/*
 * This file is part of the SSH Library
 *
 * Copyright (c) 2009 by Aris Adamantiadis
 *
 * The SSH Library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 *
 * The SSH Library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the SSH Library; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#include "config.h"

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#include "libssh/priv.h"
#include "libssh/session.h"
#include "libssh/crypto.h"
#include "libssh/wrapper.h"
#include "libssh/libcrypto.h"

#ifdef HAVE_LIBCRYPTO

#include <openssl/sha.h>
#include <openssl/md5.h>
#include <openssl/dsa.h>
#include <openssl/rsa.h>
#include <openssl/hmac.h>
#include <openssl/opensslv.h>
#include <openssl/rand.h>
#include "libcrypto-compat.h"

#ifdef HAVE_OPENSSL_AES_H
#define HAS_AES
#include <openssl/aes.h>
#endif
#ifdef HAVE_OPENSSL_DES_H
#define HAS_DES
#include <openssl/des.h>
#endif

#if (defined(HAVE_VALGRIND_VALGRIND_H) && defined(HAVE_OPENSSL_IA32CAP_LOC))
#include <valgrind/valgrind.h>
#define CAN_DISABLE_AESNI
#endif

#include "libssh/crypto.h"

struct ssh_mac_ctx_struct {
  enum ssh_mac_e mac_type;
  union {
    SHACTX sha1_ctx;
    SHA256CTX sha256_ctx;
    SHA384CTX sha384_ctx;
    SHA512CTX sha512_ctx;
  } ctx;
};

static int libcrypto_initialized = 0;

void ssh_reseed(void){
#ifndef _WIN32
    struct timeval tv;
    gettimeofday(&tv, NULL);
    RAND_add(&tv, sizeof(tv), 0.0);
#endif
}

/**
 * @brief Get random bytes
 *
 * Make sure to always check the return code of this function!
 *
 * @param[in]  where    The buffer to fill with random bytes
 *
 * @param[in]  len      The size of the buffer to fill.
 *
 * @param[in]  strong   Use a strong or private RNG source.
 *
 * @return 1 on success, 0 on error.
 */
int ssh_get_random(void *where, int len, int strong)
{
#ifdef HAVE_OPENSSL_RAND_PRIV_BYTES
    if (strong) {
        /* Returns -1 when not supported, 0 on error, 1 on success */
        return !!RAND_priv_bytes(where, len);
    }
#else
    (void)strong;
#endif /* HAVE_RAND_PRIV_BYTES */

    /* Returns -1 when not supported, 0 on error, 1 on success */
    return !!RAND_bytes(where, len);
}

SHACTX sha1_init(void)
{
    int rc;
    SHACTX c = EVP_MD_CTX_create();
    if (c == NULL) {
        return NULL;
    }
    EVP_MD_CTX_init(c);
    rc = EVP_DigestInit_ex(c, EVP_sha1(), NULL);
    if (rc == 0) {
        EVP_MD_CTX_destroy(c);
        c = NULL;
    }
    return c;
}

void sha1_update(SHACTX c, const void *data, unsigned long len)
{
    EVP_DigestUpdate(c, data, len);
}

void sha1_final(unsigned char *md, SHACTX c)
{
    unsigned int mdlen = 0;

    EVP_DigestFinal(c, md, &mdlen);
    EVP_MD_CTX_destroy(c);
}

void sha1(unsigned char *digest, int len, unsigned char *hash)
{
    SHACTX c = sha1_init();
    if (c != NULL) {
        sha1_update(c, digest, len);
        sha1_final(hash, c);
    }
}

#ifdef HAVE_OPENSSL_ECC
static const EVP_MD *nid_to_evpmd(int nid)
{
    switch (nid) {
        case NID_X9_62_prime256v1:
            return EVP_sha256();
        case NID_secp384r1:
            return EVP_sha384();
        case NID_secp521r1:
            return EVP_sha512();
        default:
            return NULL;
    }

    return NULL;
}

void evp(int nid, unsigned char *digest, int len, unsigned char *hash, unsigned int *hlen)
{
    const EVP_MD *evp_md = nid_to_evpmd(nid);
    EVP_MD_CTX *md = EVP_MD_CTX_new();

    EVP_DigestInit(md, evp_md);
    EVP_DigestUpdate(md, digest, len);
    EVP_DigestFinal(md, hash, hlen);
    EVP_MD_CTX_free(md);
}

