Received-SPF: softfail (google.com: domain of transitioning linux-crypto-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Fri, 13 May 2022 11:55:07 +0100
From:   Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= <berrange@redhat.com>
To:     zhenwei pi <pizhenwei@bytedance.com>
Cc:     mst@redhat.com, arei.gonglei@huawei.com, qemu-devel@nongnu.org,
        virtualization@lists.linux-foundation.org,
        linux-crypto@vger.kernel.org, helei.sig11@bytedance.com,
        jasowang@redhat.com, cohuck@redhat.com
Subject: Re: [PATCH v5 5/9] crypto: Implement RSA algorithm by hogweed
Message-ID: <Yn45CxgJ+KNIxXek@redhat.com>
Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= <berrange@redhat.com>
References: <20220428135943.178254-1-pizhenwei@bytedance.com>
 <20220428135943.178254-6-pizhenwei@bytedance.com>
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In-Reply-To: <20220428135943.178254-6-pizhenwei@bytedance.com>
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On Thu, Apr 28, 2022 at 09:59:39PM +0800, zhenwei pi wrote:
> From: Lei He <helei.sig11@bytedance.com>
> 
> Implement RSA algorithm by hogweed from nettle. Thus QEMU supports
> a 'real' RSA backend to handle request from guest side. It's
> important to test RSA offload case without OS & hardware requirement.
> 
> Signed-off-by: lei he <helei.sig11@bytedance.com>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  crypto/akcipher-nettle.c.inc | 432 +++++++++++++++++++++++++++++++++++
>  crypto/akcipher.c            |   4 +
>  crypto/meson.build           |   4 +
>  crypto/rsakey-builtin.c.inc  | 209 +++++++++++++++++
>  crypto/rsakey-nettle.c.inc   | 154 +++++++++++++
>  crypto/rsakey.c              |  44 ++++
>  crypto/rsakey.h              |  94 ++++++++
>  meson.build                  |  11 +
>  8 files changed, 952 insertions(+)
>  create mode 100644 crypto/akcipher-nettle.c.inc
>  create mode 100644 crypto/rsakey-builtin.c.inc
>  create mode 100644 crypto/rsakey-nettle.c.inc
>  create mode 100644 crypto/rsakey.c
>  create mode 100644 crypto/rsakey.h
> 


> +
> +static void wrap_nettle_random_func(void *ctx, size_t len, uint8_t *out)
> +{
> +    /* TODO: check result */
> +    qcrypto_random_bytes(out, len, NULL);
> +}

Unfortunate meson requires this function to be void.

Since we've no way to report errors, then our only option is assume
qcrypto_random_bytes will never fail, and enforce that assumptiomn
by passing '&error_abort' for the last parameter.

> +
> +static int qcrypto_nettle_rsa_encrypt(QCryptoAkCipher *akcipher,
> +                                      const void *data, size_t data_len,
> +                                      void *enc, size_t enc_len,
> +                                      Error **errp)
> +{
> +
> +    QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
> +    mpz_t c;
> +    int ret = -1;
> +
> +    if (data_len > rsa->pub.size || enc_len != rsa->pub.size) {
> +        error_setg(errp, "Invalid buffer size");
> +        return ret;
> +    }

Can you report the invalid & expect buffer sizes, as it'll
make debugging much easier. You'll need a separate check
and error reporting for enc_len and data_len.

> +
> +    /* Nettle do not support RSA encryption without any padding */
> +    switch (rsa->padding_alg) {
> +    case QCRYPTO_RSA_PADDING_ALG_RAW:
> +        error_setg(errp, "RSA with raw padding is not supported");
> +        break;
> +
> +    case QCRYPTO_RSA_PADDING_ALG_PKCS1:
> +        mpz_init(c);
> +        if (rsa_encrypt(&rsa->pub, NULL, wrap_nettle_random_func,
> +                          data_len, (uint8_t *)data, c) != 1) {
> +            error_setg(errp, "Failed to encrypt");
> +        } else {
> +            nettle_mpz_get_str_256(enc_len, (uint8_t *)enc, c);
> +            ret = enc_len;
> +        }
> +        mpz_clear(c);
> +        break;
> +
> +    default:
> +        error_setg(errp, "Unknown padding");
> +    }
> +
> +    return ret;
> +}
> +
> +static int qcrypto_nettle_rsa_decrypt(QCryptoAkCipher *akcipher,
> +                                      const void *enc, size_t enc_len,
> +                                      void *data, size_t data_len,
> +                                      Error **errp)
> +{
> +    QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
> +    mpz_t c;
> +    int ret = -1;
> +    if (enc_len > rsa->priv.size) {
> +        error_setg(errp, "Invalid buffer size");
> +        return ret;
> +    }

Again please report the invalid & expected sizes in the message

We don't need to validate 'data_len' in the decrypt case,
as you did in encrypt ?

