Migrating remote provisioning service functionality
The initial implementation of the IRemotelyProvisionedComponent HAL had
everything being done in the userspace portion of the process, including
the sensitive crypto. This change ports that functionality to
system/keymaster. This includes changes to the following components to
work in this module to AndroidKeymaster:
-Additions to keymaster_messages to support the two new methods:
GenerateCsr and GenerateRkpKey.
-The creation of a new RemoteProvisioningContext class to abstract away
the implementation specific details from AndroidKeymaster.
-A handful of added utility functions/files.
Test: atest VtsHalRemotelyProvisionedComponentTargetTest
Change-Id: Ic901cea79e075a170635cb3697c065fbbd020417
diff --git a/cppcose/cppcose.cpp b/cppcose/cppcose.cpp
new file mode 100644
index 0000000..a40b440
--- /dev/null
+++ b/cppcose/cppcose.cpp
@@ -0,0 +1,446 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <keymaster/cppcose/cppcose.h>
+
+#include <iostream>
+#include <stdio.h>
+
+#include <cppbor.h>
+#include <cppbor_parse.h>
+
+#include <openssl/err.h>
+
+namespace cppcose {
+
+namespace {
+
+ErrMsgOr<bssl::UniquePtr<EVP_CIPHER_CTX>> aesGcmInitAndProcessAad(const bytevec& key,
+ const bytevec& nonce,
+ const bytevec& aad,
+ bool encrypt) {
+ if (key.size() != kAesGcmKeySize) return "Invalid key size";
+
+ bssl::UniquePtr<EVP_CIPHER_CTX> ctx(EVP_CIPHER_CTX_new());
+ if (!ctx) return "Failed to allocate cipher context";
+
+ if (!EVP_CipherInit_ex(ctx.get(), EVP_aes_256_gcm(), nullptr /* engine */, key.data(),
+ nonce.data(), encrypt ? 1 : 0)) {
+ return "Failed to initialize cipher";
+ }
+
+ int outlen;
+ if (!aad.empty() && !EVP_CipherUpdate(ctx.get(), nullptr /* out; null means AAD */, &outlen,
+ aad.data(), aad.size())) {
+ return "Failed to process AAD";
+ }
+
+ return std::move(ctx);
+}
+
+} // namespace
+
+ErrMsgOr<bytevec> generateCoseMac0Mac(const bytevec& macKey, const bytevec& externalAad,
+ const bytevec& payload) {
+ auto macStructure = cppbor::Array()
+ .add("MAC0")
+ .add(cppbor::Map().add(ALGORITHM, HMAC_256).canonicalize().encode())
+ .add(externalAad)
+ .add(payload)
+ .encode();
+
+ bytevec macTag(SHA256_DIGEST_LENGTH);
+ uint8_t* out = macTag.data();
+ unsigned int outLen;
+ out = HMAC(EVP_sha256(), //
+ macKey.data(), macKey.size(), //
+ macStructure.data(), macStructure.size(), //
+ out, &outLen);
+
+ assert(out != nullptr && outLen == macTag.size());
+ if (out == nullptr || outLen != macTag.size()) {
+ return "Error computing public key MAC";
+ }
+
+ return macTag;
+}
+
+ErrMsgOr<cppbor::Array> constructCoseMac0(const bytevec& macKey, const bytevec& externalAad,
+ const bytevec& payload) {
+ auto tag = generateCoseMac0Mac(macKey, externalAad, payload);
+ if (!tag) return tag.moveMessage();
+
+ return cppbor::Array()
+ .add(cppbor::Map().add(ALGORITHM, HMAC_256).canonicalize().encode())
+ .add(cppbor::Map() /* unprotected */)
+ .add(payload)
+ .add(tag.moveValue());
+}
+
+ErrMsgOr<bytevec /* payload */> verifyAndParseCoseMac0(const cppbor::Item* macItem,
+ const bytevec& macKey) {
+ auto mac = macItem ? macItem->asArray() : nullptr;
