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      1 /* Copyright (C) 1995-1997 Eric Young (eay (at) cryptsoft.com)
      2  * All rights reserved.
      3  *
      4  * This package is an SSL implementation written
      5  * by Eric Young (eay (at) cryptsoft.com).
      6  * The implementation was written so as to conform with Netscapes SSL.
      7  *
      8  * This library is free for commercial and non-commercial use as long as
      9  * the following conditions are aheared to.  The following conditions
     10  * apply to all code found in this distribution, be it the RC4, RSA,
     11  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
     12  * included with this distribution is covered by the same copyright terms
     13  * except that the holder is Tim Hudson (tjh (at) cryptsoft.com).
     14  *
     15  * Copyright remains Eric Young's, and as such any Copyright notices in
     16  * the code are not to be removed.
     17  * If this package is used in a product, Eric Young should be given attribution
     18  * as the author of the parts of the library used.
     19  * This can be in the form of a textual message at program startup or
     20  * in documentation (online or textual) provided with the package.
     21  *
     22  * Redistribution and use in source and binary forms, with or without
     23  * modification, are permitted provided that the following conditions
     24  * are met:
     25  * 1. Redistributions of source code must retain the copyright
     26  *    notice, this list of conditions and the following disclaimer.
     27  * 2. Redistributions in binary form must reproduce the above copyright
     28  *    notice, this list of conditions and the following disclaimer in the
     29  *    documentation and/or other materials provided with the distribution.
     30  * 3. All advertising materials mentioning features or use of this software
     31  *    must display the following acknowledgement:
     32  *    "This product includes cryptographic software written by
     33  *     Eric Young (eay (at) cryptsoft.com)"
     34  *    The word 'cryptographic' can be left out if the rouines from the library
     35  *    being used are not cryptographic related :-).
     36  * 4. If you include any Windows specific code (or a derivative thereof) from
     37  *    the apps directory (application code) you must include an acknowledgement:
     38  *    "This product includes software written by Tim Hudson (tjh (at) cryptsoft.com)"
     39  *
     40  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
     41  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     42  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     43  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     44  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     45  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     46  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     48  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     49  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     50  * SUCH DAMAGE.
     51  *
     52  * The licence and distribution terms for any publically available version or
     53  * derivative of this code cannot be changed.  i.e. this code cannot simply be
     54  * copied and put under another distribution licence
     55  * [including the GNU Public Licence.]
     56  */
     57 /* ====================================================================
     58  * Copyright (c) 1998-2006 The OpenSSL Project.  All rights reserved.
     59  *
     60  * Redistribution and use in source and binary forms, with or without
     61  * modification, are permitted provided that the following conditions
     62  * are met:
     63  *
     64  * 1. Redistributions of source code must retain the above copyright
     65  *    notice, this list of conditions and the following disclaimer.
     66  *
     67  * 2. Redistributions in binary form must reproduce the above copyright
     68  *    notice, this list of conditions and the following disclaimer in
     69  *    the documentation and/or other materials provided with the
     70  *    distribution.
     71  *
     72  * 3. All advertising materials mentioning features or use of this
     73  *    software must display the following acknowledgment:
     74  *    "This product includes software developed by the OpenSSL Project
     75  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
     76  *
     77  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
     78  *    endorse or promote products derived from this software without
     79  *    prior written permission. For written permission, please contact
     80  *    openssl-core (at) openssl.org.
     81  *
     82  * 5. Products derived from this software may not be called "OpenSSL"
     83  *    nor may "OpenSSL" appear in their names without prior written
     84  *    permission of the OpenSSL Project.
     85  *
     86  * 6. Redistributions of any form whatsoever must retain the following
     87  *    acknowledgment:
     88  *    "This product includes software developed by the OpenSSL Project
     89  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
     90  *
     91  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
     92  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     93  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     94  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
     95  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     96  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     97  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     98  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     99  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
    100  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    101  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
    102  * OF THE POSSIBILITY OF SUCH DAMAGE.
    103  * ====================================================================
    104  *
    105  * This product includes cryptographic software written by Eric Young
    106  * (eay (at) cryptsoft.com).  This product includes software written by Tim
    107  * Hudson (tjh (at) cryptsoft.com).
    108  *
    109  */
    110 /* ====================================================================
    111  * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
    112  *
    113  * Portions of the attached software ("Contribution") are developed by
    114  * SUN MICROSYSTEMS, INC., and are contributed to the OpenSSL project.
    115  *
    116  * The Contribution is licensed pursuant to the Eric Young open source
    117  * license provided above.
    118  *
    119  * The binary polynomial arithmetic software is originally written by
    120  * Sheueling Chang Shantz and Douglas Stebila of Sun Microsystems
    121  * Laboratories. */
    122 
    123 #ifndef OPENSSL_HEADER_BN_H
    124 #define OPENSSL_HEADER_BN_H
    125 
    126 #include <openssl/base.h>
    127 #include <openssl/thread.h>
    128 
    129 #include <inttypes.h>  // for PRIu64 and friends
    130 #include <stdio.h>  // for FILE*
    131 
    132 #if defined(__cplusplus)
    133 extern "C" {
    134 #endif
    135 
    136 
    137 // BN provides support for working with arbitrary sized integers. For example,
    138 // although the largest integer supported by the compiler might be 64 bits, BN
    139 // will allow you to work with numbers until you run out of memory.
    140 
    141 
    142 // BN_ULONG is the native word size when working with big integers.
    143 //
    144 // Note: on some platforms, inttypes.h does not define print format macros in
    145 // C++ unless |__STDC_FORMAT_MACROS| defined. As this is a public header, bn.h
    146 // does not define |__STDC_FORMAT_MACROS| itself. C++ source files which use the
    147 // FMT macros must define it externally.
    148 #if defined(OPENSSL_64_BIT)
    149 #define BN_ULONG uint64_t
    150 #define BN_BITS2 64
    151 #define BN_DEC_FMT1 "%" PRIu64
    152 #define BN_DEC_FMT2 "%019" PRIu64
    153 #define BN_HEX_FMT1 "%" PRIx64
    154 #define BN_HEX_FMT2 "%016" PRIx64
    155 #elif defined(OPENSSL_32_BIT)
    156 #define BN_ULONG uint32_t
    157 #define BN_BITS2 32
    158 #define BN_DEC_FMT1 "%" PRIu32
    159 #define BN_DEC_FMT2 "%09" PRIu32
    160 #define BN_HEX_FMT1 "%" PRIx32
    161 #define BN_HEX_FMT2 "%08" PRIx64
    162 #else
    163 #error "Must define either OPENSSL_32_BIT or OPENSSL_64_BIT"
    164 #endif
    165 
    166 
    167 // Allocation and freeing.
    168 
    169 // BN_new creates a new, allocated BIGNUM and initialises it.
