mpi_alloc_like( MPI a )
#endif
{
MPI b;
if( a && (a->flags & 4) ) {
void *p = m_is_secure(a->d)? xmalloc_secure( a->nbits )
: xmalloc( a->nbits );
memcpy( p, a->d, a->nbits );
b = mpi_set_opaque( NULL, p, a->nbits );
}
else if( a ) {
#ifdef M_DEBUG
b = mpi_is_secure(a)? mpi_debug_alloc_secure( a->nlimbs, info )
: mpi_debug_alloc( a->nlimbs, info );
#else
b = mpi_is_secure(a)? mpi_alloc_secure( a->nlimbs )
: mpi_alloc( a->nlimbs );
#endif
b->nlimbs = 0;
b->sign = 0;
b->flags = a->flags;
b->nbits = 0;
}
else
b = NULL;
return b;
}
void
_gcry_mpi_randomize (gcry_mpi_t w,
unsigned int nbits, enum gcry_random_level level)
{
unsigned char *p;
size_t nbytes = (nbits+7)/8;
if (mpi_is_immutable (w))
{
mpi_immutable_failed ();
return;
}
if (level == GCRY_WEAK_RANDOM)
{
p = mpi_is_secure(w) ? xmalloc_secure (nbytes)
: xmalloc (nbytes);
_gcry_create_nonce (p, nbytes);
}
else
{
p = mpi_is_secure(w) ? _gcry_random_bytes_secure (nbytes, level)
: _gcry_random_bytes (nbytes, level);
}
_gcry_mpi_set_buffer( w, p, nbytes, 0 );
xfree (p);
}
mpi_copy_gpg( MPI a )
#endif
{
int i;
MPI b;
if( a && (a->flags & 4) ) {
void *p = m_is_secure(a->d)? xmalloc_secure( a->nbits )
: xmalloc( a->nbits );
memcpy( p, a->d, a->nbits );
b = mpi_set_opaque( NULL, p, a->nbits );
}
else if( a ) {
#ifdef M_DEBUG
b = mpi_is_secure(a)? mpi_debug_alloc_secure( a->nlimbs, info )
: mpi_debug_alloc( a->nlimbs, info );
#else
b = mpi_is_secure(a)? mpi_alloc_secure( a->nlimbs )
: mpi_alloc( a->nlimbs );
#endif
b->nlimbs = a->nlimbs;
b->sign = a->sign;
b->flags = a->flags;
b->nbits = a->nbits;
for(i=0; i < b->nlimbs; i++ )
b->d[i] = a->d[i];
}
else
b = NULL;
return b;
}
/****************
* Note: This copy function should not interpret the MPI
* but copy it transparently.
*/
gcry_mpi_t
_gcry_mpi_copy (gcry_mpi_t a)
{
int i;
gcry_mpi_t b;
if( a && (a->flags & 4) ) {
void *p = _gcry_is_secure(a->d)? xmalloc_secure ((a->sign+7)/8)
: xmalloc ((a->sign+7)/8);
memcpy( p, a->d, (a->sign+7)/8 );
b = mpi_set_opaque( NULL, p, a->sign );
b->flags &= ~(16|32); /* Reset the immutable and constant flags. */
}
else if( a ) {
b = mpi_is_secure(a)? mpi_alloc_secure( a->nlimbs )
: mpi_alloc( a->nlimbs );
b->nlimbs = a->nlimbs;
b->sign = a->sign;
b->flags = a->flags;
b->flags &= ~(16|32); /* Reset the immutable and constant flags. */
for(i=0; i < b->nlimbs; i++ )
b->d[i] = a->d[i];
}
else
b = NULL;
return b;
}
/****************
* Note: This copy function should not interpret the MPI
* but copy it transparently.
