gnupg/common/sexputil.c

/* sexputil.c - Utility fnctions for S-expressions.
 * Copyright (C) 2005 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG 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.
 *
 * GnuPG 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

/* This file implements a few utility functions useful when working
   with canonical encrypted S-expresions (i.e. not the S-exprssion
   objects from libgcrypt).  */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#ifdef HAVE_LOCALE_H
#include <locale.h>
#endif

#include "util.h"


/* Return the so called "keygrip" which is the SHA-1 hash of the
   public key parameters expressed in a way depended on the algorithm.

   KEY is expected to be an canonical encoded S-expression with a
   public or private key. KEYLEN is the length of that buffer.

   GRIP must be at least 20 bytes long On success 0 is return, on
   error an aerror code. */
gpg_error_t
keygrip_from_canon_sexp (const unsigned char *key, size_t keylen,
                         unsigned char *grip)
{
  gpg_error_t err;
  gcry_sexp_t sexp;

  if (!grip)
    return gpg_error (GPG_ERR_INV_VALUE);
  err = gcry_sexp_sscan (&sexp, NULL, key, keylen);
  if (err)
    return err;
  if (!gcry_pk_get_keygrip (sexp, grip))
    err = gpg_error (GPG_ERR_INTERNAL);
  gcry_sexp_release (sexp);
  return err;
}


/* Compare two simple S-expressions like "(3:foo)".  Returns 0 if they
   are identical or !0 if they are not.  Not that this function can't
   be used for sorting. */
int
cmp_simple_canon_sexp (const unsigned char *a, const unsigned char *b)
{
  unsigned long n1, n2;
  char *endp;

  if (!a && !b)
    return 0; /* Both are NULL, they are identical. */
  if (!a || !b)
    return 1; /* One is NULL, they are not identical. */
  if (*a != '(' || *b != '(')
    log_bug ("invalid S-exp in cmp_simple_canon_sexp\n");

  a++;
  n1 = strtoul (a, &endp, 10);
  a = endp;
  b++;
  n2 = strtoul (b, &endp, 10);
  b = endp;

  if (*a != ':' || *b != ':' )
    log_bug ("invalid S-exp in cmp_simple_canon_sexp\n");
  if (n1 != n2)
    return 1; /* Not the same. */

  for (a++, b++; n1; n1--, a++, b++)
    if (*a != *b)
      return 1; /* Not the same. */
  return 0;
}


/* Create a simple S-expression from the hex string at LIBNE.  Returns
   a newly allocated buffer with that canonical encoded S-expression
   or NULL in case of an error.  On return the number of characters
   scanned in LINE will be stored at NSCANNED.  This fucntions stops
   converting at the first character not representing a hexdigit. Odd
   numbers of hex digits are allowed; a leading zero is then
   assumed. If no characters have been found, NULL is returned.*/
unsigned char *
make_simple_sexp_from_hexstr (const char *line, size_t *nscanned)
{
  size_t n, len;
  const char *s;
  unsigned char *buf;
  unsigned char *p;
  char numbuf[50];

  for (n=0, s=line; hexdigitp (s); s++, n++)
    ;
  if (nscanned)
    *nscanned = n;
  if (!n)
    return NULL;
  len = ((n+1) & ~0x01)/2; 
  sprintf (numbuf, "(%u:", (unsigned int)len);
  buf = xtrymalloc (strlen (numbuf) + len + 1 + 1);
  if (!buf)
    return NULL;
  p = stpcpy (buf, numbuf);
  s = line;
  if ((n&1))
    {
      *p++ = xtoi_1 (s);
      s++;
      n--;
    }
  for (; n > 1; n -=2, s += 2)
    *p++ = xtoi_2 (s);
  *p++ = ')';
  *p = 0; /* (Not really neaded.) */

  return buf;
}