gnupg/g10/verify.c

/* verify.c - Verify signed data
 * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2005, 2006,
 *               2007, 2010 Free Software Foundation, Inc.
 * Copyright (C) 2003, 2006-2008, 2010-2011, 2015-2017,
 *               2020, 2023 g10 Code GmbH
 *
 * 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/>.
 * SPDX-License-Identifier: GPL-3.0-or-later
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include "gpg.h"
#include "options.h"
#include "packet.h"
#include "../common/status.h"
#include "../common/iobuf.h"
#include "keydb.h"
#include "../common/util.h"
#include "main.h"
#include "filter.h"
#include "../common/ttyio.h"
#include "../common/i18n.h"


/****************
 * Assume that the input is a signature and verify it without
 * generating any output.  With no arguments, the signature packet
 * is read from stdin (it may be a detached signature when not
 * used in batch mode). If only a sigfile is given, it may be a complete
 * signature or a detached signature in which case the signed stuff
 * is expected from stdin. With more than 1 argument, the first should
 * be a detached signature and the remaining files are the signed stuff.
 */

int
verify_signatures (ctrl_t ctrl, int nfiles, char **files )
{
    IOBUF fp;
    armor_filter_context_t *afx = NULL;
    progress_filter_context_t *pfx = new_progress_context ();
    const char *sigfile;
    int i, rc;
    strlist_t sl;

    /* Decide whether we should handle a detached or a normal signature,
     * which is needed so that the code later can hash the correct data and
     * not have a normal signature act as detached signature and ignoring the
     * intended signed material from the 2nd file or stdin.
     * 1. gpg <file        - normal
     * 2. gpg file         - normal (or detached)
     * 3. gpg file <file2  - detached
     * 4. gpg file file2   - detached
     * The question is how decide between case 2 and 3?  The only way
     * we can do it is by reading one byte from stdin and then unget
     * it; the problem here is that we may be reading from the
     * terminal (which could be detected using isatty() but won't work
     * when under control of a pty using program (e.g. expect)) and
     * might get us in trouble when stdin is used for another purpose
     * (--passphrase-fd 0).  So we have to break with the behaviour
     * prior to gpg 1.0.4 by assuming that case 3 is a normal
     * signature (where file2 is ignored and require for a detached
     * signature to indicate signed material comes from stdin by using
     * case 4 with a file2 of "-".
     *
     * Actually we don't have to change anything here but can handle
     * that all quite easily in mainproc.c
     */

    sigfile = nfiles? *files : NULL;

    /* open the signature file */
    fp = iobuf_open(sigfile);
    if (fp && is_secured_file (iobuf_get_fd (fp)))
      {
        iobuf_close (fp);
        fp = NULL;
        gpg_err_set_errno (EPERM);
      }
    if( !fp ) {
        rc = gpg_error_from_syserror ();
	log_error(_("can't open '%s': %s\n"),
                  print_fname_stdin(sigfile), gpg_strerror (rc));
        goto leave;
    }
    handle_progress (pfx, fp, sigfile);

    if ( !opt.no_armor && use_armor_filter( fp ) )
      {
        afx = new_armor_context ();
	push_armor_filter (afx, fp);
      }

    sl = NULL;
    for(i=nfiles-1 ; i > 0 ; i-- )
	add_to_strlist( &sl, files[i] );
    rc = proc_signature_packets (ctrl, NULL, fp, sl, sigfile );
    free_strlist(sl);
    iobuf_close(fp);
    if( (afx && afx->no_openpgp_data && rc == -1)
        || gpg_err_code (rc) == GPG_ERR_NO_DATA ) {
	log_error(_("the signature could not be verified.\n"
		   "Please remember that the signature file (.sig or .asc)\n"
		   "should be the first file given on the command line.\n") );
	rc = 0;
    }

 leave:
    release_armor_context (afx);
    release_progress_context (pfx);
    return rc;
}



void
print_file_status( int status, const char *name, int what )
{
    char *p = xmalloc(strlen(name)+10);
    sprintf(p, "%d %s", what, name );
    write_status_text( status, p );
    xfree(p);
}


static int
verify_one_file (ctrl_t ctrl, const char *name )
{
    IOBUF fp;
    armor_filter_context_t *afx = NULL;
    progress_filter_context_t *pfx = new_progress_context ();
    int rc;

