Extract the certificate to use in the download protection pingback.

chrome/browser/safe_browsing/signature_util_win.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/safe_browsing/signature_util.h"
 
 #include <windows.h>
 #include <wincrypt.h>

[mattm, 2011/11/04 22:14:18]

nit: missing blank line

[Brian Ryner, 2011/11/04 22:20:30]

Done.

 #include "base/file_path.h"
+#include "base/logging.h"
+#include "base/scoped_ptr.h"
+#include "crypto/scoped_capi_types.h"
+#include "chrome/common/safe_browsing/csd.pb.h"
 
 namespace safe_browsing {
-namespace signature_util {
+namespace {
+using crypto::ScopedCAPIHandle;
+using crypto::CAPIDestroyer;
+using crypto::CAPIDestroyerWithFlags;
 
-bool IsSigned(const FilePath& file_path) {
+// Free functor for scoped_ptr_malloc.
+class FreeConstCertContext {
+ public:
+  void operator()(const CERT_CONTEXT* cert_context) const {
+    CertFreeCertificateContext(cert_context);
+  }
+};
+
+// Tries to extract the signing certificate from |file_path|.  On success,
+// the |certificate_contents| field of |signature_info| is populated with the
+// DER-encoded X.509 certificate.
+void GetCertificateContents(
+    const FilePath& file_path,
+    ClientDownloadRequest_SignatureInfo* signature_info) {
+  // Largely based on http://support.microsoft.com/kb/323809
   // Get message handle and store handle from the signed file.
-  BOOL result = CryptQueryObject(CERT_QUERY_OBJECT_FILE,
-                                 file_path.value().c_str(),
-                                 CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED,
-                                 CERT_QUERY_FORMAT_FLAG_BINARY,
-                                 0,      // flags
-                                 NULL,   // encoding
-                                 NULL,   // content type
-                                 NULL,   // format type
-                                 NULL,   // HCERTSTORE
-                                 NULL,   // HCRYPTMSG
-                                 NULL);  // context
-  return result == TRUE;
+  typedef CAPIDestroyer<HCRYPTMSG, CryptMsgClose> CryptMsgDestroyer;
+  ScopedCAPIHandle<HCRYPTMSG, CryptMsgDestroyer> crypt_msg;
+  typedef CAPIDestroyerWithFlags<
+      HCERTSTORE, CertCloseStore, 0> CertStoreDestroyer;
+  ScopedCAPIHandle<HCERTSTORE, CertStoreDestroyer> cert_store;
+
+  VLOG(2) << "Looking for signature in: " << file_path.value();
+  if (!CryptQueryObject(CERT_QUERY_OBJECT_FILE,
+                        file_path.value().c_str(),
+                        CERT_QUERY_CONTENT_FLAG_PKCS7_SIGNED_EMBED,
+                        CERT_QUERY_FORMAT_FLAG_BINARY,
+                        0,      // flags
+                        NULL,   // encoding
+                        NULL,   // content type
+                        NULL,   // format type
+                        cert_store.receive(),
+                        crypt_msg.receive(),
+                        NULL)) {  // context
+    VLOG(2) << "No signature found.";
+    return;
+  }
+
+  // Get the signer information size.
+  DWORD signer_info_size;
+  if (!CryptMsgGetParam(crypt_msg.get(),
+                        CMSG_SIGNER_INFO_PARAM,
+                        0,  // index
+                        NULL,  // no buffer when checking the size
+                        &signer_info_size)) {
+    VLOG(2) << "Failed to get signer info size";
+    return;
+  }
+
+  // Get the signer information.
+  scoped_array<BYTE> signer_info_buffer(new BYTE[signer_info_size]);
+  CMSG_SIGNER_INFO* signer_info =
+      reinterpret_cast<CMSG_SIGNER_INFO*>(signer_info_buffer.get());
+  if (!CryptMsgGetParam(crypt_msg.get(),
+                        CMSG_SIGNER_INFO_PARAM,
+                        0,  // index
+                        signer_info,
+                        &signer_info_size)) {
+    VLOG(2) << "Failed to get signer info";
+    return;
+  }
+
+  // Search for the signer certificate in the temporary certificate store.
+  CERT_INFO cert_info;
+  cert_info.Issuer = signer_info->Issuer;
+  cert_info.SerialNumber = signer_info->SerialNumber;
+
+  scoped_ptr_malloc<const CERT_CONTEXT, FreeConstCertContext> cert_context(
+      CertFindCertificateInStore(
+          cert_store.get(),
+          X509_ASN_ENCODING | PKCS_7_ASN_ENCODING,
+          0, // flags
+          CERT_FIND_SUBJECT_CERT,
+          &cert_info,
+          NULL));  // no previous context
+  if (!cert_context.get()) {
+    VLOG(2) << "Failed to get CERT_CONTEXT";
+    return;
+  }
+
+  signature_info->set_certificate_contents(cert_context->pbCertEncoded,
+                                           cert_context->cbCertEncoded);
+  VLOG(2) << "Successfully extracted cert";
+}
+}  // namespace
+
+SignatureUtil::SignatureUtil() {}
+
+SignatureUtil::~SignatureUtil() {}
+
+void SignatureUtil::CheckSignature(
+    const FilePath& file_path,
+    ClientDownloadRequest_SignatureInfo* signature_info) {
+  GetCertificateContents(file_path, signature_info);
+  // TODO(bryner): Populate is_trusted.
 }
 
-}  // namespace signature_util
 }  // namespace safe_browsing