EVPCTX evp_init(int nid)
{
    const EVP_MD *evp_md = nid_to_evpmd(nid);

    EVPCTX ctx = EVP_MD_CTX_new();
    if (ctx == NULL) {
        return NULL;
    }

    EVP_DigestInit(ctx, evp_md);

    return ctx;
}

void evp_update(EVPCTX ctx, const void *data, unsigned long len)
{
    EVP_DigestUpdate(ctx, data, len);
}

void evp_final(EVPCTX ctx, unsigned char *md, unsigned int *mdlen)
{
    EVP_DigestFinal(ctx, md, mdlen);
    EVP_MD_CTX_free(ctx);
}
#endif

SHA256CTX sha256_init(void)
{
    int rc;
    SHA256CTX c = EVP_MD_CTX_create();
    if (c == NULL) {
        return NULL;
    }
    EVP_MD_CTX_init(c);
    rc = EVP_DigestInit_ex(c, EVP_sha256(), NULL);
    if (rc == 0) {
        EVP_MD_CTX_destroy(c);
        c = NULL;
    }
    return c;
}

void sha256_update(SHA256CTX c, const void *data, unsigned long len)
{
    EVP_DigestUpdate(c, data, len);
}

void sha256_final(unsigned char *md, SHA256CTX c)
{
    unsigned int mdlen = 0;

    EVP_DigestFinal(c, md, &mdlen);
    EVP_MD_CTX_destroy(c);
}

void sha256(unsigned char *digest, int len, unsigned char *hash)
{
    SHA256CTX c = sha256_init();
    if (c != NULL) {
        sha256_update(c, digest, len);
        sha256_final(hash, c);
    }
}

SHA384CTX sha384_init(void)
{
    int rc;
    SHA384CTX c = EVP_MD_CTX_create();
    if (c == NULL) {
        return NULL;
    }
    EVP_MD_CTX_init(c);
    rc = EVP_DigestInit_ex(c, EVP_sha384(), NULL);
    if (rc == 0) {
        EVP_MD_CTX_destroy(c);
        c = NULL;
    }
    return c;
}

void sha384_update(SHA384CTX c, const void *data, unsigned long len)
{
    EVP_DigestUpdate(c, data, len);
}

void sha384_final(unsigned char *md, SHA384CTX c)
{
    unsigned int mdlen = 0;

    EVP_DigestFinal(c, md, &mdlen);
    EVP_MD_CTX_destroy(c);
}

void sha384(unsigned char *digest, int len, unsigned char *hash)
{
    SHA384CTX c = sha384_init();
    if (c != NULL) {
        sha384_update(c, digest, len);
        sha384_final(hash, c);
    }
}

SHA512CTX sha512_init(void)
{
    int rc = 0;
    SHA512CTX c = EVP_MD_CTX_create();
    if (c == NULL) {
        return NULL;
    }
    EVP_MD_CTX_init(c);
    rc = EVP_DigestInit_ex(c, EVP_sha512(), NULL);
    if (rc == 0) {
        EVP_MD_CTX_destroy(c);
        c = NULL;
    }
    return c;
}

void sha512_update(SHA512CTX c, const void *data, unsigned long len)
{
    EVP_DigestUpdate(c, data, len);
}

void sha512_final(unsigned char *md, SHA512CTX c)
{
    unsigned int mdlen = 0;

    EVP_DigestFinal(c, md, &mdlen);
    EVP_MD_CTX_destroy(c);
}

void sha512(unsigned char *digest, int len, unsigned char *hash)
{
    SHA512CTX c = sha512_init();
    if (c != NULL) {
        sha512_update(c, digest, len);
        sha512_final(hash, c);
    }
}

MD5CTX md5_init(void)
{
    int rc;
    MD5CTX c = EVP_MD_CTX_create();
    if (c == NULL) {
        return NULL;
    }
    EVP_MD_CTX_init(c);
    rc = EVP_DigestInit_ex(c, EVP_md5(), NULL);
    if(rc == 0) {
        EVP_MD_CTX_destroy(c);
        c = NULL;
    }
    return c;
}

void md5_update(MD5CTX c, const void *data, unsigned long len)
{
    EVP_DigestUpdate(c, data, len);
}

void md5_final(unsigned char *md, MD5CTX c)
{
    unsigned int mdlen = 0;