    print_file_status( STATUS_FILE_START, name, 1 );
    fp = iobuf_open(name);
    if (fp)
      iobuf_ioctl (fp, IOBUF_IOCTL_NO_CACHE, 1, NULL);
    if (fp && is_secured_file (iobuf_get_fd (fp)))
      {
        iobuf_close (fp);
        fp = NULL;
        gpg_err_set_errno (EPERM);
      }
    if( !fp ) {
        rc = gpg_error_from_syserror ();
	log_error(_("can't open '%s': %s\n"),
                  print_fname_stdin(name), strerror (errno));
	print_file_status( STATUS_FILE_ERROR, name, 1 );
        goto leave;
    }
    handle_progress (pfx, fp, name);

    if( !opt.no_armor ) {
	if( use_armor_filter( fp ) ) {
            afx = new_armor_context ();
	    push_armor_filter (afx, fp);
	}
    }

    rc = proc_signature_packets (ctrl, NULL, fp, NULL, name );
    iobuf_close(fp);
    write_status( STATUS_FILE_DONE );

    reset_literals_seen();

 leave:
    release_armor_context (afx);
    release_progress_context (pfx);
    return rc;
}

/****************
 * Verify each file given in the files array or read the names of the
 * files from stdin.
 * Note:  This function can not handle detached signatures.
 */
int
verify_files (ctrl_t ctrl, int nfiles, char **files )
{
    int i, rc;
    int first_rc = 0;

    if( !nfiles ) { /* read the filenames from stdin */
	char line[2048];
	unsigned int lno = 0;

	while( fgets(line, DIM(line), stdin) ) {
	    lno++;
	    if( !*line || line[strlen(line)-1] != '\n' ) {
		log_error(_("input line %u too long or missing LF\n"), lno );
		return GPG_ERR_GENERAL;
	    }
	    /* This code does not work on MSDOS but hwo cares there are
	     * also no script languages available.  We don't strip any
	     * spaces, so that we can process nearly all filenames */
	    line[strlen(line)-1] = 0;
	    rc = verify_one_file (ctrl, line);
            if (!first_rc)
              first_rc = rc;
	}

    }
    else {  /* take filenames from the array */
	for(i=0; i < nfiles; i++ )
          {
            rc = verify_one_file (ctrl, files[i]);
            if (!first_rc)
              first_rc = rc;
          }
    }

    return first_rc;
}




/* Perform a verify operation.  To verify detached signatures, DATA_FD
   shall be the descriptor of the signed data; for regular signatures
   it needs to be -1.  If OUT_FP is not NULL and DATA_FD is not -1 the
   the signed material gets written that stream.

   FIXME: OUTFP is not yet implemented.
*/
int
gpg_verify (ctrl_t ctrl, int sig_fd, int data_fd, estream_t out_fp)
{
  int rc;
  iobuf_t fp;
  armor_filter_context_t *afx = NULL;
  progress_filter_context_t *pfx = new_progress_context ();

  (void)ctrl;
  (void)out_fp;

  if (is_secured_file (sig_fd))
    {
      fp = NULL;
      gpg_err_set_errno (EPERM);
    }
  else
    fp = iobuf_fdopen_nc (sig_fd, "rb");
  if (!fp)
    {
      rc = gpg_error_from_syserror ();
      log_error (_("can't open fd %d: %s\n"), sig_fd, strerror (errno));
      goto leave;
    }

  handle_progress (pfx, fp, NULL);

  if ( !opt.no_armor && use_armor_filter (fp) )
    {
      afx = new_armor_context ();
      push_armor_filter (afx, fp);
    }

  rc = proc_signature_packets_by_fd (ctrl, NULL, fp, data_fd);

  if ( afx && afx->no_openpgp_data
       && (rc == -1 || gpg_err_code (rc) == GPG_ERR_EOF) )
    rc = gpg_error (GPG_ERR_NO_DATA);

 leave:
  iobuf_close (fp);
  release_progress_context (pfx);
  release_armor_context (afx);
  return rc;
}


static int
is_fingerprint (const char *string)
{
  int n;

  if (!string || !*string)
    return 0;
  for (n=0; hexdigitp (string); string++)
    n++;
  if (!*string && (n == 40 || n == 64))
    return 1;  /* v4 or v5 fingerprint.  */