*/
gcry_mpi_t
gcry_mpi_copy( gcry_mpi_t a )
{
int i;
gcry_mpi_t b;
if( a && (a->flags & 4) ) {
void *p = gcry_is_secure(a->d)? gcry_xmalloc_secure( (a->sign+7)/8 )
: gcry_xmalloc( (a->sign+7)/8 );
memcpy( p, a->d, (a->sign+7)/8 );
b = gcry_mpi_set_opaque( NULL, p, a->sign );
}
else if( a ) {
b = mpi_is_secure(a)? mpi_alloc_secure( a->nlimbs )
: mpi_alloc( a->nlimbs );
b->nlimbs = a->nlimbs;
b->sign = a->sign;
b->flags = a->flags;
for(i=0; i < b->nlimbs; i++ )
b->d[i] = a->d[i];
}
else
b = NULL;
return b;
}
/* Turn VALUE into an octet string and store it in an allocated buffer
at R_FRAME. If the resulting octet string is shorter than NBYTES
the result will be left padded with zeroes. If VALUE does not fit
into NBYTES an error code is returned. */
static gpg_err_code_t
int2octets (unsigned char **r_frame, gcry_mpi_t value, size_t nbytes)
{
gpg_err_code_t rc;
size_t nframe, noff, n;
unsigned char *frame;
rc = _gcry_mpi_print (GCRYMPI_FMT_USG, NULL, 0, &nframe, value);
if (rc)
return rc;
if (nframe > nbytes)
return GPG_ERR_TOO_LARGE; /* Value too long to fit into NBYTES. */
noff = (nframe < nbytes)? nbytes - nframe : 0;
n = nframe + noff;
frame = mpi_is_secure (value)? xtrymalloc_secure (n) : xtrymalloc (n);
if (!frame)
return gpg_err_code_from_syserror ();
if (noff)
memset (frame, 0, noff);
nframe += noff;
rc = _gcry_mpi_print (GCRYMPI_FMT_USG, frame+noff, nframe-noff, NULL, value);
if (rc)
{
xfree (frame);
return rc;
}
*r_frame = frame;
return 0;
}
void
gcry_mpi_randomize( gcry_mpi_t w,
unsigned int nbits, enum gcry_random_level level )
{
unsigned char *p;
size_t nbytes = (nbits+7)/8;
if (level == GCRY_WEAK_RANDOM)
{
p = mpi_is_secure(w) ? gcry_xmalloc_secure (nbytes)
: gcry_xmalloc (nbytes);
gcry_create_nonce (p, nbytes);
}
else
{
p = mpi_is_secure(w) ? gcry_random_bytes_secure (nbytes, level)
: gcry_random_bytes (nbytes, level);
}
_gcry_mpi_set_buffer( w, p, nbytes, 0 );
gcry_free (p);
}
/* Return an allocated buffer with the MPI (msb first). NBYTES
receives the length of this buffer. Caller must free the return
string. This function returns an allocated buffer with NBYTES set
to zero if the value of A is zero. If sign is not NULL, it will be
set to the sign of the A. On error NULL is returned and ERRNO set
appropriately. */
static unsigned char *
do_get_buffer (gcry_mpi_t a, unsigned int *nbytes, int *sign, int force_secure)
{
unsigned char *p, *buffer;
mpi_limb_t alimb;
int i;
size_t n;
if (sign)
*sign = a->sign;
*nbytes = a->nlimbs * BYTES_PER_MPI_LIMB;
n = *nbytes? *nbytes:1; /* Allocate at least one byte. */
p = buffer = (force_secure || mpi_is_secure(a))? gcry_malloc_secure (n)
: gcry_malloc (n);
if (!buffer)
return NULL;
for (i=a->nlimbs-1; i >= 0; i--)
{
alimb = a->d[i];
#if BYTES_PER_MPI_LIMB == 4
*p++ = alimb >> 24;
*p++ = alimb >> 16;
*p++ = alimb >> 8;
*p++ = alimb ;
#elif BYTES_PER_MPI_LIMB == 8
*p++ = alimb >> 56;
*p++ = alimb >> 48;
*p++ = alimb >> 40;
*p++ = alimb >> 32;
*p++ = alimb >> 24;
*p++ = alimb >> 16;
*p++ = alimb >> 8;
*p++ = alimb ;
#else
# error please implement for this limb size.
#endif
}
/* This is sub-optimal but we need to do the shift operation because
the caller has to free the returned buffer. */
for (p=buffer; *nbytes && !*p; p++, --*nbytes)
;
if (p != buffer)
memmove (buffer,p, *nbytes);
return buffer;
}
/****************
* Return an xmalloced buffer with the MPI (msb first).
* NBYTES receives the length of this buffer. Caller must free the
* return string (This function does return a 0 byte buffer with NBYTES
* set to zero if the value of A is zero. If sign is not NULL, it will
* be set to the sign of the A.
*/
static byte *
do_get_buffer( MPI a, unsigned *nbytes, int *sign, int force_secure )
{
byte *p, *buffer;
mpi_limb_t alimb;
int i;
unsigned int n;
if( sign )
*sign = a->sign;
*nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
if (!n)
n++; /* avoid zero length allocation */
p = buffer = force_secure || mpi_is_secure(a) ? xmalloc_secure(n)
: xmalloc(n);
for(i=a->nlimbs-1; i >= 0; i-- ) {
alimb = a->d[i];
#if BYTES_PER_MPI_LIMB == 4
*p++ = alimb >> 24;
*p++ = alimb >> 16;
*p++ = alimb >> 8;
*p++ = alimb ;
#elif BYTES_PER_MPI_LIMB == 8
*p++ = alimb >> 56;
*p++ = alimb >> 48;
*p++ = alimb >> 40;
*p++ = alimb >> 32;
*p++ = alimb >> 24;
*p++ = alimb >> 16;
*p++ = alimb >> 8;
*p++ = alimb ;
#else
#error please implement for this limb size.
