e_padlock.c

/*
 * Copyright 2004-2023 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/*
 * This file uses the low level AES and engine functions (which are deprecated
 * for non-internal use) in order to implement the padlock engine AES ciphers.
 */
#define OPENSSL_SUPPRESS_DEPRECATED

#include <stdio.h>
#include <string.h>

#include <openssl/opensslconf.h>
#include <openssl/crypto.h>
#include <openssl/engine.h>
#include <openssl/evp.h>
#include <openssl/aes.h>
#include <openssl/rand.h>
#include <openssl/err.h>
#include <openssl/modes.h>

#ifndef OPENSSL_NO_PADLOCKENG

/*
 * VIA PadLock AES is available *ONLY* on some x86 CPUs. Not only that it
 * doesn't exist elsewhere, but it even can't be compiled on other platforms!
 */

#undef COMPILE_PADLOCKENG
#if defined(PADLOCK_ASM)
#define COMPILE_PADLOCKENG
#ifdef OPENSSL_NO_DYNAMIC_ENGINE
static ENGINE *ENGINE_padlock(void);
#endif
#endif

#ifdef OPENSSL_NO_DYNAMIC_ENGINE
void engine_load_padlock_int(void);
void engine_load_padlock_int(void)
{
/* On non-x86 CPUs it just returns. */
#ifdef COMPILE_PADLOCKENG
    ENGINE *toadd = ENGINE_padlock();
    if (!toadd)
        return;
    ERR_set_mark();
    ENGINE_add(toadd);
    /*
     * If the "add" worked, it gets a structural reference. So either way, we
     * release our just-created reference.
     */
    ENGINE_free(toadd);
    /*
     * If the "add" didn't work, it was probably a conflict because it was
     * already added (eg. someone calling ENGINE_load_blah then calling
     * ENGINE_load_builtin_engines() perhaps).
     */
    ERR_pop_to_mark();
#endif
}

#endif

#ifdef COMPILE_PADLOCKENG

/* Function for ENGINE detection and control */
static int padlock_available(void);
static int padlock_init(ENGINE *e);

/* RNG Stuff */
static RAND_METHOD padlock_rand;

/* Cipher Stuff */
static int padlock_ciphers(ENGINE *e, const EVP_CIPHER **cipher,
    const int **nids, int nid);

/* Engine names */
static const char *padlock_id = "padlock";
static char padlock_name[100];

/* Available features */
static int padlock_use_ace = 0; /* Advanced Cryptography Engine */
static int padlock_use_rng = 0; /* Random Number Generator */

/* ===== Engine "management" functions ===== */

/* Prepare the ENGINE structure for registration */
static int padlock_bind_helper(ENGINE *e)
{
    /* Check available features */
    padlock_available();

    /*
     * RNG is currently disabled for reasons discussed in commentary just
     * before padlock_rand_bytes function.
     */
    padlock_use_rng = 0;

    /* Generate a nice engine name with available features */
    BIO_snprintf(padlock_name, sizeof(padlock_name),
        "VIA PadLock (%s, %s)",
        padlock_use_rng ? "RNG" : "no-RNG",
        padlock_use_ace ? "ACE" : "no-ACE");

    /* Register everything or return with an error */
    if (!ENGINE_set_id(e, padlock_id) || !ENGINE_set_name(e, padlock_name) || !ENGINE_set_init_function(e, padlock_init) || (padlock_use_ace && !ENGINE_set_ciphers(e, padlock_ciphers)) || (padlock_use_rng && !ENGINE_set_RAND(e, &padlock_rand))) {
        return 0;
    }

    /* Everything looks good */
    return 1;
}

#ifdef OPENSSL_NO_DYNAMIC_ENGINE
/* Constructor */
static ENGINE *ENGINE_padlock(void)
{
    ENGINE *eng = ENGINE_new();

    if (eng == NULL) {
        return NULL;
    }

    if (!padlock_bind_helper(eng)) {
        ENGINE_free(eng);
        return NULL;
    }

    return eng;
}
#endif

/* Check availability of the engine */
static int padlock_init(ENGINE *e)
{
    return (padlock_use_rng || padlock_use_ace);
}

