libartbase/base/hiddenapi_flags.h

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef ART_LIBARTBASE_BASE_HIDDENAPI_FLAGS_H_
#define ART_LIBARTBASE_BASE_HIDDENAPI_FLAGS_H_

#include "sdk_version.h"

#include <vector>

#include "android-base/logging.h"
#include "base/bit_utils.h"
#include "base/dumpable.h"
#include "base/macros.h"

namespace art {
namespace hiddenapi {

// Helper methods used inside ApiList. These were moved outside of the ApiList
// class so that they can be used in static_asserts. If they were inside, they
// would be part of an unfinished type.
namespace helper {
  // Casts enum value to uint32_t.
  template<typename T>
  constexpr uint32_t ToUint(T val) { return static_cast<uint32_t>(val); }

  // Returns uint32_t with one bit set at an index given by an enum value.
  template<typename T>
  constexpr uint32_t ToBit(T val) { return 1u << ToUint(val); }

  // Returns a bit mask with `size` least significant bits set.
  constexpr uint32_t BitMask(uint32_t size) { return (1u << size) - 1; }

  // Returns a bit mask formed from an enum defining kMin and kMax. The values
  // are assumed to be indices of min/max bits and the resulting bitmask has
  // bits [kMin, kMax] set.
  template<typename T>
  constexpr uint32_t BitMask() {
    return BitMask(ToUint(T::kMax) + 1) & (~BitMask(ToUint(T::kMin)));
  }

  // Returns true if `val` is a bitwise subset of `mask`.
  constexpr bool MatchesBitMask(uint32_t val, uint32_t mask) { return (val & mask) == val; }

  // Returns true if the uint32_t value of `val` is a bitwise subset of `mask`.
  template<typename T>
  constexpr bool MatchesBitMask(T val, uint32_t mask) { return MatchesBitMask(ToUint(val), mask); }

  // Returns the number of values defined in an enum, assuming the enum defines
  // kMin and kMax and no integer values are skipped between them.
  template<typename T>
  constexpr uint32_t NumValues() { return ToUint(T::kMax) - ToUint(T::kMin) + 1; }
}  // namespace helper

/*
 * This class represents the information whether a field/method is in
 * public API (whitelist) or if it isn't, apps targeting which SDK
 * versions are allowed to access it.
 */
class ApiList {
 private:
  // Number of bits reserved for Value in dex flags, and the corresponding bit mask.
  static constexpr uint32_t kValueBitSize = 3;
  static constexpr uint32_t kValueBitMask = helper::BitMask(kValueBitSize);

  enum class Value : uint32_t {
    // Values independent of target SDK version of app
    kWhitelist =    0,
    kGreylist =     1,
    kBlacklist =    2,

    // Values dependent on target SDK version of app. Put these last as
    // their list will be extended in future releases.
    // The max release code implicitly includes all maintenance releases,
    // e.g. GreylistMaxO is accessible to targetSdkVersion <= 27 (O_MR1).
    kGreylistMaxO = 3,
    kGreylistMaxP = 4,

    // Special values
    kInvalid =      (static_cast<uint32_t>(-1) & kValueBitMask),
    kMin =          kWhitelist,
    kMax =          kGreylistMaxP,
  };

  // Additional bit flags after the first kValueBitSize bits in dex flags.
  // These are used for domain-specific API.
  enum class DomainApi : uint32_t {
    kCorePlatformApi = kValueBitSize,

    // Special values
    kMin =             kCorePlatformApi,
    kMax =             kCorePlatformApi,
  };

  // Bit mask of all domain API flags.
  static constexpr uint32_t kDomainApiBitMask = helper::BitMask<DomainApi>();

  // Check that Values fit in the designated number of bits.
  static_assert(kValueBitSize >= MinimumBitsToStore(helper::ToUint(Value::kMax)),
                "Not enough bits to store all ApiList values");

