Re: SECURITY: psql allows symlink games in /tmp - Mailing list pgsql-hackers

Thanks for the pointer.  Here is a diff to fix the problem.  How does it
look to you?

> This code in psql/command.c allows *any* system user to place a
> predictably named symbolic link in /tmp and use it to alter/destroy
> files owned by the user running psql. (tested - postgresql 7.0.2).
>
> All the information a potential attacker would need are available via a
> simple 'ps'.
>
> It might (untested) also allow an another user to exploit the race
> between the closing of the file by the editor and the re-reading of its
> contents to execute arbitrary SQL commands.
>
> IMHO these files, if they must be created in /tmp should at least be
> created O_EXCL, but there are still editor vulnerabilities with opening
> any files in a world writeable directory (see recent joe Vulnerability:
> http://lwn.net/2000/1123/a/sec-joe.php3)
>
> My system is RedHat 6.2 on an i686, with Postgresql 7.0.2 but the same
> code currently exists in CVS (or at least CVS-web).
>
> I am not subscribed to this list, so please CC me for replies.  (Also
> tell me if there is a more appropriate forum for this, but
> www.postgresql.org doesn't have a listed security issue address).
> --
> Andrew Bartlett
> abartlet@pcug.org.au
>


--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026
? config.log
? config.cache
? config.status
? GNUmakefile
? src/Makefile.custom
? src/GNUmakefile
? src/Makefile.global
? src/log
? src/crtags
? src/backend/postgres
? src/backend/catalog/global.description
? src/backend/catalog/global.bki
? src/backend/catalog/template1.bki
? src/backend/catalog/template1.description
? src/backend/port/Makefile
? src/bin/initdb/initdb
? src/bin/initlocation/initlocation
? src/bin/ipcclean/ipcclean
? src/bin/pg_config/pg_config
? src/bin/pg_ctl/pg_ctl
? src/bin/pg_dump/pg_dump
? src/bin/pg_dump/pg_restore
? src/bin/pg_dump/pg_dumpall
? src/bin/pg_id/pg_id
? src/bin/pg_passwd/pg_passwd
? src/bin/pgaccess/pgaccess
? src/bin/pgtclsh/Makefile.tkdefs
? src/bin/pgtclsh/Makefile.tcldefs
? src/bin/pgtclsh/pgtclsh
? src/bin/pgtclsh/pgtksh
? src/bin/psql/psql
? src/bin/scripts/createlang
? src/include/config.h
? src/include/stamp-h
? src/interfaces/ecpg/lib/libecpg.so.3.2.0
? src/interfaces/ecpg/preproc/ecpg
? src/interfaces/libpgeasy/libpgeasy.so.2.1
? src/interfaces/libpgtcl/libpgtcl.so.2.1
? src/interfaces/libpq/libpq.so.2.1
? src/interfaces/perl5/blib
? src/interfaces/perl5/Makefile
? src/interfaces/perl5/pm_to_blib
? src/interfaces/perl5/Pg.c
? src/interfaces/perl5/Pg.bs
? src/pl/plperl/blib
? src/pl/plperl/Makefile
? src/pl/plperl/pm_to_blib
? src/pl/plperl/SPI.c
? src/pl/plperl/plperl.bs
? src/pl/plpgsql/src/libplpgsql.so.1.0
? src/pl/tcl/Makefile.tcldefs
Index: src/bin/psql/command.c
===================================================================
RCS file: /home/projects/pgsql/cvsroot/pgsql/src/bin/psql/command.c,v
retrieving revision 1.38
diff -c -r1.38 command.c
*** src/bin/psql/command.c    2000/11/13 23:37:53    1.38
--- src/bin/psql/command.c    2000/11/25 06:18:33
***************
*** 13,19 ****
  #include <ctype.h>
  #ifndef WIN32
  #include <sys/types.h>            /* for umask() */
! #include <sys/stat.h>            /* for umask(), stat() */
  #include <unistd.h>                /* for geteuid(), getpid(), stat() */
  #else
  #include <win32.h>
--- 13,20 ----
  #include <ctype.h>
  #ifndef WIN32
  #include <sys/types.h>            /* for umask() */
! #include <sys/stat.h>            /* for stat() */
! #include <fcntl.h>                /* open() flags */
  #include <unistd.h>                /* for geteuid(), getpid(), stat() */
  #else
  #include <win32.h>
***************
*** 1397,1403 ****
      FILE       *stream;
      const char *fname;
      bool        error = false;
!
  #ifndef WIN32
      struct stat before,
                  after;
--- 1398,1405 ----
      FILE       *stream;
      const char *fname;
      bool        error = false;
!     int            fd;
!
  #ifndef WIN32
      struct stat before,
                  after;
***************
*** 1411,1417 ****
      {
          /* make a temp file to edit */
  #ifndef WIN32
-         mode_t        oldumask;
          const char *tmpdirenv = getenv("TMPDIR");

          sprintf(fnametmp, "%s/psql.edit.%ld.%ld",
--- 1413,1418 ----
***************
*** 1422,1436 ****
  #endif
          fname = (const char *) fnametmp;

! #ifndef WIN32
!         oldumask = umask(0177);
! #endif
!         stream = fopen(fname, "w");
! #ifndef WIN32
!         umask(oldumask);
! #endif

!         if (!stream)
          {
              psql_error("couldn't open temp file %s: %s\n", fname, strerror(errno));
              error = true;
--- 1423,1433 ----
  #endif
          fname = (const char *) fnametmp;

!         fd = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0600);
!         if (fd != -1)
!             stream = fdopen(fd, "w");

!         if (fd == -1 || !stream)
          {
              psql_error("couldn't open temp file %s: %s\n", fname, strerror(errno));
              error = true;