gnupg/kbx/kbxserver.c

/* kbxserver.c - Handle Assuan commands send to the keyboxd
 * Copyright (C) 2019 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+
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>

#include "keyboxd.h"
#include <assuan.h>
#include "../common/i18n.h"
#include "../common/server-help.h"
#include "../common/userids.h"
#include "../common/asshelp.h"
#include "../common/host2net.h"
#include "frontend.h"



#define PARM_ERROR(t) assuan_set_error (ctx, \
                                        gpg_error (GPG_ERR_ASS_PARAMETER), (t))
#define set_error(e,t) (ctx ? assuan_set_error (ctx, gpg_error (e), (t)) \
                        /**/: gpg_error (e))



/* Control structure per connection. */
struct server_local_s
{
  /* Data used to associate an Assuan context with local server data */
  assuan_context_t assuan_ctx;

  /* The session id (a counter).  */
  unsigned int session_id;

  /* If this flag is set to true this process will be terminated after
   * the end of this session.  */
  int stopme;

  /* If the first both flags are set the assuan logging of data lines
   * is suppressed.  The count variable is used to show the number of
   * non-logged bytes.  */
  size_t inhibit_data_logging_count;
  unsigned int inhibit_data_logging : 1;
  unsigned int inhibit_data_logging_now : 1;

  /* This flag is set if the last search command was called with --more.  */
  unsigned int search_expecting_more : 1;

  /* This flag is set if the last search command was successful.  */
  unsigned int search_any_found : 1;

  /* The first is the current search description as parsed by the
   * cmd_search.  If more than one pattern is required, cmd_search
   * also allocates and sets multi_search_desc and
   * multi_search_desc_len.  If a search description has ever been
   * allocated the allocated size is stored at
   * multi_search_desc_size.  */
  KEYBOX_SEARCH_DESC search_desc;
  KEYBOX_SEARCH_DESC *multi_search_desc;
  unsigned int multi_search_desc_size;
  unsigned int multi_search_desc_len;

  /* If not NULL write output to this stream instead of using D lines.  */
  estream_t outstream;
};




/* Return the assuan contxt from the local server info in CTRL.  */
static assuan_context_t
get_assuan_ctx_from_ctrl (ctrl_t ctrl)
{
  if (!ctrl || !ctrl->server_local)
    return NULL;
  return ctrl->server_local->assuan_ctx;
}


/* If OUTPUT has been used prepare the output FD for use.  This needs
 * to be called by all functions which will in any way use
 * kbxd_write_data_line later.  Whether the output goes to the output
 * stream is decided by this function.  */
static gpg_error_t
prepare_outstream (ctrl_t ctrl)
{
  int fd;

  log_assert (ctrl && ctrl->server_local);

  if (ctrl->server_local->outstream)
    return 0;  /* Already enabled.  */

  fd = translate_sys2libc_fd
    (assuan_get_output_fd (get_assuan_ctx_from_ctrl (ctrl)), 1);
  if (fd == -1)
    return 0;  /* No Output command active.  */

  ctrl->server_local->outstream = es_fdopen_nc (fd, "w");
  if (!ctrl->server_local->outstream)
    return gpg_err_code_from_syserror ();
  return 0;
}


/* The usual writen function; here with diagnostic output.  */
static gpg_error_t
kbxd_writen (estream_t fp, const void *buffer, size_t length)
{
  gpg_error_t err;
  size_t nwritten;

  if (es_write (fp, buffer, length, &nwritten))
    {
      err = gpg_error_from_syserror ();
      log_error ("error writing OUTPUT: %s\n", gpg_strerror (err));
    }
  else if (length != nwritten)
    {
      err = gpg_error (GPG_ERR_EIO);
      log_error ("error writing OUTPUT: %s\n", "short write");
    }
  else
    err = 0;

  return err;
}


/* A wrapper around assuan_send_data which makes debugging the output
 * in verbose mode easier.  It also takes CTRL as argument.  */
gpg_error_t
kbxd_write_data_line (ctrl_t ctrl, const void *buffer_arg, size_t size)
{
  const char *buffer = buffer_arg;
  assuan_context_t ctx = get_assuan_ctx_from_ctrl (ctrl);
  gpg_error_t err;

  if (!ctx) /* Oops - no assuan context.  */
    return gpg_error (GPG_ERR_NOT_PROCESSED);