  // Sanity checks that all Values are covered by kValueBitMask.
  static_assert(helper::MatchesBitMask(Value::kMin, kValueBitMask));
  static_assert(helper::MatchesBitMask(Value::kMax, kValueBitMask));

  // Assert that Value::kInvalid is larger than the maximum Value.
  static_assert(helper::ToUint(Value::kMax) < helper::ToUint(Value::kInvalid));

  // Names corresponding to Values.
  static constexpr const char* kValueNames[] = {
    "whitelist",
    "greylist",
    "blacklist",
    "greylist-max-o",
    "greylist-max-p",
  };

  // Names corresponding to DomainApis.
  static constexpr const char* kDomainApiNames[] {
    "core-platform-api",
  };

  // Maximum SDK versions allowed to access ApiList of given Value.
  static constexpr SdkVersion kMaxSdkVersions[] {
    /* whitelist */ SdkVersion::kMax,
    /* greylist */ SdkVersion::kMax,
    /* blacklist */ SdkVersion::kMin,
    /* greylist-max-o */ SdkVersion::kO_MR1,
    /* greylist-max-p */ SdkVersion::kP,
  };

  explicit ApiList(Value val, uint32_t domain_apis = 0u)
      : dex_flags_(helper::ToUint(val) | domain_apis) {
    DCHECK(GetValue() == val);
    DCHECK_EQ(GetDomainApis(), domain_apis);
  }

  explicit ApiList(DomainApi val) : ApiList(Value::kInvalid, helper::ToBit(val)) {}

  Value GetValue() const {
    uint32_t value = (dex_flags_ & kValueBitMask);

    // Treat all ones as invalid value
    if (value == helper::ToUint(Value::kInvalid)) {
      return Value::kInvalid;
    } else {
      DCHECK_GE(value, helper::ToUint(Value::kMin));
      DCHECK_LE(value, helper::ToUint(Value::kMax));
      return static_cast<Value>(value);
    }
  }

  uint32_t GetDomainApis() const { return (dex_flags_ & kDomainApiBitMask); }

  uint32_t dex_flags_;

 public:
  ApiList() : ApiList(Value::kInvalid) {}

  explicit ApiList(uint32_t dex_flags) : dex_flags_(dex_flags) {
    DCHECK_EQ(dex_flags_, (dex_flags_ & kValueBitMask) | (dex_flags_ & kDomainApiBitMask));
  }

  // Helpers for conveniently constructing ApiList instances.
  static ApiList Whitelist() { return ApiList(Value::kWhitelist); }
  static ApiList Greylist() { return ApiList(Value::kGreylist); }
  static ApiList Blacklist() { return ApiList(Value::kBlacklist); }
  static ApiList GreylistMaxO() { return ApiList(Value::kGreylistMaxO); }
  static ApiList GreylistMaxP() { return ApiList(Value::kGreylistMaxP); }
  static ApiList CorePlatformApi() { return ApiList(DomainApi::kCorePlatformApi); }

  uint32_t GetDexFlags() const { return dex_flags_; }
  uint32_t GetIntValue() const { return helper::ToUint(GetValue()) - helper::ToUint(Value::kMin); }

  // Returns the ApiList with a flag of a given name, or an empty ApiList if not matched.
  static ApiList FromName(const std::string& str) {
    for (uint32_t i = 0; i < kValueCount; ++i) {
      if (str == kValueNames[i]) {
        return ApiList(static_cast<Value>(i + helper::ToUint(Value::kMin)));
      }
    }
    for (uint32_t i = 0; i < kDomainApiCount; ++i) {
      if (str == kDomainApiNames[i]) {
        return ApiList(static_cast<DomainApi>(i + helper::ToUint(DomainApi::kMin)));
      }
    }
    return ApiList();
  }

