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Revision f5c7f5dfbaf0d2f7d946d0fe86f08e6bcb36ed0d authored by Matt Caswell on 30 June 2016, 12:17:08 UTC, committed by Matt Caswell on 22 August 2016, 09:53:55 UTC
Fix DTLS buffered message DoS attack
DTLS can handle out of order record delivery. Additionally since
handshake messages can be bigger than will fit into a single packet, the
messages can be fragmented across multiple records (as with normal TLS).
That means that the messages can arrive mixed up, and we have to
reassemble them. We keep a queue of buffered messages that are "from the
future", i.e. messages we're not ready to deal with yet but have arrived
early. The messages held there may not be full yet - they could be one
or more fragments that are still in the process of being reassembled.

The code assumes that we will eventually complete the reassembly and
when that occurs the complete message is removed from the queue at the
point that we need to use it.

However, DTLS is also tolerant of packet loss. To get around that DTLS
messages can be retransmitted. If we receive a full (non-fragmented)
message from the peer after previously having received a fragment of
that message, then we ignore the message in the queue and just use the
non-fragmented version. At that point the queued message will never get
removed.

Additionally the peer could send "future" messages that we never get to
in order to complete the handshake. Each message has a sequence number
(starting from 0). We will accept a message fragment for the current
message sequence number, or for any sequence up to 10 into the future.
However if the Finished message has a sequence number of 2, anything
greater than that in the queue is just left there.

So, in those two ways we can end up with "orphaned" data in the queue
that will never get removed - except when the connection is closed. At
that point all the queues are flushed.

An attacker could seek to exploit this by filling up the queues with
lots of large messages that are never going to be used in order to
attempt a DoS by memory exhaustion.

I will assume that we are only concerned with servers here. It does not
seem reasonable to be concerned about a memory exhaustion attack on a
client. They are unlikely to process enough connections for this to be
an issue.

A "long" handshake with many messages might be 5 messages long (in the
incoming direction), e.g. ClientHello, Certificate, ClientKeyExchange,
CertificateVerify, Finished. So this would be message sequence numbers 0
to 4. Additionally we can buffer up to 10 messages in the future.
Therefore the maximum number of messages that an attacker could send
that could get orphaned would typically be 15.

The maximum size that a DTLS message is allowed to be is defined by
max_cert_list, which by default is 100k. Therefore the maximum amount of
"orphaned" memory per connection is 1500k.

Message sequence numbers get reset after the Finished message, so
renegotiation will not extend the maximum number of messages that can be
orphaned per connection.

As noted above, the queues do get cleared when the connection is closed.
Therefore in order to mount an effective attack, an attacker would have
to open many simultaneous connections.

Issue reported by Quan Luo.

CVE-2016-2179

Reviewed-by: Richard Levitte <levitte@openssl.org>
1 parent 5dfd038
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  • c0c9b13
  • /
  • test
  • /
  • bntest.c
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bntest.c
/*
 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
 *
 * 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
 */

/* ====================================================================
 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
 *
 * Portions of the attached software ("Contribution") are developed by
 * SUN MICROSYSTEMS, INC., and are contributed to the OpenSSL project.
 *
 * The Contribution is licensed pursuant to the Eric Young open source
 * license provided above.
 *
 * The binary polynomial arithmetic software is originally written by
 * Sheueling Chang Shantz and Douglas Stebila of Sun Microsystems Laboratories.
 *
 */

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

#include "e_os.h"

#include <openssl/bio.h>
#include <openssl/bn.h>
#include <openssl/rand.h>
#include <openssl/x509.h>
#include <openssl/err.h>

/*
 * In bn_lcl.h, bn_expand() is defined as a static ossl_inline function.
 * This is fine in itself, it will end up as an unused static function in
 * the worst case.  However, it referenses bn_expand2(), which is a private
 * function in libcrypto and therefore unavailable on some systems.  This
 * may result in a linker error because of unresolved symbols.
 *
 * To avoid this, we define a dummy variant of bn_expand2() here, and to
 * avoid possible clashes with libcrypto, we rename it first, using a macro.
 */
#define bn_expand2 dummy_bn_expand2
BIGNUM *bn_expand2(BIGNUM *b, int words);
BIGNUM *bn_expand2(BIGNUM *b, int words) { return NULL; }

#include "../crypto/bn/bn_lcl.h"

static const int num0 = 100;           /* number of tests */
static const int num1 = 50;            /* additional tests for some functions */
static const int num2 = 5;             /* number of tests for slow functions */

int test_add(BIO *bp);
int test_sub(BIO *bp);
int test_lshift1(BIO *bp);
int test_lshift(BIO *bp, BN_CTX *ctx, BIGNUM *a_);
int test_rshift1(BIO *bp);
int test_rshift(BIO *bp, BN_CTX *ctx);
int test_div(BIO *bp, BN_CTX *ctx);
int test_div_word(BIO *bp);
int test_div_recp(BIO *bp, BN_CTX *ctx);
int test_mul(BIO *bp);
int test_sqr(BIO *bp, BN_CTX *ctx);
int test_mont(BIO *bp, BN_CTX *ctx);
int test_mod(BIO *bp, BN_CTX *ctx);
int test_mod_mul(BIO *bp, BN_CTX *ctx);
int test_mod_exp(BIO *bp, BN_CTX *ctx);
int test_mod_exp_mont_consttime(BIO *bp, BN_CTX *ctx);
int test_mod_exp_mont5(BIO *bp, BN_CTX *ctx);
int test_exp(BIO *bp, BN_CTX *ctx);
int test_gf2m_add(BIO *bp);
int test_gf2m_mod(BIO *bp);
int test_gf2m_mod_mul(BIO *bp, BN_CTX *ctx);
int test_gf2m_mod_sqr(BIO *bp, BN_CTX *ctx);
int test_gf2m_mod_inv(BIO *bp, BN_CTX *ctx);
int test_gf2m_mod_div(BIO *bp, BN_CTX *ctx);
int test_gf2m_mod_exp(BIO *bp, BN_CTX *ctx);
int test_gf2m_mod_sqrt(BIO *bp, BN_CTX *ctx);
int test_gf2m_mod_solve_quad(BIO *bp, BN_CTX *ctx);
int test_kron(BIO *bp, BN_CTX *ctx);
int test_sqrt(BIO *bp, BN_CTX *ctx);
int test_small_prime(BIO *bp, BN_CTX *ctx);
int rand_neg(void);
static int results = 0;

static unsigned char lst[] =
    "\xC6\x4F\x43\x04\x2A\xEA\xCA\x6E\x58\x36\x80\x5B\xE8\xC9"
    "\x9B\x04\x5D\x48\x36\xC2\xFD\x16\xC9\x64\xF0";

static const char rnd_seed[] =
    "string to make the random number generator think it has entropy";

static void message(BIO *out, char *m)
{
    fprintf(stderr, "test %s\n", m);
    BIO_puts(out, "print \"test ");
    BIO_puts(out, m);
    BIO_puts(out, "\\n\"\n");
}

int main(int argc, char *argv[])
{
    BN_CTX *ctx;
    BIO *out;
    char *outfile = NULL;

