crypto/bio/bio_test.cc

/* Copyright (c) 2014, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#include <algorithm>
#include <string>

#include <gtest/gtest.h>

#include <openssl/bio.h>
#include <openssl/crypto.h>
#include <openssl/err.h>
#include <openssl/mem.h>

#include "../internal.h"
#include "../test/test_util.h"

#if !defined(OPENSSL_WINDOWS)
#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#else
#include <io.h>
OPENSSL_MSVC_PRAGMA(warning(push, 3))
#include <winsock2.h>
#include <ws2tcpip.h>
OPENSSL_MSVC_PRAGMA(warning(pop))
#endif


#if !defined(OPENSSL_WINDOWS)
static int closesocket(int sock) { return close(sock); }
static std::string LastSocketError() { return strerror(errno); }
#else
static std::string LastSocketError() {
  char buf[DECIMAL_SIZE(int) + 1];
  BIO_snprintf(buf, sizeof(buf), "%d", WSAGetLastError());
  return buf;
}
#endif

class ScopedSocket {
 public:
  explicit ScopedSocket(int sock) : sock_(sock) {}
  ~ScopedSocket() {
    closesocket(sock_);
  }

 private:
  const int sock_;
};

TEST(BIOTest, SocketConnect) {
  static const char kTestMessage[] = "test";
  int listening_sock = -1;
  socklen_t len = 0;
  sockaddr_storage ss;
  struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) &ss;
  struct sockaddr_in *sin = (struct sockaddr_in *) &ss;
  OPENSSL_memset(&ss, 0, sizeof(ss));

  ss.ss_family = AF_INET6;
  listening_sock = socket(AF_INET6, SOCK_STREAM, 0);
  ASSERT_NE(-1, listening_sock) << LastSocketError();
  len = sizeof(*sin6);
  ASSERT_EQ(1, inet_pton(AF_INET6, "::1", &sin6->sin6_addr))
      << LastSocketError();
  if (bind(listening_sock, (struct sockaddr *)sin6, sizeof(*sin6)) == -1) {
    closesocket(listening_sock);

    ss.ss_family = AF_INET;
    listening_sock = socket(AF_INET, SOCK_STREAM, 0);
    ASSERT_NE(-1, listening_sock) << LastSocketError();
    len = sizeof(*sin);
    ASSERT_EQ(1, inet_pton(AF_INET, "127.0.0.1", &sin->sin_addr))
        << LastSocketError();
    ASSERT_EQ(0, bind(listening_sock, (struct sockaddr *)sin, sizeof(*sin)))
        << LastSocketError();
  }

  ScopedSocket listening_sock_closer(listening_sock);
  ASSERT_EQ(0, listen(listening_sock, 1)) << LastSocketError();
  ASSERT_EQ(0, getsockname(listening_sock, (struct sockaddr *)&ss, &len))
        << LastSocketError();

  char hostname[80];
  if (ss.ss_family == AF_INET6) {
    BIO_snprintf(hostname, sizeof(hostname), "[::1]:%d",
                 ntohs(sin6->sin6_port));
  } else if (ss.ss_family == AF_INET) {
    BIO_snprintf(hostname, sizeof(hostname), "127.0.0.1:%d",
                 ntohs(sin->sin_port));
  }

  // Connect to it with a connect BIO.
  bssl::UniquePtr<BIO> bio(BIO_new_connect(hostname));
  ASSERT_TRUE(bio);

  // Write a test message to the BIO.
  ASSERT_EQ(static_cast<int>(sizeof(kTestMessage)),
            BIO_write(bio.get(), kTestMessage, sizeof(kTestMessage)));

  // Accept the socket.
  int sock = accept(listening_sock, (struct sockaddr *) &ss, &len);
  ASSERT_NE(-1, sock) << LastSocketError();
  ScopedSocket sock_closer(sock);

  // Check the same message is read back out.
  char buf[sizeof(kTestMessage)];
  ASSERT_EQ(static_cast<int>(sizeof(kTestMessage)),
            recv(sock, buf, sizeof(buf), 0))
      << LastSocketError();
  EXPECT_EQ(Bytes(kTestMessage, sizeof(kTestMessage)), Bytes(buf, sizeof(buf)));
}

