code for encrypting sensitive tcmalloc metadata

third_party/tcmalloc/chromium/src/metadata_encode_posix.cc

+// Copyright (c) 2011, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// ---
+// Author: Rebecca Shapiro
+//
+// Posix metadata encryption/encoding implementation.
+
+#include "config.h"
+#include <errno.h>
+#include <fcntl.h>
+#ifdef HAVE_STDINT_H
+#include <stdint.h>                     // for uintptr_t
+#endif
+#include "base/logging.h"
+
+
+namespace {
+static uintptr_t key_ = 0;
+static uintptr_t ReadFromFD(int fd, size_t size) {
+  uintptr_t ret;
+  size_t num_read_bytes = 0;
+  while (num_read_bytes < size) {
+    ssize_t num_bytes = read(fd, reinterpret_cast<void *>(&ret)+num_read_bytes,
+                            size-num_read_bytes);
+    if (num_bytes < 0) {
+      CHECK(errno == EINTR);
+    } else if (num_bytes == 0) {
+      break;
+    }
+    num_read_bytes += num_bytes;
+  }
+  CHECK(num_read_bytes == size);
+  return ret;
+}
+
+// Initialization code is not thread safe.
+void InitMetadataEncoderPosix() {  // TODO: doesn't link when not inline
+  // Ensure this function only executes once.
+  CHECK(key_ == false);
+
+  // Read random bytes from urandom to initialize key.
+  int fd = open("/dev/urandom", O_RDONLY);
+  if (fd > 0 && errno == ENOENT) { // If urandom doesn't exist.
+    fd = open("/dev/random", O_RDONLY);
+  }
+  CHECK(fd > 0);
+  key_ = ReadFromFD(fd, sizeof(uintptr_t));
+  if (key_ == 0 ) { // Try reading from (u)random again.
+    key_ = ReadFromFD(fd, sizeof(uintptr_t));
+  }
+  CHECK(key_ != 0);
+  close(fd);
+}
+
+uintptr_t EncodeUintptrPosix(uintptr_t ptr) { return ptr ^ key_; }
+
+uintptr_t DecodeUintptrPosix(uintptr_t ptr) { return EncodeUintptrPosix(ptr); }
+
+}
+
+namespace tcmalloc {
+
+void InitMetadataEncoder() {  InitMetadataEncoderPosix(); }
+
+uintptr_t EncodeUintptr(uintptr_t ptr){ return EncodeUintptrPosix(ptr); }
+
+uintptr_t DecodeUintptr(uintptr_t ptr){ return DecodeUintptrPosix(ptr); }
+
+}