    170 OPENSSL_EXPORT BIGNUM *BN_new(void);
    171 
    172 // BN_init initialises a stack allocated |BIGNUM|.
    173 OPENSSL_EXPORT void BN_init(BIGNUM *bn);
    174 
    175 // BN_free frees the data referenced by |bn| and, if |bn| was originally
    176 // allocated on the heap, frees |bn| also.
    177 OPENSSL_EXPORT void BN_free(BIGNUM *bn);
    178 
    179 // BN_clear_free erases and frees the data referenced by |bn| and, if |bn| was
    180 // originally allocated on the heap, frees |bn| also.
    181 OPENSSL_EXPORT void BN_clear_free(BIGNUM *bn);
    182 
    183 // BN_dup allocates a new BIGNUM and sets it equal to |src|. It returns the
    184 // allocated BIGNUM on success or NULL otherwise.
    185 OPENSSL_EXPORT BIGNUM *BN_dup(const BIGNUM *src);
    186 
    187 // BN_copy sets |dest| equal to |src| and returns |dest| or NULL on allocation
    188 // failure.
    189 OPENSSL_EXPORT BIGNUM *BN_copy(BIGNUM *dest, const BIGNUM *src);
    190 
    191 // BN_clear sets |bn| to zero and erases the old data.
    192 OPENSSL_EXPORT void BN_clear(BIGNUM *bn);
    193 
    194 // BN_value_one returns a static BIGNUM with value 1.
    195 OPENSSL_EXPORT const BIGNUM *BN_value_one(void);
    196 
    197 
    198 // Basic functions.
    199 
    200 // BN_num_bits returns the minimum number of bits needed to represent the
    201 // absolute value of |bn|.
    202 OPENSSL_EXPORT unsigned BN_num_bits(const BIGNUM *bn);
    203 
    204 // BN_num_bytes returns the minimum number of bytes needed to represent the
    205 // absolute value of |bn|.
    206 OPENSSL_EXPORT unsigned BN_num_bytes(const BIGNUM *bn);
    207 
    208 // BN_zero sets |bn| to zero.
    209 OPENSSL_EXPORT void BN_zero(BIGNUM *bn);
    210 
    211 // BN_one sets |bn| to one. It returns one on success or zero on allocation
    212 // failure.
    213 OPENSSL_EXPORT int BN_one(BIGNUM *bn);
    214 
    215 // BN_set_word sets |bn| to |value|. It returns one on success or zero on
    216 // allocation failure.
    217 OPENSSL_EXPORT int BN_set_word(BIGNUM *bn, BN_ULONG value);
    218 
    219 // BN_set_u64 sets |bn| to |value|. It returns one on success or zero on
    220 // allocation failure.
    221 OPENSSL_EXPORT int BN_set_u64(BIGNUM *bn, uint64_t value);
    222 
    223 // BN_set_negative sets the sign of |bn|.
    224 OPENSSL_EXPORT void BN_set_negative(BIGNUM *bn, int sign);
    225 
    226 // BN_is_negative returns one if |bn| is negative and zero otherwise.
    227 OPENSSL_EXPORT int BN_is_negative(const BIGNUM *bn);
    228 
    229 
    230 // Conversion functions.
    231 
    232 // BN_bin2bn sets |*ret| to the value of |len| bytes from |in|, interpreted as
    233 // a big-endian number, and returns |ret|. If |ret| is NULL then a fresh
    234 // |BIGNUM| is allocated and returned. It returns NULL on allocation
    235 // failure.
    236 OPENSSL_EXPORT BIGNUM *BN_bin2bn(const uint8_t *in, size_t len, BIGNUM *ret);
    237 
    238 // BN_bn2bin serialises the absolute value of |in| to |out| as a big-endian
    239 // integer, which must have |BN_num_bytes| of space available. It returns the
    240 // number of bytes written.
    241 OPENSSL_EXPORT size_t BN_bn2bin(const BIGNUM *in, uint8_t *out);
    242 
    243 // BN_le2bn sets |*ret| to the value of |len| bytes from |in|, interpreted as
    244 // a little-endian number, and returns |ret|. If |ret| is NULL then a fresh
    245 // |BIGNUM| is allocated and returned. It returns NULL on allocation
    246 // failure.
    247 OPENSSL_EXPORT BIGNUM *BN_le2bn(const uint8_t *in, size_t len, BIGNUM *ret);
    248 
    249 // BN_bn2le_padded serialises the absolute value of |in| to |out| as a
    250 // little-endian integer, which must have |len| of space available, padding
    251 // out the remainder of out with zeros. If |len| is smaller than |BN_num_bytes|,
    252 // the function fails and returns 0. Otherwise, it returns 1.
    253 OPENSSL_EXPORT int BN_bn2le_padded(uint8_t *out, size_t len, const BIGNUM *in);
    254 
    255 // BN_bn2bin_padded serialises the absolute value of |in| to |out| as a
    256 // big-endian integer. The integer is padded with leading zeros up to size
    257 // |len|. If |len| is smaller than |BN_num_bytes|, the function fails and
    258 // returns 0. Otherwise, it returns 1.
    259 OPENSSL_EXPORT int BN_bn2bin_padded(uint8_t *out, size_t len, const BIGNUM *in);
    260 
    261 // BN_bn2cbb_padded behaves like |BN_bn2bin_padded| but writes to a |CBB|.
    262 OPENSSL_EXPORT int BN_bn2cbb_padded(CBB *out, size_t len, const BIGNUM *in);
    263 
    264 // BN_bn2hex returns an allocated string that contains a NUL-terminated, hex
    265 // representation of |bn|. If |bn| is negative, the first char in the resulting
    266 // string will be '-'. Returns NULL on allocation failure.
    267 OPENSSL_EXPORT char *BN_bn2hex(const BIGNUM *bn);
    268 
    269 // BN_hex2bn parses the leading hex number from |in|, which may be proceeded by
    270 // a '-' to indicate a negative number and may contain trailing, non-hex data.
    271 // If |outp| is not NULL, it constructs a BIGNUM equal to the hex number and
    272 // stores it in |*outp|. If |*outp| is NULL then it allocates a new BIGNUM and
    273 // updates |*outp|. It returns the number of bytes of |in| processed or zero on
    274 // error.
    275 OPENSSL_EXPORT int BN_hex2bn(BIGNUM **outp, const char *in);
    276 
    277 // BN_bn2dec returns an allocated string that contains a NUL-terminated,
    278 // decimal representation of |bn|. If |bn| is negative, the first char in the
    279 // resulting string will be '-'. Returns NULL on allocation failure.
