library/pk_wrap.c

/*
 *  Public Key abstraction layer: wrapper functions
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 */

#include "common.h"

#if defined(MBEDTLS_PK_C)
#include "mbedtls/pk_internal.h"
#include "mbedtls/error.h"

/* Even if RSA not activated, for the sake of RSA-alt */
#include "mbedtls/rsa.h"

#include <string.h>

#if defined(MBEDTLS_ECP_C)
#include "mbedtls/ecp.h"
#endif

#if defined(MBEDTLS_ECDSA_C)
#include "mbedtls/ecdsa.h"
#endif

#if defined(MBEDTLS_USE_PSA_CRYPTO)
#include "mbedtls/asn1write.h"
#endif

#if defined(MBEDTLS_PK_RSA_ALT_SUPPORT)
#include "mbedtls/platform_util.h"
#endif

#if defined(MBEDTLS_USE_PSA_CRYPTO)
#include "psa/crypto.h"
#include "mbedtls/psa_util.h"
#include "mbedtls/asn1.h"
#endif

#include "mbedtls/platform.h"

#include <limits.h>
#include <stdint.h>

#if defined(MBEDTLS_RSA_C)
static int rsa_can_do(mbedtls_pk_type_t type)
{
    return type == MBEDTLS_PK_RSA ||
           type == MBEDTLS_PK_RSASSA_PSS;
}

static size_t rsa_get_bitlen(const void *ctx)
{
    const mbedtls_rsa_context *rsa = (const mbedtls_rsa_context *) ctx;
    /* Unfortunately, the rsa.h interface does not have a direct way
     * to access the bit-length that works with MBEDTLS_RSA_ALT.
     * So we have to do a little work here.
     */
    mbedtls_mpi N;
    mbedtls_mpi_init(&N);
    int ret = mbedtls_rsa_export(rsa, &N, NULL, NULL, NULL, NULL);
    /* If the export fails for some reason (e.g. the RSA_ALT implementation
     * does not support export, or there is not enough memory),
     * we have no way of returning an error from this function.
     * As a fallback, return the byte-length converted in bits, which is
     * the correct  value if the modulus size is a multiple of 8 bits, which
     * is very often the case in practice. */
    size_t bitlen = (ret == 0 ? mbedtls_mpi_bitlen(&N) :
                     8 * mbedtls_rsa_get_len(rsa));
    mbedtls_mpi_free(&N);
    return bitlen;
}

static int rsa_verify_wrap(void *ctx, mbedtls_md_type_t md_alg,
                           const unsigned char *hash, size_t hash_len,
                           const unsigned char *sig, size_t sig_len)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    mbedtls_rsa_context *rsa = (mbedtls_rsa_context *) ctx;
    size_t rsa_len = mbedtls_rsa_get_len(rsa);

#if SIZE_MAX > UINT_MAX
    if (md_alg == MBEDTLS_MD_NONE && UINT_MAX < hash_len) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }
#endif /* SIZE_MAX > UINT_MAX */

    if (sig_len < rsa_len) {
        return MBEDTLS_ERR_RSA_VERIFY_FAILED;
    }

    if ((ret = mbedtls_rsa_pkcs1_verify(rsa, NULL, NULL,
                                        MBEDTLS_RSA_PUBLIC, md_alg,
                                        (unsigned int) hash_len, hash, sig)) != 0) {
        return ret;
    }

    /* The buffer contains a valid signature followed by extra data.
     * We have a special error code for that so that so that callers can
     * use mbedtls_pk_verify() to check "Does the buffer start with a
     * valid signature?" and not just "Does the buffer contain a valid
     * signature?". */
    if (sig_len > rsa_len) {
        return MBEDTLS_ERR_PK_SIG_LEN_MISMATCH;
    }

    return 0;
}

static int rsa_sign_wrap(void *ctx, mbedtls_md_type_t md_alg,
                         const unsigned char *hash, size_t hash_len,
                         unsigned char *sig, size_t *sig_len,
                         int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
    mbedtls_rsa_context *rsa = (mbedtls_rsa_context *) ctx;

#if SIZE_MAX > UINT_MAX
    if (md_alg == MBEDTLS_MD_NONE && UINT_MAX < hash_len) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }
#endif /* SIZE_MAX > UINT_MAX */

