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rufus/src/pki.c

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/*
* Rufus: The Reliable USB Formatting Utility
* PKI functions (code signing, etc.)
* Copyright © 2015 Pete Batard <pete@akeo.ie>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/* Memory leaks detection - define _CRTDBG_MAP_ALLOC as preprocessor macro */
#ifdef _CRTDBG_MAP_ALLOC
#include <stdlib.h>
#include <crtdbg.h>
#endif
#include <windows.h>
#include <stdio.h>
#include <wincrypt.h>
#include <wintrust.h>
#include "rufus.h"
#include "msapi_utf8.h"
#include "resource.h"
#include "localization.h"
#define ENCODING (X509_ASN_ENCODING | PKCS_7_ASN_ENCODING)
// Signatures names we accept (may be suffixed, but the signature should start with one of those)
const char* valid_cert_names[] = { "Akeo Consulting", "Akeo Systems", "Pete Batard" };
typedef struct {
LPWSTR lpszProgramName;
LPWSTR lpszPublisherLink;
LPWSTR lpszMoreInfoLink;
} SPROG_PUBLISHERINFO, *PSPROG_PUBLISHERINFO;
// Mostly from https://support.microsoft.com/en-us/kb/323809
static char* GetSignatureName(const char* path)
{
static char szSubjectName[128];
char* p = NULL;
BOOL r;
HCERTSTORE hStore = NULL;
HCRYPTMSG hMsg = NULL;
PCCERT_CONTEXT pCertContext = NULL;
DWORD dwEncoding, dwContentType, dwFormatType, dwSubjectSize;
PCMSG_SIGNER_INFO pSignerInfo = NULL;
PCMSG_SIGNER_INFO pCounterSignerInfo = NULL;
DWORD dwSignerInfo = 0;
CERT_INFO CertInfo = { 0 };
SPROG_PUBLISHERINFO ProgPubInfo = { 0 };
wchar_t *szFileName = utf8_to_wchar(path);
// Get message handle and store handle from the signed file.
r = CryptQueryObject(CERT_QUERY_OBJECT_FILE, szFileName,
CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED, CERT_QUERY_FORMAT_FLAG_BINARY,
0, &dwEncoding, &dwContentType, &dwFormatType, &hStore, &hMsg, NULL);
if (!r) {
uprintf("PKI: Failed to get store handle for '%s': %s", path, WindowsErrorString());
goto out;
}
// Get signer information size.
r = CryptMsgGetParam(hMsg, CMSG_SIGNER_INFO_PARAM, 0, NULL, &dwSignerInfo);
if (!r) {
uprintf("PKI: Failed to get signer size: %s", WindowsErrorString);
goto out;
}
// Allocate memory for signer information.
pSignerInfo = (PCMSG_SIGNER_INFO)calloc(dwSignerInfo, 1);
if (!pSignerInfo) {
uprintf("PKI: Could not allocate memory for signer information");
goto out;
}
// Get Signer Information.
r = CryptMsgGetParam(hMsg, CMSG_SIGNER_INFO_PARAM, 0, (PVOID)pSignerInfo, &dwSignerInfo);
if (!r) {
uprintf("PKI: Failed to get signer information: %s", WindowsErrorString());
goto out;
}
// Search for the signer certificate in the temporary certificate store.
