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/*

 *  Elliptic curve DSA

 *

 *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved

 *  SPDX-License-Identifier: GPL-2.0

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; either version 2 of the License, or

 *  (at your option) any later version.

 *

 *  This program 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 General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License along

 *  with this program; if not, write to the Free Software Foundation, Inc.,

 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 *  This file is part of mbed TLS (https://tls.mbed.org)

 */

/*

 * References:

 *

 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg

 */

#if !defined(MBEDTLS_CONFIG_FILE)

#include "mbedtls/config.h"

#else

#include MBEDTLS_CONFIG_FILE

#endif

#if defined(MBEDTLS_ECDSA_C)

#include "mbedtls/ecdsa.h"

#include "mbedtls/asn1write.h"

#include 

#if defined(MBEDTLS_ECDSA_DETERMINISTIC)

#include "mbedtls/hmac_drbg.h"

#endif

#if defined(MBEDTLS_PLATFORM_C)

#include "mbedtls/platform.h"

#else

#include 

#define mbedtls_calloc    calloc

#define mbedtls_free       free

#endif

#include "mbedtls/platform_util.h"

/* Parameter validation macros based on platform_util.h */

#define ECDSA_VALIDATE_RET( cond )    \

    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_ECP_BAD_INPUT_DATA )

#define ECDSA_VALIDATE( cond )        \

    MBEDTLS_INTERNAL_VALIDATE( cond )

#if defined(MBEDTLS_ECP_RESTARTABLE)

/*

 * Sub-context for ecdsa_verify()

 */

struct mbedtls_ecdsa_restart_ver

{

    mbedtls_mpi u1, u2;     /* intermediate values  */

    enum {                  /* what to do next?     */

        ecdsa_ver_init = 0, /* getting started      */

        ecdsa_ver_muladd,   /* muladd step          */

    } state;

};

/*

 * Init verify restart sub-context

 */

static void ecdsa_restart_ver_init( mbedtls_ecdsa_restart_ver_ctx *ctx )

{

    mbedtls_mpi_init( &ctx->u1 );

    mbedtls_mpi_init( &ctx->u2 );

    ctx->state = ecdsa_ver_init;

}

/*

 * Free the components of a verify restart sub-context

 */

static void ecdsa_restart_ver_free( mbedtls_ecdsa_restart_ver_ctx *ctx )

{

    if( ctx == NULL )

        return;

    mbedtls_mpi_free( &ctx->u1 );

    mbedtls_mpi_free( &ctx->u2 );

    ecdsa_restart_ver_init( ctx );

}

/*

 * Sub-context for ecdsa_sign()

 */

struct mbedtls_ecdsa_restart_sig

{

    int sign_tries;

    int key_tries;

    mbedtls_mpi k;          /* per-signature random */

    mbedtls_mpi r;          /* r value              */

    enum {                  /* what to do next?     */

        ecdsa_sig_init = 0, /* getting started      */

        ecdsa_sig_mul,      /* doing ecp_mul()      */

        ecdsa_sig_modn,     /* mod N computations   */

    } state;

};

/*

 * Init verify sign sub-context

 */

static void ecdsa_restart_sig_init( mbedtls_ecdsa_restart_sig_ctx *ctx )

{

    ctx->sign_tries = 0;

    ctx->key_tries = 0;

    mbedtls_mpi_init( &ctx->k );

    mbedtls_mpi_init( &ctx->r );

    ctx->state = ecdsa_sig_init;

}

/*

 * Free the components of a sign restart sub-context

 */

static void ecdsa_restart_sig_free( mbedtls_ecdsa_restart_sig_ctx *ctx )

{

    if( ctx == NULL )

        return;

    mbedtls_mpi_free( &ctx->k );

    mbedtls_mpi_free( &ctx->r );

}

#if defined(MBEDTLS_ECDSA_DETERMINISTIC)

/*

 * Sub-context for ecdsa_sign_det()

 */

struct mbedtls_ecdsa_restart_det

{

    mbedtls_hmac_drbg_context rng_ctx;  /* DRBG state   */

    enum {                      /* what to do next?     */

        ecdsa_det_init = 0,     /* getting started      */

        ecdsa_det_sign,         /* make signature       */

    } state;

