gnupg/agent/command.c

/* command.c - gpg-agent command handler
 *	Copyright (C) 2001, 2002 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

/* FIXME: we should not use the default assuan buffering but setup
   some buffering in secure mempory to protect session keys etc. */

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

#include "agent.h"
#include "../assuan/assuan.h"

/* maximum allowed size of the inquired ciphertext */
#define MAXLEN_CIPHERTEXT 4096
/* maximum allowed size of the key parameters */
#define MAXLEN_KEYPARAM 1024

#define set_error(e,t) assuan_set_error (ctx, ASSUAN_ ## e, (t))


#if MAX_DIGEST_LEN < 20
#error MAX_DIGEST_LEN shorter than keygrip
#endif

/* Data used to associate an Assuan context with local server data */
struct server_local_s {
  ASSUAN_CONTEXT assuan_ctx;
  int message_fd;
  int use_cache_for_signing;
};





static void
reset_notify (ASSUAN_CONTEXT ctx)
{
  CTRL ctrl = assuan_get_pointer (ctx);

  memset (ctrl->keygrip, 0, 20);
  ctrl->have_keygrip = 0;
  ctrl->digest.valuelen = 0;
}


/* Check whether the option NAME appears in LINE */
static int
has_option (const char *line, const char *name)
{
  const char *s;
  int n = strlen (name);

  s = strstr (line, name);
  return (s && (s == line || spacep (s-1)) && (!s[n] || spacep (s+n)));
}

/* Parse a hex string.  Return an Assuan error code or 0 on success and the
   length of the parsed string in LEN. */
static int
parse_hexstring (ASSUAN_CONTEXT ctx, const char *string, size_t *len)
{
  const char *p;
  size_t n;

  /* parse the hash value */
  for (p=string, n=0; hexdigitp (p); p++, n++)
    ;
  if (*p)
    return set_error (Parameter_Error, "invalid hexstring");
  if ((n&1))
    return set_error (Parameter_Error, "odd number of digits");
  *len = n;
  return 0;
}

/* Parse the keygrip in STRING into the provided buffer BUF.  BUF must
   provide space for 20 bytes. BUF is not changed if the fucntions
   returns an error. */
static int
parse_keygrip (ASSUAN_CONTEXT ctx, const char *string, unsigned char *buf)
{
  int rc;
  size_t n;
  const unsigned char *p;

  rc = parse_hexstring (ctx, string, &n);
  if (rc)
    return rc;
  n /= 2;
  if (n != 20)
    return set_error (Parameter_Error, "invalid length of keygrip");

  for (p=string, n=0; n < 20; p += 2, n++)
    buf[n] = xtoi_2 (p);

  return 0;
}




/* ISTRUSTED <hexstring_with_fingerprint>

   Return OK when we have an entry with this fingerprint in our
   trustlist */
static int
cmd_istrusted (ASSUAN_CONTEXT ctx, char *line)
{
  int rc, n, i;
  char *p;
  char fpr[41];

  /* parse the fingerprint value */
  for (p=line,n=0; hexdigitp (p); p++, n++)
    ;
  if (*p || !(n == 40 || n == 32))
    return set_error (Parameter_Error, "invalid fingerprint");
  i = 0;
  if (n==32)
    {
      strcpy (fpr, "00000000");
      i += 8;
    }
  for (p=line; i < 40; p++, i++)
    fpr[i] = *p >= 'a'? (*p & 0xdf): *p;
  fpr[i] = 0;
  rc = agent_istrusted (fpr);
  if (!rc)
    return 0;
  else if (rc == -1)
    return ASSUAN_Not_Trusted;
  else
    {
      log_error ("command is_trusted failed: %s\n", gnupg_strerror (rc));
      return map_to_assuan_status (rc);
    }
}

/* LISTTRUSTED 

   List all entries from the trustlist */
static int
cmd_listtrusted (ASSUAN_CONTEXT ctx, char *line)
{
  int rc = agent_listtrusted (ctx);
  if (rc)
    log_error ("command listtrusted failed: %s\n", gnupg_strerror (rc));
  return map_to_assuan_status (rc);
}


/* MARKTRUSTED <hexstring_with_fingerprint> <flag> <display_name>

   Store a new key in into the trustlist*/
static int
cmd_marktrusted (ASSUAN_CONTEXT ctx, char *line)
{
  CTRL ctrl = assuan_get_pointer (ctx);
  int rc, n, i;
  char *p;
  char fpr[41];
  int flag;

