zaphkito/segatools
1
0
Fork 0
forked from TeamTofuShop/segatools
Code Pull Requests Activity

Simplify DLL hook mechanism

Browse Source 
This change deletes the GetProcAddress hook and exports symbols
corresponding to the hooked functions from each hook DLL instead;
we stop at redirecting LoadLibrary/GetModuleHandle calls to the
hook DLL. This simplified approach has less hidden magic going on
behind the scenes and is more readily composable (i.e. a hook DLL
can export redirect symbols for more than one dynamically-loaded
DLL).
This commit is contained in:
Tau
2021-05-22 12:29:39 -04:00
parent b4cd868f85
commit 45e2416702
11 changed files with 84 additions and 126 deletions
Download Patch File Download Diff File Expand all files Collapse all files

118
hooklib/dll.c
View File

@ -15,8 +15,6 @@
struct dll_hook_reg {
const wchar_t *name;
HMODULE redir_mod;
const struct hook_symbol *syms;
size_t nsyms;
};
/* Helper functions */
@ -26,6 +24,7 @@ static HMODULE dll_hook_search_dll(const wchar_t *name);
/* Hook functions */
static BOOL WINAPI hook_FreeLibrary(HMODULE mod);
static HMODULE WINAPI hook_GetModuleHandleA(const char *name);
static HMODULE WINAPI hook_GetModuleHandleW(const wchar_t *name);
static HMODULE WINAPI hook_LoadLibraryA(const char *name);
@ -34,6 +33,7 @@ static void * WINAPI hook_GetProcAddress(HMODULE mod, const char *name);
/* Link pointers */
static BOOL (WINAPI *next_FreeLibrary)(HMODULE mod);
static HMODULE (WINAPI *next_GetModuleHandleA)(const char *name);
static HMODULE (WINAPI *next_GetModuleHandleW)(const wchar_t *name);
static HMODULE (WINAPI *next_LoadLibraryA)(const char *name);
@ -42,6 +42,10 @@ static void * (WINAPI *next_GetProcAddress)(HMODULE mod, const char *name);
static const struct hook_symbol dll_loader_syms[] = {
{
.name = "FreeLibrary",
.patch = hook_FreeLibrary,
.link = (void **) &next_FreeLibrary,
}, {
.name = "GetModuleHandleA",
.patch = hook_GetModuleHandleA,
.link = (void **) &next_GetModuleHandleA,
@ -57,10 +61,6 @@ static const struct hook_symbol dll_loader_syms[] = {
.name = "LoadLibraryW",
.patch = hook_LoadLibraryW,
.link = (void **) &next_LoadLibraryW,
}, {
.name = "GetProcAddress",
.patch = hook_GetProcAddress,
.link = (void **) &next_GetProcAddress,
}
};
@ -71,16 +71,13 @@ static size_t dll_hook_count;
HRESULT dll_hook_push(
HMODULE redir_mod,
const wchar_t *name,
const struct hook_symbol *syms,
size_t nsyms)
const wchar_t *name)
{
struct dll_hook_reg *new_item;
struct dll_hook_reg *new_mem;
HRESULT hr;
assert(name != NULL);
assert(syms != NULL);
dll_hook_init();
@ -99,8 +96,6 @@ HRESULT dll_hook_push(
new_item = &new_mem[dll_hook_count];
new_item->name = name;
new_item->redir_mod = redir_mod;
new_item->syms = syms;
new_item->nsyms = nsyms;
dll_hook_list = new_mem;
dll_hook_count++;
@ -167,6 +162,39 @@ static HMODULE dll_hook_search_dll(const wchar_t *name)
return result;
}
static BOOL WINAPI hook_FreeLibrary(HMODULE mod)
{
bool match;
size_t i;
match = false;
EnterCriticalSection(&dll_hook_lock);
for (i = 0 ; i < dll_hook_count ; i++) {
if (mod == dll_hook_list[i].redir_mod) {
match = true;
break;
}
}
LeaveCriticalSection(&dll_hook_lock);
if (match) {
/* Block attempts to unload redirected modules, since this could cause
a hook DLL to unexpectedly vanish and crash the whole application.
Reference counting might be another solution, although it is
possible that a buggy application might cause a hook DLL unload in
that case. */
SetLastError(ERROR_SUCCESS);
return TRUE;
}
return next_FreeLibrary(mod);
}
static HMODULE WINAPI hook_GetModuleHandleA(const char *name)
{
HMODULE result;
@ -262,69 +290,3 @@ static HMODULE WINAPI hook_LoadLibraryW(const wchar_t *name)
}
/* TODO LoadLibraryExA, LoadLibraryExW */
static void * WINAPI hook_GetProcAddress(HMODULE mod, const char *name)
{
const struct hook_symbol *syms;
uintptr_t ordinal;
size_t nsyms;
size_t i;
if (name == NULL) {
SetLastError(ERROR_INVALID_PARAMETER);
return NULL;
}
syms = NULL;
nsyms = 0;
EnterCriticalSection(&dll_hook_lock);
for (i = 0 ; i < dll_hook_count ; i++) {
if (dll_hook_list[i].redir_mod == mod) {
syms = dll_hook_list[i].syms;
nsyms = dll_hook_list[i].nsyms;
break;
}
}
LeaveCriticalSection(&dll_hook_lock);
if (syms == NULL) {
return next_GetProcAddress(mod, name);
}
ordinal = (uintptr_t) name;
if (ordinal > 0xFFFF) {
/* Import by name */
for (i = 0 ; i < nsyms ; i++) {
if (strcmp(name, syms[i].name) == 0) {
break;
}
}
} else {
/* Import by ordinal (and name != NULL so ordinal != 0) */
for (i = 0 ; i < nsyms ; i++) {
if (ordinal == syms[i].ordinal) {
break;
}
}
}
if (i < nsyms) {
SetLastError(ERROR_SUCCESS);
return syms[i].patch;
} else {
/* GetProcAddress sets this error on failure, although of course MSDN
does not see fit to document the exact error code. */
SetLastError(ERROR_PROC_NOT_FOUND);
return NULL;
}
}