Revert "Eliminate all code related to the AutomaticProfileResetter."

chrome/browser/profile_resetter/jtl_foundation.h

+// Copyright 2013 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.
+
+#ifndef CHROME_BROWSER_PROFILE_RESETTER_JTL_FOUNDATION_H_
+#define CHROME_BROWSER_PROFILE_RESETTER_JTL_FOUNDATION_H_
+
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "crypto/hmac.h"
+
+namespace jtl_foundation {
+
+// A JTL (JSON Traversal Language) program is composed of one or more
+// sentences. Each sentence consists of a sequence of operations. The input of
+// the program is a hierarchical JSON data structure.
+//
+// The execution of each sentence starts at the root of an input dictionary. The
+// operations include navigation in the JSON data structure, as well as
+// comparing the current (leaf) node to fixed values. The program also has a
+// separate dictionary as working memory, into which it can memorize data, then
+// later recall it for comparisons.
+//
+// Example program:
+// NAVIGATE_ANY
+// NAVIGATE(hash("bar"))
+// COMPARE_NODE_BOOL(1)
+// STORE_BOOL(hash("found_foo"), 1)
+// STOP_EXECUTING_SENTENCE
+//
+// Example input:
+// {
+//   'key1': 1,
+//   'key2': {'foo': 0, 'bar': false, 'baz': 2}
+//   'key3': {'foo': 0, 'bar': true, 'baz': 2}
+//   'key4': {'foo': 0, 'bar': true, 'baz': 2}
+// }
+//
+// This program navigates from the root of the dictionary to all children
+// ("key1", "key2", "key3", "key4") and executes the remaining program on each
+// of the children. The navigation happens in depth-first pre-order. On each of
+// the children it tries to navigate into the child "bar", which fails for
+// "key1", so execution stops for this sub-branch. On key2 the program navigates
+// to "bar" and moves the execution context to this node which has the value
+// "false". Therefore, the following COMPARE_NODE_BOOL is not fulfilled and the
+// execution does not continue on this branch, so we back track and proceed with
+// "key3" and its "bar" child. For this node, COMPARE_NODE_BOOL is fulfilled and
+// the execution continues to store "found_foo = true" into the working memory
+// of the interpreter. Next the interpreter executes STOP_EXECUTING_SENTENCE
+// which prevents the traversal from descending into the "key4" branch from the
+// NAVIGATE_ANY operation and can therefore speedup the processing.
+//
+// All node names, and node values of type string, integer and double are hashed
+// before being compared to hash values listed in |program|.
+
+// JTL byte code consists of uint8 opcodes followed by parameters. Parameters
+// are either boolean (uint8 with value \x00 or \x01), uint32 (in little-endian
+// notation), or hash string of 32 bytes.
+// The following opcodes are defined:
+enum OpCodes {
+  // Continues execution with the next operation on the element of a
+  // dictionary that matches the passed key parameter. If no such element
+  // exists, the command execution returns from the current instruction.
+  // Parameters:
+  // - a 32 byte hash of the target dictionary key.
+  NAVIGATE = 0x00,
+  // Continues execution with the next operation on each element of a
+  // dictionary or list. If no such element exists or the current element is
+  // neither a dictionary or list, the command execution returns from the
+  // current instruction.
+  NAVIGATE_ANY = 0x01,
+  // Continues execution with the next operation on the parent node of the
+  // current node. If the current node is the root of the input dictionary, the
+  // program execution fails with a runtime error.
+  NAVIGATE_BACK = 0x02,
+  // Stores a boolean value in the working memory.
+  // Parameters:
+  // - a 32 byte hash of the parameter name,
+  // - the value to store (\x00 or \x01)
+  STORE_BOOL = 0x10,
+  // Checks whether a boolean stored in working memory matches the expected
+  // value and continues execution with the next operation in case of a match.
+  // Parameters:
+  // - a 32 byte hash of the parameter name,
+  // - the expected value (\x00 or \x01),
+  // - the default value in case the working memory contains no corresponding
+  //   entry (\x00 or\x01).
+  COMPARE_STORED_BOOL = 0x11,
+  // Same as STORE_BOOL but takes a hash instead of a boolean value as
+  // parameter.
+  STORE_HASH = 0x12,
+  // Same as COMPARE_STORED_BOOL but takes a hash instead of two boolean values
+  // as parameters.
+  COMPARE_STORED_HASH = 0x13,
+  // Stores the current node into the working memory. If the current node is not
+  // a boolean value, the program execution returns from the current
+  // instruction.
