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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2020, Google Inc.
*
* Public key signature verification
*/
#include "libcamera/internal/pub_key.h"
#if HAVE_CRYPTO
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/sha.h>
#include <openssl/x509.h>
#elif HAVE_GNUTLS
#include <gnutls/abstract.h>
#endif
/**
* \file pub_key.h
* \brief Public key signature verification
*/
namespace libcamera {
/**
* \class PubKey
* \brief Public key wrapper for signature verification
*
* The PubKey class wraps a public key and implements signature verification. It
* only supports RSA keys and the RSA-SHA256 signature algorithm.
*/
/**
* \brief Construct a PubKey from key data
* \param[in] key Key data encoded in DER format
*/
PubKey::PubKey([[maybe_unused]] Span<const uint8_t> key)
: valid_(false)
{
#if HAVE_CRYPTO
const uint8_t *data = key.data();
pubkey_ = d2i_PUBKEY(nullptr, &data, key.size());
if (!pubkey_)
return;
valid_ = true;
#elif HAVE_GNUTLS
int ret = gnutls_pubkey_init(&pubkey_);
if (ret < 0)
return;
const gnutls_datum_t gnuTlsKey{
const_cast<unsigned char *>(key.data()),
static_cast<unsigned int>(key.size())
};
ret = gnutls_pubkey_import(pubkey_, &gnuTlsKey, GNUTLS_X509_FMT_DER);
if (ret < 0)
return;
valid_ = true;
#endif
}
PubKey::~PubKey()
{
#if HAVE_CRYPTO
EVP_PKEY_free(pubkey_);
#elif HAVE_GNUTLS
gnutls_pubkey_deinit(pubkey_);
#endif
}
/**
* \fn bool PubKey::isValid() const
* \brief Check is the public key is valid
* \return True if the public key is valid, false otherwise
*/
/**
* \brief Verify signature on data
* \param[in] data The signed data
* \param[in] sig The signature
*
* Verify that the signature \a sig matches the signed \a data for the public
* key. The signture algorithm is hardcoded to RSA-SHA256.
*
* \return True if the signature is valid, false otherwise
*/
bool PubKey::verify([[maybe_unused]] Span<const uint8_t> data,
[[maybe_unused]] Span<const uint8_t> sig) const
{
if (!valid_)
return false;
#if HAVE_CRYPTO
/*
* Create and initialize a public key algorithm context for signature
* verification.
*/
EVP_PKEY_CTX *ctx = EVP_PKEY_CTX_new(pubkey_, nullptr);
if (!ctx)
return false;
if (EVP_PKEY_verify_init(ctx) <= 0 ||
EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0 ||
EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) {
EVP_PKEY_CTX_free(ctx);
return false;
}
/* Calculate the SHA256 digest of the data. */
uint8_t digest[SHA256_DIGEST_LENGTH];
SHA256(data.data(), data.size(), digest);
/* Decrypt the signature and verify it matches the digest. */
int ret = EVP_PKEY_verify(ctx, sig.data(), sig.size(), digest,
SHA256_DIGEST_LENGTH);
EVP_PKEY_CTX_free(ctx);
return ret == 1;
#elif HAVE_GNUTLS
const gnutls_datum_t gnuTlsData{
const_cast<unsigned char *>(data.data()),
static_cast<unsigned int>(data.size())
};
const gnutls_datum_t gnuTlsSig{
const_cast<unsigned char *>(sig.data()),
static_cast<unsigned int>(sig.size())
};
int ret = gnutls_pubkey_verify_data2(pubkey_, GNUTLS_SIGN_RSA_SHA256, 0,
&gnuTlsData, &gnuTlsSig);
return ret >= 0;
#else
return false;
#endif
}
} /* namespace libcamera */
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