ssl/internal.h

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */
/* ====================================================================
 * Copyright (c) 1998-2007 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */
/* ====================================================================
 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
 * ECC cipher suite support in OpenSSL originally developed by
 * SUN MICROSYSTEMS, INC., and contributed to the OpenSSL project.
 */
/* ====================================================================
 * Copyright 2005 Nokia. All rights reserved.
 *
 * The portions of the attached software ("Contribution") is developed by
 * Nokia Corporation and is licensed pursuant to the OpenSSL open source
 * license.
 *
 * The Contribution, originally written by Mika Kousa and Pasi Eronen of
 * Nokia Corporation, consists of the "PSK" (Pre-Shared Key) ciphersuites
 * support (see RFC 4279) to OpenSSL.
 *
 * No patent licenses or other rights except those expressly stated in
 * the OpenSSL open source license shall be deemed granted or received
 * expressly, by implication, estoppel, or otherwise.
 *
 * No assurances are provided by Nokia that the Contribution does not
 * infringe the patent or other intellectual property rights of any third
 * party or that the license provides you with all the necessary rights
 * to make use of the Contribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. IN
 * ADDITION TO THE DISCLAIMERS INCLUDED IN THE LICENSE, NOKIA
 * SPECIFICALLY DISCLAIMS ANY LIABILITY FOR CLAIMS BROUGHT BY YOU OR ANY
 * OTHER ENTITY BASED ON INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS OR
 * OTHERWISE.
 */

#ifndef OPENSSL_HEADER_SSL_INTERNAL_H
#define OPENSSL_HEADER_SSL_INTERNAL_H

#include <openssl/base.h>

#include <openssl/aead.h>
#include <openssl/ssl.h>
#include <openssl/stack.h>

#if defined(OPENSSL_WINDOWS)
/* Windows defines struct timeval in winsock2.h. */
OPENSSL_MSVC_PRAGMA(warning(push, 3))
#include <winsock2.h>
OPENSSL_MSVC_PRAGMA(warning(pop))
#else
#include <sys/time.h>
#endif

#if defined(__cplusplus)
extern "C" {
#endif


/* Cipher suites. */

/* Bits for |algorithm_mkey| (key exchange algorithm). */
#define SSL_kRSA 0x00000001L
#define SSL_kDHE 0x00000002L
#define SSL_kECDHE 0x00000004L
/* SSL_kPSK is only set for plain PSK, not ECDHE_PSK. */
#define SSL_kPSK 0x00000008L
#define SSL_kCECPQ1 0x00000010L

/* Bits for |algorithm_auth| (server authentication). */
#define SSL_aRSA 0x00000001L
#define SSL_aECDSA 0x00000002L
/* SSL_aPSK is set for both PSK and ECDHE_PSK. */
#define SSL_aPSK 0x00000004L

#define SSL_aCERT (SSL_aRSA | SSL_aECDSA)

/* Bits for |algorithm_enc| (symmetric encryption). */
#define SSL_3DES 0x00000001L
#define SSL_RC4 0x00000002L
#define SSL_AES128 0x00000004L
#define SSL_AES256 0x00000008L
#define SSL_AES128GCM 0x00000010L
#define SSL_AES256GCM 0x00000020L
#define SSL_CHACHA20POLY1305_OLD 0x00000040L
#define SSL_eNULL 0x00000080L
#define SSL_CHACHA20POLY1305 0x00000100L

#define SSL_AES (SSL_AES128 | SSL_AES256 | SSL_AES128GCM | SSL_AES256GCM)

/* Bits for |algorithm_mac| (symmetric authentication). */
#define SSL_MD5 0x00000001L
#define SSL_SHA1 0x00000002L
#define SSL_SHA256 0x00000004L
#define SSL_SHA384 0x00000008L
/* SSL_AEAD is set for all AEADs. */
#define SSL_AEAD 0x00000010L

/* Bits for |algorithm_prf| (handshake digest). */
#define SSL_HANDSHAKE_MAC_DEFAULT 0x1
#define SSL_HANDSHAKE_MAC_SHA256 0x2
#define SSL_HANDSHAKE_MAC_SHA384 0x4

/* SSL_MAX_DIGEST is the number of digest types which exist. When adding a new
 * one, update the table in ssl_cipher.c. */
#define SSL_MAX_DIGEST 4

/* ssl_cipher_get_evp_aead sets |*out_aead| to point to the correct EVP_AEAD
 * object for |cipher| protocol version |version|. It sets |*out_mac_secret_len|
 * and |*out_fixed_iv_len| to the MAC key length and fixed IV length,
 * respectively. The MAC key length is zero except for legacy block and stream
 * ciphers. It returns 1 on success and 0 on error. */
int ssl_cipher_get_evp_aead(const EVP_AEAD **out_aead,
                            size_t *out_mac_secret_len,
                            size_t *out_fixed_iv_len,
                            const SSL_CIPHER *cipher, uint16_t version);

/* ssl_get_handshake_digest returns the |EVP_MD| corresponding to
 * |algorithm_prf|. It returns SHA-1 for |SSL_HANDSHAKE_DEFAULT|. The caller is
 * responsible for maintaining the additional MD5 digest and switching to
 * SHA-256 in TLS 1.2. */
const EVP_MD *ssl_get_handshake_digest(uint32_t algorithm_prf);

/* ssl_create_cipher_list evaluates |rule_str| according to the ciphers in
 * |ssl_method|. It sets |*out_cipher_list| to a newly-allocated
 * |ssl_cipher_preference_list_st| containing the result.
 * |*out_cipher_list_by_id| is set to a list of selected ciphers sorted by
 * id. It returns |(*out_cipher_list)->ciphers| on success and NULL on
 * failure. */
STACK_OF(SSL_CIPHER) *
ssl_create_cipher_list(const SSL_PROTOCOL_METHOD *ssl_method,
                       struct ssl_cipher_preference_list_st **out_cipher_list,
                       STACK_OF(SSL_CIPHER) **out_cipher_list_by_id,
                       const char *rule_str);

/* ssl_cipher_get_value returns the cipher suite id of |cipher|. */
uint16_t ssl_cipher_get_value(const SSL_CIPHER *cipher);

/* ssl_cipher_get_key_type returns the |EVP_PKEY_*| value corresponding to the
 * server key used in |cipher| or |EVP_PKEY_NONE| if there is none. */
int ssl_cipher_get_key_type(const SSL_CIPHER *cipher);

/* ssl_cipher_uses_certificate_auth returns one if |cipher| authenticates the
 * server and, optionally, the client with a certificate. Otherwise it returns
 * zero. */
int ssl_cipher_uses_certificate_auth(const SSL_CIPHER *cipher);

/* ssl_cipher_requires_server_key_exchange returns 1 if |cipher| requires a
 * ServerKeyExchange message. Otherwise it returns 0.
 *
 * This function may return zero while still allowing |cipher| an optional
 * ServerKeyExchange. This is the case for plain PSK ciphers. */
int ssl_cipher_requires_server_key_exchange(const SSL_CIPHER *cipher);

/* ssl_cipher_get_record_split_len, for TLS 1.0 CBC mode ciphers, returns the
 * length of an encrypted 1-byte record, for use in record-splitting. Otherwise
 * it returns zero. */
size_t ssl_cipher_get_record_split_len(const SSL_CIPHER *cipher);


/* Encryption layer. */

/* SSL_AEAD_CTX contains information about an AEAD that is being used to encrypt
 * an SSL connection. */
struct ssl_aead_ctx_st {
  const SSL_CIPHER *cipher;
  EVP_AEAD_CTX ctx;
  /* fixed_nonce contains any bytes of the nonce that are fixed for all
   * records. */
  uint8_t fixed_nonce[12];
  uint8_t fixed_nonce_len, variable_nonce_len;
  /* variable_nonce_included_in_record is non-zero if the variable nonce
   * for a record is included as a prefix before the ciphertext. */
  char variable_nonce_included_in_record;
  /* random_variable_nonce is non-zero if the variable nonce is
   * randomly generated, rather than derived from the sequence
   * number. */
  char random_variable_nonce;
  /* omit_length_in_ad is non-zero if the length should be omitted in the
   * AEAD's ad parameter. */
  char omit_length_in_ad;
  /* omit_version_in_ad is non-zero if the version should be omitted
   * in the AEAD's ad parameter. */
  char omit_version_in_ad;
  /* omit_ad is non-zero if the AEAD's ad parameter should be omitted. */
  char omit_ad;
  /* xor_fixed_nonce is non-zero if the fixed nonce should be XOR'd into the
   * variable nonce rather than prepended. */
  char xor_fixed_nonce;
} /* SSL_AEAD_CTX */;

