gnupg/agent/call-scd.c

/* call-scd.c - fork of the scdaemon to do SC operations
 *	Copyright (C) 2001, 2002, 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

/* Fixme: For now we have serialized all access to the scdaemon which
   make sense becuase the scdaemon can't handle concurrent connections
   right now.  We should however keep a list of connections and lock
   just that connection - it migth make sense to implemtn parts of
   this in Assuan.*/

#include <config.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <assert.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#ifndef HAVE_W32_SYSTEM
#include <sys/wait.h>
#endif
#ifdef USE_GNU_PTH
# include <pth.h>
#endif

#include "agent.h"
#include <assuan.h>

#ifdef _POSIX_OPEN_MAX
#define MAX_OPEN_FDS _POSIX_OPEN_MAX
#else
#define MAX_OPEN_FDS 20
#endif

static ASSUAN_CONTEXT scd_ctx = NULL;
#ifdef USE_GNU_PTH
static pth_mutex_t scd_lock;
#endif
/* We need to keep track of the connection currently using the SCD.
   For a pipe server this is all a NOP because the connection will
   always have the connection indicator -1.  agent_reset_scd releases
   the active connection; i.e. sets it back to -1, so that a new
   connection can start using the SCD.  If we eventually allow
   multiple SCD session we will either make scdaemon multi-threaded or
   fork of a new scdaemon and let it see how it can get access to a
   reader. 
*/
static int active_connection_fd = -1;
static int active_connection = 0;

/* Callback parameter for learn card */
struct learn_parm_s {
  void (*kpinfo_cb)(void*, const char *);
  void *kpinfo_cb_arg;
  void (*certinfo_cb)(void*, const char *);
  void *certinfo_cb_arg;
  void (*sinfo_cb)(void*, const char *, size_t, const char *);
  void *sinfo_cb_arg;
};

struct inq_needpin_s {
  ASSUAN_CONTEXT ctx;
  int (*getpin_cb)(void *, const char *, char*, size_t);
  void *getpin_cb_arg;
};



/* This function must be called once to initialize this module.  This
   has to be done before a second thread is spawned.  We can't do the
   static initialization because Pth emulation code might not be able
   to do a static init; in particular, it is not possible for W32. */
void
initialize_module_call_scd (void)
{
#ifdef USE_GNU_PTH
  static int initialized;

  if (!initialized)
    if (pth_mutex_init (&scd_lock))
      initialized = 1;
#endif /*USE_GNU_PTH*/
}


static int 
unlock_scd (int rc)
{
#ifdef USE_GNU_PTH
  if (!pth_mutex_release (&scd_lock))
    {
      log_error ("failed to release the SCD lock\n");
      if (!rc)
        rc = gpg_error (GPG_ERR_INTERNAL);
    }
#endif /*USE_GNU_PTH*/
  return rc;
}

/* To make sure we leave no secrets in our image after forking of the
   scdaemon, we use this callback. */
static void
atfork_cb (void *opaque, int where)
{
  if (!where)
    gcry_control (GCRYCTL_TERM_SECMEM);
}


/* Fork off the SCdaemon if this has not already been done.  Note that
   this fucntion alos locks the daemon.  */
static int
start_scd (ctrl_t ctrl)
{
  int rc;
  const char *pgmname;
  ASSUAN_CONTEXT ctx;
  const char *argv[3];
  int no_close_list[3];
  int i;

  if (opt.disable_scdaemon)
    return gpg_error (GPG_ERR_NOT_SUPPORTED);

#ifdef USE_GNU_PTH
  if (!pth_mutex_acquire (&scd_lock, 0, NULL))
    {
      log_error ("failed to acquire the SCD lock\n");
      return gpg_error (GPG_ERR_INTERNAL);
    }
#endif

  if (scd_ctx)
    {
      pid_t pid;

      /* If we are not the connection currently using the SCD, return
         an error. */
      if (!active_connection)
        {
          active_connection_fd = ctrl->connection_fd;
          active_connection = 1;
        }
      else if (ctrl->connection_fd != active_connection_fd)
        return unlock_scd (gpg_error (GPG_ERR_CONFLICT));
      