> +
> +    switch (rsa->padding_alg) {
> +    case QCRYPTO_RSA_PADDING_ALG_RAW:
> +        error_setg(errp, "RSA with raw padding is not supported");
> +        break;
> +
> +    case QCRYPTO_RSA_PADDING_ALG_PKCS1:
> +        nettle_mpz_init_set_str_256_u(c, enc_len, enc);
> +        if (!rsa_decrypt(&rsa->priv, &data_len, (uint8_t *)data, c)) {
> +            error_setg(errp, "Failed to decrypt");
> +        } else {
> +            ret = data_len;
> +        }
> +
> +        mpz_clear(c);
> +        break;
> +
> +    default:
> +        ret = -1;

'ret' was initialized to '-1' at time of declaration

> +        error_setg(errp, "Unknown padding");
> +    }
> +
> +    return ret;
> +}
> +
> +static int qcrypto_nettle_rsa_sign(QCryptoAkCipher *akcipher,
> +                                   const void *data, size_t data_len,
> +                                   void *sig, size_t sig_len, Error **errp)
> +{
> +    QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
> +    int ret;

For consistency with the earlier methods, initialize this to -1

> +    mpz_t s;
> +
> +    /**
> +     * The RSA algorithm cannot be used for signature/verification
> +     * without padding.
> +     */
> +    if (rsa->padding_alg == QCRYPTO_RSA_PADDING_ALG_RAW) {
> +        error_setg(errp, "Try to make signature without padding");
> +        return -1;
> +    }
> +
> +    if (data_len > rsa->priv.size || sig_len != rsa->priv.size) {
> +        error_setg(errp, "Invalid buffer size");
> +        return -1;
> +    }

Same note about reporting the lengths.

> +
> +    mpz_init(s);
> +    switch (rsa->hash_alg) {
> +    case QCRYPTO_HASH_ALG_MD5:
> +        ret = rsa_md5_sign_digest(&rsa->priv, data, s);

I'd suggest using a separate variable 'rv' here, as I
find it can be confusing to re-use a variable for two
different purposes. Keep 'ret' exclusively for holdnig
the method return value.

> +        break;
> +
> +    case QCRYPTO_HASH_ALG_SHA1:
> +        ret = rsa_sha1_sign_digest(&rsa->priv, data, s);
> +        break;
> +
> +    case QCRYPTO_HASH_ALG_SHA256:
> +        ret = rsa_sha256_sign_digest(&rsa->priv, data, s);
> +        break;
> +
> +    case QCRYPTO_HASH_ALG_SHA512:
> +        ret = rsa_sha512_sign_digest(&rsa->priv, data, s);
> +        break;
> +
> +    default:
> +        error_setg(errp, "Unknown hash algorithm");
> +        ret = -1;

No need if we initialize 'ret' upfront.

> +        goto cleanup;
> +    }
> +
> +    if (ret != 1) {
> +        error_setg(errp, "Failed to make signature");
> +        ret = -1;
> +        goto cleanup;
> +    }
> +    nettle_mpz_get_str_256(sig_len, (uint8_t *)sig, s);
> +    ret = sig_len;
> +
> +cleanup:
> +    mpz_clear(s);
> +
> +    return ret;
> +}
> +
> +static int qcrypto_nettle_rsa_verify(QCryptoAkCipher *akcipher,
> +                                     const void *sig, size_t sig_len,
> +                                     const void *data, size_t data_len,
> +                                     Error **errp)
> +{
> +    QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
> +
> +    int ret;

Initialize to -1 here.

