bn_lib.c 22.9 KB
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/*
 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
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 *
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 * Licensed under the OpenSSL license (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
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 */

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#include <assert.h>
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#include <limits.h>
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#include "internal/cryptlib.h"
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#include "bn_lcl.h"
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#include <openssl/opensslconf.h>
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/* This stuff appears to be completely unused, so is deprecated */
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#if OPENSSL_API_COMPAT < 0x00908000L
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/*-
 * For a 32 bit machine
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 * 2 -   4 ==  128
 * 3 -   8 ==  256
 * 4 -  16 ==  512
 * 5 -  32 == 1024
 * 6 -  64 == 2048
 * 7 - 128 == 4096
 * 8 - 256 == 8192
 */
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static int bn_limit_bits = 0;
static int bn_limit_num = 8;    /* (1<<bn_limit_bits) */
static int bn_limit_bits_low = 0;
static int bn_limit_num_low = 8; /* (1<<bn_limit_bits_low) */
static int bn_limit_bits_high = 0;
static int bn_limit_num_high = 8; /* (1<<bn_limit_bits_high) */
static int bn_limit_bits_mont = 0;
static int bn_limit_num_mont = 8; /* (1<<bn_limit_bits_mont) */
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void BN_set_params(int mult, int high, int low, int mont)
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{
    if (mult >= 0) {
        if (mult > (int)(sizeof(int) * 8) - 1)
            mult = sizeof(int) * 8 - 1;
        bn_limit_bits = mult;
        bn_limit_num = 1 << mult;
    }
    if (high >= 0) {
        if (high > (int)(sizeof(int) * 8) - 1)
            high = sizeof(int) * 8 - 1;
        bn_limit_bits_high = high;
        bn_limit_num_high = 1 << high;
    }
    if (low >= 0) {
        if (low > (int)(sizeof(int) * 8) - 1)
            low = sizeof(int) * 8 - 1;
        bn_limit_bits_low = low;
        bn_limit_num_low = 1 << low;
    }
    if (mont >= 0) {
        if (mont > (int)(sizeof(int) * 8) - 1)
            mont = sizeof(int) * 8 - 1;
        bn_limit_bits_mont = mont;
        bn_limit_num_mont = 1 << mont;
    }
}
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int BN_get_params(int which)
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{
    if (which == 0)
        return (bn_limit_bits);
    else if (which == 1)
        return (bn_limit_bits_high);
    else if (which == 2)
        return (bn_limit_bits_low);
    else if (which == 3)
        return (bn_limit_bits_mont);
    else
        return (0);
}
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#endif
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const BIGNUM *BN_value_one(void)
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{
    static const BN_ULONG data_one = 1L;
    static const BIGNUM const_one =
        { (BN_ULONG *)&data_one, 1, 1, 0, BN_FLG_STATIC_DATA };
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    return (&const_one);
}
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int BN_num_bits_word(BN_ULONG l)
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{
    static const unsigned char bits[256] = {
        0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
        5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
        7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
        7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
        7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
        7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    };
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#if defined(SIXTY_FOUR_BIT_LONG)
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    if (l & 0xffffffff00000000L) {
        if (l & 0xffff000000000000L) {
            if (l & 0xff00000000000000L) {
                return (bits[(int)(l >> 56)] + 56);
            } else
                return (bits[(int)(l >> 48)] + 48);
        } else {
            if (l & 0x0000ff0000000000L) {
                return (bits[(int)(l >> 40)] + 40);
            } else
                return (bits[(int)(l >> 32)] + 32);
        }
    } else
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#else
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# ifdef SIXTY_FOUR_BIT
    if (l & 0xffffffff00000000LL) {
        if (l & 0xffff000000000000LL) {
            if (l & 0xff00000000000000LL) {
                return (bits[(int)(l >> 56)] + 56);
            } else
                return (bits[(int)(l >> 48)] + 48);
        } else {
            if (l & 0x0000ff0000000000LL) {
                return (bits[(int)(l >> 40)] + 40);
            } else
                return (bits[(int)(l >> 32)] + 32);
        }
    } else
# endif
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#endif
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    {
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#if defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)
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        if (l & 0xffff0000L) {
            if (l & 0xff000000L)
                return (bits[(int)(l >> 24L)] + 24);
            else
                return (bits[(int)(l >> 16L)] + 16);
        } else
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#endif
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        {
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#if defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)
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            if (l & 0xff00L)
                return (bits[(int)(l >> 8)] + 8);
            else
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#endif
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                return (bits[(int)(l)]);
        }
    }
}
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int BN_num_bits(const BIGNUM *a)
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{
    int i = a->top - 1;
    bn_check_top(a);
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    if (BN_is_zero(a))
        return 0;
    return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
}
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static void bn_free_d(BIGNUM *a)
{
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    if (BN_get_flags(a, BN_FLG_SECURE))
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        OPENSSL_secure_free(a->d);
    else
        OPENSSL_free(a->d);
}