  /* parse the fingerprint value */
  for (p=line,n=0; hexdigitp (p); p++, n++)
    ;
  if (!spacep (p) || !(n == 40 || n == 32))
    return set_error (Parameter_Error, "invalid fingerprint");
  i = 0;
  if (n==32)
    {
      strcpy (fpr, "00000000");
      i += 8;
    }
  for (p=line; i < 40; p++, i++)
    fpr[i] = *p >= 'a'? (*p & 0xdf): *p;
  fpr[i] = 0;
  
  while (spacep (p))
    p++;
  flag = *p++;
  if ( (flag != 'S' && flag != 'P') || !spacep (p) )
    return set_error (Parameter_Error, "invalid flag - must be P or S");
  while (spacep (p))
    p++;

  rc = agent_marktrusted (ctrl, p, fpr, flag);
  if (rc)
    log_error ("command marktrusted failed: %s\n", gnupg_strerror (rc));
  return map_to_assuan_status (rc);
}




/* HAVEKEY <hexstring_with_keygrip>
  
   Return success when the secret key is available */
static int
cmd_havekey (ASSUAN_CONTEXT ctx, char *line)
{
  int rc;
  unsigned char buf[20];

  rc = parse_keygrip (ctx, line, buf);
  if (rc)
    return rc;

  if (agent_key_available (buf))
    return ASSUAN_No_Secret_Key;

  return 0;
}


/* SIGKEY <hexstring_with_keygrip>
   SETKEY <hexstring_with_keygrip>
  
   Set the  key used for a sign or decrypt operation */
static int
cmd_sigkey (ASSUAN_CONTEXT ctx, char *line)
{
  int rc;
  CTRL ctrl = assuan_get_pointer (ctx);

  rc = parse_keygrip (ctx, line, ctrl->keygrip);
  if (rc)
    return rc;
  ctrl->have_keygrip = 1;
  return 0;
}


/* SETHASH <algonumber> <hexstring> 

  The client can use this command to tell the server about the data
  (which usually is a hash) to be signed. */
static int
cmd_sethash (ASSUAN_CONTEXT ctx, char *line)
{
  int rc;
  size_t n;
  char *p;
  CTRL ctrl = assuan_get_pointer (ctx);
  unsigned char *buf;
  char *endp;
  int algo;

  /* parse the algo number and check it */
  algo = (int)strtoul (line, &endp, 10);
  for (line = endp; *line == ' ' || *line == '\t'; line++)
    ;
  if (!algo || gcry_md_test_algo (algo))
    return set_error (Unsupported_Algorithm, NULL);
  ctrl->digest.algo = algo;

  /* parse the hash value */
  rc = parse_hexstring (ctx, line, &n);
  if (rc)
    return rc;
  n /= 2;
  if (n != 16 && n != 20 && n != 24 && n != 32)
    return set_error (Parameter_Error, "unsupported length of hash");
  if (n > MAX_DIGEST_LEN)
    return set_error (Parameter_Error, "hash value to long");

  buf = ctrl->digest.value;
  ctrl->digest.valuelen = n;
  for (p=line, n=0; n < ctrl->digest.valuelen; p += 2, n++)
    buf[n] = xtoi_2 (p);
  for (; n < ctrl->digest.valuelen; n++)
    buf[n] = 0;
  return 0;
}


/* PKSIGN <options>

   Perform the actual sign operation. Neither input nor output are
   sensitive to eavesdropping */
static int
cmd_pksign (ASSUAN_CONTEXT ctx, char *line)
{
  int rc;
  int ignore_cache = 0;
  CTRL ctrl = assuan_get_pointer (ctx);

  if (opt.ignore_cache_for_signing)
    ignore_cache = 1;
  else if (!ctrl->server_local->use_cache_for_signing)
    ignore_cache = 1;

  rc = agent_pksign (ctrl, assuan_get_data_fp (ctx), ignore_cache);
  if (rc)
    log_error ("command pksign failed: %s\n", gnupg_strerror (rc));
  return map_to_assuan_status (rc);
}

/* PKDECRYPT <options>

   Perform the actual decrypt operation.  Input is not 
   sensitive to eavesdropping */
static int
cmd_pkdecrypt (ASSUAN_CONTEXT ctx, char *line)
{
  int rc;
  CTRL ctrl = assuan_get_pointer (ctx);
  char *value;
  size_t valuelen;

