/*
 * Copyright (c) 2016 DeNA Co., Ltd., Kazuho Oku
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#ifdef _WINDOWS
#include "wincompat.h"
#else
#include <unistd.h>
#endif
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define OPENSSL_API_COMPAT 0x00908000L
#include <openssl/bn.h>
#include <openssl/crypto.h>
#ifdef OPENSSL_IS_BORINGSSL
#include <openssl/curve25519.h>
#include <openssl/chacha.h>
#include <openssl/poly1305.h>
#endif
#include <openssl/ec.h>
#include <openssl/ecdh.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/objects.h>
#include <openssl/rand.h>
#include <openssl/rsa.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>
#include <openssl/x509_vfy.h>
#include "picotls.h"
#include "picotls/openssl.h"

#ifdef _WINDOWS
#ifndef _CRT_SECURE_NO_WARNINGS
#define _CRT_SECURE_NO_WARNINGS
#endif
#pragma warning(disable : 4996)
#endif

#if !defined(LIBRESSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x10100000L
#define OPENSSL_1_1_API 1
#elif defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER >= 0x2070000fL
#define OPENSSL_1_1_API 1
#else
#define OPENSSL_1_1_API 0
#endif

#if !OPENSSL_1_1_API

#define EVP_PKEY_up_ref(p) CRYPTO_add(&(p)->references, 1, CRYPTO_LOCK_EVP_PKEY)
#define X509_STORE_up_ref(p) CRYPTO_add(&(p)->references, 1, CRYPTO_LOCK_X509_STORE)
#define X509_STORE_get0_param(p) ((p)->param)

static HMAC_CTX *HMAC_CTX_new(void)
{
    HMAC_CTX *ctx;

    if ((ctx = OPENSSL_malloc(sizeof(*ctx))) == NULL)
        return NULL;
    HMAC_CTX_init(ctx);
    return ctx;
}

static void HMAC_CTX_free(HMAC_CTX *ctx)
{
    HMAC_CTX_cleanup(ctx);
    OPENSSL_free(ctx);
}

static int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx)
{
    return EVP_CIPHER_CTX_cleanup(ctx);
}

#endif

static const ptls_openssl_signature_scheme_t rsa_signature_schemes[] = {{PTLS_SIGNATURE_RSA_PSS_RSAE_SHA256, EVP_sha256},
                                                                                  {PTLS_SIGNATURE_RSA_PSS_RSAE_SHA384, EVP_sha384},
                                                                                  {PTLS_SIGNATURE_RSA_PSS_RSAE_SHA512, EVP_sha512},
                                                                                  {UINT16_MAX, NULL}};
static const ptls_openssl_signature_scheme_t secp256r1_signature_schemes[] = {
    {PTLS_SIGNATURE_ECDSA_SECP256R1_SHA256, EVP_sha256}, {UINT16_MAX, NULL}};
#if PTLS_OPENSSL_HAVE_SECP384R1
static const ptls_openssl_signature_scheme_t secp384r1_signature_schemes[] = {
    {PTLS_SIGNATURE_ECDSA_SECP384R1_SHA384, EVP_sha384}, {UINT16_MAX, NULL}};
#endif
#if PTLS_OPENSSL_HAVE_SECP521R1
static const ptls_openssl_signature_scheme_t secp521r1_signature_schemes[] = {
    {PTLS_SIGNATURE_ECDSA_SECP521R1_SHA512, EVP_sha512}, {UINT16_MAX, NULL}};
#endif
#if PTLS_OPENSSL_HAVE_ED25519
static const ptls_openssl_signature_scheme_t ed25519_signature_schemes[] = {{PTLS_SIGNATURE_ED25519, NULL},
                                                                                      {UINT16_MAX, NULL}};
#endif

/**
 * The default list sent in ClientHello.signature_algorithms. ECDSA certificates are preferred.
 */
static const uint16_t default_signature_schemes[] = {
#if PTLS_OPENSSL_HAVE_ED25519
    PTLS_SIGNATURE_ED25519,
#endif
    PTLS_SIGNATURE_ECDSA_SECP256R1_SHA256,
#if PTLS_OPENSSL_HAVE_SECP384R1
    PTLS_SIGNATURE_ECDSA_SECP384R1_SHA384,
#endif
#if PTLS_OPENSSL_HAVE_SECP521R1
    PTLS_SIGNATURE_ECDSA_SECP521R1_SHA512,
#endif
    PTLS_SIGNATURE_RSA_PSS_RSAE_SHA512,
    PTLS_SIGNATURE_RSA_PSS_RSAE_SHA384,
    PTLS_SIGNATURE_RSA_PSS_RSAE_SHA256,
    UINT16_MAX};

const ptls_openssl_signature_scheme_t *ptls_openssl_lookup_signature_schemes(EVP_PKEY *key)
{
    const ptls_openssl_signature_scheme_t *schemes = NULL;

    switch (EVP_PKEY_id(key)) {
    case EVP_PKEY_RSA:
        schemes = rsa_signature_schemes;
        break;
    case EVP_PKEY_EC: {
        EC_KEY *eckey = EVP_PKEY_get1_EC_KEY(key);
        switch (EC_GROUP_get_curve_name(EC_KEY_get0_group(eckey))) {
        case NID_X9_62_prime256v1:
            schemes = secp256r1_signature_schemes;
            break;
#if PTLS_OPENSSL_HAVE_SECP384R1
        case NID_secp384r1:
            schemes = secp384r1_signature_schemes;
            break;
#endif
#if PTLS_OPENSSL_HAVE_SECP521R1
        case NID_secp521r1:
            schemes = secp521r1_signature_schemes;
            break;
#endif
        default:
            break;
        }
        EC_KEY_free(eckey);
    } break;
#if PTLS_OPENSSL_HAVE_ED25519
    case EVP_PKEY_ED25519:
        schemes = ed25519_signature_schemes;
        break;
#endif
    default:
        break;
    }

    return schemes;
}

const ptls_openssl_signature_scheme_t *ptls_openssl_select_signature_scheme(const ptls_openssl_signature_scheme_t *available,
                                                                            const uint16_t *algorithms, size_t num_algorithms)
{
    const ptls_openssl_signature_scheme_t *scheme;

    /* select the algorithm, driven by server-isde preference of `available` */
    for (scheme = available; scheme->scheme_id != UINT16_MAX; ++scheme)
        for (size_t i = 0; i != num_algorithms; ++i)
            if (algorithms[i] == scheme->scheme_id)
                return scheme;

    return NULL;
}

void ptls_openssl_random_bytes(void *buf, size_t len)
{
    int ret = RAND_bytes(buf, (int)len);
    if (ret != 1) {
        fprintf(stderr, "RAND_bytes() failed with code: %d\n", ret);
        abort();
    }
}

static EC_KEY *ecdh_gerenate_key(EC_GROUP *group)
{
    EC_KEY *key;

    if ((key = EC_KEY_new()) == NULL)
        return NULL;
    if (!EC_KEY_set_group(key, group) || !EC_KEY_generate_key(key)) {
        EC_KEY_free(key);
        return NULL;
    }

    return key;
}

static int ecdh_calc_secret(ptls_iovec_t *out, const EC_GROUP *group, EC_KEY *privkey, EC_POINT *peer_point)
{
    ptls_iovec_t secret;
    int ret;

    secret.len = (EC_GROUP_get_degree(group) + 7) / 8;
    if ((secret.base = malloc(secret.len)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if (ECDH_compute_key(secret.base, secret.len, peer_point, privkey, NULL) <= 0) {
        ret = PTLS_ALERT_HANDSHAKE_FAILURE; /* ??? */
        goto Exit;
    }
    ret = 0;

Exit:
    if (ret == 0) {
        *out = secret;
    } else {
        free(secret.base);
        *out = (ptls_iovec_t){NULL};
    }
    return ret;
}

static EC_POINT *x9_62_decode_point(const EC_GROUP *group, ptls_iovec_t vec, BN_CTX *bn_ctx)
{
    EC_POINT *point = NULL;

    if ((point = EC_POINT_new(group)) == NULL)
        return NULL;
    if (!EC_POINT_oct2point(group, point, vec.base, vec.len, bn_ctx)) {
        EC_POINT_free(point);
        return NULL;
    }

    return point;
}

static ptls_iovec_t x9_62_encode_point(const EC_GROUP *group, const EC_POINT *point, BN_CTX *bn_ctx)
{
    ptls_iovec_t vec;

    if ((vec.len = EC_POINT_point2oct(group, point, POINT_CONVERSION_UNCOMPRESSED, NULL, 0, bn_ctx)) == 0)
        return (ptls_iovec_t){NULL};
    if ((vec.base = malloc(vec.len)) == NULL)
        return (ptls_iovec_t){NULL};
    if (EC_POINT_point2oct(group, point, POINT_CONVERSION_UNCOMPRESSED, vec.base, vec.len, bn_ctx) != vec.len) {
        free(vec.base);
        return (ptls_iovec_t){NULL};
    }

    return vec;
}

struct st_x9_62_keyex_context_t {
    ptls_key_exchange_context_t super;
    BN_CTX *bn_ctx;
    EC_KEY *privkey;
};

static void x9_62_free_context(struct st_x9_62_keyex_context_t *ctx)
{
    free(ctx->super.pubkey.base);
    if (ctx->privkey != NULL)
        EC_KEY_free(ctx->privkey);
    if (ctx->bn_ctx != NULL)
        BN_CTX_free(ctx->bn_ctx);
    free(ctx);
}

static int x9_62_on_exchange(ptls_key_exchange_context_t **_ctx, int release, ptls_iovec_t *secret, ptls_iovec_t peerkey)
{
    struct st_x9_62_keyex_context_t *ctx = (struct st_x9_62_keyex_context_t *)*_ctx;
    const EC_GROUP *group = EC_KEY_get0_group(ctx->privkey);
    EC_POINT *peer_point = NULL;
    int ret;

    if (secret == NULL) {
        ret = 0;
        goto Exit;
    }

    if ((peer_point = x9_62_decode_point(group, peerkey, ctx->bn_ctx)) == NULL) {
        ret = PTLS_ALERT_DECODE_ERROR;
        goto Exit;
    }
    if ((ret = ecdh_calc_secret(secret, group, ctx->privkey, peer_point)) != 0)
        goto Exit;