+ if (!mac || mac->size() != kCoseMac0EntryCount) {
+ return "Invalid COSE_Mac0";
+ }
+
+ auto protectedParms = mac->get(kCoseMac0ProtectedParams)->asBstr();
+ auto unprotectedParms = mac->get(kCoseMac0UnprotectedParams)->asMap();
+ auto payload = mac->get(kCoseMac0Payload)->asBstr();
+ auto tag = mac->get(kCoseMac0Tag)->asBstr();
+ if (!protectedParms || !unprotectedParms || !payload || !tag) {
+ return "Invalid COSE_Mac0 contents";
+ }
+
+ auto [protectedMap, _, errMsg] = cppbor::parse(protectedParms);
+ if (!protectedMap || !protectedMap->asMap()) {
+ return "Invalid Mac0 protected: " + errMsg;
+ }
+ auto& algo = protectedMap->asMap()->get(ALGORITHM);
+ if (!algo || !algo->asInt() || algo->asInt()->value() != HMAC_256) {
+ return "Unsupported Mac0 algorithm";
+ }
+
+ auto macTag = generateCoseMac0Mac(macKey, {} /* external_aad */, payload->value());
+ if (!macTag) return macTag.moveMessage();
+
+ if (macTag->size() != tag->value().size() ||
+ CRYPTO_memcmp(macTag->data(), tag->value().data(), macTag->size()) != 0) {
+ return "MAC tag mismatch";
+ }
+
+ return payload->value();
+}
+
+ErrMsgOr<bytevec> createCoseSign1Signature(const bytevec& key, const bytevec& protectedParams,
+ const bytevec& payload, const bytevec& aad) {
+ bytevec signatureInput = cppbor::Array()
+ .add("Signature1") //
+ .add(protectedParams)
+ .add(aad)
+ .add(payload)
+ .encode();
+
+ if (key.size() != ED25519_PRIVATE_KEY_LEN) return "Invalid signing key";
+ bytevec signature(ED25519_SIGNATURE_LEN);
+ if (!ED25519_sign(signature.data(), signatureInput.data(), signatureInput.size(), key.data())) {
+ return "Signing failed";
+ }
+
+ return signature;
+}
+
+ErrMsgOr<cppbor::Array> constructCoseSign1(const bytevec& key, cppbor::Map protectedParams,
+ const bytevec& payload, const bytevec& aad) {
+ bytevec protParms = protectedParams.add(ALGORITHM, EDDSA).canonicalize().encode();
+ auto signature = createCoseSign1Signature(key, protParms, payload, aad);
+ if (!signature) return signature.moveMessage();
+
+ return cppbor::Array()
+ .add(std::move(protParms))
+ .add(cppbor::Map() /* unprotected parameters */)
+ .add(std::move(payload))
+ .add(std::move(*signature));
+}
+
+ErrMsgOr<cppbor::Array> constructCoseSign1(const bytevec& key, const bytevec& payload,
+ const bytevec& aad) {
+ return constructCoseSign1(key, {} /* protectedParams */, payload, aad);
+}
+
+ErrMsgOr<bytevec> verifyAndParseCoseSign1(bool ignoreSignature, const cppbor::Array* coseSign1,
+ const bytevec& signingCoseKey, const bytevec& aad) {
+ if (!coseSign1 || coseSign1->size() != kCoseSign1EntryCount) {
+ return "Invalid COSE_Sign1";
+ }
+
+ const cppbor::Bstr* protectedParams = coseSign1->get(kCoseSign1ProtectedParams)->asBstr();
+ const cppbor::Map* unprotectedParams = coseSign1->get(kCoseSign1UnprotectedParams)->asMap();
+ const cppbor::Bstr* payload = coseSign1->get(kCoseSign1Payload)->asBstr();
+ const cppbor::Bstr* signature = coseSign1->get(kCoseSign1Signature)->asBstr();
+
+ if (!protectedParams || !unprotectedParams || !payload || !signature) {
+ return "Invalid COSE_Sign1";
+ }
+
+ auto [parsedProtParams, _, errMsg] = cppbor::parse(protectedParams);