> +    mpz_t s;
> +
> +    /**
> +     * The RSA algorithm cannot be used for signature/verification
> +     * without padding.
> +     */
> +    if (rsa->padding_alg == QCRYPTO_RSA_PADDING_ALG_RAW) {
> +        error_setg(errp, "Operation not supported");
> +        return -1;
> +    }
> +    if (data_len > rsa->pub.size || sig_len < rsa->pub.size) {
> +        error_setg(errp, "Invalid buffer size");
> +        return -1;
> +    }

Ssame note as earlier methods

> +
> +    nettle_mpz_init_set_str_256_u(s, sig_len, sig);
> +    switch (rsa->hash_alg) {
> +    case QCRYPTO_HASH_ALG_MD5:
> +        ret = rsa_md5_verify_digest(&rsa->pub, data, s);
> +        break;
> +
> +    case QCRYPTO_HASH_ALG_SHA1:
> +        ret = rsa_sha1_verify_digest(&rsa->pub, data, s);
> +        break;
> +
> +    case QCRYPTO_HASH_ALG_SHA256:
> +        ret = rsa_sha256_verify_digest(&rsa->pub, data, s);
> +        break;
> +
> +    case QCRYPTO_HASH_ALG_SHA512:
> +        ret = rsa_sha512_verify_digest(&rsa->pub, data, s);
> +        break;
> +
> +    default:
> +        error_setg(errp, "Unsupported hash algorithm");
> +        ret = -1;