TEST(BIOTest, Printf) {
  // Test a short output, a very long one, and various sizes around
  // 256 (the size of the buffer) to ensure edge cases are correct.
  static const size_t kLengths[] = {5, 250, 251, 252, 253, 254, 1023};

  bssl::UniquePtr<BIO> bio(BIO_new(BIO_s_mem()));
  ASSERT_TRUE(bio);

  for (size_t length : kLengths) {
    SCOPED_TRACE(length);

    std::string in(length, 'a');

    int ret = BIO_printf(bio.get(), "test %s", in.c_str());
    ASSERT_GE(ret, 0);
    EXPECT_EQ(5 + length, static_cast<size_t>(ret));

    const uint8_t *contents;
    size_t len;
    ASSERT_TRUE(BIO_mem_contents(bio.get(), &contents, &len));
    EXPECT_EQ("test " + in,
              std::string(reinterpret_cast<const char *>(contents), len));

    ASSERT_TRUE(BIO_reset(bio.get()));
  }
}

TEST(BIOTest, ReadASN1) {
  static const size_t kLargeASN1PayloadLen = 8000;

  struct ASN1Test {
    bool should_succeed;
    std::vector<uint8_t> input;
    // suffix_len is the number of zeros to append to |input|.
    size_t suffix_len;
    // expected_len, if |should_succeed| is true, is the expected length of the
    // ASN.1 element.
    size_t expected_len;
    size_t max_len;
  } kASN1Tests[] = {
      {true, {0x30, 2, 1, 2, 0, 0}, 0, 4, 100},
      {false /* truncated */, {0x30, 3, 1, 2}, 0, 0, 100},
      {false /* should be short len */, {0x30, 0x81, 1, 1}, 0, 0, 100},
      {false /* zero padded */, {0x30, 0x82, 0, 1, 1}, 0, 0, 100},

      // Test a large payload.
      {true,
       {0x30, 0x82, kLargeASN1PayloadLen >> 8, kLargeASN1PayloadLen & 0xff},
       kLargeASN1PayloadLen,
       4 + kLargeASN1PayloadLen,
       kLargeASN1PayloadLen * 2},
      {false /* max_len too short */,
       {0x30, 0x82, kLargeASN1PayloadLen >> 8, kLargeASN1PayloadLen & 0xff},
       kLargeASN1PayloadLen,
       4 + kLargeASN1PayloadLen,
       3 + kLargeASN1PayloadLen},

      // Test an indefinite-length input.
      {true,
       {0x30, 0x80},
       kLargeASN1PayloadLen + 2,
       2 + kLargeASN1PayloadLen + 2,
       kLargeASN1PayloadLen * 2},
      {false /* max_len too short */,
       {0x30, 0x80},
       kLargeASN1PayloadLen + 2,
       2 + kLargeASN1PayloadLen + 2,
       2 + kLargeASN1PayloadLen + 1},
  };

  for (const auto &t : kASN1Tests) {
    std::vector<uint8_t> input = t.input;
    input.resize(input.size() + t.suffix_len, 0);

    bssl::UniquePtr<BIO> bio(BIO_new_mem_buf(input.data(), input.size()));
    ASSERT_TRUE(bio);

    uint8_t *out;
    size_t out_len;
    int ok = BIO_read_asn1(bio.get(), &out, &out_len, t.max_len);
    if (!ok) {
      out = nullptr;
    }
    bssl::UniquePtr<uint8_t> out_storage(out);

    ASSERT_EQ(t.should_succeed, (ok == 1));
    if (t.should_succeed) {
      EXPECT_EQ(Bytes(input.data(), t.expected_len), Bytes(out, out_len));
    }
  }
}

TEST(BIOTest, MemReadOnly) {
  // A memory BIO created from |BIO_new_mem_buf| is a read-only buffer.
  static const char kData[] = "abcdefghijklmno";
  bssl::UniquePtr<BIO> bio(BIO_new_mem_buf(kData, strlen(kData)));
  ASSERT_TRUE(bio);

  // Writing to read-only buffers should fail.
  EXPECT_EQ(BIO_write(bio.get(), kData, strlen(kData)), -1);

  const uint8_t *contents;
  size_t len;
  ASSERT_TRUE(BIO_mem_contents(bio.get(), &contents, &len));
  EXPECT_EQ(Bytes(contents, len), Bytes(kData));
  EXPECT_EQ(BIO_eof(bio.get()), 0);

  // Read less than the whole buffer.
  char buf[6];
  int ret = BIO_read(bio.get(), buf, sizeof(buf));
  ASSERT_GT(ret, 0);
  EXPECT_EQ(Bytes(buf, ret), Bytes("abcdef"));