      /* Okay, we already started the scdaemon and it is used by us.*/

      /* We better do a sanity check now to see whether it has
         accidently died. */
#ifndef HAVE_W32_SYSTEM 
      pid = assuan_get_pid (scd_ctx);
      if (pid != (pid_t)(-1) && pid
          && ((rc=waitpid (pid, NULL, WNOHANG))==-1 || (rc == pid)) )
        {
          assuan_disconnect (scd_ctx);
          scd_ctx = NULL;
        }
      else
#endif
        return 0; 
    }

  if (opt.verbose)
    log_info ("no running SCdaemon - starting it\n");
      
  if (fflush (NULL))
    {
      gpg_error_t tmperr = gpg_error (gpg_err_code_from_errno (errno));
      log_error ("error flushing pending output: %s\n", strerror (errno));
      return unlock_scd (tmperr);
    }

  if (!opt.scdaemon_program || !*opt.scdaemon_program)
    opt.scdaemon_program = GNUPG_DEFAULT_SCDAEMON;
  if ( !(pgmname = strrchr (opt.scdaemon_program, '/')))
    pgmname = opt.scdaemon_program;
  else
    pgmname++;

  argv[0] = pgmname;
  argv[1] = "--server";
  argv[2] = NULL;

  i=0;
  if (!opt.running_detached)
    {
      if (log_get_fd () != -1)
        no_close_list[i++] = log_get_fd ();
      no_close_list[i++] = fileno (stderr);
    }
  no_close_list[i] = -1;

  /* Connect to the pinentry and perform initial handshaking */
  rc = assuan_pipe_connect2 (&ctx, opt.scdaemon_program, (char**)argv,
                             no_close_list, atfork_cb, NULL);
  if (rc)
    {
      log_error ("can't connect to the SCdaemon: %s\n",
                 assuan_strerror (rc));
      return unlock_scd (gpg_error (GPG_ERR_NO_SCDAEMON));
    }
  scd_ctx = ctx;
  active_connection_fd = ctrl->connection_fd;
  active_connection = 1;

  if (DBG_ASSUAN)
    log_debug ("connection to SCdaemon established\n");

  /* Tell the scdaemon that we want him to send us an event signal.
     But only do this if we are running as a regular sever and not
     simply as a pipe server. */
  /* Fixme: gpg-agent does not use this signal yet.  */
/*   if (ctrl->connection_fd != -1) */
/*   { */
/* #ifndef HAVE_W32_SYSTEM */
/*     char buf[100]; */

/*     sprintf (buf, "OPTION event-signal=%d", SIGUSR2); */
/*     assuan_transact (scd_ctx, buf, NULL, NULL, NULL, NULL, NULL, NULL); */
/* #endif */
/*   } */

  return 0;
}



/* Reset the SCD if it has been used. */
int
agent_reset_scd (ctrl_t ctrl)
{
  int rc = 0;

#ifdef USE_GNU_PTH
  if (!pth_mutex_acquire (&scd_lock, 0, NULL))
    {
      log_error ("failed to acquire the SCD lock for reset\n");
      return gpg_error (GPG_ERR_INTERNAL);
    }
#endif
  if (active_connection && active_connection_fd == ctrl->connection_fd)
    {
      if (scd_ctx)
        rc = assuan_transact (scd_ctx, "RESET", NULL, NULL,
                              NULL, NULL, NULL, NULL);
      active_connection_fd = -1;
      active_connection = 0;
    }

  return unlock_scd (map_assuan_err (rc));
}



/* Return a new malloced string by unescaping the string S.  Escaping
   is percent escaping and '+'/space mapping.  A binary Nul will
   silently be replaced by a 0xFF.  Function returns NULL to indicate
   an out of memory status. */
static char *
unescape_status_string (const unsigned char *s)
{
  char *buffer, *d;