    280 OPENSSL_EXPORT char *BN_bn2dec(const BIGNUM *a);
    281 
    282 // BN_dec2bn parses the leading decimal number from |in|, which may be
    283 // proceeded by a '-' to indicate a negative number and may contain trailing,
    284 // non-decimal data. If |outp| is not NULL, it constructs a BIGNUM equal to the
    285 // decimal number and stores it in |*outp|. If |*outp| is NULL then it
    286 // allocates a new BIGNUM and updates |*outp|. It returns the number of bytes
    287 // of |in| processed or zero on error.
    288 OPENSSL_EXPORT int BN_dec2bn(BIGNUM **outp, const char *in);
    289 
    290 // BN_asc2bn acts like |BN_dec2bn| or |BN_hex2bn| depending on whether |in|
    291 // begins with "0X" or "0x" (indicating hex) or not (indicating decimal). A
    292 // leading '-' is still permitted and comes before the optional 0X/0x. It
    293 // returns one on success or zero on error.
    294 OPENSSL_EXPORT int BN_asc2bn(BIGNUM **outp, const char *in);
    295 
    296 // BN_print writes a hex encoding of |a| to |bio|. It returns one on success
    297 // and zero on error.
    298 OPENSSL_EXPORT int BN_print(BIO *bio, const BIGNUM *a);
    299 
    300 // BN_print_fp acts like |BIO_print|, but wraps |fp| in a |BIO| first.
    301 OPENSSL_EXPORT int BN_print_fp(FILE *fp, const BIGNUM *a);
    302 
    303 // BN_get_word returns the absolute value of |bn| as a single word. If |bn| is
    304 // too large to be represented as a single word, the maximum possible value
    305 // will be returned.
    306 OPENSSL_EXPORT BN_ULONG BN_get_word(const BIGNUM *bn);
    307 
    308 // BN_get_u64 sets |*out| to the absolute value of |bn| as a |uint64_t| and
    309 // returns one. If |bn| is too large to be represented as a |uint64_t|, it
    310 // returns zero.
    311 OPENSSL_EXPORT int BN_get_u64(const BIGNUM *bn, uint64_t *out);
    312 
    313 
    314 // ASN.1 functions.
    315 
    316 // BN_parse_asn1_unsigned parses a non-negative DER INTEGER from |cbs| writes
    317 // the result to |ret|. It returns one on success and zero on failure.
    318 OPENSSL_EXPORT int BN_parse_asn1_unsigned(CBS *cbs, BIGNUM *ret);
    319 
    320 // BN_marshal_asn1 marshals |bn| as a non-negative DER INTEGER and appends the
    321 // result to |cbb|. It returns one on success and zero on failure.
    322 OPENSSL_EXPORT int BN_marshal_asn1(CBB *cbb, const BIGNUM *bn);
    323 
    324 
    325 // BIGNUM pools.
    326 //
    327 // Certain BIGNUM operations need to use many temporary variables and
    328 // allocating and freeing them can be quite slow. Thus such operations typically
    329 // take a |BN_CTX| parameter, which contains a pool of |BIGNUMs|. The |ctx|
    330 // argument to a public function may be NULL, in which case a local |BN_CTX|
    331 // will be created just for the lifetime of that call.
    332 //
    333 // A function must call |BN_CTX_start| first. Then, |BN_CTX_get| may be called
    334 // repeatedly to obtain temporary |BIGNUM|s. All |BN_CTX_get| calls must be made
    335 // before calling any other functions that use the |ctx| as an argument.
    336 //
    337 // Finally, |BN_CTX_end| must be called before returning from the function.
    338 // When |BN_CTX_end| is called, the |BIGNUM| pointers obtained from
    339 // |BN_CTX_get| become invalid.
    340 
    341 // BN_CTX_new returns a new, empty BN_CTX or NULL on allocation failure.
    342 OPENSSL_EXPORT BN_CTX *BN_CTX_new(void);
    343 
    344 // BN_CTX_free frees all BIGNUMs contained in |ctx| and then frees |ctx|
    345 // itself.
    346 OPENSSL_EXPORT void BN_CTX_free(BN_CTX *ctx);
    347 
    348 // BN_CTX_start "pushes" a new entry onto the |ctx| stack and allows future
    349 // calls to |BN_CTX_get|.
    350 OPENSSL_EXPORT void BN_CTX_start(BN_CTX *ctx);
    351 
    352 // BN_CTX_get returns a new |BIGNUM|, or NULL on allocation failure. Once
    353 // |BN_CTX_get| has returned NULL, all future calls will also return NULL until
    354 // |BN_CTX_end| is called.
    355 OPENSSL_EXPORT BIGNUM *BN_CTX_get(BN_CTX *ctx);
    356 
    357 // BN_CTX_end invalidates all |BIGNUM|s returned from |BN_CTX_get| since the
    358 // matching |BN_CTX_start| call.
    359 OPENSSL_EXPORT void BN_CTX_end(BN_CTX *ctx);
    360 
    361 
    362 // Simple arithmetic
    363 
    364 // BN_add sets |r| = |a| + |b|, where |r| may be the same pointer as either |a|
    365 // or |b|. It returns one on success and zero on allocation failure.
    366 OPENSSL_EXPORT int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
    367 
    368 // BN_uadd sets |r| = |a| + |b|, where |a| and |b| are non-negative and |r| may
    369 // be the same pointer as either |a| or |b|. It returns one on success and zero
    370 // on allocation failure.
    371 OPENSSL_EXPORT int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
    372 
    373 // BN_add_word adds |w| to |a|. It returns one on success and zero otherwise.
    374 OPENSSL_EXPORT int BN_add_word(BIGNUM *a, BN_ULONG w);
    375 
    376 // BN_sub sets |r| = |a| - |b|, where |r| may be the same pointer as either |a|
    377 // or |b|. It returns one on success and zero on allocation failure.
    378 OPENSSL_EXPORT int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
    379 
    380 // BN_usub sets |r| = |a| - |b|, where |a| and |b| are non-negative integers,
    381 // |b| < |a| and |r| may be the same pointer as either |a| or |b|. It returns
    382 // one on success and zero on allocation failure.
    383 OPENSSL_EXPORT int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b);
    384 
    385 // BN_sub_word subtracts |w| from |a|. It returns one on success and zero on
    386 // allocation failure.
    387 OPENSSL_EXPORT int BN_sub_word(BIGNUM *a, BN_ULONG w);
    388 
    389 // BN_mul sets |r| = |a| * |b|, where |r| may be the same pointer as |a| or
    390 // |b|. Returns one on success and zero otherwise.
    391 OPENSSL_EXPORT int BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
    392                           BN_CTX *ctx);
    393 
    394 // BN_mul_word sets |bn| = |bn| * |w|. It returns one on success or zero on
    395 // allocation failure.