    *sig_len = mbedtls_rsa_get_len(rsa);

    return mbedtls_rsa_pkcs1_sign(rsa, f_rng, p_rng, MBEDTLS_RSA_PRIVATE,
                                  md_alg, (unsigned int) hash_len, hash, sig);
}

static int rsa_decrypt_wrap(void *ctx,
                            const unsigned char *input, size_t ilen,
                            unsigned char *output, size_t *olen, size_t osize,
                            int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
    mbedtls_rsa_context *rsa = (mbedtls_rsa_context *) ctx;

    if (ilen != mbedtls_rsa_get_len(rsa)) {
        return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
    }

    return mbedtls_rsa_pkcs1_decrypt(rsa, f_rng, p_rng,
                                     MBEDTLS_RSA_PRIVATE, olen, input, output, osize);
}

static int rsa_encrypt_wrap(void *ctx,
                            const unsigned char *input, size_t ilen,
                            unsigned char *output, size_t *olen, size_t osize,
                            int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
    mbedtls_rsa_context *rsa = (mbedtls_rsa_context *) ctx;
    *olen = mbedtls_rsa_get_len(rsa);

    if (*olen > osize) {
        return MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE;
    }

    return mbedtls_rsa_pkcs1_encrypt(rsa, f_rng, p_rng, MBEDTLS_RSA_PUBLIC,
                                     ilen, input, output);
}

static int rsa_check_pair_wrap(const void *pub, const void *prv)
{
    return mbedtls_rsa_check_pub_priv((const mbedtls_rsa_context *) pub,
                                      (const mbedtls_rsa_context *) prv);
}

static void *rsa_alloc_wrap(void)
{
    void *ctx = mbedtls_calloc(1, sizeof(mbedtls_rsa_context));

    if (ctx != NULL) {
        mbedtls_rsa_init((mbedtls_rsa_context *) ctx, 0, 0);
    }

    return ctx;
}

static void rsa_free_wrap(void *ctx)
{
    mbedtls_rsa_free((mbedtls_rsa_context *) ctx);
    mbedtls_free(ctx);
}

static void rsa_debug(const void *ctx, mbedtls_pk_debug_item *items)
{
    items->type = MBEDTLS_PK_DEBUG_MPI;
    items->name = "rsa.N";
    items->value = &(((mbedtls_rsa_context *) ctx)->N);

    items++;

    items->type = MBEDTLS_PK_DEBUG_MPI;
    items->name = "rsa.E";
    items->value = &(((mbedtls_rsa_context *) ctx)->E);
}

const mbedtls_pk_info_t mbedtls_rsa_info = {
    MBEDTLS_PK_RSA,
    "RSA",
    rsa_get_bitlen,
    rsa_can_do,
    rsa_verify_wrap,
    rsa_sign_wrap,
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    NULL,
    NULL,
#endif
    rsa_decrypt_wrap,
    rsa_encrypt_wrap,
    rsa_check_pair_wrap,
    rsa_alloc_wrap,
    rsa_free_wrap,
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    NULL,
    NULL,
#endif
    rsa_debug,
};
#endif /* MBEDTLS_RSA_C */

#if defined(MBEDTLS_ECP_C)
/*
 * Generic EC key
 */
static int eckey_can_do(mbedtls_pk_type_t type)
{
    return type == MBEDTLS_PK_ECKEY ||
           type == MBEDTLS_PK_ECKEY_DH ||
           type == MBEDTLS_PK_ECDSA;
}

static size_t eckey_get_bitlen(const void *ctx)
{
    return ((mbedtls_ecp_keypair *) ctx)->grp.pbits;
}

#if defined(MBEDTLS_ECDSA_C)
/* Forward declarations */
static int ecdsa_verify_wrap(void *ctx, mbedtls_md_type_t md_alg,
                             const unsigned char *hash, size_t hash_len,
                             const unsigned char *sig, size_t sig_len);

static int ecdsa_sign_wrap(void *ctx, mbedtls_md_type_t md_alg,
                           const unsigned char *hash, size_t hash_len,
                           unsigned char *sig, size_t *sig_len,
                           int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);

static int eckey_verify_wrap(void *ctx, mbedtls_md_type_t md_alg,
                             const unsigned char *hash, size_t hash_len,
                             const unsigned char *sig, size_t sig_len)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    mbedtls_ecdsa_context ecdsa;

    mbedtls_ecdsa_init(&ecdsa);

    if ((ret = mbedtls_ecdsa_from_keypair(&ecdsa, ctx)) == 0) {
        ret = ecdsa_verify_wrap(&ecdsa, md_alg, hash, hash_len, sig, sig_len);
    }

    mbedtls_ecdsa_free(&ecdsa);

    return ret;
}

static int eckey_sign_wrap(void *ctx, mbedtls_md_type_t md_alg,
                           const unsigned char *hash, size_t hash_len,
                           unsigned char *sig, size_t *sig_len,
                           int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    mbedtls_ecdsa_context ecdsa;

