/*
* Copyright 2015 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 "keymaster0_engine.h"
#include <assert.h>
#include <string.h>
#include <memory>
#define LOG_TAG "Keymaster0Engine"
#include <cutils/log.h>
#include "keymaster/android_keymaster_utils.h"
#include <openssl/bn.h>
#include <openssl/ec_key.h>
#include <openssl/ecdsa.h>
#include "openssl_utils.h"
using std::shared_ptr;
using std::unique_ptr;
namespace keymaster {
Keymaster0Engine* Keymaster0Engine::instance_ = nullptr;
Keymaster0Engine::Keymaster0Engine(const keymaster0_device_t* keymaster0_device)
: keymaster0_device_(keymaster0_device), engine_(ENGINE_new()), supports_ec_(false) {
assert(!instance_);
instance_ = this;
rsa_index_ = RSA_get_ex_new_index(0 /* argl */, NULL /* argp */, NULL /* new_func */,
keyblob_dup, keyblob_free);
ec_key_index_ = EC_KEY_get_ex_new_index(0 /* argl */, NULL /* argp */, NULL /* new_func */,
keyblob_dup, keyblob_free);
memset(&rsa_method_, 0, sizeof(rsa_method_));
rsa_method_.common.is_static = 1;
rsa_method_.private_transform = Keymaster0Engine::rsa_private_transform;
rsa_method_.flags = RSA_FLAG_OPAQUE;
ENGINE_set_RSA_method(engine_, &rsa_method_, sizeof(rsa_method_));
if ((keymaster0_device_->flags & KEYMASTER_SUPPORTS_EC) != 0) {
supports_ec_ = true;
memset(&ecdsa_method_, 0, sizeof(ecdsa_method_));
ecdsa_method_.common.is_static = 1;
ecdsa_method_.sign = Keymaster0Engine::ecdsa_sign;
ecdsa_method_.flags = ECDSA_FLAG_OPAQUE;
ENGINE_set_ECDSA_method(engine_, &ecdsa_method_, sizeof(ecdsa_method_));
}
}
Keymaster0Engine::~Keymaster0Engine() {
if (keymaster0_device_)
keymaster0_device_->common.close(
reinterpret_cast<hw_device_t*>(const_cast<keymaster0_device_t*>(keymaster0_device_)));
ENGINE_free(engine_);
instance_ = nullptr;
}
bool Keymaster0Engine::GenerateRsaKey(uint64_t public_exponent, uint32_t public_modulus,
KeymasterKeyBlob* key_material) const {
assert(key_material);
keymaster_rsa_keygen_params_t params;
params.public_exponent = public_exponent;
params.modulus_size = public_modulus;
uint8_t* key_blob = 0;
if (keymaster0_device_->generate_keypair(keymaster0_device_, TYPE_RSA, ¶ms, &key_blob,
&key_material->key_material_size) < 0) {
ALOGE("Error generating RSA key pair with keymaster0 device");
return false;
}
unique_ptr<uint8_t, Malloc_Delete> key_blob_deleter(key_blob);
key_material->key_material = dup_buffer(key_blob, key_material->key_material_size);
return true;
}
bool Keymaster0Engine::GenerateEcKey(uint32_t key_size, KeymasterKeyBlob* key_material) const {
assert(key_material);
keymaster_ec_keygen_params_t params;
params.field_size = key_size;
uint8_t* key_blob = 0;
if (keymaster0_device_->generate_keypair(keymaster0_device_, TYPE_EC, ¶ms, &key_blob,
&key_material->key_material_size) < 0) {
ALOGE("Error generating EC key pair with keymaster0 device");
return false;
}
unique_ptr<uint8_t, Malloc_Delete> key_blob_deleter(key_blob);
key_material->key_material = dup_buffer(key_blob, key_material->key_material_size);
return true;
}
bool Keymaster0Engine::ImportKey(keymaster_key_format_t key_format,
const KeymasterKeyBlob& to_import,
KeymasterKeyBlob* imported_key) const {
assert(imported_key);
if (key_format != KM_KEY_FORMAT_PKCS8)
return false;
uint8_t* key_blob = 0;
if (keymaster0_device_->import_keypair(keymaster0_device_, to_import.key_material,
to_import.key_material_size, &key_blob,
&imported_key->key_material_size) < 0) {
ALOGW("Error importing keypair with keymaster0 device");
return false;
}
unique_ptr<uint8_t, Malloc_Delete> key_blob_deleter(key_blob);
imported_key->key_material = dup_buffer(key_blob, imported_key->key_material_size);
return true;
}
bool Keymaster0Engine::DeleteKey(const KeymasterKeyBlob& blob) const {
if (!keymaster0_device_->delete_keypair)
return true;
return (keymaster0_device_->delete_keypair(keymaster0_device_, blob.key_material,
blob.key_material_size) == 0);
}
bool Keymaster0Engine::DeleteAllKeys() const {
if (!keymaster0_device_->delete_all)
return true;
return (keymaster0_device_->delete_all(keymaster0_device_) == 0);
}
static keymaster_key_blob_t* duplicate_blob(const uint8_t* key_data, size_t key_data_size) {
unique_ptr<uint8_t[]> key_material_copy(dup_buffer(key_data, key_data_size));
if (!key_material_copy)
return nullptr;
unique_ptr<keymaster_key_blob_t> blob_copy(new (std::nothrow) keymaster_key_blob_t);
if (!blob_copy.get())
return nullptr;
blob_copy->key_material_size = key_data_size;
blob_copy->key_material = key_material_copy.release();
return blob_copy.release();
}
inline keymaster_key_blob_t* duplicate_blob(const keymaster_key_blob_t& blob) {
return duplicate_blob(blob.key_material, blob.key_material_size);
}
RSA* Keymaster0Engine::BlobToRsaKey(const KeymasterKeyBlob& blob) const {
// Create new RSA key (with engine methods) and insert blob
unique_ptr<RSA, RSA_Delete> rsa(RSA_new_method(engine_));
if (!rsa)
return nullptr;
keymaster_key_blob_t* blob_copy = duplicate_blob(blob);
if (!blob_copy->key_material || !RSA_set_ex_data(rsa.get(), rsa_index_, blob_copy))
return nullptr;
// Copy public key into new RSA key
unique_ptr<EVP_PKEY, EVP_PKEY_Delete> pkey(GetKeymaster0PublicKey(blob));
if (!pkey)
return nullptr;
unique_ptr<RSA, RSA_Delete> public_rsa(EVP_PKEY_get1_RSA(pkey.get()));
if (!public_rsa)
return nullptr;
rsa->n = BN_dup(public_rsa->n);
rsa->e = BN_dup(public_rsa->e);
if (!rsa->n || !rsa->e)
return nullptr;
return rsa.release();
}
EC_KEY* Keymaster0Engine::BlobToEcKey(const KeymasterKeyBlob& blob) const {
// Create new EC key (with engine methods) and insert blob
unique_ptr<EC_KEY, EC_KEY_Delete> ec_key(EC_KEY_new_method(engine_));
if (!ec_key)
return nullptr;
keymaster_key_blob_t* blob_copy = duplicate_blob(blob);
if (!blob_copy->key_material || !EC_KEY_set_ex_data(ec_key.get(), ec_key_index_, blob_copy))
return nullptr;
// Copy public key into new EC key
unique_ptr<EVP_PKEY, EVP_PKEY_Delete> pkey(GetKeymaster0PublicKey(blob));
if (!pkey)
return nullptr;
unique_ptr<EC_KEY, EC_KEY_Delete> public_ec_key(EVP_PKEY_get1_EC_KEY(pkey.get()));
if (!public_ec_key)
return nullptr;
if (!EC_KEY_set_group(ec_key.get(), EC_KEY_get0_group(public_ec_key.get())) ||
!EC_KEY_set_public_key(ec_key.get(), EC_KEY_get0_public_key(public_ec_key.get())))
return nullptr;
return ec_key.release();
}
const keymaster_key_blob_t* Keymaster0Engine::RsaKeyToBlob(const RSA* rsa) const {
return reinterpret_cast<keymaster_key_blob_t*>(RSA_get_ex_data(rsa, rsa_index_));
}
const keymaster_key_blob_t* Keymaster0Engine::EcKeyToBlob(const EC_KEY* ec_key) const {
return reinterpret_cast<keymaster_key_blob_t*>(EC_KEY_get_ex_data(ec_key, ec_key_index_));
}
/* static */
int Keymaster0Engine::keyblob_dup(CRYPTO_EX_DATA* /* to */, const CRYPTO_EX_DATA* /* from */,
void** from_d, int /* index */, long /* argl */,
void* /* argp */) {
keymaster_key_blob_t* blob = reinterpret_cast<keymaster_key_blob_t*>(*from_d);
if (!blob)
return 1;
*from_d = duplicate_blob(*blob);
if (*from_d)
return 1;
return 0;
}
/* static */
void Keymaster0Engine::keyblob_free(void* /* parent */, void* ptr, CRYPTO_EX_DATA* /* data */,
int /* index*/, long /* argl */, void* /* argp */) {
keymaster_key_blob_t* blob = reinterpret_cast<keymaster_key_blob_t*>(ptr);
if (blob) {
delete[] blob->key_material;
delete blob;
}
}
/* static */
int Keymaster0Engine::rsa_private_transform(RSA* rsa, uint8_t* out, const uint8_t* in, size_t len) {
ALOGV("rsa_private_transform(%p, %p, %p, %u)", rsa, out, in, (unsigned)len);
assert(instance_);
return instance_->RsaPrivateTransform(rsa, out, in, len);
}
/* static */
int Keymaster0Engine::ecdsa_sign(const uint8_t* digest, size_t digest_len, uint8_t* sig,
unsigned int* sig_len, EC_KEY* ec_key) {
ALOGV("ecdsa_sign(%p, %u, %p)", digest, (unsigned)digest_len, ec_key);
assert(instance_);
return instance_->EcdsaSign(digest, digest_len, sig, sig_len, ec_key);
}
bool Keymaster0Engine::Keymaster0Sign(const void* signing_params, const keymaster_key_blob_t& blob,
const uint8_t* data, const size_t data_length,
unique_ptr<uint8_t[], Malloc_Delete>* signature,
size_t* signature_length) const {