    CRYPTO_set_mem_debug(1);
    CRYPTO_mem_ctrl(CRYPTO_MEM_CHECK_ON);

    results = 0;

    RAND_seed(rnd_seed, sizeof rnd_seed); /* or BN_generate_prime may fail */

    argc--;
    argv++;
    while (argc >= 1) {
        if (strcmp(*argv, "-results") == 0)
            results = 1;
        else if (strcmp(*argv, "-out") == 0) {
            if (--argc < 1)
                break;
            outfile = *(++argv);
        }
        argc--;
        argv++;
    }

    ctx = BN_CTX_new();
    if (ctx == NULL)
        EXIT(1);

    out = BIO_new(BIO_s_file());
    if (out == NULL)
        EXIT(1);
    if (outfile == NULL) {
        BIO_set_fp(out, stdout, BIO_NOCLOSE | BIO_FP_TEXT);
    } else {
        if (!BIO_write_filename(out, outfile)) {
            perror(outfile);
            EXIT(1);
        }
    }
#ifdef OPENSSL_SYS_VMS
    {
        BIO *tmpbio = BIO_new(BIO_f_linebuffer());
        out = BIO_push(tmpbio, out);
    }
#endif

    if (!results)
        BIO_puts(out, "obase=16\nibase=16\n");

    message(out, "BN_add");
    if (!test_add(out))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_sub");
    if (!test_sub(out))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_lshift1");
    if (!test_lshift1(out))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_lshift (fixed)");
    if (!test_lshift(out, ctx, BN_bin2bn(lst, sizeof(lst) - 1, NULL)))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_lshift");
    if (!test_lshift(out, ctx, NULL))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_rshift1");
    if (!test_rshift1(out))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_rshift");
    if (!test_rshift(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_sqr");
    if (!test_sqr(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_mul");
    if (!test_mul(out))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_div");
    if (!test_div(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_div_word");
    if (!test_div_word(out))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_div_recp");
    if (!test_div_recp(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_mod");
    if (!test_mod(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_mod_mul");
    if (!test_mod_mul(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_mont");
    if (!test_mont(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_mod_exp");
    if (!test_mod_exp(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_mod_exp_mont_consttime");
    if (!test_mod_exp_mont_consttime(out, ctx))
        goto err;
    if (!test_mod_exp_mont5(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_exp");
    if (!test_exp(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_kronecker");
    if (!test_kron(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_mod_sqrt");
    if (!test_sqrt(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "Small prime generation");
    if (!test_small_prime(out, ctx))
        goto err;
    (void)BIO_flush(out);

#ifndef OPENSSL_NO_EC2M
    message(out, "BN_GF2m_add");
    if (!test_gf2m_add(out))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_GF2m_mod");
    if (!test_gf2m_mod(out))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_GF2m_mod_mul");
    if (!test_gf2m_mod_mul(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_GF2m_mod_sqr");
    if (!test_gf2m_mod_sqr(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_GF2m_mod_inv");
    if (!test_gf2m_mod_inv(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_GF2m_mod_div");
    if (!test_gf2m_mod_div(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_GF2m_mod_exp");
    if (!test_gf2m_mod_exp(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_GF2m_mod_sqrt");
    if (!test_gf2m_mod_sqrt(out, ctx))
        goto err;
    (void)BIO_flush(out);

    message(out, "BN_GF2m_mod_solve_quad");
    if (!test_gf2m_mod_solve_quad(out, ctx))
        goto err;
    (void)BIO_flush(out);
#endif
    BN_CTX_free(ctx);
    BIO_free(out);

    ERR_print_errors_fp(stderr);

#ifndef OPENSSL_NO_CRYPTO_MDEBUG
    if (CRYPTO_mem_leaks_fp(stderr) <= 0)
        EXIT(1);
#endif
    EXIT(0);
 err:
    BIO_puts(out, "1\n");       /* make sure the Perl script fed by bc
                                 * notices the failure, see test_bn in
                                 * test/Makefile.ssl */
    (void)BIO_flush(out);
    BN_CTX_free(ctx);
    BIO_free(out);

    ERR_print_errors_fp(stderr);
    EXIT(1);
}

int test_add(BIO *bp)
{
    BIGNUM *a, *b, *c;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();

    BN_bntest_rand(a, 512, 0, 0);
    for (i = 0; i < num0; i++) {
        BN_bntest_rand(b, 450 + i, 0, 0);
        a->neg = rand_neg();
        b->neg = rand_neg();
        BN_add(c, a, b);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " + ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, c);
            BIO_puts(bp, "\n");
        }
        a->neg = !a->neg;
        b->neg = !b->neg;
        BN_add(c, c, b);
        BN_add(c, c, a);
        if (!BN_is_zero(c)) {
            fprintf(stderr, "Add test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    return (1);
}

int test_sub(BIO *bp)
{
    BIGNUM *a, *b, *c;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();

    for (i = 0; i < num0 + num1; i++) {
        if (i < num1) {
            BN_bntest_rand(a, 512, 0, 0);
            BN_copy(b, a);
            if (BN_set_bit(a, i) == 0)
                return (0);
            BN_add_word(b, i);
        } else {
            BN_bntest_rand(b, 400 + i - num1, 0, 0);
            a->neg = rand_neg();
            b->neg = rand_neg();
        }
        BN_sub(c, a, b);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " - ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, c);
            BIO_puts(bp, "\n");
        }
        BN_add(c, c, b);
        BN_sub(c, c, a);
        if (!BN_is_zero(c)) {
            fprintf(stderr, "Subtract test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    return (1);
}

int test_div(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *c, *d, *e;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    BN_one(a);
    BN_zero(b);

    if (BN_div(d, c, a, b, ctx)) {
        fprintf(stderr, "Division by zero succeeded!\n");
        return 0;
    }

    for (i = 0; i < num0 + num1; i++) {
        if (i < num1) {
            BN_bntest_rand(a, 400, 0, 0);
            BN_copy(b, a);
            BN_lshift(a, a, i);
            BN_add_word(a, i);
        } else
            BN_bntest_rand(b, 50 + 3 * (i - num1), 0, 0);
        a->neg = rand_neg();
        b->neg = rand_neg();
        BN_div(d, c, a, b, ctx);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " / ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, d);
            BIO_puts(bp, "\n");

