From ebf9a2d776474181936a720ce811d72bbd1da3b6 Mon Sep 17 00:00:00 2001
From: Pavel Raiskup <praiskup@redhat.com>
Date: Tue, 26 Jan 2016 23:17:54 +0100
Subject: [PATCH] CVE-2016-2037 - 1 byte out-of-bounds write

Ensure that cpio_safer_name_suffix always works with dynamically
allocated buffer, and that it has size of at least 32 bytes.
Then, any call to cpio_safer_name_suffix is safe (it requires at
least 2 bytes in the buffer).

Also ensure that c_namesize is always correctly initialized (by
cpio_set_c_name) to avoid undefined behavior when reading
file_hdr.c_namesize (previously happened for tar archives).

References:
http://www.mail-archive.com/bug-cpio@gnu.org/msg00545.html

* src/copyin.c (query_rename): Drop the hack, as we now work with
dynamically allocated buffer.  Use cpio_set_c_name.
(create_defered_links_to_skipped): Use cpio_set_c_name rather than
manual assignment.
(read_name_from_file): New function to avoid C&P.
(read_in_old_ascii, read_in_new_ascii, read_in_binary): Use
read_name_from_file.
(process_copy_in): Initialize file_hdr.c_namesize.
* src/copyout.c (process_copy_out): Use cpio_set_c_name.
* src/cpiohdr.h (cpio_set_c_name): New prototype.
* src/tar.c (read_in_tar_header): Use cpio_set_c_name.
* src/util.c (cpio_set_c_name): New function to set
file_hdr->c_name and c_namesize from arbitrary string.
(cpio_safer_name_suffix): Some docs fixes.
* tests/inout.at: Also test copy-in, and try various formats.

CVE: CVE-2016-2037

Upstream-Status: Backport [http://git.savannah.gnu.org/cgit/cpio.git/commit/?id=d36ec5f4e93130efb24fb9678aafd88e8070095b]

Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
---
 src/copyin.c   | 68 +++++++++++++++++++---------------------------------------
 src/copyout.c  | 13 +++++------
 src/cpiohdr.h  |  1 +
 src/tar.c      | 10 +++++----
 src/util.c     | 32 ++++++++++++++++++++++++++-
 tests/inout.at | 19 ++++++++++++++--
 6 files changed, 82 insertions(+), 61 deletions(-)

diff --git a/src/copyin.c b/src/copyin.c
index cde911e..972f8a6 100644
--- a/src/copyin.c
+++ b/src/copyin.c
@@ -76,28 +76,7 @@ query_rename(struct cpio_file_stat* file_hdr, FILE *tty_in, FILE *tty_out,
       return -1;
     }
   else
-  /* Debian hack: file_hrd.c_name is sometimes set to
-     point to static memory by code in tar.c.  This
-     causes a segfault.  This has been fixed and an
-     additional check to ensure that the file name
-     is not too long has been added.  (Reported by
-     Horst Knobloch.)  This bug has been reported to
-     "bug-gnu-utils@prep.ai.mit.edu". (99/1/6) -BEM */
-    {
-      if (archive_format != arf_tar && archive_format != arf_ustar)
-	{
-	  free (file_hdr->c_name);
-	  file_hdr->c_name = xstrdup (new_name.ds_string);
-	}
-      else
-	{
-	  if (is_tar_filename_too_long (new_name.ds_string))
-	    error (0, 0, _("%s: file name too long"),
-		   new_name.ds_string);
-	  else
-	    strcpy (file_hdr->c_name, new_name.ds_string);
-	}
-    }
+    cpio_set_c_name (file_hdr, new_name.ds_string);
   return 0;
 }
 
