source: trunk/third/ssh/authfd.c @ 12646

/*

authfd.c

Author: Tatu Ylonen <ylo@cs.hut.fi>

Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
                   All rights reserved

Created: Wed Mar 29 01:30:28 1995 ylo

Functions for connecting the local authentication agent.

*/

/*
 * $Id: authfd.c,v 1.1.1.4 1999-03-08 17:43:16 danw Exp $
 * $Log: not supported by cvs2svn $
 * Revision 1.16  1998/05/23  20:20:49  kivinen
 *      Changed () -> (void).
 *
 * Revision 1.15  1998/03/27  16:56:30  kivinen
 *      Allow authentication socket to be symlink, if not suid. Fixed
 *      authsocketdir freeing.
 *
 * Revision 1.14  1998/01/02 06:15:49  kivinen
 *      Fixed agent socket opening routine.
 *
 * Revision 1.13  1997/04/17 04:00:46  kivinen
 *      Removed extra namelen variable.
 *
 * Revision 1.12  1997/03/26 07:00:57  kivinen
 *      Changed uid 0 to UID_ROOT.
 *      Fixed memory leak.
 *      Removed ssh_close_authentication function.
 *
 * Revision 1.11  1996/11/19 22:44:03  kivinen
 *      Changed socket directory checks so that if the
 *      original_real_uid is root do not check the file owner.
 *
 * Revision 1.10  1996/10/29 22:34:52  kivinen
 *      log -> log_msg. Removed userfile.h.
 *
 * Revision 1.9  1996/10/24 14:05:44  ttsalo
 *       Cleaning up old fd-auth trash
 *
 * Revision 1.8  1996/10/21 16:15:40  ttsalo
 *       Fixed auth socket name handling
 *
 * Revision 1.7  1996/10/20 16:26:17  ttsalo
 *      Modified the routines to use agent socket directly
 *
 * Revision 1.6  1996/10/03 18:46:13  ylo
 *      Fixed a bug that caused "Received signal 14" errors.
 *
 * Revision 1.5  1996/09/27 13:56:35  ttsalo
 *      Fixed a memory deallocation bug
 *
 * Revision 1.4  1996/09/11 17:54:22  kivinen
 *      Added check for bind errors in
 *      ssh_get_authentication_connection_fd.
 *      Fixed bug in old alarm / timeout restoration.
 *      Changed limit of messages from 256 kB to 30 kB.
 *
 * Revision 1.3  1996/09/08 17:21:04  ttsalo
 *      A lot of changes in agent-socket handling
 *
 * Revision 1.2  1996/09/04 12:41:50  ttsalo
 *      Minor fixes
 *
 * Revision 1.1.1.1  1996/02/18 21:38:11  ylo
 *      Imported ssh-1.2.13.
 *
 * Revision 1.7  1995/09/21  17:08:11  ylo
 *      Support AF_UNIX_SIZE.
 *
 * Revision 1.6  1995/09/09  21:26:38  ylo
 * /m/shadows/u2/users/ylo/ssh/README
 *
 * Revision 1.5  1995/08/29  22:18:58  ylo
 *      Added remove_all_identities.
 *
 * Revision 1.4  1995/08/21  23:21:04  ylo
 *      Deleted ssh_authenticate().
 *      Pass session key and response_type in agent request.
 *
 * Revision 1.3  1995/07/13  01:14:40  ylo
 *      Removed the "Last modified" header.
 *
 * Revision 1.2  1995/07/13  01:11:31  ylo
 *      Added cvs log.
 *
 * $Endlog$
 */

#include "includes.h"
#include "ssh.h"
#include "rsa.h"
#include "authfd.h"
#include "buffer.h"
#include "bufaux.h"
#include "xmalloc.h"
#include "getput.h"