Exit:
    if (peer_point != NULL)
        EC_POINT_free(peer_point);
    if (release) {
        x9_62_free_context(ctx);
        *_ctx = NULL;
    }
    return ret;
}

static int x9_62_create_context(ptls_key_exchange_algorithm_t *algo, struct st_x9_62_keyex_context_t **ctx)
{
    int ret;

    if ((*ctx = (struct st_x9_62_keyex_context_t *)malloc(sizeof(**ctx))) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    **ctx = (struct st_x9_62_keyex_context_t){{algo, {NULL}, x9_62_on_exchange}};

    if (((*ctx)->bn_ctx = BN_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    ret = 0;
Exit:
    if (ret != 0 && *ctx != NULL) {
        x9_62_free_context(*ctx);
        *ctx = NULL;
    }
    return ret;
}

static int x9_62_setup_pubkey(struct st_x9_62_keyex_context_t *ctx)
{
    const EC_GROUP *group = EC_KEY_get0_group(ctx->privkey);
    const EC_POINT *pubkey = EC_KEY_get0_public_key(ctx->privkey);
    if ((ctx->super.pubkey = x9_62_encode_point(group, pubkey, ctx->bn_ctx)).base == NULL)
        return PTLS_ERROR_NO_MEMORY;
    return 0;
}

static int x9_62_create_key_exchange(ptls_key_exchange_algorithm_t *algo, ptls_key_exchange_context_t **_ctx)
{
    EC_GROUP *group = NULL;
    struct st_x9_62_keyex_context_t *ctx = NULL;
    int ret;

    /* FIXME use a global? */
    if ((group = EC_GROUP_new_by_curve_name((int)algo->data)) == NULL) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if ((ret = x9_62_create_context(algo, &ctx)) != 0)
        goto Exit;
    if ((ctx->privkey = ecdh_gerenate_key(group)) == NULL) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if ((ret = x9_62_setup_pubkey(ctx)) != 0)
        goto Exit;
    ret = 0;

Exit:
    if (group != NULL)
        EC_GROUP_free(group);
    if (ret == 0) {
        *_ctx = &ctx->super;
    } else {
        if (ctx != NULL)
            x9_62_free_context(ctx);
        *_ctx = NULL;
    }

    return ret;
}

static int x9_62_init_key(ptls_key_exchange_algorithm_t *algo, ptls_key_exchange_context_t **_ctx, EC_KEY *eckey)
{
    struct st_x9_62_keyex_context_t *ctx = NULL;
    int ret;

    if ((ret = x9_62_create_context(algo, &ctx)) != 0)
        goto Exit;
    ctx->privkey = eckey;
    if ((ret = x9_62_setup_pubkey(ctx)) != 0)
        goto Exit;
    ret = 0;

Exit:
    if (ret == 0) {
        *_ctx = &ctx->super;
    } else {
        if (ctx != NULL)
            x9_62_free_context(ctx);
        *_ctx = NULL;
    }
    return ret;
}

static int x9_62_key_exchange(EC_GROUP *group, ptls_iovec_t *pubkey, ptls_iovec_t *secret, ptls_iovec_t peerkey, BN_CTX *bn_ctx)
{
    EC_POINT *peer_point = NULL;
    EC_KEY *privkey = NULL;
    int ret;

    *pubkey = (ptls_iovec_t){NULL};
    *secret = (ptls_iovec_t){NULL};

    /* decode peer key */
    if ((peer_point = x9_62_decode_point(group, peerkey, bn_ctx)) == NULL) {
        ret = PTLS_ALERT_DECODE_ERROR;
        goto Exit;
    }

    /* create private key */
    if ((privkey = ecdh_gerenate_key(group)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    /* encode public key */
    if ((*pubkey = x9_62_encode_point(group, EC_KEY_get0_public_key(privkey), bn_ctx)).base == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    /* calc secret */
    secret->len = (EC_GROUP_get_degree(group) + 7) / 8;
    if ((secret->base = malloc(secret->len)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    /* ecdh! */
    if (ECDH_compute_key(secret->base, secret->len, peer_point, privkey, NULL) <= 0) {
        ret = PTLS_ALERT_HANDSHAKE_FAILURE; /* ??? */
        goto Exit;
    }

    ret = 0;

Exit:
    if (peer_point != NULL)
        EC_POINT_free(peer_point);
    if (privkey != NULL)
        EC_KEY_free(privkey);
    if (ret != 0) {
        free(pubkey->base);
        *pubkey = (ptls_iovec_t){NULL};
        free(secret->base);
        *secret = (ptls_iovec_t){NULL};
    }
    return ret;
}

static int secp_key_exchange(ptls_key_exchange_algorithm_t *algo, ptls_iovec_t *pubkey, ptls_iovec_t *secret, ptls_iovec_t peerkey)
{
    EC_GROUP *group = NULL;
    BN_CTX *bn_ctx = NULL;
    int ret;

    if ((group = EC_GROUP_new_by_curve_name((int)algo->data)) == NULL) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if ((bn_ctx = BN_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    ret = x9_62_key_exchange(group, pubkey, secret, peerkey, bn_ctx);

Exit:
    if (bn_ctx != NULL)
        BN_CTX_free(bn_ctx);
    if (group != NULL)
        EC_GROUP_free(group);
    return ret;
}

#if PTLS_OPENSSL_HAVE_X25519

struct st_evp_keyex_context_t {
    ptls_key_exchange_context_t super;
    EVP_PKEY *privkey;
};

static void evp_keyex_free(struct st_evp_keyex_context_t *ctx)
{
    if (ctx->privkey != NULL)
        EVP_PKEY_free(ctx->privkey);
    if (ctx->super.pubkey.base != NULL)
        OPENSSL_free(ctx->super.pubkey.base);
    free(ctx);
}

static int evp_keyex_on_exchange(ptls_key_exchange_context_t **_ctx, int release, ptls_iovec_t *secret, ptls_iovec_t peerkey)
{
    struct st_evp_keyex_context_t *ctx = (void *)*_ctx;
    EVP_PKEY *evppeer = NULL;
    EVP_PKEY_CTX *evpctx = NULL;
    int ret;

    if (secret == NULL) {
        ret = 0;
        goto Exit;
    }

    secret->base = NULL;

    if (peerkey.len != ctx->super.pubkey.len) {
        ret = PTLS_ALERT_DECRYPT_ERROR;
        goto Exit;
    }

#ifdef OPENSSL_IS_BORINGSSL
    if (ctx->super.algo->id == PTLS_GROUP_X25519) {
        secret->len = peerkey.len;
        if ((secret->base = malloc(secret->len)) == NULL) {
            ret = PTLS_ERROR_NO_MEMORY;
            goto Exit;
        }
        uint8_t sk_raw[32];
        size_t sk_raw_len = sizeof(sk_raw);
        if (EVP_PKEY_get_raw_private_key(ctx->privkey, sk_raw, &sk_raw_len) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
        X25519(secret->base, sk_raw, peerkey.base);
        ret = 0;
        goto Exit;
    }
#endif

    if ((evppeer = EVP_PKEY_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if (EVP_PKEY_copy_parameters(evppeer, ctx->privkey) <= 0) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if (EVP_PKEY_set1_tls_encodedpoint(evppeer, peerkey.base, peerkey.len) <= 0) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if ((evpctx = EVP_PKEY_CTX_new(ctx->privkey, NULL)) == NULL) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if (EVP_PKEY_derive_init(evpctx) <= 0) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if (EVP_PKEY_derive_set_peer(evpctx, evppeer) <= 0) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if (EVP_PKEY_derive(evpctx, NULL, &secret->len) <= 0) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if ((secret->base = malloc(secret->len)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if (EVP_PKEY_derive(evpctx, secret->base, &secret->len) <= 0) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }

    ret = 0;
Exit:
    if (evpctx != NULL)
        EVP_PKEY_CTX_free(evpctx);
    if (evppeer != NULL)
        EVP_PKEY_free(evppeer);
    if (ret != 0)
        free(secret->base);
    if (release) {
        evp_keyex_free(ctx);
        *_ctx = NULL;
    }
    return ret;
}

static int evp_keyex_init(ptls_key_exchange_algorithm_t *algo, ptls_key_exchange_context_t **_ctx, EVP_PKEY *pkey)
{
    struct st_evp_keyex_context_t *ctx = NULL;
    int ret;

    /* instantiate */
    if ((ctx = malloc(sizeof(*ctx))) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    *ctx = (struct st_evp_keyex_context_t){{algo, {NULL}, evp_keyex_on_exchange}, pkey};

    /* set public key */
    if ((ctx->super.pubkey.len = EVP_PKEY_get1_tls_encodedpoint(ctx->privkey, &ctx->super.pubkey.base)) == 0) {
        ctx->super.pubkey.base = NULL;
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    *_ctx = &ctx->super;
    ret = 0;
Exit:
    if (ret != 0 && ctx != NULL)
        evp_keyex_free(ctx);
    return ret;
}

static int evp_keyex_create(ptls_key_exchange_algorithm_t *algo, ptls_key_exchange_context_t **ctx)
{
    EVP_PKEY_CTX *evpctx = NULL;
    EVP_PKEY *pkey = NULL;
    int ret;

    /* generate private key */
    if ((evpctx = EVP_PKEY_CTX_new_id((int)algo->data, NULL)) == NULL) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if (EVP_PKEY_keygen_init(evpctx) <= 0) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if (EVP_PKEY_keygen(evpctx, &pkey) <= 0) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }

    /* setup */
    if ((ret = evp_keyex_init(algo, ctx, pkey)) != 0)
        goto Exit;
    pkey = NULL;
    ret = 0;

Exit:
    if (pkey != NULL)
        EVP_PKEY_free(pkey);
    if (evpctx != NULL)
        EVP_PKEY_CTX_free(evpctx);
    return ret;
}

static int evp_keyex_exchange(ptls_key_exchange_algorithm_t *algo, ptls_iovec_t *outpubkey, ptls_iovec_t *secret,
                              ptls_iovec_t peerkey)
{
    ptls_key_exchange_context_t *ctx = NULL;
    int ret;

    outpubkey->base = NULL;

    if ((ret = evp_keyex_create(algo, &ctx)) != 0)
        goto Exit;
    if ((outpubkey->base = malloc(ctx->pubkey.len)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    memcpy(outpubkey->base, ctx->pubkey.base, ctx->pubkey.len);
    outpubkey->len = ctx->pubkey.len;
    ret = evp_keyex_on_exchange(&ctx, 1, secret, peerkey);
    assert(ctx == NULL);

Exit:
    if (ctx != NULL)
        evp_keyex_on_exchange(&ctx, 1, NULL, ptls_iovec_init(NULL, 0));
    if (ret != 0)
        free(outpubkey->base);
    return ret;
}

#endif

int ptls_openssl_create_key_exchange(ptls_key_exchange_context_t **ctx, EVP_PKEY *pkey)
{
    int ret, id;

    switch (id = EVP_PKEY_id(pkey)) {

    case EVP_PKEY_EC: {
        /* obtain eckey */
        EC_KEY *eckey = EVP_PKEY_get1_EC_KEY(pkey);