    396 OPENSSL_EXPORT int BN_mul_word(BIGNUM *bn, BN_ULONG w);
    397 
    398 // BN_sqr sets |r| = |a|^2 (i.e. squares), where |r| may be the same pointer as
    399 // |a|. Returns one on success and zero otherwise. This is more efficient than
    400 // BN_mul(r, a, a, ctx).
    401 OPENSSL_EXPORT int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx);
    402 
    403 // BN_div divides |numerator| by |divisor| and places the result in |quotient|
    404 // and the remainder in |rem|. Either of |quotient| or |rem| may be NULL, in
    405 // which case the respective value is not returned. The result is rounded
    406 // towards zero; thus if |numerator| is negative, the remainder will be zero or
    407 // negative. It returns one on success or zero on error.
    408 OPENSSL_EXPORT int BN_div(BIGNUM *quotient, BIGNUM *rem,
    409                           const BIGNUM *numerator, const BIGNUM *divisor,
    410                           BN_CTX *ctx);
    411 
    412 // BN_div_word sets |numerator| = |numerator|/|divisor| and returns the
    413 // remainder or (BN_ULONG)-1 on error.
    414 OPENSSL_EXPORT BN_ULONG BN_div_word(BIGNUM *numerator, BN_ULONG divisor);
    415 
    416 // BN_sqrt sets |*out_sqrt| (which may be the same |BIGNUM| as |in|) to the
    417 // square root of |in|, using |ctx|. It returns one on success or zero on
    418 // error. Negative numbers and non-square numbers will result in an error with
    419 // appropriate errors on the error queue.
    420 OPENSSL_EXPORT int BN_sqrt(BIGNUM *out_sqrt, const BIGNUM *in, BN_CTX *ctx);
    421 
    422 
    423 // Comparison functions
    424 
    425 // BN_cmp returns a value less than, equal to or greater than zero if |a| is
    426 // less than, equal to or greater than |b|, respectively.
    427 OPENSSL_EXPORT int BN_cmp(const BIGNUM *a, const BIGNUM *b);
    428 
    429 // BN_cmp_word is like |BN_cmp| except it takes its second argument as a
    430 // |BN_ULONG| instead of a |BIGNUM|.
    431 OPENSSL_EXPORT int BN_cmp_word(const BIGNUM *a, BN_ULONG b);
    432 
    433 // BN_ucmp returns a value less than, equal to or greater than zero if the
    434 // absolute value of |a| is less than, equal to or greater than the absolute
    435 // value of |b|, respectively.
    436 OPENSSL_EXPORT int BN_ucmp(const BIGNUM *a, const BIGNUM *b);
    437 
    438 // BN_equal_consttime returns one if |a| is equal to |b|, and zero otherwise.
    439 // It takes an amount of time dependent on the sizes of |a| and |b|, but
    440 // independent of the contents (including the signs) of |a| and |b|.
    441 OPENSSL_EXPORT int BN_equal_consttime(const BIGNUM *a, const BIGNUM *b);
    442 
    443 // BN_less_than_consttime returns one if |a| is less than |b|, and zero
    444 // otherwise. It takes an amount of time dependent on the sizes and signs of |a|
    445 // and |b|, but independent of the contents of |a| and |b|.
    446 OPENSSL_EXPORT int BN_less_than_consttime(const BIGNUM *a, const BIGNUM *b);
    447 
    448 // BN_abs_is_word returns one if the absolute value of |bn| equals |w| and zero
    449 // otherwise.
    450 OPENSSL_EXPORT int BN_abs_is_word(const BIGNUM *bn, BN_ULONG w);
    451 
    452 // BN_is_zero returns one if |bn| is zero and zero otherwise.
    453 OPENSSL_EXPORT int BN_is_zero(const BIGNUM *bn);
    454 
    455 // BN_is_one returns one if |bn| equals one and zero otherwise.
    456 OPENSSL_EXPORT int BN_is_one(const BIGNUM *bn);
    457 
    458 // BN_is_word returns one if |bn| is exactly |w| and zero otherwise.
    459 OPENSSL_EXPORT int BN_is_word(const BIGNUM *bn, BN_ULONG w);
    460 
    461 // BN_is_odd returns one if |bn| is odd and zero otherwise.
    462 OPENSSL_EXPORT int BN_is_odd(const BIGNUM *bn);
    463 
    464 // BN_is_pow2 returns 1 if |a| is a power of two, and 0 otherwise.
    465 OPENSSL_EXPORT int BN_is_pow2(const BIGNUM *a);
    466 
    467 // Bitwise operations.
    468 
    469 // BN_lshift sets |r| equal to |a| << n. The |a| and |r| arguments may be the
    470 // same |BIGNUM|. It returns one on success and zero on allocation failure.
    471 OPENSSL_EXPORT int BN_lshift(BIGNUM *r, const BIGNUM *a, int n);
    472 
    473 // BN_lshift1 sets |r| equal to |a| << 1, where |r| and |a| may be the same
    474 // pointer. It returns one on success and zero on allocation failure.
    475 OPENSSL_EXPORT int BN_lshift1(BIGNUM *r, const BIGNUM *a);
    476 
    477 // BN_rshift sets |r| equal to |a| >> n, where |r| and |a| may be the same
    478 // pointer. It returns one on success and zero on allocation failure.
    479 OPENSSL_EXPORT int BN_rshift(BIGNUM *r, const BIGNUM *a, int n);
    480 
    481 // BN_rshift1 sets |r| equal to |a| >> 1, where |r| and |a| may be the same
    482 // pointer. It returns one on success and zero on allocation failure.
    483 OPENSSL_EXPORT int BN_rshift1(BIGNUM *r, const BIGNUM *a);
    484 
    485 // BN_set_bit sets the |n|th, least-significant bit in |a|. For example, if |a|
    486 // is 2 then setting bit zero will make it 3. It returns one on success or zero
    487 // on allocation failure.
    488 OPENSSL_EXPORT int BN_set_bit(BIGNUM *a, int n);
    489 
    490 // BN_clear_bit clears the |n|th, least-significant bit in |a|. For example, if
    491 // |a| is 3, clearing bit zero will make it two. It returns one on success or
    492 // zero on allocation failure.
    493 OPENSSL_EXPORT int BN_clear_bit(BIGNUM *a, int n);
    494 
    495 // BN_is_bit_set returns one if the |n|th least-significant bit in |a| exists
    496 // and is set. Otherwise, it returns zero.
    497 OPENSSL_EXPORT int BN_is_bit_set(const BIGNUM *a, int n);
    498 
    499 // BN_mask_bits truncates |a| so that it is only |n| bits long. It returns one
    500 // on success or zero if |n| is greater than the length of |a| already.
    501 OPENSSL_EXPORT int BN_mask_bits(BIGNUM *a, int n);
    502 
    503 
    504 // Modulo arithmetic.
    505 
    506 // BN_mod_word returns |a| mod |w| or (BN_ULONG)-1 on error.
