openssl.c

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/*
 * openssl.c
 *      Wrapper for OpenSSL library.
 *
 * Copyright (c) 2001 Marko Kreen
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * contrib/pgcrypto/openssl.c
 */
 
#include "postgres.h"
 
#include <openssl/evp.h>
#include <openssl/err.h>
#include <openssl/rand.h>
 
#include "px.h"
#include "utils/memutils.h"
#include "utils/resowner.h"
 
/*
 * Max lengths we might want to handle.
 */
#define MAX_KEY     (512/8)
#define MAX_IV      (128/8)
 
/*
 * Hashes
 */
 
/*
 * To make sure we don't leak OpenSSL handles on abort, we keep OSSLDigest
 * objects in a linked list, allocated in TopMemoryContext. We use the
 * ResourceOwner mechanism to free them on abort.
 */
typedef struct OSSLDigest
{
    const EVP_MD *algo;
    EVP_MD_CTX *ctx;
 
    ResourceOwner owner;
    struct OSSLDigest *next;
    struct OSSLDigest *prev;
} OSSLDigest;
 
static OSSLDigest *open_digests = NULL;
static bool digest_resowner_callback_registered = false;
 
static void
free_openssl_digest(OSSLDigest *digest)
{
    EVP_MD_CTX_destroy(digest->ctx);
    if (digest->prev)
        digest->prev->next = digest->next;
    else
        open_digests = digest->next;
    if (digest->next)
        digest->next->prev = digest->prev;
    pfree(digest);
}
 
/*
 * Close any open OpenSSL handles on abort.
 */
static void
digest_free_callback(ResourceReleasePhase phase,
                     bool isCommit,
                     bool isTopLevel,
                     void *arg)
{
    OSSLDigest *curr;
    OSSLDigest *next;
 
    if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
        return;
 
    next = open_digests;
    while (next)
    {
        curr = next;
        next = curr->next;
 
        if (curr->owner == CurrentResourceOwner)
        {
            if (isCommit)
                elog(WARNING, "pgcrypto digest reference leak: digest %p still referenced", curr);
            free_openssl_digest(curr);
        }
    }
}
 
static unsigned
digest_result_size(PX_MD *h)
{
    OSSLDigest *digest = (OSSLDigest *) h->p.ptr;
    int         result = EVP_MD_CTX_size(digest->ctx);
 
    if (result < 0)
        elog(ERROR, "EVP_MD_CTX_size() failed");
 
    return result;
}
 
static unsigned
digest_block_size(PX_MD *h)
{
    OSSLDigest *digest = (OSSLDigest *) h->p.ptr;
    int         result = EVP_MD_CTX_block_size(digest->ctx);
 
    if (result < 0)
        elog(ERROR, "EVP_MD_CTX_block_size() failed");
 
    return result;
}
 
static void
digest_reset(PX_MD *h)
{
    OSSLDigest *digest = (OSSLDigest *) h->p.ptr;
 
    if (!EVP_DigestInit_ex(digest->ctx, digest->algo, NULL))
        elog(ERROR, "EVP_DigestInit_ex() failed");
}
 
static void
digest_update(PX_MD *h, const uint8 *data, unsigned dlen)
{
    OSSLDigest *digest = (OSSLDigest *) h->p.ptr;
 
    if (!EVP_DigestUpdate(digest->ctx, data, dlen))
        elog(ERROR, "EVP_DigestUpdate() failed");
}
 
static void
digest_finish(PX_MD *h, uint8 *dst)
{
    OSSLDigest *digest = (OSSLDigest *) h->p.ptr;
 
    if (!EVP_DigestFinal_ex(digest->ctx, dst, NULL))
        elog(ERROR, "EVP_DigestFinal_ex() failed");
}
 
static void
digest_free(PX_MD *h)
{
    OSSLDigest *digest = (OSSLDigest *) h->p.ptr;
 
    free_openssl_digest(digest);
    pfree(h);
}
 
static int  px_openssl_initialized = 0;
 
/* PUBLIC functions */
 
int
px_find_digest(const char *name, PX_MD **res)
{
    const EVP_MD *md;
    EVP_MD_CTX *ctx;
    PX_MD      *h;
    OSSLDigest *digest;
 
    if (!px_openssl_initialized)
    {
        px_openssl_initialized = 1;
        OpenSSL_add_all_algorithms();
    }
 
    if (!digest_resowner_callback_registered)
    {
        RegisterResourceReleaseCallback(digest_free_callback, NULL);
        digest_resowner_callback_registered = true;
    }
 
    md = EVP_get_digestbyname(name);
    if (md == NULL)
        return PXE_NO_HASH;
 
    /*
     * Create an OSSLDigest object, an OpenSSL MD object, and a PX_MD object.
     * The order is crucial, to make sure we don't leak anything on
     * out-of-memory or other error.
     */
    digest = MemoryContextAlloc(TopMemoryContext, sizeof(*digest));
 
    ctx = EVP_MD_CTX_create();
    if (!ctx)
    {
        pfree(digest);
        return -1;
    }
    if (EVP_DigestInit_ex(ctx, md, NULL) == 0)
    {
        EVP_MD_CTX_destroy(ctx);
        pfree(digest);
        return -1;
    }
 
    digest->algo = md;
    digest->ctx = ctx;
    digest->owner = CurrentResourceOwner;
    digest->next = open_digests;
    digest->prev = NULL;
    open_digests = digest;
 
    /* The PX_MD object is allocated in the current memory context. */
    h = palloc(sizeof(*h));
    h->result_size = digest_result_size;
    h->block_size = digest_block_size;
    h->reset = digest_reset;
    h->update = digest_update;
    h->finish = digest_finish;
    h->free = digest_free;
    h->p.ptr = (void *) digest;
 
    *res = h;
    return 0;
}
 
/*
 * Ciphers
 *
 * We use OpenSSL's EVP* family of functions for these.
 */
 
/*
 * prototype for the EVP functions that return an algorithm, e.g.
 * EVP_aes_128_cbc().
 */
typedef const EVP_CIPHER *(*ossl_EVP_cipher_func) (void);
 
/*
 * ossl_cipher contains the static information about each cipher.
 */
struct ossl_cipher
{
    int         (*init) (PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv);
    ossl_EVP_cipher_func cipher_func;
    int         block_size;
    int         max_key_size;
};
 
/*
 * OSSLCipher contains the state for using a cipher. A separate OSSLCipher
 * object is allocated in each px_find_cipher() call.
 *
 * To make sure we don't leak OpenSSL handles on abort, we keep OSSLCipher
 * objects in a linked list, allocated in TopMemoryContext. We use the
 * ResourceOwner mechanism to free them on abort.
 */
typedef struct OSSLCipher
{
    EVP_CIPHER_CTX *evp_ctx;
    const EVP_CIPHER *evp_ciph;
    uint8       key[MAX_KEY];
    uint8       iv[MAX_IV];
    unsigned    klen;
    unsigned    init;
    const struct ossl_cipher *ciph;
 
    ResourceOwner owner;
    struct OSSLCipher *next;
    struct OSSLCipher *prev;
} OSSLCipher;
 
static OSSLCipher *open_ciphers = NULL;
static bool cipher_resowner_callback_registered = false;
 
static void
free_openssl_cipher(OSSLCipher *od)
{
    EVP_CIPHER_CTX_free(od->evp_ctx);
    if (od->prev)
        od->prev->next = od->next;
    else
        open_ciphers = od->next;
    if (od->next)
        od->next->prev = od->prev;
    pfree(od);
}
 
/*
 * Close any open OpenSSL cipher handles on abort.
 */
static void
cipher_free_callback(ResourceReleasePhase phase,
                     bool isCommit,
                     bool isTopLevel,
                     void *arg)
{
    OSSLCipher *curr;
    OSSLCipher *next;
 
    if (phase != RESOURCE_RELEASE_AFTER_LOCKS)
        return;
 
    next = open_ciphers;
    while (next)
    {
        curr = next;
        next = curr->next;
 
        if (curr->owner == CurrentResourceOwner)
        {
            if (isCommit)
                elog(WARNING, "pgcrypto cipher reference leak: cipher %p still referenced", curr);
            free_openssl_cipher(curr);
        }
    }
}
 
/* Common routines for all algorithms */
 
static unsigned
gen_ossl_block_size(PX_Cipher *c)
{
    OSSLCipher *od = (OSSLCipher *) c->ptr;
 
    return od->ciph->block_size;
}
 
static unsigned
gen_ossl_key_size(PX_Cipher *c)
{
    OSSLCipher *od = (OSSLCipher *) c->ptr;
 
    return od->ciph->max_key_size;
}
 
static unsigned
gen_ossl_iv_size(PX_Cipher *c)
{
    unsigned    ivlen;
    OSSLCipher *od = (OSSLCipher *) c->ptr;
 
    ivlen = od->ciph->block_size;
    return ivlen;
}
 
static void
gen_ossl_free(PX_Cipher *c)
{
    OSSLCipher *od = (OSSLCipher *) c->ptr;
 
    free_openssl_cipher(od);
    pfree(c);
}
 
static int
gen_ossl_decrypt(PX_Cipher *c, const uint8 *data, unsigned dlen,
                 uint8 *res)
{
    OSSLCipher *od = c->ptr;
    int         outlen;
 
    if (!od->init)
    {
        if (!EVP_DecryptInit_ex(od->evp_ctx, od->evp_ciph, NULL, NULL, NULL))
            return PXE_CIPHER_INIT;
        if (!EVP_CIPHER_CTX_set_padding(od->evp_ctx, 0))
            return PXE_CIPHER_INIT;
        if (!EVP_CIPHER_CTX_set_key_length(od->evp_ctx, od->klen))
            return PXE_CIPHER_INIT;
        if (!EVP_DecryptInit_ex(od->evp_ctx, NULL, NULL, od->key, od->iv))
            return PXE_CIPHER_INIT;
        od->init = true;
    }
 
    if (!EVP_DecryptUpdate(od->evp_ctx, res, &outlen, data, dlen))
        return PXE_DECRYPT_FAILED;
 
    return 0;
}
 
static int
gen_ossl_encrypt(PX_Cipher *c, const uint8 *data, unsigned dlen,
                 uint8 *res)
{
    OSSLCipher *od = c->ptr;
    int         outlen;
 
    if (!od->init)
    {
        if (!EVP_EncryptInit_ex(od->evp_ctx, od->evp_ciph, NULL, NULL, NULL))
            return PXE_CIPHER_INIT;
        if (!EVP_CIPHER_CTX_set_padding(od->evp_ctx, 0))
            return PXE_CIPHER_INIT;
        if (!EVP_CIPHER_CTX_set_key_length(od->evp_ctx, od->klen))
            return PXE_CIPHER_INIT;
        if (!EVP_EncryptInit_ex(od->evp_ctx, NULL, NULL, od->key, od->iv))
            return PXE_CIPHER_INIT;
        od->init = true;
    }
 
    if (!EVP_EncryptUpdate(od->evp_ctx, res, &outlen, data, dlen))
        return PXE_ENCRYPT_FAILED;
 
    return 0;
}
 
/* Blowfish */
 
/*
 * Check if strong crypto is supported. Some OpenSSL installations
 * support only short keys and unfortunately BF_set_key does not return any
 * error value. This function tests if is possible to use strong key.
 */
static int
bf_check_supported_key_len(void)
{
    static const uint8 key[56] = {
        0xf0, 0xe1, 0xd2, 0xc3, 0xb4, 0xa5, 0x96, 0x87, 0x78, 0x69,
        0x5a, 0x4b, 0x3c, 0x2d, 0x1e, 0x0f, 0x00, 0x11, 0x22, 0x33,
        0x44, 0x55, 0x66, 0x77, 0x04, 0x68, 0x91, 0x04, 0xc2, 0xfd,
        0x3b, 0x2f, 0x58, 0x40, 0x23, 0x64, 0x1a, 0xba, 0x61, 0x76,
        0x1f, 0x1f, 0x1f, 0x1f, 0x0e, 0x0e, 0x0e, 0x0e, 0xff, 0xff,
        0xff, 0xff, 0xff, 0xff, 0xff, 0xff
    };
 
    static const uint8 data[8] = {0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54, 0x32, 0x10};
    static const uint8 res[8] = {0xc0, 0x45, 0x04, 0x01, 0x2e, 0x4e, 0x1f, 0x53};
    uint8       out[8];
    EVP_CIPHER_CTX *evp_ctx;
    int         outlen;
    int         status = 0;
 
    /* encrypt with 448bits key and verify output */
    evp_ctx = EVP_CIPHER_CTX_new();
    if (!evp_ctx)
        return 0;
    if (!EVP_EncryptInit_ex(evp_ctx, EVP_bf_ecb(), NULL, NULL, NULL))
        goto leave;
    if (!EVP_CIPHER_CTX_set_key_length(evp_ctx, 56))
        goto leave;
    if (!EVP_EncryptInit_ex(evp_ctx, NULL, NULL, key, NULL))
        goto leave;
 
    if (!EVP_EncryptUpdate(evp_ctx, out, &outlen, data, 8))
        goto leave;
 
    if (memcmp(out, res, 8) != 0)
        goto leave;             /* Output does not match -> strong cipher is
                                 * not supported */
    status = 1;
 
leave:
    EVP_CIPHER_CTX_free(evp_ctx);
    return status;
}
 
static int
bf_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv)
{
    OSSLCipher *od = c->ptr;
    unsigned    bs = gen_ossl_block_size(c);
    static int  bf_is_strong = -1;
 
    /*
     * Test if key len is supported. BF_set_key silently cut large keys and it
     * could be a problem when user transfer crypted data from one server to
     * another.
     */
 
    if (bf_is_strong == -1)
        bf_is_strong = bf_check_supported_key_len();
 
    if (!bf_is_strong && klen > 16)
        return PXE_KEY_TOO_BIG;
 
    /* Key len is supported. We can use it. */
    od->klen = klen;
    memcpy(od->key, key, klen);
 
    if (iv)
        memcpy(od->iv, iv, bs);
    else
        memset(od->iv, 0, bs);
    return 0;
}
 
/* DES */
 
static int
ossl_des_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv)
{
    OSSLCipher *od = c->ptr;
    unsigned    bs = gen_ossl_block_size(c);
 
    od->klen = 8;
    memset(od->key, 0, 8);
    memcpy(od->key, key, klen > 8 ? 8 : klen);
 
    if (iv)
        memcpy(od->iv, iv, bs);
    else
        memset(od->iv, 0, bs);
    return 0;
}
 
/* DES3 */
 
static int
ossl_des3_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv)
{
    OSSLCipher *od = c->ptr;
    unsigned    bs = gen_ossl_block_size(c);
 
    od->klen = 24;
    memset(od->key, 0, 24);
    memcpy(od->key, key, klen > 24 ? 24 : klen);
 
    if (iv)
        memcpy(od->iv, iv, bs);
    else
        memset(od->iv, 0, bs);
    return 0;
}
 
/* CAST5 */
 
static int
ossl_cast_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv)
{
    OSSLCipher *od = c->ptr;
    unsigned    bs = gen_ossl_block_size(c);
 
    od->klen = klen;
    memcpy(od->key, key, klen);
 
    if (iv)
        memcpy(od->iv, iv, bs);
    else
        memset(od->iv, 0, bs);
    return 0;
}
 
/* AES */
 
static int
ossl_aes_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv)
{
    OSSLCipher *od = c->ptr;
    unsigned    bs = gen_ossl_block_size(c);
 
    if (klen <= 128 / 8)
        od->klen = 128 / 8;
    else if (klen <= 192 / 8)
        od->klen = 192 / 8;
    else if (klen <= 256 / 8)
        od->klen = 256 / 8;
    else
        return PXE_KEY_TOO_BIG;
 
    memcpy(od->key, key, klen);
 
    if (iv)
        memcpy(od->iv, iv, bs);
    else
        memset(od->iv, 0, bs);
 
    return 0;
}
 
static int
ossl_aes_ecb_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv)
{
    OSSLCipher *od = c->ptr;
    int         err;
 
    err = ossl_aes_init(c, key, klen, iv);
    if (err)
        return err;
 
    switch (od->klen)
    {
        case 128 / 8:
            od->evp_ciph = EVP_aes_128_ecb();
            break;
        case 192 / 8:
            od->evp_ciph = EVP_aes_192_ecb();
            break;
        case 256 / 8:
            od->evp_ciph = EVP_aes_256_ecb();
            break;
        default:
            /* shouldn't happen */
            err = PXE_CIPHER_INIT;
            break;
    }
 
    return err;
}
 
static int
ossl_aes_cbc_init(PX_Cipher *c, const uint8 *key, unsigned klen, const uint8 *iv)
{
    OSSLCipher *od = c->ptr;
    int         err;
 
    err = ossl_aes_init(c, key, klen, iv);
    if (err)
        return err;
 
    switch (od->klen)
    {
        case 128 / 8:
            od->evp_ciph = EVP_aes_128_cbc();
            break;
        case 192 / 8:
            od->evp_ciph = EVP_aes_192_cbc();
            break;
        case 256 / 8:
            od->evp_ciph = EVP_aes_256_cbc();
            break;
        default:
            /* shouldn't happen */
            err = PXE_CIPHER_INIT;
            break;
    }
 
    return err;
}
 
/*
 * aliases
 */
 
static PX_Alias ossl_aliases[] = {
    {"bf", "bf-cbc"},
    {"blowfish", "bf-cbc"},
    {"blowfish-cbc", "bf-cbc"},
    {"blowfish-ecb", "bf-ecb"},
    {"blowfish-cfb", "bf-cfb"},
    {"des", "des-cbc"},
    {"3des", "des3-cbc"},
    {"3des-ecb", "des3-ecb"},
    {"3des-cbc", "des3-cbc"},
    {"cast5", "cast5-cbc"},
    {"aes", "aes-cbc"},
    {"rijndael", "aes-cbc"},
    {"rijndael-cbc", "aes-cbc"},
    {"rijndael-ecb", "aes-ecb"},
    {NULL}
};
 
static const struct ossl_cipher ossl_bf_cbc = {
    bf_init,
    EVP_bf_cbc,
    64 / 8, 448 / 8
};
 
static const struct ossl_cipher ossl_bf_ecb = {
    bf_init,
    EVP_bf_ecb,
    64 / 8, 448 / 8
};
 
static const struct ossl_cipher ossl_bf_cfb = {
    bf_init,
    EVP_bf_cfb,
    64 / 8, 448 / 8
};
 
static const struct ossl_cipher ossl_des_ecb = {
    ossl_des_init,
    EVP_des_ecb,
    64 / 8, 64 / 8
};
 
static const struct ossl_cipher ossl_des_cbc = {
    ossl_des_init,
    EVP_des_cbc,
    64 / 8, 64 / 8
};
 
static const struct ossl_cipher ossl_des3_ecb = {
    ossl_des3_init,
    EVP_des_ede3_ecb,
    64 / 8, 192 / 8
};
 
static const struct ossl_cipher ossl_des3_cbc = {
    ossl_des3_init,
    EVP_des_ede3_cbc,
    64 / 8, 192 / 8
};
 
static const struct ossl_cipher ossl_cast_ecb = {
    ossl_cast_init,
    EVP_cast5_ecb,
    64 / 8, 128 / 8
};
 
static const struct ossl_cipher ossl_cast_cbc = {
    ossl_cast_init,
    EVP_cast5_cbc,
    64 / 8, 128 / 8
};
 
static const struct ossl_cipher ossl_aes_ecb = {
    ossl_aes_ecb_init,
    NULL,                       /* EVP_aes_XXX_ecb(), determined in init
                                 * function */
    128 / 8, 256 / 8
};
 
static const struct ossl_cipher ossl_aes_cbc = {
    ossl_aes_cbc_init,
    NULL,                       /* EVP_aes_XXX_cbc(), determined in init
                                 * function */
    128 / 8, 256 / 8
};
 
/*
 * Special handlers
 */
struct ossl_cipher_lookup
{
    const char *name;
    const struct ossl_cipher *ciph;
};
 
static const struct ossl_cipher_lookup ossl_cipher_types[] = {
    {"bf-cbc", &ossl_bf_cbc},
    {"bf-ecb", &ossl_bf_ecb},
    {"bf-cfb", &ossl_bf_cfb},
    {"des-ecb", &ossl_des_ecb},
    {"des-cbc", &ossl_des_cbc},
    {"des3-ecb", &ossl_des3_ecb},
    {"des3-cbc", &ossl_des3_cbc},
    {"cast5-ecb", &ossl_cast_ecb},
    {"cast5-cbc", &ossl_cast_cbc},
    {"aes-ecb", &ossl_aes_ecb},
    {"aes-cbc", &ossl_aes_cbc},
    {NULL}
};
 
/* PUBLIC functions */
 
int
px_find_cipher(const char *name, PX_Cipher **res)
{
    const struct ossl_cipher_lookup *i;
    PX_Cipher  *c = NULL;
    EVP_CIPHER_CTX *ctx;
    OSSLCipher *od;
 
    name = px_resolve_alias(ossl_aliases, name);
    for (i = ossl_cipher_types; i->name; i++)
        if (strcmp(i->name, name) == 0)
            break;
    if (i->name == NULL)
        return PXE_NO_CIPHER;
 
    if (!cipher_resowner_callback_registered)
    {
        RegisterResourceReleaseCallback(cipher_free_callback, NULL);
        cipher_resowner_callback_registered = true;
    }
 
    /*
     * Create an OSSLCipher object, an EVP_CIPHER_CTX object and a PX_Cipher.
     * The order is crucial, to make sure we don't leak anything on
     * out-of-memory or other error.
     */
    od = MemoryContextAllocZero(TopMemoryContext, sizeof(*od));
    od->ciph = i->ciph;
 
    /* Allocate an EVP_CIPHER_CTX object. */
    ctx = EVP_CIPHER_CTX_new();
    if (!ctx)
    {
        pfree(od);
        return PXE_CIPHER_INIT;
    }
 
    od->evp_ctx = ctx;
    od->owner = CurrentResourceOwner;
    od->next = open_ciphers;
    od->prev = NULL;
    open_ciphers = od;
 
    if (i->ciph->cipher_func)
        od->evp_ciph = i->ciph->cipher_func();
 
    /* The PX_Cipher is allocated in current memory context */
    c = palloc(sizeof(*c));
    c->block_size = gen_ossl_block_size;
    c->key_size = gen_ossl_key_size;
    c->iv_size = gen_ossl_iv_size;
    c->free = gen_ossl_free;
    c->init = od->ciph->init;
    c->encrypt = gen_ossl_encrypt;
    c->decrypt = gen_ossl_decrypt;
    c->ptr = od;
 
    *res = c;
    return 0;
}