            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " % ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, c);
            BIO_puts(bp, "\n");
        }
        BN_mul(e, d, b, ctx);
        BN_add(d, e, c);
        BN_sub(d, d, a);
        if (!BN_is_zero(d)) {
            fprintf(stderr, "Division test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return (1);
}

static void print_word(BIO *bp, BN_ULONG w)
{
    int i = sizeof(w) * 8;
    char *fmt = NULL;
    unsigned char byte;

    do {
        i -= 8;
        byte = (unsigned char)(w >> i);
        if (fmt == NULL)
            fmt = byte ? "%X" : NULL;
        else
            fmt = "%02X";

        if (fmt != NULL)
            BIO_printf(bp, fmt, byte);
    } while (i);

    /* If we haven't printed anything, at least print a zero! */
    if (fmt == NULL)
        BIO_printf(bp, "0");
}

int test_div_word(BIO *bp)
{
    BIGNUM *a, *b;
    BN_ULONG r, rmod, s;
    int i;

    a = BN_new();
    b = BN_new();

    for (i = 0; i < num0; i++) {
        do {
            BN_bntest_rand(a, 512, -1, 0);
            BN_bntest_rand(b, BN_BITS2, -1, 0);
        } while (BN_is_zero(b));

        s = b->d[0];
        BN_copy(b, a);
        rmod = BN_mod_word(b, s);
        r = BN_div_word(b, s);

        if (rmod != r) {
            fprintf(stderr, "Mod (word) test failed!\n");
            return 0;
        }

        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " / ");
                print_word(bp, s);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, b);
            BIO_puts(bp, "\n");

            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " % ");
                print_word(bp, s);
                BIO_puts(bp, " - ");
            }
            print_word(bp, r);
            BIO_puts(bp, "\n");
        }
        BN_mul_word(b, s);
        BN_add_word(b, r);
        BN_sub(b, a, b);
        if (!BN_is_zero(b)) {
            fprintf(stderr, "Division (word) test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    return (1);
}

int test_div_recp(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *c, *d, *e;
    BN_RECP_CTX *recp;
    int i;

    recp = BN_RECP_CTX_new();
    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    for (i = 0; i < num0 + num1; i++) {
        if (i < num1) {
            BN_bntest_rand(a, 400, 0, 0);
            BN_copy(b, a);
            BN_lshift(a, a, i);
            BN_add_word(a, i);
        } else
            BN_bntest_rand(b, 50 + 3 * (i - num1), 0, 0);
        a->neg = rand_neg();
        b->neg = rand_neg();
        BN_RECP_CTX_set(recp, b, ctx);
        BN_div_recp(d, c, a, recp, ctx);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " / ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, d);
            BIO_puts(bp, "\n");

            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " % ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, c);
            BIO_puts(bp, "\n");
        }
        BN_mul(e, d, b, ctx);
        BN_add(d, e, c);
        BN_sub(d, d, a);
        if (!BN_is_zero(d)) {
            fprintf(stderr, "Reciprocal division test failed!\n");
            fprintf(stderr, "a=");
            BN_print_fp(stderr, a);
            fprintf(stderr, "\nb=");
            BN_print_fp(stderr, b);
            fprintf(stderr, "\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    BN_RECP_CTX_free(recp);
    return (1);
}

int test_mul(BIO *bp)
{
    BIGNUM *a, *b, *c, *d, *e;
    int i;
    BN_CTX *ctx;

    ctx = BN_CTX_new();
    if (ctx == NULL)
        EXIT(1);

    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    for (i = 0; i < num0 + num1; i++) {
        if (i <= num1) {
            BN_bntest_rand(a, 100, 0, 0);
            BN_bntest_rand(b, 100, 0, 0);
        } else
            BN_bntest_rand(b, i - num1, 0, 0);
        a->neg = rand_neg();
        b->neg = rand_neg();
        BN_mul(c, a, b, ctx);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " * ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, c);
            BIO_puts(bp, "\n");
        }
        BN_div(d, e, c, a, ctx);
        BN_sub(d, d, b);
        if (!BN_is_zero(d) || !BN_is_zero(e)) {
            fprintf(stderr, "Multiplication test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    BN_CTX_free(ctx);
    return (1);
}

int test_sqr(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *c, *d, *e;
    int i, ret = 0;

    a = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();
    if (a == NULL || c == NULL || d == NULL || e == NULL) {
        goto err;
    }

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 40 + i * 10, 0, 0);
        a->neg = rand_neg();
        BN_sqr(c, a, ctx);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " * ");
                BN_print(bp, a);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, c);
            BIO_puts(bp, "\n");
        }
        BN_div(d, e, c, a, ctx);
        BN_sub(d, d, a);
        if (!BN_is_zero(d) || !BN_is_zero(e)) {
            fprintf(stderr, "Square test failed!\n");
            goto err;
        }
    }

    /* Regression test for a BN_sqr overflow bug. */
    BN_hex2bn(&a,
              "80000000000000008000000000000001"
              "FFFFFFFFFFFFFFFE0000000000000000");
    BN_sqr(c, a, ctx);
    if (bp != NULL) {
        if (!results) {
            BN_print(bp, a);
            BIO_puts(bp, " * ");
            BN_print(bp, a);
            BIO_puts(bp, " - ");
        }
        BN_print(bp, c);
        BIO_puts(bp, "\n");
    }
    BN_mul(d, a, a, ctx);
    if (BN_cmp(c, d)) {
        fprintf(stderr, "Square test failed: BN_sqr and BN_mul produce "
                "different results!\n");
        goto err;
    }

