey(ctx context.Context, name string) (*ExternalAccountKey, error)
+	CreateExternalAccountKey(ctx context.Context, provisionerName string, name string) (*ExternalAccountKey, error)
-	GetExternalAccountKey(ctx context.Context, keyID string) (*ExternalAccountKey, error)
+	GetExternalAccountKey(ctx context.Context, provisionerName string, keyID string) (*ExternalAccountKey, error)
-	UpdateExternalAccountKey(ctx context.Context, eak *ExternalAccountKey) error
+	UpdateExternalAccountKey(ctx context.Context, provisionerName string, eak *ExternalAccountKey) error
 
 	CreateNonce(ctx context.Context) (Nonce, error)
 	DeleteNonce(ctx context.Context, nonce Nonce) error
@@ -51,9 +51,9 @@ type MockDB struct {
 	MockGetAccountByKeyID func(ctx context.Context, kid string) (*Account, error)
 	MockUpdateAccount     func(ctx context.Context, acc *Account) error
 
-	MockCreateExternalAccountKey func(ctx context.Context, name string) (*ExternalAccountKey, error)
+	MockCreateExternalAccountKey func(ctx context.Context, provisionerName string, name string) (*ExternalAccountKey, error)
-	MockGetExternalAccountKey    func(ctx context.Context, keyID string) (*ExternalAccountKey, error)
+	MockGetExternalAccountKey    func(ctx context.Context, provisionerName string, keyID string) (*ExternalAccountKey, error)
-	MockUpdateExternalAccountKey func(ctx context.Context, eak *ExternalAccountKey) error
+	MockUpdateExternalAccountKey func(ctx context.Context, provisionerName string, eak *ExternalAccountKey) error
 
 	MockCreateNonce func(ctx context.Context) (Nonce, error)
 	MockDeleteNonce func(ctx context.Context, nonce Nonce) error
@@ -119,9 +119,9 @@ func (m *MockDB) UpdateAccount(ctx context.Context, acc *Account) error {
 }
 
 // CreateExternalAccountKey mock
-func (m *MockDB) CreateExternalAccountKey(ctx context.Context, name string) (*ExternalAccountKey, error) {
+func (m *MockDB) CreateExternalAccountKey(ctx context.Context, provisionerName string, name string) (*ExternalAccountKey, error) {
 	if m.MockCreateExternalAccountKey != nil {
-		return m.MockCreateExternalAccountKey(ctx, name)
+		return m.MockCreateExternalAccountKey(ctx, provisionerName, name)
 	} else if m.MockError != nil {
 		return nil, m.MockError
 	}
@@ -129,18 +129,18 @@ func (m *MockDB) CreateExternalAccountKey(ctx context.Context, name string) (*Ex
 }
 
 // GetExternalAccountKey mock
-func (m *MockDB) GetExternalAccountKey(ctx context.Context, keyID string) (*ExternalAccountKey, error) {
+func (m *MockDB) GetExternalAccountKey(ctx context.Context, provisionerName string, keyID string) (*ExternalAccountKey, error) {
 	if m.MockGetExternalAccountKey != nil {
-		return m.MockGetExternalAccountKey(ctx, keyID)
+		return m.MockGetExternalAccountKey(ctx, provisionerName, keyID)
 	} else if m.MockError != nil {
 		return nil, m.MockError
 	}
 	return m.MockRet1.(*ExternalAccountKey), m.MockError
 }
 
-func (m *MockDB) UpdateExternalAccountKey(ctx context.Context, eak *ExternalAccountKey) error {
+func (m *MockDB) UpdateExternalAccountKey(ctx context.Context, provisionerName string, eak *ExternalAccountKey) error {
 	if m.MockUpdateExternalAccountKey != nil {
-		return m.MockUpdateExternalAccountKey(ctx, eak)
+		return m.MockUpdateExternalAccountKey(ctx, provisionerName, eak)
 	} else if m.MockError != nil {
 		return m.MockError
 	}

acme/db/nosql/account.go

@@ -29,6 +29,7 @@ func (dba *dbAccount) clone() *dbAccount {
 
 type dbExternalAccountKey struct {
 	ID              string    `json:"id"`
+	ProvisionerName string    `json:"provisioner_name"`
 	Name            string    `json:"name"`
 	AccountID       string    `json:"accountID,omitempty"`
 	KeyBytes        []byte    `json:"key"`
@@ -164,7 +165,7 @@ func (db *DB) UpdateAccount(ctx context.Context, acc *acme.Account) error {
 }
 
