Secure.cpp

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/*******************************************************************************
* Copyright (C) 2005, Quest Software, Inc. All rights reserved.
* Copyright (C) 2006, Novell, Inc. All rights reserved.
* 
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* 
*     * Redistributions of source code must retain the above copyright notice,
*       this list of conditions and the following disclaimer.
*     * Redistributions in binary form must reproduce the above copyright
*       notice, this list of conditions and the following disclaimer in the
*       documentation and/or other materials provided with the distribution.
*     * Neither the name of 
*       Quest Software, Inc., 
*       nor Novell, Inc., 
*       nor the names of its contributors or employees may be used to 
*       endorse or promote products derived from this software without 
*       specific prior written permission.
* 
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
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#include "blocxx/BLOCXX_config.h"
#include "blocxx/Array.hpp"
#include "blocxx/Secure.hpp"
#include "blocxx/FileSystem.hpp"
#include "blocxx/String.hpp"
#include "blocxx/Paths.hpp"
#include "blocxx/Format.hpp"
#include "blocxx/LazyGlobal.hpp"
#ifdef BLOCXX_HAVE_DIRENT_H
#include <dirent.h>
#endif
#include <fcntl.h>
#ifndef BLOCXX_WIN32
#include <grp.h>
#endif
#include <limits.h>
#ifdef BLOCXX_HAVE_PWD_H
#include <pwd.h>
#endif
#ifdef BLOCXX_HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#ifdef BLOCXX_HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <cstdlib>
#include <cstdio>
#include <cerrno>
#include <vector>
#include <algorithm>
 
#ifdef AIX
#include "blocxx/StringBuffer.hpp"
#include "blocxx/NonRecursiveMutex.hpp"
#include "blocxx/NonRecursiveMutexLock.hpp"
#include <fstream>
#include <cctype>
#endif
 
#if defined(BLOCXX_NO_SETRESGID_PROTO) && defined(BLOCXX_HAVE_SETRESGID)
extern "C" { int setresgid(gid_t rgid, gid_t egid, gid_t sgid); }
#endif
 
#if defined(BLOCXX_NO_SETRESUID_PROTO) && defined(BLOCXX_HAVE_SETRESUID)
extern "C" { int setresuid(uid_t ruid, uid_t euid, uid_t suid); }
#endif
 
using namespace blocxx;
 
#define THRBLOCXX_IF(tst, ExceptionClass, msg) \
   do \
   { \
      if (tst) \
      { \
         BLOCXX_THROW(ExceptionClass, (msg)); \
      } \
   } while (false)
 
#define THRBLOCXX_ERRNO_IF(tst, ExceptionClass, msg) \
   do \
   { \
      if (tst) \
      { \
         BLOCXX_THROW_ERRNO_MSG(ExceptionClass, (msg)); \
      } \
   } while (false)
 
#define ABORT_IF(tst, msg) THRBLOCXX_IF((tst), Secure::ProcessAbortException, (msg))
 
#define ABORT_ERRNO_IF(tst, msg) \
  THRBLOCXX_ERRNO_IF((tst), Secure::ProcessAbortException, (msg))
 
namespace
{
#if !defined(BLOCXX_HAVE_SETEUID) && defined(BLOCXX_HAVE_SETREUID)
int seteuid(uid_t euid)
{
   return (setreuid(-1, euid));
}
 
#endif
 
#if !defined(BLOCXX_HAVE_SETEGID) && defined(BLOCXX_HAVE_SETRESGID)
int setegid(uid_t egid)
{
   return(setresgid(-1, egid, -1));
}
#endif
 
} // end anonymous namespace
 
namespace BLOCXX_NAMESPACE
{
namespace Secure
{
   BLOCXX_DEFINE_EXCEPTION(ProcessAbort);
 
   // Original source: Item 1.3, _Secure Programming Cookbook for C and C++_, by
   // John Viega and Matt Messier. 
   // Original C code reformatted and modified for C++.
   // Some inspiration provided by uidswap.c from openssh-portable
   void dropPrivilegesPermanently(::uid_t newuid, ::gid_t newgid, EChildGroupAction extendedGroupAction)
   {
#ifdef BLOCXX_WIN32
#pragma message(Reminder "TODO: implement it for Win!")
#else
      // Note: If any manipulation of privileges cannot be completed
      // successfully, it is safest to assume that the process is in an
      // unknown state and not allow it to continue (abort).
 