  buffer = d = xtrymalloc (strlen (s)+1);
  if (!buffer)
    return NULL;
  while (*s)
    {
      if (*s == '%' && s[1] && s[2])
        { 
          s++;
          *d = xtoi_2 (s);
          if (!*d)
            *d = '\xff';
          d++;
          s += 2;
        }
      else if (*s == '+')
        {
          *d++ = ' ';
          s++;
        }
      else
        *d++ = *s++;
    }
  *d = 0; 
  return buffer;
}



static AssuanError
learn_status_cb (void *opaque, const char *line)
{
  struct learn_parm_s *parm = opaque;
  const char *keyword = line;
  int keywordlen;

  for (keywordlen=0; *line && !spacep (line); line++, keywordlen++)
    ;
  while (spacep (line))
    line++;
  if (keywordlen == 8 && !memcmp (keyword, "CERTINFO", keywordlen))
    {
      parm->certinfo_cb (parm->certinfo_cb_arg, line);
    }
  else if (keywordlen == 11 && !memcmp (keyword, "KEYPAIRINFO", keywordlen))
    {
      parm->kpinfo_cb (parm->kpinfo_cb_arg, line);
    }
  else if (keywordlen && *line)
    {
      parm->sinfo_cb (parm->sinfo_cb_arg, keyword, keywordlen, line);
    }
  
  return 0;
}

/* Perform the LEARN command and return a list of all private keys
   stored on the card. */
int
agent_card_learn (ctrl_t ctrl,
                  void (*kpinfo_cb)(void*, const char *),
                  void *kpinfo_cb_arg,
                  void (*certinfo_cb)(void*, const char *),
                  void *certinfo_cb_arg,
                  void (*sinfo_cb)(void*, const char *, size_t, const char *),
                  void *sinfo_cb_arg)
{
  int rc;
  struct learn_parm_s parm;

  rc = start_scd (ctrl);
  if (rc)
    return rc;

  memset (&parm, 0, sizeof parm);
  parm.kpinfo_cb = kpinfo_cb;
  parm.kpinfo_cb_arg = kpinfo_cb_arg;
  parm.certinfo_cb = certinfo_cb;
  parm.certinfo_cb_arg = certinfo_cb_arg;
  parm.sinfo_cb = sinfo_cb;
  parm.sinfo_cb_arg = sinfo_cb_arg;
  rc = assuan_transact (scd_ctx, "LEARN --force",
                        NULL, NULL, NULL, NULL,
                        learn_status_cb, &parm);
  if (rc)
    return unlock_scd (map_assuan_err (rc));

  return unlock_scd (0);
}



static AssuanError
get_serialno_cb (void *opaque, const char *line)
{
  char **serialno = opaque;
  const char *keyword = line;
  const char *s;
  int keywordlen, n;

  for (keywordlen=0; *line && !spacep (line); line++, keywordlen++)
    ;
  while (spacep (line))
    line++;

  if (keywordlen == 8 && !memcmp (keyword, "SERIALNO", keywordlen))
    {
      if (*serialno)
        return ASSUAN_Unexpected_Status;
      for (n=0,s=line; hexdigitp (s); s++, n++)
        ;
      if (!n || (n&1)|| !(spacep (s) || !*s) )
        return ASSUAN_Invalid_Status;
      *serialno = xtrymalloc (n+1);
      if (!*serialno)
        return ASSUAN_Out_Of_Core;
      memcpy (*serialno, line, n);
      (*serialno)[n] = 0;
    }
  
  return 0;
}

/* Return the serial number of the card or an appropriate error.  The
   serial number is returned as a hexstring. */
int
agent_card_serialno (ctrl_t ctrl, char **r_serialno)
{
  int rc;
  char *serialno = NULL;

  rc = start_scd (ctrl);
  if (rc)
    return rc;

  rc = assuan_transact (scd_ctx, "SERIALNO",
                        NULL, NULL, NULL, NULL,
                        get_serialno_cb, &serialno);
  if (rc)
    {
      xfree (serialno);
      return unlock_scd (map_assuan_err (rc));
    }
  *r_serialno = serialno;
  return unlock_scd (0);
}