#endif
}
/* this is sub-optimal but we need to do the shift operation
* because the caller has to free the returned buffer */
for(p=buffer; !*p && *nbytes; p++, --*nbytes )
;
if( p != buffer )
memmove(buffer,p, *nbytes);
return buffer;
}
/****************
* This function allocates an MPI which is optimized to hold
* a value as large as the one given in the argument and allocates it
* with the same flags as A.
*/
gcry_mpi_t
_gcry_mpi_alloc_like( gcry_mpi_t a )
{
gcry_mpi_t b;
if( a && (a->flags & 4) ) {
int n = (a->sign+7)/8;
void *p = _gcry_is_secure(a->d)? xtrymalloc_secure (n)
: xtrymalloc (n);
memcpy( p, a->d, n );
b = mpi_set_opaque( NULL, p, a->sign );
}
else if( a ) {
b = mpi_is_secure(a)? mpi_alloc_secure( a->nlimbs )
: mpi_alloc( a->nlimbs );
b->nlimbs = 0;
b->sign = 0;
b->flags = a->flags;
}
else
b = NULL;
return b;
}
void
mpi_mul( MPI w, MPI u, MPI v)
{
mpi_size_t usize, vsize, wsize;
mpi_ptr_t up, vp, wp;
mpi_limb_t cy;
int usign, vsign, usecure, vsecure, sign_product;
int assign_wp=0;
mpi_ptr_t tmp_limb=NULL;
if( u->nlimbs < v->nlimbs ) { /* Swap U and V. */
usize = v->nlimbs;
usign = v->sign;
usecure = mpi_is_secure(v);
up = v->d;
vsize = u->nlimbs;
vsign = u->sign;
vsecure = mpi_is_secure(u);
vp = u->d;
}
else {
usize = u->nlimbs;
usign = u->sign;
usecure = mpi_is_secure(u);
up = u->d;
vsize = v->nlimbs;
vsign = v->sign;
vsecure = mpi_is_secure(v);
vp = v->d;
}
sign_product = usign ^ vsign;
wp = w->d;
/* Ensure W has space enough to store the result. */
wsize = usize + vsize;
if ( !mpi_is_secure (w) && (mpi_is_secure (u) || mpi_is_secure (v)) ) {
/* w is not allocated in secure space but u or v is. To make sure
* that no temporray results are stored in w, we temporary use
* a newly allocated limb space for w */
wp = mpi_alloc_limb_space( wsize, 1 );
assign_wp = 2; /* mark it as 2 so that we can later copy it back to
* mormal memory */
}
else if( w->alloced < wsize ) {
if( wp == up || wp == vp ) {
wp = mpi_alloc_limb_space( wsize, mpi_is_secure(w) );
assign_wp = 1;
}
else {
mpi_resize(w, wsize );
wp = w->d;
}
}
else { /* Make U and V not overlap with W. */
if( wp == up ) {
/* W and U are identical. Allocate temporary space for U. */
up = tmp_limb = mpi_alloc_limb_space( usize, usecure );
/* Is V identical too? Keep it identical with U. */
if( wp == vp )
vp = up;
/* Copy to the temporary space. */
MPN_COPY( up, wp, usize );
}
else if( wp == vp ) {
/* W and V are identical. Allocate temporary space for V. */
vp = tmp_limb = mpi_alloc_limb_space( vsize, vsecure );
/* Copy to the temporary space. */
MPN_COPY( vp, wp, vsize );
}
}
if( !vsize )
wsize = 0;
else {
cy = mpihelp_mul( wp, up, usize, vp, vsize );
wsize -= cy? 0:1;
}
if( assign_wp ) {
if (assign_wp == 2) {
/* copy the temp wp from secure memory back to normal memory */
mpi_ptr_t tmp_wp = mpi_alloc_limb_space (wsize, 0);
MPN_COPY (tmp_wp, wp, wsize);
mpi_free_limb_space (wp);
wp = tmp_wp;
}
mpi_assign_limb_space( w, wp, wsize );
}
w->nlimbs = wsize;
w->sign = sign_product;
if( tmp_limb )
mpi_free_limb_space( tmp_limb );
}
void
mpi_tdiv_qr( MPI quot, MPI rem, MPI num, MPI den)
{
mpi_ptr_t np, dp;
mpi_ptr_t qp, rp;
mpi_size_t nsize = num->nlimbs;
mpi_size_t dsize = den->nlimbs;
mpi_size_t qsize, rsize;
mpi_size_t sign_remainder = num->sign;
mpi_size_t sign_quotient = num->sign ^ den->sign;
unsigned normalization_steps;
mpi_limb_t q_limb;
mpi_ptr_t marker[5];
int markidx=0;
/* Ensure space is enough for quotient and remainder.
