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Allow ASLR to be disabled on Windows

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On Windows, it is possible to disable ASLR when creating a process.
This patch adds code to do this, and hooks it up to gdb's existing
disable-randomization feature.  Because the Windows documentation
cautions that this isn't available on all versions of Windows, the
CreateProcess wrapper function is updated to make the attempt, and
then fall back to the current approach if it fails.
This commit is contained in:
Tom Tromey 2021-09-08 08:20:29 -06:00
parent 8fea1a81c7
commit bcb9251f02
6 changed files with 164 additions and 4 deletions
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2
gdb/NEWS
View File

@ -71,6 +71,8 @@ maintenance info line-table
Python 2. From GDB 13, it will only be possible to build GDB itself
with Python 3 support.
* The disable-randomization setting now works on Windows.
* Improved C++ template support
GDB now treats functions/types involving C++ templates like it does function

115
gdb/nat/windows-nat.c
View File

@ -69,6 +69,10 @@ GenerateConsoleCtrlEvent_ftype *GenerateConsoleCtrlEvent;
typedef HRESULT WINAPI (GetThreadDescription_ftype) (HANDLE, PWSTR *);
static GetThreadDescription_ftype *GetThreadDescription;
InitializeProcThreadAttributeList_ftype *InitializeProcThreadAttributeList;
UpdateProcThreadAttribute_ftype *UpdateProcThreadAttribute;
DeleteProcThreadAttributeList_ftype *DeleteProcThreadAttributeList;
/* Note that 'debug_events' must be locally defined in the relevant
functions. */
#define DEBUG_EVENTS(fmt, ...) \
@ -741,15 +745,104 @@ wait_for_debug_event (DEBUG_EVENT *event, DWORD timeout)
return result;
}
/* Helper template for the CreateProcess wrappers. */
/* Flags to pass to UpdateProcThreadAttribute. */
#define relocate_aslr_flags ((0x2 << 8) | (0x2 << 16))
/* Attribute to pass to UpdateProcThreadAttribute. */
#define mitigation_policy 0x00020007
/* Pick one of the symbols as a sentinel. */
#ifdef PROCESS_CREATION_MITIGATION_POLICY_FORCE_RELOCATE_IMAGES_ALWAYS_OFF
static_assert ((PROCESS_CREATION_MITIGATION_POLICY_FORCE_RELOCATE_IMAGES_ALWAYS_OFF
| PROCESS_CREATION_MITIGATION_POLICY_BOTTOM_UP_ASLR_ALWAYS_OFF)
== relocate_aslr_flags,
"check that ASLR flag values are correct");
static_assert (PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY == mitigation_policy,
"check that mitigation policy value is correct");
#endif
/* Helper template for the CreateProcess wrappers.
FUNC is the type of the underlying CreateProcess call. CHAR is the
character type to use, and INFO is the "startupinfo" type to use.
DO_CREATE_PROCESS is the underlying CreateProcess function to use;
the remaining arguments are passed to it. */
template<typename FUNC, typename CHAR, typename INFO>
BOOL
create_process_wrapper (FUNC *do_create_process, const CHAR *image,
CHAR *command_line, DWORD flags,
void *environment, const CHAR *cur_dir,
bool no_randomization,
INFO *startup_info,
PROCESS_INFORMATION *process_info)
{
if (no_randomization && disable_randomization_available ())
