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From 123eaff0d5d1aebe128295959435b9ca5909c26d Mon Sep 17 00:00:00 2001
From: Andreas Gruenbacher <agruen@gnu.org>
Date: Fri, 6 Apr 2018 12:14:49 +0200
Subject: 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.
Without test to avoid automake due to @system package.
---
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 <io.h>
#endif
#include <safe.h>
+#include <sys/wait.h>
#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)
{
--
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