/* Copyright (C) 2009, 2010 Simon Josefsson
 * Copyright (C) 2006, 2007 The Written Word, Inc.  All rights reserved.
 * Copyright (c) 2004-2006, Sara Golemon <sarag@libssh2.org>
 *
 * Author: Simon Josefsson
 *
 * Redistribution and use in source and binary forms,
 * with or without modification, are permitted provided
 * that the following conditions are met:
 *
 *   Redistributions of source code must retain the above
 *   copyright notice, this list of conditions and the
 *   following disclaimer.
 *
 *   Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 *   Neither the name of the copyright holder nor the names
 *   of any other contributors may be used to endorse or
 *   promote products derived from this software without
 *   specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 */

#include "libssh2_priv.h"

#ifdef LIBSSH2_OPENSSL /* compile only if we build with openssl */

#include <string.h>

#ifndef EVP_MAX_BLOCK_LENGTH
#define EVP_MAX_BLOCK_LENGTH 32
#endif

int
_libssh2_rsa_new(libssh2_rsa_ctx ** rsa,
                 const unsigned char *edata,
                 unsigned long elen,
                 const unsigned char *ndata,
                 unsigned long nlen,
                 const unsigned char *ddata,
                 unsigned long dlen,
                 const unsigned char *pdata,
                 unsigned long plen,
                 const unsigned char *qdata,
                 unsigned long qlen,
                 const unsigned char *e1data,
                 unsigned long e1len,
                 const unsigned char *e2data,
                 unsigned long e2len,
                 const unsigned char *coeffdata, unsigned long coefflen)
{
    *rsa = RSA_new();

    (*rsa)->e = BN_new();
    BN_bin2bn(edata, elen, (*rsa)->e);

    (*rsa)->n = BN_new();
    BN_bin2bn(ndata, nlen, (*rsa)->n);

    if (ddata) {
        (*rsa)->d = BN_new();
        BN_bin2bn(ddata, dlen, (*rsa)->d);

        (*rsa)->p = BN_new();
        BN_bin2bn(pdata, plen, (*rsa)->p);

        (*rsa)->q = BN_new();
        BN_bin2bn(qdata, qlen, (*rsa)->q);

        (*rsa)->dmp1 = BN_new();
        BN_bin2bn(e1data, e1len, (*rsa)->dmp1);

        (*rsa)->dmq1 = BN_new();
        BN_bin2bn(e2data, e2len, (*rsa)->dmq1);

        (*rsa)->iqmp = BN_new();
        BN_bin2bn(coeffdata, coefflen, (*rsa)->iqmp);
    }
    return 0;
}

int
_libssh2_rsa_sha1_verify(libssh2_rsa_ctx * rsactx,
                         const unsigned char *sig,
                         unsigned long sig_len,
                         const unsigned char *m, unsigned long m_len)
{
    unsigned char hash[SHA_DIGEST_LENGTH];
    int ret;

    if (_libssh2_sha1(m, m_len, hash))
        return -1; /* failure */
    ret = RSA_verify(NID_sha1, hash, SHA_DIGEST_LENGTH,
                     (unsigned char *) sig, sig_len, rsactx);
    return (ret == 1) ? 0 : -1;
}

#if LIBSSH2_DSA
int
_libssh2_dsa_new(libssh2_dsa_ctx ** dsactx,
                 const unsigned char *p,
                 unsigned long p_len,
                 const unsigned char *q,
                 unsigned long q_len,
                 const unsigned char *g,
                 unsigned long g_len,
                 const unsigned char *y,
                 unsigned long y_len,
                 const unsigned char *x, unsigned long x_len)
{
    *dsactx = DSA_new();

    (*dsactx)->p = BN_new();
    BN_bin2bn(p, p_len, (*dsactx)->p);

    (*dsactx)->q = BN_new();
    BN_bin2bn(q, q_len, (*dsactx)->q);

    (*dsactx)->g = BN_new();
    BN_bin2bn(g, g_len, (*dsactx)->g);