    mbedtls_ecdsa_init(&ecdsa);

    if ((ret = mbedtls_ecdsa_from_keypair(&ecdsa, ctx)) == 0) {
        ret = ecdsa_sign_wrap(&ecdsa, md_alg, hash, hash_len, sig, sig_len,
                              f_rng, p_rng);
    }

    mbedtls_ecdsa_free(&ecdsa);

    return ret;
}

#if defined(MBEDTLS_ECP_RESTARTABLE)
/* Forward declarations */
static int ecdsa_verify_rs_wrap(void *ctx, mbedtls_md_type_t md_alg,
                                const unsigned char *hash, size_t hash_len,
                                const unsigned char *sig, size_t sig_len,
                                void *rs_ctx);

static int ecdsa_sign_rs_wrap(void *ctx, mbedtls_md_type_t md_alg,
                              const unsigned char *hash, size_t hash_len,
                              unsigned char *sig, size_t *sig_len,
                              int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
                              void *rs_ctx);

/*
 * Restart context for ECDSA operations with ECKEY context
 *
 * We need to store an actual ECDSA context, as we need to pass the same to
 * the underlying ecdsa function, so we can't create it on the fly every time.
 */
typedef struct {
    mbedtls_ecdsa_restart_ctx ecdsa_rs;
    mbedtls_ecdsa_context ecdsa_ctx;
} eckey_restart_ctx;

static void *eckey_rs_alloc(void)
{
    eckey_restart_ctx *rs_ctx;

    void *ctx = mbedtls_calloc(1, sizeof(eckey_restart_ctx));

    if (ctx != NULL) {
        rs_ctx = ctx;
        mbedtls_ecdsa_restart_init(&rs_ctx->ecdsa_rs);
        mbedtls_ecdsa_init(&rs_ctx->ecdsa_ctx);
    }

    return ctx;
}

static void eckey_rs_free(void *ctx)
{
    eckey_restart_ctx *rs_ctx;

    if (ctx == NULL) {
        return;
    }

    rs_ctx = ctx;
    mbedtls_ecdsa_restart_free(&rs_ctx->ecdsa_rs);
    mbedtls_ecdsa_free(&rs_ctx->ecdsa_ctx);

    mbedtls_free(ctx);
}

static int eckey_verify_rs_wrap(void *ctx, mbedtls_md_type_t md_alg,
                                const unsigned char *hash, size_t hash_len,
                                const unsigned char *sig, size_t sig_len,
                                void *rs_ctx)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    eckey_restart_ctx *rs = rs_ctx;

    /* Should never happen */
    if (rs == NULL) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }

    /* set up our own sub-context if needed (that is, on first run) */
    if (rs->ecdsa_ctx.grp.pbits == 0) {
        MBEDTLS_MPI_CHK(mbedtls_ecdsa_from_keypair(&rs->ecdsa_ctx, ctx));
    }

    MBEDTLS_MPI_CHK(ecdsa_verify_rs_wrap(&rs->ecdsa_ctx,
                                         md_alg, hash, hash_len,
                                         sig, sig_len, &rs->ecdsa_rs));

cleanup:
    return ret;
}

static int eckey_sign_rs_wrap(void *ctx, mbedtls_md_type_t md_alg,
                              const unsigned char *hash, size_t hash_len,
                              unsigned char *sig, size_t *sig_len,
                              int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
                              void *rs_ctx)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    eckey_restart_ctx *rs = rs_ctx;

    /* Should never happen */
    if (rs == NULL) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }

    /* set up our own sub-context if needed (that is, on first run) */
    if (rs->ecdsa_ctx.grp.pbits == 0) {
        MBEDTLS_MPI_CHK(mbedtls_ecdsa_from_keypair(&rs->ecdsa_ctx, ctx));
    }

    MBEDTLS_MPI_CHK(ecdsa_sign_rs_wrap(&rs->ecdsa_ctx, md_alg,
                                       hash, hash_len, sig, sig_len,
                                       f_rng, p_rng, &rs->ecdsa_rs));

cleanup:
    return ret;
}
#endif /* MBEDTLS_ECP_RESTARTABLE */
#endif /* MBEDTLS_ECDSA_C */

static int eckey_check_pair(const void *pub, const void *prv)
{
    return mbedtls_ecp_check_pub_priv((const mbedtls_ecp_keypair *) pub,
                                      (const mbedtls_ecp_keypair *) prv);
}

static void *eckey_alloc_wrap(void)
{
    void *ctx = mbedtls_calloc(1, sizeof(mbedtls_ecp_keypair));