    EVP_DigestFinal(c, md, &mdlen);
    EVP_MD_CTX_destroy(c);
}

ssh_mac_ctx ssh_mac_ctx_init(enum ssh_mac_e type){
  ssh_mac_ctx ctx = malloc(sizeof(struct ssh_mac_ctx_struct));
  if (ctx == NULL) {
    return NULL;
  }

  ctx->mac_type=type;
  switch(type){
    case SSH_MAC_SHA1:
      ctx->ctx.sha1_ctx = sha1_init();
      return ctx;
    case SSH_MAC_SHA256:
      ctx->ctx.sha256_ctx = sha256_init();
      return ctx;
    case SSH_MAC_SHA384:
      ctx->ctx.sha384_ctx = sha384_init();
      return ctx;
    case SSH_MAC_SHA512:
      ctx->ctx.sha512_ctx = sha512_init();
      return ctx;
    default:
      SAFE_FREE(ctx);
      return NULL;
  }
}

void ssh_mac_update(ssh_mac_ctx ctx, const void *data, unsigned long len) {
  switch(ctx->mac_type){
    case SSH_MAC_SHA1:
      sha1_update(ctx->ctx.sha1_ctx, data, len);
      break;
    case SSH_MAC_SHA256:
      sha256_update(ctx->ctx.sha256_ctx, data, len);
      break;
    case SSH_MAC_SHA384:
      sha384_update(ctx->ctx.sha384_ctx, data, len);
      break;
    case SSH_MAC_SHA512:
      sha512_update(ctx->ctx.sha512_ctx, data, len);
      break;
    default:
      break;
  }
}

void ssh_mac_final(unsigned char *md, ssh_mac_ctx ctx) {
  switch(ctx->mac_type){
    case SSH_MAC_SHA1:
      sha1_final(md,ctx->ctx.sha1_ctx);
      break;
    case SSH_MAC_SHA256:
      sha256_final(md,ctx->ctx.sha256_ctx);
      break;
    case SSH_MAC_SHA384:
      sha384_final(md,ctx->ctx.sha384_ctx);
      break;
    case SSH_MAC_SHA512:
      sha512_final(md,ctx->ctx.sha512_ctx);
      break;
    default:
      break;
  }
  SAFE_FREE(ctx);
}

HMACCTX hmac_init(const void *key, int len, enum ssh_hmac_e type) {
  HMACCTX ctx = NULL;

  ctx = HMAC_CTX_new();
  if (ctx == NULL) {
    return NULL;
  }


  switch(type) {
    case SSH_HMAC_SHA1:
      HMAC_Init_ex(ctx, key, len, EVP_sha1(), NULL);
      break;
    case SSH_HMAC_SHA256:
      HMAC_Init_ex(ctx, key, len, EVP_sha256(), NULL);
      break;
    case SSH_HMAC_SHA384:
      HMAC_Init_ex(ctx, key, len, EVP_sha384(), NULL);
      break;
    case SSH_HMAC_SHA512:
      HMAC_Init_ex(ctx, key, len, EVP_sha512(), NULL);
      break;
    case SSH_HMAC_MD5:
      HMAC_Init_ex(ctx, key, len, EVP_md5(), NULL);
      break;
    default:
      HMAC_CTX_free(ctx);
      ctx = NULL;
  }

  return ctx;
}

void hmac_update(HMACCTX ctx, const void *data, unsigned long len) {
  HMAC_Update(ctx, data, len);
}

void hmac_final(HMACCTX ctx, unsigned char *hashmacbuf, unsigned int *len) {
  HMAC_Final(ctx,hashmacbuf,len);

#if OPENSSL_VERSION_NUMBER > 0x10100000L
  HMAC_CTX_free(ctx);
  ctx = NULL;
#else
  HMAC_cleanup(ctx);
  SAFE_FREE(ctx);
  ctx = NULL;
#endif
}

static void evp_cipher_init(struct ssh_cipher_struct *cipher) {
    if (cipher->ctx == NULL) {
        cipher->ctx = EVP_CIPHER_CTX_new();
    }