    /* Regression test for a BN_sqr overflow bug. */
    BN_hex2bn(&a,
              "80000000000000000000000080000001"
              "FFFFFFFE000000000000000000000000");
    BN_sqr(c, a, ctx);
    if (bp != NULL) {
        if (!results) {
            BN_print(bp, a);
            BIO_puts(bp, " * ");
            BN_print(bp, a);
            BIO_puts(bp, " - ");
        }
        BN_print(bp, c);
        BIO_puts(bp, "\n");
    }
    BN_mul(d, a, a, ctx);
    if (BN_cmp(c, d)) {
        fprintf(stderr, "Square test failed: BN_sqr and BN_mul produce "
                "different results!\n");
        goto err;
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return ret;
}

int test_mont(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *c, *d, *A, *B;
    BIGNUM *n;
    int i;
    BN_MONT_CTX *mont;

    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    A = BN_new();
    B = BN_new();
    n = BN_new();

    mont = BN_MONT_CTX_new();
    if (mont == NULL)
        return 0;

    BN_zero(n);
    if (BN_MONT_CTX_set(mont, n, ctx)) {
        fprintf(stderr, "BN_MONT_CTX_set succeeded for zero modulus!\n");
        return 0;
    }

    BN_set_word(n, 16);
    if (BN_MONT_CTX_set(mont, n, ctx)) {
        fprintf(stderr, "BN_MONT_CTX_set succeeded for even modulus!\n");
        return 0;
    }

    BN_bntest_rand(a, 100, 0, 0);
    BN_bntest_rand(b, 100, 0, 0);
    for (i = 0; i < num2; i++) {
        int bits = (200 * (i + 1)) / num2;

        if (bits == 0)
            continue;
        BN_bntest_rand(n, bits, 0, 1);
        BN_MONT_CTX_set(mont, n, ctx);

        BN_nnmod(a, a, n, ctx);
        BN_nnmod(b, b, n, ctx);

        BN_to_montgomery(A, a, mont, ctx);
        BN_to_montgomery(B, b, mont, ctx);

        BN_mod_mul_montgomery(c, A, B, mont, ctx);
        BN_from_montgomery(A, c, mont, ctx);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " * ");
                BN_print(bp, b);
                BIO_puts(bp, " % ");
                BN_print(bp, &mont->N);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, A);
            BIO_puts(bp, "\n");
        }
        BN_mod_mul(d, a, b, n, ctx);
        BN_sub(d, d, A);
        if (!BN_is_zero(d)) {
            fprintf(stderr, "Montgomery multiplication test failed!\n");
            return 0;
        }
    }
    BN_MONT_CTX_free(mont);
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(A);
    BN_free(B);
    BN_free(n);
    return (1);
}

int test_mod(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *c, *d, *e;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    BN_bntest_rand(a, 1024, 0, 0);
    for (i = 0; i < num0; i++) {
        BN_bntest_rand(b, 450 + i * 10, 0, 0);
        a->neg = rand_neg();
        b->neg = rand_neg();
        BN_mod(c, a, b, ctx);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " % ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, c);
            BIO_puts(bp, "\n");
        }
        BN_div(d, e, a, b, ctx);
        BN_sub(e, e, c);
        if (!BN_is_zero(e)) {
            fprintf(stderr, "Modulo test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return (1);
}

int test_mod_mul(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *c, *d, *e;
    int i, j;

    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    BN_one(a);
    BN_one(b);
    BN_zero(c);
    if (BN_mod_mul(e, a, b, c, ctx)) {
        fprintf(stderr, "BN_mod_mul with zero modulus succeeded!\n");
        return 0;
    }

    for (j = 0; j < 3; j++) {
        BN_bntest_rand(c, 1024, 0, 0);
        for (i = 0; i < num0; i++) {
            BN_bntest_rand(a, 475 + i * 10, 0, 0);
            BN_bntest_rand(b, 425 + i * 11, 0, 0);
            a->neg = rand_neg();
            b->neg = rand_neg();
            if (!BN_mod_mul(e, a, b, c, ctx)) {
                unsigned long l;

                while ((l = ERR_get_error()))
                    fprintf(stderr, "ERROR:%s\n", ERR_error_string(l, NULL));
                EXIT(1);
            }
            if (bp != NULL) {
                if (!results) {
                    BN_print(bp, a);
                    BIO_puts(bp, " * ");
                    BN_print(bp, b);
                    BIO_puts(bp, " % ");
                    BN_print(bp, c);
                    if ((a->neg ^ b->neg) && !BN_is_zero(e)) {
                        /*
                         * If (a*b) % c is negative, c must be added in order
                         * to obtain the normalized remainder (new with
                         * OpenSSL 0.9.7, previous versions of BN_mod_mul
                         * could generate negative results)
                         */
                        BIO_puts(bp, " + ");
                        BN_print(bp, c);
                    }
                    BIO_puts(bp, " - ");
                }
                BN_print(bp, e);
                BIO_puts(bp, "\n");
            }
            BN_mul(d, a, b, ctx);
            BN_sub(d, d, e);
            BN_div(a, b, d, c, ctx);
            if (!BN_is_zero(b)) {
                fprintf(stderr, "Modulo multiply test failed!\n");
                ERR_print_errors_fp(stderr);
                return 0;
            }
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return (1);
}

int test_mod_exp(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *c, *d, *e;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    BN_one(a);
    BN_one(b);
    BN_zero(c);
    if (BN_mod_exp(d, a, b, c, ctx)) {
        fprintf(stderr, "BN_mod_exp with zero modulus succeeded!\n");
        return 0;
    }

    BN_bntest_rand(c, 30, 0, 1); /* must be odd for montgomery */
    for (i = 0; i < num2; i++) {
        BN_bntest_rand(a, 20 + i * 5, 0, 0);
        BN_bntest_rand(b, 2 + i, 0, 0);

        if (!BN_mod_exp(d, a, b, c, ctx))
            return (0);

        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " ^ ");
                BN_print(bp, b);
                BIO_puts(bp, " % ");
                BN_print(bp, c);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, d);
            BIO_puts(bp, "\n");
        }
        BN_exp(e, a, b, ctx);
        BN_sub(e, e, d);
        BN_div(a, b, e, c, ctx);
        if (!BN_is_zero(b)) {
            fprintf(stderr, "Modulo exponentiation test failed!\n");
            return 0;
        }
    }

    /* Regression test for carry propagation bug in sqr8x_reduction */
    BN_hex2bn(&a, "050505050505");
    BN_hex2bn(&b, "02");
    BN_hex2bn(&c,
        "4141414141414141414141274141414141414141414141414141414141414141"
        "4141414141414141414141414141414141414141414141414141414141414141"
        "4141414141414141414141800000000000000000000000000000000000000000"
        "0000000000000000000000000000000000000000000000000000000000000000"
        "0000000000000000000000000000000000000000000000000000000000000000"
        "0000000000000000000000000000000000000000000000000000000001");
    BN_mod_exp(d, a, b, c, ctx);
    BN_mul(e, a, a, ctx);
    if (BN_cmp(d, e)) {
        fprintf(stderr, "BN_mod_exp and BN_mul produce different results!\n");
        return 0;
    }

