1480778148

Committed 03 Oct 2024 06:26PM UTC coverage: 76.372% (+0.06%) from 76.31%

Build # 1480778148

Build Type

push

gitlab-ci

Committed by

danielskinstad

Commit Message

fix: explicitly initialize ssl

From the OpenSSL man pages:
Numerous internal OpenSSL functions call OPENSSL_init_ssl().
Therefore, in order to perform nondefault initialisation,
OPENSSL_init_ssl() MUST be called by application code prior to any other OpenSSL function calls.
See: https://docs.openssl.org/3.3/man3/OPENSSL_init_ssl/#description

This fixes errors where e.g. the openssl config configures ssl_conf,
which requires ssl to be initialized.

Ticket: MEN-7549
Changelog: Fix error while loading OpenSSL config file, by explicitly
initializing the SSL context prior to loading. Without the explicit
initialisation of SSL, the config might not be properly loaded if e.g.
it has sections specifying ssl settings. This was the case with the
example configuration for OpenSSL 1.1.1w from Debian Bullseye.

Signed-off-by: Daniel Skinstad Drabitzius <daniel.drabitzius@northern.tech>

Run Details

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97 existing lines in 3 files now uncovered.

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63.49

/src/common/crypto/platform/openssl/crypto.cpp

// Copyright 2023 Northern.tech AS
//
//    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 <common/crypto.hpp>

#include <common/crypto/platform/openssl/openssl_config.h>

#include <cstdint>
#include <string>
#include <vector>
#include <memory>

#include <openssl/bn.h>
#include <openssl/ecdsa.h>
#include <openssl/err.h>
#include <openssl/engine.h>
#include <openssl/ui.h>
#include <openssl/ssl.h>
#ifndef MENDER_CRYPTO_OPENSSL_LEGACY
#include <openssl/provider.h>
#include <openssl/store.h>
#endif // MENDER_CRYPTO_OPENSSL_LEGACY

#include <openssl/evp.h>
#include <openssl/conf.h>
#include <openssl/pem.h>
#include <openssl/rsa.h>

#include <common/io.hpp>
#include <common/error.hpp>
#include <common/expected.hpp>
#include <common/common.hpp>

#include <artifact/sha/sha.hpp>


namespace mender {
namespace common {
namespace crypto {

const size_t MENDER_DIGEST_SHA256_LENGTH = 32;

const size_t OPENSSL_SUCCESS = 1;

using namespace std;

namespace error = mender::common::error;
namespace io = mender::common::io;

using EnginePtr = unique_ptr<ENGINE, void (*)(ENGINE *)>;
#ifndef MENDER_CRYPTO_OPENSSL_LEGACY
using ProviderPtr = unique_ptr<OSSL_PROVIDER, int (*)(OSSL_PROVIDER *)>;
#endif // MENDER_CRYPTO_OPENSSL_LEGACY

class OpenSSLResourceHandle {
public:
        EnginePtr engine;
};

auto resource_handle_free_func = [](OpenSSLResourceHandle *h) {
        if (h) {
                delete h;
        }
};

auto pkey_ctx_free_func = [](EVP_PKEY_CTX *ctx) {
        if (ctx) {
                EVP_PKEY_CTX_free(ctx);
        }
};
auto pkey_free_func = [](EVP_PKEY *key) {
        if (key) {
                EVP_PKEY_free(key);
        }
};
auto bio_free_func = [](BIO *bio) {
        if (bio) {
                BIO_free(bio);
        }
};
auto bio_free_all_func = [](BIO *bio) {
        if (bio) {
                BIO_free_all(bio);
        }
};
auto bn_free = [](BIGNUM *bn) {
        if (bn) {
                BN_free(bn);
        }
};
auto engine_free_func = [](ENGINE *e) {
        if (e) {
                ENGINE_free(e);
        }
};

auto password_callback = [](char *buf, int size, int rwflag, void *u) {
        // We'll only use this callback for reading passphrases, not for
        // writing them.
        assert(rwflag == 0);

        if (u == nullptr) {
                return 0;
        }

        // NB: buf is not expected to be null terminated.
        char *const pass = static_cast<char *>(u);
        strncpy(buf, pass, size);

        return static_cast<int>(strnlen(pass, size));
};