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void BN_clear_free(BIGNUM *a)
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{
    int i;

    if (a == NULL)
        return;
    bn_check_top(a);
    if (a->d != NULL) {
        OPENSSL_cleanse(a->d, a->dmax * sizeof(a->d[0]));
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        if (!BN_get_flags(a, BN_FLG_STATIC_DATA))
            bn_free_d(a);
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    }
    i = BN_get_flags(a, BN_FLG_MALLOCED);
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    OPENSSL_cleanse(a, sizeof(*a));
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    if (i)
        OPENSSL_free(a);
}
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void BN_free(BIGNUM *a)
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{
    if (a == NULL)
        return;
    bn_check_top(a);
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    if (!BN_get_flags(a, BN_FLG_STATIC_DATA))
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        bn_free_d(a);
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    if (a->flags & BN_FLG_MALLOCED)
        OPENSSL_free(a);
    else {
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#if OPENSSL_API_COMPAT < 0x00908000L
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        a->flags |= BN_FLG_FREE;
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#endif
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        a->d = NULL;
    }
}
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void bn_init(BIGNUM *a)
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{
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    static BIGNUM nilbn;

    *a = nilbn;
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    bn_check_top(a);
}
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BIGNUM *BN_new(void)
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{
    BIGNUM *ret;

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    if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {
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        BNerr(BN_F_BN_NEW, ERR_R_MALLOC_FAILURE);
        return (NULL);
    }
    ret->flags = BN_FLG_MALLOCED;
    bn_check_top(ret);
    return (ret);
}
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 BIGNUM *BN_secure_new(void)
 {
     BIGNUM *ret = BN_new();
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     if (ret != NULL)
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         ret->flags |= BN_FLG_SECURE;
     return (ret);
 }

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/* This is used by bn_expand2() */
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/* The caller MUST check that words > b->dmax before calling this */
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static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
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{
    BN_ULONG *A, *a = NULL;
    const BN_ULONG *B;
    int i;

    bn_check_top(b);

    if (words > (INT_MAX / (4 * BN_BITS2))) {
        BNerr(BN_F_BN_EXPAND_INTERNAL, BN_R_BIGNUM_TOO_LONG);
        return NULL;
    }
    if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
        BNerr(BN_F_BN_EXPAND_INTERNAL, BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
        return (NULL);
    }
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    if (BN_get_flags(b, BN_FLG_SECURE))
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        a = A = OPENSSL_secure_zalloc(words * sizeof(*a));
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    else
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        a = A = OPENSSL_zalloc(words * sizeof(*a));
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    if (A == NULL) {
        BNerr(BN_F_BN_EXPAND_INTERNAL, ERR_R_MALLOC_FAILURE);
        return (NULL);
    }
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#if 1
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    B = b->d;
    /* Check if the previous number needs to be copied */
    if (B != NULL) {
        for (i = b->top >> 2; i > 0; i--, A += 4, B += 4) {
            /*
             * The fact that the loop is unrolled
             * 4-wise is a tribute to Intel. It's
             * the one that doesn't have enough
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             * registers to accommodate more data.
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             * I'd unroll it 8-wise otherwise:-)
             *
             *              <appro@fy.chalmers.se>
             */
            BN_ULONG a0, a1, a2, a3;
            a0 = B[0];
            a1 = B[1];
            a2 = B[2];
            a3 = B[3];
            A[0] = a0;
            A[1] = a1;
            A[2] = a2;
            A[3] = a3;
        }
        switch (b->top & 3) {
        case 3:
            A[2] = B[2];
        case 2:
            A[1] = B[1];
        case 1:
            A[0] = B[0];
        case 0:
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            /* Without the "case 0" some old optimizers got this wrong. */
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            ;
        }
    }
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#else
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    memset(A, 0, sizeof(*A) * words);
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    memcpy(A, b->d, sizeof(b->d[0]) * b->top);
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#endif