  ASSERT_TRUE(BIO_mem_contents(bio.get(), &contents, &len));
  EXPECT_EQ(Bytes(contents, len), Bytes("ghijklmno"));
  EXPECT_EQ(BIO_eof(bio.get()), 0);

  ret = BIO_read(bio.get(), buf, sizeof(buf));
  ASSERT_GT(ret, 0);
  EXPECT_EQ(Bytes(buf, ret), Bytes("ghijkl"));

  ASSERT_TRUE(BIO_mem_contents(bio.get(), &contents, &len));
  EXPECT_EQ(Bytes(contents, len), Bytes("mno"));
  EXPECT_EQ(BIO_eof(bio.get()), 0);

  // Read the remainder of the buffer.
  ret = BIO_read(bio.get(), buf, sizeof(buf));
  ASSERT_GT(ret, 0);
  EXPECT_EQ(Bytes(buf, ret), Bytes("mno"));

  ASSERT_TRUE(BIO_mem_contents(bio.get(), &contents, &len));
  EXPECT_EQ(Bytes(contents, len), Bytes(""));
  EXPECT_EQ(BIO_eof(bio.get()), 1);

  // By default, reading from a consumed read-only buffer returns EOF.
  EXPECT_EQ(BIO_read(bio.get(), buf, sizeof(buf)), 0);
  EXPECT_FALSE(BIO_should_read(bio.get()));

  // A memory BIO can be configured to return an error instead of EOF. This is
  // error is returned as retryable. (This is not especially useful here. It
  // makes more sense for a writable BIO.)
  EXPECT_EQ(BIO_set_mem_eof_return(bio.get(), -1), 1);
  EXPECT_EQ(BIO_read(bio.get(), buf, sizeof(buf)), -1);
  EXPECT_TRUE(BIO_should_read(bio.get()));

  // Read exactly the right number of bytes, to test the boundary condition is
  // correct.
  bio.reset(BIO_new_mem_buf("abc", 3));
  ASSERT_TRUE(bio);
  ret = BIO_read(bio.get(), buf, 3);
  ASSERT_GT(ret, 0);
  EXPECT_EQ(Bytes(buf, ret), Bytes("abc"));
  EXPECT_EQ(BIO_eof(bio.get()), 1);
}

TEST(BIOTest, MemWritable) {
  // A memory BIO created from |BIO_new| is writable.
  bssl::UniquePtr<BIO> bio(BIO_new(BIO_s_mem()));
  ASSERT_TRUE(bio);

  auto check_bio_contents = [&](Bytes b) {
    const uint8_t *contents;
    size_t len;
    ASSERT_TRUE(BIO_mem_contents(bio.get(), &contents, &len));
    EXPECT_EQ(Bytes(contents, len), b);

    char *contents_c;
    long len_l = BIO_get_mem_data(bio.get(), &contents_c);
    ASSERT_GE(len_l, 0);
    EXPECT_EQ(Bytes(contents_c, len_l), b);

    BUF_MEM *buf;
    ASSERT_EQ(BIO_get_mem_ptr(bio.get(), &buf), 1);
    EXPECT_EQ(Bytes(buf->data, buf->length), b);
  };

  // It is initially empty.
  check_bio_contents(Bytes(""));
  EXPECT_EQ(BIO_eof(bio.get()), 1);

  // Reading from it should default to returning a retryable error.
  char buf[32];
  EXPECT_EQ(BIO_read(bio.get(), buf, sizeof(buf)), -1);
  EXPECT_TRUE(BIO_should_read(bio.get()));

  // This can be configured to return an EOF.
  EXPECT_EQ(BIO_set_mem_eof_return(bio.get(), 0), 1);
  EXPECT_EQ(BIO_read(bio.get(), buf, sizeof(buf)), 0);
  EXPECT_FALSE(BIO_should_read(bio.get()));

  // Restore the default. A writable memory |BIO| is typically used in this mode
  // so additional data can be written when exhausted.
  EXPECT_EQ(BIO_set_mem_eof_return(bio.get(), -1), 1);

  // Writes append to the buffer.
  ASSERT_EQ(BIO_write(bio.get(), "abcdef", 6), 6);
  check_bio_contents(Bytes("abcdef"));
  EXPECT_EQ(BIO_eof(bio.get()), 0);