  /* Write toa file descriptor if enabled.  */
  if (ctrl && ctrl->server_local && ctrl->server_local->outstream)
    {
      unsigned char lenbuf[4];

      ulongtobuf (lenbuf, size);
      err = kbxd_writen (ctrl->server_local->outstream, lenbuf, 4);
      if (!err)
        err = kbxd_writen (ctrl->server_local->outstream, buffer, size);
      if (!err && es_fflush (ctrl->server_local->outstream))
        {
          err = gpg_error_from_syserror ();
          log_error ("error writing OUTPUT: %s\n", gpg_strerror (err));
        }

      goto leave;
    }

  /* If we do not want logging, enable it here.  */
  if (ctrl && ctrl->server_local && ctrl->server_local->inhibit_data_logging)
    ctrl->server_local->inhibit_data_logging_now = 1;

  if (0 && opt.verbose && buffer && size)
    {
      /* Ease reading of output by limiting the line length.  */
      size_t n, nbytes;

      nbytes = size;
      do
        {
          n = nbytes > 64? 64 : nbytes;
          err = assuan_send_data (ctx, buffer, n);
          if (err)
            {
              gpg_err_set_errno (EIO);
              goto leave;
            }
          buffer += n;
          nbytes -= n;
          if (nbytes && (err=assuan_send_data (ctx, NULL, 0))) /* Flush line. */
            {
              gpg_err_set_errno (EIO);
              goto leave;
            }
        }
      while (nbytes);
    }
  else
    {
      err = assuan_send_data (ctx, buffer, size);
      if (err)
        {
          gpg_err_set_errno (EIO);  /* For use by data_line_cookie_write.  */
          goto leave;
        }
    }

 leave:
  if (ctrl && ctrl->server_local && ctrl->server_local->inhibit_data_logging)
    {
      ctrl->server_local->inhibit_data_logging_count += size;
      ctrl->server_local->inhibit_data_logging_now = 0;
    }

  return err;
}



/* Helper to print a message while leaving a command.  */
static gpg_error_t
leave_cmd (assuan_context_t ctx, gpg_error_t err)
{
  if (err && opt.verbose)
    {
      const char *name = assuan_get_command_name (ctx);
      if (!name)
        name = "?";
      if (gpg_err_source (err) == GPG_ERR_SOURCE_DEFAULT)
        log_error ("command '%s' failed: %s\n", name,
                   gpg_strerror (err));
      else
        log_error ("command '%s' failed: %s <%s>\n", name,
                   gpg_strerror (err), gpg_strsource (err));
    }
  return err;
}



/* Handle OPTION commands. */
static gpg_error_t
option_handler (assuan_context_t ctx, const char *key, const char *value)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  gpg_error_t err = 0;

  if (!strcmp (key, "lc-messages"))
    {
      if (ctrl->lc_messages)
        xfree (ctrl->lc_messages);
      ctrl->lc_messages = xtrystrdup (value);
      if (!ctrl->lc_messages)
        return out_of_core ();
    }
  else
    err = gpg_error (GPG_ERR_UNKNOWN_OPTION);

  return err;
}



static const char hlp_search[] =
  "SEARCH [--no-data] [[--more] PATTERN]\n"
  "\n"
  "Search for the keys identified by PATTERN.  With --more more\n"
  "patterns to be used for the search are expected with the next\n"
  "command.  With --no-data only the search status is returned but\n"
  "not the actual data.  See also \"NEXT\".";
static gpg_error_t
cmd_search (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int opt_more, opt_no_data;
  gpg_error_t err;
  unsigned int n, k;

  opt_no_data = has_option (line, "--no-data");
  opt_more = has_option (line, "--more");
  line = skip_options (line);

  ctrl->server_local->search_any_found = 0;

  if (!*line)
    {
      if (opt_more)
        {
          err = set_error (GPG_ERR_INV_ARG, "--more but no pattern");
          goto leave;
        }
      else if (!*line && ctrl->server_local->search_expecting_more)
        {
          /* It would be too surprising to first set a pattern but
           * finally add no pattern to search the entire DB.  */
          err = set_error (GPG_ERR_INV_ARG, "--more pending but no pattern");
          goto leave;
        }
      else /* No pattern - return the first item.  */
        {
          memset (&ctrl->server_local->search_desc, 0,
                  sizeof ctrl->server_local->search_desc);
          ctrl->server_local->search_desc.mode = KEYDB_SEARCH_MODE_FIRST;
        }
    }
  else
    {
      err = classify_user_id (line, &ctrl->server_local->search_desc, 0);
      if (err)
        goto leave;
    }