Skip this

> +        goto cleanup;
> +    }
> +
> +    if (ret != 1) {
> +        error_setg(errp, "Failed to verify");
> +        ret = -1;
> +        goto cleanup;
> +    }
> +    ret = 0;
> +
> +cleanup:
> +    mpz_clear(s);
> +
> +    return ret;
> +}
> +
> +QCryptoAkCipherDriver nettle_rsa = {
> +    .encrypt = qcrypto_nettle_rsa_encrypt,
> +    .decrypt = qcrypto_nettle_rsa_decrypt,
> +    .sign = qcrypto_nettle_rsa_sign,
> +    .verify = qcrypto_nettle_rsa_verify,
> +    .free = qcrypto_nettle_rsa_free,
> +};
> +
> +static QCryptoAkCipher *qcrypto_nettle_rsa_new(
> +    const QCryptoAkCipherOptionsRSA *opt,
> +    QCryptoAkCipherKeyType type,
> +    const uint8_t *key, size_t keylen,
> +    Error **errp)
> +{
> +    QCryptoNettleRSA *rsa = g_new0(QCryptoNettleRSA, 1);
> +
> +    rsa->padding_alg = opt->padding_alg;
> +    rsa->hash_alg = opt->hash_alg;
> +    rsa->akcipher.driver = &nettle_rsa;
> +    rsa_public_key_init(&rsa->pub);
> +    rsa_private_key_init(&rsa->priv);
> +
> +    switch (type) {
> +    case QCRYPTO_AKCIPHER_KEY_TYPE_PRIVATE:
> +        if (qcrypt_nettle_parse_rsa_private_key(rsa, key, keylen) != 0) {
> +            error_setg(errp, "Failed to parse rsa private key");
> +            goto error;
> +        }
> +        break;
> +
> +    case QCRYPTO_AKCIPHER_KEY_TYPE_PUBLIC:
> +        if (qcrypt_nettle_parse_rsa_public_key(rsa, key, keylen) != 0) {
> +            error_setg(errp, "Failed to parse rsa public rsa key");
> +            goto error;
> +        }
> +        break;
> +
> +    default:
> +        error_setg(errp, "Unknown akcipher key type %d", type);
> +        goto error;
> +    }
> +
> +    return (QCryptoAkCipher *)rsa;
> +
> +error:
> +    qcrypto_nettle_rsa_free((QCryptoAkCipher *)rsa);
> +    return NULL;
> +}
> +
> +
> +bool qcrypto_akcipher_supports(QCryptoAkCipherOptions *opts)
> +{
> +    switch (opts->alg) {
> +    case QCRYPTO_AKCIPHER_ALG_RSA:
> +        switch (opts->u.rsa.padding_alg) {
> +        case QCRYPTO_RSA_PADDING_ALG_PKCS1:
> +            switch (opts->u.rsa.hash_alg) {
> +            case QCRYPTO_HASH_ALG_MD5:
> +            case QCRYPTO_HASH_ALG_SHA1:
> +            case QCRYPTO_HASH_ALG_SHA256:
> +            case QCRYPTO_HASH_ALG_SHA512:
> +                return true;
> +
> +            default:
> +                return false;
> +            }
> +
> +        case QCRYPTO_RSA_PADDING_ALG_RAW:
> +        default:
> +            return false;
> +        }
> +        break;
> +
> +    default:
> +        return false;
> +    }
> +}
> diff --git a/crypto/akcipher.c b/crypto/akcipher.c
> index ab28bf415b..f287083f92 100644
> --- a/crypto/akcipher.c
> +++ b/crypto/akcipher.c
> @@ -23,6 +23,9 @@
>  #include "crypto/akcipher.h"
>  #include "akcipherpriv.h"
>  
> +#if defined(CONFIG_NETTLE) && defined(CONFIG_HOGWEED)
> +#include "akcipher-nettle.c.inc"
> +#else
>  QCryptoAkCipher *qcrypto_akcipher_new(const QCryptoAkCipherOptions *opts,
>                                        QCryptoAkCipherKeyType type,
>                                        const uint8_t *key, size_t keylen,
> @@ -37,6 +40,7 @@ bool qcrypto_akcipher_supports(QCryptoAkCipherOptions *opts)
>  {
>      return false;
>  }
> +#endif
>  
>  int qcrypto_akcipher_encrypt(QCryptoAkCipher *akcipher,
>                               const void *in, size_t in_len,
> diff --git a/crypto/meson.build b/crypto/meson.build
> index c9b36857a6..d9294eed83 100644
> --- a/crypto/meson.build
> +++ b/crypto/meson.build
> @@ -21,10 +21,14 @@ crypto_ss.add(files(
>    'tlscredspsk.c',
>    'tlscredsx509.c',
>    'tlssession.c',
> +  'rsakey.c',
>  ))
>  
>  if nettle.found()
>    crypto_ss.add(nettle, files('hash-nettle.c', 'hmac-nettle.c', 'pbkdf-nettle.c'))
> +  if hogweed.found()
> +    crypto_ss.add(gmp, hogweed)
> +  endif
>    if xts == 'private'
>      crypto_ss.add(files('xts.c'))
>    endif
> diff --git a/crypto/rsakey-builtin.c.inc b/crypto/rsakey-builtin.c.inc
> new file mode 100644
> index 0000000000..0a93712f4f
> --- /dev/null
> +++ b/crypto/rsakey-builtin.c.inc
> @@ -0,0 +1,209 @@
> +/*
> + * QEMU Crypto akcipher algorithms
> + *
> + * Copyright (c) 2022 Bytedance
> + * Author: lei he <helei.sig11@bytedance.com>
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> + *
> + */
> +
> +#include "der.h"
> +#include "rsakey.h"
> +
> +static int extract_mpi(void *ctx, const uint8_t *value,
> +                       size_t vlen, Error **errp)
> +{
> +    QCryptoAkCipherMPI *mpi = (QCryptoAkCipherMPI *)ctx;
> +    if (vlen == 0) {
> +        error_setg(errp, "Empty mpi field");
> +        return -1;
> +    }
> +    mpi->data = g_memdup2(value, vlen);
> +    mpi->len = vlen;
> +    return 0;
> +}
> +
> +static int extract_version(void *ctx, const uint8_t *value,
> +                           size_t vlen, Error **errp)
> +{
> +    uint8_t *version = (uint8_t *)ctx;
> +    if (vlen != 1 || *value > 1) {
> +        error_setg(errp, "Invalid rsakey version");
> +        return -1;
> +    }
> +    *version = *value;
> +    return 0;
> +}
> +
> +static int extract_seq_content(void *ctx, const uint8_t *value,
> +                               size_t vlen, Error **errp)
> +{
> +    const uint8_t **content = (const uint8_t **)ctx;
> +    if (vlen == 0) {
> +        error_setg(errp, "Empty sequence");
> +        return -1;
> +    }
> +    *content = value;
> +    return 0;
> +}
> +
> +/**
> + *
> + *        RsaPubKey ::= SEQUENCE {
> + *             n           INTEGER
> + *             e           INTEGER
> + *         }
> + */
> +static QCryptoAkCipherRSAKey *qcrypto_builtin_rsa_public_key_parse(
> +    const uint8_t *key, size_t keylen)
> +{
> +    QCryptoAkCipherRSAKey *rsa = g_new0(QCryptoAkCipherRSAKey, 1);
> +    const uint8_t *seq;
> +    size_t seq_length;
> +    int decode_ret;
> +    Error *local_error = NULL;
> +
> +    decode_ret = qcrypto_der_decode_seq(&key, &keylen,
> +        extract_seq_content, &seq, &local_error);
> +    if (decode_ret < 0) {
> +        error_report_err(local_error);

Nothing in the crypto/ directory should ever call error_report_err.
Any methods  which can fail need to have an 'Error **errp' parameter
and propagate this back to the caller(s).