  // Writes can include embedded NULs.
  ASSERT_EQ(BIO_write(bio.get(), "\0ghijk", 6), 6);
  check_bio_contents(Bytes("abcdef\0ghijk", 12));
  EXPECT_EQ(BIO_eof(bio.get()), 0);

  // Do a partial read.
  int ret = BIO_read(bio.get(), buf, 4);
  ASSERT_GT(ret, 0);
  EXPECT_EQ(Bytes(buf, ret), Bytes("abcd"));
  check_bio_contents(Bytes("ef\0ghijk", 8));
  EXPECT_EQ(BIO_eof(bio.get()), 0);

  // Reads and writes may alternate.
  ASSERT_EQ(BIO_write(bio.get(), "lmnopq", 6), 6);
  check_bio_contents(Bytes("ef\0ghijklmnopq", 14));
  EXPECT_EQ(BIO_eof(bio.get()), 0);

  // Reads may consume embedded NULs.
  ret = BIO_read(bio.get(), buf, 4);
  ASSERT_GT(ret, 0);
  EXPECT_EQ(Bytes(buf, ret), Bytes("ef\0g", 4));
  check_bio_contents(Bytes("hijklmnopq"));
  EXPECT_EQ(BIO_eof(bio.get()), 0);

  // The read buffer exceeds the |BIO|, so we consume everything.
  ret = BIO_read(bio.get(), buf, sizeof(buf));
  ASSERT_GT(ret, 0);
  EXPECT_EQ(Bytes(buf, ret), Bytes("hijklmnopq"));
  check_bio_contents(Bytes(""));
  EXPECT_EQ(BIO_eof(bio.get()), 1);

  // The |BIO| is now empty.
  EXPECT_EQ(BIO_read(bio.get(), buf, sizeof(buf)), -1);
  EXPECT_TRUE(BIO_should_read(bio.get()));

  // Repeat the above, reading exactly the right number of bytes, to test the
  // boundary condition is correct.
  ASSERT_EQ(BIO_write(bio.get(), "abc", 3), 3);
  ret = BIO_read(bio.get(), buf, 3);
  EXPECT_EQ(Bytes(buf, ret), Bytes("abc"));
  EXPECT_EQ(BIO_read(bio.get(), buf, sizeof(buf)), -1);
  EXPECT_TRUE(BIO_should_read(bio.get()));
  EXPECT_EQ(BIO_eof(bio.get()), 1);
}

TEST(BIOTest, Gets) {
  const struct {
    std::string bio;
    int gets_len;
    std::string gets_result;
  } kGetsTests[] = {
      // BIO_gets should stop at the first newline. If the buffer is too small,
      // stop there instead. Note the buffer size
      // includes a trailing NUL.
      {"123456789\n123456789", 5, "1234"},
      {"123456789\n123456789", 9, "12345678"},
      {"123456789\n123456789", 10, "123456789"},
      {"123456789\n123456789", 11, "123456789\n"},
      {"123456789\n123456789", 12, "123456789\n"},
      {"123456789\n123456789", 256, "123456789\n"},

      // If we run out of buffer, read the whole buffer.
      {"12345", 5, "1234"},
      {"12345", 6, "12345"},
      {"12345", 10, "12345"},

      // NUL bytes do not terminate gets.
      {std::string("abc\0def\nghi", 11), 256, std::string("abc\0def\n", 8)},

      // An output size of one means we cannot read any bytes. Only the trailing
      // NUL is included.
      {"12345", 1, ""},

      // Empty line.
      {"\nabcdef", 256, "\n"},
      // Empty BIO.
      {"", 256, ""},
  };
  for (const auto& t : kGetsTests) {
    SCOPED_TRACE(t.bio);
    SCOPED_TRACE(t.gets_len);

    auto check_bio_gets = [&](BIO *bio) {
      std::vector<char> buf(t.gets_len, 'a');
      int ret = BIO_gets(bio, buf.data(), t.gets_len);
      ASSERT_GE(ret, 0);
      // |BIO_gets| should write a NUL terminator, not counted in the return
      // value.
      EXPECT_EQ(Bytes(buf.data(), ret + 1),
                Bytes(t.gets_result.data(), t.gets_result.size() + 1));

      // The remaining data should still be in the BIO.
      buf.resize(t.bio.size() + 1);
      ret = BIO_read(bio, buf.data(), static_cast<int>(buf.size()));
      ASSERT_GE(ret, 0);
      EXPECT_EQ(Bytes(buf.data(), ret),
                Bytes(t.bio.substr(t.gets_result.size())));
    };