    if (ctx != NULL) {
        mbedtls_ecp_keypair_init(ctx);
    }

    return ctx;
}

static void eckey_free_wrap(void *ctx)
{
    mbedtls_ecp_keypair_free((mbedtls_ecp_keypair *) ctx);
    mbedtls_free(ctx);
}

static void eckey_debug(const void *ctx, mbedtls_pk_debug_item *items)
{
    items->type = MBEDTLS_PK_DEBUG_ECP;
    items->name = "eckey.Q";
    items->value = &(((mbedtls_ecp_keypair *) ctx)->Q);
}

const mbedtls_pk_info_t mbedtls_eckey_info = {
    MBEDTLS_PK_ECKEY,
    "EC",
    eckey_get_bitlen,
    eckey_can_do,
#if defined(MBEDTLS_ECDSA_C)
    eckey_verify_wrap,
    eckey_sign_wrap,
#if defined(MBEDTLS_ECP_RESTARTABLE)
    eckey_verify_rs_wrap,
    eckey_sign_rs_wrap,
#endif
#else /* MBEDTLS_ECDSA_C */
    NULL,
    NULL,
#endif /* MBEDTLS_ECDSA_C */
    NULL,
    NULL,
    eckey_check_pair,
    eckey_alloc_wrap,
    eckey_free_wrap,
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    eckey_rs_alloc,
    eckey_rs_free,
#endif
    eckey_debug,
};

/*
 * EC key restricted to ECDH
 */
static int eckeydh_can_do(mbedtls_pk_type_t type)
{
    return type == MBEDTLS_PK_ECKEY ||
           type == MBEDTLS_PK_ECKEY_DH;
}

const mbedtls_pk_info_t mbedtls_eckeydh_info = {
    MBEDTLS_PK_ECKEY_DH,
    "EC_DH",
    eckey_get_bitlen,         /* Same underlying key structure */
    eckeydh_can_do,
    NULL,
    NULL,
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    NULL,
    NULL,
#endif
    NULL,
    NULL,
    eckey_check_pair,
    eckey_alloc_wrap,       /* Same underlying key structure */
    eckey_free_wrap,        /* Same underlying key structure */
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    NULL,
    NULL,
#endif
    eckey_debug,            /* Same underlying key structure */
};
#endif /* MBEDTLS_ECP_C */

#if defined(MBEDTLS_ECDSA_C)
static int ecdsa_can_do(mbedtls_pk_type_t type)
{
    return type == MBEDTLS_PK_ECDSA;
}

#if defined(MBEDTLS_USE_PSA_CRYPTO)
/*
 * An ASN.1 encoded signature is a sequence of two ASN.1 integers. Parse one of
 * those integers and convert it to the fixed-length encoding expected by PSA.
 */
static int extract_ecdsa_sig_int(unsigned char **from, const unsigned char *end,
                                 unsigned char *to, size_t to_len)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t unpadded_len, padding_len;

    if ((ret = mbedtls_asn1_get_tag(from, end, &unpadded_len,
                                    MBEDTLS_ASN1_INTEGER)) != 0) {
        return ret;
    }

    while (unpadded_len > 0 && **from == 0x00) {
        (*from)++;
        unpadded_len--;
    }

    if (unpadded_len > to_len || unpadded_len == 0) {
        return MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
    }

    padding_len = to_len - unpadded_len;
    memset(to, 0x00, padding_len);
    memcpy(to + padding_len, *from, unpadded_len);
    (*from) += unpadded_len;

    return 0;
}

/*
 * Convert a signature from an ASN.1 sequence of two integers
 * to a raw {r,s} buffer. Note: the provided sig buffer must be at least
 * twice as big as int_size.
 */
static int extract_ecdsa_sig(unsigned char **p, const unsigned char *end,
                             unsigned char *sig, size_t int_size)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t tmp_size;

    if ((ret = mbedtls_asn1_get_tag(p, end, &tmp_size,
                                    MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
        return ret;
    }

