crypto/pool/pool.cc

// Copyright 2016 The BoringSSL Authors
//
// 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
//
//     https://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.

#include <openssl/pool.h>

#include <assert.h>
#include <string.h>

#include <openssl/bytestring.h>
#include <openssl/mem.h>
#include <openssl/rand.h>
#include <openssl/siphash.h>

#include "../internal.h"
#include "../mem_internal.h"
#include "internal.h"


using namespace bssl;

static uint32_t hash_data(const CryptoBufferPool *pool,
                          Span<const uint8_t> in) {
  return static_cast<uint32_t>(
      SIPHASH_24(pool->hash_key, in.data(), in.size()));
}

static uint32_t CRYPTO_BUFFER_hash(const CryptoBuffer *buf) {
  return hash_data(buf->pool, Span(buf->data, buf->len));
}

static int CRYPTO_BUFFER_cmp(const CryptoBuffer *a, const CryptoBuffer *b) {
  // Only |CRYPTO_BUFFER|s from the same pool have compatible hashes.
  assert(a->pool != nullptr);
  assert(a->pool == b->pool);
  if (a->len != b->len) {
    return 1;
  }
  return OPENSSL_memcmp(a->data, b->data, a->len);
}

CRYPTO_BUFFER_POOL *CRYPTO_BUFFER_POOL_new() {
  CryptoBufferPool *pool = NewZeroed<CryptoBufferPool>();
  if (pool == nullptr) {
    return nullptr;
  }

  pool->bufs = lh_CryptoBuffer_new(CRYPTO_BUFFER_hash, CRYPTO_BUFFER_cmp);
  if (pool->bufs == nullptr) {
    Delete(pool);
    return nullptr;
  }

  CRYPTO_MUTEX_init(&pool->lock);
  RAND_bytes((uint8_t *)&pool->hash_key, sizeof(pool->hash_key));

  return pool;
}

void CRYPTO_BUFFER_POOL_free(CRYPTO_BUFFER_POOL *pool) {
  auto *impl = FromOpaque(pool);
  if (impl == nullptr) {
    return;
  }

#if !defined(NDEBUG)
  CRYPTO_MUTEX_lock_write(&impl->lock);
  assert(lh_CryptoBuffer_num_items(impl->bufs) == 0);
  CRYPTO_MUTEX_unlock_write(&impl->lock);
#endif

  lh_CryptoBuffer_free(impl->bufs);
  CRYPTO_MUTEX_cleanup(&impl->lock);
  Delete(impl);
}

static void crypto_buffer_free_object(CryptoBuffer *buf) {
  if (!buf->data_is_static) {
    OPENSSL_free(buf->data);
  }
  Delete(buf);
}

static CryptoBuffer *crypto_buffer_new(Span<const uint8_t> data,
                                       bool data_is_static,
                                       CryptoBufferPool *pool) {
  if (pool != nullptr) {
    // Look for a matching buffer in the pool.
    uint32_t hash = hash_data(pool, data);
    CRYPTO_MUTEX_lock_read(&pool->lock);
    CryptoBuffer *duplicate = lh_CryptoBuffer_retrieve_key(
        pool->bufs, &data, hash,
        [](const void *key_v, const CryptoBuffer *buf) -> int {
          Span<const uint8_t> key =
              *static_cast<const Span<const uint8_t> *>(key_v);
          return key == Span(buf->data, buf->len) ? 0 : 1;
        });
    if (data_is_static && duplicate != nullptr && !duplicate->data_is_static) {
      // If the new |CRYPTO_BUFFER| would have static data, but the duplicate
      // does not, we replace the old one with the new static version.
      duplicate = nullptr;
    }
    if (duplicate != nullptr) {
      CRYPTO_refcount_inc(&duplicate->references);
    }
    CRYPTO_MUTEX_unlock_read(&pool->lock);

    if (duplicate != nullptr) {
      return duplicate;
    }
  }

  CryptoBuffer *const buf = NewZeroed<CryptoBuffer>();
  if (buf == nullptr) {
    return nullptr;
  }

  if (data_is_static) {
    buf->data = const_cast<uint8_t *>(data.data());
    buf->data_is_static = 1;
  } else {
    buf->data =
        static_cast<uint8_t *>(OPENSSL_memdup(data.data(), data.size()));
    if (!data.empty() && buf->data == nullptr) {
      Delete(buf);
      return nullptr;
    }
  }

  buf->len = data.size();
  buf->references = 1;

  if (pool == nullptr) {
    return buf;
  }

  buf->pool = pool;