> +        goto error;
> +    }
> +    if (keylen != 0) {
> +        goto error;
> +    }
> +    seq_length = decode_ret;
> +
> +    if (qcrypto_der_decode_int(&seq, &seq_length, extract_mpi,
> +                               &rsa->n, &local_error) < 0 ||
> +        qcrypto_der_decode_int(&seq, &seq_length, extract_mpi,
> +                               &rsa->e, &local_error) < 0) {
> +        error_report_err(local_error);
> +        goto error;
> +    }
> +    if (seq_length != 0) {
> +        goto error;
> +    }
> +
> +    return rsa;
> +
> +error:
> +    qcrypto_akcipher_rsakey_free(rsa);
> +    return NULL;
> +}
> +
> +/**
> + *        RsaPrivKey ::= SEQUENCE {
> + *             version     INTEGER
> + *             n           INTEGER
> + *             e           INTEGER
> + *             d           INTEGER
> + *             p           INTEGER
> + *             q           INTEGER
> + *             dp          INTEGER
> + *             dq          INTEGER
> + *             u           INTEGER
> + *       otherPrimeInfos   OtherPrimeInfos OPTIONAL
> + *         }
> + */
> +static QCryptoAkCipherRSAKey *qcrypto_builtin_rsa_private_key_parse(
> +    const uint8_t *key, size_t keylen)
> +{
> +    QCryptoAkCipherRSAKey *rsa = g_new0(QCryptoAkCipherRSAKey, 1);
> +    uint8_t version;
> +    const uint8_t *seq;
> +    int decode_ret;
> +    size_t seq_length;
> +    Error *local_error = NULL;
> +
> +    decode_ret = qcrypto_der_decode_seq(&key, &keylen,
> +        extract_seq_content, &seq, &local_error);
> +    if (decode_ret < 0) {
> +        error_report_err(local_error);
> +        goto error;
> +    }
> +    if (keylen != 0) {
> +        goto error;
> +    }
> +    seq_length = decode_ret;
> +
> +    decode_ret = qcrypto_der_decode_int(&seq, &seq_length, extract_version,
> +                                        &version, &local_error);
> +    if (decode_ret < 0) {
> +        error_report_err(local_error);
> +        goto error;
> +    }
> +
> +    if (qcrypto_der_decode_int(&seq, &seq_length, extract_mpi,
> +                               &rsa->n, &local_error) < 0 ||
> +        qcrypto_der_decode_int(&seq, &seq_length, extract_mpi,
> +                               &rsa->e, &local_error) < 0 ||
> +        qcrypto_der_decode_int(&seq, &seq_length, extract_mpi,
> +                               &rsa->d, &local_error) < 0 ||
> +        qcrypto_der_decode_int(&seq, &seq_length, extract_mpi, &rsa->p,
> +                               &local_error) < 0 ||
> +        qcrypto_der_decode_int(&seq, &seq_length, extract_mpi, &rsa->q,
> +                               &local_error) < 0 ||
> +        qcrypto_der_decode_int(&seq, &seq_length, extract_mpi, &rsa->dp,
> +                               &local_error) < 0 ||
> +        qcrypto_der_decode_int(&seq, &seq_length, extract_mpi, &rsa->dq,
> +                               &local_error) < 0 ||
> +        qcrypto_der_decode_int(&seq, &seq_length, extract_mpi, &rsa->u,
> +                               &local_error) < 0) {
> +        error_report_err(local_error);
> +        goto error;
> +    }
> +    /**
> +     * According to the standard, otherPrimeInfos must be present for version 1.
> +     * There is no strict verification here, this is to be compatible with
> +     * the unit test of the kernel. TODO: remove this until linux kernel's
> +     * unit-test is fixed.
> +     */
> +    if (version == 1 && seq_length != 0) {
> +        if (qcrypto_der_decode_seq(&seq, &seq_length,