 // CreateExternalAccountKey creates a new External Account Binding key with a name
-func (db *DB) CreateExternalAccountKey(ctx context.Context, name string) (*acme.ExternalAccountKey, error) {
+func (db *DB) CreateExternalAccountKey(ctx context.Context, provisionerName string, name string) (*acme.ExternalAccountKey, error) {
 	keyID, err := randID()
 	if err != nil {
 		return nil, err
@@ -178,6 +179,7 @@ func (db *DB) CreateExternalAccountKey(ctx context.Context, name string) (*acme.
 
 	dbeak := &dbExternalAccountKey{
 		ID:              keyID,
+		ProvisionerName: provisionerName,
 		Name:            name,
 		KeyBytes:        random,
 		CreatedAt:       clock.Now(),
@@ -188,6 +190,7 @@ func (db *DB) CreateExternalAccountKey(ctx context.Context, name string) (*acme.
 	}
 	return &acme.ExternalAccountKey{
 		ID:              dbeak.ID,
+		ProvisionerName: dbeak.ProvisionerName,
 		Name:            dbeak.Name,
 		AccountID:       dbeak.AccountID,
 		KeyBytes:        dbeak.KeyBytes,
@@ -197,14 +200,19 @@ func (db *DB) CreateExternalAccountKey(ctx context.Context, name string) (*acme.
 }
 
 // GetExternalAccountKey retrieves an External Account Binding key by KeyID
-func (db *DB) GetExternalAccountKey(ctx context.Context, keyID string) (*acme.ExternalAccountKey, error) {
+func (db *DB) GetExternalAccountKey(ctx context.Context, provisionerName string, keyID string) (*acme.ExternalAccountKey, error) {
 	dbeak, err := db.getDBExternalAccountKey(ctx, keyID)
 	if err != nil {
 		return nil, err
 	}
 
+	if dbeak.ProvisionerName != provisionerName {
+		return nil, acme.NewError(acme.ErrorUnauthorizedType, "name of provisioner does not match provisioner for which the EAB key was created")
+	}
+
 	return &acme.ExternalAccountKey{
 		ID:              dbeak.ID,
+		ProvisionerName: dbeak.ProvisionerName,
 		Name:            dbeak.Name,
 		AccountID:       dbeak.AccountID,
 		KeyBytes:        dbeak.KeyBytes,
@@ -213,14 +221,19 @@ func (db *DB) GetExternalAccountKey(ctx context.Context, keyID string) (*acme.Ex
 	}, nil
 }
 
-func (db *DB) UpdateExternalAccountKey(ctx context.Context, eak *acme.ExternalAccountKey) error {
+func (db *DB) UpdateExternalAccountKey(ctx context.Context, provisionerName string, eak *acme.ExternalAccountKey) error {
 	old, err := db.getDBExternalAccountKey(ctx, eak.ID)
 	if err != nil {
 		return err
 	}
 
+	if old.ProvisionerName != provisionerName {
+		return acme.NewError(acme.ErrorUnauthorizedType, "name of provisioner does not match provisioner for which the EAB key was created")
+	}
+
 	nu := dbExternalAccountKey{
 		ID:              eak.ID,
+		ProvisionerName: eak.ProvisionerName,
 		Name:            eak.Name,
 		AccountID:       eak.AccountID,
 		KeyBytes:        eak.KeyBytes,

authority/admin/api/acme.go

@@ -9,11 +9,13 @@ import (
 
 // CreateExternalAccountKeyRequest is the type for POST /admin/acme/eab requests
 type CreateExternalAccountKeyRequest struct {
+	ProvisionerName string `json:"provisioner"`
 	Name            string `json:"name"`
 }
 
 // CreateExternalAccountKeyResponse is the type for POST /admin/acme/eab responses
 type CreateExternalAccountKeyResponse struct {
+	ProvisionerName string `json:"provisioner"`
 	KeyID           string `json:"keyID"`
 	Name            string `json:"name"`
 	Key             []byte `json:"key"`
@@ -35,13 +37,14 @@ func (h *Handler) CreateExternalAccountKey(w http.ResponseWriter, r *http.Reques
 
 	// TODO: Validate input
 
-	eak, err := h.acmeDB.CreateExternalAccountKey(r.Context(), body.Name)
+	eak, err := h.acmeDB.CreateExternalAccountKey(r.Context(), body.ProvisionerName, body.Name)
 	if err != nil {
 		api.WriteError(w, admin.WrapErrorISE(err, "error creating external account key %s", body.Name))
 		return
 	}
 
 	eakResponse := CreateExternalAccountKeyResponse{
+		ProvisionerName: eak.ProvisionerName,
 		KeyID:           eak.ID,
 		Name:            eak.Name,
 		Key:             eak.KeyBytes,