/* SSL_AEAD_CTX_new creates a newly-allocated |SSL_AEAD_CTX| using the supplied
 * key material. It returns NULL on error. Only one of |SSL_AEAD_CTX_open| or
 * |SSL_AEAD_CTX_seal| may be used with the resulting object, depending on
 * |direction|. |version| is the normalized protocol version, so DTLS 1.0 is
 * represented as 0x0301, not 0xffef. */
SSL_AEAD_CTX *SSL_AEAD_CTX_new(enum evp_aead_direction_t direction,
                               uint16_t version, const SSL_CIPHER *cipher,
                               const uint8_t *enc_key, size_t enc_key_len,
                               const uint8_t *mac_key, size_t mac_key_len,
                               const uint8_t *fixed_iv, size_t fixed_iv_len);

/* SSL_AEAD_CTX_free frees |ctx|. */
void SSL_AEAD_CTX_free(SSL_AEAD_CTX *ctx);

/* SSL_AEAD_CTX_explicit_nonce_len returns the length of the explicit nonce for
 * |ctx|, if any. |ctx| may be NULL to denote the null cipher. */
size_t SSL_AEAD_CTX_explicit_nonce_len(SSL_AEAD_CTX *ctx);

/* SSL_AEAD_CTX_max_overhead returns the maximum overhead of calling
 * |SSL_AEAD_CTX_seal|. |ctx| may be NULL to denote the null cipher. */
size_t SSL_AEAD_CTX_max_overhead(SSL_AEAD_CTX *ctx);

/* SSL_AEAD_CTX_open authenticates and decrypts |in_len| bytes from |in|
 * in-place. On success, it sets |*out| to the plaintext in |in| and returns
 * one. Otherwise, it returns zero. |ctx| may be NULL to denote the null cipher.
 * The output will always be |explicit_nonce_len| bytes ahead of |in|. */
int SSL_AEAD_CTX_open(SSL_AEAD_CTX *ctx, CBS *out, uint8_t type,
                      uint16_t wire_version, const uint8_t seqnum[8],
                      uint8_t *in, size_t in_len);

/* SSL_AEAD_CTX_seal encrypts and authenticates |in_len| bytes from |in| and
 * writes the result to |out|. It returns one on success and zero on
 * error. |ctx| may be NULL to denote the null cipher.
 *
 * If |in| and |out| alias then |out| + |explicit_nonce_len| must be == |in|. */
int SSL_AEAD_CTX_seal(SSL_AEAD_CTX *ctx, uint8_t *out, size_t *out_len,
                      size_t max_out, uint8_t type, uint16_t wire_version,
                      const uint8_t seqnum[8], const uint8_t *in,
                      size_t in_len);


/* DTLS replay bitmap. */

/* DTLS1_BITMAP maintains a sliding window of 64 sequence numbers to detect
 * replayed packets. It should be initialized by zeroing every field. */
typedef struct dtls1_bitmap_st {
  /* map is a bit mask of the last 64 sequence numbers. Bit
   * |1<<i| corresponds to |max_seq_num - i|. */
  uint64_t map;
  /* max_seq_num is the largest sequence number seen so far as a 64-bit
   * integer. */
  uint64_t max_seq_num;
} DTLS1_BITMAP;


/* Record layer. */

/* ssl_record_sequence_update increments the sequence number in |seq|. It
 * returns one on success and zero on wraparound. */
int ssl_record_sequence_update(uint8_t *seq, size_t seq_len);

/* ssl_record_prefix_len returns the length of the prefix before the ciphertext
 * of a record for |ssl|.
 *
 * TODO(davidben): Expose this as part of public API once the high-level
 * buffer-free APIs are available. */
size_t ssl_record_prefix_len(const SSL *ssl);

enum ssl_open_record_t {
  ssl_open_record_success,
  ssl_open_record_discard,
  ssl_open_record_partial,
  ssl_open_record_close_notify,
  ssl_open_record_fatal_alert,
  ssl_open_record_error,
};

/* tls_open_record decrypts a record from |in| in-place.
 *
 * If the input did not contain a complete record, it returns
 * |ssl_open_record_partial|. It sets |*out_consumed| to the total number of
 * bytes necessary. It is guaranteed that a successful call to |tls_open_record|
 * will consume at least that many bytes.
 *
 * Otherwise, it sets |*out_consumed| to the number of bytes of input
 * consumed. Note that input may be consumed on all return codes if a record was
 * decrypted.
 *
 * On success, it returns |ssl_open_record_success|. It sets |*out_type| to the
 * record type and |*out| to the record body in |in|. Note that |*out| may be
 * empty.
 *
 * If a record was successfully processed but should be discarded, it returns
 * |ssl_open_record_discard|.
 *
 * If a record was successfully processed but is a close_notify or fatal alert,
 * it returns |ssl_open_record_close_notify| or |ssl_open_record_fatal_alert|.
 *
 * On failure, it returns |ssl_open_record_error| and sets |*out_alert| to an
 * alert to emit. */
enum ssl_open_record_t tls_open_record(SSL *ssl, uint8_t *out_type, CBS *out,
                                       size_t *out_consumed, uint8_t *out_alert,
                                       uint8_t *in, size_t in_len);

/* dtls_open_record implements |tls_open_record| for DTLS. It never returns
 * |ssl_open_record_partial| but otherwise behaves analogously. */
enum ssl_open_record_t dtls_open_record(SSL *ssl, uint8_t *out_type, CBS *out,
                                        size_t *out_consumed,
                                        uint8_t *out_alert, uint8_t *in,
                                        size_t in_len);

/* ssl_seal_align_prefix_len returns the length of the prefix before the start
 * of the bulk of the ciphertext when sealing a record with |ssl|. Callers may
 * use this to align buffers.
 *
 * Note when TLS 1.0 CBC record-splitting is enabled, this includes the one byte
 * record and is the offset into second record's ciphertext. Thus this value may
 * differ from |ssl_record_prefix_len| and sealing a small record may result in
 * a smaller output than this value.
 *
 * TODO(davidben): Expose this as part of public API once the high-level
 * buffer-free APIs are available. */
size_t ssl_seal_align_prefix_len(const SSL *ssl);

/* ssl_max_seal_overhead returns the maximum overhead of sealing a record with
 * |ssl|.
 *
 * TODO(davidben): Expose this as part of public API once the high-level
 * buffer-free APIs are available. */
size_t ssl_max_seal_overhead(const SSL *ssl);

/* tls_seal_record seals a new record of type |type| and body |in| and writes it
 * to |out|. At most |max_out| bytes will be written. It returns one on success
 * and zero on error. If enabled, |tls_seal_record| implements TLS 1.0 CBC 1/n-1
 * record splitting and may write two records concatenated.
 *
 * For a large record, the bulk of the ciphertext will begin
 * |ssl_seal_align_prefix_len| bytes into out. Aligning |out| appropriately may
 * improve performance. It writes at most |in_len| + |ssl_max_seal_overhead|
 * bytes to |out|.
 *
 * |in| and |out| may not alias. */
int tls_seal_record(SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out,
                    uint8_t type, const uint8_t *in, size_t in_len);

enum dtls1_use_epoch_t {
  dtls1_use_previous_epoch,
  dtls1_use_current_epoch,
};

/* dtls_seal_record implements |tls_seal_record| for DTLS. |use_epoch| selects
 * which epoch's cipher state to use. */
int dtls_seal_record(SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out,
                     uint8_t type, const uint8_t *in, size_t in_len,
                     enum dtls1_use_epoch_t use_epoch);