#ifndef AES_ASM
static int padlock_aes_set_encrypt_key(const unsigned char *userKey,
    const int bits,
    AES_KEY *key);
static int padlock_aes_set_decrypt_key(const unsigned char *userKey,
    const int bits,
    AES_KEY *key);
#define AES_ASM
#define AES_set_encrypt_key padlock_aes_set_encrypt_key
#define AES_set_decrypt_key padlock_aes_set_decrypt_key
/* clang-format off */
#   include "../crypto/aes/aes_core.c"
/* clang-format on */
#endif

/*
 * This stuff is needed if this ENGINE is being compiled into a
 * self-contained shared-library.
 */
#ifndef OPENSSL_NO_DYNAMIC_ENGINE
static int padlock_bind_fn(ENGINE *e, const char *id)
{
    if (id && (strcmp(id, padlock_id) != 0)) {
        return 0;
    }

    if (!padlock_bind_helper(e)) {
        return 0;
    }

    return 1;
}

IMPLEMENT_DYNAMIC_CHECK_FN()
IMPLEMENT_DYNAMIC_BIND_FN(padlock_bind_fn)
#endif /* !OPENSSL_NO_DYNAMIC_ENGINE */
/* ===== Here comes the "real" engine ===== */

/* Some AES-related constants */
#define AES_BLOCK_SIZE 16
#define AES_KEY_SIZE_128 16
#define AES_KEY_SIZE_192 24
#define AES_KEY_SIZE_256 32
/*
 * Here we store the status information relevant to the current context.
 */
/*
 * BIG FAT WARNING: Inline assembler in PADLOCK_XCRYPT_ASM() depends on
 * the order of items in this structure.  Don't blindly modify, reorder,
 * etc!
 */
struct padlock_cipher_data {
    unsigned char iv[AES_BLOCK_SIZE]; /* Initialization vector */
    union {
        unsigned int pad[4];
        struct {
            int rounds : 4;
            int dgst : 1; /* n/a in C3 */
            int align : 1; /* n/a in C3 */
            int ciphr : 1; /* n/a in C3 */ /* codespell:ignore */
            unsigned int keygen : 1;
            int interm : 1; /* codespell:ignore */
            unsigned int encdec : 1;
            int ksize : 2;
        } b;
    } cword; /* Control word */
    AES_KEY ks; /* Encryption key */
};

/* Interface to assembler module */
unsigned int padlock_capability(void);
void padlock_key_bswap(AES_KEY *key);
void padlock_verify_context(struct padlock_cipher_data *ctx);
void padlock_reload_key(void);
void padlock_aes_block(void *out, const void *inp,
    struct padlock_cipher_data *ctx);
int padlock_ecb_encrypt(void *out, const void *inp,
    struct padlock_cipher_data *ctx, size_t len);
int padlock_cbc_encrypt(void *out, const void *inp,
    struct padlock_cipher_data *ctx, size_t len);
int padlock_cfb_encrypt(void *out, const void *inp,
    struct padlock_cipher_data *ctx, size_t len);
int padlock_ofb_encrypt(void *out, const void *inp,
    struct padlock_cipher_data *ctx, size_t len);
int padlock_ctr32_encrypt(void *out, const void *inp,
    struct padlock_cipher_data *ctx, size_t len);
int padlock_xstore(void *out, int edx);
void padlock_sha1_oneshot(void *ctx, const void *inp, size_t len);
void padlock_sha1(void *ctx, const void *inp, size_t len);
void padlock_sha256_oneshot(void *ctx, const void *inp, size_t len);
void padlock_sha256(void *ctx, const void *inp, size_t len);

/*
 * Load supported features of the CPU to see if the PadLock is available.
 */
static int padlock_available(void)
{
    unsigned int edx = padlock_capability();