{
static bool tried_and_failed;
if (!tried_and_failed)
{
/* Windows 8 is required for the real declaration, but to
allow building on earlier versions of Windows, we declare
the type locally. */
struct gdb_extended_info
{
INFO StartupInfo;
gdb_lpproc_thread_attribute_list lpAttributeList;
};
gdb_extended_info info_ex {};
if (startup_info != nullptr)
info_ex.StartupInfo = *startup_info;
info_ex.StartupInfo.cb = sizeof (info_ex);
SIZE_T size = 0;
/* Ignore the result here. The documentation says the first
call always fails, by design. */
InitializeProcThreadAttributeList (nullptr, 1, 0, &size);
info_ex.lpAttributeList
= (PPROC_THREAD_ATTRIBUTE_LIST) alloca (size);
InitializeProcThreadAttributeList (info_ex.lpAttributeList,
1, 0, &size);
gdb::optional<BOOL> return_value;
DWORD attr_flags = relocate_aslr_flags;
if (!UpdateProcThreadAttribute (info_ex.lpAttributeList, 0,
mitigation_policy,
&attr_flags,
sizeof (attr_flags),
nullptr, nullptr))
tried_and_failed = true;
else
{
BOOL result = do_create_process (image, command_line,
nullptr, nullptr,
TRUE,
(flags
| EXTENDED_STARTUPINFO_PRESENT),
environment,
cur_dir,
(STARTUPINFO *) &info_ex,
process_info);
if (result)
return_value = result;
else if (GetLastError () == ERROR_INVALID_PARAMETER)
tried_and_failed = true;
else
return_value = FALSE;
}
DeleteProcThreadAttributeList (info_ex.lpAttributeList);
if (return_value.has_value ())
return *return_value;
}
}
return do_create_process (image,
command_line, /* command line */
nullptr, /* Security */
@ -767,11 +860,12 @@ create_process_wrapper (FUNC *do_create_process, const CHAR *image,
BOOL
create_process (const char *image, char *command_line, DWORD flags,
void *environment, const char *cur_dir,
bool no_randomization,
STARTUPINFOA *startup_info,
PROCESS_INFORMATION *process_info)
{
return create_process_wrapper (CreateProcessA, image, command_line, flags,
environment, cur_dir,
environment, cur_dir, no_randomization,
startup_info, process_info);
}
@ -782,11 +876,12 @@ create_process (const char *image, char *command_line, DWORD flags,
BOOL
create_process (const wchar_t *image, wchar_t *command_line, DWORD flags,
void *environment, const wchar_t *cur_dir,
bool no_randomization,
STARTUPINFOW *startup_info,
PROCESS_INFORMATION *process_info);
{
return create_process_wrapper (CreateProcessW, image, command_line, flags,
environment, cur_dir,
environment, cur_dir, no_randomization,
startup_info, process_info);
}
@ -826,6 +921,16 @@ bad_GetConsoleFontSize (HANDLE w, DWORD nFont)
/* See windows-nat.h. */
bool
disable_randomization_available ()
{
return (InitializeProcThreadAttributeList != nullptr
&& UpdateProcThreadAttribute != nullptr
&& DeleteProcThreadAttributeList != nullptr);
}
/* See windows-nat.h. */
bool
initialize_loadable ()
{
@ -852,6 +957,10 @@ initialize_loadable ()
#endif
GPA (hm, GenerateConsoleCtrlEvent);
GPA (hm, GetThreadDescription);
GPA (hm, InitializeProcThreadAttributeList);
GPA (hm, UpdateProcThreadAttribute);
GPA (hm, DeleteProcThreadAttributeList);
}
/* Set variables to dummy versions of these processes if the function

