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566 lines (470 loc) · 15.9 KB
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#include <Python.h>
#include <windows.h>
#include <mscat.h>
#include <softpub.h>
#include <string>
#include <vector>
#include "helpers.h"
extern "C" {
PyObject *verify_trust(PyObject *, PyObject *args, PyObject *kwargs);
}
static std::vector<BYTE> nameinfo_from_blob(CERT_NAME_BLOB *name)
{
DWORD cb = 0;
if (!CryptDecodeObjectEx(
X509_ASN_ENCODING,
X509_NAME,
name->pbData,
name->cbData,
0,
nullptr,
nullptr,
&cb
) || cb == 0) {
return {};
}
std::vector<BYTE> buf(cb);
if (!CryptDecodeObjectEx(
X509_ASN_ENCODING,
X509_NAME,
name->pbData,
name->cbData,
0,
nullptr,
buf.data(),
&cb
)) {
return {};
}
buf.resize(cb);
return buf;
}
static std::vector<BYTE> nameinfo_from_name(const wchar_t *name)
{
DWORD encoded_size = 0;
if (!CertStrToNameW(X509_ASN_ENCODING, name, CERT_X500_NAME_STR,
nullptr, nullptr, &encoded_size, nullptr)) {
return {};
}
std::vector<BYTE> encoded(encoded_size);
if (!CertStrToNameW(X509_ASN_ENCODING, name, CERT_X500_NAME_STR,
nullptr, encoded.data(), &encoded_size, nullptr)) {
return {};
}
CERT_NAME_BLOB expected_name = {};
expected_name.cbData = encoded_size;
expected_name.pbData = encoded.data();
return nameinfo_from_blob(&expected_name);
}
static std::wstring read_rdn_attr(CERT_RDN_ATTR &attr) {
DWORD cb = CertRDNValueToStrW(attr.dwValueType, &attr.Value, nullptr, 0);
if (cb > 1024) {
return {};
}
std::wstring v(cb, L'\0');
v.resize(CertRDNValueToStrW(attr.dwValueType, &attr.Value, v.data(), cb));
return v;
}
static bool cert_subject_matches(PCCERT_CONTEXT pCert, const wchar_t *expected)
{
if (!pCert || !expected || !*expected) {
return true;
}
auto expected_info_buf = nameinfo_from_name(expected);
auto actual_info_buf = nameinfo_from_blob(&pCert->pCertInfo->Subject);
if (expected_info_buf.empty() || actual_info_buf.empty()) {
return false;
}
const CERT_NAME_INFO *expected_info =
reinterpret_cast<const CERT_NAME_INFO *>(expected_info_buf.data());
const CERT_NAME_INFO *actual_info =
reinterpret_cast<const CERT_NAME_INFO *>(actual_info_buf.data());
// Turn constraints into a vector of (oid, value) pairs.
// Each pair must be present in the actual name.
std::vector<std::pair<std::string, std::wstring>> expected_pairs;
expected_pairs.reserve(8);
for (DWORD i = 0; i < expected_info->cRDN; ++i) {
CERT_RDN &rdn = expected_info->rgRDN[i];
for (DWORD j = 0; j < rdn.cRDNAttr; ++j) {
CERT_RDN_ATTR &attr = rdn.rgRDNAttr[j];
if (!attr.pszObjId) {
return false;
}
auto v = read_rdn_attr(attr);
if (!v.empty()) {
expected_pairs.emplace_back(std::string(attr.pszObjId), std::move(v));
}
}
}
// For each expected (OID, value), find an identical (OID, value) in the actual name.
