Subject: Re: bug#27429: Stack clash (CVE-2017-1000366 etc)

From: [email-masked] (Ludovic Courtès)
Date: Thu, 29 Jun 2017 12:58:49 +0200

Hello gentlefolks!

As discussed yesterday on IRC, here’s a patch that applies the glibc
patches for CVE-2017-1000366 in ‘core-updates’.

That’s a rebuild-the-world change but we still have work to do in
‘core-updates’ anyway, notably regarding the Perl dot-in-@INC issue.

OK for you?

Thanks,
Ludo’.

>From 0118abc2ffd880c704f66294cf76ce0b8ddae803 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <[email-masked]>
Date: Thu, 29 Jun 2017 12:53:14 +0200
Subject: [PATCH] gnu: glibc/linux: Add patches for CVE-2017-1000366.

* gnu/packages/patches/glibc-CVE-2017-1000366-pt1.patch,
gnu/packages/patches/glibc-CVE-2017-1000366-pt2.patch,
gnu/packages/patches/glibc-CVE-2017-1000366-pt3.patch: New files.
* gnu/local.mk (dist_patch_DATA): Add them.
* gnu/packages/base.scm (glibc/linux)[source](patches): Add them.
---
 gnu/local.mk                                       |   3 +
 gnu/packages/base.scm                              |   5 +-
 .../patches/glibc-CVE-2017-1000366-pt1.patch       |  36 ++++
 .../patches/glibc-CVE-2017-1000366-pt2.patch       | 124 +++++++++++++
 .../patches/glibc-CVE-2017-1000366-pt3.patch       | 206 +++++++++++++++++++++
 5 files changed, 373 insertions(+), 1 deletion(-)
 create mode 100644 gnu/packages/patches/glibc-CVE-2017-1000366-pt1.patch
 create mode 100644 gnu/packages/patches/glibc-CVE-2017-1000366-pt2.patch
 create mode 100644 gnu/packages/patches/glibc-CVE-2017-1000366-pt3.patch

diff --git a/gnu/local.mk b/gnu/local.mk
index 1ae2a2d26..06bd98112 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -622,6 +622,9 @@ dist_patch_DATA =						\
   %D%/packages/patches/ghostscript-runpath.patch		\
   %D%/packages/patches/glib-networking-ssl-cert-file.patch	\
   %D%/packages/patches/glib-tests-timer.patch			\
+  %D%/packages/patches/glibc-CVE-2017-1000366-pt1.patch		\
+  %D%/packages/patches/glibc-CVE-2017-1000366-pt2.patch		\
+  %D%/packages/patches/glibc-CVE-2017-1000366-pt3.patch		\
   %D%/packages/patches/glibc-bootstrap-system.patch		\
   %D%/packages/patches/glibc-ldd-x86_64.patch			\
   %D%/packages/patches/glibc-locales.patch			\
diff --git a/gnu/packages/base.scm b/gnu/packages/base.scm
index b9364f81f..f5aea0812 100644
--- a/gnu/packages/base.scm
+++ b/gnu/packages/base.scm
@@ -532,7 +532,10 @@ store.")
             (patches (search-patches "glibc-ldd-x86_64.patch"
                                      "glibc-versioned-locpath.patch"
                                      "glibc-o-largefile.patch"
-                                     "glibc-memchr-overflow-i686.patch"))))
+                                     "glibc-memchr-overflow-i686.patch"
+                                     "glibc-CVE-2017-1000366-pt1.patch"
+                                     "glibc-CVE-2017-1000366-pt2.patch"
+                                     "glibc-CVE-2017-1000366-pt3.patch"))))
    (build-system gnu-build-system)
 