};

/*

 * Init verify sign_det sub-context

 */

static void ecdsa_restart_det_init( mbedtls_ecdsa_restart_det_ctx *ctx )

{

    mbedtls_hmac_drbg_init( &ctx->rng_ctx );

    ctx->state = ecdsa_det_init;

}

/*

 * Free the components of a sign_det restart sub-context

 */

static void ecdsa_restart_det_free( mbedtls_ecdsa_restart_det_ctx *ctx )

{

    if( ctx == NULL )

        return;

    mbedtls_hmac_drbg_free( &ctx->rng_ctx );

    ecdsa_restart_det_init( ctx );

}

#endif /* MBEDTLS_ECDSA_DETERMINISTIC */

#define ECDSA_RS_ECP    ( rs_ctx == NULL ? NULL : &rs_ctx->ecp )

/* Utility macro for checking and updating ops budget */

#define ECDSA_BUDGET( ops )   \

    MBEDTLS_MPI_CHK( mbedtls_ecp_check_budget( grp, ECDSA_RS_ECP, ops ) );

/* Call this when entering a function that needs its own sub-context */

#define ECDSA_RS_ENTER( SUB )   do {                                 \

    /* reset ops count for this call if top-level */                 \

    if( rs_ctx != NULL && rs_ctx->ecp.depth++ == 0 )                 \

        rs_ctx->ecp.ops_done = 0;                                    \

                                                                     \

    /* set up our own sub-context if needed */                       \

    if( mbedtls_ecp_restart_is_enabled() &&                          \

        rs_ctx != NULL && rs_ctx->SUB == NULL )                      \

    {                                                                \

        rs_ctx->SUB = mbedtls_calloc( 1, sizeof( *rs_ctx->SUB ) );   \

        if( rs_ctx->SUB == NULL )                                    \

            return( MBEDTLS_ERR_ECP_ALLOC_FAILED );                  \

                                                                     \

        ecdsa_restart_## SUB ##_init( rs_ctx->SUB );                 \

    }                                                                \

} while( 0 )

/* Call this when leaving a function that needs its own sub-context */

#define ECDSA_RS_LEAVE( SUB )   do {                                 \

    /* clear our sub-context when not in progress (done or error) */ \

    if( rs_ctx != NULL && rs_ctx->SUB != NULL &&                     \

        ret != MBEDTLS_ERR_ECP_IN_PROGRESS )                         \

    {                                                                \

        ecdsa_restart_## SUB ##_free( rs_ctx->SUB );                 \

        mbedtls_free( rs_ctx->SUB );                                 \

        rs_ctx->SUB = NULL;                                          \

    }                                                                \

                                                                     \

    if( rs_ctx != NULL )                                             \

        rs_ctx->ecp.depth--;                                         \

} while( 0 )

#else /* MBEDTLS_ECP_RESTARTABLE */

#define ECDSA_RS_ECP    NULL

#define ECDSA_BUDGET( ops )   /* no-op; for compatibility */

#define ECDSA_RS_ENTER( SUB )   (void) rs_ctx

#define ECDSA_RS_LEAVE( SUB )   (void) rs_ctx

#endif /* MBEDTLS_ECP_RESTARTABLE */

/*

 * Derive a suitable integer for group grp from a buffer of length len

 * SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3

 */

static int derive_mpi( const mbedtls_ecp_group *grp, mbedtls_mpi *x,

                       const unsigned char *buf, size_t blen )

{

    int ret;

    size_t n_size = ( grp->nbits + 7 ) / 8;

    size_t use_size = blen > n_size ? n_size : blen;

    MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( x, buf, use_size ) );

    if( use_size * 8 > grp->nbits )

        MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( x, use_size * 8 - grp->nbits ) );

    /* While at it, reduce modulo N */

    if( mbedtls_mpi_cmp_mpi( x, &grp->N ) >= 0 )

        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( x, x, &grp->N ) );

cleanup:

    return( ret );

}

#if !defined(MBEDTLS_ECDSA_SIGN_ALT)

/*

 * Compute ECDSA signature of a hashed message (SEC1 4.1.3)

 * Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message)

 */

static int ecdsa_sign_restartable( mbedtls_ecp_group *grp,

                mbedtls_mpi *r, mbedtls_mpi *s,

                const mbedtls_mpi *d, const unsigned char *buf, size_t blen,

                int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,

                int (*f_rng_blind)(void *, unsigned char *, size_t),

                void *p_rng_blind,

                mbedtls_ecdsa_restart_ctx *rs_ctx )

{

    int ret, key_tries, sign_tries;

    int *p_sign_tries = &sign_tries, *p_key_tries = &key_tries;

    mbedtls_ecp_point R;

    mbedtls_mpi k, e, t;

    mbedtls_mpi *pk = &k, *pr = r;

    /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */

    if( grp->N.p == NULL )

        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );

    /* Make sure d is in range 1..n-1 */

    if( mbedtls_mpi_cmp_int( d, 1 ) < 0 || mbedtls_mpi_cmp_mpi( d, &grp->N ) >= 0 )

        return( MBEDTLS_ERR_ECP_INVALID_KEY );

    mbedtls_ecp_point_init( &R );

    mbedtls_mpi_init( &k ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &t );

    ECDSA_RS_ENTER( sig );

#if defined(MBEDTLS_ECP_RESTARTABLE)

    if( rs_ctx != NULL && rs_ctx->sig != NULL )

    {

        /* redirect to our context */

        p_sign_tries = &rs_ctx->sig->sign_tries;

        p_key_tries = &rs_ctx->sig->key_tries;

        pk = &rs_ctx->sig->k;

        pr = &rs_ctx->sig->r;

        /* jump to current step */

        if( rs_ctx->sig->state == ecdsa_sig_mul )

            goto mul;

        if( rs_ctx->sig->state == ecdsa_sig_modn )

            goto modn;

    }

#endif /* MBEDTLS_ECP_RESTARTABLE */

    *p_sign_tries = 0;

    do

    {

        if( (*p_sign_tries)++ > 10 )

        {

            ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;

            goto cleanup;

        }

        /*

         * Steps 1-3: generate a suitable ephemeral keypair

         * and set r = xR mod n

         */

        *p_key_tries = 0;

        do

        {

            if( (*p_key_tries)++ > 10 )

            {

                ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;

                goto cleanup;

            }

            MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, pk, f_rng, p_rng ) );

#if defined(MBEDTLS_ECP_RESTARTABLE)

            if( rs_ctx != NULL && rs_ctx->sig != NULL )

                rs_ctx->sig->state = ecdsa_sig_mul;

mul:

#endif

            MBEDTLS_MPI_CHK( mbedtls_ecp_mul_restartable( grp, &R, pk, &grp->G,

                                                          f_rng_blind,

                                                          p_rng_blind,

                                                          ECDSA_RS_ECP ) );

            MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pr, &R.X, &grp->N ) );

        }

        while( mbedtls_mpi_cmp_int( pr, 0 ) == 0 );

#if defined(MBEDTLS_ECP_RESTARTABLE)

        if( rs_ctx != NULL && rs_ctx->sig != NULL )

            rs_ctx->sig->state = ecdsa_sig_modn;

modn:

#endif

        /*

         * Accounting for everything up to the end of the loop

         * (step 6, but checking now avoids saving e and t)

         */

        ECDSA_BUDGET( MBEDTLS_ECP_OPS_INV + 4 );

        /*

         * Step 5: derive MPI from hashed message

         */

        MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );

        /*

         * Generate a random value to blind inv_mod in next step,

         * avoiding a potential timing leak.

