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rtld direct exec: add -d option

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to ignore lack of execute permission on the binary.  The check is a
bad security theatre anyway.

Reviewed by:	arichardson, imp
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D32464
This commit is contained in:
Konstantin Belousov 2021-10-12 01:26:54 +03:00
parent b82168e657
commit ba7f9c1b61
2 changed files with 18 additions and 6 deletions
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6
libexec/rtld-elf/rtld.1
View File

@ -330,6 +330,7 @@ The syntax of the direct invocation is
.Bd -ragged -offset indent
.Pa /libexec/ld-elf.so.1
.Op Fl b Ar exe
.Op Fl d
.Op Fl f Ar fd
.Op Fl p
.Op Fl u
@ -352,6 +353,8 @@ If this option is specified,
is only used to provide the
.Va argv[0]
value to the program.
.It Fl d
Turn off the emulation of the binary execute permission.
.It Fl f Ar fd
File descriptor
.Ar fd
@ -403,6 +406,9 @@ ignores
and is naturally prone to race conditions.
Environments which rely on such restrictions are weak
and breakable on their own.
It can be turned off with the
.Fl d
option.
.Sh VERSIONING
Newer
.Nm

18
libexec/rtld-elf/rtld.c
View File

@ -140,7 +140,7 @@ static void objlist_remove(Objlist *, Obj_Entry *);
static int open_binary_fd(const char *argv0, bool search_in_path,
const char **binpath_res);
static int parse_args(char* argv[], int argc, bool *use_pathp, int *fdp,
const char **argv0);
const char **argv0, bool *dir_ignore);
static int parse_integer(const char *);
static void *path_enumerate(const char *, path_enum_proc, const char *, void *);
static void print_usage(const char *argv0);
@ -503,7 +503,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
#ifdef __powerpc__
int old_auxv_format = 1;
#endif
bool dir_enable, direct_exec, explicit_fd, search_in_path;
bool dir_enable, dir_ignore, direct_exec, explicit_fd, search_in_path;
/*
* On entry, the dynamic linker itself has not been relocated yet.
@ -589,7 +589,8 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
dbg("opening main program in direct exec mode");
if (argc >= 2) {
rtld_argc = parse_args(argv, argc, &search_in_path, &fd, &argv0);
rtld_argc = parse_args(argv, argc, &search_in_path, &fd,
&argv0, &dir_ignore);
explicit_fd = (fd != -1);
binpath = NULL;
if (!explicit_fd)
@ -621,7 +622,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
} else if ((st.st_mode & S_IXOTH) != 0) {
dir_enable = true;
}
if (!dir_enable) {
if (!dir_enable && !dir_ignore) {
_rtld_error("No execute permission for binary %s",
argv0);
rtld_die();
@ -5842,7 +5843,7 @@ open_binary_fd(const char *argv0, bool search_in_path,
*/
static int
parse_args(char* argv[], int argc, bool *use_pathp, int *fdp,
const char **argv0)
const char **argv0, bool *dir_ignore)
{
const char *arg;
char machine[64];
@ -5854,6 +5855,7 @@ parse_args(char* argv[], int argc, bool *use_pathp, int *fdp,
dbg("Parsing command-line arguments");
*use_pathp = false;
*fdp = -1;
*dir_ignore = false;
seen_b = seen_f = false;
for (i = 1; i < argc; i++ ) {
@ -5890,6 +5892,9 @@ parse_args(char* argv[], int argc, bool *use_pathp, int *fdp,
*argv0 = argv[i];
seen_b = true;
break;
} else if (opt == 'd') {
*dir_ignore = true;
break;
} else if (opt == 'f') {
if (seen_b) {
_rtld_error("Both -b and -f specified");
@ -5988,11 +5993,12 @@ print_usage(const char *argv0)
{
rtld_printf(
"Usage: %s [-h] [-b <exe>] [-f <FD>] [-p] [--] <binary> [<args>]\n"
"Usage: %s [-h] [-b <exe>] [-d] [-f <FD>] [-p] [--] <binary> [<args>]\n"
"\n"
"Options:\n"
" -h Display this help message\n"
" -b <exe> Execute <exe> instead of <binary>, arg0 is <binary>\n"
" -d Ignore lack of exec permissions for the binary\n"
" -f <FD> Execute <FD> instead of searching for <binary>\n"
" -p Search in PATH for named binary\n"
" -u Ignore LD_ environment variables\n"