    ;; Glibc's <limits.h> refers to <linux/limit.h>, for instance, so glibc
diff --git a/gnu/packages/patches/glibc-CVE-2017-1000366-pt1.patch b/gnu/packages/patches/glibc-CVE-2017-1000366-pt1.patch
new file mode 100644
index 000000000..71e80968b
--- /dev/null
+++ b/gnu/packages/patches/glibc-CVE-2017-1000366-pt1.patch
@@ -0,0 +1,36 @@
+From f6110a8fee2ca36f8e2d2abecf3cba9fa7b8ea7d Mon Sep 17 00:00:00 2001
+From: Florian Weimer <[email-masked]>
+Date: Mon, 19 Jun 2017 17:09:55 +0200
+Subject: [PATCH] CVE-2017-1000366: Ignore LD_LIBRARY_PATH for AT_SECURE=1
+ programs [BZ #21624]
+
+LD_LIBRARY_PATH can only be used to reorder system search paths, which
+is not useful functionality.
+
+This makes an exploitable unbounded alloca in _dl_init_paths unreachable
+for AT_SECURE=1 programs.
+
+patch from:
+https://sourceware.org/git/?p=glibc.git;a=commit;h=f6110a8fee2ca36f8e2d2abecf3cba9fa7b8ea7d
+---
+ ChangeLog  | 7 +++++++
+ elf/rtld.c | 3 ++-
+ 2 files changed, 9 insertions(+), 1 deletion(-)
+
+diff --git a/elf/rtld.c b/elf/rtld.c
+index 2446a87..2269dbe 100644
+--- a/elf/rtld.c
++++ b/elf/rtld.c
+@@ -2422,7 +2422,8 @@ process_envvars (enum mode *modep)
+ 
+ 	case 12:
+ 	  /* The library search path.  */
+-	  if (memcmp (envline, "LIBRARY_PATH", 12) == 0)
++	  if (!__libc_enable_secure
++	      && memcmp (envline, "LIBRARY_PATH", 12) == 0)
+ 	    {
+ 	      library_path = &envline[13];
+ 	      break;
+-- 
+2.9.3
+
diff --git a/gnu/packages/patches/glibc-CVE-2017-1000366-pt2.patch b/gnu/packages/patches/glibc-CVE-2017-1000366-pt2.patch
new file mode 100644
index 000000000..4b859c4bf
--- /dev/null
+++ b/gnu/packages/patches/glibc-CVE-2017-1000366-pt2.patch
@@ -0,0 +1,124 @@
+From 6d0ba622891bed9d8394eef1935add53003b12e8 Mon Sep 17 00:00:00 2001
+From: Florian Weimer <[email-masked]>
+Date: Mon, 19 Jun 2017 22:31:04 +0200
+Subject: [PATCH] ld.so: Reject overly long LD_PRELOAD path elements
+
+patch from:
+https://sourceware.org/git/?p=glibc.git;a=patch;h=6d0ba622891bed9d8394eef1935add53003b12e8
+
+---
+ ChangeLog  |  7 ++++++
+ elf/rtld.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++------------
+ 2 files changed, 73 insertions(+), 16 deletions(-)
+
+diff --git a/elf/rtld.c b/elf/rtld.c
+index 2269dbe..86ae20c 100644
+--- a/elf/rtld.c
++++ b/elf/rtld.c
+@@ -99,6 +99,35 @@ uintptr_t __pointer_chk_guard_local
+ strong_alias (__pointer_chk_guard_local, __pointer_chk_guard)
+ #endif
+ 
++/* Length limits for names and paths, to protect the dynamic linker,
++   particularly when __libc_enable_secure is active.  */
++#ifdef NAME_MAX
++# define SECURE_NAME_LIMIT NAME_MAX
++#else
++# define SECURE_NAME_LIMIT 255
++#endif
++#ifdef PATH_MAX
++# define SECURE_PATH_LIMIT PATH_MAX
++#else
++# define SECURE_PATH_LIMIT 1024
++#endif
++
++/* Check that AT_SECURE=0, or that the passed name does not contain
++   directories and is not overly long.  Reject empty names
++   unconditionally.  */
++static bool
++dso_name_valid_for_suid (const char *p)
++{
++  if (__glibc_unlikely (__libc_enable_secure))
++    {
++      /* Ignore pathnames with directories for AT_SECURE=1
++	 programs, and also skip overlong names.  */
++      size_t len = strlen (p);
++      if (len >= SECURE_NAME_LIMIT || memchr (p, '/', len) != NULL)
++	return false;
++    }
++  return *p != '\0';
++}
+ 
+ /* List of auditing DSOs.  */
+ static struct audit_list
+@@ -718,6 +747,42 @@ static const char *preloadlist attribute_relro;
+ /* Nonzero if information about versions has to be printed.  */
+ static int version_info attribute_relro;
+ 
++/* The LD_PRELOAD environment variable gives list of libraries
++   separated by white space or colons that are loaded before the
++   executable's dependencies and prepended to the global scope list.
++   (If the binary is running setuid all elements containing a '/' are
++   ignored since it is insecure.)  Return the number of preloads
++   performed.  */
++unsigned int
++handle_ld_preload (const char *preloadlist, struct link_map *main_map)
++{
++  unsigned int npreloads = 0;
++  const char *p = preloadlist;
++  char fname[SECURE_PATH_LIMIT];
++
++  while (*p != '\0')
++    {
++      /* Split preload list at space/colon.  */
++      size_t len = strcspn (p, " :");