// NOTE: GetOpenSSLErrorMessage should be called upon all OpenSSL errors, as
// the errors are queued, and if not harvested, the FIFO structure of the
// queue will mean that if you just get one, you might actually get the wrong
// one.
string GetOpenSSLErrorMessage() {
        const auto sysErrorCode = errno;
        auto sslErrorCode = ERR_get_error();

        std::string errorDescription {};
        while (sslErrorCode != 0) {
                if (!errorDescription.empty()) {
                        errorDescription += '\n';
                }
                errorDescription += ERR_error_string(sslErrorCode, nullptr);
                sslErrorCode = ERR_get_error();
        }
        if (sysErrorCode != 0) {
                if (!errorDescription.empty()) {
                        errorDescription += '\n';
                }
                errorDescription += "System error, code=" + std::to_string(sysErrorCode);
                errorDescription += ", ";
                errorDescription += strerror(sysErrorCode);
        }
        return errorDescription;
}

ExpectedPrivateKey LoadFromHSMEngine(const Args &args) {
        log::Trace("Loading the private key from HSM");

        ENGINE_load_builtin_engines();
        auto engine = EnginePtr(ENGINE_by_id(args.ssl_engine.c_str()), engine_free_func);

        if (engine == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to get the " + args.ssl_engine
                                + " engine. No engine with the ID found: " + GetOpenSSLErrorMessage()));
        }
        log::Debug("Loaded the HSM engine successfully!");

        int res = ENGINE_init(engine.get());
        if (not res) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to initialise the hardware security module (HSM): "
                                + GetOpenSSLErrorMessage()));
        }
        log::Debug("Successfully initialised the HSM engine");

        auto private_key = unique_ptr<EVP_PKEY, void (*)(EVP_PKEY *)>(
                ENGINE_load_private_key(
                        engine.get(),
                        args.private_key_path.c_str(),
                        (UI_METHOD *) nullptr,
                        nullptr /*callback_data */),
                pkey_free_func);
        if (private_key == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to load the private key from the hardware security module: "
                                + GetOpenSSLErrorMessage()));
        }
        log::Debug("Successfully loaded the private key from the HSM Engine: " + args.ssl_engine);

        auto handle = unique_ptr<OpenSSLResourceHandle, void (*)(OpenSSLResourceHandle *)>(
                new OpenSSLResourceHandle {std::move(engine)}, resource_handle_free_func);
        return PrivateKey(std::move(private_key), std::move(handle));
}

#ifdef MENDER_CRYPTO_OPENSSL_LEGACY
ExpectedPrivateKey LoadFrom(const Args &args) {
        log::Trace("Loading private key from file: " + args.private_key_path);
        auto private_bio_key = unique_ptr<BIO, void (*)(BIO *)>(
                BIO_new_file(args.private_key_path.c_str(), "r"), bio_free_func);
        if (private_bio_key == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to load the private key file " + args.private_key_path + ": "
                                + GetOpenSSLErrorMessage()));
        }

        char *passphrase = const_cast<char *>(args.private_key_passphrase.c_str());

        auto private_key = unique_ptr<EVP_PKEY, void (*)(EVP_PKEY *)>(
                PEM_read_bio_PrivateKey(private_bio_key.get(), nullptr, password_callback, passphrase),
                pkey_free_func);
        if (private_key == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to load the private key: " + args.private_key_path + " "
                                + GetOpenSSLErrorMessage()));
        }

        return PrivateKey(std::move(private_key));
}
#endif // MENDER_CRYPTO_OPENSSL_LEGACY

