diff --git a/csu/libc-start.c b/csu/libc-start.c index a14ed71616..8b3f436f46 100644 --- a/csu/libc-start.c +++ b/csu/libc-start.c @@ -140,7 +140,7 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL), __pthread_initialize_minimal (); /* Set up the stack checker's canary. */ - uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (); + uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random); # ifdef THREAD_SET_STACK_GUARD THREAD_SET_STACK_GUARD (stack_chk_guard); # else diff --git a/elf/dl-support.c b/elf/dl-support.c index 2c11ac6881..321ed07a18 100644 --- a/elf/dl-support.c +++ b/elf/dl-support.c @@ -84,6 +84,9 @@ struct r_scope_elem _dl_initial_searchlist; int _dl_starting_up = 1; #endif +/* Random data provided by the kernel. */ +void *_dl_random; + /* Get architecture specific initializer. */ #include @@ -216,6 +219,9 @@ _dl_aux_init (ElfW(auxv_t) *av) __libc_enable_secure = av->a_un.a_val; __libc_enable_secure_decided = 1; break; + case AT_RANDOM: + _dl_random = (void *) av->a_un.a_val; + break; # ifdef DL_PLATFORM_AUXV DL_PLATFORM_AUXV # endif diff --git a/elf/dl-sysdep.c b/elf/dl-sysdep.c index 85e331a90f..6ce20b5150 100644 --- a/elf/dl-sysdep.c +++ b/elf/dl-sysdep.c @@ -62,6 +62,7 @@ int __libc_multiple_libcs = 0; /* Defining this here avoids the inclusion void *__libc_stack_end attribute_relro = NULL; rtld_hidden_data_def(__libc_stack_end) static ElfW(auxv_t) *_dl_auxv attribute_relro; +void *_dl_random attribute_relro = NULL; #ifndef DL_FIND_ARG_COMPONENTS # define DL_FIND_ARG_COMPONENTS(cookie, argc, argv, envp, auxp) \ @@ -173,6 +174,9 @@ _dl_sysdep_start (void **start_argptr, GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val; break; #endif + case AT_RANDOM: + _dl_random = (void *) av->a_un.a_val; + break; #ifdef DL_PLATFORM_AUXV DL_PLATFORM_AUXV #endif @@ -293,6 +297,7 @@ _dl_show_auxv (void) [AT_SECURE - 2] = { "AT_SECURE: ", dec }, [AT_SYSINFO - 2] = { "AT_SYSINFO: 0x", hex }, [AT_SYSINFO_EHDR - 2] = { "AT_SYSINFO_EHDR: 0x", hex }, + [AT_RANDOM - 2] = { "AT_RANDOM: 0x", hex }, }; unsigned int idx = (unsigned int) (av->a_type - 2); diff --git a/elf/rtld.c b/elf/rtld.c index 7612a69324..e77ac43713 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -1816,7 +1816,7 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n", tcbp = init_tls (); /* Set up the stack checker's canary. */ - uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (); + uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random); #ifdef THREAD_SET_STACK_GUARD THREAD_SET_STACK_GUARD (stack_chk_guard); #else diff --git a/sysdeps/generic/dl-osinfo.h b/sysdeps/generic/dl-osinfo.h index 60b84a900d..02ec28d424 100644 --- a/sysdeps/generic/dl-osinfo.h +++ b/sysdeps/generic/dl-osinfo.h @@ -1,12 +1,29 @@ #include static inline uintptr_t __attribute__ ((always_inline)) -_dl_setup_stack_chk_guard (void) +_dl_setup_stack_chk_guard (void *dl_random) { - uintptr_t ret = 0; - unsigned char *p = (unsigned char *) &ret; - p[sizeof (ret) - 1] = 255; - p[sizeof (ret) - 2] = '\n'; - p[0] = 0; + uintptr_t ret; + if (dl_random == NULL) + { + ret = 0; + unsigned char *p = (unsigned char *) &ret; + p[sizeof (ret) - 1] = 255; + p[sizeof (ret) - 2] = '\n'; + p[0] = 0; + } + else + memcmp (&ret, dl_random, sizeof (ret)); + return ret; +} + +static inline uintptr_t __attribute__ ((always_inline)) +_dl_setup_pointer_guard (void *dl_random, uintptr_t stack_chk_guard) +{ + uintptr_t ret; + if (dl_random == NULL) + ret = stack_chk_guard; + else + memcmp (&ret, (char *) dl_random + sizeof (ret), sizeof (ret)); return ret; } diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 958a099b82..c4d2874085 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -726,6 +726,9 @@ weak_extern (_dl_starting_up) extern int _dl_starting_up_internal attribute_hidden; #endif +/* Random data provided by the kernel. */ +extern void *_dl_random attribute_hidden; + /* OS-dependent function to open the zero-fill device. */ extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */ diff --git a/sysdeps/unix/sysv/linux/dl-osinfo.h b/sysdeps/unix/sysv/linux/dl-osinfo.h index 082790f63b..d90f228942 100644 --- a/sysdeps/unix/sysv/linux/dl-osinfo.h +++ b/sysdeps/unix/sysv/linux/dl-osinfo.h @@ -154,22 +154,20 @@ _dl_discover_osversion (void) } while (0) static inline uintptr_t __attribute__ ((always_inline)) -_dl_setup_stack_chk_guard (void) +_dl_setup_stack_chk_guard (void *dl_random) { uintptr_t ret; -#ifdef ENABLE_STACKGUARD_RANDOMIZE - int fd = __open ("/dev/urandom", O_RDONLY); - if (fd >= 0) - { - ssize_t reslen = __read (fd, &ret, sizeof (ret)); - __close (fd); - if (reslen == (ssize_t) sizeof (ret)) - return ret; - } -#endif - ret = 0; - unsigned char *p = (unsigned char *) &ret; - p[sizeof (ret) - 1] = 255; - p[sizeof (ret) - 2] = '\n'; + /* We need in the moment only 8 bytes on 32-bit platforms and 16 + bytes on 64-bit platforms. Therefore we can use the data + directly and not use the kernel-provided data to seed a PRNG. */ + memcpy (&ret, dl_random, sizeof (ret)); + return ret; +} + +static inline uintptr_t __attribute__ ((always_inline)) +_dl_setup_pointer_guard (void *dl_random, uintptr_t stack_chk_guard) +{ + uintptr_t ret; + memcpy (&ret, (char *) dl_random + sizeof (ret), sizeof (ret)); return ret; }