  if (opt_more || ctrl->server_local->search_expecting_more)
    {
      /* More pattern are expected - store the current one and return
       * success.  */
      if (!ctrl->server_local->multi_search_desc_size)
        {
          n = 10;
          ctrl->server_local->multi_search_desc
            = xtrycalloc (n, sizeof *ctrl->server_local->multi_search_desc);
          if (!ctrl->server_local->multi_search_desc)
            {
              err = gpg_error_from_syserror ();
              goto leave;
            }
          ctrl->server_local->multi_search_desc_size = n;
        }

      if (ctrl->server_local->multi_search_desc_len
          == ctrl->server_local->multi_search_desc_size)
        {
          KEYBOX_SEARCH_DESC *desc;
          n = ctrl->server_local->multi_search_desc_size + 10;
          desc = xtrycalloc (n, sizeof *desc);
          if (!desc)
            {
              err = gpg_error_from_syserror ();
              goto leave;
            }
          for (k=0; k < ctrl->server_local->multi_search_desc_size; k++)
            desc[k] = ctrl->server_local->multi_search_desc[k];
          xfree (ctrl->server_local->multi_search_desc);
          ctrl->server_local->multi_search_desc = desc;
          ctrl->server_local->multi_search_desc_size = n;
        }
      /* Actually store.  */
      ctrl->server_local->multi_search_desc
        [ctrl->server_local->multi_search_desc_len++]
        = ctrl->server_local->search_desc;

      if (opt_more)
        {
          /* We need to be called aagain with more pattern.  */
          ctrl->server_local->search_expecting_more = 1;
          goto leave;
        }
      ctrl->server_local->search_expecting_more = 0;
      /* Continue with the actual search.  */
    }
  else
    ctrl->server_local->multi_search_desc_len = 0;

  ctrl->server_local->inhibit_data_logging = 1;
  ctrl->server_local->inhibit_data_logging_now = 0;
  ctrl->server_local->inhibit_data_logging_count = 0;
  ctrl->no_data_return = opt_no_data;
  err = prepare_outstream (ctrl);
  if (err)
    ;
  else if (ctrl->server_local->multi_search_desc_len)
    err = kbxd_search (ctrl, ctrl->server_local->multi_search_desc,
                       ctrl->server_local->multi_search_desc_len, 1);
  else
    err = kbxd_search (ctrl, &ctrl->server_local->search_desc, 1, 1);
  if (err)
    goto leave;

  /* Set a flag for use by NEXT.  */
  ctrl->server_local->search_any_found = 1;

 leave:
  if (err)
    ctrl->server_local->multi_search_desc_len = 0;
  ctrl->no_data_return = 0;
  ctrl->server_local->inhibit_data_logging = 0;
  return leave_cmd (ctx, err);
}


static const char hlp_next[] =
  "NEXT [--no-data]\n"
  "\n"
  "Get the next search result from a previus search.";
static gpg_error_t
cmd_next (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int opt_no_data;
  gpg_error_t err;

  opt_no_data = has_option (line, "--no-data");
  line = skip_options (line);

  if (*line)
    {
      err = set_error (GPG_ERR_INV_ARG, "no args expected");
      goto leave;
    }

  if (!ctrl->server_local->search_any_found)
    {
      err = set_error (GPG_ERR_NOTHING_FOUND, "no previous SEARCH");
      goto leave;
    }

  ctrl->server_local->inhibit_data_logging = 1;
  ctrl->server_local->inhibit_data_logging_now = 0;
  ctrl->server_local->inhibit_data_logging_count = 0;
  ctrl->no_data_return = opt_no_data;
  err = prepare_outstream (ctrl);
  if (err)
    ;
  else if (ctrl->server_local->multi_search_desc_len)
    {
      /* The next condition should never be tru but we better handle
       * the first/next transition anyway.  */
      if (ctrl->server_local->multi_search_desc[0].mode
          == KEYDB_SEARCH_MODE_FIRST)
        ctrl->server_local->multi_search_desc[0].mode = KEYDB_SEARCH_MODE_NEXT;

      err = kbxd_search (ctrl, ctrl->server_local->multi_search_desc,
                         ctrl->server_local->multi_search_desc_len, 0);
    }
  else
    {
      /* We need to do the transition from first to next here.  */
      if (ctrl->server_local->search_desc.mode == KEYDB_SEARCH_MODE_FIRST)
        ctrl->server_local->search_desc.mode = KEYDB_SEARCH_MODE_NEXT;

      err = kbxd_search (ctrl, &ctrl->server_local->search_desc, 1, 0);
    }
  if (err)
    goto leave;