    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return (1);
}

int test_mod_exp_mont_consttime(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *c, *d, *e;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    BN_one(a);
    BN_one(b);
    BN_zero(c);
    if (BN_mod_exp_mont_consttime(d, a, b, c, ctx, NULL)) {
        fprintf(stderr, "BN_mod_exp_mont_consttime with zero modulus "
                "succeeded\n");
        return 0;
    }

    BN_set_word(c, 16);
    if (BN_mod_exp_mont_consttime(d, a, b, c, ctx, NULL)) {
        fprintf(stderr, "BN_mod_exp_mont_consttime with even modulus "
                "succeeded\n");
        return 0;
    }

    BN_bntest_rand(c, 30, 0, 1); /* must be odd for montgomery */
    for (i = 0; i < num2; i++) {
        BN_bntest_rand(a, 20 + i * 5, 0, 0);
        BN_bntest_rand(b, 2 + i, 0, 0);

        if (!BN_mod_exp_mont_consttime(d, a, b, c, ctx, NULL))
            return (00);

        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " ^ ");
                BN_print(bp, b);
                BIO_puts(bp, " % ");
                BN_print(bp, c);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, d);
            BIO_puts(bp, "\n");
        }
        BN_exp(e, a, b, ctx);
        BN_sub(e, e, d);
        BN_div(a, b, e, c, ctx);
        if (!BN_is_zero(b)) {
            fprintf(stderr, "Modulo exponentiation test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return (1);
}

/*
 * Test constant-time modular exponentiation with 1024-bit inputs, which on
 * x86_64 cause a different code branch to be taken.
 */
int test_mod_exp_mont5(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *p, *m, *d, *e;
    BN_MONT_CTX *mont;

    a = BN_new();
    p = BN_new();
    m = BN_new();
    d = BN_new();
    e = BN_new();
    mont = BN_MONT_CTX_new();

    BN_bntest_rand(m, 1024, 0, 1); /* must be odd for montgomery */
    /* Zero exponent */
    BN_bntest_rand(a, 1024, 0, 0);
    BN_zero(p);
    if (!BN_mod_exp_mont_consttime(d, a, p, m, ctx, NULL))
        return 0;
    if (!BN_is_one(d)) {
        fprintf(stderr, "Modular exponentiation test failed!\n");
        return 0;
    }
    /* Zero input */
    BN_bntest_rand(p, 1024, 0, 0);
    BN_zero(a);
    if (!BN_mod_exp_mont_consttime(d, a, p, m, ctx, NULL))
        return 0;
    if (!BN_is_zero(d)) {
        fprintf(stderr, "Modular exponentiation test failed!\n");
        return 0;
    }
    /*
     * Craft an input whose Montgomery representation is 1, i.e., shorter
     * than the modulus m, in order to test the const time precomputation
     * scattering/gathering.
     */
    BN_one(a);
    BN_MONT_CTX_set(mont, m, ctx);
    if (!BN_from_montgomery(e, a, mont, ctx))
        return 0;
    if (!BN_mod_exp_mont_consttime(d, e, p, m, ctx, NULL))
        return 0;
    if (!BN_mod_exp_simple(a, e, p, m, ctx))
        return 0;
    if (BN_cmp(a, d) != 0) {
        fprintf(stderr, "Modular exponentiation test failed!\n");
        return 0;
    }
    /* Finally, some regular test vectors. */
    BN_bntest_rand(e, 1024, 0, 0);
    if (!BN_mod_exp_mont_consttime(d, e, p, m, ctx, NULL))
        return 0;
    if (!BN_mod_exp_simple(a, e, p, m, ctx))
        return 0;
    if (BN_cmp(a, d) != 0) {
        fprintf(stderr, "Modular exponentiation test failed!\n");
        return 0;
    }
    BN_MONT_CTX_free(mont);
    BN_free(a);
    BN_free(p);
    BN_free(m);
    BN_free(d);
    BN_free(e);
    return (1);
}

int test_exp(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *d, *e, *one;
    int i;

    a = BN_new();
    b = BN_new();
    d = BN_new();
    e = BN_new();
    one = BN_new();
    BN_one(one);

    for (i = 0; i < num2; i++) {
        BN_bntest_rand(a, 20 + i * 5, 0, 0);
        BN_bntest_rand(b, 2 + i, 0, 0);

        if (BN_exp(d, a, b, ctx) <= 0)
            return (0);

        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " ^ ");
                BN_print(bp, b);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, d);
            BIO_puts(bp, "\n");
        }
        BN_one(e);
        for (; !BN_is_zero(b); BN_sub(b, b, one))
            BN_mul(e, e, a, ctx);
        BN_sub(e, e, d);
        if (!BN_is_zero(e)) {
            fprintf(stderr, "Exponentiation test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(d);
    BN_free(e);
    BN_free(one);
    return (1);
}

#ifndef OPENSSL_NO_EC2M
int test_gf2m_add(BIO *bp)
{
    BIGNUM *a, *b, *c;
    int i, ret = 0;

    a = BN_new();
    b = BN_new();
    c = BN_new();

    for (i = 0; i < num0; i++) {
        BN_rand(a, 512, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY);
        BN_copy(b, BN_value_one());
        a->neg = rand_neg();
        b->neg = rand_neg();
        BN_GF2m_add(c, a, b);
        /* Test that two added values have the correct parity. */
        if ((BN_is_odd(a) && BN_is_odd(c))
            || (!BN_is_odd(a) && !BN_is_odd(c))) {
            fprintf(stderr, "GF(2^m) addition test (a) failed!\n");
            goto err;
        }
        BN_GF2m_add(c, c, c);
        /* Test that c + c = 0. */
        if (!BN_is_zero(c)) {
            fprintf(stderr, "GF(2^m) addition test (b) failed!\n");
            goto err;
        }
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b);
    BN_free(c);
    return ret;
}

int test_gf2m_mod(BIO *bp)
{
    BIGNUM *a, *b[2], *c, *d, *e;
    int i, j, ret = 0;
    int p0[] = { 163, 7, 6, 3, 0, -1 };
    int p1[] = { 193, 15, 0, -1 };

    a = BN_new();
    b[0] = BN_new();
    b[1] = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    BN_GF2m_arr2poly(p0, b[0]);
    BN_GF2m_arr2poly(p1, b[1]);