         */

        MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, &t, f_rng_blind,

                                                  p_rng_blind ) );

        /*

         * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n

         */

        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, pr, d ) );

        MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) );

        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) );

        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pk, pk, &t ) );

        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pk, pk, &grp->N ) );

        MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, pk, &grp->N ) );

        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) );

        MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) );

    }

    while( mbedtls_mpi_cmp_int( s, 0 ) == 0 );

#if defined(MBEDTLS_ECP_RESTARTABLE)

    if( rs_ctx != NULL && rs_ctx->sig != NULL )

        mbedtls_mpi_copy( r, pr );

#endif

cleanup:

    mbedtls_ecp_point_free( &R );

    mbedtls_mpi_free( &k ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &t );

    ECDSA_RS_LEAVE( sig );

    return( ret );

}

/*

 * Compute ECDSA signature of a hashed message

 */

int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,

                const mbedtls_mpi *d, const unsigned char *buf, size_t blen,

                int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )

{

    ECDSA_VALIDATE_RET( grp   != NULL );

    ECDSA_VALIDATE_RET( r     != NULL );

    ECDSA_VALIDATE_RET( s     != NULL );

    ECDSA_VALIDATE_RET( d     != NULL );

    ECDSA_VALIDATE_RET( f_rng != NULL );

    ECDSA_VALIDATE_RET( buf   != NULL || blen == 0 );

    /* Use the same RNG for both blinding and ephemeral key generation */

    return( ecdsa_sign_restartable( grp, r, s, d, buf, blen,

                                    f_rng, p_rng, f_rng, p_rng, NULL ) );

}

#endif /* !MBEDTLS_ECDSA_SIGN_ALT */

#if defined(MBEDTLS_ECDSA_DETERMINISTIC)

/*

 * Deterministic signature wrapper

 */

static int ecdsa_sign_det_restartable( mbedtls_ecp_group *grp,

                    mbedtls_mpi *r, mbedtls_mpi *s,

                    const mbedtls_mpi *d, const unsigned char *buf, size_t blen,

                    mbedtls_md_type_t md_alg,

                    int (*f_rng_blind)(void *, unsigned char *, size_t),

                    void *p_rng_blind,

                    mbedtls_ecdsa_restart_ctx *rs_ctx )

{

    int ret;

    mbedtls_hmac_drbg_context rng_ctx;

    mbedtls_hmac_drbg_context *p_rng = &rng_ctx;

    unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES];

    size_t grp_len = ( grp->nbits + 7 ) / 8;

    const mbedtls_md_info_t *md_info;

    mbedtls_mpi h;

    if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL )

        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );

    mbedtls_mpi_init( &h );

    mbedtls_hmac_drbg_init( &rng_ctx );

    ECDSA_RS_ENTER( det );

#if defined(MBEDTLS_ECP_RESTARTABLE)

    if( rs_ctx != NULL && rs_ctx->det != NULL )

    {

        /* redirect to our context */

        p_rng = &rs_ctx->det->rng_ctx;

        /* jump to current step */

        if( rs_ctx->det->state == ecdsa_det_sign )

            goto sign;

    }

#endif /* MBEDTLS_ECP_RESTARTABLE */

    /* Use private key and message hash (reduced) to initialize HMAC_DRBG */

    MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, data, grp_len ) );

    MBEDTLS_MPI_CHK( derive_mpi( grp, &h, buf, blen ) );

    MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, data + grp_len, grp_len ) );

    mbedtls_hmac_drbg_seed_buf( p_rng, md_info, data, 2 * grp_len );

#if defined(MBEDTLS_ECP_RESTARTABLE)

    if( rs_ctx != NULL && rs_ctx->det != NULL )

        rs_ctx->det->state = ecdsa_det_sign;

sign:

#endif

#if defined(MBEDTLS_ECDSA_SIGN_ALT)

    ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen,

                              mbedtls_hmac_drbg_random, p_rng );

#else

    if( f_rng_blind != NULL )

        ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen,

                                      mbedtls_hmac_drbg_random, p_rng,

                                      f_rng_blind, p_rng_blind, rs_ctx );

    else

    {

        mbedtls_hmac_drbg_context *p_rng_blind_det;

#if !defined(MBEDTLS_ECP_RESTARTABLE)

        /*

         * To avoid reusing rng_ctx and risking incorrect behavior we seed a

         * second HMAC-DRBG with the same seed. We also apply a label to avoid

         * reusing the bits of the ephemeral key for blinding and eliminate the

         * risk that they leak this way.

