usertable.cpp


/// inotify cron daemon user tables implementation
/**
 * \file usertable.cpp
 *
 * inotify cron system
 *
 * Copyright (C) 2006, 2007, 2008, 2012 Lukas Jelinek, <lukas@aiken.cz>
 *
 * This program is free software; you can use it, redistribute
 * it and/or modify it under the terms of the GNU General Public
 * License, version 2 (see LICENSE-GPL).
 *
 * Credits:
 *   David Santinoli (supplementary groups)
 *   Boris Lechner (spaces in event-related file names)
 *   Christian Ruppert (new include to build with GCC 4.4+)
 *
 */


#include <pwd.h>
#include <syslog.h>
#include <errno.h>
#include <dirent.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <unistd.h>
#include <grp.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <cstdio>
#include <cstring>

#include "usertable.h"
#include "incroncfg.h"
#include "incrontab.h"

#ifdef IN_DONT_FOLLOW
#define DONT_FOLLOW(mask) InotifyEvent::IsType(mask, IN_DONT_FOLLOW)
#else // IN_DONT_FOLLOW
#define DONT_FOLLOW(mask) (false)
#endif // IN_DONT_FOLLOW

// this is not enough, but...
#define DEFAULT_PATH "/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin"


PROC_MAP UserTable::s_procMap;

extern volatile bool g_fFinish;
extern SUT_MAP g_ut;


void on_proc_done(InotifyWatch* pW)
{
  pW->SetEnabled(true);
}


EventDispatcher::EventDispatcher(int iPipeFd, Inotify* pIn, InotifyWatch* pSys, InotifyWatch* pUser)
{
  m_iPipeFd = iPipeFd;
  m_iMgmtFd = pIn->GetDescriptor();
  m_pIn = pIn;
  m_pSys = pSys;
  m_pUser = pUser;
  m_size = 0;
  m_pPoll = NULL;
}

EventDispatcher::~EventDispatcher()
{
  if (m_pPoll != NULL)
    delete[] m_pPoll;
}

bool EventDispatcher::ProcessEvents()
{
  // consume pipe events if any (and report back)
  bool pipe = (m_pPoll[0].revents & POLLIN);
  if (pipe) {
    char c;
    while (read(m_pPoll[0].fd, &c, 1) > 0) {}
    m_pPoll[0].revents = 0;
  }

  // process table management events if any
  if (m_pPoll[1].revents & POLLIN) {
    ProcessMgmtEvents();
    m_pPoll[1].revents = 0;
  }

  InotifyEvent evt;

  for (size_t i=2; i<m_size; i++) {

    // process events if occurred
    if (m_pPoll[i].revents & POLLIN) {
      FDUT_MAP::iterator it = m_maps.find(m_pPoll[i].fd);
      if (it != m_maps.end()) {
        Inotify* pIn = ((*it).second)->GetInotify();
        pIn->WaitForEvents(true);

        // process events for this object
        while (pIn->GetEvent(evt)) {
          ((*it).second)->OnEvent(evt);
        }
      }
      m_pPoll[i].revents = 0;
    }
  }

  return pipe;
}

void EventDispatcher::Register(UserTable* pTab)
{
  if (pTab != NULL) {
    Inotify* pIn = pTab->GetInotify();
    if (pIn != NULL) {
      int fd = pIn->GetDescriptor();
      if (fd != -1) {
        m_maps.insert(FDUT_MAP::value_type(fd, pTab));
        Rebuild();
      }
    }
  }
}

void EventDispatcher::Unregister(UserTable* pTab)
{
  FDUT_MAP::iterator it = m_maps.find(pTab->GetInotify()->GetDescriptor());
  if (it != m_maps.end()) {
    m_maps.erase(it);
    Rebuild();
  }
}

void EventDispatcher::Rebuild()
{
  // delete old data if exists
  if (m_pPoll != NULL)
    delete[] m_pPoll;

  // allocate memory
  m_size = m_maps.size() + 2;
  m_pPoll = new struct pollfd[m_size];

  // add pipe descriptor
  m_pPoll[0].fd = m_iPipeFd;
  m_pPoll[0].events = POLLIN;
  m_pPoll[0].revents = 0;