38
gdb/nat/windows-nat.h
View File

@ -294,17 +294,21 @@ extern BOOL continue_last_debug_event (DWORD continue_status,
extern BOOL wait_for_debug_event (DEBUG_EVENT *event, DWORD timeout);
/* Wrappers for CreateProcess. */
/* Wrappers for CreateProcess. These exist primarily so that the
"disable randomization" feature can be implemented in a single
place. */
extern BOOL create_process (const char *image, char *command_line,
DWORD flags, void *environment,
const char *cur_dir,
bool no_randomization,
STARTUPINFOA *startup_info,
PROCESS_INFORMATION *process_info);
#ifdef __CYGWIN__
extern BOOL create_process (const wchar_t *image, wchar_t *command_line,
DWORD flags, void *environment,
const wchar_t *cur_dir,
bool no_randomization,
STARTUPINFOW *startup_info,
PROCESS_INFORMATION *process_info);
#endif /* __CYGWIN__ */
@ -313,10 +317,15 @@ extern BOOL create_process (const wchar_t *image, wchar_t *command_line,
#define DebugActiveProcessStop dyn_DebugActiveProcessStop
#define DebugBreakProcess dyn_DebugBreakProcess
#define DebugSetProcessKillOnExit dyn_DebugSetProcessKillOnExit
#undef EnumProcessModules
#define EnumProcessModules dyn_EnumProcessModules
#undef EnumProcessModulesEx
#define EnumProcessModulesEx dyn_EnumProcessModulesEx
#undef GetModuleInformation
#define GetModuleInformation dyn_GetModuleInformation
#undef GetModuleFileNameExA
#define GetModuleFileNameExA dyn_GetModuleFileNameExA
#undef GetModuleFileNameExW
#define GetModuleFileNameExW dyn_GetModuleFileNameExW
#define LookupPrivilegeValueA dyn_LookupPrivilegeValueA
#define OpenProcessToken dyn_OpenProcessToken
@ -327,6 +336,9 @@ extern BOOL create_process (const wchar_t *image, wchar_t *command_line,
#define Wow64SetThreadContext dyn_Wow64SetThreadContext
#define Wow64GetThreadSelectorEntry dyn_Wow64GetThreadSelectorEntry
#define GenerateConsoleCtrlEvent dyn_GenerateConsoleCtrlEvent
#define InitializeProcThreadAttributeList dyn_InitializeProcThreadAttributeList
#define UpdateProcThreadAttribute dyn_UpdateProcThreadAttribute
#define DeleteProcThreadAttributeList dyn_DeleteProcThreadAttributeList
typedef BOOL WINAPI (AdjustTokenPrivileges_ftype) (HANDLE, BOOL,
PTOKEN_PRIVILEGES,
@ -397,6 +409,30 @@ extern Wow64GetThreadSelectorEntry_ftype *Wow64GetThreadSelectorEntry;
typedef BOOL WINAPI (GenerateConsoleCtrlEvent_ftype) (DWORD, DWORD);
extern GenerateConsoleCtrlEvent_ftype *GenerateConsoleCtrlEvent;
/* We use a local typedef for this type to avoid depending on
Windows 8. */
typedef void *gdb_lpproc_thread_attribute_list;
typedef BOOL WINAPI (InitializeProcThreadAttributeList_ftype)
(gdb_lpproc_thread_attribute_list lpAttributeList,
DWORD dwAttributeCount, DWORD dwFlags, PSIZE_T lpSize);
extern InitializeProcThreadAttributeList_ftype *InitializeProcThreadAttributeList;
typedef BOOL WINAPI (UpdateProcThreadAttribute_ftype)
(gdb_lpproc_thread_attribute_list lpAttributeList,
DWORD dwFlags, DWORD_PTR Attribute, PVOID lpValue, SIZE_T cbSize,
PVOID lpPreviousValue, PSIZE_T lpReturnSize);
extern UpdateProcThreadAttribute_ftype *UpdateProcThreadAttribute;
typedef void WINAPI (DeleteProcThreadAttributeList_ftype)
(gdb_lpproc_thread_attribute_list lpAttributeList);
extern DeleteProcThreadAttributeList_ftype *DeleteProcThreadAttributeList;
/* Return true if it's possible to disable randomization on this
host. */
extern bool disable_randomization_available ();
/* Load any functions which may not be available in ancient versions
of Windows. */

7
gdb/windows-nat.c
View File

@ -281,6 +281,11 @@ struct windows_nat_target final : public x86_nat_target<inf_child_target>
int get_windows_debug_event (int pid, struct target_waitstatus *ourstatus);
void do_initial_windows_stuff (DWORD pid, bool attaching);
bool supports_disable_randomization () override
{
return disable_randomization_available ();
}
};
static windows_nat_target the_windows_nat_target;
@ -2493,6 +2498,7 @@ windows_nat_target::create_inferior (const char *exec_file,
windows_init_thread_list ();
ret = create_process (args, flags, w32_env,
inferior_cwd != nullptr ? infcwd : nullptr,
disable_randomization,
&si, &pi);
if (w32_env)
/* Just free the Win32 environment, if it could be created. */
@ -2612,6 +2618,7 @@ windows_nat_target::create_inferior (const char *exec_file,
flags, /* start flags */
w32env, /* environment */
inferior_cwd, /* current directory */
disable_randomization,
&si,
&pi);
if (tty != INVALID_HANDLE_VALUE)

1
gdbserver/win32-low.cc
View File

@ -586,6 +586,7 @@ create_process (const char *program, char *args,
(inferior_cwd.empty ()
? NULL
: gdb_tilde_expand (inferior_cwd.c_str ()).c_str()),
get_client_state ().disable_randomization,
&si, /* start info */
pi); /* proc info */

5
gdbserver/win32-low.h
View File

@ -165,6 +165,11 @@ class win32_process_target : public process_stratum_target
{ return true; }
const char *pid_to_exec_file (int pid) override;
bool supports_disable_randomization () override
{
return windows_nat::disable_randomization_available ();
}
};
/* The sole Windows process. */