| /* mpicoder.c - Coder for the external representation of MPIs |
| * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 |
| * 2008 Free Software Foundation, Inc. |
| * |
| * This file is part of Libgcrypt. |
| * |
| * Libgcrypt is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU Lesser General Public License as |
| * published by the Free Software Foundation; either version 2.1 of |
| * the License, or (at your option) any later version. |
| * |
| * Libgcrypt 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 Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with this program; if not, see <http://www.gnu.org/licenses/>. |
| */ |
| |
| #include <config.h> |
| #include <stdio.h> |
| #include <string.h> |
| #include <stdlib.h> |
| |
| #include "mpi-internal.h" |
| #include "g10lib.h" |
| |
| #define MAX_EXTERN_MPI_BITS 16384 |
| |
| /* Helper used to scan PGP style MPIs. Returns NULL on failure. */ |
| static gcry_mpi_t |
| mpi_read_from_buffer (const unsigned char *buffer, unsigned *ret_nread, |
| int secure) |
| { |
| int i, j; |
| unsigned int nbits, nbytes, nlimbs, nread=0; |
| mpi_limb_t a; |
| gcry_mpi_t val = MPI_NULL; |
| |
| if ( *ret_nread < 2 ) |
| goto leave; |
| nbits = buffer[0] << 8 | buffer[1]; |
| if ( nbits > MAX_EXTERN_MPI_BITS ) |
| { |
| /* log_debug ("mpi too large (%u bits)\n", nbits); */ |
| goto leave; |
| } |
| else if( !nbits ) |
| { |
| /* log_debug ("an mpi of size 0 is not allowed\n"); */ |
| goto leave; |
| } |
| buffer += 2; |
| nread = 2; |
| |
| nbytes = (nbits+7) / 8; |
| nlimbs = (nbytes+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB; |
| val = secure? mpi_alloc_secure (nlimbs) : mpi_alloc (nlimbs); |
| i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; |
| i %= BYTES_PER_MPI_LIMB; |
| j= val->nlimbs = nlimbs; |
| val->sign = 0; |
| for ( ; j > 0; j-- ) |
| { |
| a = 0; |
| for (; i < BYTES_PER_MPI_LIMB; i++ ) |
| { |
| if ( ++nread > *ret_nread ) |
| { |
| /* log_debug ("mpi larger than buffer"); */ |
| mpi_free (val); |
| val = NULL; |
| goto leave; |
| } |
| a <<= 8; |
| a |= *buffer++; |
| } |
| i = 0; |
| val->d[j-1] = a; |
| } |
| |
| leave: |
| *ret_nread = nread; |
| return val; |
| } |
| |
| |
| /**************** |
| * Fill the mpi VAL from the hex string in STR. |
| */ |
| static int |
| mpi_fromstr (gcry_mpi_t val, const char *str) |
| { |
| int sign = 0; |
| int prepend_zero = 0; |
| int i, j, c, c1, c2; |
| unsigned int nbits, nbytes, nlimbs; |
| mpi_limb_t a; |
| |
| if ( *str == '-' ) |
| { |
| sign = 1; |
| str++; |
| } |
| |
| /* Skip optional hex prefix. */ |
| if ( *str == '0' && str[1] == 'x' ) |
| str += 2; |
| |
| nbits = 4 * strlen (str); |
| if ((nbits % 8)) |
| prepend_zero = 1; |
| |
| nbytes = (nbits+7) / 8; |
| nlimbs = (nbytes+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB; |
| |
| if ( val->alloced < nlimbs ) |
| mpi_resize (val, nlimbs); |
| |
| i = BYTES_PER_MPI_LIMB - (nbytes % BYTES_PER_MPI_LIMB); |
| i %= BYTES_PER_MPI_LIMB; |
| j = val->nlimbs = nlimbs; |
| val->sign = sign; |
| for (; j > 0; j--) |
| { |
| a = 0; |
| for (; i < BYTES_PER_MPI_LIMB; i++) |
| { |
| if (prepend_zero) |
| { |
| c1 = '0'; |
| prepend_zero = 0; |
| } |
