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[PATCH v3] elf: Check for empty tokens before dynamic string token expansion [BZ #22625]
- From: Aurelien Jarno <aurelien at aurel32 dot net>
- To: libc-alpha at sourceware dot org
- Cc: "Dmitry V . Levin" <ldv at altlinux dot org>, Aurelien Jarno <aurelien at aurel32 dot net>
- Date: Wed, 20 Dec 2017 21:23:59 +0100
- Subject: [PATCH v3] elf: Check for empty tokens before dynamic string token expansion [BZ #22625]
- Authentication-results: sourceware.org; auth=none
The fillin_rpath function in elf/dl-load.c loops over each RPATH or
RUNPATH tokens and interprets empty tokens as the current directory
("./"). In practice the check for empty token is done *after* the
dynamic string token expansion. The expansion process can return an
empty string for the $ORIGIN token if __libc_enable_secure is set
or if the path of the binary can not be determined (/proc not mounted).
Fix that by moving the check for empty tokens before the dynamic string
token expansion. In addition, check for NULL pointer or empty strings
return by expand_dynamic_string_token.
The above changes highlighted a bug in decompose_rpath, an empty array
is represented by the first element being NULL at the fillin_rpath
level, but by using a -1 pointer in decompose_rpath and other functions.
Changelog:
[BZ #22625]
* elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic
string token expansion. Check for NULL pointer or empty string possibly
returned by expand_dynamic_string_token.
(decompose_rpath): Check for empty path after dynamic string
token expansion.
---
ChangeLog | 10 ++++++++++
NEWS | 4 ++++
elf/dl-load.c | 35 ++++++++++++++++++++++++++---------
3 files changed, 40 insertions(+), 9 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 35d1d102f6..0ed4d0ab15 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2017-12-20 Aurelien Jarno <aurelien@aurel32.net>
+ Dmitry V. Levin <ldv@altlinux.org>
+
+ [BZ #22625]
+ * elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic
+ string token expansion. Check for NULL pointer or empty string possibly
+ returned by expand_dynamic_string_token.
+ (decompose_rpath): Check for empty path after dynamic string
+ token expansion.
+
2017-12-20 Adhemerval Zanella <adhemerval.zanella@linaro.org>
* nptl/Makefile (libpthread-routines): Add pthread_join_common.
diff --git a/NEWS b/NEWS
index a43ff26e83..0d43e93a17 100644
--- a/NEWS
+++ b/NEWS
@@ -149,6 +149,10 @@ Security related changes:
CVE-2017-1000366 has been applied, but it is mentioned here only because
of the CVE assignment.) Reported by Qualys.
+ CVE-2017-16997: Incorrect handling of RPATH or RUNPATH containing $ORIGIN
+ for AT_SECURE or SUID binaries could be used to load libraries from the
+ current directory.
+
The following bugs are resolved with this release:
[The release manager will add the list generated by
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 2964464158..955eb49ecb 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -414,22 +414,31 @@ fillin_rpath (char *rpath, struct r_search_path_elem **result, const char *sep,
{
char *cp;
size_t nelems = 0;
- char *to_free;
while ((cp = __strsep (&rpath, sep)) != NULL)
{
struct r_search_path_elem *dirp;
+ char *to_free = NULL;
+ size_t len = 0;
- to_free = cp = expand_dynamic_string_token (l, cp, 1);
+ /* `strsep' can pass an empty string. */
+ if (*cp != '\0')
+ {
+ to_free = cp = expand_dynamic_string_token (l, cp, 1);
- size_t len = strlen (cp);
+ /* expand_dynamic_string_token can return NULL in case of empty
+ path or memory allocation failure. */
+ if (cp == NULL)
+ continue;
- /* `strsep' can pass an empty string. This has to be
- interpreted as `use the current directory'. */
- if (len == 0)
- {
- static const char curwd[] = "./";
- cp = (char *) curwd;
+ /* Compute the length after dynamic string token expansion and
+ ignore empty paths. */
+ len = strlen (cp);
+ if (len == 0)
+ {
+ free (to_free);
+ continue;
+ }
}
/* Remove trailing slashes (except for "/"). */
@@ -594,6 +603,14 @@ decompose_rpath (struct r_search_path_struct *sps,
necessary. */
free (copy);
+ /* There is no path after expansion. */
+ if (result[0] == NULL)
+ {
+ free (result);
+ sps->dirs = (struct r_search_path_elem **) -1;
+ return false;
+ }
+
sps->dirs = result;
/* The caller will change this value if we haven't used a real malloc. */
sps->malloced = 1;
--
2.15.1