+ if (!parsedProtParams) {
+ return errMsg + " when parsing protected params.";
+ }
+ if (!parsedProtParams->asMap()) {
+ return "Protected params must be a map";
+ }
+
+ auto& algorithm = parsedProtParams->asMap()->get(ALGORITHM);
+ if (!algorithm || !algorithm->asInt() || algorithm->asInt()->value() != EDDSA) {
+ return "Unsupported signature algorithm";
+ }
+
+ if (!ignoreSignature) {
+ bool selfSigned = signingCoseKey.empty();
+ auto key = CoseKey::parseEd25519(selfSigned ? payload->value() : signingCoseKey);
+ if (!key) return "Bad signing key: " + key.moveMessage();
+
+ bytevec signatureInput =
+ cppbor::Array().add("Signature1").add(*protectedParams).add(aad).add(*payload).encode();
+
+ if (!ED25519_verify(signatureInput.data(), signatureInput.size(), signature->value().data(),
+ key->getBstrValue(CoseKey::PUBKEY_X)->data())) {
+ return "Signature verification failed";
+ }
+ }
+
+ return payload->value();
+}
+
+ErrMsgOr<bytevec> createCoseEncryptCiphertext(const bytevec& key, const bytevec& nonce,
+ const bytevec& protectedParams,
+ const bytevec& plaintextPayload, const bytevec& aad) {
+ auto ciphertext = aesGcmEncrypt(key, nonce,
+ cppbor::Array() // Enc strucure as AAD
+ .add("Encrypt") // Context
+ .add(protectedParams) // Protected
+ .add(aad) // External AAD
+ .encode(),
+ plaintextPayload);
+
+ if (!ciphertext) return ciphertext.moveMessage();
+ return ciphertext.moveValue();
+}
+
+ErrMsgOr<cppbor::Array> constructCoseEncrypt(const bytevec& key, const bytevec& nonce,
+ const bytevec& plaintextPayload, const bytevec& aad,
+ cppbor::Array recipients) {
+ auto encryptProtectedHeader = cppbor::Map() //
+ .add(ALGORITHM, AES_GCM_256)
+ .canonicalize()
+ .encode();
+
+ auto ciphertext =
+ createCoseEncryptCiphertext(key, nonce, encryptProtectedHeader, plaintextPayload, aad);
+ if (!ciphertext) return ciphertext.moveMessage();
+
+ return cppbor::Array()
+ .add(encryptProtectedHeader) // Protected
+ .add(cppbor::Map().add(IV, nonce).canonicalize()) // Unprotected
+ .add(*ciphertext) // Payload
+ .add(std::move(recipients));
+}
+
+ErrMsgOr<std::pair<bytevec /* pubkey */, bytevec /* key ID */>>
+getSenderPubKeyFromCoseEncrypt(const cppbor::Item* coseEncrypt) {
+ if (!coseEncrypt || !coseEncrypt->asArray() ||
+ coseEncrypt->asArray()->size() != kCoseEncryptEntryCount) {
+ return "Invalid COSE_Encrypt";
+ }
+
+ auto& recipients = coseEncrypt->asArray()->get(kCoseEncryptRecipients);
+ if (!recipients || !recipients->asArray() || recipients->asArray()->size() != 1) {
+ return "Invalid recipients list";
+ }
+
+ auto& recipient = recipients->asArray()->get(0);
+ if (!recipient || !recipient->asArray() || recipient->asArray()->size() != 3) {
+ return "Invalid COSE_recipient";
+ }
+
+ auto& ciphertext = recipient->asArray()->get(2);
+ if (!ciphertext->asSimple() || !ciphertext->asSimple()->asNull()) {
+ return "Unexpected value in recipients ciphertext field " +
+ cppbor::prettyPrint(ciphertext.get());
+ }
+
+ auto& protParms = recipient->asArray()->get(0);
+ if (!protParms || !protParms->asBstr()) return "Invalid protected params";