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    return (a);
}

/*
 * This is an internal function that should not be used in applications. It
 * ensures that 'b' has enough room for a 'words' word number and initialises
 * any unused part of b->d with leading zeros. It is mostly used by the
 * various BIGNUM routines. If there is an error, NULL is returned. If not,
 * 'b' is returned.
 */
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BIGNUM *bn_expand2(BIGNUM *b, int words)
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{
    bn_check_top(b);

    if (words > b->dmax) {
        BN_ULONG *a = bn_expand_internal(b, words);
        if (!a)
            return NULL;
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        if (b->d) {
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            OPENSSL_cleanse(b->d, b->dmax * sizeof(b->d[0]));
            bn_free_d(b);
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        }
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        b->d = a;
        b->dmax = words;
    }
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    bn_check_top(b);
    return b;
}
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BIGNUM *BN_dup(const BIGNUM *a)
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{
    BIGNUM *t;

    if (a == NULL)
        return NULL;
    bn_check_top(a);

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    t = BN_get_flags(a, BN_FLG_SECURE) ? BN_secure_new() : BN_new();
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    if (t == NULL)
        return NULL;
    if (!BN_copy(t, a)) {
        BN_free(t);
        return NULL;
    }
    bn_check_top(t);
    return t;
}
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BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
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{
    int i;
    BN_ULONG *A;
    const BN_ULONG *B;
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    bn_check_top(b);
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    if (a == b)
        return (a);
    if (bn_wexpand(a, b->top) == NULL)
        return (NULL);
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    A = a->d;
    B = b->d;
    for (i = b->top >> 2; i > 0; i--, A += 4, B += 4) {
        BN_ULONG a0, a1, a2, a3;
        a0 = B[0];
        a1 = B[1];
        a2 = B[2];
        a3 = B[3];
        A[0] = a0;
        A[1] = a1;
        A[2] = a2;
        A[3] = a3;
    }
    /* ultrix cc workaround, see comments in bn_expand_internal */
    switch (b->top & 3) {
    case 3:
        A[2] = B[2];
    case 2:
        A[1] = B[1];
    case 1:
        A[0] = B[0];
    case 0:;
    }
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#else
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    memcpy(a->d, b->d, sizeof(b->d[0]) * b->top);
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#endif

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    a->top = b->top;
    a->neg = b->neg;
    bn_check_top(a);
    return (a);
}
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void BN_swap(BIGNUM *a, BIGNUM *b)
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{
    int flags_old_a, flags_old_b;
    BN_ULONG *tmp_d;
    int tmp_top, tmp_dmax, tmp_neg;

    bn_check_top(a);
    bn_check_top(b);

    flags_old_a = a->flags;
    flags_old_b = b->flags;

    tmp_d = a->d;
    tmp_top = a->top;
    tmp_dmax = a->dmax;
    tmp_neg = a->neg;

    a->d = b->d;
    a->top = b->top;
    a->dmax = b->dmax;
    a->neg = b->neg;

    b->d = tmp_d;
    b->top = tmp_top;
    b->dmax = tmp_dmax;
    b->neg = tmp_neg;