      if (newgid == ::gid_t(-1))
      {
         newgid = ::getgid();
      }
      ::gid_t oldegid = ::getegid();
      ::gid_t oldgid = ::getgid();
      if (newuid == ::uid_t(-1))
      {
         newuid = ::getuid();
      }
      ::uid_t oldeuid = ::geteuid();
      ::uid_t olduid = ::getuid();
 
      // If root privileges are to be dropped, be sure to pare down the
      // ancillary groups for the process before doing anything else because
      // the setgroups() system call requires root privileges.  Drop ancillary
      // groups regardless of whether privileges are being dropped temporarily
      // or permanently.
      if (oldeuid == 0)
      {
         struct passwd *newuser(NULL);
         if (extendedGroupAction == E_SOURCE_EXTENDED_GROUPS)
         {
            newuser = ::getpwuid(newuid);
         }
         if (newuser)
         {
            ::initgroups(newuser->pw_name, newgid);
         }
         else
         {
         ::setgroups(1, &newgid);
      }
      }
 
      if (newgid != oldegid)
      {
#if defined(BLOCXX_HAVE_SETRESGID) && !defined(BLOCXX_BROKEN_SETRESGID)
         ABORT_ERRNO_IF(::setresgid(newgid, newgid, newgid) == -1, "drop_privileges [1]");
#elif defined(BLOCXX_HAVE_SETREGID) && !defined(BLOCXX_BROKEN_SETREGID)
         ABORT_ERRNO_IF(::setregid(newgid, newgid) == -1, "drop_privileges [1]");
#else
         ABORT_ERRNO_IF(::setegid(newgid) == -1, "drop_privileges [1]");
         ABORT_ERRNO_IF(::setgid(newgid) == -1, "drop_privileges [1.1]");
#endif
      }
 
      if (newuid != oldeuid)
      {
#if defined(BLOCXX_HAVE_SETRESUID) && !defined(BLOCXX_BROKEN_SETRESUID)
         ABORT_ERRNO_IF(::setresuid(newuid, newuid, newuid) == -1, "drop_privileges [2]");
#elif defined(BLOCXX_HAVE_SETREUID) && !defined(BLOCXX_BROKEN_SETREUID)
         ABORT_ERRNO_IF(::setreuid(newuid, newuid) == -1, "drop_privileges [2]");
#else
#if !defined(BLOCXX_SETEUID_BREAKS_SETUID)
         ABORT_ERRNO_IF(::seteuid(newuid) == -1, "drop_privileges [2]");
#endif
         ABORT_ERRNO_IF(::setuid(newuid) == -1, "drop_privileges [2.1]");
#endif
      }
 
      // verify that the changes were successful
      // make sure gid drop was successful
      ABORT_IF(::getgid() != newgid || ::getegid() != newgid, "drop_privileges [3]");
 
      // make sure gid restoration fails
      ABORT_IF(
         newuid != 0 && newgid != oldegid &&
#if defined(BLOCXX_HAVE_SETRESGID) && !defined(BLOCXX_BROKEN_SETRESGID)
         (::setresgid(oldegid, oldegid, oldegid) != -1 || ::setgid(oldgid) != -1),
#elif defined(BLOCXX_HAVE_SETREGID) && !defined(BLOCXX_BROKEN_SETREGID)
         (::setregid(oldegid, oldegid) != -1 || ::setgid(oldgid) != -1),
#else
         (::setegid(oldegid) != -1 || ::setgid(oldgid) != -1),
#endif
         "drop_privileges [4]"
      );
 
      // make sure uid drop was successful
      ABORT_IF(::getuid() != newuid || ::geteuid() != newuid, "drop_privileges [5]");
 
      // make sure uid restoration fails
      ABORT_IF(
         newuid != 0 && newuid != oldeuid &&
#if defined(BLOCXX_HAVE_SETRESUID) && !defined(BLOCXX_BROKEN_SETRESUID)
         (::setresuid(oldeuid, oldeuid, oldeuid) != -1 || ::setuid(olduid) != -1),
#elif defined(BLOCXX_HAVE_SETREUID) && !defined(BLOCXX_BROKEN_SETREUID)
         (::setreuid(oldeuid, oldeuid) != -1 || ::setuid(olduid) != -1),
#else
         (::seteuid(oldeuid) != -1 || ::setuid(olduid) != -1),
#endif
         "drop_privileges [6]"
      );
#endif
   }
 
namespace
{
#ifdef AIX
   NonRecursiveMutex envMutex;
   String odmdir;
 
   char const default_odmdir[] = "ODMDIR=/etc/objrepos";
 