CertInfo.Issuer = pSignerInfo->Issuer;
CertInfo.SerialNumber = pSignerInfo->SerialNumber;
pCertContext = CertFindCertificateInStore(hStore, ENCODING, 0, CERT_FIND_SUBJECT_CERT, (PVOID)&CertInfo, NULL);
if (!pCertContext) {
uprintf("PKI: Failed to locate signer certificate in temporary store: %s", WindowsErrorString());
goto out;
}
// Isolate the signing certificate subject name
dwSubjectSize = CertGetNameStringA(pCertContext, CERT_NAME_SIMPLE_DISPLAY_TYPE, 0, NULL,
szSubjectName, sizeof(szSubjectName));
if (dwSubjectSize <= 1) {
uprintf("PKI: Failed to get Subject Name");
goto out;
}
uprintf("Downloaded executable is signed by '%s'", szSubjectName);
p = szSubjectName;
out:
safe_free(szFileName);
safe_free(ProgPubInfo.lpszProgramName);
safe_free(ProgPubInfo.lpszPublisherLink);
safe_free(ProgPubInfo.lpszMoreInfoLink);
safe_free(pSignerInfo);
safe_free(pCounterSignerInfo);
if (pCertContext != NULL)
CertFreeCertificateContext(pCertContext);
if (hStore != NULL)
CertCloseStore(hStore, 0);
if (hMsg != NULL)
CryptMsgClose(hMsg);
return p;
}
// From https://msdn.microsoft.com/en-us/library/windows/desktop/aa382384.aspx
LONG ValidateSignature(HWND hDlg, const char* path)
{
LONG r;
WINTRUST_DATA trust_data = { 0 };
WINTRUST_FILE_INFO trust_file = { 0 };
GUID guid_generic_verify = // WINTRUST_ACTION_GENERIC_VERIFY_V2
{ 0xaac56b, 0xcd44, 0x11d0,{ 0x8c, 0xc2, 0x0, 0xc0, 0x4f, 0xc2, 0x95, 0xee } };
char *signature_name;
size_t i, len;
// Check the signature name. Make it specific enough (i.e. don't simply check for "Akeo")
// so that, besides hacking our server, it'll place an extra hurdle on any malicious entity
// into also fooling a C.A. to issue a certificate that passes our test.
signature_name = GetSignatureName(path);
if (signature_name == NULL) {
uprintf("PKI: Could not get signature name");
MessageBoxExU(hDlg, lmprintf(MSG_284), lmprintf(MSG_283), MB_OK | MB_ICONERROR | MB_IS_RTL, selected_langid);
return TRUST_E_NOSIGNATURE;
}
for (i = 0; i < ARRAYSIZE(valid_cert_names); i++) {
len = strlen(valid_cert_names[i]);
if (strncmp(signature_name, valid_cert_names[i], len) == 0) {
// Test for whitespace after the part we match, for added safety
if ((len >= strlen(signature_name)) || isspace(signature_name[len]))
break;
}
}
if (i >= ARRAYSIZE(valid_cert_names)) {
uprintf("PKI: Signature '%s' is unexpected...", signature_name);
if (MessageBoxExU(hDlg, lmprintf(MSG_285, signature_name), lmprintf(MSG_283),
MB_YESNO | MB_ICONWARNING | MB_IS_RTL, selected_langid) != IDYES)
return TRUST_E_EXPLICIT_DISTRUST;
}
trust_file.cbStruct = sizeof(trust_file);
trust_file.pcwszFilePath = utf8_to_wchar(path);
if (trust_file.pcwszFilePath == NULL) {
uprintf("PKI: Unable to convert '%s' to UTF16", path);
return ERROR_SEVERITY_ERROR | FAC(FACILITY_CERT) | ERROR_NOT_ENOUGH_MEMORY;
}
trust_data.cbStruct = sizeof(trust_data);
trust_data.dwUIChoice = WTD_UI_ALL;
// We just downloaded from the Internet, so we should be able to check revocation
trust_data.fdwRevocationChecks = WTD_REVOKE_WHOLECHAIN;
// 0x400 = WTD_MOTW for Windows 8.1 or later
trust_data.dwProvFlags = WTD_REVOCATION_CHECK_CHAIN | 0x400;
trust_data.dwUnionChoice = WTD_CHOICE_FILE;
trust_data.pFile = &trust_file;
r = WinVerifyTrust(NULL, &guid_generic_verify, &trust_data);
safe_free(trust_file.pcwszFilePath);
return r;
}