    /* Fill up some flags */
    padlock_use_ace = ((edx & (0x3 << 6)) == (0x3 << 6));
    padlock_use_rng = ((edx & (0x3 << 2)) == (0x3 << 2));

    return padlock_use_ace + padlock_use_rng;
}

/* ===== AES encryption/decryption ===== */

#if defined(NID_aes_128_cfb128) && !defined(NID_aes_128_cfb)
#define NID_aes_128_cfb NID_aes_128_cfb128
#endif

#if defined(NID_aes_128_ofb128) && !defined(NID_aes_128_ofb)
#define NID_aes_128_ofb NID_aes_128_ofb128
#endif

#if defined(NID_aes_192_cfb128) && !defined(NID_aes_192_cfb)
#define NID_aes_192_cfb NID_aes_192_cfb128
#endif

#if defined(NID_aes_192_ofb128) && !defined(NID_aes_192_ofb)
#define NID_aes_192_ofb NID_aes_192_ofb128
#endif

#if defined(NID_aes_256_cfb128) && !defined(NID_aes_256_cfb)
#define NID_aes_256_cfb NID_aes_256_cfb128
#endif

#if defined(NID_aes_256_ofb128) && !defined(NID_aes_256_ofb)
#define NID_aes_256_ofb NID_aes_256_ofb128
#endif

/* List of supported ciphers. */
static const int padlock_cipher_nids[] = {
    NID_aes_128_ecb,
    NID_aes_128_cbc,
    NID_aes_128_cfb,
    NID_aes_128_ofb,
    NID_aes_128_ctr,

    NID_aes_192_ecb,
    NID_aes_192_cbc,
    NID_aes_192_cfb,
    NID_aes_192_ofb,
    NID_aes_192_ctr,

    NID_aes_256_ecb,
    NID_aes_256_cbc,
    NID_aes_256_cfb,
    NID_aes_256_ofb,
    NID_aes_256_ctr
};

static int padlock_cipher_nids_num = (sizeof(padlock_cipher_nids) / sizeof(padlock_cipher_nids[0]));

/* Function prototypes ... */
static int padlock_aes_init_key(EVP_CIPHER_CTX *ctx, const unsigned char *key,
    const unsigned char *iv, int enc);

#define NEAREST_ALIGNED(ptr) ((unsigned char *)(ptr) + ((0x10 - ((size_t)(ptr) & 0x0F)) & 0x0F))
#define ALIGNED_CIPHER_DATA(ctx) ((struct padlock_cipher_data *) \
        NEAREST_ALIGNED(EVP_CIPHER_CTX_get_cipher_data(ctx)))

static int
padlock_ecb_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out_arg,
    const unsigned char *in_arg, size_t nbytes)
{
    return padlock_ecb_encrypt(out_arg, in_arg,
        ALIGNED_CIPHER_DATA(ctx), nbytes);
}

static int
padlock_cbc_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out_arg,
    const unsigned char *in_arg, size_t nbytes)
{
    struct padlock_cipher_data *cdata = ALIGNED_CIPHER_DATA(ctx);
    int ret;

    memcpy(cdata->iv, EVP_CIPHER_CTX_iv(ctx), AES_BLOCK_SIZE);
    if ((ret = padlock_cbc_encrypt(out_arg, in_arg, cdata, nbytes)))
        memcpy(EVP_CIPHER_CTX_iv_noconst(ctx), cdata->iv, AES_BLOCK_SIZE);
    return ret;
}

static int
padlock_cfb_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out_arg,
    const unsigned char *in_arg, size_t nbytes)
{
    struct padlock_cipher_data *cdata = ALIGNED_CIPHER_DATA(ctx);
    size_t chunk;

    if ((chunk = EVP_CIPHER_CTX_get_num(ctx))) { /* borrow chunk variable */
        unsigned char *ivp = EVP_CIPHER_CTX_iv_noconst(ctx);

        if (chunk >= AES_BLOCK_SIZE)
            return 0; /* bogus value */

        if (EVP_CIPHER_CTX_is_encrypting(ctx))
            while (chunk < AES_BLOCK_SIZE && nbytes != 0) {
                ivp[chunk] = *(out_arg++) = *(in_arg++) ^ ivp[chunk];
                chunk++, nbytes--;
            }
        else
            while (chunk < AES_BLOCK_SIZE && nbytes != 0) {
                unsigned char c = *(in_arg++);
                *(out_arg++) = c ^ ivp[chunk];
                ivp[chunk++] = c, nbytes--;
            }