    a->flags =
        (flags_old_a & BN_FLG_MALLOCED) | (flags_old_b & BN_FLG_STATIC_DATA);
    b->flags =
        (flags_old_b & BN_FLG_MALLOCED) | (flags_old_a & BN_FLG_STATIC_DATA);
    bn_check_top(a);
    bn_check_top(b);
}
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void BN_clear(BIGNUM *a)
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{
    bn_check_top(a);
    if (a->d != NULL)
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        OPENSSL_cleanse(a->d, sizeof(*a->d) * a->dmax);
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    a->top = 0;
    a->neg = 0;
}
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BN_ULONG BN_get_word(const BIGNUM *a)
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{
    if (a->top > 1)
        return BN_MASK2;
    else if (a->top == 1)
        return a->d[0];
    /* a->top == 0 */
    return 0;
}
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int BN_set_word(BIGNUM *a, BN_ULONG w)
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{
    bn_check_top(a);
    if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
        return (0);
    a->neg = 0;
    a->d[0] = w;
    a->top = (w ? 1 : 0);
    bn_check_top(a);
    return (1);
}
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BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
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{
    unsigned int i, m;
    unsigned int n;
    BN_ULONG l;
    BIGNUM *bn = NULL;

    if (ret == NULL)
        ret = bn = BN_new();
    if (ret == NULL)
        return (NULL);
    bn_check_top(ret);
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    /* Skip leading zero's. */
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    for ( ; len > 0 && *s == 0; s++, len--)
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        continue;
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    n = len;
    if (n == 0) {
        ret->top = 0;
        return (ret);
    }
    i = ((n - 1) / BN_BYTES) + 1;
    m = ((n - 1) % (BN_BYTES));
    if (bn_wexpand(ret, (int)i) == NULL) {
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        BN_free(bn);
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        return NULL;
    }
    ret->top = i;
    ret->neg = 0;
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    l = 0;
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    while (n--) {
        l = (l << 8L) | *(s++);
        if (m-- == 0) {
            ret->d[--i] = l;
            l = 0;
            m = BN_BYTES - 1;
        }
    }
    /*
     * need to call this due to clear byte at top if avoiding having the top
     * bit set (-ve number)
     */
    bn_correct_top(ret);
    return (ret);
}
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/* ignore negative */
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static int bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
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{
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    int i;
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    BN_ULONG l;

    bn_check_top(a);
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    i = BN_num_bytes(a);
    if (tolen == -1)
        tolen = i;
    else if (tolen < i)
        return -1;
    /* Add leading zeroes if necessary */
    if (tolen > i) {
        memset(to, 0, tolen - i);
        to += tolen - i;
    }
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    while (i--) {
        l = a->d[i / BN_BYTES];
        *(to++) = (unsigned char)(l >> (8 * (i % BN_BYTES))) & 0xff;
    }
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    return tolen;
}

int BN_bn2binpad(const BIGNUM *a, unsigned char *to, int tolen)
{
    if (tolen < 0)
        return -1;
    return bn2binpad(a, to, tolen);
}

int BN_bn2bin(const BIGNUM *a, unsigned char *to)
{
    return bn2binpad(a, to, -1);
}

BIGNUM *BN_lebin2bn(const unsigned char *s, int len, BIGNUM *ret)
{
    unsigned int i, m;
    unsigned int n;
    BN_ULONG l;
    BIGNUM *bn = NULL;

    if (ret == NULL)
        ret = bn = BN_new();
    if (ret == NULL)
        return (NULL);
    bn_check_top(ret);
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    s += len;
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    /* Skip trailing zeroes. */
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    for ( ; len > 0 && s[-1] == 0; s--, len--)
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        continue;
    n = len;
    if (n == 0) {
        ret->top = 0;
        return ret;
    }
    i = ((n - 1) / BN_BYTES) + 1;
    m = ((n - 1) % (BN_BYTES));
    if (bn_wexpand(ret, (int)i) == NULL) {
        BN_free(bn);
        return NULL;
    }
    ret->top = i;
    ret->neg = 0;
    l = 0;
    while (n--) {
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        s--;
        l = (l << 8L) | *s;
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        if (m-- == 0) {
            ret->d[--i] = l;
            l = 0;
            m = BN_BYTES - 1;
        }
    }
    /*
     * need to call this due to clear byte at top if avoiding having the top
     * bit set (-ve number)
     */
    bn_correct_top(ret);
    return ret;
}