| else |
| c1 = *str++; |
| |
| if (!c1) |
| { |
| mpi_clear (val); |
| return 1; /* Error. */ |
| } |
| c2 = *str++; |
| if (!c2) |
| { |
| mpi_clear (val); |
| return 1; /* Error. */ |
| } |
| if ( c1 >= '0' && c1 <= '9' ) |
| c = c1 - '0'; |
| else if ( c1 >= 'a' && c1 <= 'f' ) |
| c = c1 - 'a' + 10; |
| else if ( c1 >= 'A' && c1 <= 'F' ) |
| c = c1 - 'A' + 10; |
| else |
| { |
| mpi_clear (val); |
| return 1; /* Error. */ |
| } |
| c <<= 4; |
| if ( c2 >= '0' && c2 <= '9' ) |
| c |= c2 - '0'; |
| else if( c2 >= 'a' && c2 <= 'f' ) |
| c |= c2 - 'a' + 10; |
| else if( c2 >= 'A' && c2 <= 'F' ) |
| c |= c2 - 'A' + 10; |
| else |
| { |
| mpi_clear(val); |
| return 1; /* Error. */ |
| } |
| a <<= 8; |
| a |= c; |
| } |
| i = 0; |
| val->d[j-1] = a; |
| } |
| |
| return 0; /* Okay. */ |
| } |
| |
| |
| /* Dump the value of A in a format suitable for debugging to |
| Libgcrypt's logging stream. Note that one leading space but no |
| trailing space or linefeed will be printed. It is okay to pass |
| NULL for A. */ |
| void |
| gcry_mpi_dump (const gcry_mpi_t a) |
| { |
| int i; |
| |
| log_printf (" "); |
| if (!a) |
| log_printf ("[MPI_NULL]"); |
| else |
| { |
| if (a->sign) |
| log_printf ( "-"); |
| #if BYTES_PER_MPI_LIMB == 2 |
| # define X "4" |
| #elif BYTES_PER_MPI_LIMB == 4 |
| # define X "8" |
| #elif BYTES_PER_MPI_LIMB == 8 |
| # define X "16" |
| #elif BYTES_PER_MPI_LIMB == 16 |
| # define X "32" |
| #else |
| # error please define the format here |
| #endif |
| for (i=a->nlimbs; i > 0 ; i-- ) |
| { |
| log_printf (i != a->nlimbs? "%0" X "lX":"%lX", (ulong)a->d[i-1]); |
| } |
| #undef X |
| if (!a->nlimbs) |
| log_printf ("0"); |
| } |
| } |
| |
| /* Convience function used internally. */ |
| void |
| _gcry_log_mpidump (const char *text, gcry_mpi_t a) |
| { |
| log_printf ("%s:", text); |
| gcry_mpi_dump (a); |
| log_printf ("\n"); |
| } |
| |
| |
| /* 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; !*p && *nbytes; p++, --*nbytes) |
| ; |
| if (p != buffer) |
| memmove (buffer,p, *nbytes); |
| return buffer; |
| } |
| |
| |
| byte * |
| _gcry_mpi_get_buffer (gcry_mpi_t a, unsigned int *nbytes, int *sign) |
| { |
| return do_get_buffer (a, nbytes, sign, 0); |
| } |
| |
| byte * |
| _gcry_mpi_get_secure_buffer (gcry_mpi_t a, unsigned *nbytes, int *sign) |
| { |
| return do_get_buffer (a, nbytes, sign, 1); |
| } |
| |
| |
| /* |
| * Use the NBYTES at BUFFER_ARG to update A. Set the sign of a to |
| * SIGN. |
| */ |
| void |
| _gcry_mpi_set_buffer (gcry_mpi_t a, const void *buffer_arg, |
| unsigned int nbytes, int sign) |
| { |
| const unsigned char *buffer = (const unsigned char*)buffer_arg; |
| const unsigned char *p; |
| mpi_limb_t alimb; |
| int nlimbs; |
| int i; |
| |
| nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB; |
| RESIZE_IF_NEEDED(a, nlimbs); |
| a->sign = sign; |
| |
| for (i=0, p = buffer+nbytes-1; p >= buffer+BYTES_PER_MPI_LIMB; ) |
| { |
| #if BYTES_PER_MPI_LIMB == 4 |
| alimb = *p-- ; |
| alimb |= *p-- << 8 ; |
| alimb |= *p-- << 16 ; |
| alimb |= *p-- << 24 ; |
| #elif BYTES_PER_MPI_LIMB == 8 |
| alimb = (mpi_limb_t)*p-- ; |
| alimb |= (mpi_limb_t)*p-- << 8 ; |
| alimb |= (mpi_limb_t)*p-- << 16 ; |