#ifndef MENDER_CRYPTO_OPENSSL_LEGACY
ExpectedPrivateKey LoadFrom(const Args &args) {
        char *passphrase = const_cast<char *>(args.private_key_passphrase.c_str());

        auto ui_method = unique_ptr<UI_METHOD, void (*)(UI_METHOD *)>(
                UI_UTIL_wrap_read_pem_callback(password_callback, 0 /* rw_flag */), UI_destroy_method);
        auto ctx = unique_ptr<OSSL_STORE_CTX, int (*)(OSSL_STORE_CTX *)>(
                OSSL_STORE_open(
                        args.private_key_path.c_str(),
                        ui_method.get(),
                        passphrase,
                        nullptr, /* OSSL_PARAM params[] */
                        nullptr),
                OSSL_STORE_close);

        if (ctx == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to load the private key from: " + args.private_key_path
                                + " error: " + GetOpenSSLErrorMessage()));
        }

        // Go through all objects in the context till we find the first private key
        while (not OSSL_STORE_eof(ctx.get())) {
                auto info = unique_ptr<OSSL_STORE_INFO, void (*)(OSSL_STORE_INFO *)>(
                        OSSL_STORE_load(ctx.get()), OSSL_STORE_INFO_free);

                if (info == nullptr) {
                        log::Error(
                                "Failed to load the the private key: " + args.private_key_path
                                + " trying the next object in the context: " + GetOpenSSLErrorMessage());
                        continue;
                }

                const int type_info {OSSL_STORE_INFO_get_type(info.get())};
                switch (type_info) {
                case OSSL_STORE_INFO_PKEY: {
                        // NOTE: get1 creates a duplicate of the pkey from the info, which can be
                        // used after the info ctx is destroyed
                        auto private_key = unique_ptr<EVP_PKEY, void (*)(EVP_PKEY *)>(
                                OSSL_STORE_INFO_get1_PKEY(info.get()), pkey_free_func);
                        if (private_key == nullptr) {
                                return expected::unexpected(MakeError(
                                        SetupError,
                                        "Failed to load the private key: " + args.private_key_path
                                                + " error: " + GetOpenSSLErrorMessage()));
                        }

                        return PrivateKey(std::move(private_key));
                }
                default:
                        const string info_type_string = OSSL_STORE_INFO_type_string(type_info);
                        log::Debug("Unhandled OpenSSL type: expected PrivateKey, got: " + info_type_string);
                        continue;
                }
        }

        return expected::unexpected(
                MakeError(SetupError, "Failed to load the private key: " + GetOpenSSLErrorMessage()));
}
#endif // ndef MENDER_CRYPTO_OPENSSL_LEGACY

ExpectedPrivateKey PrivateKey::Load(const Args &args) {
        // Numerous internal OpenSSL functions call OPENSSL_init_ssl().
        // Therefore, in order to perform nondefault initialisation,
        // OPENSSL_init_ssl() MUST be called by application code prior to any other OpenSSL function
        // calls. See: https://docs.openssl.org/3.3/man3/OPENSSL_init_ssl/#description
        if (OPENSSL_init_ssl(0, nullptr) != OPENSSL_SUCCESS) {
                log::Warning("Error initializing libssl: " + GetOpenSSLErrorMessage());
        }
        // Load OpenSSL config
        if (CONF_modules_load_file(nullptr, nullptr, 0) != OPENSSL_SUCCESS) {
                log::Warning("Failed to load OpenSSL configuration file: " + GetOpenSSLErrorMessage());
        }

        log::Trace("Loading private key");
        if (args.ssl_engine != "") {
                return LoadFromHSMEngine(args);
        }
        return LoadFrom(args);
}