* We need space for an extra limb in the remainder, because it's
* up-shifted (normalized) below. */
rsize = nsize + 1;
mpi_resize( rem, rsize);
qsize = rsize - dsize; /* qsize cannot be bigger than this. */
if( qsize <= 0 ) {
if( num != rem ) {
rem->nlimbs = num->nlimbs;
rem->sign = num->sign;
MPN_COPY(rem->d, num->d, nsize);
}
if( quot ) {
/* This needs to follow the assignment to rem, in case the
* numerator and quotient are the same. */
quot->nlimbs = 0;
quot->sign = 0;
}
return;
}
if( quot )
mpi_resize( quot, qsize);
/* Read pointers here, when reallocation is finished. */
np = num->d;
dp = den->d;
rp = rem->d;
/* Optimize division by a single-limb divisor. */
if( dsize == 1 ) {
mpi_limb_t rlimb;
if( quot ) {
qp = quot->d;
rlimb = mpihelp_divmod_1( qp, np, nsize, dp[0] );
qsize -= qp[qsize - 1] == 0;
quot->nlimbs = qsize;
quot->sign = sign_quotient;
}
else
rlimb = mpihelp_mod_1( np, nsize, dp[0] );
rp[0] = rlimb;
rsize = rlimb != 0?1:0;
rem->nlimbs = rsize;
rem->sign = sign_remainder;
return;
}
if( quot ) {
qp = quot->d;
/* Make sure QP and NP point to different objects. Otherwise the
* numerator would be gradually overwritten by the quotient limbs. */
if(qp == np) { /* Copy NP object to temporary space. */
np = marker[markidx++] = mpi_alloc_limb_space(nsize,
mpi_is_secure(quot));
MPN_COPY(np, qp, nsize);
}
}
else /* Put quotient at top of remainder. */
qp = rp + dsize;
count_leading_zeros( normalization_steps, dp[dsize - 1] );
/* Normalize the denominator, i.e. make its most significant bit set by
* shifting it NORMALIZATION_STEPS bits to the left. Also shift the
* numerator the same number of steps (to keep the quotient the same!).
*/
if( normalization_steps ) {
mpi_ptr_t tp;
mpi_limb_t nlimb;
/* Shift up the denominator setting the most significant bit of
* the most significant word. Use temporary storage not to clobber
* the original contents of the denominator. */
tp = marker[markidx++] = mpi_alloc_limb_space(dsize,mpi_is_secure(den));
mpihelp_lshift( tp, dp, dsize, normalization_steps );
dp = tp;
/* Shift up the numerator, possibly introducing a new most
* significant word. Move the shifted numerator in the remainder
* meanwhile. */
nlimb = mpihelp_lshift(rp, np, nsize, normalization_steps);
if( nlimb ) {
rp[nsize] = nlimb;
rsize = nsize + 1;
}
else
rsize = nsize;
}
else {
/* The denominator is already normalized, as required. Copy it to
* temporary space if it overlaps with the quotient or remainder. */
if( dp == rp || (quot && (dp == qp))) {
mpi_ptr_t tp;
tp = marker[markidx++] = mpi_alloc_limb_space(dsize, mpi_is_secure(den));
MPN_COPY( tp, dp, dsize );
dp = tp;
}
/* Move the numerator to the remainder. */
if( rp != np )
MPN_COPY(rp, np, nsize);
rsize = nsize;
}
q_limb = mpihelp_divrem( qp, 0, rp, rsize, dp, dsize );
if( quot ) {
qsize = rsize - dsize;
if(q_limb) {
qp[qsize] = q_limb;
qsize += 1;
}
quot->nlimbs = qsize;
quot->sign = sign_quotient;
}
rsize = dsize;
MPN_NORMALIZE (rp, rsize);
if( normalization_steps && rsize ) {
mpihelp_rshift(rp, rp, rsize, normalization_steps);
rsize -= rp[rsize - 1] == 0?1:0;
}
rem->nlimbs = rsize;
rem->sign = sign_remainder;
while( markidx )
mpi_free_gpg_limb_space(marker[--markidx]);
}
/****************
* RES = BASE ^ EXPO mod MOD
*/
void
gcry_mpi_powm (gcry_mpi_t res,
gcry_mpi_t base, gcry_mpi_t expo, gcry_mpi_t mod)
{
/* Pointer to the limbs of the arguments, their size and signs. */
mpi_ptr_t rp, ep, mp, bp;
mpi_size_t esize, msize, bsize, rsize;
int msign, bsign, rsign;