    /* Extract r */
    if ((ret = extract_ecdsa_sig_int(p, end, sig, int_size)) != 0) {
        return ret;
    }
    /* Extract s */
    if ((ret = extract_ecdsa_sig_int(p, end, sig + int_size, int_size)) != 0) {
        return ret;
    }

    return 0;
}

static int ecdsa_verify_wrap(void *ctx_arg, mbedtls_md_type_t md_alg,
                             const unsigned char *hash, size_t hash_len,
                             const unsigned char *sig, size_t sig_len)
{
    mbedtls_ecdsa_context *ctx = ctx_arg;
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
    psa_key_id_t key_id = 0;
    psa_status_t status;
    mbedtls_pk_context key;
    int key_len;
    /* see ECP_PUB_DER_MAX_BYTES in pkwrite.c */
    unsigned char buf[30 + 2 * MBEDTLS_ECP_MAX_BYTES];
    unsigned char *p;
    mbedtls_pk_info_t pk_info = mbedtls_eckey_info;
    psa_algorithm_t psa_sig_md = PSA_ALG_ECDSA_ANY;
    size_t curve_bits;
    psa_ecc_family_t curve =
        mbedtls_ecc_group_to_psa(ctx->grp.id, &curve_bits);
    const size_t signature_part_size = (ctx->grp.nbits + 7) / 8;
    ((void) md_alg);

    if (curve == 0) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }

    /* mbedtls_pk_write_pubkey() expects a full PK context;
     * re-construct one to make it happy */
    key.pk_info = &pk_info;
    key.pk_ctx = ctx;
    p = buf + sizeof(buf);
    key_len = mbedtls_pk_write_pubkey(&p, buf, &key);
    if (key_len <= 0) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }

    psa_set_key_type(&attributes, PSA_KEY_TYPE_ECC_PUBLIC_KEY(curve));
    psa_set_key_usage_flags(&attributes, PSA_KEY_USAGE_VERIFY_HASH);
    psa_set_key_algorithm(&attributes, psa_sig_md);

    status = psa_import_key(&attributes,
                            buf + sizeof(buf) - key_len, key_len,
                            &key_id);
    if (status != PSA_SUCCESS) {
        ret = mbedtls_psa_err_translate_pk(status);
        goto cleanup;
    }

    /* We don't need the exported key anymore and can
     * reuse its buffer for signature extraction. */
    if (2 * signature_part_size > sizeof(buf)) {
        ret = MBEDTLS_ERR_PK_BAD_INPUT_DATA;
        goto cleanup;
    }

    p = (unsigned char *) sig;
    if ((ret = extract_ecdsa_sig(&p, sig + sig_len, buf,
                                 signature_part_size)) != 0) {
        goto cleanup;
    }

    if (psa_verify_hash(key_id, psa_sig_md,
                        hash, hash_len,
                        buf, 2 * signature_part_size)
        != PSA_SUCCESS) {
        ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
        goto cleanup;
    }

    if (p != sig + sig_len) {
        ret = MBEDTLS_ERR_PK_SIG_LEN_MISMATCH;
        goto cleanup;
    }
    ret = 0;

cleanup:
    psa_destroy_key(key_id);
    return ret;
}
#else /* MBEDTLS_USE_PSA_CRYPTO */
static int ecdsa_verify_wrap(void *ctx, mbedtls_md_type_t md_alg,
                             const unsigned char *hash, size_t hash_len,
                             const unsigned char *sig, size_t sig_len)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    ((void) md_alg);

    ret = mbedtls_ecdsa_read_signature((mbedtls_ecdsa_context *) ctx,
                                       hash, hash_len, sig, sig_len);

    if (ret == MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH) {
        return MBEDTLS_ERR_PK_SIG_LEN_MISMATCH;
    }

    return ret;
}
#endif /* MBEDTLS_USE_PSA_CRYPTO */

static int ecdsa_sign_wrap(void *ctx, mbedtls_md_type_t md_alg,
                           const unsigned char *hash, size_t hash_len,
                           unsigned char *sig, size_t *sig_len,
                           int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
    return mbedtls_ecdsa_write_signature((mbedtls_ecdsa_context *) ctx,
                                         md_alg, hash, hash_len, sig, sig_len, f_rng, p_rng);
}

#if defined(MBEDTLS_ECP_RESTARTABLE)
static int ecdsa_verify_rs_wrap(void *ctx, mbedtls_md_type_t md_alg,
                                const unsigned char *hash, size_t hash_len,
                                const unsigned char *sig, size_t sig_len,
                                void *rs_ctx)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    ((void) md_alg);

    ret = mbedtls_ecdsa_read_signature_restartable(
        (mbedtls_ecdsa_context *) ctx,
        hash, hash_len, sig, sig_len,
        (mbedtls_ecdsa_restart_ctx *) rs_ctx);

    if (ret == MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH) {
        return MBEDTLS_ERR_PK_SIG_LEN_MISMATCH;
    }

    return ret;
}

static int ecdsa_sign_rs_wrap(void *ctx, mbedtls_md_type_t md_alg,
                              const unsigned char *hash, size_t hash_len,
                              unsigned char *sig, size_t *sig_len,
                              int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
                              void *rs_ctx)
{
    return mbedtls_ecdsa_write_signature_restartable(
        (mbedtls_ecdsa_context *) ctx,
        md_alg, hash, hash_len, sig, sig_len, f_rng, p_rng,
        (mbedtls_ecdsa_restart_ctx *) rs_ctx);