| alimb |= (mpi_limb_t)*p-- << 24 ; |
| alimb |= (mpi_limb_t)*p-- << 32 ; |
| alimb |= (mpi_limb_t)*p-- << 40 ; |
| alimb |= (mpi_limb_t)*p-- << 48 ; |
| alimb |= (mpi_limb_t)*p-- << 56 ; |
| #else |
| # error please implement for this limb size. |
| #endif |
| a->d[i++] = alimb; |
| } |
| if ( p >= buffer ) |
| { |
| #if BYTES_PER_MPI_LIMB == 4 |
| alimb = *p--; |
| if (p >= buffer) |
| alimb |= *p-- << 8; |
| if (p >= buffer) |
| alimb |= *p-- << 16; |
| if (p >= buffer) |
| alimb |= *p-- << 24; |
| #elif BYTES_PER_MPI_LIMB == 8 |
| alimb = (mpi_limb_t)*p--; |
| if (p >= buffer) |
| alimb |= (mpi_limb_t)*p-- << 8; |
| if (p >= buffer) |
| alimb |= (mpi_limb_t)*p-- << 16; |
| if (p >= buffer) |
| alimb |= (mpi_limb_t)*p-- << 24; |
| if (p >= buffer) |
| alimb |= (mpi_limb_t)*p-- << 32; |
| if (p >= buffer) |
| alimb |= (mpi_limb_t)*p-- << 40; |
| if (p >= buffer) |
| alimb |= (mpi_limb_t)*p-- << 48; |
| if (p >= buffer) |
| alimb |= (mpi_limb_t)*p-- << 56; |
| #else |
| # error please implement for this limb size. |
| #endif |
| a->d[i++] = alimb; |
| } |
| a->nlimbs = i; |
| gcry_assert (i == nlimbs); |
| } |
| |
| |
| /* Convert the external representation of an integer stored in BUFFER |
| with a length of BUFLEN into a newly create MPI returned in |
| RET_MPI. If NBYTES is not NULL, it will receive the number of |
| bytes actually scanned after a successful operation. */ |
| gcry_error_t |
| gcry_mpi_scan (struct gcry_mpi **ret_mpi, enum gcry_mpi_format format, |
| const void *buffer_arg, size_t buflen, size_t *nscanned) |
| { |
| const unsigned char *buffer = (const unsigned char*)buffer_arg; |
| struct gcry_mpi *a = NULL; |
| unsigned int len; |
| int secure = (buffer && gcry_is_secure (buffer)); |
| |
| if (format == GCRYMPI_FMT_SSH) |
| len = 0; |
| else |
| len = buflen; |
| |
| if (format == GCRYMPI_FMT_STD) |
| { |
| const unsigned char *s = buffer; |
| |
| a = secure? mpi_alloc_secure ((len+BYTES_PER_MPI_LIMB-1) |
| /BYTES_PER_MPI_LIMB) |
| : mpi_alloc ((len+BYTES_PER_MPI_LIMB-1)/BYTES_PER_MPI_LIMB); |
| if (len) |
| { |
| a->sign = !!(*s & 0x80); |
| if (a->sign) |
| { |
| /* FIXME: we have to convert from 2compl to magnitude format */ |
| mpi_free (a); |
| return gcry_error (GPG_ERR_INTERNAL); |
| } |
| else |
| _gcry_mpi_set_buffer (a, s, len, 0); |
| } |
| if (ret_mpi) |
| { |
| mpi_normalize ( a ); |
| *ret_mpi = a; |
| } |
| else |
| mpi_free(a); |
| return 0; |
| } |
| else if (format == GCRYMPI_FMT_USG) |
| { |
| a = secure? mpi_alloc_secure ((len+BYTES_PER_MPI_LIMB-1) |
| /BYTES_PER_MPI_LIMB) |
| : mpi_alloc ((len+BYTES_PER_MPI_LIMB-1)/BYTES_PER_MPI_LIMB); |
| |
| if (len) |
| _gcry_mpi_set_buffer (a, buffer, len, 0); |
| if (ret_mpi) |
| { |
| mpi_normalize ( a ); |
| *ret_mpi = a; |
| } |
| else |
| mpi_free(a); |
| return 0; |
| } |
| else if (format == GCRYMPI_FMT_PGP) |
| { |
| a = mpi_read_from_buffer (buffer, &len, secure); |
| if (nscanned) |
| *nscanned = len; |
| if (ret_mpi && a) |
| { |
| mpi_normalize (a); |
| *ret_mpi = a; |
| } |
| else if (a) |
| { |
| mpi_free(a); |
| a = NULL; |
| } |
| return a? 0 : gcry_error (GPG_ERR_INV_OBJ); |
| } |
| else if (format == GCRYMPI_FMT_SSH) |
| { |