+ auto [parsedProtParms, _, errMsg] = cppbor::parse(protParms->asBstr());
+ if (!parsedProtParms) return "Failed to parse protected params: " + errMsg;
+ if (!parsedProtParms->asMap()) return "Invalid protected params";
+
+ auto& algorithm = parsedProtParms->asMap()->get(ALGORITHM);
+ if (!algorithm || !algorithm->asInt() || algorithm->asInt()->value() != ECDH_ES_HKDF_256) {
+ return "Invalid algorithm";
+ }
+
+ auto& unprotParms = recipient->asArray()->get(1);
+ if (!unprotParms || !unprotParms->asMap()) return "Invalid unprotected params";
+
+ auto& senderCoseKey = unprotParms->asMap()->get(COSE_KEY);
+ if (!senderCoseKey || !senderCoseKey->asMap()) return "Invalid sender COSE_Key";
+
+ auto& keyType = senderCoseKey->asMap()->get(CoseKey::KEY_TYPE);
+ if (!keyType || !keyType->asInt() || keyType->asInt()->value() != OCTET_KEY_PAIR) {
+ return "Invalid key type";
+ }
+
+ auto& curve = senderCoseKey->asMap()->get(CoseKey::CURVE);
+ if (!curve || !curve->asInt() || curve->asInt()->value() != X25519) {
+ return "Unsupported curve";
+ }
+
+ auto& pubkey = senderCoseKey->asMap()->get(CoseKey::PUBKEY_X);
+ if (!pubkey || !pubkey->asBstr() ||
+ pubkey->asBstr()->value().size() != X25519_PUBLIC_VALUE_LEN) {
+ return "Invalid X25519 public key";
+ }
+
+ auto& key_id = unprotParms->asMap()->get(KEY_ID);
+ if (key_id && key_id->asBstr()) {
+ return std::make_pair(pubkey->asBstr()->value(), key_id->asBstr()->value());
+ }
+
+ // If no key ID, just return an empty vector.
+ return std::make_pair(pubkey->asBstr()->value(), bytevec{});
+}
+
+ErrMsgOr<bytevec> decryptCoseEncrypt(const bytevec& key, const cppbor::Item* coseEncrypt,
+ const bytevec& external_aad) {
+ if (!coseEncrypt || !coseEncrypt->asArray() ||
+ coseEncrypt->asArray()->size() != kCoseEncryptEntryCount) {
+ return "Invalid COSE_Encrypt";
+ }
+
+ auto& protParms = coseEncrypt->asArray()->get(kCoseEncryptProtectedParams);
+ auto& unprotParms = coseEncrypt->asArray()->get(kCoseEncryptUnprotectedParams);
+ auto& ciphertext = coseEncrypt->asArray()->get(kCoseEncryptPayload);
+ auto& recipients = coseEncrypt->asArray()->get(kCoseEncryptRecipients);
+
+ if (!protParms || !protParms->asBstr() || !unprotParms || !ciphertext || !recipients) {
+ return "Invalid COSE_Encrypt";
+ }
+
+ auto [parsedProtParams, _, errMsg] = cppbor::parse(protParms->asBstr()->value());
+ if (!parsedProtParams) {
+ return errMsg + " when parsing protected params.";
+ }
+ if (!parsedProtParams->asMap()) {
+ return "Protected params must be a map";
+ }
+
+ auto& algorithm = parsedProtParams->asMap()->get(ALGORITHM);
+ if (!algorithm || !algorithm->asInt() || algorithm->asInt()->value() != AES_GCM_256) {
+ return "Unsupported encryption algorithm";
+ }
+
+ if (!unprotParms->asMap() || unprotParms->asMap()->size() != 1) {
+ return "Invalid unprotected params";
+ }
+
+ auto& nonce = unprotParms->asMap()->get(IV);
+ if (!nonce || !nonce->asBstr() || nonce->asBstr()->value().size() != kAesGcmNonceLength) {
+ return "Invalid nonce";
+ }
+
+ if (!ciphertext->asBstr()) return "Invalid ciphertext";
+
+ auto aad = cppbor::Array() // Enc strucure as AAD
+ .add("Encrypt") // Context
