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acme_jws.go
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acme_jws.go
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// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package pki
import (
"bytes"
"crypto"
"encoding/base64"
"encoding/json"
"fmt"
"strings"
"github.com/go-jose/go-jose/v3"
)
var AllowedOuterJWSTypes = map[string]interface{}{
"RS256": true,
"RS384": true,
"RS512": true,
"PS256": true,
"PS384": true,
"PS512": true,
"ES256": true,
"ES384": true,
"ES512": true,
"EdDSA2": true,
}
var AllowedEabJWSTypes = map[string]interface{}{
"HS256": true,
"HS384": true,
"HS512": true,
}
// This wraps a JWS message structure.
type jwsCtx struct {
Algo string `json:"alg"`
Kid string `json:"kid"`
Jwk json.RawMessage `json:"jwk"`
Nonce string `json:"nonce"`
Url string `json:"url"`
Key jose.JSONWebKey `json:"-"`
Existing bool `json:"-"`
}
func (c *jwsCtx) GetKeyThumbprint() (string, error) {
keyThumbprint, err := c.Key.Thumbprint(crypto.SHA256)
if err != nil {
return "", fmt.Errorf("failed creating thumbprint: %w", err)
}
return base64.RawURLEncoding.EncodeToString(keyThumbprint), nil
}
func UnmarshalEabJwsJson(eabBytes []byte) (*jwsCtx, error) {
var eabJws jwsCtx
var err error
if err = json.Unmarshal(eabBytes, &eabJws); err != nil {
return nil, err
}
if eabJws.Kid == "" {
return nil, fmt.Errorf("invalid header: got missing required field 'kid': %w", ErrMalformed)
}
if _, present := AllowedEabJWSTypes[eabJws.Algo]; !present {
return nil, fmt.Errorf("invalid header: unexpected value for 'algo': %w", ErrMalformed)
}
return &eabJws, nil
}
func (c *jwsCtx) UnmarshalOuterJwsJson(a *acmeState, ac *acmeContext, jws []byte) error {
var err error
if err = json.Unmarshal(jws, c); err != nil {
return err
}
if c.Kid != "" && len(c.Jwk) > 0 {
// See RFC 8555 Section 6.2. Request Authentication:
//
// > The "jwk" and "kid" fields are mutually exclusive. Servers MUST
// > reject requests that contain both.
return fmt.Errorf("invalid header: got both account 'kid' and 'jwk' in the same message; expected only one: %w", ErrMalformed)
}
if c.Kid == "" && len(c.Jwk) == 0 {
// See RFC 8555 Section 6.2. Request Authentication:
//
// > Either "jwk" (JSON Web Key) or "kid" (Key ID) as specified
// > below
return fmt.Errorf("invalid header: got neither required fields of 'kid' nor 'jwk': %w", ErrMalformed)
}
if _, present := AllowedOuterJWSTypes[c.Algo]; !present {
// See RFC 8555 Section 6.2. Request Authentication:
//
// > The JWS Protected Header MUST include the following fields:
// >
// > - "alg" (Algorithm)
// >
// > * This field MUST NOT contain "none" or a Message
// > Authentication Code (MAC) algorithm (e.g. one in which the
// > algorithm registry description mentions MAC/HMAC).
return fmt.Errorf("invalid header: unexpected value for 'algo': %w", ErrMalformed)
}
if c.Kid != "" {
// Load KID from storage first.
kid := getKeyIdFromAccountUrl(c.Kid)
c.Jwk, err = a.LoadJWK(ac, kid)
if err != nil {
return err
}
c.Kid = kid // Use the uuid itself, not the full account url that was originally provided to us.
c.Existing = true
}
if err = c.Key.UnmarshalJSON(c.Jwk); err != nil {
return err
}
if !c.Key.Valid() {
return fmt.Errorf("received invalid jwk: %w", ErrMalformed)
}
if c.Kid == "" {
c.Kid = genUuid()
c.Existing = false
}
return nil
}
func getKeyIdFromAccountUrl(accountUrl string) string {
pieces := strings.Split(accountUrl, "/")
return pieces[len(pieces)-1]
}
func hasValues(h jose.Header) bool {
return h.KeyID != "" || h.JSONWebKey != nil || h.Algorithm != "" || h.Nonce != "" || len(h.ExtraHeaders) > 0
}
func (c *jwsCtx) VerifyJWS(signature string) (map[string]interface{}, error) {
// See RFC 8555 Section 6.2. Request Authentication:
//
// > The JWS Unencoded Payload Option [RFC7797] MUST NOT be used
//
// This is validated by go-jose.