> +                                   NULL, NULL, &local_error) < 0) {
> +            error_report_err(local_error);
> +            goto error;
> +        }
> +        if (seq_length != 0) {
> +            goto error;
> +        }
> +        return rsa;
> +    }
> +    if (seq_length != 0) {
> +        goto error;
> +    }
> +
> +    return rsa;
> +
> +error:
> +    qcrypto_akcipher_rsakey_free(rsa);
> +    return NULL;
> +}
> +
> +QCryptoAkCipherRSAKey *qcrypto_akcipher_rsakey_parse(
> +    QCryptoAkCipherKeyType type, const uint8_t *key, size_t keylen)
> +{
> +    switch (type) {
> +    case QCRYPTO_AKCIPHER_KEY_TYPE_PRIVATE:
> +        return qcrypto_builtin_rsa_private_key_parse(key, keylen);
> +
> +    case QCRYPTO_AKCIPHER_KEY_TYPE_PUBLIC:
> +        return qcrypto_builtin_rsa_public_key_parse(key, keylen);
> +
> +    default:
> +        return NULL;
> +    }
> +}
> diff --git a/crypto/rsakey-nettle.c.inc b/crypto/rsakey-nettle.c.inc
> new file mode 100644
> index 0000000000..2c89b3be88
> --- /dev/null
> +++ b/crypto/rsakey-nettle.c.inc
> @@ -0,0 +1,154 @@
> +/*
> + * QEMU Crypto akcipher algorithms
> + *
> + * Copyright (c) 2022 Bytedance
> + * Author: lei he <helei.sig11@bytedance.com>
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> + *
> + */
> +
> +#include <nettle/asn1.h>
> +#include <stdbool.h>
> +
> +#include "rsakey.h"
> +
> +static bool DumpMPI(struct asn1_der_iterator *i, QCryptoAkCipherMPI *mpi)
> +{
> +    mpi->data = g_memdup2(i->data, i->length);
> +    mpi->len = i->length;
> +    return true;
> +}
> +
> +static bool GetMPI(struct asn1_der_iterator *i, QCryptoAkCipherMPI *mpi)
> +{
> +    if (asn1_der_iterator_next(i) != ASN1_ITERATOR_PRIMITIVE ||
> +        i->type != ASN1_INTEGER) {
> +        return false;
> +    }
> +    return DumpMPI(i, mpi);
> +}
> +
> +
> +/**
> + *        RsaPrivKey ::= SEQUENCE {
> + *             version     INTEGER
> + *             n           INTEGER
> + *             e           INTEGER
> + *             d           INTEGER
> + *             p           INTEGER
> + *             q           INTEGER
> + *             dp          INTEGER
> + *             dq          INTEGER
> + *             u           INTEGER
> + *       otherPrimeInfos   OtherPrimeInfos OPTIONAL
> + *         }
> + */
> +static QCryptoAkCipherRSAKey *qcrypto_nettle_rsa_private_key_parse(
> +    const uint8_t *key, size_t keylen)
> +{
> +    QCryptoAkCipherRSAKey *rsa = g_new0(QCryptoAkCipherRSAKey, 1);
> +    struct asn1_der_iterator i;
> +    uint32_t version;
> +    int tag;
> +
> +    /* Parse entire struct */
> +    if (asn1_der_iterator_first(&i, keylen, key) != ASN1_ITERATOR_CONSTRUCTED ||
> +        i.type != ASN1_SEQUENCE ||
> +        asn1_der_decode_constructed_last(&i) != ASN1_ITERATOR_PRIMITIVE ||
> +        i.type != ASN1_INTEGER ||
> +        !asn1_der_get_uint32(&i, &version) ||
> +        version > 1 ||
> +        !GetMPI(&i, &rsa->n) ||
> +        !GetMPI(&i, &rsa->e) ||
> +        !GetMPI(&i, &rsa->d) ||
> +        !GetMPI(&i, &rsa->p) ||
> +        !GetMPI(&i, &rsa->q) ||
> +        !GetMPI(&i, &rsa->dp) ||
> +        !GetMPI(&i, &rsa->dq) ||
> +        !GetMPI(&i, &rsa->u)) {
> +        goto error;
> +    }
> +
> +    if (version == 1) {
> +        tag = asn1_der_iterator_next(&i);
> +        /**
> +         * According to the standard otherPrimeInfos must be present for
> +         * version 1. There is no strict verification here, this is to be