    switch(cipher->ciphertype){
    case SSH_AES128_CBC:
        cipher->cipher = EVP_aes_128_cbc();
        break;
    case SSH_AES192_CBC:
        cipher->cipher = EVP_aes_192_cbc();
        break;
    case SSH_AES256_CBC:
        cipher->cipher = EVP_aes_256_cbc();
        break;
#ifdef HAVE_OPENSSL_EVP_AES_CTR
    case SSH_AES128_CTR:
        cipher->cipher = EVP_aes_128_ctr();
        break;
    case SSH_AES192_CTR:
        cipher->cipher = EVP_aes_192_ctr();
        break;
    case SSH_AES256_CTR:
        cipher->cipher = EVP_aes_256_ctr();
        break;
#else
    case SSH_AES128_CTR:
    case SSH_AES192_CTR:
    case SSH_AES256_CTR:
        SSH_LOG(SSH_LOG_WARNING, "This cipher is not available in evp_cipher_init");
        break;
#endif
#ifdef HAVE_OPENSSL_EVP_AES_GCM
    case SSH_AEAD_AES128_GCM:
        cipher->cipher = EVP_aes_128_gcm();
        break;
    case SSH_AEAD_AES256_GCM:
        cipher->cipher = EVP_aes_256_gcm();
        break;
#else
    case SSH_AEAD_AES128_GCM:
    case SSH_AEAD_AES256_GCM:
        SSH_LOG(SSH_LOG_WARNING, "This cipher is not available in evp_cipher_init");
        break;
#endif /* HAVE_OPENSSL_EVP_AES_GCM */
    case SSH_3DES_CBC:
        cipher->cipher = EVP_des_ede3_cbc();
        break;
#ifdef WITH_BLOWFISH_CIPHER
    case SSH_BLOWFISH_CBC:
        cipher->cipher = EVP_bf_cbc();
        break;
        /* ciphers not using EVP */
#endif
    case SSH_AEAD_CHACHA20_POLY1305:
        SSH_LOG(SSH_LOG_WARNING, "The ChaCha cipher cannot be handled here");
        break;
    case SSH_NO_CIPHER:
        SSH_LOG(SSH_LOG_WARNING, "No valid ciphertype found");
        break;
    }
}

static int evp_cipher_set_encrypt_key(struct ssh_cipher_struct *cipher,
            void *key, void *IV)
{
    int rc;

    evp_cipher_init(cipher);
    EVP_CIPHER_CTX_init(cipher->ctx);

    rc = EVP_EncryptInit_ex(cipher->ctx, cipher->cipher, NULL, key, IV);
    if (rc != 1){
        SSH_LOG(SSH_LOG_WARNING, "EVP_EncryptInit_ex failed");
        return SSH_ERROR;
    }

#ifdef HAVE_OPENSSL_EVP_AES_GCM
    /* For AES-GCM we need to set IV in specific way */
    if (cipher->ciphertype == SSH_AEAD_AES128_GCM ||
        cipher->ciphertype == SSH_AEAD_AES256_GCM) {
        rc = EVP_CIPHER_CTX_ctrl(cipher->ctx,
                                 EVP_CTRL_GCM_SET_IV_FIXED,
                                 -1,
                                 (u_char *)IV);
        if (rc != 1) {
            SSH_LOG(SSH_LOG_WARNING, "EVP_CTRL_GCM_SET_IV_FIXED failed");
            return SSH_ERROR;
        }
    }
#endif /* HAVE_OPENSSL_EVP_AES_GCM */

    EVP_CIPHER_CTX_set_padding(cipher->ctx, 0);

    return SSH_OK;
}

static int evp_cipher_set_decrypt_key(struct ssh_cipher_struct *cipher,
            void *key, void *IV) {
    int rc;

    evp_cipher_init(cipher);
    EVP_CIPHER_CTX_init(cipher->ctx);

    rc = EVP_DecryptInit_ex(cipher->ctx, cipher->cipher, NULL, key, IV);
    if (rc != 1){
        SSH_LOG(SSH_LOG_WARNING, "EVP_DecryptInit_ex failed");
        return SSH_ERROR;
    }

#ifdef HAVE_OPENSSL_EVP_AES_GCM
    /* For AES-GCM we need to set IV in specific way */
    if (cipher->ciphertype == SSH_AEAD_AES128_GCM ||
        cipher->ciphertype == SSH_AEAD_AES256_GCM) {
        rc = EVP_CIPHER_CTX_ctrl(cipher->ctx,
                                 EVP_CTRL_GCM_SET_IV_FIXED,
                                 -1,
                                 (u_char *)IV);
        if (rc != 1) {
            SSH_LOG(SSH_LOG_WARNING, "EVP_CTRL_GCM_SET_IV_FIXED failed");
            return SSH_ERROR;
        }
    }
#endif /* HAVE_OPENSSL_EVP_AES_GCM */