        /* determine algo */
        ptls_key_exchange_algorithm_t *algo;
        switch (EC_GROUP_get_curve_name(EC_KEY_get0_group(eckey))) {
        case NID_X9_62_prime256v1:
            algo = &ptls_openssl_secp256r1;
            break;
#if PTLS_OPENSSL_HAVE_SECP384R1
        case NID_secp384r1:
            algo = &ptls_openssl_secp384r1;
            break;
#endif
#if PTLS_OPENSSL_HAVE_SECP521R1
        case NID_secp521r1:
            algo = &ptls_openssl_secp521r1;
            break;
#endif
        default:
            EC_KEY_free(eckey);
            return PTLS_ERROR_INCOMPATIBLE_KEY;
        }

        /* load key */
        if ((ret = x9_62_init_key(algo, ctx, eckey)) != 0) {
            EC_KEY_free(eckey);
            return ret;
        }

        return 0;
    } break;

#if PTLS_OPENSSL_HAVE_X25519
    case NID_X25519:
        if ((ret = evp_keyex_init(&ptls_openssl_x25519, ctx, pkey)) != 0)
            return ret;
        EVP_PKEY_up_ref(pkey);
        return 0;
#endif

    default:
        return PTLS_ERROR_INCOMPATIBLE_KEY;
    }
}

#if PTLS_OPENSSL_HAVE_ASYNC

struct async_sign_ctx {
    ptls_async_job_t super;
    const ptls_openssl_signature_scheme_t *scheme;
    EVP_MD_CTX *ctx;
    ASYNC_WAIT_CTX *waitctx;
    ASYNC_JOB *job;
    size_t siglen;
    uint8_t sig[0]; // must be last, see `async_sign_ctx_new`
};

static void async_sign_ctx_free(ptls_async_job_t *_self)
{
    struct async_sign_ctx *self = (void *)_self;

    /* Once the async operation is complete, the user might call `ptls_free` instead of `ptls_handshake`. In such case, to avoid
     * desynchronization, let the backend read the result from the socket. The code below is a loop, but it is not going to block;
     * it is the responsibility of the user to refrain from calling `ptls_free` until the asynchronous operation is complete. */
    if (self->job != NULL) {
        int ret;
        while (ASYNC_start_job(&self->job, self->waitctx, &ret, NULL, NULL, 0) == ASYNC_PAUSE)
            ;
    }

    EVP_MD_CTX_destroy(self->ctx);
    ASYNC_WAIT_CTX_free(self->waitctx);
    free(self);
}

int async_sign_ctx_get_fd(ptls_async_job_t *_self)
{
    struct async_sign_ctx *self = (void *)_self;
    OSSL_ASYNC_FD fds[1];
    size_t numfds;

    ASYNC_WAIT_CTX_get_all_fds(self->waitctx, NULL, &numfds);
    assert(numfds == 1);
    ASYNC_WAIT_CTX_get_all_fds(self->waitctx, fds, &numfds);
    return (int)fds[0];
}

static ptls_async_job_t *async_sign_ctx_new(const ptls_openssl_signature_scheme_t *scheme, EVP_MD_CTX *ctx, size_t siglen)
{
    struct async_sign_ctx *self;

    if ((self = malloc(offsetof(struct async_sign_ctx, sig) + siglen)) == NULL)
        return NULL;

    self->super = (ptls_async_job_t){async_sign_ctx_free, async_sign_ctx_get_fd};
    self->scheme = scheme;
    self->ctx = ctx;
    self->waitctx = ASYNC_WAIT_CTX_new();
    self->job = NULL;
    self->siglen = siglen;
    memset(self->sig, 0, siglen);

    return &self->super;
}

static int do_sign_async_job(void *_async)
{
    struct async_sign_ctx *async = *(struct async_sign_ctx **)_async;
    return EVP_DigestSignFinal(async->ctx, async->sig, &async->siglen);
}

static int do_sign_async(ptls_buffer_t *outbuf, ptls_async_job_t **_async)
{
    struct async_sign_ctx *async = (void *)*_async;
    int ret;

    switch (ASYNC_start_job(&async->job, async->waitctx, &ret, do_sign_async_job, &async, sizeof(async))) {
    case ASYNC_PAUSE:
        return PTLS_ERROR_ASYNC_OPERATION; // async operation inflight; bail out without getting rid of async context
    case ASYNC_ERR:
        ret = PTLS_ERROR_LIBRARY;
        break;
    case ASYNC_NO_JOBS:
        ret = PTLS_ERROR_LIBRARY;
        break;
    case ASYNC_FINISH:
        async->job = NULL;
        ptls_buffer_pushv(outbuf, async->sig, async->siglen);
        ret = 0;
        break;
    default:
        ret = PTLS_ERROR_LIBRARY;
        break;
    }

Exit:
    async_sign_ctx_free(&async->super);
    *_async = NULL;
    return ret;
}

#endif

static int do_sign(EVP_PKEY *key, const ptls_openssl_signature_scheme_t *scheme, ptls_buffer_t *outbuf,
                   ptls_iovec_t input, ptls_async_job_t **async)
{
    EVP_MD_CTX *ctx = NULL;
    const EVP_MD *md = scheme->scheme_md != NULL ? scheme->scheme_md() : NULL;
    EVP_PKEY_CTX *pkey_ctx;
    size_t siglen;
    int ret;

    if ((ctx = EVP_MD_CTX_create()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    if (EVP_DigestSignInit(ctx, &pkey_ctx, md, NULL, key) != 1) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }

#if PTLS_OPENSSL_HAVE_ED25519
    if (EVP_PKEY_id(key) == EVP_PKEY_ED25519) {
        /* ED25519 requires the use of the all-at-once function that appeared in OpenSSL 1.1.1, hence different path */
        if (EVP_DigestSign(ctx, NULL, &siglen, input.base, input.len) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
        if ((ret = ptls_buffer_reserve(outbuf, siglen)) != 0)
            goto Exit;
        if (EVP_DigestSign(ctx, outbuf->base + outbuf->off, &siglen, input.base, input.len) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
    } else
#endif
    {
        if (EVP_PKEY_id(key) == EVP_PKEY_RSA) {
            if (EVP_PKEY_CTX_set_rsa_padding(pkey_ctx, RSA_PKCS1_PSS_PADDING) != 1) {
                ret = PTLS_ERROR_LIBRARY;
                goto Exit;
            }
            if (EVP_PKEY_CTX_set_rsa_pss_saltlen(pkey_ctx, -1) != 1) {
                ret = PTLS_ERROR_LIBRARY;
                goto Exit;
            }
            if (EVP_PKEY_CTX_set_rsa_mgf1_md(pkey_ctx, md) != 1) {
                ret = PTLS_ERROR_LIBRARY;
                goto Exit;
            }
        }
        if (EVP_DigestSignUpdate(ctx, input.base, input.len) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
        if (EVP_DigestSignFinal(ctx, NULL, &siglen) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
        /* If permitted by the caller (by providing a non-NULL `async` slot), use the asynchronous signing method and return
         * immediately. */
#if PTLS_OPENSSL_HAVE_ASYNC
        if (async != NULL) {
            if ((*async = async_sign_ctx_new(scheme, ctx, siglen)) == NULL) {
                ret = PTLS_ERROR_NO_MEMORY;
                goto Exit;
            }
            return do_sign_async(outbuf, async);
        }
#endif
        /* Otherwise, generate signature synchronously. */
        if ((ret = ptls_buffer_reserve(outbuf, siglen)) != 0)
            goto Exit;
        if (EVP_DigestSignFinal(ctx, outbuf->base + outbuf->off, &siglen) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
    }

    outbuf->off += siglen;

    ret = 0;
Exit:
    if (ctx != NULL)
        EVP_MD_CTX_destroy(ctx);
    return ret;
}

struct cipher_context_t {
    ptls_cipher_context_t super;
    EVP_CIPHER_CTX *evp;
};

static void cipher_dispose(ptls_cipher_context_t *_ctx)
{
    struct cipher_context_t *ctx = (struct cipher_context_t *)_ctx;
    EVP_CIPHER_CTX_free(ctx->evp);
}

static void cipher_do_init(ptls_cipher_context_t *_ctx, const void *iv)
{
    struct cipher_context_t *ctx = (struct cipher_context_t *)_ctx;
    int ret;
    ret = EVP_EncryptInit_ex(ctx->evp, NULL, NULL, NULL, iv);
    assert(ret);
}

static int cipher_setup_crypto(ptls_cipher_context_t *_ctx, int is_enc, const void *key, const EVP_CIPHER *cipher,
                               void (*do_transform)(ptls_cipher_context_t *, void *, const void *, size_t))
{
    struct cipher_context_t *ctx = (struct cipher_context_t *)_ctx;

    ctx->super.do_dispose = cipher_dispose;
    ctx->super.do_init = cipher_do_init;
    ctx->super.do_transform = do_transform;

    if ((ctx->evp = EVP_CIPHER_CTX_new()) == NULL)
        return PTLS_ERROR_NO_MEMORY;

    if (is_enc) {
        if (!EVP_EncryptInit_ex(ctx->evp, cipher, NULL, key, NULL))
            goto Error;
    } else {
        if (!EVP_DecryptInit_ex(ctx->evp, cipher, NULL, key, NULL))
            goto Error;
        EVP_CIPHER_CTX_set_padding(ctx->evp, 0); /* required to disable one block buffering in ECB mode */
    }

    return 0;
Error:
    EVP_CIPHER_CTX_free(ctx->evp);
    return PTLS_ERROR_LIBRARY;
}

static void cipher_encrypt(ptls_cipher_context_t *_ctx, void *output, const void *input, size_t _len)
{
    struct cipher_context_t *ctx = (struct cipher_context_t *)_ctx;
    int len = (int)_len, ret = EVP_EncryptUpdate(ctx->evp, output, &len, input, len);
    assert(ret);
    assert(len == (int)_len);
}

static void cipher_decrypt(ptls_cipher_context_t *_ctx, void *output, const void *input, size_t _len)
{
    struct cipher_context_t *ctx = (struct cipher_context_t *)_ctx;
    int len = (int)_len, ret = EVP_DecryptUpdate(ctx->evp, output, &len, input, len);
    assert(ret);
    assert(len == (int)_len);
}

static int aes128ecb_setup_crypto(ptls_cipher_context_t *ctx, int is_enc, const void *key)
{
    return cipher_setup_crypto(ctx, is_enc, key, EVP_aes_128_ecb(), is_enc ? cipher_encrypt : cipher_decrypt);
}

static int aes256ecb_setup_crypto(ptls_cipher_context_t *ctx, int is_enc, const void *key)
{
    return cipher_setup_crypto(ctx, is_enc, key, EVP_aes_256_ecb(), is_enc ? cipher_encrypt : cipher_decrypt);
}

static int aes128ctr_setup_crypto(ptls_cipher_context_t *ctx, int is_enc, const void *key)
{
    return cipher_setup_crypto(ctx, 1, key, EVP_aes_128_ctr(), cipher_encrypt);
}

static int aes256ctr_setup_crypto(ptls_cipher_context_t *ctx, int is_enc, const void *key)
{
    return cipher_setup_crypto(ctx, 1, key, EVP_aes_256_ctr(), cipher_encrypt);
}