/* Flags telling the secure allocation status of the arguments. */
int esec, msec, bsec;
/* Size of the result including space for temporary values. */
mpi_size_t size;
/* Helper. */
int mod_shift_cnt;
int negative_result;
mpi_ptr_t mp_marker = NULL;
mpi_ptr_t bp_marker = NULL;
mpi_ptr_t ep_marker = NULL;
mpi_ptr_t xp_marker = NULL;
unsigned int mp_nlimbs = 0;
unsigned int bp_nlimbs = 0;
unsigned int ep_nlimbs = 0;
unsigned int xp_nlimbs = 0;
mpi_ptr_t tspace = NULL;
mpi_size_t tsize = 0;
esize = expo->nlimbs;
msize = mod->nlimbs;
size = 2 * msize;
msign = mod->sign;
esec = mpi_is_secure(expo);
msec = mpi_is_secure(mod);
bsec = mpi_is_secure(base);
rp = res->d;
ep = expo->d;
if (!msize)
grub_fatal ("mpi division by zero");
if (!esize)
{
/* Exponent is zero, result is 1 mod MOD, i.e., 1 or 0 depending
on if MOD equals 1. */
res->nlimbs = (msize == 1 && mod->d[0] == 1) ? 0 : 1;
if (res->nlimbs)
{
RESIZE_IF_NEEDED (res, 1);
rp = res->d;
rp[0] = 1;
}
res->sign = 0;
goto leave;
}
/* Normalize MOD (i.e. make its most significant bit set) as
required by mpn_divrem. This will make the intermediate values
in the calculation slightly larger, but the correct result is
obtained after a final reduction using the original MOD value. */
mp_nlimbs = msec? msize:0;
mp = mp_marker = mpi_alloc_limb_space(msize, msec);
count_leading_zeros (mod_shift_cnt, mod->d[msize-1]);
if (mod_shift_cnt)
_gcry_mpih_lshift (mp, mod->d, msize, mod_shift_cnt);
else
MPN_COPY( mp, mod->d, msize );
bsize = base->nlimbs;
bsign = base->sign;
if (bsize > msize)
{
/* The base is larger than the module. Reduce it.
Allocate (BSIZE + 1) with space for remainder and quotient.
(The quotient is (bsize - msize + 1) limbs.) */
bp_nlimbs = bsec ? (bsize + 1):0;
bp = bp_marker = mpi_alloc_limb_space( bsize + 1, bsec );
MPN_COPY ( bp, base->d, bsize );
/* We don't care about the quotient, store it above the
* remainder, at BP + MSIZE. */
_gcry_mpih_divrem( bp + msize, 0, bp, bsize, mp, msize );
bsize = msize;
/* Canonicalize the base, since we are going to multiply with it
quite a few times. */
MPN_NORMALIZE( bp, bsize );
}
else
bp = base->d;
if (!bsize)
{
res->nlimbs = 0;
res->sign = 0;
goto leave;
}
/* Make BASE, EXPO and MOD not overlap with RES. */
if ( rp == bp )
{
/* RES and BASE are identical. Allocate temp. space for BASE. */
gcry_assert (!bp_marker);
bp_nlimbs = bsec? bsize:0;
bp = bp_marker = mpi_alloc_limb_space( bsize, bsec );
MPN_COPY(bp, rp, bsize);
}
if ( rp == ep )
{
/* RES and EXPO are identical. Allocate temp. space for EXPO. */
ep_nlimbs = esec? esize:0;
ep = ep_marker = mpi_alloc_limb_space( esize, esec );
MPN_COPY(ep, rp, esize);
}
if ( rp == mp )
{
/* RES and MOD are identical. Allocate temporary space for MOD.*/
gcry_assert (!mp_marker);
mp_nlimbs = msec?msize:0;
mp = mp_marker = mpi_alloc_limb_space( msize, msec );
MPN_COPY(mp, rp, msize);
}
/* Copy base to the result. */
if (res->alloced < size)
{
mpi_resize (res, size);
rp = res->d;
}
MPN_COPY ( rp, bp, bsize );
rsize = bsize;
rsign = bsign;
/* Main processing. */
{
mpi_size_t i;
mpi_ptr_t xp;
int c;
mpi_limb_t e;
mpi_limb_t carry_limb;
struct karatsuba_ctx karactx;
xp_nlimbs = msec? (2 * (msize + 1)):0;
xp = xp_marker = mpi_alloc_limb_space( 2 * (msize + 1), msec );
memset( &karactx, 0, sizeof karactx );
negative_result = (ep[0] & 1) && base->sign;
i = esize - 1;
e = ep[i];
count_leading_zeros (c, e);
e = (e << c) << 1; /* Shift the expo bits to the left, lose msb. */
c = BITS_PER_MPI_LIMB - 1 - c;
/* Main loop.
