From 21c5d14bfb4e08bee86f94fd815535d3be2c3869 Mon Sep 17 00:00:00 2001 From: Aurelien Jarno Date: Sat, 30 Dec 2017 10:54:23 +0100 Subject: elf: Check for empty tokens before dynamic string token expansion [BZ #22625] 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. (cherry picked from commit 3e3c904daef69b8bf7d5cc07f793c9f07c3553ef) --- ChangeLog | 10 ++++++++++ NEWS | 4 ++++ elf/dl-load.c | 49 +++++++++++++++++++++++++++++++++---------------- 3 files changed, 47 insertions(+), 16 deletions(-) diff --git a/ChangeLog b/ChangeLog index f7e20898af..066b0d2402 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,13 @@ +2017-12-30 Aurelien Jarno + Dmitry V. Levin + + [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. + 2017-02-27 Florian Weimer [BZ #21115] diff --git a/NEWS b/NEWS index fc6ee5267e..3a33aeeea1 100644 --- a/NEWS +++ b/NEWS @@ -66,6 +66,10 @@ Version 2.22.1 * A use-after-free vulnerability in clntudp_call in the Sun RPC system has been fixed (CVE-2017-12133). + +* 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. Version 2.22 diff --git a/elf/dl-load.c b/elf/dl-load.c index 7e6f4c52d1..d0ac65e650 100644 --- a/elf/dl-load.c +++ b/elf/dl-load.c @@ -432,31 +432,40 @@ 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 "/"). */ - while (len > 1 && cp[len - 1] == '/') - --len; + /* Remove trailing slashes (except for "/"). */ + while (len > 1 && cp[len - 1] == '/') + --len; - /* Now add one if there is none so far. */ - if (len > 0 && cp[len - 1] != '/') - cp[len++] = '/'; + /* Now add one if there is none so far. */ + if (len > 0 && cp[len - 1] != '/') + cp[len++] = '/'; + } /* Make sure we don't use untrusted directories if we run SUID. */ if (__glibc_unlikely (check_trusted) && !is_trusted_path (cp, len)) @@ -620,6 +629,14 @@ 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; -- cgit 1.4.1