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#include "winsup.h"
#include "cygerrno.h"
#include "security.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "cygheap.h"
#include <stdlib.h>
#include <imagehlp.h>
#include <alloca.h>
#define rva(coerce, base, addr) (coerce) ((char *) (base) + (addr))
#define rvacyg(coerce, addr) rva (coerce, cygwin_hmodule, addr)
struct function_hook
{
const char *name; // Function name, e.g. "DirectDrawCreateEx".
const void *hookfn; // Address of your function.
void *origfn; // Stored by HookAPICalls, the address of the original function.
};
/* Given an HMODULE, returns a pointer to the PE header */
static PIMAGE_NT_HEADERS
PEHeaderFromHModule (HMODULE hModule)
{
PIMAGE_NT_HEADERS pNTHeader;
if (PIMAGE_DOS_HEADER(hModule) ->e_magic != IMAGE_DOS_SIGNATURE)
pNTHeader = NULL;
else
{
pNTHeader = PIMAGE_NT_HEADERS (PBYTE (hModule)
+ PIMAGE_DOS_HEADER (hModule) ->e_lfanew);
if (pNTHeader->Signature != IMAGE_NT_SIGNATURE)
pNTHeader = NULL;
}
return pNTHeader;
}
long
rvadelta (PIMAGE_NT_HEADERS pnt, DWORD import_rva)
{
PIMAGE_SECTION_HEADER section = (PIMAGE_SECTION_HEADER) (pnt + 1);
for (int i = 0; i < pnt->FileHeader.NumberOfSections; i++)
if (section[i].VirtualAddress <= import_rva
&& (section[i].VirtualAddress + section[i].Misc.VirtualSize) >= import_rva)
// if (strncasematch ((char *) section[i].Name, ".idata", IMAGE_SIZEOF_SHORT_NAME))
return section[i].VirtualAddress - section[i].PointerToRawData;
return -1;
}
void *
putmem (PIMAGE_THUNK_DATA pi, const void *hookfn)
{
DWORD ofl;
if (!VirtualProtect (pi, sizeof (PVOID), PAGE_READWRITE, &ofl) )
return NULL;
void *origfn = (void *) pi->u1.Function;
pi->u1.Function = (DWORD) hookfn;
VirtualProtect (pi, sizeof (PVOID), ofl, &ofl);
return origfn;
}
/* Builds stubs for and redirects the IAT for one DLL (pImportDesc) */
static bool
RedirectIAT (function_hook& fh, PIMAGE_IMPORT_DESCRIPTOR pImportDesc,
HMODULE hm)
{
// If no import names table, we can't redirect this, so bail
if (pImportDesc->OriginalFirstThunk == 0)
return false;
/* import address table */
PIMAGE_THUNK_DATA pt = rva (PIMAGE_THUNK_DATA, hm, pImportDesc->FirstThunk);
/* import names table */
PIMAGE_THUNK_DATA pn = rva (PIMAGE_THUNK_DATA, hm, pImportDesc->OriginalFirstThunk);
/* Scan through the IAT, completing the stubs and redirecting the IAT
entries to point to the stubs. */
for (PIMAGE_THUNK_DATA pi = pt; pn->u1.Ordinal; pi++, pn++)
{
if (IMAGE_SNAP_BY_ORDINAL (pn->u1.Ordinal) )
continue;
/* import by name */
PIMAGE_IMPORT_BY_NAME pimp = rva (PIMAGE_IMPORT_BY_NAME, hm, pn->u1.AddressOfData);
if (strcmp (fh.name, (char *) pimp->Name) == 0)
{
fh.origfn = putmem (pi, fh.hookfn);
if (!fh.origfn)
return false;
hook_chain *hc;
for (hc = &cygheap->hooks; hc->next; hc = hc->next)
continue;
hc->next = (hook_chain *) cmalloc (HEAP_1_HOOK, sizeof (hook_chain));
hc->next->loc = (void **) pi;
hc->next->func = fh.hookfn;
hc->next->next = NULL;
break;
}
}
return true;
}
void