/* Returns the authentication fd, or -1 if there is none.
   Socket directory privileges are checked to prevent anyone
   from connecting to other users' sockets with suid root ssh. */

int ssh_get_authentication_fd(void)
{
  char *authsocket, *authsocketdir, *newauthsockdir, *last_dir;
  char *origauthsocket;
  int sock;
  struct sockaddr_un sunaddr;
  struct stat socket_st, dir_st, dot_st, dotdot_st, parent_st, link_st;
  struct passwd *pw;
  int i;

  newauthsockdir = NULL;

  origauthsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
  if (!origauthsocket)
    return -1;
  else
    authsocketdir = xstrdup(origauthsocket);

  /* Point to the end of the name */
  authsocket = authsocketdir + strlen(authsocketdir);

  /* Cut the authsocketdir and make authsocket point to
     the bare socket name */
  while (authsocket != authsocketdir && *authsocket != '/')
    authsocket--;

  *authsocket = '\0';
  authsocket++;

  /* Find parent directory */
  last_dir = strrchr(authsocketdir, '/');
  if (last_dir == NULL || last_dir == authsocketdir)
    {
      error("Invalid %s `%.100s', it should contain at least one /.",
            SSH_AUTHSOCKET_ENV_NAME, authsocketdir);
      xfree(authsocketdir);
      return -1;
    }

  /* Stat parent directory */
  *last_dir = '\0';
  if (stat(authsocketdir, &parent_st) != 0)
    {
      error("Parent directory stat failed `%.100s'", authsocketdir);
      xfree(authsocketdir);
      return -1;
    }
  *last_dir = '/';

  pw = getpwuid(original_real_uid);
  
  /* Change to the socket directory so it's privileges can be
     reliably checked */

  /* Stat it */
  if (lstat(authsocketdir, &dir_st) != 0)
    {
      error("Cannot stat authentication socket directory %.100s",
            authsocketdir);
      xfree(authsocketdir);
      return -1;
    }
  
  chdir(authsocketdir);

  if (stat(".", &dot_st) != 0)
    {
      perror("stat . failed");
      xfree(authsocketdir);
      return -1;
    }

  /* Check that stat of real directory name and . matches. */
  if (dot_st.st_dev != dir_st.st_dev || dot_st.st_ino != dir_st.st_ino)
    {
      error("Wrong directory after chdir");
      return -1;
    }
  
  if (original_real_uid != UID_ROOT && dot_st.st_uid != pw->pw_uid)
    {
      error("Invalid owner of authentication socket directory %.100s",
            authsocketdir);
      xfree(authsocketdir);
      return -1;
    }

  if ((dot_st.st_mode & 077) != 0)
    {
      error("Invalid modes for authentication socket directory %.100s",
            authsocketdir);
      xfree(authsocketdir);
      return -1;
    }

  if (lstat(authsocket, &socket_st) != 0)
    {
      error("Cannot find authentication socket %.100s/%.100s",
            authsocketdir, authsocket);
      xfree(authsocketdir);
      return -1;
    }
  if (S_ISLNK(socket_st.st_mode))
    {
      if (original_real_uid != geteuid())
        {
          error("Authentication socket `%.100s' is symlink", origauthsocket);
          xfree(authsocketdir);
          return -1;
        }
    }

  /* Check if we are suid process */
  if (original_real_uid != geteuid())
    {
      /* Something wierd code here again. We need to make sure the socket is
         not symlink to somebody elses socket. We cannot use stat/lstat because
         user might change the inode after we have stat/lstat'ed it. We cannot
         use fstat, because it doesn't work for sockets, so we need some magic
         spell here.

         Create temporary directory at same position where the real agent
         directory is, allow only owner to modify it (==root). Change current
         working directory to there and make sure we ended where we wanted
         (stat "." and real path and check that they match, and check that
         parent is what it is supposed to be (stat of .. and real parent
         matches)). Then check that the parent directory ("..") is sticky so
         nobody can mess with this directory. Now we are at safe place where
         nobody else have any permissions. Now make hard link from the real
         authentication socket to this directory. Hard link to symlink will
         point to destination of that symlink, so if the agent socket was
         symlink to somebody elses socket then the stat of our hardlink and
         agent socket given by user differs and we give an error. Otherwise we
         know that the hard link points to real socket that (at least used to
         be) at the directory that was owned by user, so we can safely open the
         hardlink socket (not the original it might be changed after we have
         checked the permissions). */

      newauthsockdir = xmalloc(strlen(authsocketdir) + 20);
      sprintf(newauthsockdir, "%s-%d", authsocketdir, getpid());

      /* Create directory */
      if (mkdir(newauthsockdir, S_IRWXU) != 0)
        {
          error("Cannot make temporary authentication socket directory %.100s",
                newauthsockdir);
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;
        }

      /* Stat it */
      if (lstat(newauthsockdir, &dir_st) != 0)
        {
          error("Cannot stat newly created temporary authentication socket directory %.100s",
                newauthsockdir);
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;
        }

      /* Move to there */
      chdir(newauthsockdir);

      /* Stat . */
      if (stat(".", &dot_st) != 0)
        {
          error("Cannot stat . in newly created temporary authentication socket directory %.100s",
                newauthsockdir);
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;
        }

      /* Check that stat of real directory name and . matches. */
      if (dot_st.st_dev != dir_st.st_dev || dot_st.st_ino != dir_st.st_ino)
        {
          error("Wrong directory after chdir");
          return -1;
        }

      /* Stat .. (it should match the parent directory and it must be sticky)*/
      if (stat("..", &dotdot_st) != 0)
        {
          error("Cannot stat .. in newly created temporary authentication socket directory %.100s",
                newauthsockdir);
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;
        }
      if ((dotdot_st.st_mode & 01000) == 0)
        {
          error("Agent parent directory is not sticky, mode is %o it should be 041777",
                dotdot_st.st_mode);
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;  
        }
      if (dotdot_st.st_dev != parent_st.st_dev ||
          dotdot_st.st_ino != parent_st.st_ino)
        {
          error("Wrong parent directory after chdir to temp directory");
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;  
        }

      /* Now we are at safe place, make hardlink to agent socket */
      if (link(origauthsocket, authsocket) != 0)
        {
          error("Hard link to auth socket failed");
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;
        }
      
      /* Check that it match the original socket */
      if (stat(authsocket, &link_st) != 0)
        {
          error("Stat to hard link of authentication socket failed");
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;
        }
      if (link_st.st_dev != socket_st.st_dev ||
          link_st.st_ino != socket_st.st_ino)
        {
          error("Hard link and orignal socket are not same");
          xfree(authsocketdir);
          xfree(newauthsockdir);
          return -1;
        }
      /* Note! here we are still at the newly created directory, so the connect
         will use the hard link of socket instead of real socket */
    }

  sunaddr.sun_family = AF_UNIX;
  strncpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));

  sock = socket(AF_UNIX, SOCK_STREAM, 0);
  if (sock < 0)
    {
      error("Socket failed");
      if (newauthsockdir != NULL)
        {
          unlink(authsocket);
          chdir("/");
          rmdir(newauthsockdir);
          xfree(newauthsockdir);
        }
      xfree(authsocketdir);
      return -1;
    }

  if (connect(sock, (struct sockaddr *)&sunaddr,
              AF_UNIX_SIZE(sunaddr)) < 0)
    {
      close(sock);
      if (newauthsockdir != NULL)
        {
          unlink(authsocket);
          chdir("/");
          rmdir(newauthsockdir);
          xfree(newauthsockdir);
        }
      xfree(authsocketdir);
      return -1;
    }
  if (newauthsockdir != NULL)
    {
      unlink(authsocket);
      chdir("/");
      rmdir(newauthsockdir);
      xfree(newauthsockdir);
    }
  xfree(authsocketdir);
  fcntl(sock, F_SETFL, 0);  /* Set the socket to blocking mode */
  return sock;
}