    507 OPENSSL_EXPORT BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w);
    508 
    509 // BN_mod_pow2 sets |r| = |a| mod 2^|e|. It returns 1 on success and
    510 // 0 on error.
    511 OPENSSL_EXPORT int BN_mod_pow2(BIGNUM *r, const BIGNUM *a, size_t e);
    512 
    513 // BN_nnmod_pow2 sets |r| = |a| mod 2^|e| where |r| is always positive.
    514 // It returns 1 on success and 0 on error.
    515 OPENSSL_EXPORT int BN_nnmod_pow2(BIGNUM *r, const BIGNUM *a, size_t e);
    516 
    517 // BN_mod is a helper macro that calls |BN_div| and discards the quotient.
    518 #define BN_mod(rem, numerator, divisor, ctx) \
    519   BN_div(NULL, (rem), (numerator), (divisor), (ctx))
    520 
    521 // BN_nnmod is a non-negative modulo function. It acts like |BN_mod|, but 0 <=
    522 // |rem| < |divisor| is always true. It returns one on success and zero on
    523 // error.
    524 OPENSSL_EXPORT int BN_nnmod(BIGNUM *rem, const BIGNUM *numerator,
    525                             const BIGNUM *divisor, BN_CTX *ctx);
    526 
    527 // BN_mod_add sets |r| = |a| + |b| mod |m|. It returns one on success and zero
    528 // on error.
    529 OPENSSL_EXPORT int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
    530                               const BIGNUM *m, BN_CTX *ctx);
    531 
    532 // BN_mod_add_quick acts like |BN_mod_add| but requires that |a| and |b| be
    533 // non-negative and less than |m|.
    534 OPENSSL_EXPORT int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
    535                                     const BIGNUM *m);
    536 
    537 // BN_mod_sub sets |r| = |a| - |b| mod |m|. It returns one on success and zero
    538 // on error.
    539 OPENSSL_EXPORT int BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
    540                               const BIGNUM *m, BN_CTX *ctx);
    541 
    542 // BN_mod_sub_quick acts like |BN_mod_sub| but requires that |a| and |b| be
    543 // non-negative and less than |m|.
    544 OPENSSL_EXPORT int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
    545                                     const BIGNUM *m);
    546 
    547 // BN_mod_mul sets |r| = |a|*|b| mod |m|. It returns one on success and zero
    548 // on error.
    549 OPENSSL_EXPORT int BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
    550                               const BIGNUM *m, BN_CTX *ctx);
    551 
    552 // BN_mod_sqr sets |r| = |a|^2 mod |m|. It returns one on success and zero
    553 // on error.
    554 OPENSSL_EXPORT int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m,
    555                               BN_CTX *ctx);
    556 
    557 // BN_mod_lshift sets |r| = (|a| << n) mod |m|, where |r| and |a| may be the
    558 // same pointer. It returns one on success and zero on error.
    559 OPENSSL_EXPORT int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n,
    560                                  const BIGNUM *m, BN_CTX *ctx);
    561 
    562 // BN_mod_lshift_quick acts like |BN_mod_lshift| but requires that |a| be
    563 // non-negative and less than |m|.
    564 OPENSSL_EXPORT int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n,
    565                                        const BIGNUM *m);
    566 
    567 // BN_mod_lshift1 sets |r| = (|a| << 1) mod |m|, where |r| and |a| may be the
    568 // same pointer. It returns one on success and zero on error.
    569 OPENSSL_EXPORT int BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m,
    570                                   BN_CTX *ctx);
    571 
    572 // BN_mod_lshift1_quick acts like |BN_mod_lshift1| but requires that |a| be
    573 // non-negative and less than |m|.
    574 OPENSSL_EXPORT int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a,
    575                                         const BIGNUM *m);
    576 
    577 // BN_mod_sqrt returns a newly-allocated |BIGNUM|, r, such that
    578 // r^2 == a (mod p). |p| must be a prime. It returns NULL on error or if |a| is
    579 // not a square mod |p|. In the latter case, it will add |BN_R_NOT_A_SQUARE| to
    580 // the error queue.
    581 OPENSSL_EXPORT BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p,
    582                                    BN_CTX *ctx);
    583 
    584 
    585 // Random and prime number generation.
    586 
    587 // The following are values for the |top| parameter of |BN_rand|.
    588 #define BN_RAND_TOP_ANY    (-1)
    589 #define BN_RAND_TOP_ONE     0
    590 #define BN_RAND_TOP_TWO     1
    591 
    592 // The following are values for the |bottom| parameter of |BN_rand|.
    593 #define BN_RAND_BOTTOM_ANY  0
    594 #define BN_RAND_BOTTOM_ODD  1
    595 
    596 // BN_rand sets |rnd| to a random number of length |bits|. It returns one on
    597 // success and zero otherwise.
    598 //
    599 // |top| must be one of the |BN_RAND_TOP_*| values. If |BN_RAND_TOP_ONE|, the
    600 // most-significant bit, if any, will be set. If |BN_RAND_TOP_TWO|, the two
    601 // most significant bits, if any, will be set. If |BN_RAND_TOP_ANY|, no extra
    602 // action will be taken and |BN_num_bits(rnd)| may not equal |bits| if the most
    603 // significant bits randomly ended up as zeros.
    604 //
    605 // |bottom| must be one of the |BN_RAND_BOTTOM_*| values. If
    606 // |BN_RAND_BOTTOM_ODD|, the least-significant bit, if any, will be set. If
    607 // |BN_RAND_BOTTOM_ANY|, no extra action will be taken.
    608 OPENSSL_EXPORT int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
    609 
    610 // BN_pseudo_rand is an alias for |BN_rand|.
    611 OPENSSL_EXPORT int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
    612 
    613 // BN_rand_range is equivalent to |BN_rand_range_ex| with |min_inclusive| set
    614 // to zero and |max_exclusive| set to |range|.
    615 OPENSSL_EXPORT int BN_rand_range(BIGNUM *rnd, const BIGNUM *range);
    616 
    617 // BN_rand_range_ex sets |rnd| to a random value in
    618 // [min_inclusive..max_exclusive). It returns one on success and zero
    619 // otherwise.
    620 OPENSSL_EXPORT int BN_rand_range_ex(BIGNUM *r, BN_ULONG min_inclusive,
    621                                     const BIGNUM *max_exclusive);
    622 
    623 // BN_pseudo_rand_range is an alias for BN_rand_range.
    624 OPENSSL_EXPORT int BN_pseudo_rand_range(BIGNUM *rnd, const BIGNUM *range);
    625 
    626 // BN_GENCB holds a callback function that is used by generation functions that
    627 // can take a very long time to complete. Use |BN_GENCB_set| to initialise a
    628 // |BN_GENCB| structure.
