/* misc.c - Miscellaneous functions
 * Copyright (C) 2004, 2009, 2011 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 3 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, see <https://www.gnu.org/licenses/>.
 */

#include <config.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#ifdef HAVE_LOCALE_H
#include <locale.h>
#endif

#include "gpgsm.h"
#include "../common/i18n.h"
#include "../common/sysutils.h"
#include "../common/tlv.h"
#include "../common/sexp-parse.h"


/* Setup the environment so that the pinentry is able to get all
   required information.  This is used prior to an exec of the
   protect-tool. */
void
setup_pinentry_env (void)
{
#ifndef HAVE_W32_SYSTEM
  char *lc;
  const char *name, *value;
  int iterator;

  /* Try to make sure that GPG_TTY has been set.  This is needed if we
     call for example the protect-tools with redirected stdin and thus
     it won't be able to ge a default by itself.  Try to do it here
     but print a warning.  */
  value = session_env_getenv (opt.session_env, "GPG_TTY");
  if (value)
    gnupg_setenv ("GPG_TTY", value, 1);
  else if (!(lc=getenv ("GPG_TTY")) || !*lc)
    {
      log_error (_("GPG_TTY has not been set - "
                   "using maybe bogus default\n"));
      lc = gnupg_ttyname (0);
      if (!lc)
        lc = "/dev/tty";
      gnupg_setenv ("GPG_TTY", lc, 1);
    }

  if (opt.lc_ctype)
    gnupg_setenv ("LC_CTYPE", opt.lc_ctype, 1);
#if defined(HAVE_SETLOCALE) && defined(LC_CTYPE)
  else if ( (lc = setlocale (LC_CTYPE, "")) )
    gnupg_setenv ("LC_CTYPE", lc, 1);
#endif

  if (opt.lc_messages)
    gnupg_setenv ("LC_MESSAGES", opt.lc_messages, 1);
#if defined(HAVE_SETLOCALE) && defined(LC_MESSAGES)
  else if ( (lc = setlocale (LC_MESSAGES, "")) )
    gnupg_setenv ("LC_MESSAGES", lc, 1);
#endif

  iterator = 0;
  while ((name = session_env_list_stdenvnames (&iterator, NULL)))
    {
      if (!strcmp (name, "GPG_TTY"))
        continue;  /* Already set.  */
      value = session_env_getenv (opt.session_env, name);
      if (value)
        gnupg_setenv (name, value, 1);
    }

#endif /*!HAVE_W32_SYSTEM*/
}



/* Transform a sig-val style s-expression as returned by Libgcrypt to
   one which includes an algorithm identifier encoding the public key
   and the hash algorithm.  The public key algorithm is taken directly
   from SIGVAL and the hash algorithm is given by MDALGO.  This is
   required because X.509 merges the public key algorithm and the hash
   algorithm into one OID but Libgcrypt is not aware of that.  The
   function ignores missing parameters so that it can also be used to
   create an siginfo value as expected by ksba_certreq_set_siginfo.
   To create a siginfo s-expression a public-key s-expression may be
   used instead of a sig-val.  We only support RSA for now.  */
gpg_error_t
transform_sigval (const unsigned char *sigval, size_t sigvallen, int mdalgo,
                  unsigned char **r_newsigval, size_t *r_newsigvallen)
{
  gpg_error_t err;
  const unsigned char *buf, *tok;
  size_t buflen, toklen;
  int depth, last_depth1, last_depth2;
  int is_pubkey = 0;
  const unsigned char *rsa_s = NULL;
  size_t rsa_s_len = 0;
  const char *oid;
  gcry_sexp_t sexp;

  *r_newsigval = NULL;
  if (r_newsigvallen)
    *r_newsigvallen = 0;

  buf = sigval;
  buflen = sigvallen;
  depth = 0;
  if ((err = parse_sexp (&buf, &buflen, &depth, &tok, &toklen)))
    return err;
  if ((err = parse_sexp (&buf, &buflen, &depth, &tok, &toklen)))
    return err;
  if (tok && toklen == 7 && !memcmp ("sig-val", tok, toklen))
    ;
  else if (tok && toklen == 10 && !memcmp ("public-key", tok, toklen))
    is_pubkey = 1;
  else
    return gpg_error (GPG_ERR_UNKNOWN_SEXP);
  if ((err = parse_sexp (&buf, &buflen, &depth, &tok, &toklen)))
    return err;
  if ((err = parse_sexp (&buf, &buflen, &depth, &tok, &toklen)))
    return err;
  if (!tok || toklen != 3 || memcmp ("rsa", tok, toklen))
    return gpg_error (GPG_ERR_WRONG_PUBKEY_ALGO);

  last_depth1 = depth;
  while (!(err = parse_sexp (&buf, &buflen, &depth, &tok, &toklen))
         && depth && depth >= last_depth1)
    {
      if (tok)
        return gpg_error (GPG_ERR_UNKNOWN_SEXP);
      if ((err = parse_sexp (&buf, &buflen, &depth, &tok, &toklen)))
        return err;
      if (tok && toklen == 1)
        {
          const unsigned char **mpi;
          size_t *mpi_len;

          switch (*tok)
            {
            case 's': mpi = &rsa_s; mpi_len = &rsa_s_len; break;
            default:  mpi = NULL;   mpi_len = NULL; break;
            }
          if (mpi && *mpi)
            return gpg_error (GPG_ERR_DUP_VALUE);

          if ((err = parse_sexp (&buf, &buflen, &depth, &tok, &toklen)))
            return err;
          if (tok && mpi)
            {
              *mpi = tok;
              *mpi_len = toklen;
            }
        }