ExpectedPrivateKey PrivateKey::Generate() {
#ifdef MENDER_CRYPTO_OPENSSL_LEGACY
        auto pkey_gen_ctx = unique_ptr<EVP_PKEY_CTX, void (*)(EVP_PKEY_CTX *)>(
                EVP_PKEY_CTX_new_id(EVP_PKEY_ED25519, nullptr), pkey_ctx_free_func);
#else
        auto pkey_gen_ctx = unique_ptr<EVP_PKEY_CTX, void (*)(EVP_PKEY_CTX *)>(
                EVP_PKEY_CTX_new_from_name(nullptr, "ED25519", nullptr), pkey_ctx_free_func);
#endif // MENDER_CRYPTO_OPENSSL_LEGACY

        int ret = EVP_PKEY_keygen_init(pkey_gen_ctx.get());
        if (ret != OPENSSL_SUCCESS) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to generate a private key. Initialization failed: "
                                + GetOpenSSLErrorMessage()));
        }
        EVP_PKEY *pkey = nullptr;
#ifdef MENDER_CRYPTO_OPENSSL_LEGACY
        ret = EVP_PKEY_keygen(pkey_gen_ctx.get(), &pkey);
#else
        ret = EVP_PKEY_generate(pkey_gen_ctx.get(), &pkey);
#endif // MENDER_CRYPTO_OPENSSL_LEGACY
        if (ret != OPENSSL_SUCCESS) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to generate a private key. Generation failed: " + GetOpenSSLErrorMessage()));
        }

        auto private_key = unique_ptr<EVP_PKEY, void (*)(EVP_PKEY *)>(pkey, pkey_free_func);
        return PrivateKey(std::move(private_key));
}

expected::ExpectedString EncodeBase64(vector<uint8_t> to_encode) {
        // Predict the len of the decoded for later verification. From man page:
        // For every 3 bytes of input provided 4 bytes of output
        // data will be produced. If n is not divisible by 3 (...)
        // the output is padded such that it is always divisible by 4.
        const uint64_t predicted_len {4 * ((to_encode.size() + 2) / 3)};

        // Add space for a NUL terminator. From man page:
        // Additionally a NUL terminator character will be added
        auto buffer {vector<unsigned char>(predicted_len + 1)};

        const int64_t output_len {
                EVP_EncodeBlock(buffer.data(), to_encode.data(), static_cast<int>(to_encode.size()))};
        assert(output_len >= 0);

        if (predicted_len != static_cast<uint64_t>(output_len)) {
                return expected::unexpected(
                        MakeError(Base64Error, "The predicted and the actual length differ"));
        }

        return string(buffer.begin(), buffer.end() - 1); // Remove the last zero byte
}

expected::ExpectedBytes DecodeBase64(string to_decode) {
        // Predict the len of the decoded for later verification. From man page:
        // For every 4 input bytes exactly 3 output bytes will be
        // produced. The output will be padded with 0 bits if necessary
        // to ensure that the output is always 3 bytes.
        const uint64_t predicted_len {3 * ((to_decode.size() + 3) / 4)};

        auto buffer {vector<unsigned char>(predicted_len)};

        const int64_t output_len {EVP_DecodeBlock(
                buffer.data(),
                common::ByteVectorFromString(to_decode).data(),
                static_cast<int>(to_decode.size()))};
        assert(output_len >= 0);

        if (predicted_len != static_cast<uint64_t>(output_len)) {
                return expected::unexpected(MakeError(
                        Base64Error,
                        "The predicted (" + std::to_string(predicted_len) + ") and the actual ("
                                + std::to_string(output_len) + ") length differ"));
        }

        // Subtract padding bytes. Inspired by internal OpenSSL code from:
        // https://github.com/openssl/openssl/blob/ff88545e02ab48a52952350c52013cf765455dd3/crypto/ct/ct_b64.c#L46
        for (auto it = to_decode.crbegin(); *it == '='; it++) {
                buffer.pop_back();
        }

        return buffer;
}


expected::ExpectedString ExtractPublicKey(const Args &args) {
        auto exp_private_key = PrivateKey::Load(args);
        if (!exp_private_key) {
                return expected::unexpected(exp_private_key.error());
        }

        auto bio_public_key = unique_ptr<BIO, void (*)(BIO *)>(BIO_new(BIO_s_mem()), bio_free_all_func);

        if (!bio_public_key.get()) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to extract the public key from the private key " + args.private_key_path
                                + "):" + GetOpenSSLErrorMessage()));
        }

        int ret = PEM_write_bio_PUBKEY(bio_public_key.get(), exp_private_key.value().Get());
        if (ret != OPENSSL_SUCCESS) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to extract the public key from the private key (" + args.private_key_path
                                + "): OpenSSL BIO write failed: " + GetOpenSSLErrorMessage()));
        }

