/* *  The RSA public-key cryptosystem * *  Copyright (C) 2006-2007  Christophe Devine * *  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. *//* *  RSA was designed by Ron Rivest, Adi Shamir and Len Adleman. * *  http://theory.lcs.mit.edu/~rivest/rsapaper.pdf *  http://www.cacr.math.uwaterloo.ca/hac/about/chap8.pdf */#include "config.h"#if defined(XYSSL_RSA_C)#include "rsa.h"#include <stdlib.h>#include <string.h>#include <stdio.h>/* * Initialize an RSA context */void rsa_init( rsa_context *ctx,               int padding,               int hash_id,               int (*f_rng)(void *),               void *p_rng ){    memset( ctx, 0, sizeof( rsa_context ) );    ctx->padding = padding;    ctx->hash_id = hash_id;    ctx->f_rng = f_rng;    ctx->p_rng = p_rng;}#if defined(XYSSL_GENPRIME)/* * Generate an RSA keypair */int rsa_gen_key( rsa_context *ctx, int nbits, int exponent ){    int ret;    mpi P1, Q1, H, G;    if( ctx->f_rng == NULL || nbits < 128 || exponent < 3 )        return( XYSSL_ERR_RSA_BAD_INPUT_DATA );    mpi_init( &P1, &Q1, &H, &G, NULL );    /*     * find primes P and Q with Q < P so that:     * GCD( E, (P-1)*(Q-1) ) == 1     */    MPI_CHK( mpi_lset( &ctx->E, exponent ) );    do    {        MPI_CHK( mpi_gen_prime( &ctx->P, ( nbits + 1 ) >> 1, 0,                                 ctx->f_rng, ctx->p_rng ) );        MPI_CHK( mpi_gen_prime( &ctx->Q, ( nbits + 1 ) >> 1, 0,                                ctx->f_rng, ctx->p_rng ) );        if( mpi_cmp_mpi( &ctx->P, &ctx->Q ) < 0 )            mpi_swap( &ctx->P, &ctx->Q );        if( mpi_cmp_mpi( &ctx->P, &ctx->Q ) == 0 )            continue;        MPI_CHK( mpi_mul_mpi( &ctx->N, &ctx->P, &ctx->Q ) );        if( mpi_msb( &ctx->N ) != nbits )            continue;        MPI_CHK( mpi_sub_int( &P1, &ctx->P, 1 ) );        MPI_CHK( mpi_sub_int( &Q1, &ctx->Q, 1 ) );        MPI_CHK( mpi_mul_mpi( &H, &P1, &Q1 ) );        MPI_CHK( mpi_gcd( &G, &ctx->E, &H  ) );    }    while( mpi_cmp_int( &G, 1 ) != 0 );    /*     * D  = E^-1 mod ((P-1)*(Q-1))     * DP = D mod (P - 1)     * DQ = D mod (Q - 1)     * QP = Q^-1 mod P     */    MPI_CHK( mpi_inv_mod( &ctx->D , &ctx->E, &H  ) );    MPI_CHK( mpi_mod_mpi( &ctx->DP, &ctx->D, &P1 ) );    MPI_CHK( mpi_mod_mpi( &ctx->DQ, &ctx->D, &Q1 ) );    MPI_CHK( mpi_inv_mod( &ctx->QP, &ctx->Q, &ctx->P ) );    ctx->len = ( mpi_msb( &ctx->N ) + 7 ) >> 3;cleanup:    mpi_free( &G, &H, &Q1, &P1, NULL );    if( ret != 0 )    {        rsa_free( ctx );        return( XYSSL_ERR_RSA_KEY_GEN_FAILED | ret );    }    return( 0 );   }#endif/* * Check a public RSA key */int rsa_check_pubkey( rsa_context *ctx ){    if( ( ctx->N.p[0] & 1 ) == 0 ||         ( ctx->E.p[0] & 1 ) == 0 )        return( XYSSL_ERR_RSA_KEY_CHECK_FAILED );    if( mpi_msb( &ctx->N ) < 128 ||        mpi_msb( &ctx->N ) > 4096 )        return( XYSSL_ERR_RSA_KEY_CHECK_FAILED );    if( mpi_msb( &ctx->E ) < 2 ||        mpi_msb( &ctx->E ) > 64 )        return( XYSSL_ERR_RSA_KEY_CHECK_FAILED );    return( 0 );}/* * Check a private RSA key */int rsa_check_privkey( rsa_context *ctx ){    int ret;    mpi PQ, DE, P1, Q1, H, I, G;    if( ( ret = rsa_check_pubkey( ctx ) ) != 0 )        return( ret );    mpi_init( &PQ, &DE, &P1, &Q1, &H, &I, &G, NULL );    MPI_CHK( mpi_mul_mpi( &PQ, &ctx->P, &ctx->Q ) );    MPI_CHK( mpi_mul_mpi( &DE, &ctx->D, &ctx->E ) );    MPI_CHK( mpi_sub_int( &P1, &ctx->P, 1 ) );    MPI_CHK( mpi_sub_int( &Q1, &ctx->Q, 1 ) );    MPI_CHK( mpi_mul_mpi( &H, &P1, &Q1 ) );    MPI_CHK( mpi_mod_mpi( &I, &DE, &H  ) );    MPI_CHK( mpi_gcd( &G, &ctx->E, &H  ) );    if( mpi_cmp_mpi( &PQ, &ctx->N ) == 0 &&        mpi_cmp_int( &I, 1 ) == 0 &&        mpi_cmp_int( &G, 1 ) == 0 )    {        mpi_free( &G, &I, &H, &Q1, &P1, &DE, &PQ, NULL );        return( 0 );    }cleanup:    mpi_free( &G, &I, &H, &Q1, &P1, &DE, &PQ, NULL );    return( XYSSL_ERR_RSA_KEY_CHECK_FAILED | ret );}/* * Do