crypto/x509_generator.cpp

/*
 * Copyright (C) 2019 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 "adb/crypto/x509_generator.h"

#include <vector>

#include <android-base/logging.h>
#include <crypto_utils/android_pubkey.h>
#include <openssl/bn.h>
#include <openssl/pem.h>
#include <openssl/rsa.h>

namespace adb {
namespace crypto {

namespace {

const char kBasicConstraints[] = "critical,CA:TRUE";
const char kKeyUsage[] = "critical,keyCertSign,cRLSign,digitalSignature";
const char kSubjectKeyIdentifier[] = "hash";
constexpr int kCertLifetimeSeconds = 10 * 365 * 24 * 60 * 60;

bool add_ext(X509* cert, int nid, const char* value) {
    size_t len = strlen(value) + 1;
    std::vector<char> mutableValue(value, value + len);
    X509V3_CTX context;

    X509V3_set_ctx_nodb(&context);

    X509V3_set_ctx(&context, cert, cert, nullptr, nullptr, 0);
    X509_EXTENSION* ex = X509V3_EXT_nconf_nid(nullptr, &context, nid, mutableValue.data());
    if (!ex) {
        return false;
    }

    X509_add_ext(cert, ex, -1);
    X509_EXTENSION_free(ex);
    return true;
}

}  // namespace

bssl::UniquePtr<X509> GenerateX509Certificate(EVP_PKEY* pkey) {
    CHECK(pkey);
    bssl::UniquePtr<X509> x509(X509_new());
    if (!x509) {
        LOG(ERROR) << "Unable to allocate x509 container";
        return nullptr;
    }
    X509_set_version(x509.get(), 2);

    ASN1_INTEGER_set(X509_get_serialNumber(x509.get()), 1);
    X509_gmtime_adj(X509_get_notBefore(x509.get()), 0);
    X509_gmtime_adj(X509_get_notAfter(x509.get()), kCertLifetimeSeconds);

    if (!X509_set_pubkey(x509.get(), pkey)) {
        LOG(ERROR) << "Unable to set x509 public key";
        return nullptr;
    }

    X509_NAME* name = X509_get_subject_name(x509.get());
    if (!name) {
        LOG(ERROR) << "Unable to get x509 subject name";
        return nullptr;
    }
    X509_NAME_add_entry_by_txt(name, "C", MBSTRING_ASC,
                               reinterpret_cast<const unsigned char*>("US"), -1, -1, 0);
    X509_NAME_add_entry_by_txt(name, "O", MBSTRING_ASC,
                               reinterpret_cast<const unsigned char*>("Android"), -1, -1, 0);
    X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_ASC,
                               reinterpret_cast<const unsigned char*>("Adb"), -1, -1, 0);
    if (!X509_set_issuer_name(x509.get(), name)) {
        LOG(ERROR) << "Unable to set x509 issuer name";
        return nullptr;
    }

    add_ext(x509.get(), NID_basic_constraints, kBasicConstraints);
    add_ext(x509.get(), NID_key_usage, kKeyUsage);
    add_ext(x509.get(), NID_subject_key_identifier, kSubjectKeyIdentifier);

    int bytes = X509_sign(x509.get(), pkey, EVP_sha256());
    if (bytes <= 0) {
        LOG(ERROR) << "Unable to sign x509 certificate";
        return nullptr;
    }

    return x509;
}

std::string X509ToPEMString(X509* x509) {
    bssl::UniquePtr<BIO> bio(BIO_new(BIO_s_mem()));
    int rc = PEM_write_bio_X509(bio.get(), x509);
    if (rc != 1) {
        LOG(ERROR) << "PEM_write_bio_X509 failed";
        return "";
    }

    BUF_MEM* mem = nullptr;
    BIO_get_mem_ptr(bio.get(), &mem);
    if (!mem || !mem->data || !mem->length) {
        LOG(ERROR) << "BIO_get_mem_ptr failed";
        return "";
    }

    return std::string(mem->data, mem->length);
}

}  // namespace crypto
}  // namespace adb