    {
      SCOPED_TRACE("memory");
      bssl::UniquePtr<BIO> bio(BIO_new_mem_buf(t.bio.data(), t.bio.size()));
      ASSERT_TRUE(bio);
      check_bio_gets(bio.get());
    }

    using ScopedFILE = std::unique_ptr<FILE, decltype(&fclose)>;
    ScopedFILE file(tmpfile(), fclose);
#if defined(OPENSSL_ANDROID)
    // On Android, when running from an APK, |tmpfile| does not work. See
    // b/36991167#comment8.
    if (!file) {
      fprintf(stderr, "tmpfile failed: %s (%d). Skipping file-based tests.\n",
              strerror(errno), errno);
      continue;
    }
#else
    ASSERT_TRUE(file);
#endif

    if (!t.bio.empty()) {
      ASSERT_EQ(1u,
                fwrite(t.bio.data(), t.bio.size(), /*nitems=*/1, file.get()));
      ASSERT_EQ(0, fseek(file.get(), 0, SEEK_SET));
    }

    // TODO(crbug.com/boringssl/585): If the line has an embedded NUL, file
    // BIOs do not currently report the answer correctly.
    if (t.bio.find('\0') == std::string::npos) {
      SCOPED_TRACE("file");
      bssl::UniquePtr<BIO> bio(BIO_new_fp(file.get(), BIO_NOCLOSE));
      ASSERT_TRUE(bio);
      check_bio_gets(bio.get());
    }

    ASSERT_EQ(0, fseek(file.get(), 0, SEEK_SET));

    {
      SCOPED_TRACE("fd");
#if defined(OPENSSL_WINDOWS)
      int fd = _fileno(file.get());
#else
      int fd = fileno(file.get());
#endif
      bssl::UniquePtr<BIO> bio(BIO_new_fd(fd, BIO_NOCLOSE));
      ASSERT_TRUE(bio);
      check_bio_gets(bio.get());
    }
  }

  // Negative and zero lengths should not output anything, even a trailing NUL.
  bssl::UniquePtr<BIO> bio(BIO_new_mem_buf("12345", -1));
  ASSERT_TRUE(bio);
  char c = 'a';
  EXPECT_EQ(0, BIO_gets(bio.get(), &c, -1));
  EXPECT_EQ(0, BIO_gets(bio.get(), &c, 0));
  EXPECT_EQ(c, 'a');
}

// Run through the tests twice, swapping |bio1| and |bio2|, for symmetry.
class BIOPairTest : public testing::TestWithParam<bool> {};

TEST_P(BIOPairTest, TestPair) {
  BIO *bio1, *bio2;
  ASSERT_TRUE(BIO_new_bio_pair(&bio1, 10, &bio2, 10));
  bssl::UniquePtr<BIO> free_bio1(bio1), free_bio2(bio2);

  if (GetParam()) {
    std::swap(bio1, bio2);
  }

  // Check initial states.
  EXPECT_EQ(10u, BIO_ctrl_get_write_guarantee(bio1));
  EXPECT_EQ(0u, BIO_ctrl_get_read_request(bio1));

  // Data written in one end may be read out the other.
  uint8_t buf[20];
  EXPECT_EQ(5, BIO_write(bio1, "12345", 5));
  EXPECT_EQ(5u, BIO_ctrl_get_write_guarantee(bio1));
  ASSERT_EQ(5, BIO_read(bio2, buf, sizeof(buf)));
  EXPECT_EQ(Bytes("12345"), Bytes(buf, 5));
  EXPECT_EQ(10u, BIO_ctrl_get_write_guarantee(bio1));

  // Attempting to write more than 10 bytes will write partially.
  EXPECT_EQ(10, BIO_write(bio1, "1234567890___", 13));
  EXPECT_EQ(0u, BIO_ctrl_get_write_guarantee(bio1));
  EXPECT_EQ(-1, BIO_write(bio1, "z", 1));
  EXPECT_TRUE(BIO_should_write(bio1));
  ASSERT_EQ(10, BIO_read(bio2, buf, sizeof(buf)));
  EXPECT_EQ(Bytes("1234567890"), Bytes(buf, 10));
  EXPECT_EQ(10u, BIO_ctrl_get_write_guarantee(bio1));

