commit 123eaff0d5d1aebe128295959435b9ca5909c26d

Author: Andreas Gruenbacher <agruen@gnu.org>

Date:   Fri Apr 6 12:14:49 2018 +0200

    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.

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)

       {

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 <

+0a

+foo

+.

+EOF

+

+check 'patch -e foo -i ed1.diff' <

+EOF

+

+check 'cat foo' <

+foo

+EOF

+

+cat > ed2.diff <

+1337a

+r !echo bar

+,p

+EOF

+

+check 'patch -e foo -i ed2.diff 2> /dev/null || echo "Status: $?"' <

+?

+Status: 2

+EOF

+

+check 'cat foo' <

+foo

+EOF