    (*dsactx)->pub_key = BN_new();
    BN_bin2bn(y, y_len, (*dsactx)->pub_key);

    if (x_len) {
        (*dsactx)->priv_key = BN_new();
        BN_bin2bn(x, x_len, (*dsactx)->priv_key);
    }

    return 0;
}

int
_libssh2_dsa_sha1_verify(libssh2_dsa_ctx * dsactx,
                         const unsigned char *sig,
                         const unsigned char *m, unsigned long m_len)
{
    unsigned char hash[SHA_DIGEST_LENGTH];
    DSA_SIG dsasig;
    int ret = -1;

    dsasig.r = BN_new();
    BN_bin2bn(sig, 20, dsasig.r);
    dsasig.s = BN_new();
    BN_bin2bn(sig + 20, 20, dsasig.s);

    if (!_libssh2_sha1(m, m_len, hash))
        /* _libssh2_sha1() succeeded */
        ret = DSA_do_verify(hash, SHA_DIGEST_LENGTH, &dsasig, dsactx);

    BN_clear_free(dsasig.s);
    BN_clear_free(dsasig.r);

    return (ret == 1) ? 0 : -1;
}
#endif /* LIBSSH_DSA */

int
_libssh2_cipher_init(_libssh2_cipher_ctx * h,
                     _libssh2_cipher_type(algo),
                     unsigned char *iv, unsigned char *secret, int encrypt)
{
#ifdef HAVE_OPAQUE_STRUCTS
    *h = EVP_CIPHER_CTX_new();
    return !EVP_CipherInit(*h, algo(), secret, iv, encrypt);
#else
    EVP_CIPHER_CTX_init(h);
    return !EVP_CipherInit(h, algo(), secret, iv, encrypt);
#endif
}

int
_libssh2_cipher_crypt(_libssh2_cipher_ctx * ctx,
                      _libssh2_cipher_type(algo),
                      int encrypt, unsigned char *block, size_t blocksize)
{
    unsigned char buf[EVP_MAX_BLOCK_LENGTH];
    int ret;
    (void) algo;
    (void) encrypt;

#ifdef HAVE_OPAQUE_STRUCTS
    ret = EVP_Cipher(*ctx, buf, block, blocksize);
#else
    ret = EVP_Cipher(ctx, buf, block, blocksize);
#endif
    if (ret == 1) {
        memcpy(block, buf, blocksize);
    }
    return ret == 1 ? 0 : 1;
}

#if LIBSSH2_AES_CTR

#include <openssl/aes.h>
#include <openssl/evp.h>

typedef struct
{
    AES_KEY       key;
    EVP_CIPHER_CTX *aes_ctx;
    unsigned char ctr[AES_BLOCK_SIZE];
} aes_ctr_ctx;

static int
aes_ctr_init(EVP_CIPHER_CTX *ctx, const unsigned char *key,
             const unsigned char *iv, int enc) /* init key */
{
    /*
     * variable "c" is leaked from this scope, but is later freed
     * in aes_ctr_cleanup
     */
    aes_ctr_ctx *c;
    const EVP_CIPHER *aes_cipher;
    (void) enc;

    switch (EVP_CIPHER_CTX_key_length(ctx)) {
    case 16:
        aes_cipher = EVP_aes_128_ecb();
        break;
    case 24:
        aes_cipher = EVP_aes_192_ecb();
        break;
    case 32:
        aes_cipher = EVP_aes_256_ecb();
        break;
    default:
        return 0;
    }

    c = malloc(sizeof(*c));
    if (c == NULL)
        return 0;

#ifdef HAVE_OPAQUE_STRUCTS
    c->aes_ctx = EVP_CIPHER_CTX_new();
#else
    c->aes_ctx = malloc(sizeof(EVP_CIPHER_CTX));
#endif
    if (c->aes_ctx == NULL) {
        free(c);
        return 0;
    }

    if (EVP_EncryptInit(c->aes_ctx, aes_cipher, key, NULL) != 1) {
#ifdef HAVE_OPAQUE_STRUCTS
        EVP_CIPHER_CTX_free(c->aes_ctx);
#else
        free(c->aes_ctx);
#endif
        free(c);
        return 0;
    }

    EVP_CIPHER_CTX_set_padding(c->aes_ctx, 0);

    memcpy(c->ctr, iv, AES_BLOCK_SIZE);