/* Opens a socket to the authentication server.  Returns the number of
   that socket, or -1 if no connection could be made. */

int ssh_get_authentication_connection_fd(void)
{
  int authfd;

  /* Get the the socket number from the environment. */
  authfd = ssh_get_authentication_fd();

  if (authfd >= 0)
    debug("Connection to authentication agent opened.");
  else
    debug("No agent.");
  
  return authfd;
}  

/* Opens and connects a private socket for communication with the
   authentication agent.  Returns the file descriptor (which must be
   shut down and closed by the caller when no longer needed).
   Returns NULL if an error occurred and the connection could not be
   opened. */

AuthenticationConnection *
ssh_get_authentication_connection(void)
{
  AuthenticationConnection *auth;
  int sock;
  
  /* Get a connection to the authentication agent. */
  sock = ssh_get_authentication_connection_fd();

  /* Fail if we couldn't obtain a connection.  This happens if we exited
     due to a timeout. */
  if (sock < 0)
    return NULL;

  /* Allocate the connection structure and initialize it. */
  auth = xmalloc(sizeof(*auth));
  auth->fd = sock;
  buffer_init(&auth->packet);
  buffer_init(&auth->identities);
  auth->num_identities = 0;

  return auth;
}

/* Closes the connection to the authentication agent and frees any associated
   memory. */

void ssh_close_authentication_connection(AuthenticationConnection *ac)
{
  /* Close the connection. */
  shutdown(ac->fd, 2);
  close(ac->fd);

  /* Free the buffers. */
  buffer_free(&ac->packet);
  buffer_free(&ac->identities);
  
  /* Free the connection data structure. */
  xfree(ac);
}

/* Returns the first authentication identity held by the agent.
   Returns true if an identity is available, 0 otherwise.
   The caller must initialize the integers before the call, and free the
   comment after a successful call (before calling ssh_get_next_identity). */

int ssh_get_first_identity(AuthenticationConnection *auth,
                           int *bitsp, MP_INT *e, MP_INT *n, char **comment)
{
  unsigned char msg[8192];
  int len, l;

  /* Send a message to the agent requesting for a list of the identities
     it can represent. */
  msg[0] = 0;
  msg[1] = 0;
  msg[2] = 0;
  msg[3] = 1;
  msg[4] = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
  if (write(auth->fd, msg, 5) != 5)
    {
      error("write auth->fd: %.100s", strerror(errno));
      return 0;
    }

  /* Read the length of the response.  XXX implement timeouts here. */
  len = 4;
  while (len > 0)
    {
      l = read(auth->fd, msg + 4 - len, len);
      if (l <= 0)
        {
          error("read auth->fd: %.100s", strerror(errno));
          return 0;
        }
      len -= l;
    }

  /* Extract the length, and check it for sanity.  (We cannot trust
     authentication agents). */
  len = GET_32BIT(msg);
  if (len < 1 || len > 30*1024)
    fatal("Authentication reply message too long: %d\n", len);

  /* Read the packet itself. */
  buffer_clear(&auth->identities);
  while (len > 0)
    {
      l = len;
      if (l > sizeof(msg))
        l = sizeof(msg);
      l = read(auth->fd, msg, l);
      if (l <= 0)
        fatal("Incomplete authentication reply.");
      buffer_append(&auth->identities, (char *)msg, l);
      len -= l;
    }
  
  /* Get message type, and verify that we got a proper answer. */
  buffer_get(&auth->identities, (char *)msg, 1);
  if (msg[0] != SSH_AGENT_RSA_IDENTITIES_ANSWER)
    fatal("Bad authentication reply message type: %d", msg[0]);
  
  /* Get the number of entries in the response and check it for sanity. */
  auth->num_identities = buffer_get_int(&auth->identities);
  if (auth->num_identities > 1024)
    fatal("Too many identities in authentication reply: %d\n", 
          auth->num_identities);