/* ssl_process_alert processes |in| as an alert and updates |ssl|'s shutdown
 * state. It returns one of |ssl_open_record_discard|, |ssl_open_record_error|,
 * |ssl_open_record_close_notify|, or |ssl_open_record_fatal_alert| as
 * appropriate. */
enum ssl_open_record_t ssl_process_alert(SSL *ssl, uint8_t *out_alert,
                                         const uint8_t *in, size_t in_len);


/* Private key operations. */

/* ssl_has_private_key returns one if |ssl| has a private key
 * configured and zero otherwise. */
int ssl_has_private_key(const SSL *ssl);

/* ssl_is_ecdsa_key_type returns one if |type| is an ECDSA key type and zero
 * otherwise. */
int ssl_is_ecdsa_key_type(int type);

/* ssl_private_key_* call the corresponding function on the
 * |SSL_PRIVATE_KEY_METHOD| for |ssl|, if configured. Otherwise, they implement
 * the operation with |EVP_PKEY|. */

int ssl_private_key_type(SSL *ssl);

size_t ssl_private_key_max_signature_len(SSL *ssl);

enum ssl_private_key_result_t ssl_private_key_sign(
    SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out,
    uint16_t signature_algorithm, const uint8_t *in, size_t in_len);

enum ssl_private_key_result_t ssl_private_key_decrypt(
    SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out,
    const uint8_t *in, size_t in_len);

enum ssl_private_key_result_t ssl_private_key_complete(SSL *ssl, uint8_t *out,
                                                       size_t *out_len,
                                                       size_t max_out);

/* ssl_private_key_supports_signature_algorithm returns one if |ssl|'s private
 * key supports |signature_algorithm| and zero otherwise. */
int ssl_private_key_supports_signature_algorithm(SSL *ssl,
                                                 uint16_t signature_algorithm);

/* ssl_public_key_verify verifies that the |signature| is valid for the public
 * key |pkey| and input |in|, using the |signature_algorithm| specified. */
int ssl_public_key_verify(
    SSL *ssl, const uint8_t *signature, size_t signature_len,
    uint16_t signature_algorithm, EVP_PKEY *pkey,
    const uint8_t *in, size_t in_len);


/* Custom extensions */

/* ssl_custom_extension (a.k.a. SSL_CUSTOM_EXTENSION) is a structure that
 * contains information about custom-extension callbacks. */
struct ssl_custom_extension {
  SSL_custom_ext_add_cb add_callback;
  void *add_arg;
  SSL_custom_ext_free_cb free_callback;
  SSL_custom_ext_parse_cb parse_callback;
  void *parse_arg;
  uint16_t value;
};

void SSL_CUSTOM_EXTENSION_free(SSL_CUSTOM_EXTENSION *custom_extension);

int custom_ext_add_clienthello(SSL *ssl, CBB *extensions);
int custom_ext_parse_serverhello(SSL *ssl, int *out_alert, uint16_t value,
                                 const CBS *extension);
int custom_ext_parse_clienthello(SSL *ssl, int *out_alert, uint16_t value,
                                 const CBS *extension);
int custom_ext_add_serverhello(SSL *ssl, CBB *extensions);


/* Handshake hash.
 *
 * The TLS handshake maintains a transcript of all handshake messages. At
 * various points in the protocol, this is either a handshake buffer, a rolling
 * hash (selected by cipher suite) or both. */

/* ssl3_init_handshake_buffer initializes the handshake buffer and resets the
 * handshake hash. It returns one success and zero on failure. */
int ssl3_init_handshake_buffer(SSL *ssl);

/* ssl3_init_handshake_hash initializes the handshake hash based on the pending
 * cipher and the contents of the handshake buffer. Subsequent calls to
 * |ssl3_update_handshake_hash| will update the rolling hash. It returns one on
 * success and zero on failure. It is an error to call this function after the
 * handshake buffer is released. */
int ssl3_init_handshake_hash(SSL *ssl);

/* ssl3_free_handshake_buffer releases the handshake buffer. Subsequent calls
 * to |ssl3_update_handshake_hash| will not update the handshake buffer. */
void ssl3_free_handshake_buffer(SSL *ssl);

/* ssl3_free_handshake_hash releases the handshake hash. */
void ssl3_free_handshake_hash(SSL *ssl);

/* ssl3_update_handshake_hash adds |in| to the handshake buffer and handshake
 * hash, whichever is enabled. It returns one on success and zero on failure. */
int ssl3_update_handshake_hash(SSL *ssl, const uint8_t *in, size_t in_len);


/* ECDH groups. */

/* An SSL_ECDH_METHOD is an implementation of ECDH-like key exchanges for
 * TLS. */
struct ssl_ecdh_method_st {
  int nid;
  uint16_t group_id;
  const char name[8];

  /* cleanup releases state in |ctx|. */
  void (*cleanup)(SSL_ECDH_CTX *ctx);

  /* offer generates a keypair and writes the public value to
   * |out_public_key|. It returns one on success and zero on error. */
  int (*offer)(SSL_ECDH_CTX *ctx, CBB *out_public_key);

  /* accept performs a key exchange against the |peer_key| generated by |offer|.
   * On success, it returns one, writes the public value to |out_public_key|,
   * and sets |*out_secret| and |*out_secret_len| to a newly-allocated buffer
   * containing the shared secret. The caller must release this buffer with
   * |OPENSSL_free|. On failure, it returns zero and sets |*out_alert| to an
   * alert to send to the peer. */
  int (*accept)(SSL_ECDH_CTX *ctx, CBB *out_public_key, uint8_t **out_secret,
                size_t *out_secret_len, uint8_t *out_alert,
                const uint8_t *peer_key, size_t peer_key_len);

  /* finish performs a key exchange against the |peer_key| generated by
   * |accept|. On success, it returns one and sets |*out_secret| and
   * |*out_secret_len| to a newly-allocated buffer containing the shared
   * secret. The caller must release this buffer with |OPENSSL_free|. On
   * failure, it returns zero and sets |*out_alert| to an alert to send to the
   * peer. */
  int (*finish)(SSL_ECDH_CTX *ctx, uint8_t **out_secret, size_t *out_secret_len,
                uint8_t *out_alert, const uint8_t *peer_key,
                size_t peer_key_len);

  /* get_key initializes |out| with a length-prefixed key from |cbs|. It returns
   * one on success and zero on error. */
  int (*get_key)(CBS *cbs, CBS *out);

  /* add_key initializes |out_contents| to receive a key. Typically it will then
   * be passed to |offer| or |accept|. It returns one on success and zero on
   * error. */
  int (*add_key)(CBB *cbb, CBB *out_contents);
} /* SSL_ECDH_METHOD */;

/* ssl_nid_to_group_id looks up the group corresponding to |nid|. On success, it
 * sets |*out_group_id| to the group ID and returns one. Otherwise, it returns
 * zero. */
int ssl_nid_to_group_id(uint16_t *out_group_id, int nid);

/* SSL_ECDH_CTX_init sets up |ctx| for use with curve |group_id|. It returns one
 * on success and zero on error. */
int SSL_ECDH_CTX_init(SSL_ECDH_CTX *ctx, uint16_t group_id);

/* SSL_ECDH_CTX_init_for_dhe sets up |ctx| for use with legacy DHE-based ciphers
 * where the server specifies a group. It takes ownership of |params|. */
void SSL_ECDH_CTX_init_for_dhe(SSL_ECDH_CTX *ctx, DH *params);

/* SSL_ECDH_CTX_init_for_cecpq1 sets up |ctx| for use with CECPQ1. */
void SSL_ECDH_CTX_init_for_cecpq1(SSL_ECDH_CTX *ctx);

/* SSL_ECDH_CTX_cleanup releases memory associated with |ctx|. It is legal to
 * call it in the zero state. */
void SSL_ECDH_CTX_cleanup(SSL_ECDH_CTX *ctx);

/* SSL_ECDH_CTX_get_id returns the group ID for |ctx|. */
uint16_t SSL_ECDH_CTX_get_id(const SSL_ECDH_CTX *ctx);