    EVP_CIPHER_CTX_set_app_data(ctx, c);

    return 1;
}

static int
aes_ctr_do_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
                  const unsigned char *in,
                  size_t inl) /* encrypt/decrypt data */
{
    aes_ctr_ctx *c = EVP_CIPHER_CTX_get_app_data(ctx);
    unsigned char b1[AES_BLOCK_SIZE];
    size_t i = 0;
    int outlen = 0;

    if (inl != 16) /* libssh2 only ever encrypt one block */
        return 0;

    if (c == NULL) {
        return 0;
    }

/*
  To encrypt a packet P=P1||P2||...||Pn (where P1, P2, ..., Pn are each
  blocks of length L), the encryptor first encrypts <X> with <cipher>
  to obtain a block B1.  The block B1 is then XORed with P1 to generate
  the ciphertext block C1.  The counter X is then incremented
*/

    if (EVP_EncryptUpdate(c->aes_ctx, b1, &outlen, c->ctr, AES_BLOCK_SIZE) != 1) {
        return 0;
    }

    for (i = 0; i < 16; i++)
        *out++ = *in++ ^ b1[i];

    i = 15;
    while (c->ctr[i]++ == 0xFF) {
        if (i == 0)
            break;
        i--;
    }

    return 1;
}

static int
aes_ctr_cleanup(EVP_CIPHER_CTX *ctx) /* cleanup ctx */
{
    aes_ctr_ctx *c = EVP_CIPHER_CTX_get_app_data(ctx);

    if (c == NULL) {
        return 1;
    }

    if (c->aes_ctx != NULL) {
#ifdef HAVE_OPAQUE_STRUCTS
        EVP_CIPHER_CTX_free(c->aes_ctx);
#else
        _libssh2_cipher_dtor(c->aes_ctx);
        free(c->aes_ctx);
#endif
    }

    free(c);

    return 1;
}

static const EVP_CIPHER *
make_ctr_evp (size_t keylen, EVP_CIPHER *aes_ctr_cipher, int type)
{
#ifdef HAVE_OPAQUE_STRUCTS
    aes_ctr_cipher = EVP_CIPHER_meth_new(type, 16, keylen);
    if (aes_ctr_cipher) {
        EVP_CIPHER_meth_set_iv_length(aes_ctr_cipher, 16);
        EVP_CIPHER_meth_set_init(aes_ctr_cipher, aes_ctr_init);
        EVP_CIPHER_meth_set_do_cipher(aes_ctr_cipher, aes_ctr_do_cipher);
        EVP_CIPHER_meth_set_cleanup(aes_ctr_cipher, aes_ctr_cleanup);
    }
#else
    aes_ctr_cipher->nid = type;
    aes_ctr_cipher->block_size = 16;
    aes_ctr_cipher->key_len = keylen;
    aes_ctr_cipher->iv_len = 16;
    aes_ctr_cipher->init = aes_ctr_init;
    aes_ctr_cipher->do_cipher = aes_ctr_do_cipher;
    aes_ctr_cipher->cleanup = aes_ctr_cleanup;
#endif

    return aes_ctr_cipher;
}

const EVP_CIPHER *
_libssh2_EVP_aes_128_ctr(void)
{
#ifdef HAVE_OPAQUE_STRUCTS
    static EVP_CIPHER * aes_ctr_cipher;
    return !aes_ctr_cipher?
        make_ctr_evp (16, aes_ctr_cipher, NID_aes_128_ctr) : aes_ctr_cipher;
#else
    static EVP_CIPHER aes_ctr_cipher;
    return !aes_ctr_cipher.key_len?
        make_ctr_evp (16, &aes_ctr_cipher, 0) : &aes_ctr_cipher;
#endif
}

const EVP_CIPHER *
_libssh2_EVP_aes_192_ctr(void)
{
#ifdef HAVE_OPAQUE_STRUCTS
    static EVP_CIPHER * aes_ctr_cipher;
    return !aes_ctr_cipher?
        make_ctr_evp (24, aes_ctr_cipher, NID_aes_192_ctr) : aes_ctr_cipher;
#else
    static EVP_CIPHER aes_ctr_cipher;
    return !aes_ctr_cipher.key_len?
        make_ctr_evp (24, &aes_ctr_cipher, 0) : &aes_ctr_cipher;
#endif
}

