gnupg/sm/certlist.c

/* certlist.c - build list of certificates
 *	Copyright (C) 2001, 2003, 2004, 2005 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * GnuPG is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 * USA.
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h> 
#include <time.h>
#include <assert.h>

#include "gpgsm.h"
#include <gcrypt.h>
#include <ksba.h>

#include "keydb.h"
#include "i18n.h"


static const char oid_kp_serverAuth[]     = "1.3.6.1.5.5.7.3.1";
static const char oid_kp_clientAuth[]     = "1.3.6.1.5.5.7.3.2";
static const char oid_kp_codeSigning[]    = "1.3.6.1.5.5.7.3.3";
static const char oid_kp_emailProtection[]= "1.3.6.1.5.5.7.3.4";
static const char oid_kp_timeStamping[]   = "1.3.6.1.5.5.7.3.8";
static const char oid_kp_ocspSigning[]    = "1.3.6.1.5.5.7.3.9";

/* Return 0 if the cert is usable for encryption.  A MODE of 0 checks
   for signing a MODE of 1 checks for encryption, a MODE of 2 checks
   for verification and a MODE of 3 for decryption (just for
   debugging).  MODE 4 is for certificate signing, MODE for COSP
   response signing. */
static int
cert_usage_p (ksba_cert_t cert, int mode)
{
  gpg_error_t err;
  unsigned int use;
  char *extkeyusages;
  int have_ocsp_signing = 0;

  err = ksba_cert_get_ext_key_usages (cert, &extkeyusages);
  if (gpg_err_code (err) == GPG_ERR_NO_DATA
      || gpg_err_code (err) == GPG_ERR_NO_VALUE)
    err = 0; /* no policy given */
  if (!err)
    {
      unsigned int extusemask = ~0; /* Allow all. */

      if (extkeyusages)
        {
          char *p, *pend;
          int any_critical = 0;

          extusemask = 0;

          p = extkeyusages;
          while (p && (pend=strchr (p, ':')))
            {
              *pend++ = 0;
              /* Only care about critical flagged usages. */
              if ( *pend == 'C' )
                {
                  any_critical = 1;
                  if ( !strcmp (p, oid_kp_serverAuth))
                    extusemask |= (KSBA_KEYUSAGE_DIGITAL_SIGNATURE
                                   | KSBA_KEYUSAGE_KEY_ENCIPHERMENT
                                   | KSBA_KEYUSAGE_KEY_AGREEMENT);
                  else if ( !strcmp (p, oid_kp_clientAuth))
                    extusemask |= (KSBA_KEYUSAGE_DIGITAL_SIGNATURE
                                   | KSBA_KEYUSAGE_KEY_AGREEMENT);
                  else if ( !strcmp (p, oid_kp_codeSigning))
                    extusemask |= (KSBA_KEYUSAGE_DIGITAL_SIGNATURE);
                  else if ( !strcmp (p, oid_kp_emailProtection))
                    extusemask |= (KSBA_KEYUSAGE_DIGITAL_SIGNATURE
                                   | KSBA_KEYUSAGE_NON_REPUDIATION
                                   | KSBA_KEYUSAGE_KEY_ENCIPHERMENT
                                   | KSBA_KEYUSAGE_KEY_AGREEMENT);
                  else if ( !strcmp (p, oid_kp_timeStamping))
                    extusemask |= (KSBA_KEYUSAGE_DIGITAL_SIGNATURE
                                   | KSBA_KEYUSAGE_NON_REPUDIATION);
                }
              
              /* This is a hack to cope with OCSP.  Note that we do
                 not yet fully comply with the requirements and that
                 the entire CRL/OCSP checking thing should undergo a
                 thorough review and probably redesign. */
              if ( !strcmp (p, oid_kp_ocspSigning))
                have_ocsp_signing = 1;

              if ((p = strchr (pend, '\n')))
                p++;
            }
          xfree (extkeyusages);
          extkeyusages = NULL;
          
          if (!any_critical)
            extusemask = ~0; /* Reset to the don't care mask. */
        }


      err = ksba_cert_get_key_usage (cert, &use);
      if (gpg_err_code (err) == GPG_ERR_NO_DATA
          || gpg_err_code (err) == GPG_ERR_NO_VALUE)
        {
          err = 0;
          if (opt.verbose && mode < 2)
            log_info (_("no key usage specified - assuming all usages\n"));
          use = ~0;
        }

      /* Apply extKeyUsage. */
      use &= extusemask;