+ .add(protParms->asBstr()->value()) // Protected
+ .add(external_aad) // External AAD
+ .encode();
+
+ return aesGcmDecrypt(key, nonce->asBstr()->value(), aad, ciphertext->asBstr()->value());
+}
+
+ErrMsgOr<bytevec> x25519_HKDF_DeriveKey(const bytevec& pubKeyA, const bytevec& privKeyA,
+ const bytevec& pubKeyB, bool senderIsA) {
+ bytevec rawSharedKey(X25519_SHARED_KEY_LEN);
+ if (!::X25519(rawSharedKey.data(), privKeyA.data(), pubKeyB.data())) {
+ return "ECDH operation failed";
+ }
+
+ bytevec kdfContext = cppbor::Array()
+ .add(AES_GCM_256)
+ .add(cppbor::Array() // Sender Info
+ .add(cppbor::Bstr("client"))
+ .add(bytevec{} /* nonce */)
+ .add(senderIsA ? pubKeyA : pubKeyB))
+ .add(cppbor::Array() // Recipient Info
+ .add(cppbor::Bstr("server"))
+ .add(bytevec{} /* nonce */)
+ .add(senderIsA ? pubKeyB : pubKeyA))
+ .add(cppbor::Array() // SuppPubInfo
+ .add(kAesGcmKeySizeBits) // output key length
+ .add(bytevec{})) // protected
+ .encode();
+
+ bytevec retval(SHA256_DIGEST_LENGTH);
+ bytevec salt{};
+ if (!HKDF(retval.data(), retval.size(), //
+ EVP_sha256(), //
+ rawSharedKey.data(), rawSharedKey.size(), //
+ salt.data(), salt.size(), //
+ kdfContext.data(), kdfContext.size())) {
+ return "ECDH HKDF failed";
+ }
+
+ return retval;
+}
+
+ErrMsgOr<bytevec> aesGcmEncrypt(const bytevec& key, const bytevec& nonce, const bytevec& aad,
+ const bytevec& plaintext) {
+ auto ctx = aesGcmInitAndProcessAad(key, nonce, aad, true /* encrypt */);
+ if (!ctx) return ctx.moveMessage();
+
+ bytevec ciphertext(plaintext.size() + kAesGcmTagSize);
+ int outlen;
+ if (!EVP_CipherUpdate(ctx->get(), ciphertext.data(), &outlen, plaintext.data(),
+ plaintext.size())) {
+ return "Failed to encrypt plaintext";
+ }
+ assert(plaintext.size() == outlen);
+
+ if (!EVP_CipherFinal_ex(ctx->get(), ciphertext.data() + outlen, &outlen)) {
+ return "Failed to finalize encryption";
+ }
+ assert(outlen == 0);
+
+ if (!EVP_CIPHER_CTX_ctrl(ctx->get(), EVP_CTRL_GCM_GET_TAG, kAesGcmTagSize,
+ ciphertext.data() + plaintext.size())) {
+ return "Failed to retrieve tag";
+ }
+
+ return ciphertext;
+}
+
+ErrMsgOr<bytevec> aesGcmDecrypt(const bytevec& key, const bytevec& nonce, const bytevec& aad,
+ const bytevec& ciphertextWithTag) {
+ auto ctx = aesGcmInitAndProcessAad(key, nonce, aad, false /* encrypt */);
+ if (!ctx) return ctx.moveMessage();
+
+ if (ciphertextWithTag.size() < kAesGcmTagSize) return "Missing tag";
+
+ bytevec plaintext(ciphertextWithTag.size() - kAesGcmTagSize);
+ int outlen;
+ if (!EVP_CipherUpdate(ctx->get(), plaintext.data(), &outlen, ciphertextWithTag.data(),
+ ciphertextWithTag.size() - kAesGcmTagSize)) {
+ return "Failed to decrypt plaintext";
+ }
+ assert(plaintext.size() == outlen);
+
+ bytevec tag(ciphertextWithTag.end() - kAesGcmTagSize, ciphertextWithTag.end());
+ if (!EVP_CIPHER_CTX_ctrl(ctx->get(), EVP_CTRL_GCM_SET_TAG, kAesGcmTagSize, tag.data())) {
+ return "Failed to set tag: " + std::to_string(ERR_peek_last_error());
+ }
+
+ if (!EVP_CipherFinal_ex(ctx->get(), nullptr, &outlen)) {
+ return "Failed to finalize encryption";
+ }
+ assert(outlen == 0);
+
+ return plaintext;
+}
+
+} // namespace cppcose