static AssuanError
membuf_data_cb (void *opaque, const void *buffer, size_t length)
{
  membuf_t *data = opaque;

  if (buffer)
    put_membuf (data, buffer, length);
  return 0;
}
  
/* Handle the NEEDPIN inquiry. */
static AssuanError
inq_needpin (void *opaque, const char *line)
{
  struct inq_needpin_s *parm = opaque;
  char *pin;
  size_t pinlen;
  int rc;

  if (!(!strncmp (line, "NEEDPIN", 7) && (line[7] == ' ' || !line[7])))
    {
      log_error ("unsupported inquiry `%s'\n", line);
      return ASSUAN_Inquire_Unknown;
    }
  line += 7;

  pinlen = 90;
  pin = gcry_malloc_secure (pinlen);
  if (!pin)
    return ASSUAN_Out_Of_Core;

  rc = parm->getpin_cb (parm->getpin_cb_arg, line, pin, pinlen);
  if (rc)
    rc = ASSUAN_Canceled;
  if (!rc)
    rc = assuan_send_data (parm->ctx, pin, pinlen);
  xfree (pin);

  return rc;
}



/* Create a signature using the current card */
int
agent_card_pksign (ctrl_t ctrl,
                   const char *keyid,
                   int (*getpin_cb)(void *, const char *, char*, size_t),
                   void *getpin_cb_arg,
                   const unsigned char *indata, size_t indatalen,
                   char **r_buf, size_t *r_buflen)
{
  int rc, i;
  char *p, line[ASSUAN_LINELENGTH];
  membuf_t data;
  struct inq_needpin_s inqparm;
  size_t len;
  unsigned char *sigbuf;
  size_t sigbuflen;

  *r_buf = NULL;
  rc = start_scd (ctrl);
  if (rc)
    return rc;

  if (indatalen*2 + 50 > DIM(line))
    return unlock_scd (gpg_error (GPG_ERR_GENERAL));

  sprintf (line, "SETDATA ");
  p = line + strlen (line);
  for (i=0; i < indatalen ; i++, p += 2 )
    sprintf (p, "%02X", indata[i]);
  rc = assuan_transact (scd_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
  if (rc)
    return unlock_scd (map_assuan_err (rc));

  init_membuf (&data, 1024);
  inqparm.ctx = scd_ctx;
  inqparm.getpin_cb = getpin_cb;
  inqparm.getpin_cb_arg = getpin_cb_arg;
  snprintf (line, DIM(line)-1, 
            ctrl->use_auth_call? "PKAUTH %s":"PKSIGN %s", keyid);
  line[DIM(line)-1] = 0;
  rc = assuan_transact (scd_ctx, line,
                        membuf_data_cb, &data,
                        inq_needpin, &inqparm,
                        NULL, NULL);
  if (rc)
    {
      xfree (get_membuf (&data, &len));
      return unlock_scd (map_assuan_err (rc));
    }
  sigbuf = get_membuf (&data, &sigbuflen);

  /* Create an S-expression from it which is formatted like this:
     "(7:sig-val(3:rsa(1:sSIGBUFLEN:SIGBUF)))" */
  *r_buflen = 21 + 11 + sigbuflen + 4;
  *r_buf = xtrymalloc (*r_buflen);
  if (!*r_buf)
    {
      gpg_error_t tmperr = out_of_core ();
      xfree (*r_buf);
      return unlock_scd (tmperr);
    }
  p = stpcpy (*r_buf, "(7:sig-val(3:rsa(1:s" );
  sprintf (p, "%u:", (unsigned int)sigbuflen);
  p += strlen (p);
  memcpy (p, sigbuf, sigbuflen);
  p += sigbuflen;
  strcpy (p, ")))");
  xfree (sigbuf);

  assert (gcry_sexp_canon_len (*r_buf, *r_buflen, NULL, NULL));
  return unlock_scd (0);
}

