scd/app-help.c

   1 /* app-help.c - Application helper functions
   2  * Copyright (C) 2004, 2009 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
  32 /* Count the number of bits, assuming the A represents an unsigned big
  33    integer of length LEN bytes.  If A is NULL a length of 0 is
  34    returned. */
  35 unsigned int
  36 app_help_count_bits (const unsigned char *a, size_t len)
  37 {
  38   unsigned int n = len * 8;
  39   int i;
  40
  41   if (!a)
  42     return 0;
  43
  44   for (; len && !*a; len--, a++, n -=8)
  45     ;
  46   if (len)
  47     {
  48       for (i=7; i && !(*a & (1<<i)); i--)
  49         n--;
  50     }
  51   return n;
  52 }
  53
  54
  55 /* Return the KEYGRIP for the certificate CERT as an hex encoded
  56    string in the user provided buffer HEXKEYGRIP which must be of at
  57    least 41 bytes. */
  58 gpg_error_t
  59 app_help_get_keygrip_string (ksba_cert_t cert, char *hexkeygrip)
  60 {
  61   gpg_error_t err;
  62   gcry_sexp_t s_pkey;
  63   ksba_sexp_t p;
  64   size_t n;
  65   unsigned char array[20];
  66
  67   p = ksba_cert_get_public_key (cert);
  68   if (!p)
  69     return gpg_error (GPG_ERR_BUG);
  70   n = gcry_sexp_canon_len (p, 0, NULL, NULL);
  71   if (!n)
  72     return gpg_error (GPG_ERR_INV_SEXP);
  73   err = gcry_sexp_sscan (&s_pkey, NULL, (char*)p, n);
  74   xfree (p);
  75   if (err)
  76     return err; /* Can't parse that S-expression. */
  77   if (!gcry_pk_get_keygrip (s_pkey, array))
  78     {
  79       gcry_sexp_release (s_pkey);
  80       return gpg_error (GPG_ERR_GENERAL); /* Failed to calculate the keygrip.*/
  81     }
  82   gcry_sexp_release (s_pkey);
  83
  84   bin2hex (array, 20, hexkeygrip);
  85
  86   return 0;
  87 }
  88
  89
  90
  91 /* Given the SLOT and the File ID FID, return the length of the
  92    certificate contained in that file. Returns 0 if the file does not
  93    exists or does not contain a certificate.  If R_CERTOFF is not
  94    NULL, the length the header will be stored at this address; thus to
  95    parse the X.509 certificate a read should start at that offset.
  96
  97    On success the file is still selected.
  98 */
  99 size_t
 100 app_help_read_length_of_cert (int slot, int fid, size_t *r_certoff)
 101 {
 102   gpg_error_t err;
 103   unsigned char *buffer;
 104   const unsigned char *p;
 105   size_t buflen, n;
 106   int class, tag, constructed, ndef;
 107   size_t resultlen, objlen, hdrlen;
 108
 109   err = iso7816_select_file (slot, fid, 0, NULL, NULL);
 110   if (err)
 111     {
 112       log_info ("error selecting FID 0x%04X: %s\n", fid, gpg_strerror (err));
 113       return 0;
 114     }
 115
 116   err = iso7816_read_binary (slot, 0, 32, &buffer, &buflen);
 117   if (err)
 118     {
 119       log_info ("error reading certificate from FID 0x%04X: %s\n",
 120                  fid, gpg_strerror (err));
 121       return 0;
 122     }
 123
 124   if (!buflen || *buffer == 0xff)
 125     {
 126       log_info ("no certificate contained in FID 0x%04X\n", fid);
 127       xfree (buffer);
 128       return 0;
 129     }
 130
 131   p = buffer;
 132   n = buflen;
 133   err = parse_ber_header (&p, &n, &class, &tag, &constructed,
 134                           &ndef, &objlen, &hdrlen);
 135   if (err)
 136     {
 137       log_info ("error parsing certificate in FID 0x%04X: %s\n",
 138                 fid, gpg_strerror (err));
 139       xfree (buffer);
 140       return 0;
 141     }
 142
 143   /* All certificates should commence with a SEQUENCE except for the
 144      special ROOT CA which are enclosed in a SET. */
 145   if ( !(class == CLASS_UNIVERSAL &&  constructed
 146          && (tag == TAG_SEQUENCE || tag == TAG_SET)))
 147     {
 148       log_info ("data at FID 0x%04X does not look like a certificate\n", fid);
 149       return 0;
 150     }
 151
 152   resultlen = objlen + hdrlen;
 153   if (r_certoff)
 154     {
 155       /* The callers want the offset to the actual certificate. */
 156       *r_certoff = hdrlen;
 157
 158       err = parse_ber_header (&p, &n, &class, &tag, &constructed,
 159                               &ndef, &objlen, &hdrlen);
 160       if (err)
 161         return 0;
 162
 163       if (class == CLASS_UNIVERSAL && tag == TAG_OBJECT_ID && !constructed)
 164         {
 165           /* The certificate seems to be contained in a
 166              userCertificate container.  Assume the following sequence
 167              is the certificate. */
 168           *r_certoff += hdrlen + objlen;
 169           if (*r_certoff > resultlen)
 170             {
 171               *r_certoff = 0;
 172               return 0; /* That should never happen. */
 173             }
 174         }
 175       else
 176         *r_certoff = 0;
 177     }
 178
 179   return resultlen;
 180 }
 181
 182