/* SSL_ECDH_CTX_get_key calls the |get_key| method of |SSL_ECDH_METHOD|. */
int SSL_ECDH_CTX_get_key(SSL_ECDH_CTX *ctx, CBS *cbs, CBS *out);

/* SSL_ECDH_CTX_add_key calls the |add_key| method of |SSL_ECDH_METHOD|. */
int SSL_ECDH_CTX_add_key(SSL_ECDH_CTX *ctx, CBB *cbb, CBB *out_contents);

/* SSL_ECDH_CTX_offer calls the |offer| method of |SSL_ECDH_METHOD|. */
int SSL_ECDH_CTX_offer(SSL_ECDH_CTX *ctx, CBB *out_public_key);

/* SSL_ECDH_CTX_accept calls the |accept| method of |SSL_ECDH_METHOD|. */
int SSL_ECDH_CTX_accept(SSL_ECDH_CTX *ctx, CBB *out_public_key,
                        uint8_t **out_secret, size_t *out_secret_len,
                        uint8_t *out_alert, const uint8_t *peer_key,
                        size_t peer_key_len);

/* SSL_ECDH_CTX_finish the |finish| method of |SSL_ECDH_METHOD|. */
int SSL_ECDH_CTX_finish(SSL_ECDH_CTX *ctx, uint8_t **out_secret,
                        size_t *out_secret_len, uint8_t *out_alert,
                        const uint8_t *peer_key, size_t peer_key_len);

/* Handshake messages. */

/* SSL_MAX_HANDSHAKE_FLIGHT is the number of messages, including
 * ChangeCipherSpec, in the longest handshake flight. Currently this is the
 * client's second leg in a full handshake when client certificates, NPN, and
 * Channel ID, are all enabled. */
#define SSL_MAX_HANDSHAKE_FLIGHT 7

/* ssl_max_handshake_message_len returns the maximum number of bytes permitted
 * in a handshake message for |ssl|. */
size_t ssl_max_handshake_message_len(const SSL *ssl);

/* dtls_clear_incoming_messages releases all buffered incoming messages. */
void dtls_clear_incoming_messages(SSL *ssl);

/* dtls_has_incoming_messages returns one if there are buffered incoming
 * messages ahead of the current message and zero otherwise. */
int dtls_has_incoming_messages(const SSL *ssl);

typedef struct dtls_outgoing_message_st {
  uint8_t *data;
  uint32_t len;
  uint16_t epoch;
  char is_ccs;
} DTLS_OUTGOING_MESSAGE;

/* dtls_clear_outgoing_messages releases all buffered outgoing messages. */
void dtls_clear_outgoing_messages(SSL *ssl);


/* Callbacks. */

/* ssl_do_info_callback calls |ssl|'s info callback, if set. */
void ssl_do_info_callback(const SSL *ssl, int type, int value);

/* ssl_do_msg_callback calls |ssl|'s message callback, if set. */
void ssl_do_msg_callback(SSL *ssl, int is_write, int version, int content_type,
                         const void *buf, size_t len);


/* Transport buffers. */

/* ssl_read_buffer returns a pointer to contents of the read buffer. */
uint8_t *ssl_read_buffer(SSL *ssl);

/* ssl_read_buffer_len returns the length of the read buffer. */
size_t ssl_read_buffer_len(const SSL *ssl);

/* ssl_read_buffer_extend_to extends the read buffer to the desired length. For
 * TLS, it reads to the end of the buffer until the buffer is |len| bytes
 * long. For DTLS, it reads a new packet and ignores |len|. It returns one on
 * success, zero on EOF, and a negative number on error.
 *
 * It is an error to call |ssl_read_buffer_extend_to| in DTLS when the buffer is
 * non-empty. */
int ssl_read_buffer_extend_to(SSL *ssl, size_t len);

/* ssl_read_buffer_consume consumes |len| bytes from the read buffer. It
 * advances the data pointer and decrements the length. The memory consumed will
 * remain valid until the next call to |ssl_read_buffer_extend| or it is
 * discarded with |ssl_read_buffer_discard|. */
void ssl_read_buffer_consume(SSL *ssl, size_t len);

/* ssl_read_buffer_discard discards the consumed bytes from the read buffer. If
 * the buffer is now empty, it releases memory used by it. */
void ssl_read_buffer_discard(SSL *ssl);

/* ssl_read_buffer_clear releases all memory associated with the read buffer and
 * zero-initializes it. */
void ssl_read_buffer_clear(SSL *ssl);

/* ssl_write_buffer_is_pending returns one if the write buffer has pending data
 * and zero if is empty. */
int ssl_write_buffer_is_pending(const SSL *ssl);

/* ssl_write_buffer_init initializes the write buffer. On success, it sets
 * |*out_ptr| to the start of the write buffer with space for up to |max_len|
 * bytes. It returns one on success and zero on failure. Call
 * |ssl_write_buffer_set_len| to complete initialization. */
int ssl_write_buffer_init(SSL *ssl, uint8_t **out_ptr, size_t max_len);

/* ssl_write_buffer_set_len is called after |ssl_write_buffer_init| to complete
 * initialization after |len| bytes are written to the buffer. */
void ssl_write_buffer_set_len(SSL *ssl, size_t len);

/* ssl_write_buffer_flush flushes the write buffer to the transport. It returns
 * one on success and <= 0 on error. For DTLS, whether or not the write
 * succeeds, the write buffer will be cleared. */
int ssl_write_buffer_flush(SSL *ssl);

/* ssl_write_buffer_clear releases all memory associated with the write buffer
 * and zero-initializes it. */
void ssl_write_buffer_clear(SSL *ssl);


/* Certificate functions. */

/* ssl_has_certificate returns one if a certificate and private key are
 * configured and zero otherwise. */
int ssl_has_certificate(const SSL *ssl);

/* ssl_parse_cert_chain parses a certificate list from |cbs| in the format used
 * by a TLS Certificate message. On success, it returns a newly-allocated
 * |X509| list and advances |cbs|. Otherwise, it returns NULL and sets
 * |*out_alert| to an alert to send to the peer. If the list is non-empty and
 * |out_leaf_sha256| is non-NULL, it writes the SHA-256 hash of the leaf to
 * |out_leaf_sha256|. */
STACK_OF(X509) *ssl_parse_cert_chain(SSL *ssl, uint8_t *out_alert,
                                     uint8_t *out_leaf_sha256, CBS *cbs);

/* ssl_add_cert_to_cbb adds |x509| to |cbb|. It returns one on success and zero
 * on error. */
int ssl_add_cert_to_cbb(CBB *cbb, X509 *x509);

/* ssl_add_cert_chain adds |ssl|'s certificate chain to |cbb| in the format used
 * by a TLS Certificate message. If there is no certificate chain, it emits an
 * empty certificate list. It returns one on success and zero on error. */
int ssl_add_cert_chain(SSL *ssl, CBB *cbb);

/* ssl_parse_client_CA_list parses a CA list from |cbs| in the format used by a
 * TLS CertificateRequest message. On success, it returns a newly-allocated
 * |X509_NAME| list and advances |cbs|. Otherwise, it returns NULL and sets
 * |*out_alert| to an alert to send to the peer. */
STACK_OF(X509_NAME) *
    ssl_parse_client_CA_list(SSL *ssl, uint8_t *out_alert, CBS *cbs);

/* ssl_add_client_CA_list adds the configured CA list to |cbb| in the format
 * used by a TLS CertificateRequest message. It returns one on success and zero
 * on error. */
int ssl_add_client_CA_list(SSL *ssl, CBB *cbb);

/* ssl_check_leaf_certificate returns one if |leaf| is a suitable leaf server
 * certificate for |ssl|. Otherwise, it returns zero and pushes an error on the
 * error queue. */
int ssl_check_leaf_certificate(SSL *ssl, X509 *leaf);

/* ssl_do_client_cert_cb runs the client_cert_cb, if any, and returns one on
 * success and zero on error. On error, it sets |*out_should_retry| to one if
 * the callback failed and should be retried and zero otherwise. */
int ssl_do_client_cert_cb(SSL *ssl, int *out_should_retry);