int BN_bn2lebinpad(const BIGNUM *a, unsigned char *to, int tolen)
{
    int i;
    BN_ULONG l;
    bn_check_top(a);
    i = BN_num_bytes(a);
    if (tolen < i)
        return -1;
    /* Add trailing zeroes if necessary */
    if (tolen > i)
        memset(to + i, 0, tolen - i);
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    to += i;
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    while (i--) {
        l = a->d[i / BN_BYTES];
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        to--;
        *to = (unsigned char)(l >> (8 * (i % BN_BYTES))) & 0xff;
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    }
    return tolen;
621
}
622

623
int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643
{
    int i;
    BN_ULONG t1, t2, *ap, *bp;

    bn_check_top(a);
    bn_check_top(b);

    i = a->top - b->top;
    if (i != 0)
        return (i);
    ap = a->d;
    bp = b->d;
    for (i = a->top - 1; i >= 0; i--) {
        t1 = ap[i];
        t2 = bp[i];
        if (t1 != t2)
            return ((t1 > t2) ? 1 : -1);
    }
    return (0);
}
644

645
int BN_cmp(const BIGNUM *a, const BIGNUM *b)
646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690
{
    int i;
    int gt, lt;
    BN_ULONG t1, t2;

    if ((a == NULL) || (b == NULL)) {
        if (a != NULL)
            return (-1);
        else if (b != NULL)
            return (1);
        else
            return (0);
    }

    bn_check_top(a);
    bn_check_top(b);

    if (a->neg != b->neg) {
        if (a->neg)
            return (-1);
        else
            return (1);
    }
    if (a->neg == 0) {
        gt = 1;
        lt = -1;
    } else {
        gt = -1;
        lt = 1;
    }

    if (a->top > b->top)
        return (gt);
    if (a->top < b->top)
        return (lt);
    for (i = a->top - 1; i >= 0; i--) {
        t1 = a->d[i];
        t2 = b->d[i];
        if (t1 > t2)
            return (gt);
        if (t1 < t2)
            return (lt);
    }
    return (0);
}
691

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int BN_set_bit(BIGNUM *a, int n)
693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712
{
    int i, j, k;

    if (n < 0)
        return 0;

    i = n / BN_BITS2;
    j = n % BN_BITS2;
    if (a->top <= i) {
        if (bn_wexpand(a, i + 1) == NULL)
            return (0);
        for (k = a->top; k < i + 1; k++)
            a->d[k] = 0;
        a->top = i + 1;
    }

    a->d[i] |= (((BN_ULONG)1) << j);
    bn_check_top(a);
    return (1);
}
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int BN_clear_bit(BIGNUM *a, int n)
715 716
{
    int i, j;
717

718 719 720
    bn_check_top(a);
    if (n < 0)
        return 0;
721

722 723 724 725
    i = n / BN_BITS2;
    j = n % BN_BITS2;
    if (a->top <= i)
        return (0);
726

727 728 729 730
    a->d[i] &= (~(((BN_ULONG)1) << j));
    bn_correct_top(a);
    return (1);
}
731

732
int BN_is_bit_set(const BIGNUM *a, int n)
733 734 735 736 737 738 739 740 741 742 743 744
{
    int i, j;

    bn_check_top(a);
    if (n < 0)
        return 0;
    i = n / BN_BITS2;
    j = n % BN_BITS2;
    if (a->top <= i)
        return 0;
    return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
}
745

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int BN_mask_bits(BIGNUM *a, int n)
747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766
{
    int b, w;

    bn_check_top(a);
    if (n < 0)
        return 0;

    w = n / BN_BITS2;
    b = n % BN_BITS2;
    if (w >= a->top)
        return 0;
    if (b == 0)
        a->top = w;
    else {
        a->top = w + 1;
        a->d[w] &= ~(BN_MASK2 << b);
    }
    bn_correct_top(a);
    return (1);
}
767

768
void BN_set_negative(BIGNUM *a, int b)
769 770 771 772 773 774
{
    if (b && !BN_is_zero(a))
        a->neg = 1;
    else
        a->neg = 0;
}
775