        // NOTE: At this point we already have a public key available for extraction.
        // However, when using some providers in OpenSSL3 the external provider might
        // write the key in the old PKCS#1 format. The format is not deprecated, but
        // our older backends only understand the format if it is in the PKCS#8
        // (SubjectPublicKey) format:
        //
        // For us who don't speak OpenSSL:
        //
        // -- BEGIN RSA PUBLIC KEY -- <- PKCS#1 (old format)
        // -- BEGIN PUBLIC KEY -- <- PKCS#8 (new format - can hold different key types)


        auto evp_public_key = PkeyPtr(
                PEM_read_bio_PUBKEY(bio_public_key.get(), nullptr, nullptr, nullptr), pkey_free_func);

        if (evp_public_key == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to extract the public key from the private key " + args.private_key_path
                                + "):" + GetOpenSSLErrorMessage()));
        }

        auto bio_public_key_new =
                unique_ptr<BIO, void (*)(BIO *)>(BIO_new(BIO_s_mem()), bio_free_all_func);

        if (bio_public_key_new == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to extract the public key from the public key " + args.private_key_path
                                + "):" + GetOpenSSLErrorMessage()));
        }

        ret = PEM_write_bio_PUBKEY(bio_public_key_new.get(), evp_public_key.get());
        if (ret != OPENSSL_SUCCESS) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to extract the public key from the private key: (" + args.private_key_path
                                + "): OpenSSL BIO write failed: " + GetOpenSSLErrorMessage()));
        }

        int pending = BIO_ctrl_pending(bio_public_key_new.get());
        if (pending <= 0) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to extract the public key from bio ctrl: (" + args.private_key_path
                                + "): Zero byte key unexpected: " + GetOpenSSLErrorMessage()));
        }

        vector<uint8_t> key_vector(pending);

        size_t read = BIO_read(bio_public_key_new.get(), key_vector.data(), pending);

        if (read == 0) {
                MakeError(
                        SetupError,
                        "Failed to extract the public key from (" + args.private_key_path
                                + "): Zero bytes read from BIO: " + GetOpenSSLErrorMessage());
        }

        return string(key_vector.begin(), key_vector.end());
}

static expected::ExpectedBytes SignED25519(EVP_PKEY *pkey, const vector<uint8_t> &raw_data) {
        size_t sig_len;

        auto md_ctx = unique_ptr<EVP_MD_CTX, void (*)(EVP_MD_CTX *)>(EVP_MD_CTX_new(), EVP_MD_CTX_free);
        if (md_ctx == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError, "Failed to initialize the OpenSSL md_ctx: " + GetOpenSSLErrorMessage()));
        }

        int ret {EVP_DigestSignInit(md_ctx.get(), nullptr, nullptr, nullptr, pkey)};
        if (ret != OPENSSL_SUCCESS) {
                return expected::unexpected(MakeError(
                        SetupError, "Failed to initialize the OpenSSL signature: " + GetOpenSSLErrorMessage()));
        }

        /* Calculate the required size for the signature by passing a nullptr buffer */
        ret = EVP_DigestSign(md_ctx.get(), nullptr, &sig_len, raw_data.data(), raw_data.size());
        if (ret != OPENSSL_SUCCESS) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to find the required size of the signature buffer: "
                                + GetOpenSSLErrorMessage()));
        }

        vector<uint8_t> sig(sig_len);
        ret = EVP_DigestSign(md_ctx.get(), sig.data(), &sig_len, raw_data.data(), raw_data.size());
        if (ret != OPENSSL_SUCCESS) {
                return expected::unexpected(
                        MakeError(SetupError, "Failed to sign the message: " + GetOpenSSLErrorMessage()));
        }