    EVP_CIPHER_CTX_set_padding(cipher->ctx, 0);

    return SSH_OK;
}

/* EVP wrapper function for encrypt/decrypt */
static void evp_cipher_encrypt(struct ssh_cipher_struct *cipher,
                               void *in,
                               void *out,
                               size_t len)
{
    int outlen = 0;
    int rc = 0;

    rc = EVP_EncryptUpdate(cipher->ctx,
                           (unsigned char *)out,
                           &outlen,
                           (unsigned char *)in,
                           (int)len);
    if (rc != 1){
        SSH_LOG(SSH_LOG_WARNING, "EVP_EncryptUpdate failed");
        return;
    }
    if (outlen != (int)len){
        SSH_LOG(SSH_LOG_WARNING,
                "EVP_EncryptUpdate: output size %d for %zu in",
                outlen,
                len);
        return;
    }
}

static void evp_cipher_decrypt(struct ssh_cipher_struct *cipher,
                               void *in,
                               void *out,
                               size_t len)
{
    int outlen = 0;
    int rc = 0;

    rc = EVP_DecryptUpdate(cipher->ctx,
                           (unsigned char *)out,
                           &outlen,
                           (unsigned char *)in,
                           (int)len);
    if (rc != 1){
        SSH_LOG(SSH_LOG_WARNING, "EVP_DecryptUpdate failed");
        return;
    }
    if (outlen != (int)len){
        SSH_LOG(SSH_LOG_WARNING,
                "EVP_DecryptUpdate: output size %d for %zu in",
                outlen,
                len);
        return;
    }
}

static void evp_cipher_cleanup(struct ssh_cipher_struct *cipher) {
    if (cipher->ctx != NULL) {
        EVP_CIPHER_CTX_cleanup(cipher->ctx);
        EVP_CIPHER_CTX_free(cipher->ctx);
    }
}

#ifndef HAVE_OPENSSL_EVP_AES_CTR
/* Some OS (osx, OpenIndiana, ...) have no support for CTR ciphers in EVP_aes */

struct ssh_aes_key_schedule {
    AES_KEY key;
    uint8_t IV[AES_BLOCK_SIZE];
};

static int aes_ctr_set_key(struct ssh_cipher_struct *cipher, void *key,
    void *IV) {
    int rc;

    if (cipher->aes_key == NULL) {
        cipher->aes_key = malloc(sizeof (struct ssh_aes_key_schedule));
    }
    if (cipher->aes_key == NULL) {
        return SSH_ERROR;
    }
    ZERO_STRUCTP(cipher->aes_key);
    /* CTR doesn't need a decryption key */
    rc = AES_set_encrypt_key(key, cipher->keysize, &cipher->aes_key->key);
    if (rc < 0) {
        SAFE_FREE(cipher->aes_key);
        return SSH_ERROR;
    }
    memcpy(cipher->aes_key->IV, IV, AES_BLOCK_SIZE);
    return SSH_OK;
}

static void aes_ctr_encrypt(struct ssh_cipher_struct *cipher, void *in, void *out,
    unsigned long len) {
  unsigned char tmp_buffer[AES_BLOCK_SIZE];
  unsigned int num=0;
  /* Some things are special with ctr128 :
   * In this case, tmp_buffer is not being used, because it is used to store temporary data
   * when an encryption is made on lengths that are not multiple of blocksize.
   * Same for num, which is being used to store the current offset in blocksize in CTR
   * function.
   */
#ifdef HAVE_OPENSSL_CRYPTO_CTR128_ENCRYPT
  CRYPTO_ctr128_encrypt(in, out, len, &cipher->aes_key->key, cipher->aes_key->IV, tmp_buffer, &num, (block128_f)AES_encrypt);
#else
  AES_ctr128_encrypt(in, out, len, &cipher->aes_key->key, cipher->aes_key->IV, tmp_buffer, &num);
#endif /* HAVE_OPENSSL_CRYPTO_CTR128_ENCRYPT */
}

static void aes_ctr_cleanup(struct ssh_cipher_struct *cipher){
    explicit_bzero(cipher->aes_key, sizeof(*cipher->aes_key));
    SAFE_FREE(cipher->aes_key);
}