uint8_t* signed_data;
int err = keymaster0_device_->sign_data(keymaster0_device_, signing_params, blob.key_material,
blob.key_material_size, data, data_length, &signed_data,
signature_length);
if (err < 0) {
ALOGE("Keymaster0 signing failed with error %d", err);
return false;
}
signature->reset(signed_data);
return true;
}
EVP_PKEY* Keymaster0Engine::GetKeymaster0PublicKey(const KeymasterKeyBlob& blob) const {
uint8_t* pub_key_data;
size_t pub_key_data_length;
int err = keymaster0_device_->get_keypair_public(keymaster0_device_, blob.key_material,
blob.key_material_size, &pub_key_data,
&pub_key_data_length);
if (err < 0) {
ALOGE("Error %d extracting public key", err);
return nullptr;
}
unique_ptr<uint8_t, Malloc_Delete> pub_key(pub_key_data);
const uint8_t* p = pub_key_data;
return d2i_PUBKEY(nullptr /* allocate new struct */, &p, pub_key_data_length);
}
static bool data_too_large_for_public_modulus(const uint8_t* data, size_t len, const RSA* rsa) {
unique_ptr<BIGNUM, BIGNUM_Delete> input_as_bn(
BN_bin2bn(data, len, nullptr /* allocate result */));
return input_as_bn && BN_ucmp(input_as_bn.get(), rsa->n) >= 0;
}
int Keymaster0Engine::RsaPrivateTransform(RSA* rsa, uint8_t* out, const uint8_t* in,
size_t len) const {
const keymaster_key_blob_t* key_blob = RsaKeyToBlob(rsa);
if (key_blob == NULL) {
ALOGE("key had no key_blob!");
return 0;
}
keymaster_rsa_sign_params_t sign_params = {DIGEST_NONE, PADDING_NONE};
unique_ptr<uint8_t[], Malloc_Delete> signature;
size_t signature_length;
if (!Keymaster0Sign(&sign_params, *key_blob, in, len, &signature, &signature_length)) {
if (data_too_large_for_public_modulus(in, len, rsa)) {
ALOGE("Keymaster0 signing failed because data is too large.");
OPENSSL_PUT_ERROR(RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
} else {
// We don't know what error code is correct; force an "unknown error" return
OPENSSL_PUT_ERROR(USER, KM_ERROR_UNKNOWN_ERROR);
}
return 0;
}
Eraser eraser(signature.get(), signature_length);
if (signature_length > len) {
/* The result of the RSA operation can never be larger than the size of
* the modulus so we assume that the result has extra zeros on the
* left. This provides attackers with an oracle, but there's nothing
* that we can do about it here. */
memcpy(out, signature.get() + signature_length - len, len);
} else if (signature_length < len) {
/* If the keymaster0 implementation returns a short value we assume that
* it's because it removed leading zeros from the left side. This is
* bad because it provides attackers with an oracle but we cannot do
* anything about a broken keymaster0 implementation here. */
memset(out, 0, len);
memcpy(out + len - signature_length, signature.get(), signature_length);
} else {
memcpy(out, signature.get(), len);
}
ALOGV("rsa=%p keystore_rsa_priv_dec successful", rsa);
return 1;
}
int Keymaster0Engine::EcdsaSign(const uint8_t* digest, size_t digest_len, uint8_t* sig,
unsigned int* sig_len, EC_KEY* ec_key) const {
const keymaster_key_blob_t* key_blob = EcKeyToBlob(ec_key);
if (key_blob == NULL) {
ALOGE("key had no key_blob!");
return 0;
}
// Truncate digest if it's too long
size_t max_input_len = (ec_group_size_bits(ec_key) + 7) / 8;
if (digest_len > max_input_len)
digest_len = max_input_len;
keymaster_ec_sign_params_t sign_params = {DIGEST_NONE};
unique_ptr<uint8_t[], Malloc_Delete> signature;
size_t signature_length;
if (!Keymaster0Sign(&sign_params, *key_blob, digest, digest_len, &signature,
&signature_length)) {
// We don't know what error code is correct; force an "unknown error" return
OPENSSL_PUT_ERROR(USER, KM_ERROR_UNKNOWN_ERROR);
return 0;
}
Eraser eraser(signature.get(), signature_length);
if (signature_length == 0) {
ALOGW("No valid signature returned");
return 0;
} else if (signature_length > ECDSA_size(ec_key)) {
ALOGW("Signature is too large");
return 0;
} else {
memcpy(sig, signature.get(), signature_length);
*sig_len = signature_length;
}
ALOGV("ecdsa_sign(%p, %u, %p) => success", digest, (unsigned)digest_len, ec_key);
return 1;
}
} // namespace keymaster