  // add table management descriptor
  m_pPoll[1].fd = m_iMgmtFd;
  m_pPoll[1].events = POLLIN;
  m_pPoll[1].revents = 0;

  // add all inotify descriptors
  FDUT_MAP::iterator it = m_maps.begin();
  for (size_t i=2; i<m_size; i++, it++) {
    m_pPoll[i].fd = (*it).first;
    m_pPoll[i].events = POLLIN;
    m_pPoll[i].revents = 0;
  }
}

void EventDispatcher::ProcessMgmtEvents()
{
  m_pIn->WaitForEvents(true);

  InotifyEvent e;

  while (m_pIn->GetEvent(e)) {
    if (e.GetWatch() == m_pSys) {
      if (e.IsType(IN_DELETE_SELF) || e.IsType(IN_UNMOUNT)) {
        syslog(LOG_CRIT, "base directory destroyed, exitting");
        g_fFinish = true;
      }
      else if (!e.GetName().empty()) {
        SUT_MAP::iterator it = g_ut.find(IncronCfg::BuildPath(m_pSys->GetPath(), e.GetName()));
        if (it != g_ut.end()) {
          UserTable* pUt = (*it).second;
          if (e.IsType(IN_CLOSE_WRITE) || e.IsType(IN_MOVED_TO)) {
            syslog(LOG_INFO, "system table %s changed, reloading", e.GetName().c_str());
            pUt->Dispose();
            pUt->Load();
          }
          else if (e.IsType(IN_MOVED_FROM) || e.IsType(IN_DELETE)) {
            syslog(LOG_INFO, "system table %s destroyed, removing", e.GetName().c_str());
            delete pUt;
            g_ut.erase(it);
          }
        }
        else if (e.IsType(IN_CLOSE_WRITE) || e.IsType(IN_MOVED_TO)) {
          syslog(LOG_INFO, "system table %s created, loading", e.GetName().c_str());
          UserTable* pUt = new UserTable(this, e.GetName(), true);
          g_ut.insert(SUT_MAP::value_type(IncronTab::GetSystemTablePath(e.GetName()), pUt));
          pUt->Load();
        }
      }
    }
    else if (e.GetWatch() == m_pUser) {
      if (e.IsType(IN_DELETE_SELF) || e.IsType(IN_UNMOUNT)) {
        syslog(LOG_CRIT, "base directory destroyed, exitting");
        g_fFinish = true;
      }
      else if (!e.GetName().empty()) {
        SUT_MAP::iterator it = g_ut.find(IncronCfg::BuildPath(m_pUser->GetPath(), e.GetName()));
        if (it != g_ut.end()) {
          UserTable* pUt = (*it).second;
          if (e.IsType(IN_CLOSE_WRITE) || e.IsType(IN_MOVED_TO)) {
            syslog(LOG_INFO, "table for user %s changed, reloading", e.GetName().c_str());
            pUt->Dispose();
            pUt->Load();
          }
          else if (e.IsType(IN_MOVED_FROM) || e.IsType(IN_DELETE)) {
            syslog(LOG_INFO, "table for user %s destroyed, removing",  e.GetName().c_str());
            delete pUt;
            g_ut.erase(it);
          }
        }
        else if (e.IsType(IN_CLOSE_WRITE) || e.IsType(IN_MOVED_TO)) {
          if (UserTable::CheckUser(e.GetName().c_str())) {
            syslog(LOG_INFO, "table for user %s created, loading", e.GetName().c_str());
            UserTable* pUt = new UserTable(this, e.GetName(), false);
            g_ut.insert(SUT_MAP::value_type(IncronTab::GetUserTablePath(e.GetName()), pUt));
            pUt->Load();
          }
        }
      }
    }
  }
}


size_t UserTable::m_maxForks = 0;
bool UserTable::m_recursive = false;