#endif /* HAVE_OPENSSL_EVP_AES_CTR */

#ifdef HAVE_OPENSSL_EVP_AES_GCM
static int
evp_cipher_aead_get_length(struct ssh_cipher_struct *cipher,
                           void *in,
                           uint8_t *out,
                           size_t len,
                           uint64_t seq)
{
    (void)cipher;
    (void)seq;

    /* The length is not encrypted: Copy it to the result buffer */
    memcpy(out, in, len);

    return SSH_OK;
}

static void
evp_cipher_aead_encrypt(struct ssh_cipher_struct *cipher,
                        void *in,
                        void *out,
                        size_t len,
                        uint8_t *tag,
                        uint64_t seq)
{
    size_t authlen, aadlen;
    u_char lastiv[1];
    int tmplen = 0;
    size_t outlen;
    int rc;

    (void) seq;

    aadlen = cipher->lenfield_blocksize;
    authlen = cipher->tag_size;

    /* increment IV */
    rc = EVP_CIPHER_CTX_ctrl(cipher->ctx,
                             EVP_CTRL_GCM_IV_GEN,
                             1,
                             lastiv);
    if (rc == 0) {
        SSH_LOG(SSH_LOG_WARNING, "EVP_CTRL_GCM_IV_GEN failed");
        return;
    }

    /* Pass over the authenticated data (not encrypted) */
    rc = EVP_EncryptUpdate(cipher->ctx,
                           NULL,
                           &tmplen,
                           (unsigned char *)in,
                           (int)aadlen);
    outlen = tmplen;
    if (rc == 0 || outlen != aadlen) {
        SSH_LOG(SSH_LOG_WARNING, "Failed to pass authenticated data");
        return;
    }
    memcpy(out, in, aadlen);

    /* Encrypt the rest of the data */
    rc = EVP_EncryptUpdate(cipher->ctx,
                           (unsigned char *)out + aadlen,
                           &tmplen,
                           (unsigned char *)in + aadlen,
                           (int)len - aadlen);
    outlen = tmplen;
    if (rc != 1 || outlen != (int)len - aadlen) {
        SSH_LOG(SSH_LOG_WARNING, "EVP_EncryptUpdate failed");
        return;
    }

    /* compute tag */
    rc = EVP_EncryptFinal(cipher->ctx,
                          NULL,
                          &tmplen);
    if (rc < 0) {
        SSH_LOG(SSH_LOG_WARNING, "EVP_EncryptFinal failed: Failed to create a tag");
        return;
    }

    rc = EVP_CIPHER_CTX_ctrl(cipher->ctx,
                             EVP_CTRL_GCM_GET_TAG,
                             authlen,
                             (unsigned char *)tag);
    if (rc != 1) {
        SSH_LOG(SSH_LOG_WARNING, "EVP_CTRL_GCM_GET_TAG failed");
        return;
    }
}

static int
evp_cipher_aead_decrypt(struct ssh_cipher_struct *cipher,
                        void *complete_packet,
                        uint8_t *out,
                        size_t encrypted_size,
                        uint64_t seq)
{
    size_t authlen, aadlen;
    u_char lastiv[1];
    int outlen = 0;
    int rc = 0;

    (void)seq;

    aadlen = cipher->lenfield_blocksize;
    authlen = cipher->tag_size;

    /* increment IV */
    rc = EVP_CIPHER_CTX_ctrl(cipher->ctx,
                             EVP_CTRL_GCM_IV_GEN,
                             1,
                             lastiv);
    if (rc == 0) {
        SSH_LOG(SSH_LOG_WARNING, "EVP_CTRL_GCM_IV_GEN failed");
        return SSH_ERROR;
    }

    /* set tag for authentication */
    rc = EVP_CIPHER_CTX_ctrl(cipher->ctx,
                             EVP_CTRL_GCM_SET_TAG,
                             authlen,
                             (unsigned char *)complete_packet + aadlen + encrypted_size);
    if (rc == 0) {
        SSH_LOG(SSH_LOG_WARNING, "EVP_CTRL_GCM_SET_TAG failed");
        return SSH_ERROR;
    }

    /* Pass over the authenticated data (not encrypted) */
    rc = EVP_DecryptUpdate(cipher->ctx,
                           NULL,
                           &outlen,
                           (unsigned char *)complete_packet,
                           (int)aadlen);
    if (rc == 0) {
        SSH_LOG(SSH_LOG_WARNING, "Failed to pass authenticated data");
        return SSH_ERROR;
    }
    /* Do not copy the length to the target buffer, because it is already processed */
    //memcpy(out, complete_packet, aadlen);