@@ -344,8 +323,7 @@ create_defered_links_to_skipped (struct cpio_file_stat *file_hdr,
 	    d_prev->next = d->next;
 	  else
 	    deferments = d->next;
-	  free (file_hdr->c_name);
-	  file_hdr->c_name = xstrdup(d->header.c_name);
+	  cpio_set_c_name (file_hdr, d->header.c_name);
 	  free_deferment (d);
 	  copyin_regular_file(file_hdr, in_file_des);
 	  return 0;
@@ -1064,6 +1042,22 @@ read_in_header (struct cpio_file_stat *file_hdr, int in_des)
     }
 }
 
+static void
+read_name_from_file (struct cpio_file_stat *file_hdr, int fd, uintmax_t len)
+{
+  static char *tmp_filename;
+  static size_t buflen;
+
+  if (buflen < len)
+    {
+      buflen = len;
+      tmp_filename = xrealloc (tmp_filename, buflen);
+    }
+
+  tape_buffered_read (tmp_filename, fd, len);
+  cpio_set_c_name (file_hdr, tmp_filename);
+}
+
 /* Fill in FILE_HDR by reading an old-format ASCII format cpio header from
    file descriptor IN_DES, except for the magic number, which is
    already filled in.  */
@@ -1090,14 +1084,8 @@ read_in_old_ascii (struct cpio_file_stat *file_hdr, int in_des)
   file_hdr->c_rdev_min = minor (dev);
 
   file_hdr->c_mtime = FROM_OCTAL (ascii_header.c_mtime);
-  file_hdr->c_namesize = FROM_OCTAL (ascii_header.c_namesize);
   file_hdr->c_filesize = FROM_OCTAL (ascii_header.c_filesize);
-  
-  /* Read file name from input.  */
-  if (file_hdr->c_name != NULL)
-    free (file_hdr->c_name);
-  file_hdr->c_name = (char *) xmalloc (file_hdr->c_namesize + 1);
-  tape_buffered_read (file_hdr->c_name, in_des, (long) file_hdr->c_namesize);
+  read_name_from_file (file_hdr, in_des, FROM_OCTAL (ascii_header.c_namesize));
 
   /* HP/UX cpio creates archives that look just like ordinary archives,
      but for devices it sets major = 0, minor = 1, and puts the
@@ -1152,14 +1140,8 @@ read_in_new_ascii (struct cpio_file_stat *file_hdr, int in_des)
   file_hdr->c_dev_min = FROM_HEX (ascii_header.c_dev_min);
   file_hdr->c_rdev_maj = FROM_HEX (ascii_header.c_rdev_maj);
   file_hdr->c_rdev_min = FROM_HEX (ascii_header.c_rdev_min);
-  file_hdr->c_namesize = FROM_HEX (ascii_header.c_namesize);
   file_hdr->c_chksum = FROM_HEX (ascii_header.c_chksum);
-  
-  /* Read file name from input.  */
-  if (file_hdr->c_name != NULL)
-    free (file_hdr->c_name);
-  file_hdr->c_name = (char *) xmalloc (file_hdr->c_namesize);
-  tape_buffered_read (file_hdr->c_name, in_des, (long) file_hdr->c_namesize);
+  read_name_from_file (file_hdr, in_des, FROM_HEX (ascii_header.c_namesize));
 
   /* In SVR4 ASCII format, the amount of space allocated for the header
      is rounded up to the next long-word, so we might need to drop
@@ -1207,16 +1189,9 @@ read_in_binary (struct cpio_file_stat *file_hdr,
   file_hdr->c_rdev_min = minor (short_hdr->c_rdev);
   file_hdr->c_mtime = (unsigned long) short_hdr->c_mtimes[0] << 16
                       | short_hdr->c_mtimes[1];
-
-  file_hdr->c_namesize = short_hdr->c_namesize;
   file_hdr->c_filesize = (unsigned long) short_hdr->c_filesizes[0] << 16
                       | short_hdr->c_filesizes[1];
-
-  /* Read file name from input.  */
-  if (file_hdr->c_name != NULL)
-    free (file_hdr->c_name);
-  file_hdr->c_name = (char *) xmalloc (file_hdr->c_namesize);
-  tape_buffered_read (file_hdr->c_name, in_des, (long) file_hdr->c_namesize);
+  read_name_from_file (file_hdr, in_des, short_hdr->c_namesize);
 
