fuchsia / third_party / rust-crates / aef4e8b03b20ca2996b737480945754f258b10fe / . / rustc_deps / vendor / ring / crypto / fipsmodule / bn / montgomery.c

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) | |

* All rights reserved. | |

* | |

* This package is an SSL implementation written | |

* by Eric Young (eay@cryptsoft.com). | |

* The implementation was written so as to conform with Netscapes SSL. | |

* | |

* This library is free for commercial and non-commercial use as long as | |

* the following conditions are aheared to. The following conditions | |

* apply to all code found in this distribution, be it the RC4, RSA, | |

* lhash, DES, etc., code; not just the SSL code. The SSL documentation | |

* included with this distribution is covered by the same copyright terms | |

* except that the holder is Tim Hudson (tjh@cryptsoft.com). | |

* | |

* Copyright remains Eric Young's, and as such any Copyright notices in | |

* the code are not to be removed. | |

* If this package is used in a product, Eric Young should be given attribution | |

* as the author of the parts of the library used. | |

* This can be in the form of a textual message at program startup or | |

* in documentation (online or textual) provided with the package. | |

* | |

* Redistribution and use in source and binary forms, with or without | |

* modification, are permitted provided that the following conditions | |

* are met: | |

* 1. Redistributions of source code must retain the copyright | |

* notice, this list of conditions and the following disclaimer. | |

* 2. Redistributions in binary form must reproduce the above copyright | |

* notice, this list of conditions and the following disclaimer in the | |

* documentation and/or other materials provided with the distribution. | |

* 3. All advertising materials mentioning features or use of this software | |

* must display the following acknowledgement: | |

* "This product includes cryptographic software written by | |

* Eric Young (eay@cryptsoft.com)" | |

* The word 'cryptographic' can be left out if the rouines from the library | |

* being used are not cryptographic related :-). | |

* 4. If you include any Windows specific code (or a derivative thereof) from | |

* the apps directory (application code) you must include an acknowledgement: | |

* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" | |

* | |

* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND | |

* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |

* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |

* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE | |

* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |

* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |

* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |

* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |

* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |

* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |

* SUCH DAMAGE. | |

* | |

* The licence and distribution terms for any publically available version or | |

* derivative of this code cannot be changed. i.e. this code cannot simply be | |

* copied and put under another distribution licence | |

* [including the GNU Public Licence.] | |

*/ | |

/* ==================================================================== | |

* Copyright (c) 1998-2006 The OpenSSL Project. All rights reserved. | |

* | |

* Redistribution and use in source and binary forms, with or without | |

* modification, are permitted provided that the following conditions | |

* are met: | |

* | |

* 1. Redistributions of source code must retain the above copyright | |

* notice, this list of conditions and the following disclaimer. | |

* | |

* 2. Redistributions in binary form must reproduce the above copyright | |

* notice, this list of conditions and the following disclaimer in | |

* the documentation and/or other materials provided with the | |

* distribution. | |

* | |

* 3. All advertising materials mentioning features or use of this | |

* software must display the following acknowledgment: | |

* "This product includes software developed by the OpenSSL Project | |

* for use in the OpenSSL Toolkit. (http://www.openssl.org/)" | |

* | |

* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to | |

* endorse or promote products derived from this software without | |

* prior written permission. For written permission, please contact | |

* openssl-core@openssl.org. | |

* | |

* 5. Products derived from this software may not be called "OpenSSL" | |

* nor may "OpenSSL" appear in their names without prior written | |

* permission of the OpenSSL Project. | |

* | |

* 6. Redistributions of any form whatsoever must retain the following | |

* acknowledgment: | |

* "This product includes software developed by the OpenSSL Project | |

* for use in the OpenSSL Toolkit (http://www.openssl.org/)" | |

* | |

* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY | |

* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |

* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR | |

* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR | |

* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |

* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |

* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | |

* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |

* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | |

* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |

* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED | |

* OF THE POSSIBILITY OF SUCH DAMAGE. | |

* ==================================================================== | |

* | |

* This product includes cryptographic software written by Eric Young | |

* (eay@cryptsoft.com). This product includes software written by Tim | |

* Hudson (tjh@cryptsoft.com). */ | |

#include "internal.h" | |

#include "../../internal.h" | |

#include "../../limbs/limbs.inl" | |

// Avoid -Wmissing-prototypes warnings. | |

int GFp_bn_from_montgomery_in_place(BN_ULONG r[], size_t num_r, BN_ULONG a[], | |

size_t num_a, const BN_ULONG n[], | |

size_t num_n, | |

const BN_ULONG n0_[BN_MONT_CTX_N0_LIMBS]); | |

OPENSSL_STATIC_ASSERT(BN_MONT_CTX_N0_LIMBS == 1 || BN_MONT_CTX_N0_LIMBS == 2, | |

"BN_MONT_CTX_N0_LIMBS value is invalid"); | |

OPENSSL_STATIC_ASSERT( | |

sizeof(BN_ULONG) * BN_MONT_CTX_N0_LIMBS == sizeof(uint64_t), | |

"uint64_t is insufficient precision for n0"); | |

int GFp_bn_from_montgomery_in_place(BN_ULONG r[], size_t num_r, BN_ULONG a[], | |

size_t num_a, const BN_ULONG n[], | |

size_t num_n, | |

const BN_ULONG n0_[BN_MONT_CTX_N0_LIMBS]) { | |

assert(num_n != 0); | |

if (num_r != num_n || num_a != 2 * num_n) { | |

return 0; | |

} | |

// Add multiples of |n| to |r| until R = 2^(nl * BN_BITS2) divides it. On | |

// input, we had |r| < |n| * R, so now |r| < 2 * |n| * R. Note that |r| | |

// includes |carry| which is stored separately. | |

BN_ULONG n0 = n0_[0]; | |

BN_ULONG carry = 0; | |

for (size_t i = 0; i < num_n; i++) { | |

BN_ULONG v = GFp_bn_mul_add_words(a + i, n, num_n, a[i] * n0); | |

v += carry + a[i + num_n]; | |

carry |= (v != a[i + num_n]); | |

carry &= (v <= a[i + num_n]); | |

a[i + num_n] = v; | |

} | |

// Shift |num_n| words to divide by R. We have |a| < 2 * |n|. Note that |a| | |

// includes |carry| which is stored separately. | |

a += num_n; | |

// |a| thus requires at most one additional subtraction |n| to be reduced. | |

// Subtract |n| and select the answer in constant time. | |

BN_ULONG v = limbs_sub(r, a, n, num_n) - carry; | |

// |v| is one if |a| - |n| underflowed or zero if it did not. Note |v| cannot | |

// be -1. That would imply the subtraction did not fit in |num_n| words, and | |

// we know at most one subtraction is needed. | |

v = 0u - v; | |

for (size_t i = 0; i < num_n; i++) { | |

r[i] = constant_time_select_w(v, a[i], r[i]); | |

a[i] = 0; | |

} | |

return 1; | |

} |