sig, err := jose.ParseSigned(signature)
if err != nil {
return nil, fmt.Errorf("error parsing signature: %s: %w", err, ErrMalformed)
}
if len(sig.Signatures) > 1 {
// See RFC 8555 Section 6.2. Request Authentication:
//
// > The JWS MUST NOT have multiple signatures
return nil, fmt.Errorf("request had multiple signatures: %w", ErrMalformed)
}
if hasValues(sig.Signatures[0].Unprotected) {
// See RFC 8555 Section 6.2. Request Authentication:
//
// > The JWS Unprotected Header [RFC7515] MUST NOT be used
return nil, fmt.Errorf("request had unprotected headers: %w", ErrMalformed)
}
payload, err := sig.Verify(c.Key)
if err != nil {
return nil, err
}
if len(payload) == 0 {
// Distinguish POST-AS-GET from POST-with-an-empty-body.
return nil, nil
}
var m map[string]interface{}
if err := json.Unmarshal(payload, &m); err != nil {
return nil, fmt.Errorf("failed to json unmarshal 'payload': %s: %w", err, ErrMalformed)
}
return m, nil
}
func verifyEabPayload(acmeState *acmeState, ac *acmeContext, outer *jwsCtx, expectedPath string, payload map[string]interface{}) (*eabType, error) {
// Parse the key out.
rawProtectedBase64, ok := payload["protected"]
if !ok {
return nil, fmt.Errorf("missing required field 'protected': %w", ErrMalformed)
}
jwkBase64 := rawProtectedBase64.(string)
jwkBytes, err := base64.RawURLEncoding.DecodeString(jwkBase64)
if err != nil {
return nil, fmt.Errorf("failed to base64 parse eab 'protected': %s: %w", err, ErrMalformed)
}
eabJws, err := UnmarshalEabJwsJson(jwkBytes)
if err != nil {
return nil, fmt.Errorf("failed to json unmarshal eab 'protected': %w", err)
}
if len(eabJws.Url) == 0 {
return nil, fmt.Errorf("missing required parameter 'url' in eab 'protected': %w", ErrMalformed)
}
expectedUrl := ac.clusterUrl.JoinPath(expectedPath).String()
if expectedUrl != eabJws.Url {
return nil, fmt.Errorf("invalid value for 'url' in eab 'protected': got '%v' expected '%v': %w", eabJws.Url, expectedUrl, ErrUnauthorized)
}
if len(eabJws.Nonce) != 0 {
return nil, fmt.Errorf("nonce should not be provided in eab 'protected': %w", ErrMalformed)
}
rawPayloadBase64, ok := payload["payload"]
if !ok {
return nil, fmt.Errorf("missing required field eab 'payload': %w", ErrMalformed)
}
payloadBase64, ok := rawPayloadBase64.(string)
if !ok {
return nil, fmt.Errorf("failed to parse 'payload' field: %w", ErrMalformed)
}
rawSignatureBase64, ok := payload["signature"]
if !ok {
return nil, fmt.Errorf("missing required field 'signature': %w", ErrMalformed)
}
signatureBase64, ok := rawSignatureBase64.(string)
if !ok {
return nil, fmt.Errorf("failed to parse 'signature' field: %w", ErrMalformed)
}
// go-jose only seems to support compact signature encodings.
compactSig := fmt.Sprintf("%v.%v.%v", jwkBase64, payloadBase64, signatureBase64)
sig, err := jose.ParseSigned(compactSig)
if err != nil {
return nil, fmt.Errorf("error parsing eab signature: %s: %w", err, ErrMalformed)
}
if len(sig.Signatures) > 1 {
// See RFC 8555 Section 6.2. Request Authentication:
//
// > The JWS MUST NOT have multiple signatures
return nil, fmt.Errorf("eab had multiple signatures: %w", ErrMalformed)
}
if hasValues(sig.Signatures[0].Unprotected) {
// See RFC 8555 Section 6.2. Request Authentication:
//
// > The JWS Unprotected Header [RFC7515] MUST NOT be used
return nil, fmt.Errorf("eab had unprotected headers: %w", ErrMalformed)
}
// Load the EAB to validate the signature against
eabEntry, err := acmeState.LoadEab(ac.sc, eabJws.Kid)
if err != nil {
return nil, fmt.Errorf("%w: failed to verify eab", ErrUnauthorized)
}
verifiedPayload, err := sig.Verify(eabEntry.PrivateBytes)
if err != nil {
return nil, err
}
// Make sure how eab payload matches the outer JWK key value
if !bytes.Equal(outer.Jwk, verifiedPayload) {
return nil, fmt.Errorf("eab payload does not match outer JWK key: %w", ErrMalformed)
}
if eabEntry.AcmeDirectory != ac.acmeDirectory {
// This EAB was not created for this specific ACME directory, reject it
return nil, fmt.Errorf("%w: failed to verify eab", ErrUnauthorized)
}
return eabEntry, nil
}