    /* Decrypt the rest of the data */
    rc = EVP_DecryptUpdate(cipher->ctx,
                           (unsigned char *)out,
                           &outlen,
                           (unsigned char *)complete_packet + aadlen,
                           encrypted_size /* already substracted aadlen*/);
    if (rc != 1) {
        SSH_LOG(SSH_LOG_WARNING, "EVP_DecryptUpdate failed");
        return SSH_ERROR;
    }

    if (outlen != (int)encrypted_size) {
        SSH_LOG(SSH_LOG_WARNING,
                "EVP_DecryptUpdate: output size %d for %zd in",
                outlen,
                encrypted_size);
        return SSH_ERROR;
    }

    /* verify tag */
    rc = EVP_DecryptFinal(cipher->ctx,
                          NULL,
                          &outlen);
    if (rc < 0) {
        SSH_LOG(SSH_LOG_WARNING, "EVP_DecryptFinal failed: Failed authentication");
        return SSH_ERROR;
    }

    return SSH_OK;
}

#endif /* HAVE_OPENSSL_EVP_AES_GCM */

/*
 * The table of supported ciphers
 */
static struct ssh_cipher_struct ssh_ciphertab[] = {
#ifdef WITH_BLOWFISH_CIPHER
  {
    .name = "blowfish-cbc",
    .blocksize = 8,
    .ciphertype = SSH_BLOWFISH_CBC,
    .keysize = 128,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .encrypt = evp_cipher_encrypt,
    .decrypt = evp_cipher_decrypt,
    .cleanup = evp_cipher_cleanup
  },
#endif
#ifdef HAS_AES
#ifndef BROKEN_AES_CTR
/* OpenSSL until 0.9.7c has a broken AES_ctr128_encrypt implementation which
 * increments the counter from 2^64 instead of 1. It's better not to use it
 */
#ifdef HAVE_OPENSSL_EVP_AES_CTR
  {
    .name = "aes128-ctr",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES128_CTR,
    .keysize = 128,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .encrypt = evp_cipher_encrypt,
    .decrypt = evp_cipher_decrypt,
    .cleanup = evp_cipher_cleanup
  },
  {
    .name = "aes192-ctr",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES192_CTR,
    .keysize = 192,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .encrypt = evp_cipher_encrypt,
    .decrypt = evp_cipher_decrypt,
    .cleanup = evp_cipher_cleanup
  },
  {
    .name = "aes256-ctr",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES256_CTR,
    .keysize = 256,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .encrypt = evp_cipher_encrypt,
    .decrypt = evp_cipher_decrypt,
    .cleanup = evp_cipher_cleanup
  },
#else /* HAVE_OPENSSL_EVP_AES_CTR */
  {
    .name = "aes128-ctr",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES128_CTR,
    .keysize = 128,
    .set_encrypt_key = aes_ctr_set_key,
    .set_decrypt_key = aes_ctr_set_key,
    .encrypt = aes_ctr_encrypt,
    .decrypt = aes_ctr_encrypt,
    .cleanup = aes_ctr_cleanup
  },
  {
    .name = "aes192-ctr",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES192_CTR,
    .keysize = 192,
    .set_encrypt_key = aes_ctr_set_key,
    .set_decrypt_key = aes_ctr_set_key,
    .encrypt = aes_ctr_encrypt,
    .decrypt = aes_ctr_encrypt,
    .cleanup = aes_ctr_cleanup
  },
  {
    .name = "aes256-ctr",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES256_CTR,
    .keysize = 256,
    .set_encrypt_key = aes_ctr_set_key,
    .set_decrypt_key = aes_ctr_set_key,
    .encrypt = aes_ctr_encrypt,
    .decrypt = aes_ctr_encrypt,
    .cleanup = aes_ctr_cleanup
  },
#endif /* HAVE_OPENSSL_EVP_AES_CTR */
#endif /* BROKEN_AES_CTR */
  {
    .name = "aes128-cbc",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES128_CBC,
    .keysize = 128,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .encrypt = evp_cipher_encrypt,
    .decrypt = evp_cipher_decrypt,
    .cleanup = evp_cipher_cleanup
  },
  {
    .name = "aes192-cbc",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES192_CBC,
    .keysize = 192,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .encrypt = evp_cipher_encrypt,
    .decrypt = evp_cipher_decrypt,
    .cleanup = evp_cipher_cleanup
  },
  {
    .name = "aes256-cbc",
    .blocksize = AES_BLOCK_SIZE,
    .ciphertype = SSH_AES256_CBC,
    .keysize = 256,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .encrypt = evp_cipher_encrypt,
    .decrypt = evp_cipher_decrypt,
    .cleanup = evp_cipher_cleanup
  },
#ifdef HAVE_OPENSSL_EVP_AES_GCM
  {
    .name = "aes128-gcm@openssh.com",
    .blocksize = AES_BLOCK_SIZE,
    .lenfield_blocksize = 4, /* not encrypted, but authenticated */
    .ciphertype = SSH_AEAD_AES128_GCM,
    .keysize = 128,
    .tag_size = AES_GCM_TAGLEN,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .aead_encrypt = evp_cipher_aead_encrypt,
    .aead_decrypt_length = evp_cipher_aead_get_length,
    .aead_decrypt = evp_cipher_aead_decrypt,
    .cleanup = evp_cipher_cleanup
  },
  {
    .name = "aes256-gcm@openssh.com",
    .blocksize = AES_BLOCK_SIZE,
    .lenfield_blocksize = 4, /* not encrypted, but authenticated */
    .ciphertype = SSH_AEAD_AES256_GCM,
    .keysize = 256,
    .tag_size = AES_GCM_TAGLEN,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .aead_encrypt = evp_cipher_aead_encrypt,
    .aead_decrypt_length = evp_cipher_aead_get_length,
    .aead_decrypt = evp_cipher_aead_decrypt,
    .cleanup = evp_cipher_cleanup
  },
#endif /* HAVE_OPENSSL_EVP_AES_GCM */
#endif /* HAS_AES */
#ifdef HAS_DES
  {
    .name = "3des-cbc",
    .blocksize = 8,
    .ciphertype = SSH_3DES_CBC,
    .keysize = 192,
    .set_encrypt_key = evp_cipher_set_encrypt_key,
    .set_decrypt_key = evp_cipher_set_decrypt_key,
    .encrypt = evp_cipher_encrypt,
    .decrypt = evp_cipher_decrypt,
    .cleanup = evp_cipher_cleanup
  },
#endif /* HAS_DES */
  {
    .name = "chacha20-poly1305@openssh.com"
  },
  {
    .name = NULL
  }
};