Make the result be pointed to alternately by XP and RP. This
helps us avoid block copying, which would otherwise be
necessary with the overlap restrictions of
_gcry_mpih_divmod. With 50% probability the result after this
loop will be in the area originally pointed by RP (==RES->d),
and with 50% probability in the area originally pointed to by XP. */
for (;;)
{
while (c)
{
mpi_ptr_t tp;
mpi_size_t xsize;
/*mpih_mul_n(xp, rp, rp, rsize);*/
if ( rsize < KARATSUBA_THRESHOLD )
_gcry_mpih_sqr_n_basecase( xp, rp, rsize );
else
{
if ( !tspace )
{
tsize = 2 * rsize;
tspace = mpi_alloc_limb_space( tsize, 0 );
}
else if ( tsize < (2*rsize) )
{
_gcry_mpi_free_limb_space (tspace, 0);
tsize = 2 * rsize;
tspace = mpi_alloc_limb_space (tsize, 0 );
}
_gcry_mpih_sqr_n (xp, rp, rsize, tspace);
}
xsize = 2 * rsize;
if ( xsize > msize )
{
_gcry_mpih_divrem(xp + msize, 0, xp, xsize, mp, msize);
xsize = msize;
}
tp = rp; rp = xp; xp = tp;
rsize = xsize;
/* To mitigate the Yarom/Falkner flush+reload cache
* side-channel attack on the RSA secret exponent, we do
* the multiplication regardless of the value of the
* high-bit of E. But to avoid this performance penalty
* we do it only if the exponent has been stored in secure
* memory and we can thus assume it is a secret exponent. */
if (esec || (mpi_limb_signed_t)e < 0)
{
/*mpih_mul( xp, rp, rsize, bp, bsize );*/
if( bsize < KARATSUBA_THRESHOLD )
_gcry_mpih_mul ( xp, rp, rsize, bp, bsize );
else
_gcry_mpih_mul_karatsuba_case (xp, rp, rsize, bp, bsize,
&karactx);
xsize = rsize + bsize;
if ( xsize > msize )
{
_gcry_mpih_divrem(xp + msize, 0, xp, xsize, mp, msize);
xsize = msize;
}
}
if ( (mpi_limb_signed_t)e < 0 )
{
tp = rp; rp = xp; xp = tp;
rsize = xsize;
}
e <<= 1;
c--;
}
i--;
if ( i < 0 )
break;
e = ep[i];
c = BITS_PER_MPI_LIMB;
}
/* We shifted MOD, the modulo reduction argument, left
MOD_SHIFT_CNT steps. Adjust the result by reducing it with the
original MOD.
Also make sure the result is put in RES->d (where it already
might be, see above). */
if ( mod_shift_cnt )
{
carry_limb = _gcry_mpih_lshift( res->d, rp, rsize, mod_shift_cnt);
rp = res->d;
if ( carry_limb )
{
rp[rsize] = carry_limb;
rsize++;
}
}
else if (res->d != rp)
{
MPN_COPY (res->d, rp, rsize);
rp = res->d;
}
if ( rsize >= msize )
{
_gcry_mpih_divrem(rp + msize, 0, rp, rsize, mp, msize);
rsize = msize;
}
/* Remove any leading zero words from the result. */
if ( mod_shift_cnt )
_gcry_mpih_rshift( rp, rp, rsize, mod_shift_cnt);
MPN_NORMALIZE (rp, rsize);
_gcry_mpih_release_karatsuba_ctx (&karactx );
}
/* Fixup for negative results. */
if ( negative_result && rsize )
{
if ( mod_shift_cnt )
_gcry_mpih_rshift( mp, mp, msize, mod_shift_cnt);
_gcry_mpih_sub( rp, mp, msize, rp, rsize);
rsize = msize;
rsign = msign;
MPN_NORMALIZE(rp, rsize);
}
gcry_assert (res->d == rp);
res->nlimbs = rsize;
res->sign = rsign;
leave:
if (mp_marker)
_gcry_mpi_free_limb_space( mp_marker, mp_nlimbs );
if (bp_marker)
_gcry_mpi_free_limb_space( bp_marker, bp_nlimbs );
if (ep_marker)
_gcry_mpi_free_limb_space( ep_marker, ep_nlimbs );
if (xp_marker)
_gcry_mpi_free_limb_space( xp_marker, xp_nlimbs );
if (tspace)
_gcry_mpi_free_limb_space( tspace, 0 );
}
/****************
* RES = BASE ^ EXPO mod MOD
*/
void
gcry_mpi_powm( gcry_mpi_t res, gcry_mpi_t base, gcry_mpi_t expo, gcry_mpi_t mod)
{
mpi_ptr_t rp, ep, mp, bp;
mpi_size_t esize, msize, bsize, rsize;
int esign, msign, bsign, rsign;
int esec, msec, bsec, rsec;
mpi_size_t size;
int mod_shift_cnt;
int negative_result;