  /* Return the first entry (if any). */
  return ssh_get_next_identity(auth, bitsp, e, n, comment);
}

/* Returns the next authentication identity for the agent.  Other functions
   can be called between this and ssh_get_first_identity or two calls of this
   function.  This returns 0 if there are no more identities.  The caller
   must free comment after a successful return. */

int ssh_get_next_identity(AuthenticationConnection *auth,
                          int *bitsp, MP_INT *e, MP_INT *n, char **comment)
{
  /* Return failure if no more entries. */
  if (auth->num_identities <= 0)
    return 0;

  /* Get the next entry from the packet.  These will abort with a fatal
     error if the packet is too short or contains corrupt data. */
  *bitsp = buffer_get_int(&auth->identities);
  buffer_get_mp_int(&auth->identities, e);
  buffer_get_mp_int(&auth->identities, n);
  *comment = buffer_get_string(&auth->identities, NULL);

  /* Decrement the number of remaining entries. */
  auth->num_identities--;

  return 1;
}

/* Generates a random challenge, sends it to the agent, and waits for response
   from the agent.  Returns true (non-zero) if the agent gave the correct
   answer, zero otherwise.  Response type selects the style of response
   desired, with 0 corresponding to protocol version 1.0 (no longer supported)
   and 1 corresponding to protocol version 1.1. */

int ssh_decrypt_challenge(AuthenticationConnection *auth,
                          int bits, MP_INT *e, MP_INT *n, MP_INT *challenge,
                          unsigned char session_id[16],
                          unsigned int response_type,
                          unsigned char response[16])
{
  Buffer buffer;
  unsigned char buf[8192];
  int len, l, i;

  /* Response type 0 is no longer supported. */
  if (response_type == 0)
    fatal("Compatibility with ssh protocol version 1.0 no longer supported.");

  /* Format a message to the agent. */
  buf[0] = SSH_AGENTC_RSA_CHALLENGE;
  buffer_init(&buffer);
  buffer_append(&buffer, (char *)buf, 1);
  buffer_put_int(&buffer, bits);
  buffer_put_mp_int(&buffer, e);
  buffer_put_mp_int(&buffer, n);
  buffer_put_mp_int(&buffer, challenge);
  buffer_append(&buffer, (char *)session_id, 16);
  buffer_put_int(&buffer, response_type);

  /* Get the length of the message, and format it in the buffer. */
  len = buffer_len(&buffer);
  PUT_32BIT(buf, len);

  /* Send the length and then the packet to the agent. */
  if (write(auth->fd, buf, 4) != 4 ||
      write(auth->fd, buffer_ptr(&buffer), buffer_len(&buffer)) !=
        buffer_len(&buffer))
    {
      error("Error writing to authentication socket.");
    error_cleanup:
      buffer_free(&buffer);
      return 0;
    }

  /* Wait for response from the agent.  First read the length of the
     response packet. */
  len = 4;
  while (len > 0)
    {
      l = read(auth->fd, buf + 4 - len, len);
      if (l <= 0)
        {
          error("Error reading response length from authentication socket.");
          goto error_cleanup;
        }
      len -= l;
    }

  /* Extract the length, and check it for sanity. */
  len = GET_32BIT(buf);
  if (len > 30*1024)
    fatal("Authentication response too long: %d", len);

  /* Read the rest of the response in to the buffer. */
  buffer_clear(&buffer);
  while (len > 0)
    {
      l = len;
      if (l > sizeof(buf))
        l = sizeof(buf);
      l = read(auth->fd, buf, l);
      if (l <= 0)
        {
          error("Error reading response from authentication socket.");
          goto error_cleanup;
        }
      buffer_append(&buffer, (char *)buf, l);
      len -= l;
    }

  /* Get the type of the packet. */
  buffer_get(&buffer, (char *)buf, 1);

