library/pkwrite.c

/*
 *  Public Key layer for writing key files and structures
 *
 *  Copyright (C) 2006-2013, Brainspark B.V.
 *
 *  This file is part of PolarSSL (http://www.polarssl.org)
 *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
 *
 *  All rights reserved.
 *
 *  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.
 */

#include "polarssl/config.h"

#if defined(POLARSSL_PK_C)

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

#if defined(POLARSSL_RSA_C)
#include "polarssl/rsa.h"
#endif
#if defined(POLARSSL_ECP_C)
#include "polarssl/ecp.h"
#endif
#if defined(POLARSSL_ECDSA_C)
#include "polarssl/ecdsa.h"
#endif
#if defined(POLARSSL_BASE64_C)
#include "polarssl/base64.h"
#endif

#if defined(POLARSSL_MEMORY_C)
#include "polarssl/memory.h"
#else
#include <stdlib.h>
#define polarssl_malloc     malloc
#define polarssl_free       free
#endif

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

    ASN1_CHK_ADD( len, asn1_write_mpi( p, start, &rsa->E ) );
    ASN1_CHK_ADD( len, asn1_write_mpi( p, start, &rsa->N ) );

    ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
    ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

    return( len );
}
#endif /* POLARSSL_RSA_C */

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

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

    if( *p - start < (int) len )
        return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );

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

    return( len );
}

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

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

    ASN1_CHK_ADD( len, asn1_write_oid( p, start, oid, oid_len ) );

    return( len );
}
#endif /* POLARSSL_ECP_C */

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

#if defined(POLARSSL_RSA_C)
    if( pk_get_type( key ) == POLARSSL_PK_RSA )
        ASN1_CHK_ADD( len, pk_write_rsa_pubkey( p, start, pk_rsa( *key ) ) );
    else
#endif
#if defined(POLARSSL_ECP_C)
    if( pk_get_type( key ) == POLARSSL_PK_ECKEY )
        ASN1_CHK_ADD( len, pk_write_ec_pubkey( p, start, pk_ec( *key ) ) );
    else
#endif
        return( POLARSSL_ERR_PK_FEATURE_UNAVAILABLE );

    return( len );
}

int pk_write_pubkey_der( 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;

    ASN1_CHK_ADD( len, pk_write_pubkey( &c, buf, key ) );

    if( c - buf < 1 )
        return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );

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

    ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
    ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_BIT_STRING ) );

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

#if defined(POLARSSL_ECP_C)
    if( pk_get_type( key ) == POLARSSL_PK_ECKEY )
    {
        ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, pk_ec( *key ) ) );
    }
#endif

    ASN1_CHK_ADD( len, asn1_write_algorithm_identifier( &c, buf, oid, oid_len,
                                                        par_len ) );

    ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
    ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );

    return( len );
}

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

#if defined(POLARSSL_RSA_C)
    if( pk_get_type( key ) == POLARSSL_PK_RSA )
    {
        rsa_context *rsa = pk_rsa( *key );

        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->QP ) );
        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DQ ) );
        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->DP ) );
        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->Q ) );
        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->P ) );
        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->D ) );
        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->E ) );
        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &rsa->N ) );
        ASN1_CHK_ADD( len, asn1_write_int( &c, buf, 0 ) );

        ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
        ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
    }
    else
#endif
#if defined(POLARSSL_ECP_C)
    if( pk_get_type( key ) == POLARSSL_PK_ECKEY )
    {
        ecp_keypair *ec = 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 */
        ASN1_CHK_ADD( pub_len, pk_write_ec_pubkey( &c, buf, ec ) );

        if( c - buf < 1 )
            return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
        *--c = 0;
        pub_len += 1;

        ASN1_CHK_ADD( pub_len, asn1_write_len( &c, buf, pub_len ) );
        ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, buf, ASN1_BIT_STRING ) );

        ASN1_CHK_ADD( pub_len, asn1_write_len( &c, buf, pub_len ) );
        ASN1_CHK_ADD( pub_len, asn1_write_tag( &c, buf,
                            ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 1 ) );
        len += pub_len;

        /* parameters */
        ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, ec ) );

        ASN1_CHK_ADD( par_len, asn1_write_len( &c, buf, par_len ) );
        ASN1_CHK_ADD( par_len, asn1_write_tag( &c, buf,
                            ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 0 ) );
        len += par_len;

        /* privateKey: write as MPI then fix tag */
        ASN1_CHK_ADD( len, asn1_write_mpi( &c, buf, &ec->d ) );
        *c = ASN1_OCTET_STRING;

        /* version */
        ASN1_CHK_ADD( len, asn1_write_int( &c, buf, 1 ) );

        ASN1_CHK_ADD( len, asn1_write_len( &c, buf, len ) );
        ASN1_CHK_ADD( len, asn1_write_tag( &c, buf, ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
    }
    else
#endif
        return( POLARSSL_ERR_PK_FEATURE_UNAVAILABLE );

    return( len );
}

#if defined(POLARSSL_BASE64_C)
static int pk_write_pemify( const char *begin_str, const char *end_str,
                             const unsigned char *der_data, size_t der_len,
                             unsigned char *buf, size_t size )
{
    int ret;
    unsigned char base_buf[4096];
    unsigned char *c = base_buf, *p = buf;
    size_t len = 0, olen = sizeof(base_buf);

    if( ( ret = base64_encode( base_buf, &olen, der_data, der_len ) ) != 0 )
        return( ret );

    if( olen + strlen( begin_str ) + strlen( end_str ) +
        olen / 64 > size )
    {
        return( POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL );
    }

    memcpy( p, begin_str, strlen( begin_str ) );
    p += strlen( begin_str );

    while( olen )
    {
        len = ( olen > 64 ) ? 64 : olen;
        memcpy( p, c, len );
        olen -= len;
        p += len;
        c += len;
        *p++ = '\n';
    }

    memcpy( p, end_str, strlen( end_str ) );
    p += strlen( end_str );

    *p = '\0';

    return( 0 );
}

#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"

int pk_write_pubkey_pem( pk_context *key, unsigned char *buf, size_t size )
{
    int ret;
    unsigned char output_buf[4096];

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

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

    return( 0 );
}

int pk_write_key_pem( pk_context *key, unsigned char *buf, size_t size )
{
    int ret;
    unsigned char output_buf[4096];
    char *begin, *end;

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

#if defined(POLARSSL_RSA_C)
    if( pk_get_type( key ) == POLARSSL_PK_RSA )
    {
        begin = PEM_BEGIN_PRIVATE_KEY_RSA;
        end = PEM_END_PRIVATE_KEY_RSA;
    }
    else
#endif
#if defined(POLARSSL_ECP_C)
    if( pk_get_type( key ) == POLARSSL_PK_ECKEY )
    {
        begin = PEM_BEGIN_PRIVATE_KEY_EC;
        end = PEM_END_PRIVATE_KEY_EC;
    }
    else
#endif
        return( POLARSSL_ERR_PK_FEATURE_UNAVAILABLE );

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

    return( 0 );
}
#endif /* POLARSSL_BASE64_C */

#endif /* POLARSSL_PK_C */