> +         * compatible with the unit test of the kernel. TODO: remove this
> +         * until linux-kernel's unit-test is fixed;
> +         */
> +        if (tag == ASN1_ITERATOR_END) {
> +            return rsa;
> +        }
> +        if (tag != ASN1_ITERATOR_CONSTRUCTED ||
> +            i.type != ASN1_SEQUENCE) {
> +            goto error;
> +        }
> +    }
> +
> +    if (asn1_der_iterator_next(&i) != ASN1_ITERATOR_END) {
> +        goto error;
> +    }
> +
> +    return rsa;
> +
> +error:
> +    qcrypto_akcipher_rsakey_free(rsa);
> +    return NULL;
> +}
> +
> +/**
> + *        RsaPubKey ::= SEQUENCE {
> + *             n           INTEGER
> + *             e           INTEGER
> + *         }
> + */
> +static QCryptoAkCipherRSAKey *qcrypto_nettle_rsa_public_key_parse(
> +    const uint8_t *key, size_t keylen)
> +{
> +
> +    QCryptoAkCipherRSAKey *rsa = g_new0(QCryptoAkCipherRSAKey, 1);
> +    struct asn1_der_iterator i;
> +
> +    if (asn1_der_iterator_first(&i, keylen, key) != ASN1_ITERATOR_CONSTRUCTED ||
> +        i.type != ASN1_SEQUENCE ||
> +        asn1_der_decode_constructed_last(&i) != ASN1_ITERATOR_PRIMITIVE ||
> +        !DumpMPI(&i, &rsa->n) ||
> +        !GetMPI(&i, &rsa->e) ||
> +        asn1_der_iterator_next(&i) != ASN1_ITERATOR_END) {
> +        goto error;
> +    }
> +
> +    return rsa;
> +
> +error:
> +    qcrypto_akcipher_rsakey_free(rsa);
> +    return NULL;
> +}
> +
> +QCryptoAkCipherRSAKey *qcrypto_akcipher_rsakey_parse(
> +    QCryptoAkCipherKeyType type, const uint8_t *key, size_t keylen)
> +{
> +    switch (type) {
> +    case QCRYPTO_AKCIPHER_KEY_TYPE_PRIVATE:
> +        return qcrypto_nettle_rsa_private_key_parse(key, keylen);
> +
> +    case QCRYPTO_AKCIPHER_KEY_TYPE_PUBLIC:
> +        return qcrypto_nettle_rsa_public_key_parse(key, keylen);
> +
> +    default:
> +        return NULL;
> +    }
> +}
> diff --git a/crypto/rsakey.c b/crypto/rsakey.c
> new file mode 100644
> index 0000000000..cc40e072f0
> --- /dev/null
> +++ b/crypto/rsakey.c
> @@ -0,0 +1,44 @@
> +/*
> + * QEMU Crypto RSA key parser
> + *
> + * Copyright (c) 2022 Bytedance
> + * Author: lei he <helei.sig11@bytedance.com>
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> + *
> + */
> +
> +#include "rsakey.h"
> +
> +void qcrypto_akcipher_rsakey_free(QCryptoAkCipherRSAKey *rsa_key)
> +{
> +    if (!rsa_key) {
> +        return;
> +    }
> +    g_free(rsa_key->n.data);
> +    g_free(rsa_key->e.data);
> +    g_free(rsa_key->d.data);
> +    g_free(rsa_key->p.data);
> +    g_free(rsa_key->q.data);
> +    g_free(rsa_key->dp.data);
> +    g_free(rsa_key->dq.data);
> +    g_free(rsa_key->u.data);
> +    g_free(rsa_key);
> +}
> +
> +#if defined(CONFIG_NETTLE) && defined(CONFIG_HOGWEED)
> +#include "rsakey-nettle.c.inc"
> +#else
> +#include "rsakey-builtin.c.inc"
> +#endif
> diff --git a/crypto/rsakey.h b/crypto/rsakey.h
> new file mode 100644
> index 0000000000..a1e04ae021
> --- /dev/null
> +++ b/crypto/rsakey.h
> @@ -0,0 +1,94 @@
> +/*
> + * QEMU Crypto RSA key parser
> + *
> + * Copyright (c) 2022 Bytedance
> + * Author: lei he <helei.sig11@bytedance.com>
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see <http://www.gnu.org/licenses/>.
> + *
> + */
> +
> +#ifndef QCRYPTO_RSAKEY_H
> +#define QCRYPTO_RSAKEY_H
> +
> +#include <nettle/bignum.h>
> +
> +#include "qemu/osdep.h"
> +#include "qemu/host-utils.h"
> +#include "crypto/akcipher.h"
> +
> +typedef struct QCryptoAkCipherRSAKey QCryptoAkCipherRSAKey;
