From bcb9251f029da8dcf360a4f5acfa3b4211c87bb0 Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Wed, 8 Sep 2021 08:20:29 -0600 Subject: Allow ASLR to be disabled on Windows 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. --- gdb/nat/windows-nat.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++-- gdb/nat/windows-nat.h | 38 ++++++++++++++++- 2 files changed, 149 insertions(+), 4 deletions(-) (limited to 'gdb/nat') diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c index 8048344..e52da16 100644 --- a/gdb/nat/windows-nat.c +++ b/gdb/nat/windows-nat.c @@ -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 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 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); } @@ -827,6 +922,16 @@ 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 () { bool result = true; @@ -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 diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h index d8c498e..65b789f 100644 --- a/gdb/nat/windows-nat.h +++ b/gdb/nat/windows-nat.h @@ -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. */ -- cgit v1.1