+  // Parameters:
+  // - a 32 byte hash of the parameter name.
+  STORE_NODE_BOOL = 0x14,
+  // Stores the hashed value of the current node into the working memory. If
+  // the current node is not a string, integer or double, the program execution
+  // returns from the current instruction.
+  // Parameters:
+  // - a 32 byte hash of the parameter name.
+  STORE_NODE_HASH = 0x15,
+  // Parses the value of the current node as a URL, extracts the subcomponent of
+  // the domain name that is immediately below the registrar-controlled portion,
+  // and stores the hash of this subcomponent into working memory. In case the
+  // domain name ends in a suffix not on the Public Suffix List (i.e. is neither
+  // an ICANN, nor a private domain suffix), the last subcomponent is assumed to
+  // be the registry, and the second-to-last subcomponent is extracted.
+  // If the current node is not a string that represents a URL, or if this URL
+  // does not have a domain component as described above, the program execution
+  // returns from the current instruction.
+  // For example, "foo.com", "www.foo.co.uk", "foo.appspot.com", and "foo.bar"
+  // will all yield (the hash of) "foo" as a result.
+  // See the unit test for more details.
+  // Parameters:
+  // - a 32 byte hash of the parameter name.
+  STORE_NODE_REGISTERABLE_DOMAIN_HASH = 0x16,
+  // Compares the current node against a boolean value and continues execution
+  // with the next operation in case of a match. If the current node does not
+  // match or is not a boolean value, the program execution returns from the
+  // current instruction.
+  // Parameters:
+  // - a boolean value (\x00 or \x01).
+  COMPARE_NODE_BOOL = 0x20,
+  // Compares the hashed value of the current node against the given hash, and
+  // continues execution with the next operation in case of a match. If the
+  // current node is not a string, integer or double, or if it is either, but
+  // its hash does not match, the program execution returns from the current
+  // instruction.
+  // Parameters:
+  // - a 32 byte hash of the expected value.
+  COMPARE_NODE_HASH = 0x21,
+  // The negation of the above.
+  COMPARE_NODE_HASH_NOT = 0x22,
+  // Compares the current node against a boolean value stored in working memory,
+  // and continues with the next operation in case of a match. If the current
+  // node is not a boolean value, the working memory contains no corresponding
+  // boolean value, or if they do not match, the program execution returns from
+  // the current instruction.
+  // Parameters:
+  // - a 32 byte hash of the parameter name.
+  COMPARE_NODE_TO_STORED_BOOL = 0x23,
+  // Compares the hashed value of the current node against a hash value stored
+  // in working memory, and continues with the next operation in case of a
+  // match. If the current node is not a string, integer or double, or if the
+  // working memory contains no corresponding hash string, or if the hashes do
+  // not match, the program execution returns from the current instruction.
+  // Parameters:
+  // - a 32 byte hash of the parameter name.
+  COMPARE_NODE_TO_STORED_HASH = 0x24,
+  // Checks whether the current node is a string value that contains the given
+  // pattern as a substring, and continues execution with the next operation in
+  // case it does. If the current node is not a string, or if does not match the
+  // pattern, the program execution returns from the current instruction.
+  // Parameters:
+  // - a 32 byte hash of the pattern,
+  // - a 4 byte unsigned integer: the length (>0) of the pattern in bytes,
+  // - a 4 byte unsigned integer: the sum of all bytes in the pattern, serving
+  //   as a heuristic to reduce the number of actual SHA-256 calculations.
+  COMPARE_NODE_SUBSTRING = 0x25,
+  // Stop execution in this specific sentence.
+  STOP_EXECUTING_SENTENCE = 0x30,
+  // Separator between sentences, starts a new sentence.
+  END_OF_SENTENCE = 0x31
+};
+
+const size_t kHashSizeInBytes = 32u;
+
+// A class that provides SHA256 hash values for strings using a fixed hash seed.
+class Hasher {
+ public:
+  explicit Hasher(const std::string& seed);
+  ~Hasher();
+
+  std::string GetHash(const std::string& input) const;
+
+  static bool IsHash(const std::string& maybe_hash);
+
+ private:
+  crypto::HMAC hmac_;
+  mutable std::map<std::string, std::string> cached_hashes_;
+  DISALLOW_COPY_AND_ASSIGN(Hasher);
+};
+
+}  // namespace jtl_foundation
+
+#endif  // CHROME_BROWSER_PROFILE_RESETTER_JTL_FOUNDATION_H_