On hardened system it could be useful to disable the use of LD_PRELOAD environment variable for preloading shared objects before the system libraries. So this patch add a config option, LDSO_PRELOAD_ENV_SUPPORT, to control this behaviour. It is enabled by default.
Signed-off-by: Carmelo Amoroso <[email protected]> --- extra/Configs/Config.in | 12 ++++++++++++ ldso/ldso/ldso.c | 8 ++++++++ 2 files changed, 20 insertions(+), 0 deletions(-) diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in index 90094ca..13e0d17 100644 --- a/extra/Configs/Config.in +++ b/extra/Configs/Config.in @@ -309,6 +309,18 @@ config LDSO_PRELOAD_FILE_SUPPORT whitespace separated list of shared libraries to be loaded before the program. +config LDSO_PRELOAD_ENV_SUPPORT + bool "Enable library loader LD_PRELOAD environment" + depends on HAVE_SHARED + default y + help + Enable this to make use of LD_PRELOAD environment variable. + A whitespace-separated list of additional, user-specified, ELF shared + libraries to be loaded before all others. This can be used to + selectively override functions in other shared libraries. For + set-user-ID/set-group-ID ELF binaries, only libraries in the standard + search directories that are also set-user-ID will be loaded. + config LDSO_BASE_FILENAME string "Shared library loader naming prefix" depends on HAVE_SHARED && (LDSO_CACHE_SUPPORT || LDSO_PRELOAD_FILE_SUPPORT) diff --git a/ldso/ldso/ldso.c b/ldso/ldso/ldso.c index 74da588..ea4ad0f 100644 --- a/ldso/ldso/ldso.c +++ b/ldso/ldso/ldso.c @@ -47,7 +47,9 @@ /* Global variables used within the shared library loader */ char *_dl_library_path = NULL; /* Where we look for libraries */ +#ifdef __LDSO_PRELOAD_ENV_SUPPORT__ char *_dl_preload = NULL; /* Things to be loaded before the libs */ +#endif char *_dl_ldsopath = NULL; /* Location of the shared lib loader */ int _dl_errno = 0; /* We can't use the real errno in ldso */ size_t _dl_pagesize = 0; /* Store the page size for use later */ @@ -348,7 +350,9 @@ void _dl_get_ready_to_run(struct elf_resolve *tpnt, DL_LOADADDR_TYPE load_addr, auxvt[AT_UID].a_un.a_val == auxvt[AT_EUID].a_un.a_val && auxvt[AT_GID].a_un.a_val == auxvt[AT_EGID].a_un.a_val)) { _dl_secure = 0; +#ifdef __LDSO_PRELOAD_ENV_SUPPORT__ _dl_preload = _dl_getenv("LD_PRELOAD", envp); +#endif _dl_library_path = _dl_getenv("LD_LIBRARY_PATH", envp); } else { static const char unsecure_envvars[] = @@ -365,7 +369,9 @@ void _dl_get_ready_to_run(struct elf_resolve *tpnt, DL_LOADADDR_TYPE load_addr, /* We could use rawmemchr but this need not be fast. */ nextp = _dl_strchr(nextp, '\0') + 1; } while (*nextp != '\0'); +#ifdef __LDSO_PRELOAD_ENV_SUPPORT__ _dl_preload = NULL; +#endif _dl_library_path = NULL; /* SUID binaries can be exploited if they do LAZY relocation. */ unlazy = RTLD_NOW; @@ -612,6 +618,7 @@ void _dl_get_ready_to_run(struct elf_resolve *tpnt, DL_LOADADDR_TYPE load_addr, _dl_map_cache(); +#ifdef __LDSO_PRELOAD_ENV_SUPPORT__ if (_dl_preload) { char c, *str, *str2; @@ -667,6 +674,7 @@ void _dl_get_ready_to_run(struct elf_resolve *tpnt, DL_LOADADDR_TYPE load_addr, str++; } } +#endif /* __LDSO_PRELOAD_ENV_SUPPORT__ */ #ifdef __LDSO_PRELOAD_FILE_SUPPORT__ do { -- 1.6.3.3 _______________________________________________ uClibc mailing list [email protected] http://lists.busybox.net/mailman/listinfo/uclibc