}
#endif /* MBEDTLS_ECP_RESTARTABLE */

static void *ecdsa_alloc_wrap(void)
{
    void *ctx = mbedtls_calloc(1, sizeof(mbedtls_ecdsa_context));

    if (ctx != NULL) {
        mbedtls_ecdsa_init((mbedtls_ecdsa_context *) ctx);
    }

    return ctx;
}

static void ecdsa_free_wrap(void *ctx)
{
    mbedtls_ecdsa_free((mbedtls_ecdsa_context *) ctx);
    mbedtls_free(ctx);
}

#if defined(MBEDTLS_ECP_RESTARTABLE)
static void *ecdsa_rs_alloc(void)
{
    void *ctx = mbedtls_calloc(1, sizeof(mbedtls_ecdsa_restart_ctx));

    if (ctx != NULL) {
        mbedtls_ecdsa_restart_init(ctx);
    }

    return ctx;
}

static void ecdsa_rs_free(void *ctx)
{
    mbedtls_ecdsa_restart_free(ctx);
    mbedtls_free(ctx);
}
#endif /* MBEDTLS_ECP_RESTARTABLE */

const mbedtls_pk_info_t mbedtls_ecdsa_info = {
    MBEDTLS_PK_ECDSA,
    "ECDSA",
    eckey_get_bitlen,     /* Compatible key structures */
    ecdsa_can_do,
    ecdsa_verify_wrap,
    ecdsa_sign_wrap,
#if defined(MBEDTLS_ECP_RESTARTABLE)
    ecdsa_verify_rs_wrap,
    ecdsa_sign_rs_wrap,
#endif
    NULL,
    NULL,
    eckey_check_pair,   /* Compatible key structures */
    ecdsa_alloc_wrap,
    ecdsa_free_wrap,
#if defined(MBEDTLS_ECP_RESTARTABLE)
    ecdsa_rs_alloc,
    ecdsa_rs_free,
#endif
    eckey_debug,        /* Compatible key structures */
};
#endif /* MBEDTLS_ECDSA_C */

#if defined(MBEDTLS_PK_RSA_ALT_SUPPORT)
/*
 * Support for alternative RSA-private implementations
 */

static int rsa_alt_can_do(mbedtls_pk_type_t type)
{
    return type == MBEDTLS_PK_RSA;
}

static size_t rsa_alt_get_bitlen(const void *ctx)
{
    const mbedtls_rsa_alt_context *rsa_alt = (const mbedtls_rsa_alt_context *) ctx;

    return 8 * rsa_alt->key_len_func(rsa_alt->key);
}

static int rsa_alt_sign_wrap(void *ctx, mbedtls_md_type_t md_alg,
                             const unsigned char *hash, size_t hash_len,
                             unsigned char *sig, size_t *sig_len,
                             int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
    mbedtls_rsa_alt_context *rsa_alt = (mbedtls_rsa_alt_context *) ctx;

#if SIZE_MAX > UINT_MAX
    if (UINT_MAX < hash_len) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }
#endif /* SIZE_MAX > UINT_MAX */

    *sig_len = rsa_alt->key_len_func(rsa_alt->key);
    if (*sig_len > MBEDTLS_PK_SIGNATURE_MAX_SIZE) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }

    return rsa_alt->sign_func(rsa_alt->key, f_rng, p_rng, MBEDTLS_RSA_PRIVATE,
                              md_alg, (unsigned int) hash_len, hash, sig);
}

static int rsa_alt_decrypt_wrap(void *ctx,
                                const unsigned char *input, size_t ilen,
                                unsigned char *output, size_t *olen, size_t osize,
                                int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
    mbedtls_rsa_alt_context *rsa_alt = (mbedtls_rsa_alt_context *) ctx;

    ((void) f_rng);
    ((void) p_rng);

    if (ilen != rsa_alt->key_len_func(rsa_alt->key)) {
        return MBEDTLS_ERR_RSA_BAD_INPUT_DATA;
    }

    return rsa_alt->decrypt_func(rsa_alt->key,
                                 MBEDTLS_RSA_PRIVATE, olen, input, output, osize);
}