  /* Check for agent failure message. */
  if (buf[0] == SSH_AGENT_FAILURE)
    {
      log_msg("Agent admitted failure to authenticate using the key.");
      goto error_cleanup;
    }
      
  /* Now it must be an authentication response packet. */
  if (buf[0] != SSH_AGENT_RSA_RESPONSE)
    fatal("Bad authentication response: %d", buf[0]);

  /* Get the response from the packet.  This will abort with a fatal error
     if the packet is corrupt. */
  for (i = 0; i < 16; i++)
    response[i] = buffer_get_char(&buffer);

  /* The buffer containing the packet is no longer needed. */
  buffer_free(&buffer);

  /* Correct answer. */
  return 1;
}  

/* Adds an identity to the authentication server.  This call is not meant to
   be used by normal applications. */

int ssh_add_identity(AuthenticationConnection *auth,
                     RSAPrivateKey *key, const char *comment)
{
  Buffer buffer;
  unsigned char buf[8192];
  int len, l, type;

  /* Format a message to the agent. */
  buffer_init(&buffer);
  buffer_put_char(&buffer, SSH_AGENTC_ADD_RSA_IDENTITY);
  buffer_put_int(&buffer, key->bits);
  buffer_put_mp_int(&buffer, &key->n);
  buffer_put_mp_int(&buffer, &key->e);
  buffer_put_mp_int(&buffer, &key->d);
  buffer_put_mp_int(&buffer, &key->u);
  buffer_put_mp_int(&buffer, &key->p);
  buffer_put_mp_int(&buffer, &key->q);
  buffer_put_string(&buffer, comment, strlen(comment));

  /* Get the length of the message, and format it in the buffer. */
  len = buffer_len(&buffer);
  PUT_32BIT(buf, len);

  /* Send the length and then the packet to the agent. */
  if (write(auth->fd, buf, 4) != 4 ||
      write(auth->fd, buffer_ptr(&buffer), buffer_len(&buffer)) !=
        buffer_len(&buffer))
    {
      error("Error writing to authentication socket.");
    error_cleanup:
      buffer_free(&buffer);
      return 0;
    }

  /* Wait for response from the agent.  First read the length of the
     response packet. */
  len = 4;
  while (len > 0)
    {
      l = read(auth->fd, buf + 4 - len, len);
      if (l <= 0)
        {
          error("Error reading response length from authentication socket.");
          goto error_cleanup;
        }
      len -= l;
    }

  /* Extract the length, and check it for sanity. */
  len = GET_32BIT(buf);
  if (len > 30*1024)
    fatal("Add identity response too long: %d", len);

  /* Read the rest of the response in tothe buffer. */
  buffer_clear(&buffer);
  while (len > 0)
    {
      l = len;
      if (l > sizeof(buf))
        l = sizeof(buf);
      l = read(auth->fd, buf, l);
      if (l <= 0)
        {
          error("Error reading response from authentication socket.");
          goto error_cleanup;
        }
      buffer_append(&buffer, (char *)buf, l);
      len -= l;
    }

  /* Get the type of the packet. */
  type = buffer_get_char(&buffer);
  switch (type)
    {
    case SSH_AGENT_FAILURE:
      buffer_free(&buffer);
      return 0;
    case SSH_AGENT_SUCCESS:
      buffer_free(&buffer);
      return 1;
    default:
      fatal("Bad response to add identity from authentication agent: %d", 
            type);
    }
  /*NOTREACHED*/
  return 0;
}  

/* Removes an identity from the authentication server.  This call is not meant 
   to be used by normal applications. */

int ssh_remove_identity(AuthenticationConnection *auth, RSAPublicKey *key)
{
  Buffer buffer;
  unsigned char buf[8192];
  int len, l, type;

  /* Format a message to the agent. */
  buffer_init(&buffer);
  buffer_put_char(&buffer, SSH_AGENTC_REMOVE_RSA_IDENTITY);
  buffer_put_int(&buffer, key->bits);
  buffer_put_mp_int(&buffer, &key->e);
  buffer_put_mp_int(&buffer, &key->n);