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 1024, 0, 0);
        for (j = 0; j < 2; j++) {
            BN_GF2m_mod(c, a, b[j]);
            BN_GF2m_add(d, a, c);
            BN_GF2m_mod(e, d, b[j]);
            /* Test that a + (a mod p) mod p == 0. */
            if (!BN_is_zero(e)) {
                fprintf(stderr, "GF(2^m) modulo test failed!\n");
                goto err;
            }
        }
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b[0]);
    BN_free(b[1]);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return ret;
}

int test_gf2m_mod_mul(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b[2], *c, *d, *e, *f, *g, *h;
    int i, j, ret = 0;
    int p0[] = { 163, 7, 6, 3, 0, -1 };
    int p1[] = { 193, 15, 0, -1 };

    a = BN_new();
    b[0] = BN_new();
    b[1] = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();
    f = BN_new();
    g = BN_new();
    h = BN_new();

    BN_GF2m_arr2poly(p0, b[0]);
    BN_GF2m_arr2poly(p1, b[1]);

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 1024, 0, 0);
        BN_bntest_rand(c, 1024, 0, 0);
        BN_bntest_rand(d, 1024, 0, 0);
        for (j = 0; j < 2; j++) {
            BN_GF2m_mod_mul(e, a, c, b[j], ctx);
            BN_GF2m_add(f, a, d);
            BN_GF2m_mod_mul(g, f, c, b[j], ctx);
            BN_GF2m_mod_mul(h, d, c, b[j], ctx);
            BN_GF2m_add(f, e, g);
            BN_GF2m_add(f, f, h);
            /* Test that (a+d)*c = a*c + d*c. */
            if (!BN_is_zero(f)) {
                fprintf(stderr,
                        "GF(2^m) modular multiplication test failed!\n");
                goto err;
            }
        }
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b[0]);
    BN_free(b[1]);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    BN_free(f);
    BN_free(g);
    BN_free(h);
    return ret;
}

int test_gf2m_mod_sqr(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b[2], *c, *d;
    int i, j, ret = 0;
    int p0[] = { 163, 7, 6, 3, 0, -1 };
    int p1[] = { 193, 15, 0, -1 };

    a = BN_new();
    b[0] = BN_new();
    b[1] = BN_new();
    c = BN_new();
    d = BN_new();

    BN_GF2m_arr2poly(p0, b[0]);
    BN_GF2m_arr2poly(p1, b[1]);

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 1024, 0, 0);
        for (j = 0; j < 2; j++) {
            BN_GF2m_mod_sqr(c, a, b[j], ctx);
            BN_copy(d, a);
            BN_GF2m_mod_mul(d, a, d, b[j], ctx);
            BN_GF2m_add(d, c, d);
            /* Test that a*a = a^2. */
            if (!BN_is_zero(d)) {
                fprintf(stderr, "GF(2^m) modular squaring test failed!\n");
                goto err;
            }
        }
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b[0]);
    BN_free(b[1]);
    BN_free(c);
    BN_free(d);
    return ret;
}

int test_gf2m_mod_inv(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b[2], *c, *d;
    int i, j, ret = 0;
    int p0[] = { 163, 7, 6, 3, 0, -1 };
    int p1[] = { 193, 15, 0, -1 };

    a = BN_new();
    b[0] = BN_new();
    b[1] = BN_new();
    c = BN_new();
    d = BN_new();

    BN_GF2m_arr2poly(p0, b[0]);
    BN_GF2m_arr2poly(p1, b[1]);

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 512, 0, 0);
        for (j = 0; j < 2; j++) {
            BN_GF2m_mod_inv(c, a, b[j], ctx);
            BN_GF2m_mod_mul(d, a, c, b[j], ctx);
            /* Test that ((1/a)*a) = 1. */
            if (!BN_is_one(d)) {
                fprintf(stderr, "GF(2^m) modular inversion test failed!\n");
                goto err;
            }
        }
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b[0]);
    BN_free(b[1]);
    BN_free(c);
    BN_free(d);
    return ret;
}

int test_gf2m_mod_div(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b[2], *c, *d, *e, *f;
    int i, j, ret = 0;
    int p0[] = { 163, 7, 6, 3, 0, -1 };
    int p1[] = { 193, 15, 0, -1 };

    a = BN_new();
    b[0] = BN_new();
    b[1] = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();
    f = BN_new();

    BN_GF2m_arr2poly(p0, b[0]);
    BN_GF2m_arr2poly(p1, b[1]);

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 512, 0, 0);
        BN_bntest_rand(c, 512, 0, 0);
        for (j = 0; j < 2; j++) {
            BN_GF2m_mod_div(d, a, c, b[j], ctx);
            BN_GF2m_mod_mul(e, d, c, b[j], ctx);
            BN_GF2m_mod_div(f, a, e, b[j], ctx);
            /* Test that ((a/c)*c)/a = 1. */
            if (!BN_is_one(f)) {
                fprintf(stderr, "GF(2^m) modular division test failed!\n");
                goto err;
            }
        }
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b[0]);
    BN_free(b[1]);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    BN_free(f);
    return ret;
}

int test_gf2m_mod_exp(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b[2], *c, *d, *e, *f;
    int i, j, ret = 0;
    int p0[] = { 163, 7, 6, 3, 0, -1 };
    int p1[] = { 193, 15, 0, -1 };

    a = BN_new();
    b[0] = BN_new();
    b[1] = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();
    f = BN_new();

    BN_GF2m_arr2poly(p0, b[0]);
    BN_GF2m_arr2poly(p1, b[1]);

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 512, 0, 0);
        BN_bntest_rand(c, 512, 0, 0);
        BN_bntest_rand(d, 512, 0, 0);
        for (j = 0; j < 2; j++) {
            BN_GF2m_mod_exp(e, a, c, b[j], ctx);
            BN_GF2m_mod_exp(f, a, d, b[j], ctx);
            BN_GF2m_mod_mul(e, e, f, b[j], ctx);
            BN_add(f, c, d);
            BN_GF2m_mod_exp(f, a, f, b[j], ctx);
            BN_GF2m_add(f, e, f);
            /* Test that a^(c+d)=a^c*a^d. */
            if (!BN_is_zero(f)) {
                fprintf(stderr,
                        "GF(2^m) modular exponentiation test failed!\n");
                goto err;
            }
        }
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b[0]);
    BN_free(b[1]);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    BN_free(f);
    return ret;
}

int test_gf2m_mod_sqrt(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b[2], *c, *d, *e, *f;
    int i, j, ret = 0;
    int p0[] = { 163, 7, 6, 3, 0, -1 };
    int p1[] = { 193, 15, 0, -1 };

    a = BN_new();
    b[0] = BN_new();
    b[1] = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();
    f = BN_new();