  /* First inquire the data to decrypt */
  rc = assuan_inquire (ctx, "CIPHERTEXT",
                       &value, &valuelen, MAXLEN_CIPHERTEXT);
  if (rc)
    return rc;

  rc = agent_pkdecrypt (ctrl, value, valuelen, assuan_get_data_fp (ctx));
  xfree (value);
  if (rc)
    log_error ("command pkdecrypt failed: %s\n", gnupg_strerror (rc));
  return map_to_assuan_status (rc);
}


/* GENKEY

   Generate a new key, store the secret part and return the public
   part.  Here is an example transaction:

   C: GENKEY
   S: INQUIRE KEYPARM
   C: D (genkey (rsa (nbits  1024)))
   C: END
   S: D (public-key
   S: D   (rsa (n 326487324683264) (e 10001)))
   S  OK key created
*/

static int
cmd_genkey (ASSUAN_CONTEXT ctx, char *line)
{
  CTRL ctrl = assuan_get_pointer (ctx);
  int rc;
  char *value;
  size_t valuelen;

  /* First inquire the parameters */
  rc = assuan_inquire (ctx, "KEYPARAM", &value, &valuelen, MAXLEN_KEYPARAM);
  if (rc)
    return rc;

  rc = agent_genkey (ctrl, value, valuelen, assuan_get_data_fp (ctx));
  xfree (value);
  if (rc)
    log_error ("command genkey failed: %s\n", gnupg_strerror (rc));
  return map_to_assuan_status (rc);
}


static void
plus_to_blank (char *s)
{
  for (; *s; s++)
    {
      if (*s == '+')
        *s = ' ';
    }
}

/* GET_PASSPHRASE <cache_id> [<error_message> <prompt> <description>]

   This function is usually used to ask for a passphrase to be used
   for conventional encryption, but may also be used by programs which
   need specal handling of passphrases.  This command uses a syntax
   which helps clients to use the agent with minimum effort.  The
   agent either returns with an error or with a OK followed by the hex
   encoded passphrase.  Note that the length of the strings is
   implicitly limited by the maximum length of a command.
*/

static int
cmd_get_passphrase (ASSUAN_CONTEXT ctx, char *line)
{
  CTRL ctrl = assuan_get_pointer (ctx);
  int rc;
  const char *pw;
  char *response;
  char *cacheid = NULL, *desc = NULL, *prompt = NULL, *errtext = NULL;
  char *p;
  void *cache_marker;

  /* parse the stuff */
  for (p=line; *p == ' '; p++)
    ;
  cacheid = p;
  p = strchr (cacheid, ' ');
  if (p)
    {
      *p++ = 0;
      while (*p == ' ')
        p++;
      errtext = p;
      p = strchr (errtext, ' ');
      if (p)
        {
          *p++ = 0;
          while (*p == ' ')
            p++;
          prompt = p;
          p = strchr (prompt, ' ');
          if (p)
            {
              *p++ = 0;
              while (*p == ' ')
                p++;
              desc = p;
              p = strchr (desc, ' ');
              if (p)
                *p = 0; /* ignore garbage */
            }
        }
    }
  if (!cacheid || !*cacheid || strlen (cacheid) > 50)
    return set_error (Parameter_Error, "invalid length of cacheID");
  if (!desc)
    return set_error (Parameter_Error, "no description given");

  if (!strcmp (cacheid, "X"))
    cacheid = NULL;
  if (!strcmp (errtext, "X"))
    errtext = NULL;
  if (!strcmp (prompt, "X"))
    prompt = NULL;
  if (!strcmp (desc, "X"))
    desc = NULL;

  /* Note: we store the hexified versions in the cache. */
  pw = cacheid ? agent_get_cache (cacheid, &cache_marker) : NULL;
  if (pw)
    {
      assuan_begin_confidential (ctx);
      rc = assuan_set_okay_line (ctx, pw);
      agent_unlock_cache_entry (&cache_marker);
    }
  else
    {
      /* Note, that we only need to replace the + characters and
         should leave the other escaping in place because the escaped
         string is send verbatim to the pinentry which does the
         unescaping (but not the + replacing) */
      if (errtext)
        plus_to_blank (errtext);
      if (prompt)
        plus_to_blank (prompt);
      if (desc)
        plus_to_blank (desc);

      rc = agent_get_passphrase (ctrl, &response, desc, prompt, errtext);
      if (!rc)
        {
          if (cacheid)
            agent_put_cache (cacheid, response, 0);
          assuan_begin_confidential (ctx);
          rc = assuan_set_okay_line (ctx, response);
          xfree (response);
        }
    }

  if (rc)
    log_error ("command get_passphrase failed: %s\n", gnupg_strerror (rc));
  return map_to_assuan_status (rc);
}


