agent/pkdecrypt.c

   1 /* pkdecrypt.c - public key decryption (well, acually using a secret key)
   2  *      Copyright (C) 2001, 2003 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 3 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, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <config.h>
  21 #include <errno.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <ctype.h>
  26 #include <assert.h>
  27 #include <unistd.h>
  28 #include <sys/stat.h>
  29
  30 #include "agent.h"
  31
  32
  33 /* DECRYPT the stuff in ciphertext which is expected to be a S-Exp.
  34    Try to get the key from CTRL and write the decoded stuff back to
  35    OUTFP. */
  36 int
  37 agent_pkdecrypt (ctrl_t ctrl, const char *desc_text,
  38                  const unsigned char *ciphertext, size_t ciphertextlen,
  39                  membuf_t *outbuf)
  40 {
  41   gcry_sexp_t s_skey = NULL, s_cipher = NULL, s_plain = NULL;
  42   unsigned char *shadow_info = NULL;
  43   int rc;
  44   char *buf = NULL;
  45   size_t len;
  46
  47   if (!ctrl->have_keygrip)
  48     {
  49       log_error ("speculative decryption not yet supported\n");
  50       rc = gpg_error (GPG_ERR_NO_SECKEY);
  51       goto leave;
  52     }
  53
  54   rc = gcry_sexp_sscan (&s_cipher, NULL, (char*)ciphertext, ciphertextlen);
  55   if (rc)
  56     {
  57       log_error ("failed to convert ciphertext: %s\n", gpg_strerror (rc));
  58       rc = gpg_error (GPG_ERR_INV_DATA);
  59       goto leave;
  60     }
  61
  62   if (DBG_CRYPTO)
  63     {
  64       log_printhex ("keygrip:", ctrl->keygrip, 20);
  65       log_printhex ("cipher: ", ciphertext, ciphertextlen);
  66     }
  67   rc = agent_key_from_file (ctrl, desc_text,
  68                             ctrl->keygrip, &shadow_info,
  69                             CACHE_MODE_NORMAL, &s_skey);
  70   if (rc)
  71     {
  72       if (gpg_err_code (rc) == GPG_ERR_ENOENT)
  73         rc = gpg_error (GPG_ERR_NO_SECKEY);
  74       else
  75         log_error ("failed to read the secret key\n");
  76       goto leave;
  77     }
  78
  79   if (!s_skey)
  80     { /* divert operation to the smartcard */
  81
  82       if (!gcry_sexp_canon_len (ciphertext, ciphertextlen, NULL, NULL))
  83         {
  84           rc = gpg_error (GPG_ERR_INV_SEXP);
  85           goto leave;
  86         }
  87
  88       rc = divert_pkdecrypt (ctrl, ciphertext, shadow_info, &buf, &len );
  89       if (rc)
  90         {
  91           log_error ("smartcard decryption failed: %s\n", gpg_strerror (rc));
  92           goto leave;
  93         }
  94
  95       {
  96         char tmpbuf[60];
  97
  98         sprintf (tmpbuf, "(5:value%u:", (unsigned int)len);
  99         put_membuf (outbuf, tmpbuf, strlen (tmpbuf));
 100         put_membuf (outbuf, buf, len);
 101         put_membuf (outbuf, ")", 2);
 102       }
 103     }
 104   else
 105     { /* No smartcard, but a private key */
 106 /*       if (DBG_CRYPTO ) */
 107 /*         { */
 108 /*           log_debug ("skey: "); */
 109 /*           gcry_sexp_dump (s_skey); */
 110 /*         } */
 111
 112       rc = gcry_pk_decrypt (&s_plain, s_cipher, s_skey);
 113       if (rc)
 114         {
 115           log_error ("decryption failed: %s\n", gpg_strerror (rc));
 116           goto leave;
 117         }
 118
 119       if (DBG_CRYPTO)
 120         {
 121           log_debug ("plain: ");
 122           gcry_sexp_dump (s_plain);
 123         }
 124       len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, NULL, 0);
 125       assert (len);
 126       buf = xmalloc (len);
 127       len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, buf, len);
 128       assert (len);
 129       if (*buf == '(')
 130         put_membuf (outbuf, buf, len);
 131       else
 132         {
 133           /* Old style libgcrypt: This is only an S-expression
 134              part. Turn it into a complete S-expression. */
 135           put_membuf (outbuf, "(5:value", 8);
 136           put_membuf (outbuf, buf, len);
 137           put_membuf (outbuf, ")", 2);
 138         }
 139     }
 140
 141
 142  leave:
 143   gcry_sexp_release (s_skey);
 144   gcry_sexp_release (s_plain);
 145   gcry_sexp_release (s_cipher);
 146   xfree (buf);
 147   xfree (shadow_info);
 148   return rc;
 149 }
 150
 151