| const unsigned char *s = buffer; |
| size_t n; |
| |
| if (len && len < 4) |
| return gcry_error (GPG_ERR_TOO_SHORT); |
| |
| n = (s[0] << 24 | s[1] << 16 | s[2] << 8 | s[3]); |
| s += 4; |
| if (len) |
| len -= 4; |
| if (len && n > len) |
| return gcry_error (GPG_ERR_TOO_LARGE); |
| |
| a = secure? mpi_alloc_secure ((n+BYTES_PER_MPI_LIMB-1) |
| /BYTES_PER_MPI_LIMB) |
| : mpi_alloc ((n+BYTES_PER_MPI_LIMB-1)/BYTES_PER_MPI_LIMB); |
| if (n) |
| { |
| a->sign = !!(*s & 0x80); |
| if (a->sign) |
| { |
| /* FIXME: we have to convert from 2compl to magnitude format */ |
| mpi_free(a); |
| return gcry_error (GPG_ERR_INTERNAL); |
| } |
| else |
| _gcry_mpi_set_buffer( a, s, n, 0 ); |
| } |
| if (nscanned) |
| *nscanned = n+4; |
| if (ret_mpi) |
| { |
| mpi_normalize ( a ); |
| *ret_mpi = a; |
| } |
| else |
| mpi_free(a); |
| return 0; |
| } |
| else if (format == GCRYMPI_FMT_HEX) |
| { |
| /* We can only handle C strings for now. */ |
| if (buflen) |
| return gcry_error (GPG_ERR_INV_ARG); |
| |
| a = secure? mpi_alloc_secure (0) : mpi_alloc(0); |
| if (mpi_fromstr (a, (const char *)buffer)) |
| { |
| mpi_free (a); |
| return gcry_error (GPG_ERR_INV_OBJ); |
| } |
| if (ret_mpi) |
| { |
| mpi_normalize ( a ); |
| *ret_mpi = a; |
| } |
| else |
| mpi_free(a); |
| return 0; |
| } |
| else |
| return gcry_error (GPG_ERR_INV_ARG); |
| } |
| |
| |
| /* Convert the big integer A into the external representation |
| described by FORMAT and store it in the provided BUFFER which has |
| been allocated by the user with a size of BUFLEN bytes. NWRITTEN |
| receives the actual length of the external representation unless it |
| has been passed as NULL. BUFFER may be NULL to query the required |
| length. */ |
| gcry_error_t |
| gcry_mpi_print (enum gcry_mpi_format format, |
| unsigned char *buffer, size_t buflen, |
| size_t *nwritten, struct gcry_mpi *a) |
| { |
| unsigned int nbits = mpi_get_nbits (a); |
| size_t len; |
| size_t dummy_nwritten; |
| |
| if (!nwritten) |
| nwritten = &dummy_nwritten; |
| |
| len = buflen; |
| *nwritten = 0; |
| if (format == GCRYMPI_FMT_STD) |
| { |
| unsigned char *tmp; |
| int extra = 0; |
| unsigned int n; |
| |
| if (a->sign) |
| return gcry_error (GPG_ERR_INTERNAL); /* Can't handle it yet. */ |
| |
| tmp = _gcry_mpi_get_buffer (a, &n, NULL); |
| if (!tmp) |
| return gpg_error_from_syserror (); |
| if (n && (*tmp & 0x80)) |
| { |
| n++; |
| extra=1; |
| } |
| |
| if (buffer && n > len) |
| { |
| /* The provided buffer is too short. */ |
| gcry_free (tmp); |
| return gcry_error (GPG_ERR_TOO_SHORT); |
| } |
| if (buffer) |
| { |
| unsigned char *s = buffer; |
| |
| if (extra) |
| *s++ = 0; |
| memcpy (s, tmp, n-extra); |
| } |
| gcry_free(tmp); |
| *nwritten = n; |
| return 0; |
| } |
| else if (format == GCRYMPI_FMT_USG) |
| { |
| unsigned int n = (nbits + 7)/8; |
| |
| /* Note: We ignore the sign for this format. */ |
| /* FIXME: for performance reasons we should put this into |
| mpi_aprint because we can then use the buffer directly. */ |
| if (buffer && n > len) |
| return gcry_error (GPG_ERR_TOO_SHORT); |
| if (buffer) |
| { |
| unsigned char *tmp; |
| |
| tmp = _gcry_mpi_get_buffer (a, &n, NULL); |
| if (!tmp) |