/* CLEAR_PASSPHRASE <cache_id>

   may be used to invalidate the cache entry for a passphrase.  The
   function returns with OK even when there is no cached passphrase.
*/

static int
cmd_clear_passphrase (ASSUAN_CONTEXT ctx, char *line)
{
  char *cacheid = NULL;
  char *p;

  /* parse the stuff */
  for (p=line; *p == ' '; p++)
    ;
  cacheid = p;
  p = strchr (cacheid, ' ');
  if (p)
    *p = 0; /* ignore garbage */
  if (!cacheid || !*cacheid || strlen (cacheid) > 50)
    return set_error (Parameter_Error, "invalid length of cacheID");

  agent_put_cache (cacheid, NULL, 0);
  return 0;
}


/* LEARN [--send]

   Learn something about the currently inserted smartcard.  With
   --send the new certificates are send back.  */
static int
cmd_learn (ASSUAN_CONTEXT ctx, char *line)
{
  int rc;

  rc = agent_handle_learn (has_option (line, "--send")? ctx : NULL);
  if (rc)
    log_error ("command learn failed: %s\n", gnupg_strerror (rc));
  return map_to_assuan_status (rc);
}



/* PASSWD <hexstring_with_keygrip>
  
   Change the passphrase/PID for the key identified by keygrip in LINE. */
static int
cmd_passwd (ASSUAN_CONTEXT ctx, char *line)
{
  CTRL ctrl = assuan_get_pointer (ctx);
  int rc;
  unsigned char grip[20];
  GCRY_SEXP s_skey = NULL;
  unsigned char *shadow_info = NULL;

  rc = parse_keygrip (ctx, line, grip);
  if (rc)
    return rc; /* we can't jump to leave because this is already an
                  Assuan error code. */

  s_skey = agent_key_from_file (ctrl, grip, &shadow_info, 1);
  if (!s_skey && !shadow_info)
    rc = seterr (No_Secret_Key);
  else if (!s_skey)
    {
      log_error ("changing a smartcard PIN is not yet supported\n");
      rc = seterr (Not_Implemented);
    }
  else
    rc = agent_protect_and_store (ctrl, s_skey);

  gcry_sexp_release (s_skey);
  xfree (shadow_info);
  if (rc)
    log_error ("command passwd failed: %s\n", gnupg_strerror (rc));
  return map_to_assuan_status (rc);
}



static int
option_handler (ASSUAN_CONTEXT ctx, const char *key, const char *value)
{
   CTRL ctrl = assuan_get_pointer (ctx);

  if (!strcmp (key, "display"))
    {
      if (ctrl->display)
        free (ctrl->display);
      ctrl->display = strdup (value);
      if (!ctrl->display)
        return ASSUAN_Out_Of_Core;
    }
  else if (!strcmp (key, "ttyname"))
    {
      if (!opt.keep_tty)
        {
          if (ctrl->ttyname)
            free (ctrl->ttyname);
          ctrl->ttyname = strdup (value);
          if (!ctrl->ttyname)
            return ASSUAN_Out_Of_Core;
        }
    }
  else if (!strcmp (key, "ttytype"))
    {
      if (!opt.keep_tty)
        {
          if (ctrl->ttytype)
            free (ctrl->ttytype);
          ctrl->ttytype = strdup (value);
          if (!ctrl->ttytype)
            return ASSUAN_Out_Of_Core;
        }
    }
  else if (!strcmp (key, "lc-ctype"))
    {
      if (ctrl->lc_ctype)
        free (ctrl->lc_ctype);
      ctrl->lc_ctype = strdup (value);
      if (!ctrl->lc_ctype)
        return ASSUAN_Out_Of_Core;
    }
  else if (!strcmp (key, "lc-messages"))
    {
      if (ctrl->lc_messages)
        free (ctrl->lc_messages);
      ctrl->lc_messages = strdup (value);
      if (!ctrl->lc_messages)
        return ASSUAN_Out_Of_Core;
    }
  else if (!strcmp (key, "use-cache-for-signing"))
    ctrl->server_local->use_cache_for_signing = *value? atoi (value) : 0;
  else
    return ASSUAN_Invalid_Option;

