Added ES256 sig algo to ACMEv2

Author: jcoffland

src/cbang/acmev2/Account.cpp

@@ -127,7 +127,7 @@ void Account::update() {
   if (state != STATE_IDLE || !certsReadyForRenewal()) return;
 
   if (directory.isNull()) state = STATE_GET_DIR;
-  else if (kid.empty()) state = STATE_REGISTER;
+  else if (kid.empty())   state = STATE_REGISTER;
   else {
     currentKeyCert = 0;
     state = STATE_NEW_ORDER;
@@ -171,7 +171,8 @@ string Account::getURL(const string &url) const {
 
 
 string Account::getThumbprint() const {
-  return URLBase64().encode(Digest::hash(getJWK()->toString(), "sha256"));
+  string jwk = getJWK()->toString(0, true); // No indent, compact
+  return URLBase64().encode(Digest::hash(jwk, "sha256"));
 }
 
 
@@ -183,24 +184,30 @@ string Account::getKeyAuthorization() const {
 JSON::ValuePtr Account::getJWK() const {
   auto d = SmartPtr(new JSON::Dict);
 
+  // Insert order matters (lexicographical by key)
   if (key.isRSA()) {
-    // Insert order matters
     d->insert("e", URLBase64().encode(key.getRSA_E().toBinString()));
     d->insert("kty", "RSA");
     d->insert("n", URLBase64().encode(key.getRSA_N().toBinString()));
 
+  } else if (key.isEC()) {
+    d->insert("crv", "P-256");
+    d->insert("kty", "EC");
+    d->insert("x", URLBase64().encode(key.getEC_X().toBinString()));
+    d->insert("y", URLBase64().encode(key.getEC_Y().toBinString()));
+
   } else THROW("Unsupported key type");
 
   return d;
 }
 
 
 string Account::getProtected(const URI &uri) const {
-  // TODO Implement ES256 (RFC7518 Section 3.1) and EdDSA var. Ed25519 (RFC8037)
-  // signature algorithms.  See IETF ACME draft "Request Authentication".
-
+  // See IETF ACME draft "Request Authentication".
   auto d = SmartPtr(new JSON::Dict);
-  d->insert("alg", "RS256");
+
+  if      (key.isRSA()) d->insert("alg", "RS256");
+  else if (key.isEC())  d->insert("alg", "ES256");
 
   if (!kid.empty()) d->insert("kid", kid);
   else d->insert("jwk", getJWK());
@@ -215,14 +222,17 @@ string Account::getProtected(const URI &uri) const {
 
 string Account::getSignedRequest(const URI &uri, const string &payload) const {
   string protected64 = URLBase64().encode(getProtected(uri));
-  string payload64 = URLBase64().encode(payload);
-  string signed64 =
-    URLBase64().encode(key.signSHA256(protected64 + "." + payload64));
+  string payload64   = URLBase64().encode(payload);
+  string hash        = Digest::hash(protected64 + "." + payload64, "sha256");
+
+  string sig;
+  if      (key.isRSA()) sig = key.sign(hash);
+  else if (key.isEC())  sig = key.signECP1363(hash);
 
   auto d = SmartPtr(new JSON::Dict);
   d->insert("protected", protected64);
-  d->insert("payload", payload64);
-  d->insert("signature", signed64);
+  d->insert("payload",   payload64);
+  d->insert("signature", URLBase64().encode(sig));
   return d->toString();
 }
 

src/cbang/openssl/KeyPair.cpp

@@ -166,6 +166,18 @@ BigNum KeyPair::getRSA_N() const {
 }
 
 
+BigNum KeyPair::getEC_X() const {
+  if (!isEC()) THROW("Not an EC key");
+  return getParam(OSSL_PKEY_PARAM_EC_PUB_X);
+}
+
+
+BigNum KeyPair::getEC_Y() const {
+  if (!isEC()) THROW("Not an EC key");
+  return getParam(OSSL_PKEY_PARAM_EC_PUB_Y);
+}
+
+
 unsigned KeyPair::size() const {return EVP_PKEY_size(key);}
 
 
@@ -393,6 +405,26 @@ string KeyPair::signBase64SHA256(const string &data) const {
 }
 
 
+string KeyPair::signECP1363(const string &data) const {
+  string sder = sign(data);
+
+  unsigned char raw_rs[64]; // This will be our P1363 output
+  auto p   = (const unsigned char *)sder.c_str();
+  auto sig = d2i_ECDSA_SIG(0, &p, sder.length());
+
+  const BIGNUM *r, *s;
+  ECDSA_SIG_get0(sig, &r, &s);
+
+  // BN_bn2binpad ensures exactly 32 bytes with leading zeros
+  BN_bn2binpad(r, raw_rs, 32);      // Fill first 32 bytes
+  BN_bn2binpad(s, raw_rs + 32, 32); // Fill last 32 bytes
+
+  ECDSA_SIG_free(sig);
+
+  return string((char *)raw_rs, 64);
+}
+
+
 void KeyPair::verify(const string &signature, const string &data) const {
   KeyContext ctx(*this);
   ctx.verifyInit();

src/cbang/openssl/KeyPair.h

@@ -76,6 +76,8 @@ namespace cb {
     BigNum getParam(const char *id) const;
     BigNum getRSA_E() const;
     BigNum getRSA_N() const;
+    BigNum getEC_X() const;
+    BigNum getEC_Y() const;
 
     unsigned size() const; ///< In bytes
 
@@ -124,6 +126,7 @@ namespace cb {
     std::string sign(const std::string &data) const;
     std::string signSHA256(const std::string &data) const;
     std::string signBase64SHA256(const std::string &data) const;
+    std::string signECP1363(const std::string &data) const;
     void verify(const std::string &signature, const std::string &data) const;
     void verifyBase64SHA256(const std::string &sig64,
                             const std::string &data) const;