mpi_ptr_t mp_marker=NULL, bp_marker=NULL, ep_marker=NULL;
mpi_ptr_t xp_marker=NULL;
unsigned int mp_nlimbs = 0, bp_nlimbs = 0, ep_nlimbs = 0;
unsigned int xp_nlimbs = 0;
int assign_rp = 0;
mpi_ptr_t tspace = NULL;
mpi_size_t tsize=0; /* to avoid compiler warning */
/* fixme: we should check that the warning is void*/
esize = expo->nlimbs;
msize = mod->nlimbs;
size = 2 * msize;
esign = expo->sign;
msign = mod->sign;
esec = mpi_is_secure(expo);
msec = mpi_is_secure(mod);
bsec = mpi_is_secure(base);
rsec = mpi_is_secure(res);
rp = res->d;
ep = expo->d;
if( !msize )
msize = 1 / msize; /* provoke a signal */
if( !esize ) {
/* Exponent is zero, result is 1 mod MOD, i.e., 1 or 0
* depending on if MOD equals 1. */
rp[0] = 1;
res->nlimbs = (msize == 1 && mod->d[0] == 1) ? 0 : 1;
res->sign = 0;
goto leave;
}
/* Normalize MOD (i.e. make its most significant bit set) as required by
* mpn_divrem. This will make the intermediate values in the calculation
* slightly larger, but the correct result is obtained after a final
* reduction using the original MOD value. */
mp_nlimbs = msec? msize:0;
mp = mp_marker = mpi_alloc_limb_space(msize, msec);
count_leading_zeros( mod_shift_cnt, mod->d[msize-1] );
if( mod_shift_cnt )
_gcry_mpih_lshift( mp, mod->d, msize, mod_shift_cnt );
else
MPN_COPY( mp, mod->d, msize );
bsize = base->nlimbs;
bsign = base->sign;
if( bsize > msize ) { /* The base is larger than the module. Reduce it. */
/* Allocate (BSIZE + 1) with space for remainder and quotient.
* (The quotient is (bsize - msize + 1) limbs.) */
bp_nlimbs = bsec ? (bsize + 1):0;
bp = bp_marker = mpi_alloc_limb_space( bsize + 1, bsec );
MPN_COPY( bp, base->d, bsize );
/* We don't care about the quotient, store it above the remainder,
* at BP + MSIZE. */
_gcry_mpih_divrem( bp + msize, 0, bp, bsize, mp, msize );
bsize = msize;
/* Canonicalize the base, since we are going to multiply with it
* quite a few times. */
MPN_NORMALIZE( bp, bsize );
}
else
bp = base->d;
if( !bsize ) {
res->nlimbs = 0;
res->sign = 0;
goto leave;
}
if( res->alloced < size ) {
/* We have to allocate more space for RES. If any of the input
* parameters are identical to RES, defer deallocation of the old
* space. */
if( rp == ep || rp == mp || rp == bp ) {
rp = mpi_alloc_limb_space( size, rsec );
assign_rp = 1;
}
else {
mpi_resize( res, size );
rp = res->d;
}
}
else { /* Make BASE, EXPO and MOD not overlap with RES. */
if( rp == bp ) {
/* RES and BASE are identical. Allocate temp. space for BASE. */
assert( !bp_marker );
bp_nlimbs = bsec? bsize:0;
bp = bp_marker = mpi_alloc_limb_space( bsize, bsec );
MPN_COPY(bp, rp, bsize);
}
if( rp == ep ) {
/* RES and EXPO are identical. Allocate temp. space for EXPO. */
ep_nlimbs = esec? esize:0;
ep = ep_marker = mpi_alloc_limb_space( esize, esec );
MPN_COPY(ep, rp, esize);
}
if( rp == mp ) {
/* RES and MOD are identical. Allocate temporary space for MOD.*/
assert( !mp_marker );
mp_nlimbs = msec?msize:0;
mp = mp_marker = mpi_alloc_limb_space( msize, msec );
MPN_COPY(mp, rp, msize);
}
}
MPN_COPY( rp, bp, bsize );
rsize = bsize;
rsign = bsign;
{
mpi_size_t i;
mpi_ptr_t xp;
int c;
mpi_limb_t e;
mpi_limb_t carry_limb;
struct karatsuba_ctx karactx;
xp_nlimbs = msec? (2 * (msize + 1)):0;
xp = xp_marker = mpi_alloc_limb_space( 2 * (msize + 1), msec );
memset( &karactx, 0, sizeof karactx );
negative_result = (ep[0] & 1) && base->sign;
i = esize - 1;
e = ep[i];
count_leading_zeros (c, e);
e = (e << c) << 1; /* shift the expo bits to the left, lose msb */
c = BITS_PER_MPI_LIMB - 1 - c;
/* Main loop.