776
int bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795
{
    int i;
    BN_ULONG aa, bb;

    aa = a[n - 1];
    bb = b[n - 1];
    if (aa != bb)
        return ((aa > bb) ? 1 : -1);
    for (i = n - 2; i >= 0; i--) {
        aa = a[i];
        bb = b[i];
        if (aa != bb)
            return ((aa > bb) ? 1 : -1);
    }
    return (0);
}

/*
 * Here follows a specialised variants of bn_cmp_words().  It has the
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 * capability of performing the operation on arrays of different sizes. The
797
 * sizes of those arrays is expressed through cl, which is the common length
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 * ( basically, min(len(a),len(b)) ), and dl, which is the delta between the
799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824
 * two lengths, calculated as len(a)-len(b). All lengths are the number of
 * BN_ULONGs...
 */

int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
{
    int n, i;
    n = cl - 1;

    if (dl < 0) {
        for (i = dl; i < 0; i++) {
            if (b[n - i] != 0)
                return -1;      /* a < b */
        }
    }
    if (dl > 0) {
        for (i = dl; i > 0; i--) {
            if (a[n + i] != 0)
                return 1;       /* a > b */
        }
    }
    return bn_cmp_words(a, b, cl);
}

/*
 * Constant-time conditional swap of a and b.
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 * a and b are swapped if condition is not 0.  The code assumes that at most one bit of condition is set.
 * nwords is the number of words to swap.  The code assumes that at least nwords are allocated in both a and b,
 * and that no more than nwords are used by either a or b.
 * a and b cannot be the same number
 */
void BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
831 832 833
{
    BN_ULONG t;
    int i;
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835 836
    bn_wcheck_size(a, nwords);
    bn_wcheck_size(b, nwords);
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838 839 840
    assert(a != b);
    assert((condition & (condition - 1)) == 0);
    assert(sizeof(BN_ULONG) >= sizeof(int));
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841

842
    condition = ((condition - 1) >> (BN_BITS2 - 1)) - 1;
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843

844 845 846
    t = (a->top ^ b->top) & condition;
    a->top ^= t;
    b->top ^= t;
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#define BN_CONSTTIME_SWAP(ind) \
849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880
        do { \
                t = (a->d[ind] ^ b->d[ind]) & condition; \
                a->d[ind] ^= t; \
                b->d[ind] ^= t; \
        } while (0)

    switch (nwords) {
    default:
        for (i = 10; i < nwords; i++)
            BN_CONSTTIME_SWAP(i);
        /* Fallthrough */
    case 10:
        BN_CONSTTIME_SWAP(9);   /* Fallthrough */
    case 9:
        BN_CONSTTIME_SWAP(8);   /* Fallthrough */
    case 8:
        BN_CONSTTIME_SWAP(7);   /* Fallthrough */
    case 7:
        BN_CONSTTIME_SWAP(6);   /* Fallthrough */
    case 6:
        BN_CONSTTIME_SWAP(5);   /* Fallthrough */
    case 5:
        BN_CONSTTIME_SWAP(4);   /* Fallthrough */
    case 4:
        BN_CONSTTIME_SWAP(3);   /* Fallthrough */
    case 3:
        BN_CONSTTIME_SWAP(2);   /* Fallthrough */
    case 2:
        BN_CONSTTIME_SWAP(1);   /* Fallthrough */
    case 1:
        BN_CONSTTIME_SWAP(0);
    }
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#undef BN_CONSTTIME_SWAP
}
883 884 885 886