/* Decipher INDATA using the current card. Note that the returned value is */
int
agent_card_pkdecrypt (ctrl_t ctrl,
                      const char *keyid,
                      int (*getpin_cb)(void *, const char *, char*, size_t),
                      void *getpin_cb_arg,
                      const unsigned char *indata, size_t indatalen,
                      char **r_buf, size_t *r_buflen)
{
  int rc, i;
  char *p, line[ASSUAN_LINELENGTH];
  membuf_t data;
  struct inq_needpin_s inqparm;
  size_t len;

  *r_buf = NULL;
  rc = start_scd (ctrl);
  if (rc)
    return rc;

  /* FIXME: use secure memory where appropriate */
  if (indatalen*2 + 50 > DIM(line))
    return unlock_scd (gpg_error (GPG_ERR_GENERAL));

  sprintf (line, "SETDATA ");
  p = line + strlen (line);
  for (i=0; i < indatalen ; i++, p += 2 )
    sprintf (p, "%02X", indata[i]);
  rc = assuan_transact (scd_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
  if (rc)
    return unlock_scd (map_assuan_err (rc));

  init_membuf (&data, 1024);
  inqparm.ctx = scd_ctx;
  inqparm.getpin_cb = getpin_cb;
  inqparm.getpin_cb_arg = getpin_cb_arg;
  snprintf (line, DIM(line)-1, "PKDECRYPT %s", keyid);
  line[DIM(line)-1] = 0;
  rc = assuan_transact (scd_ctx, line,
                        membuf_data_cb, &data,
                        inq_needpin, &inqparm,
                        NULL, NULL);
  if (rc)
    {
      xfree (get_membuf (&data, &len));
      return unlock_scd (map_assuan_err (rc));
    }
  *r_buf = get_membuf (&data, r_buflen);
  if (!*r_buf)
    return unlock_scd (gpg_error (GPG_ERR_ENOMEM));

  return unlock_scd (0);
}



/* Read a certificate with ID into R_BUF and R_BUFLEN. */
int
agent_card_readcert (ctrl_t ctrl,
                     const char *id, char **r_buf, size_t *r_buflen)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  membuf_t data;
  size_t len;

  *r_buf = NULL;
  rc = start_scd (ctrl);
  if (rc)
    return rc;

  init_membuf (&data, 1024);
  snprintf (line, DIM(line)-1, "READCERT %s", id);
  line[DIM(line)-1] = 0;
  rc = assuan_transact (scd_ctx, line,
                        membuf_data_cb, &data,
                        NULL, NULL,
                        NULL, NULL);
  if (rc)
    {
      xfree (get_membuf (&data, &len));
      return unlock_scd (map_assuan_err (rc));
    }
  *r_buf = get_membuf (&data, r_buflen);
  if (!*r_buf)
    return unlock_scd (gpg_error (GPG_ERR_ENOMEM));

  return unlock_scd (0);
}



/* Read a key with ID and return it in an allocate buffer pointed to
   by r_BUF as a valid S-expression. */
int
agent_card_readkey (ctrl_t ctrl, const char *id, unsigned char **r_buf)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  membuf_t data;
  size_t len, buflen;

  *r_buf = NULL;
  rc = start_scd (ctrl);
  if (rc)
    return rc;

  init_membuf (&data, 1024);
  snprintf (line, DIM(line)-1, "READKEY %s", id);
  line[DIM(line)-1] = 0;
  rc = assuan_transact (scd_ctx, line,
                        membuf_data_cb, &data,
                        NULL, NULL,
                        NULL, NULL);
  if (rc)
    {
      xfree (get_membuf (&data, &len));
      return unlock_scd (map_assuan_err (rc));
    }
  *r_buf = get_membuf (&data, &buflen);
  if (!*r_buf)
    return unlock_scd (gpg_error (GPG_ERR_ENOMEM));

  if (!gcry_sexp_canon_len (*r_buf, buflen, NULL, NULL))
    {
      xfree (*r_buf); *r_buf = NULL;
      return unlock_scd (gpg_error (GPG_ERR_INV_VALUE));
    }

  return unlock_scd (0);
}



/* Type used with the card_getattr_cb.  */
struct card_getattr_parm_s {
  const char *keyword;  /* Keyword to look for.  */
  size_t keywordlen;    /* strlen of KEYWORD.  */
  char *data;           /* Malloced and unescaped data.  */
  int error;            /* ERRNO value or 0 on success. */
};