UserTable::UserTable(EventDispatcher* pEd, const std::string& rUser, bool fSysTable)
: m_user(rUser),
  m_fSysTable(fSysTable)
{
  m_pEd = pEd;

  m_in.SetNonBlock(true);
  m_in.SetCloseOnExec(true);
}

UserTable::~UserTable()
{
  Dispose();
}

bool UserTable::IsDirectory(const std::string& sPath)
{
  static struct stat64 sStat;

  if (-1 != lstat64(sPath.c_str(), &sStat) && S_ISDIR(sStat.st_mode)) {
    return true;
  }
  else {
    return false;
  }
}

void UserTable::GetDirectoryTree(const std::string& sPath, TPathList& rResults)
{
  struct dirent* ent;
  DIR* dir;

  dir = opendir(sPath.c_str());
  if (!dir) {
    syslog(LOG_WARNING, "could not open directory %s: %s", sPath.c_str(), strerror(errno));
    return;
  }

  rResults.push_back(sPath);

  ent = readdir(dir);
  while (ent) {
    std::string sFullPath = sPath + "/" + ent->d_name;
    std::string sEntry(ent->d_name);
    if ("." != sEntry && ".." != sEntry && IsDirectory(sFullPath)) {
      GetDirectoryTree(sFullPath, rResults);
    }
    ent = readdir(dir);
  }
  closedir(dir);
}

void UserTable::AddWatch(const std::string& sPath, IncronTabEntry* pEntry)
{
  InotifyWatch* pW = new InotifyWatch(sPath, pEntry->GetMask());

  syslog(LOG_DEBUG, "adding directory watch %s", sPath.c_str());

  // warning only - permissions may change later
  if (!(m_fSysTable || MayAccess(sPath, DONT_FOLLOW(pEntry->GetMask()))))
    syslog(LOG_WARNING, "access denied on %s - events will be discarded silently", sPath.c_str());

  try {
    m_in.Add(pW);
    m_map.insert(IWCE_MAP::value_type(pW, pEntry));
  } catch (InotifyException& e) {
    if (m_fSysTable)
      syslog(LOG_ERR, "cannot create watch for system table %s: (%i) %s", m_user.c_str(), e.GetErrorNumber(), strerror(e.GetErrorNumber()));
    else
      syslog(LOG_ERR, "cannot create watch for user %s: (%i) %s", m_user.c_str(), e.GetErrorNumber(), strerror(e.GetErrorNumber()));
    delete pW;
  }
}

void UserTable::RemoveWatch(const std::string& sPath)
{
  IWCE_MAP::iterator it = m_map.begin();
  for (; it != m_map.end(); ++it) {
    if (it->first->GetPath() == sPath) {
      syslog(LOG_DEBUG, "removing directory watch %s", sPath.c_str());
      m_in.Remove(it->first);
      delete it->first;
      m_map.erase(it);
      return;
    }
  }
}

void UserTable::Load()
{
  m_tab.Load(m_fSysTable
      ? IncronTab::GetSystemTablePath(m_user)
      : IncronTab::GetUserTablePath(m_user));

  int cnt = m_tab.GetCount();
  for (int i=0; i<cnt; i++) {
    IncronTabEntry& rE = m_tab.GetEntry(i);

    TPathList Paths;
    if (m_recursive && IsDirectory(rE.GetPath()))
      GetDirectoryTree(rE.GetPath(), Paths);
    else
      Paths.push_back(rE.GetPath());

    for (TPathList::const_iterator iter = Paths.begin(); iter != Paths.end(); ++iter) {
      AddWatch(*iter, &rE);
    }
  }

  m_pEd->Register(this);
}

void UserTable::Dispose()
{
  m_pEd->Unregister(this);

  IWCE_MAP::iterator it = m_map.begin();
  while (it != m_map.end()) {
    InotifyWatch* pW = (*it).first;
    m_in.Remove(pW);

    PROC_MAP::iterator it2 = s_procMap.begin();
    while (it2 != s_procMap.end()) {
      if ((*it2).second.pWatch == pW) {
        PROC_MAP::iterator it3 = it2;
        it2++;
        s_procMap.erase(it3);
      }
      else {
        it2++;
      }
    }

    delete pW;
    it++;
  }

  m_map.clear();
}

void UserTable::OnEventDirectory(const InotifyEvent& rEvt, InotifyWatch* pWatch, IncronTabEntry* pEntry)
{
  if (rEvt.IsType(IN_ISDIR)) {
    std::string sDirectoryPath = pWatch->GetPath() + "/" + IncronTabEntry::GetSafePath(rEvt.GetName());

    if (rEvt.IsType(IN_DELETE) || rEvt.IsType(IN_MOVED_FROM)) {
      RemoveWatch(sDirectoryPath);
    }
  }
}

void UserTable::OnEvent(InotifyEvent& rEvt)
{
  InotifyWatch* pW = rEvt.GetWatch();
  IncronTabEntry* pE = FindEntry(pW);