  return 0;
}


/* This function shall be called with the main and subkey fingerprint
 * iff a signature is fully valid.  If the option --assert-signer is
 * active it check whether the signing key matches one of the keys
 * given by this option and if so, sets a global flag.  */
void
check_assert_signer_list (const char *mainpkhex, const char *pkhex)
{
  gpg_error_t err;
  strlist_t item;
  const char *fname;
  estream_t fp = NULL;
  int lnr;
  int n, c;
  char *p, *pend;
  char line[256];

  if (!opt.assert_signer_list)
    return;  /* Nothing to do.  */
  if (assert_signer_true)
    return;  /* Already one valid signature seen.  */

  for (item = opt.assert_signer_list; item; item = item->next)
    {
      if (is_fingerprint (item->d))
        {
          ascii_strupr (item->d);
          if (!strcmp (item->d, mainpkhex) || !strcmp (item->d, pkhex))
            {
              assert_signer_true = 1;
              write_status_text (STATUS_ASSERT_SIGNER, item->d);
              if (!opt.quiet)
                log_info ("asserted signer '%s'\n", item->d);
              goto leave;
            }
        }
      else  /* Assume this is a file - read and compare.  */
        {
          fname = item->d;
          es_fclose (fp);
          fp = es_fopen (fname, "r");
          if (!fp)
            {
              err = gpg_error_from_syserror ();
              log_error (_("error opening '%s': %s\n"),
                         fname, gpg_strerror (err));
              continue;
            }

          lnr = 0;
          err = 0;
          while (es_fgets (line, DIM(line)-1, fp))
            {
              lnr++;

              n = strlen (line);
              if (!n || line[n-1] != '\n')
                {
                  /* Eat until end of line. */
                  while ( (c=es_getc (fp)) != EOF && c != '\n')
                    ;
                  err = gpg_error (GPG_ERR_INCOMPLETE_LINE);
                  log_error (_("file '%s', line %d: %s\n"),
                             fname, lnr, gpg_strerror (err));
                  continue;
                }
              line[--n] = 0; /* Chop the LF. */
              if (n && line[n-1] == '\r')
                line[--n] = 0; /* Chop an optional CR. */

              /* Allow for empty lines and spaces */
              for (p=line; spacep (p); p++)
                ;
              if (!*p || *p == '#')
                continue;

              /* Get the first token and ignore trailing stuff.  */
              for (pend = p; *pend && !spacep (pend); pend++)
                ;
              *pend = 0;
              ascii_strupr (p);

              if (!strcmp (p, mainpkhex) || !strcmp (p, pkhex))
                {
                  assert_signer_true = 1;
                  write_status_text (STATUS_ASSERT_SIGNER, p);
                  if (!opt.quiet)
                    log_info ("asserted signer '%s' (%s:%d)\n",
                              p, fname, lnr);
                  goto leave;
                }
            }
          if (!err && !es_feof (fp))
            {
              err = gpg_error_from_syserror ();
              log_error (_("error reading '%s', line %d: %s\n"),
                         fname, lnr, gpg_strerror (err));
            }
        }
    }

 leave:
  es_fclose (fp);
}


/* This function shall be called with the signer's public key
 * algorithm ALGOSTR iff a signature is fully valid.  If the option
 * --assert-pubkey-algo is active the functions checks whether the
 * signing key's algo is valid according to that list; in this case a
 * global flag is set.  */
void
check_assert_pubkey_algo (const char *algostr, const char *pkhex)
{
  if (!opt.assert_pubkey_algos)
    return;  /* Nothing to do.  */

  if (compare_pubkey_string (algostr, opt.assert_pubkey_algos))
    {
      write_status_strings (STATUS_ASSERT_PUBKEY_ALGO,
                            pkhex, " 1 ", algostr, NULL);
      if (!opt.quiet)
        log_info ("asserted signer '%s' with algo %s\n", pkhex, algostr);
    }
  else
    {
      if (!opt.quiet)
        log_info ("denied signer '%s' with algo %s\n", pkhex, algostr);
      assert_pubkey_algo_false = 1;
      write_status_strings (STATUS_ASSERT_PUBKEY_ALGO,
                            pkhex, " 0 ", algostr, NULL);
    }
}