++      if (len > 0 && len < sizeof (fname))
++	{
++	  memcpy (fname, p, len);
++	  fname[len] = '\0';
++	}
++      else
++	fname[0] = '\0';
++
++      /* Skip over the substring and the following delimiter.  */
++      p += len;
++      if (*p != '\0')
++	++p;
++
++      if (dso_name_valid_for_suid (fname))
++	npreloads += do_preload (fname, main_map, "LD_PRELOAD");
++    }
++  return npreloads;
++}
++
+ static void
+ dl_main (const ElfW(Phdr) *phdr,
+ 	 ElfW(Word) phnum,
+@@ -1464,23 +1529,8 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
+ 
+   if (__glibc_unlikely (preloadlist != NULL))
+     {
+-      /* The LD_PRELOAD environment variable gives list of libraries
+-	 separated by white space or colons that are loaded before the
+-	 executable's dependencies and prepended to the global scope
+-	 list.  If the binary is running setuid all elements
+-	 containing a '/' are ignored since it is insecure.  */
+-      char *list = strdupa (preloadlist);
+-      char *p;
+-
+       HP_TIMING_NOW (start);
+-
+-      /* Prevent optimizing strsep.  Speed is not important here.  */
+-      while ((p = (strsep) (&list, " :")) != NULL)
+-	if (p[0] != '\0'
+-	    && (__builtin_expect (! __libc_enable_secure, 1)
+-		|| strchr (p, '/') == NULL))
+-	  npreloads += do_preload (p, main_map, "LD_PRELOAD");
+-
++      npreloads += handle_ld_preload (preloadlist, main_map);
+       HP_TIMING_NOW (stop);
+       HP_TIMING_DIFF (diff, start, stop);
+       HP_TIMING_ACCUM_NT (load_time, diff);
+-- 
+2.9.3
+
diff --git a/gnu/packages/patches/glibc-CVE-2017-1000366-pt3.patch b/gnu/packages/patches/glibc-CVE-2017-1000366-pt3.patch
new file mode 100644
index 000000000..3d8f6d2bf
--- /dev/null
+++ b/gnu/packages/patches/glibc-CVE-2017-1000366-pt3.patch
@@ -0,0 +1,206 @@
+From 81b82fb966ffbd94353f793ad17116c6088dedd9 Mon Sep 17 00:00:00 2001
+From: Florian Weimer <[email-masked]>
+Date: Mon, 19 Jun 2017 22:32:12 +0200
+Subject: [PATCH] ld.so: Reject overly long LD_AUDIT path elements
+
+Also only process the last LD_AUDIT entry.
+
+patch from:
+https://sourceware.org/git/?p=glibc.git;a=commit;h=81b82fb966ffbd94353f793ad17116c6088dedd9
+
+---
+ ChangeLog  |  11 +++++++
+ elf/rtld.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++---------
+ 2 files changed, 106 insertions(+), 15 deletions(-)
+
+diff --git a/elf/rtld.c b/elf/rtld.c
+index 86ae20c..65647fb 100644
+--- a/elf/rtld.c
++++ b/elf/rtld.c
+@@ -129,13 +129,91 @@ dso_name_valid_for_suid (const char *p)
+   return *p != '\0';
+ }
+ 
+-/* List of auditing DSOs.  */
++/* LD_AUDIT variable contents.  Must be processed before the
++   audit_list below.  */
++const char *audit_list_string;
++
++/* Cyclic list of auditing DSOs.  audit_list->next is the first
++   element.  */
+ static struct audit_list
+ {
+   const char *name;
+   struct audit_list *next;
+ } *audit_list;
+ 
++/* Iterator for audit_list_string followed by audit_list.  */
++struct audit_list_iter
++{
++  /* Tail of audit_list_string still needing processing, or NULL.  */
++  const char *audit_list_tail;
++
++  /* The list element returned in the previous iteration.  NULL before
++     the first element.  */
++  struct audit_list *previous;
++
++  /* Scratch buffer for returning a name which is part of
++     audit_list_string.  */
++  char fname[SECURE_NAME_LIMIT];
++};
++
++/* Initialize an audit list iterator.  */
++static void
++audit_list_iter_init (struct audit_list_iter *iter)
++{
++  iter->audit_list_tail = audit_list_string;
++  iter->previous = NULL;
++}
++
++/* Iterate through both audit_list_string and audit_list.  */
++static const char *
++audit_list_iter_next (struct audit_list_iter *iter)
++{
++  if (iter->audit_list_tail != NULL)
++    {
++      /* First iterate over audit_list_string.  */
++      while (*iter->audit_list_tail != '\0')
++	{
++	  /* Split audit list at colon.  */
++	  size_t len = strcspn (iter->audit_list_tail, ":");
++	  if (len > 0 && len < sizeof (iter->fname))
++	    {
++	      memcpy (iter->fname, iter->audit_list_tail, len);
++	      iter->fname[len] = '\0';
++	    }
++	  else
++	    /* Do not return this name to the caller.  */
++	    iter->fname[0] = '\0';
++
++	  /* Skip over the substring and the following delimiter.  */