        // The signature may in some cases be shorter than the previously allocated
        // length (which is the max)
        sig.resize(sig_len);

        return sig;
}

expected::ExpectedBytes SignGeneric(PrivateKey &private_key, const vector<uint8_t> &digest) {
        auto pkey_signer_ctx = unique_ptr<EVP_PKEY_CTX, void (*)(EVP_PKEY_CTX *)>(
                EVP_PKEY_CTX_new(private_key.Get(), nullptr), pkey_ctx_free_func);

        if (EVP_PKEY_sign_init(pkey_signer_ctx.get()) <= 0) {
                return expected::unexpected(MakeError(
                        SetupError, "Failed to initialize the OpenSSL signer: " + GetOpenSSLErrorMessage()));
        }
        if (EVP_PKEY_CTX_set_signature_md(pkey_signer_ctx.get(), EVP_sha256()) <= 0) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to set the OpenSSL signature to sha256: " + GetOpenSSLErrorMessage()));
        }

        vector<uint8_t> signature {};

        // Set the needed signature buffer length
        size_t digestlength = MENDER_DIGEST_SHA256_LENGTH, siglength;
        if (EVP_PKEY_sign(pkey_signer_ctx.get(), nullptr, &siglength, digest.data(), digestlength)
                <= 0) {
                return expected::unexpected(MakeError(
                        SetupError, "Failed to get the signature buffer length: " + GetOpenSSLErrorMessage()));
        }
        signature.resize(siglength);

        if (EVP_PKEY_sign(
                        pkey_signer_ctx.get(), signature.data(), &siglength, digest.data(), digestlength)
                <= 0) {
                return expected::unexpected(
                        MakeError(SetupError, "Failed to sign the digest: " + GetOpenSSLErrorMessage()));
        }

        // The signature may in some cases be shorter than the previously allocated
        // length (which is the max)
        signature.resize(siglength);

        return signature;
}

expected::ExpectedBytes SignData(const Args &args, const vector<uint8_t> &raw_data) {
        auto exp_private_key = PrivateKey::Load(args);
        if (!exp_private_key) {
                return expected::unexpected(exp_private_key.error());
        }

        log::Info("Signing with: " + args.private_key_path);

        auto key_type = EVP_PKEY_base_id(exp_private_key.value().Get());

        // ED25519 signatures need to be handled independently, because of how the
        // signature scheme is designed.
        if (key_type == EVP_PKEY_ED25519) {
                return SignED25519(exp_private_key.value().Get(), raw_data);
        }

        auto exp_shasum = mender::sha::Shasum(raw_data);
        if (!exp_shasum) {
                return expected::unexpected(exp_shasum.error());
        }
        auto digest = exp_shasum.value(); /* The shasummed data = digest in crypto world */
        log::Debug("Shasum is: " + digest.String());

        return SignGeneric(exp_private_key.value(), digest);
}

expected::ExpectedString Sign(const Args &args, const vector<uint8_t> &raw_data) {
        auto exp_signed_data = SignData(args, raw_data);
        if (!exp_signed_data) {
                return expected::unexpected(exp_signed_data.error());
        }
        vector<uint8_t> signature = exp_signed_data.value();

        return EncodeBase64(signature);
}

const size_t mender_decode_buf_size = 256;
const size_t ecdsa256keySize = 32;