for (const auto &need : expected_pairs) {
const std::string &oid = need.first;
const std::wstring &expect = need.second;
bool found = false;
for (DWORD i = 0; i < actual_info->cRDN && !found; ++i) {
CERT_RDN &rdn = actual_info->rgRDN[i];
for (DWORD j = 0; j < rdn.cRDNAttr; ++j) {
CERT_RDN_ATTR &attr = rdn.rgRDNAttr[j];
if (!attr.pszObjId || oid != attr.pszObjId) {
continue;
}
auto v = read_rdn_attr(attr);
if (CompareStringOrdinal(v.c_str(), -1, expect.c_str(), -1, TRUE) == CSTR_EQUAL) {
found = true;
break;
}
}
}
if (!found) {
return false;
}
}
return true;
}
static bool cert_has_explicit_eku(PCCERT_CONTEXT pCert, const wchar_t *eku_in) {
// No cert or no EKU passes this check
if (!pCert || !eku_in || !*eku_in) {
return true;
}
std::string expect_oid;
int n = WideCharToMultiByte(CP_UTF8, 0, eku_in, -1, NULL, 0, NULL, NULL);
if (n <= 0) {
return false;
}
expect_oid.resize((size_t)n - 1);
WideCharToMultiByte(CP_UTF8, 0, eku_in, -1, expect_oid.data(), n, NULL, NULL);
DWORD cbUsage = 0;
SetLastError(0);
if (!CertGetEnhancedKeyUsage(pCert, 0, NULL, &cbUsage) || !cbUsage) {
// CRYPT_E_NOT_FOUND => "all uses" => NOT acceptable when checking for a specific EKU
return false;
}
std::vector<BYTE> buf(cbUsage);
PCERT_ENHKEY_USAGE pUsage = (PCERT_ENHKEY_USAGE)buf.data();
SetLastError(0);
if (!CertGetEnhancedKeyUsage(pCert, 0, pUsage, &cbUsage)) {
// Failed to get the info means we fail the match
return false;
}
for (DWORD i = 0; i < pUsage->cUsageIdentifier; ++i) {
const char *oid = pUsage->rgpszUsageIdentifier[i];
if (oid && _stricmp(oid, expect_oid.c_str()) == 0) return true;
}
return false;
}
static void bytes_to_member_tag_hex(const BYTE *pb, DWORD cb, std::wstring &out) {
out.clear();
out.resize((size_t)cb * 2);
for (DWORD i = 0; i < cb; ++i) {
wchar_t tmp[3] = {0};
swprintf(tmp, 3, L"%02X", (unsigned)pb[i]);
out[(size_t)i * 2 + 0] = tmp[0];
out[(size_t)i * 2 + 1] = tmp[1];
}
}
static DWORD file_hash_in_catalog(const wchar_t *file_path, const wchar_t *cat_path) {
DWORD err = ERROR_NOT_FOUND;
HANDLE hFile = INVALID_HANDLE_VALUE;
HMODULE hWintrust = NULL;
HCATADMIN hCatAdmin = NULL;
HANDLE hCat = NULL;
BYTE *pbHash = NULL;
DWORD cbHash = 0;
typedef BOOL (WINAPI *pfnCalcHash2)(HCATADMIN, HANDLE, DWORD*, BYTE*, DWORD);
pfnCalcHash2 CalcHash2 = NULL;
hFile = CreateFileW(file_path, GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile == INVALID_HANDLE_VALUE) {
goto error;
}
hWintrust = LoadLibraryExW(L"wintrust.dll", NULL, LOAD_LIBRARY_SEARCH_SYSTEM32);
if (!hWintrust) {
goto error;
}
CalcHash2 = (pfnCalcHash2)GetProcAddress(hWintrust, "CryptCATAdminCalcHashFromFileHandle2");
if (!CalcHash2) {
goto error;
}
// Try SHA256 then SHA1 (common cases). If both fail, treat as not found.
static const wchar_t *algs[] = { L"SHA256", L"SHA1" };
for (auto alg : algs) {
if (hCatAdmin) {
CryptCATAdminReleaseContext(hCatAdmin, 0);
hCatAdmin = NULL;
}
cbHash = 0;
// alg name needs to be mutable for silly reasons. Fine, we'll play along
std::wstring alg_str = alg;
alg_str.push_back(L'\0');
if (!CryptCATAdminAcquireContext2(&hCatAdmin, NULL, alg_str.data(), NULL, 0) || !hCatAdmin) {
continue;
}
// Rewind file (previous hash has read it)
(void)SetFilePointer(hFile, 0, NULL, FILE_BEGIN);
DWORD tmp = 0;
SetLastError(0);
if (!CalcHash2(hCatAdmin, hFile, &tmp, NULL, 0)) {
DWORD gle = GetLastError();
if (gle != ERROR_INSUFFICIENT_BUFFER) {
// Try next algorithm
continue;
}
}
cbHash = tmp;
if (cbHash == 0) {
continue;
}
if (pbHash) {
LocalFree(pbHash);
pbHash = NULL;
}
pbHash = (BYTE*)LocalAlloc(LPTR, cbHash);
if (!pbHash) {
err = ERROR_OUTOFMEMORY;
goto cleanup;
}
DWORD cbOut = cbHash;
SetLastError(0);
if (!CalcHash2(hCatAdmin, hFile, &cbOut, pbHash, 0) || cbOut == 0) {
// Try next algorithm
continue;
}
cbHash = cbOut;
std::wstring memberTag;
bytes_to_member_tag_hex(pbHash, cbHash, memberTag);
if (hCat) {
CryptCATClose(hCat);
hCat = NULL;
}
// Catalog path also needs to be writable...