const EVP_CIPHER *
_libssh2_EVP_aes_256_ctr(void)
{
#ifdef HAVE_OPAQUE_STRUCTS
    static EVP_CIPHER * aes_ctr_cipher;
    return !aes_ctr_cipher?
        make_ctr_evp (32, aes_ctr_cipher, NID_aes_256_ctr) : aes_ctr_cipher;
#else
    static EVP_CIPHER aes_ctr_cipher;
    return !aes_ctr_cipher.key_len?
        make_ctr_evp (32, &aes_ctr_cipher, 0) : &aes_ctr_cipher;
#endif
}

void _libssh2_init_aes_ctr(void)
{
    _libssh2_EVP_aes_128_ctr();
    _libssh2_EVP_aes_192_ctr();
    _libssh2_EVP_aes_256_ctr();
}

#else
void _libssh2_init_aes_ctr(void) {}
#endif /* LIBSSH2_AES_CTR */

/* TODO: Optionally call a passphrase callback specified by the
 * calling program
 */
static int
passphrase_cb(char *buf, int size, int rwflag, char *passphrase)
{
    int passphrase_len = strlen(passphrase);
    (void) rwflag;

    if (passphrase_len > (size - 1)) {
        passphrase_len = size - 1;
    }
    memcpy(buf, passphrase, passphrase_len);
    buf[passphrase_len] = '\0';

    return passphrase_len;
}

typedef void * (*pem_read_bio_func)(BIO *, void **, pem_password_cb *,
                                    void * u);

static int
read_private_key_from_memory(void ** key_ctx,
                             pem_read_bio_func read_private_key,
                             const char * filedata,
                             size_t filedata_len,
                             unsigned const char *passphrase)
{
    BIO * bp;

    *key_ctx = NULL;

    bp = BIO_new_mem_buf((char *)filedata, filedata_len);
    if (!bp) {
        return -1;
    }
    *key_ctx = read_private_key(bp, NULL, (pem_password_cb *) passphrase_cb,
                                (void *) passphrase);

    BIO_free(bp);
    return (*key_ctx) ? 0 : -1;
}

static int
read_private_key_from_file(void ** key_ctx,
                           pem_read_bio_func read_private_key,
                           const char * filename,
                           unsigned const char *passphrase)
{
    BIO * bp;

    *key_ctx = NULL;

    bp = BIO_new_file(filename, "r");
    if (!bp) {
        return -1;
    }

    *key_ctx = read_private_key(bp, NULL, (pem_password_cb *) passphrase_cb,
                                (void *) passphrase);

    BIO_free(bp);
    return (*key_ctx) ? 0 : -1;
}

int
_libssh2_rsa_new_private_frommemory(libssh2_rsa_ctx ** rsa,
                                    LIBSSH2_SESSION * session,
                                    const char *filedata, size_t filedata_len,
                                    unsigned const char *passphrase)
{
    pem_read_bio_func read_rsa =
        (pem_read_bio_func) &PEM_read_bio_RSAPrivateKey;
    (void) session;

    _libssh2_init_if_needed();

    return read_private_key_from_memory((void **) rsa, read_rsa,
                                        filedata, filedata_len, passphrase);
}

int
_libssh2_rsa_new_private(libssh2_rsa_ctx ** rsa,
                         LIBSSH2_SESSION * session,
                         const char *filename, unsigned const char *passphrase)
{
    pem_read_bio_func read_rsa =
        (pem_read_bio_func) &PEM_read_bio_RSAPrivateKey;
    (void) session;

    _libssh2_init_if_needed ();

    return read_private_key_from_file((void **) rsa, read_rsa,
                                      filename, passphrase);
}

#if LIBSSH2_DSA
int
_libssh2_dsa_new_private_frommemory(libssh2_dsa_ctx ** dsa,
                                    LIBSSH2_SESSION * session,
                                    const char *filedata, size_t filedata_len,
                                    unsigned const char *passphrase)
{
    pem_read_bio_func read_dsa =
        (pem_read_bio_func) &PEM_read_bio_DSAPrivateKey;
    (void) session;

    _libssh2_init_if_needed();

    return read_private_key_from_memory((void **) dsa, read_dsa,
                                        filedata, filedata_len, passphrase);
}

int
_libssh2_dsa_new_private(libssh2_dsa_ctx ** dsa,
                         LIBSSH2_SESSION * session,
                         const char *filename, unsigned const char *passphrase)
{
    pem_read_bio_func read_dsa =
        (pem_read_bio_func) &PEM_read_bio_DSAPrivateKey;
    (void) session;

