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Loader.so+LibELF: Do not read environment variables if AT_SECURE is set

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AT_SECURE is set in the auxiliary vector when we execute setuid/setgid
programs.
In those cases, we do not want to read environment variables that
influence the logic of the dynamic loader, as they can be controlled
by the user.
This commit is contained in:
Itamar 2021-01-09 09:51:44 +02:00 • committed by Andreas Kling
parent 20974b0772
commit a4b74cba0b
3 changed files with 22 additions and 8 deletions
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22
Libraries/LibELF/DynamicLinker.cpp
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@ -71,6 +71,9 @@ size_t g_current_tls_offset = 0;
size_t g_total_tls_size = 0;
char** g_envp = nullptr;
LibCExitFunction g_libc_exit = nullptr;
bool g_allowed_to_check_environment_variables { false };
bool g_do_breakpoint_trap_before_entry { false };
}
DynamicObject::SymbolLookupResult DynamicLinker::lookup_global_symbol(const char* symbol_name)
@ -228,15 +231,22 @@ static NonnullRefPtr<DynamicLoader> commit_elf(const String& name)
return loader;
}
void ELF::DynamicLinker::linker_main(String&& main_program_name, int main_program_fd, int argc, char** argv, char** envp)
static void read_environment_variables()
{
g_envp = envp;
bool do_breakpoint_trap_before_entry = false;
for (char** env = envp; *env; ++env) {
for (char** env = g_envp; *env; ++env) {
if (StringView { *env } == "_LOADER_BREAKPOINT=1") {
do_breakpoint_trap_before_entry = true;
g_do_breakpoint_trap_before_entry = true;
}
}
}
void ELF::DynamicLinker::linker_main(String&& main_program_name, int main_program_fd, bool is_secure, int argc, char** argv, char** envp)
{
g_envp = envp;
g_allowed_to_check_environment_variables = !is_secure;
if (g_allowed_to_check_environment_variables)
read_environment_variables();
map_library(main_program_name, main_program_fd);
map_dependencies(main_program_name);
@ -260,7 +270,7 @@ void ELF::DynamicLinker::linker_main(String&& main_program_name, int main_progra
MainFunction main_function = (MainFunction)(entry_point);
VERBOSE("jumping to main program entry point: %p\n", main_function);
if (do_breakpoint_trap_before_entry) {
if (g_do_breakpoint_trap_before_entry) {
asm("int3");
}
int rc = main_function(argc, argv, envp);