  // Parses a vector of flag names into a single ApiList value. If successful,
  // returns true and assigns the new ApiList to `out_api_list`.
  static bool FromNames(std::vector<std::string>::iterator begin,
                        std::vector<std::string>::iterator end,
                        /* out */ ApiList* out_api_list) {
    ApiList api_list;
    for (std::vector<std::string>::iterator it = begin; it != end; it++) {
      ApiList current = FromName(*it);
      if (current.IsEmpty() || !api_list.CanCombineWith(current)) {
        return false;
      }
      api_list |= current;
    }
    if (out_api_list != nullptr) {
      *out_api_list = api_list;
    }
    return true;
  }

  bool operator==(const ApiList& other) const { return dex_flags_ == other.dex_flags_; }
  bool operator!=(const ApiList& other) const { return !(*this == other); }

  // Returns true if combining this ApiList with `other` will succeed.
  bool CanCombineWith(const ApiList& other) const {
    const Value val1 = GetValue();
    const Value val2 = other.GetValue();
    return (val1 == val2) || (val1 == Value::kInvalid) || (val2 == Value::kInvalid);
  }

  // Combine two ApiList instances.
  ApiList operator|(const ApiList& other) {
    // DomainApis are not mutually exclusive. Simply OR them.
    const uint32_t domain_apis = GetDomainApis() | other.GetDomainApis();

    // Values are mutually exclusive. Check if `this` and `other` have the same Value
    // or if at most one is set.
    const Value val1 = GetValue();
    const Value val2 = other.GetValue();
    if (val1 == val2) {
      return ApiList(val1, domain_apis);
    } else if (val1 == Value::kInvalid) {
      return ApiList(val2, domain_apis);
    } else if (val2 == Value::kInvalid) {
      return ApiList(val1, domain_apis);
    } else {
      LOG(FATAL) << "Invalid combination of values " << Dumpable(ApiList(val1))
          << " and " << Dumpable(ApiList(val2));
      UNREACHABLE();
    }
  }

  const ApiList& operator|=(const ApiList& other) {
    (*this) = (*this) | other;
    return *this;
  }

  // Returns true if all flags set in `other` are also set in `this`.
  bool Contains(const ApiList& other) const {
    return ((other.GetValue() == Value::kInvalid) || (GetValue() == other.GetValue())) &&
           helper::MatchesBitMask(other.GetDomainApis(), GetDomainApis());
  }

  // Returns true whether the configuration is valid for runtime use.
  bool IsValid() const { return GetValue() != Value::kInvalid; }

  // Returns true when no ApiList is specified and no domain_api flags either.
  bool IsEmpty() const { return (GetValue() == Value::kInvalid) && (GetDomainApis() == 0); }

  // Returns the maximum target SDK version allowed to access this ApiList.
  SdkVersion GetMaxAllowedSdkVersion() const { return kMaxSdkVersions[GetIntValue()]; }

  void Dump(std::ostream& os) const {
    bool is_first = true;

    if (GetValue() != Value::kInvalid) {
      os << kValueNames[GetIntValue()];
      is_first = false;
    }

    const uint32_t domain_apis = GetDomainApis();
    for (uint32_t i = helper::ToUint(DomainApi::kMin); i <= helper::ToUint(DomainApi::kMax); i++) {
      if (helper::MatchesBitMask(helper::ToBit(i), domain_apis)) {
        if (is_first) {
          is_first = false;
        } else {
          os << ",";
        }
        os << kDomainApiNames[i];
      }
    }

    DCHECK_EQ(IsEmpty(), is_first);
  }

  static constexpr uint32_t kValueCount = helper::NumValues<Value>();
  static constexpr uint32_t kDomainApiCount = helper::NumValues<DomainApi>();
};

inline std::ostream& operator<<(std::ostream& os, ApiList value) {
  value.Dump(os);
  return os;
}

}  // namespace hiddenapi
}  // namespace art


#endif  // ART_LIBARTBASE_BASE_HIDDENAPI_FLAGS_H_