#if defined(MBEDTLS_RSA_C)
static int rsa_alt_check_pair(const void *pub, const void *prv)
{
    unsigned char sig[MBEDTLS_MPI_MAX_SIZE];
    unsigned char hash[32];
    size_t sig_len = 0;
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    if (rsa_alt_get_bitlen(prv) != rsa_get_bitlen(pub)) {
        return MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
    }

    memset(hash, 0x2a, sizeof(hash));

    if ((ret = rsa_alt_sign_wrap((void *) prv, MBEDTLS_MD_NONE,
                                 hash, sizeof(hash),
                                 sig, &sig_len, NULL, NULL)) != 0) {
        return ret;
    }

    if (rsa_verify_wrap((void *) pub, MBEDTLS_MD_NONE,
                        hash, sizeof(hash), sig, sig_len) != 0) {
        return MBEDTLS_ERR_RSA_KEY_CHECK_FAILED;
    }

    return 0;
}
#endif /* MBEDTLS_RSA_C */

static void *rsa_alt_alloc_wrap(void)
{
    void *ctx = mbedtls_calloc(1, sizeof(mbedtls_rsa_alt_context));

    if (ctx != NULL) {
        memset(ctx, 0, sizeof(mbedtls_rsa_alt_context));
    }

    return ctx;
}

static void rsa_alt_free_wrap(void *ctx)
{
    mbedtls_platform_zeroize(ctx, sizeof(mbedtls_rsa_alt_context));
    mbedtls_free(ctx);
}

const mbedtls_pk_info_t mbedtls_rsa_alt_info = {
    MBEDTLS_PK_RSA_ALT,
    "RSA-alt",
    rsa_alt_get_bitlen,
    rsa_alt_can_do,
    NULL,
    rsa_alt_sign_wrap,
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    NULL,
    NULL,
#endif
    rsa_alt_decrypt_wrap,
    NULL,
#if defined(MBEDTLS_RSA_C)
    rsa_alt_check_pair,
#else
    NULL,
#endif
    rsa_alt_alloc_wrap,
    rsa_alt_free_wrap,
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    NULL,
    NULL,
#endif
    NULL,
};

#endif /* MBEDTLS_PK_RSA_ALT_SUPPORT */

#if defined(MBEDTLS_USE_PSA_CRYPTO)

static void *pk_opaque_alloc_wrap(void)
{
    void *ctx = mbedtls_calloc(1, sizeof(psa_key_id_t));

    /* no _init() function to call, as calloc() already zeroized */

    return ctx;
}

static void pk_opaque_free_wrap(void *ctx)
{
    mbedtls_platform_zeroize(ctx, sizeof(psa_key_id_t));
    mbedtls_free(ctx);
}

static size_t pk_opaque_get_bitlen(const void *ctx)
{
    const psa_key_id_t *key = (const psa_key_id_t *) ctx;
    size_t bits;
    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;

    if (PSA_SUCCESS != psa_get_key_attributes(*key, &attributes)) {
        return 0;
    }

    bits = psa_get_key_bits(&attributes);
    psa_reset_key_attributes(&attributes);
    return bits;
}

static int pk_opaque_can_do(mbedtls_pk_type_t type)
{
    /* For now opaque PSA keys can only wrap ECC keypairs,
     * as checked by setup_psa().
     * Also, ECKEY_DH does not really make sense with the current API. */
    return type == MBEDTLS_PK_ECKEY ||
           type == MBEDTLS_PK_ECDSA;
}

#if defined(MBEDTLS_ECDSA_C)

/*
 * Simultaneously convert and move raw MPI from the beginning of a buffer
 * to an ASN.1 MPI at the end of the buffer.
 * See also mbedtls_asn1_write_mpi().
 *
 * p: pointer to the end of the output buffer
 * start: start of the output buffer, and also of the mpi to write at the end
 * n_len: length of the mpi to read from start
 */
static int asn1_write_mpibuf(unsigned char **p, unsigned char *start,
                             size_t n_len)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t len = 0;

    if ((size_t) (*p - start) < n_len) {
        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
    }

    len = n_len;
    *p -= len;
    memmove(*p, start, len);

    /* ASN.1 DER encoding requires minimal length, so skip leading 0s.
     * Neither r nor s should be 0, but as a failsafe measure, still detect
     * that rather than overflowing the buffer in case of a PSA error. */
    while (len > 0 && **p == 0x00) {
        ++(*p);
        --len;
    }

    /* this is only reached if the signature was invalid */
    if (len == 0) {
        return MBEDTLS_ERR_PK_HW_ACCEL_FAILED;
    }