    }
  if (err)
    { 
      log_error (_("error getting key usage information: %s\n"),
                 gpg_strerror (err));
      xfree (extkeyusages);
      return err;
    } 

  if (mode == 4)
    {
      if ((use & (KSBA_KEYUSAGE_KEY_CERT_SIGN)))
        return 0;
      log_info (_("certificate should have not "
                  "been used for certification\n"));
      return gpg_error (GPG_ERR_WRONG_KEY_USAGE);
    }

  if (mode == 5)
    {
      if (use != ~0 
          && (have_ocsp_signing
              || (use & (KSBA_KEYUSAGE_KEY_CERT_SIGN
                         |KSBA_KEYUSAGE_CRL_SIGN))))
        return 0;
      log_info (_("certificate should have not "
                  "been used for OCSP response signing\n"));
      return gpg_error (GPG_ERR_WRONG_KEY_USAGE);
    }

  if ((use & ((mode&1)?
              (KSBA_KEYUSAGE_KEY_ENCIPHERMENT|KSBA_KEYUSAGE_DATA_ENCIPHERMENT):
              (KSBA_KEYUSAGE_DIGITAL_SIGNATURE|KSBA_KEYUSAGE_NON_REPUDIATION)))
      )
    return 0;

  log_info (mode==3? _("certificate should have not been used for encryption\n"):
            mode==2? _("certificate should have not been used for signing\n"):
            mode==1? _("certificate is not usable for encryption\n"):
                     _("certificate is not usable for signing\n"));
  return gpg_error (GPG_ERR_WRONG_KEY_USAGE);
}


/* Return 0 if the cert is usable for signing */
int
gpgsm_cert_use_sign_p (ksba_cert_t cert)
{
  return cert_usage_p (cert, 0);
}


/* Return 0 if the cert is usable for encryption */
int
gpgsm_cert_use_encrypt_p (ksba_cert_t cert)
{
  return cert_usage_p (cert, 1);
}

int
gpgsm_cert_use_verify_p (ksba_cert_t cert)
{
  return cert_usage_p (cert, 2);
}

int
gpgsm_cert_use_decrypt_p (ksba_cert_t cert)
{
  return cert_usage_p (cert, 3);
}

int
gpgsm_cert_use_cert_p (ksba_cert_t cert)
{
  return cert_usage_p (cert, 4);
}

int
gpgsm_cert_use_ocsp_p (ksba_cert_t cert)
{
  return cert_usage_p (cert, 5);
}


static int
same_subject_issuer (const char *subject, const char *issuer, ksba_cert_t cert)
{
  char *subject2 = ksba_cert_get_subject (cert, 0);
  char *issuer2 = ksba_cert_get_subject (cert, 0);
  int tmp;
  
  tmp = (subject && subject2
         && !strcmp (subject, subject2)
         && issuer && issuer2
         && !strcmp (issuer, issuer2));
  xfree (subject2);
  xfree (issuer2);
  return tmp;
}

/* Return true if CERT is already contained in CERTLIST. */
static int
is_cert_in_certlist (ksba_cert_t cert, certlist_t certlist)
{
  const unsigned char *img_a, *img_b;
  size_t len_a, len_b;

  img_a = ksba_cert_get_image (cert, &len_a);
  if (img_a)
    {
      for ( ; certlist; certlist = certlist->next)
        {
          img_b = ksba_cert_get_image (certlist->cert, &len_b);
          if (img_b && len_a == len_b && !memcmp (img_a, img_b, len_a))
            return 1; /* Already contained. */
        }
    }
  return 0;
}


/* Add CERT to the list of certificates at CERTADDR but avoid
   duplicates. */
int 
gpgsm_add_cert_to_certlist (ctrl_t ctrl, ksba_cert_t cert,
                            certlist_t *listaddr, int is_encrypt_to)
{
  if (!is_cert_in_certlist (cert, *listaddr))
    {
      certlist_t cl = xtrycalloc (1, sizeof *cl);
      if (!cl)
        return out_of_core ();
      cl->cert = cert;
      ksba_cert_ref (cert);
      cl->next = *listaddr;
      cl->is_encrypt_to = is_encrypt_to;
      *listaddr = cl;
    }
   return 0;
}

/* Add a certificate to a list of certificate and make sure that it is
   a valid certificate.  With SECRET set to true a secret key must be
   available for the certificate. IS_ENCRYPT_TO sets the corresponding
   flag in the new create LISTADDR item.  */
int
gpgsm_add_to_certlist (ctrl_t ctrl, const char *name, int secret,
                       certlist_t *listaddr, int is_encrypt_to)
{
  int rc;
  KEYDB_SEARCH_DESC desc;
  KEYDB_HANDLE kh = NULL;
  ksba_cert_t cert = NULL;

  rc = keydb_classify_name (name, &desc);
  if (!rc)
    {
      kh = keydb_new (0);
      if (!kh)
        rc = gpg_error (GPG_ERR_ENOMEM);
      else
        {
          int wrong_usage = 0;
          char *subject = NULL;
          char *issuer = NULL;

        get_next:
          rc = keydb_search (kh, &desc, 1);
          if (!rc)
            rc = keydb_get_cert (kh, &cert);
          if (!rc)
            {
              rc = secret? gpgsm_cert_use_sign_p (cert)
                         : gpgsm_cert_use_encrypt_p (cert);
              if (gpg_err_code (rc) == GPG_ERR_WRONG_KEY_USAGE)
                {
                  /* There might be another certificate with the
                     correct usage, so we try again */
                  if (!wrong_usage)
                    { /* save the first match */
                      wrong_usage = rc;
                      subject = ksba_cert_get_subject (cert, 0);
                      issuer = ksba_cert_get_subject (cert, 0);
                      ksba_cert_release (cert);
                      cert = NULL;
                      goto get_next;
                    }
                  else if (same_subject_issuer (subject, issuer, cert))
                    {
                      wrong_usage = rc;
                      ksba_cert_release (cert);
                      cert = NULL;
                      goto get_next;
                    }
                  else
                    wrong_usage = rc;

