proxmark3/common/mbedtls/pkwrite.c

/*
 *  Public Key layer for writing key files and structures
 *
 *  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)
 */

#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#if defined(MBEDTLS_PK_WRITE_C)

#include "mbedtls/pk.h"
#include "mbedtls/asn1write.h"
#include "mbedtls/oid.h"

#include <string.h>

#if defined(MBEDTLS_RSA_C)
#include "mbedtls/rsa.h"
#endif
#if defined(MBEDTLS_ECP_C)
#include "mbedtls/ecp.h"
#endif
#if defined(MBEDTLS_ECDSA_C)
#include "mbedtls/ecdsa.h"
#endif
#if defined(MBEDTLS_PEM_WRITE_C)
#include "mbedtls/pem.h"
#endif

#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdlib.h>
#define mbedtls_calloc    calloc
#define mbedtls_free       free
#endif

#if defined(MBEDTLS_RSA_C)
/*
 *  RSAPublicKey ::= SEQUENCE {
 *      modulus           INTEGER,  -- n
 *      publicExponent    INTEGER   -- e
 *  }
 */
static int pk_write_rsa_pubkey(unsigned char **p, unsigned char *start,
                               mbedtls_rsa_context *rsa) {
    int ret;
    size_t len = 0;
    mbedtls_mpi T;

    mbedtls_mpi_init(&T);

    /* Export E */
    if ((ret = mbedtls_rsa_export(rsa, NULL, NULL, NULL, NULL, &T)) != 0 ||
            (ret = mbedtls_asn1_write_mpi(p, start, &T)) < 0)
        goto end_of_export;
    len += ret;

    /* Export N */
    if ((ret = mbedtls_rsa_export(rsa, &T, NULL, NULL, NULL, NULL)) != 0 ||
            (ret = mbedtls_asn1_write_mpi(p, start, &T)) < 0)
        goto end_of_export;
    len += ret;

end_of_export:

    mbedtls_mpi_free(&T);
    if (ret < 0)
        return (ret);

    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_CONSTRUCTED |
                                                     MBEDTLS_ASN1_SEQUENCE));

    return ((int) len);
}
#endif /* MBEDTLS_RSA_C */

#if defined(MBEDTLS_ECP_C)
/*
 * EC public key is an EC point
 */
static int pk_write_ec_pubkey(unsigned char **p, unsigned char *start,
                              mbedtls_ecp_keypair *ec) {
    int ret;
    size_t len = 0;
    unsigned char buf[MBEDTLS_ECP_MAX_PT_LEN];

    if ((ret = mbedtls_ecp_point_write_binary(&ec->grp, &ec->Q,
                                              MBEDTLS_ECP_PF_UNCOMPRESSED,
                                              &len, buf, sizeof(buf))) != 0) {
        return (ret);
    }

    if (*p < start || (size_t)(*p - start) < len)
        return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

    *p -= len;
    memcpy(*p, buf, len);

    return ((int) len);
}

/*
 * ECParameters ::= CHOICE {
 *   namedCurve         OBJECT IDENTIFIER
 * }
 */
static int pk_write_ec_param(unsigned char **p, unsigned char *start,
                             mbedtls_ecp_keypair *ec) {
    int ret;
    size_t len = 0;
    const char *oid;
    size_t oid_len;

    if ((ret = mbedtls_oid_get_oid_by_ec_grp(ec->grp.id, &oid, &oid_len)) != 0)
        return (ret);

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_oid(p, start, oid, oid_len));

    return ((int) len);
}
#endif /* MBEDTLS_ECP_C */

int mbedtls_pk_write_pubkey(unsigned char **p, unsigned char *start,
                            const mbedtls_pk_context *key) {
    int ret;
    size_t len = 0;

#if defined(MBEDTLS_RSA_C)
    if (mbedtls_pk_get_type(key) == MBEDTLS_PK_RSA)
        MBEDTLS_ASN1_CHK_ADD(len, pk_write_rsa_pubkey(p, start, mbedtls_pk_rsa(*key)));
    else
#endif
#if defined(MBEDTLS_ECP_C)
        if (mbedtls_pk_get_type(key) == MBEDTLS_PK_ECKEY)
            MBEDTLS_ASN1_CHK_ADD(len, pk_write_ec_pubkey(p, start, mbedtls_pk_ec(*key)));
        else
#endif
            return (MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE);

    return ((int) len);
}

int mbedtls_pk_write_pubkey_der(mbedtls_pk_context *key, unsigned char *buf, size_t size) {
    int ret;
    unsigned char *c;
    size_t len = 0, par_len = 0, oid_len;
    const char *oid;

    c = buf + size;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_pk_write_pubkey(&c, buf, key));

    if (c - buf < 1)
        return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);

