svn commit: r281936 - stable/10/usr.bin/ar

[Ed Maste]

Author: emaste
Date: Fri Apr 24 15:48:23 2015
New Revision: 281936
URL: https://svnweb.freebsd.org/changeset/base/281936

Log:
  MFC r281311: ar: Disallow directory traversal
  
    Set ARCHIVE_EXTRACT_SECURE_SYMLINKS and ARCHIVE_EXTRACT_SECURE_NODOTDOT
    as in bsdtar to prevent extraction of archive entries whose pathnames
    contain .. or whose target directory would be altered by a symlink.
    Also disallow absolute pathnames.
  
    We don't currently provide an option to disable this behaviour (as
    bsdtar's -P does). It is unlikely to be a problem in practice for ar(1),
    but the -P option is not currently used and available if we want to
    consider it for this purpose.
  
  Obtained from:	ELF tool chain ar, Ticket #474
  Relnotes:	Yes
  Sponsored by:	The FreeBSD Foundation

Modified:
  stable/10/usr.bin/ar/read.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/usr.bin/ar/read.c
==============================================================================
--- stable/10/usr.bin/ar/read.c	Fri Apr 24 15:36:58 2015	(r281935)
+++ stable/10/usr.bin/ar/read.c	Fri Apr 24 15:48:23 2015	(r281936)
@@ -186,7 +186,15 @@ read_archive(struct bsdar *bsdar, char m
 
 				if (bsdar->options & AR_V)
 					(void)fprintf(stdout, "x - %s\n", name);
-				flags = 0;
+				/* Disallow absolute paths. */
+				if (name[0] == '/') {
+					bsdar_warnc(bsdar, 0,
+					    "Absolute path '%s'", name);
+					continue;
+				}
+				/* Basic path security flags. */
+				flags = ARCHIVE_EXTRACT_SECURE_SYMLINKS | \
+				    ARCHIVE_EXTRACT_SECURE_NODOTDOT;
 				if (bsdar->options & AR_O)
 					flags |= ARCHIVE_EXTRACT_TIME;