  // Unsuccessful reads update the read request.
  EXPECT_EQ(-1, BIO_read(bio2, buf, 5));
  EXPECT_TRUE(BIO_should_read(bio2));
  EXPECT_EQ(5u, BIO_ctrl_get_read_request(bio1));

  // The read request is clamped to the size of the buffer.
  EXPECT_EQ(-1, BIO_read(bio2, buf, 20));
  EXPECT_TRUE(BIO_should_read(bio2));
  EXPECT_EQ(10u, BIO_ctrl_get_read_request(bio1));

  // Data may be written and read in chunks.
  EXPECT_EQ(5, BIO_write(bio1, "12345", 5));
  EXPECT_EQ(5u, BIO_ctrl_get_write_guarantee(bio1));
  EXPECT_EQ(5, BIO_write(bio1, "67890___", 8));
  EXPECT_EQ(0u, BIO_ctrl_get_write_guarantee(bio1));
  ASSERT_EQ(3, BIO_read(bio2, buf, 3));
  EXPECT_EQ(Bytes("123"), Bytes(buf, 3));
  EXPECT_EQ(3u, BIO_ctrl_get_write_guarantee(bio1));
  ASSERT_EQ(7, BIO_read(bio2, buf, sizeof(buf)));
  EXPECT_EQ(Bytes("4567890"), Bytes(buf, 7));
  EXPECT_EQ(10u, BIO_ctrl_get_write_guarantee(bio1));

  // Successful reads reset the read request.
  EXPECT_EQ(0u, BIO_ctrl_get_read_request(bio1));

  // Test writes and reads starting in the middle of the ring buffer and
  // wrapping to front.
  EXPECT_EQ(8, BIO_write(bio1, "abcdefgh", 8));
  EXPECT_EQ(2u, BIO_ctrl_get_write_guarantee(bio1));
  ASSERT_EQ(3, BIO_read(bio2, buf, 3));
  EXPECT_EQ(Bytes("abc"), Bytes(buf, 3));
  EXPECT_EQ(5u, BIO_ctrl_get_write_guarantee(bio1));
  EXPECT_EQ(5, BIO_write(bio1, "ijklm___", 8));
  EXPECT_EQ(0u, BIO_ctrl_get_write_guarantee(bio1));
  ASSERT_EQ(10, BIO_read(bio2, buf, sizeof(buf)));
  EXPECT_EQ(Bytes("defghijklm"), Bytes(buf, 10));
  EXPECT_EQ(10u, BIO_ctrl_get_write_guarantee(bio1));

  // Data may flow from both ends in parallel.
  EXPECT_EQ(5, BIO_write(bio1, "12345", 5));
  EXPECT_EQ(5, BIO_write(bio2, "67890", 5));
  ASSERT_EQ(5, BIO_read(bio2, buf, sizeof(buf)));
  EXPECT_EQ(Bytes("12345"), Bytes(buf, 5));
  ASSERT_EQ(5, BIO_read(bio1, buf, sizeof(buf)));
  EXPECT_EQ(Bytes("67890"), Bytes(buf, 5));

  // Closing the write end causes an EOF on the read half, after draining.
  EXPECT_EQ(5, BIO_write(bio1, "12345", 5));
  EXPECT_TRUE(BIO_shutdown_wr(bio1));
  ASSERT_EQ(5, BIO_read(bio2, buf, sizeof(buf)));
  EXPECT_EQ(Bytes("12345"), Bytes(buf, 5));
  EXPECT_EQ(0, BIO_read(bio2, buf, sizeof(buf)));

  // A closed write end may not be written to.
  EXPECT_EQ(0u, BIO_ctrl_get_write_guarantee(bio1));
  EXPECT_EQ(-1, BIO_write(bio1, "_____", 5));

  uint32_t err = ERR_get_error();
  EXPECT_EQ(ERR_LIB_BIO, ERR_GET_LIB(err));
  EXPECT_EQ(BIO_R_BROKEN_PIPE, ERR_GET_REASON(err));

  // The other end is still functional.
  EXPECT_EQ(5, BIO_write(bio2, "12345", 5));
  ASSERT_EQ(5, BIO_read(bio1, buf, sizeof(buf)));
  EXPECT_EQ(Bytes("12345"), Bytes(buf, 5));
}

INSTANTIATE_TEST_SUITE_P(All, BIOPairTest, testing::Values(false, true));