   /* In binary mode, the amount of space allocated in the header for
      the filename is `c_namesize' rounded up to the next short-word,
@@ -1297,6 +1272,7 @@ process_copy_in ()
       read_pattern_file ();
     }
   file_hdr.c_name = NULL;
+  file_hdr.c_namesize = 0;
 
   if (rename_batch_file)
     {
diff --git a/src/copyout.c b/src/copyout.c
index 1f0987a..bb39559 100644
--- a/src/copyout.c
+++ b/src/copyout.c
@@ -660,8 +660,7 @@ process_copy_out ()
 	  cpio_safer_name_suffix (input_name.ds_string, false,
 				  !no_abs_paths_flag, true);
 #ifndef HPUX_CDF
-	  file_hdr.c_name = input_name.ds_string;
-	  file_hdr.c_namesize = strlen (input_name.ds_string) + 1;
+	  cpio_set_c_name (&file_hdr, input_name.ds_string);
 #else
 	  if ( (archive_format != arf_tar) && (archive_format != arf_ustar) )
 	    {
@@ -670,16 +669,15 @@ process_copy_out ()
 		 properly recreate the directory as hidden (in case the
 		 files of a directory go into the archive before the
 		 directory itself (e.g from "find ... -depth ... | cpio")).  */
-	      file_hdr.c_name = add_cdf_double_slashes (input_name.ds_string);
-	      file_hdr.c_namesize = strlen (file_hdr.c_name) + 1;
+              cpio_set_c_name (&file_hdr,
+                               add_cdf_double_slashes (input_name.ds_string));
 	    }
 	  else
 	    {
 	      /* We don't mark CDF's in tar files.  We assume the "hidden"
 		 directory will always go into the archive before any of
 		 its files.  */
-	      file_hdr.c_name = input_name.ds_string;
-	      file_hdr.c_namesize = strlen (input_name.ds_string) + 1;
+              cpio_set_c_name (&file_hdr, input_name.ds_string);
 	    }
 #endif
 
@@ -866,8 +864,7 @@ process_copy_out ()
   file_hdr.c_chksum = 0;
 
   file_hdr.c_filesize = 0;
-  file_hdr.c_namesize = 11;
-  file_hdr.c_name = CPIO_TRAILER_NAME;
+  cpio_set_c_name (&file_hdr, CPIO_TRAILER_NAME);
   if (archive_format != arf_tar && archive_format != arf_ustar)
     write_out_header (&file_hdr, out_file_des);
   else
diff --git a/src/cpiohdr.h b/src/cpiohdr.h
index b29e6fb..f4c63be 100644
--- a/src/cpiohdr.h
+++ b/src/cpiohdr.h
@@ -129,5 +129,6 @@ struct cpio_file_stat /* Internal representation of a CPIO header */
   char *c_tar_linkname;
 };
 
+void cpio_set_c_name(struct cpio_file_stat *file_hdr, char *name);
 
 #endif /* cpiohdr.h */
diff --git a/src/tar.c b/src/tar.c
index a2ce171..e41f89d 100644
--- a/src/tar.c
+++ b/src/tar.c
@@ -282,7 +282,7 @@ read_in_tar_header (struct cpio_file_stat *file_hdr, int in_des)
       if (null_block ((long *) &tar_rec, TARRECORDSIZE))
 #endif
 	{
-	  file_hdr->c_name = CPIO_TRAILER_NAME;
+	  cpio_set_c_name (file_hdr, CPIO_TRAILER_NAME);
 	  return;
 	}
 #if 0
@@ -316,9 +316,11 @@ read_in_tar_header (struct cpio_file_stat *file_hdr, int in_des)
 	}
 