struct ssh_cipher_struct *ssh_get_ciphertab(void)
{
  return ssh_ciphertab;
}

/**
 * @internal
 * @brief Initialize libcrypto's subsystem
 */
int ssh_crypto_init(void)
{
    size_t i;

    if (libcrypto_initialized) {
        return SSH_OK;
    }
    if (SSLeay() != OPENSSL_VERSION_NUMBER){
        SSH_LOG(SSH_LOG_WARNING, "libssh compiled with %s "
            "headers, currently running with %s.",
            OPENSSL_VERSION_TEXT,
            SSLeay_version(SSLeay())
        );
    }
#ifdef CAN_DISABLE_AESNI
    /*
     * disable AES-NI when running within Valgrind, because they generate
     * too many "uninitialized memory access" false positives
     */
    if (RUNNING_ON_VALGRIND){
        SSH_LOG(SSH_LOG_INFO, "Running within Valgrind, disabling AES-NI");
        /* Bit #57 denotes AES-NI instruction set extension */
        OPENSSL_ia32cap &= ~(1LL << 57);
    }
#endif
    OpenSSL_add_all_algorithms();

    for (i = 0; ssh_ciphertab[i].name != NULL; i++) {
        int cmp;

        cmp = strcmp(ssh_ciphertab[i].name, "chacha20-poly1305@openssh.com");
        if (cmp == 0) {
            memcpy(&ssh_ciphertab[i],
                   ssh_get_chacha20poly1305_cipher(),
                   sizeof(struct ssh_cipher_struct));
            break;
        }
    }

    libcrypto_initialized = 1;

    return SSH_OK;
}

/**
 * @internal
 * @brief Finalize libcrypto's subsystem
 */
void ssh_crypto_finalize(void)
{
    if (!libcrypto_initialized) {
        return;
    }

    EVP_cleanup();
    CRYPTO_cleanup_all_ex_data();

    libcrypto_initialized = 0;
}

#endif /* LIBCRYPTO */