  // no entry found - this shouldn't occur
  if (pE == NULL)
    return;

  // discard event if user has no access rights to watch path
  if (!(m_fSysTable || MayAccess(pW->GetPath(), DONT_FOLLOW(rEvt.GetMask()))))
    return;

  std::string cmd;
  const std::string& cs = pE->GetCmd();
  size_t pos = 0;
  size_t oldpos = 0;
  size_t len = cs.length();
  while ((pos = cs.find('$', oldpos)) != std::string::npos) {
    if (pos < len - 1) {
      size_t px = pos + 1;
      if (cs[px] == '$') {
        cmd.append(cs.substr(oldpos, pos-oldpos+1));
        oldpos = pos + 2;
      }
      else {
        cmd.append(cs.substr(oldpos, pos-oldpos));
        if (cs[px] == '@') {          // base path
          cmd.append(IncronTabEntry::GetSafePath(pW->GetPath()));
          oldpos = pos + 2;
        }
        else if (cs[px] == '#') {     // file name
          cmd.append(IncronTabEntry::GetSafePath(rEvt.GetName()));
          oldpos = pos + 2;
        }
        else if (cs[px] == '%') {     // mask symbols
          std::string s;
          rEvt.DumpTypes(s);
          cmd.append(s);
          oldpos = pos + 2;
        }
        else if (cs[px] == '&') {     // numeric mask
          char s[11];
          snprintf(s, sizeof(s), "%u", (unsigned) rEvt.GetMask());
          cmd.append(s);
          oldpos = pos + 2;
        }
        else {
          oldpos = pos + 1;
        }
      }
    }
    else {
      cmd.append(cs.substr(oldpos, pos-oldpos));
      oldpos = pos + 1;
    }
  }
  cmd.append(cs.substr(oldpos));

  int argc;
  char** argv;
  if (!PrepareArgs(cmd, argc, argv)) {
    syslog(LOG_ERR, "cannot prepare command arguments");
    return;
  }

  if (m_fSysTable)
    syslog(LOG_INFO, "(system::%s) CMD (%s)", m_user.c_str(), cmd.c_str());
  else
    syslog(LOG_INFO, "(%s) CMD (%s)", m_user.c_str(), cmd.c_str());

  if (pE->IsNoLoop())
    pW->SetEnabled(false);

  if (m_maxForks > 0 && s_procMap.size() >= m_maxForks) {
    // time to wait for a forked process to finish before we continue
    int status;
    pid_t res = wait(&status);
    UserTable::ClearProcess(res);
  }

  pid_t pid = fork();
  if (pid == 0) {

    // for system table
    if (m_fSysTable) {
      if (execvp(argv[0], argv) != 0) // exec failed
      {
        syslog(LOG_ERR, "cannot exec process: %s", strerror(errno));
        _exit(1);
      }
    }
    else {
      // for user table
      RunAsUser(argv);
    }
  }
  else if (pid > 0) {
    ProcData_t pd;
    if (pE->IsNoLoop()) {
      pd.onDone = on_proc_done;
      pd.pWatch = pW;
    }
    else {
      pd.onDone = NULL;
      pd.pWatch = NULL;
    }

    s_procMap.insert(PROC_MAP::value_type(pid, pd));

    // Remove watches if it's a directory
    OnEventDirectory(rEvt, pW, pE);
  }
  else {
    if (pE->IsNoLoop())
      pW->SetEnabled(true);

    syslog(LOG_ERR, "cannot fork process: %s", strerror(errno));
  }

  CleanupArgs(argc, argv);
}

IncronTabEntry* UserTable::FindEntry(InotifyWatch* pWatch)
{
  IWCE_MAP::iterator it = m_map.find(pWatch);
  if (it == m_map.end())
    return NULL;

  return (*it).second;
}

bool UserTable::PrepareArgs(const std::string& rCmd, int& argc, char**& argv)
{
  if (rCmd.empty())
    return false;

