agent/pksign.c

   1 /* pksign.c - public key signing (well, actually using a secret key)
   2  * Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  19  */
  20
  21 #include <config.h>
  22 #include <errno.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <ctype.h>
  27 #include <assert.h>
  28 #include <unistd.h>
  29 #include <sys/stat.h>
  30
  31 #include "agent.h"
  32
  33
  34 static int
  35 do_encode_md (const byte * md, size_t mdlen, int algo, gcry_sexp_t * r_hash)
  36 {
  37   gcry_sexp_t hash;
  38   const char *s;
  39   char tmp[16+1];
  40   int i, rc;
  41
  42   s = gcry_md_algo_name (algo);
  43   if (s && strlen (s) < 16)
  44     {
  45       for (i=0; i < strlen (s); i++)
  46         tmp[i] = tolower (s[i]);
  47       tmp[i] = '\0';
  48     }
  49   rc = gcry_sexp_build (&hash, NULL,
  50                         "(data (flags pkcs1) (hash %s %b))",
  51                         tmp,
  52                         mdlen, md);
  53   *r_hash = hash;
  54   return rc;
  55 }
  56
  57
  58 /* SIGN whatever information we have accumulated in CTRL and write it
  59    back to OUTFP. */
  60 int
  61 agent_pksign (CTRL ctrl, const char *desc_text, FILE *outfp, int ignore_cache)
  62 {
  63   gcry_sexp_t s_skey = NULL, s_hash = NULL, s_sig = NULL;
  64   unsigned char *shadow_info = NULL;
  65   int rc;
  66   char *buf = NULL;
  67   size_t len;
  68
  69   if (!ctrl->have_keygrip)
  70     return gpg_error (GPG_ERR_NO_SECKEY);
  71
  72   rc = agent_key_from_file (ctrl, desc_text, ctrl->keygrip,
  73                             &shadow_info, ignore_cache, &s_skey);
  74   if (rc)
  75     {
  76       log_error ("failed to read the secret key\n");
  77       goto leave;
  78     }
  79
  80   if (!s_skey)
  81     { /* divert operation to the smartcard */
  82       unsigned char *sigbuf;
  83
  84       rc = divert_pksign (ctrl,
  85                           ctrl->digest.value,
  86                           ctrl->digest.valuelen,
  87                           ctrl->digest.algo,
  88                           shadow_info, &sigbuf);
  89       if (rc)
  90         {
  91           log_error ("smartcard signing failed: %s\n", gpg_strerror (rc));
  92           goto leave;
  93         }
  94       len = gcry_sexp_canon_len (sigbuf, 0, NULL, NULL);
  95       assert (len);
  96       buf = sigbuf;
  97     }
  98   else
  99     { /* no smartcard, but a private key */
 100
 101       /* put the hash into a sexp */
 102       rc = do_encode_md (ctrl->digest.value,
 103                          ctrl->digest.valuelen,
 104                          ctrl->digest.algo,
 105                          &s_hash);
 106       if (rc)
 107         goto leave;
 108
 109       if (DBG_CRYPTO)
 110         {
 111           log_debug ("skey: ");
 112           gcry_sexp_dump (s_skey);
 113         }
 114
 115       /* sign */
 116       rc = gcry_pk_sign (&s_sig, s_hash, s_skey);
 117       if (rc)
 118         {
 119           log_error ("signing failed: %s\n", gpg_strerror (rc));
 120           goto leave;
 121         }
 122
 123       if (DBG_CRYPTO)
 124         {
 125           log_debug ("result: ");
 126           gcry_sexp_dump (s_sig);
 127         }
 128
 129       len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, NULL, 0);
 130       assert (len);
 131       buf = xmalloc (len);
 132       len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, buf, len);
 133       assert (len);
 134     }
 135
 136   /* FIXME: we must make sure that no buffering takes place or we are
 137      in full control of the buffer memory (easy to do) - should go
 138      into assuan. */
 139   fwrite (buf, 1, len, outfp);
 140
 141  leave:
 142   gcry_sexp_release (s_skey);
 143   gcry_sexp_release (s_hash);
 144   gcry_sexp_release (s_sig);
 145   xfree (buf);
 146   xfree (shadow_info);
 147   return rc;
 148 }
 149
 150