Add rollback support to DeleteRegKeyWorkItem....

chrome/installer/util/delete_reg_key_work_item.cc

Index: chrome/installer/util/delete_reg_key_work_item.cc
===================================================================
--- chrome/installer/util/delete_reg_key_work_item.cc	(revision 76372)
+++ chrome/installer/util/delete_reg_key_work_item.cc	(working copy)
@@ -2,14 +2,268 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "chrome/installer/util/delete_reg_key_work_item.h"
+
 #include <shlwapi.h>
+#include <algorithm>
+#include <limits>
+#include <vector>
 
-#include "chrome/installer/util/delete_reg_key_work_item.h"
-
 #include "base/logging.h"
+#include "base/rand_util.h"
+#include "base/stringprintf.h"
+#include "base/win/registry.h"
 #include "chrome/installer/util/logging_installer.h"
 
+using base::win::RegKey;
 
+namespace {
+const REGSAM kKeyReadNoNotify = (KEY_READ) & ~(KEY_NOTIFY);
+}
+
+// A container for a registry key, its values, and its subkeys.  We don't use
+// more obvious methods for various reasons:
+// - RegCopyTree isn't supported pre-Vista, so we'd have to do something
+//   different for XP anyway.
+// - SHCopyKey can't copy subkeys into a volatile destination, so we'd have to
+//   worry about polluting the registry.
+// We don't persist security attributes since we only delete keys that we own,
+// and we don't set custom attributes on them anyway.
+class DeleteRegKeyWorkItem::RegKeyBackup {
+ public:
+  RegKeyBackup();
+  bool Initialize(const RegKey& key);
+  bool WriteTo(RegKey* key) const;
+
+ private:
+  // A container for a registry value.
+  class RegValueBackup {
+   public:
+    RegValueBackup();
+    void Initialize(const wchar_t* name_buffer, DWORD name_size,
+                    DWORD type, const uint8* data, DWORD data_size);
+    const std::wstring& name_str() const { return name_; }
+    const wchar_t* name() const { return name_.empty() ? NULL : name_.c_str(); }
+    DWORD type() const { return type_; }
+    const uint8* data() const { return data_.empty() ? NULL : &data_[0]; }
+    DWORD data_len() const { return static_cast<DWORD>(data_.size()); }
+
+   private:
+    std::wstring name_;
+    std::vector<uint8> data_;
+    DWORD type_;
+
+    DISALLOW_COPY_AND_ASSIGN(RegValueBackup);
+  };
+
+  scoped_array<RegValueBackup> values_;
+  scoped_array<std::wstring> subkey_names_;
+  scoped_array<RegKeyBackup> subkeys_;
+  ptrdiff_t num_values_;
+  ptrdiff_t num_subkeys_;
+
+  DISALLOW_COPY_AND_ASSIGN(RegKeyBackup);
+};
+
+DeleteRegKeyWorkItem::RegKeyBackup::RegValueBackup::RegValueBackup()
+    : type_(REG_NONE) {
+}
+
+void DeleteRegKeyWorkItem::RegKeyBackup::RegValueBackup::Initialize(
+    const wchar_t* name_buffer,
+    DWORD name_size,
+    DWORD type, const uint8* data,
+    DWORD data_size) {
+  name_.assign(name_buffer, name_size);
+  type_ = type;
+  data_.assign(data, data + data_size);
+}
+
+DeleteRegKeyWorkItem::RegKeyBackup::RegKeyBackup()
+    : num_values_(0),
+      num_subkeys_(0) {
+}
+
+// Initializes this object by reading the values and subkeys of |key|.
+// Security descriptors are not backed up.
+bool DeleteRegKeyWorkItem::RegKeyBackup::Initialize(const RegKey& key) {
+  DCHECK(key.Valid());
+
+  scoped_array<RegValueBackup> values;
+  scoped_array<std::wstring> subkey_names;
+  scoped_array<RegKeyBackup> subkeys;
+
+  DWORD num_subkeys = 0;
+  DWORD max_subkey_name_len = 0;
+  DWORD num_values = 0;
+  DWORD max_value_name_len = 0;
+  DWORD max_value_len = 0;
+  LONG result = RegQueryInfoKey(key.Handle(), NULL, NULL, NULL,
+                                &num_subkeys, &max_subkey_name_len, NULL,
+                                &num_values, &max_value_name_len,
+                                &max_value_len, NULL, NULL);
+  if (result != ERROR_SUCCESS) {
+    LOG(ERROR) << "Failed getting info of key to backup, result: " << result;
+    return false;
+  }
+  if (max_subkey_name_len >= std::numeric_limits<DWORD>::max() - 1 ||
+      max_value_name_len >= std::numeric_limits<DWORD>::max() - 1) {
+    LOG(ERROR)
+        << "Failed backing up key; subkeys and/or names are out of range.";
+    return false;
+  }
+  DWORD max_name_len = std::max(max_subkey_name_len, max_value_name_len) + 1;
+  scoped_array<wchar_t> name_buffer(new wchar_t[max_name_len]);
+
+  // Backup the values.
+  if (num_values != 0) {
+    values.reset(new RegValueBackup[num_values]);
+    scoped_array<uint8> value_buffer(new uint8[max_value_len]);
+    DWORD name_size = 0;
+    DWORD value_type = REG_NONE;
+    DWORD value_size = 0;
+
+    for (DWORD i = 0; i < num_values; ) {
+      name_size = max_name_len;
+      value_size = max_value_len;
+      result = RegEnumValue(key.Handle(), i, name_buffer.get(), &name_size,
+                            NULL, &value_type, value_buffer.get(), &value_size);