/* TLS 1.3 key derivation. */

/* tls13_init_key_schedule initializes the handshake hash and key derivation
 * state with the given resumption context. The cipher suite and PRF hash must
 * have been selected at this point. It returns one on success and zero on
 * error. */
int tls13_init_key_schedule(SSL *ssl, const uint8_t *resumption_ctx,
                            size_t resumption_ctx_len);

/* tls13_advance_key_schedule incorporates |in| into the key schedule with
 * HKDF-Extract. It returns one on success and zero on error. */
int tls13_advance_key_schedule(SSL *ssl, const uint8_t *in, size_t len);

/* tls13_get_context_hashes writes Hash(Handshake Context) +
 * Hash(resumption_context) to |out| which much have room for at least 2 *
 * |EVP_MAX_MD_SIZE| bytes. On success, it returns one and sets |*out_len| to
 * the number of bytes written. Otherwise, it returns zero. */
int tls13_get_context_hashes(SSL *ssl, uint8_t *out, size_t *out_len);

enum tls_record_type_t {
  type_early_handshake,
  type_early_data,
  type_handshake,
  type_data,
};

/* tls13_set_traffic_key sets the read or write traffic keys to |traffic_secret|
 * for the given traffic phase |type|. It returns one on success and zero on
 * error. */
int tls13_set_traffic_key(SSL *ssl, enum tls_record_type_t type,
                          enum evp_aead_direction_t direction,
                          const uint8_t *traffic_secret,
                          size_t traffic_secret_len);

/* tls13_set_handshake_traffic derives the handshake traffic secret and
 * switches both read and write traffic to it. It returns one on success and
 * zero on error. */
int tls13_set_handshake_traffic(SSL *ssl);

/* tls13_rotate_traffic_key derives the next read or write traffic secret. It
 * returns one on success and zero on error. */
int tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction);

/* tls13_derive_traffic_secret_0 derives the initial application data traffic
 * secret based on the handshake transcripts and |master_secret|. It returns one
 * on success and zero on error. */
int tls13_derive_traffic_secret_0(SSL *ssl);

/* tls13_finalize_keys derives the |exporter_secret| and |resumption_secret|. */
int tls13_finalize_keys(SSL *ssl);

/* tls13_export_keying_material provides and exporter interface to use the
 * |exporter_secret|. */
int tls13_export_keying_material(SSL *ssl, uint8_t *out, size_t out_len,
                                 const char *label, size_t label_len,
                                 const uint8_t *context, size_t context_len,
                                 int use_context);

/* tls13_finished_mac calculates the MAC of the handshake transcript to verify
 * the integrity of the Finished message, and stores the result in |out| and
 * length in |out_len|. |is_server| is 1 if this is for the Server Finished and
 * 0 for the Client Finished. */
int tls13_finished_mac(SSL *ssl, uint8_t *out, size_t *out_len, int is_server);


/* Handshake functions. */

enum ssl_hs_wait_t {
  ssl_hs_error,
  ssl_hs_ok,
  ssl_hs_read_message,
  ssl_hs_write_message,
  ssl_hs_flush,
  ssl_hs_flush_and_read_message,
  ssl_hs_x509_lookup,
  ssl_hs_private_key_operation,
};

struct ssl_handshake_st {
  /* wait contains the operation |do_handshake| is currently blocking on or
   * |ssl_hs_ok| if none. */
  enum ssl_hs_wait_t wait;

  /* do_handshake runs the handshake. On completion, it returns |ssl_hs_ok|.
   * Otherwise, it returns a value corresponding to what operation is needed to
   * progress. */
  enum ssl_hs_wait_t (*do_handshake)(SSL *ssl);

  int state;

  size_t hash_len;
  uint8_t resumption_hash[EVP_MAX_MD_SIZE];
  uint8_t secret[EVP_MAX_MD_SIZE];
  uint8_t traffic_secret_0[EVP_MAX_MD_SIZE];

  SSL_ECDH_CTX *groups;
  size_t groups_len;
  /* retry_group is the group ID selected by the server in HelloRetryRequest. */
  uint16_t retry_group;
  /* key_share_bytes is the value of the previously sent KeyShare extension. */
  uint8_t *key_share_bytes;
  size_t key_share_bytes_len;
  uint8_t *public_key;
  size_t public_key_len;

  uint8_t *cert_context;
  size_t cert_context_len;

  uint8_t session_tickets_sent;
} /* SSL_HANDSHAKE */;

SSL_HANDSHAKE *ssl_handshake_new(enum ssl_hs_wait_t (*do_handshake)(SSL *ssl));

void ssl_handshake_clear_groups(SSL_HANDSHAKE *hs);

/* ssl_handshake_free releases all memory associated with |hs|. */
void ssl_handshake_free(SSL_HANDSHAKE *hs);

/* tls13_handshake runs the TLS 1.3 handshake. It returns one on success and <=
 * 0 on error. */
int tls13_handshake(SSL *ssl);

/* The following are implementations of |do_handshake| for the client and
 * server. */
enum ssl_hs_wait_t tls13_client_handshake(SSL *ssl);
enum ssl_hs_wait_t tls13_server_handshake(SSL *ssl);

/* tls13_post_handshake processes a post-handshake message. It returns one on
 * success and zero on failure. */
int tls13_post_handshake(SSL *ssl);

/* tls13_check_message_type checks if the current message has type |type|. If so
 * it returns one. Otherwise, it sends an alert and returns zero. */
int tls13_check_message_type(SSL *ssl, int type);

int tls13_process_certificate(SSL *ssl);
int tls13_process_certificate_verify(SSL *ssl);
int tls13_process_finished(SSL *ssl);

int tls13_prepare_certificate(SSL *ssl);
enum ssl_private_key_result_t tls13_prepare_certificate_verify(
    SSL *ssl, int is_first_run);
int tls13_prepare_finished(SSL *ssl);
int tls13_process_new_session_ticket(SSL *ssl);

int ssl_ext_key_share_parse_serverhello(SSL *ssl, uint8_t **out_secret,
                                        size_t *out_secret_len,
                                        uint8_t *out_alert, CBS *contents);
int ssl_ext_key_share_parse_clienthello(SSL *ssl, int *out_found,
                                        uint8_t **out_secret,
                                        size_t *out_secret_len,
                                        uint8_t *out_alert, CBS *contents);
int ssl_ext_key_share_add_serverhello(SSL *ssl, CBB *out);

int ssl_add_client_hello_body(SSL *ssl, CBB *body);


/* SSLKEYLOGFILE functions. */

/* ssl_log_rsa_client_key_exchange logs |premaster|, if logging is enabled for
 * |ssl|. It returns one on success and zero on failure. The entry is identified
 * by the first 8 bytes of |encrypted_premaster|. */
int ssl_log_rsa_client_key_exchange(const SSL *ssl,
                                    const uint8_t *encrypted_premaster,
                                    size_t encrypted_premaster_len,
                                    const uint8_t *premaster,
                                    size_t premaster_len);

/* ssl_log_secret logs |secret| with label |label|, if logging is enabled for
 * |ssl|. It returns one on success and zero on failure. */
int ssl_log_secret(const SSL *ssl, const char *label, const uint8_t *secret,
                   size_t secret_len);


/* Underdocumented functions.
 *
 * Functions below here haven't been touched up and may be underdocumented. */

#define TLSEXT_CHANNEL_ID_SIZE 128

/* From RFC4492, used in encoding the curve type in ECParameters */
#define NAMED_CURVE_TYPE 3

enum ssl_hash_message_t {
  ssl_dont_hash_message,
  ssl_hash_message,
};

typedef struct cert_st {
  X509 *x509;
  EVP_PKEY *privatekey;
  /* Chain for this certificate */
  STACK_OF(X509) *chain;

  /* key_method, if non-NULL, is a set of callbacks to call for private key
   * operations. */
  const SSL_PRIVATE_KEY_METHOD *key_method;

  /* For clients the following masks are of *disabled* key and auth algorithms
   * based on the current configuration.
   *
   * TODO(davidben): Remove these. They get checked twice: when sending the
   * ClientHello and when processing the ServerHello. */
  uint32_t mask_k;
  uint32_t mask_a;