        EVP_CIPHER_CTX_set_num(ctx, chunk % AES_BLOCK_SIZE);
    }

    if (nbytes == 0)
        return 1;

    memcpy(cdata->iv, EVP_CIPHER_CTX_iv(ctx), AES_BLOCK_SIZE);

    if ((chunk = nbytes & ~(AES_BLOCK_SIZE - 1))) {
        if (!padlock_cfb_encrypt(out_arg, in_arg, cdata, chunk))
            return 0;
        nbytes -= chunk;
    }

    if (nbytes) {
        unsigned char *ivp = cdata->iv;

        out_arg += chunk;
        in_arg += chunk;
        EVP_CIPHER_CTX_set_num(ctx, nbytes);
        if (cdata->cword.b.encdec) {
            cdata->cword.b.encdec = 0;
            padlock_reload_key();
            padlock_aes_block(ivp, ivp, cdata);
            cdata->cword.b.encdec = 1;
            padlock_reload_key();
            while (nbytes) {
                unsigned char c = *(in_arg++);
                *(out_arg++) = c ^ *ivp;
                *(ivp++) = c, nbytes--;
            }
        } else {
            padlock_reload_key();
            padlock_aes_block(ivp, ivp, cdata);
            padlock_reload_key();
            while (nbytes) {
                *ivp = *(out_arg++) = *(in_arg++) ^ *ivp;
                ivp++, nbytes--;
            }
        }
    }

    memcpy(EVP_CIPHER_CTX_iv_noconst(ctx), cdata->iv, AES_BLOCK_SIZE);

    return 1;
}

static int
padlock_ofb_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out_arg,
    const unsigned char *in_arg, size_t nbytes)
{
    struct padlock_cipher_data *cdata = ALIGNED_CIPHER_DATA(ctx);
    size_t chunk;

    /*
     * ctx->num is maintained in byte-oriented modes, such as CFB and OFB...
     */
    if ((chunk = EVP_CIPHER_CTX_get_num(ctx))) { /* borrow chunk variable */
        unsigned char *ivp = EVP_CIPHER_CTX_iv_noconst(ctx);

        if (chunk >= AES_BLOCK_SIZE)
            return 0; /* bogus value */

        while (chunk < AES_BLOCK_SIZE && nbytes != 0) {
            *(out_arg++) = *(in_arg++) ^ ivp[chunk];
            chunk++, nbytes--;
        }

        EVP_CIPHER_CTX_set_num(ctx, chunk % AES_BLOCK_SIZE);
    }

    if (nbytes == 0)
        return 1;

    memcpy(cdata->iv, EVP_CIPHER_CTX_iv(ctx), AES_BLOCK_SIZE);

    if ((chunk = nbytes & ~(AES_BLOCK_SIZE - 1))) {
        if (!padlock_ofb_encrypt(out_arg, in_arg, cdata, chunk))
            return 0;
        nbytes -= chunk;
    }

    if (nbytes) {
        unsigned char *ivp = cdata->iv;

        out_arg += chunk;
        in_arg += chunk;
        EVP_CIPHER_CTX_set_num(ctx, nbytes);
        padlock_reload_key(); /* empirically found */
        padlock_aes_block(ivp, ivp, cdata);
        padlock_reload_key(); /* empirically found */
        while (nbytes) {
            *(out_arg++) = *(in_arg++) ^ *ivp;
            ivp++, nbytes--;
        }
    }