| return gpg_error_from_syserror (); |
| memcpy (buffer, tmp, n); |
| gcry_free (tmp); |
| } |
| *nwritten = n; |
| return 0; |
| } |
| else if (format == GCRYMPI_FMT_PGP) |
| { |
| unsigned int n = (nbits + 7)/8; |
| |
| /* The PGP format can only handle unsigned integers. */ |
| if( a->sign ) |
| return gcry_error (GPG_ERR_INV_ARG); |
| |
| if (buffer && n+2 > len) |
| return gcry_error (GPG_ERR_TOO_SHORT); |
| |
| if (buffer) |
| { |
| unsigned char *tmp; |
| unsigned char *s = buffer; |
| |
| s[0] = nbits >> 8; |
| s[1] = nbits; |
| |
| tmp = _gcry_mpi_get_buffer (a, &n, NULL); |
| if (!tmp) |
| return gpg_error_from_syserror (); |
| memcpy (s+2, tmp, n); |
| gcry_free (tmp); |
| } |
| *nwritten = n+2; |
| return 0; |
| } |
| else if (format == GCRYMPI_FMT_SSH) |
| { |
| unsigned char *tmp; |
| int extra = 0; |
| unsigned int n; |
| |
| if (a->sign) |
| return gcry_error (GPG_ERR_INTERNAL); /* Can't handle it yet. */ |
| |
| tmp = _gcry_mpi_get_buffer (a, &n, NULL); |
| if (!tmp) |
| return gpg_error_from_syserror (); |
| if (n && (*tmp & 0x80)) |
| { |
| n++; |
| extra=1; |
| } |
| |
| if (buffer && n+4 > len) |
| { |
| gcry_free(tmp); |
| return gcry_error (GPG_ERR_TOO_SHORT); |
| } |
| |
| if (buffer) |
| { |
| unsigned char *s = buffer; |
| |
| *s++ = n >> 24; |
| *s++ = n >> 16; |
| *s++ = n >> 8; |
| *s++ = n; |
| if (extra) |
| *s++ = 0; |
| |
| memcpy (s, tmp, n-extra); |
| } |
| gcry_free (tmp); |
| *nwritten = 4+n; |
| return 0; |
| } |
| else if (format == GCRYMPI_FMT_HEX) |
| { |
| unsigned char *tmp; |
| int i; |
| int extra = 0; |
| unsigned int n = 0; |
| |
| tmp = _gcry_mpi_get_buffer (a, &n, NULL); |
| if (!tmp) |
| return gpg_error_from_syserror (); |
| if (!n || (*tmp & 0x80)) |
| extra = 2; |
| |
| if (buffer && 2*n + extra + !!a->sign + 1 > len) |
| { |
| gcry_free(tmp); |
| return gcry_error (GPG_ERR_TOO_SHORT); |
| } |
| if (buffer) |
| { |
| unsigned char *s = buffer; |
| |
| if (a->sign) |
| *s++ = '-'; |
| if (extra) |
| { |
| *s++ = '0'; |
| *s++ = '0'; |
| } |
| |
| for (i=0; i < n; i++) |
| { |
| unsigned int c = tmp[i]; |
| |
| *s++ = (c >> 4) < 10? '0'+(c>>4) : 'A'+(c>>4)-10 ; |
| c &= 15; |
| *s++ = c < 10? '0'+c : 'A'+c-10 ; |
| } |
| *s++ = 0; |
| *nwritten = s - buffer; |
| } |
| else |
| { |
| *nwritten = 2*n + extra + !!a->sign + 1; |
| } |
| gcry_free (tmp); |
| return 0; |
| } |
| else |
| return gcry_error (GPG_ERR_INV_ARG); |
| } |
| |
| |
| /* |
| * Like gcry_mpi_print but this function allocates the buffer itself. |
| * The caller has to supply the address of a pointer. NWRITTEN may be |
| * NULL. |
| */ |
| gcry_error_t |
| gcry_mpi_aprint (enum gcry_mpi_format format, |
| unsigned char **buffer, size_t *nwritten, |
| struct gcry_mpi *a) |
| { |
| size_t n; |
| gcry_error_t rc; |
| |
| *buffer = NULL; |
| rc = gcry_mpi_print (format, NULL, 0, &n, a); |
| if (rc) |
| return rc; |
| |
| *buffer = mpi_is_secure(a) ? gcry_malloc_secure (n) : gcry_malloc (n); |
| if (!*buffer) |
| return gpg_error_from_syserror (); |
| rc = gcry_mpi_print( format, *buffer, n, &n, a ); |
| if (rc) |
| { |
| gcry_free(*buffer); |
| *buffer = NULL; |
| } |
| else if (nwritten) |
| *nwritten = n; |
| return rc; |
| } |
| |