    BN_GF2m_arr2poly(p0, b[0]);
    BN_GF2m_arr2poly(p1, b[1]);

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 512, 0, 0);
        for (j = 0; j < 2; j++) {
            BN_GF2m_mod(c, a, b[j]);
            BN_GF2m_mod_sqrt(d, a, b[j], ctx);
            BN_GF2m_mod_sqr(e, d, b[j], ctx);
            BN_GF2m_add(f, c, e);
            /* Test that d^2 = a, where d = sqrt(a). */
            if (!BN_is_zero(f)) {
                fprintf(stderr, "GF(2^m) modular square root test failed!\n");
                goto err;
            }
        }
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b[0]);
    BN_free(b[1]);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    BN_free(f);
    return ret;
}

int test_gf2m_mod_solve_quad(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b[2], *c, *d, *e;
    int i, j, s = 0, t, ret = 0;
    int p0[] = { 163, 7, 6, 3, 0, -1 };
    int p1[] = { 193, 15, 0, -1 };

    a = BN_new();
    b[0] = BN_new();
    b[1] = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();

    BN_GF2m_arr2poly(p0, b[0]);
    BN_GF2m_arr2poly(p1, b[1]);

    for (i = 0; i < num0; i++) {
        BN_bntest_rand(a, 512, 0, 0);
        for (j = 0; j < 2; j++) {
            t = BN_GF2m_mod_solve_quad(c, a, b[j], ctx);
            if (t) {
                s++;
                BN_GF2m_mod_sqr(d, c, b[j], ctx);
                BN_GF2m_add(d, c, d);
                BN_GF2m_mod(e, a, b[j]);
                BN_GF2m_add(e, e, d);
                /*
                 * Test that solution of quadratic c satisfies c^2 + c = a.
                 */
                if (!BN_is_zero(e)) {
                    fprintf(stderr,
                            "GF(2^m) modular solve quadratic test failed!\n");
                    goto err;
                }

            }
        }
    }
    if (s == 0) {
        fprintf(stderr,
                "All %i tests of GF(2^m) modular solve quadratic resulted in no roots;\n",
                num0);
        fprintf(stderr,
                "this is very unlikely and probably indicates an error.\n");
        goto err;
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(b[0]);
    BN_free(b[1]);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return ret;
}
#endif
static int genprime_cb(int p, int n, BN_GENCB *arg)
{
    char c = '*';

    if (p == 0)
        c = '.';
    if (p == 1)
        c = '+';
    if (p == 2)
        c = '*';
    if (p == 3)
        c = '\n';
    putc(c, stderr);
    fflush(stderr);
    return 1;
}

int test_kron(BIO *bp, BN_CTX *ctx)
{
    BN_GENCB cb;
    BIGNUM *a, *b, *r, *t;
    int i;
    int legendre, kronecker;
    int ret = 0;

    a = BN_new();
    b = BN_new();
    r = BN_new();
    t = BN_new();
    if (a == NULL || b == NULL || r == NULL || t == NULL)
        goto err;

    BN_GENCB_set(&cb, genprime_cb, NULL);

    /*
     * We test BN_kronecker(a, b, ctx) just for b odd (Jacobi symbol). In
     * this case we know that if b is prime, then BN_kronecker(a, b, ctx) is
     * congruent to $a^{(b-1)/2}$, modulo $b$ (Legendre symbol). So we
     * generate a random prime b and compare these values for a number of
     * random a's.  (That is, we run the Solovay-Strassen primality test to
     * confirm that b is prime, except that we don't want to test whether b
     * is prime but whether BN_kronecker works.)
     */

    if (!BN_generate_prime_ex(b, 512, 0, NULL, NULL, &cb))
        goto err;
    b->neg = rand_neg();
    putc('\n', stderr);

    for (i = 0; i < num0; i++) {
        if (!BN_bntest_rand(a, 512, 0, 0))
            goto err;
        a->neg = rand_neg();

        /* t := (|b|-1)/2  (note that b is odd) */
        if (!BN_copy(t, b))
            goto err;
        t->neg = 0;
        if (!BN_sub_word(t, 1))
            goto err;
        if (!BN_rshift1(t, t))
            goto err;
        /* r := a^t mod b */
        b->neg = 0;

        if (!BN_mod_exp_recp(r, a, t, b, ctx))
            goto err;
        b->neg = 1;

        if (BN_is_word(r, 1))
            legendre = 1;
        else if (BN_is_zero(r))
            legendre = 0;
        else {
            if (!BN_add_word(r, 1))
                goto err;
            if (0 != BN_ucmp(r, b)) {
                fprintf(stderr, "Legendre symbol computation failed\n");
                goto err;
            }
            legendre = -1;
        }

        kronecker = BN_kronecker(a, b, ctx);
        if (kronecker < -1)
            goto err;
        /* we actually need BN_kronecker(a, |b|) */
        if (a->neg && b->neg)
            kronecker = -kronecker;

        if (legendre != kronecker) {
            fprintf(stderr, "legendre != kronecker; a = ");
            BN_print_fp(stderr, a);
            fprintf(stderr, ", b = ");
            BN_print_fp(stderr, b);
            fprintf(stderr, "\n");
            goto err;
        }

        putc('.', stderr);
        fflush(stderr);
    }

    putc('\n', stderr);
    fflush(stderr);
    ret = 1;
 err:
    BN_free(a);
    BN_free(b);
    BN_free(r);
    BN_free(t);
    return ret;
}

int test_sqrt(BIO *bp, BN_CTX *ctx)
{
    BN_GENCB cb;
    BIGNUM *a, *p, *r;
    int i, j;
    int ret = 0;

    a = BN_new();
    p = BN_new();
    r = BN_new();
    if (a == NULL || p == NULL || r == NULL)
        goto err;