    memcpy(EVP_CIPHER_CTX_iv_noconst(ctx), cdata->iv, AES_BLOCK_SIZE);

    return 1;
}

static void padlock_ctr32_encrypt_glue(const unsigned char *in,
    unsigned char *out, size_t blocks,
    struct padlock_cipher_data *ctx,
    const unsigned char *ivec)
{
    memcpy(ctx->iv, ivec, AES_BLOCK_SIZE);
    padlock_ctr32_encrypt(out, in, ctx, AES_BLOCK_SIZE * blocks);
}

static int
padlock_ctr_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out_arg,
    const unsigned char *in_arg, size_t nbytes)
{
    struct padlock_cipher_data *cdata = ALIGNED_CIPHER_DATA(ctx);
    int n = EVP_CIPHER_CTX_get_num(ctx);
    unsigned int num;

    if (n < 0)
        return 0;
    num = (unsigned int)n;

    CRYPTO_ctr128_encrypt_ctr32(in_arg, out_arg, nbytes,
        cdata, EVP_CIPHER_CTX_iv_noconst(ctx),
        EVP_CIPHER_CTX_buf_noconst(ctx), &num,
        (ctr128_f)padlock_ctr32_encrypt_glue);

    EVP_CIPHER_CTX_set_num(ctx, (size_t)num);
    return 1;
}

#define EVP_CIPHER_block_size_ECB AES_BLOCK_SIZE
#define EVP_CIPHER_block_size_CBC AES_BLOCK_SIZE
#define EVP_CIPHER_block_size_OFB 1
#define EVP_CIPHER_block_size_CFB 1
#define EVP_CIPHER_block_size_CTR 1

/*
 * Declaring so many ciphers by hand would be a pain. Instead introduce a bit
 * of preprocessor magic :-)
 */
#define DECLARE_AES_EVP(ksize, lmode, umode)                                                    \
    static EVP_CIPHER *_hidden_aes_##ksize##_##lmode = NULL;                                    \
    static const EVP_CIPHER *padlock_aes_##ksize##_##lmode(void)                                \
    {                                                                                           \
        if (_hidden_aes_##ksize##_##lmode == NULL                                               \
            && ((_hidden_aes_##ksize##_##lmode = EVP_CIPHER_meth_new(NID_aes_##ksize##_##lmode, \
                     EVP_CIPHER_block_size_##umode,                                             \
                     AES_KEY_SIZE_##ksize))                                                     \
                    == NULL                                                                     \
                || !EVP_CIPHER_meth_set_iv_length(_hidden_aes_##ksize##_##lmode,                \
                    AES_BLOCK_SIZE)                                                             \
                || !EVP_CIPHER_meth_set_flags(_hidden_aes_##ksize##_##lmode,                    \
                    0 | EVP_CIPH_##umode##_MODE)                                                \
                || !EVP_CIPHER_meth_set_init(_hidden_aes_##ksize##_##lmode,                     \
                    padlock_aes_init_key)                                                       \
                || !EVP_CIPHER_meth_set_do_cipher(_hidden_aes_##ksize##_##lmode,                \
                    padlock_##lmode##_cipher)                                                   \
                || !EVP_CIPHER_meth_set_impl_ctx_size(_hidden_aes_##ksize##_##lmode,            \
                    sizeof(struct padlock_cipher_data) + 16)                                    \
                || !EVP_CIPHER_meth_set_set_asn1_params(_hidden_aes_##ksize##_##lmode,          \
                    EVP_CIPHER_set_asn1_iv)                                                     \
                || !EVP_CIPHER_meth_set_get_asn1_params(_hidden_aes_##ksize##_##lmode,          \
                    EVP_CIPHER_get_asn1_iv))) {                                                 \
            EVP_CIPHER_meth_free(_hidden_aes_##ksize##_##lmode);                                \
            _hidden_aes_##ksize##_##lmode = NULL;                                               \
        }                                                                                       \
        return _hidden_aes_##ksize##_##lmode;                                                   \
    }