+      switch (result) {
+        case ERROR_NO_MORE_ITEMS:
+          num_values = i;
+          break;
+        case ERROR_SUCCESS:
+          values[i].Initialize(name_buffer.get(), name_size, value_type,
+                               value_buffer.get(), value_size);
+          ++i;
+          break;
+        case ERROR_MORE_DATA:
+          if (value_size > max_value_len) {
+            max_value_len = value_size;
+            value_buffer.reset(new uint8[max_value_len]);
+          } else {
+            DCHECK(max_name_len - 1 < name_size);
+            if (name_size >= std::numeric_limits<DWORD>::max() - 1) {
+              LOG(ERROR) << "Failed backing up key; value name out of range.";
+              return false;
+            }
+            max_name_len = name_size + 1;
+            name_buffer.reset(new wchar_t[max_name_len]);
+          }
+          break;
+        default:
+          LOG(ERROR) << "Failed backing up value " << i << ", result: "
+                     << result;
+          return false;
+      }
+    }
+    DLOG_IF(WARNING, RegEnumValue(key.Handle(), num_values, name_buffer.get(),
+                                  &name_size, NULL, &value_type, NULL,
+                                  NULL) != ERROR_NO_MORE_ITEMS)
+        << "Concurrent modifications to registry key during backup operation.";
+  }
+
+  // Backup the subkeys.
+  if (num_subkeys != 0) {
+    subkey_names.reset(new std::wstring[num_subkeys]);
+    subkeys.reset(new RegKeyBackup[num_subkeys]);
+    DWORD name_size = 0;
+
+    // Get the names of them.
+    for (DWORD i = 0; i < num_subkeys; ) {
+      name_size = max_name_len;
+      result = RegEnumKeyEx(key.Handle(), i, name_buffer.get(), &name_size,
+                            NULL, NULL, NULL, NULL);
+      switch (result) {
+        case ERROR_NO_MORE_ITEMS:
+          num_subkeys = i;
+          break;
+        case ERROR_SUCCESS:
+          subkey_names[i].assign(name_buffer.get(), name_size);
+          ++i;
+          break;
+        case ERROR_MORE_DATA:
+          if (name_size >= std::numeric_limits<DWORD>::max() - 1) {
+            LOG(ERROR) << "Failed backing up key; subkey name out of range.";
+            return false;
+          }
+          max_name_len = name_size + 1;
+          name_buffer.reset(new wchar_t[max_name_len]);
+          break;
+        default:
+          LOG(ERROR) << "Failed getting name of subkey " << i
+                     << " for backup, result: " << result;
+          return false;
+      }
+    }
+    DLOG_IF(WARNING,
+            RegEnumKeyEx(key.Handle(), num_subkeys, NULL, &name_size, NULL,
+                         NULL, NULL, NULL) != ERROR_NO_MORE_ITEMS)
+        << "Concurrent modifications to registry key during backup operation.";
+
+    // Get their values.
+    RegKey subkey;
+    for (DWORD i = 0; i < num_subkeys; ++i) {
+      result = subkey.Open(key.Handle(), subkey_names[i].c_str(),
+                           kKeyReadNoNotify);
+      if (result != ERROR_SUCCESS) {
+        LOG(ERROR) << "Failed opening subkey \"" << subkey_names[i]
+                   << "\" for backup, result: " << result;
+        return false;
+      }
+      if (!subkeys[i].Initialize(subkey)) {
+        LOG(ERROR) << "Failed backing up subkey \"" << subkey_names[i] << "\"";
+        return false;
+      }
+    }
+  }
+
+  values_.swap(values);
+  subkey_names_.swap(subkey_names);
+  subkeys_.swap(subkeys);
+  num_values_ = num_values;
+  num_subkeys_ = num_subkeys;
+
+  return true;
+}
+
+// Writes the values and subkeys of this object into |key|.
+bool DeleteRegKeyWorkItem::RegKeyBackup::WriteTo(RegKey* key) const {
+  LONG result = ERROR_SUCCESS;
+
+  // Write the values.
+  for (int i = 0; i < num_values_; ++i) {
+    const RegValueBackup& value = values_[i];
+    result = RegSetValueEx(key->Handle(), value.name(), 0, value.type(),
+                           value.data(), value.data_len());
+    if (result != ERROR_SUCCESS) {
+      LOG(ERROR) << "Failed writing value \"" << value.name_str()
+                 << "\", result: " << result;
+      return false;
+    }
+  }
+
+  // Write the subkeys.
+  RegKey subkey;
+  for (int i = 0; i < num_subkeys_; ++i) {
+    const std::wstring& name = subkey_names_[i];
+
+    result = subkey.Create(key->Handle(), name.c_str(), KEY_WRITE);
+    if (result != ERROR_SUCCESS) {
+      LOG(ERROR) << "Failed creating subkey \"" << name << "\", result: "
+                 << result;
+      return false;
+    }
+    if (!subkeys_[i].WriteTo(&subkey)) {
+      LOG(ERROR) << "Failed writing subkey \"" << name << "\", result: "
+                 << result;
+      return false;
+    }
+  }
+
+  return true;
+}
+
 DeleteRegKeyWorkItem::~DeleteRegKeyWorkItem() {
 }
 