         */

        const char* blind_label = "BLINDING CONTEXT";

        mbedtls_hmac_drbg_context rng_ctx_blind;

        mbedtls_hmac_drbg_init( &rng_ctx_blind );

        p_rng_blind_det = &rng_ctx_blind;

        mbedtls_hmac_drbg_seed_buf( p_rng_blind_det, md_info,

                                    data, 2 * grp_len );

        ret = mbedtls_hmac_drbg_update_ret( p_rng_blind_det,

                                            (const unsigned char*) blind_label,

                                            strlen( blind_label ) );

        if( ret != 0 )

        {

            mbedtls_hmac_drbg_free( &rng_ctx_blind );

            goto cleanup;

        }

#else

        /*

         * In the case of restartable computations we would either need to store

         * the second RNG in the restart context too or set it up at every

         * restart. The first option would penalize the correct application of

         * the function and the second would defeat the purpose of the

         * restartable feature.

         *

         * Therefore in this case we reuse the original RNG. This comes with the

         * price that the resulting signature might not be a valid deterministic

         * ECDSA signature with a very low probability (same magnitude as

         * successfully guessing the private key). However even then it is still

         * a valid ECDSA signature.

         */

        p_rng_blind_det = p_rng;

#endif /* MBEDTLS_ECP_RESTARTABLE */

        /*

         * Since the output of the RNGs is always the same for the same key and

         * message, this limits the efficiency of blinding and leaks information

         * through side channels. After mbedtls_ecdsa_sign_det() is removed NULL

         * won't be a valid value for f_rng_blind anymore. Therefore it should

         * be checked by the caller and this branch and check can be removed.

         */

        ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen,

                                      mbedtls_hmac_drbg_random, p_rng,

                                      mbedtls_hmac_drbg_random, p_rng_blind_det,

                                      rs_ctx );

#if !defined(MBEDTLS_ECP_RESTARTABLE)

        mbedtls_hmac_drbg_free( &rng_ctx_blind );

#endif

    }

#endif /* MBEDTLS_ECDSA_SIGN_ALT */

cleanup:

    mbedtls_hmac_drbg_free( &rng_ctx );

    mbedtls_mpi_free( &h );

    ECDSA_RS_LEAVE( det );

    return( ret );

}

/*

 * Deterministic signature wrappers

 */

int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r,

                            mbedtls_mpi *s, const mbedtls_mpi *d,

                            const unsigned char *buf, size_t blen,

                            mbedtls_md_type_t md_alg )

{

    ECDSA_VALIDATE_RET( grp   != NULL );

    ECDSA_VALIDATE_RET( r     != NULL );

    ECDSA_VALIDATE_RET( s     != NULL );

    ECDSA_VALIDATE_RET( d     != NULL );

    ECDSA_VALIDATE_RET( buf   != NULL || blen == 0 );

    return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg,

                                        NULL, NULL, NULL ) );

}

int mbedtls_ecdsa_sign_det_ext( mbedtls_ecp_group *grp, mbedtls_mpi *r,

                                mbedtls_mpi *s, const mbedtls_mpi *d,

                                const unsigned char *buf, size_t blen,

                                mbedtls_md_type_t md_alg,

                                int (*f_rng_blind)(void *, unsigned char *,

                                                   size_t),

                                void *p_rng_blind )

{

    ECDSA_VALIDATE_RET( grp   != NULL );

    ECDSA_VALIDATE_RET( r     != NULL );

    ECDSA_VALIDATE_RET( s     != NULL );

    ECDSA_VALIDATE_RET( d     != NULL );

    ECDSA_VALIDATE_RET( buf   != NULL || blen == 0 );

    ECDSA_VALIDATE_RET( f_rng_blind != NULL );

    return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg,

                                        f_rng_blind, p_rng_blind, NULL ) );

}

#endif /* MBEDTLS_ECDSA_DETERMINISTIC */

#if !defined(MBEDTLS_ECDSA_VERIFY_ALT)

/*

 * Verify ECDSA signature of hashed message (SEC1 4.1.4)

 * Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message)

 */

static int ecdsa_verify_restartable( mbedtls_ecp_group *grp,

                                     const unsigned char *buf, size_t blen,

                                     const mbedtls_ecp_point *Q,

                                     const mbedtls_mpi *r, const mbedtls_mpi *s,

                                     mbedtls_ecdsa_restart_ctx *rs_ctx )