++	  iter->audit_list_tail += len;
++	  if (*iter->audit_list_tail == ':')
++	    ++iter->audit_list_tail;
++
++	  /* If the name is valid, return it.  */
++	  if (dso_name_valid_for_suid (iter->fname))
++	    return iter->fname;
++	  /* Otherwise, wrap around and try the next name.  */
++	}
++      /* Fall through to the procesing of audit_list.  */
++    }
++
++  if (iter->previous == NULL)
++    {
++      if (audit_list == NULL)
++	/* No pre-parsed audit list.  */
++	return NULL;
++      /* Start of audit list.  The first list element is at
++	 audit_list->next (cyclic list).  */
++      iter->previous = audit_list->next;
++      return iter->previous->name;
++    }
++  if (iter->previous == audit_list)
++    /* Cyclic list wrap-around.  */
++    return NULL;
++  iter->previous = iter->previous->next;
++  return iter->previous->name;
++}
++
+ #ifndef HAVE_INLINED_SYSCALLS
+ /* Set nonzero during loading and initialization of executable and
+    libraries, cleared before the executable's entry point runs.  This
+@@ -1305,11 +1383,13 @@ of this helper program; chances are you did not intend to run this program.\n\
+     GL(dl_rtld_map).l_tls_modid = _dl_next_tls_modid ();
+ 
+   /* If we have auditing DSOs to load, do it now.  */
+-  if (__glibc_unlikely (audit_list != NULL))
++  bool need_security_init = true;
++  if (__glibc_unlikely (audit_list != NULL)
++      || __glibc_unlikely (audit_list_string != NULL))
+     {
+-      /* Iterate over all entries in the list.  The order is important.  */
+       struct audit_ifaces *last_audit = NULL;
+-      struct audit_list *al = audit_list->next;
++      struct audit_list_iter al_iter;
++      audit_list_iter_init (&al_iter);
+ 
+       /* Since we start using the auditing DSOs right away we need to
+ 	 initialize the data structures now.  */
+@@ -1320,9 +1400,14 @@ of this helper program; chances are you did not intend to run this program.\n\
+ 	 use different values (especially the pointer guard) and will
+ 	 fail later on.  */
+       security_init ();
++      need_security_init = false;
+ 
+-      do
++      while (true)
+ 	{
++	  const char *name = audit_list_iter_next (&al_iter);
++	  if (name == NULL)
++	    break;
++
+ 	  int tls_idx = GL(dl_tls_max_dtv_idx);
+ 
+ 	  /* Now it is time to determine the layout of the static TLS
+@@ -1331,7 +1416,7 @@ of this helper program; chances are you did not intend to run this program.\n\
+ 	     no DF_STATIC_TLS bit is set.  The reason is that we know
+ 	     glibc will use the static model.  */
+ 	  struct dlmopen_args dlmargs;
+-	  dlmargs.fname = al->name;
++	  dlmargs.fname = name;
+ 	  dlmargs.map = NULL;
+ 
+ 	  const char *objname;
+@@ -1344,7 +1429,7 @@ of this helper program; chances are you did not intend to run this program.\n\
+ 	    not_loaded:
+ 	      _dl_error_printf ("\
+ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
+-				al->name, err_str);
++				name, err_str);
+ 	      if (malloced)
+ 		free ((char *) err_str);
+ 	    }
+@@ -1448,10 +1533,7 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
+ 		  goto not_loaded;
+ 		}
+ 	    }
+-
+-	  al = al->next;
+ 	}
+-      while (al != audit_list->next);
+ 
+       /* If we have any auditing modules, announce that we already
+ 	 have two objects loaded.  */
+@@ -1715,7 +1797,7 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
+   if (tcbp == NULL)
+     tcbp = init_tls ();
+ 
+-  if (__glibc_likely (audit_list == NULL))
++  if (__glibc_likely (need_security_init))
+     /* Initialize security features.  But only if we have not done it
+        earlier.  */
+     security_init ();
+@@ -2346,9 +2428,7 @@ process_dl_audit (char *str)
+   char *p;
+ 
+   while ((p = (strsep) (&str, ":")) != NULL)
+-    if (p[0] != '\0'
+-	&& (__builtin_expect (! __libc_enable_secure, 1)
+-	    || strchr (p, '/') == NULL))
++    if (dso_name_valid_for_suid (p))
+       {
+ 	/* This is using the local malloc, not the system malloc.  The
+ 	   memory can never be freed.  */
+@@ -2412,7 +2492,7 @@ process_envvars (enum mode *modep)
+ 	      break;
+ 	    }
+ 	  if (memcmp (envline, "AUDIT", 5) == 0)
+-	    process_dl_audit (&envline[6]);
++	    audit_list_string = &envline[6];
+ 	  break;
+ 
+ 	case 7:
+-- 
+2.9.3
+
-- 
2.13.1