                }
            }
          /* We want the error code from the first match in this case. */
          if (rc && wrong_usage)
            rc = wrong_usage;
          
          if (!rc)
            {
            next_ambigious:
              rc = keydb_search (kh, &desc, 1);
              if (rc == -1)
                rc = 0;
              else if (!rc)
                {
                  ksba_cert_t cert2 = NULL;

                  /* We have to ignore ambigious names as long as
                     there only fault is a bad key usage */
                  if (!keydb_get_cert (kh, &cert2))
                    {
                      int tmp = (same_subject_issuer (subject, issuer, cert2)
                                 && ((gpg_err_code (
                                      secret? gpgsm_cert_use_sign_p (cert2)
                                            : gpgsm_cert_use_encrypt_p (cert2)
                                      )
                                     )  == GPG_ERR_WRONG_KEY_USAGE));
                      ksba_cert_release (cert2);
                      if (tmp)
                        goto next_ambigious;
                    }
                  rc = gpg_error (GPG_ERR_AMBIGUOUS_NAME);
                }
            }
          xfree (subject);
          xfree (issuer);

          if (!rc && !is_cert_in_certlist (cert, *listaddr))
            {
              if (!rc && secret) 
                {
                  char *p;
                  
                  rc = gpg_error (GPG_ERR_NO_SECKEY);
                  p = gpgsm_get_keygrip_hexstring (cert);
                  if (p)
                    {
                      if (!gpgsm_agent_havekey (ctrl, p))
                        rc = 0;
                      xfree (p);
                    }
                }
              if (!rc)
                rc = gpgsm_validate_chain (ctrl, cert, NULL, 0, NULL, 0);
              if (!rc)
                {
                  certlist_t cl = xtrycalloc (1, sizeof *cl);
                  if (!cl)
                    rc = out_of_core ();
                  else 
                    {
                      cl->cert = cert; cert = NULL;
                      cl->next = *listaddr;
                      cl->is_encrypt_to = is_encrypt_to;
                      *listaddr = cl;
                    }
                }
            }
        }
    }
  
  keydb_release (kh);
  ksba_cert_release (cert);
  return rc == -1? gpg_error (GPG_ERR_NO_PUBKEY): rc;
}

void
gpgsm_release_certlist (certlist_t list)
{
  while (list)
    {
      certlist_t cl = list->next;
      ksba_cert_release (list->cert);
      xfree (list);
      list = cl;
    }
}


/* Like gpgsm_add_to_certlist, but look only for one certificate.  No
   chain validation is done. If KEYID is not NULL it is take as an
   additional filter value which must match the
   subjectKeyIdentifier. */
int
gpgsm_find_cert (const char *name, ksba_sexp_t keyid, ksba_cert_t *r_cert)
{
  int rc;
  KEYDB_SEARCH_DESC desc;
  KEYDB_HANDLE kh = NULL;

  *r_cert = NULL;
  rc = keydb_classify_name (name, &desc);
  if (!rc)
    {
      kh = keydb_new (0);
      if (!kh)
        rc = gpg_error (GPG_ERR_ENOMEM);
      else
        {
        nextone:
          rc = keydb_search (kh, &desc, 1);
          if (!rc)
            {
              rc = keydb_get_cert (kh, r_cert);
              if (!rc && keyid)
                {
                  ksba_sexp_t subj;
                  
                  rc = ksba_cert_get_subj_key_id (*r_cert, NULL, &subj);
                  if (!rc)
                    {
                      if (cmp_simple_canon_sexp (keyid, subj))
                        {
                          xfree (subj);
                          goto nextone;
                        }
                      xfree (subj);
                      /* Okay: Here we know that the certificate's
                         subjectKeyIdentifier matches the requested
                         one. */
                    }
                  else if (gpg_err_code (rc) == GPG_ERR_NO_DATA
                           || gpg_err_code (rc) == GPG_ERR_NO_VALUE)
                    goto nextone;
                }
            }

          /* If we don't have the KEYID filter we need to check for
             ambigious search results.  Note, that it is somehwat
             reasonable to assume that a specification of a KEYID
             won't lead to ambiguous names. */
          if (!rc && !keyid)
            {
              rc = keydb_search (kh, &desc, 1);
              if (rc == -1)
                rc = 0;
              else 
                {
                  if (!rc)
                    rc = gpg_error (GPG_ERR_AMBIGUOUS_NAME);
                  ksba_cert_release (*r_cert);
                  *r_cert = NULL;
                }
            }
        }
    }
  
  keydb_release (kh);
  return rc == -1? gpg_error (GPG_ERR_NO_PUBKEY): rc;
}