get_export (function_hook& fh)
{
extern HMODULE cygwin_hmodule;
PIMAGE_DOS_HEADER pdh = (PIMAGE_DOS_HEADER) cygwin_hmodule;
if (pdh->e_magic != IMAGE_DOS_SIGNATURE)
return;
PIMAGE_NT_HEADERS pnt = (PIMAGE_NT_HEADERS) ((char *) pdh + pdh->e_lfanew);
if (pnt->Signature != IMAGE_NT_SIGNATURE || pnt->FileHeader.SizeOfOptionalHeader == 0)
return;
PIMAGE_EXPORT_DIRECTORY pexp =
rvacyg (PIMAGE_EXPORT_DIRECTORY,
pnt->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress);
if (!pexp)
return;
PDWORD pfuncs = rvacyg (PDWORD, pexp->AddressOfFunctions);
PDWORD pnames = rvacyg (PDWORD, pexp->AddressOfNames);
for (DWORD i = 0; i < pexp->NumberOfNames; i++)
if (strcmp (fh.name, rvacyg (char *, pnames[i])) == 0)
{
fh.origfn = rvacyg (void *, pfuncs[i]);
break;
}
}
static const char *
makename (const char *name, char *&buf, int& i, int inc)
{
i += inc;
static const char *testers[] = {"NOTUSED", "64", "32"};
if (i < 0 || i >= (int) (sizeof (testers) / sizeof (testers[0])))
return NULL;
if (i)
{
__small_sprintf (buf, "_%s%s", name, testers[i]);
name = buf;
}
return name;
}
// Top level routine to find the EXE's imports, and redirect them
void *
hook_or_detect_cygwin (const char *name, const void *fn)
{
HMODULE hm = fn ? GetModuleHandle (NULL) : (HMODULE) name;
PIMAGE_NT_HEADERS pExeNTHdr = PEHeaderFromHModule (hm);
if (!pExeNTHdr)
return false;
DWORD importRVA = pExeNTHdr->OptionalHeader.DataDirectory
[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress;
if (!importRVA)
return false;
long delta = fn ? 0 : rvadelta (pExeNTHdr, importRVA);
if (delta < 0)
return false;
// Convert imports RVA to a usable pointer
PIMAGE_IMPORT_DESCRIPTOR pdfirst = rva (PIMAGE_IMPORT_DESCRIPTOR, hm, importRVA - delta);
function_hook fh;
fh.origfn = NULL;
fh.hookfn = fn;
char *buf = (char *) alloca (strlen (name) + sizeof ("_64"));
int i;
// Iterate through each import descriptor, and redirect if appropriate
for (PIMAGE_IMPORT_DESCRIPTOR pd = pdfirst; pd->FirstThunk; pd++)
{
if (!strcasematch (rva (PSTR, hm, pd->Name - delta), "cygwin1.dll"))
continue;
if (!fn)
return (void *) "found it"; // just checking if executable used cygwin1.dll
i = -1;
while (!fh.origfn && (fh.name = makename (name, buf, i, 1)))
RedirectIAT (fh, pd, hm);
if (fh.origfn)
break;
}
while (!fh.origfn && (fh.name = makename (name, buf, i, -1)))
get_export (fh);
return fh.origfn;
}
void
ld_preload ()
{
char *p = getenv ("LD_PRELOAD");
if (!p)
return;
char *s = (char *) alloca (strlen (p) + 1);
strcpy (s, p);
char *here = NULL;
for (p = strtok_r (s, ":\t\n", &here); p; p = strtok_r (NULL, ":\t\n", &here))
{
path_conv lib (p);
if (!LoadLibrary (lib))
{
__seterrno ();
api_fatal ("error while loading shared libraries: %s: "
"cannot open shared object file: %s", p,
strerror (get_errno ()));
}
}
}
void
fixup_hooks_after_fork ()
{
for (hook_chain *hc = &cygheap->hooks; (hc = hc->next); )
putmem ((PIMAGE_THUNK_DATA) hc->loc, hc->func);
}
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