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- From b56779aed483f0036a32a65e62ab7b5e461b07cc Mon Sep 17 00:00:00 2001
- From: Andreas Gruenbacher <agruen@gnu.org>
- 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 | 89 +++++++++++++++++++++++++++++++++++------------
- tests/Makefile.am | 1 +
- tests/ed-style | 41 ++++++++++++++++++++++
- 3 files changed, 108 insertions(+), 23 deletions(-)
- create mode 100644 tests/ed-style
-
- --- a/src/pch.c
- +++ b/src/pch.c
- @@ -33,6 +33,7 @@
- # include <io.h>
- #endif
- #include <safe.h>
- +#include <sys/wait.h>
-
- #define INITHUNKMAX 125 /* initial dynamic allocation size */
-
- @@ -2389,22 +2390,28 @@ do_ed_script (char const *inname, char c
- 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;
- - assert (! inerrno);
- - *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);
- @@ -2415,14 +2422,14 @@ do_ed_script (char const *inname, char c
- }
- 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;
- @@ -2435,13 +2442,49 @@ do_ed_script (char const *inname, char c
- 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)
- {
- --- 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 \
- --- /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 <<EOF
- +0a
- +foo
- +.
- +EOF
- +
- +check 'patch -e foo -i ed1.diff' <<EOF
- +EOF
- +
- +check 'cat foo' <<EOF
- +foo
- +EOF
- +
- +cat > ed2.diff <<EOF
- +1337a
- +r !echo bar
- +,p
- +EOF
- +
- +check 'patch -e foo -i ed2.diff 2> /dev/null || echo "Status: $?"' <<EOF
- +?
- +Status: 2
- +EOF
- +
- +check 'cat foo' <<EOF
- +foo
- +EOF
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