    629 //
    630 // The callback receives the address of that |BN_GENCB| structure as its last
    631 // argument and the user is free to put an arbitrary pointer in |arg|. The other
    632 // arguments are set as follows:
    633 //   event=BN_GENCB_GENERATED, n=i:   after generating the i'th possible prime
    634 //                                    number.
    635 //   event=BN_GENCB_PRIME_TEST, n=-1: when finished trial division primality
    636 //                                    checks.
    637 //   event=BN_GENCB_PRIME_TEST, n=i:  when the i'th primality test has finished.
    638 //
    639 // The callback can return zero to abort the generation progress or one to
    640 // allow it to continue.
    641 //
    642 // When other code needs to call a BN generation function it will often take a
    643 // BN_GENCB argument and may call the function with other argument values.
    644 #define BN_GENCB_GENERATED 0
    645 #define BN_GENCB_PRIME_TEST 1
    646 
    647 struct bn_gencb_st {
    648   void *arg;        // callback-specific data
    649   int (*callback)(int event, int n, struct bn_gencb_st *);
    650 };
    651 
    652 // BN_GENCB_set configures |callback| to call |f| and sets |callout->arg| to
    653 // |arg|.
    654 OPENSSL_EXPORT void BN_GENCB_set(BN_GENCB *callback,
    655                                  int (*f)(int event, int n,
    656                                           struct bn_gencb_st *),
    657                                  void *arg);
    658 
    659 // BN_GENCB_call calls |callback|, if not NULL, and returns the return value of
    660 // the callback, or 1 if |callback| is NULL.
    661 OPENSSL_EXPORT int BN_GENCB_call(BN_GENCB *callback, int event, int n);
    662 
    663 // BN_generate_prime_ex sets |ret| to a prime number of |bits| length. If safe
    664 // is non-zero then the prime will be such that (ret-1)/2 is also a prime.
    665 // (This is needed for Diffie-Hellman groups to ensure that the only subgroups
    666 // are of size 2 and (p-1)/2.).
    667 //
    668 // If |add| is not NULL, the prime will fulfill the condition |ret| % |add| ==
    669 // |rem| in order to suit a given generator. (If |rem| is NULL then |ret| %
    670 // |add| == 1.)
    671 //
    672 // If |cb| is not NULL, it will be called during processing to give an
    673 // indication of progress. See the comments for |BN_GENCB|. It returns one on
    674 // success and zero otherwise.
    675 OPENSSL_EXPORT int BN_generate_prime_ex(BIGNUM *ret, int bits, int safe,
    676                                         const BIGNUM *add, const BIGNUM *rem,
    677                                         BN_GENCB *cb);
    678 
    679 // BN_prime_checks is magic value that can be used as the |checks| argument to
    680 // the primality testing functions in order to automatically select a number of
    681 // Miller-Rabin checks that gives a false positive rate of ~2^{-80}.
    682 #define BN_prime_checks 0
    683 
    684 // bn_primality_result_t enumerates the outcomes of primality-testing.
    685 enum bn_primality_result_t {
    686   bn_probably_prime,
    687   bn_composite,
    688   bn_non_prime_power_composite,
    689 };
    690 
    691 // BN_enhanced_miller_rabin_primality_test tests whether |w| is probably a prime
    692 // number using the Enhanced Miller-Rabin Test (FIPS 186-4 C.3.2) with
    693 // |iterations| iterations and returns the result in |out_result|. Enhanced
    694 // Miller-Rabin tests primality for odd integers greater than 3, returning
    695 // |bn_probably_prime| if the number is probably prime,
    696 // |bn_non_prime_power_composite| if the number is a composite that is not the
    697 // power of a single prime, and |bn_composite| otherwise.  If |iterations| is
    698 // |BN_prime_checks|, then a value that results in a false positive rate lower
    699 // than the number-field sieve security level of |w| is used. It returns one on
    700 // success and zero on failure. If |cb| is not NULL, then it is called during
    701 // each iteration of the primality test.
    702 int BN_enhanced_miller_rabin_primality_test(
    703     enum bn_primality_result_t *out_result, const BIGNUM *w, int iterations,
    704     BN_CTX *ctx, BN_GENCB *cb);
    705 
    706 // BN_primality_test sets |*is_probably_prime| to one if |candidate| is
    707 // probably a prime number by the Miller-Rabin test or zero if it's certainly
    708 // not.
    709 //
    710 // If |do_trial_division| is non-zero then |candidate| will be tested against a
    711 // list of small primes before Miller-Rabin tests. The probability of this
    712 // function returning a false positive is 2^{2*checks}. If |checks| is
    713 // |BN_prime_checks| then a value that results in a false positive rate lower
    714 // than the number-field sieve security level of |candidate| is used. If |cb| is
    715 // not NULL then it is called during the checking process. See the comment above
    716 // |BN_GENCB|.
    717 //
    718 // The function returns one on success and zero on error.
    719 //
    720 // (If you are unsure whether you want |do_trial_division|, don't set it.)
    721 OPENSSL_EXPORT int BN_primality_test(int *is_probably_prime,
    722                                      const BIGNUM *candidate, int checks,
    723                                      BN_CTX *ctx, int do_trial_division,
    724                                      BN_GENCB *cb);
    725 
    726 // BN_is_prime_fasttest_ex returns one if |candidate| is probably a prime
    727 // number by the Miller-Rabin test, zero if it's certainly not and -1 on error.
    728 //
    729 // If |do_trial_division| is non-zero then |candidate| will be tested against a
    730 // list of small primes before Miller-Rabin tests. The probability of this
    731 // function returning one when |candidate| is composite is 2^{2*checks}. If
    732 // |checks| is |BN_prime_checks| then a value that results in a false positive
    733 // rate lower than the number-field sieve security level of |candidate| is used.
    734 // If |cb| is not NULL then it is called during the checking process. See the
    735 // comment above |BN_GENCB|.
    736 //
    737 // WARNING: deprecated. Use |BN_primality_test|.
    738 OPENSSL_EXPORT int BN_is_prime_fasttest_ex(const BIGNUM *candidate, int checks,
    739                                            BN_CTX *ctx, int do_trial_division,
    740                                            BN_GENCB *cb);
    741 
    742 // BN_is_prime_ex acts the same as |BN_is_prime_fasttest_ex| with
    743 // |do_trial_division| set to zero.
    744 //
    745 // WARNING: deprecated: Use |BN_primality_test|.
    746 OPENSSL_EXPORT int BN_is_prime_ex(const BIGNUM *candidate, int checks,
    747                                   BN_CTX *ctx, BN_GENCB *cb);
    748 
    749 
    750 // Number theory functions
    751 
    752 // BN_gcd sets |r| = gcd(|a|, |b|). It returns one on success and zero
    753 // otherwise.