std::wstring cat_path_str = cat_path;
cat_path_str.push_back(L'\0');
hCat = CryptCATOpen(cat_path_str.data(), CRYPTCAT_OPEN_EXISTING, 0, 0, 0);
if (!hCat) {
goto error;
}
// Check that member hash exists in this catalog
memberTag.push_back(L'\0');
CRYPTCATMEMBER *pMember = CryptCATGetMemberInfo(hCat, memberTag.data());
if (pMember) {
// Success! Clear the error code and let's go home
err = 0;
break;
}
}
cleanup:
if (pbHash) LocalFree(pbHash);
if (hCat) CryptCATClose(hCat);
if (hCatAdmin) CryptCATAdminReleaseContext(hCatAdmin, 0);
if (hWintrust) FreeLibrary(hWintrust);
if (hFile != INVALID_HANDLE_VALUE) CloseHandle(hFile);
return err;
error:
err = GetLastError();
goto cleanup;
}
static DWORD extract_certs(
const wchar_t *signed_path,
PCCERT_CONTEXT &leaf_out,
PCCERT_CONTEXT &root_out
) {
leaf_out = NULL;
root_out = NULL;
HCERTSTORE hStore = NULL;
HCRYPTMSG hMsg = NULL;
PCCERT_CONTEXT pLeaf = NULL;
PCCERT_CONTEXT pRoot = NULL;
PCCERT_CONTEXT pRootCtx = NULL;
PCERT_SIMPLE_CHAIN pSimple = NULL;
PCCERT_CHAIN_CONTEXT pChain = NULL;
PCMSG_SIGNER_INFO pSignerInfo = NULL;
DWORD cbSignerInfo = 0;
DWORD dwEncoding = 0, dwContentType = 0, dwFormatType = 0;
DWORD err = 0;
if (!CryptQueryObject(
CERT_QUERY_OBJECT_FILE,
signed_path,
CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED,
CERT_QUERY_FORMAT_FLAG_BINARY,
0,
&dwEncoding, &dwContentType, &dwFormatType,
&hStore, &hMsg, NULL
)) {
err = GetLastError();
if (!err) {
err = ERROR_INVALID_DATA;
}
goto cleanup;
}
if (!CryptMsgGetParam(hMsg, CMSG_SIGNER_INFO_PARAM, 0, NULL, &cbSignerInfo) || !cbSignerInfo) {
err = GetLastError();
if (!err) err = ERROR_INVALID_DATA;
goto cleanup;
}
pSignerInfo = (PCMSG_SIGNER_INFO)LocalAlloc(LPTR, cbSignerInfo);
if (!pSignerInfo) {
err = ERROR_OUTOFMEMORY;
goto cleanup;
}
if (!CryptMsgGetParam(hMsg, CMSG_SIGNER_INFO_PARAM, 0, pSignerInfo, &cbSignerInfo)) {
err = GetLastError();
LocalFree(pSignerInfo);
if (!err) err = ERROR_INVALID_DATA;
goto cleanup;
}
CERT_INFO ci;
memset(&ci, 0, sizeof(ci));
ci.Issuer = pSignerInfo->Issuer;
ci.SerialNumber = pSignerInfo->SerialNumber;
pLeaf = CertFindCertificateInStore(
hStore,
X509_ASN_ENCODING | PKCS_7_ASN_ENCODING,
0,
CERT_FIND_SUBJECT_CERT,
&ci,
NULL
);
LocalFree(pSignerInfo);
if (!pLeaf) {
err = GetLastError();
if (!err) err = ERROR_INVALID_DATA;
goto cleanup;
}
CERT_CHAIN_PARA chainPara;
memset(&chainPara, 0, sizeof(chainPara));
chainPara.cbSize = sizeof(chainPara);
if (!CertGetCertificateChain(
NULL,
pLeaf,
NULL,
pLeaf->hCertStore,
&chainPara,
0,
NULL,
&pChain
) || !pChain || pChain->cChain == 0) {
err = GetLastError();
if (!err) err = ERROR_INVALID_DATA;
goto cleanup;
}
pSimple = pChain->rgpChain[0];
if (!pSimple || pSimple->cElement == 0) {
err = ERROR_INVALID_DATA;
goto cleanup;
}
pRootCtx = pSimple->rgpElement[pSimple->cElement - 1]->pCertContext;
if (!pRootCtx) {
err = ERROR_INVALID_DATA;
goto cleanup;
}
pRoot = CertDuplicateCertificateContext(pRootCtx);
if (!pRoot) {
err = ERROR_OUTOFMEMORY;
goto cleanup;
}
leaf_out = pLeaf;
root_out = pRoot;
pLeaf = NULL; // transferred
pRoot = NULL; // transferred
cleanup:
if (pChain) CertFreeCertificateChain(pChain);
if (pRoot) CertFreeCertificateContext(pRoot);
if (pLeaf) CertFreeCertificateContext(pLeaf);
if (hMsg) CryptMsgClose(hMsg);