#if PTLS_OPENSSL_HAVE_CHACHA20_POLY1305
#ifdef OPENSSL_IS_BORINGSSL

struct boringssl_chacha20_context_t {
    ptls_cipher_context_t super;
    uint8_t key[PTLS_CHACHA20_KEY_SIZE];
    uint8_t iv[12];
    struct {
        uint32_t ctr;
        uint8_t bytes[64];
        size_t len;
    } keystream;
};

static void boringssl_chacha20_dispose(ptls_cipher_context_t *_ctx)
{
    struct boringssl_chacha20_context_t *ctx = (struct boringssl_chacha20_context_t *)_ctx;

    ptls_clear_memory(ctx->key, sizeof(ctx->key));
    ptls_clear_memory(ctx->iv, sizeof(ctx->iv));
    ptls_clear_memory(ctx->keysream.bytes, sizeof(ctx->keystream.bytes));
}

static void boringssl_chacha20_init(ptls_cipher_context_t *_ctx, const void *_iv)
{
    struct boringssl_chacha20_context_t *ctx = (struct boringssl_chacha20_context_t *)_ctx;
    const uint8_t *iv = _iv;

    memcpy(ctx->iv, iv + 4, sizeof(ctx->iv));
    ctx->keystream.ctr = iv[0] | ((uint32_t)iv[1] << 8) | ((uint32_t)iv[2] << 16) | ((uint32_t)iv[3] << 24);
    ctx->keystream.len = 0;
}

static inline void boringssl_chacha20_transform_buffered(struct boringssl_chacha20_context_t *ctx, uint8_t **output,
                                                         const uint8_t **input, size_t *len)
{
    size_t apply_len = *len < ctx->keystream.len ? *len : ctx->keystream.len;
    const uint8_t *ks = ctx->keystream.bytes + sizeof(ctx->keystream.bytes) - ctx->keystream.len;
    ctx->keystream.len -= apply_len;

    *len -= apply_len;
    for (size_t i = 0; i < apply_len; ++i)
        *(*output)++ = *(*input)++ ^ *ks++;
}

static void boringssl_chacha20_transform(ptls_cipher_context_t *_ctx, void *_output, const void *_input, size_t len)
{
    struct boringssl_chacha20_context_t *ctx = (struct boringssl_chacha20_context_t *)_ctx;
    uint8_t *output = _output;
    const uint8_t *input = _input;

    if (len == 0)
        return;

    if (ctx->keystream.len != 0) {
        boringssl_chacha20_transform_buffered(ctx, &output, &input, &len);
        if (len == 0)
            return;
    }

    assert(ctx->keystream.len == 0);

    if (len >= sizeof(ctx->keystream.bytes)) {
        size_t apply_len = len / sizeof(ctx->keystream.bytes) * sizeof(ctx->keystream.bytes);
        CRYPTO_chacha_20(output, input, apply_len, ctx->key, ctx->iv, ctx->keystream.ctr);
        ctx->keystream.ctr += apply_len / sizeof(ctx->keystream.bytes);
        output += apply_len;
        input += apply_len;
        len -= apply_len;
        if (len == 0)
            return;
    }

    memset(ctx->keystream.bytes, 0, sizeof(ctx->keystream.bytes));
    CRYPTO_chacha_20(ctx->keystream.bytes, ctx->keystream.bytes, sizeof(ctx->keystream.bytes), ctx->key, ctx->iv,
                     ctx->keystream.ctr++);
    ctx->keystream.len = sizeof(ctx->keystream.bytes);

    boringssl_chacha20_transform_buffered(ctx, &output, &input, &len);
    assert(len == 0);
}

static int boringssl_chacha20_setup_crypto(ptls_cipher_context_t *_ctx, int is_enc, const void *key)
{
    struct boringssl_chacha20_context_t *ctx = (struct boringssl_chacha20_context_t *)_ctx;

    ctx->super.do_dispose = boringssl_chacha20_dispose;
    ctx->super.do_init = boringssl_chacha20_init;
    ctx->super.do_transform = boringssl_chacha20_transform;
    memcpy(ctx->key, key, sizeof(ctx->key));

    return 0;
}

#else

static int chacha20_setup_crypto(ptls_cipher_context_t *ctx, int is_enc, const void *key)
{
    return cipher_setup_crypto(ctx, 1, key, EVP_chacha20(), cipher_encrypt);
}

#endif
#endif

#if PTLS_OPENSSL_HAVE_BF

static int bfecb_setup_crypto(ptls_cipher_context_t *ctx, int is_enc, const void *key)
{
    return cipher_setup_crypto(ctx, is_enc, key, EVP_bf_ecb(), is_enc ? cipher_encrypt : cipher_decrypt);
}

#endif

struct aead_crypto_context_t {
    ptls_aead_context_t super;
    EVP_CIPHER_CTX *evp_ctx;
    uint8_t static_iv[PTLS_MAX_IV_SIZE];
};

static void aead_dispose_crypto(ptls_aead_context_t *_ctx)
{
    struct aead_crypto_context_t *ctx = (struct aead_crypto_context_t *)_ctx;

    if (ctx->evp_ctx != NULL)
        EVP_CIPHER_CTX_free(ctx->evp_ctx);
}

static void aead_xor_iv(ptls_aead_context_t *_ctx, const void *_bytes, size_t len)
{
    struct aead_crypto_context_t *ctx = (struct aead_crypto_context_t *)_ctx;
    const uint8_t *bytes = _bytes;

    for (size_t i = 0; i < len; ++i)
        ctx->static_iv[i] ^= bytes[i];
}

static void aead_do_encrypt_init(ptls_aead_context_t *_ctx, uint64_t seq, const void *aad, size_t aadlen)
{
    struct aead_crypto_context_t *ctx = (struct aead_crypto_context_t *)_ctx;
    uint8_t iv[PTLS_MAX_IV_SIZE];
    int ret;

    ptls_aead__build_iv(ctx->super.algo, iv, ctx->static_iv, seq);
    ret = EVP_EncryptInit_ex(ctx->evp_ctx, NULL, NULL, NULL, iv);
    assert(ret);

    if (aadlen != 0) {
        int blocklen;
        ret = EVP_EncryptUpdate(ctx->evp_ctx, NULL, &blocklen, aad, (int)aadlen);
        assert(ret);
    }
}

static size_t aead_do_encrypt_update(ptls_aead_context_t *_ctx, void *output, const void *input, size_t inlen)
{
    struct aead_crypto_context_t *ctx = (struct aead_crypto_context_t *)_ctx;
    int blocklen, ret;

    ret = EVP_EncryptUpdate(ctx->evp_ctx, output, &blocklen, input, (int)inlen);
    assert(ret);

    return blocklen;
}

static size_t aead_do_encrypt_final(ptls_aead_context_t *_ctx, void *_output)
{
    struct aead_crypto_context_t *ctx = (struct aead_crypto_context_t *)_ctx;
    uint8_t *output = _output;
    size_t off = 0, tag_size = ctx->super.algo->tag_size;
    int blocklen, ret;

    ret = EVP_EncryptFinal_ex(ctx->evp_ctx, output + off, &blocklen);
    assert(ret);
    off += blocklen;
    ret = EVP_CIPHER_CTX_ctrl(ctx->evp_ctx, EVP_CTRL_GCM_GET_TAG, (int)tag_size, output + off);
    assert(ret);
    off += tag_size;

    return off;
}

static size_t aead_do_decrypt(ptls_aead_context_t *_ctx, void *_output, const void *input, size_t inlen, uint64_t seq,
                              const void *aad, size_t aadlen)
{
    struct aead_crypto_context_t *ctx = (struct aead_crypto_context_t *)_ctx;
    uint8_t *output = _output, iv[PTLS_MAX_IV_SIZE];
    size_t off = 0, tag_size = ctx->super.algo->tag_size;
    int blocklen, ret;

    if (inlen < tag_size)
        return SIZE_MAX;

    ptls_aead__build_iv(ctx->super.algo, iv, ctx->static_iv, seq);
    ret = EVP_DecryptInit_ex(ctx->evp_ctx, NULL, NULL, NULL, iv);
    assert(ret);
    if (aadlen != 0) {
        ret = EVP_DecryptUpdate(ctx->evp_ctx, NULL, &blocklen, aad, (int)aadlen);
        assert(ret);
    }
    ret = EVP_DecryptUpdate(ctx->evp_ctx, output + off, &blocklen, input, (int)(inlen - tag_size));
    assert(ret);
    off += blocklen;
    if (!EVP_CIPHER_CTX_ctrl(ctx->evp_ctx, EVP_CTRL_GCM_SET_TAG, (int)tag_size, (void *)((uint8_t *)input + inlen - tag_size)))
        return SIZE_MAX;
    if (!EVP_DecryptFinal_ex(ctx->evp_ctx, output + off, &blocklen))
        return SIZE_MAX;
    off += blocklen;

    return off;
}

static int aead_setup_crypto(ptls_aead_context_t *_ctx, int is_enc, const void *key, const void *iv, const EVP_CIPHER *cipher)
{
    struct aead_crypto_context_t *ctx = (struct aead_crypto_context_t *)_ctx;
    int ret;

    memcpy(ctx->static_iv, iv, ctx->super.algo->iv_size);
    if (key == NULL)
        return 0;

    ctx->super.dispose_crypto = aead_dispose_crypto;
    ctx->super.do_xor_iv = aead_xor_iv;
    if (is_enc) {
        ctx->super.do_encrypt_init = aead_do_encrypt_init;
        ctx->super.do_encrypt_update = aead_do_encrypt_update;
        ctx->super.do_encrypt_final = aead_do_encrypt_final;
        ctx->super.do_encrypt = ptls_aead__do_encrypt;
        ctx->super.do_encrypt_v = ptls_aead__do_encrypt_v;
        ctx->super.do_decrypt = NULL;
    } else {
        ctx->super.do_encrypt_init = NULL;
        ctx->super.do_encrypt_update = NULL;
        ctx->super.do_encrypt_final = NULL;
        ctx->super.do_encrypt = NULL;
        ctx->super.do_encrypt_v = NULL;
        ctx->super.do_decrypt = aead_do_decrypt;
    }
    ctx->evp_ctx = NULL;

    if ((ctx->evp_ctx = EVP_CIPHER_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Error;
    }
    if (is_enc) {
        if (!EVP_EncryptInit_ex(ctx->evp_ctx, cipher, NULL, key, NULL)) {
            ret = PTLS_ERROR_LIBRARY;
            goto Error;
        }
    } else {
        if (!EVP_DecryptInit_ex(ctx->evp_ctx, cipher, NULL, key, NULL)) {
            ret = PTLS_ERROR_LIBRARY;
            goto Error;
        }
    }
    if (!EVP_CIPHER_CTX_ctrl(ctx->evp_ctx, EVP_CTRL_GCM_SET_IVLEN, (int)ctx->super.algo->iv_size, NULL)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Error;
    }

    return 0;