    754 OPENSSL_EXPORT int BN_gcd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
    755                           BN_CTX *ctx);
    756 
    757 // BN_mod_inverse sets |out| equal to |a|^-1, mod |n|. If |out| is NULL, a
    758 // fresh BIGNUM is allocated. It returns the result or NULL on error.
    759 //
    760 // If |n| is even then the operation is performed using an algorithm that avoids
    761 // some branches but which isn't constant-time. This function shouldn't be used
    762 // for secret values; use |BN_mod_inverse_blinded| instead. Or, if |n| is
    763 // guaranteed to be prime, use
    764 // |BN_mod_exp_mont_consttime(out, a, m_minus_2, m, ctx, m_mont)|, taking
    765 // advantage of Fermat's Little Theorem.
    766 OPENSSL_EXPORT BIGNUM *BN_mod_inverse(BIGNUM *out, const BIGNUM *a,
    767                                       const BIGNUM *n, BN_CTX *ctx);
    768 
    769 // BN_mod_inverse_blinded sets |out| equal to |a|^-1, mod |n|, where |n| is the
    770 // Montgomery modulus for |mont|. |a| must be non-negative and must be less
    771 // than |n|. |n| must be greater than 1. |a| is blinded (masked by a random
    772 // value) to protect it against side-channel attacks. On failure, if the failure
    773 // was caused by |a| having no inverse mod |n| then |*out_no_inverse| will be
    774 // set to one; otherwise it will be set to zero.
    775 int BN_mod_inverse_blinded(BIGNUM *out, int *out_no_inverse, const BIGNUM *a,
    776                            const BN_MONT_CTX *mont, BN_CTX *ctx);
    777 
    778 // BN_mod_inverse_odd sets |out| equal to |a|^-1, mod |n|. |a| must be
    779 // non-negative and must be less than |n|. |n| must be odd. This function
    780 // shouldn't be used for secret values; use |BN_mod_inverse_blinded| instead.
    781 // Or, if |n| is guaranteed to be prime, use
    782 // |BN_mod_exp_mont_consttime(out, a, m_minus_2, m, ctx, m_mont)|, taking
    783 // advantage of Fermat's Little Theorem. It returns one on success or zero on
    784 // failure. On failure, if the failure was caused by |a| having no inverse mod
    785 // |n| then |*out_no_inverse| will be set to one; otherwise it will be set to
    786 // zero.
    787 int BN_mod_inverse_odd(BIGNUM *out, int *out_no_inverse, const BIGNUM *a,
    788                        const BIGNUM *n, BN_CTX *ctx);
    789 
    790 
    791 // Montgomery arithmetic.
    792 
    793 // BN_MONT_CTX contains the precomputed values needed to work in a specific
    794 // Montgomery domain.
    795 
    796 // BN_MONT_CTX_new_for_modulus returns a fresh |BN_MONT_CTX| given the modulus,
    797 // |mod| or NULL on error.
    798 OPENSSL_EXPORT BN_MONT_CTX *BN_MONT_CTX_new_for_modulus(const BIGNUM *mod,
    799                                                         BN_CTX *ctx);
    800 
    801 // BN_MONT_CTX_free frees memory associated with |mont|.
    802 OPENSSL_EXPORT void BN_MONT_CTX_free(BN_MONT_CTX *mont);
    803 
    804 // BN_MONT_CTX_copy sets |to| equal to |from|. It returns |to| on success or
    805 // NULL on error.
    806 OPENSSL_EXPORT BN_MONT_CTX *BN_MONT_CTX_copy(BN_MONT_CTX *to,
    807                                              const BN_MONT_CTX *from);
    808 
    809 // BN_MONT_CTX_set_locked takes |lock| and checks whether |*pmont| is NULL. If
    810 // so, it creates a new |BN_MONT_CTX| and sets the modulus for it to |mod|. It
    811 // then stores it as |*pmont|. It returns one on success and zero on error.
    812 //
    813 // If |*pmont| is already non-NULL then it does nothing and returns one.
    814 int BN_MONT_CTX_set_locked(BN_MONT_CTX **pmont, CRYPTO_MUTEX *lock,
    815                            const BIGNUM *mod, BN_CTX *bn_ctx);
    816 
    817 // BN_to_montgomery sets |ret| equal to |a| in the Montgomery domain. |a| is
    818 // assumed to be in the range [0, n), where |n| is the Montgomery modulus. It
    819 // returns one on success or zero on error.
    820 OPENSSL_EXPORT int BN_to_montgomery(BIGNUM *ret, const BIGNUM *a,
    821                                     const BN_MONT_CTX *mont, BN_CTX *ctx);
    822 
    823 // BN_from_montgomery sets |ret| equal to |a| * R^-1, i.e. translates values out
    824 // of the Montgomery domain. |a| is assumed to be in the range [0, n), where |n|
    825 // is the Montgomery modulus. It returns one on success or zero on error.
    826 OPENSSL_EXPORT int BN_from_montgomery(BIGNUM *ret, const BIGNUM *a,
    827                                       const BN_MONT_CTX *mont, BN_CTX *ctx);
    828 
    829 // BN_mod_mul_montgomery set |r| equal to |a| * |b|, in the Montgomery domain.
    830 // Both |a| and |b| must already be in the Montgomery domain (by
    831 // |BN_to_montgomery|). In particular, |a| and |b| are assumed to be in the
    832 // range [0, n), where |n| is the Montgomery modulus. It returns one on success
    833 // or zero on error.
    834 OPENSSL_EXPORT int BN_mod_mul_montgomery(BIGNUM *r, const BIGNUM *a,
    835                                          const BIGNUM *b,
    836                                          const BN_MONT_CTX *mont, BN_CTX *ctx);
    837 
    838 
    839 // Exponentiation.
    840 
    841 // BN_exp sets |r| equal to |a|^{|p|}. It does so with a square-and-multiply
    842 // algorithm that leaks side-channel information. It returns one on success or
    843 // zero otherwise.
    844 OPENSSL_EXPORT int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
    845                           BN_CTX *ctx);
    846 
    847 // BN_mod_exp sets |r| equal to |a|^{|p|} mod |m|. It does so with the best
    848 // algorithm for the values provided. It returns one on success or zero
    849 // otherwise. The |BN_mod_exp_mont_consttime| variant must be used if the
    850 // exponent is secret.