{

    int ret;

    mbedtls_mpi e, s_inv, u1, u2;

    mbedtls_ecp_point R;

    mbedtls_mpi *pu1 = &u1, *pu2 = &u2;

    mbedtls_ecp_point_init( &R );

    mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv );

    mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );

    /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */

    if( grp->N.p == NULL )

        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );

    ECDSA_RS_ENTER( ver );

#if defined(MBEDTLS_ECP_RESTARTABLE)

    if( rs_ctx != NULL && rs_ctx->ver != NULL )

    {

        /* redirect to our context */

        pu1 = &rs_ctx->ver->u1;

        pu2 = &rs_ctx->ver->u2;

        /* jump to current step */

        if( rs_ctx->ver->state == ecdsa_ver_muladd )

            goto muladd;

    }

#endif /* MBEDTLS_ECP_RESTARTABLE */

    /*

     * Step 1: make sure r and s are in range 1..n-1

     */

    if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 ||

        mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 )

    {

        ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;

        goto cleanup;

    }

    /*

     * Step 3: derive MPI from hashed message

     */

    MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );

    /*

     * Step 4: u1 = e / s mod n, u2 = r / s mod n

     */

    ECDSA_BUDGET( MBEDTLS_ECP_OPS_CHK + MBEDTLS_ECP_OPS_INV + 2 );

    MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) );

    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu1, &e, &s_inv ) );

    MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu1, pu1, &grp->N ) );

    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu2, r, &s_inv ) );

    MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu2, pu2, &grp->N ) );

#if defined(MBEDTLS_ECP_RESTARTABLE)

    if( rs_ctx != NULL && rs_ctx->ver != NULL )

        rs_ctx->ver->state = ecdsa_ver_muladd;

muladd:

#endif

    /*

     * Step 5: R = u1 G + u2 Q

     */

    MBEDTLS_MPI_CHK( mbedtls_ecp_muladd_restartable( grp,

                     &R, pu1, &grp->G, pu2, Q, ECDSA_RS_ECP ) );

    if( mbedtls_ecp_is_zero( &R ) )

    {

        ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;

        goto cleanup;

    }

    /*

     * Step 6: convert xR to an integer (no-op)

     * Step 7: reduce xR mod n (gives v)

     */

    MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) );

    /*

     * Step 8: check if v (that is, R.X) is equal to r

     */

    if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 )

    {

        ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;

        goto cleanup;

    }

cleanup:

    mbedtls_ecp_point_free( &R );

    mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv );

    mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 );

    ECDSA_RS_LEAVE( ver );

    return( ret );

}

/*

 * Verify ECDSA signature of hashed message

 */

int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,

                          const unsigned char *buf, size_t blen,

                          const mbedtls_ecp_point *Q,

                          const mbedtls_mpi *r,

                          const mbedtls_mpi *s)

{

    ECDSA_VALIDATE_RET( grp != NULL );

    ECDSA_VALIDATE_RET( Q   != NULL );

    ECDSA_VALIDATE_RET( r   != NULL );

    ECDSA_VALIDATE_RET( s   != NULL );

    ECDSA_VALIDATE_RET( buf != NULL || blen == 0 );

    return( ecdsa_verify_restartable( grp, buf, blen, Q, r, s, NULL ) );

}

#endif /* !MBEDTLS_ECDSA_VERIFY_ALT */

/*

 * Convert a signature (given by context) to ASN.1

 */

static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s,

                                    unsigned char *sig, size_t *slen )

{

    int ret;

    unsigned char buf[MBEDTLS_ECDSA_MAX_LEN];

    unsigned char *p = buf + sizeof( buf );

    size_t len = 0;

    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, s ) );

    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, r ) );

    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) );

    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf,

                                       MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );

    memcpy( sig, p, len );

    *slen = len;

    return( 0 );

}

/*

 * Compute and write signature

 */

int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx,

                           mbedtls_md_type_t md_alg,

                           const unsigned char *hash, size_t hlen,

                           unsigned char *sig, size_t *slen,

                           int (*f_rng)(void *, unsigned char *, size_t),

                           void *p_rng,

                           mbedtls_ecdsa_restart_ctx *rs_ctx )