// Try and decode the keys from pure binary, assuming that the points on the
// curve (r,s), have been concatenated together (r || s), and simply dumped to
// binary. Which is what we did in the `mender-artifact` tool.
// (See MEN-1740) for some insight into previous issues, and the chosen fix.
static expected::ExpectedBytes TryASN1EncodeMenderCustomBinaryECFormat(
        const vector<uint8_t> &signature,
        const mender::sha::SHA &shasum,
        std::function<BIGNUM *(const unsigned char *signature, int length, BIGNUM *_unused)>
                BinaryDecoderFn) {
        // Verify that the marshalled keys match our expectation
        const size_t assumed_signature_size {2 * ecdsa256keySize};
        if (signature.size() > assumed_signature_size) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Unexpected size of the signature for ECDSA. Expected 2*" + to_string(ecdsa256keySize)
                                + " bytes. Got: " + to_string(signature.size())));
        }
        auto ecSig = unique_ptr<ECDSA_SIG, void (*)(ECDSA_SIG *)>(ECDSA_SIG_new(), ECDSA_SIG_free);
        if (ecSig == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to allocate the structure for the ECDSA signature: "
                                + GetOpenSSLErrorMessage()));
        }

        auto r = unique_ptr<BIGNUM, void (*)(BIGNUM *)>(
                BinaryDecoderFn(signature.data(), ecdsa256keySize, nullptr /* allocate new memory for r */),
                bn_free);
        if (r == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to extract the r(andom) part from the ECDSA signature in the binary representation: "
                                + GetOpenSSLErrorMessage()));
        }
        auto s = unique_ptr<BIGNUM, void (*)(BIGNUM *)>(
                BinaryDecoderFn(
                        signature.data() + ecdsa256keySize,
                        ecdsa256keySize,
                        nullptr /* allocate new memory for s */),
                bn_free);
        if (s == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to extract the s(ignature) part from the ECDSA signature in the binary representation: "
                                + GetOpenSSLErrorMessage()));
        }

        // Set the r&s values in the SIG struct
        // r & s now owned by ecSig
        int ret {ECDSA_SIG_set0(ecSig.get(), r.get(), s.get())};
        if (ret != OPENSSL_SUCCESS) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to set the signature parts in the ECDSA structure: "
                                + GetOpenSSLErrorMessage()));
        }
        r.release();
        s.release();

        /* Allocate some array guaranteed to hold the DER-encoded structure */
        vector<uint8_t> der_encoded_byte_array(mender_decode_buf_size);
        unsigned char *arr_p = &der_encoded_byte_array[0];
        int len = i2d_ECDSA_SIG(ecSig.get(), &arr_p);
        if (len < 0) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to set the signature parts in the ECDSA structure: "
                                + GetOpenSSLErrorMessage()));
        }
        /* Resize to the actual size of the DER-encoded signature */
        der_encoded_byte_array.resize(len);

        return der_encoded_byte_array;
}


expected::ExpectedBool VerifySignData(
        const string &public_key_path,
        const mender::sha::SHA &shasum,
        const vector<uint8_t> &signature);

static expected::ExpectedBool VerifyECDSASignData(
        const string &public_key_path,
        const mender::sha::SHA &shasum,
        const vector<uint8_t> &signature) {
        expected::ExpectedBytes exp_der_encoded_signature =
                TryASN1EncodeMenderCustomBinaryECFormat(signature, shasum, BN_bin2bn)
                        .or_else([&signature, &shasum](error::Error big_endian_error) {
                                log::Debug(
                                        "Failed to decode the signature binary blob from our custom binary format assuming the big-endian encoding, error: "
                                        + big_endian_error.String()
                                        + " falling back and trying anew assuming it is little-endian encoded: ");
                                return TryASN1EncodeMenderCustomBinaryECFormat(signature, shasum, BN_lebin2bn);
                        });
        if (!exp_der_encoded_signature) {
                return expected::unexpected(
                        MakeError(VerificationError, exp_der_encoded_signature.error().message));
        }

        vector<uint8_t> der_encoded_signature = exp_der_encoded_signature.value();