 leave:
  ctrl->no_data_return = 0;
  ctrl->server_local->inhibit_data_logging = 0;
  return leave_cmd (ctx, err);
}



static const char hlp_getinfo[] =
  "GETINFO <what>\n"
  "\n"
  "Multi purpose command to return certain information.  \n"
  "Supported values of WHAT are:\n"
  "\n"
  "version     - Return the version of the program.\n"
  "pid         - Return the process id of the server.\n"
  "socket_name - Return the name of the socket.\n"
  "session_id  - Return the current session_id.\n"
  "getenv NAME - Return value of envvar NAME\n";
static gpg_error_t
cmd_getinfo (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  gpg_error_t err;
  char numbuf[50];

  if (!strcmp (line, "version"))
    {
      const char *s = VERSION;
      err = assuan_send_data (ctx, s, strlen (s));
    }
  else if (!strcmp (line, "pid"))
    {
      snprintf (numbuf, sizeof numbuf, "%lu", (unsigned long)getpid ());
      err = assuan_send_data (ctx, numbuf, strlen (numbuf));
    }
  else if (!strcmp (line, "socket_name"))
    {
      const char *s = get_kbxd_socket_name ();
      if (!s)
        s = "[none]";
      err = assuan_send_data (ctx, s, strlen (s));
    }
  else if (!strcmp (line, "session_id"))
    {
      snprintf (numbuf, sizeof numbuf, "%u", ctrl->server_local->session_id);
      err = assuan_send_data (ctx, numbuf, strlen (numbuf));
    }
  else if (!strncmp (line, "getenv", 6)
           && (line[6] == ' ' || line[6] == '\t' || !line[6]))
    {
      line += 6;
      while (*line == ' ' || *line == '\t')
        line++;
      if (!*line)
        err = gpg_error (GPG_ERR_MISSING_VALUE);
      else
        {
          const char *s = getenv (line);
          if (!s)
            err = set_error (GPG_ERR_NOT_FOUND, "No such envvar");
          else
            err = assuan_send_data (ctx, s, strlen (s));
        }
    }
  else
    err = set_error (GPG_ERR_ASS_PARAMETER, "unknown value for WHAT");

  return leave_cmd (ctx, err);
}



static const char hlp_killkeyboxd[] =
  "KILLKEYBOXD\n"
  "\n"
  "This command allows a user - given sufficient permissions -\n"
  "to kill this keyboxd process.\n";
static gpg_error_t
cmd_killkeyboxd (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);

  (void)line;

  ctrl->server_local->stopme = 1;
  assuan_set_flag (ctx, ASSUAN_FORCE_CLOSE, 1);
  return gpg_error (GPG_ERR_EOF);
}


static const char hlp_reloadkeyboxd[] =
  "RELOADKEYBOXD\n"
  "\n"
  "This command is an alternative to SIGHUP\n"
  "to reload the configuration.";
static gpg_error_t
cmd_reloadkeyboxd (assuan_context_t ctx, char *line)
{
  (void)ctx;
  (void)line;

  kbxd_sighup_action ();
  return 0;
}


static const char hlp_output[] =
  "OUTPUT FD[=<n>]\n"
  "\n"
  "Set the file descriptor to write the output data to N.  If N is not\n"
  "given and the operating system supports file descriptor passing, the\n"
  "file descriptor currently in flight will be used.";


/* Tell the assuan library about our commands. */
static int
register_commands (assuan_context_t ctx)
{
  static struct {
    const char *name;
    assuan_handler_t handler;
    const char * const help;
  } table[] = {
    { "SEARCH",     cmd_search,     hlp_search },
    { "NEXT",       cmd_next,       hlp_next   },
    { "GETINFO",    cmd_getinfo,    hlp_getinfo },
    { "OUTPUT",     NULL,           hlp_output },
    { "KILLKEYBOXD",cmd_killkeyboxd,hlp_killkeyboxd },
    { "RELOADKEYBOXD",cmd_reloadkeyboxd,hlp_reloadkeyboxd },
    { NULL, NULL }
  };
  int i, j, rc;

  for (i=j=0; table[i].name; i++)
    {
      rc = assuan_register_command (ctx, table[i].name, table[i].handler,
                                    table[i].help);
      if (rc)
        return rc;
    }
  return 0;
}


/* Note that we do not reset the list of configured keyservers.  */
static gpg_error_t
reset_notify (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);