    _libssh2_init_if_needed ();

    return read_private_key_from_file((void **) dsa, read_dsa,
                                      filename, passphrase);
}
#endif /* LIBSSH_DSA */

int
_libssh2_rsa_sha1_sign(LIBSSH2_SESSION * session,
                       libssh2_rsa_ctx * rsactx,
                       const unsigned char *hash,
                       size_t hash_len,
                       unsigned char **signature, size_t *signature_len)
{
    int ret;
    unsigned char *sig;
    unsigned int sig_len;

    sig_len = RSA_size(rsactx);
    sig = LIBSSH2_ALLOC(session, sig_len);

    if (!sig) {
        return -1;
    }

    ret = RSA_sign(NID_sha1, hash, hash_len, sig, &sig_len, rsactx);

    if (!ret) {
        LIBSSH2_FREE(session, sig);
        return -1;
    }

    *signature = sig;
    *signature_len = sig_len;

    return 0;
}

#if LIBSSH2_DSA
int
_libssh2_dsa_sha1_sign(libssh2_dsa_ctx * dsactx,
                       const unsigned char *hash,
                       unsigned long hash_len, unsigned char *signature)
{
    DSA_SIG *sig;
    int r_len, s_len;
    (void) hash_len;

    sig = DSA_do_sign(hash, SHA_DIGEST_LENGTH, dsactx);
    if (!sig) {
        return -1;
    }

    r_len = BN_num_bytes(sig->r);
    if (r_len < 1 || r_len > 20) {
        DSA_SIG_free(sig);
        return -1;
    }
    s_len = BN_num_bytes(sig->s);
    if (s_len < 1 || s_len > 20) {
        DSA_SIG_free(sig);
        return -1;
    }

    memset(signature, 0, 40);

    BN_bn2bin(sig->r, signature + (20 - r_len));
    BN_bn2bin(sig->s, signature + 20 + (20 - s_len));

    DSA_SIG_free(sig);

    return 0;
}
#endif /* LIBSSH_DSA */

int
_libssh2_sha1_init(libssh2_sha1_ctx *ctx)
{
#ifdef HAVE_OPAQUE_STRUCTS
    *ctx = EVP_MD_CTX_new();

    if (*ctx == NULL)
        return 0;

    if (EVP_DigestInit(*ctx, EVP_get_digestbyname("sha1")))
        return 1;

    EVP_MD_CTX_free(*ctx);
    *ctx = NULL;

    return 0;
#else
    EVP_MD_CTX_init(ctx);
    return EVP_DigestInit(ctx, EVP_get_digestbyname("sha1"));
#endif
}

int
_libssh2_sha1(const unsigned char *message, unsigned long len,
              unsigned char *out)
{
#ifdef HAVE_OPAQUE_STRUCTS
    EVP_MD_CTX * ctx = EVP_MD_CTX_new();

    if (ctx == NULL)
        return 1; /* error */

    if (EVP_DigestInit(ctx, EVP_get_digestbyname("sha1"))) {
        EVP_DigestUpdate(ctx, message, len);
        EVP_DigestFinal(ctx, out, NULL);
        EVP_MD_CTX_free(ctx);
        return 0; /* success */
    }
    EVP_MD_CTX_free(ctx);
#else
    EVP_MD_CTX ctx;

    EVP_MD_CTX_init(&ctx);
    if (EVP_DigestInit(&ctx, EVP_get_digestbyname("sha1"))) {
        EVP_DigestUpdate(&ctx, message, len);
        EVP_DigestFinal(&ctx, out, NULL);
        return 0; /* success */
    }
#endif
    return 1; /* error */
}

int
_libssh2_sha256_init(libssh2_sha256_ctx *ctx)
{
#ifdef HAVE_OPAQUE_STRUCTS
    *ctx = EVP_MD_CTX_new();

    if (*ctx == NULL)
        return 0;

    if (EVP_DigestInit(*ctx, EVP_get_digestbyname("sha256")))
        return 1;