  StringTokenizer tok(rCmd, ' ', '\\');
  std::deque<std::string> args;
  while (tok.HasMoreTokens()) {
    args.push_back(tok.GetNextToken());
  }

  if (args.empty())
    return false;

  argc = (int) args.size();
  argv = new char*[argc+1];
  argv[argc] = NULL;

  for (int i=0; i<argc; i++) {
    const std::string& s = args[i];
    size_t len = s.length();
    argv[i] = new char[len+1];
    strcpy(argv[i], s.c_str());
  }

  return true;
}

void UserTable::CleanupArgs(int argc, char** argv)
{
  for (int i=0; i<argc; i++) {
    delete[] argv[i];
  }

  delete[] argv;
}

void UserTable::FinishDone()
{
  pid_t res = 0;
  int status = 0;
  while ((res = waitpid(-1, &status, WNOHANG)) > 0) {
    ClearProcess(res);
  }
}

void UserTable::ClearProcess(pid_t pid)
{
  PROC_MAP::iterator it = s_procMap.find(pid);
  if (it != s_procMap.end()) {
    ProcData_t pd = (*it).second;
    if (pd.onDone != NULL)
      (*pd.onDone)(pd.pWatch);
    s_procMap.erase(it);
  }
}

void UserTable::ClearProcesses()
{
  int status = 0;

  PROC_MAP::iterator it = s_procMap.begin();
  while (it != s_procMap.end()) {
    if (waitpid(it->first, &status, WNOHANG) > 0) {
      ClearProcess(it->first);
    }
    it++;
  }
}

bool UserTable::MayAccess(const std::string& rPath, bool fNoFollow) const
{
  // first, retrieve file permissions
  struct stat st;
  int res = fNoFollow
      ? lstat(rPath.c_str(), &st) // don't follow symlink
      : stat(rPath.c_str(), &st);
  if (res != 0)
    return false; // retrieving permissions failed

  // file accessible to everyone
  if (st.st_mode & S_IRWXO)
    return true;

  // retrieve user data
  struct passwd* pwd = getpwnam(m_user.c_str());

  // root may always access
  if (pwd->pw_uid == 0)
    return true;

  // file accessible to group
  if (st.st_mode & S_IRWXG) {

    // user's primary group
    if (pwd != NULL && pwd->pw_gid == st.st_gid)
        return true;

    // now check group database
    struct group *gr = getgrgid(st.st_gid);
    if (gr != NULL) {
      int pos = 0;
      const char* un;
      while ((un = gr->gr_mem[pos]) != NULL) {
        if (strcmp(un, m_user.c_str()) == 0)
          return true;
        pos++;
      }
    }
  }

  // file accessible to owner
  if (st.st_mode & S_IRWXU) {
    if (pwd != NULL && pwd->pw_uid == st.st_uid)
      return true;
  }

  return false; // no access right found
}

void UserTable::RunAsUser(char* const* argv) const
{
  struct passwd* pwd = getpwnam(m_user.c_str());
  if (    pwd == NULL                 // check query result
      ||  setgid(pwd->pw_gid) != 0    // check GID
      ||  initgroups(m_user.c_str(),pwd->pw_gid) != 0 // check supplementary groups
      ||  setuid(pwd->pw_uid) != 0)    // check UID
  {
    goto failed;
  }

  if (pwd->pw_uid != 0) {
    if (clearenv() != 0)
      goto failed;

    if (    setenv("LOGNAME",   pwd->pw_name,   1) != 0
        ||  setenv("USER",      pwd->pw_name,   1) != 0
        ||  setenv("USERNAME",  pwd->pw_name,   1) != 0
        ||  setenv("HOME",      pwd->pw_dir,    1) != 0
        ||  setenv("SHELL",     pwd->pw_shell,  1) != 0
        ||  setenv("PATH",      DEFAULT_PATH,   1) != 0)
    {
      goto failed;
    }
  }

  execvp(argv[0], argv);  // this may return only on failure

failed:

  syslog(LOG_ERR, "cannot exec process: %s", strerror(errno));
  _exit(1);
}