  /* Get the length of the message, and format it in the buffer. */
  len = buffer_len(&buffer);
  PUT_32BIT(buf, len);

  /* Send the length and then the packet to the agent. */
  if (write(auth->fd, buf, 4) != 4 ||
      write(auth->fd, buffer_ptr(&buffer), buffer_len(&buffer)) !=
        buffer_len(&buffer))
    {
      error("Error writing to authentication socket.");
    error_cleanup:
      buffer_free(&buffer);
      return 0;
    }

  /* Wait for response from the agent.  First read the length of the
     response packet. */
  len = 4;
  while (len > 0)
    {
      l = read(auth->fd, buf + 4 - len, len);
      if (l <= 0)
        {
          error("Error reading response length from authentication socket.");
          goto error_cleanup;
        }
      len -= l;
    }

  /* Extract the length, and check it for sanity. */
  len = GET_32BIT(buf);
  if (len > 30*1024)
    fatal("Remove identity response too long: %d", len);

  /* Read the rest of the response in tothe buffer. */
  buffer_clear(&buffer);
  while (len > 0)
    {
      l = len;
      if (l > sizeof(buf))
        l = sizeof(buf);
      l = read(auth->fd, buf, l);
      if (l <= 0)
        {
          error("Error reading response from authentication socket.");
          goto error_cleanup;
        }
      buffer_append(&buffer, (char *)buf, l);
      len -= l;
    }

  /* Get the type of the packet. */
  type = buffer_get_char(&buffer);
  switch (type)
    {
    case SSH_AGENT_FAILURE:
      buffer_free(&buffer);
      return 0;
    case SSH_AGENT_SUCCESS:
      buffer_free(&buffer);
      return 1;
    default:
      fatal("Bad response to remove identity from authentication agent: %d", 
            type);
    }
  /*NOTREACHED*/
  return 0;
}  

/* Removes all identities from the agent.  This call is not meant 
   to be used by normal applications. */

int ssh_remove_all_identities(AuthenticationConnection *auth)
{
  Buffer buffer;
  unsigned char buf[8192];
  int len, l, type;

  /* Get the length of the message, and format it in the buffer. */
  PUT_32BIT(buf, 1);
  buf[4] = SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES;

  /* Send the length and then the packet to the agent. */
  if (write(auth->fd, buf, 5) != 5)
    {
      error("Error writing to authentication socket.");
      return 0;
    }

  /* Wait for response from the agent.  First read the length of the
     response packet. */
  len = 4;
  while (len > 0)
    {
      l = read(auth->fd, buf + 4 - len, len);
      if (l <= 0)
        {
          error("Error reading response length from authentication socket.");
          return 0;
        }
      len -= l;
    }

  /* Extract the length, and check it for sanity. */
  len = GET_32BIT(buf);
  if (len > 30*1024)
    fatal("Remove identity response too long: %d", len);

  /* Read the rest of the response into the buffer. */
  buffer_init(&buffer);
  while (len > 0)
    {
      l = len;
      if (l > sizeof(buf))
        l = sizeof(buf);
      l = read(auth->fd, buf, l);
      if (l <= 0)
        {
          error("Error reading response from authentication socket.");
          buffer_free(&buffer);
          return 0;
        }
      buffer_append(&buffer, (char *)buf, l);
      len -= l;
    }

  /* Get the type of the packet. */
  type = buffer_get_char(&buffer);
  switch (type)
    {
    case SSH_AGENT_FAILURE:
      buffer_free(&buffer);
      return 0;
    case SSH_AGENT_SUCCESS:
      buffer_free(&buffer);
      return 1;
    default:
      fatal("Bad response to remove identity from authentication agent: %d", 
            type);
    }
  /*NOTREACHED*/
  return 0;
}