Error:
    aead_dispose_crypto(&ctx->super);
    return ret;
}

static int aead_aes128gcm_setup_crypto(ptls_aead_context_t *ctx, int is_enc, const void *key, const void *iv)
{
    return aead_setup_crypto(ctx, is_enc, key, iv, EVP_aes_128_gcm());
}

static int aead_aes256gcm_setup_crypto(ptls_aead_context_t *ctx, int is_enc, const void *key, const void *iv)
{
    return aead_setup_crypto(ctx, is_enc, key, iv, EVP_aes_256_gcm());
}

#if PTLS_OPENSSL_HAVE_CHACHA20_POLY1305
#ifdef OPENSSL_IS_BORINGSSL

#include "./chacha20poly1305.h"

struct boringssl_chacha20poly1305_context_t {
    struct chacha20poly1305_context_t super;
    poly1305_state poly1305;
};

static void boringssl_poly1305_init(struct chacha20poly1305_context_t *_ctx, const void *key)
{
    struct boringssl_chacha20poly1305_context_t *ctx = (struct boringssl_chacha20poly1305_context_t *)_ctx;
    CRYPTO_poly1305_init(&ctx->poly1305, key);
}

static void boringssl_poly1305_update(struct chacha20poly1305_context_t *_ctx, const void *input, size_t len)
{
    struct boringssl_chacha20poly1305_context_t *ctx = (struct boringssl_chacha20poly1305_context_t *)_ctx;
    CRYPTO_poly1305_update(&ctx->poly1305, input, len);
}

static void boringssl_poly1305_finish(struct chacha20poly1305_context_t *_ctx, void *tag)
{
    struct boringssl_chacha20poly1305_context_t *ctx = (struct boringssl_chacha20poly1305_context_t *)_ctx;
    CRYPTO_poly1305_finish(&ctx->poly1305, tag);
}

static int boringssl_chacha20poly1305_setup_crypto(ptls_aead_context_t *ctx, int is_enc, const void *key, const void *iv)
{
    return chacha20poly1305_setup_crypto(ctx, is_enc, key, iv, &ptls_openssl_chacha20, boringssl_poly1305_init,
                                         boringssl_poly1305_update, boringssl_poly1305_finish);
}

#else

static int aead_chacha20poly1305_setup_crypto(ptls_aead_context_t *ctx, int is_enc, const void *key, const void *iv)
{
    return aead_setup_crypto(ctx, is_enc, key, iv, EVP_chacha20_poly1305());
}

#endif
#endif

#define _sha256_final(ctx, md) SHA256_Final((md), (ctx))
ptls_define_hash(sha256, SHA256_CTX, SHA256_Init, SHA256_Update, _sha256_final);

#define _sha384_final(ctx, md) SHA384_Final((md), (ctx))
ptls_define_hash(sha384, SHA512_CTX, SHA384_Init, SHA384_Update, _sha384_final);

#define _sha512_final(ctx, md) SHA512_Final((md), (ctx))
ptls_define_hash(sha512, SHA512_CTX, SHA512_Init, SHA512_Update, _sha512_final);

static int sign_certificate(ptls_sign_certificate_t *_self, ptls_t *tls, ptls_async_job_t **async, uint16_t *selected_algorithm,
                            ptls_buffer_t *outbuf, ptls_iovec_t input, const uint16_t *algorithms, size_t num_algorithms)
{
    ptls_openssl_sign_certificate_t *self = (ptls_openssl_sign_certificate_t *)_self;
    const ptls_openssl_signature_scheme_t *scheme;

    /* Just resume the asynchronous operation, if one is in flight. */
#if PTLS_OPENSSL_HAVE_ASYNC
    if (async != NULL && *async != NULL) {
        struct async_sign_ctx *sign_ctx = (struct async_sign_ctx *)(*async);
        *selected_algorithm = sign_ctx->scheme->scheme_id;
        return do_sign_async(outbuf, async);
    }
#endif

    /* Select the algorithm or return failure if none found. */
    if ((scheme = ptls_openssl_select_signature_scheme(self->schemes, algorithms, num_algorithms)) == NULL)
        return PTLS_ALERT_HANDSHAKE_FAILURE;
    *selected_algorithm = scheme->scheme_id;

#if PTLS_OPENSSL_HAVE_ASYNC
    if (!self->async && async != NULL) {
        /* indicate to `do_sign` that async mode is disabled for this operation */
        assert(*async == NULL);
        async = NULL;
    }
#endif
    return do_sign(self->key, scheme, outbuf, input, async);
}

static X509 *to_x509(ptls_iovec_t vec)
{
    const uint8_t *p = vec.base;
    return d2i_X509(NULL, &p, (long)vec.len);
}

static int verify_sign(void *verify_ctx, uint16_t algo, ptls_iovec_t data, ptls_iovec_t signature)
{
    EVP_PKEY *key = verify_ctx;
    const ptls_openssl_signature_scheme_t *scheme;
    EVP_MD_CTX *ctx = NULL;
    EVP_PKEY_CTX *pkey_ctx = NULL;
    int ret = 0;

    if (data.base == NULL)
        goto Exit;

    if ((scheme = ptls_openssl_lookup_signature_schemes(key)) == NULL) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    for (; scheme->scheme_id != UINT16_MAX; ++scheme)
        if (scheme->scheme_id == algo)
            goto SchemeFound;
    ret = PTLS_ALERT_ILLEGAL_PARAMETER;
    goto Exit;

SchemeFound:
    if ((ctx = EVP_MD_CTX_create()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

#if PTLS_OPENSSL_HAVE_ED25519
    if (EVP_PKEY_id(key) == EVP_PKEY_ED25519) {
        /* ED25519 requires the use of the all-at-once function that appeared in OpenSSL 1.1.1, hence different path */
        if (EVP_DigestVerifyInit(ctx, &pkey_ctx, NULL, NULL, key) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
        if (EVP_DigestVerify(ctx, signature.base, signature.len, data.base, data.len) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
    } else
#endif
    {
        if (EVP_DigestVerifyInit(ctx, &pkey_ctx, scheme->scheme_md(), NULL, key) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }

        if (EVP_PKEY_id(key) == EVP_PKEY_RSA) {
            if (EVP_PKEY_CTX_set_rsa_padding(pkey_ctx, RSA_PKCS1_PSS_PADDING) != 1) {
                ret = PTLS_ERROR_LIBRARY;
                goto Exit;
            }
            if (EVP_PKEY_CTX_set_rsa_pss_saltlen(pkey_ctx, -1) != 1) {
                ret = PTLS_ERROR_LIBRARY;
                goto Exit;
            }
            if (EVP_PKEY_CTX_set_rsa_mgf1_md(pkey_ctx, scheme->scheme_md()) != 1) {
                ret = PTLS_ERROR_LIBRARY;
                goto Exit;
            }
        }
        if (EVP_DigestVerifyUpdate(ctx, data.base, data.len) != 1) {
            ret = PTLS_ERROR_LIBRARY;
            goto Exit;
        }
        if (EVP_DigestVerifyFinal(ctx, signature.base, signature.len) != 1) {
            ret = PTLS_ALERT_DECRYPT_ERROR;
            goto Exit;
        }
    }

    ret = 0;

Exit:
    if (ctx != NULL)
        EVP_MD_CTX_destroy(ctx);
    EVP_PKEY_free(key);
    return ret;
}

int ptls_openssl_init_sign_certificate(ptls_openssl_sign_certificate_t *self, EVP_PKEY *key)
{
    *self = (ptls_openssl_sign_certificate_t){.super = {sign_certificate}, .async = 0 /* libssl has it off by default too */};

    if ((self->schemes = ptls_openssl_lookup_signature_schemes(key)) == NULL)
        return PTLS_ERROR_INCOMPATIBLE_KEY;
    EVP_PKEY_up_ref(key);
    self->key = key;

    return 0;
}

void ptls_openssl_dispose_sign_certificate(ptls_openssl_sign_certificate_t *self)
{
    EVP_PKEY_free(self->key);
}

static int serialize_cert(X509 *cert, ptls_iovec_t *dst)
{
    int len = i2d_X509(cert, NULL);
    assert(len > 0);

    if ((dst->base = malloc(len)) == NULL)
        return PTLS_ERROR_NO_MEMORY;
    unsigned char *p = dst->base;
    dst->len = i2d_X509(cert, &p);
    assert(len == dst->len);

    return 0;
}

int ptls_openssl_load_certificates(ptls_context_t *ctx, X509 *cert, STACK_OF(X509) * chain)
{
    ptls_iovec_t *list = NULL;
    size_t slot = 0, count = (cert != NULL) + (chain != NULL ? sk_X509_num(chain) : 0);
    int ret;

    assert(ctx->certificates.list == NULL);

    if ((list = malloc(sizeof(*list) * count)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if (cert != NULL) {
        if ((ret = serialize_cert(cert, list + slot++)) != 0)
            goto Exit;
    }
    if (chain != NULL) {
        int i;
        for (i = 0; i != sk_X509_num(chain); ++i) {
            if ((ret = serialize_cert(sk_X509_value(chain, i), list + slot++)) != 0)
                goto Exit;
        }
    }

    assert(slot == count);

    ctx->certificates.list = list;
    ctx->certificates.count = count;
    ret = 0;

Exit:
    if (ret != 0 && list != NULL) {
        size_t i;
        for (i = 0; i != slot; ++i)
            free(list[i].base);
        free(list);
    }
    return ret;
}

static int verify_cert_chain(X509_STORE *store, X509 *cert, STACK_OF(X509) * chain, int is_server, const char *server_name,
                             int *ossl_x509_err)
{
    X509_STORE_CTX *verify_ctx;
    int ret;
    *ossl_x509_err = 0;

    /* verify certificate chain */
    if ((verify_ctx = X509_STORE_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if (X509_STORE_CTX_init(verify_ctx, store, cert, chain) != 1) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }

    { /* setup verify params */
        X509_VERIFY_PARAM *params = X509_STORE_CTX_get0_param(verify_ctx);
        X509_VERIFY_PARAM_set_purpose(params, is_server ? X509_PURPOSE_SSL_CLIENT : X509_PURPOSE_SSL_SERVER);
        X509_VERIFY_PARAM_set_depth(params, 98); /* use the default of OpenSSL 1.0.2 and above; see `man SSL_CTX_set_verify` */
        /* when _acting_ as client, set the server name */
        if (!is_server) {
            assert(server_name != NULL && "ptls_set_server_name MUST be called");
            if (ptls_server_name_is_ipaddr(server_name)) {
                X509_VERIFY_PARAM_set1_ip_asc(params, server_name);
            } else {
                X509_VERIFY_PARAM_set1_host(params, server_name, strlen(server_name));
                X509_VERIFY_PARAM_set_hostflags(params, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS);
            }
        }
    }

    if (X509_verify_cert(verify_ctx) != 1) {
        *ossl_x509_err = X509_STORE_CTX_get_error(verify_ctx);
        switch (*ossl_x509_err) {
        case X509_V_ERR_OUT_OF_MEM:
            ret = PTLS_ERROR_NO_MEMORY;
            break;
        case X509_V_ERR_CERT_REVOKED:
            ret = PTLS_ALERT_CERTIFICATE_REVOKED;
            break;
        case X509_V_ERR_CERT_NOT_YET_VALID:
        case X509_V_ERR_CERT_HAS_EXPIRED:
            ret = PTLS_ALERT_CERTIFICATE_EXPIRED;
            break;
        case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:
        case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY:
        case X509_V_ERR_CERT_UNTRUSTED:
        case X509_V_ERR_CERT_REJECTED:
            ret = PTLS_ALERT_UNKNOWN_CA;
            break;
        case X509_V_ERR_HOSTNAME_MISMATCH:
        case X509_V_ERR_INVALID_CA:
            ret = PTLS_ALERT_BAD_CERTIFICATE;
            break;
        default:
            ret = PTLS_ALERT_CERTIFICATE_UNKNOWN;
            break;
        }
        goto Exit;
    }

    ret = 0;

Exit:
    if (verify_ctx != NULL)
        X509_STORE_CTX_free(verify_ctx);
    return ret;
}

static int verify_cert(ptls_verify_certificate_t *_self, ptls_t *tls, const char *server_name,
                       int (**verifier)(void *, uint16_t, ptls_iovec_t, ptls_iovec_t), void **verify_data, ptls_iovec_t *certs,
                       size_t num_certs)
{
    ptls_openssl_verify_certificate_t *self = (ptls_openssl_verify_certificate_t *)_self;
    X509 *cert = NULL;
    STACK_OF(X509) *chain = sk_X509_new_null();
    size_t i;
    int ossl_x509_err, ret;

    /* If any certs are given, convert them to OpenSSL representation, then verify the cert chain. If no certs are given, just give
     * the override_callback to see if we want to stay fail open. */
    if (num_certs != 0) {
        if ((cert = to_x509(certs[0])) == NULL) {
            ret = PTLS_ALERT_BAD_CERTIFICATE;
            goto Exit;
        }
        for (i = 1; i != num_certs; ++i) {
            X509 *interm = to_x509(certs[i]);
            if (interm == NULL) {
                ret = PTLS_ALERT_BAD_CERTIFICATE;
                goto Exit;
            }
            sk_X509_push(chain, interm);
        }
        ret = verify_cert_chain(self->cert_store, cert, chain, ptls_is_server(tls), server_name, &ossl_x509_err);
    } else {
        ret = PTLS_ALERT_CERTIFICATE_REQUIRED;
        ossl_x509_err = 0;
    }

    /* When override callback is available, let it override the error. */
    if (self->override_callback != NULL)
        ret = self->override_callback->cb(self->override_callback, tls, ret, ossl_x509_err, cert, chain);

    if (ret != 0 || num_certs == 0)
        goto Exit;

    /* extract public key for verifying the TLS handshake signature */
    if ((*verify_data = X509_get_pubkey(cert)) == NULL) {
        ret = PTLS_ALERT_BAD_CERTIFICATE;
        goto Exit;
    }
    *verifier = verify_sign;

Exit:
    if (chain != NULL)
        sk_X509_pop_free(chain, X509_free);
    if (cert != NULL)
        X509_free(cert);
    return ret;
}

int ptls_openssl_init_verify_certificate(ptls_openssl_verify_certificate_t *self, X509_STORE *store)
{
    *self = (ptls_openssl_verify_certificate_t){{verify_cert, default_signature_schemes}, NULL};

    if (store != NULL) {
        X509_STORE_up_ref(store);
        self->cert_store = store;
    } else {
        /* use default store */
        if ((self->cert_store = ptls_openssl_create_default_certificate_store()) == NULL)
            return -1;
    }

    return 0;
}

void ptls_openssl_dispose_verify_certificate(ptls_openssl_verify_certificate_t *self)
{
    X509_STORE_free(self->cert_store);
}

X509_STORE *ptls_openssl_create_default_certificate_store(void)
{
    X509_STORE *store;
    X509_LOOKUP *lookup;

    if ((store = X509_STORE_new()) == NULL)
        goto Error;
    if ((lookup = X509_STORE_add_lookup(store, X509_LOOKUP_file())) == NULL)
        goto Error;
    X509_LOOKUP_load_file(lookup, NULL, X509_FILETYPE_DEFAULT);
    if ((lookup = X509_STORE_add_lookup(store, X509_LOOKUP_hash_dir())) == NULL)
        goto Error;
    X509_LOOKUP_add_dir(lookup, NULL, X509_FILETYPE_DEFAULT);

    return store;
Error:
    if (store != NULL)
        X509_STORE_free(store);
    return NULL;
}

static int verify_raw_cert(ptls_verify_certificate_t *_self, ptls_t *tls, const char *server_name,
                           int (**verifier)(void *, uint16_t algo, ptls_iovec_t, ptls_iovec_t), void **verify_data,
                           ptls_iovec_t *certs, size_t num_certs)
{
    ptls_openssl_raw_pubkey_verify_certificate_t *self = (ptls_openssl_raw_pubkey_verify_certificate_t *)_self;
    int ret = PTLS_ALERT_BAD_CERTIFICATE;
    ptls_iovec_t expected_pubkey = {0};

    assert(num_certs != 0);

    if (num_certs != 1)
        goto Exit;

    int r = i2d_PUBKEY(self->expected_pubkey, &expected_pubkey.base);
    if (r <= 0) {
        ret = PTLS_ALERT_BAD_CERTIFICATE;
        goto Exit;
    }

    expected_pubkey.len = r;
    if (certs[0].len != expected_pubkey.len)
        goto Exit;

    if (!ptls_mem_equal(expected_pubkey.base, certs[0].base, certs[0].len))
        goto Exit;

    EVP_PKEY_up_ref(self->expected_pubkey);
    *verify_data = self->expected_pubkey;
    *verifier = verify_sign;
    ret = 0;
Exit:
    free(expected_pubkey.base);
    return ret;
}

int ptls_openssl_raw_pubkey_init_verify_certificate(ptls_openssl_raw_pubkey_verify_certificate_t *self, EVP_PKEY *expected_pubkey)
{
    EVP_PKEY_up_ref(expected_pubkey);
    *self = (ptls_openssl_raw_pubkey_verify_certificate_t){{verify_raw_cert, default_signature_schemes}, expected_pubkey};
    return 0;
}
void ptls_openssl_raw_pubkey_dispose_verify_certificate(ptls_openssl_raw_pubkey_verify_certificate_t *self)
{
    EVP_PKEY_free(self->expected_pubkey);
}

#define TICKET_LABEL_SIZE 16
#define TICKET_IV_SIZE EVP_MAX_IV_LENGTH

int ptls_openssl_encrypt_ticket(ptls_buffer_t *buf, ptls_iovec_t src,
                                int (*cb)(unsigned char *key_name, unsigned char *iv, EVP_CIPHER_CTX *ctx, HMAC_CTX *hctx, int enc))
{
    EVP_CIPHER_CTX *cctx = NULL;
    HMAC_CTX *hctx = NULL;
    uint8_t *dst;
    int clen, ret;

    if ((cctx = EVP_CIPHER_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if ((hctx = HMAC_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    if ((ret = ptls_buffer_reserve(buf, TICKET_LABEL_SIZE + TICKET_IV_SIZE + src.len + EVP_MAX_BLOCK_LENGTH + EVP_MAX_MD_SIZE)) !=
        0)
        goto Exit;
    dst = buf->base + buf->off;

    /* fill label and iv, as well as obtaining the keys */
    if (!(*cb)(dst, dst + TICKET_LABEL_SIZE, cctx, hctx, 1)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    dst += TICKET_LABEL_SIZE + TICKET_IV_SIZE;

    /* encrypt */
    if (!EVP_EncryptUpdate(cctx, dst, &clen, src.base, (int)src.len)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    dst += clen;
    if (!EVP_EncryptFinal_ex(cctx, dst, &clen)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    dst += clen;

    /* append hmac */
    if (!HMAC_Update(hctx, buf->base + buf->off, dst - (buf->base + buf->off)) || !HMAC_Final(hctx, dst, NULL)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    dst += HMAC_size(hctx);

    assert(dst <= buf->base + buf->capacity);
    buf->off += dst - (buf->base + buf->off);
    ret = 0;

Exit:
    if (cctx != NULL)
        EVP_CIPHER_CTX_free(cctx);
    if (hctx != NULL)
        HMAC_CTX_free(hctx);
    return ret;
}

int ptls_openssl_decrypt_ticket(ptls_buffer_t *buf, ptls_iovec_t src,
                                int (*cb)(unsigned char *key_name, unsigned char *iv, EVP_CIPHER_CTX *ctx, HMAC_CTX *hctx, int enc))
{
    EVP_CIPHER_CTX *cctx = NULL;
    HMAC_CTX *hctx = NULL;
    int clen, ret;

    if ((cctx = EVP_CIPHER_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if ((hctx = HMAC_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    /* obtain cipher and hash context.
     * Note: no need to handle renew, since in picotls we always send a new ticket to minimize the chance of ticket reuse */
    if (src.len < TICKET_LABEL_SIZE + TICKET_IV_SIZE) {
        ret = PTLS_ALERT_DECODE_ERROR;
        goto Exit;
    }
    if (!(*cb)(src.base, src.base + TICKET_LABEL_SIZE, cctx, hctx, 0)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }

    /* check hmac, and exclude label, iv, hmac */
    size_t hmac_size = HMAC_size(hctx);
    if (src.len < TICKET_LABEL_SIZE + TICKET_IV_SIZE + hmac_size) {
        ret = PTLS_ALERT_DECODE_ERROR;
        goto Exit;
    }
    src.len -= hmac_size;
    uint8_t hmac[EVP_MAX_MD_SIZE];
    if (!HMAC_Update(hctx, src.base, src.len) || !HMAC_Final(hctx, hmac, NULL)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if (!ptls_mem_equal(src.base + src.len, hmac, hmac_size)) {
        ret = PTLS_ALERT_HANDSHAKE_FAILURE;
        goto Exit;
    }
    src.base += TICKET_LABEL_SIZE + TICKET_IV_SIZE;
    src.len -= TICKET_LABEL_SIZE + TICKET_IV_SIZE;