  DH *dh_tmp;
  DH *(*dh_tmp_cb)(SSL *ssl, int is_export, int keysize);

  /* peer_sigalgs are the algorithm/hash pairs that the peer supports. These
   * are taken from the contents of signature algorithms extension for a server
   * or from the CertificateRequest for a client. */
  uint16_t *peer_sigalgs;
  /* peer_sigalgslen is the number of entries in |peer_sigalgs|. */
  size_t peer_sigalgslen;

  /* sigalgs, if non-NULL, is the set of digests supported by |privatekey| in
   * decreasing order of preference. */
  uint16_t *sigalgs;
  size_t sigalgs_len;

  /* Certificate setup callback: if set is called whenever a
   * certificate may be required (client or server). the callback
   * can then examine any appropriate parameters and setup any
   * certificates required. This allows advanced applications
   * to select certificates on the fly: for example based on
   * supported signature algorithms or curves. */
  int (*cert_cb)(SSL *ssl, void *arg);
  void *cert_cb_arg;

  /* Optional X509_STORE for certificate validation. If NULL the parent SSL_CTX
   * store is used instead. */
  X509_STORE *verify_store;
} CERT;

/* SSL_METHOD is a compatibility structure to support the legacy version-locked
 * methods. */
struct ssl_method_st {
  /* version, if non-zero, is the only protocol version acceptable to an
   * SSL_CTX initialized from this method. */
  uint16_t version;
  /* method is the underlying SSL_PROTOCOL_METHOD that initializes the
   * SSL_CTX. */
  const SSL_PROTOCOL_METHOD *method;
};

/* Used to hold functions for SSLv2 or SSLv3/TLSv1 functions */
struct ssl_protocol_method_st {
  /* is_dtls is one if the protocol is DTLS and zero otherwise. */
  char is_dtls;
  /* min_version is the minimum implemented version. */
  uint16_t min_version;
  /* max_version is the maximum implemented version. */
  uint16_t max_version;
  /* version_from_wire maps |wire_version| to a protocol version. For
   * SSLv3/TLS, the version is returned as-is. For DTLS, the corresponding TLS
   * version is used. Note that this mapping is not injective but preserves
   * comparisons.
   *
   * TODO(davidben): To normalize some DTLS-specific code, move away from using
   * the wire version except at API boundaries. */
  uint16_t (*version_from_wire)(uint16_t wire_version);
  /* version_to_wire maps |version| to the wire representation. It is an error
   * to call it with an invalid version. */
  uint16_t (*version_to_wire)(uint16_t version);
  int (*ssl_new)(SSL *ssl);
  void (*ssl_free)(SSL *ssl);
  /* ssl_get_message reads the next handshake message. If |msg_type| is not -1,
   * the message must have the specified type. On success, it returns one and
   * sets |ssl->s3->tmp.message_type|, |ssl->init_msg|, and |ssl->init_num|.
   * Otherwise, it returns <= 0. */
  int (*ssl_get_message)(SSL *ssl, int msg_type,
                         enum ssl_hash_message_t hash_message);
  /* hash_current_message incorporates the current handshake message into the
   * handshake hash. It returns one on success and zero on allocation
   * failure. */
  int (*hash_current_message)(SSL *ssl);
  /* release_current_message is called to release the current handshake message.
   * If |free_buffer| is one, buffers will also be released. */
  void (*release_current_message)(SSL *ssl, int free_buffer);
  /* read_app_data reads up to |len| bytes of application data into |buf|. On
   * success, it returns the number of bytes read. Otherwise, it returns <= 0
   * and sets |*out_got_handshake| to whether the failure was due to a
   * post-handshake handshake message. If so, it fills in the current message as
   * in |ssl_get_message|. */
  int (*read_app_data)(SSL *ssl, int *out_got_handshake,  uint8_t *buf, int len,
                       int peek);
  int (*read_change_cipher_spec)(SSL *ssl);
  void (*read_close_notify)(SSL *ssl);
  int (*write_app_data)(SSL *ssl, const void *buf_, int len);
  int (*dispatch_alert)(SSL *ssl);
  /* supports_cipher returns one if |cipher| is supported by this protocol and
   * zero otherwise. */
  int (*supports_cipher)(const SSL_CIPHER *cipher);
  /* init_message begins a new handshake message of type |type|. |cbb| is the
   * root CBB to be passed into |finish_message|. |*body| is set to a child CBB
   * the caller should write to. It returns one on success and zero on error. */
  int (*init_message)(SSL *ssl, CBB *cbb, CBB *body, uint8_t type);
  /* finish_message finishes a handshake message and prepares it to be
   * written. It returns one on success and zero on error. */
  int (*finish_message)(SSL *ssl, CBB *cbb);
  /* write_message writes the next message to the transport. It returns one on
   * success and <= 0 on error. */
  int (*write_message)(SSL *ssl);
  /* send_change_cipher_spec sends a ChangeCipherSpec message. */
  int (*send_change_cipher_spec)(SSL *ssl);
  /* expect_flight is called when the handshake expects a flight of messages from
   * the peer. */
  void (*expect_flight)(SSL *ssl);
  /* received_flight is called when the handshake has received a flight of
   * messages from the peer. */
  void (*received_flight)(SSL *ssl);
  /* set_read_state sets |ssl|'s read cipher state to |aead_ctx|. It takes
   * ownership of |aead_ctx|. It returns one on success and zero if changing the
   * read state is forbidden at this point. */
  int (*set_read_state)(SSL *ssl, SSL_AEAD_CTX *aead_ctx);
  /* set_write_state sets |ssl|'s write cipher state to |aead_ctx|. It takes
   * ownership of |aead_ctx|. It returns one on success and zero if changing the
   * write state is forbidden at this point. */
  int (*set_write_state)(SSL *ssl, SSL_AEAD_CTX *aead_ctx);
};

/* This is for the SSLv3/TLSv1.0 differences in crypto/hash stuff It is a bit
 * of a mess of functions, but hell, think of it as an opaque structure. */
struct ssl3_enc_method {
  /* prf computes the PRF function for |ssl|. It writes |out_len| bytes to
   * |out|, using |secret| as the secret and |label| as the label. |seed1| and
   * |seed2| are concatenated to form the seed parameter. It returns one on
   * success and zero on failure. */
  int (*prf)(const SSL *ssl, uint8_t *out, size_t out_len,
             const uint8_t *secret, size_t secret_len, const char *label,
             size_t label_len, const uint8_t *seed1, size_t seed1_len,
             const uint8_t *seed2, size_t seed2_len);
  int (*final_finish_mac)(SSL *ssl, int from_server, uint8_t *out);
};

/* lengths of messages */
#define DTLS1_COOKIE_LENGTH 256

#define DTLS1_RT_HEADER_LENGTH 13

#define DTLS1_HM_HEADER_LENGTH 12

#define DTLS1_CCS_HEADER_LENGTH 1

#define DTLS1_AL_HEADER_LENGTH 2

struct hm_header_st {
  uint8_t type;
  uint32_t msg_len;
  uint16_t seq;
  uint32_t frag_off;
  uint32_t frag_len;
};

/* An hm_fragment is an incoming DTLS message, possibly not yet assembled. */
typedef struct hm_fragment_st {
  /* type is the type of the message. */
  uint8_t type;
  /* seq is the sequence number of this message. */
  uint16_t seq;
  /* msg_len is the length of the message body. */
  uint32_t msg_len;
  /* data is a pointer to the message, including message header. It has length
   * |DTLS1_HM_HEADER_LENGTH| + |msg_len|. */
  uint8_t *data;
  /* reassembly is a bitmask of |msg_len| bits corresponding to which parts of
   * the message have been received. It is NULL if the message is complete. */
  uint8_t *reassembly;
} hm_fragment;

typedef struct dtls1_state_st {
  /* send_cookie is true if we are resending the ClientHello
   * with a cookie from a HelloVerifyRequest. */
  unsigned int send_cookie;

  uint8_t cookie[DTLS1_COOKIE_LENGTH];
  size_t cookie_len;

