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
  43   p = ksba_cert_get_public_key (cert);
  44   if (!p)
  45     return gpg_error (GPG_ERR_BUG);
  46   n = gcry_sexp_canon_len (p, 0, NULL, NULL);
  47   if (!n)
  48     return gpg_error (GPG_ERR_INV_SEXP);
  49   err = gcry_sexp_sscan (&s_pkey, NULL, (char*)p, n);
  50   xfree (p);
  51   if (err)
  52     return err; /* Can't parse that S-expression. */
  53   if (!gcry_pk_get_keygrip (s_pkey, array))
  54     {
  55       gcry_sexp_release (s_pkey);
  56       return gpg_error (GPG_ERR_GENERAL); /* Failed to calculate the keygrip.*/
  57     }
  58   gcry_sexp_release (s_pkey);
  59
  60   bin2hex (array, 20, hexkeygrip);
  61
  62   return 0;
  63 }
  64
  65
  66
  67 /* Given the SLOT and the File ID FID, return the length of the
  68    certificate contained in that file. Returns 0 if the file does not
  69    exists or does not contain a certificate.  If R_CERTOFF is not
  70    NULL, the length the header will be stored at this address; thus to
  71    parse the X.509 certificate a read should start at that offset.
  72
  73    On success the file is still selected.
  74 */
  75 size_t
  76 app_help_read_length_of_cert (int slot, int fid, size_t *r_certoff)
  77 {
  78   gpg_error_t err;
  79   unsigned char *buffer;
  80   const unsigned char *p;
  81   size_t buflen, n;
  82   int class, tag, constructed, ndef;
  83   size_t resultlen, objlen, hdrlen;
  84
  85   err = iso7816_select_file (slot, fid, 0, NULL, NULL);
  86   if (err)
  87     {
  88       log_info ("error selecting FID 0x%04X: %s\n", fid, gpg_strerror (err));
  89       return 0;
  90     }
  91
  92   err = iso7816_read_binary (slot, 0, 32, &buffer, &buflen);
  93   if (err)
  94     {
  95       log_info ("error reading certificate from FID 0x%04X: %s\n",
  96                  fid, gpg_strerror (err));
  97       return 0;
  98     }
  99
 100   if (!buflen || *buffer == 0xff)
 101     {
 102       log_info ("no certificate contained in FID 0x%04X\n", fid);
 103       xfree (buffer);
 104       return 0;
 105     }
 106
 107   p = buffer;
 108   n = buflen;
 109   err = parse_ber_header (&p, &n, &class, &tag, &constructed,
 110                           &ndef, &objlen, &hdrlen);
 111   if (err)
 112     {
 113       log_info ("error parsing certificate in FID 0x%04X: %s\n",
 114                 fid, gpg_strerror (err));
 115       xfree (buffer);
 116       return 0;
 117     }
 118
 119   /* All certificates should commence with a SEQUENCE except for the
 120      special ROOT CA which are enclosed in a SET. */
 121   if ( !(class == CLASS_UNIVERSAL &&  constructed
 122          && (tag == TAG_SEQUENCE || tag == TAG_SET)))
 123     {
 124       log_info ("data at FID 0x%04X does not look like a certificate\n", fid);
 125       return 0;
 126     }
 127
 128   resultlen = objlen + hdrlen;
 129   if (r_certoff)
 130     {
 131       /* The callers want the offset to the actual certificate. */
 132       *r_certoff = hdrlen;
 133
 134       err = parse_ber_header (&p, &n, &class, &tag, &constructed,
 135                               &ndef, &objlen, &hdrlen);
 136       if (err)
 137         return 0;
 138
 139       if (class == CLASS_UNIVERSAL && tag == TAG_OBJECT_ID && !constructed)
 140         {
 141           /* The certificate seems to be contained in a
 142              userCertificate container.  Assume the following sequence
 143              is the certificate. */
 144           *r_certoff += hdrlen + objlen;
 145           if (*r_certoff > resultlen)
 146             {
 147               *r_certoff = 0;
 148               return 0; /* That should never happen. */
 149             }
 150         }
 151       else
 152         *r_certoff = 0;
 153     }
 154
 155   return resultlen;
 156 }
 157
 158