HMAC-SHA1 implementation for Mac based on CommonCrypto

base/hmac_win.cc

Index: base/hmac_win.cc
===================================================================
--- base/hmac_win.cc	(revision 1686)
+++ base/hmac_win.cc	(working copy)
@@ -3,8 +3,14 @@
 // found in the LICENSE file.
 
 #include "base/hmac.h"
+
+#include <algorithm>
+#include <vector>
+
 #include "base/logging.h"
 
+namespace base {
+
 HMAC::HMAC(HashAlgorithm hash_alg, const unsigned char* key, int key_length)
     : hash_alg_(hash_alg),
       provider_(NULL),
@@ -41,30 +47,36 @@
 }
 
 void HMAC::ImportKey(const unsigned char* key, int key_length) {
-  if (key_length > kMaxKeySize) {
-    NOTREACHED();
-    return;
-  }
+  // This code doesn't work on Win2k because PLAINTEXTKEYBLOB and
+  // CRYPT_IPSEC_HMAC_KEY are not supported on Windows 2000.  PLAINTEXTKEYBLOB
+  // allows the import of an unencrypted key.  For Win2k support, a cubmbersome
+  // exponent-of-one key procedure must be used:
+  //     http://support.microsoft.com/kb/228786/en-us
+  // CRYPT_IPSEC_HMAC_KEY allows keys longer than 16 bytes.
 
-  struct {
+  struct KeyBlob {
     BLOBHEADER header;
     DWORD key_size;
-    BYTE key_data[kMaxKeySize];
-  } key_blob;
-  key_blob.header.bType = PLAINTEXTKEYBLOB;
-  key_blob.header.bVersion = CUR_BLOB_VERSION;
-  key_blob.header.reserved = 0;
-  key_blob.header.aiKeyAlg = CALG_RC2;
-  key_blob.key_size = key_length;
-  memcpy(key_blob.key_data, key, key_length);
+    BYTE key_data[1];
+  };
+  size_t key_blob_size = std::max(offsetof(KeyBlob, key_data) + key_length,
+                                  sizeof(KeyBlob));
+  std::vector<BYTE> key_blob_storage = std::vector<BYTE>(key_blob_size);
+  KeyBlob* key_blob = reinterpret_cast<KeyBlob*>(&key_blob_storage[0]);
+  key_blob->header.bType = PLAINTEXTKEYBLOB;
+  key_blob->header.bVersion = CUR_BLOB_VERSION;
+  key_blob->header.reserved = 0;
+  key_blob->header.aiKeyAlg = CALG_RC2;
+  key_blob->key_size = key_length;
+  memcpy(key_blob->key_data, key, key_length);
 
-  if (!CryptImportKey(provider_,
-                      reinterpret_cast<const BYTE *>(&key_blob),
-                      sizeof(key_blob), 0, 0, &hkey_))
+  if (!CryptImportKey(provider_, &key_blob_storage[0], key_blob_storage.size(),
+                      0, CRYPT_IPSEC_HMAC_KEY, &hkey_)) {
     hkey_ = NULL;
+  }
 
   // Destroy the copy of the key.
-  SecureZeroMemory(key_blob.key_data, key_length);
+  SecureZeroMemory(key_blob->key_data, key_length);
 }
 
 bool HMAC::SignWithSHA1(const std::string& data,
@@ -95,3 +107,4 @@
   return true;
 }
 
+}  // namespace base