DECLARE_AES_EVP(128, ecb, ECB)
DECLARE_AES_EVP(128, cbc, CBC)
DECLARE_AES_EVP(128, cfb, CFB)
DECLARE_AES_EVP(128, ofb, OFB)
DECLARE_AES_EVP(128, ctr, CTR)

DECLARE_AES_EVP(192, ecb, ECB)
DECLARE_AES_EVP(192, cbc, CBC)
DECLARE_AES_EVP(192, cfb, CFB)
DECLARE_AES_EVP(192, ofb, OFB)
DECLARE_AES_EVP(192, ctr, CTR)

DECLARE_AES_EVP(256, ecb, ECB)
DECLARE_AES_EVP(256, cbc, CBC)
DECLARE_AES_EVP(256, cfb, CFB)
DECLARE_AES_EVP(256, ofb, OFB)
DECLARE_AES_EVP(256, ctr, CTR)

static int
padlock_ciphers(ENGINE *e, const EVP_CIPHER **cipher, const int **nids,
    int nid)
{
    /* No specific cipher => return a list of supported nids ... */
    if (!cipher) {
        *nids = padlock_cipher_nids;
        return padlock_cipher_nids_num;
    }

    /* ... or the requested "cipher" otherwise */
    switch (nid) {
    case NID_aes_128_ecb:
        *cipher = padlock_aes_128_ecb();
        break;
    case NID_aes_128_cbc:
        *cipher = padlock_aes_128_cbc();
        break;
    case NID_aes_128_cfb:
        *cipher = padlock_aes_128_cfb();
        break;
    case NID_aes_128_ofb:
        *cipher = padlock_aes_128_ofb();
        break;
    case NID_aes_128_ctr:
        *cipher = padlock_aes_128_ctr();
        break;

    case NID_aes_192_ecb:
        *cipher = padlock_aes_192_ecb();
        break;
    case NID_aes_192_cbc:
        *cipher = padlock_aes_192_cbc();
        break;
    case NID_aes_192_cfb:
        *cipher = padlock_aes_192_cfb();
        break;
    case NID_aes_192_ofb:
        *cipher = padlock_aes_192_ofb();
        break;
    case NID_aes_192_ctr:
        *cipher = padlock_aes_192_ctr();
        break;

    case NID_aes_256_ecb:
        *cipher = padlock_aes_256_ecb();
        break;
    case NID_aes_256_cbc:
        *cipher = padlock_aes_256_cbc();
        break;
    case NID_aes_256_cfb:
        *cipher = padlock_aes_256_cfb();
        break;
    case NID_aes_256_ofb:
        *cipher = padlock_aes_256_ofb();
        break;
    case NID_aes_256_ctr:
        *cipher = padlock_aes_256_ctr();
        break;

    default:
        /* Sorry, we don't support this NID */
        *cipher = NULL;
        return 0;
    }

    return 1;
}

/* Prepare the encryption key for PadLock usage */
static int
padlock_aes_init_key(EVP_CIPHER_CTX *ctx, const unsigned char *key,
    const unsigned char *iv, int enc)
{
    struct padlock_cipher_data *cdata;
    int key_len = EVP_CIPHER_CTX_get_key_length(ctx) * 8;
    unsigned long mode = EVP_CIPHER_CTX_get_mode(ctx);

    if (key == NULL)
        return 0; /* ERROR */

    cdata = ALIGNED_CIPHER_DATA(ctx);
    memset(cdata, 0, sizeof(*cdata));

