scd/app-help.c

   1 /* app-help.c - Application helper functions
   2  *      Copyright (C) 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 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
  26 #include "scdaemon.h"
  27 #include "app-common.h"
  28 #include "iso7816.h"
  29 #include "tlv.h"
  30
  31 /* Return the KEYGRIP for the certificate CERT as an hex encoded
  32    string in the user provided buffer HEXKEYGRIP which must be of at
  33    least 41 bytes. */
  34 gpg_error_t
  35 app_help_get_keygrip_string (ksba_cert_t cert, char *hexkeygrip)
  36 {
  37   gpg_error_t err;
  38   gcry_sexp_t s_pkey;
  39   ksba_sexp_t p;
  40   size_t n;
  41   unsigned char array[20];
  42   int i;
  43
  44   p = ksba_cert_get_public_key (cert);
  45   if (!p)
  46     return gpg_error (GPG_ERR_BUG);
  47   n = gcry_sexp_canon_len (p, 0, NULL, NULL);
  48   if (!n)
  49     return gpg_error (GPG_ERR_INV_SEXP);
  50   err = gcry_sexp_sscan (&s_pkey, NULL, (char*)p, n);
  51   xfree (p);
  52   if (err)
  53     return err; /* Can't parse that S-expression. */
  54   if (!gcry_pk_get_keygrip (s_pkey, array))
  55     {
  56       gcry_sexp_release (s_pkey);
  57       return gpg_error (GPG_ERR_GENERAL); /* Failed to calculate the keygrip.*/
  58     }
  59   gcry_sexp_release (s_pkey);
  60
  61   for (i=0; i < 20; i++)
  62     sprintf (hexkeygrip+i*2, "%02X", array[i]);
  63
  64   return 0;
  65 }
  66
  67
  68
  69 /* Given the SLOT and the File ID FID, return the length of the
  70    certificate contained in that file. Returns 0 if the file does not
  71    exists or does not contain a certificate.  If R_CERTOFF is not
  72    NULL, the length the header will be stored at this address; thus to
  73    parse the X.509 certificate a read should start at that offset.
  74
  75    On success the file is still selected.
  76 */
  77 size_t
  78 app_help_read_length_of_cert (int slot, int fid, size_t *r_certoff)
  79 {
  80   gpg_error_t err;
  81   unsigned char *buffer;
  82   const unsigned char *p;
  83   size_t buflen, n;
  84   int class, tag, constructed, ndef;
  85   size_t resultlen, objlen, hdrlen;
  86
  87   err = iso7816_select_file (slot, fid, 0, NULL, NULL);
  88   if (err)
  89     {
  90       log_info ("error selecting FID 0x%04X: %s\n", fid, gpg_strerror (err));
  91       return 0;
  92     }
  93
  94   err = iso7816_read_binary (slot, 0, 32, &buffer, &buflen);
  95   if (err)
  96     {
  97       log_info ("error reading certificate from FID 0x%04X: %s\n",
  98                  fid, gpg_strerror (err));
  99       return 0;
 100     }
 101
 102   if (!buflen || *buffer == 0xff)
 103     {
 104       log_info ("no certificate contained in FID 0x%04X\n", fid);
 105       xfree (buffer);
 106       return 0;
 107     }
 108
 109   p = buffer;
 110   n = buflen;
 111   err = parse_ber_header (&p, &n, &class, &tag, &constructed,
 112                           &ndef, &objlen, &hdrlen);
 113   if (err)
 114     {
 115       log_info ("error parsing certificate in FID 0x%04X: %s\n",
 116                 fid, gpg_strerror (err));
 117       xfree (buffer);
 118       return 0;
 119     }
 120
 121   /* All certificates should commence with a SEQUENCE except for the
 122      special ROOT CA which are enclosed in a SET. */
 123   if ( !(class == CLASS_UNIVERSAL &&  constructed
 124          && (tag == TAG_SEQUENCE || tag == TAG_SET)))
 125     {
 126       log_info ("contents of FID 0x%04X does not look like a certificate\n",
 127                 fid);
 128       return 0;
 129     }
 130
 131   resultlen = objlen + hdrlen;
 132   if (r_certoff)
 133     {
 134       /* The callers want the offset to the actual certificate. */
 135       *r_certoff = hdrlen;
 136
 137       err = parse_ber_header (&p, &n, &class, &tag, &constructed,
 138                               &ndef, &objlen, &hdrlen);
 139       if (err)
 140         return 0;
 141
 142       if (class == CLASS_UNIVERSAL && tag == TAG_OBJECT_ID && !constructed)
 143         {
 144           /* The certificate seems to be contained in a
 145              userCertificate container.  Assume the following sequence
 146              is the certificate. */
 147           *r_certoff += hdrlen + objlen;
 148           if (*r_certoff > resultlen)
 149             {
 150               *r_certoff = 0;
 151               return 0; /* That should never happen. */
 152             }
 153         }
 154       else
 155         *r_certoff = 0;
 156     }
 157
 158   return resultlen;
 159 }
 160
 161