{

    int ret;

    mbedtls_mpi r, s;

    ECDSA_VALIDATE_RET( ctx  != NULL );

    ECDSA_VALIDATE_RET( hash != NULL );

    ECDSA_VALIDATE_RET( sig  != NULL );

    ECDSA_VALIDATE_RET( slen != NULL );

    mbedtls_mpi_init( &r );

    mbedtls_mpi_init( &s );

#if defined(MBEDTLS_ECDSA_DETERMINISTIC)

    MBEDTLS_MPI_CHK( ecdsa_sign_det_restartable( &ctx->grp, &r, &s, &ctx->d,

                                                 hash, hlen, md_alg, f_rng,

                                                 p_rng, rs_ctx ) );

#else

    (void) md_alg;

#if defined(MBEDTLS_ECDSA_SIGN_ALT)

    MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d,

                         hash, hlen, f_rng, p_rng ) );

#else

    /* Use the same RNG for both blinding and ephemeral key generation */

    MBEDTLS_MPI_CHK( ecdsa_sign_restartable( &ctx->grp, &r, &s, &ctx->d,

                                             hash, hlen, f_rng, p_rng, f_rng,

                                             p_rng, rs_ctx ) );

#endif /* MBEDTLS_ECDSA_SIGN_ALT */

#endif /* MBEDTLS_ECDSA_DETERMINISTIC */

    MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) );

cleanup:

    mbedtls_mpi_free( &r );

    mbedtls_mpi_free( &s );

    return( ret );

}

/*

 * Compute and write signature

 */

int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx,

                                 mbedtls_md_type_t md_alg,

                                 const unsigned char *hash, size_t hlen,

                                 unsigned char *sig, size_t *slen,

                                 int (*f_rng)(void *, unsigned char *, size_t),

                                 void *p_rng )

{

    ECDSA_VALIDATE_RET( ctx  != NULL );

    ECDSA_VALIDATE_RET( hash != NULL );

    ECDSA_VALIDATE_RET( sig  != NULL );

    ECDSA_VALIDATE_RET( slen != NULL );

    return( mbedtls_ecdsa_write_signature_restartable(

                ctx, md_alg, hash, hlen, sig, slen, f_rng, p_rng, NULL ) );

}

#if !defined(MBEDTLS_DEPRECATED_REMOVED) && \

    defined(MBEDTLS_ECDSA_DETERMINISTIC)

int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx,

                               const unsigned char *hash, size_t hlen,

                               unsigned char *sig, size_t *slen,

                               mbedtls_md_type_t md_alg )

{

    ECDSA_VALIDATE_RET( ctx  != NULL );

    ECDSA_VALIDATE_RET( hash != NULL );

    ECDSA_VALIDATE_RET( sig  != NULL );

    ECDSA_VALIDATE_RET( slen != NULL );

    return( mbedtls_ecdsa_write_signature( ctx, md_alg, hash, hlen, sig, slen,

                                   NULL, NULL ) );

}

#endif

/*

 * Read and check signature

 */

int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx,

                          const unsigned char *hash, size_t hlen,

                          const unsigned char *sig, size_t slen )

{

    ECDSA_VALIDATE_RET( ctx  != NULL );

    ECDSA_VALIDATE_RET( hash != NULL );

    ECDSA_VALIDATE_RET( sig  != NULL );

    return( mbedtls_ecdsa_read_signature_restartable(

                ctx, hash, hlen, sig, slen, NULL ) );

}

/*

 * Restartable read and check signature

 */

int mbedtls_ecdsa_read_signature_restartable( mbedtls_ecdsa_context *ctx,

                          const unsigned char *hash, size_t hlen,

                          const unsigned char *sig, size_t slen,

                          mbedtls_ecdsa_restart_ctx *rs_ctx )

{

    int ret;

    unsigned char *p = (unsigned char *) sig;

    const unsigned char *end = sig + slen;

    size_t len;

    mbedtls_mpi r, s;

    ECDSA_VALIDATE_RET( ctx  != NULL );

    ECDSA_VALIDATE_RET( hash != NULL );