  /* The current data and handshake epoch.  This is initially undefined, and
   * starts at zero once the initial handshake is completed. */
  uint16_t r_epoch;
  uint16_t w_epoch;

  /* records being received in the current epoch */
  DTLS1_BITMAP bitmap;

  uint16_t handshake_write_seq;
  uint16_t handshake_read_seq;

  /* save last sequence number for retransmissions */
  uint8_t last_write_sequence[8];

  /* incoming_messages is a ring buffer of incoming handshake messages that have
   * yet to be processed. The front of the ring buffer is message number
   * |handshake_read_seq|, at position |handshake_read_seq| %
   * |SSL_MAX_HANDSHAKE_FLIGHT|. */
  hm_fragment *incoming_messages[SSL_MAX_HANDSHAKE_FLIGHT];

  /* outgoing_messages is the queue of outgoing messages from the last handshake
   * flight. */
  DTLS_OUTGOING_MESSAGE outgoing_messages[SSL_MAX_HANDSHAKE_FLIGHT];
  uint8_t outgoing_messages_len;

  unsigned int mtu; /* max DTLS packet size */

  /* num_timeouts is the number of times the retransmit timer has fired since
   * the last time it was reset. */
  unsigned int num_timeouts;

  /* Indicates when the last handshake msg or heartbeat sent will
   * timeout. */
  struct timeval next_timeout;

  /* timeout_duration_ms is the timeout duration in milliseconds. */
  unsigned timeout_duration_ms;
} DTLS1_STATE;

extern const SSL3_ENC_METHOD TLSv1_enc_data;
extern const SSL3_ENC_METHOD SSLv3_enc_data;

/* From draft-ietf-tls-tls13-14, used in determining ticket validity. */
#define SSL_TICKET_ALLOW_EARLY_DATA 1
#define SSL_TICKET_ALLOW_DHE_RESUMPTION 2
#define SSL_TICKET_ALLOW_PSK_RESUMPTION 4

CERT *ssl_cert_new(void);
CERT *ssl_cert_dup(CERT *cert);
void ssl_cert_clear_certs(CERT *c);
void ssl_cert_free(CERT *c);
int ssl_get_new_session(SSL *ssl, int is_server);
int ssl_encrypt_ticket(SSL *ssl, CBB *out, const SSL_SESSION *session);

enum ssl_session_result_t {
  ssl_session_success,
  ssl_session_error,
  ssl_session_retry,
};

/* ssl_get_prev_session looks up the previous session based on |ctx|. On
 * success, it sets |*out_session| to the session or NULL if none was found. It
 * sets |*out_send_ticket| to whether a ticket should be sent at the end of the
 * handshake. If the session could not be looked up synchronously, it returns
 * |ssl_session_retry| and should be called again. Otherwise, it returns
 * |ssl_session_error|.  */
enum ssl_session_result_t ssl_get_prev_session(
    SSL *ssl, SSL_SESSION **out_session, int *out_send_ticket,
    const struct ssl_early_callback_ctx *ctx);

/* SSL_SESSION_dup returns a newly-allocated |SSL_SESSION| with a copy of the
 * fields in |session| or NULL on error. The new session is non-resumable and
 * must be explicitly marked resumable once it has been filled in. */
OPENSSL_EXPORT SSL_SESSION *SSL_SESSION_dup(SSL_SESSION *session,
                                            int include_ticket);

STACK_OF(SSL_CIPHER) *
    ssl_bytes_to_cipher_list(SSL *ssl, const CBS *cbs, uint16_t max_version);
void ssl_cipher_preference_list_free(
    struct ssl_cipher_preference_list_st *cipher_list);
struct ssl_cipher_preference_list_st *ssl_get_cipher_preferences(SSL *ssl);

int ssl_cert_set0_chain(CERT *cert, STACK_OF(X509) *chain);
int ssl_cert_set1_chain(CERT *cert, STACK_OF(X509) *chain);
int ssl_cert_add0_chain_cert(CERT *cert, X509 *x509);
int ssl_cert_add1_chain_cert(CERT *cert, X509 *x509);
void ssl_cert_set_cert_cb(CERT *cert,
                          int (*cb)(SSL *ssl, void *arg), void *arg);

int ssl_verify_cert_chain(SSL *ssl, STACK_OF(X509) *cert_chain);
void ssl_update_cache(SSL *ssl, int mode);

/* ssl_get_compatible_server_ciphers determines the key exchange and
 * authentication cipher suite masks compatible with the server configuration
 * and current ClientHello parameters of |ssl|. It sets |*out_mask_k| to the key
 * exchange mask and |*out_mask_a| to the authentication mask. */
void ssl_get_compatible_server_ciphers(SSL *ssl, uint32_t *out_mask_k,
                                       uint32_t *out_mask_a);

STACK_OF(SSL_CIPHER) *ssl_get_ciphers_by_id(SSL *ssl);
int ssl_verify_alarm_type(long type);

int ssl3_get_finished(SSL *ssl);
int ssl3_send_change_cipher_spec(SSL *ssl);
void ssl3_cleanup_key_block(SSL *ssl);
int ssl3_send_alert(SSL *ssl, int level, int desc);
int ssl3_get_message(SSL *ssl, int msg_type,
                     enum ssl_hash_message_t hash_message);
int ssl3_hash_current_message(SSL *ssl);
void ssl3_release_current_message(SSL *ssl, int free_buffer);

/* ssl3_cert_verify_hash writes the SSL 3.0 CertificateVerify hash into the
 * bytes pointed to by |out| and writes the number of bytes to |*out_len|. |out|
 * must have room for |EVP_MAX_MD_SIZE| bytes. It sets |*out_md| to the hash
 * function used. It returns one on success and zero on failure. */
int ssl3_cert_verify_hash(SSL *ssl, const EVP_MD **out_md, uint8_t *out,
                          size_t *out_len, uint16_t signature_algorithm);

int ssl3_send_finished(SSL *ssl, int a, int b);
int ssl3_supports_cipher(const SSL_CIPHER *cipher);
int ssl3_dispatch_alert(SSL *ssl);
int ssl3_read_app_data(SSL *ssl, int *out_got_handshake, uint8_t *buf, int len,
                       int peek);
int ssl3_read_change_cipher_spec(SSL *ssl);
void ssl3_read_close_notify(SSL *ssl);
int ssl3_read_handshake_bytes(SSL *ssl, uint8_t *buf, int len);
int ssl3_write_app_data(SSL *ssl, const void *buf, int len);
int ssl3_write_bytes(SSL *ssl, int type, const void *buf, int len);
int ssl3_output_cert_chain(SSL *ssl);
const SSL_CIPHER *ssl3_choose_cipher(
    SSL *ssl, STACK_OF(SSL_CIPHER) *clnt,
    struct ssl_cipher_preference_list_st *srvr);

int ssl3_new(SSL *ssl);
void ssl3_free(SSL *ssl);
int ssl3_accept(SSL *ssl);
int ssl3_connect(SSL *ssl);

int ssl3_init_message(SSL *ssl, CBB *cbb, CBB *body, uint8_t type);
int ssl3_finish_message(SSL *ssl, CBB *cbb);
int ssl3_write_message(SSL *ssl);

void ssl3_expect_flight(SSL *ssl);
void ssl3_received_flight(SSL *ssl);

int dtls1_init_message(SSL *ssl, CBB *cbb, CBB *body, uint8_t type);
int dtls1_finish_message(SSL *ssl, CBB *cbb);
int dtls1_write_message(SSL *ssl);

/* dtls1_get_record reads a new input record. On success, it places it in
 * |ssl->s3->rrec| and returns one. Otherwise it returns <= 0 on error or if
 * more data is needed. */
int dtls1_get_record(SSL *ssl);

int dtls1_read_app_data(SSL *ssl, int *out_got_handshake, uint8_t *buf, int len,
                        int peek);
int dtls1_read_change_cipher_spec(SSL *ssl);
void dtls1_read_close_notify(SSL *ssl);

int dtls1_write_app_data(SSL *ssl, const void *buf, int len);