    /* decrypt */
    if ((ret = ptls_buffer_reserve(buf, src.len)) != 0)
        goto Exit;
    if (!EVP_DecryptUpdate(cctx, buf->base + buf->off, &clen, src.base, (int)src.len)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    buf->off += clen;
    if (!EVP_DecryptFinal_ex(cctx, buf->base + buf->off, &clen)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    buf->off += clen;

    ret = 0;

Exit:
    if (cctx != NULL)
        EVP_CIPHER_CTX_free(cctx);
    if (hctx != NULL)
        HMAC_CTX_free(hctx);
    return ret;
}

#if OPENSSL_VERSION_NUMBER >= 0x30000000L
int ptls_openssl_encrypt_ticket_evp(ptls_buffer_t *buf, ptls_iovec_t src,
                                    int (*cb)(unsigned char *key_name, unsigned char *iv, EVP_CIPHER_CTX *ctx, EVP_MAC_CTX *hctx,
                                              int enc))
{
    EVP_CIPHER_CTX *cctx = NULL;
    EVP_MAC *mac = NULL;
    EVP_MAC_CTX *hctx = NULL;
    size_t hlen;
    uint8_t *dst;
    int clen, ret;

    if ((cctx = EVP_CIPHER_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if ((mac = EVP_MAC_fetch(NULL, "HMAC", NULL)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if ((hctx = EVP_MAC_CTX_new(mac)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    if ((ret = ptls_buffer_reserve(buf, TICKET_LABEL_SIZE + TICKET_IV_SIZE + src.len + EVP_MAX_BLOCK_LENGTH + EVP_MAX_MD_SIZE)) !=
        0)
        goto Exit;
    dst = buf->base + buf->off;

    /* fill label and iv, as well as obtaining the keys */
    if (!(*cb)(dst, dst + TICKET_LABEL_SIZE, cctx, hctx, 1)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    dst += TICKET_LABEL_SIZE + TICKET_IV_SIZE;

    /* encrypt */
    if (!EVP_EncryptUpdate(cctx, dst, &clen, src.base, (int)src.len)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    dst += clen;
    if (!EVP_EncryptFinal_ex(cctx, dst, &clen)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    dst += clen;

    /* append hmac */
    if (!EVP_MAC_update(hctx, buf->base + buf->off, dst - (buf->base + buf->off)) ||
        !EVP_MAC_final(hctx, dst, &hlen, EVP_MAC_CTX_get_mac_size(hctx))) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    dst += hlen;

    assert(dst <= buf->base + buf->capacity);
    buf->off += dst - (buf->base + buf->off);
    ret = 0;

Exit:
    if (cctx != NULL)
        EVP_CIPHER_CTX_free(cctx);
    if (hctx != NULL)
        EVP_MAC_CTX_free(hctx);
    if (mac != NULL)
        EVP_MAC_free(mac);
    return ret;
}

int ptls_openssl_decrypt_ticket_evp(ptls_buffer_t *buf, ptls_iovec_t src,
                                    int (*cb)(unsigned char *key_name, unsigned char *iv, EVP_CIPHER_CTX *ctx, EVP_MAC_CTX *hctx,
                                              int enc))
{
    EVP_CIPHER_CTX *cctx = NULL;
    EVP_MAC *mac = NULL;
    EVP_MAC_CTX *hctx = NULL;
    size_t hlen;
    int clen, ret;

    if ((cctx = EVP_CIPHER_CTX_new()) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if ((mac = EVP_MAC_fetch(NULL, "HMAC", NULL)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }
    if ((hctx = EVP_MAC_CTX_new(mac)) == NULL) {
        ret = PTLS_ERROR_NO_MEMORY;
        goto Exit;
    }

    /* obtain cipher and hash context.
     * Note: no need to handle renew, since in picotls we always send a new ticket to minimize the chance of ticket reuse */
    if (src.len < TICKET_LABEL_SIZE + TICKET_IV_SIZE) {
        ret = PTLS_ALERT_DECODE_ERROR;
        goto Exit;
    }
    if (!(*cb)(src.base, src.base + TICKET_LABEL_SIZE, cctx, hctx, 0)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }

    /* check hmac, and exclude label, iv, hmac */
    size_t hmac_size = EVP_MAC_CTX_get_mac_size(hctx);
    if (src.len < TICKET_LABEL_SIZE + TICKET_IV_SIZE + hmac_size) {
        ret = PTLS_ALERT_DECODE_ERROR;
        goto Exit;
    }
    src.len -= hmac_size;
    uint8_t hmac[EVP_MAX_MD_SIZE];
    if (!EVP_MAC_update(hctx, src.base, src.len) || !EVP_MAC_final(hctx, hmac, &hlen, sizeof(hmac))) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    if (!ptls_mem_equal(src.base + src.len, hmac, hmac_size)) {
        ret = PTLS_ALERT_HANDSHAKE_FAILURE;
        goto Exit;
    }
    src.base += TICKET_LABEL_SIZE + TICKET_IV_SIZE;
    src.len -= TICKET_LABEL_SIZE + TICKET_IV_SIZE;

    /* decrypt */
    if ((ret = ptls_buffer_reserve(buf, src.len)) != 0)
        goto Exit;
    if (!EVP_DecryptUpdate(cctx, buf->base + buf->off, &clen, src.base, (int)src.len)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    buf->off += clen;
    if (!EVP_DecryptFinal_ex(cctx, buf->base + buf->off, &clen)) {
        ret = PTLS_ERROR_LIBRARY;
        goto Exit;
    }
    buf->off += clen;

    ret = 0;

Exit:
    if (cctx != NULL)
        EVP_CIPHER_CTX_free(cctx);
    if (hctx != NULL)
        EVP_MAC_CTX_free(hctx);
    if (mac != NULL)
        EVP_MAC_free(mac);
    return ret;
}
#endif

