diff options
Diffstat (limited to 'winsup/cygwin/hookapi.cc')
| -rw-r--r-- | winsup/cygwin/hookapi.cc | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/winsup/cygwin/hookapi.cc b/winsup/cygwin/hookapi.cc new file mode 100644 index 000000000..09c70c24b --- /dev/null +++ b/winsup/cygwin/hookapi.cc @@ -0,0 +1,218 @@ +#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 = NULL; + + if (PIMAGE_DOS_HEADER(hModule) ->e_magic != IMAGE_DOS_SIGNATURE) + /* nothing */; + else + { + pNTHeader = PIMAGE_NT_HEADERS (PBYTE (hModule) + + PIMAGE_DOS_HEADER (hModule) ->e_lfanew); + if (pNTHeader->Signature != IMAGE_NT_SIGNATURE) + pNTHeader = NULL; + } + + return pNTHeader; +} + +void * +putmem (PIMAGE_THUNK_DATA pi, const void *hookfn) +{ + + DWORD flOldProtect, flNewProtect, flDontCare; + MEMORY_BASIC_INFORMATION mbi; + + /* Get the current protection attributes */ + VirtualQuery (pi, &mbi, sizeof (mbi)); + + /* Remove ReadOnly and ExecuteRead attributes, add on ReadWrite flag */ + flNewProtect = mbi.Protect; + flNewProtect &= ~(PAGE_READONLY | PAGE_EXECUTE_READ); + flNewProtect |= PAGE_READWRITE; + + if (!VirtualProtect (pi, sizeof (PVOID), flNewProtect, &flOldProtect) ) + return NULL; + + void *origfn = (void *) pi->u1.Function; + pi->u1.Function = (DWORD) hookfn; + + (void) VirtualProtect (pi, sizeof (PVOID), flOldProtect, &flDontCare); + 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_cygwin (const char *name, const void *fn) +{ + HMODULE hm = GetModuleHandle (NULL); + PIMAGE_NT_HEADERS pExeNTHdr = PEHeaderFromHModule (hm); + + if (!pExeNTHdr) + return false; + + DWORD importRVA = pExeNTHdr->OptionalHeader.DataDirectory + [IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress; + if (!importRVA) + return false; + + // Convert imports RVA to a usable pointer + PIMAGE_IMPORT_DESCRIPTOR pdfirst = rva (PIMAGE_IMPORT_DESCRIPTOR, hm, importRVA); + + function_hook fh; + fh.origfn = NULL; + fh.hookfn = fn; + char *buf = (char *) alloca (strlen (name) + strlen ("64") + sizeof ("_")); + int i = -1; + while (!fh.origfn && (fh.name = makename (name, buf, i, 1))) + { + // Iterate through each import descriptor, and redirect if appropriate + for (PIMAGE_IMPORT_DESCRIPTOR pd = pdfirst; pd->FirstThunk; pd++) + { + PSTR modname = rva (PSTR, hm, pd->Name); + if (strcasematch (modname, "cygwin1.dll")) + RedirectIAT (fh, pd, hm); + } + } + + 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); +} |