*
* Make the result be pointed to alternately by XP and RP. This
* helps us avoid block copying, which would otherwise be necessary
* with the overlap restrictions of _gcry_mpih_divmod. With 50% probability
* the result after this loop will be in the area originally pointed
* by RP (==RES->d), and with 50% probability in the area originally
* pointed to by XP.
*/
for(;;) {
while( c ) {
mpi_ptr_t tp;
mpi_size_t xsize;
/*mpih_mul_n(xp, rp, rp, rsize);*/
if( rsize < KARATSUBA_THRESHOLD )
_gcry_mpih_sqr_n_basecase( xp, rp, rsize );
else {
if( !tspace ) {
tsize = 2 * rsize;
tspace = mpi_alloc_limb_space( tsize, 0 );
}
else if( tsize < (2*rsize) ) {
_gcry_mpi_free_limb_space (tspace, 0);
tsize = 2 * rsize;
tspace = mpi_alloc_limb_space( tsize, 0 );
}
_gcry_mpih_sqr_n( xp, rp, rsize, tspace );
}
xsize = 2 * rsize;
if( xsize > msize ) {
_gcry_mpih_divrem(xp + msize, 0, xp, xsize, mp, msize);
xsize = msize;
}
tp = rp; rp = xp; xp = tp;
rsize = xsize;
if( (mpi_limb_signed_t)e < 0 ) {
/*mpih_mul( xp, rp, rsize, bp, bsize );*/
if( bsize < KARATSUBA_THRESHOLD ) {
_gcry_mpih_mul( xp, rp, rsize, bp, bsize );
}
else {
_gcry_mpih_mul_karatsuba_case(
xp, rp, rsize, bp, bsize, &karactx );
}
xsize = rsize + bsize;
if( xsize > msize ) {
_gcry_mpih_divrem(xp + msize, 0, xp, xsize, mp, msize);
xsize = msize;
}
tp = rp; rp = xp; xp = tp;
rsize = xsize;
}
e <<= 1;
c--;
}
i--;
if( i < 0 )
break;
e = ep[i];
c = BITS_PER_MPI_LIMB;
}
/* We shifted MOD, the modulo reduction argument, left MOD_SHIFT_CNT
* steps. Adjust the result by reducing it with the original MOD.
*
* Also make sure the result is put in RES->d (where it already
* might be, see above).
*/
if( mod_shift_cnt ) {
carry_limb = _gcry_mpih_lshift( res->d, rp, rsize, mod_shift_cnt);
rp = res->d;
if( carry_limb ) {
rp[rsize] = carry_limb;
rsize++;
}
}
else {
MPN_COPY( res->d, rp, rsize);
rp = res->d;
}
if( rsize >= msize ) {
_gcry_mpih_divrem(rp + msize, 0, rp, rsize, mp, msize);
rsize = msize;
}
/* Remove any leading zero words from the result. */
if( mod_shift_cnt )
_gcry_mpih_rshift( rp, rp, rsize, mod_shift_cnt);
MPN_NORMALIZE (rp, rsize);
_gcry_mpih_release_karatsuba_ctx( &karactx );
}
if( negative_result && rsize ) {
if( mod_shift_cnt )
_gcry_mpih_rshift( mp, mp, msize, mod_shift_cnt);
_gcry_mpih_sub( rp, mp, msize, rp, rsize);
rsize = msize;
rsign = msign;
MPN_NORMALIZE(rp, rsize);
}
res->nlimbs = rsize;
res->sign = rsign;
leave:
if( assign_rp ) _gcry_mpi_assign_limb_space( res, rp, size );
if( mp_marker ) _gcry_mpi_free_limb_space( mp_marker, mp_nlimbs );
if( bp_marker ) _gcry_mpi_free_limb_space( bp_marker, bp_nlimbs );
if( ep_marker ) _gcry_mpi_free_limb_space( ep_marker, ep_nlimbs );
if( xp_marker ) _gcry_mpi_free_limb_space( xp_marker, xp_nlimbs );
if( tspace ) _gcry_mpi_free_limb_space( tspace, 0 );
}