path: root/src/authenticate.cc

/**
 *  @file authenticate.cc
 *  @brief  Implementation of the common (C/R) authentication mechanism.
 *  @author Andreas Aardal Hanssen, Erwin Hoffmann
 *  @date 2002-2005, 2023
 */

#include <string>
#include <vector>

#include <errno.h>
#include <signal.h>

#include <grp.h>
#include <pwd.h>
#include <sys/types.h>
#include <unistd.h>

// #ifndef HAVE_SYS_WAIT_H
// #include <wait.h>
// #else
#include <sys/wait.h>
// #endif

#include "authenticate.h"
#include "convert.h"
#include "globals.h"
#include "iodevice.h"
#include "iofactory.h"
#include "session.h"

using namespace Binc;
using std::endl;
using std::string;

// 0 = ok
// 1 = internal error
// 2 = failed
// 3 = timeout
// -1 = abort

int Binc::authenticate(Depot &depot,
                       const string &username,
                       const string &password,
                       const string &challenge)
{
  Session &session = Session::getInstance();
  session.setUserID(username);

  // check if checkpassword is present
  if (access(session.unparsedArgs[0], X_OK) != 0) {  // x is enough
    bincError << "unable to start authenticator " << session.unparsedArgs[0] << ": "
              << strerror(errno) << endl;
    return 1;
  }

  // The information supplied on descriptor 3 is a login name
  // terminated by \0, a password terminated by \0, a timestamp
  // terminated by \0, and possibly more data. There are no other
  // restrictions on the form of the login name, password, and
  // timestamp.
  int authintercom[2];
  int intercomw[2];
  int intercomr[2];
  bool authenticated = false;

  if (pipe(authintercom) == -1) {
    session.setLastError("An error occurred when creating pipes: " + string(strerror(errno)));
    return -1;
  }

  if (pipe(intercomw) == -1) {
    session.setLastError("An error occurred when creating pipes: " + string(strerror(errno)));
    close(authintercom[0]);
    close(authintercom[1]);
    return -1;
  }

  if (pipe(intercomr) == -1) {
    session.setLastError("An error occurred when creating pipes: " + string(strerror(errno)));
    close(intercomw[0]);
    close(intercomr[0]);
    close(authintercom[0]);
    close(authintercom[1]);
    return -1;
  }

  string timestamp;
  time_t t = time(nullptr);
  char *c;
  if ((c = ctime(&t)) != nullptr) {
    timestamp = c;
    trim(timestamp);
  } else {
    timestamp = "unknown timestamp";
  }

  string pid = std::to_string(session.getPid());

  // execute authentication module
  int result;
  int childspid = fork();
  if (childspid == -1) {
    bincLog << "bincimap-up: pid " << pid
            << " failed to start main server: " << strerror(errno) << endl;
    return 1;
  }

  if (childspid == 0) {
    close(authintercom[1]);
    close(intercomr[0]);
    close(intercomw[1]);

    if (dup2(intercomr[1], 1) == -1) {
      bincDebug << "bincimap-up: pid " << pid
                << " authenticate(), [auth module] dup2 failed: " << strerror(errno) << endl;
      bincDebug.flush();
      exit(111);
    }

    if (dup2(intercomw[0], 0) == -1) {
      bincDebug << "bincimap-up: pid " << pid
                << " authenticate(), [auth module] dup2 failed: " << strerror(errno) << endl;
      bincDebug.flush();
      exit(111);
    }

    if (dup2(authintercom[0], 3) == -1) {
      bincDebug << "bincimap-up: pid " << pid
                << " authenticate(), [auth module] dup2 failed: " << strerror(errno) << endl;
      bincDebug.flush();
      exit(111);
    }

    if (session.unparsedArgs[0] != nullptr) {
      execvp(session.unparsedArgs[0], &session.unparsedArgs[0]);
      bincDebug << "bincimap-up: pid " << pid
                << " authenticate(), [auth module] invocation of " << session.unparsedArgs[0]
                << " failed: " << strerror(errno) << endl;
      bincDebug.flush();
      exit(111);
    }

    bincLog << "bincimap-up: pid " << pid
            << " missing mandatory -- in argument list,"
               " after bincimap-up + arguments, before authenticator."
               " Please check your run scripts and the man page bincimap(1) for"
               " more on how to invoke Binc IMAP."
            << endl;
    bincDebug.flush();
    exit(111);
  }

  close(authintercom[0]);

  // create the string of data to be passed to the checkpassword stub
  int dataSize = username.length() + password.length() + challenge.length()
                 + timestamp.length();
  dataSize += 4;
  char *checkpasswordData = new char[dataSize];
  char *cpTmp = checkpasswordData;
  strcpy(cpTmp, username.c_str());
  cpTmp += username.length();
  *cpTmp++ = '\0';
  strcpy(cpTmp, password.c_str());
  cpTmp += password.length();
  *cpTmp++ = '\0';
  // add challenge
  strcpy(cpTmp, challenge.c_str());
  cpTmp += challenge.length();
  *cpTmp++ = '\0';
  strcpy(cpTmp, timestamp.c_str());
  cpTmp += timestamp.length();
  *cpTmp++ = '\0';

  bincDebug << "bincimap-up: pid " << pid << " authenticate(), writing username/password to "
            << session.unparsedArgs[0] << endl;