    ECDSA_VALIDATE_RET( sig  != NULL );

    mbedtls_mpi_init( &r );

    mbedtls_mpi_init( &s );

    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,

                    MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )

    {

        ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;

        goto cleanup;

    }

    if( p + len != end )

    {

        ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA +

              MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;

        goto cleanup;

    }

    if( ( ret = mbedtls_asn1_get_mpi( &p, end, &r ) ) != 0 ||

        ( ret = mbedtls_asn1_get_mpi( &p, end, &s ) ) != 0 )

    {

        ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;

        goto cleanup;

    }

#if defined(MBEDTLS_ECDSA_VERIFY_ALT)

    if( ( ret = mbedtls_ecdsa_verify( &ctx->grp, hash, hlen,

                                      &ctx->Q, &r, &s ) ) != 0 )

        goto cleanup;

#else

    if( ( ret = ecdsa_verify_restartable( &ctx->grp, hash, hlen,

                              &ctx->Q, &r, &s, rs_ctx ) ) != 0 )

        goto cleanup;

#endif /* MBEDTLS_ECDSA_VERIFY_ALT */

    /* At this point we know that the buffer starts with a valid signature.

     * Return 0 if the buffer just contains the signature, and a specific

     * error code if the valid signature is followed by more data. */

    if( p != end )

        ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH;

cleanup:

    mbedtls_mpi_free( &r );

    mbedtls_mpi_free( &s );

    return( ret );

}

#if !defined(MBEDTLS_ECDSA_GENKEY_ALT)

/*

 * Generate key pair

 */

int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,

                  int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )

{

    int ret = 0;

    ECDSA_VALIDATE_RET( ctx   != NULL );

    ECDSA_VALIDATE_RET( f_rng != NULL );

    ret = mbedtls_ecp_group_load( &ctx->grp, gid );

    if( ret != 0 )

        return( ret );

   return( mbedtls_ecp_gen_keypair( &ctx->grp, &ctx->d,

                                    &ctx->Q, f_rng, p_rng ) );

}

#endif /* !MBEDTLS_ECDSA_GENKEY_ALT */

/*

 * Set context from an mbedtls_ecp_keypair

 */

int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key )

{

    int ret;

    ECDSA_VALIDATE_RET( ctx != NULL );

    ECDSA_VALIDATE_RET( key != NULL );

    if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 ||

        ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 ||

        ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 )

    {

        mbedtls_ecdsa_free( ctx );

    }

    return( ret );

}

/*

 * Initialize context

 */

void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx )

{

    ECDSA_VALIDATE( ctx != NULL );

    mbedtls_ecp_keypair_init( ctx );

}

/*

 * Free context

 */

void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx )

{

    if( ctx == NULL )

        return;

    mbedtls_ecp_keypair_free( ctx );

}

#if defined(MBEDTLS_ECP_RESTARTABLE)

/*

 * Initialize a restart context

 */

void mbedtls_ecdsa_restart_init( mbedtls_ecdsa_restart_ctx *ctx )

{

    ECDSA_VALIDATE( ctx != NULL );

    mbedtls_ecp_restart_init( &ctx->ecp );

    ctx->ver = NULL;

    ctx->sig = NULL;

#if defined(MBEDTLS_ECDSA_DETERMINISTIC)

    ctx->det = NULL;

#endif

}

/*

 * Free the components of a restart context

 */

void mbedtls_ecdsa_restart_free( mbedtls_ecdsa_restart_ctx *ctx )

{

    if( ctx == NULL )

        return;

    mbedtls_ecp_restart_free( &ctx->ecp );

    ecdsa_restart_ver_free( ctx->ver );

    mbedtls_free( ctx->ver );

    ctx->ver = NULL;

    ecdsa_restart_sig_free( ctx->sig );

    mbedtls_free( ctx->sig );

    ctx->sig = NULL;

#if defined(MBEDTLS_ECDSA_DETERMINISTIC)

    ecdsa_restart_det_free( ctx->det );

    mbedtls_free( ctx->det );

    ctx->det = NULL;

#endif

}

#endif /* MBEDTLS_ECP_RESTARTABLE */

#endif /* MBEDTLS_ECDSA_C */