    /*
     *  SubjectPublicKeyInfo  ::=  SEQUENCE  {
     *       algorithm            AlgorithmIdentifier,
     *       subjectPublicKey     BIT STRING }
     */
    *--c = 0;
    len += 1;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_BIT_STRING));

    if ((ret = mbedtls_oid_get_oid_by_pk_alg(mbedtls_pk_get_type(key),
                                             &oid, &oid_len)) != 0) {
        return (ret);
    }

#if defined(MBEDTLS_ECP_C)
    if (mbedtls_pk_get_type(key) == MBEDTLS_PK_ECKEY) {
        MBEDTLS_ASN1_CHK_ADD(par_len, pk_write_ec_param(&c, buf, mbedtls_pk_ec(*key)));
    }
#endif

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_algorithm_identifier(&c, buf, oid, oid_len,
                         par_len));

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                     MBEDTLS_ASN1_SEQUENCE));

    return ((int) len);
}

int mbedtls_pk_write_key_der(mbedtls_pk_context *key, unsigned char *buf, size_t size) {
    int ret;
    unsigned char *c = buf + size;
    size_t len = 0;

#if defined(MBEDTLS_RSA_C)
    if (mbedtls_pk_get_type(key) == MBEDTLS_PK_RSA) {
        mbedtls_mpi T; /* Temporary holding the exported parameters */
        mbedtls_rsa_context *rsa = mbedtls_pk_rsa(*key);

        /*
         * Export the parameters one after another to avoid simultaneous copies.
         */

        mbedtls_mpi_init(&T);

        /* Export QP */
        if ((ret = mbedtls_rsa_export_crt(rsa, NULL, NULL, &T)) != 0 ||
                (ret = mbedtls_asn1_write_mpi(&c, buf, &T)) < 0)
            goto end_of_export;
        len += ret;

        /* Export DQ */
        if ((ret = mbedtls_rsa_export_crt(rsa, NULL, &T, NULL)) != 0 ||
                (ret = mbedtls_asn1_write_mpi(&c, buf, &T)) < 0)
            goto end_of_export;
        len += ret;

        /* Export DP */
        if ((ret = mbedtls_rsa_export_crt(rsa, &T, NULL, NULL)) != 0 ||
                (ret = mbedtls_asn1_write_mpi(&c, buf, &T)) < 0)
            goto end_of_export;
        len += ret;

        /* Export Q */
        if ((ret = mbedtls_rsa_export(rsa, NULL, NULL,
                                      &T, NULL, NULL)) != 0 ||
                (ret = mbedtls_asn1_write_mpi(&c, buf, &T)) < 0)
            goto end_of_export;
        len += ret;

        /* Export P */
        if ((ret = mbedtls_rsa_export(rsa, NULL, &T,
                                      NULL, NULL, NULL)) != 0 ||
                (ret = mbedtls_asn1_write_mpi(&c, buf, &T)) < 0)
            goto end_of_export;
        len += ret;

        /* Export D */
        if ((ret = mbedtls_rsa_export(rsa, NULL, NULL,
                                      NULL, &T, NULL)) != 0 ||
                (ret = mbedtls_asn1_write_mpi(&c, buf, &T)) < 0)
            goto end_of_export;
        len += ret;

        /* Export E */
        if ((ret = mbedtls_rsa_export(rsa, NULL, NULL,
                                      NULL, NULL, &T)) != 0 ||
                (ret = mbedtls_asn1_write_mpi(&c, buf, &T)) < 0)
            goto end_of_export;
        len += ret;

        /* Export N */
        if ((ret = mbedtls_rsa_export(rsa, &T, NULL,
                                      NULL, NULL, NULL)) != 0 ||
                (ret = mbedtls_asn1_write_mpi(&c, buf, &T)) < 0)
            goto end_of_export;
        len += ret;

end_of_export:

        mbedtls_mpi_free(&T);
        if (ret < 0)
            return (ret);