   String check_line(String const & line)
   {
      StringBuffer sb;
      char const * s;
      char c;
      for (s = line.c_str(); (c = *s) && !std::isspace(c); ++s)
      {
         switch (c)
         {
            case '\\':
               if (s[1] == '\0')
               {
                  // Unexpected format
                  return default_odmdir;
               }
               c = *++s;
               break;
            case '$':
            case '`':
            case '"':
            case '\'':
               // Unexpected format
               return default_odmdir;
            default:
               ;
         }
         sb += c;
      }
      if (c == '\0')
      {
         return sb.releaseString();
      }
      while (std::isspace(*s))
      {
         ++s;
      }
      if (*s == '#')
      {
         return sb.releaseString();
      }
      // Unexpected format
      return default_odmdir;
   }
 
   String setODMDIR()
   {
      String retval(default_odmdir);
      std::ifstream is("/etc/environment");
      while (is)
      {
         String s = String::getLine(is).trim();
         if (s.startsWith("ODMDIR="))
         {
            retval = check_line(s);
         }
      }
      return retval;
   }
 
   void addPlatformSpecificEnvVars(StringArray & environ)
   {
      NonRecursiveMutexLock lock(envMutex);
      if (odmdir.empty())
      {
         odmdir = setODMDIR();
      }
      environ.push_back(odmdir);
   }
 
#else
 
   void addPlatformSpecificEnvVars(StringArray &absEnvironment)
   {
#ifdef BLOCXX_WIN32
      char* const lpInheritedEnvironment = GetEnvironmentStrings();
      char* lpInheritedEnvIterator = lpInheritedEnvironment;
      if (lpInheritedEnvironment && *lpInheritedEnvironment && lpInheritedEnvironment[1])
      {
         for ( ; *lpInheritedEnvIterator; lpInheritedEnvIterator++)
         {
            absEnvironment.push_back( String( lpInheritedEnvIterator ) );
            lpInheritedEnvIterator += lstrlen(lpInheritedEnvIterator);
         }
         FreeEnvironmentStrings( (LPTCH)lpInheritedEnvironment );
      }
#endif
   }
 
#endif
 
   struct MinimalEnvironmentConstructor
   {
      static StringArray* create(int dummy)
      {
         AutoPtr<StringArray> retval(new StringArray);
         retval->push_back("IFS= \t\n");
         retval->push_back("PATH=" _PATH_STDPATH);
         char * tzstr = ::getenv("TZ");
         if (tzstr)
         {
            retval->push_back(String("TZ=") + tzstr);
         }
         addPlatformSpecificEnvVars(*retval);
         return retval.release();
      }
   };
 
   LazyGlobal<StringArray, int, MinimalEnvironmentConstructor> g_minimalEnvironment = BLOCXX_LAZY_GLOBAL_INIT(0);
} // end unnamed namespace
 
   StringArray minimalEnvironment()
   {
      return g_minimalEnvironment;
   }
 
   void runAs(char const * username, EChildGroupAction extendedGroupAction)
   {
#ifdef BLOCXX_WIN32
#pragma message(Reminder "TODO: implement it for Win!")
#else
      ABORT_IF(!username, "null user name");
      ABORT_IF(*username == '\0', "empty user name");
      ABORT_IF(::getuid() != 0 || ::geteuid() != 0, "non-root user calling runAs");
      errno = 0;
      struct passwd * pwent = ::getpwnam(username);
      // return value from getpwnam is a static, so don't free it.
      ABORT_ERRNO_IF(!pwent && errno != 0, Format("getpwnam(\"%1\") failed", username).c_str());
      ABORT_IF(!pwent, Format("user name (%1) not found", username).c_str());
      int rc = ::chdir("/");
      ABORT_ERRNO_IF(rc != 0, "chdir failed");
      Secure::dropPrivilegesPermanently(pwent->pw_uid, pwent->pw_gid, extendedGroupAction);
#endif
   }
 
} // namespace Secure
} // namespace BLOCXX_NAMESPACE