    851 OPENSSL_EXPORT int BN_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
    852                               const BIGNUM *m, BN_CTX *ctx);
    853 
    854 OPENSSL_EXPORT int BN_mod_exp_mont(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
    855                                    const BIGNUM *m, BN_CTX *ctx,
    856                                    const BN_MONT_CTX *mont);
    857 
    858 OPENSSL_EXPORT int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a,
    859                                              const BIGNUM *p, const BIGNUM *m,
    860                                              BN_CTX *ctx,
    861                                              const BN_MONT_CTX *mont);
    862 
    863 
    864 // Deprecated functions
    865 
    866 // BN_bn2mpi serialises the value of |in| to |out|, using a format that consists
    867 // of the number's length in bytes represented as a 4-byte big-endian number,
    868 // and the number itself in big-endian format, where the most significant bit
    869 // signals a negative number. (The representation of numbers with the MSB set is
    870 // prefixed with null byte). |out| must have sufficient space available; to
    871 // find the needed amount of space, call the function with |out| set to NULL.
    872 OPENSSL_EXPORT size_t BN_bn2mpi(const BIGNUM *in, uint8_t *out);
    873 
    874 // BN_mpi2bn parses |len| bytes from |in| and returns the resulting value. The
    875 // bytes at |in| are expected to be in the format emitted by |BN_bn2mpi|.
    876 //
    877 // If |out| is NULL then a fresh |BIGNUM| is allocated and returned, otherwise
    878 // |out| is reused and returned. On error, NULL is returned and the error queue
    879 // is updated.
    880 OPENSSL_EXPORT BIGNUM *BN_mpi2bn(const uint8_t *in, size_t len, BIGNUM *out);
    881 
    882 // BN_mod_exp_mont_word is like |BN_mod_exp_mont| except that the base |a| is
    883 // given as a |BN_ULONG| instead of a |BIGNUM *|. It returns one on success
    884 // or zero otherwise.
    885 OPENSSL_EXPORT int BN_mod_exp_mont_word(BIGNUM *r, BN_ULONG a, const BIGNUM *p,
    886                                         const BIGNUM *m, BN_CTX *ctx,
    887                                         const BN_MONT_CTX *mont);
    888 
    889 // BN_mod_exp2_mont calculates (a1^p1) * (a2^p2) mod m. It returns 1 on success
    890 // or zero otherwise.
    891 OPENSSL_EXPORT int BN_mod_exp2_mont(BIGNUM *r, const BIGNUM *a1,
    892                                     const BIGNUM *p1, const BIGNUM *a2,
    893                                     const BIGNUM *p2, const BIGNUM *m,
    894                                     BN_CTX *ctx, const BN_MONT_CTX *mont);
    895 
    896 // BN_MONT_CTX_new returns a fresh |BN_MONT_CTX| or NULL on allocation failure.
    897 // Use |BN_MONT_CTX_new_for_modulus| instead.
    898 OPENSSL_EXPORT BN_MONT_CTX *BN_MONT_CTX_new(void);
    899 
    900 // BN_MONT_CTX_set sets up a Montgomery context given the modulus, |mod|. It
    901 // returns one on success and zero on error. Use |BN_MONT_CTX_new_for_modulus|
    902 // instead.
    903 OPENSSL_EXPORT int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod,
    904                                    BN_CTX *ctx);
    905 
    906 
    907 // Private functions
    908 
    909 struct bignum_st {
    910   BN_ULONG *d; /* Pointer to an array of 'BN_BITS2' bit chunks in little-endian
    911                   order. */
    912   int top;    // Index of last used element in |d|, plus one.
    913   int dmax;   // Size of |d|, in words.
    914   int neg;    // one if the number is negative
    915   int flags;  // bitmask of BN_FLG_* values
    916 };
    917 
    918 struct bn_mont_ctx_st {
    919   // RR is R^2, reduced modulo |N|. It is used to convert to Montgomery form.
    920   BIGNUM RR;
    921   // N is the modulus. It is always stored in minimal form, so |N.top|
    922   // determines R.
    923   BIGNUM N;
    924   BN_ULONG n0[2];  // least significant words of (R*Ri-1)/N
    925 };
    926 
    927 OPENSSL_EXPORT unsigned BN_num_bits_word(BN_ULONG l);
    928 
    929 #define BN_FLG_MALLOCED 0x01
    930 #define BN_FLG_STATIC_DATA 0x02
    931 // |BN_FLG_CONSTTIME| has been removed and intentionally omitted so code relying
    932 // on it will not compile. Consumers outside BoringSSL should use the
    933 // higher-level cryptographic algorithms exposed by other modules. Consumers
    934 // within the library should call the appropriate timing-sensitive algorithm
    935 // directly.
    936 
    937 
    938 #if defined(__cplusplus)
    939 }  // extern C
    940 
    941 #if !defined(BORINGSSL_NO_CXX)
    942 extern "C++" {
    943 
    944 namespace bssl {
    945 
    946 BORINGSSL_MAKE_DELETER(BIGNUM, BN_free)
    947 BORINGSSL_MAKE_DELETER(BN_CTX, BN_CTX_free)
    948 BORINGSSL_MAKE_DELETER(BN_MONT_CTX, BN_MONT_CTX_free)
    949 
    950 class BN_CTXScope {
    951  public:
    952   BN_CTXScope(BN_CTX *ctx) : ctx_(ctx) { BN_CTX_start(ctx_); }
    953   ~BN_CTXScope() { BN_CTX_end(ctx_); }
    954 
    955  private:
    956   BN_CTX *ctx_;
    957 
    958   BN_CTXScope(BN_CTXScope &) = delete;
    959   BN_CTXScope &operator=(BN_CTXScope &) = delete;
    960 };
    961 
    962 }  // namespace bssl
    963 
    964 }  // extern C++
    965 #endif
    966 
    967 #endif
    968 
    969 #define BN_R_ARG2_LT_ARG3 100
    970 #define BN_R_BAD_RECIPROCAL 101
    971 #define BN_R_BIGNUM_TOO_LONG 102
    972 #define BN_R_BITS_TOO_SMALL 103
    973 #define BN_R_CALLED_WITH_EVEN_MODULUS 104
    974 #define BN_R_DIV_BY_ZERO 105
    975 #define BN_R_EXPAND_ON_STATIC_BIGNUM_DATA 106
    976 #define BN_R_INPUT_NOT_REDUCED 107
    977 #define BN_R_INVALID_RANGE 108
    978 #define BN_R_NEGATIVE_NUMBER 109
    979 #define BN_R_NOT_A_SQUARE 110
    980 #define BN_R_NOT_INITIALIZED 111
    981 #define BN_R_NO_INVERSE 112
    982 #define BN_R_PRIVATE_KEY_TOO_LARGE 113
    983 #define BN_R_P_IS_NOT_PRIME 114
    984 #define BN_R_TOO_MANY_ITERATIONS 115
    985 #define BN_R_TOO_MANY_TEMPORARY_VARIABLES 116
    986 #define BN_R_BAD_ENCODING 117
    987 #define BN_R_ENCODE_ERROR 118
    988 #define BN_R_INVALID_INPUT 119
    989 
    990 #endif  // OPENSSL_HEADER_BN_H
    991