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 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  19  * USA.
  20  */
  21
  22 #include <config.h>
  23 #include <errno.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <ctype.h>
  28 #include <assert.h>
  29 #include <unistd.h>
  30 #include <sys/stat.h>
  31
  32 #include "agent.h"
  33
  34
  35 /* DECRYPT the stuff in ciphertext which is expected to be a S-Exp.
  36    Try to get the key from CTRL and write the decoded stuff back to
  37    OUTFP. */
  38 int
  39 agent_pkdecrypt (ctrl_t ctrl, const char *desc_text,
  40                  const unsigned char *ciphertext, size_t ciphertextlen,
  41                  membuf_t *outbuf)
  42 {
  43   gcry_sexp_t s_skey = NULL, s_cipher = NULL, s_plain = NULL;
  44   unsigned char *shadow_info = NULL;
  45   int rc;
  46   char *buf = NULL;
  47   size_t len;
  48
  49   if (!ctrl->have_keygrip)
  50     {
  51       log_error ("speculative decryption not yet supported\n");
  52       rc = gpg_error (GPG_ERR_NO_SECKEY);
  53       goto leave;
  54     }
  55
  56   rc = gcry_sexp_sscan (&s_cipher, NULL, (char*)ciphertext, ciphertextlen);
  57   if (rc)
  58     {
  59       log_error ("failed to convert ciphertext: %s\n", gpg_strerror (rc));
  60       rc = gpg_error (GPG_ERR_INV_DATA);
  61       goto leave;
  62     }
  63
  64   if (DBG_CRYPTO)
  65     {
  66       log_printhex ("keygrip:", ctrl->keygrip, 20);
  67       log_printhex ("cipher: ", ciphertext, ciphertextlen);
  68     }
  69   rc = agent_key_from_file (ctrl, desc_text,
  70                             ctrl->keygrip, &shadow_info,
  71                             CACHE_MODE_NORMAL, &s_skey);
  72   if (rc)
  73     {
  74       log_error ("failed to read the secret key\n");
  75       goto leave;
  76     }
  77
  78   if (!s_skey)
  79     { /* divert operation to the smartcard */
  80
  81       if (!gcry_sexp_canon_len (ciphertext, ciphertextlen, NULL, NULL))
  82         {
  83           rc = gpg_error (GPG_ERR_INV_SEXP);
  84           goto leave;
  85         }
  86
  87       rc = divert_pkdecrypt (ctrl, ciphertext, shadow_info, &buf, &len );
  88       if (rc)
  89         {
  90           log_error ("smartcard decryption failed: %s\n", gpg_strerror (rc));
  91           goto leave;
  92         }
  93
  94       {
  95         char tmpbuf[60];
  96
  97         sprintf (tmpbuf, "(5:value%u:", (unsigned int)len);
  98         put_membuf (outbuf, tmpbuf, strlen (tmpbuf));
  99         put_membuf (outbuf, buf, len);
 100         put_membuf (outbuf, ")", 2);
 101       }
 102     }
 103   else
 104     { /* No smartcard, but a private key */
 105 /*       if (DBG_CRYPTO ) */
 106 /*         { */
 107 /*           log_debug ("skey: "); */
 108 /*           gcry_sexp_dump (s_skey); */
 109 /*         } */
 110
 111       rc = gcry_pk_decrypt (&s_plain, s_cipher, s_skey);
 112       if (rc)
 113         {
 114           log_error ("decryption failed: %s\n", gpg_strerror (rc));
 115           goto leave;
 116         }
 117
 118       if (DBG_CRYPTO)
 119         {
 120           log_debug ("plain: ");
 121           gcry_sexp_dump (s_plain);
 122         }
 123       len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, NULL, 0);
 124       assert (len);
 125       buf = xmalloc (len);
 126       len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, buf, len);
 127       assert (len);
 128       if (*buf == '(')
 129         put_membuf (outbuf, buf, len);
 130       else
 131         {
 132           /* Old style libgcrypt: This is only an S-expression
 133              part. Turn it into a complete S-expression. */
 134           put_membuf (outbuf, "(5:value", 8);
 135           put_membuf (outbuf, buf, len);
 136           put_membuf (outbuf, ")", 2);
 137         }
 138     }
 139
 140
 141  leave:
 142   gcry_sexp_release (s_skey);
 143   gcry_sexp_release (s_plain);
 144   gcry_sexp_release (s_cipher);
 145   xfree (buf);
 146   xfree (shadow_info);
 147   return rc;
 148 }
 149
 150