  return 0;
}


/* Tell the assuan library about our commands */
static int
register_commands (ASSUAN_CONTEXT ctx)
{
  static struct {
    const char *name;
    int cmd_id;
    int (*handler)(ASSUAN_CONTEXT, char *line);
  } table[] = {
    { "ISTRUSTED",  0,  cmd_istrusted },
    { "HAVEKEY",    0,  cmd_havekey },
    { "SIGKEY",     0,  cmd_sigkey },
    { "SETKEY",     0,  cmd_sigkey },
    { "SETHASH",    0,  cmd_sethash },
    { "PKSIGN",     0,  cmd_pksign },
    { "PKDECRYPT",  0,  cmd_pkdecrypt },
    { "GENKEY",     0,  cmd_genkey },
    { "GET_PASSPHRASE",0, cmd_get_passphrase },
    { "CLEAR_PASSPHRASE",0, cmd_clear_passphrase },
    { "LISTTRUSTED",  0,  cmd_listtrusted },
    { "MARKTRUSTED",  0,  cmd_marktrusted },
    { "LEARN",        0,  cmd_learn },
    { "PASSWD",       0,  cmd_passwd },
    { "",     ASSUAN_CMD_INPUT, NULL }, 
    { "",     ASSUAN_CMD_OUTPUT, NULL }, 
    { NULL }
  };
  int i, j, rc;

  for (i=j=0; table[i].name; i++)
    {
      rc = assuan_register_command (ctx,
                                    table[i].cmd_id? table[i].cmd_id
                                                   : (ASSUAN_CMD_USER + j++),
                                    table[i].name, table[i].handler);
      if (rc)
        return rc;
    } 
  assuan_register_reset_notify (ctx, reset_notify);
  assuan_register_option_handler (ctx, option_handler);
  return 0;
}


/* Startup the server.  If LISTEN_FD and FD is given as -1, this is a simple
   piper server, otherwise it is a regular server */
void
start_command_handler (int listen_fd, int fd)
{
  int rc;
  ASSUAN_CONTEXT ctx;
  struct server_control_s ctrl;

  memset (&ctrl, 0, sizeof ctrl);
  agent_init_default_ctrl (&ctrl);
  
  if (listen_fd == -1 && fd == -1)
    {
      int filedes[2];

      filedes[0] = 0;
      filedes[1] = 1;
      rc = assuan_init_pipe_server (&ctx, filedes);
    }
  else if (listen_fd != -1)
    {
      rc = assuan_init_socket_server (&ctx, listen_fd);
    }
  else 
    {
      rc = assuan_init_connected_socket_server (&ctx, fd);
    }
  if (rc)
    {
      log_error ("failed to initialize the server: %s\n",
                 assuan_strerror(rc));
      agent_exit (2);
    }
  rc = register_commands (ctx);
  if (rc)
    {
      log_error ("failed to register commands with Assuan: %s\n",
                 assuan_strerror(rc));
      agent_exit (2);
    }

  assuan_set_pointer (ctx, &ctrl);
  ctrl.server_local = xcalloc (1, sizeof *ctrl.server_local);
  ctrl.server_local->assuan_ctx = ctx;
  ctrl.server_local->message_fd = -1;
  ctrl.server_local->use_cache_for_signing = 1;

  if (DBG_ASSUAN)
    assuan_set_log_stream (ctx, log_get_stream ());

  for (;;)
    {
      rc = assuan_accept (ctx);
      if (rc == -1)
        {
          break;
        }
      else if (rc)
        {
          log_info ("Assuan accept problem: %s\n", assuan_strerror (rc));
          break;
        }
      
      rc = assuan_process (ctx);
      if (rc)
        {
          log_info ("Assuan processing failed: %s\n", assuan_strerror (rc));
          continue;
        }
    }


  assuan_deinit_server (ctx);
  if (ctrl.display)
    free (ctrl.display);
  if (ctrl.ttyname)
    free (ctrl.ttyname);
  if (ctrl.ttytype)
    free (ctrl.ttytype);
  if (ctrl.lc_ctype)
    free (ctrl.lc_ctype);
  if (ctrl.lc_messages)
    free (ctrl.lc_messages);
}