an RSA public key operation */int rsa_public( rsa_context *ctx,                unsigned char *input,                unsigned char *output ){    int ret, olen;    mpi T;    mpi_init( &T, NULL );    MPI_CHK( mpi_read_binary( &T, input, ctx->len ) );    if( mpi_cmp_mpi( &T, &ctx->N ) >= 0 )    {        mpi_free( &T, NULL );        return( XYSSL_ERR_RSA_BAD_INPUT_DATA );    }    olen = ctx->len;    MPI_CHK( mpi_exp_mod( &T, &T, &ctx->E, &ctx->N, &ctx->RN ) );    MPI_CHK( mpi_write_binary( &T, output, olen ) );cleanup:    mpi_free( &T, NULL );    if( ret != 0 )        return( XYSSL_ERR_RSA_PUBLIC_FAILED | ret );    return( 0 );}/* * Do an RSA private key operation */int rsa_private( rsa_context *ctx,                 unsigned char *input,                 unsigned char *output ){    int ret, olen;    mpi T, T1, T2;    mpi_init( &T, &T1, &T2, NULL );    MPI_CHK( mpi_read_binary( &T, input, ctx->len ) );    if( mpi_cmp_mpi( &T, &ctx->N ) >= 0 )    {        mpi_free( &T, NULL );        return( XYSSL_ERR_RSA_BAD_INPUT_DATA );    }#if 0    MPI_CHK( mpi_exp_mod( &T, &T, &ctx->D, &ctx->N, &ctx->RN ) );#else    /*     * faster decryption using the CRT     *     * T1 = input ^ dP mod P     * T2 = input ^ dQ mod Q     */    MPI_CHK( mpi_exp_mod( &T1, &T, &ctx->DP, &ctx->P, &ctx->RP ) );    MPI_CHK( mpi_exp_mod( &T2, &T, &ctx->DQ, &ctx->Q, &ctx->RQ ) );    /*     * T = (T1 - T2) * (Q^-1 mod P) mod P     */    MPI_CHK( mpi_sub_mpi( &T, &T1, &T2 ) );    MPI_CHK( mpi_mul_mpi( &T1, &T, &ctx->QP ) );    MPI_CHK( mpi_mod_mpi( &T, &T1, &ctx->P ) );    /*     * output = T2 + T * Q     */    MPI_CHK( mpi_mul_mpi( &T1, &T, &ctx->Q ) );    MPI_CHK( mpi_add_mpi( &T, &T2, &T1 ) );#endif    olen = ctx->len;    MPI_CHK( mpi_write_binary( &T, output, olen ) );cleanup:    mpi_free( &T, &T1, &T2, NULL );    if( ret != 0 )        return( XYSSL_ERR_RSA_PRIVATE_FAILED | ret );    return( 0 );}/* * Add the message padding, then do an RSA operation */int rsa_pkcs1_encrypt( rsa_context *ctx,                       int mode, int  ilen,                       unsigned char *input,                       unsigned char *output ){    int nb_pad, olen;    unsigned char *p = output;    olen = ctx->len;    switch( ctx->padding )    {        case RSA_PKCS_V15:            if( ilen < 0 || olen < ilen + 11 )                return( XYSSL_ERR_RSA_BAD_INPUT_DATA );            nb_pad = olen - 3 - ilen;            *p++ = 0;            *p++ = RSA_CRYPT;            while( nb_pad-- > 0 )            {                do {                    *p = (unsigned char) rand();                } while( *p == 0 );                p++;            }            *p++ = 0;            memcpy( p, input, ilen );            break;        default:            return( XYSSL_ERR_RSA_INVALID_PADDING );    }    return( ( mode == RSA_PUBLIC )            ? rsa_public(  ctx, output, output )            : rsa_private( ctx, output, output ) );}/* * Do an RSA operation, then remove the message padding */int rsa_pkcs1_decrypt( rsa_context *ctx,                       int mode, int *olen,                       unsigned char *input,                       unsigned char *output ){    int ret, ilen;    unsigned char *p;    unsigned char buf[512];    ilen = ctx->len;    if( ilen < 16 || ilen > (int) sizeof( buf ) )        return( XYSSL_ERR_RSA_BAD_INPUT_DATA );    ret = ( mode == RSA_PUBLIC )          ? rsa_public(  ctx, input, buf )          : rsa_private( ctx, input, buf );    if( ret != 0 )        return( ret );    p = buf;    switch( ctx->padding )    {        case RSA_PKCS_V15:            if( *p++ != 0 || *p++ != RSA_CRYPT )                return( XYSSL_ERR_RSA_INVALID_PADDING );            while( *p != 0 )            {                if( p >= buf + ilen - 1 )                    return( XYSSL_ERR_RSA_INVALID_PADDING );                p++;            }            p++;            break;        default: