tunnel.c

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#include "config.h"
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "private.h"
#include "mutt/lib.h"
#include "config/lib.h"
#include "core/lib.h"
#include "connaccount.h"
#include "connection.h"

struct TunnelSockData
{
  pid_t pid;    
  int fd_read;  
  int fd_write; 
};

static int tunnel_socket_open(struct Connection *conn)
{
  int pin[2] = { 0 };
  int pout[2] = { 0 };
 
  struct TunnelSockData *tunnel = MUTT_MEM_MALLOC(1, struct TunnelSockData);
  conn->sockdata = tunnel;
 
  const char *const c_tunnel = cs_subset_string(NeoMutt->sub, "tunnel");
  mutt_message(_("Connecting with \"%s\"..."), c_tunnel);
 
  int rc = pipe(pin);
  if (rc == -1)
  {
    mutt_perror("pipe");
    FREE(&conn->sockdata);
    return -1;
  }
  rc = pipe(pout);
  if (rc == -1)
  {
    mutt_perror("pipe");
    close(pin[0]);
    close(pin[1]);
    FREE(&conn->sockdata);
    return -1;
  }
 
  mutt_sig_block_system();
  int pid = fork();
  if (pid == 0)
  {
    mutt_sig_unblock_system(false);
    mutt_sig_reset_child_signals();
    const int fd_null = open("/dev/null", O_RDWR);
    if ((fd_null < 0) || (dup2(pout[0], STDIN_FILENO) < 0) ||
        (dup2(pin[1], STDOUT_FILENO) < 0) || (dup2(fd_null, STDERR_FILENO) < 0))
    {
      _exit(127);
    }
    close(pin[0]);
    close(pin[1]);
    close(pout[0]);
    close(pout[1]);
    close(fd_null);
 
    /* Don't let the subprocess think it can use the controlling tty */
    setsid();
 
    execle(EXEC_SHELL, "sh", "-c", c_tunnel, NULL, NeoMutt->env);
    _exit(127);
  }
  mutt_sig_unblock_system(true);
 
  if (pid == -1)
  {
    mutt_perror("fork");
    close(pin[0]);
    close(pin[1]);
    close(pout[0]);
    close(pout[1]);
    FREE(&conn->sockdata);
    return -1;
  }
  if ((close(pin[1]) < 0) || (close(pout[0]) < 0))
    mutt_perror("close");
 
  // These are unlikely to fail
  (void) fcntl(pin[0], F_SETFD, FD_CLOEXEC);
  (void) fcntl(pout[1], F_SETFD, FD_CLOEXEC);
 
  tunnel->fd_read = pin[0];
  tunnel->fd_write = pout[1];
  tunnel->pid = pid;
 
  conn->fd = 42; /* stupid hack */
 
  /* Note we are using ssf as a boolean in this case.  See the notes in
   * conn/connection.h */
  const bool c_tunnel_is_secure = cs_subset_bool(NeoMutt->sub, "tunnel_is_secure");
  if (c_tunnel_is_secure)
    conn->ssf = 1;
 
  return 0;
}

static int tunnel_socket_read(struct Connection *conn, char *buf, size_t count)
{
  struct TunnelSockData *tunnel = conn->sockdata;
  int rc;
 
  do
  {
    rc = read(tunnel->fd_read, buf, count);
  } while (rc < 0 && errno == EINTR);
 
  if (rc < 0)
  {
    mutt_error(_("Tunnel error talking to %s: %s"), conn->account.host, strerror(errno));
    return -1;
  }
 
  return rc;
}

static int tunnel_socket_write(struct Connection *conn, const char *buf, size_t count)
{
  struct TunnelSockData *tunnel = conn->sockdata;
  ssize_t rc;
  size_t sent = 0;
 
  do
  {
    do
    {
      rc = write(tunnel->fd_write, buf + sent, count - sent);
    } while (rc < 0 && errno == EINTR);
 
    if (rc < 0)
    {
      mutt_error(_("Tunnel error talking to %s: %s"), conn->account.host, strerror(errno));
      return -1;
    }
 
    sent += rc;
  } while (sent < count);
 
  return sent;
}

static int tunnel_socket_poll(struct Connection *conn, time_t wait_secs)
{
  struct TunnelSockData *tunnel = conn->sockdata;
  int ofd;
  int rc;
 
  ofd = conn->fd;
  conn->fd = tunnel->fd_read;
  rc = raw_socket_poll(conn, wait_secs);
  conn->fd = ofd;
 
  return rc;
}

static int tunnel_socket_close(struct Connection *conn)
{
  struct TunnelSockData *tunnel = conn->sockdata;
  if (!tunnel)
  {
    return 0;
  }
 
  int status = 0;
 
  close(tunnel->fd_read);
  close(tunnel->fd_write);
  waitpid(tunnel->pid, &status, 0);
  if (!WIFEXITED(status) || WEXITSTATUS(status))
  {
    mutt_error(_("Tunnel to %s returned error %d (%s)"), conn->account.host,
               WEXITSTATUS(status), NONULL(mutt_str_sysexit(WEXITSTATUS(status))));
  }
  FREE(&conn->sockdata);
 
  return 0;
}

void mutt_tunnel_socket_setup(struct Connection *conn)
{
  conn->open = tunnel_socket_open;
  conn->close = tunnel_socket_close;
  conn->read = tunnel_socket_read;
  conn->write = tunnel_socket_write;
  conn->poll = tunnel_socket_poll;
}