       if (archive_format != arf_ustar)
-	file_hdr->c_name = stash_tar_filename (NULL, tar_hdr->name);
+        cpio_set_c_name (file_hdr, stash_tar_filename (NULL, tar_hdr->name));
       else
-	file_hdr->c_name = stash_tar_filename (tar_hdr->prefix, tar_hdr->name);
+        cpio_set_c_name (file_hdr, stash_tar_filename (tar_hdr->prefix,
+                                                      tar_hdr->name));
+
       file_hdr->c_nlink = 1;
       file_hdr->c_mode = FROM_OCTAL (tar_hdr->mode);
       file_hdr->c_mode = file_hdr->c_mode & 07777;
@@ -398,7 +400,7 @@ read_in_tar_header (struct cpio_file_stat *file_hdr, int in_des)
 	case AREGTYPE:
 	  /* Old tar format; if the last char in filename is '/' then it is
 	     a directory, otherwise it's a regular file.  */
-	  if (file_hdr->c_name[strlen (file_hdr->c_name) - 1] == '/')
+	  if (file_hdr->c_name[file_hdr->c_namesize - 1] == '/')
 	    file_hdr->c_mode |= CP_IFDIR;
 	  else
 	    file_hdr->c_mode |= CP_IFREG;
diff --git a/src/util.c b/src/util.c
index 6ff6032..4f3c073 100644
--- a/src/util.c
+++ b/src/util.c
@@ -1410,8 +1410,34 @@ set_file_times (int fd,
     utime_error (name);
 }
 
+
+void
+cpio_set_c_name (struct cpio_file_stat *file_hdr, char *name)
+{
+  static size_t buflen = 0;
+  size_t len = strlen (name) + 1;
+
+  if (buflen == 0)
+    {
+      buflen = len;
+      if (buflen < 32)
+        buflen = 32;
+      file_hdr->c_name = xmalloc (buflen);
+    }
+  else if (buflen < len)
+    {
+      buflen = len;
+      file_hdr->c_name = xrealloc (file_hdr->c_name, buflen);
+    }
+
+  file_hdr->c_namesize = len;
+  memmove (file_hdr->c_name, name, len);
+}
+
 /* Do we have to ignore absolute paths, and if so, does the filename
-   have an absolute path?  */
+   have an absolute path?  Before calling this function make sure that the
+   allocated NAME buffer has capacity at least 2 bytes. */
+
 void
 cpio_safer_name_suffix (char *name, bool link_target, bool absolute_names,
 			bool strip_leading_dots)
@@ -1426,6 +1452,10 @@ cpio_safer_name_suffix (char *name, bool link_target, bool absolute_names,
 	  ++p;
       }
   if (p != name)
+    /* The 'p' string is shortened version of 'name' with one exception;  when
+       the 'name' points to an empty string (buffer where name[0] == '\0') the
+       'p' then points to static string ".".  So caller needs to ensure there
+       are at least two bytes available in 'name' buffer so memmove succeeds. */
     memmove (name, p, (size_t)(strlen (p) + 1));
 }
 
diff --git a/tests/inout.at b/tests/inout.at
index 60c3716..730cbd2 100644
--- a/tests/inout.at
+++ b/tests/inout.at
@@ -35,7 +35,22 @@ while read NAME LENGTH
 do
 	genfile --length $LENGTH > $NAME
 	echo $NAME
-done < filelist |
- cpio --quiet -o > archive])
+done < filelist > filelist_raw
+
+for format in bin odc newc crc tar ustar hpbin hpodc
+do
+    cpio --format=$format --quiet -o < filelist_raw > archive.$format
+    rm -rf output
+    mkdir output && cd output
+    cpio -i --quiet < ../archive.$format
+
+    while read file
+    do
+        test -f $file || echo "$file not found"
+    done < ../filelist_raw
+
+    cd ..
+done
+])
 
 AT_CLEANUP
-- 
1.9.1