/* dtls1_write_record sends a record. It returns one on success and <= 0 on
 * error. */
int dtls1_write_record(SSL *ssl, int type, const uint8_t *buf, size_t len,
                       enum dtls1_use_epoch_t use_epoch);

int dtls1_send_change_cipher_spec(SSL *ssl);
int dtls1_send_finished(SSL *ssl, int a, int b, const char *sender, int slen);
int dtls1_retransmit_outgoing_messages(SSL *ssl);
void dtls1_clear_record_buffer(SSL *ssl);
int dtls1_parse_fragment(CBS *cbs, struct hm_header_st *out_hdr,
                         CBS *out_body);
int dtls1_check_timeout_num(SSL *ssl);
int dtls1_handshake_write(SSL *ssl);
void dtls1_expect_flight(SSL *ssl);
void dtls1_received_flight(SSL *ssl);

int dtls1_supports_cipher(const SSL_CIPHER *cipher);
void dtls1_start_timer(SSL *ssl);
void dtls1_stop_timer(SSL *ssl);
int dtls1_is_timer_expired(SSL *ssl);
void dtls1_double_timeout(SSL *ssl);
unsigned int dtls1_min_mtu(void);

int dtls1_new(SSL *ssl);
int dtls1_accept(SSL *ssl);
int dtls1_connect(SSL *ssl);
void dtls1_free(SSL *ssl);

int dtls1_get_message(SSL *ssl, int mt, enum ssl_hash_message_t hash_message);
int dtls1_hash_current_message(SSL *ssl);
void dtls1_release_current_message(SSL *ssl, int free_buffer);
int dtls1_dispatch_alert(SSL *ssl);

/* ssl_is_wbio_buffered returns one if |ssl|'s write BIO is buffered and zero
 * otherwise. */
int ssl_is_wbio_buffered(const SSL *ssl);

int ssl_init_wbio_buffer(SSL *ssl);
void ssl_free_wbio_buffer(SSL *ssl);

int tls1_change_cipher_state(SSL *ssl, int which);
int tls1_setup_key_block(SSL *ssl);
int tls1_handshake_digest(SSL *ssl, uint8_t *out, size_t out_len);
int tls1_generate_master_secret(SSL *ssl, uint8_t *out, const uint8_t *premaster,
                                size_t premaster_len);

int ssl_early_callback_init(SSL *ssl, struct ssl_early_callback_ctx *ctx,
                            const uint8_t *in, size_t in_len);

int ssl_early_callback_get_extension(const struct ssl_early_callback_ctx *ctx,
                                     CBS *out, uint16_t extension_type);

/* tls1_get_grouplist sets |*out_group_ids| and |*out_group_ids_len| to the
 * list of allowed group IDs. If |get_peer_groups| is non-zero, return the
 * peer's group list. Otherwise, return the preferred list. */
void tls1_get_grouplist(SSL *ssl, int get_peer_groups,
                        const uint16_t **out_group_ids,
                        size_t *out_group_ids_len);

/* tls1_check_group_id returns one if |group_id| is consistent with both our
 * and the peer's group preferences. Note: if called as the client, only our
 * preferences are checked; the peer (the server) does not send preferences. */
int tls1_check_group_id(SSL *ssl, uint16_t group_id);

/* tls1_get_shared_group sets |*out_group_id| to the first preferred shared
 * group between client and server preferences and returns one. If none may be
 * found, it returns zero. */
int tls1_get_shared_group(SSL *ssl, uint16_t *out_group_id);

/* tls1_set_curves converts the array of |ncurves| NIDs pointed to by |curves|
 * into a newly allocated array of TLS group IDs. On success, the function
 * returns one and writes the array to |*out_group_ids| and its size to
 * |*out_group_ids_len|. Otherwise, it returns zero. */
int tls1_set_curves(uint16_t **out_group_ids, size_t *out_group_ids_len,
                    const int *curves, size_t ncurves);

/* tls1_check_ec_cert returns one if |x| is an ECC certificate with curve and
 * point format compatible with the client's preferences. Otherwise it returns
 * zero. */
int tls1_check_ec_cert(SSL *ssl, X509 *x);

/* ssl_add_clienthello_tlsext writes ClientHello extensions to |out|. It
 * returns one on success and zero on failure. The |header_len| argument is the
 * length of the ClientHello written so far and is used to compute the padding
 * length. (It does not include the record header.) */
int ssl_add_clienthello_tlsext(SSL *ssl, CBB *out, size_t header_len);

int ssl_add_serverhello_tlsext(SSL *ssl, CBB *out);
int ssl_parse_clienthello_tlsext(SSL *ssl, CBS *cbs);
int ssl_parse_serverhello_tlsext(SSL *ssl, CBS *cbs);

#define tlsext_tick_md EVP_sha256

/* tls_process_ticket processes a session ticket from the client. On success,
 * it sets |*out_session| to the decrypted session or NULL if the ticket was
 * rejected. If the ticket was valid, it sets |*out_renew_ticket| to whether
 * the ticket should be renewed. It returns one on success and zero on fatal
 * error. */
int tls_process_ticket(SSL *ssl, SSL_SESSION **out_session,
                       int *out_renew_ticket, const uint8_t *ticket,
                       size_t ticket_len, const uint8_t *session_id,
                       size_t session_id_len);

/* tls1_channel_id_hash computes the hash to be signed by Channel ID and writes
 * it to |out|, which must contain at least |EVP_MAX_MD_SIZE| bytes. It returns
 * one on success and zero on failure. */
int tls1_channel_id_hash(SSL *ssl, uint8_t *out, size_t *out_len);

int tls1_record_handshake_hashes_for_channel_id(SSL *ssl);

/* ssl3_can_false_start returns one if |ssl| is allowed to False Start and zero
 * otherwise. */
int ssl3_can_false_start(const SSL *ssl);

/* ssl3_get_enc_method returns the SSL3_ENC_METHOD corresponding to
 * |version|. */
const SSL3_ENC_METHOD *ssl3_get_enc_method(uint16_t version);

/* ssl_get_full_version_range sets |*out_min_version|, |*out_fallback_version|,
 * and |*out_max_version| to the minimum, fallback, and maximum enabled protocol
 * versions, respectively. The fallback version is the effective maximium
 * version used throughout the stack and the maximum version is the true maximum
 * for downgrade purposes. */
int ssl_get_full_version_range(const SSL *ssl, uint16_t *out_min_version,
                               uint16_t *out_fallback_version,
                               uint16_t *out_max_version);

/* ssl_get_version_range sets |*out_min_version| and
 * |*out_effective_max_version| to the minimum and maximum enabled protocol
 * versions, respectively. Note that, if there is a fallback version set, it
 * returns it as the maximum version. */
int ssl_get_version_range(const SSL *ssl, uint16_t *out_min_version,
                          uint16_t *out_effective_max_version);

/* ssl3_protocol_version returns |ssl|'s protocol version. It is an error to
 * call this function before the version is determined. */
uint16_t ssl3_protocol_version(const SSL *ssl);

uint32_t ssl_get_algorithm_prf(const SSL *ssl);
int tls1_parse_peer_sigalgs(SSL *ssl, const CBS *sigalgs);

/* tls1_choose_signature_algorithm sets |*out| to a signature algorithm for use
 * with |ssl|'s private key based on the peer's preferences and the digests
 * supported. It returns one on success and zero on error. */
int tls1_choose_signature_algorithm(SSL *ssl, uint16_t *out);

size_t tls12_get_psigalgs(SSL *ssl, const uint16_t **psigs);

/* tls12_check_peer_sigalg checks that |signature_algorithm| is consistent with
 * |ssl|'s sent, supported signature algorithms and returns 1. Otherwise it
 * returns 0 and writes an alert into |*out_alert|. */
int tls12_check_peer_sigalg(SSL *ssl, int *out_alert,
                            uint16_t signature_algorithm);
void ssl_set_client_disabled(SSL *ssl);

void ssl_get_current_time(const SSL *ssl, struct timeval *out_clock);


#if defined(__cplusplus)
} /* extern C */
#endif

#endif /* OPENSSL_HEADER_SSL_INTERNAL_H */