ptls_key_exchange_algorithm_t ptls_openssl_secp256r1 = {.id = PTLS_GROUP_SECP256R1,
                                                        .name = PTLS_GROUP_NAME_SECP256R1,
                                                        .create = x9_62_create_key_exchange,
                                                        .exchange = secp_key_exchange,
                                                        .data = NID_X9_62_prime256v1};
#if PTLS_OPENSSL_HAVE_SECP384R1
ptls_key_exchange_algorithm_t ptls_openssl_secp384r1 = {.id = PTLS_GROUP_SECP384R1,
                                                        .name = PTLS_GROUP_NAME_SECP384R1,
                                                        .create = x9_62_create_key_exchange,
                                                        .exchange = secp_key_exchange,
                                                        .data = NID_secp384r1};
#endif
#if PTLS_OPENSSL_HAVE_SECP521R1
ptls_key_exchange_algorithm_t ptls_openssl_secp521r1 = {.id = PTLS_GROUP_SECP521R1,
                                                        .name = PTLS_GROUP_NAME_SECP521R1,
                                                        .create = x9_62_create_key_exchange,
                                                        .exchange = secp_key_exchange,
                                                        .data = NID_secp521r1};
#endif
#if PTLS_OPENSSL_HAVE_X25519
ptls_key_exchange_algorithm_t ptls_openssl_x25519 = {.id = PTLS_GROUP_X25519,
                                                     .name = PTLS_GROUP_NAME_X25519,
                                                     .create = evp_keyex_create,
                                                     .exchange = evp_keyex_exchange,
                                                     .data = NID_X25519};
#endif
ptls_key_exchange_algorithm_t *ptls_openssl_key_exchanges[] = {&ptls_openssl_secp256r1, NULL};
ptls_cipher_algorithm_t ptls_openssl_aes128ecb = {
    "AES128-ECB",          PTLS_AES128_KEY_SIZE, PTLS_AES_BLOCK_SIZE, 0 /* iv size */, sizeof(struct cipher_context_t),
    aes128ecb_setup_crypto};
ptls_cipher_algorithm_t ptls_openssl_aes128ctr = {
    "AES128-CTR", PTLS_AES128_KEY_SIZE, 1, PTLS_AES_IV_SIZE, sizeof(struct cipher_context_t), aes128ctr_setup_crypto};
ptls_aead_algorithm_t ptls_openssl_aes128gcm = {"AES128-GCM",
                                                PTLS_AESGCM_CONFIDENTIALITY_LIMIT,
                                                PTLS_AESGCM_INTEGRITY_LIMIT,
                                                &ptls_openssl_aes128ctr,
                                                &ptls_openssl_aes128ecb,
                                                PTLS_AES128_KEY_SIZE,
                                                PTLS_AESGCM_IV_SIZE,
                                                PTLS_AESGCM_TAG_SIZE,
                                                {PTLS_TLS12_AESGCM_FIXED_IV_SIZE, PTLS_TLS12_AESGCM_RECORD_IV_SIZE},
                                                0,
                                                0,
                                                sizeof(struct aead_crypto_context_t),
                                                aead_aes128gcm_setup_crypto};
ptls_cipher_algorithm_t ptls_openssl_aes256ecb = {
    "AES256-ECB",          PTLS_AES256_KEY_SIZE, PTLS_AES_BLOCK_SIZE, 0 /* iv size */, sizeof(struct cipher_context_t),
    aes256ecb_setup_crypto};
ptls_cipher_algorithm_t ptls_openssl_aes256ctr = {
    "AES256-CTR",          PTLS_AES256_KEY_SIZE, 1 /* block size */, PTLS_AES_IV_SIZE, sizeof(struct cipher_context_t),
    aes256ctr_setup_crypto};
ptls_aead_algorithm_t ptls_openssl_aes256gcm = {"AES256-GCM",
                                                PTLS_AESGCM_CONFIDENTIALITY_LIMIT,
                                                PTLS_AESGCM_INTEGRITY_LIMIT,
                                                &ptls_openssl_aes256ctr,
                                                &ptls_openssl_aes256ecb,
                                                PTLS_AES256_KEY_SIZE,
                                                PTLS_AESGCM_IV_SIZE,
                                                PTLS_AESGCM_TAG_SIZE,
                                                {PTLS_TLS12_AESGCM_FIXED_IV_SIZE, PTLS_TLS12_AESGCM_RECORD_IV_SIZE},
                                                0,
                                                0,
                                                sizeof(struct aead_crypto_context_t),
                                                aead_aes256gcm_setup_crypto};
ptls_hash_algorithm_t ptls_openssl_sha256 = {"sha256", PTLS_SHA256_BLOCK_SIZE, PTLS_SHA256_DIGEST_SIZE, sha256_create,
                                             PTLS_ZERO_DIGEST_SHA256};
ptls_hash_algorithm_t ptls_openssl_sha384 = {"sha384", PTLS_SHA384_BLOCK_SIZE, PTLS_SHA384_DIGEST_SIZE, sha384_create,
                                             PTLS_ZERO_DIGEST_SHA384};
ptls_hash_algorithm_t ptls_openssl_sha512 = {"sha512", PTLS_SHA512_BLOCK_SIZE, PTLS_SHA512_DIGEST_SIZE, sha512_create,
                                             PTLS_ZERO_DIGEST_SHA512};
ptls_cipher_suite_t ptls_openssl_aes128gcmsha256 = {.id = PTLS_CIPHER_SUITE_AES_128_GCM_SHA256,
                                                    .name = PTLS_CIPHER_SUITE_NAME_AES_128_GCM_SHA256,
                                                    .aead = &ptls_openssl_aes128gcm,
                                                    .hash = &ptls_openssl_sha256};
ptls_cipher_suite_t ptls_openssl_tls12_ecdhe_rsa_aes128gcmsha256 = {.id = PTLS_CIPHER_SUITE_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
                                                                    .name =
                                                                        PTLS_CIPHER_SUITE_NAME_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
                                                                    .aead = &ptls_openssl_aes128gcm,
                                                                    .hash = &ptls_openssl_sha256};
ptls_cipher_suite_t ptls_openssl_tls12_ecdhe_ecdsa_aes128gcmsha256 = {
    .id = PTLS_CIPHER_SUITE_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
    .name = PTLS_CIPHER_SUITE_NAME_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
    .aead = &ptls_openssl_aes128gcm,
    .hash = &ptls_openssl_sha256};
ptls_cipher_suite_t ptls_openssl_aes256gcmsha384 = {.id = PTLS_CIPHER_SUITE_AES_256_GCM_SHA384,
                                                    .name = PTLS_CIPHER_SUITE_NAME_AES_256_GCM_SHA384,
                                                    .aead = &ptls_openssl_aes256gcm,
                                                    .hash = &ptls_openssl_sha384};
ptls_cipher_suite_t ptls_openssl_tls12_ecdhe_rsa_aes256gcmsha384 = {.id = PTLS_CIPHER_SUITE_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
                                                                    .name =
                                                                        PTLS_CIPHER_SUITE_NAME_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
                                                                    .aead = &ptls_openssl_aes256gcm,
                                                                    .hash = &ptls_openssl_sha384};
ptls_cipher_suite_t ptls_openssl_tls12_ecdhe_ecdsa_aes256gcmsha384 = {
    .id = PTLS_CIPHER_SUITE_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
    .name = PTLS_CIPHER_SUITE_NAME_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
    .aead = &ptls_openssl_aes256gcm,
    .hash = &ptls_openssl_sha384};
#if PTLS_OPENSSL_HAVE_CHACHA20_POLY1305
ptls_cipher_algorithm_t ptls_openssl_chacha20 = {
    .name = "CHACHA20",
    .key_size = PTLS_CHACHA20_KEY_SIZE,
    .block_size = 1,
    .iv_size = PTLS_CHACHA20_IV_SIZE,
#ifdef OPENSSL_IS_BORINGSSL
    .context_size = sizeof(struct boringssl_chacha20_context_t),
    .setup_crypto = boringssl_chacha20_setup_crypto,
#else
    .context_size = sizeof(struct cipher_context_t),
    .setup_crypto = chacha20_setup_crypto,
#endif
};
ptls_aead_algorithm_t ptls_openssl_chacha20poly1305 = {
    .name = "CHACHA20-POLY1305",
    .confidentiality_limit = PTLS_CHACHA20POLY1305_CONFIDENTIALITY_LIMIT,
    .integrity_limit = PTLS_CHACHA20POLY1305_INTEGRITY_LIMIT,
    .ctr_cipher = &ptls_openssl_chacha20,
    .ecb_cipher = NULL,
    .key_size = PTLS_CHACHA20_KEY_SIZE,
    .iv_size = PTLS_CHACHA20POLY1305_IV_SIZE,
    .tag_size = PTLS_CHACHA20POLY1305_TAG_SIZE,
    .tls12 = {.fixed_iv_size = PTLS_TLS12_CHACHAPOLY_FIXED_IV_SIZE, .record_iv_size = PTLS_TLS12_CHACHAPOLY_RECORD_IV_SIZE},
    .non_temporal = 0,
    .align_bits = 0,
#ifdef OPENSSL_IS_BORINGSSL
    .context_size = sizeof(struct boringssl_chacha20poly1305_context_t),
    .setup_crypto = boringssl_chacha20poly1305_setup_crypto,
#else
    .context_size = sizeof(struct aead_crypto_context_t),
    .setup_crypto = aead_chacha20poly1305_setup_crypto,
#endif
};
ptls_cipher_suite_t ptls_openssl_chacha20poly1305sha256 = {.id = PTLS_CIPHER_SUITE_CHACHA20_POLY1305_SHA256,
                                                           .name = PTLS_CIPHER_SUITE_NAME_CHACHA20_POLY1305_SHA256,
                                                           .aead = &ptls_openssl_chacha20poly1305,
                                                           .hash = &ptls_openssl_sha256};
ptls_cipher_suite_t ptls_openssl_tls12_ecdhe_rsa_chacha20poly1305sha256 = {
    .id = PTLS_CIPHER_SUITE_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
    .name = PTLS_CIPHER_SUITE_NAME_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
    .aead = &ptls_openssl_chacha20poly1305,
    .hash = &ptls_openssl_sha256};
ptls_cipher_suite_t ptls_openssl_tls12_ecdhe_ecdsa_chacha20poly1305sha256 = {
    .id = PTLS_CIPHER_SUITE_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
    .name = PTLS_CIPHER_SUITE_NAME_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
    .aead = &ptls_openssl_chacha20poly1305,
    .hash = &ptls_openssl_sha256};
#endif
ptls_cipher_suite_t *ptls_openssl_cipher_suites[] = {&ptls_openssl_aes256gcmsha384, &ptls_openssl_aes128gcmsha256,
#if PTLS_OPENSSL_HAVE_CHACHA20_POLY1305
                                                     &ptls_openssl_chacha20poly1305sha256,
#endif
                                                     NULL};

ptls_cipher_suite_t *ptls_openssl_tls12_cipher_suites[] = {&ptls_openssl_tls12_ecdhe_rsa_aes128gcmsha256,
                                                           &ptls_openssl_tls12_ecdhe_ecdsa_aes128gcmsha256,
                                                           &ptls_openssl_tls12_ecdhe_rsa_aes256gcmsha384,
                                                           &ptls_openssl_tls12_ecdhe_ecdsa_aes256gcmsha384,
#if PTLS_OPENSSL_HAVE_CHACHA20_POLY1305
                                                           &ptls_openssl_tls12_ecdhe_rsa_chacha20poly1305sha256,
                                                           &ptls_openssl_tls12_ecdhe_ecdsa_chacha20poly1305sha256,
#endif
                                                           NULL};

#if PTLS_OPENSSL_HAVE_BF
ptls_cipher_algorithm_t ptls_openssl_bfecb = {"BF-ECB",        PTLS_BLOWFISH_KEY_SIZE,          PTLS_BLOWFISH_BLOCK_SIZE,
                                              0 /* iv size */, sizeof(struct cipher_context_t), bfecb_setup_crypto};
#endif

ptls_hpke_kem_t ptls_openssl_hpke_kem_p256sha256 = {PTLS_HPKE_KEM_P256_SHA256, &ptls_openssl_secp256r1, &ptls_openssl_sha256};
ptls_hpke_kem_t ptls_openssl_hpke_kem_p384sha384 = {PTLS_HPKE_KEM_P384_SHA384, &ptls_openssl_secp384r1, &ptls_openssl_sha384};
#if PTLS_OPENSSL_HAVE_X25519
ptls_hpke_kem_t ptls_openssl_hpke_kem_x25519sha256 = {PTLS_HPKE_KEM_X25519_SHA256, &ptls_openssl_x25519, &ptls_openssl_sha256};
#endif
ptls_hpke_kem_t *ptls_openssl_hpke_kems[] = {&ptls_openssl_hpke_kem_p384sha384,
#if PTLS_OPENSSL_HAVE_X25519
                                             &ptls_openssl_hpke_kem_x25519sha256,
#endif
                                             &ptls_openssl_hpke_kem_p256sha256, NULL};

ptls_hpke_cipher_suite_t ptls_openssl_hpke_aes128gcmsha256 = {
    .id = {.kdf = PTLS_HPKE_HKDF_SHA256, .aead = PTLS_HPKE_AEAD_AES_128_GCM},
    .name = "HKDF-SHA256/AES-128-GCM",
    .hash = &ptls_openssl_sha256,
    .aead = &ptls_openssl_aes128gcm};
ptls_hpke_cipher_suite_t ptls_openssl_hpke_aes128gcmsha512 = {
    .id = {.kdf = PTLS_HPKE_HKDF_SHA512, .aead = PTLS_HPKE_AEAD_AES_128_GCM},
    .name = "HKDF-SHA512/AES-128-GCM",
    .hash = &ptls_openssl_sha512,
    .aead = &ptls_openssl_aes128gcm};
ptls_hpke_cipher_suite_t ptls_openssl_hpke_aes256gcmsha384 = {
    .id = {.kdf = PTLS_HPKE_HKDF_SHA384, .aead = PTLS_HPKE_AEAD_AES_256_GCM},
    .name = "HKDF-SHA384/AES-256-GCM",
    .hash = &ptls_openssl_sha384,
    .aead = &ptls_openssl_aes256gcm};
#if PTLS_OPENSSL_HAVE_CHACHA20_POLY1305
ptls_hpke_cipher_suite_t ptls_openssl_hpke_chacha20poly1305sha256 = {
    .id = {.kdf = PTLS_HPKE_HKDF_SHA256, .aead = PTLS_HPKE_AEAD_CHACHA20POLY1305},
    .name = "HKDF-SHA256/ChaCha20Poly1305",
    .hash = &ptls_openssl_sha256,
    .aead = &ptls_openssl_chacha20poly1305};
#endif
ptls_hpke_cipher_suite_t *ptls_openssl_hpke_cipher_suites[] = {&ptls_openssl_hpke_aes128gcmsha256,
                                                               &ptls_openssl_hpke_aes256gcmsha384,
#if PTLS_OPENSSL_HAVE_CHACHA20_POLY1305
                                                               &ptls_openssl_hpke_chacha20poly1305sha256,
#endif
                                                               &ptls_openssl_hpke_aes128gcmsha512, /* likely only for tests */
                                                               NULL};