    EVP_MD_CTX_free(*ctx);
    *ctx = NULL;

    return 0;
#else
    EVP_MD_CTX_init(ctx);
    return EVP_DigestInit(ctx, EVP_get_digestbyname("sha256"));
#endif
}

int
_libssh2_sha256(const unsigned char *message, unsigned long len,
                unsigned char *out)
{
#ifdef HAVE_OPAQUE_STRUCTS
    EVP_MD_CTX * ctx = EVP_MD_CTX_new();

    if (ctx == NULL)
        return 1; /* error */

    if(EVP_DigestInit(ctx, EVP_get_digestbyname("sha256"))) {
        EVP_DigestUpdate(ctx, message, len);
        EVP_DigestFinal(ctx, out, NULL);
        EVP_MD_CTX_free(ctx);
        return 0; /* success */
    }
    EVP_MD_CTX_free(ctx);
#else
    EVP_MD_CTX ctx;

    EVP_MD_CTX_init(&ctx);
    if(EVP_DigestInit(&ctx, EVP_get_digestbyname("sha256"))) {
        EVP_DigestUpdate(&ctx, message, len);
        EVP_DigestFinal(&ctx, out, NULL);
        return 0; /* success */
    }
#endif
    return 1; /* error */
}

int
_libssh2_md5_init(libssh2_md5_ctx *ctx)
{
#ifdef HAVE_OPAQUE_STRUCTS
    *ctx = EVP_MD_CTX_new();

    if (*ctx == NULL)
        return 0;

    if (EVP_DigestInit(*ctx, EVP_get_digestbyname("md5")))
        return 1;

    EVP_MD_CTX_free(*ctx);
    *ctx = NULL;

    return 0;
#else
    EVP_MD_CTX_init(ctx);
    return EVP_DigestInit(ctx, EVP_get_digestbyname("md5"));
#endif
}

static unsigned char *
write_bn(unsigned char *buf, const BIGNUM *bn, int bn_bytes)
{
    unsigned char *p = buf;

    /* Left space for bn size which will be written below. */
    p += 4;

    *p = 0;
    BN_bn2bin(bn, p + 1);
    if (!(*(p + 1) & 0x80)) {
        memmove(p, p + 1, --bn_bytes);
    }
    _libssh2_htonu32(p - 4, bn_bytes);  /* Post write bn size. */

    return p + bn_bytes;
}

static unsigned char *
gen_publickey_from_rsa(LIBSSH2_SESSION *session, RSA *rsa,
                       size_t *key_len)
{
    int            e_bytes, n_bytes;
    unsigned long  len;
    unsigned char* key;
    unsigned char* p;

    e_bytes = BN_num_bytes(rsa->e) + 1;
    n_bytes = BN_num_bytes(rsa->n) + 1;

    /* Key form is "ssh-rsa" + e + n. */
    len = 4 + 7 + 4 + e_bytes + 4 + n_bytes;

    key = LIBSSH2_ALLOC(session, len);
    if (key == NULL) {
        return NULL;
    }

    /* Process key encoding. */
    p = key;

    _libssh2_htonu32(p, 7);  /* Key type. */
    p += 4;
    memcpy(p, "ssh-rsa", 7);
    p += 7;

    p = write_bn(p, rsa->e, e_bytes);
    p = write_bn(p, rsa->n, n_bytes);

    *key_len = (size_t)(p - key);
    return key;
}

#if LIBSSH2_DSA
static unsigned char *
gen_publickey_from_dsa(LIBSSH2_SESSION* session, DSA *dsa,
                       size_t *key_len)
{
    int            p_bytes, q_bytes, g_bytes, k_bytes;
    unsigned long  len;
    unsigned char* key;
    unsigned char* p;

    p_bytes = BN_num_bytes(dsa->p) + 1;
    q_bytes = BN_num_bytes(dsa->q) + 1;
    g_bytes = BN_num_bytes(dsa->g) + 1;
    k_bytes = BN_num_bytes(dsa->pub_key) + 1;

    /* Key form is "ssh-dss" + p + q + g + pub_key. */
    len = 4 + 7 + 4 + p_bytes + 4 + q_bytes + 4 + g_bytes + 4 + k_bytes;

    key = LIBSSH2_ALLOC(session, len);
    if (key == NULL) {
        return NULL;
    }

    /* Process key encoding. */
    p = key;