    BN_GENCB_set(&cb, genprime_cb, NULL);

    for (i = 0; i < 16; i++) {
        if (i < 8) {
            unsigned primes[8] = { 2, 3, 5, 7, 11, 13, 17, 19 };

            if (!BN_set_word(p, primes[i]))
                goto err;
        } else {
            if (!BN_set_word(a, 32))
                goto err;
            if (!BN_set_word(r, 2 * i + 1))
                goto err;

            if (!BN_generate_prime_ex(p, 256, 0, a, r, &cb))
                goto err;
            putc('\n', stderr);
        }
        p->neg = rand_neg();

        for (j = 0; j < num2; j++) {
            /*
             * construct 'a' such that it is a square modulo p, but in
             * general not a proper square and not reduced modulo p
             */
            if (!BN_bntest_rand(r, 256, 0, 3))
                goto err;
            if (!BN_nnmod(r, r, p, ctx))
                goto err;
            if (!BN_mod_sqr(r, r, p, ctx))
                goto err;
            if (!BN_bntest_rand(a, 256, 0, 3))
                goto err;
            if (!BN_nnmod(a, a, p, ctx))
                goto err;
            if (!BN_mod_sqr(a, a, p, ctx))
                goto err;
            if (!BN_mul(a, a, r, ctx))
                goto err;
            if (rand_neg())
                if (!BN_sub(a, a, p))
                    goto err;

            if (!BN_mod_sqrt(r, a, p, ctx))
                goto err;
            if (!BN_mod_sqr(r, r, p, ctx))
                goto err;

            if (!BN_nnmod(a, a, p, ctx))
                goto err;

            if (BN_cmp(a, r) != 0) {
                fprintf(stderr, "BN_mod_sqrt failed: a = ");
                BN_print_fp(stderr, a);
                fprintf(stderr, ", r = ");
                BN_print_fp(stderr, r);
                fprintf(stderr, ", p = ");
                BN_print_fp(stderr, p);
                fprintf(stderr, "\n");
                goto err;
            }

            putc('.', stderr);
            fflush(stderr);
        }

        putc('\n', stderr);
        fflush(stderr);
    }
    ret = 1;
 err:
    BN_free(a);
    BN_free(p);
    BN_free(r);
    return ret;
}

int test_small_prime(BIO *bp, BN_CTX *ctx)
{
    static const int bits = 10;
    int ret = 0;
    BIGNUM *r;

    r = BN_new();
    if (!BN_generate_prime_ex(r, bits, 0, NULL, NULL, NULL))
        goto err;
    if (BN_num_bits(r) != bits) {
        BIO_printf(bp, "Expected %d bit prime, got %d bit number\n", bits,
                   BN_num_bits(r));
        goto err;
    }

    ret = 1;

 err:
    BN_clear_free(r);
    return ret;
}

int test_lshift(BIO *bp, BN_CTX *ctx, BIGNUM *a_)
{
    BIGNUM *a, *b, *c, *d;
    int i;

    b = BN_new();
    c = BN_new();
    d = BN_new();
    BN_one(c);

    if (a_)
        a = a_;
    else {
        a = BN_new();
        BN_bntest_rand(a, 200, 0, 0);
        a->neg = rand_neg();
    }
    for (i = 0; i < num0; i++) {
        BN_lshift(b, a, i + 1);
        BN_add(c, c, c);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " * ");
                BN_print(bp, c);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, b);
            BIO_puts(bp, "\n");
        }
        BN_mul(d, a, c, ctx);
        BN_sub(d, d, b);
        if (!BN_is_zero(d)) {
            fprintf(stderr, "Left shift test failed!\n");
            fprintf(stderr, "a=");
            BN_print_fp(stderr, a);
            fprintf(stderr, "\nb=");
            BN_print_fp(stderr, b);
            fprintf(stderr, "\nc=");
            BN_print_fp(stderr, c);
            fprintf(stderr, "\nd=");
            BN_print_fp(stderr, d);
            fprintf(stderr, "\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    return (1);
}

int test_lshift1(BIO *bp)
{
    BIGNUM *a, *b, *c;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();

    BN_bntest_rand(a, 200, 0, 0);
    a->neg = rand_neg();
    for (i = 0; i < num0; i++) {
        BN_lshift1(b, a);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " * 2");
                BIO_puts(bp, " - ");
            }
            BN_print(bp, b);
            BIO_puts(bp, "\n");
        }
        BN_add(c, a, a);
        BN_sub(a, b, c);
        if (!BN_is_zero(a)) {
            fprintf(stderr, "Left shift one test failed!\n");
            return 0;
        }

        BN_copy(a, b);
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    return (1);
}

int test_rshift(BIO *bp, BN_CTX *ctx)
{
    BIGNUM *a, *b, *c, *d, *e;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();
    d = BN_new();
    e = BN_new();
    BN_one(c);

    BN_bntest_rand(a, 200, 0, 0);
    a->neg = rand_neg();
    for (i = 0; i < num0; i++) {
        BN_rshift(b, a, i + 1);
        BN_add(c, c, c);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " / ");
                BN_print(bp, c);
                BIO_puts(bp, " - ");
            }
            BN_print(bp, b);
            BIO_puts(bp, "\n");
        }
        BN_div(d, e, a, c, ctx);
        BN_sub(d, d, b);
        if (!BN_is_zero(d)) {
            fprintf(stderr, "Right shift test failed!\n");
            return 0;
        }
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    BN_free(d);
    BN_free(e);
    return (1);
}

int test_rshift1(BIO *bp)
{
    BIGNUM *a, *b, *c;
    int i;

    a = BN_new();
    b = BN_new();
    c = BN_new();

    BN_bntest_rand(a, 200, 0, 0);
    a->neg = rand_neg();
    for (i = 0; i < num0; i++) {
        BN_rshift1(b, a);
        if (bp != NULL) {
            if (!results) {
                BN_print(bp, a);
                BIO_puts(bp, " / 2");
                BIO_puts(bp, " - ");
            }
            BN_print(bp, b);
            BIO_puts(bp, "\n");
        }
        BN_sub(c, a, b);
        BN_sub(c, c, b);
        if (!BN_is_zero(c) && !BN_abs_is_word(c, 1)) {
            fprintf(stderr, "Right shift one test failed!\n");
            return 0;
        }
        BN_copy(a, b);
    }
    BN_free(a);
    BN_free(b);
    BN_free(c);
    return (1);
}

int rand_neg(void)
{
    static unsigned int neg = 0;
    static int sign[8] = { 0, 0, 0, 1, 1, 0, 1, 1 };

    return (sign[(neg++) % 8]);
}
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