/* Bits of security, see SP800-57 */

int BN_security_bits(int L, int N)
887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907
{
    int secbits, bits;
    if (L >= 15360)
        secbits = 256;
    else if (L >= 7690)
        secbits = 192;
    else if (L >= 3072)
        secbits = 128;
    else if (L >= 2048)
        secbits = 112;
    else if (L >= 1024)
        secbits = 80;
    else
        return 0;
    if (N == -1)
        return secbits;
    bits = N / 2;
    if (bits < 80)
        return 0;
    return bits >= secbits ? secbits : bits;
}
908 909

void BN_zero_ex(BIGNUM *a)
910 911 912 913
{
    a->top = 0;
    a->neg = 0;
}
914 915

int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
916 917 918
{
    return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
}
919 920

int BN_is_zero(const BIGNUM *a)
921 922 923
{
    return a->top == 0;
}
924 925

int BN_is_one(const BIGNUM *a)
926 927 928
{
    return BN_abs_is_word(a, 1) && !a->neg;
}
929 930

int BN_is_word(const BIGNUM *a, const BN_ULONG w)
931 932 933
{
    return BN_abs_is_word(a, w) && (!w || !a->neg);
}
934 935

int BN_is_odd(const BIGNUM *a)
936 937 938
{
    return (a->top > 0) && (a->d[0] & 1);
}
939 940

int BN_is_negative(const BIGNUM *a)
941 942 943
{
    return (a->neg != 0);
}
944

945 946 947 948 949
int BN_to_montgomery(BIGNUM *r, const BIGNUM *a, BN_MONT_CTX *mont,
                     BN_CTX *ctx)
{
    return BN_mod_mul_montgomery(r, a, &(mont->RR), mont, ctx);
}
950

951
void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags)
952 953 954 955 956 957 958
{
    dest->d = b->d;
    dest->top = b->top;
    dest->dmax = b->dmax;
    dest->neg = b->neg;
    dest->flags = ((dest->flags & BN_FLG_MALLOCED)
                   | (b->flags & ~BN_FLG_MALLOCED)
959
                   | BN_FLG_STATIC_DATA | flags);
960
}
961 962

BN_GENCB *BN_GENCB_new(void)
963 964
{
    BN_GENCB *ret;
965

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    if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL) {
967 968 969
        BNerr(BN_F_BN_GENCB_NEW, ERR_R_MALLOC_FAILURE);
        return (NULL);
    }
970

971 972
    return ret;
}
973 974

void BN_GENCB_free(BN_GENCB *cb)
975 976 977 978 979
{
    if (cb == NULL)
        return;
    OPENSSL_free(cb);
}
980 981

void BN_set_flags(BIGNUM *b, int n)
982 983 984
{
    b->flags |= n;
}
985 986

int BN_get_flags(const BIGNUM *b, int n)
987 988 989
{
    return b->flags & n;
}
990 991

/* Populate a BN_GENCB structure with an "old"-style callback */
992 993 994 995 996 997 998 999
void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback) (int, int, void *),
                      void *cb_arg)
{
    BN_GENCB *tmp_gencb = gencb;
    tmp_gencb->ver = 1;
    tmp_gencb->arg = cb_arg;
    tmp_gencb->cb.cb_1 = callback;
}
1000 1001

/* Populate a BN_GENCB structure with a "new"-style callback */
1002 1003 1004 1005 1006 1007 1008 1009
void BN_GENCB_set(BN_GENCB *gencb, int (*callback) (int, int, BN_GENCB *),
                  void *cb_arg)
{
    BN_GENCB *tmp_gencb = gencb;
    tmp_gencb->ver = 2;
    tmp_gencb->arg = cb_arg;
    tmp_gencb->cb.cb_2 = callback;
}
1010 1011

void *BN_GENCB_get_arg(BN_GENCB *cb)
1012 1013 1014
{
    return cb->arg;
}
1015 1016

BIGNUM *bn_wexpand(BIGNUM *a, int words)
1017 1018 1019
{
    return (words <= a->dmax) ? a : bn_expand2(a, words);
}
1020 1021

void bn_correct_top(BIGNUM *a)
1022 1023 1024 1025 1026
{
    BN_ULONG *ftl;
    int tmp_top = a->top;

    if (tmp_top > 0) {
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1027 1028 1029
        for (ftl = &(a->d[tmp_top]); tmp_top > 0; tmp_top--) {
            ftl--;
            if (*ftl != 0)
1030
                break;
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        }
1032 1033 1034 1035
        a->top = tmp_top;
    }
    bn_pollute(a);
}