> +typedef struct QCryptoAkCipherMPI QCryptoAkCipherMPI;
> +
> +/**
> + * Multiple precious integer, encoded as two' complement,
> + * copied directly from DER encoded ASN.1 structures.
> + */
> +struct QCryptoAkCipherMPI {
> +    uint8_t *data;
> +    size_t len;
> +};
> +
> +/* See rfc2437: https://datatracker.ietf.org/doc/html/rfc2437 */
> +struct QCryptoAkCipherRSAKey {
> +    /* The modulus */
> +    QCryptoAkCipherMPI n;
> +    /* The public exponent */
> +    QCryptoAkCipherMPI e;
> +    /* The private exponent */
> +    QCryptoAkCipherMPI d;
> +    /* The first factor */
> +    QCryptoAkCipherMPI p;
> +    /* The second factor */
> +    QCryptoAkCipherMPI q;
> +    /* The first factor's exponent */
> +    QCryptoAkCipherMPI dp;
> +    /* The second factor's exponent */
> +    QCryptoAkCipherMPI dq;
> +    /* The CRT coefficient */
> +    QCryptoAkCipherMPI u;
> +};
> +
> +/**
> + * Parse DER encoded ASN.1 RSA keys, expected ASN.1 schemas:
> + *        RsaPrivKey ::= SEQUENCE {
> + *             version     INTEGER
> + *             n           INTEGER
> + *             e           INTEGER
> + *             d           INTEGER
> + *             p           INTEGER
> + *             q           INTEGER
> + *             dp          INTEGER
> + *             dq          INTEGER
> + *             u           INTEGER
> + *       otherPrimeInfos   OtherPrimeInfos OPTIONAL
> + *         }
> + *
> + *        RsaPubKey ::= SEQUENCE {
> + *             n           INTEGER
> + *             e           INTEGER
> + *         }
> + *
> + * Returns: On success QCryptoAkCipherRSAKey is returned, otherwise returns NULL
> + */
> +QCryptoAkCipherRSAKey *qcrypto_akcipher_rsakey_parse(
> +    QCryptoAkCipherKeyType type,
> +    const uint8_t *key, size_t keylen);
> +
> +void qcrypto_akcipher_rsakey_free(QCryptoAkCipherRSAKey *key);
> +
> +G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoAkCipherRSAKey,
> +                              qcrypto_akcipher_rsakey_free);
> +
> +#endif
> diff --git a/meson.build b/meson.build
> index d083c6b7bf..fd0bf7aa5d 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -1049,6 +1049,7 @@ endif
>  # gcrypt over nettle for performance reasons.
>  gcrypt = not_found
>  nettle = not_found
> +hogweed = not_found
>  xts = 'none'
>  
>  if get_option('nettle').enabled() and get_option('gcrypt').enabled()
> @@ -1086,6 +1087,15 @@ if not gnutls_crypto.found()
>    endif
>  endif
>  
> +gmp = dependency('gmp', required: false, method: 'pkg-config', kwargs: static_kwargs)
> +if nettle.found() and gmp.found()
> +  hogweed = dependency('hogweed', version: '>=3.4',
> +                       method: 'pkg-config',
> +                       required: get_option('nettle'),
> +                       kwargs: static_kwargs)
> +endif
> +
> +
>  gtk = not_found
>  gtkx11 = not_found
>  vte = not_found
> @@ -1567,6 +1577,7 @@ config_host_data.set('CONFIG_GNUTLS', gnutls.found())
>  config_host_data.set('CONFIG_GNUTLS_CRYPTO', gnutls_crypto.found())
>  config_host_data.set('CONFIG_GCRYPT', gcrypt.found())
>  config_host_data.set('CONFIG_NETTLE', nettle.found())
> +config_host_data.set('CONFIG_HOGWEED', hogweed.found())
>  config_host_data.set('CONFIG_QEMU_PRIVATE_XTS', xts == 'private')
>  config_host_data.set('CONFIG_MALLOC_TRIM', has_malloc_trim)
>  config_host_data.set('CONFIG_STATX', has_statx)
> -- 
> 2.20.1
> 

With regards,
Daniel
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