  // write the userid
  signal(SIGPIPE, SIG_IGN);
  int res = write(authintercom[1], checkpasswordData, dataSize);
  delete[] checkpasswordData;
  if (res != dataSize) {
    bincWarning << "bincimap-up: pid " << pid << " error writing to authenticator "
                << session.unparsedArgs[0] << ": " << strerror(errno) << endl;
    return 1;
  }

  // close the write channel. this is necessary for the checkpassword
  // module to see an EOF.
  close(authintercom[1]);
  close(intercomr[1]);
  close(intercomw[0]);

  fd_set rmask;
  FD_ZERO(&rmask);
  FD_SET(fileno(stdin), &rmask);
  FD_SET(intercomr[0], &rmask);

  int maxfd = intercomr[0];
  bool disconnected = false;
  bool timedout = false;
  bincClient.clearFlags(IODevice::HasInputLimit);

  bool eof = false;
  while (!eof) {
    fd_set rtmp = rmask;
    struct timeval timeout;

    // time out 5 minutes after the idle timeout. we expect the main
    // server to time out at the right time, but will shut down at
    // T+5m in case of a server lockup.
    timeout.tv_sec = IDLE_TIMEOUT + AUTH_PENALTY * AUTH_TIMEOUT;
    timeout.tv_usec = 0;

    // select sometimes returns when we attach to the process with
    // tracing tools such as ktrace and strace, setting errno to
    // EINTR.
    int n;
    do {
      n = select(maxfd + 1, &rtmp, nullptr, nullptr, &timeout);
    } while (n < 0 && errno == EINTR);

    if (n < 0) {
      bincWarning << "bincimpa-up: pid " << pid << " error: invalid exit from select, "
                  << strerror(errno) << endl;
      break;
    }

    if (n == 0) {
      bincLog << "bincimap-up: pid " << pid << " server timed out after " << IDLE_TIMEOUT
              << " seconds" << endl;
      timedout = true;
      break;
    }

    if (FD_ISSET(fileno(stdin), &rtmp)) {
      authenticated = true;

      do {
        string data;
        int ret = bincClient.readStr(&data);
        if (ret == 0 || ret == -1) {
          session.setLastError("client disconnected");
          eof = true;
          disconnected = true;
          break;
        }

        // Fall through. Triggered when there was no data
        // to read, even though no error has occurred
        if (ret == -2) continue;

        int w;
        do {
          w = write(intercomw[1], data.c_str(), data.length());
        } while (w < 0 && errno == EINTR);

        if (w > 0) Session::getInstance().addReadBytes(w);

        if (w < 0) {
          bincDebug << "bincimap-up:  pid " << pid
                    << " error writing to server: " << strerror(errno) << endl;
          eof = true;
        }
      } while (bincClient.canRead());
    }

    if (FD_ISSET(intercomr[0], &rtmp)) {
      char buf[8192];
      int ret = read(intercomr[0], buf, sizeof(buf));
      if (ret == 0) {
        // Main server has shut down
        eof = true;
        break;
      } else if (ret == -1) {
        bincDebug << "bincimap-up:  pid " << pid
                  << " error reading from server: " << strerror(errno) << endl;
        eof = true;
        break;
      } else {
        //	  umask(0);
        Session::getInstance().addWriteBytes(ret);

        bincClient << string(buf, ret);
        bincClient.flush();
      }
    }
  }

  close(intercomr[0]);
  close(intercomw[1]);

  // catch the dead baby
  if (waitpid(childspid, &result, 0) != childspid) {
    bincLog << "bincimap-up: pid " << pid << " <" << username << "> authentication failed: "
            << (authenticated ? "server " : session.unparsedArgs[0])
            << " waitpid returned unexpected value" << endl;
    string tmp = strerror(errno);

    return -1;
  }

  // if the server died because we closed the sockets after a timeout, exit 3.
  if (timedout) return 3;

  if (disconnected) return 0;

  if (WIFSIGNALED(result)) {
    bincLog << "bincimap-up: pid " << pid << " <" << username << "> authentication failed: "
            << (authenticated ? "server" : session.unparsedArgs[0]) << " died by signal "
            << WTERMSIG(result) << endl;
    sleep(AUTH_PENALTY);
    session.setState(Session::LOGOUT);
    return -1;
  }

  bincDebug << "bincimap-up: pid " << pid << " authenticate() ,"
            << (authenticated ? "authenticator" : "server") << " exited with code "
            << WEXITSTATUS(result) << endl;

  switch (WEXITSTATUS(result)) {
  case 0:
    break;
  case 1:
    // authentication failed - sleep
    bincLog << "bincimap-up: pid " << pid << " <" << username << "> failed to log in" << endl;
    sleep(AUTH_PENALTY);
    return 2;
  case 2:
  case 111:  // wrong call or missing auth data
             // abused
    bincLog << "bincimap-up: pid " << pid << " <" << username
            << "> authentication failed: " << (authenticated ? "authenticator" : "server")
            << " reports wrong usage" << endl;
    sleep(AUTH_PENALTY);
    return 2;
  default:
    // internal error -- or authenticator fooled us
    bincLog << "bincimap-up: pid " << pid << " <" << username
            << "> authentication failed: " << (authenticated ? "authenticator" : "server")
            << " returned " << WEXITSTATUS(result) << endl;
    return -1;
  }

  return 0;
}