  (void)line;
  (void)ctrl;

  return 0;
}


/* This function is called by our assuan log handler to test whether a
 * log message shall really be printed.  The function must return
 * false to inhibit the logging of MSG.  CAT gives the requested log
 * category.  MSG might be NULL. */
int
kbxd_assuan_log_monitor (assuan_context_t ctx, unsigned int cat,
                         const char *msg)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);

  (void)cat;
  (void)msg;

  if (!ctrl || !ctrl->server_local)
    return 1; /* Can't decide - allow logging.  */

  if (!ctrl->server_local->inhibit_data_logging)
    return 1; /* Not requested - allow logging.  */

  /* Disallow logging if *_now is true.  */
  return !ctrl->server_local->inhibit_data_logging_now;
}


/* Startup the server and run the main command loop.  With FD = -1,
 * use stdin/stdout.  SESSION_ID is either 0 or a unique number
 * identifying a session. */
void
kbxd_start_command_handler (ctrl_t ctrl, gnupg_fd_t fd, unsigned int session_id)
{
  static const char hello[] = "Keyboxd " VERSION " at your service";
  static char *hello_line;
  int rc;
  assuan_context_t ctx;

  ctrl->server_local = xtrycalloc (1, sizeof *ctrl->server_local);
  if (!ctrl->server_local)
    {
      log_error (_("can't allocate control structure: %s\n"),
                 gpg_strerror (gpg_error_from_syserror ()));
      xfree (ctrl);
      return;
    }

  rc = assuan_new (&ctx);
  if (rc)
    {
      log_error (_("failed to allocate assuan context: %s\n"),
		 gpg_strerror (rc));
      kbxd_exit (2);
    }

  if (fd == GNUPG_INVALID_FD)
    {
      assuan_fd_t filedes[2];

      filedes[0] = assuan_fdopen (0);
      filedes[1] = assuan_fdopen (1);
      rc = assuan_init_pipe_server (ctx, filedes);
    }
  else
    {
      rc = assuan_init_socket_server (ctx, fd,
                                      (ASSUAN_SOCKET_SERVER_ACCEPTED
                                       |ASSUAN_SOCKET_SERVER_FDPASSING));
    }

  if (rc)
    {
      assuan_release (ctx);
      log_error (_("failed to initialize the server: %s\n"),
                 gpg_strerror (rc));
      kbxd_exit (2);
    }

  rc = register_commands (ctx);
  if (rc)
    {
      log_error (_("failed to the register commands with Assuan: %s\n"),
                 gpg_strerror(rc));
      kbxd_exit (2);
    }


  if (!hello_line)
    {
      hello_line = xtryasprintf
        ("Home: %s\n"
         "Config: %s\n"
         "%s",
         gnupg_homedir (),
         /*opt.config_filename? opt.config_filename :*/ "[none]",
         hello);
    }

  ctrl->server_local->assuan_ctx = ctx;
  assuan_set_pointer (ctx, ctrl);

  assuan_set_hello_line (ctx, hello_line);
  assuan_register_option_handler (ctx, option_handler);
  assuan_register_reset_notify (ctx, reset_notify);

  ctrl->server_local->session_id = session_id;

  /* The next call enable the use of status_printf.  */
  set_assuan_context_func (get_assuan_ctx_from_ctrl);

  for (;;)
    {
      rc = assuan_accept (ctx);
      if (rc == -1)
        break;
      if (rc)
        {
          log_info (_("Assuan accept problem: %s\n"), gpg_strerror (rc));
          break;
        }

#ifndef HAVE_W32_SYSTEM
      if (opt.verbose)
        {
	  assuan_peercred_t peercred;

          if (!assuan_get_peercred (ctx, &peercred))
            log_info ("connection from process %ld (%ld:%ld)\n",
                      (long)peercred->pid, (long)peercred->uid,
		      (long)peercred->gid);
        }
#endif

      rc = assuan_process (ctx);
      if (rc)
        {
          log_info (_("Assuan processing failed: %s\n"), gpg_strerror (rc));
          continue;
        }
    }

  assuan_close_output_fd (ctx);

  set_assuan_context_func (NULL);
  ctrl->server_local->assuan_ctx = NULL;
  assuan_release (ctx);

  if (ctrl->server_local->stopme)
    kbxd_exit (0);

  if (ctrl->refcount)
    log_error ("oops: connection control structure still referenced (%d)\n",
               ctrl->refcount);
  else
    {
      xfree (ctrl->server_local->multi_search_desc);
      xfree (ctrl->server_local);
      ctrl->server_local = NULL;
    }
}