    /* Prepare Control word. */
    if (mode == EVP_CIPH_OFB_MODE || mode == EVP_CIPH_CTR_MODE)
        cdata->cword.b.encdec = 0;
    else
        cdata->cword.b.encdec = (EVP_CIPHER_CTX_is_encrypting(ctx) == 0);
    cdata->cword.b.rounds = 10 + (key_len - 128) / 32;
    cdata->cword.b.ksize = (key_len - 128) / 64;

    switch (key_len) {
    case 128:
        /*
         * PadLock can generate an extended key for AES128 in hardware
         */
        memcpy(cdata->ks.rd_key, key, AES_KEY_SIZE_128);
        cdata->cword.b.keygen = 0;
        break;

    case 192:
    case 256:
        /*
         * Generate an extended AES key in software. Needed for AES192/AES256
         */
        /*
         * Well, the above applies to Stepping 8 CPUs and is listed as
         * hardware errata. They most likely will fix it at some point and
         * then a check for stepping would be due here.
         */
        if ((mode == EVP_CIPH_ECB_MODE || mode == EVP_CIPH_CBC_MODE)
            && !enc)
            AES_set_decrypt_key(key, key_len, &cdata->ks);
        else
            AES_set_encrypt_key(key, key_len, &cdata->ks);
        /*
         * OpenSSL C functions use byte-swapped extended key.
         */
        padlock_key_bswap(&cdata->ks);
        cdata->cword.b.keygen = 1;
        break;

    default:
        /* ERROR */
        return 0;
    }

    /*
     * This is done to cover for cases when user reuses the
     * context for new key. The catch is that if we don't do
     * this, padlock_eas_cipher might proceed with old key...
     */
    padlock_reload_key();

    return 1;
}

/* ===== Random Number Generator ===== */
/*
 * This code is not engaged. The reason is that it does not comply
 * with recommendations for VIA RNG usage for secure applications
 * (posted at http://www.via.com.tw/en/viac3/c3.jsp) nor does it
 * provide meaningful error control...
 */
/*
 * Wrapper that provides an interface between the API and the raw PadLock
 * RNG
 */
static int padlock_rand_bytes(unsigned char *output, int count)
{
    unsigned int eax, buf;

    while (count >= 8) {
        eax = padlock_xstore(output, 0);
        if (!(eax & (1 << 6)))
            return 0; /* RNG disabled */
        /* this ---vv--- covers DC bias, Raw Bits and String Filter */
        if (eax & (0x1F << 10))
            return 0;
        if ((eax & 0x1F) == 0)
            continue; /* no data, retry... */
        if ((eax & 0x1F) != 8)
            return 0; /* fatal failure...  */
        output += 8;
        count -= 8;
    }
    while (count > 0) {
        eax = padlock_xstore(&buf, 3);
        if (!(eax & (1 << 6)))
            return 0; /* RNG disabled */
        /* this ---vv--- covers DC bias, Raw Bits and String Filter */
        if (eax & (0x1F << 10))
            return 0;
        if ((eax & 0x1F) == 0)
            continue; /* no data, retry... */
        if ((eax & 0x1F) != 1)
            return 0; /* fatal failure...  */
        *output++ = (unsigned char)buf;
        count--;
    }
    OPENSSL_cleanse(&buf, sizeof(buf));

    return 1;
}

/* Dummy but necessary function */
static int padlock_rand_status(void)
{
    return 1;
}

/* Prepare structure for registration */
static RAND_METHOD padlock_rand = {
    NULL, /* seed */
    padlock_rand_bytes, /* bytes */
    NULL, /* cleanup */
    NULL, /* add */
    padlock_rand_bytes, /* pseudorand */
    padlock_rand_status, /* rand status */
};

#endif /* COMPILE_PADLOCKENG */
#endif /* !OPENSSL_NO_PADLOCKENG */

#if defined(OPENSSL_NO_PADLOCKENG) || !defined(COMPILE_PADLOCKENG)
#ifndef OPENSSL_NO_DYNAMIC_ENGINE
OPENSSL_EXPORT
int bind_engine(ENGINE *e, const char *id, const dynamic_fns *fns);
OPENSSL_EXPORT
int bind_engine(ENGINE *e, const char *id, const dynamic_fns *fns)
{
    return 0;
}

IMPLEMENT_DYNAMIC_CHECK_FN()
#endif
#endif