        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(&c, buf, 0));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c,
                                                         buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                         MBEDTLS_ASN1_SEQUENCE));
    } else
#endif /* MBEDTLS_RSA_C */
#if defined(MBEDTLS_ECP_C)
        if (mbedtls_pk_get_type(key) == MBEDTLS_PK_ECKEY) {
            mbedtls_ecp_keypair *ec = mbedtls_pk_ec(*key);
            size_t pub_len = 0, par_len = 0;

            /*
             * RFC 5915, or SEC1 Appendix C.4
             *
             * ECPrivateKey ::= SEQUENCE {
             *      version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
             *      privateKey     OCTET STRING,
             *      parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
             *      publicKey  [1] BIT STRING OPTIONAL
             *    }
             */

            /* publicKey */
            MBEDTLS_ASN1_CHK_ADD(pub_len, pk_write_ec_pubkey(&c, buf, ec));

            if (c - buf < 1)
                return (MBEDTLS_ERR_ASN1_BUF_TOO_SMALL);
            *--c = 0;
            pub_len += 1;

            MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_asn1_write_len(&c, buf, pub_len));
            MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_BIT_STRING));

            MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_asn1_write_len(&c, buf, pub_len));
            MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_asn1_write_tag(&c, buf,
                                                                 MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 1));
            len += pub_len;

            /* parameters */
            MBEDTLS_ASN1_CHK_ADD(par_len, pk_write_ec_param(&c, buf, ec));

            MBEDTLS_ASN1_CHK_ADD(par_len, mbedtls_asn1_write_len(&c, buf, par_len));
            MBEDTLS_ASN1_CHK_ADD(par_len, mbedtls_asn1_write_tag(&c, buf,
                                                                 MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 0));
            len += par_len;

            /* privateKey: write as MPI then fix tag */
            MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_mpi(&c, buf, &ec->d));
            *c = MBEDTLS_ASN1_OCTET_STRING;

            /* version */
            MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(&c, buf, 1));

            MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, len));
            MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED |
                                                             MBEDTLS_ASN1_SEQUENCE));
        } else
#endif /* MBEDTLS_ECP_C */
            return (MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE);

    return ((int) len);
}

#if defined(MBEDTLS_PEM_WRITE_C)

#define PEM_BEGIN_PUBLIC_KEY    "-----BEGIN PUBLIC KEY-----\n"
#define PEM_END_PUBLIC_KEY      "-----END PUBLIC KEY-----\n"

#define PEM_BEGIN_PRIVATE_KEY_RSA   "-----BEGIN RSA PRIVATE KEY-----\n"
#define PEM_END_PRIVATE_KEY_RSA     "-----END RSA PRIVATE KEY-----\n"
#define PEM_BEGIN_PRIVATE_KEY_EC    "-----BEGIN EC PRIVATE KEY-----\n"
#define PEM_END_PRIVATE_KEY_EC      "-----END EC PRIVATE KEY-----\n"

/*
 * Max sizes of key per types. Shown as tag + len (+ content).
 */

#if defined(MBEDTLS_RSA_C)
/*
 * RSA public keys:
 *  SubjectPublicKeyInfo  ::=  SEQUENCE  {          1 + 3
 *       algorithm            AlgorithmIdentifier,  1 + 1 (sequence)
 *                                                + 1 + 1 + 9 (rsa oid)
 *                                                + 1 + 1 (params null)
 *       subjectPublicKey     BIT STRING }          1 + 3 + (1 + below)
 *  RSAPublicKey ::= SEQUENCE {                     1 + 3
 *      modulus           INTEGER,  -- n            1 + 3 + MPI_MAX + 1
 *      publicExponent    INTEGER   -- e            1 + 3 + MPI_MAX + 1
 *  }
 */
#define RSA_PUB_DER_MAX_BYTES   38 + 2 * MBEDTLS_MPI_MAX_SIZE

/*
 * RSA private keys:
 *  RSAPrivateKey ::= SEQUENCE {                    1 + 3
 *      version           Version,                  1 + 1 + 1
 *      modulus           INTEGER,                  1 + 3 + MPI_MAX + 1
 *      publicExponent    INTEGER,                  1 + 3 + MPI_MAX + 1
 *      privateExponent   INTEGER,                  1 + 3 + MPI_MAX + 1
 *      prime1            INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 *      prime2            INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 *      exponent1         INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 *      exponent2         INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 *      coefficient       INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
 *      otherPrimeInfos   OtherPrimeInfos OPTIONAL  0 (not supported)
 *  }
 */
#define MPI_MAX_SIZE_2          MBEDTLS_MPI_MAX_SIZE / 2 + \
    MBEDTLS_MPI_MAX_SIZE % 2
#define RSA_PRV_DER_MAX_BYTES   47 + 3 * MBEDTLS_MPI_MAX_SIZE \
    + 5 * MPI_MAX_SIZE_2