    _libssh2_htonu32(p, 7);  /* Key type. */
    p += 4;
    memcpy(p, "ssh-dss", 7);
    p += 7;

    p = write_bn(p, dsa->p, p_bytes);
    p = write_bn(p, dsa->q, q_bytes);
    p = write_bn(p, dsa->g, g_bytes);
    p = write_bn(p, dsa->pub_key, k_bytes);

    *key_len = (size_t)(p - key);
    return key;
}
#endif /* LIBSSH_DSA */

static int
gen_publickey_from_rsa_evp(LIBSSH2_SESSION *session,
                           unsigned char **method,
                           size_t *method_len,
                           unsigned char **pubkeydata,
                           size_t *pubkeydata_len,
                           EVP_PKEY *pk)
{
    RSA*           rsa = NULL;
    unsigned char* key;
    unsigned char* method_buf = NULL;
    size_t  key_len;

    _libssh2_debug(session,
                   LIBSSH2_TRACE_AUTH,
                   "Computing public key from RSA private key envelop");

    rsa = EVP_PKEY_get1_RSA(pk);
    if (rsa == NULL) {
        /* Assume memory allocation error... what else could it be ? */
        goto __alloc_error;
    }

    method_buf = LIBSSH2_ALLOC(session, 7);  /* ssh-rsa. */
    if (method_buf == NULL) {
        goto __alloc_error;
    }

    key = gen_publickey_from_rsa(session, rsa, &key_len);
    if (key == NULL) {
        goto __alloc_error;
    }
    RSA_free(rsa);

    memcpy(method_buf, "ssh-rsa", 7);
    *method         = method_buf;
    *method_len     = 7;
    *pubkeydata     = key;
    *pubkeydata_len = key_len;
    return 0;

  __alloc_error:
    if (rsa != NULL) {
        RSA_free(rsa);
    }
    if (method_buf != NULL) {
        LIBSSH2_FREE(session, method_buf);
    }

    return _libssh2_error(session,
                          LIBSSH2_ERROR_ALLOC,
                          "Unable to allocate memory for private key data");
}

#if LIBSSH2_DSA
static int
gen_publickey_from_dsa_evp(LIBSSH2_SESSION *session,
                           unsigned char **method,
                           size_t *method_len,
                           unsigned char **pubkeydata,
                           size_t *pubkeydata_len,
                           EVP_PKEY *pk)
{
    DSA*           dsa = NULL;
    unsigned char* key;
    unsigned char* method_buf = NULL;
    size_t  key_len;

    _libssh2_debug(session,
                   LIBSSH2_TRACE_AUTH,
                   "Computing public key from DSA private key envelop");

    dsa = EVP_PKEY_get1_DSA(pk);
    if (dsa == NULL) {
        /* Assume memory allocation error... what else could it be ? */
        goto __alloc_error;
    }

    method_buf = LIBSSH2_ALLOC(session, 7);  /* ssh-dss. */
    if (method_buf == NULL) {
        goto __alloc_error;
    }

    key = gen_publickey_from_dsa(session, dsa, &key_len);
    if (key == NULL) {
        goto __alloc_error;
    }
    DSA_free(dsa);

    memcpy(method_buf, "ssh-dss", 7);
    *method         = method_buf;
    *method_len     = 7;
    *pubkeydata     = key;
    *pubkeydata_len = key_len;
    return 0;

  __alloc_error:
    if (dsa != NULL) {
        DSA_free(dsa);
    }
    if (method_buf != NULL) {
        LIBSSH2_FREE(session, method_buf);
    }

    return _libssh2_error(session,
                          LIBSSH2_ERROR_ALLOC,
                          "Unable to allocate memory for private key data");
}
#endif /* LIBSSH_DSA */

int
_libssh2_pub_priv_keyfile(LIBSSH2_SESSION *session,
                          unsigned char **method,
                          size_t *method_len,
                          unsigned char **pubkeydata,
                          size_t *pubkeydata_len,
                          const char *privatekey,
                          const char *passphrase)
{
    int       st;
    BIO*      bp;
    EVP_PKEY* pk;
    int       pktype;