      /* Skip to the end of the list. */
      last_depth2 = depth;
      while (!(err = parse_sexp (&buf, &buflen, &depth, &tok, &toklen))
             && depth && depth >= last_depth2)
        ;
      if (err)
        return err;
    }
  if (err)
    return err;

  /* Map the hash algorithm to an OID.  */
  switch (mdalgo)
    {
    case GCRY_MD_SHA1:
      oid = "1.2.840.113549.1.1.5";  /* sha1WithRSAEncryption */
      break;

    case GCRY_MD_SHA256:
      oid = "1.2.840.113549.1.1.11"; /* sha256WithRSAEncryption */
      break;

    case GCRY_MD_SHA384:
      oid = "1.2.840.113549.1.1.12"; /* sha384WithRSAEncryption */
      break;

    case GCRY_MD_SHA512:
      oid = "1.2.840.113549.1.1.13"; /* sha512WithRSAEncryption */
      break;

    default:
      return gpg_error (GPG_ERR_DIGEST_ALGO);
    }

  if (rsa_s && !is_pubkey)
    err = gcry_sexp_build (&sexp, NULL, "(sig-val(%s(s%b)))",
                           oid, (int)rsa_s_len, rsa_s);
  else
    err = gcry_sexp_build (&sexp, NULL, "(sig-val(%s))", oid);
  if (err)
    return err;
  err = make_canon_sexp (sexp, r_newsigval, r_newsigvallen);
  gcry_sexp_release (sexp);

  return err;
}


/* Wrapper around ksba_cms_get_sig_val to return a gcrypt object
 * instaed of ksba's canonical s-expression.  On errror NULL is return
 * and in some cases an error message is printed.  */
gcry_sexp_t
gpgsm_ksba_cms_get_sig_val (ksba_cms_t cms, int idx)
{
  gpg_error_t err;
  ksba_sexp_t sigval;
  gcry_sexp_t s_sigval;
  size_t n;

  sigval = ksba_cms_get_sig_val (cms, idx);
  if (!sigval)
    return NULL;
  n = gcry_sexp_canon_len (sigval, 0, NULL, NULL);
  if (!n)
    {
      log_error ("%s: libksba did not return a proper S-Exp\n", __func__);
      ksba_free (sigval);
      return NULL;
    }
  err = gcry_sexp_sscan (&s_sigval, NULL, (char*)sigval, n);
  ksba_free (sigval);
  if (err)
    {
      log_error ("%s: gcry_sexp_scan failed: %s\n",
                 __func__, gpg_strerror (err));
      s_sigval = NULL;
    }

  return s_sigval;
}


/* Return the hash algorithm from the S-expression SIGVAL.  Returns 0
 * if the hash algorithm is not encoded in SIGVAL or it is not
 * supported by libgcrypt.  It further stores flag values for the
 * public key algorithm at R_PKALGO_FLAGS; the only flag we currently
 * support is PK_ALGO_FLAG_RSAPSS.  */
int
gpgsm_get_hash_algo_from_sigval (gcry_sexp_t sigval_arg,
                                 unsigned int *r_pkalgo_flags)
{
  gcry_sexp_t sigval, l1;
  size_t n;
  const char *s;
  char *string;
  int hashalgo;
  int i;

  *r_pkalgo_flags = 0;

  sigval = gcry_sexp_find_token (sigval_arg, "sig-val", 0);
  if (!sigval)
    return 0;   /* Not a sig-val.  */

  /* First check whether this is a rsaPSS signature and return that as
   * additional info.  */
  l1 = gcry_sexp_find_token (sigval, "flags", 0);
  if (l1)
    {
      /* Note that the flag parser assumes that the list of flags
       * contains only strings and in particular not a sub-list.  This
       * is always the case for the current libksba. */
      for (i=1; (s = gcry_sexp_nth_data (l1, i, &n)); i++)
        if (n == 3 && !memcmp (s, "pss", 3))
          {
            *r_pkalgo_flags |= PK_ALGO_FLAG_RSAPSS;
            break;
          }
      gcry_sexp_release (l1);
    }

  l1 = gcry_sexp_find_token (sigval, "hash", 0);
  if (!l1)
    {
      gcry_sexp_release (sigval);
      return 0; /* hash algorithm not given in sigval. */
    }
  string = gcry_sexp_nth_string (l1, 1);
  gcry_sexp_release (sigval);
  if (!string)
    return 0; /* hash algorithm has no value. */
  hashalgo = gcry_md_map_name (string);
  gcry_free (string);

  return hashalgo;
}