if (hStore) CertCloseStore(hStore, 0);
// Ensure outputs are NULL on failure
if (err != 0) {
if (leaf_out) { CertFreeCertificateContext(leaf_out); leaf_out = NULL; }
if (root_out) { CertFreeCertificateContext(root_out); root_out = NULL; }
}
return err;
}
PyObject *verify_trust(PyObject *, PyObject *args, PyObject *kwargs) {
static const char * keywords[] = {"path", "cat_path", "root_subject", "leaf_subject", "leaf_eku", NULL};
wchar_t *path = NULL;
wchar_t *cat_path = NULL;
wchar_t *root_subject = NULL;
wchar_t *leaf_subject = NULL;
wchar_t *leaf_eku = NULL;
if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O&O&O&O&O&:verify_trust", keywords,
as_utf16, &path, as_utf16, &cat_path,
as_utf16, &root_subject, as_utf16, &leaf_subject, as_utf16, &leaf_eku
)) {
return NULL;
}
PyObject *r = Py_NewRef(Py_None);
PCCERT_CONTEXT pLeafCert = NULL;
PCCERT_CONTEXT pRootCert = NULL;
DWORD err = 0;
// 1) Validate catalog file signature.
{
GUID policy = WINTRUST_ACTION_GENERIC_VERIFY_V2;
WINTRUST_FILE_INFO fi;
memset(&fi, 0, sizeof(fi));
fi.cbStruct = sizeof(fi);
fi.pcwszFilePath = cat_path;
fi.hFile = NULL;
WINTRUST_DATA wd;
memset(&wd, 0, sizeof(wd));
wd.cbStruct = sizeof(wd);
wd.dwUnionChoice = WTD_CHOICE_FILE;
wd.pFile = &fi;
wd.dwUIChoice = WTD_UI_NONE;
// Do a real validation pass (including revocation).
wd.fdwRevocationChecks = WTD_REVOKE_WHOLECHAIN;
wd.dwStateAction = WTD_STATEACTION_VERIFY;
wd.dwUIChoice = WTD_UI_NONE;
wd.dwProvFlags = WTD_USE_DEFAULT_OSVER_CHECK;
LONG st = WinVerifyTrust(NULL, &policy, &wd);
wd.dwStateAction = WTD_STATEACTION_CLOSE;
(void)WinVerifyTrust(NULL, &policy, &wd);
if (st != ERROR_SUCCESS) {
err_SetFromWindowsErrWithMessage(st, "WinVerifyTrust failed for catalog: 0x%08lX", NULL);
Py_CLEAR(r);
goto done;
}
}
// 2) Extract signer leaf and chain root certs from the signed catalog
err = extract_certs(cat_path, pLeafCert, pRootCert);
if (err) {
err_SetFromWindowsErrWithMessage(err, "Failed to extract certificates from catalog signature", NULL);
Py_CLEAR(r);
goto done;
}
// 3) Optional subject checks
if (!cert_subject_matches(pRootCert, root_subject)) {
// Strictly speaking ValueError makes more sense here, but we're already
// going to be catching OSError so may as well be consistent.
PyErr_SetString(PyExc_OSError, "Catalog root certificate subject mismatch");
Py_CLEAR(r);
goto done;
}
if (!cert_subject_matches(pLeafCert, leaf_subject)) {
PyErr_SetString(PyExc_OSError, "Catalog leaf certificate subject mismatch");
Py_CLEAR(r);
goto done;
}
// 4) Optional EKU check (strict: if specified, must be explicitly present; otherwise skip entirely)
if (!cert_has_explicit_eku(pLeafCert, leaf_eku)) {
PyErr_SetString(PyExc_OSError, "Leaf certificate does not explicitly include required EKU");
Py_CLEAR(r);
goto done;
}
// 5) Ensure the target file’s catalog hash is present in the provided catalog file.
err = file_hash_in_catalog(path, cat_path);
if (err) {
err_SetFromWindowsErrWithMessage(err, "File hash not present in the specified catalog", NULL);
Py_CLEAR(r);
goto done;
}
done:
if (pRootCert) CertFreeCertificateContext(pRootCert);
if (pLeafCert) CertFreeCertificateContext(pLeafCert);
PyMem_Free(path);
PyMem_Free(cat_path);
PyMem_Free(root_subject);
PyMem_Free(leaf_subject);
PyMem_Free(leaf_eku);
return r;
}