    _libssh2_debug(session,
                   LIBSSH2_TRACE_AUTH,
                   "Computing public key from private key file: %s",
                   privatekey);

    bp = BIO_new_file(privatekey, "r");
    if (bp == NULL) {
        return _libssh2_error(session,
                              LIBSSH2_ERROR_FILE,
                              "Unable to extract public key from private key "
                              "file: Unable to open private key file");
    }
    if (!EVP_get_cipherbyname("des")) {
        /* If this cipher isn't loaded it's a pretty good indication that none
         * are.  I have *NO DOUBT* that there's a better way to deal with this
         * ($#&%#$(%$#( Someone buy me an OpenSSL manual and I'll read up on
         * it.
         */
        OpenSSL_add_all_ciphers();
    }
    BIO_reset(bp);
    pk = PEM_read_bio_PrivateKey(bp, NULL, NULL, (void*)passphrase);
    BIO_free(bp);

    if (pk == NULL) {
        return _libssh2_error(session,
                              LIBSSH2_ERROR_FILE,
                              "Unable to extract public key "
                              "from private key file: "
                              "Wrong passphrase or invalid/unrecognized "
                              "private key file format");
    }

#ifdef HAVE_OPAQUE_STRUCTS
    pktype = EVP_PKEY_id(pk);
#else
    pktype = pk->type;
#endif

    switch (pktype) {
    case EVP_PKEY_RSA :
        st = gen_publickey_from_rsa_evp(
            session, method, method_len, pubkeydata, pubkeydata_len, pk);
        break;

#if LIBSSH2_DSA
    case EVP_PKEY_DSA :
        st = gen_publickey_from_dsa_evp(
            session, method, method_len, pubkeydata, pubkeydata_len, pk);
        break;
#endif /* LIBSSH_DSA */

    default :
        st = _libssh2_error(session,
                            LIBSSH2_ERROR_FILE,
                            "Unable to extract public key "
                            "from private key file: "
                            "Unsupported private key file format");
        break;
    }

    EVP_PKEY_free(pk);
    return st;
}

int
_libssh2_pub_priv_keyfilememory(LIBSSH2_SESSION *session,
                                unsigned char **method,
                                size_t *method_len,
                                unsigned char **pubkeydata,
                                size_t *pubkeydata_len,
                                const char *privatekeydata,
                                size_t privatekeydata_len,
                                const char *passphrase)
{
    int       st;
    BIO*      bp;
    EVP_PKEY* pk;
    int       pktype;

    _libssh2_debug(session,
                   LIBSSH2_TRACE_AUTH,
                   "Computing public key from private key.");

    bp = BIO_new_mem_buf((char *)privatekeydata, privatekeydata_len);
    if (!bp) {
        return -1;
    }
    if (!EVP_get_cipherbyname("des")) {
        /* If this cipher isn't loaded it's a pretty good indication that none
         * are.  I have *NO DOUBT* that there's a better way to deal with this
         * ($#&%#$(%$#( Someone buy me an OpenSSL manual and I'll read up on
         * it.
         */
        OpenSSL_add_all_ciphers();
    }
    BIO_reset(bp);
    pk = PEM_read_bio_PrivateKey(bp, NULL, NULL, (void*)passphrase);
    BIO_free(bp);

    if (pk == NULL) {
        return _libssh2_error(session,
                              LIBSSH2_ERROR_FILE,
                              "Unable to extract public key "
                              "from private key file: "
                              "Wrong passphrase or invalid/unrecognized "
                              "private key file format");
    }

#ifdef HAVE_OPAQUE_STRUCTS
    pktype = EVP_PKEY_id(pk);
#else
    pktype = pk->type;
#endif

    switch (pktype) {
    case EVP_PKEY_RSA :
        st = gen_publickey_from_rsa_evp(session, method, method_len,
                                        pubkeydata, pubkeydata_len, pk);
        break;
#if LIBSSH2_DSA
    case EVP_PKEY_DSA :
        st = gen_publickey_from_dsa_evp(session, method, method_len,
                                        pubkeydata, pubkeydata_len, pk);
        break;
#endif /* LIBSSH_DSA */
    default :
        st = _libssh2_error(session,
                            LIBSSH2_ERROR_FILE,
                            "Unable to extract public key "
                            "from private key file: "
                            "Unsupported private key file format");
        break;
    }

    EVP_PKEY_free(pk);
    return st;
}

#endif /* LIBSSH2_OPENSSL */