  CRYPTO_MUTEX_lock_write(&pool->lock);
  CryptoBuffer *duplicate = lh_CryptoBuffer_retrieve(pool->bufs, buf);
  if (data_is_static && duplicate != nullptr && !duplicate->data_is_static) {
    // If the new |CRYPTO_BUFFER| would have static data, but the duplicate does
    // not, we replace the old one with the new static version.
    duplicate = nullptr;
  }
  int inserted = 0;
  if (duplicate == nullptr) {
    CryptoBuffer *old = nullptr;
    inserted = lh_CryptoBuffer_insert(pool->bufs, &old, buf);
    // |old| may be non-NULL if a match was found but ignored. |pool->bufs| does
    // not increment refcounts, so there is no need to clean up after the
    // replacement.
  } else {
    CRYPTO_refcount_inc(&duplicate->references);
  }
  CRYPTO_MUTEX_unlock_write(&pool->lock);

  if (!inserted) {
    // We raced to insert |buf| into the pool and lost, or else there was an
    // error inserting.
    crypto_buffer_free_object(buf);
    return duplicate;
  }

  return buf;
}

CRYPTO_BUFFER *CRYPTO_BUFFER_new(const uint8_t *data, size_t len,
                                 CRYPTO_BUFFER_POOL *pool) {
  return crypto_buffer_new(Span(data, len), /*data_is_static=*/false,
                           FromOpaque(pool));
}

CRYPTO_BUFFER *CRYPTO_BUFFER_alloc(uint8_t **out_data, size_t len) {
  CryptoBuffer *const buf = NewZeroed<CryptoBuffer>();
  if (buf == nullptr) {
    return nullptr;
  }

  buf->data = reinterpret_cast<uint8_t *>(OPENSSL_malloc(len));
  if (len != 0 && buf->data == nullptr) {
    Delete(buf);
    return nullptr;
  }
  buf->len = len;
  buf->references = 1;

  *out_data = buf->data;
  return buf;
}

CRYPTO_BUFFER *CRYPTO_BUFFER_new_from_CBS(const CBS *cbs,
                                          CRYPTO_BUFFER_POOL *pool) {
  return CRYPTO_BUFFER_new(CBS_data(cbs), CBS_len(cbs), pool);
}

CRYPTO_BUFFER *CRYPTO_BUFFER_new_from_static_data_unsafe(
    const uint8_t *data, size_t len, CRYPTO_BUFFER_POOL *pool) {
  return crypto_buffer_new(Span(data, len), /*data_is_static=*/true,
                           FromOpaque(pool));
}

void CRYPTO_BUFFER_free(CRYPTO_BUFFER *buf) {
  if (buf == nullptr) {
    return;
  }
  auto *impl = FromOpaque(buf);

  CryptoBufferPool *const pool = impl->pool;
  if (pool == nullptr) {
    if (CRYPTO_refcount_dec_and_test_zero(&impl->references)) {
      // If a reference count of zero is observed, there cannot be a reference
      // from any pool to this buffer and thus we are able to free this
      // buffer.
      crypto_buffer_free_object(impl);
    }

    return;
  }

  CRYPTO_MUTEX_lock_write(&pool->lock);
  if (!CRYPTO_refcount_dec_and_test_zero(&impl->references)) {
    CRYPTO_MUTEX_unlock_write(&impl->pool->lock);
    return;
  }

  // We have an exclusive lock on the pool, therefore no concurrent lookups can
  // find this buffer and increment the reference count. Thus, if the count is
  // zero there are and can never be any more references and thus we can free
  // this buffer.
  //
  // Note it is possible |buf| is no longer in the pool, if it was replaced by a
  // static version. If that static version was since removed, it is even
  // possible for |found| to be NULL.
  CryptoBuffer *found = lh_CryptoBuffer_retrieve(pool->bufs, impl);
  if (found == impl) {
    found = lh_CryptoBuffer_delete(pool->bufs, impl);
    assert(found == impl);
    (void)found;
  }

  CRYPTO_MUTEX_unlock_write(&impl->pool->lock);
  crypto_buffer_free_object(impl);
}

int CRYPTO_BUFFER_up_ref(CRYPTO_BUFFER *buf) {
  auto *impl = FromOpaque(buf);
  // This is safe in the case that |buf->pool| is NULL because it's just
  // standard reference counting in that case.
  //
  // This is also safe if |buf->pool| is non-NULL because, if it were racing
  // with |CRYPTO_BUFFER_free| then the two callers must have independent
  // references already and so the reference count will never hit zero.
  CRYPTO_refcount_inc(&impl->references);
  return 1;
}

const uint8_t *CRYPTO_BUFFER_data(const CRYPTO_BUFFER *buf) {
  auto *impl = FromOpaque(buf);
  return impl->data;
}

size_t CRYPTO_BUFFER_len(const CRYPTO_BUFFER *buf) {
  auto *impl = FromOpaque(buf);
  return impl->len;
}

void CRYPTO_BUFFER_init_CBS(const CRYPTO_BUFFER *buf, CBS *out) {
  auto *impl = FromOpaque(buf);
  CBS_init(out, impl->data, impl->len);
}