@@ -17,28 +271,68 @@
                                            const std::wstring& path)
     : predefined_root_(predefined_root),
       path_(path) {
+  // It's a safe bet that we don't want to delete one of the root trees.
+  DCHECK(!path.empty());
 }
 
 bool DeleteRegKeyWorkItem::Do() {
-  // TODO(robertshield): Implement rollback for this work item. Consider using
-  // RegSaveKey or RegCopyKey.
+  scoped_ptr<RegKeyBackup> backup;
+
+  // Only try to make a backup if we're not configured to ignore failures.
   if (!ignore_failure_) {
-    NOTREACHED();
-    LOG(ERROR) << "Unexpected configuration in DeleteRegKeyWorkItem.";
-    return false;
+    RegKey original_key;
+
+    // Does the key exist?
+    LONG result = original_key.Open(predefined_root_, path_.c_str(),
+                                    kKeyReadNoNotify);
+    if (result == ERROR_SUCCESS) {
+      backup.reset(new RegKeyBackup());
+      if (!backup->Initialize(original_key)) {
+        LOG(ERROR) << "Failed to backup key at " << path_;
+        return ignore_failure_;
+      }
+    } else if (result != ERROR_FILE_NOT_FOUND) {
+      LOG(ERROR) << "Failed to open key at " << path_
+                 << " to create backup, result: " << result;
+      return ignore_failure_;
+    }
   }
 
-  LSTATUS result = SHDeleteKey(predefined_root_, path_.c_str());
-  if (result != ERROR_SUCCESS) {
-    LOG(ERROR) << "Failed to delete key at " << path_ << ", result: " << result;
+  // Delete the key.
+  LONG result = SHDeleteKey(predefined_root_, path_.c_str());
+  if (result != ERROR_SUCCESS && result != ERROR_FILE_NOT_FOUND) {
+    LOG(ERROR) << "Failed to delete key at " << path_ << ", result: "
+               << result;
+    return ignore_failure_;
   }
 
+  // We've succeeded, so remember any backup we may have made.
+  backup_.swap(backup);
+
   return true;
 }
 
 void DeleteRegKeyWorkItem::Rollback() {
-  if (ignore_failure_)
+  if (ignore_failure_ || backup_.get() == NULL)
     return;
-  NOTREACHED();
+
+  // Delete anything in the key before restoring the backup in case someone else
+  // put new data in the key after Do().
+  LONG result = SHDeleteKey(predefined_root_, path_.c_str());
+  if (result != ERROR_SUCCESS && result != ERROR_FILE_NOT_FOUND) {
+    LOG(ERROR) << "Failed to delete key at " << path_ << " in rollback, "
+                  "result: " << result;
+  }
+
+  // Restore the old contents.  The restoration takes on its default security
+  // attributes; any custom attributes are lost.
+  RegKey original_key;
+  result = original_key.Create(predefined_root_, path_.c_str(), KEY_WRITE);
+  if (result != ERROR_SUCCESS) {
+    LOG(ERROR) << "Failed to create original key at " << path_
+               << " in rollback, result: " << result;
+  } else {
+    if (!backup_->WriteTo(&original_key))
+      LOG(ERROR) << "Failed to restore key in rollback, result: " << result;
+  }
 }
-