From 123eaff0d5d1aebe128295959435b9ca5909c26d Mon Sep 17 00:00:00 2001 From: Andreas Gruenbacher Date: Fri, 6 Apr 2018 12:14:49 +0200 Subject: [PATCH] Fix arbitrary command execution in ed-style patches (CVE-2018-1000156) * src/pch.c (do_ed_script): Write ed script to a temporary file instead of piping it to ed: this will cause ed to abort on invalid commands instead of rejecting them and carrying on. * tests/ed-style: New test case. * tests/Makefile.am (TESTS): Add test case. --- src/pch.c | 91 ++++++++++++++++++++++++++++++++++------------- tests/Makefile.am | 1 + tests/ed-style | 41 +++++++++++++++++++++ 3 files changed, 108 insertions(+), 25 deletions(-) create mode 100644 tests/ed-style diff --git a/src/pch.c b/src/pch.c index 0c5cc26..4fd5a05 100644 --- a/src/pch.c +++ b/src/pch.c @@ -33,6 +33,7 @@ # include #endif #include +#include #define INITHUNKMAX 125 /* initial dynamic allocation size */ @@ -2389,24 +2390,28 @@ do_ed_script (char const *inname, char const *outname, static char const editor_program[] = EDITOR_PROGRAM; file_offset beginning_of_this_line; - FILE *pipefp = 0; size_t chars_read; + FILE *tmpfp = 0; + char const *tmpname; + int tmpfd; + pid_t pid; + + if (! dry_run && ! skip_rest_of_patch) + { + /* Write ed script to a temporary file. This causes ed to abort on + invalid commands such as when line numbers or ranges exceed the + number of available lines. When ed reads from a pipe, it rejects + invalid commands and treats the next line as a new command, which + can lead to arbitrary command execution. */ + + tmpfd = make_tempfile (&tmpname, 'e', NULL, O_RDWR | O_BINARY, 0); + if (tmpfd == -1) + pfatal ("Can't create temporary file %s", quotearg (tmpname)); + tmpfp = fdopen (tmpfd, "w+b"); + if (! tmpfp) + pfatal ("Can't open stream for file %s", quotearg (tmpname)); + } - if (! dry_run && ! skip_rest_of_patch) { - int exclusive = *outname_needs_removal ? 0 : O_EXCL; - if (inerrno != ENOENT) - { - *outname_needs_removal = true; - copy_file (inname, outname, 0, exclusive, instat.st_mode, true); - } - sprintf (buf, "%s %s%s", editor_program, - verbosity == VERBOSE ? "" : "- ", - outname); - fflush (stdout); - pipefp = popen(buf, binary_transput ? "wb" : "w"); - if (!pipefp) - pfatal ("Can't open pipe to %s", quotearg (buf)); - } for (;;) { char ed_command_letter; beginning_of_this_line = file_tell (pfp); @@ -2417,14 +2422,14 @@ do_ed_script (char const *inname, char const *outname, } ed_command_letter = get_ed_command_letter (buf); if (ed_command_letter) { - if (pipefp) - if (! fwrite (buf, sizeof *buf, chars_read, pipefp)) + if (tmpfp) + if (! fwrite (buf, sizeof *buf, chars_read, tmpfp)) write_fatal (); if (ed_command_letter != 'd' && ed_command_letter != 's') { p_pass_comments_through = true; while ((chars_read = get_line ()) != 0) { - if (pipefp) - if (! fwrite (buf, sizeof *buf, chars_read, pipefp)) + if (tmpfp) + if (! fwrite (buf, sizeof *buf, chars_read, tmpfp)) write_fatal (); if (chars_read == 2 && strEQ (buf, ".\n")) break; @@ -2437,13 +2442,49 @@ do_ed_script (char const *inname, char const *outname, break; } } - if (!pipefp) + if (!tmpfp) return; - if (fwrite ("w\nq\n", sizeof (char), (size_t) 4, pipefp) == 0 - || fflush (pipefp) != 0) + if (fwrite ("w\nq\n", sizeof (char), (size_t) 4, tmpfp) == 0 + || fflush (tmpfp) != 0) write_fatal (); - if (pclose (pipefp) != 0) - fatal ("%s FAILED", editor_program); + + if (lseek (tmpfd, 0, SEEK_SET) == -1) + pfatal ("Can't rewind to the beginning of file %s", quotearg (tmpname)); + + if (! dry_run && ! skip_rest_of_patch) { + int exclusive = *outname_needs_removal ? 0 : O_EXCL; + *outname_needs_removal = true; + if (inerrno != ENOENT) + { + *outname_needs_removal = true; + copy_file (inname, outname, 0, exclusive, instat.st_mode, true); + } + sprintf (buf, "%s %s%s", editor_program, + verbosity == VERBOSE ? "" : "- ", + outname); + fflush (stdout); + + pid = fork(); + if (pid == -1) + pfatal ("Can't fork"); + else if (pid == 0) + { + dup2 (tmpfd, 0); + execl ("/bin/sh", "sh", "-c", buf, (char *) 0); + _exit (2); + } + else + { + int wstatus; + if (waitpid (pid, &wstatus, 0) == -1 + || ! WIFEXITED (wstatus) + || WEXITSTATUS (wstatus) != 0) + fatal ("%s FAILED", editor_program); + } + } + + fclose (tmpfp); + safe_unlink (tmpname); if (ofp) { diff --git a/tests/Makefile.am b/tests/Makefile.am index 6b6df63..16f8693 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -32,6 +32,7 @@ TESTS = \ crlf-handling \ dash-o-append \ deep-directories \ + ed-style \ empty-files \ false-match \ fifo \ diff --git a/tests/ed-style b/tests/ed-style new file mode 100644 index 0000000..d8c0689 --- /dev/null +++ b/tests/ed-style @@ -0,0 +1,41 @@ +# Copyright (C) 2018 Free Software Foundation, Inc. +# +# Copying and distribution of this file, with or without modification, +# in any medium, are permitted without royalty provided the copyright +# notice and this notice are preserved. + +. $srcdir/test-lib.sh + +require cat +use_local_patch +use_tmpdir + +# ============================================================== + +cat > ed1.diff < ed2.diff < /dev/null || echo "Status: $?"' <