    /* if the msb is 1, ASN.1 requires that we prepend a 0.
     * Neither r nor s can be 0, so we can assume len > 0 at all times. */
    if (**p & 0x80) {
        if (*p - start < 1) {
            return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
        }

        *--(*p) = 0x00;
        len += 1;
    }

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start,
                                                     MBEDTLS_ASN1_INTEGER));

    return (int) len;
}

/* Transcode signature from PSA format to ASN.1 sequence.
 * See ecdsa_signature_to_asn1 in ecdsa.c, but with byte buffers instead of
 * MPIs, and in-place.
 *
 * [in/out] sig: the signature pre- and post-transcoding
 * [in/out] sig_len: signature length pre- and post-transcoding
 * [int] buf_len: the available size the in/out buffer
 */
static int pk_ecdsa_sig_asn1_from_psa(unsigned char *sig, size_t *sig_len,
                                      size_t buf_len)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t len = 0;
    const size_t rs_len = *sig_len / 2;
    unsigned char *p = sig + buf_len;

    MBEDTLS_ASN1_CHK_ADD(len, asn1_write_mpibuf(&p, sig + rs_len, rs_len));
    MBEDTLS_ASN1_CHK_ADD(len, asn1_write_mpibuf(&p, sig, rs_len));

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&p, sig, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&p, sig,
                                                     MBEDTLS_ASN1_CONSTRUCTED |
                                                     MBEDTLS_ASN1_SEQUENCE));

    memmove(sig, p, len);
    *sig_len = len;

    return 0;
}

#endif /* MBEDTLS_ECDSA_C */

static int pk_opaque_sign_wrap(void *ctx, mbedtls_md_type_t md_alg,
                               const unsigned char *hash, size_t hash_len,
                               unsigned char *sig, size_t *sig_len,
                               int (*f_rng)(void *, unsigned char *, size_t), void *p_rng)
{
#if !defined(MBEDTLS_ECDSA_C)
    ((void) ctx);
    ((void) md_alg);
    ((void) hash);
    ((void) hash_len);
    ((void) sig);
    ((void) sig_len);
    ((void) f_rng);
    ((void) p_rng);
    return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
#else /* !MBEDTLS_ECDSA_C */
    const psa_key_id_t *key = (const psa_key_id_t *) ctx;
    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
    psa_algorithm_t alg = PSA_ALG_ECDSA(mbedtls_psa_translate_md(md_alg));
    size_t buf_len;
    psa_status_t status;

    /* PSA has its own RNG */
    (void) f_rng;
    (void) p_rng;

    /* PSA needs an output buffer of known size, but our API doesn't provide
     * that information. Assume that the buffer is large enough for a
     * maximal-length signature with that key (otherwise the application is
     * buggy anyway). */
    status = psa_get_key_attributes(*key, &attributes);
    if (status != PSA_SUCCESS) {
        return mbedtls_psa_err_translate_pk(status);
    }
    buf_len = MBEDTLS_ECDSA_MAX_SIG_LEN(psa_get_key_bits(&attributes));
    psa_reset_key_attributes(&attributes);
    if (buf_len > MBEDTLS_PK_SIGNATURE_MAX_SIZE) {
        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
    }

    /* make the signature */
    status = psa_sign_hash(*key, alg, hash, hash_len,
                           sig, buf_len, sig_len);
    if (status != PSA_SUCCESS) {
        return mbedtls_psa_err_translate_pk(status);
    }

    /* transcode it to ASN.1 sequence */
    return pk_ecdsa_sig_asn1_from_psa(sig, sig_len, buf_len);
#endif /* !MBEDTLS_ECDSA_C */
}

const mbedtls_pk_info_t mbedtls_pk_opaque_info = {
    MBEDTLS_PK_OPAQUE,
    "Opaque",
    pk_opaque_get_bitlen,
    pk_opaque_can_do,
    NULL, /* verify - will be done later */
    pk_opaque_sign_wrap,
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    NULL, /* restartable verify - not relevant */
    NULL, /* restartable sign - not relevant */
#endif
    NULL, /* decrypt - will be done later */
    NULL, /* encrypt - will be done later */
    NULL, /* check_pair - could be done later or left NULL */
    pk_opaque_alloc_wrap,
    pk_opaque_free_wrap,
#if defined(MBEDTLS_ECDSA_C) && defined(MBEDTLS_ECP_RESTARTABLE)
    NULL, /* restart alloc - not relevant */
    NULL, /* restart free - not relevant */
#endif
    NULL, /* debug - could be done later, or even left NULL */
};

#endif /* MBEDTLS_USE_PSA_CRYPTO */

#endif /* MBEDTLS_PK_C */