/* Callback function for agent_card_getattr.  */
static assuan_error_t
card_getattr_cb (void *opaque, const char *line)
{
  struct card_getattr_parm_s *parm = opaque;
  const char *keyword = line;
  int keywordlen;

  if (parm->data)
    return 0; /* We want only the first occurrence.  */

  for (keywordlen=0; *line && !spacep (line); line++, keywordlen++)
    ;
  while (spacep (line))
    line++;

  if (keywordlen == parm->keywordlen
      && !memcmp (keyword, parm->keyword, keywordlen))
    {
      parm->data = unescape_status_string (line);
      if (!parm->data)
        parm->error = errno;
    }
  
  return 0;
}


/* Call the agent to retrieve a single line data object. On success
   the object is malloced and stored at RESULT; it is guaranteed that
   NULL is never stored in this case.  On error an error code is
   returned and NULL stored at RESULT. */
gpg_error_t
agent_card_getattr (ctrl_t ctrl, const char *name, char **result)
{
  int err;
  struct card_getattr_parm_s parm;
  char line[ASSUAN_LINELENGTH];

  *result = NULL;

  if (!*name)
    return gpg_error (GPG_ERR_INV_VALUE);

  memset (&parm, 0, sizeof parm);
  parm.keyword = name;
  parm.keywordlen = strlen (name);

  /* We assume that NAME does not need escaping. */
  if (8 + strlen (name) > DIM(line)-1)
    return gpg_error (GPG_ERR_TOO_LARGE);
  stpcpy (stpcpy (line, "GETATTR "), name); 

  err = start_scd (ctrl);
  if (err)
    return err;

  err = map_assuan_err (assuan_transact (scd_ctx, line,
                                         NULL, NULL, NULL, NULL,
                                         card_getattr_cb, &parm));
  if (!err && parm.error)
    err = gpg_error_from_errno (parm.error);
  
  if (!err && !parm.data)
    err = gpg_error (GPG_ERR_NO_DATA);
  
  if (!err)
    *result = parm.data;
  else
    xfree (parm.data);

  return unlock_scd (err);
}




static AssuanError
pass_status_thru (void *opaque, const char *line)
{
  ASSUAN_CONTEXT ctx = opaque;
  char keyword[200];
  int i;

  for (i=0; *line && !spacep (line) && i < DIM(keyword)-1; line++, i++)
    keyword[i] = *line;
  keyword[i] = 0;
  /* truncate any remaining keyword stuff. */
  for (; *line && !spacep (line); line++)
    ;
  while (spacep (line))
    line++;

  assuan_write_status (ctx, keyword, line);
  return 0;
}

static AssuanError
pass_data_thru (void *opaque, const void *buffer, size_t length)
{
  ASSUAN_CONTEXT ctx = opaque;

  assuan_send_data (ctx, buffer, length);
  return 0;
}


/* Send the line CMDLINE with command for the SCDdaemon to it and send
   all status messages back.  This command is used as a general quoting
   mechanism to pass everything verbatim to SCDAEMOPN.  The PIN
   inquirey is handled inside gpg-agent. */
int
agent_card_scd (ctrl_t ctrl, const char *cmdline,
                int (*getpin_cb)(void *, const char *, char*, size_t),
                void *getpin_cb_arg, void *assuan_context)
{
  int rc;
  struct inq_needpin_s inqparm;

  rc = start_scd (ctrl);
  if (rc)
    return rc;

  inqparm.ctx = scd_ctx;
  inqparm.getpin_cb = getpin_cb;
  inqparm.getpin_cb_arg = getpin_cb_arg;
  rc = assuan_transact (scd_ctx, cmdline,
                        pass_data_thru, assuan_context,
                        inq_needpin, &inqparm,
                        pass_status_thru, assuan_context);
  if (rc)
    {
      return unlock_scd (map_assuan_err (rc));
    }

  return unlock_scd (0);
}