        return VerifySignData(public_key_path, shasum, der_encoded_signature);
}

static bool OpenSSLSignatureVerificationError(int a) {
        /*
         * The signature check errored. This is different from the signature being
         * wrong. We simply were not able to perform the check in this instance.
         * Therefore, we fall back to trying the custom marshalled binary ECDSA
         * signature, which we have been using in Mender.
         */
        return a < 0;
}

expected::ExpectedBool VerifySignData(
        const string &public_key_path,
        const mender::sha::SHA &shasum,
        const vector<uint8_t> &signature) {
        auto bio_key =
                unique_ptr<BIO, void (*)(BIO *)>(BIO_new_file(public_key_path.c_str(), "r"), bio_free_func);
        if (bio_key == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to open the public key file from (" + public_key_path
                                + "):" + GetOpenSSLErrorMessage()));
        }

        auto pkey = unique_ptr<EVP_PKEY, void (*)(EVP_PKEY *)>(
                PEM_read_bio_PUBKEY(bio_key.get(), nullptr, nullptr, nullptr), pkey_free_func);
        if (pkey == nullptr) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to load the public key from(" + public_key_path
                                + "): " + GetOpenSSLErrorMessage()));
        }

        auto pkey_signer_ctx = unique_ptr<EVP_PKEY_CTX, void (*)(EVP_PKEY_CTX *)>(
                EVP_PKEY_CTX_new(pkey.get(), nullptr), pkey_ctx_free_func);

        auto ret = EVP_PKEY_verify_init(pkey_signer_ctx.get());
        if (ret <= 0) {
                return expected::unexpected(MakeError(
                        SetupError, "Failed to initialize the OpenSSL signer: " + GetOpenSSLErrorMessage()));
        }
        ret = EVP_PKEY_CTX_set_signature_md(pkey_signer_ctx.get(), EVP_sha256());
        if (ret <= 0) {
                return expected::unexpected(MakeError(
                        SetupError,
                        "Failed to set the OpenSSL signature to sha256: " + GetOpenSSLErrorMessage()));
        }

        // verify signature
        ret = EVP_PKEY_verify(
                pkey_signer_ctx.get(), signature.data(), signature.size(), shasum.data(), shasum.size());
        if (OpenSSLSignatureVerificationError(ret)) {
                log::Debug(
                        "Failed to verify the signature with the supported OpenSSL binary formats. Falling back to the custom Mender encoded binary format for ECDSA signatures: "
                        + GetOpenSSLErrorMessage());
                return VerifyECDSASignData(public_key_path, shasum, signature);
        }
        if (ret == OPENSSL_SUCCESS) {
                return true;
        }
        /* This is the case where ret == 0. The signature is simply wrong */
        return false;
}

expected::ExpectedBool VerifySign(
        const string &public_key_path, const mender::sha::SHA &shasum, const string &signature) {
        // signature: decode base64
        auto exp_decoded_signature = DecodeBase64(signature);
        if (!exp_decoded_signature) {
                return expected::unexpected(exp_decoded_signature.error());
        }
        auto decoded_signature = exp_decoded_signature.value();

        return VerifySignData(public_key_path, shasum, decoded_signature);
}

error::Error PrivateKey::SaveToPEM(const string &private_key_path) {
        auto bio_key = unique_ptr<BIO, void (*)(BIO *)>(
                BIO_new_file(private_key_path.c_str(), "w"), bio_free_func);
        if (bio_key == nullptr) {
                return MakeError(
                        SetupError,
                        "Failed to open the private key file (" + private_key_path
                                + "): " + GetOpenSSLErrorMessage());
        }

        auto ret =
                PEM_write_bio_PrivateKey(bio_key.get(), key.get(), nullptr, nullptr, 0, nullptr, nullptr);
        if (ret != OPENSSL_SUCCESS) {
                return MakeError(
                        SetupError,
                        "Failed to save the private key to file (" + private_key_path
                                + "): " + GetOpenSSLErrorMessage());
        }

        return error::NoError;
}

} // namespace crypto
} // namespace common
} // namespace mender

mendersoftware / mender / 1480778148

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