#else /* MBEDTLS_RSA_C */

#define RSA_PUB_DER_MAX_BYTES   0
#define RSA_PRV_DER_MAX_BYTES   0

#endif /* MBEDTLS_RSA_C */

#if defined(MBEDTLS_ECP_C)
/*
 * EC public keys:
 *  SubjectPublicKeyInfo  ::=  SEQUENCE  {      1 + 2
 *    algorithm         AlgorithmIdentifier,    1 + 1 (sequence)
 *                                            + 1 + 1 + 7 (ec oid)
 *                                            + 1 + 1 + 9 (namedCurve oid)
 *    subjectPublicKey  BIT STRING              1 + 2 + 1               [1]
 *                                            + 1 (point format)        [1]
 *                                            + 2 * ECP_MAX (coords)    [1]
 *  }
 */
#define ECP_PUB_DER_MAX_BYTES   30 + 2 * MBEDTLS_ECP_MAX_BYTES

/*
 * EC private keys:
 * ECPrivateKey ::= SEQUENCE {                  1 + 2
 *      version        INTEGER ,                1 + 1 + 1
 *      privateKey     OCTET STRING,            1 + 1 + ECP_MAX
 *      parameters [0] ECParameters OPTIONAL,   1 + 1 + (1 + 1 + 9)
 *      publicKey  [1] BIT STRING OPTIONAL      1 + 2 + [1] above
 *    }
 */
#define ECP_PRV_DER_MAX_BYTES   29 + 3 * MBEDTLS_ECP_MAX_BYTES

#else /* MBEDTLS_ECP_C */

#define ECP_PUB_DER_MAX_BYTES   0
#define ECP_PRV_DER_MAX_BYTES   0

#endif /* MBEDTLS_ECP_C */

#define PUB_DER_MAX_BYTES   RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \
    RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES
#define PRV_DER_MAX_BYTES   RSA_PRV_DER_MAX_BYTES > ECP_PRV_DER_MAX_BYTES ? \
    RSA_PRV_DER_MAX_BYTES : ECP_PRV_DER_MAX_BYTES

int mbedtls_pk_write_pubkey_pem(mbedtls_pk_context *key, unsigned char *buf, size_t size) {
    int ret;
    unsigned char output_buf[PUB_DER_MAX_BYTES];
    size_t olen = 0;

    if ((ret = mbedtls_pk_write_pubkey_der(key, output_buf,
                                           sizeof(output_buf))) < 0) {
        return (ret);
    }

    if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_PUBLIC_KEY, PEM_END_PUBLIC_KEY,
                                        output_buf + sizeof(output_buf) - ret,
                                        ret, buf, size, &olen)) != 0) {
        return (ret);
    }

    return (0);
}

int mbedtls_pk_write_key_pem(mbedtls_pk_context *key, unsigned char *buf, size_t size) {
    int ret;
    unsigned char output_buf[PRV_DER_MAX_BYTES];
    const char *begin, *end;
    size_t olen = 0;

    if ((ret = mbedtls_pk_write_key_der(key, output_buf, sizeof(output_buf))) < 0)
        return (ret);

#if defined(MBEDTLS_RSA_C)
    if (mbedtls_pk_get_type(key) == MBEDTLS_PK_RSA) {
        begin = PEM_BEGIN_PRIVATE_KEY_RSA;
        end = PEM_END_PRIVATE_KEY_RSA;
    } else
#endif
#if defined(MBEDTLS_ECP_C)
        if (mbedtls_pk_get_type(key) == MBEDTLS_PK_ECKEY) {
            begin = PEM_BEGIN_PRIVATE_KEY_EC;
            end = PEM_END_PRIVATE_KEY_EC;
        } else
#endif
            return (MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE);

    if ((ret = mbedtls_pem_write_buffer(begin, end,
                                        output_buf + sizeof(output_buf) - ret,
                                        ret, buf, size, &olen)) != 0) {
        return (ret);
    }

    return (0);
}
#endif /* MBEDTLS_PEM_WRITE_C */

#endif /* MBEDTLS_PK_WRITE_C */